Imaging device

Abstract

An imaging device 1 comprises: a variable focus lens 10; and an imaging sensor 15 that outputs a signal corresponding to light. The imaging sensor 15 includes: a photoelectric conversion unit PD that converts light to an electric charge; electric charge reading regions R1-R4; transfer control electrodes E1-E4; a gate control circuit 26 that sequentially applies control signals TG1-TG4 to the transfer control electrodes E1-E4 corresponding to the position of a focus P of the variable focus lens 10; and a reading circuit 27 that outputs a signal corresponding to an electric charge amount transferred to the electric charge reading regions R1-R4. The gate control circuit 26 repeats an operation of respectively outputting the control signals TG1-TG4 when the position of the focus P is in focus ranges BF1-BF4 within a frame period.

Description

[Technical field]

[0001] The present invention relates to an imaging device. [Background technology]

[0002] Generally, the focal length of a lens is a value specific to each individual lens. On the other hand, so-called variable-focus lenses, which can change the focal length, are known. For example, Patent Document 1 discloses a technique related to a variable-focus lens. The variable-focus lens of Patent Document 1 uses a liquid as an element for refracting light. When the liquid is subjected to resonant vibration, a density distribution occurs. As a result, the focal length of the variable-focus lens fluctuates at a speed determined by the frequency of the vibration. The frequency of the vibration is, for example, in the range of several tens of Hz to several hundreds of kHz. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2013 / 0321927 Summary of the Invention [Problem to be solved by the invention]

[0004] An imaging device using a variable-focus lens and an image sensor has been considered. A variable-focus lens using liquid changes its focal length by resonant vibration. Therefore, the focal length of the variable-focus lens is constantly fluctuating. When an imaging range is set so that the focal position is included in the range in which it fluctuates, exposure is performed only during the period during which the focal point is in the imaging range. However, since the period during which the focal point is in the imaging range is extremely short, the exposure period is also short. When the exposure period is short, the amount of light incident on the image sensor is insufficient. In other words, the brightness of the obtained image is low.

[0005] Therefore, the present invention provides an imaging device capable of increasing the brightness of an obtained image. [Means for solving the problem]

[0006] An imaging device according to one aspect of the present invention includes a variable-focus lens whose focal position changes periodically between a farthest point and a nearest point during a frame period, and a pixel circuit unit arranged so as to overlap with the optical axis of the variable-focus lens, receiving light that has passed through the variable-focus lens and outputting a signal corresponding to the light. The pixel circuit unit includes a photoelectric conversion unit that converts light into electric charges, a charge readout region arranged adjacent to the photoelectric conversion unit, a transfer control electrode arranged between the photoelectric conversion unit and the charge readout region and receiving a transfer control signal for charge transfer between the photoelectric conversion unit and the charge readout region, a charge discharge region arranged adjacent to the photoelectric conversion unit and spaced apart from the charge readout region and discharging electric charges that are not used to read out a signal corresponding to the light, a discharge control electrode arranged between the photoelectric conversion unit and the charge discharge region and receiving a discharge control signal for charge transfer between the photoelectric conversion unit and the charge discharge region, control means for applying a transfer control signal to the transfer control electrode and a discharge control signal to the discharge control electrode in accordance with the position of the focal point of the variable-focus lens, and signal readout means for outputting a signal corresponding to the amount of electric charge transferred to the charge readout region. The control means repeats, within a frame period, an operation of outputting a transfer control signal when the focal position is within a focus range set in the imaging range, and an operation of outputting a discharge control signal when the focal position is within a non-imaging range that does not overlap with the imaging range.

[0007] The imaging device includes a variable-focus lens. The variable-focus lens periodically changes the position of the focal point between the farthest point and the nearest point during a frame period. The charge transfer control means transfers the charge generated in the photoelectric conversion unit to the charge readout region when the focal point is in the imaging range. The charge transfer control means transfers the charge to the charge discharge region when the focal point is in the non-imaging range. The charge transfer control means repeats the transfer to the charge readout region and the transfer to the charge discharge region during the frame period. As a result, each time these transfer operations are repeated, the charge obtained when the focal point is in the imaging range is accumulated in the charge readout region. That is, even if the amount of charge transferred in one transfer operation is small, the amount of charge accumulated in the charge readout region increases by repeating the transfer operation. Therefore, the increase in the amount of charge can increase the brightness of the obtained image.

[0008] The pixel circuit section of the imaging device in one embodiment may further include one or more additional charge readout regions provided adjacent to the photoelectric conversion section and spaced apart from the charge readout region, and one or more additional transfer control electrodes provided between the photoelectric conversion section and the additional charge readout region, for receiving an additional transfer control signal for charge transfer between the photoelectric conversion section and the additional charge readout region. The control means may further perform an operation of outputting an additional transfer control signal when the focal position is in an additional focal range set in the imaging range and not overlapping with the focal range during the frame period. The signal readout means may further output a signal corresponding to the charge amount, which is the amount of charge transferred to the additional charge readout region. According to this configuration, it is possible to set a plurality of focal ranges in the imaging range. Therefore, a sharp image in focus can be obtained.

[0009] In one embodiment, the control means of the imaging device may generate the transfer control signal and the additional transfer control signal so that the length of the period during which charge transfer from the photoelectric conversion unit to the charge readout region is permitted and the length of the period during which charge transfer from the photoelectric conversion unit to one or more additional charge readout regions are permitted are equal to each other. With this configuration, the transfer operation is switched at regular time intervals. Therefore, the control by the charge transfer control means can be simplified.

[0010] In one embodiment, the control means of the imaging device may generate the transfer control signal and the additional transfer control signal so that the amount by which the position of the focal point changes during a period in which the transfer of charges from the photoelectric conversion unit to the charge readout region is permitted and the amount by which the position of the focal point changes during a period in which the transfer of charges from the photoelectric conversion unit to the one or more additional charge readout regions is permitted are equal to each other. With this configuration, the length of each focal range can be made constant.

[0011] In one embodiment, the control means of the imaging device may set a plurality of subframe periods included in the frame period. The control means may set an imaging range for each of the plurality of subframe periods. With this configuration, it is possible to finely set a focus range included in the imaging range.

[0012] In one embodiment, imaging ranges set for each of a plurality of subframe periods do not need to overlap with each other. With this configuration, it is possible to widen the imaging range.

[0013] In one embodiment, the imaging ranges set for each of a plurality of subframe periods may overlap each other. With this configuration, the focal range included in the imaging range can be set more finely.

[0014] In one embodiment, the control means of the imaging device may perform an operation of outputting the transfer control signal twice during one period of change in the position of the focus. With this configuration, the amount of charge transferred to the charge readout means increases. Therefore, the brightness of the obtained image can be further increased.

[0015] In one embodiment, the control means of the imaging device may perform an operation of outputting a transfer control signal once during one period of change in the focal position. With this configuration, it is possible to ease the synchronization condition between the periodic movement of the focal position of the variable-focus lens and the transfer operation in the pixel circuit unit.

[0016] In one embodiment, the variable-focus lens of the imaging device may include a lens unit through which light passes, and a lens driver that periodically changes the focal position of the lens unit by providing a lens drive signal to the lens unit. The variable-focus lens may further include a pixel controller that receives the lens drive signal from the lens driver and provides a control signal for the pixel circuit unit to the pixel circuit unit based on the lens drive signal. With this configuration, the operation of the lens unit and the operation of the pixel circuit unit can be synchronized.

[0017] In one embodiment, the charge readout region of the imaging device may have a two-stage transfer structure. The two-stage transfer structure may be configured with a charge storage section that receives charges from the photoelectric conversion section, a floating diffusion section that receives charges from the charge storage section and is connected to the signal readout means, a reset drain that receives charges from the floating diffusion section, a transfer gate electrode that controls the transfer of charges from the charge storage section to the floating diffusion section, and a reset gate electrode that controls the transfer of charges from the floating diffusion section to the reset drain. With this configuration, it is possible to reduce noise caused by the reset operation of the floating diffusion section.

[0018] In one embodiment, the charge readout region of the imaging device may have a single-stage transfer structure. The charge readout region may have a single-stage transfer structure. The single-stage transfer structure may be configured with a floating diffusion region that receives charges from a photoelectric conversion region, a reset drain that receives charges from the floating diffusion region, and a reset gate electrode that controls the transfer of charges from the floating diffusion region to the reset drain. This configuration can simplify the configuration of the charge readout region. In other words, the configuration of the pixel circuit section can be simplified.

[0019] In one embodiment, the control means of the imaging device may perform an operation of outputting a transfer control signal, an operation of outputting a discharge control signal after the operation of outputting the transfer control signal, an operation of outputting an additional transfer control signal after the operation of outputting the discharge control signal, and an operation of outputting a discharge control signal again after the operation of outputting the additional transfer control signal. With this configuration, each focal range can be set to a discrete narrow range. As a result, the focal range in which light from different focal points is averaged becomes narrow, and the clarity of images in each focal range can be improved. Effect of the Invention

[0020] According to the present invention, there is provided an imaging device capable of increasing the brightness of an obtained image. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing the configuration of an imaging apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of the image sensor shown in FIG. [Diagram 3] FIG. 3 is a diagram showing a state of connection of signal lines to the pixels shown in FIG. [Figure 4] FIG. 4 is a diagram showing a configuration of the pixel shown in FIG. [Diagram 5] FIG. 5 is an enlarged view of a main part of the pixel shown in FIG. [Figure 6] FIG. 6 is a diagram showing the relationship between the operation of the variable focus lens and the focus range. [Figure 7] FIG. 7 is a diagram for explaining the operation of the imaging device. [Figure 8] Part (a) of Fig. 8 is a graph showing the variation in focus in the imaging device of the embodiment, and part (b) of Fig. 8 is a timing chart showing the operation of the embodiment. [Figure 9] Part (a) of Fig. 9 is a graph showing the fluctuation of focus in the imaging device of Modification 1. Part (b) of Fig. 9 is a timing chart showing the operation of Modification 1. [Figure 10]Parts (a) and (c) of Fig. 10 are graphs showing focus fluctuations in the imaging device of Modification 2. Parts (b) and (d) of Fig. 10 are timing charts showing the operation of Modification 2. [Figure 11] 11A and 11C are graphs showing focus fluctuations in the imaging device of Modification 3. FIG. 11B and FIG. 11D are timing charts showing the operation of Modification 3. [Figure 12] FIG. 12 is a diagram for explaining the imaging range in the imaging device of the third modification. [Figure 13] Part (a) of Fig. 13 is a graph showing the fluctuation of focus in the imaging device of Modification 4. Part (b) of Fig. 13 is a timing chart showing the operation of Modification 4. [Figure 14] Part (a) of Fig. 14 is a graph showing the fluctuation of focus in the imaging device of Modification 5. Part (b) of Fig. 14 is a timing chart showing the operation of Modification 5. [Figure 15] FIG. 15 is an enlarged view showing a main part of a pixel included in an imaging device according to the sixth modification. [Figure 16] FIG. 16 is a diagram showing the configuration of an image sensor according to the seventh modification. [Figure 17] FIG. 17 is a diagram showing a configuration of the pixel shown in FIG. [Figure 18] Part (a) of Fig. 18 is a graph showing the focus position and focus range of the variable focus lens, and part (b) of Fig. 18 is a timing chart showing the operation of the pixel shown in Figs. [Figure 19] FIG. 19 is a diagram showing the imaging range of an imaging device according to the eighth modification. [Figure 20] Part (a) of Fig. 20 is a graph showing the fluctuation of focus in the imaging device of Modification 8. Part (b) of Fig. 20 is a timing chart showing the operation of Modification 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0023] As shown in FIG. 1, the imaging device 1 includes a variable-focus lens 10 and an imaging sensor 15.

[0024] The variable-focus lens 10 forms an image of an object to be imaged on an imaging sensor 15. The variable-focus lens 10 has a focal position that changes periodically between a farthest point and a nearest point. The variable-focus lens 10 has a lens unit 11 and a lens driving unit 12. The lens driving unit 12 provides a lens driving signal to the lens unit 11. As a result, the focal position of the lens unit 11 changes periodically. As such a variable-focus lens 10, for example, the lens disclosed in U.S. Patent Application Publication No. 2013 / 0321927 may be used.

[0025] [Image sensor] The imaging sensor 15 obtains an image of an object to be imaged. The imaging sensor 15 has a pixel circuit section 20, a pixel control section 50, and an image processing section 60. The pixel circuit section 20 is connected to the pixel control section 50. The pixel circuit section 20 operates in response to a control signal provided from the pixel control section 50. The operation here includes, for example, an exposure operation and a transfer operation. The pixel circuit section 20 is also connected to the image processing section 60. The pixel circuit section 20 provides an output signal to the image processing section 60. The pixel circuit section 20 has a pixel array 21 and a peripheral circuit 25. The pixel array 21 and the peripheral circuit 25 are provided on the same semiconductor chip.

[0026] [Pixel Control Unit] The operation of the variable-focus lens 10 and the operation of the pixel circuit unit 20 are synchronized with each other. Therefore, the pixel control unit 50 receives a reference signal from the variable-focus lens 10. The frequency of the reference signal is the same as the frequency of the lens driving signal. Meanwhile, the difference between the phase of the reference signal and the phase of the lens driving signal may be zero or may include a predetermined value. For example, the reference signal may be the lens driving signal itself. Then, the pixel control unit 50 provides a control signal generated based on the reference signal to the pixel circuit unit 20.

[0027] [Image processing section] The image processing unit 60 generates a composite image using the signal provided from the pixel circuit unit 20. The image processing unit 60 generates first to fourth partial images using the signal obtained from the pixel circuit unit 20. These partial images refer to images acquired at different focal positions. Furthermore, the image processing unit 60 generates a composite image using the first to fourth partial images.

[0028] [Pixel circuit section] The pixel circuit unit 20 is disposed so as to overlap with the optical axis of the variable-focus lens 10. The pixel circuit unit 20 receives light that has passed through the variable-focus lens 10 and outputs a signal according to the light. As shown in Fig. 2, a pixel array 21 of the pixel circuit unit 20 has a plurality of pixels 22. The plurality of pixels 22 are disposed two-dimensionally. The pixel 22 includes a photoelectric conversion unit PD, charge readout regions R1, R2, R3, and R4, buffer amplifiers A1, A2, A3, and A4, and a drain DR (charge discharge region).

[0029] Here, the charge read region R1 is a charge read region as defined in the claims, the charge read regions R2, R3, and R4 are additional charge read regions as defined in the claims, and the drain DR is a charge discharge region as defined in the claims.

[0030] The peripheral circuit 25 has a gate control circuit 26 (control means), a readout circuit 27 (signal readout means), and an AD conversion circuit 28. The gate control circuit 26 and the readout circuit 27 are connected to the pixel control unit 50 and the pixel array 21, respectively. Specifically, the gate control circuit 26 and the readout circuit 27 are connected to each of the pixels 22 of the pixel array 21. The gate control circuit 26 and the readout circuit 27 output various signals for controlling the pixel array 21 to the pixels 22.

[0031] The gate control circuit 26 operates based on a signal from the pixel control unit 50. The pixel control unit 50 operates based on a reference signal from the lens driving unit 12. That is, the gate control circuit 26 operates based on the reference signal from the lens driving unit 12. On the other hand, the readout circuit 27 may operate based on the reference signal from the lens driving unit 12. Also, the readout circuit 27 may operate without being based on the reference signal. That is, the readout circuit 27 can also operate based on a reference signal other than the reference signal.

[0032] The AD conversion circuit 28 is connected to the pixel array 21. The AD conversion circuit 28 converts an output signal received from the pixel array 21 from an analog signal to a digital signal. The AD conversion circuit 28 may have a folding integral type conversion circuit section 28a and a cyclic conversion circuit 28b. The AD conversion circuit 28 includes a circuit unit including the folding integral type conversion circuit section 28a and the cyclic conversion circuit 28b. The circuit unit is provided for each column. The output of the pixel array 21 is connected to the input of the folding integral type conversion circuit section 28a. The output of the folding integral type conversion circuit section 28a is connected to the input of the cyclic conversion circuit 28b. The output of the cyclic conversion circuit 28b is connected to the image processing unit 60. The AD conversion circuit 28 outputs the output signal converted into a digital signal to the image processing unit 60.

[0033] Such an AD conversion circuit 28 performs a folding-integral type AD conversion operation. The folding-integral type AD conversion operation can expand the dynamic range. Furthermore, by performing K folding-integral type AD conversion operations, the signal components of the pixels 22 are multiplied by K. Meanwhile, the random noise components are multiplied by √K (the square root of K). Therefore, the S / N ratio can be improved by √K.

[0034] The AD conversion circuit 28 may also include the folding and integral type conversion circuit section 28a and the cyclic type conversion circuit section 28b as separate circuits. In this case, the folding and integral type conversion operation and the cyclic type conversion operation can be performed in parallel. In other words, pipeline processing can be applied. As a result, the AD conversion operation can be accelerated.

[0035] On the other hand, the AD conversion circuit 28 may realize the folding integral type conversion circuit section 28a and the cyclic type conversion circuit 28b by changing the circuit configuration with a switch in one circuit. With this configuration, the AD conversion circuit 28 can be configured as a single end.

[0036] The AD conversion circuit 28 may include a correlated double sampling circuit (a so-called CDS circuit). The CDS circuit reduces noise caused by reset operations in the charge readout regions R1, R2, R3, and R4 described below. The CDS circuit outputs a signal obtained by removing a reset level component from a signal provided from the pixel 22. The CDS circuit receives the output of the pixel array 21. The CDS circuit outputs a processed signal to a folding integral type conversion circuit unit 28a.

[0037] There is no particular limitation on the layout of the gate control circuit 26, the readout circuit 27, and the AD conversion circuit 28 in the semiconductor chip. The gate control circuit 26, the readout circuit 27, and the AD conversion circuit 28 may be set appropriately depending on the configuration of the pixel circuit unit 20, etc.

[0038] More specifically, as shown in Fig. 3, a plurality of signal lines are connected to the pixel 22. The transfer control electrodes E1, E2, E3, E4 and the discharge control electrode ED of the pixel 22 are connected to the gate control circuit 26 via the signal lines. The transfer control electrode E1 receives a control signal TG1. The transfer control electrode E2 receives a control signal TG2. The transfer control electrode E3 receives a control signal TG3. The transfer control electrode E4 receives a control signal TG4. The discharge control electrode ED receives a control signal TD.

[0039] The charge readout regions R1, R2, R3, and R4 of the pixel 22 are connected to a power supply 29 via a power supply line. The charge readout regions R1, R2, R3, and R4 receive a voltage VDD from the power supply line. The charge readout regions R1, R2, R3, and R4 are also connected to a gate control circuit 26 via a signal line. The charge readout regions R1, R2, R3, and R4 receive control signals RT and TX from the gate control circuit 26. The charge readout regions R1, R2, R3, and R4 are also connected to buffer amplifiers A1, A2, A3, and A4 via signal lines, respectively. The buffer amplifiers A1, A2, A3, and A4 are connected to an AD conversion circuit 28.

[0040] The drain DR is connected to a power supply 29 via a power supply line. The drain DR receives a voltage VDD from the power supply line.

[0041] The buffer amplifiers A1, A2, A3, and A4 are each connected via a signal line to the read circuit 27. The buffer amplifiers A1, A2, A3, and A4 receive a control signal SEL from the read circuit 27.

[0042] 4 is a diagram showing a configuration of the pixel 22. The pixel 22 has a photodetection section 22a and an amplifier unit 22b. The photodetection section 22a receives light and generates an electric charge. The electric charge is output as a voltage to the AD conversion circuit 28 via the amplifier unit 22b.

[0043] The photodetection section 22a has a photoelectric conversion section PD and a charge transfer section 30. The photodetection section 22a has a structure based on the principle of a lateral electric field controlled charge modulator (LEFM) developed by the present inventors. The lateral electric field controlled charge modulator controls the electric field of the charge transport path by utilizing a lateral electric field caused by multiple gates provided on the side of the charge transport path, thereby controlling the transport of electrons at high speed. As the lateral electric field controlled charge modulator, for example, the configuration shown in Japanese Patent No. 6476138 by the present inventors can be adopted.

[0044] The photoelectric conversion unit PD generates charges according to the light received through the aperture AP. The photoelectric conversion unit PD provides the charges to the charge transfer unit 30.

[0045] The charge transfer unit 30 receives the charges provided from the photoelectric conversion unit PD. The charge transfer unit 30 provides voltages based on the charges to the buffer amplifiers A1, A2, A3, and A4. The charge transfer unit 30 has a charge collection region 31, a charge distribution unit 32, a drain 33, and charge readout regions R1, R2, R3, and R4.

[0046] The charge collecting region 31 collects the charges generated in the photoelectric conversion unit PD. Then, the charge distributing unit 32 transfers the collected charges to any one of the charge readout regions R1, R2, R3, and R4 or the drain 33.

[0047] The charge distribution unit 32 distributes charges according to the position of the focal point P of the variable-focus lens 10. The charge distribution unit 32 has transfer control electrodes E1, E2, E3, E4 (transfer control electrodes) and a discharge control electrode ED. Signal lines are connected to the transfer control electrodes E1, E2, E3, E4, respectively. The transfer control electrode E1 receives a control signal TG1. The transfer control electrode E2 receives a control signal TG2. The transfer control electrode E3 receives a control signal TG3. The transfer control electrode E4 receives a control signal TG4. The transfer control electrodes E1, E2, E3, E4 transfer charges from the charge collection region 31 to any one of the charge readout regions R1, R2, R3, R4 in response to the control signals TG1, TG2, TG3, TG4.

[0048] A signal line is connected to the discharge control electrode ED. The discharge control electrode ED receives a control signal TD. The discharge control electrode ED controls the transfer of charges from the charge collecting region 31 to the drain 33 in response to the control signal TD provided from the signal line.

[0049] A power source 29 is connected to the drain 33. During the period when the photoelectric conversion unit PD receives light, the photoelectric conversion unit PD continues to generate charges. On the other hand, during the period when a predetermined process is being performed on the charges in the charge readout regions R1, R2, R3, and R4, the transfer of the charges to the charge readout regions R1, R2, R3, and R4 is prohibited. The predetermined process on the charges is, for example, a readout operation. Therefore, the drain 33 receives the charges generated during the period when the transfer of the charges to the charge readout regions R1, R2, R3, and R4 is prohibited. In other words, during the period when the drain 33 receives the charges, the charges are not stored in the charge readout regions R1, R2, R3, and R4.

[0050] The charge readout regions R1, R2, R3, and R4 provide voltages corresponding to the transferred charges to the buffer amplifiers A1, A2, A3, and A4, respectively. The charge readout regions R1, R2, R3, and R4 differ from each other only in their arrangement and connection configuration. Therefore, the charge readout region R1 will be described in detail.

[0051] 5, the charge readout region R1 has a charge accumulation portion 41, a floating diffusion portion 42, and a reset drain 43. The charge accumulation portion 41 is adjacent to the charge collection region 31. The floating diffusion portion 42 is adjacent to the charge accumulation portion 41. The floating diffusion portion 42 is also connected to the buffer amplifier A1 via an output line. The reset drain 43 is adjacent to the floating diffusion portion 42. The power supply 29 is connected to the reset drain 43, and receives a voltage VDD.

[0052] These regions are regions for temporarily storing electric charges. The transfer of electric charges between these regions is controlled by voltages applied from several electrodes. The charge readout region R1 has a transfer gate electrode 44 and a reset gate electrode 45. The transfer gate electrode 44 controls the transfer of electric charges from the charge storage region 41 to the floating diffusion region 42 in response to a control signal TX provided from a signal line. The reset gate electrode 45 resets the floating diffusion region 42 to a voltage VDD through a reset drain 43 in response to a control signal RT provided from the signal line.

[0053] The buffer amplifiers A1, A2, A3, and A4 differ from one another only in their arrangement and connection configurations. Therefore, the buffer amplifier A1 will be described in detail.

[0054] The buffer amplifier A1 has a transistor TA and a transistor TS. The drain of the transistor TA is connected to the power supply 29. The gate of the transistor TA is connected to the floating diffusion region 42 of the charge readout region R1. The source of the transistor TA is connected to the transistor TS. The transistor TS performs switching control as to whether or not an output signal is output from the buffer amplifier A1. The drain of the transistor TS is connected to the source of the transistor TA. The gate of the transistor TS is connected to a signal line for a control signal SEL. The source of the transistor TS is connected to a signal line for the AD conversion circuit 28. The buffer amplifier A1 outputs a voltage corresponding to the charge accumulated in the floating diffusion region 42 to the signal line in response to a control signal SEL provided to the gate of the transistor TS.

[0055] [Gate control circuit] The gate control circuit 26 generates a control signal to be provided to the pixel array 21 in response to a control signal provided from the pixel control unit 50. Hereinafter, the operation of the gate control circuit 26 will be described with reference to FIGS. 6, 7, 8, and 9.

[0056] 6 conceptually illustrates how the position of the focal point P of the variable-focus lens 10 changes periodically. Graph G6 illustrates the relationship between time (phase) and the position of the focal point P. As shown in graph G6, the position of the focal point P changes periodically with the passage of time. For example, the position of the focal point P changes sinusoidally with the passage of time.

[0057] The position of the focal point P of the variable-focus lens 10 is indicated by a nearest point Pc, a furthest point Pd, and a central point Pm. The nearest point Pc is the point that is the shortest distance from the variable-focus lens 10. For example, the distance from the variable-focus lens 10 to the nearest point Pc is indicated as a distance Lc. The furthest point Pd is the point that is the furthest distance from the variable-focus lens 10. For example, the distance from the variable-focus lens 10 to the furthest point Pd is indicated as a distance Ld. The central point Pm is the center of the distances from the nearest point Pc to the furthest point Pd. In other words, the distance Lmc from the central point Pm to the nearest point Pc is equal to the distance Lmd from the central point Pm to the furthest point Pd. The position of the focal point P changes periodically between the nearest point Pc and the furthest point Pd.

[0058] The imaging range B of the variable-focus lens 10 can be set to any range between the nearest point Pc and the farthest point Pd. The imaging range B is defined by the imaging near point Fc and the imaging far point Fd. The imaging near point Fc and the imaging far point Fd are set between the nearest point Pc and the farthest point Pd. For example, the imaging range B becomes maximum by setting the imaging near point Fc to the position of the nearest point Pc and setting the imaging far point Fd to the farthest point Pd. Various imaging variations can be realized depending on how the imaging near point Fc and the imaging far point Fd are set. Some variations will be described later as modified examples 1 to 4. The imaging near point Fc of this embodiment is set between the nearest point Pc and the central point Pm. Furthermore, the imaging far point Fd of this embodiment is set between the farthest point Pd and the central point Pm. According to these settings, the imaging range B becomes a range including the central point Pm.

[0059] Various imaging targets may exist in the imaging range B. For example, if the imaging target 100 exists on the side closer to the variable-focus lens 10, a clear image of the imaging target 100 can be obtained by performing exposure when the position of the focal point P of the variable-focus lens 10 is the position of the imaging target 100 (see reference symbol P1 in FIG. 7). However, if exposure is performed when the position of the focal point P of the variable-focus lens 10 is not the position of the imaging target 100 (see reference symbol P2 in FIG. 7), a clear image of the imaging target 100 cannot be obtained. Therefore, the imaging range B is divided into several parts. For example, as shown in FIG. 6, four parts are set in the imaging range B. These parts are called focal ranges BF1, BF2, BF3, and BF4. Here, the focal range BF1 is the focal range defined in the claims. Also, the focal ranges BF2, BF3, and BF4 are additional focal ranges defined in the claims. The manner of exposure operation is changed for each of the focal ranges BF1, BF2, BF3, and BF4. The exposure operation refers to the operation of accumulating the electric charge obtained by exposure, and changing the mode of the exposure operation refers to changing the region in which the electric charge obtained by exposure is accumulated for each of the focal ranges BF1, BF2, BF3, and BF4.

[0060] For example, when the position of the focus P is in the focus range BF1, the image sensor 15 accumulates the charge in the charge readout region R1. When the position of the focus P is in the focus range BF2, the image sensor 15 accumulates the charge in the charge readout region R2. When the position of the focus P is in the focus range BF3, the image sensor 15 accumulates the charge in the charge readout region R3. When the position of the focus P is in the focus range BF4, the image sensor 15 accumulates the charge in the charge readout region R4. Note that the correspondence between the focus ranges and the charge readout regions is not limited to the above examples, and may be set appropriately depending on the configuration and operation of the imaging device.

[0061] The position of the focal point P changes periodically as shown in graph G6 of FIG. 6. Then, during one period of the position of the focal point P, for example, the position of the focal point P passes through each of the focal ranges BF1, BF2, BF3, and BF4 twice. Therefore, during one period, the image sensor 15 distributes the charge to one of the corresponding charge readout regions R1, R2, R3, and R4 each time the position of the focal point P passes through the focal ranges BF1, BF2, BF3, and BF4. Then, for example, the charge obtained when the position of the focal point P is in the focal range BF1 is accumulated each time the position of the focal point P passes through the focal range BF1. Therefore, even if the amount of charge accumulated in one exposure operation (accumulation operation) is small, the amount of charge used to obtain an image corresponding to the focal range BF1 can be increased by performing the exposure operation multiple times. As a result, it is possible to increase the brightness of the obtained image.

[0062] In this embodiment, the exposure period S1 corresponding to the focal range BF1, the exposure period S2 corresponding to the focal range BF2, the exposure period S3 corresponding to the focal range BF3, and the exposure period S4 corresponding to the focal range BF4 are set to be equal in length. In this case, the lengths of the focal ranges BF1 and BF4 are different from the lengths of the focal ranges BF2 and BF3.

[0063] The gate control circuit 26 provides the pixel array 21 with control signals TG1, TG2, TG3, TG4, and TD shown in the timing chart of Fig. 8. The control signal TG1 is a transfer control signal. The control signals TG2, TG3, and TG4 are additional transfer control signals. The control signal TD is a discharge control signal.

[0064] First, the gate control circuit 26 applies the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during the period S2 from phase φ1 to phase φ2. The period S2 from phase φ1 to phase φ2 corresponds to the focal range BF2. According to the control signals TG1, TG2, TG3, TG4, and TD, charge is accumulated in the charge readout region R2. Note that "LOW" means that charge transfer is prohibited. "HIGH" means that charge transfer is permitted. TG1:LOW. TG2: HIGH. TG3:LOW. TG4:LOW. T.D.: LOW.

[0065] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD (first control signals) to the pixel array 21 during a period S1 from phase φ2 to phase φ3. The period S1 from phase φ2 to phase φ3 corresponds to a focal range BF1. According to the control signals TG1, TG2, TG3, TG4, and TD, charges are accumulated in the charge readout region R1. TG1: HIGH. TG2:LOW. TG3:LOW. TG4:LOW. T.D.: LOW.

[0066] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period SD from phase φ3 to phase φ4. The period SD from phase φ3 to phase φ4 is a non-imaging period. According to the control signals TG1, TG2, TG3, TG4, and TD, charges are discharged to the drain 33. TG1:LOW. TG2:LOW. TG3:LOW. TG4:LOW. T.D.:HIGH.

[0067] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S1 from phase φ4 to phase φ5. The period S1 from phase φ4 to phase φ5 corresponds to the focal range BF1. According to the control signals TG1, TG2, TG3, TG4, and TD, the charges are stored again in the charge readout region R1. TG1: HIGH. TG2:LOW. TG3:LOW. TG4:LOW. T.D.: LOW.

[0068] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S2 from phase φ5 to phase φ6. The period S2 from phase φ5 to phase φ6 corresponds to the focal range BF2. According to the control signals TG1, TG2, TG3, TG4, and TD, the charges are stored again in the charge readout region R2. TG1:LOW. TG2: HIGH. TG3:LOW. TG4:LOW. T.D.: LOW.

[0069] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S3 from phase φ6 to phase φ7. The period S3 from phase φ6 to phase φ7 corresponds to the focal range BF3. According to the control signals TG1, TG2, TG3, TG4, and TD, charges are accumulated in the charge readout region R3. TG1:LOW. TG2:LOW. TG3: HIGH. TG4:LOW. T.D.: LOW.

[0070] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S4 from phase φ7 to phase φ8. The period S4 from phase φ7 to phase φ8 corresponds to a focal range BF4. According to the control signals TG1, TG2, TG3, TG4, and TD, charges are accumulated in the charge readout region R4. TG1:LOW. TG2:LOW. TG3:LOW. TG4: HIGH. T.D.: LOW.

[0071] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period SD from phase φ8 to phase φ9. The period SD from phase φ8 to phase φ9 is a non-imaging period. According to the control signals TG1, TG2, TG3, TG4, and TD, charges are discharged to the drain 33. TG1:LOW. TG2:LOW. TG3:LOW. TG4:LOW. T.D.:HIGH.

[0072] Next, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S4 from phase φ9 to phase φ10. The period S4 from phase φ9 to phase φ10 corresponds to the focal range BF4. According to the control signals TG1, TG2, TG3, TG4, and TD, the charges are stored again in the charge readout region R4. TG1:LOW. TG2:LOW. TG3:LOW. TG4: HIGH. T.D.: LOW.

[0073] Then, the gate control circuit 26 provides the following control signals TG1, TG2, TG3, TG4, and TD to the pixel array 21 during a period S3 from phase φ10 to phase φ1. The period from phase φ10 to phase φ1 corresponds to the focal range BF3. According to the control signals TG1, TG2, TG3, TG4, and TD, the charges are stored again in the charge readout region R3. TG1:LOW. TG2:LOW. TG3: HIGH. TG4:LOW. T.D.: LOW.

[0074] The above operation completes the exposure operation for one period of the position of the focal point P. Thereafter, the above exposure operation is repeated during the frame period.

[0075] After the frame period has elapsed, the readout circuit 27 outputs voltages corresponding to the charges accumulated in each of the charge readout regions R1, R2, R3, and R4 to the AD conversion circuit 28. Then, the image processing unit 60 generates an image for each of the charge readout regions R1, R2, R3, and R4 using the signals output from the AD conversion circuit 28. As a result, first to fourth partial images are obtained. The image processing unit 60 may output the partial images as a result, or may output the result as a composite image in which the partial images are combined into a single image.

[0076] <Action and effect> The imaging device 1 includes a variable-focus lens 10. In the variable-focus lens 10, the position of the focal point P periodically changes between the farthest point Pd and the nearest point Pc during a frame period. The gate control circuit 26 transfers the electric charge generated in the photoelectric conversion unit PD to the charge readout region R1 when the position of the focal point P is in the focal range BF1, and transfers the electric charge to the drain DR when the position of the focal point P is in the non-imaging range C. The gate control circuit 26 repeats the transfer to the charge readout region R1 and the transfer to the drain DR during a frame period. As a result, each time these transfer operations are repeated, the electric charge obtained when the position of the focal point P is in the focal range BF1 is accumulated in the charge readout region R1. That is, even if the amount of electric charge transferred in one transfer operation is small, the amount of electric charge accumulated in the charge readout region R1 increases by repeating the transfer operation. Therefore, the increase in the amount of electric charge can increase the brightness of the obtained image.

[0077] The pixel circuit section 20 of the imaging device 1 includes charge readout regions R2 to R4 in addition to the charge readout region R1. This configuration makes it possible to set a plurality of focal ranges BF1 to BF4 in the imaging range B. Therefore, a sharp, in-focus image can be obtained.

[0078] The gate control circuit 26 generates the first control signal and the second control signal so that the period S1 during which the charge transfer from the photoelectric conversion unit PD to the charge readout region R1 is permitted and the period S2 during which the charge transfer from the photoelectric conversion unit PD to the charge readout region R2 is permitted are equal to each other. With this configuration, the transfer operation is switched at regular time intervals. Therefore, the control by the gate control circuit 26 can be simplified.

[0079] Furthermore, switching the transfer operation at regular time intervals means that the exposure time for each of the focal ranges BF1 to BF4 is constant. Assuming that the intensity of light incident on the image sensor 15 does not change over time, the amount of charge obtained for each of the focal ranges BF1 to BF4 is roughly constant when the exposure time is constant. The amount of charge ultimately corresponds to the brightness (luminance) of the image. In other words, the brightness of each image obtained for each of the focal ranges BF1 to BF4 can be made constant.

[0080] The gate control circuit 26 performs the operation of outputting the first control signal twice and the operation of outputting the second control signal twice during one period of change in the position of the focal point P. With this configuration, the amount of charge transferred to the gate control circuit 26 increases. Therefore, the brightness of the obtained image can be further increased.

[0081] The variable-focus lens 10 includes a lens unit 11 through which light passes, and a lens driver 12 that periodically changes the position of a focal point P of the lens unit 11 by providing a lens driver signal to the lens unit 11. The gate control circuit 26 receives the lens driver signal from the lens driver 12. The gate control circuit 26 generates first and second control signals based on the lens driver signal. With this configuration, the operation of the lens unit 11 and the operation of the pixel circuit unit 20 can be synchronized.

[0082] The present invention is not limited to the above-described embodiment. For example, the gate control circuit 26 may output control signals based on the timing charts shown in Figures 9, 10, 11, 12, 13, and 14 instead of the timing chart shown in Figure 8.

[0083] <Variation 1> In the embodiment, the imaging range B is set to a wide area from the vicinity of the nearest point Pc to the vicinity of the farthest point Pd. That is, the imaging range B is set to an area that can be considered equivalent to the range from the nearest point Pc to the farthest point Pd of the variable-focus lens 10. The imaging range B may be set in a desired manner within the range from the nearest point Pc to the farthest point Pd. FIG. 9 shows a timing chart of the first modification. As shown in FIG. 9, the imaging range B1 may be narrower than half the amplitude of the focal point P. The imaging range B1 may be set between the nearest point Pc and the central point Pm. In the focal range (non-imaging range C) not included in the imaging range B1, all the charges generated in the photoelectric conversion unit PD are discharged to the drain DR. For example, the gate control circuit 26 sets the control signal TD to HIGH in the period SD shown in FIG. 9. According to such an imaging range B1, the ranges of the focal ranges BF1, BF2, BF3, and BF4 can be narrowed. Therefore, the imaging target can be more precisely focused. That is, a clearer image can be obtained.

[0084] <Variation 2> In the operation of the modified example 1, the imaging target can be more precisely focused. On the other hand, the imaging range B1 is limited. Therefore, in the modified example 2, an operation is shown that can expand the imaging range while maintaining precise focusing. FIG. 10 shows a timing chart of the modified example 2.

[0085] In the second modification, the concept of a so-called subframe period is introduced. In a frame period, the periodic variation of the focal point P is repeated, for example, N times. The gate control circuit 26 performs an operation (part (a) of FIG. 10 and part (b) of FIG. 10) targeting the imaging range B2a in n times out of the N times of operation. The period of one cycle shown in the same timing chart as the first modification is called the first subframe operation. The period during which the first subframe operation is repeated n times is called the first subframe period. Furthermore, the gate control circuit 26 performs an operation (part (c) of FIG. 10 and part (d) of FIG. 10) targeting the imaging range B2b in the remaining (Nn) times, as shown in another timing chart. The period of one cycle shown in part (c) of FIG. 10 and part (d) of FIG. 10 is called the second subframe operation. The period during which the second subframe operation is repeated n times is called the second subframe period.

[0086] That is, the frame period includes a first subframe period in which the first subframe operation is performed multiple times, and a second subframe period in which the second subframe operation is performed multiple times.

[0087] The imaging range B2b set in the second subframe operation does not overlap with the imaging range B2a set in the first subframe operation. That is, in the second subframe operation, the imaging range B2b is set in a region different from that in the first subframe operation. As shown in part (c) of FIG. 10 and part (d) of FIG. 10, the imaging range B2b in the second subframe operation may be set between the farthest point Pd and the center point Pm. Then, in the operation of the modification example 2, the imaging range B2a related to the first subframe operation and the imaging range B2b related to the second subframe operation are combined to form the overall imaging range B2. That is, it is possible to widen the imaging range B2, and further, it is possible to more precisely focus on the imaging target for each of the imaging ranges B2a and B2b.

[0088] In short, the gate control circuit 26 sets a first subframe period and a second subframe period included in a frame period. In the first subframe period, an imaging range B2a is set between the center point Pm and the nearest point Pc. In the second subframe period, an imaging range B2b is set between the center point Pm and the farthest point. With this configuration, it is possible to set a fine focus range. Furthermore, it is possible to set a wide imaging range B2.

[0089] Furthermore, the number of subframe periods set in a frame period is not limited to 2. For example, a frame period may include a first subframe period in which the first subframe operation is performed multiple times, a second subframe period in which the second subframe operation is performed multiple times, and a third subframe period in which the third subframe operation is performed multiple times.

[0090] <Variation 3> In the second modification, an imaging range B2a (see part (a) of FIG. 10) is set in a first subframe period, and an imaging range B2b (see part (c) of FIG. 10) is set in a second subframe period. These imaging ranges B2a, B2b do not overlap with each other in the movement direction of the focal point P of the variable-focus lens 10. The imaging ranges set for each subframe period are not limited to those that do not overlap with each other. In other words, the imaging ranges set for each subframe period may overlap with each other. This overlap may be a complete match or a partial overlap.

[0091] 11 and 12 show an example in which the imaging ranges overlap. Part (a) of FIG. 11 shows an imaging range B2a in the first subframe period. Part (b) of FIG. 11 shows a timing chart in the first subframe period. The operation in this first subframe period is the same as in the second modification.

[0092] Part (c) of FIG. 11 shows an imaging range B2a' in the second subframe period. Part (d) of FIG. 11 shows a timing chart in the second subframe period. The imaging range B2a in the first subframe period is set between the center point Pm and the closest point Pc. The imaging range B2a' in the second subframe period is also set between the center point Pm and the closest point Pc. As shown in parts (c) and (d) of FIG. 11, in the second subframe operation repeated in the second subframe period, the control signals TG1 to TG4 and TD are output with a delay of a period ΔS from the time when the position of the focal point P is the center point Pm. Then, the focal range BF1' to BF4' corresponding to the control signals TG1 to TG4 is set closer to the closest point Pc as shown in part (c) of FIG. 11.

[0093] 12, in the first sub-frame period, a focal range BF1-BF4 is set in the imaging range B2a. Similarly, in the second sub-frame period, a focal range BF1'-BF4' is set in the imaging range B2a'. These focal ranges BF1-BF4 and BF1'-BF4' constitute an overlapping range BD. In this overlapping range BD, images Q1-Q4 are obtained from the first sub-frame period. In addition, in this overlapping range BD, images Q1'-Q4' are obtained from the second sub-frame period.

[0094] The imaging range constituted by images Q1-Q4 and the imaging range constituted by images Q1'-Q4' overlap each other in a range BD. Meanwhile, in this overlap range BD, the focal range BF1-BF4 corresponding to images Q1-Q4 and the focal range BF1'-BF4' corresponding to images Q1'-Q4' are different from each other. In other words, according to the operation of the third modification, a plurality of images Q1-Q4 and Q1'-Q4' can be obtained by dividing the same range into different focal ranges.

[0095] That is, according to the sub-frame operation of the modification 3, a plurality of images Q1-Q4, Q1'-Q4' having different focal ranges can be obtained in the overlapping range BD. As a result, it is possible to obtain a clear image when imaging an imaging target having a complex uneven shape.

[0096] <Variation 4> During one cycle of the focus P, the focus passes through the same focus range BF1, BF2, BF3, BF4 twice. In the operations of the embodiment and the first and second modifications, two transfer operations are performed in each of the focus ranges BF1, BF2, BF3, BF4 during one cycle of the focus P. However, the transfer operation may be performed only once during one cycle of the focus P.

[0097] Part (a) of FIG. 13 and part (b) of FIG. 13 show timing charts of the fourth modification. As shown in part (a) of FIG. 13, even if the fluctuation of the position of the focus P is a sine wave as shown in the graph G11a, the waveform of the reference signal obtained from the variable-focus lens 10 may be distorted as shown in the graph G11b. Even in such a case, the focus P passes through the same focus ranges BF1, BF2, BF3, and BF4 twice. However, it is difficult to accurately control the transfer by knowing the timing of the first pass and the timing of the second pass. If this timing is shifted, the charge stored in a certain charge readout region may originate from two focus ranges. In addition, even if the waveform of the reference signal is not distorted, the same thing may occur if a phase shift occurs between the waveform indicating the actual fluctuation of the focus P and the waveform of the reference signal.

[0098] Therefore, in the operation of the fourth modification, the transfer operation to the charge readout regions R1, R2, R3, and R4 is performed only once while the focus P makes one cycle. This operation can suppress the influence of an unintended deviation between the waveform indicating the actual fluctuation of the focus P and the reference signal. This unintended deviation includes the above-mentioned waveform distortion and phase shift. In other words, this configuration can ease the synchronization conditions between the periodic movement of the focus position of the varifocal lens 10 and the transfer operation by the gate control circuit 26.

[0099] <Variation 5> In the operations of the embodiment and the first to fourth modifications, the transfer time from the photoelectric conversion unit PD to the charge readout regions R1, R2, R3, and R4 was constant. For example, as shown in part (b) of FIG. 8, the periods S1, S2, S3, and S4 during which the control signals TG1, TG2, TG3, and TG4 are output were equal to each other. That is, in the operations of the embodiment and the first to fourth modifications, time was selected as the basis of the operation. Time may be regarded as a phase. The amount of movement of the focus P per unit time differs depending on the frequency of the focus P. Then, when the time is constant, the focus range differs depending on the frequency of the focus P.

[0100] For example, focal ranges BF1, BF2, BF3, and BF4 may be selected as the operation standard instead of time. That is, in the fifth modification, the focal ranges BF1, BF2, BF3, and BF4 are constant as shown in part (a) of Fig. 14. Then, as shown in part (b) of Fig. 14, the periods S1, S2, S3, and S4 during which the control signals TG1, TG2, TG3, and TG4 are output are adjusted. Therefore, the lengths of the periods S1, S2, S3, and S4 are not constant.

[0101] In short, the gate control circuit 26 generates the first control signal and the second control signal so that the amount by which the position of the focal point P changes during the period S1 during which the transfer of charges from the photoelectric conversion unit PD to the charge readout region R1 is permitted is equal to the amount by which the position of the focal point P changes during the period S2 during which the transfer of charges from the photoelectric conversion unit PD to the charge readout region R2 is permitted. With this configuration, the length of each focal range can be made constant.

[0102] As described in the effects of the embodiment, the length of each of the periods S1 to S4 corresponds to the brightness of each image. When the length of each of the periods S1 to S4 is constant as in the embodiment, the brightness of each image can be constant. On the other hand, when the periods S1 to S4 are set so that the length of the focal range is constant as in the fifth modification, the lengths of the periods S1, S2, S3, and S4 are not constant. As a result, the brightness of each image may differ. Therefore, in the fifth modification, the brightness of the images may be corrected (brightness correction). For example, the images obtained for each of the focal ranges BF1 to BF4 may be multiplied by a correction coefficient according to the length of the periods S1 to S4.

[0103] Modifications relating to the timing charts have been shown in Modifications 1 to 4. As other modifications, modifications of hardware such as those shown in Modifications 6 and 7 can also be applied.

[0104] <Variation 6> In the embodiment, the charge readout region R1 and the like adopt a so-called two-stage transfer structure. For example, as in an imaging device 1A of a sixth modified example shown in FIG. 15, the charge readout region R1s may adopt a one-stage transfer structure instead of the two-stage transfer structure. In the charge readout region R1s, the transfer gate electrode 44 is omitted. The charge readout region R1s is an element in which the charge storage region 41 and the floating diffusion region 42 are electrically integrated. With this configuration, the configuration of the charge readout region R1s can be simplified.

[0105] <Variation 7> The pixel 22 of the embodiment includes a photoelectric conversion unit PD, four charge readout regions R1, R2, R3, and R4, four buffer amplifiers A1, A2, A3, and A4, and a drain DR. The number of charge readout regions and buffer amplifiers corresponds to the number of focal ranges set in the imaging range. In the embodiment, the number of focal ranges set in the imaging range was four. Therefore, the number of charge readout regions and buffer amplifiers was four.

[0106] The number of focal ranges set in the imaging range may be one, two, or three. The number of focal ranges set in the imaging range may be five or more. For example, when the number of focal ranges set in the imaging range is one, as shown in FIG. 16, the pixel 22A constituting the pixel circuit unit 20A may include a photoelectric conversion unit PD, one charge readout region R1, one buffer amplifier A1, and a drain DR.

[0107] 17, the pixel 22A includes a photodetector 22aA and an amplifier unit 22bA. The photodetector 22aA includes a photoelectric converter PD and a charge transfer unit 30A. The charge transfer unit 30A includes a charge collection region 31, a drain 33, and one charge readout region R1. The amplifier unit 22bA includes one buffer amplifier A1.

[0108] As shown in part (a) of FIG. 18, in the seventh modification, one focal range BF1 is set in the imaging range B. That is, the imaging range B coincides with the focal range BF1. When the focal position of the variable-focus lens 10 is in the focal range BF1, the gate control circuit 26 outputs a control signal TG1 (HIGH) and also outputs a control signal TD (LOW). When the focal position of the variable-focus lens 10 is in the non-imaging range C, the gate control circuit 26 outputs a control signal TG1 (LOW) and also outputs a control signal TD (HIGH). According to this control, there are two timings for accumulating charges in the charge transfer unit 30A during one period of the focal position.

[0109] The imaging device 1A including the pixel 22A of the seventh modification can also achieve the same effects as the imaging device 1 of the embodiment.

[0110] <Variation 8> 8(b), the imaging device 1 of the embodiment provides an exposure period S2 corresponding to the focal range BF2, and then immediately provides an exposure period S1 corresponding to the focal range BF1. That is, the focal ranges BF1, BF2, BF3, and BF4 in the imaging device 1 of the embodiment are adjacent to each other. The settings of the focal ranges BF1, BF2, BF3, and BF4 are not limited to being adjacent to each other.

[0111] As shown in FIG. 19, the variable-focus lens 10 can set a focus within the imaging range B. In the eighth modification, the focal range BF1 is set to the closest position to the variable-focus lens 10. The focal range BF4 is set to the farthest position to the variable-focus lens 10. Here, a non-imaging range C is set between the focal range BF1 and the focal range BF2. Similarly, a non-imaging range C is set between the focal range BF3 and the focal range BF4, and a non-imaging range C is set between the focal range BF2 and the focal range BF3. That is, in the operation of the eighth modification, the regions are set in the following order in the direction away from the variable-focus lens 10: non-imaging range C, focal range BF1, non-imaging range C, focal range BF2, non-imaging range C, focal range BF3, non-imaging range C, focal range BF4, and non-imaging range C.

[0112] According to such a setting, when the focal position is in the focal range BF1 (see point K1 in FIG. 19), charges are transferred to the charge readout region R1. The operation of transferring charges to the charge readout regions is also called an exposure operation. Similarly, when the focal position is in the focal ranges BF2, BF3, and BF4 (see points K2, K3, and K4 in FIG. 19), charges are transferred to the charge readout regions R2, R3, and R4, respectively.

[0113] The duration (S1 to S4) of the operation of transferring charges to the charge readout region is, for example, about 200 nanoseconds to 2000 nanoseconds. In other words, the duration of the operation of transferring charges to the charge readout region is the exposure time. The duration (SD) of the operation of discharging charges to the charge discharge region when the focus is in the non-imaging range C is also about the same. In addition, the time interval (TTAG ) is, for example, about 14.5 microseconds. frame ) is about 10 milliseconds.

[0114] The operation of the modified example 8 will be described using a timing chart. As shown in part (a) of Fig. 20, the imaging range B of the modified example 8 includes a focal range BF1 set near the closest point Pc, a focal range BF2 including the central point Pm, a focal range BF4 set near the farthest point Pd, and a focal range BF3 set between the focal range BF2 and the focal range BF4. A non-imaging range C is set between each of the focal ranges BF1, BF2, BF3, and BF4.

[0115] As shown in FIG. 20(b), first, in a period S2 in which the focus is in the focal range BF2, the gate control circuit 26 transfers charges to the charge readout region R2. Next, in a period SD in which the focus is in the non-imaging range C between the focal range BF2 and the focal range BF1, the gate control circuit 26 causes the drain DR to discharge charges. Next, in a period S1 in which the focus is in the focal range BF1, the gate control circuit 26 transfers charges to the charge readout region R1. Then, in a period SD in which the focus is in the non-imaging range C between the focal range BF1 and the focal range BF2, the gate control circuit 26 causes the drain DR to discharge charges again. As described above, the gate control circuit 26 alternates between an operation of transferring charges to the charge readout regions R1, R2, R3, and R4 and an operation of discharging charges to the drain DR.

[0116] That is, the gate control circuit 26 of the eighth modification performs an operation of outputting a transfer control signal, an operation of outputting a discharge control signal after the operation of outputting the transfer control signal, an operation of outputting an additional transfer control signal after the operation of outputting the discharge control signal, and an operation of outputting a discharge control signal again after the operation of outputting the additional transfer control signal. With this configuration, each focal range can be set discretely to a narrow range. As a result, the focal range in which light from different focal points is averaged becomes narrow, and the clarity of the image in each focal range can be improved.

[0117] Furthermore, with this operation, for example, immediately before and after the transfer operation to the charge readout region R2 is switched to the transfer operation to the charge readout region R1, the charge that should be transferred to the charge readout region R2 is not transferred to the charge readout region R1. In other words, with this operation, it is possible to reliably separate the charge that should be transferred to the charge readout region R1 from the charge that should be transferred to the charge readout region R2. [Explanation of symbols]

[0118] 1...imaging device, 10...variable focus lens, 11...lens section, 12...lens driving section, 15...imaging sensor, 20...pixel circuit section, 21...pixel array, 25...peripheral circuit, 26...gate control circuit (control means), 27...readout circuit (signal readout means), 50...pixel control section, 60...image processing section, B...imaging range, BF1, BF2, BF3, BF4...focal range, DR...drain (charge discharge region), E1, E2, E3, E4...transfer control electrode, ED...discharge control electrode, P...focus, Pc...closest point, PD...photoelectric conversion section, Pd...farthest point, Pm...central point, R1, R1s, R2, R3, R4...charge readout region.

Claims

1. a variable-focus lens whose focal position changes periodically between a farthest point and a nearest point during a frame period; a pixel circuit unit that is disposed so as to overlap with an optical axis of the variable-focus lens, receives light that has passed through the variable-focus lens, and outputs a signal according to the light, The pixel circuit unit includes: A photoelectric conversion unit that converts the light into an electric charge; a charge readout region provided adjacent to the photoelectric conversion unit; a transfer control electrode provided between the photoelectric conversion unit and the charge readout region, the transfer control electrode receiving a transfer control signal for charge transfer between the photoelectric conversion unit and the charge readout region; one or more additional charge readout regions provided adjacent to the photoelectric conversion unit and spaced apart from the charge readout region; one or more additional transfer control electrodes provided between the photoelectric conversion unit and the additional charge readout region, the additional transfer control electrodes receiving additional transfer control signals for charge transfer between the photoelectric conversion unit and the additional charge readout region; a charge discharge region that is provided adjacent to the photoelectric conversion unit and spaced apart from the charge readout region and that discharges the charge that is not used for reading out a signal corresponding to the light; a discharge control electrode provided between the photoelectric conversion unit and the charge discharge region, the discharge control electrode receiving a discharge control signal for charge transfer between the photoelectric conversion unit and the charge discharge region; a control means for applying the transfer control signal to the transfer control electrode and the ejection control signal to the ejection control electrode in response to the focal position of the variable focus lens; a signal readout means for outputting the signal corresponding to the amount of charge transferred to the charge readout region; the control means repeats, within the frame period, an operation of outputting the transfer control signal when the focus position is within a focus range set in an imaging range, an operation of outputting the discharge control signal when the focus position is within a non-imaging range that does not overlap with the imaging range, and an operation of outputting the additional transfer control signal when the focus position is within an additional focus range that is set in the imaging range and does not overlap with the focus range; The signal readout means, after the frame period has elapsed, outputs the signal corresponding to the amount of charge transferred to the charge readout region, and further outputs the signal corresponding to the amount of charge, which is the amount of charge transferred to the additional charge readout region.

2. (delete)

3. The imaging device described in claim 1, wherein the control means generates the transfer control signal and the additional transfer control signal so that the length of the period during which the charges are permitted to be transferred from the photoelectric conversion unit to the charge readout region and the length of the period during which the charges are permitted to be transferred from the photoelectric conversion unit to one or more of the additional charge readout regions are equal to each other.

4. The imaging device of claim 1, wherein the control means generates the transfer control signal and the additional transfer control signal so that the amount by which the focal position changes during a period in which the charge is permitted to be transferred from the photoelectric conversion unit to the charge readout region and the amount by which the focal position changes during a period in which the charge is permitted to be transferred from the photoelectric conversion unit to one or more of the additional charge readout regions are equal to each other.

5. the control means sets a plurality of subframe periods included in the frame period; The imaging device according to claim 1 , wherein the control means sets the imaging range for each of the plurality of subframe periods.

6. The imaging device according to claim 5 , wherein the imaging ranges set for the plurality of subframe periods do not overlap with each other.

7. The imaging device according to claim 5 , wherein the imaging ranges set for the plurality of subframe periods overlap each other.

8. 8. The imaging device according to claim 1, wherein the control means performs an operation of outputting the transfer control signal twice during one period of change in the position of the focus.

9. 8. The imaging device according to claim 1, wherein the control means performs an operation of outputting the transfer control signal once during one period of change in the position of the focus.

10. The variable focus lens is A lens portion through which the light passes; a lens driving unit that periodically changes a focal position of the lens unit by providing a lens driving signal to the lens unit; The imaging device according to any one of claims 1, 3 to 9, further comprising a pixel control unit that receives the lens drive signal from the lens drive unit and provides a control signal for the pixel circuit unit to the pixel circuit unit based on the lens drive signal.

11. The charge readout region has a two-stage transfer structure, The two-stage transfer structure includes: a charge storage unit that receives the charges from the photoelectric conversion unit; a floating diffusion region that receives the charges from the charge storage region and is connected to the signal readout means; a reset drain that receives the charge from the floating diffusion region; a transfer gate electrode that controls transfer of the charges from the charge storage portion to the floating diffusion portion; 11. The imaging device according to claim 1, further comprising: a reset gate electrode that controls transfer of the charges from the floating diffusion region to the reset drain.

12. The charge readout region has a one-stage transfer structure, The single stage transfer structure includes: a floating diffusion portion that receives the charges from the photoelectric conversion portion; a reset drain that receives the charge from the floating diffusion region; 11. The imaging device according to claim 1, further comprising: a reset gate electrode that controls transfer of the charges from the floating diffusion region to the reset drain.

13. The control means outputting the transfer control signal; After the operation of outputting the transfer control signal, an operation of outputting the ejection control signal is performed; performing an operation of outputting the additional transfer control signal after the operation of outputting the discharge control signal; The imaging device according to claim 1 , further comprising an operation of outputting the ejection control signal again after the operation of outputting the additional transfer control signal.

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