JP2013165415A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily acquire a moving image to which a residual image effect is applied even if processing for synthesizing a plurality of images is not performed.SOLUTION: An imaging apparatus includes: an imaging element including a pixel for generating and accumulating a signal charge corresponding to incident light; driving means for outputting a pixel signal depending on a part of the signal charge accumulated in the pixel and allowing the residual signal charge to remain in the pixel; and control means for controlling driving of the imaging element by the driving means.

Description

  The present invention relates to an imaging apparatus including an imaging element such as a CMOS image sensor.

  Conventionally, an image obtained at the time of shooting is generally subjected to image processing according to shooting conditions. Recently, there has also been proposed an imaging apparatus that generates an image with an afterimage effect by performing a process of combining a plurality of images obtained by moving image shooting or continuous shooting (see Patent Document 1).

JP 2010-114757 A

  However, in such an imaging apparatus, since it is necessary to perform a process of combining a plurality of images after performing an image process according to a shooting condition, there is a problem that a processing load related to the image process increases.

  An object of the present invention is to provide an imaging apparatus that can easily acquire a moving image with an afterimage effect without performing a process of combining a plurality of images.

  In order to solve the above-described problems, an imaging apparatus according to the present invention is based on an imaging element including a pixel that generates and accumulates signal charges according to incident light, and a part of the signal charges accumulated in the pixels. A driving unit that outputs a pixel signal and causes the remaining signal charges to remain in the pixel, and a control unit that controls driving of the imaging element by the driving unit are provided.

  In addition, the pixel includes a photoelectric conversion unit that photoelectrically converts the incident light to generate the signal charge and accumulates the signal charge, and the driving unit includes one of the signal charges accumulated in the photoelectric conversion unit. The unit is preferably output as the pixel signal.

  In addition, the pixel includes a charge-voltage conversion unit that converts a signal charge output from the photoelectric conversion unit into a voltage, and whether to transfer the signal charge accumulated in the photoelectric conversion unit to the charge-voltage conversion unit. A transfer transistor that is switched by an on / off operation, and the driving unit changes a time related to the on operation of the transfer transistor to change a part of the signal charge accumulated in the photoelectric conversion unit to the charge voltage conversion unit. It is preferable to transfer to.

  Further, the pixel includes a reset transistor that resets the charge-voltage conversion unit, and the driving unit acquires an image immediately after the acquisition of the plurality of images is started when the plurality of images are continuously acquired. At the time of acquisition, the transfer transistor and the reset transistor are turned on to reset the photoelectric conversion unit and the charge-voltage conversion unit, and the remaining images are acquired except for the image immediately after the acquisition of the plurality of images is started. In some cases, it is preferable that only the charge-voltage converter is reset by turning on only the reset transistor to leave the signal charge accumulated in the photoelectric converter.

  In addition, the pixel includes a selection transistor that switches whether to output the voltage converted by the charge-voltage conversion unit as a pixel signal by an on / off operation, and the driving unit performs an on operation of the selection transistor. Preferably, the pixel signal based on the voltage converted by the charge-voltage converter is output.

  In addition, the driving unit may be a first mode for outputting the pixel signal based on a part of the signal charge accumulated in the pixel when acquiring the plurality of images, or all the pixels accumulated in the pixel. It is preferable that the image sensor is driven in any one of a second mode in which the pixel signal based on the signal charge is output.

  In this case, an operation member that is operated when switching to one of the first mode and the second mode is provided, and the control means receives the operation of the operation member, and the imaging by the drive means It is preferable to switch the driving of the element between the first mode and the second mode.

  Furthermore, the control means drives the image sensor by the drive means between the first mode and the second mode when the operation member is operated during the acquisition of the plurality of continuous images. It is preferable to switch with.

  Further, it is preferable that the plurality of images include any one of a moving image, a through image, and an image obtained during continuous shooting.

  According to the present invention, a moving image with an afterimage effect can be easily acquired without performing a process of combining a plurality of images.

It is a figure which shows the electrical constitution of a digital camera. It is a figure which shows the structure of the image pick-up element in 1st Embodiment. It is explanatory drawing which shows the position of the to-be-photographed object in each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel O of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel O of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel P of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel P of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel Q of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel Q of each frame image. It is a figure which shows a to-be-photographed object and an afterimage effect typically. It is a figure which shows the structure of the image pick-up element in 2nd Embodiment. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel O of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel O of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel P of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel P of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel Q of each frame image. It is a figure which shows the change of the electric charge amount of the signal charge in the pixel Q of each frame image.

<First Embodiment>
FIG. 1 shows an electrical configuration of the digital camera 10 according to the first embodiment. The digital camera 10 can perform still image shooting (still image shooting) and moving image shooting (moving image shooting) using preset shooting conditions, and can also perform moving image shooting with an afterimage effect. it can. Hereinafter, each image obtained continuously at the time of moving image shooting based on a preset frame rate will be referred to as a frame image. Note that the above-described video shooting with the afterimage effect will be described later in detail, but at the time of acquiring each frame image, a process of reading out a part of the signal charge photoelectrically converted in each pixel, The processing using the signal charge remaining at the time of acquisition of the frame image is executed. Hereinafter, in the first embodiment, a case will be described in which moving image capturing with an afterimage effect is performed by acquiring each frame image while leaving a part of the signal charge in the photodiode of each pixel.

  As is well known, the digital camera 10 photoelectrically converts the subject light captured by the imaging optical system 15 for each of a plurality of pixels provided in the imaging element 16, and converts the signal charges obtained by the photoelectric conversion in each pixel into an image signal. Get as.

  The imaging optical system 15 includes a lens group including a zoom lens, a focus lens, and the like that are not shown. These zoom lens and focus lens are moved in the direction of the optical axis L by a lens driving mechanism (not shown). The image sensor 16 is a CMOS image sensor. The configuration of the image sensor 16 will be described later. The image sensor 16 operates based on a control signal output from a timing generator (TG) 17.

  An AFE (Analog Front End) circuit 18 performs a correlated double sampling process, a gain control process, and the like on the image signal output from the image sensor 16 and then converts the analog image signal into a digital image signal. The digital image signal is output to the DFE circuit 18.

  A DFE (Digital Front End) circuit 19 performs defect correction processing and noise correction processing on the image signal output from the AFE circuit 18. The image signal that has been subjected to defect correction processing and noise correction processing by the DFE circuit 19 is written into the buffer memory 25.

  The image processing circuit 30 performs image processing such as white balance (WB) processing, color interpolation processing, contour compensation processing, and gamma processing on the image signal stored in the buffer memory 25. After these processes, the image processing circuit 30 performs a compression encoding process using a preset compression rate. By executing this compression encoding process, for example, JPEG image data is generated.

  The connection I / F 32 is connected to a storage medium 33 such as a memory card, an optical disk, or a magnetic disk. Recording of image data to the recording medium 33 and reading of image data from the storage medium 33 are executed via the connection I / F 32.

  The display device 35 includes an LCD, an organic EL display, or the like. The display device 35 displays a through image, an image obtained at the time of shooting, and an image for setting when the digital camera 10 is set. Reference numeral 36 denotes a display control circuit that performs drive control of the display device 35.

  The CPU 41 is electrically connected to the buffer memory 25, the image processing circuit 30, the connection I / F 32, the display control circuit 36, the built-in memory 43, and the like via the bus 42. The CPU 41 controls each part of the digital camera 10 based on a control program stored in the built-in memory 43. Further, the CPU 41 executes processing based on operation signals from operation members such as the release button 45, the afterimage imparting button 46, and the setting operation unit 47.

  The release button 45 is a button operated by the user at the time of shooting. For example, when the release button 45 is fully pressed, an imaging process may be executed after the AE process or the AF process by the CPU 41, or the AE described above when the release button 45 is pressed halfway. Processing, AF processing, or the like may be executed, and imaging processing based on AE processing or AF processing may be executed when the button is fully pressed.

  The afterimage imparting button 46 is a button that is operated when an afterimage effect is imparted to a through image, a moving image, or a still image obtained by continuous shooting, or when the provision of the afterimage effect is stopped. . By operating the afterimage imparting button 46, the drive control of the image sensor 16 is changed. It should be noted that by operating this afterimage giving button 46 immediately before shooting a movie, it is possible to switch whether or not to perform movie shooting that gives an afterimage effect. You may make it switch whether the moving image shooting currently performed by operating is set as the moving image shooting which gives an afterimage effect. In addition, whether or not to perform moving image shooting for adding an afterimage effect by operating the afterimage adding button 46 is switched. In addition to this, whether or not shooting for adding an afterimage effect in advance by operating the setting operation unit 47 is performed. May be set, and the afterimage effect button 46 may be operated to give an afterimage effect or stop giving the afterimage effect.

As shown in FIG. 2, the image sensor 16 includes a plurality of pixels A _ij (i = 1, 2,..., J = 1, 2,...) _{Arranged in} a two-dimensional shape, a vertical scanning circuit 51, A horizontal scanning circuit 52, a vertical line selection transistor 53, a column amplifier 54, a CDS circuit 55, and an output amplifier 56 are provided. Note that the vertical scanning circuit 51, the horizontal scanning circuit 52, and the CDS circuit 55 each operate based on a control signal from the timing generator 17.

The plurality of pixels A _ij are stored in a photodiode (PD) 61 that generates a signal charge by photoelectric conversion, a floating diffusion (FD) 62 that stores the signal charge generated by the photodiode 61 as a voltage, and the photodiode 61. A transfer transistor (TX-Tr) 63 that transfers signal charges to the floating diffusion 62, an amplification transistor (AMI-Tr) 64 that has a gate connected to the floating diffusion 62 and converts potential fluctuations of the floating diffusion 62 into an electric signal, and signal charges Selection transistor (SEL-Tr) 65 for selecting pixels for reading out in units of rows, and reset transistor (FDRST-Tr) 66 for resetting the potential of the floating diffusion 62 to the power supply potential. It has.

The plurality of pixels A _ij are electrically connected by a plurality of signal lines 71, 72, 73, 74 extending in the horizontal direction from the vertical scanning circuit 21, respectively. Among these signal lines, the signal line 71 is a transfer signal line, the signal line 72 is a reset signal line, the signal line 73 is a row selection signal line, and the signal line 74 is a power supply signal line. . The signal line 75 is a vertical signal line.

The vertical scanning circuit 51 receives a control signal from the timing generator 17 and outputs a transfer signal, a reset signal, a selection signal, and the like to each pixel A _ij . Further, the horizontal scanning circuit 52 outputs a column selection signal to the vertical line selection transistor 53.

The vertical line selection transistor 53 is turned on in response to the selection signal from the horizontal scanning circuit 52, and inputs the pixel signal of the pixel A _ij arranged in the column to be read out to the column amplifier 54. The pixel signal amplified by the column amplifier 54 is input to the CDS circuit 55. The CDS circuit 55 performs a correlated double sampling process on the input pixel signal, thereby removing noise components due to variations in transistors provided in each pixel. The pixel signal output from the CDS circuit 55 is output via the horizontal signal line 76 and the output amplifier 56. An image signal is a collection of pixel signals output from all pixels.

  Next, the imaging process of the digital camera at the time of moving image shooting will be described. In the imaging process of this digital camera, an imaging process using a so-called rolling shutter system in which the shutter is sequentially released for each scanning line is executed. When this imaging process is executed, (1) pixels regardless of the mode for performing moving image shooting that gives an afterimage effect or the mode for performing general moving image shooting that does not give an afterimage effect (hereinafter, normal moving image shooting). The reset processing, (2) charge accumulation processing, (3) charge transfer processing, and (4) charge readout processing are performed for each pixel arranged in each row, ie, for each scanning line, among a plurality of pixels arranged in two dimensions. Executed.

(1) Pixel reset processing When the moving image shooting is started, in the normal moving image shooting mode, the vertical scanning circuit 51 receives the control signal from the timing generator 17 and transfers the transfer signal and the reset signal to the transfer signal. , Output in the order of reset signals. When the transfer signal is received, the transfer transistor 63 is turned on. When a reset signal is output in this state, the reset transistor 66 is turned on, and a reset voltage is applied to the phototransistor 61 and the floating diffusion 62. Thereby, the phototransistor 61 and the floating diffusion 62 are reset.

  In the case of the mode for performing moving image shooting that gives an afterimage effect, the same processing as that in the mode for performing normal moving image shooting is executed for the first frame image obtained immediately after shooting is started. . And when acquiring the frame image after the 2nd frame, control of the image sensor 16 is changed. Specifically, the vertical scanning circuit 51 outputs only the reset signal without outputting the transfer signal among the signals described above. That is, at the time of acquiring the frame images from the second frame onward, only the floating diffusion 62 is reset, and the signal charge accumulated in the photodiode 61 remains without being reset.

(2) Charge Accumulation Processing Subject light is incident on each pixel A _ij of the image sensor 16 via the imaging optical system 15. The photodiode 61 receives subject light and photoelectrically converts the received subject light. Note that the photoelectrically converted signal charge is accumulated in the photodiode 61.

(3) Charge Transfer Processing The vertical scanning circuit 51 receives a control signal from the timing generator 17 and outputs a transfer signal. Since the transfer transistor 63 is turned on by the output of the transfer signal, the signal charge accumulated in the photodiode 61 is transferred to the floating diffusion 62. Here, the time for which the transfer transistor 63 is turned on, in other words, the time for transferring the signal charge from the photodiode 61 to the floating diffusion 62 (transfer time) is a fixed time. That is, the transfer amount (transfer rate) per unit time transferred from the photodiode 61 to the floating diffusion 62 increases in proportion to the amount of accumulated signal charge.

For example, when the transfer time T ₀ is set when the mode for performing the normal moving image shooting is selected, the transfer time T ₁ when the mode for performing the moving image shooting giving the afterimage effect is selected is T ₁ = αT ₀ ( The coefficient α <1) is set. The transfer time T ₀ is a time for transferring all the signal charges accumulated in the photodiode 61 to the floating diffusion 62. The coefficient α is a coefficient for causing a part of the signal charge accumulated in the photodiode 61 to remain in the photodiode 61 without being transferred to the floating diffusion 62. The amount of charge is reduced. That is, the smaller the amount of signal charge that remains in the photodiode 61, the lower the afterimage effect for each frame image.

Hereinafter, a case where the coefficient α is set to α = 0.9 will be described. The coefficient α may be automatically determined based on the brightness (luminance) of the through image obtained before shooting or the brightness (luminance) of the frame image obtained by moving image shooting. Alternatively, it may be determined by a user setting operation. Immediately after the transfer transistor 63 is turned on, from the photodiode 61 since the transfer rate of the signal charges transferred are not stable to the floating diffusion 62, until the transfer time T ₁ of the signal charges, the transfer rate is stabilized It is also possible to set the coefficient α so as to be a value that takes into account the shortage.

(4) Charge Read Processing The vertical scanning circuit 51 receives a control signal from the timing generator 17 and outputs a selection signal. Due to the output of this selection signal, the selection transistor 65 is turned on, and the voltage converted by the floating diffusion 62 is output to the vertical signal line 75 as a pixel signal via the amplification transistor 64 and the selection transistor 65. In this charge reading process, a control signal from the timing generator 17 is output to the horizontal scanning circuit 52 and the CDS circuit 55. That is, the pixel signal output to the vertical signal line 75 is input to the column amplifier 54 via the vertical line selection transistor 53. Note that the pixel signal input to the column amplifier 54 is amplified by the column amplifier 54 and then input to the CDS circuit 55. The CDS circuit 55 performs correlated double sampling processing on the input pixel signal and outputs it to the horizontal signal line 76. The pixel signal output to the horizontal signal line 76 is output via the output amplifier 56.

Next, a specific example in the case of taking a moving image with an afterimage effect will be described. 3, with respect to the frame image FI _n of the n th frame (n + 6) th frame of the frame image FI n _{+ 6,} and shows the case of performing the granted videos taken afterimage effect. Note that the subject V is a moving body that moves from the left to the right in FIG. 3, and the amount of signal charges based on the amount of light of the subject V (hereinafter, the amount of charges of signal charges in the subject V) is 10e ⁻ , and the background. A case where the amount of signal charge based on the amount of light (hereinafter, the amount of signal charge in the background) is 5e ⁻ will be described.

First, the pixel O will be described with reference to FIGS. The signal charges remaining in the photodiode 61 and the floating diffusion 62 of the pixel O are reset by the pixel reset process. That is, the signal charges of the photodiode 61 and the floating diffusion 62 are each zero. In the acquired frame image FI _n , since the pixel O is a pixel included in the region of the subject V, the charge amount 10e ⁻ of the signal charge in the subject V is accumulated in the photodiode 61. As described above, in moving image shooting with an afterimage effect, the signal charge transfer time in the charge transfer process is changed, that is, the transfer time is changed to T ₁ (= 0.9T ₀ ). That is, when the charge transfer process is executed, out of the signal charge amount 10e ⁻ accumulated in the photodiode 61, the signal charge amount 9e ⁻ is transferred to the floating diffusion 62, and the signal charge amount 1e ^−. Remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 9e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

In this state, the next frame image FI _{n + 1} is acquired. Also in the frame image FI _{n + 1} , the pixel O is a pixel included in the region of the subject V. In the present embodiment, when the frame image FI _{n + 1} is acquired, the charge accumulation process is performed with the signal charge amount 1e ⁻ remaining in the photodiode 61. By executing this charge accumulation processing, the amount of signal charge accumulated in the photodiode 61 becomes 11e ⁻ . When the charge transfer process is executed, the signal charge amount 9.9e ⁻ out of the signal charge amount 11e ⁻ accumulated in the photodiode 61 is transferred from the photodiode 61 to the floating diffusion 62, and the signal A charge amount 1.1e ⁻ of charge remains in the photodiode 61. Note that these numerical values in the present embodiment described above and below are examples used for specifically describing the present embodiment, and are not limited to these numerical values.

Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 9.9e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

Further, when the frame image FI _{n + 2} is acquired, the pixel O is a pixel included in the region of the subject V as in the frame image FI _{n + 1} . When the frame image FI _{n + 2} is acquired, the charge accumulation process is performed with the signal charge amount 1.1e ⁻ remaining in the photodiode 61. By executing this charge accumulation process, the amount of signal charge accumulated in the photodiode 61 becomes 11.1e ⁻ . When the charge transfer process is executed, the signal charge charge amount 9.99e ⁻ out of the signal charge charge amount 11.1e ⁻ accumulated in the photodiode 61 is transferred to the floating diffusion 62, and the signal charge charge A charge amount of 1.11e ⁻ remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 9.99e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

When the frame image FI _{n + 3} is acquired, the pixel O is not a pixel included in the subject V area but a pixel included in the background area. When acquiring the frame image FI _{n + 3} , the charge accumulation process is performed in a state where the charge amount 1.1e ⁻ of the signal charge remains in the photodiode 61. As described above, since the signal charge amount in the background is 5e ⁻ , the charge amount of the signal charge accumulated in the photodiode 61 is 6.11e ⁻ by executing the charge accumulation process. When the charge transfer process is executed, the charge amount 6.11e of the signal charge accumulated in the photodiode 61 ^- of the charge amount 5.499e signal charges ^- are transferred to the floating diffusion 62, the signal charges A charge amount of 0.611e ⁻ remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 5.499e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

In the frame image FI _{n + 4} acquired after the frame image FI _{n + 3} , the pixel O is a pixel included in the background area, like the frame image FI _{n + 3} . When the frame image FI _{n + 4} is acquired, the charge accumulation process is performed with the signal charge amount 0.611e ⁻ remaining in the photodiode 61. By executing this charge accumulation process, the amount of signal charge accumulated in the photodiode 61 becomes 5.611e ⁻ . When the charge transfer process is executed, the signal charge charge amount 5.0499e ⁻ out of the signal charge charge amount 5.611e ⁻ accumulated in the photodiode 61 is transferred to the floating diffusion 62, and the signal charge A charge amount of 0.5611e ⁻ remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 5.0499e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

Similarly, also in the frame image FI _{n + 5} , the pixel O is a pixel included in the background area. When acquiring the frame image FI _{n + 5} , the charge accumulation process is performed in a state where the charge amount 0.5611e ⁻ of the signal charge remains in the photodiode 61. By executing this charge accumulation process, the amount of signal charge accumulated in the photodiode 61 becomes 5.5611e ⁻ . When the charge transfer process is executed, the signal charge charge amount 5.00499e ⁻ out of the signal charge charge amount 5.5561e ⁻ accumulated in the photodiode 61 is transferred to the floating diffusion 62, and the signal charge amount A charge amount of 0.55611e ⁻ remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 5.00499e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

Further, in the case of the frame image FI _{n + 6} , the charge accumulation process is executed in a state where the charge amount 0.55611e ⁻ of the signal charge remains. That is, the amount of signal charges accumulated in the photodiode 61 is 5.55561e ⁻ . In this case, out of the signal charge amount 5.55611e ⁻ accumulated in the photodiode 61, the signal charge amount 5.000499e ⁻ is transferred to the floating diffusion 62, and the signal charge amount 0.555611e ⁻ It remains in the diode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 5.000499e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

As described above, the amount of signal charges (reading light amount) in each frame image output from the pixel O is 9e ⁻ →, 9.9e ⁻ → 9.99e ⁻ → 5499e ⁻ → 5.0499e ⁻ → 5. .00499e ⁻ → 5.000499e ^−, and converge to the charge amount 5e ⁻ based on the amount of light in the background region. That is, in the frame image FI n _{+ 3} and later frame image, since the afterimage effect is gradually reduced, in the frame image FI n _{+ 3} and later frame image, it is possible to appropriately impart an afterimage effect.

Next, the pixel P will be described with reference to FIGS. 3, 6, and 7. When the frame image FI _n and the frame image FI _{n + 1} are acquired, the pixel P is a pixel included in the region of the subject V. Therefore, the charge amount of the signal charge read when acquiring the frame image, the photodiode 61 The remaining signal charge has the same value as that of the pixel O. When acquiring the frame image FI _{n + 2} , the pixel P is not a region of the subject V but a pixel included in the background region. For this reason, in the present embodiment, in the charge accumulation process, the charge amount 5e ⁻ of the signal charge in the background is accumulated in the photodiode 61. That is, the photodiode 61 stores a signal charge amount 6.1e ⁻ . By charge transfer process after the charge accumulation process is executed, the charge amount 6.1e signal charge accumulated in the photodiode 61 ^- transfer to the floating diffusion 62 ^- Of the amount of charge 5.49e signal charges As a result, a signal charge amount of 0.61e ⁻ remains in the photodiode 61. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 5.49e ⁻ ) converted by the floating diffusion 61 is output as a pixel signal.

In the present embodiment, in the frame image FI _{n + 3 and} later (the frame image FI _{n + 3} , the frame image FI _{n + 4} , the frame image FI _{n + 5} and the frame image FI _{n + 6} ), the pixel P is a pixel included in the background region. Similarly to the frame image FI _{n + 2} , the charge amount 5e ⁻ based on the amount of light in the background region is received by the photodiode 61, and 90% of the signal charge accumulated in the photodiode 61 is transferred to the floating diffusion 62, and the rest 10% remains in the photodiode 61. Then, by executing the charge reading process, a voltage based on the signal charge converted by the floating diffusion 61 is output as a pixel signal.

Thus, the read amount of the signal charge in each frame image output from the pixel P is 9e ⁻ →, 9.9e ⁻ → 5.49e ⁻ → 5.049e ⁻ → 5.0049e ⁻ → 5.00049e ⁻ → It changes to 5.000049e ⁻ and converges to a charge amount 5e ⁻ based on the amount of light in the background area. That is, since the afterimage effect is gradually reduced in the frame images after the frame image FI _{n + 2} , the pixel P can appropriately impart the afterimage effect in the frame images after the frame image FI _{n + 2} .

Finally, the pixel Q will be described with reference to FIG. 3, FIG. 8, and FIG. The pixel Q is a pixel included in the background region, not the subject V region. In other words, in the present embodiment, the amount of charge 5e ⁻ based on the amount of light in the background region is accumulated in the photodiode 61 when each frame image is acquired. Also in this pixel Q, since the same processing as that of the pixel O and the pixel P is executed, 90% of the signal charge accumulated in the photodiode 61 is transferred to the floating diffusion 62, and the remaining 10% is the photodiode 61. To remain. Then, by executing the charge reading process, a voltage based on the signal charge converted by the floating diffusion 61 is output as a pixel signal. Note that the read amount of the signal charge in each frame image output from the pixel Q is 4.5e ⁻ → 4.95e ⁻ → 4.9995e ⁻ → 4.999995e ⁻ → 4.999995e ⁻ → 4.999995e ^−. → 4.99999999e ⁻ and converge to the charge amount 5e ⁻ based on the amount of light in the background area. Note that the pixel Q is a pixel included in the background area during moving image shooting, and thus it is understood that the afterimage effect is not given to the pixel Q.

  In this way, the image signal output from the image sensor 16 is an image signal with an afterimage effect. As shown in FIG. 10, when the acquired moving image is displayed, an appropriate afterimage effect is applied to the moving subject, and the background region is displayed as a moving image without the afterimage effect. According to this, it is possible to easily obtain a moving image with an afterimage effect by simply changing the control on the image sensor 16 without performing a process of combining a plurality of frame images obtained by normal moving image shooting. Can do. Further, since the image processing circuit 30 only needs to perform image processing on a normal moving image, it is not necessary to increase the processing load on the image processing circuit 30.

  In the first embodiment, since the amount of signal charge based on the amount of light read from each pixel is lower than the actual amount of charge in the frame image immediately after the start of moving image capturing that imparts an afterimage effect, the afterimage It is also possible to delete the frame images up to the second and third frames obtained from the start of the moving image shooting that gives the effect without recording them.

  In addition, the pixel values of each pixel in the frame image (the pixel signal output from each pixel of the image sensor 16) are deleted without deleting the frame images up to the second and third frames obtained from the start of moving image shooting that gives an afterimage effect Output value) can be amplified. In this case, the above-described column amplifier 54 and output amplifier 56 amplify the pixel value of each pixel, amplify the pixel value of each pixel by the gain control process in the AFE circuit 18, or the gradation conversion process in the image processing circuit 30. In this case, any one of processes such as correcting the gradation value may be performed on the frame images up to the second and third frames.

  In the first embodiment, the case where a part of the signal charge remains in the photodiode 61 has been described as one form in which the signal charge remains in each pixel of the image pickup device. However, the present invention is not limited to this. It is also possible to provide a plurality of floating diffusions for each pixel of the image sensor and to leave signal charges in any of the plurality of floating diffusions. Hereinafter, a case where signal charges remain in any of a plurality of floating diffusions provided in the imaging device will be described as a second embodiment.

Second Embodiment
In the digital camera according to the second embodiment, the configuration other than the image sensor is the same. Hereinafter, in the second embodiment, an image sensor 81 shown in the figure is used instead of the image sensor 16 shown in the first embodiment. Hereinafter, the same configurations as those of the first embodiment will be described with the same reference numerals.

As shown in FIG. 11, the image sensor 81 includes a plurality of pixels B _ij (i = 1, 2,..., J = 1, 2,...), A vertical scanning circuit 82, A horizontal scanning circuit 83, a vertical line selection transistor 84, a column amplifier 85, a CDS circuit 86, and an output amplifier 87 are provided. The vertical scanning circuit 82, the horizontal scanning circuit 83, and the CDS circuit 85 operate based on control signals from the timing generator 17, respectively.
The plurality of pixels B _ij include a photodiode (PD) 91, a floating diffusion (FD1) 92, a floating diffusion (FD2) 93, a floating diffusion (FD3) 94, a transfer transistor (TX-Tr) 95, and a switching transistor (SW1). 96, a switching transistor (SW2) 97, a switching transistor (SW3) 98, an amplification transistor (AMI-Tr) 99, a selection transistor (SEL-Tr) 100, and a reset transistor (FDRST-Tr) 101. Each floating diffusion is set so that the capacity ratio of the floating diffusion 92, the floating diffusion 93, and the floating diffusion 94 is, for example, 9: 1: 1. The capacity ratio of each floating diffusion is an example, and is set as appropriate.

The plurality of pixels B _ij are electrically connected to each other by a plurality of signal lines 102, 103, 104, 105, 106, 107, 108 extending from the vertical scanning circuit 82 in the horizontal direction. Among these signal lines, the signal line 102 is a transfer signal line, the signal line 103 is a reset signal line, and the signal lines 104, 105, and 106 are individually switched on and off of the switching transistors 96, 97, and 98. The signal line for switching, the signal line 107 is a signal line for row selection, and the signal line 108 is a signal line for power supply. The signal line 109 is a vertical signal line.

The vertical scanning circuit 82 receives the control signal from the timing generator 17 and outputs a transfer signal, a reset signal, a switching signal, a row selection signal, and the like to each pixel _Bij . Further, the horizontal scanning circuit 83 outputs a column selection signal to the vertical line selection transistor 84. Hereinafter, the switching signal for the switching transistor 96 is referred to as a first switching signal, the switching signal for the switching transistor 97 is referred to as a second switching signal, and the switching signal for the switching transistor 98 is referred to as a third switching signal.

The vertical line selection transistor 84 is turned on in response to the selection signal from the horizontal scanning circuit 83, and inputs the pixel signal of the pixel B _ij arranged in the column to be read out to the column amplifier 85. The pixel signal amplified by the column amplifier 85 is input to the CDS circuit 86. The CDS circuit 86 performs correlated double sampling processing on the input pixel signal, thereby removing noise components due to variations in transistors provided in each pixel. The pixel signal output from the CDS circuit 86 is output via the horizontal signal line 110 and the output amplifier 87.

  Next, the imaging process of the digital camera at the time of moving image shooting will be described. In the imaging process of this digital camera, an imaging process using a so-called rolling shutter system in which the shutter is sequentially released for each scanning line is executed. When a mode for performing normal moving image shooting is selected, pixel reset processing, charge accumulation processing, charge transfer processing, and charge readout processing are executed as imaging processing.

  When the pixel reset process is executed, a transfer signal, a first switching signal, a second switching signal, a third switching signal, and a reset signal are sequentially output from the vertical scanning circuit 82. When the transfer signal is output, the transfer transistor is turned on, and when the first to third switching signals are output, the switching transistors 96, 97, and 98 are turned on. When a reset signal is output in this state, the reset transistor 95 is turned on, and a reset voltage is applied to each of the photodiode 91 and the floating diffusions 92, 93, 94. As a result, the photodiode 91 and the floating diffusions 92, 93, 94 are reset.

  In the charge accumulation process executed after the pixel reset process, photoelectric conversion is performed by the photodiode 91 in the same manner as the charge accumulation process of the first embodiment, and signal charges generated by the photoelectric conversion are accumulated. Go.

  When the charge transfer process is executed, the vertical scanning circuit 82 outputs a first switching signal and turns on the switching transistor 96. Thereafter, the vertical scanning circuit 82 outputs a transfer signal and turns on the transfer transistor. As a result, the signal charge accumulated in the photodiode 91 is transferred to the floating diffusion 92.

  When the charge reading process is started, the vertical scanning circuit 82 outputs a first switching signal. At the same time, the vertical scanning circuit 82 outputs a row selection signal and turns on the selection transistor 96. As a result, a pixel signal based on the signal charge transferred by the floating diffusion 92 is output to the vertical signal line 109. Since the horizontal scanning circuit 83 outputs a selection signal, the pixel signal output to the hydraulic signal line 109 is input to the column amplifier 85. The pixel signal input to the column amplifier 85 is amplified by the column amplifier 85 and then input to the CDS circuit 86. The CDS circuit 86 performs correlated double sampling processing on the input pixel signal and outputs it to the horizontal signal line 110. The pixel signal output to the horizontal signal line 110 is output via the output amplifier 87.

  In normal moving image shooting, the signal charge is transferred only to the floating diffusion 92. However, the present invention is not limited to this, and the signal charge is transferred to all the floating diffusions 92, 93, 94. The signal charges transferred to the floating diffusions 92, 93, and 94 can be read out as pixel signals during the charge reading process.

  On the other hand, when the mode for executing the moving image shooting to give the afterimage effect is selected, (5) pixel reset processing, (6) charge accumulation processing, (7) charge transfer processing, (8) charge distribution processing, (9) The charge reading process is sequentially executed for each scanning line.

(5) Pixel reset processing In moving image shooting that imparts an afterimage effect, pixel reset processing is executed as in normal moving image shooting. Immediately after the start of moving image shooting to give an afterimage effect, in other words, when acquiring the frame image of the first frame, processing similar to normal moving image shooting is executed.

  When acquiring the second and subsequent frame images after moving image shooting is started, the pixel reset process is changed. That is, the vertical scanning circuit 82 outputs a signal other than the third switching signal among the first switching signal, the second switching signal, the third switching signal, and the reset signal described above. That is, at the time of acquiring the second and subsequent frame images, the phototransistor 91 and the floating diffusions 92 and 93 are reset, and the floating diffusion 94 is not reset. That is, the signal charge transferred to the floating diffusion 94 remains as it is.

(6) Charge Accumulation Processing In moving image shooting that gives an afterimage effect, the same charge accumulation processing as in normal moving image shooting is executed.

(7) Charge Transfer Processing The vertical scanning circuit 82 receives the control signal from the timing generator 17 and outputs a first switching signal and a second switching signal. In response, the switching transistors 96 and 97 are turned on. After these switching signals are output, the vertical scanning circuit 82 outputs a transfer signal. Since the transfer transistor 95 is turned on by the output of the transfer signal, the signal charges accumulated in the photodiode 91 are transferred to the floating diffusions 92 and 93, respectively. Since the capacitance ratio of the floating diffusion 92 and the floating diffusion 93 is set to 9: 1, 90% of the amount of signal charges accumulated in the photodiode 91 is transferred to the floating diffusion 92, and the photodiode 10% of the signal charge accumulated in 91 is transferred to the floating diffusion 93.

(8) Charge Distribution Process As described above, the signal charge is transferred to the floating diffusion 93 by performing the charge transfer process. The vertical scanning circuit 82 receives the control signal from the timing generator 17 and outputs a second switching signal and a third switching signal. Thereby, the switching transistor 97 and the switching transistor 98 are turned on. Immediately after the above-described charge transfer process is completed, signal charges are accumulated in the floating diffusion 93 and no signal charges are transferred to the floating diffusion 94. When the switching transistor 97 and the switching transistor 98 are turned on by the output of the second switching signal and the third switching signal, the floating diffusions 93 and 94 have the same potential. Since the capacitance ratio of the floating diffusion 93 and the floating diffusion 94 is 1: 1, the signal charge is transferred from the floating diffusion 93 to the floating diffusion 94 until the charge amount of the signal charge transferred to the floating diffusion becomes equal. . As a result, the signal charge is distributed from the floating diffusion 93 to the floating diffusion 94. When this process ends, the output of each signal described above is stopped.

(9) Charge Reading Process The vertical scanning circuit 82 receives the control signal from the timing generator 17 and outputs a first switching signal and a second switching signal. As a result, the switching transistors 96 and 97 are turned on. After these switching signals are output, the vertical scanning circuit 82 outputs a row selection signal. By the output of this row selection signal, the selection transistor 100 is turned on, and the signal charge accumulated in the floating diffusion 92 and the floating diffusion 93 is output to the vertical signal line 109 as a pixel signal. In this charge reading process, a control signal from the timing generator 17 is output to the horizontal scanning circuit 83 and the CDS circuit 86. That is, the pixel signal output to the vertical signal line 109 is input to the column amplifier 85 via the vertical line selection transistor 84. The pixel signal input to the column amplifier 85 is amplified by the column amplifier 85 and then input to the CDS circuit 86. The CDS circuit 86 performs correlated double sampling processing on the input pixel signal and outputs it to the horizontal signal line 110. The pixel signal output to the horizontal signal line 110 is output via the output amplifier 87.

Next, a specific example in the case of taking a moving image with an afterimage effect will be described. Note that the moving image shooting with the afterimage effect of the second embodiment is a moving object in which the subject V moves from the left to the right in FIG. The case where the amount is 10e ⁻ and the amount of signal charges in the background is 5e ⁻ will be described as an example.

First, the pixel O will be described with reference to FIGS. 3, 12, and 13. The signal charges remaining in the photodiode 91 and the floating diffusions 92, 93, 94 of the pixel O are reset by the pixel reset process. That is, the signal charges of the photodiode 91 and the floating diffusions 92, 93, 94 are each 0. In the frame image FI _n acquired, the pixel O is a pixel included in a region of the object V. That is, when the charge accumulation process is executed, the charge amount 10e ⁻ of the signal charge in the subject V is accumulated in the photodiode 91. When the charge transfer process is executed after this process, the signal charges accumulated in the photodiode 91 are transferred to the floating diffusions 92 and 93. At this time, since the capacitance ratio of the floating diffusion 92 and the floating diffusion 93 is 9: 1, the signal charge charge amount 9e ⁻ out of the signal charge charge amount 10e ⁻ stored in the photodiode 91 is the floating diffusion 92. And the signal charge amount 1 e ⁻ is transferred to the floating diffusion 93.

When the charge distribution process is executed, the floating diffusions 93 and 94 become equipotential, so that signal charges are distributed (transferred) from the respective floating diffusions 93 to the floating diffusion 94. That is, the voltage based on the signal charge having the charge amount of 0.5e ⁻ is accumulated in the floating diffusion 93 and the floating diffusion 94, respectively. Finally, by executing the charge reading process, a voltage based on the signal charge (charge amount 9.5e ⁻ ) transferred to the floating diffusions 92 and 93 is output as a pixel signal. Note that the signal charge of the charge amount 0.5e ⁻ distributed to the floating diffusion 94 remains as it is.

In this state, the next frame image FI _{n + 1} is acquired. Also in the frame image FI _{n + 1} , the pixel O is a pixel included in the region of the subject V. Note that in the charge reset process executed when the frame image FI _{n + 1} is acquired, the charge reset process is not executed for the floating diffusion 94. By the charge accumulation process executed after the pixel reset process, signal charges having a charge amount of 10e ⁻ are accumulated in the photodiode 91. When the charge transfer process is executed, out of the signal charge amount 10e ⁻ accumulated in the photodiode 91, the signal charge amount 9e ⁻ is transferred from the photodiode 91 to the floating diffusion 92, and the signal charge The charge amount 1e ⁻ is transferred from the photodiode 91 to the floating diffusion 93. Immediately after this charge accumulation process is performed, the floating diffusion 93 stores a signal charge having a charge amount of 1e ⁻ , and the floating diffusion 94 stores a signal charge having a charge amount of 0.5e ⁻ . When the charge distribution process is executed, the floating diffusions 93 and 94 become equipotential, so that signal charges are distributed (transferred) from the respective floating diffusions 93 to the floating diffusion 94. Due to the distribution of the signal charges, signal charges having a charge amount of 0.75e ⁻ are accumulated in the floating diffusion 93 and the floating diffusion 94, respectively. Finally, by executing the charge reading process, the signal charges (charge amount 9.75e ⁻ ) transferred to the floating diffusions 92 and 93 are output as pixel signals. Note that the signal charge having the charge amount of 0.75e ⁻ distributed to the floating diffusion 94 remains as it is.

Further, when the frame image FI _{n + 2} is acquired, the pixel O is a pixel included in the region of the subject V as in the frame image FI _{n + 1} . When the frame image FI _{n + 2} is acquired, the reset process, the charge accumulation process, and the charge transfer process are performed in a state where the signal charge having the charge amount of 0.75e ⁻ remains in the floating diffusion 94. In other words, the charge amount 10e of the signal charge accumulated in the photodiode 91 ^- of the charge amount 9e signal charges ^- are transferred to the floating diffusion 92, the charge amount 1e signal charges ^- are transferred to the floating diffusion 93. By subsequent charge sharing processing is performed, to the floating diffusion 93 and the floating diffusion 94, the charge amount 0.875E ^- a state in which the signal charge is accumulated. Finally, by performing the charge reading process, the signal charges (charge amount 9.875e ⁻ ) transferred to the floating diffusions 92 and 93 are output as pixel signals. Note that the signal charge of the charge amount 0.875e ⁻ distributed to the floating diffusion 94 remains as it is.

When the frame image FI _{n + 3} is acquired, the pixel O is not a pixel included in the subject V area but a pixel included in the background area. When this frame image FI _{n + 3} is acquired, when this frame image FI _{n + 2} is acquired, reset processing, charge accumulation processing, and charge transfer processing are executed with the signal charge having a charge amount of 0.875e ⁻ remaining in the floating diffusion 94. Is done. In this case, the signal charge amount 5 e ⁻ is accumulated in the photodiode 91. The signal charges of the charge amount 5e ^- of the charge amount 4.5e signal charges ^- are transferred to the floating diffusion 92, the charge amount 0.5e signal charges ^- are transferred to the floating diffusion 93. By subsequent charge sharing processing is performed, to the floating diffusion 93 and the floating diffusion 94, the charge amount 0.6875E ^- a state in which the signal charge is accumulated. Finally, by executing the charge reading process, the signal charges (charge amount 5.1875e ⁻ ) transferred to the floating diffusions 92 and 93 are output as pixel signals. Note that the signal charge of 0.6875e ⁻ distributed to the floating diffusion 94 remains as it is.

In the frame image FI _{n + 4} acquired after the frame image FI _{n + 3} , the pixel O is a pixel included in the background area, like the frame image FI _{n + 3} . When the frame image FI _{n + 4} is acquired, the reset process, the charge accumulation process, and the charge transfer process are executed with the signal charge amount 0.6875e ⁻ remaining in the floating diffusion 94. Also in this case, the signal charge amount 5 e ⁻ is accumulated in the photodiode 91. The signal charges of the charge amount 5e ^- of the charge amount 4.5e signal charges ^- are transferred to the floating diffusion 92, the charge amount 0.5e signal charges ^- are transferred to the floating diffusion 93. By subsequent charge sharing processing is performed, to the floating diffusion 93 and the floating diffusion 94, the charge amount 0.59375E ^- a state in which the signal charge is accumulated. Finally, by executing the charge reading process, the signal charge (charge amount 5.09375e ⁻ ) transferred to the floating diffusions 92 and 93 is output as a pixel signal. Note that the signal charge having a charge amount of 0.59375e ⁻ distributed to the floating diffusion 94 remains as it is.

Similarly, in the frame image FI _{n + 5} , the reset process, the charge accumulation process, the charge transfer process, and the charge read process are executed in a state where the signal charge amount of 0.59375e ⁻ remains in the floating diffusion 94. When the frame image FI _{n + 5} is acquired, signal charges having a charge amount of 0.546875e ⁻ are accumulated in the floating diffusion 93 and the floating diffusion 94 by the charge distribution process described above. In this case, the signal charge (charge amount 5.046875e ⁻ ) transferred to the floating diffusions 92 and 93 by the charge reading process is output as a pixel signal. Note that the signal charge having a charge amount of 0.546875e ⁻ distributed to the floating diffusion 94 remains as it is. The frame image FI _{n + 6} is also subjected to reset processing, charge storage processing, charge transfer processing, and charge reading processing in a state where the charge amount 0.546875e ⁻ of the signal charge remains in the floating diffusion 94. When the frame image FI _{n + 6} is acquired, signal charges having a charge amount of 0.5234375e ⁻ are accumulated in the floating diffusion 93 and the floating diffusion 94 by the charge distribution process described above. In this case, the signal charge (charge amount 5.0234375e ⁻ ) transferred to the floating diffusions 92 and 93 by the charge reading process is output as a pixel signal. Note that the signal charge having a charge amount of 0.5234375e ⁻ distributed to the floating diffusion 94 remains as it is.

Thus, the amount of signal charge in each frame image output from the pixel O is 9.5e ⁻ →, 9.75e ⁻ → 9.9.875e ⁻ → 5.1875e ⁻ → 5.09375e ⁻ → 5. .046875e ⁻ → 5.0234375e ⁻ and converges to a charge amount 5e ⁻ based on the amount of light in the background region. That is, in the frame image FI n _{+ 3} and later frame image, since the afterimage effect is gradually reduced, in the frame image FI n _{+ 3} and later frame image, it is possible to appropriately impart an afterimage effect.

Next, the pixel P will be described with reference to FIGS. 3, 14, and 15. When the frame image FI _n and the frame image FI _{n + 1} are acquired, the pixel P is a pixel included in the region of the subject V. Therefore, the charge amount of the signal charge read out when the frame images FI _n and FI _{n + 1} are acquired, The amount of signal charge remaining in the floating diffusion 94 (reading light amount) has the same value as that of the pixel O. When acquiring the frame image FI _{n + 2} , the pixel P is not a region of the subject V but a pixel included in the background region. For this reason, in the charge accumulation process, the charge amount 5e ⁻ of the signal charge in the background is accumulated in the photodiode 91. That is, when the charge transfer process is performed, the signal charge amount 4.5 e ⁻ is transferred to the floating diffusion 92, and the signal charge amount 0.5 e ⁻ is transferred to the floating diffusion 93. At this time, since the signal charge amount 0.75e ⁻ is accumulated in the floating diffusion 94, the signal charge accumulated in the floating diffusion 93 and the floating diffusion 94 by the charge distribution processing is the charge amount 0.625e. ^- . That is, when the charge reading process is executed, the signal charges (charge amount 5.125e ⁻ ) transferred to the floating diffusion 92 and the floating diffusion 93 are output as pixel signals. At this time, the signal charge accumulated in the floating diffusion 94 remains as it is.

Note that in the frame image FI _{n + 3 and} later (the frame image FI _{n + 3} , the frame image FI _{n + 4} , the frame image FI _{n + 5,} and the frame image FI _{n + 6} ), the pixel P is a pixel included in the background region, and therefore the frame image FI _{n + 2} Similarly, the charge amount 5e ⁻ based on the amount of light in the background region is received by the photodiode 91, 90% of the signal charge accumulated in the photodiode 91 is transferred to the floating diffusion 92, and the remaining 10% is floating. It is transferred to the diffusion 93. Thereafter, the signal charges accumulated in the floating diffusion 93 and the floating diffusion 94 are equalized by the charge distribution process, and then the voltage based on the signal charges accumulated in the floating diffusion 92 and the floating diffusion 93 is obtained by the charge reading process. Output as a signal.

Thus, the amount of signal charge in each frame image output from the pixel P is 9.5e ⁻ →, 9.75e ⁻ → 5.125e ⁻ → 5.0625e ⁻ → 5.03125e ⁻ → 5.015625e. ⁻ → 5.0078125e ^−, and converges to a charge amount 5e ⁻ based on the amount of light in the background region. That is, since the afterimage effect is gradually reduced in the frame images after the frame image FI _{n + 2} , the pixel P can appropriately impart the afterimage effect in the frame images after the frame image FI _{n + 2} .

Finally, the pixel Q will be described with reference to FIG. 3, FIG. 16, and FIG. The pixel Q is a pixel included in the background region, not the subject V region. That is, in this pixel Q, the charge amount 5e ⁻ based on the light amount in the background region is accumulated in the photodiode 91 when each frame image is acquired. Also in this pixel Q, since the same processing as that of the pixel O and the pixel P is executed, 90% of the signal charge accumulated in the photodiode 91 is transferred to the floating diffusion 92, and the remaining 10% is the floating diffusion 93. To remain. Then, by performing the charge distribution process, the signal charges accumulated in the floating diffusion 93 and the floating diffusion 94 are equalized. Finally, a voltage based on the signal charge accumulated in the floating diffusion 92 and the floating diffusion 93 by the charge reading process is output as a pixel signal. The amount of signal charge in each frame image output from the pixel Q is 4.75e ⁻ → 4.875e ⁻ → 4.37575e ⁻ → 4.96875e ⁻ → 4.984375e ⁻ → 4.921875e ⁻ → 4 .99609375e ⁻ and the charge amount 5e ⁻ based on the amount of light in the background area. Note that the pixel Q is a pixel included in the background area during moving image shooting, and thus it is understood that the afterimage effect is not given to the pixel Q.

  In this way, the image signal output from the image sensor 16 is an image signal with an afterimage effect. As shown in FIG. 10, when the acquired moving image is displayed, an appropriate afterimage effect is applied to the moving subject, and the background region is displayed as a moving image without the afterimage effect. That is, by increasing the configuration of each pixel of the image sensor, in other words, the number of floating diffusions, and changing the control on the image sensor 16, a moving image with an afterimage effect can be easily acquired. Also in this case, it is not necessary to perform image processing that gives an afterimage effect to a moving image obtained by normal moving image shooting. Accordingly, it is possible to easily acquire a moving image with an afterimage effect without increasing the processing load of the image processing circuit 30.

  Also in the second embodiment, as in the first embodiment, the amount of signal charge based on the amount of light read from each pixel is the actual amount of charge in the frame image immediately after the start of moving image capturing that imparts an afterimage effect. Therefore, it is possible to delete without recording the frame images up to the second and third frames obtained from the start of the moving image shooting that gives the afterimage effect. In addition to this, with respect to frame images up to the second and third frames obtained from the start of moving image capturing to give an afterimage effect, for example, the column amplifier 85 or output amplifier 87 provided in the image sensor 81 outputs the frame image. It is also possible to amplify the value. In addition, the output value from each pixel can be amplified by the gain control processing in the AFE circuit 18. Further, it is possible to correct the frame images up to the second and third frames at the time of gradation conversion processing in the image processing circuit 30.

  In the second embodiment, the floating diffusion 94 is an embodiment in which the remaining signal charge is accumulated until the next frame image is acquired. However, the present invention is not limited to this, and the floating diffusion 94 is accumulated in the floating diffusion 93. It is also possible to accumulate signal charges. In addition to this, for each frame image, it is also possible to switch the floating diffusion for accumulating signal charges that remain until the next frame image is acquired.

  In the second embodiment described above, the number of floating diffusions provided in each pixel is three. However, the number is not limited to this, and the number of floating diffusions provided in each pixel may be two or more. When the number of floating diffusions provided in each pixel is two, it is not necessary to perform the above-described charge distribution process. For example, when the floating diffusion provided in the pixel is a floating diffusion X and a floating diffusion Y, the capacitance ratio of the floating diffusion X and the floating diffusion Y is 9: 1. In this case, when the signal charge accumulated in the photodiode during the charge transfer process described above is transferred to the floating diffusions X and Y, 90% of the signal charge is transferred to the floating diffusion X and 10% of the signal is transferred to the floating diffusion Y. Charge is transferred. When the charge reading process is executed, the signal charge stored in the floating diffusion X is output as a pixel signal, and the signal charge stored in the floating diffusion Y is left. Then, when acquiring the next frame image, the signal charges accumulated in the photodiode are transferred to the floating diffusions X and Y, respectively. At this time, signal charges are accumulated in the floating diffusion Y. Since the floating diffusions X and Y are equipotential, the floating diffusion is such that the sum of the signal charge accumulated in the photodiode and the signal charge accumulated in the floating diffusion Y becomes a capacitance ratio of 9: 1. Distributed to X and Y. Then, a voltage based on the signal charge transferred to the floating diffusion X in the charge reading process may be output as a pixel signal. The signal charge transferred to the floating diffusion Y remains until the next frame image is acquired.

  In this case as well, it is possible to easily obtain a moving image with an afterimage effect by increasing the configuration of each pixel of the image sensor, in other words, increasing the number of floating diffusions and changing the control on the image sensor 16. Therefore, it is not necessary to provide an afterimage effect by image processing, and the processing load of the image processing circuit can be reduced.

  In the first embodiment and the second embodiment, moving image shooting is taken as an example, but it is obtained by so-called continuous shooting that continuously captures a through image or a still image obtained in a shooting standby state. The present invention can also be applied to obtaining a captured image.

  Although the digital camera provided with the CMOS image sensor has been described as the imaging device in the first embodiment and the second embodiment, the present invention is not limited to this, and a CCD image sensor can also be used. .

  The present invention has been described by taking a digital camera as an example of an imaging device, but is not limited thereto, and for example, if a camera function is added to a portable electronic device such as a portable phone, The present invention can be used for such portable electronic devices.

  DESCRIPTION OF SYMBOLS 10 ... Digital camera 16,81 ... Image pick-up element, 17 ... Timing generator, 46 ... Afterimage provision button, 51, 82 ... Vertical scanning circuit, 52, 83 ... Horizontal scanning circuit, 61, 91 ... Photodiode, 62, 92, 93, 94 ... floating diffusion, 63, 95 ... transfer transistor, 66, 101 ... reset transistor, 96, 97, 98 ... switching transistor

Claims (9)

An imaging device including a pixel that generates and accumulates signal charges according to incident light; and
Driving means for outputting a pixel signal based on a part of the signal charge accumulated in the pixel and causing the remaining signal charge to remain in the pixel;
Control means for controlling driving of the image sensor by the driving means;
An imaging apparatus comprising: The imaging device according to claim 1,
The pixel is
A photoelectric conversion unit for photoelectrically converting the incident light to generate the signal charge and storing the signal charge;
The image pickup apparatus, wherein the driving unit outputs a part of signal charges accumulated in the photoelectric conversion unit as the pixel signal. The imaging device according to claim 2,
The pixel is
A charge-to-voltage converter that converts signal charges output from the photoelectric converter into a voltage;
A transfer transistor that switches whether or not to transfer the signal charge accumulated in the photoelectric conversion unit to the charge-voltage conversion unit by an on / off operation;
With
The image pickup apparatus, wherein the driving unit transfers a part of the signal charge accumulated in the photoelectric conversion unit to the charge-voltage conversion unit by changing a time related to an ON operation of the transfer transistor. The imaging device according to claim 3.
The pixel is
A reset transistor for resetting the charge-voltage converter,
In the case of acquiring a plurality of images continuously, the driving means turns on the transfer transistor and the reset transistor when acquiring an image immediately after the acquisition of the plurality of images is started, thereby the photoelectric conversion unit And resetting only the charge-voltage converter by turning on only the reset transistor when acquiring the remaining images except for the image immediately after the acquisition of the plurality of images is reset. Then, the signal charge accumulated in the photoelectric conversion unit is left to remain. In the imaging device according to claim 3 or 4,
The pixel is
A selection transistor for switching whether to output the voltage converted by the charge-voltage converter as a pixel signal by an on / off operation;
The image pickup apparatus according to claim 1, wherein the driving unit outputs the pixel signal based on the voltage converted by the charge-voltage conversion unit by turning on the selection transistor. The imaging device according to claim 1,
The driving means outputs the pixel signal based on a part of the signal charges accumulated in the pixels when acquiring the plurality of images, or all signal charges accumulated in the pixels. An image pickup apparatus, wherein the image pickup device is driven in any one of a second mode for outputting the pixel signal based on the first mode. The imaging device according to claim 6,
An operation member that is operated when switching to one of the first mode and the second mode;
The control unit is configured to switch the driving of the imaging element by the driving unit between the first mode and the second mode in response to an operation of the operation member. The imaging apparatus according to claim 7,
The control unit switches driving of the image sensor by the driving unit between the first mode and the second mode when the operation member is operated at the time of acquiring the plurality of continuous images. An imaging apparatus characterized by that. In the imaging device according to any one of claims 6 to 8,
The image pickup apparatus according to claim 1, wherein the plurality of images include any one of a moving image, a through image, and an image obtained during continuous shooting.

Images