JP6706138B2 - Imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus that performs drive control so as to remove an afterimage caused by charge transfer from a photodiode to a charge-voltage conversion unit in a solid-state image pickup element.

In a CMOS type solid-state image sensor that is widely used in image pickup devices such as cameras in recent years, charges induced by light are accumulated in a photodiode (PD) for a certain period of time, and a charge-voltage converter (FDA: It is often transferred to a floating diffusion amplifier) and read out as a voltage. Then, in the solid-state imaging device, normally, the potential gradient when the charge transfer gate is turned on is designed so that all the charges are transferred from the PD to the charge-voltage conversion unit. However, there is a case where the potential gradient as designed is not obtained, and the electric charge is not transferred and remains in the PD. In the moving image shooting, such electric charge is transferred at the time of the next reading and thereafter, and becomes an afterimage. Appear in.

Insufficiency of the potential gradient that causes afterimages essentially requires reviewing the pixel design and manufacturing conditions, and in general, adjustment of pixel design and manufacturing conditions prevents inadequate potential gradients that cause afterimages. I'm out.

On the other hand, as the image pickup apparatus, it may be inevitable to use a solid-state image pickup element that may cause an afterimage due to driving conditions or the like according to the apparatus specifications.

Therefore, there is a technique of using a bias light in order to reduce the influence of the afterimage by using a solid-state image sensor that can cause an afterimage. This technique applies a constant amount of light to the image pickup surface of the image sensor by the mechanism of the camera, and always causes a fixed amount of charge offset in the photodiode, thereby affecting the image remaining charge in the photodiode. Is to suppress.

Further, as another technique for reducing the influence of the afterimage, in a solid-state image sensor connected to the drain through the reset gate to the charge-voltage converter, the charge transfer gate and the reset gate are opened (on state). There is also proposed a technique of suppressing the occurrence of an afterimage by varying the potential of the drain and injecting charges from the drain to always leave a constant amount of charge in the PD (for example, refer to Patent Document 1).

JP 2001-309243 A

Occurrence of an afterimage due to charge transfer from the photodiode (PD) in the solid-state image pickup device to the charge-voltage converter is not preferable in terms of image quality of the image pickup apparatus.

Therefore, as described above, there is known a technique of reducing the influence of an afterimage by using a bias light generated by the mechanism of the camera, but the image quality is deteriorated by the influence of shot noise generated by applying the light of the bias light. However, there is a concern that it is difficult to apply a constant amount of light to the imaging surface due to the design of the camera.

Further, as in the technique of Patent Document 1, it is necessary to drive a very large load in order to change the potential of the drain of the solid-state imaging device connected to the drain of the charge-voltage converter via the reset gate. Become. Therefore, it is not easy to realize a drive circuit that changes the drain potential so as to leave a constant charge amount at a cycle corresponding to the frame frequency required for moving image shooting.

Therefore, there is a demand for a technique of suppressing the driving load in the drive circuit of the solid-state image pickup device to an extent that can be easily realized and removing or reducing the influence of the afterimage even when the solid-state image pickup device that can generate the afterimage is used.

In view of the above problems, it is an object of the present invention to provide an imaging device that removes or reduces the influence of the afterimage on a solid-state image sensor that may cause an afterimage.

The image pickup apparatus according to the present invention removes or reduces the influence of an afterimage with respect to a solid-state image pickup element in which an afterimage may occur. At the time of charge transfer, the potential of the channel of the charge transfer gate (TX) (channel potential) with respect to the reference potential of the charge-voltage conversion unit in order to leave a predetermined charge amount (in principle, always constant) in the PD. ) Causes a potential gradient to become deeper, and further includes a drive circuit that performs a predetermined dummy shutter operation that does not contribute to the readout of the pixel signal for removing the afterimage component of the PD.

That is, the image pickup device according to the present invention leaves a predetermined amount of charge in the photodiode when the charge is transferred from the photodiode to the charge-voltage converter by the charge transfer gate in the solid-state image pickup element and the solid-state image pickup element. Therefore, there is provided drive means for driving the solid-state imaging device so as to generate a potential gradient in which the potential of the channel of the charge transfer gate becomes deeper with respect to the reference potential in the charge-voltage conversion section. It is characterized in that charges are left in the channel of the charge transfer gate due to the potential gradient during transfer .

Further, in the image pickup device according to the present invention, the driving unit is for turning on/off the charge transfer gate and resetting the charge-voltage conversion unit, which does not contribute to reading a pixel signal, for removing an afterimage component in the photodiode. It is further provided with a function of performing a predetermined dummy shutter operation by a combination of operations one or more times before reading the pixel signal.

Further, in the image pickup apparatus according to the present invention, the driving unit further includes a function of performing the predetermined dummy shutter operation a plurality of times before reading the pixel signal.

In the imaging apparatus according to the present invention, the drive means is a front reading of this pixel signal, during the readout period of the previous pixel signal, a plurality of times of on-off operation of the charge transfer gate It is characterized by further having a function.

Further, in the image pickup device according to the present invention, the charge transfer gate drive voltage corresponding to the potential of the channel of the charge transfer gate that causes the potential gradient is configured to be larger than the reset voltage corresponding to the reference potential. It is characterized by

According to the present invention, even if a solid-state imaging device that can generate an afterimage is used, it is possible to obtain an image in which the influence of the afterimage is removed or reduced.

It is a block diagram showing a schematic structure of an image pick-up device of one embodiment by the present invention. It is a figure which illustrates roughly the pixel structure of the solid-state image sensor in the image pick-up device of one embodiment by the present invention. (A) thru|or (e) are figures which show the change of the potential by the conventional signal read-out operation in the solid-state image sensor which does not generate an afterimage. (A) to (i) are diagrams showing changes in potential when an afterimage is generated by a conventional signal reading operation in a solid-state imaging device in which an afterimage is generated. (A) to (g) are changes in the potential when the influence of the afterimage is removed by the signal reading operation of the first embodiment with respect to the solid-state image pickup device in which the afterimage is generated by the drive circuit in the image pickup apparatus according to the embodiment of the present invention. FIG. (A) to (h) are changes in the potential when the influence of the afterimage is removed by the signal reading operation of the second embodiment with respect to the solid-state image pickup element in which the afterimage is generated by the drive circuit in the image pickup apparatus according to the embodiment of the present invention. FIG. FIG. 7 is a diagram showing an example of a timing chart of a drive signal by a drive circuit in the image pickup apparatus according to the embodiment of the present invention. FIG. 11 is a diagram showing another example of a timing chart of drive signals by the drive circuit in the imaging device of the embodiment according to the present invention. 6 is a graph of measurement data showing an effect of Example 2 in the imaging device of the embodiment according to the present invention.

An image pickup apparatus 1 according to an embodiment of the present invention will be described below with reference to the drawings.

[Imaging device]
FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus 1 according to an embodiment of the present invention. The image pickup apparatus 1 includes a solid-state image pickup element 2 configured as an existing typical CMOS image pickup element, and a control unit 3. The control unit 3 includes a drive circuit 31 and a signal processing circuit 32. The image pickup apparatus 1 of the present embodiment can be configured as a camera capable of shooting moving images.

The image pickup apparatus 1 causes the solid-state image pickup element 2 driven by the drive circuit 31 to form an image of a subject with an image pickup lens to output a pixel signal of the solid-state image pickup element 2. The signal processing circuit 32 image-processes the pixel signal to generate a moving image. Output images such as images.

[Solid-state image sensor]
FIG. 2 is a diagram schematically illustrating the pixel structure of the solid-state image sensor 2 in the image pickup apparatus 1 according to the embodiment of the present invention. In FIG. 2, a schematic diagram illustrating a 4-transistor structure generally used in a CMOS image sensor as the solid-state image sensor 2 in a simpler manner is shown. Incident light is converted into electric charges (electrons in this case) in the photodiode (PD) 21 and accumulated during the exposure time. The charge accumulated in the PD 21 is controlled by controlling the gate voltage of the charge transfer gate (TX) of the transfer transistor 22 (here, NMOS) from low (L) to high (H) by a transfer signal (TX signal). It is transferred to the floating diffusion (FD) 23 in the charge-voltage converter. The FD 23 behaves as a capacitor having a capacitance C _FDA , and the charge-voltage converter functions as a charge-voltage converter that generates a voltage according to the transferred charges.

Before the charges are transferred from the PD 21 to the FD 23, the FD 23 is reset by controlling the gate voltage of the reset transistor 24 (here, NMOS) from low (L) to high (H) by a reset signal (RT signal). It is connected to the voltage RTVDD and is reset to a constant voltage (that is, the reference potential of the FD 23). The voltage signal generated in the charge-voltage converter is output as a pixel signal by a signal reading circuit (not shown), and the controller 3 shown in FIG. 1 is provided through an AD converter circuit (not shown) provided integrally with the solid-state image sensor 2. Is transmitted to the signal processing circuit 32.

A noise removal circuit (correlated double sampling circuit) is provided in front of the AD conversion circuit (not shown), and a reset level signal before charge transfer from the PD 21 to the FD 23 and a stored charge signal after charge transfer are performed. It is also possible to take a difference between the two and reduce the noise. After that, the signal is converted into a digital value by the AD conversion circuit and transmitted to the signal processing circuit 32 of the control unit 3.

By repeating this series of operations, the image pickup apparatus 1 can take a moving image.

Further, in the above series of operations, in order to arbitrarily control the exposure time of the PD 21, the gate voltage of the transfer transistor 22 is controlled from low to high by the TX signal to transfer the charge from the PD 21 to the FD 23, and read the signal. The operation of controlling the gate voltage of the reset transistor 24 from low to high by the RT signal and resetting the potential of the FD 23 without reading the signal voltage by the circuit is performed at an arbitrary timing during the signal reading by the signal reading circuit. It can be carried out. By performing this operation, the charges accumulated in the PD 21 up to that point are discarded, so that the exposure time of the PD 21 can be adjusted. The operations of the transfer transistor 22 and the reset transistor 24 that do not contribute to the reading of the pixel signal are defined as the electronic shutter operation. Such an electronic shutter operation can be controlled by the drive circuit 31, and has been generally performed conventionally.

(Conventional signal reading operation)
Here, in order to improve the understanding of the present invention, a conventional signal read operation will be described first. FIGS. 3A to 3E are diagrams showing potential changes due to a conventional signal reading operation in the solid-state image sensor 2 in which an afterimage does not occur.

In FIG. 3, the horizontal axis represents the plane coordinates on the pixel, and is “PD” (region of PD21), “TX” (region of TX channel of transfer transistor 22), “FD” (region of FD23), “RT”. (RT channel region of reset transistor 24) and “RTVDD” (potential region corresponding to reset voltage). The potential at each coordinate is schematically represented by a thick line, and the lower side represents a low potential (deep) state. That is, in FIG. 2, when the TX signal or RT signal is high (H), the potential is in a lower (lower) state, and when the TX signal or RT signal is low (L), the potential is higher. Therefore, it is assumed that the electric charges are directed in the direction in which the potential becomes deeper in the figure.

The initial state shown in FIG. 3A represents a state in which there is no electric charge held in each region of “PD”, “TX”, “FD”, “RT”, and “RTVDD”. After the exposure shown in FIG. 3B, the charge is accumulated in the PD 21 according to the amount of incident light. At this time, it is assumed that the electric charges are accumulated in the PD 21 up to the potential indicated by the thin line of the PD 21.

In the reset operation shown in FIG. 3C, the unnecessary electric charge accumulated in the FD 23 is discharged by the operation of the RT signal from low (L) to high (H), and the FD 23 has a reference potential (potential corresponding to the reset voltage RTVDD). To After that, the charge transfer operation shown in FIG. That is, by turning on the gate voltage of the transfer transistor 22 by the operation of the TX signal from low (L) to high (H), the potential of the FD 23 becomes lower than that of the PD 21, and the charge accumulated in the PD 21 is reduced. , FD23.

Here, in the conventional signal reading operation in the solid-state imaging device 2 in which the afterimage does not occur, as shown in FIG. 3D, the potential of the TX channel when the TX signal is high (H) (TX signal (H)). Is set to a state (higher) than the reference potential (potential corresponding to the reset voltage RTVDD) so that no charges remain in the TX channel when the charges are transferred from the PD 21 to the FD 23. This is because if electric charge remains in the TX channel during the electric charge transfer, electric charge returns to the PD 21 when the TX signal is low (L), which will cause an afterimage, which will be described later.

In the signal reading of FIG. 3E, a voltage signal corresponding to the potential of the FD 23 changing from the reference potential of FIG. 3C by the transfer charge of FIG. 3D is read as a pixel signal.

The pixel signal obtained from the FD 23 shown in FIG. 3E is transmitted to the signal reading circuit (not shown) provided outside by a source follower amplifier or the like.

On the other hand, FIGS. 4A to 4I are diagrams showing changes in potential when an afterimage is generated by a conventional signal reading operation in the solid-state imaging device 2 in which an afterimage is generated. The initial state of FIG. 4A, the state of FIG. 4B after exposure, and the state of FIG. 4C after reset are the same as those in FIG.

At the time of charge transfer in FIG. 4D, the gate voltage of the transfer transistor 22 is turned on by the operation of the TX signal from low (L) to high (H) as in the case of FIG. As a result, the potential of the FD 23 becomes low, and the charges accumulated in the PD 21 are transferred to the FD 23. However, in the pixel in which the afterimage is generated, a part of the electric charge is not transferred and remains in the PD 21 due to the insufficient potential gradient of the PD 21 and the TX channel. In the signal reading of FIG. 4E, the pixel signal is read as in the case of FIG.

In a case where a bright scene is followed by a dark scene in moving image capturing, if a dark scene is photographed with electric charges remaining in the PD 21 during a bright scene, as shown in FIG. 4F, a state diagram after exposure. In addition, a situation occurs in which the accumulated charge due to the exposure in the PD 21 is small. When the charge transfer shown in FIG. 4(h) is performed after the reset shown in FIG. 4(g) in this state, in addition to the charge generated by the exposure, a part of the charge remaining in the bright scene is also thermally excited. Is transferred to the FD 23. As a result, at the time of the next signal reading shown in FIG. 4I, a pixel signal having a voltage higher than the voltage generated by the incident light is output. The charges remaining after the charge transfer are generated by a bright scene and gradually read out and decrease when dark scenes continue, so that they appear as a trailing afterimage in the image. Such an afterimage is difficult to remove by signal processing or the like, and significantly deteriorates the quality of the video signal. In this case, the residual electric charge is substantially constant above a certain light amount without depending on the light amount. It should be noted that the residual charge in this case is different from the afterimage to be removed, which will be referred to as “distribution afterimage charge” described below.

Therefore, hereinafter, in the image pickup apparatus 1 according to the embodiment of the present invention, the drive circuit 31 is configured to remove the influence of the afterimage by the signal reading operation of the first and second embodiments with respect to the solid-state image pickup element 2 in which the afterimage occurs. .. Hereinafter, each example will be described in order. As the operation of the drive circuit 31, only the drive signals (TX signal and RT signal) according to the present invention will be described.

[Operation of drive circuit]
(Signal reading operation of the first embodiment according to the present invention)
5A to 5G, the influence of the afterimage is removed by the signal reading operation of the first embodiment on the solid-state image sensor 2 in which the afterimage is generated by the drive circuit 31 in the image pickup apparatus 1 according to the embodiment of the present invention. It is a figure which shows the change of the potential at the time. The initial state of FIG. 5A, the state of FIG. 5B after exposure, and the state of FIG. 5C after reset are the same as those in FIG.

In the first embodiment, after the reset of FIG. 5C, the following operations from FIG. 5D-1 to FIG. 5G are performed to perform the signal reading in which the influence of the afterimage is suppressed.

In the first TX ON operation of FIG. 5D-1, unlike the conventional technique shown in FIGS. 3 and 4, the potential of the TX channel when the TX signal is high (H) (TX signal (H)) is used as a reference. The state is set lower (deeper) than the potential (potential corresponding to the reset voltage RTVDD) so that charges are intentionally left in the TX channel when the charges are transferred from the PD 21 to the FD 23. In order to satisfy “potential corresponding to RTVDD>potential corresponding to TX signal (H)” shown in FIG. 6D-1, in this example, “TX signal (H)>” as the input voltage. RTVDD”.

Then, in the initial TX-on operation shown in FIG. 5D-1, as in the case of FIG. 4, in the pixel where the afterimage occurs, some charges are transferred due to the lack of the potential gradient of the PD 21 and the TX channel. Instead, it remains in the PD 21. Therefore, if the charge due to photoelectric conversion accumulated in the PD 21 at the time of FIG. 5C is Qs, the charge ΔQs remains in the PD 21, and Qs−ΔQs is transferred to the FD 23.

Next, in the first TX off operation shown in FIG. 5D-2, when the TX signal becomes low (L) (TX signal (L)), a part α of the charge remaining in the TX channel is PD21. Return to. As a result, a charge of ΔQs+α remains in the PD 21, and a charge of Qs−ΔQs−α remains in the FD 23.

Since the above operation is repeated for each frame of moving image shooting, after a steady state after several frames, by setting Qo=ΔQs+α in the state of FIG. 5A, the state of FIG. When the signal is read out after the steady state in (g), a constant charge ΔQs+α remains in the PD 21 and only a net photocharge Qs remains in the FD 23 irrespective of the amount of incident light.

As described above, in the image pickup apparatus 1 according to the first embodiment, in order to remove or reduce the influence of the afterimage with respect to the solid-state image pickup element 2 in which the afterimage occurs (or may occur), the drive circuit 31 causes the solid-state image pickup element to be removed. When the charge is transferred from the PD 21 in 2 to the FD 23 of the charge-voltage converter, a potential gradient is generated so that the potential of the channel of the charge transfer gate (TX channel potential) becomes deeper than the reference potential of the FD 23, and the photodiode is A predetermined (in principle, always constant) charge amount is left in the (PD21). As a result, the image pickup apparatus 1 according to the first embodiment can obtain an image in which the influence of the afterimage is removed or reduced even when the solid-state image pickup element 2 in which the afterimage is generated is used.

(Signal reading operation of the second embodiment according to the present invention)
6A to 6H, the drive circuit 31 in the image pickup apparatus 1 according to the embodiment of the present invention removes the influence of the afterimage by the signal reading operation of the second embodiment on the solid-state image pickup element 2 in which the afterimage occurs. It is a figure which shows the change of the potential at the time. The initial state of FIG. 6A, the state of FIG. 6B after exposure, and the state of FIG. 6C after reset are the same as those in FIG. However, here, it is assumed that the incident light is strong and a larger amount of charge Qms is accumulated in the PD 21 than in the example of FIG.

In the first TX ON operation of FIG. 6D-1, the potential of the TX channel when the TX signal is high (H) (TX signal (H)) is used as the reference potential (similar to the first embodiment shown in FIG. 5). The state is set lower (deeper) than the potential corresponding to the reset voltage RTVDD (TX signal (H)>RTVDD), so that charges are intentionally left in the TX channel when the charges are transferred from the PD 21 to the FD 23. However, this example is an example when the amount of signal charges transferred to the FD 23 is large.

Next, in the first TX off operation shown in FIG. 6D-2, when the TX signal becomes low (L) (TX signal (L)), the electric charge Q1 remains in the PD 21 among the signal charges. This will be referred to as distributed afterimage charge. In the case of the operation of the conventional technique, this charge Q1 will appear as another afterimage during the signal read operation of the next frame. As described above, even if the charge amount is not enough to overflow to the PD 21 when the TX is first turned on, the charge amount distributed to the PD 21 when the TX is turned off may increase when the signal in the FD 23 is large.

On the other hand, in the second embodiment according to the present invention, after the initial read operation of FIG. 6E, high (H) to low (L) and low (H) of the TX signal are performed during the reset operation that does not contribute to the reading of the pixel signal. ) To high (H) is performed once or more, and the dummy shutter operation shown in FIGS. 6F to 6H is performed. Here, the electronic shutter operation defined as described above is intended for exposure control, but the same driving is performed, but an operation that does not contribute to the readout of the pixel signal for removing the afterimage component of the PD 21. Therefore, it is defined separately as “dummy shutter operation”.

That is, since the distribution afterimage charge Q1 is discharged without being read out as a pixel signal by the dummy shutter operation in FIGS. 6F to 6H, the distribution afterimage charge does not appear in the image. Further, the state before the exposure of the next frame by this operation is the same as the case of FIG. 5(g) described above, as shown in FIG. 6(h). Therefore, there is no trailing afterimage. In general, Qms>>Q1 and the influence is small. Further, it is effective to perform the dummy shutter operation a plurality of times, and the distributed afterimage charge can be discharged more reliably.

As described above, in the image pickup apparatus 1 according to the second embodiment, in addition to the operation of the first embodiment, the drive circuit 31 does not contribute to the readout of the pixel signal for removing the afterimage component of the PD 21 due to the distributed afterimage charge. The operation is performed so that a constant charge amount is always left in the photodiode (PD21) regardless of the exposure charge amount. As a result, the image pickup apparatus 1 according to the second embodiment can obtain an image in which the influence of the afterimage is removed or reduced regardless of the exposure charge amount even when the solid-state image pickup device 2 in which the afterimage is generated is used. You can

FIG. 7 is a timing chart regarding the drive signals (RT signal and TX signal) of the drive circuit 31 that performs the signal read operation according to the first and second embodiments. In the example shown in FIG. 7, the pixel signal read-out operation (FIGS. 5A to 5E) is performed twice, and the dummy shutter operation (FIGS. 6F to 6H) for removing the afterimage performed between them is performed. ) Is shown once. However, in this timing chart, the reset operation performed immediately before the charge transfer by the TX signal is taken as an example of pairing with the charge transfer. Further, the reset operation of the PD 21 by the final TX signal of the dummy shutter operation also serves as a reset for starting the exposure time related to signal reading. In the afterimage removal according to the first embodiment, the relationship between the voltage of the TX signal (H) and the reset voltage RTVDD is TX signal (H)>RTVDD as described above, and a certain amount of charge remains in the PD 21.

Then, in the dummy shutter operation for removing the afterimage according to the second embodiment, the high (H) and the low (L) of the TX signal are repeated once or more (preferably a plurality of times) to discharge the distributed afterimage charge. I have to. The dummy shutter operation for removing the afterimage can be performed at any timing in the read period of the adjacent pixel signal, and the TH for reading the next pixel signal from the last TH signal (H) in the dummy shutter operation. The period up to the signal (H) is the exposure time read out as a pixel signal. Therefore, by performing the dummy shutter operation immediately after reading the pixel signal, the afterimage can be removed with almost no loss in the exposure time.

However, as shown in FIG. 8, the operations of Examples 1 and 2 are performed before the pixel signal of this time is read, and the TX signal (H) is output a plurality of times during the reading period of the pixel signal of the last time. Even when driven, the afterimage reducing effect based on the same principle can be expected.

FIG. 9 is a graph of measurement data showing an effect of Example 2 in the image pickup apparatus 1 according to the embodiment of the present invention. The horizontal axis represents the number of frames for signal readout in a dark state after a bright signal having a constant brightness is incident, and the vertical axis represents the afterimage amount on an arbitrary scale. When the conventional driving by the signal reading operation is used, the charges remaining in the PD 21 are gradually read from the PD 21 and appear in the signal as an afterimage with a trailing tail of about 5 frames. On the other hand, by performing the driving by the signal reading operation of the second embodiment according to the present invention, it can be seen that the afterimage is below the noise level and is not observed. In addition, since the second embodiment includes the operation of the first embodiment, the operation and effect of the first embodiment can be obtained.

As described above, in the imaging device 1 according to the present invention, the drive circuit 31 partially resets the reset voltage for the charge-voltage converter and the drive voltage for the charge transfer gate when the charge transfer gate makes a transition from on to off. The drive is performed by setting the voltage value such that the charges are returned to the photodiode (PD) 21 (Examples 1 and 2). Note that the solid-state image sensor 2 exhibits a potential change according to this voltage value.

Then, after reading the electric charge accumulated in the PD 21 and before the next signal electric charge accumulation of the PD 21 is started, a dummy shutter operation that does not contribute to the reading of the pixel signal for removing the afterimage component of the PD 21 is performed from the PD 21. The charge transfer to the FD 23 and the reset operation of the FD 23 are performed. This dummy shutter operation is performed by turning on/off the charge transfer gate once or more times at a number of times that the afterimage reducing effect is obtained, thereby obtaining an image in which the effect of the afterimage is removed or reduced regardless of the exposure charge amount. Will be able to.

Although the specific example of the above-described specific embodiment has been described as an example, the present invention is not limited to the above-described example. For example, in each of the embodiments according to the present invention described above, the solid-state image sensor 2 in which an afterimage is generated has been described as a premise, but the present invention may be applied to the solid-state image sensor 2 in which an afterimage may possibly occur, or no afterimage occurs. Even if it is applied to the solid-state image pickup element 2, it does not cause a malfunction in its operation. Therefore, the degree of freedom of the solid-state image pickup element 2 applicable to the image pickup apparatus 1 according to the present invention is increased, which contributes to cost reduction of the apparatus.

According to the present invention, even if a solid-state imaging device that can generate an afterimage is used, an image in which the influence of the afterimage is removed or reduced can be obtained, and thus it is useful for applications of imaging devices such as cameras.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Solid-state imaging device 3 Control part 31 Drive circuit 32 Signal processing circuit 21 Photodiode (PD)
22 Transfer Transistor 23 Floating Diffusion (FD)
24 Reset transistor

Claims (5)

An imaging device,
A solid-state image sensor,
When transferring charges from the photodiode to the charge-voltage converter by the charge-transfer gate in the solid-state imaging device, the charge-transfer gate is used with respect to the reference potential in the charge-voltage converter to leave a predetermined amount of charge in the photodiode. Drive means for driving the solid-state imaging device so as to generate a potential gradient in which the potential of the channel of becomes deeper ,
The image pickup device according to claim 1, wherein the driving unit causes charges to remain in a channel of the charge transfer gate due to the potential gradient during the charge transfer . The driving unit performs a predetermined dummy shutter operation for removing an afterimage component in the photodiode by a combination of ON/OFF of the charge transfer gate and a reset operation of the charge/voltage conversion unit, which do not contribute to reading of a pixel signal. further characterized in that a function to be performed before the reading of one or more the pixel signal, the image pickup apparatus according to claim 1. The image pickup apparatus according to claim 2 , wherein the driving unit further has a function of performing the predetermined dummy shutter operation a plurality of times before reading the pixel signal. It said drive means is a front reading of this pixel signal, during the readout period of the previous pixel signal, characterized by further comprising a function of performing a plurality of times of on-off operation of the charge transfer gate, the imaging apparatus according to claim 2 or 3. The charge transfer gate drive voltage corresponding to the potential of the channel of the charge transfer gate that causes the potential gradient is configured to have a value higher than the reset voltage corresponding to the reference potential. The imaging device according to any one of 1 to 4 .