JP7025182B2 - Imaging device and its control method - Google Patents

Description

The present invention relates to an image pickup apparatus and a control method thereof.

Conventionally, in an image pickup device such as a digital camera, a technique of reducing the transmittance of the amount of shooting light for shooting in a very bright environment is known. This technique can be used, for example, when you want to open the aperture to achieve a subject with a shallow depth of field even in a bright environment, or when you use a long exposure without causing saturation (for example, a waterfall). ) Used when expressing the moving trajectory of the subject.

A technique for realizing the above technique by dimming with an optical filter such as an ND filter in order to reduce the transmittance of the amount of shooting light is known. Further, Patent Document 1 and Patent Document 2 disclose a technique for obtaining the same effect as an ND filter by utilizing a coloring / decoloring technique using an electrochromic (EC) material or the like.

Japanese Unexamined Patent Publication No. 6-301065 Japanese Patent No. 4384730

However, there are the following problems in the technique of utilizing the EC material as an ND filter by coloring and erasing the EC material by energization drive control as shown in Patent Document 1 and Patent Document 2. That is, in order to drive the energization of the EC layer in the EC material, it takes a predetermined static time to complete coloring and decoloring according to the reaction time of the redox reaction, and it is predetermined in response to instructions from the user or the camera. With delay time. This causes problems such as a delay in responding to a sudden change in brightness as an ND function.

The present invention has been made in view of the above problems, and is affected by the delay time until the change to the desired transmittance is completed when dimming using an optical element capable of changing the light transmittance. The purpose is to alleviate the problem and obtain a good dimming effect.

In order to achieve the above object, the image pickup apparatus of the present invention includes an optical element capable of changing the light transmittance, an image pickup element having a photoelectric conversion unit for converting light incident through the optical element into a charge, and an image pickup device. The driving means for driving the image pickup element so as to accumulate a part of the charge obtained by conversion by the photoelectric conversion unit at a predetermined storage time, and the case where the exposure amount is reduced to the target exposure amount. It has a control means for adjusting the exposure amount so as to obtain the target exposure amount by combining the control of the charge accumulation amount by the driving means and the control for changing the transmittance of the optical element.

According to the present invention, when dimming using an optical element capable of changing the transmittance of light, the influence of the delay time until the change to the desired transmittance is completed is mitigated, and a good dimming effect is obtained. Can be obtained.

The block diagram which shows the structure of the image pickup apparatus in embodiment of this invention. The circuit diagram of a part of the image pickup element in an embodiment. The timing chart of the drive control pulse of the image sensor in an embodiment. The figure which shows the potential state of the pixel corresponding to the drive control pulse of the image pickup device in embodiment. The timing chart which shows the detail of the drive control pulse φTX1A (i), φTX1A (i + 1) of the image pickup element in embodiment. It is sectional drawing schematically explaining the structure of the ECND filter in embodiment. The schematic diagram explaining the dimming adjustment method when "fastest" in an embodiment is set. The schematic diagram explaining the dimming adjustment method when "normal" in an embodiment is set. The schematic diagram explaining the dimming adjustment method when "low speed" in an embodiment is set.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the image pickup apparatus 100 according to the embodiment of the present invention. The photographing light flux passes through the photographing optical system 1 and is imaged on the image pickup element 3. Although the details will be described later, the image pickup device 3 has an exposure amount adjusting function, and the exposure amount can be adjusted by controlling the accumulation time and the accumulation number of times. In the following description, this exposure amount adjustment function is referred to as an "imager ND function". The exposure amount adjusting function in the image pickup device 3 is performed by the control of the image pickup device drive control unit 4.

An electrochromic (EC) ND filter 2, which is an optical element capable of changing the light transmittance, is disposed between the photographing optical system 1 and the image pickup element 3, and exposes the image pickup light beam incident on the image pickup element 3. The amount can be adjusted by color drive control of the incorporated EC material. The exposure amount adjustment control by the ECND filter will also be described later, but this is carried out by the ECND control unit 5. The image sensor drive control unit 4 that controls the exposure amount adjustment by the imager ND function of the image pickup element 3 and the ECND control unit 5 that controls the exposure amount adjustment by the ECND filter 2 constitute an ND control unit 9. The ND control unit 9 may be realized by a CPU (not shown) in the image pickup apparatus 100, or may be arranged as a part of a unit component of each ND function.

The image sensor drive control unit 4 has the detection result of the EC coloring detection unit 11 that detects the coloring state (light transmittance) of the EC material of the ECND filter 2 and the characteristics of the ECND filter stored in the storage unit 6 of the image pickup device 100. The imager ND function of the image sensor 3 is controlled based on the value. The shooting light flux formed on the image pickup element 3 is photoelectrically converted into an image signal, which is developed by the image processing unit 7 and then stored in the memory 8.

FIG. 2 is a circuit diagram of a part of the configuration of the image pickup device 3. The image sensor 3 is a CMOS type, and in FIG. 2, among the large number of pixels of the image sensor 3, the pixels in the first row and the first column (1,1) and the final row, the nth row and the first column (n, 1). Shows pixels. Since the pixels in the 1st row and 1st column (1,1) and the pixels in the nth row and 1st column (n, 1) have the same configuration, the components are given the same reference numbers.

As shown in FIG. 2, each pixel has a photodiode 50 (photoelectric conversion unit), a first transfer transistor 51A, a first signal holding unit 57A, and a second transfer transistor 52A. Further, it has a third transfer transistor 51B, a second signal holding unit 57B, and a fourth transfer transistor 52B. Further, it has a fifth transfer transistor 53, a floating diffusion region (FD) region 58, a reset transistor 54, an amplification transistor 55, and a selection transistor 56. The fifth transfer transistor 53 is connected to the power supply line 61, and the reset transistor 54 and the amplification transistor 55 are connected to the power supply line 60. Further, the amplification transistor 55 forms a source follower circuit with the constant current source 65 connected to the signal output line 63. The output circuit 30 outputs the signal appearing on the signal output line 63 of each row to the outside of the image pickup device 3.

The first transfer transistor 51A is controlled by the transfer pulse φTX1A, and the second transfer transistor 52A is controlled by the transfer pulse φTX2A. Further, the third transfer transistor 51B is controlled by the transfer pulse φTX1B, and the fourth transfer transistor 52B is controlled by the transfer pulse φTX2B. Further, the reset transistor 54 is controlled by the reset pulse φRES, and the selection transistor 56 is controlled by the selection pulse φSEL. Further, the fifth transfer transistor 53 is controlled by the transfer pulse φTX3. Each of the above-mentioned control pulses is transmitted from the vertical scanning circuit 20.

Since the image sensor 3 in the present embodiment has two first and second signal holding units 57A and 57B for one photodiode 50, for example, a still image and a moving image can be simultaneously captured. can. Although a detailed sequence will be described later, charges are transferred from the photodiode 50 to the first and second signal holding units 57A and 57B via the first and third transfer transistors 51A and 51B. At this time, the total accumulation time can be adjusted by adjusting the width of the transfer pulses of the first and third transfer transistors 51A and 51B and the number of transfer pulses. That is, although the details will be described later, in the present embodiment, a part of the charges converted by the photodiode 50 is transferred to the first and / or second signal holding units 57A and 57B by adjusting the total storage time. By accumulating, the imager diode function in the image sensor 3 is realized.

In the present embodiment, the image pickup device 3 has two first and second signal holding units 57A and 57B arranged, but one may be used.

Next, the imager ND function in the image pickup device 3 will be described with reference to FIGS. 3 and 4. FIG. 3 is a timing chart of a control signal of a transfer transistor and a control signal of a reset transistor when accumulating and reading using the imager ND function of the image sensor 3. FIG. 4 is a diagram showing the potential states of the pixels at a plurality of timings from immediately before the time t0 to the end of the accumulation time among the timings shown in FIG. Although the case where the first signal holding unit 57A is used will be described here, the same processing can be performed even when the second signal holding unit 57B is used. Hereinafter, the operation from the charge accumulation in the photodiode 50 to the reading of the accumulated charge will be described.

FIG. 3 shows changes in the transfer pulses φTX1A, φTX2A, φTX3 given to the control electrodes of the first, second, and fifth transfer transistors 51A, 52A, and 53, and the reset pulse φRES given to the control electrodes of the reset transistor 54. Shows. The subscripts i, i + 1, i + 2 represent the row numbers in the image pickup region of the image pickup device 3, and for example, φTX1A (i) means the pulse given to the first transfer transistor 51A of the pixel in the i-th row. There is. Although the control of the pixels for three rows is described in FIG. 3, the same control is performed in all the rows from the first row to the nth row.

First, in the initial state before the time t0, the transfer pulses φTX1A and φTX2A are at the low level, and the transfer pulses φTX3 and the reset pulse φRES are at the high level. The potential state of the pixel at this time is shown in FIG. 4A. During this period, there is a potential barrier formed by the first transfer transistor 51A between the photodiode 50 and the first signal holding portion 57A. On the other hand, there is no potential barrier for the fifth transfer transistor 53. Therefore, the electric charge (black circle in the figure) generated in the photodiode 50 does not move to the first signal holding unit 57A, but is passed through the fifth transfer transistor 53 to the overflow drain (OFD) which is a charge discharging region. It is discharged to. Here, the potential barrier formed in the first transfer transistor 51A is lower than the potential barrier formed in the second transfer transistor 52A (TX2A). The reason is that we are considering an example in which the transistor composed of the photodiode 50, the first transfer transistor 51A, and the first signal holding unit 57A is an embedded channel type.

In the period from time t0 to time t1, the transfer pulses φTX2A (i) to φTX2A (i + 2) are at a high level. As a result, the potential barrier formed in the second transfer transistor 52A between the first signal holding unit 57A and the FD region 58 is eliminated, and the electric charge held in the first signal holding unit 57A before time t0. Is transferred to the FD area 58. The potential state of the pixel in this period is shown in FIG. 4 (b). During this period, the transfer pulses φTX1A (i) to φTX1A (i + 2) are at a low level, and the transfer pulses φTX3 (i) to φTX3 (i + 2) are at a high level. Therefore, the electric charge generated by the photodiode 50 is discharged to the OFD via the fifth transfer transistor 53. Therefore, at this point in time, the charge generated by the photodiode 50 ideally does not exist in the first signal holding unit 57A. Further, since the reset pulse φRES is at a high level, the FD region 58 is reset to the reset level, and the transfer pulses φTX2A (i) to φTX2A (i + 2) are at a high level, so that the first signal holding unit 57A Is also reset.

When the transfer pulses φTX2A (i) to φTX2A (i + 2) become low level at time t1, the potential state of the pixel becomes as shown in FIG. 4 (c). This is the same as the state shown in FIG. 4 (a). Even in this period, the potential barrier formed in the first transfer transistor 51A exists, while the potential barrier does not exist in the fifth transfer transistor 53. Therefore, the electric charge generated by the photodiode 50 is discharged to the OFD via the fifth transfer transistor 53 (TX3) without moving to the first signal holding unit 57A.

Next, when the transfer pulses φTX3 (i) to φTX3 (i + 2) transition to the low level at time t3, the potential state of the pixel becomes as shown in FIG. 4 (d). At this time, the transfer pulses φTX2A (i) to φTX2A (i + 2) are also at a low level, but the potential barrier against the charge accumulated in the first signal holding unit 57A is the fifth transfer compared to the first transfer transistor 51A. Transistor 53 is higher. Therefore, the electric charge generated in the photodiode 50 exceeds the potential barrier of the photodiode 50 or the first transfer transistor 51A, and remains in the first transfer transistor 51A. Therefore, the accumulation time of each pixel is started from the timing when the transfer pulses φTX3 (i) to φTX3 (i + 2) transition to the low level at time t3.

When the transfer pulses φTX1A (i) to φTX1A (i + 2) reach a high level during the period from time t3 to time t4, the potential barrier formed in the first transfer transistor 51A disappears. As a result, the electric charge generated by the photodiode 50 is transferred to the first signal holding unit 57A (FIG. 4 (e)). After that, the period in which the transfer pulses φTX1A (i) to φTX1A (i + 2) become low level and the period in which the transfer pulse φTX1A (i + 2) becomes high level are repeated a plurality of times by time t5. From time t3 to time t5, the transfer pulses φTX3 (i) to φTX3 (i + 2) are driven so that the high level and the low level are opposite to those of the transfer pulses φTX1A (i) to φTX1A (i + 2). As a result, the electric charge generated in the photodiode 50 during the period other than the period when the transfer pulses φTX1A (i) to φTX1A (i + 2) are at the high level is discharged to the OFD via the fifth transfer transistor 53. .. The number of transfers from the photodiode 50 to the first signal holding unit 57A is not particularly limited.

By adopting such a driving method, the electric charge stored in the photodiode 50 can be periodically transferred to the first signal holding unit 57A. Further, in contrast to a normal image sensor, which continuously accumulates for a predetermined time, the image sensor 3 of the present embodiment has a plurality of accumulated times within a predetermined time and does not accumulate. Have time alternately. Utilizing this accumulation and non-accumulation time relationship, the image pickup element 3 is converted into a charge (that is, within the accumulation time) for a desired ratio of the amount of light photoelectrically converted during the accumulation time from t3 to t5. It is possible to disperse and acquire a part of the electric charge) in the time direction. Controlling the amount of charge accumulated by such driving is referred to as an imager ND function implemented by the image pickup device 3 in the present embodiment.

At time t5, instead of the transfer pulse φTX1A (i) to φTX1A (i + 2) transitioning to the low level, the transfer pulse φTX3 (i) to φTX3 (i + 2) becomes the high level, and the potential state of the pixel is shown in FIG. The state is as shown in (f). Since the electric charge generated in the photodiode 50 after the time t5 is discharged to the OFD via the fifth transfer transistor 53, the accumulation time of all the pixels ends at the time t5.

In this way, by transferring all the pixels from the photodiode 50 to the first signal holding unit 57A at the same time, the charge accumulation start time and end time of all the pixels can be adjusted, so that in-plane synchronous electronic shutter operation is realized. can.

Next, from time t6 to time t8, the transfer pulse φTX2A (i) of each line becomes high level at time t6 during the period when the reset pulse φRES1 (i) of each line becomes low level. As a result, the electric charge held by the first signal holding unit 57A of each pixel in the i-th row is transferred to the FD region 58 via the second transfer transistor 52A. At least at this timing, the selection transistor 56 is turned on, and the source follower circuit formed by the amplification transistor 55 and the constant current source 65 signals a signal at a level corresponding to the amount of charge transferred to the FD region 58. Appears on output line 63. The signal appearing on the signal output line 63 is output from the output circuit 30.

The same operation is performed for the pixels in the n + 1st row and the n + 2nd row, and a signal corresponding to the charge in each row is output from the output circuit. This completes the operation for one frame.

Although OFD is used as the charge discharge region in the present embodiment, the present invention is not limited to this. That is, the fifth transfer transistor 53 is connected to the FD region 58, and the second transfer transistor 52A discharges the electric charge from the first signal holding unit 57A to the power supply line 60 before transferring the charge to the FD region 58. It may be configured to be. Even with this method, a part of the electric charge photoelectrically converted by the photodiode 50 is discharged to the first signal holding unit 57A and a part of the electric charge is discharged through the FD region 58, so that the exposure amount adjustment operation becomes possible. ..

FIG. 5 is a timing chart showing the transfer pulses φTX1A (i) and φTX1A (i + 1) in the accumulation period from the time t3 to the time t5 in FIG. 3 in more detail. As described above, during this period, the transfer pulse φTX1A repeats the low level and the high level a plurality of times, and as a result, the imager ND function is realized, but this function may be further changed depending on the row. That is, the high-level pulse widths of the transfer pulse φTX1A that drives the first transfer transistor 51A on the i-th row and the i + 1-th row can be set differently from each other. This control can be performed by the image sensor drive control unit 4 changing the pulse control program in the vertical scanning circuit 20.

In FIG. 5, the pulse is set so that the total accumulation time in the i-th row is shorter than that in the i + 1-th row. This is as follows when the image pickup device 3 is an image pickup device having a so-called Bayer array color filter. Has an effect. For example, when the i-th row is an RG row having an RG color filter, the i + 1-th row is a GB row having a GB color filter. When a transfer pulse having a different pulse width as shown in FIG. 5 is applied to the entire surface of the image pickup device 3, an image output result in which the spectral transmittance of R is reduced with respect to B can be obtained. Further, by allocating the time for evenly transferring the electric charge to the first signal holding unit 57A within the accumulation time in this way, the accumulation blur in one frame is more natural than the simple accumulation time. Will be obtained.

FIG. 6 is a schematic cross-sectional view illustrating the configuration of the ECND filter 2. The ECND filter 2 is composed of a pair of electrodes 200 and 201, an EC material 202 existing between the electrodes, and a sealing material 203 for separating the EC material 202 from the outside. The pair of electrodes 200 and 201 are transparent electrodes and transmit the light wavelength to be photographed by the image pickup apparatus 100. For example, a known ITO electrode or the like can be used. The pair of electrodes 200 and 201 are joined by a sealing material 203 in an arrangement in which the electrode surfaces face each other. An EC material 202 is formed by EC molecules between the pair of electrodes 200 and 201. As the EC molecule, a known EC molecule such as the EC molecule described in Patent Document 1 and Patent Document 2 can be used. By applying a voltage between the pair of electrodes 200 and 201, a redox reaction occurs, and the light absorption rate of the EC molecule changes according to the characteristics of the EC molecule. The image pickup apparatus 100 performs the same exposure adjustment as the variable ND filter by changing the light transmittance by utilizing the change in the light transmittance due to the application of this voltage. The ECND filter 2 is arranged on the object side of the image pickup device 3 so that the electrodes 200 and 201 are substantially perpendicular to the photographing optical axis.

As described above, in the EC material 202 used for the ECND filter 2, a redox reaction occurs by applying a voltage to the EC molecule, and the light absorption rate of the EC molecule changes according to the characteristics of the EC molecule. I am taking advantage of that. Although it depends on the applied voltage, the environmental temperature, the composition of EC molecules, and the like, the reaction time of the redox reaction requires a predetermined time, which is the time that defines the static time as an ECND filter.

The image pickup device 100 performs dimming adjustment using the imager ND function of the image pickup element 3 and the ECND filter 2, but in the present embodiment, the user can set the time required for the dimming adjustment. .. For example, if the fastest dimming adjustment time that can be set is set, the image pickup device 100 switches instantly when the exposure amount is changed in a scene where the brightness of the main subject changes rapidly during movie shooting. Therefore, it is possible to alleviate the discomfort of the entire scene. In addition, if the longest dimming adjustment time that can be set is set, it is possible to change the exposure smoothly without any unnatural and sudden changes when the exposure is actively changed under constant brightness. It becomes. In the present embodiment, it is possible to set the dimming adjustment time in three stages of "fastest", "normal", and "low speed", and the operation will be described below with reference to FIGS. 7 to 9. However, the present invention is not limited to three stages, and may have an infinite number of stages and may be a function that the camera automatically selects instead of the user.

7 to 9 are schematic conceptual diagrams illustrating a dimming adjustment method carried out by the ND control unit 9 of the image pickup apparatus 100. In each case, the horizontal axis is the shooting frame and the vertical axis is the conceptual graph showing the dimming effect. Here, the dimming effect is a value indicating a state in which the higher the light transmittance, the lower the light transmittance. Although the expression "dimming effect" is used, it expresses the state of reduction of the exposure amount.

FIG. 7 shows the operation of the imager ND function and the ECND filter 2 when the ECND control unit 5 selects a moving image shooting mode that changes the dimming effect according to the dimming adjustment time set by the user. It is a thing. The dimming adjustment time can be arbitrarily set by the user by using a rear liquid crystal display unit (not shown) of the image pickup apparatus 100 as an interface. In FIG. 7, it is assumed that the ECND control unit 5 gives a change instruction for +3 steps as a dimming effect at a certain time _T0 of the frame 000. Further, it is assumed that the dimming adjustment time required for dimming adjustment to the target exposure amount is set to "fastest".

When the image pickup device 100 receives an instruction to change the dimming effect at time _T0 , the image sensor drive control unit 4 and the ECND control unit 5 increase the dimming effect with respect to the imager ND function and the ECND filter 2. _The instruction is given at time T1, which is the start time of frame 001. The dotted line graph in FIG. 7B shows the dimming effect of the ECND filter 2 controlled by the ECND control unit 5, and the solid line graph shows the dimming effect of the imager ND function controlled by the image sensor drive control unit 4. Show the effect. Further, the graph of the alternate long and short dash line in FIG. 7A shows the sum of the dimming effects of the ECND filter 2 and the imager ND function shown in FIG. 7B.

Here, in order to obtain the dimming effect for three stages of the ECND filter 2, the applied voltage is changed from the time T1, and in the frame 121 after 120 frames, which is the statically indeterminate time, the desired dimming effect for three stages is obtained. The growth is complete. Here, the time for 120 frames required to obtain the dimming effect for this +3 step corresponds to the statically indeterminate time of the ECND filter 2. On the other hand, in response to the luminance change detection result at time _T0 , the image sensor drive control unit 4 increases the dimming effect of the imager ND function on the frame 001 starting from time T1 by three steps.

Further, after the frame 002, the ECND filter 2 is controlled toward the target exposure amount, and the dimming effect corresponding to the amount of change from the previous frame of the dimming effect of the ECND filter 2 is reduced by the imager ND function. Control to reduce from the light effect. That is, the dimming effect of the imager ND function is changed so as to correspond to the change of the dimming effect by the ECND filter 2. As a result, the total sum of the dimming effects of the ECND filter 2 and the imager ND function is such that the effect of +3 steps is maintained. As described above, the imager ND function disperses and acquires the electric charge for a desired ratio of the light amount to be photoelectrically converted during the exposure time in one frame. That is, since the dimming effect of one frame is determined by the distributed acquisition in the time direction, the dimming effect of the imager ND function changes stepwise for each frame. In order to reduce the dimming effect of the imager ND function, in the case of the example shown in FIG. 3, the time and the number of times when the transfer pulses φTX1A (i) to φTX1A (i + 2) are at a high level are increased, and the transfer pulse φTX3 (I) Reduce the time and number of times that φTX3 (i + 2) is at a high level.

At the frame 121, the dimming effect of the ECND filter 2 reaches the target exposure amount of +3 steps, and the dimming effect of the imager ND function becomes the same as the initial state of _T0 . In response to the instruction to change the dimming effect at time _T0 , the dimming effect is exhibited by the imager ND function for _three steps at time T1, which is the start time of the next frame. The "fastest" dimming adjustment time is realized. As described above, in FIG. 7, both the imager ND function and the ECND filter 2 are controlled aiming at the dimming effect of +3 steps, which is the target exposure amount.

Similar to FIG. 7, FIG. 8 also shows the imager ND function and the ECND filter when the ECND control unit 5 selects a moving image shooting mode that changes the dimming effect according to the dimming adjustment time set by the user. It shows the operation of 2. Also in FIG. 8, it is assumed that the ECND control unit 5 gives a change instruction for +3 steps as a dimming effect at the time _T0 of the frame 000. Further, it is assumed that the dimming adjustment time required for dimming adjustment to the target exposure amount is set to "normal". The solid line and the dotted line in FIG. 8B show the dimming effect of the imager ND function controlled by the image sensor drive control unit 4 and the dimming effect of the ECND filter 2 controlled by the ECND control unit 5, respectively. The alternate long and short dash line in FIG. 8A shows the sum of the dimming effects of the ECND filter 2 and the imager ND function.

When the dimming adjustment time is set to "normal", as shown in FIG. 8, after frame 001, the imager ND function and the ECND filter 2 exhibit almost the same dimming effect, and the target exposure amount is +3. It is controlled in parallel aiming at the dimming effect of each step. Then, in frame 061 after 60 frames, the sum of the dimming effects of the imager ND function and the ECND filter 2 reaches the dimming effect of +3 steps of the target exposure amount. Then, after frame 062, the ECND control unit 5 continuously controls the ECND filter 2 until the dimming effect of +3 steps of the target exposure amount is obtained. On the other hand, the dimming effect corresponding to the amount of change from the frame before the dimming effect by the ECND filter 2 is controlled so as to be reduced from the dimming effect by the imager ND function. That is, the dimming effect of the imager ND function is changed so as to correspond to the change of the dimming effect of the ECND filter 2. When the dimming effect of the ECND filter 2 reaches the target exposure amount of +3 steps in the frame 121, the dimming effect of the imager ND function becomes the same as the initial state of _T0 . In the example shown in FIG. 8, a case where the imager ND function and the dimming effect of the ECND filter 2 are substantially the same until the target exposure amount is reached has been described, but the present invention is not limited to this, and each of them is not limited to this. It suffices to control so that the dimming effect of is gradually increased.

Similar to FIGS. 7 and 8, FIG. 9 also has an imager ND function when the ECND control unit 5 selects a moving image shooting mode in which the dimming effect is changed according to the dimming adjustment time set by the user. And the operation of the ECND filter 2. Also in FIG. 9, it is assumed that the ECND control unit 5 gives a change instruction for +3 steps as a dimming effect at the time _T0 of the frame 00. Further, it is assumed that the dimming adjustment time required for dimming adjustment to the target exposure amount is set to "low speed". The solid line and the dotted line in FIG. 9B show the dimming effect of the imager ND function controlled by the image sensor drive control unit 4 and the dimming effect of the ECND filter 2 controlled by the ECND control unit 5, respectively. .. The alternate long and short dash line in FIG. 8A shows the sum of the dimming effects of the ECND filter 2 and the imager ND function.

When the dimming adjustment time is set to "low speed", as shown in FIG. 9, after frame 001, the ECND filter 2 takes 180 frames longer than the statically indeterminate time, and the target exposure amount is applied to the frame 181. It reaches the dimming effect of +3 steps. In this case, the imager ND function is controlled to maintain the initial state, and the target exposure amount is achieved only by the ECND filter 2. That is, in FIG. 9, the period from frame 001 to frame 181 is controlled so that only the ECND filter 2 aims at the dimming effect of +3 steps, which is the target exposure amount. In the example shown in FIG. 9, the ECND filter 2 is controlled to reach the target exposure amount over 180 frames longer than the statically indeterminate time, but if the time is longer than the statically indeterminate time, the control is performed. Control can be done.

In the present embodiment, it has been described as the ECND filter 2 that the dimming effect is maintained after reaching the target exposure amount regardless of the setting of the dimming adjustment time. However, the present invention is not limited to this, and may mainly utilize the effect of the imager ND function. However, since the imager ND function is one frame of a moving image generated by distributing the exposure time in time, under the condition that the subject speed is extremely fast, the number of times of dispersion is within the width of the subject moving in the screen. The same edge image as is generated, and the quality of the moving image may be impaired. In such a case, the ECND filter 2 may be mainly used.

As described above, according to the present embodiment, by controlling the dimming effect by the imager ND function and the ECND filter 2, the dimming control can be performed at the speed (dimming adjustment time) desired by the user.

2: ECND filter, 3: image pickup element, 4: image pickup element drive control unit, 5: ECND control unit, 9: ND control unit, 11: EC coloring detection unit, 20: vertical scanning circuit, 50: photodiode, 51A: 1st transfer transistor, 51B: 3rd transfer transistor, 52A: 2nd transfer transistor, 52B: 4th transfer transistor, 53: 5th transfer transistor, 57A: 1st signal holder, 57B: 1st 2 signal holding unit, 58: floating diffusion region region, 100: imaging device

Claims (14)

Optical elements that can change the light transmittance,
An image sensor having a photoelectric conversion unit that converts light incident through the optical element into electric charges, and an image pickup device.
A driving means for driving the image pickup element so as to accumulate a part of the electric charge obtained by conversion by the photoelectric conversion unit at a predetermined storage time.
When the exposure amount is reduced to the target exposure amount, the exposure amount is adjusted so as to be the target exposure amount by combining the control of the charge accumulation amount by the driving means and the control of changing the transmittance of the optical element. An imaging device characterized by having a control means for performing an image. The control means is characterized in that while the transmittance of the optical element is lowered to a transmittance that achieves the target exposure amount, the amount of accumulated charge is controlled to adjust the transmission amount so as to reach the target exposure amount. The imaging device according to claim 1. The control means performs control for reducing the accumulated amount of electric charge and control for lowering the transmittance of the optical element in parallel, and after reaching the target exposure amount, the transmittance of the optical element. The claim is characterized in that the control of lowering the transmittance to achieve the target exposure amount is continued, and the control of increasing the charge accumulation amount while maintaining the target exposure amount is performed in parallel. Item 1. The image pickup apparatus according to Item 1. Optical elements that can change the light transmittance,
An image sensor having a photoelectric conversion unit that converts light incident through the optical element into electric charges, and an image pickup device.
A driving means for driving the image pickup element so as to accumulate a part of the electric charge obtained by conversion by the photoelectric conversion unit at a predetermined storage time.
When the exposure amount is reduced to the target exposure amount, the setting means for setting the speed until the target exposure amount is reached and the setting means.
Based on the speed set by the setting means, at least one of the control of the charge accumulation amount by the driving means and the control of changing the transmittance of the optical element so that the target exposure amount is obtained. An image pickup apparatus characterized by having a control means for adjusting an exposure amount. When the first speed is set by the setting means, the control means increases the amount of accumulated charge while lowering the transmittance of the optical element to a transmittance that achieves the target exposure amount. The image pickup apparatus according to claim 4, wherein the image pickup apparatus is controlled and adjusted so as to have the target exposure amount. The fourth aspect of the present invention is characterized in that, when the first speed is set by the setting means, the control means controls the accumulated amount of the electric charge to adjust the exposure amount to the target exposure amount. The imaging device described. When a second speed slower than the first speed is set by the setting means, the control means controls to reduce the accumulated amount of the charge and lowers the transmittance of the optical element. After reaching the target exposure amount, the control is continued to reduce the transmittance of the optical element to the transmittance that achieves the target exposure amount, and the target exposure amount is reduced. The image pickup apparatus according to claim 5 or 6, wherein the control for increasing the accumulated amount of the charge is performed in parallel while maintaining the control. When a second speed slower than the first speed is set by the setting means, the control means controls to reduce the accumulated amount of the electric charge and lowers the transmittance of the optical element. After reaching the target exposure amount, the control is continued to reduce the accumulated amount of the electric charge to the accumulated amount that achieves the target exposure amount, and the target exposure amount is maintained. However, the image pickup apparatus according to claim 5 or 6, wherein the control for increasing the transmittance of the optical element is performed in parallel. When a third speed slower than the second speed is set by the setting means, the control means reduces the transmittance of the optical element to a transmittance that achieves the target exposure amount. The image pickup apparatus according to claim 7 or 8. The image pickup device has a first transfer means for transferring the electric charge converted by the photoelectric conversion unit to the signal holding means, and a second transfer means for discharging the electric charge converted by the photoelectric conversion unit. death,
The driving means alternately transfers the charge to the signal holding means by the first transfer means and discharges the charge by the second transfer means at the predetermined storage time, so that the charge can be charged. The imaging device according to any one of claims 1 to 9, wherein the storage amount is controlled. Further having a detecting means for detecting the transmittance of the optical element,
The imaging device according to any one of claims 1 to 10, wherein the driving means controls the amount of accumulated charges based on the detected transmittance. The image pickup apparatus according to any one of claims 1 to 10, wherein the optical element is an electrochromic (EC) ND filter. An optical element capable of changing the light transmittance, an image sensor having a photoelectric conversion unit that converts light incident through the optical element into electric charges, and a predetermined storage time are converted by the photoelectric conversion unit. A control method for an image pickup device having a drive means for driving the image pickup element so as to accumulate a part of the obtained electric charge.
When the control means reduces the exposure amount to the target exposure amount, the control of the charge accumulation amount by the driving means and the control of changing the transmittance of the optical element are combined so as to obtain the target exposure amount. A control method for an image pickup device, which comprises adjusting an exposure amount. An optical element capable of changing the light transmittance, an image sensor having a photoelectric conversion unit that converts light incident through the optical element into electric charges, and a predetermined storage time are converted by the photoelectric conversion unit. A control method for an image pickup device having a drive means for driving the image pickup element so as to accumulate a part of the obtained electric charge.
When the setting means reduces the exposure amount to the target exposure amount, the setting step of setting the speed until the target exposure amount is reached, and
The control means controls the amount of charge accumulated by the driving means based on the speed set by the setting step, and controls for changing the transmittance of the optical element, thereby controlling the target exposure amount. A control method for an image pickup apparatus, which comprises a control step for adjusting an exposure amount so as to be.

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