JP2009055540A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of suppressing a dynamic range of the apparatus from becoming narrow even in the case that luminance is so high that pixels are saturated. <P>SOLUTION: The imaging apparatus includes: a plurality of pixels 7; an increase unit 10 for increasing electric charges to be accumulated in the pixels 7; and an exposure time change unit 9 for changing an exposure time of the pixels 7, and is configured so that sensitivity of the apparatus is varied by switching control of the number of times of increasing electric charges to be accumulated in the pixels 7 and control of the exposure time of the pixels 7 for the unit of a pixel group constituted of one or more pixels, in accordance with luminance of light incident to the pixels 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device, and more particularly to an imaging device whose sensitivity can be changed according to the luminance of light incident on a pixel.

  2. Description of the Related Art Conventionally, there has been known an imaging device whose sensitivity can be changed according to the luminance of light incident on a pixel (see, for example, Patent Document 1).

  Patent Document 1 discloses a CCD (Charge Coupled Device) image sensor (imaging device) that includes a plurality of gate electrodes and in which charges are increased by impact ionization in a high electric field region formed under the gate electrodes. ing. In this CCD image sensor, it is possible to increase the sensitivity of the CCD image sensor by adjusting the strength of the electric field in the high electric field region of the immediately following frame so as to be proportional to the luminance of the immediately preceding frame.

Japanese Patent No. 3484261

  However, in the imaging device described in Patent Document 1, when the luminance of light incident on a pixel is low, sensitivity can be adjusted by an operation of increasing charge due to impact ionization, while the pixel is saturated. If the brightness is high, the sensitivity cannot be adjusted. For this reason, there exists a problem that the dynamic range of an imaging device becomes narrow.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to reduce the dynamic range of the apparatus even when the luminance is so high that the pixels are saturated. It is providing the imaging device which can suppress this.

  An imaging apparatus according to an aspect of the present invention includes a plurality of pixels, an increase unit that increases charges accumulated in the pixels, and an exposure time change unit that changes the exposure time of the pixels, and is configured to detect light incident on the pixels. In accordance with the luminance, the control is performed to switch between the control of the number of times of increasing the charge accumulated in the pixel and the control of the exposure time of the pixel in units of one or more pixel groups.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram of a CMOS type imaging apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating an imaging device including a plurality of pixels of the imaging device according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the control of the pixel increase operation of the imaging apparatus according to the first embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration of a pixel of the imaging device according to the first embodiment of the present invention. The configuration of the imaging apparatus according to the first embodiment will be described with reference to FIGS.

  As shown in FIG. 1, the CMOS type imaging device according to the first embodiment includes a lens 1, an imaging device 2 including a charge increasing unit 9 described later, and a CDS (Correlated Double Sampling for reducing noise): (Correlated double sampling) and an analog processing unit 3 including an automatic gain control (AGC) for automatically controlling an amplification factor, an A / D conversion unit 4, a digital processing circuit unit 5, and an increase count holding memory 6 Has been.

  The image sensor 2 is connected to the analog processing unit 3, and the analog processing unit 3 is connected to the A / D conversion unit 4. The A / D conversion unit 4 is connected to a digital processing circuit unit 5, and the digital processing circuit unit 5 is connected to an increase count holding memory 6. Further, the digital processing circuit unit 5 is configured to control the number of times of increase in the charge in the image pickup device 2 based on the number of times of increase held in the increase number of times holding memory 6 and to control the exposure time of the pixel 7 described later. Has been.

  In addition, as shown in FIG. 2, the image pickup device 2 includes a plurality of pixels 7 arranged in a matrix. In the first embodiment, a case where the number of increases is controlled for each pixel 7 will be described. Further, instead of controlling the number of increases for each pixel 7, the number of increases may be controlled for each pixel group of two or more pixels.

  Further, as shown in FIG. 3, each pixel 7 has a photoelectric conversion function and a photodiode (PD) 8 for accumulating charges generated by the photoelectric conversion, and exposure for controlling the exposure time of the pixel 7. A time changing unit 9, a charge increasing unit 10, and a floating diffusion (FD) amplifier 11 are included. The photodiode 8 is an example of the “storage unit” in the present invention. The photodiode 8 is connected to the exposure time changing unit 9, and the exposure time changing unit 9 is connected to the increasing unit 10. The increasing unit 10 is connected to the FD amplifier 11. The digital processing circuit unit 5 connected to the FD amplifier 11 includes a signal processing circuit 5a and an exposure time / increase number switching control circuit 5b. The signal processing circuit 5a and exposure time / increase number switching control are included. The exposure time changing unit 9 and the increasing unit 10 of each pixel 7 are independently controlled by the circuit 5b. FIG. 3 shows only two pixels 7 among the plurality of pixels 7 arranged in a matrix.

  As shown in FIG. 4, the pixel 7 includes a photodiode 8, transfer gate electrodes 12 to 15 provided so as to be adjacent to the photodiode 8, read gate electrodes 16 and 17, and a gate to the read gate electrode 17. Are connected to each other, and a selection transistor 18 connected to one of the source / drain of the FD amplifier 11. Here, in the first embodiment, the transfer gate electrode 12 is included in the exposure time changing unit 9 and is configured to have a function of controlling the exposure time of the pixel 7. The transfer gate electrode 12 is an example of the “second transfer gate electrode” in the present invention. Further, the charge increasing operation is performed under the transfer gate electrodes 13 to 15. Here, in the first embodiment, the read gate electrode 16 controls the output in the column direction of the pixels 7 arranged in a matrix, and the read gate electrode 17 controls the output in the row direction. ing. The read gate electrodes 16 and 17 are examples of the “second read gate electrode” and the “first read gate electrode” in the present invention, respectively. Further, the read gate electrode 16 may control the output in the row direction of the pixel 7 and the read gate electrode 17 may control the output in the column direction.

  FIG. 5 is a flowchart showing a control flow of the operation of the imaging apparatus according to the first embodiment of the present invention. FIG. 6 is a flowchart showing a control flow of pixel selection of the imaging apparatus according to the first embodiment of the present invention. FIG. 7 is a diagram illustrating the relationship between the brightness (luminance) of light incident on a pixel, the luminance value after the charge increasing operation, and the luminance value after exposure time control. With reference to FIGS. 5 to 7, the operation of the imaging apparatus according to the first embodiment of the present invention will be described. In the operation of the imaging apparatus, the number of times of the charge increasing operation is controlled based on the image information of the immediately preceding frame, and is different for each pixel 7. Here, a case will be described in which the number of increase operations is set to 0, 100, and 1000 for each pixel 7 based on the image information of the immediately preceding frame. Further, as an example, a case where the number of pixels of the frame is composed of 25 pixels of 5 × 5 will be described.

  First, as shown in FIG. 5, in step S1, the pixel 7 is exposed for a short time. As shown in FIG. 7, this short-time exposure causes the pixel 7 to be saturated when the luminance of light incident on the pixel 7 is so high that the pixel 7 is saturated during the normal exposure time. This is done to prevent this from happening. Next, in step S2, short-time exposure is terminated. As a result, charges are accumulated in the photodiode 8. Next, in step S3, the electric charge accumulated in the photodiode 8 is accumulated under the transfer gate electrode 15 via the transfer gate electrodes 12-14.

  Next, in step S <b> 4, a predetermined pixel 7 (pixel 7 whose luminance is high and saturated) is selected, and the charge accumulated under the transfer gate electrode 15 is transferred to the FD amplifier 11. Specifically, as shown in FIG. 6, in step S41, the pixel 7 in the 0th row is first selected, and in step S42, the read gate electrode 17 is turned on. Next, in step S43, the pixels 7 in the 0th column to the 4th column are sequentially selected. Next, in step S <b> 44, in the pixel 7 having high luminance such that the pixel 7 is saturated, the readout gate electrode 16 is turned on, and the charge accumulated in the pixel 7 is transferred to the FD amplifier 11. Next, in step S45, the read gate electrode 17 is turned off. Similarly, by sequentially performing the row selection operation in step S41 from the first row to the fourth row, the electric charge accumulated in the pixel 7 having high luminance that saturates the pixel 7 is transferred to the FD amplifier 11.

  Next, as shown in FIG. 5, in step S5, the selection transistor 18 (see FIG. 4) is turned on, so that a signal is output from the FD amplifier 11 of the pixel 7 having high luminance so that the pixel 7 is saturated. Is done.

  Next, in step S6, additional exposure of the pixel 7 is performed. Thereby, the pixel 7 is exposed for the normal exposure time. Next, in step S7, the electric charge accumulated in the photodiode 8 is accumulated under the transfer gate electrode 15 via the transfer gate electrodes 12-14. Here, the charge transferred in step S3 and the charge transferred in step S7 are added.

  Next, in step S8, as in step S4, a predetermined pixel 7 (pixel 7 having high luminance) is selected, and the charge accumulated under the transfer gate electrode 15 is transferred to the FD amplifier 11. Thereafter, in step S9, the selection transistor 18 (see FIG. 4) is turned on to output a signal from the FD amplifier 11 of the pixel 7 having high luminance.

  Next, in step S10, a charge increasing operation is performed between the transfer gate electrodes 13-15. More specifically, the charge accumulation well formed under the transfer gate electrode 13 through the charge accumulated in the temporary accumulation well formed under the transfer gate electrode 15 over the charge transfer barrier formed under the transfer gate electrode 14. In the high electric field region formed at the interface between the transfer gate electrode 13 and the transfer gate electrode 14, the charge is increased by impact ionization. Here, the first embodiment is configured such that a high electric field region is formed by applying a high voltage to the transfer gate electrode 13. The high electric field region formed at the interface between the transfer gate electrode 13 and the transfer gate electrode 14 is an example of the “increasing portion” in the present invention. The transfer gate electrode 13 is an example of the “first transfer gate electrode” in the present invention. Further, by further moving the charge between the temporary accumulation well and the charge accumulation well, a further charge increasing operation is performed. Here, the charge increasing operation is performed 100 times. This charge increasing operation is performed for all the pixels 7 of the image sensor 2 (see FIG. 2), but the luminance is high enough to saturate the pixel 7 or not so much that the pixel 7 is saturated. Since signals are output in steps S5 and S9 for the pixels 7 with high luminance, even if an operation for increasing the charge is performed in the pixels 7 with high luminance, the image is not affected.

  Next, in step S <b> 11, as in step S <b> 8, the charges of the pixels 7 (pixels 7 having a medium luminance) in a predetermined region of the image sensor 2 are transferred to the FD amplifier 11. Thereafter, in step S12, a signal of the pixel 7 having a medium luminance is output.

  Next, in step S13, as in step S10, a charge increasing operation is performed between the transfer gate electrodes 13-15. Here, the charge increasing operation is performed 900 times. As a result, the increase operation is performed 1000 times in total, together with the charge increase operation in step S10. The charge increasing operation is performed for all the pixels 7 of the image sensor 2 as in step S10.

  Next, in step S <b> 14, as in steps S <b> 4, S <b> 8, and S <b> 11, the charge of the pixel 7 (pixel 7 with low luminance) in a predetermined region of the image sensor 2 is transferred to the FD amplifier 11. Thereafter, in step S15, a signal of the pixel 7 having a low luminance is output.

  Next, digital composition of images will be described with reference to FIG.

  As shown in FIG. 7, when the light incident on the pixel 7 is so bright that the pixel 7 is saturated, the exposure time of the pixel 7 is controlled to be shorter than the normal exposure time. In addition, when the light incident on the pixel 7 is not so light that the pixel 7 is saturated but bright (high luminance), the charge increasing operation is not performed (0 increasing operation). In this case, the luminance of the light incident on the pixel 7 becomes the luminance value of the pixel 7 output. When the light incident on the pixel 7 is medium (medium luminance), the charge increasing operation is performed 100 times, and the luminance of the increased charge becomes the luminance value of the output of the pixel 7. When the light incident on the pixel 7 is dark (low luminance), the charge increasing operation is performed 1000 times, and the luminance of the increased charge becomes the luminance value of the output of the pixel 7. The image is digitally synthesized with reference to the luminance values output from all the pixels 7 and the number of increase operations. As described above, in the first embodiment, when the light incident on the pixel 7 has a high luminance or higher, the sensitivity is adjusted by controlling the exposure time of the pixel 7, and the light incident on the pixel 7 has a medium luminance or lower. In this case, the exposure time control and the charge increase frequency control are switched so that the sensitivity is adjusted by controlling the charge increase frequency.

  FIG. 8 is a flowchart showing a control flow of sensitivity of the imaging apparatus according to the first embodiment of the present invention. The sensitivity control operation according to the first embodiment of the present invention will be described with reference to FIG. Here, a case where sensitivity control is performed independently for each pixel 7 in the plurality of pixels 7 included in the imaging device 2 will be described.

As shown in FIG. 8, in step S <b> 51, information is acquired as to whether the predetermined pixel 7 in the immediately preceding frame is exposure time control or charge increase frequency control. In addition, information on the exposure time (T _i-1 ), the number of increases (N _i-1 ), and the luminance value (B _i-1 ) is acquired. Next, in step S52, if the immediately preceding frame is the increase count control, the process proceeds to step S53. Here, it is determined whether the luminance value (B _i−1 ) of the predetermined pixel 7 in the immediately preceding frame is higher or lower than the saturation value level of the pixel 7. Note that the saturation level means the maximum level at which linear characteristics can be obtained in the relationship between the brightness of the light incident on the pixel 7 and the luminance value. Note that a luminance value other than the saturation value level may be used as the determination level. When the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher than the saturation value level of the pixel 7, the process proceeds to step S54, and the number of increase operations of the predetermined pixel 7 in the immediately preceding frame It is determined whether (N _i-1 ) is zero. When the increase number (N _i-1 ) is 0, the process proceeds to step S55, and the charge increase number control is switched to the exposure time control. Also, if the number of increase operation (N _i-1) is not zero, the process proceeds to step S56, the number of increased operation of a given pixel 7 of the current frame (N _i) is the number of increased operation (N _{i −1} ) is set to a value obtained by subtracting a certain number of times (β).

If the luminance value (B _i−1 ) of the immediately preceding frame is lower than the saturation value level of the pixel 7 in step S53, the process proceeds to step S57. Here, it is determined whether the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher or lower than the lowest luminance value level of the pixel 7. The lowest luminance value level means the lowest level at which a predetermined accuracy of the imaging device can be obtained in the relationship between the brightness of light incident on the pixel 7 and the luminance value. Note that a luminance value other than the lowest luminance value level may be used as the determination level. When the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is lower than the lowest luminance value level of the pixel 7, the process proceeds to step S58 and the number of times of increase operation of the predetermined pixel 7 in the current frame ( N _i ) is set to a value obtained by adding a certain number of times (β) to the number of increase operations (N _i−1 ) of the predetermined pixel 7 in the immediately preceding frame. When the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher than the lowest luminance value level of the pixel 7, the process proceeds to step S59 and the increase operation of the predetermined pixel 7 in the current frame is performed. The number of times (N _i ) is set to the same number as the number of times (N _i−1 ) of increasing operations of the predetermined pixel 7 in the immediately preceding frame.

In step S52, if the immediately preceding frame is exposure time control, the process proceeds to step S60. Here, it is determined whether the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher or lower than the saturation value level of the pixel 7. When the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher than the saturation value level of the pixel 7, the process proceeds to step S61 and the exposure time (T _i ) of the predetermined pixel 7 in the current frame. Is set to a value obtained by subtracting a certain time (α) from the exposure time (T _i-1 ) of the predetermined pixel 7 in the immediately preceding frame. If the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is lower than the saturation value level of the pixel 7, the process proceeds to step S62. Here, it is determined whether the luminance value (B _i−1 ) of the predetermined pixel 7 in the immediately preceding frame is higher or lower than the lowest luminance value level of the pixel 7. When the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is lower than the lowest luminance value level of the pixel 7, the process proceeds to step S63 and the exposure time (T _i) of the predetermined pixel 7 in the immediately preceding frame. _It is determined whether ₋₁ ) is equal to the preset longest exposure time. If the exposure time (T _i-1 ) is equal to the longest exposure time, the process proceeds to step S64, and the exposure time control is switched to the charge increase frequency control. If the exposure time (T _i-1 ) is not equal to the longest exposure time, the process proceeds to step S65, and the exposure time (T _i ) of the predetermined pixel 7 of the current frame is the predetermined pixel 7 of the previous frame. Is set to a value obtained by adding only a certain time (α) in the exposure time (T _i-1 ).

In step S62, if the luminance value (B _i-1 ) of the predetermined pixel 7 in the immediately preceding frame is higher than the minimum luminance value level of the pixel 7, the process proceeds to step S66 and the predetermined pixel 7 of the current frame. the exposure time (T _i) is such that: is set to be equal to the exposure time of a given pixel 7 of the immediately preceding frame (T _i-1).

  Note that the control of the number of times the charge is increased may be performed for each area of the image sensor 2 or may be performed in units of frames. In addition, the control of the increase in the number of charges may be performed in parallel for all the pixels 7 or sequentially for each pixel 7.

  In the first embodiment, as described above, in accordance with the luminance of light incident on the pixel 7, the number of operations for increasing the charge accumulated in the pixel 7 and the exposure time of the pixel 7 are controlled in units of pixels. By changing the sensitivity of the apparatus by switching between the two, if the luminance is high such that the pixel 7 is saturated in an image of one frame, the pixel 7 is saturated by shortening the exposure time. In addition, when the luminance is low, an increase operation of the charge can be performed by the increase unit 10, so that the dynamic range of the imaging device can be suppressed from being narrowed.

  In the first embodiment, as described above, when the luminance of the light incident on the pixel 7 is lower than a predetermined value, the sensitivity is adjusted by controlling the number of times that the increase unit 10 increases the charge, and the pixel When the brightness of the light incident on 7 is higher than a predetermined value, the sensitivity is easily adjusted by controlling the exposure time of the pixel 7 by the exposure time changing unit 9. An optimal image can be obtained by controlling the exposure time, and an optimal image can be obtained by controlling the exposure time even when the luminance is high such that the pixel 7 is saturated.

  In the first embodiment, as described above, the pixel 7 includes the transfer gate electrode 13 that transfers a charge and applies a voltage for increasing the charge, thereby easily transferring the charge. , Can increase the charge.

  In the first embodiment, as described above, the pixel 7 is formed so as to be adjacent to the photodiode 8, has a function of transferring charges, and includes the transfer gate electrode 12 included in the exposure time changing unit 9. In addition, the exposure time of the pixel 7 can be easily controlled by controlling the on / off timing of the transfer gate electrode 12 by controlling the exposure time of the pixel 7 by the transfer gate electrode 12. Can do.

(Second Embodiment)
FIG. 9 is a block diagram of the control of the pixel increase unit of the imaging apparatus according to the second embodiment of the present invention. With reference to FIG. 9, in the second embodiment, unlike the first embodiment, a configuration of an imaging device that controls the number of charge increasing operations in units of frames will be described.

  As shown in FIG. 9, the pixel 7 a of the imaging device according to the second embodiment includes a photodiode 8, an exposure time changing unit 9 that controls the exposure time of the pixel 7 a, a charge increasing unit 10, and an FD amplifier 11. It is. Further, the digital processing circuit unit 5 includes a signal processing circuit 5a and an exposure time / increase count switching control circuit 5b. The image sensor 2 includes the signal processing circuit 5a and the exposure time / increase count switching control circuit 5b. The exposure time changing unit 9 and the increasing unit 10 of all the pixels 7a included in the configuration are configured to receive the same control. FIG. 9 shows only two pixels 7a among the plurality of pixels 7a arranged in a matrix.

  In addition, the other structure of 2nd Embodiment is the same as that of the said 1st Embodiment.

  FIG. 10 is a flowchart showing a control flow of the imaging apparatus according to the second embodiment of the present invention. With reference to FIG. 10, the operation of the imaging apparatus according to the second embodiment of the present invention will be described.

  As shown in FIG. 10, in step S71, a switching control algorithm (see FIG. 8) is performed. Here, the switching control algorithm is performed in units of frames based on the image information of the immediately preceding frame. Next, in step S72, the photodiode 8 (see FIG. 9) is exposed based on the exposure time determined in step S71. Next, in step S73, a charge increasing operation is performed based on the number of increases determined in step S71. Thereafter, in step S74, charges are transferred to the FD amplifier 11 (see FIG. 9).

  In the second embodiment, as described above, according to the luminance of the light incident on the pixel 7a, the number of operations for increasing the charge accumulated in the pixel 7a and the exposure time of the pixel 7a are controlled in units of frames. If the brightness of the pixel 7a is saturated by changing the sensitivity of the apparatus by switching the pixel, the pixel 7a is suppressed from being saturated by shortening the exposure time, and the brightness is reduced. If it is low, an increase operation of the charge can be performed by the increase unit 10a, so that the dynamic range of the imaging device can be suppressed from being narrowed.

(Third embodiment)
FIG. 11 is a block diagram of the control of the pixel increase unit of the imaging apparatus according to the third embodiment of the present invention. Referring to FIG. 11, in the third embodiment, unlike the second embodiment, the configuration of a CCD type imaging device will be described.

  In the CCD type image pickup apparatus according to the third embodiment, as shown in FIG. 11, the pixel 7b includes a photodiode 8a and an exposure time changing unit 9a, and a plurality of photodiodes 8a includes the pixel 7b. It is connected to the increase part 10a provided outside. The photodiode 8a is an example of the “storage unit” in the present invention. The increasing unit 10a is connected to the amplifier 19, and the amplifier 19 is connected to the signal processing circuit 5a. An exposure time / increase count switching control circuit 5b is connected to the signal processing circuit 5a, the exposure time changing unit 9a, and the increasing unit 10a. FIG. 11 shows only two pixels 7b among the plurality of pixels 7b arranged in a matrix. Further, in the CCD type imaging device, similarly to the second embodiment, the exposure time of the pixel 7b and the number of times of the charge increasing operation are controlled in units of frames based on the information of the immediately preceding frame. Has been.

  Other configurations and operations of the third embodiment are the same as those of the second embodiment.

  The effects of the third embodiment are the same as those of the second embodiment.

(Fourth embodiment)
FIG. 12 is a flowchart showing a control flow of the imaging apparatus according to the fourth embodiment of the present invention. Referring to FIG. 12, in the fourth embodiment, unlike the first embodiment, after charges accumulated in all the pixels 7 are transferred to the FD amplifier 11, the charges in all the pixels 7 are simultaneously transferred. A configuration of the imaging device to be read will be described.

  The configuration of the pixel 7 of the imaging device according to the fourth embodiment is the same as that of the first embodiment shown in FIG.

  Next, with reference to FIG. 12, an operation of the imaging apparatus according to the fourth embodiment of the present invention will be described.

  First, as shown in FIG. 4, in step S81, the pixel 7 is exposed for a short time. Similar to the first embodiment, this short-time exposure causes the pixel 7 to be saturated when the luminance of the light incident on the pixel 7 is so high that the pixel 7 is saturated during the normal exposure time. This is to suppress this. Next, in step S82, the short-time exposure is terminated. As a result, charges are accumulated in the photodiode 8. Next, in step S83, the charge accumulated in the photodiode 8 is accumulated under the transfer gate electrode 15 via the transfer gate electrodes 12-14.

  Next, in step S <b> 84, a predetermined pixel 7 (pixel 7 whose luminance is high and saturated) is selected, and the charge accumulated under the transfer gate electrode 15 is transferred to the FD amplifier 11. Specifically, this is the same as the first embodiment shown in FIG.

  Next, in step S85, additional exposure of the pixel 7 is performed. Thereby, the pixel 7 is exposed for the normal exposure time. Next, in step S86, the electric charge accumulated in the photodiode 8 is accumulated under the transfer gate electrode 15 via the transfer gate electrodes 12-14. Here, the charge transferred in step S83 and the charge transferred in step S86 are added.

  Next, in step S87, as in step S84, a predetermined pixel 7 (pixel 7 having high luminance) is selected, and the charge accumulated under the transfer gate electrode 15 is transferred to the FD amplifier 11.

  Next, in step S88, a charge increasing operation is performed between the transfer gate electrodes 13-15. The specific operation is the same as that in the first embodiment. Here, the charge increasing operation is performed 100 times. This charge increasing operation is performed for all the pixels 7 of the image sensor 2. However, for the pixels 7 with high luminance, the signal is transferred to the FD amplifier 11 in steps S84 and S87, so that the luminance is high. Even if the charge increasing operation is performed in the pixel 7, the image is not affected.

  Next, in step S89, as in step S87, the charges of the pixels 7 (pixels 7 having a medium luminance) in the predetermined area of the image sensor 2 are transferred to the FD amplifier 11.

  Next, in step S90, the charge increasing operation is performed between the transfer gate electrodes 13 to 15 as in step S88. Here, the charge increasing operation is performed 900 times. As a result, the increase operation is performed 1000 times in total, together with the charge increase operation in step S88. This charge increasing operation is performed for all the pixels 7 of the image sensor 2 as in step S88. Thereafter, in step S91, charges are transferred to the FD amplifier 11 as in steps S84, S87, and S89.

  Next, in step S92, signals of charges accumulated in the FD amplifiers 11 of all the pixels 7 are output simultaneously. This makes it possible to output a signal in one operation, unlike the case where the pixel 7 is saturated, high luminance, medium luminance, and low luminance. 2 can be performed at high speed.

  In addition, the other structure of 4th Embodiment is the same as that of the said 1st Embodiment.

  The effect of the fourth embodiment is the same as that of the first embodiment.

(Fifth embodiment)
FIG. 13 is a block diagram illustrating pixel control of the imaging apparatus according to the fifth embodiment of the present invention. FIG. 14 is a circuit diagram showing a configuration of a pixel of the imaging apparatus according to the fifth embodiment of the present invention. With reference to FIGS. 13 and 14, in the fifth embodiment, unlike the first embodiment, a configuration of an imaging device in which an increase operation and exposure time control are performed in the pixel 7 c will be described.

  In the pixel 7c according to the fifth embodiment, as shown in FIG. 13, a photodiode 8, an exposure time changing unit 9, a charge increasing unit 10, an FD amplifier 11, a non-destructive amplifier (floating gate amplifier: FG amplifier) 20 and an in-pixel control circuit 21 are included. The photodiode 8 is connected to the exposure time changing unit 9, the exposure time changing unit 9 is connected to the increasing unit 10, and the increasing unit 10 is connected to the FD amplifier 11. The nondestructive amplifier 20 is connected to the increase unit 10 and the FD amplifier 11. In the FD amplifier 11, after the signal is detected, the signal charge is reset and the signal charge cannot be reused. However, the nondestructive amplifier 20 detects the signal while holding the signal charge. Is possible. The intra-pixel control circuit 21 is connected to the increasing unit 10 and the nondestructive amplifier 20. Further, a signal processing circuit 5 a is provided outside the pixel 7 c, and the signal processing circuit 5 a is connected to the FD amplifier 11 and the in-pixel control circuit 21. Here, in the fifth embodiment, the in-pixel control circuit 21 is configured to control the number of times of increasing the charge and the exposure time of each pixel 7c.

  As illustrated in FIG. 14, the pixel 7 c includes a gate unit 22, an amplifier unit 23, a comparison unit 24, and an increase drive control unit 25. The gate portion 22 includes a photodiode 8, transfer gate electrodes 12 to 15 provided so as to be adjacent to the photodiode 8, and a read gate electrode 17. The photodiode 8 is an example of the “storage unit” in the present invention. In addition, the charge increasing operation is performed below the transfer gate electrodes 13 to 15 during the charge increasing operation.

  The amplifier unit 23 includes the FD amplifier 11 and the selection transistor 18. The FD amplifier 11 is connected to the read gate electrode 17 of the gate unit 22 and to the selection transistor 18. Further, the signal is configured to be output via the selection transistor 18.

The comparison unit 24 includes a nondestructive amplifier 20, and the nondestructive amplifier 20 is connected between the transfer gate electrode 15 and the read gate electrode 17. In addition, the non-destructive amplifier 20 is configured to control the increase operation of the charge by comparing the charge accumulated in the pixel 7c with a predetermined voltage threshold (V _th ).

Further, the increase drive control unit 25 includes a logic circuit that selects whether or not to apply the increase register drive signal based on the output of the comparison unit 24. For example, it is composed of two AND circuits 26a and 26b shown in FIG. Each of the AND circuits 26a and 26b is configured to receive a signal comparing the electric charge accumulated in the pixel 7c with a threshold value (V _th ).

The gate of the transfer gate electrode 12 is connected to the output of a logic circuit that selects whether to apply an exposure register drive signal based on the output of the comparison unit 24. For example, it is configured by an AND circuit 27 shown in FIG. The AND circuit 27 is configured to receive an exposure register drive signal and a signal obtained by comparing the charge accumulated in the pixel 7c with a threshold value (V _th ). The exposure time of the photodiode 8 is controlled by turning on / off.

In addition, a memory 28 is provided outside the pixel 7c, and the number of times of increase control and exposure time control until the charge accumulated in the pixel 7c exceeds a threshold value (V _th ) is stored.

  The remaining configuration of the fifth embodiment is similar to that of the aforementioned first embodiment.

  FIG. 15 is a flowchart showing a pixel control flow of the imaging apparatus according to the fifth embodiment of the present invention. FIG. 16 is a flowchart showing a control flow of the exposure time of the imaging apparatus according to the fifth embodiment of the present invention. FIG. 17 is a flowchart showing a control flow of the number of times of increase in charge of the imaging apparatus according to the fifth embodiment of the present invention. The operation of the pixel 7c according to the fifth embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 15, in step S101, after the charge accumulated in the photodiode 8 is reset, the pixel 7c is exposed for a short time. As a result, charges are accumulated in the photodiode 8. Next, in step S102, control signals for exposure time control and increase frequency control are turned on. Next, in step S103, input of an exposure register drive signal for controlling exposure to the transfer gate electrode 12 (see FIG. 14) is started.

Next, in step S104, the exposure time is controlled. Specifically, as shown in FIG. 16, the exposure time is added for t seconds in step S121. Next, in step S122, the charge signal stored in the photodiode 8 and transferred to the non-destructive amplifier 20 is compared with the threshold value (V _th ). If the signal of the non-destructive amplifier 20 is large, the exposure time control is performed. The control signal is turned off. Note that the operation of adding the exposure time in step S121 for t seconds is repeated a predetermined number of times.

  Next, as shown in FIG. 15, in step S105, the input of the register drive signal for exposure ends. Thereafter, in step S106, input of an increase register drive signal for controlling the number of increase operations to the transfer gate electrodes 14 and 15 (see FIG. 14) is started.

Next, in step S107, the number of increases is controlled. Specifically, as shown in FIG. 17, in step S131, the increase count is added n times. Next, in step S132, a signal based on the charge increased under the transfer gate electrode 13 and transferred to the non-destructive amplifier 20 is compared with a threshold value (V _th ). If the signal of the non-destructive amplifier 20 is large, the signal increases. The control signal for the number control is turned off. Note that the operation of adding the number of increases in step S131 n times is repeated a predetermined number of times.

  Next, as shown in FIG. 15, in step S108, the input of the register drive signal for the charge increasing operation is completed. Thereafter, charges are transferred to the FD amplifier 11 in step S109.

  In the fifth embodiment, as described above, the pixel 7 c includes the intra-pixel control circuit 21 that switches control between the exposure time changing unit 9 and the increasing unit 10, so that the intra-pixel control circuit 21 is connected to the pixel 7 c. Unlike the case where it is provided outside, the sensitivity of the apparatus can be controlled using signals within the same frame.

(Sixth embodiment)
FIG. 18 is a circuit diagram showing a configuration of a pixel of the imaging device according to the sixth embodiment of the present invention. Referring to FIG. 18, in the sixth embodiment, unlike the first embodiment, a configuration of an imaging device that increases the charge between the photodiode 8 and the transfer gate electrodes 13a and 14a will be described.

  As shown in FIG. 18, the pixel 7 d of the imaging device according to the sixth embodiment includes a photodiode 8, transfer gate electrodes 13 a and 14 a provided adjacent to the photodiode 8, and readout gate electrodes 15 and 16. FD amplifier 11 and selection transistor 18 are included. The photodiode 8 is an example of the “storage unit” in the present invention. In addition, an operation of increasing charge is performed under the photodiode 8 and the transfer gate electrodes 13a and 14a. The read gate electrode 15 controls the output in the column direction of the pixels 7d arranged in a matrix, and the read gate electrode 16 is configured to control the output in the row direction.

  The remaining configuration of the sixth embodiment is similar to that of the aforementioned first embodiment.

  Next, with reference to FIG. 18, a charge increasing operation according to the sixth embodiment of the present invention will be described.

  First, the charges accumulated in the photodiode 8 are moved to the charge accumulation well formed under the transfer gate electrode 14a over the charge transfer barrier formed under the transfer gate electrode 13a. At this time, in the high electric field region formed at the interface between the transfer gate electrode 13a and the transfer gate electrode 14a, the charge is increased by impact ionization. The high electric field region formed at the interface between the transfer gate electrode 13a and the transfer gate electrode 14a is an example of the “increasing portion” in the present invention. Further, the charge is further increased by repeatedly moving the charge between the photodiode 8 and the charge integration well.

  The other operations in the sixth embodiment are the same as those in the first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first embodiment and the fourth embodiment, the pixels are 4 pixels, which are high brightness pixels that saturate the pixels, high brightness pixels that do not saturate the pixels, medium and low pixels. Although an example in which signals are output divided into one group has been shown, the present invention is not limited to this, and pixels may be output divided into groups other than four.

  In the first and fifth embodiments, the example in which the charge increasing operation is performed under the transfer gate electrode 13 is shown. However, the present invention is not limited to this, and transfer gate electrodes other than the transfer gate electrode 13 are used. The charge increasing operation may be performed below.

1 is a block diagram of a CMOS type imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the image pick-up element comprised from the some pixel of the imaging device by 1st Embodiment of this invention. It is a block diagram which shows control of the increase operation | movement of the pixel of the imaging device by 1st Embodiment of this invention. It is a circuit diagram showing the composition of the pixel of the imaging device by a 1st embodiment of the present invention. 3 is a flowchart illustrating a control flow of an operation of the imaging apparatus according to the first embodiment of the present invention. 5 is a flowchart showing a control flow of pixel selection of the imaging apparatus according to the first embodiment of the present invention. It is a figure which shows the relationship between the brightness (luminance) of the light which injects into a pixel, the luminance value after an increase operation of an electric charge, and the luminance value after exposure time control. It is the flowchart which showed the control flow of the sensitivity of the imaging device by 1st Embodiment of this invention. It is a block diagram of control of the increase part of the pixel of the imaging device by a 2nd embodiment of the present invention. It is the flowchart which showed the control flow of the imaging device by 2nd Embodiment of this invention. It is a block diagram of control of the increase part of the pixel of the imaging device by a 3rd embodiment of the present invention. It is the flowchart which showed the control flow of the imaging device by 4th Embodiment of this invention. It is a block diagram which shows control of the pixel of the imaging device by 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the pixel of the imaging device by 5th Embodiment of this invention. It is the flowchart which showed the control flow of the pixel of the imaging device by 5th Embodiment of this invention. It is the flowchart which showed the control flow of the exposure time of the imaging device by 5th Embodiment of this invention. It is the flowchart which showed the control flow of the electric charge increase operation frequency of the imaging device by 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the pixel of the imaging device by 6th Embodiment of this invention.

Explanation of symbols

7, 7a, 7b, 7c Pixel 8, 8a Photodiode (storage unit)
9, 9a Exposure time changing unit 10, 10a Increasing unit 12 Transfer gate electrode (second transfer gate electrode)
13 Transfer gate electrode (first transfer gate electrode)
16 Read gate electrode (second read gate electrode)
17 Read gate electrode (first read gate electrode)

Claims (6)

A plurality of pixels;
An increasing part for increasing the charge accumulated in the pixel;
An exposure time changing unit for changing the exposure time of the pixels,
It is configured to switch between control of the number of times of increasing operation of charge accumulated in the pixel and control of exposure time of the pixel in units of one or more pixel groups according to the luminance of light incident on the pixel. An imaging device.   When the luminance of the light incident on the pixel is lower than a predetermined value, the sensitivity is adjusted by controlling the number of times of the charge increasing operation by the increasing unit, and the luminance of the light incident on the pixel is lower than the predetermined value. The imaging apparatus according to claim 1, wherein the sensitivity is adjusted by controlling the exposure time of the pixel by the exposure time changing unit when the exposure time is higher.   The imaging device according to claim 1, wherein the pixel includes a first transfer gate electrode that has a function of transferring charges and applies a voltage for increasing the charges. The pixel has a photoelectric conversion function and is formed adjacent to the accumulation unit for accumulating the charge generated by the photoelectric conversion, and is included in the exposure time changing unit while transferring the charge. A second transfer gate electrode,
The imaging device according to claim 1, wherein an exposure time of the pixel is controlled by the second transfer gate electrode.   The imaging device according to claim 1, wherein the pixel includes an in-pixel control circuit that switches control between the increasing unit and the exposure time changing unit.   2. The pixel includes a first readout gate electrode for reading out a signal based on electric charges accumulated in the accumulation unit from the plurality of pixels in units of rows and a second readout gate electrode for reading out in units of columns. The imaging apparatus of any one of -5.

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