JP5044184B2 - Driving device and driving method of solid-state imaging device - Google Patents

Description

  The present invention relates to a driving device and a driving method for a solid-state imaging device.

  Imaging devices such as CCDs (Charge Coupled Devices) and C-MOSs (Complementary Metal Oxide Semiconductors) mounted on cameras are arranged in a two-dimensional matrix, and photoelectric conversion devices that convert light into electrical signals are arranged. Prepare. The photoelectric conversion element has a photoelectric conversion sensitivity from a visible light region (about 380 nm to 650 nm) to an infrared light region (about 650 nm to 1100 nm). Therefore, in order to perform color imaging, a primary color (RGB) or complementary color (YMC) color filter is disposed on the light receiving surface side of the photoelectric conversion element, and incident light is color-separated by the color filter for each wavelength region. Perform photoelectric conversion.

  FIG. 9 is a configuration diagram of a CCD solid-state imaging device 2 of a frame transfer method. The CCD solid-state imaging device 2 includes an imaging unit 2i, a storage unit 2s, a horizontal transfer unit 2h, and an output unit 2d. The imaging unit 2i includes a plurality of vertical shift registers arranged in parallel to each other in the vertical direction. Each bit of each vertical shift register constitutes a light receiving pixel, and accumulates information charges generated in accordance with the intensity of light incident from the outside during imaging. At the time of transfer, in response to a vertical clock pulse applied to the transfer electrode, information charges stored in each pixel are transferred toward the storage unit 2s. The accumulating unit 2s includes vertical shift registers arranged in parallel to each other so as to be continuous with the vertical shift registers of the imaging unit. In response to the vertical clock pulse applied to the transfer electrode, the storage unit 2s stores and transfers the information charges transferred from the imaging unit 2i in the vertical direction. The horizontal transfer unit 2h is provided on the output side of each vertical shift register of the storage unit 2s, and includes a horizontal shift register in which the output of each vertical shift register of the storage unit 2s is coupled to each bit. The horizontal transfer unit 2h sequentially transfers information charges transferred from the storage unit 2s to the output unit 2d. The output unit 2d is disposed on the output side of the horizontal transfer unit 2h and includes a capacitor that accumulates information charges and converts them into a voltage. The output unit 2d accumulates information charges transferred and output from the horizontal transfer unit 2h in a capacitor, converts the information charges into a voltage corresponding to the amount of charges, and outputs the voltage as an output signal. The voltage value of this output signal becomes an image signal.

  As shown in the plan view of FIG. 10, any one of the primary color (RGB) color filters is provided for each pixel of the imaging unit 2 i, and as a whole, red (R), green (G), and blue (B) Color imaging can also be performed by arranging the pixels in a mosaic.

Japanese Patent Laid-Open No. 10-224809

  When there is a region where the contrast is greatly different in the imaging space, a problem occurs in the dynamic range in the captured image. That is, if the imaging period is set short corresponding to a bright area, information charges corresponding to a dark area in the captured image are not sufficiently accumulated and a dynamic range cannot be obtained sufficiently. On the other hand, if the imaging period is set to be long corresponding to the dark area, the information charge corresponding to the bright area in the captured image is saturated, and a sufficient dynamic range cannot be obtained.

  An object of the present invention is to provide a driving device and a driving method for a solid-state imaging device capable of obtaining a better dynamic range in a bright region and a dark region.

The present invention provides a color filter having a plurality of photoelectric conversion elements arranged in a matrix and a plurality of vertical shift registers that sequentially transfer information charges generated by the photoelectric conversion elements in a column direction, and having the same transmission region. A driving device for driving a solid-state imaging device arranged on the light receiving surface of the photoelectric conversion device at a predetermined cycle along the column direction, wherein the information charge is generated by exposing the photoelectric conversion device. An exposure process; an electronic shutter process for discharging information charges generated by a part of the photoelectric conversion element in the first exposure process; a transfer process for transferring information charges remaining in the electronic shutter process; and the transfer after treatment, said transferred information charges exposes only a different time than the first exposure process the photoelectric conversion element in a state left on a part of the photoelectric conversion element Therefore a second exposure process of generating information charges, and performing.

Here, it is preferable that the electronic shutter process discharges the information charges generated in the first exposure process for each set, with the photoelectric conversion elements being set for each period along the column direction. . In the electronic shutter process, it is preferable to switch the set of the photoelectric conversion elements that are the discharge targets of information charges for each frame .

  In the electronic shutter process, a color filter having any one transmission region of the color filters is selected, and a part of pixels in which the color filter having a transmission region other than the selected color filter is arranged. And the transfer process is a process of transferring the information charges remaining in the electronic shutter process so as to add up the information charges remaining in the electronic shutter process. After the transfer process, a third exposure process for generating information charges by exposing the photoelectric conversion element, and a first exposure process for discharging information charges of the transferred pixels among the pixels in which the selected color filter is arranged. The second electronic shutter process and the second electronic shutter process so as to add the information charges of the other colors remaining in the second electronic shutter process. Perform a second transfer process of transferring the information charges left in Yatta process, and after the second transfer process may perform the second exposure process.

  Here, in the transfer process, it is preferable that the information charge remaining in the shutter process is transferred in the column forward direction or the reverse direction for the period.

  The exposure time in the first exposure process is preferably set longer than the exposure time in the second exposure process. Furthermore, it is preferable that the exposure time in the third exposure process is set longer than the exposure time in the second exposure process.

In addition, the present invention includes a plurality of photoelectric conversion elements arranged in a matrix and a plurality of vertical shift registers that sequentially transfer information charges generated by the photoelectric conversion elements in a column direction, and have mutually different transmission regions. A color filter is a driving method for driving a solid-state imaging device arranged at a predetermined cycle along the column direction on the light receiving surface of the photoelectric conversion device, and generates information charges by exposing the photoelectric conversion device A first exposure step, an electronic shutter step for discharging information charges generated in a part of the photoelectric conversion element in the first exposure step, and a transfer step for transferring information charges left in the electronic shutter process. after the transfer process, but a different time than the first exposure process the photoelectric conversion element in a state left on a part of the transferred information charges said photoelectric conversion element A second exposure step of generating information charges by exposing, and performs.

Here, it is preferable that the electronic shutter process discharges the information charges generated in the first exposure process for each set, with the photoelectric conversion elements being set for each period along the column direction. . In the electronic shutter process, it is preferable to switch the set of the photoelectric conversion elements that are targets for discharging information charges for each frame .

  In the electronic shutter process, a color filter having any one transmission region of the color filters is selected, and a part of pixels in which the color filter having a transmission region other than the selected color filter is arranged. The information charge of the pixel is discharged, and the transfer step is a step of transferring the information charge left in the electronic shutter process so as to add up the information charge left in the electronic shutter step. A third exposure step of generating information charges by exposing the photoelectric conversion elements after the transfer step; and a third exposure step of discharging information charges of transferred pixels among the pixels in which the selected color filter is arranged. The second electronic shutter step and the second electronic shutter step so as to add the information charges of other colors remaining in the second electronic shutter step. Perform a second transfer step of transferring the information charges left in Yatta step, after the second transfer step may perform the second exposure step.

  Here, in the transfer step, it is preferable that the information charges remaining in the shutter process are transferred in the column forward direction or the reverse direction for the period.

  The exposure time in the first exposure process is preferably set longer than the exposure time in the second exposure process. Furthermore, it is preferable that the exposure time in the third exposure step is set longer than the exposure time in the second exposure step.

  According to the present invention, the dynamic range of a captured image can be increased.

  As illustrated in FIG. 1, the solid-state imaging device 100 according to the embodiment of the present invention includes a solid-state imaging device 10, a clock control unit 12, and a signal processing unit 14. The solid-state imaging device 100 generates information charges corresponding to incident light in the solid-state imaging device 10, and information is generated by clock signals (φi, φs, φh, φr, φs) supplied from the clock control unit 12 to the solid-state imaging device 10. Transfer charge. Information charges are converted into electrical signals and sequentially output to the signal processing unit 14, and the signal processing unit 14 performs processing such as noise removal.

  In the present embodiment, the solid-state imaging device 10 will be described as a frame transfer type CCD solid-state imaging device. Similarly to FIG. 9, the imaging unit 10i, the storage unit 10s, the horizontal transfer unit 10h, and the output unit 10d are provided. The clock controller 12 includes a frame clock pulse generator, a vertical clock pulse generator, an auxiliary clock pulse generator, a horizontal clock pulse generator, a reset clock pulse generator, and a sampling clock pulse generator.

  The imaging unit 10i includes a plurality of vertical shift registers arranged in parallel to each other in the vertical direction. Each bit of each vertical shift register constitutes a light receiving pixel, and accumulates information charges generated in accordance with the intensity of light incident from the outside during imaging. As shown in FIG. 10, in the imaging unit 10i in the present embodiment, red (R), green (G), and blue (B) color filters are arranged in a mosaic pattern in association with each light receiving pixel. Yes. For example, the color filter R gradually decreases in transmittance from about 350 nm to about 420 nm, hardly transmits light in a wavelength region of about 420 nm to about 500 nm, and increases again from about 500 nm to about 550 nm. High transmittance for longer wavelength light. For example, the color filter G hardly transmits light in a wavelength region of about 360 to about 420 nm, increases transmission from light having a wavelength longer than about 420 nm, has a green peak at about 520 nm, and is directed toward about 650 nm. Thus, the transmittance gradually decreases, the transmittance gradually increases again in a wavelength region longer than about 650 nm, and has a high transmittance for infrared light having a wavelength longer than about 880 nm. For example, the color filter B has increased transmission from light having a wavelength longer than about 380 nm, has a peak at about 460 nm, which is blue, decreases in transmittance toward about 580 nm, and transmits again in a wavelength region longer than about 620 nm. The rate increases gradually, with a small peak at about 690 nm and a high transmission for infrared light longer than about 800 nm. On the other hand, when the light receiving pixel is composed of a silicon photoelectric conversion element, it has the maximum sensitivity at about 500 nm, and has sensitivity up to the infrared region of about 1100 nm, exceeding the visible light region of 780 nm. At the time of imaging, only the wavelength component of the color of each color filter is transmitted from the light incident from the outside, so that information charges corresponding to the light intensity of the wavelength component are accumulated in each pixel. That is, the light receiving pixels for accumulating information charges corresponding to red (R) and green (G) are alternately arranged along the transfer direction in the odd-numbered columns of the vertical shift register, and along the transfer direction in the even-numbered columns of the vertical shift register. Thus, light receiving pixels for accumulating information charges corresponding to green (G) and blue (B) are alternately arranged. At the time of transfer, in response to the vertical clock pulse φi applied to the transfer electrode from the frame clock pulse generator, the information charge stored in each pixel is transferred toward the storage unit 10s.

  The storage unit 10s includes vertical shift registers arranged in parallel to each other so as to be continuous with the vertical shift registers of the imaging unit 10i. The accumulating unit 10s receives the vertical clock pulse φs applied to the transfer electrode from the vertical clock pulse generating unit, accumulates information charges transferred from the imaging unit 10i, and transfers them in the vertical direction. The horizontal transfer unit 10h includes a horizontal shift register disposed on the output side of each vertical shift register of the storage unit 10s. The horizontal transfer unit 10h receives the horizontal clock pulse φh applied from the horizontal clock pulse generation unit to the horizontal transfer electrode, and sequentially transfers information charges transferred from the storage unit 10s to the output unit 10d. The output unit 10d includes a capacitor disposed on the output side of the horizontal transfer unit 10h. The output unit 10d receives the reset clock pulse φr and the sampling clock pulse φs from the reset clock pulse generation unit and the sampling clock pulse generation unit, and accumulates information charges transferred and output from the horizontal transfer unit 10h in this capacitor. The voltage is converted into a voltage corresponding to the amount of charge and output as an output signal. The voltage value of this output signal becomes an image signal.

  FIG. 2 is a plan view showing the internal structure of the imaging unit 10i of the CCD solid-state imaging device 10 in the present embodiment. The imaging unit 10i includes a plurality of vertical shift registers that are extended in parallel to each other. The vertical shift register is formed as follows. A P well (PW) which is a P type diffusion layer is formed in an N type semiconductor substrate, and an N well which is an N type diffusion layer is formed thereon. In addition, isolation regions 22 to which P-type impurities are added are provided in parallel to each other at a predetermined interval along the extending direction of the vertical shift register. The N well is electrically partitioned by the adjacent isolation region 22. An N well (NW), which is an N type diffusion layer, is formed in a P type semiconductor substrate, and a P well, which is a P type diffusion layer, is formed thereon, and an N type is formed along the extending direction of the vertical shift register. The isolation regions 22 to which impurities are added may be provided so as to be parallel to each other with a predetermined interval. In the present embodiment, the region sandwiched between the isolation regions 22 becomes the channel region 20 which is the information charge transfer path. The isolation region 22 forms a potential barrier between adjacent channel regions, and electrically isolates each channel region 20. Further, an insulating film is formed on the surface of the semiconductor substrate. On this insulating film, a plurality of transfer electrodes 24 made of a polysilicon film are arranged in parallel to each other so as to be orthogonal to the extending direction of the channel region 20.

In this embodiment, 12 electrodes of transfer electrodes 24-1 to 24-12 are repeatedly arranged along the vertical transfer direction. Also, a set of three transfer electrodes 24-1, 24-2, 24-3 adjacent in the vertical transfer direction, a set of three transfer electrodes 24-4, 24-5, 24-6, and three transfer electrodes A set of 24-7, 24-8, and 24-9, and a set of three transfer electrodes 24-10, 24-11, and 24-12 correspond to one photoelectric conversion pixel. By supplying 12-phase vertical clock pulses φi _{1 to} φi ₁₂ that can be independently controlled to the transfer electrodes 24-1 to 24-12, respectively, the transfer electrodes 24-1 to 24-12 are supported. The accumulation and transfer of information charges in the four pixels can be controlled independently.

  However, the scope of application of the present invention is not limited to the case where one pixel is composed of three transfer electrodes, and can also be applied to the case where one pixel is composed of two or four transfer electrodes. . In addition, the vertical shift register of the storage unit 10s can be configured in the same manner as the imaging unit 10i, and each vertical shift register of the storage unit 10s is arranged to be continuous with each vertical shift register of the imaging unit 10i.

Next, the clock control unit 12 will be described. Clock control unit 12 receives a timing clock signal S _CLK having a predetermined period supplied from the outside, the clock signal at a predetermined timing by measuring a timing clock signal S _CLK in counter φi, φs, φh, φr, φs Is generated. The clock signal φi is output to the imaging unit 10i, the clock signal φs is output to the storage unit 10s, the clock signal φh is output to the horizontal transfer unit 10h, and the clock signals φr and φs are output to the output unit 10d.

FIG. 3 shows a timing chart of the clock signals φi _{1 to} φi ₁₂ supplied to the imaging unit ₁₀ i in the present embodiment. FIG. 4 shows the state of the potential well generated below each transfer electrode 24-1-24-12 at each time of FIG. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the potential of the clock signals φi _{1 to} φi ₁₂ applied to the transfer electrodes 24-1 to 24-12, respectively. The downward direction of the vertical axis represents a positive potential with respect to the substrate potential, and the upward direction of the vertical axis represents a negative potential with respect to the substrate potential. In FIG. 4, the horizontal axis represents the positions along the transfer direction in the odd-numbered and even-numbered vertical shift registers, and the vertical axis represents the potential inside the semiconductor in the imaging unit 10i. The upward direction of the vertical axis represents a negative potential with respect to the substrate potential, and the downward direction of the vertical axis represents a positive potential with respect to the substrate potential.

At time t0, an electronic shutter process is performed on the entire imaging unit 10i. When the clock control unit 12 receives a shutter signal according to the operation of the shutter button of the camera from the outside, the clock control unit 12 sets all the clock signals φi _{1 to} φi ₁₂ to negative potentials and turns off the transfer electrodes 24-1 to 24-12. By setting the state, the information charges accumulated in each pixel of the imaging unit 10i are discharged to the deep part of the semiconductor substrate. Thereby, preparation for imaging of the next imaging frame is completed.

  Imaging is performed from time t1 to t2. The intensity of light incident through a color filter provided on the incident surface of each pixel by applying a positive potential to one or two of the pairs of transfer electrodes constituting each pixel to turn it on. An information charge corresponding to is generated. Here, a set of transfer electrodes 24-1, 24-2, 24-3, a set of three transfer electrodes 24-4, 24-5, 24-6, and three transfer electrodes 24-7, 24-8, 24 By applying a positive potential to the transfer electrodes 24-2, 24-5, 24-8, and 24-11 for the set of −9 and the set of three transfer electrodes 24-10, 24-11, and 24-12 As shown in FIG. 4, potential wells are generated below the transfer electrodes 24-2, 24-5, 24-8, and 24-11, and information charges corresponding to the intensity of light incident on each pixel are accumulated. . In FIG. 4, the information charge corresponding to the red wavelength region is represented by R, the information charge corresponding to the green wavelength region is represented by G, and the information charge corresponding to the blue wavelength region is represented by B.

  At time t2, an electronic shutter process is performed on a part of the imaging unit 10i. With respect to the period T in which the color filters having the same transmission region are arranged in each column of the vertical shift register, the information charge is generated every other group (every period 2T) with a pixel (photoelectric conversion element) grouped every period T. An electronic shutter process is performed so as to be discharged.

  In the present embodiment, as shown in FIG. 2, red (R) and green (G) color filters are arranged for each period T in the odd-numbered vertical shift register, and every even period T in the even-numbered vertical shift register. Are provided with blue (B) and green (G) color filters. Therefore, in the odd-numbered columns, two sets of red and green pixels corresponding to the transfer electrodes 24-1 to 24-6 are formed as one set for each period T, and red and green corresponding to the transfer electrodes 24-7 to 24-12. Two pixels are set as one set. Then, the transfer electrodes 24-8 and 24-11 are turned off so that the information charges corresponding to the transfer electrodes 24-7 to 24-12 are discharged every interval (every 2T). In the even-numbered columns, two sets of green and blue pixels corresponding to the transfer electrodes 24-1 to 24-6 are formed as one set for each period T, and two green and blue pixels corresponding to the transfer electrodes 24-7 to 24-12 are set. A pixel is set as one set. Then, the transfer electrodes 24-8 and 24-11 are turned off so that the information charges corresponding to the transfer electrodes 24-7 to 24-12 are discharged every interval (every 2T).

  From time t3 to t4, information charge transfer processing is performed. Information charges left by the electronic shutter processing at time t2 are transferred for a period T along the vertical transfer direction.

  In the present embodiment, as shown in FIG. 2, information stored in two odd-numbered red and green pixels and even-numbered green and blue pixels corresponding to the transfer electrodes 24-1 to 24-6. Since the charges remain, these information charges are separated by only the period T, that is, two odd-numbered red and green pixels corresponding to the transfer electrodes 24-7 to 24-12 that have discharged the information charges at time t2. Transfer to even-numbered green and blue pixels.

  From time t4 to t5, imaging is performed again. The intensity of light incident through a color filter provided on the incident surface of each pixel by applying a positive potential to one or two of the pairs of transfer electrodes constituting each pixel to turn it on. An information charge corresponding to is generated. Here, similarly to the times t1 to t2, a set of transfer electrodes 24-1, 24-2, 24-3, a set of three transfer electrodes 24-4, 24-5, and 24-6, and three transfer electrodes 24 are used. −7, 24-8, 24-9, and three transfer electrodes 24-10, 24-11, 24-12, transfer electrodes 24-2, 24-5, 24-8, 24-11 As shown in FIG. 4, a potential well is generated under the transfer electrodes 24-2, 24-5, 24-8, and 24-11, thereby increasing the intensity of light incident on each pixel. The corresponding information charge is accumulated.

  As a result, information charges corresponding to the intensity of light incident on each pixel between times t4 and t5 are accumulated in a set of pixels corresponding to the transfer electrodes 24-1 to 24-6. In addition, in the group of pixels corresponding to the transfer electrodes 24-7 to 24-12, information corresponding to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-1 to 24-6 between the times t1 and t2. The amount of information charge that is the sum of the charge and the information charge corresponding to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-7 to 24-12 is accumulated between times t 4 and t 5. Become.

  At this time, by setting the imaging time so that the imaging time T2 at the times t4 to t5 is sufficiently shorter than the imaging time T1 at the times t1 to t2, the transfer electrodes 24-7 to 24 are set between the times t4 and t5. The information charge corresponding to the intensity of light incident on the pixel corresponding to -12 is based on the information charge corresponding to the intensity of light incident on the pixel corresponding to the transfer electrodes 24-1 to 24-6 between times t1 and t2. Therefore, the set of pixels corresponding to the transfer electrodes 24-7 to 24-12 includes the light incident on the pixels corresponding to the transfer electrodes 24-1 to 24-6 during the time t1 to t2. This is approximately equivalent to holding the information charge corresponding to the intensity.

  As a result, at the time t5, the information charge corresponding to the intensity of light incident on each pixel is held in the set of pixels corresponding to the transfer electrodes 24-1 to 24-6 at the imaging time T2 from time t4 to t5. The set of pixels corresponding to the transfer electrodes 24-7 to 24-12 corresponds to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-1 to 24-6 at the imaging time T1 from time t1 to t2. The information charge is held. That is, the transfer electrodes 24-1 to 24-6 have a sufficiently short imaging time T2 from time t4 to t5 compared to the imaging time T1 from time t1 to t2. The information charges generated in the set of pixels corresponding to are held, and the sets of pixels corresponding to the transfer electrodes 24-7 to 24-12 have times t1 to t2 that are sufficiently longer than the imaging time T2 of times t4 to t5. The information charges generated by the set of pixels corresponding to the transfer electrodes 24-1 to 24-6 at the imaging time T1 are held.

  Therefore, for a bright region in the captured image, a sufficient dynamic range can be obtained by obtaining an image based on information charges corresponding to a short imaging time held in the transfer electrodes 24-1 to 24-6. . On the other hand, for a dark region in the captured image, a sufficient dynamic range can be obtained by obtaining an image based on information charges corresponding to a long time held in the transfer electrodes 24-7 to 24-12.

  The ratio of the imaging time T1 from time t1 to t2 and the imaging time T2 from time t4 to t5 is preferably determined according to the dynamic range of lightness in the captured image. The clock control unit 12 increases the ratio T1 / T2 when the lightness dynamic range within one frame of the captured image is large, and the ratio T1 / T2 when the lightness dynamic range within one frame of the captured image is small. It is preferable to control the clock signal φi so that becomes small. If the dynamic range of image brightness can be set in the camera, the ratio T1 / T2 may be changed according to the set value.

  From time t5 to t6, frame transfer processing is performed. Information charges accumulated in each pixel of the imaging unit 10i by time t5 are transferred to the accumulation unit 10s. In the frame transfer type CCD solid-state imaging device 10, the storage unit 10s has the same number of storage pixels as the number of pixels of the image pickup unit 10i, and information charges for one frame are transferred to the image pickup unit 10i by frame transfer processing. To the storage unit 10s.

  Thereafter, when the shutter button of the camera is pressed again, the process returns to the electronic shutter process at time t0 and the above process is repeated.

  The information charges stored in the storage unit 10s are transferred to the horizontal transfer unit 10h line by line in accordance with the clock signal φs applied to the storage unit 10s. The information charges transferred to the horizontal transfer unit 10h are transferred to the output unit 10d pixel by pixel in accordance with the clock signal φh applied to the horizontal transfer unit 10h. In the output unit 10d, the information charge amount is converted into a voltage value corresponding to the charge amount for each pixel and output to the signal processing unit 14 as an output signal. By repeating such processing, an output signal for one frame is output.

  When the output signals for one frame are combined for each row, an image X captured at a long imaging time T1 from time t1 to t2 and an image Y captured at a short imaging time T2 from time t4 to t5 can be obtained. it can. For example, the signal processing unit 14 extracts a signal corresponding to the area from the image X for an area having a predetermined brightness B1 or more in the image, and extracts a signal corresponding to the area from the image Y for the other areas. combine. This is a process suitable for widening the dynamic range of lightness of an image when the entire image is relatively dark and a region with high lightness is included in the image. Alternatively, a signal corresponding to the region is extracted from the image Y for a region having a predetermined brightness B2 or less in the image, and a signal corresponding to the region is extracted from the image X and combined for the other regions. This is a process suitable for widening the dynamic range of lightness of an image when the entire image is relatively bright and the image includes a low-lightness area.

  In addition, when performing the imaging process, it is also preferable to switch the group of pixels that leave information charges for each frame. In the processing described above, processing was performed so as to leave information charges of a set of pixels corresponding to the transfer electrodes 24-1 to 24-6 in the electronic shutter processing at time t3. At the time of imaging the next frame, as shown in FIG. 5, the information charge of the pixel group corresponding to the transfer electrodes 24-7 to 24-12 is left in the electronic shutter process at time t3, and the transfer process at time t4 is performed. The remaining information charges are transferred to the set of pixels corresponding to the transfer electrodes 24-1 to 24-6, and the information charges are stored again in the imaging process at times t4 to t5. As a result, interlaced imaging can be performed for each frame, and the dynamic range of image brightness can be increased without reducing the apparent spatial resolution in moving image shooting or the like.

<Modification>
FIG. 6 shows a timing chart of the clock signals φi _{1 to} φi ₁₂ supplied to the imaging unit ₁₀ i in the present embodiment. FIG. 7 shows the state of the potential well generated below each transfer electrode 24-1-24-12 at each time of FIG. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the potentials of the clock signals φi _{1 to} φi ₁₂ applied to the transfer electrodes 24-1 to 24-12, respectively. The downward direction of the vertical axis represents a positive potential with respect to the substrate potential, and the upward direction of the vertical axis represents a negative potential with respect to the substrate potential. In FIG. 7, the horizontal axis represents the positions along the transfer direction in the odd-numbered and even-numbered vertical shift registers, and the vertical axis represents the potential inside the semiconductor in the imaging unit 10 i. The upward direction of the vertical axis represents a negative potential with respect to the substrate potential, and the downward direction of the vertical axis represents a positive potential with respect to the substrate potential.

At time t0, an electronic shutter process is performed on the entire imaging unit 10i. When the clock control unit 12 receives a shutter signal according to the operation of the shutter button of the camera from the outside, the clock control unit 12 sets all the clock signals φi _{1 to} φi ₁₂ to negative potentials and turns off the transfer electrodes 24-1 to 24-12. By setting the state, the information charges accumulated in each pixel of the imaging unit 10i are discharged to the deep part of the semiconductor substrate. Thereby, preparation for imaging of the next imaging frame is completed.

  Imaging is performed from time t1 to t2. The intensity of light incident through a color filter provided on the incident surface of each pixel by applying a positive potential to one or two of the pairs of transfer electrodes constituting each pixel to turn it on. An information charge corresponding to is generated. Here, a set of transfer electrodes 24-1, 24-2, 24-3, a set of three transfer electrodes 24-4, 24-5, 24-6, and three transfer electrodes 24-7, 24-8, 24 By applying a positive potential to the transfer electrodes 24-2, 24-5, 24-8, and 24-11 for the set of −9 and the set of three transfer electrodes 24-10, 24-11, and 24-12 As shown in FIG. 7, potential wells are generated under the transfer electrodes 24-2, 24-5, 24-8, and 24-11, and information charges corresponding to the intensity of light incident on each pixel are accumulated. . In FIG. 7, the information charge corresponding to the red wavelength region is represented by R, the information charge corresponding to the green wavelength region is represented by G, and the information charge corresponding to the blue wavelength region is represented by B.

  At time t2, an electronic shutter process is performed on a part of the imaging unit 10i. With respect to a period T in which color filters having the same transmission region are arranged in each column of the vertical shift register, pixels (photoelectric conversion elements) every period 2T along the transfer direction of the vertical shift register are grouped into each group. A color filter having any one transmission region is selected from among the included color filters, and information charges of some of the pixels in which color filters having transmission regions other than the selected color filter are arranged are discharged. An electronic shutter process is performed as described above.

  In the present embodiment, as shown in FIG. 2, red (R) and green (G) color filters are arranged for each period T in the odd-numbered vertical shift register, and every even period T in the even-numbered vertical shift register. Are provided with blue (B) and green (G) color filters. Therefore, in the odd-numbered columns, four pixels of red and green corresponding to the transfer electrodes 24-1 to 24-12 are set as one set every cycle 2T. When a green color filter is selected from among the color filters included in each set, the pixel and the transfer electrode 24-7 corresponding to the transfer electrodes 24-1 to 24-3 in which the selected non-green red color filter is arranged. Electronic shutter processing so that a part of the pixels corresponding to .about.24-9, that is, the pixels corresponding to the transfer electrodes 24-7 to 24-9 are turned off, and the information charges accumulated in the pixels are discharged. I do.

  Similarly, in the even-numbered column, four pixels of green and blue corresponding to the transfer electrodes 24-1 to 24-12 are set as one set for every period 2T. When a blue color filter is selected from among the color filters included in each set, the pixel and the transfer electrode 24-7 corresponding to the transfer electrodes 24-1 to 24-3 in which the selected green color filter other than blue is arranged. Electronic shutter processing so that a part of the pixels corresponding to .about.24-9, that is, the pixels corresponding to the transfer electrodes 24-7 to 24-9 are turned off, and the information charges accumulated in the pixels are discharged. I do.

  From time t3 to t4, information charge transfer processing is performed. The information charges left by the electronic shutter processing at time t2 are transferred for a period T along the vertical transfer direction so that they are added together with other information charges in the same set.

  In the present embodiment, as shown in FIG. 7, two pixels corresponding to the transfer electrodes 24-1 to 24-6 and one pixel corresponding to the transfer electrodes 24-10 to 24-12 are included in the odd-numbered columns. Information charges remain. Therefore, the information charges remaining in the pixels corresponding to the transfer electrodes 24-4 to 24-6 are transferred to the pixels corresponding to the transfer electrodes 24-10 to 24-12 and selected by the electronic shutter process at time t2. The information charges corresponding to the selected colors (green for odd columns and blue for even columns) are summed.

  From time t4 to t5, imaging is performed again. The intensity of light incident through a color filter provided on the incident surface of each pixel by applying a positive potential to one or two of the pairs of transfer electrodes constituting each pixel to turn it on. An information charge corresponding to is generated. Here, similarly to the times t1 to t2, a set of transfer electrodes 24-1, 24-2, 24-3, a set of three transfer electrodes 24-4, 24-5, and 24-6, and three transfer electrodes 24 are used. −7, 24-8, 24-9, and three transfer electrodes 24-10, 24-11, 24-12, transfer electrodes 24-2, 24-5, 24-8, 24-11 As shown in FIG. 4, a potential well is generated under the transfer electrodes 24-2, 24-5, 24-8, and 24-11, thereby increasing the intensity of light incident on each pixel. The corresponding information charge is accumulated.

  As a result, the information charges corresponding to the intensity of the light incident on the pixels during the times t1 to t5 are accumulated and accumulated in the pixels corresponding to the transfer electrodes 24-1 to 24-3. In the pixels corresponding to the transfer electrodes 24-4 to 24-6 and the transfer electrodes 24-7 to 24-9, information charges corresponding to the intensity of light incident on the pixels are accumulated between times t4 and t5. become. For the pixels corresponding to the transfer electrodes 24-10 to 24-12, the information charges generated in the pixels corresponding to the transfer electrodes 24-4 to 24-6 and the transfer electrodes 24-10 to 24-24 between the times t1 and t2. The information charge generated by the pixel corresponding to -12 and the information charge corresponding to the intensity of light incident on the pixel corresponding to the transfer electrodes 24-10 to 24-12 at time t4 to t5 are added and accumulated. Will be.

  At time t5, electronic shutter processing is performed again on a part of the imaging unit 10i. With respect to a period T in which color filters having the same transmission region are arranged in each column of the vertical shift register, pixels (photoelectric conversion elements) every period 2T along the transfer direction of the vertical shift register are grouped into each group. The electronic shutter process is performed so that the information charges of some of the pixels in which the color filter selected by the electronic shutter process at time t2 is arranged among the color filters included are discharged.

  In the present embodiment, since the green color filter is selected from among the color filters included in each set at time t2 in the odd-numbered columns, the transfer electrodes 24-4 to 24 in which the selected green color filter is arranged. Among the pixels corresponding to -6 and the pixels corresponding to the transfer electrodes 24-10 to 24-12, that is, the pixels corresponding to the transfer electrodes 24-4 to 24-6 are turned off and stored in the pixels The electronic shutter process is performed so that the information charges that are present are discharged. At this time, a pixel that is not a pixel corresponding to the transfer electrodes 24-10 to 24-12 that is the transfer destination of the information charge in the transfer process from time t3 is selected and the information charge is discharged.

  Similarly, in the even-numbered column, since the blue color filter is selected from among the color filters included in each set at time t2, the transfer electrodes 24-4 to 24-6 in which the selected blue color filter is disposed are used. Information charges accumulated in the corresponding pixel and a part of the pixels corresponding to the transfer electrodes 24-10 to 24-12, that is, the pixels corresponding to the transfer electrodes 24-4 to 24-6 are turned off. The electronic shutter process is performed so as to be discharged. At this time, a pixel that is not a pixel corresponding to the transfer electrodes 24-10 to 24-12 that is the transfer destination of the information charge in the transfer process from time t3 is selected and the information charge is discharged.

  From time t6 to t7, the information charge transfer process is performed again. The information charges left by the electronic shutter processing at time t5 are transferred for a period T along the vertical transfer direction so that they are added together with other information charges in the same set.

  In the present embodiment, as shown in FIG. 7, one pixel corresponding to the transfer electrodes 24-1 to 24-3 and two pixels corresponding to the transfer electrodes 24-7 to 24-12 in the odd columns. Information charges remain. Therefore, the information charges remaining in the pixels corresponding to the transfer electrodes 24-1 to 24-3 are transferred to the pixels corresponding to the transfer electrodes 24-7 to 24-9 and selected by the electronic shutter process at time t5. The information charges corresponding to the selected colors (red for odd columns and green for even columns) are summed.

  From time t7 to t8, imaging is performed again. The intensity of light incident through a color filter provided on the incident surface of each pixel by applying a positive potential to one or two of the pairs of transfer electrodes constituting each pixel to turn it on. An information charge corresponding to is generated. Here, similarly to the times t1 to t2, a set of transfer electrodes 24-1, 24-2, 24-3, a set of three transfer electrodes 24-4, 24-5, and 24-6, and three transfer electrodes 24 are used. −7, 24-8, 24-9, and three transfer electrodes 24-10, 24-11, 24-12, transfer electrodes 24-2, 24-5, 24-8, 24-11 As shown in FIG. 4, a potential well is generated under the transfer electrodes 24-2, 24-5, 24-8, and 24-11, thereby increasing the intensity of light incident on each pixel. The corresponding information charge is accumulated.

  At this time, it is preferable to set the imaging time so that the imaging time T5 from time t7 to t8 is shorter than the total time of the imaging time T3 from time t1 to t2 and the imaging time T4 from time t4 to t5. As a result, information charges corresponding to the intensity of light incident on the two pixels corresponding to the transfer electrodes 24-1 to 24-6 between the times t7 and t8 are generated between the times t1 and t5 and transferred to the transfer electrode 24. This is sufficiently smaller than the information charge held in the two pixels corresponding to −7 to 24-12.

  As a result, at the time t8, the information charge corresponding to the intensity of light incident on each pixel is held in the set of pixels corresponding to the transfer electrodes 24-1 to 24-6 at the imaging time T5 from time t7 to t8. Is done. Information charges corresponding to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-1 to 24-3 at the imaging time T3 from time t1 to t2 are included in the pixels corresponding to the transfer electrodes 24-7 to 24-9. Information charges corresponding to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-1 to 24-3 at the imaging time T4 from time t4 to t5, and transfer electrodes 24-7 to 24 at the imaging time T4 from time t4 to t5. According to the information charge corresponding to the intensity of light incident on the pixel corresponding to -9 and the intensity of light incident on the pixel corresponding to the transfer electrodes 24-7 to 24-9 at the imaging time T5 from time t7 to t8 Thus, the information charge obtained by adding the information charges is held. The information corresponding to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-4 to 24-6 at the imaging time T3 from time t1 to t2 is included in the pixels corresponding to the transfer electrodes 24-10 to 24-12. Information charges according to the intensity of light incident on the pixels corresponding to the transfer electrodes 24-10 to 24-12 at the imaging time T3 from time t1 to t2, and the transfer electrodes 24-10 to 24 at the imaging time T4 from time t4 to t5. According to the information charge corresponding to the intensity of light incident on the pixel corresponding to -12 and the intensity of light incident on the pixel corresponding to the transfer electrodes 24-10 to 24-12 at the imaging time T5 from time t7 to t8. Thus, the information charge obtained by adding the information charges is held.

  Therefore, also in this modification, for a bright region in the captured image, sufficient dynamics can be obtained by obtaining an image based on information charges corresponding to a short imaging time held in the transfer electrodes 24-1 to 24-6. You can get a range. On the other hand, for a dark region in the captured image, a sufficient dynamic range can be obtained by obtaining an image based on information charges corresponding to a long time held in the transfer electrodes 24-7 to 24-12.

  Also in this modification, the ratio of the imaging time T5 from time t7 to t8 to the sum of the imaging time T3 from time t1 to t2 and the imaging time T4 from time t4 to t5 depends on the dynamic range of brightness in the captured image. It is preferable to determine. The clock controller 12 increases the ratio (T3 + T4) / T5 when the brightness dynamic range within one frame of the captured image is large, and the ratio (T3 + T4) / T5 when the brightness dynamic range within one frame of the captured image is small. It is preferable to control the clock signal φi so that T3 + T4) / T5 becomes small. If the dynamic range of image brightness can be set in the camera, the ratio (T3 + T4) / T5 may be changed according to the set value.

  In addition, it is preferable that the imaging time T3 from time t1 to t2 and the imaging time T4 from time t4 to t5 are set to be approximately equal. By setting as such, the imaging time for each color in the image can be made uniform.

  From time t8 to t9, frame transfer processing is performed. Information charges accumulated in each pixel of the imaging unit 10i by time t8 are transferred to the accumulation unit 10s. In the frame transfer type CCD solid-state imaging device 10, the storage unit 10s has the same number of storage pixels as the number of pixels of the image pickup unit 10i, and information charges for one frame are transferred to the image pickup unit 10i by frame transfer processing. To the storage unit 10s.

  Thereafter, when the shutter button of the camera is pressed again, the process returns to the electronic shutter process at time t0 and the above process is repeated.

  The information charges stored in the storage unit 10s are transferred to the horizontal transfer unit 10h line by line in accordance with the clock signal φs applied to the storage unit 10s. The information charges transferred to the horizontal transfer unit 10h are transferred to the output unit 10d pixel by pixel in accordance with the clock signal φh applied to the horizontal transfer unit 10h. In the output unit 10d, the information charge amount is converted into a voltage value corresponding to the charge amount for each pixel and output to the signal processing unit 14 as an output signal. By repeating such processing, an output signal for one frame is output.

  Also in this modified example, when the output signals for one frame are combined for each row, an image X captured with a longer imaging time and an image Y captured with a shorter imaging time can be obtained. For example, the signal processing unit 14 extracts a signal corresponding to the area from the image X for an area having a predetermined brightness B1 or more in the image, and extracts a signal corresponding to the area from the image Y for the other areas. combine. This is a process suitable for widening the dynamic range of lightness of an image when the entire image is relatively dark and a region with high lightness is included in the image. Alternatively, a signal corresponding to the region is extracted from the image Y for a region having a predetermined brightness B2 or less in the image, and a signal corresponding to the region is extracted from the image X and combined for the other regions. This is a process suitable for widening the dynamic range of lightness of an image when the entire image is relatively bright and the image includes a low-lightness area.

  In addition, when performing the imaging process, it is also preferable to switch the group of pixels that leave information charges for each frame. For example, at the time of imaging of the next frame, as shown in FIG. 8, the information charges of the pixels corresponding to the transfer electrodes 24-1 to 24-3 are discharged in the electronic shutter process at time t2, and The information charge remaining in the transfer process is transferred from the pixel corresponding to the transfer electrodes 24-10 to 24-12 to the next set of transfer electrodes 24-4 to 24-6, and the information charge is again performed in the imaging process from time t4 to t5. , The information charges of the pixels corresponding to the transfer electrodes 24-10 to 24-12 are discharged in the electronic shutter process at time t5, and the information charges left in the transfer process at time t6 to t7 are transferred to the transfer electrode 24-7. Are transferred from the pixels corresponding to .about.24-9 to the next set of transfer electrodes 24-1 to 24-3, and information charges are accumulated again in the imaging process at times t7 to t8. As a result, interlaced imaging can be performed for each frame, and the dynamic range of image brightness can be increased without reducing the apparent spatial resolution in moving image shooting or the like.

  Although the CCD has been described as an example of the solid-state imaging device 10, any charge transfer method may be used. For example, the FT (frame transfer) method, the IT (interline transfer) method, the FIT A CCD of a (frame interline transfer) system can be used. In addition, the photoelectric conversion element of the present invention can be configured in the same manner even in a CMOS (Complementary Metal Oxide Semiconductor).

It is a block diagram which shows the structure of the solid-state imaging device in embodiment of this invention. It is a top view which shows typically the structure of the imaging part in embodiment of this invention. 6 is a timing chart of a clock signal φi to the imaging unit in the embodiment of the present invention. It is a figure which shows the change of the potential in the imaging part in embodiment of this invention. It is a figure which shows the change of the potential in the imaging part in embodiment of this invention. It is a timing chart of clock signal (phi) i to the imaging part in the modification of this invention. It is a figure which shows the change of the potential in the imaging part in the modification of this invention. It is a figure which shows the change of the potential in the imaging part in the modification of this invention. It is a block diagram which shows the structure of the solid-state imaging device in background art. It is a figure which shows arrangement | positioning of the color filter in an imaging part.

Explanation of symbols

  2 solid-state imaging device, 2i imaging unit, 2s storage unit, 2h horizontal transfer unit, 2d output unit, 10 solid-state imaging device, 10i imaging unit, 10d output unit, 10h horizontal transfer unit, 10s storage unit, 12 clock control unit, 14 Signal processing unit, 20 channel region, 22 separation region, 24 transfer electrode, 100 solid-state imaging device.

Claims (14)

A plurality of photoelectric conversion elements arranged in a matrix and a plurality of vertical shift registers that sequentially transfer information charges generated by the photoelectric conversion elements in a column direction, and a color filter having the same transmission region is the photoelectric conversion element A solid-state imaging device arranged at a predetermined period along the column direction on the light receiving surface of the driving device,
A first exposure process for generating information charges by exposing the photoelectric conversion element;
An electronic shutter process for discharging information charges generated in a part of the photoelectric conversion element in the first exposure process;
A transfer process for transferring information charges left in the electronic shutter process;
After the transfer process, the information charge is generated by exposing the photoelectric conversion element for a time different from the first exposure process in a state where the transferred information charge remains in a part of the photoelectric conversion element. Two exposure processes;
A driving device characterized in that The drive device according to claim 1,
The electronic shutter process is configured to discharge the information charges generated in the first exposure process for each set, with the photoelectric conversion elements being set for each period along the column direction. The drive device according to claim 2,
The driving apparatus characterized in that the electronic shutter process switches the set of the photoelectric conversion elements that are the discharge targets of information charges for each frame. The drive device according to claim 1,
In the electronic shutter process, a color filter having any one transmission region of the color filters is selected, and some of the pixels in which color filters having a transmission region other than the selected color filter are arranged Is a process of discharging the information charge of
The transfer process is a process of transferring the information charges remaining in the electronic shutter process so as to add up the information charges remaining in the electronic shutter process,
A third exposure process for generating information charges by exposing the photoelectric conversion element after the transfer process;
A second electronic shutter process for discharging information charges of some of the pixels in which the selected color filter is disposed;
Performing a second transfer process for transferring the information charges remaining in the second electronic shutter process so as to add up the information charges remaining in the second electronic shutter process;
A driving apparatus that performs the second exposure process after the second transfer process. It is a drive device as described in any one of Claims 1-4, Comprising:
The transfer process transfers the information charges remaining in the shutter process in the column forward direction or the reverse direction for the period. It is a drive device as described in any one of Claims 1-5, Comprising:
The driving apparatus according to claim 1, wherein an exposure time in the first exposure process is set longer than an exposure time in the second exposure process. The drive device according to claim 4,
An exposure time in the third exposure process is set longer than an exposure time in the second exposure process. A plurality of photoelectric conversion elements arranged in a matrix and a plurality of vertical shift registers that sequentially transfer information charges generated by the photoelectric conversion elements in a column direction, and a color filter having the same transmission region is the photoelectric conversion element A solid-state imaging device arranged at a predetermined cycle along the column direction on the light receiving surface, and a driving method for driving the solid-state imaging device,
A first exposure step of generating information charges by exposing the photoelectric conversion element;
An electronic shutter step of discharging information charges generated in a part of the photoelectric conversion element in the first exposure step;
A transfer step of transferring information charges left in the electronic shutter process;
After the transfer process, the information charge is generated by exposing the photoelectric conversion element for a time different from the first exposure process in a state where the transferred information charge remains in a part of the photoelectric conversion element. Two exposure steps;
The driving method characterized by performing. The driving method according to claim 8, wherein
The electronic shutter step includes discharging the information charges generated in the first exposure step for each set, with the photoelectric conversion elements being set for each cycle along the column direction. The driving method according to claim 9, wherein
The driving method according to claim 1, wherein the electronic shutter step switches a set of the photoelectric conversion elements that are targets of discharging information charges for each frame. The driving method according to claim 8, wherein
The electronic shutter process selects a color filter having any one transmission area from among the color filters, and a part of pixels in which a color filter having a transmission area other than the selected color filter is arranged The process of discharging the information charge of
The transfer step is a step of transferring the information charges left in the electronic shutter process so as to add up the information charges left in the electronic shutter step,
Furthermore, after the transfer step, a third exposure step of generating information charges by exposing the photoelectric conversion element,
A second electronic shutter process for discharging information charges of some of the pixels in which the selected color filter is disposed;
Performing a second transfer step of transferring the information charges left in the second electronic shutter step so as to add up the information charges left in the second electronic shutter step;
A driving method comprising performing the second exposure step after the second transfer step. It is a drive method as described in any one of Claims 8-10, Comprising:
In the driving method, the information charge remaining in the shutter process is transferred in the column forward direction or the reverse direction for the period. It is a drive method as described in any one of Claims 8-11, Comprising:
The driving method according to claim 1, wherein an exposure time in the first exposure step is set longer than an exposure time in the second exposure step. It is a drive method of Claim 11, Comprising:
The driving method characterized in that the exposure time in the third exposure step is set longer than the exposure time in the second exposure step.

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