JP6318526B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

There is known an imaging apparatus that uniformly controls imaging conditions such as an exposure amount over the entire imaging area (see, for example, Patent Document 1).
Patent Document 1 Japanese Patent Application Laid-Open No. 08-22044

  In the conventional imaging apparatus, since imaging is performed under uniform imaging conditions in the entire imaging area, the optimal imaging conditions may not be obtained at all locations in the imaging area depending on the subject.

  In the aspect of the present invention, the first imaging region has a first imaging region and a second imaging region, and the first image signal generated according to the light incident on the first imaging region and the light incident on the second imaging region An imaging unit that outputs the generated second image signal, a first signal conversion unit that converts the first image signal into a first digital image signal, and a second signal that converts the second image signal into a second digital image signal. A two-signal conversion unit; a first determination unit that determines a state of at least one of the upper bits of the first digital image signal; and a state of at least one of the upper bits of the second digital image signal A second determination unit and a control unit that controls the imaging conditions of the first imaging region based on the determination result of the first determination unit and controls the imaging conditions of the second imaging region based on the determination result of the second determination unit An imaging device comprising: .

  The summary of the invention does not enumerate all the features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows an example of a structure of the imaging device 500 which concerns on embodiment of this invention. 3 is a diagram illustrating a configuration example of an imaging region 131. 5 is a timing chart illustrating an operation example of the imaging apparatus 500. 4 is a flowchart illustrating an outline of an operation of the imaging apparatus 500 illustrated in FIG. 3. 12 is a timing chart illustrating another operation example of the imaging apparatus 500. 6 is a flowchart illustrating an outline of the operation of the imaging apparatus 500 illustrated in FIG. 5. 12 is a timing chart illustrating another operation example of the imaging apparatus 500. 8 is a flowchart illustrating an outline of the operation of the imaging apparatus 500 illustrated in FIG. 7. FIG. 20 is a diagram illustrating another configuration example of the imaging apparatus 500. It is a figure which shows the other structural example of the imaging area. FIG. 20 is a diagram illustrating another configuration example of the imaging apparatus 500. It is sectional drawing of the image pick-up element 200 which concerns on this embodiment. FIG. 25 is a block diagram illustrating a more detailed configuration example of the imaging apparatus 500.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating an example of a configuration of an imaging apparatus 500 according to an embodiment of the present invention. The imaging device 500 is a camera that captures a still image or a moving image, for example. The imaging apparatus 500 of this example includes an imaging unit 100, a plurality of AD conversion units 180, a plurality of determination units 182 and a control unit 184.

  The imaging unit 100 has a plurality of imaging areas 131. Each imaging region 131 accumulates charges according to incident light. Each imaging region 131 has one or more photoelectric conversion units that convert incident light into electric charges and store them. The imaging device 500 generates an image signal corresponding to incident light by reading out the amount of charge accumulated in each imaging region 131. FIG. 1 shows a first imaging area 131-1 for generating a first image signal and a second imaging area 131-2 for generating a second image signal. The first imaging region 131-1 has one or more first photoelectric conversion units, and the second imaging region 131-2 has one or more second photoelectric conversion units.

  The AD conversion unit 180 is provided corresponding to each imaging region 131. FIG. 1 shows a first AD converter 180-1 and a second AD converter 180-2 corresponding to the first imaging region 131-1 and the second imaging region 131-2. Each AD conversion unit 180 is an example of a signal conversion unit that converts an analog image signal corresponding to a charge accumulation amount in a corresponding imaging region 131 into a digital image signal. The first AD converter 180-1 converts the first image signal into a first digital image signal, and the second AD converter 180-2 converts the second image signal into a second digital image signal. One AD converter 180 may function as a plurality of AD converters 180. In this case, one AD conversion unit 180 sequentially reads out the charges accumulated in the respective imaging regions 131 and converts them into digital image signals. Further, when the imaging region 131 includes a plurality of photoelectric conversion units, the AD conversion unit 180 may sequentially read the charge amounts generated by the plurality of photoelectric conversion units and convert them into digital image signals.

  The determination unit 182 is provided corresponding to each AD conversion unit 180. In FIG. 1, the 1st determination part 182-1 and the 2nd determination part 180-2 corresponding to the 1st AD conversion part 180-1 and the 2nd AD conversion part 180-2 are shown. Each determination unit 182 determines the state of at least one of the upper bits of the digital image signal output from the corresponding AD conversion unit 180. That is, the plurality of determination units 182 determine the state of the upper bits for each digital image signal.

  Note that the “upper bit” of the digital image signal is the side with the larger charge accumulation amount when the bits of the digital image signal are arranged in the order of the corresponding charge accumulation amount (or the luminance value of the image signal). Is half the bit. “The magnitude of the corresponding charge accumulation amount” corresponds to the magnitude of the fluctuation amount of the charge accumulation amount when the value of the bit changes. For example, in an M-bit digital image signal corresponding to a size of 2 ^ (k−1) in order from the left bit (where k is an integer from M to 1, and the leftmost bit is k = M, the rightmost bit is k = 1), and the “upper bit” refers to bits from k = M to (M / 2) +1. When M is an odd number, M / 2 may be rounded up or down.

  Of the bits of the digital image signal, the bit with the largest charge accumulation amount (in the above example, the bit with k = M) is the most significant bit (MSB), and the bit with the next largest charge accumulation amount (In the above example, k = M−1 bits) is referred to as MSB-1, and similarly, as MSB-2, MSB-3,.

  In addition, each bit of the digital image signal transitions from a first logical value indicating a small charge accumulation amount (or a luminance value of the image signal) to a second logical value indicating a large state. In this example, the first logical value is “0”, and the second logical value is “1”.

  By determining the state of the upper bits of the digital image signal, the charge accumulation amount (that is, the brightness of the incident light) accumulated in the corresponding imaging region 131 (that is, the photoelectric conversion unit in the imaging region 131) for a predetermined charge accumulation time. ) Can be easily detected. The control unit 184 controls the imaging condition in the imaging region 131 corresponding to each determination unit 182 for each imaging region 131 based on the determination result in each determination unit 182. For example, the control unit 184 controls the imaging condition of the first imaging region 131-1 based on the determination result of the first determination unit 182-1 and the second imaging based on the determination result of the second determination unit 182-2. The imaging condition of the region 131-2 is controlled. As a result, an optimum imaging condition can be set for each imaging region 131.

  For example, when the logical value of the most significant bit MSB of the digital image signal is “0”, it is estimated that the digital image signal is not saturated even if the charge accumulation time is doubled for the corresponding imaging region 131. The control unit 184 sets the charge accumulation time of the imaging region 131 to be longer in order to make maximum use of the range of the digital image signal. The control unit 184 can also control the amplification factor of the analog signal in the previous stage of the AD conversion unit 180 based on the determination result in the determination unit 182. As described above, the control unit 184 can optimize various imaging conditions for each imaging region 131. The imaging conditions include other conditions that affect the digital image signal among the parameters that can be controlled by the imaging apparatus 500, in addition to the charge accumulation time, the frame rate, and the analog signal amplification factor in the photoelectric conversion unit. .

  Further, the determination unit 182 may determine the state of upper bits other than the most significant bit MSB. For example, the determination unit 182 determines the state of the upper bit MSB-1 in addition to the most significant bit MSB. When the logical values of these bits are both “0”, it is estimated that the digital image signal is not saturated even if the charge accumulation time is quadrupled for the corresponding imaging region 131. The control unit 184 sets the charge accumulation time of the imaging region 131 to 4 times, for example.

  The plurality of AD conversion units 180 read out image signals in parallel and convert them into digital image signals, respectively. The plurality of determination units 182 determine the state of the upper bits of the digital image signal in parallel. The control unit 184 sets imaging conditions such as a charge accumulation time in parallel with each imaging region 131.

  FIG. 2 is a diagram illustrating a configuration example of the imaging region 131. In this example, each imaging region 131 includes one photoelectric conversion unit 104, a transfer transistor 152, a reset transistor 154, an amplification transistor 156, and a selection transistor 158.

  The source and drain of the transfer transistor 152 are connected to the output terminal of the photoelectric conversion unit 104 and the gate of the amplification transistor 156, respectively. The parasitic capacitance in the wiring between the output terminal of the photoelectric conversion unit 104 and the source of the transfer transistor 152 functions as a charge accumulation unit that accumulates charges generated by the photoelectric conversion unit 104. In this example, the charge storage unit is a part of the photoelectric conversion unit 104. A transfer signal Tx for controlling whether or not to transfer the amount of charge stored in the charge storage unit is input to the gate of the transfer transistor 152.

  The reference voltage VDD is input to the drain of the reset transistor 154, and the source is connected to the gate of the amplification transistor 156. A reset signal R for controlling whether or not to reset the amount of charge accumulated in the charge accumulating unit is input to the gate of the reset transistor 154.

  The reference voltage VDD is input to the drain of the amplification transistor 156, and the source is connected to the drain of the selection transistor 158. The amplification transistor 156 outputs an analog image signal corresponding to the amount of charge transferred from the transfer transistor 152. The selection signal S is input to the gate of the selection transistor 158, and the source is connected to the AD conversion unit 180. The transfer transistor 152 inputs the image signal from the transfer transistor 152 to the AD converter 180 according to the selection signal S.

  In this example, one AD conversion unit 180 and one determination unit 182 are provided for one photoelectric conversion unit 104. In addition, a transfer signal Tx, a reset signal R, and a selection signal S are independently input to each imaging region 131. For this reason, it is possible to determine the state of the upper bits of the digital image signal for each photoelectric conversion unit 104 and to control the imaging conditions such as the charge accumulation time for each photoelectric conversion unit 104. In this specification, the charge accumulated in the photoelectric conversion unit 104 and the charge accumulation time may be referred to as the charge accumulated in the imaging region 131 in which the photoelectric conversion unit 104 exists and the charge accumulation time. .

  FIG. 3 is a timing chart illustrating an operation example of the imaging apparatus 500. In FIG. 3, the horizontal axis indicates time. The imaging apparatus 500 of this example acquires one image based on a digital image signal acquired within a preset setting period. The image may be a still image or a single frame image in a moving image.

  The control unit 184 of this example controls the charge accumulation time of the n imaging regions 131 based on the most significant bit of the n digital image signals. In FIG. 3, among the bits of each digital image signal, the bit described closest to the minus direction on the time axis is the most significant bit.

  The control unit 184 in this example controls the length of the charge accumulation time of each imaging region 131 in units of frames having a predetermined length. In this example, the set period is divided into seven frames.

  First, each imaging region 131 accumulates charges using the frame 1 having a common length as a charge accumulation period. Each AD converter 180 converts the charge accumulated in the corresponding imaging region 131 into a digital image signal. Each determination unit 182 determines the state of the most significant bit of the corresponding digital image signal.

  The control unit 184 does not change the most significant bit from the first logical value indicating the small charge accumulation amount to the second logical value indicating the large state (that is, the logical value is “0”). In the case), the charge accumulation time of the corresponding imaging region 131 is set to a time longer than a preset charge accumulation time. In this example, the control unit 184 sets the charge accumulation time of the imaging region 131 to two frames.

  Next, the imaging region 131 in which the most significant bit of the corresponding digital image signal is “0” accumulates charges using the frames 2 and 3 as the charge accumulation time. The operations of the corresponding AD conversion unit 180 and determination unit 182 are the same as those of frame 1. In addition, when the most significant bit of the digital image signal transitions from the logical value “0” to the logical value “1” in the frame 1, the control unit 184 displays the corresponding imaging area until the set period elapses. The reading of the electric charges accumulated by 131 is stopped. Power consumption can be reduced by stopping the reading operation of the AD conversion unit 180. In addition, by stopping the reading of the charge in the imaging region in which the most significant bit of the digital image signal has transitioned from the logical value “0” to the logical value “1”, the number of memories (capacity) used to store the digital image signal ) Can be reduced. Furthermore, it is possible to reduce the amount of computation such as image processing in the subsequent stage as the number of memories decreases.

  The control unit 184 further doubles the charge accumulation time of the imaging region 131 in which the most significant bit of the digital image signal is determined to be “0” in the frames 2 and 3. Further, the AD conversion unit 180 in which the most significant bit of the digital image signal is determined to be “1” in the frames 2 and 3 stops the subsequent reading operation.

  As described above, the control unit 184 repeats the setting of the charge accumulation time for each imaging region 131 until a predetermined setting period elapses. The control unit 184 calculates the brightness of incident light (that is, the luminance value of the image signal) to each imaging region 131 based on the digital image signal acquired within the set period.

  The control unit 184 of this example integrates digital image signals acquired within the set period for each imaging region 131. In addition, the control unit 184 multiplies the integrated digital image signal of each imaging region 131 by a coefficient corresponding to the charge accumulation time of each imaging region 131 to calculate the luminance value of each imaging region 131. In this example, the coefficient can be calculated by dividing the length of the set period by the integrated value of the charge accumulation time of the imaging region 131.

  For example, for the imaging region 131-1 in the example of FIG. 3, the three digital image signals acquired in the frame 1, the frame 2-3, and the frame 4-7 are integrated. For the imaging region 131-1, since the accumulation of the charge accumulation time is over the entire set period, the coefficient is 1. For the imaging region 131-2, the two digital image signals acquired in the frames 1 and 2-3 are integrated. In addition, for the imaging region 131-2, the accumulation of the charge accumulation time is 3/7 of the set period. Therefore, the coefficient is 7/3.

  Similarly, for the imaging region 131-3, the digital image signal acquired in frame 1 is multiplied by a coefficient 7. By such processing, the brightness value of the image data can be calculated by compensating for the difference in the accumulated value of the charge accumulation time in each imaging region 131. In addition, the charge accumulation time of each imaging region 131 can be optimized, and the digital value range of the AD conversion unit 180 can be utilized to the maximum. Thereby, for example, the so-called overexposure in which the value of the image signal output from the imaging region 131 corresponding to the subject with high brightness is large and the digital image signal after digital conversion is saturated and the brightness becomes constant can be reduced. it can. Further, for example, it is possible to reduce so-called black crushing in which a value of an image signal output from the imaging region 131 corresponding to a low-luminance subject is small and a gradation difference does not appear in the digital image signal after digital conversion. Note that it is possible to prevent overexposure by sufficiently shortening the initial value of the charge accumulation time (for example, the length of the frame 1).

  In this example, the digital image signals acquired within the set period are integrated for each imaging region 131, but in another example, the luminance value is calculated using only the digital image signal acquired last for each imaging region 131. It's okay. In this case, the coefficient is determined by the ratio of the length of the charge accumulation time when the digital image signal is last acquired for each imaging region 131. For example, for the imaging region 131-1, the digital image signal acquired in the frame 4-7 is multiplied by a coefficient 1. For the imaging region 131-2, the digital image signal acquired in the frame 2-3 is multiplied by a coefficient 4/2 = 2. For the imaging region 131-3, the digital image signal acquired in frame 1 is multiplied by a coefficient 4/1 = 4.

  In addition, the control unit 184 of this example doubles the charge accumulation time for the imaging region 131 in which the most significant bit of the digital image signal is 1, but the magnification is not limited to double. The magnification may be a value of 2 times or less and may be a value of more than 2 times.

  In addition, the control unit 184 of this example controls the charge accumulation time based on only the most significant bit of the digital image signal. However, the control unit 184 may control the charge accumulation time based on the other upper bits of the digital image signal. . In this case, the magnification when resetting the charge accumulation time may be controlled according to the number of upper bits of the digital image signal used for resetting. For example, when the upper 2 bits of the most significant bit MSB and the upper bit MSB-1 of the digital image signal are both “0”, the control unit 184 increases the charge accumulation time of the corresponding imaging region 131 by 2 digits × 2 = 4 times. To. Similarly, when the upper p digits are all “0”, the control unit 184 may increase the charge accumulation time of the corresponding imaging region 131 by 2 × p times.

  The control unit 184 may set the charge accumulation time longer when the digital image signal does not exceed a predetermined threshold. For example, the control unit 184 sets the charge accumulation time longer when the digital image signal does not exceed 90% of the saturation value. In this case, the charge accumulation time may be set to 2 times, may be set to 10/9 times, or may be set to other magnifications.

  In the example of FIG. 3, the start points of the charge accumulation times of all the imaging regions 131 (in FIG. 3, the start points of frame 1, frame 2, and frame 4) are the same, but the start points are not the same. Also good. In the example of FIG. 3, the length of the charge accumulation time is controlled in units of frames. However, the length of the frames may be changed for each imaging region 131. The length of the charge accumulation time in each imaging region 131 can be controlled by the timing of the reset signal R and the timing of the selection signal S described in FIG.

  FIG. 4 is a flowchart showing an outline of the operation of the imaging apparatus 500 shown in FIG. When the set period starts, first, in S602, each imaging region 131 accumulates charges for a predetermined charge accumulation time. Then, the AD conversion unit 180 converts the charge accumulation amount into a digital image signal.

  In S <b> 604, each determination unit 182 determines whether the most significant bit MSB of the digital image signal is “1” for the corresponding imaging region 131. The control unit 184 resets the charge accumulation time to twice for the imaging region 131 in which the most significant bit MSB is not “1” (S606). In addition, the control unit 184 stops charge accumulation and charge amount readout for the imaging region 131 in which the most significant bit MSB is “1” (S608).

  In S610, the control unit 184 determines whether or not a predetermined set time has expired. If the set time has not ended, the processing from S602 is repeated using the charge accumulation time reset in S606. If the predetermined set time has expired, the process is terminated. After the end of the processing, the control unit 184 calculates the luminance value of each imaging region 131 based on each acquired digital image signal.

  FIG. 5 is a timing chart showing another operation example of the imaging apparatus 500. When the most significant bit of the digital image signal transitions from the first logical value “0” to the second logical value “1”, the control unit 184 of this example until the predetermined setting period elapses. The charge accumulation time setting is maintained for the corresponding imaging region 131. Then, the photoelectric conversion unit 104 in the corresponding imaging region 131 is repeatedly accumulated with the charge during the charge accumulation time, and the corresponding AD conversion unit 180 is repeatedly read out the charge accumulated with the charge accumulation time. . Other operations are the same as those described in FIGS. 3 and 4.

  For example, for the imaging region 131-2, since the most significant bit of the digital image signal read in the frame 2-3 is “1”, the control unit 184 maintains the charge accumulation time in the imaging region 131-2 for two frames. Then, charge accumulation and readout are repeated. For the imaging region 131-i, since the most significant bit of the digital image signal read in frame 1 is “1”, the control unit 184 maintains the charge accumulation time in the imaging region 131-i for one frame, Repeat charge accumulation and readout.

  When the set period ends, the control unit 184 integrates the read digital image signals for each imaging region 131. In this example, the accumulated charge accumulation times of the respective imaging regions 131 are equal. For this reason, the control unit 184 may calculate the integrated value of the digital image signal as it is as the luminance value.

  In the imaging apparatus 500 of this example, each imaging region 131 operates over the entire set period. For this reason, the noise etc. which occurred within the setting period can be averaged. In addition, since the period during which each imaging region 131 operates is the same, the imaging timing between the imaging regions 131 can be made the same.

  FIG. 6 is a flowchart showing an outline of the operation of the imaging apparatus 500 shown in FIG. The flowchart of this example is different from the flowchart shown in FIG. 4 in that S612 is provided instead of S608. In this example, the control unit 184 maintains the charge accumulation time setting for the imaging region 131 whose most significant bit MSB is “1” (S612). The imaging apparatus 500 repeats charge accumulation and readout using the charge accumulation time setting until a predetermined set time is over.

  In addition, the imaging apparatus 500 may selectively execute the operation illustrated in FIG. 3 and the operation illustrated in FIG. The imaging apparatus 500 may select any operation based on a user operation. In addition, the imaging apparatus 500 selects the power saving mode shown in FIG. 3 when the remaining amount of the battery is less than the predetermined value, and when the remaining amount of the battery is equal to or more than the predetermined value, the imaging apparatus 500 is shown in FIG. High accuracy mode may be selected.

  FIG. 7 is a timing chart showing another operation example of the imaging apparatus 500. When all the bits of the digital image signal transition from the first logical value “0” to the second logical value “1”, the control unit 184 of the present example charges the charge in the corresponding imaging region 131. The accumulation time is set to a time shorter than the currently set charge accumulation time. That is, even when the most significant bit of the digital image signal is “1”, the control unit 184 shortens the charge accumulation time when all the bits of the digital image signal are “1”. To do. Thereby, over-exposure in the image can be prevented. Other operations are the same as the operation examples described in FIGS.

  In the example of FIG. 7, all bits of the digital image signal in the imaging region 131-1 are “1” in the frame 1. The control unit 184 shortens the charge accumulation time of the imaging region 131-1 shorter than one frame. For example, the control unit 184 sets the charge accumulation time of the imaging region 131-1 to 0.5 frames. The control unit 184 gradually shortens the charge accumulation time in the imaging region 131-1 until the digital image signal in the imaging region 131-1 is no longer saturated (a state in which all bits are “1”).

  In addition, when the most significant bit of the digital image signal in the imaging region 131-1 becomes “0”, the control unit 184 may lengthen the charge accumulation time in the imaging region 131-1. At this time, it is preferable to set a time shorter than the charge accumulation time in which the digital image signal is already known to be saturated. For example, if the digital image signal is saturated in the case of the charge accumulation time for one frame, and the most significant bit of the digital image signal becomes “0” in the case of the charge accumulation time for 0.4 frame, the next charge The accumulation time is set to about 0.7 frames. In the operation example described with reference to FIGS. 3 to 7, the control unit 184 may calculate the length of the newly set charge accumulation time by dividing the remainder of the set period by an arbitrary integer.

  Further, the control unit 184 may integrate the digital image signals by excluding the saturated digital image signals for each imaging region 131. In this case, the integrated digital image signal is multiplied by a coefficient corresponding to the length of the charge accumulation time corresponding to the excluded digital image signal. Thereby, an error due to saturation of the digital image signal can be eliminated.

  In addition, the control unit 184 performs processing before the set period elapses on the condition that the most significant bit of the digital image signal is “1” and the digital image signal is not saturated for all the imaging regions 131. You may end. Thereby, processing time can be shortened.

  FIG. 8 is a flowchart showing an outline of the operation of the imaging apparatus 500 shown in FIG. In the flowchart of this example, the processes of S614 and S616 are added to the flowchart shown in FIG. If it is determined that the most significant bit of the digital image signal is “1” (S604), in S614, it is determined whether all the bits of the digital image signal are “1”, that is, whether or not it is saturated. When the digital image signal is saturated, the charge accumulation time of the corresponding imaging region 131 is halved, for example (S616). When the digital image signal is not saturated, the processing after S608 is executed. Instead of S608, the process of S612 shown in FIG. 6 may be executed.

  FIG. 9 is a diagram illustrating another configuration example of the imaging apparatus 500. The imaging apparatus 500 of this example further includes an operation unit 186 in addition to the configuration of the imaging apparatus 500 described with reference to FIG. The operation unit 186 receives user operations.

  When the operation unit 186 receives the first operation from the user, the control unit 184 sets the charge accumulation time for each imaging region 131 in the setting period as described with reference to FIGS. 3 to 8. Repeatingly, the optimum setting of the charge accumulation time is acquired in advance for each imaging region 131. Here, the optimum setting of the charge accumulation time refers to the charge accumulation time when the digital image signal is last acquired.

  For example, in the example of FIG. 3, the optimum setting of the charge accumulation time of the imaging region 131-1 is for four frames, the optimum setting of the charge accumulation time of the imaging region 131-2 is for two frames, and the imaging region 131-3 The optimum setting of the charge accumulation time is one frame. The first operation is an operation in which, for example, the shutter button of the imaging device 500 is half pressed.

  When the operation unit 186 receives the second operation from the user, the control unit 184 causes the imaging unit 100 to image the subject using the optimal setting of the charge accumulation time. In this case, the control unit 184 sets the optimum setting of the charge accumulation time for each imaging region 131, and repeats the accumulation and reading of the charge during the charge accumulation time within a predetermined imaging period. The number of repetitions may be one. The second operation is an operation in which, for example, the shutter button of the imaging device 500 is fully pressed.

  For example, the control unit 184 calculates the luminance value of each imaging region 131 by integrating digital image signals acquired within the imaging period. Further, the control unit 184 may multiply the integrated digital image signal by a coefficient corresponding to the difference in the accumulated value of the charge accumulation time between the imaging regions 131. Since the imaging apparatus 500 of this example acquires the optimum setting of the charge accumulation time of each imaging area 131 in advance, the luminance value of each imaging area 131 can be calculated efficiently.

  FIG. 10 is a diagram illustrating another configuration example of the imaging region 131. In this example, each imaging region 131 includes a plurality of photoelectric conversion units 104. Further, each of the photoelectric conversion units 104 includes a transfer transistor 152, a reset transistor 154, an amplification transistor 156, and a selection transistor 158.

  In this example, the AD conversion unit 180 sequentially reads out the charges accumulated by the plurality of photoelectric conversion units 104 included in each imaging region 131 and converts them into digital image signals. The determination unit 182 determines the state of the upper bits of each digital image signal corresponding to the plurality of photoelectric conversion units 104. For example, the determination unit 182 may determine the state of the upper bits of the average digital image signal obtained by averaging the digital image signals.

  The control unit 184 controls imaging conditions such as the charge accumulation time of the corresponding imaging region 131 based on the determination result in the determination unit 182. In this example, the imaging conditions in the respective photoelectric conversion units 104 included in the imaging region 131 are the same. The method for controlling the charge accumulation time and the like is the same as the example described in relation to FIGS. With such a configuration, appropriate imaging conditions can be set for each imaging region 131 including the plurality of photoelectric conversion units 104.

  FIG. 11 is a diagram illustrating another configuration example of the imaging apparatus 500. The imaging apparatus 500 of this example includes a plurality of amplifiers 188 in addition to the configuration of the imaging apparatus 500 described with reference to FIGS. The amplifier 188 is provided between each imaging region 131 and the AD conversion unit 180. The amplifier 188 amplifies the analog image signal from the corresponding imaging region 131 and inputs the amplified image signal to the corresponding AD conversion unit 180. In FIG. 11, a first amplifier 188-1 and a second amplifier 188-2 corresponding to the first AD converter 180-1 and the second AD converter 180-2 are shown. Note that the amplifier 188 may be incorporated in the corresponding AD conversion unit 180. That is, the amplifier 188 and the AD conversion unit 180 may be formed as one element.

  The control unit 184 independently controls the amplification factor of each amplifier 188 based on the upper bits of the corresponding digital image signal and the charge accumulation time. For example, when the charge storage time is reset to a longer time and the control unit 184 becomes longer than a predetermined time, the control unit 184 maintains the charge storage time and increases the amplification factor in the amplifier 188. This can prevent the charge accumulation time from becoming too long.

  Further, the control unit 184 determines whether the most significant bit of the digital image signal becomes “1” within the set time by increasing the charge accumulation time based on the upper bits of the digital image signal. Also good. When the control unit 184 determines that the most significant bit is not “1”, the control unit 184 may increase the amplification factor in the amplifier 188. For example, in the example of FIG. 3, when both the most significant bit MSB and the upper bit MSB-1 of the digital image signal acquired in the frame 2-3 are “0”, the digital image can be obtained even if the charge accumulation time is doubled. The most significant bit MSB of the signal is predicted not to be “0”. In such a case, the control unit 184 doubles the amplification factor of the corresponding amplifier 188 while doubling the charge accumulation time. Further, when the charge accumulation time is shorter than the frame length as in the digital image signal of the imaging region 131-1 illustrated in FIG. 7, the charge accumulation time may be maintained to reduce the amplification factor in the amplifier 188. .

  FIG. 12 is a cross-sectional view of the image sensor 200 according to the present embodiment. In this example, a so-called back-illuminated image sensor 200 is shown, but the image sensor 200 is not limited to the back-illuminated type and may be a front-illuminated type. The image sensor 200 may have a structure including a laminated chip laminated on the imaging chip 113.

  The imaging element 200 of this example includes an imaging chip 113 that outputs an image signal corresponding to incident light, a signal processing chip 111 that processes the image signal, and a memory chip 112 that stores the image signal. The imaging chip 113, the signal processing chip 111, and the memory chip 112 are stacked, and are electrically connected to each other by a plurality of conductive bumps 109 such as Cu. In this example, the signal processing chip 111 and the memory chip 112 correspond to the above-described laminated chip.

  As shown in the figure, incident light is incident mainly in the positive direction of the Z-axis indicated by a white arrow. In the present embodiment, in the imaging chip 113, the surface on the side where incident light is incident is referred to as a back surface. Further, as indicated by the coordinate axes, the right direction on the paper orthogonal to the Z axis is the X axis plus direction, and the front side of the paper orthogonal to the Z axis and the X axis is the Y axis plus direction.

  An example of the imaging chip 113 is a back-illuminated MOS image sensor. The imaging chip 113 corresponds to the imaging unit 100 illustrated in FIGS. 1 to 11. The PD layer 106 is disposed on the back side of the wiring layer 108. The PD layer 106 includes a plurality of photoelectric conversion units 104 that generate charges corresponding to light. The imaging chip 113 outputs an image signal corresponding to the charge. The PD layer 106 in this example includes a plurality of photoelectric conversion units 104 arranged two-dimensionally, and a transistor 105 provided corresponding to the photoelectric conversion unit 104. The transistor 105 corresponds to each transistor in FIG.

  A color filter 102 is provided on the incident side of incident light in the PD layer 106 via a passivation film 103. The color filter 102 has a plurality of types that transmit different wavelength regions, and has a specific arrangement corresponding to each of the photoelectric conversion units 104. A set of the color filter 102, the photoelectric conversion unit 104, and the transistor 105 forms one pixel.

  On the incident light incident side of the color filter 102, a microlens 101 is provided corresponding to each pixel. The microlens 101 condenses incident light toward the corresponding photoelectric conversion unit 104.

  The wiring layer 108 includes a wiring 107 that transmits an image signal from the PD layer 106 to the signal processing chip 111. The wiring 107 may be multilayer, and a passive element and an active element may be provided.

  A plurality of bumps 109 are disposed on the surface of the wiring layer 108. The plurality of bumps 109 are aligned with the plurality of bumps 109 provided on the opposing surfaces of the signal processing chip 111, and the imaging chip 113 and the signal processing chip 111 are pressed and aligned. The bumps 109 are joined and electrically connected.

  Similarly, a plurality of bumps 109 are disposed on the mutually facing surfaces of the signal processing chip 111 and the memory chip 112. The bumps 109 are aligned with each other, and the signal processing chip 111 and the memory chip 112 are pressurized, so that the aligned bumps 109 are joined and electrically connected.

  The bonding between the bumps 109 is not limited to Cu bump bonding by solid phase diffusion, and micro bump bonding by solder melting may be employed. Further, for example, one bump 109 may be provided for one output wiring described later, or a plurality of bumps 109 may be provided. The size of the bump 109 may be larger than the pitch of the photoelectric conversion unit 104. Further, a bump larger than the bump 109 corresponding to the pixel region may be provided in a peripheral region other than the pixel region where the pixels are arranged.

  The signal processing chip 111 receives an analog image signal output from the imaging chip 113. The signal processing chip 111 performs predetermined signal processing on the received image signal and outputs it to the memory chip 112. The memory chip 112 stores a signal received from the signal processing chip 111.

  In the signal processing chip 111 of this example, a plurality of AD conversion units 180 and a plurality of determination units 182 are provided. The signal processing chip 111 may further include a control unit 184. Each AD converter 180 converts an analog image signal output from the imaging chip 113 into a digital image signal. The signal processing chip 111 may perform a predetermined calculation such as correction on the digital image signal.

  At least some of the plurality of AD conversion units 180 are two-dimensionally arranged on an ADC arrangement plane parallel to a plane on which a plurality of pixels are provided. For example, a plurality of pixels are arranged two-dimensionally along the row direction and the column direction in the imaging chip 113, and a plurality of AD conversion units 180 are arranged two-dimensionally along the row direction and the column direction in the signal processing chip 111. Is done. The plurality of AD converters 180 are preferably arranged at equal intervals in the signal processing chip 111.

  Further, at least two or more AD conversion units 180 among the plurality of AD conversion units 180 arranged on the ADC arrangement plane operate in parallel. The parallel operation indicates that analog-digital conversion processing in the plurality of AD conversion units 180 is performed substantially simultaneously. As a result, the two or more AD converters 180 generate heat substantially simultaneously, and variations in temperature distribution can be reduced as compared to the case where a plurality of AD converters 180 move independently. In addition, it is preferable that all of the plurality of AD conversion units 180 arranged on the ADC arrangement surface operate almost simultaneously. Thereby, the temperature distribution due to the heat generation of the AD converter 180 can be made uniform. In addition, the plurality of AD conversion units 180 may be non-uniformly arranged on the ADC arrangement surface of the signal processing chip 111. For example, the plurality of AD conversion units 180 may be arranged so that the density at the end is higher than the center of the ADC arrangement surface of the signal processing chip 111.

  In addition, the plurality of AD conversion units 180 may be arranged on a plurality of ADC arrangement surfaces having different positions in the Z-axis direction in the signal processing chip 111. That is, the signal processing chip 111 is a multilayer chip, and the plurality of AD conversion units 180 may be provided in different layers. Even in this case, when the positions where the plurality of AD conversion units 180 are arranged are projected onto a single ADC arrangement plane, the AD conversion units 180 are preferably arranged at equal intervals.

  The signal processing chip 111 has TSVs (through silicon vias) 110 that connect circuits provided on the front and back surfaces to each other. The TSV 110 is preferably provided in the peripheral area. The TSV 110 may also be provided in the peripheral area of the imaging chip 113 and the memory chip 112.

  FIG. 13 is a block diagram illustrating a more detailed configuration example of the imaging apparatus 500. The imaging apparatus 500 includes a photographic lens 520 as a photographic optical system, and the photographic lens 520 guides a subject luminous flux incident along the optical axis OA to the imaging unit 100. The photographing lens 520 may be an interchangeable lens that can be attached to and detached from the imaging apparatus 500. The imaging apparatus 500 mainly includes an imaging unit 100, a system control unit 501, a drive unit 502, a photometry unit 503, a work memory 504, a recording unit 505, and a display unit 506.

  The photographing lens 520 is composed of a plurality of optical lens groups, and forms an image of a subject light flux from the scene in the vicinity of its focal plane. In FIG. 13, a single virtual lens arranged in the vicinity of the pupil is shown as a representative. The drive unit 502 is a control circuit that executes charge accumulation control such as timing control and area control of the imaging unit 100 in accordance with instructions from the system control unit 501. In this example, the drive unit 502 and the system control unit 501 function as the AD conversion unit 180, the determination unit 182, and the control unit 184 described with reference to FIGS. 1 to 12. As illustrated in FIG. 12, a part of the control circuit forming the driving unit 502 and the system control unit 501 may be formed into a chip and stacked on the imaging unit 100.

  The imaging unit 100 delivers the image signal to the image processing unit 511 of the system control unit 501. The imaging unit 100 is the same as the imaging unit 100 described with reference to FIGS. The image processing unit 511 performs various image processing using the work memory 504 as a work space, and generates image data. For example, when generating image data in JPEG file format, compression processing is executed after white balance processing, gamma processing, and the like are performed. The generated image data is recorded in the recording unit 505, converted into a display signal, and displayed on the display unit 506 for a preset time.

  The photometric unit 503 detects the luminance distribution of the scene prior to a series of shooting sequences for generating image data. The photometry unit 503 includes, for example, an AE sensor having about 1 million pixels. The calculation unit 512 of the system control unit 501 receives the output of the photometry unit 503 and calculates the luminance for each area of the scene. The calculation unit 512 determines the shutter speed, aperture value, and ISO sensitivity according to the calculated luminance distribution. Note that the pixels used in the AE sensor may be provided in the imaging unit 100. In this case, the photometric unit 503 separate from the imaging unit 100 may not be provided. Further, the control unit 184 described with reference to FIGS. 1 to 12 may control these imaging conditions.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

100 imaging unit, 101 microlens, 102 color filter, 103 passivation film, 104 photoelectric conversion unit, 105 transistor, 106 PD layer, 107 wiring, 108 wiring layer, 109 bump, 110 TSV, 111 signal processing chip, 112 memory chip, 113 imaging chip, 131 imaging region, 152 transfer transistor, 154 reset transistor, 156 amplification transistor, 158 selection transistor, 180 AD conversion unit, 182 determination unit, 184 control unit, 186 operation unit, 188 amplifier, 200 imaging device, 500 imaging Device, 520 photographing lens, 501 system control unit, 502 drive unit, 503 photometry unit, 504 work memory, 505 recording unit, 506 display unit, 511 image processing unit, 512 calculation unit

Claims (13)

An imaging unit that has a plurality of imaging regions and outputs a first image signal of a subject imaged in the first imaging region among the plurality of imaging regions;
  A first signal converter for converting the first image signal into a digital signal;
  A control unit that controls imaging conditions of the first imaging region,
  In the control unit, the upper bit value of the first image signal of the subject imaged under the imaging condition set in advance in the first imaging area converted into a digital signal by the first signal conversion unit is a first logic value. An imaging apparatus that changes an imaging condition set in the first imaging area when the value does not transition to a second logical value. In the control unit, the most significant bit value of the first image signal of the subject imaged under the imaging condition set in advance in the first imaging area converted into a digital signal by the first signal conversion unit is first. The imaging device according to claim 1, wherein an imaging condition set in the first imaging area is changed when the logical value has not changed to the second logical value.   The first imaging region includes a first photoelectric conversion unit that converts light into electric charge,
  The imaging apparatus according to claim 1, wherein the control unit controls an accumulation time of charges converted by the first photoelectric conversion unit.   The imaging device according to claim 3, wherein the control unit repeats setting of an accumulation time of the charge converted by the first photoelectric conversion unit until a preset period elapses. In the control unit, the upper bit value of the first image signal of the subject imaged under the imaging condition set in advance in the first imaging area converted into a digital signal by the first signal conversion unit is a first logic value. 5. The imaging device according to claim 4, wherein when the value transitions from a value to a second logical value, reading of the charge converted by the first photoelectric conversion unit is stopped. A first amplifier for amplifying the first image signal;
  The first signal converter converts the first image signal amplified by the first amplifier into a digital signal,
  6. The control unit according to claim 1, wherein the control unit controls an amplification factor of the first amplifier based on an upper bit value of the first image signal converted into a digital signal by the first signal conversion unit. The imaging device described in 1.   The imaging unit outputs a second image signal of a subject imaged in a second imaging region different from the first imaging region among the plurality of imaging regions,
  The imaging device according to any one of claims 1 to 6, wherein the control unit controls imaging conditions of the second imaging region.   A second signal converter for converting the second image signal into a digital signal;
  In the control unit, the upper bit value of the second image signal of the subject imaged under the imaging condition set in advance in the second imaging area converted into a digital signal by the second signal conversion unit is a first logic value. The imaging device according to claim 7, wherein an imaging condition set in the second imaging area is changed when the value does not transition to a second logical value.   In the control unit, the most significant bit value of the second image signal of the subject imaged under a preset imaging condition in the second imaging region converted into a digital signal by the second signal conversion unit is first. The imaging apparatus according to claim 8, wherein an imaging condition set in the second imaging area is changed when there is no transition from a logical value to a second logical value.   The second imaging region includes a second photoelectric conversion unit that converts light into electric charge,
  The imaging device according to claim 8 or 9, wherein the control unit controls an accumulation time of the charges converted by the second photoelectric conversion unit.   The imaging device according to claim 10, wherein the control unit repeats setting of an accumulation time of the charge converted by the second photoelectric conversion unit until a preset period elapses.   In the control unit, the upper bit value of the second image signal of the subject imaged under the imaging condition set in advance in the second imaging area converted into a digital signal by the second signal conversion unit is a first logic value. The imaging device according to claim 11, wherein when the value transitions from a value to a second logical value, reading of the charge converted by the second photoelectric conversion unit is stopped.   A second amplifier for amplifying the second image signal;
  The second signal converter converts the second image signal amplified by the second amplifier into a digital signal,
  13. The control unit according to claim 8, wherein the control unit controls an amplification factor of the second amplifier based on an upper bit value of the second image signal converted into a digital signal by the second signal conversion unit. The imaging device described in 1.

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