JP7468632B2 - Image pickup device, image pickup device and apparatus - Google Patents

Description

The present invention relates to an imaging element, an imaging device and an apparatus.

Japanese Patent Laid-Open No. 2003-233693 describes an imaging device that divides one screen into a plurality of blocks, detects the movement of each block, and controls the exposure time for each block.
[Prior Art Literature]
[Patent Documents]
[Patent Document 1] JP 2006-197192 A

General Disclosure

In a first aspect of the present invention, an imaging device is provided. The imaging device includes a plurality of pixels that generate pixel signals in response to incident light, and a setting unit that sets exposure conditions for each of a plurality of blocks, each of which includes at least two pixels, and the setting unit sets exposure conditions for each of the blocks such that the difference between the exposure conditions for each of the blocks is equal to or less than a threshold value.

In a second aspect of the present invention, an imaging device is provided. The imaging device includes a plurality of pixels that generate pixel signals in response to incident light, and a setting unit that sets exposure conditions for a plurality of blocks, each block including at least two pixels, and the setting unit sets exposure conditions for the blocks in response to at least two representative values of luminance corresponding to the pixels in the blocks.

In a third aspect of the present invention, there is provided an imaging device comprising an imaging element of the first or second aspect.

In a fourth aspect of the present invention, there is provided an apparatus. The apparatus includes an image sensor having a plurality of pixels that generate pixel signals in response to incident light, and a setting unit that sets exposure conditions for a plurality of blocks, each of which includes at least two pixels, and the setting unit sets exposure conditions for each block such that the difference between the exposure conditions for each block is equal to or smaller than a threshold value.

Note that the above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions.

1 is a cross-sectional view of an imaging element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a pixel array and blocks of an imaging chip. FIG. 2 is a circuit diagram corresponding to a block of the imaging chip. FIG. 2 is a block diagram showing a functional configuration of an imaging element. FIG. 2 is a block diagram showing the functional configuration of the image sensor 100. FIG. 2 is a block diagram showing the functional configuration of the image sensor 100. 1 is a block diagram showing a configuration of an imaging device according to an embodiment of the present invention. FIG. 11 is a flow chart showing an example of a process for setting an exposure condition. 8 is a diagram comparing an image captured under exposure conditions set according to the flow of FIG. 7 with an image captured under exposure conditions set by another method. FIG. 11 is a flow chart showing an example of a correction process of an exposure condition. 10 is a diagram showing a specific example of setting upper and lower limits of the exposure conditions shown in FIG. 9 . FIG. 11 is a diagram comparing a captured image in which the range of the exposure condition is restricted according to the example of FIG. 10 with a captured image in which the range of the exposure condition is restricted by another method. FIG. 12 is a diagram showing histograms of the exposure conditions used for the respective captured images shown in FIG. 11 . FIG. 11 is a flow chart showing another example of the exposure condition correction process. 14A and 14B are diagrams illustrating a specific example of the exposure condition smoothing process illustrated in FIG. 13 . 15 is a diagram comparing exposure conditions before and after performing the smoothing process according to the example of FIG. 14. FIG. 11 is a flowchart showing a modified example of the exposure condition setting process.

The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

Figure 1 is a cross-sectional view of an image sensor 100 according to this embodiment. The image sensor 100 comprises an image sensor chip 113 that outputs pixel signals corresponding to incident light, a signal processing chip 111 that processes the pixel signals, and a memory chip 112 that stores the pixel signals. The image sensor chip 113, the signal processing chip 111, and the memory chip 112 are stacked and electrically connected to each other by bumps 109, which are conductive connection parts made of Cu or the like.

As shown in the figure, incident light is mainly incident in the positive direction of the Z axis, as indicated by the white arrow. In this embodiment, the surface of the imaging chip 113 on which the incident light is incident is referred to as the back surface. Also, as shown on the coordinate axes, the left direction on the paper, perpendicular to the Z axis, is the positive X axis, and the front direction on the paper, perpendicular to the Z axis and the X axis, is the positive Y axis. In the following figures, the coordinate axes are displayed so that the orientation of each figure can be understood, based on the coordinate axes in Figure 1.

An example of the imaging chip 113 is a back-illuminated MOS image sensor. The PD layer 106 is disposed on the back side of the wiring layer 108. The PD layer 106 has a plurality of PDs (photodiodes) 104 arranged two-dimensionally and transistors 105 provided corresponding to the PDs 104.

A color filter 102 is provided on the incident light side of the PD layer 106 via a passivation film 103. There are multiple types of color filters 102 that transmit different wavelength ranges, and each has a specific arrangement corresponding to each PD 104. The arrangement of the color filters 102 will be described later. A set of a color filter 102, a PD 104, and a transistor 105 forms one pixel.

A microlens 101 is provided on the incident light side of the color filter 102, corresponding to each pixel. The microlens 101 focuses the incident light onto the corresponding PD 104.

The wiring layer 108 has wiring 107 that transmits pixel signals from the PD layer 106 to the signal processing chip 111. The wiring 107 may be multi-layered and may include passive and active elements.

A plurality of bumps 109, which are connection parts, are arranged on the surface of the wiring layer 108. The plurality of bumps 109 are aligned with and joined to a plurality of bumps 109 provided on the opposing surface of the signal processing chip 111, thereby electrically connecting the imaging chip 113 and the signal processing chip 111.

Similarly, a plurality of bumps 109, which are connection parts, are arranged on the opposing surfaces of the signal processing chip 111 and the memory chip 112. These bumps 109 are aligned with each other and joined, so that the signal processing chip 111 and the memory chip 112 are electrically connected.

The imaging element 100 is formed by bonding the imaging chip 113, the signal processing chip 111, and the memory chip 112 in the wafer state before they are made into chips, and then dicing the bonded wafer.

When bonding wafers together, an activation device irradiates the wafer surfaces with plasma to activate the bonding surfaces of the wafers. The wafers with activated surfaces are then bonded together through hydrogen bonds, van der Waals bonds, covalent bonds, and other bonding that occur when the wafers come into contact with each other, forming a laminated substrate. If the two wafers are hydrogen bonded through contact with each other, after the laminated substrate is formed, the laminated substrate is placed in a heating device such as an annealing furnace and heated to create covalent bonds between the wafers.

Activation includes treating the bonding surface of at least one of the substrates so that when the bonding surface of the wafer comes into contact with the bonding surface of another wafer, hydrogen bonds, van der Waals bonds, covalent bonds, etc. are generated, resulting in solid-phase bonding without melting. In other words, activation includes making it easier to form bonds by generating dangling bonds on the surface of the wafer.

More specifically, in the activation device, oxygen gas, which is the process gas, is excited to form plasma in a reduced pressure atmosphere, and oxygen ions are irradiated onto the surfaces that will become the bonding surfaces of the two substrates. For example, if the wafer is a substrate with a SiO film formed on Si, the oxygen ion irradiation breaks the SiO bonds on the wafer surface that will become the bonding surface during lamination, forming dangling bonds of Si and O. The formation of such dangling bonds on the wafer surface is sometimes referred to as activation.

For example, if a substrate with dangling bonds is exposed to the atmosphere, moisture in the air will bind to the dangling bonds and the substrate surface will become covered with hydroxyl groups (OH groups). The substrate surface will be in a state where it is likely to bind with water molecules, i.e., it will be easily hydrophilized. In other words, activation results in the substrate surface being easily hydrophilized. In solid-phase bonding, the presence of impurities such as oxides at the bonding interface, and defects at the bonding interface, affect the bonding strength. Therefore, cleaning of the bonding surface can be considered part of the activation.

Furthermore, the wafer may be activated by applying pure water or the like to the hydrophilized surface of the wafer that will become the bonding surface, using an apparatus not shown. This causes the wafer surface to have OH groups attached to it, i.e., to be terminated with OH groups.

By heating the laminated substrate, the bumps 109 on each of the bonding surfaces of the two wafers are integrated with each other, forming an electrical connection between the wafers. By forming the bumps 109 from a material that melts at a low temperature, such as indium or a tin-silver alloy, the laminated substrate can be reflowed at a low temperature of 200 degrees or less. Alternatively, if the bumps 109 are made from a conductive metal such as copper, they expand during the heating process, causing the bumps 109 between the wafers to be pressed together and bonded by solid-phase diffusion.

The bonding between the bumps 109 is not limited to Cu bump bonding by solid-phase diffusion, but may also employ micro-bump bonding by solder melting. Also, it is sufficient to provide one bump 109 for each pixel block, which will be described later. Therefore, the size of the bump 109 may be larger than the pitch of the PD 104. Also, in a peripheral region other than the pixel region where the pixels are arranged, a bump larger than the bump 109 corresponding to the pixel region may also be provided.

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

In this manner, the imaging chip 113 and the signal processing chip 111 are bonded to each other by their opposing surfaces and the bumps 109. The signal processing chip 111 and the memory chip 112 are bonded to each other by their opposing surfaces and are connected to each other by the bumps 109 and the TSVs 110 provided in the signal processing chip 111. The signal processing chip 111 and the memory chip 112 may be bonded to each other by their opposing surfaces and connected to each other by at least one of the bumps 109 and the TSVs 110.

Figure 2 is a diagram explaining the pixel arrangement of the imaging chip 113 and the block 131. In particular, it shows the imaging chip 113 observed from the back side. More than 20 million pixels are arranged in a matrix in the pixel area. These pixels are divided into blocks containing at least two pixels. In this embodiment, 16 pixels, 4 pixels x 4 adjacent pixels, form one block. The grid lines in the figure show the concept that adjacent pixels collectively form the block 131.

As shown in the enlarged partial view of the pixel area, block 131 contains four so-called Bayer arrays, each consisting of four pixels: green pixels Gb, Gr, blue pixel B, and red pixel R, arranged vertically and horizontally. The green pixels are pixels that have a green filter as the color filter 102 and receive light in the green wavelength band of the incident light. Similarly, the blue pixels are pixels that have a blue filter as the color filter 102 and receive light in the blue wavelength band, and the red pixels are pixels that have a red filter as the color filter 102 and receive light in the red wavelength band.

Figure 3 is a circuit diagram corresponding to block 131 of imaging chip 113. In the figure, a rectangle surrounded by a dotted line typically represents a circuit corresponding to one pixel. Note that at least some of the transistors described below correspond to transistor 105 in Figure 1.

As described above, the block 131 is formed of 16 pixels. The 16 PDs 104 corresponding to each pixel are connected to a transfer transistor 302, and each gate of the transfer transistor 302 is connected to a TX wiring 307 to which a transfer pulse is supplied. In this embodiment, the TX wiring 307 is commonly connected to the 16 transfer transistors 302.

The drain of each transfer transistor 302 is connected to the source of the corresponding reset transistor 303, and a so-called floating diffusion FD between the drain of the transfer transistor 302 and the source of the reset transistor 303 is connected to the gate of the amplification transistor 304. The drain of the reset transistor 303 is connected to a Vdd wiring 310 to which a power supply voltage is supplied, and its gate is connected to a reset wiring 306 to which a reset pulse is supplied. In this embodiment, the reset wiring 306 is commonly connected to the 16 reset transistors 303.

The drain of each amplification transistor 304 is connected to a Vdd wiring 310 to which a power supply voltage is supplied. The source of each amplification transistor 304 is connected to the drain of the corresponding selection transistor 305. Each gate of the selection transistor is connected to a decoder wiring 308 to which a selection pulse is supplied. In this embodiment, the decoder wiring 308 is provided independently for each of the 16 selection transistors 305. The source of each selection transistor 305 is connected to a common output wiring 309. The load current source 311 supplies a current to the output wiring 309. In other words, the output wiring 309 for the selection transistor 305 is formed by a source follower. The load current source 311 may be provided on the imaging chip 113 side or on the signal processing chip 111 side.

Here, we will explain the flow from the start of pixel exposure to the output of a pixel signal after exposure is completed. When a reset pulse is applied to the reset transistor 303 via the reset wiring 306 and at the same time a transfer pulse is applied to the transfer transistor 302 via the TX wiring 307, the potentials of the PD 104 and the floating diffusion FD are reset and exposure begins.

When the transfer pulse is released, the PD 104 converts the incident light it receives into electric charge and accumulates it. After that, when the transfer pulse is applied again without the reset pulse being applied, the exposure ends. The electric charge accumulated until the end of the exposure is transferred to the floating diffusion FD, and the potential of the floating diffusion FD changes from the reset potential to the signal potential after the exposure ends. Then, when a selection pulse is applied to the selection transistor 305 through the decoder wiring 308, the fluctuation of the signal potential of the floating diffusion FD is transmitted to the output wiring 309 via the amplification transistor 304 and the selection transistor 305. As a result, a pixel signal corresponding to the reset potential and the signal potential is output from the unit pixel to the output wiring 309.

As shown in the figure, in this embodiment, the reset wiring 306 and TX wiring 307 are common to the 16 pixels that form block 131. That is, the reset pulse and transfer pulse are each applied simultaneously to all 16 pixels. Therefore, all pixels that form block 131 start exposure at the same timing, and end exposure at the same timing. However, pixel signals corresponding to the accumulated charges are selectively output to the output wiring 309 by sequentially applying selection pulses to the respective selection transistors 305.

In this way, by configuring the circuit based on the block 131, the exposure time can be controlled for each block 131. Since the exposure time can be controlled for each block, adjacent blocks 131 can output pixel signals with different exposure times. Furthermore, a common exposure time can be set for all blocks 131, and one block 131 can be subjected to one exposure and pixel signal output, while an adjacent block 131 can be subjected to two exposures and pixel signal outputs. The latter type of repeated control of exposure and pixel signal output based on a common unit time is called unit time control. In addition, when performing unit time control, if the start and end points of exposure are synchronized for all blocks 131, the reset wiring 306 may be commonly connected to all reset transistors 303 on the imaging chip 113.

Figure 4 is a block diagram showing the functional configuration of the image sensor 100. In particular, the flow of pixel signals is explained here.

The analog multiplexer 411 sequentially selects the 16 PDs 104 that form the block 131 and outputs the pixel signals of each to the output wiring 309. The multiplexer 411 is formed in the imaging chip 113 together with the PDs 104.

The pixel signals output via the multiplexer 411 are subjected to CDS and A/D conversion by a signal processing circuit 412 formed in the signal processing chip 111, which performs correlated double sampling (CDS) and analog-to-digital (A/D) conversion. The A/D conversion converts the input analog pixel signals into 12-bit digital pixel signals. The A/D converted pixel signals are passed to an arithmetic circuit 415, also formed in the signal processing chip 111. The arithmetic circuit 415 performs arithmetic processing required for subsequent image processing on the received pixel signals, and passes them to the demultiplexer 413.

The demultiplexer 413 stores the received pixel signals in pixel memories 414 corresponding to each pixel. Each pixel memory 414 has a capacity capable of storing the pixel signals after arithmetic processing is performed. The demultiplexer 413 and the pixel memories 414 are formed in the memory chip 112.

The arithmetic circuit 415 reads out pixel signals to be used in the arithmetic processing from the pixel memory 414 via the demultiplexer 413. Alternatively, in response to a transfer request from the outside, the arithmetic circuit 415 transfers the pixel signals read out from the pixel memory 414 via the demultiplexer 413 to a downstream image processing unit. The arithmetic circuit 415 may be provided in the memory chip 112.

Although the figure shows the flow of pixel signals for one block, in reality, these exist for each block and operate in parallel. However, a calculation circuit 415 does not have to exist for each block. For example, one calculation circuit 415 may process sequentially while referring to the values of the pixel memories 414 corresponding to each block in order.

Figure 5A is a block diagram showing the functional configuration of the image sensor 100. Here, we will mainly explain the specific configuration of the signal processing chip 111 and the setting unit 460 provided in the memory chip 112.

The signal processing chip 111 includes a sensor control unit 441, a synchronization control unit 443, and a signal control unit 444 as distributed control functions, and a drive control unit 420 that controls these control units. The drive control unit 420 converts instructions from a system control unit 501 that is responsible for the overall control of the entire imaging device into control signals that can be executed by each control unit and passes them on to each unit.

The sensor control unit 441 is responsible for controlling the sending of control pulses related to charge accumulation and charge readout of each pixel to be sent to the imaging chip 113. Specifically, the sensor control unit 441 controls the start and end of exposure by sending a reset pulse and a transfer pulse to the target pixel, and outputs a pixel signal to the output wiring 309 by sending a selection pulse to the readout pixel.

The synchronization control unit 443 sends a synchronization signal to the imaging chip 113. Each pulse becomes active in the imaging chip 113 in synchronization with the synchronization signal. For example, by adjusting the synchronization signal, random control, thinning control, etc., in which only specific pixels belonging to the same block 131 are the control targets, can be realized.

The signal control unit 444 is mainly responsible for timing control of the A/D converter 412b. The pixel signal output via the output wiring 309 is input to the CDS circuit 412a and the A/D converter 412b via the multiplexer 411. The A/D converter 412b is controlled by the signal control unit 444 to convert the input pixel signal into a digital signal. The pixel signal converted into a digital signal is passed to the arithmetic circuit 415, where it is subjected to arithmetic processing. The pixel signal subjected to arithmetic processing is passed to the demultiplexer 413 of the memory chip 112, and is stored as a pixel value of digital data in the pixel memory 414 corresponding to each pixel.

In addition, the drive control unit 420 reads out the target pixel signal from the pixel memory 414 via the arithmetic circuit 415 and the demultiplexer 413 in accordance with a delivery request from the system control unit 501, and delivers it to the image processing unit 511 provided in the imaging device. The pixel memory 414 is provided with a data transfer interface that transmits the pixel signal in accordance with the delivery request. The data transfer interface is connected to a data transfer line that connects to the image processing unit 511. The data transfer line is, for example, constituted by a data bus among the bus lines. In this case, the delivery request from the system control unit 501 to the drive control unit 420 is executed by address specification using the address bus.

Transmission of pixel signals through the data transfer interface is not limited to the addressing method, and various other methods may be used. For example, a double data rate method may be used, which uses both the rising and falling edges of the clock signal used to synchronize each circuit when transferring data. A burst transfer method may also be used, which transfers data all at once by omitting some steps such as addressing, thereby increasing speed. A bus method using lines connecting the control unit, memory unit, and input/output unit in parallel, and a serial method in which data is transferred serially one bit at a time may also be used in combination.

By configuring in this manner, the image processing unit 511 can receive only the necessary pixel signals, thereby completing image processing quickly, especially when forming low-resolution images.

The memory chip 112 further includes a setting unit 460 that sets exposure conditions for each block 131. The setting unit 460 acquires the luminance distribution of the scene from the system control unit 501, and sets exposure conditions for each block 131 according to the luminance distribution. The exposure conditions are conditions that change the brightness of the image to be acquired, such as exposure time, aperture value, and ISO sensitivity.

The setting unit 460 also corrects the exposure conditions according to various requirements such as memory capacity and required dynamic range. The setting and correction process of the exposure conditions by the setting unit 460 will be described later. The setting unit 460 also determines the timing of opening and closing the shutter according to the exposure time of each block 131.

The memory chip 112 further includes a mode switching unit 470 that switches the imaging mode according to the exposure conditions. As an example, the mode switching unit 470 switches between a first mode in which the difference between the maximum exposure condition and the minimum exposure condition in the multiple blocks is a first value, and a second mode in which the difference is smaller than the first value.

Alternatively, the mode switching unit 470 may switch between a first mode in which the maximum absolute value of the difference between the exposure conditions of a first block among the multiple blocks and the exposure conditions of each of the multiple blocks adjacent to the first block is a first value, and a second mode in which the maximum value is smaller than the first value.

The setting and correction processing of exposure conditions by the setting unit 460 will be described later, but in the first mode, the exposure conditions are set so as to reduce the difference between adjacent blocks rather than the entire image, making it possible to capture images under equalized exposure conditions while minimizing the sacrifice of bright and dark areas. In the second mode, it is possible to capture images under even more equalized exposure conditions than in the first mode.

For example, the mode switching unit 470 receives an instruction from the user via the system control unit 501 and instructs the setting unit 460 to select either the first mode or the second mode. In the first mode, the setting unit 460 sets the exposure conditions for each block 131 so that the maximum value of the difference between the exposure conditions is equal to or less than the first value, and passes the set exposure conditions to the drive control unit 420. On the other hand, in the second mode, the setting unit 460 sets the exposure conditions for each block 131 so that the maximum value of the difference between the exposure conditions is smaller than the first value, and passes the set exposure conditions to the drive control unit 420. The drive control unit 420 controls the sensor control unit 441 to expose each pixel according to the acquired exposure conditions.

Alternatively, the mode switching unit 470 may switch the imaging mode between a standard mode using a first exposure condition and a correction mode using a second exposure condition obtained by correcting the first exposure condition. As an example, the first exposure condition is an exposure condition initially set by the setting unit 460 according to the luminance distribution of the scene, and the second exposure condition is an exposure condition obtained by performing a correction process on the first exposure condition.

As an example, the mode switching unit 470 receives an instruction from the user via the system control unit 501 and instructs the setting unit 460 to select either the standard mode or the correction mode. In the standard mode, the setting unit 460 sets the exposure conditions for each block 131, and then passes the set exposure conditions to the drive control unit 420 without correcting them. On the other hand, in the correction mode, the setting unit 460 sets the exposure conditions for each block 131, and then corrects the set exposure conditions, and passes the corrected exposure conditions to the drive control unit 420. The drive control unit 420 controls the sensor control unit 441 to expose each pixel according to the acquired exposure conditions.

Figure 5B is a block diagram showing the functional configuration of the image sensor 100. Here, we explain the case where the setting unit 460 is provided in the signal processing chip 111.

As in the example shown in FIG. 5A, the setting unit 460 acquires the luminance distribution of the scene from the system control unit 501, and sets the exposure conditions for each block 131 according to the luminance distribution. The setting unit 460 also corrects the exposure conditions according to various requirements such as memory capacity and required dynamic range. The setting unit 460 also determines the timing of opening and closing the shutter according to the exposure time of each block 131.

In the example shown in FIG. 5B, a mode switching unit 470 is also provided in the signal processing chip 111. As in the example shown in FIG. 5A, the mode switching unit 470 receives an instruction from the user via the system control unit 501 and instructs the setting unit 460 to select either the standard mode or the correction mode. In the standard mode, the setting unit 460 sets the exposure conditions for each block 131, and then passes the set exposure conditions to the drive control unit 420 without correcting them. On the other hand, in the correction mode, the setting unit 460 sets the exposure conditions for each block 131, and then corrects the set exposure conditions, and passes the corrected exposure conditions to the drive control unit 420.

In this way, the setting unit 460 and the mode switching unit 470 may be provided in the memory chip 112 or in the signal processing chip 111. As shown in FIG. 5A, when the setting unit 460 and the mode switching unit 470 are provided in the memory chip 112, a larger space is secured in the signal processing chip 111 while speeding up transmission via the bump 109 and the TSV 110. As shown in FIG. 5B, when the setting unit 460 and the mode switching unit 470 are provided in the signal processing chip 111, they are on the same chip as the drive control unit 420 that controls each control unit, so that high-speed processing is realized.

Figure 6 is a block diagram showing the configuration of an imaging device according to this embodiment. The imaging device 500 includes a photographing lens 520 as an imaging optical system, which guides a subject light beam incident along an optical axis O to the imaging element 100. The photographing lens 520 may be an interchangeable lens that can be attached to and detached from the imaging device 500. The imaging device 500 mainly includes the imaging element 100, a system control unit 501, a photometry unit 503, a work memory 504, a recording unit 505, and a display unit 506. The system control unit 501 functions as an imaging instruction unit that receives instructions from a user and generates imaging instructions to be sent to the imaging element 100.

The photographing lens 520 is composed of a group of multiple optical lenses, and focuses the subject light beam from the scene near its focal plane. Note that in FIG. 6, it is represented by a virtual single lens placed near the pupil. As described above, the drive control unit 420 of the image sensor 100 is a control circuit that performs exposure control of the image sensor 100 according to instructions from the system control unit 501.

The image sensor 100 passes the pixel signal to the image processing unit 511 of the system control unit 501. The image processing unit 511 performs various image processing using the work memory 504 as a workspace to generate image data. For example, when generating image data in a JPEG file format, compression processing is performed after white balance processing, gamma processing, etc. The generated image data is recorded in the recording unit 505 and converted into a display signal and displayed on the display unit 506 for a preset time. The image processing unit 511 may be configured as an ASIC independent of the system control unit 501, or may be provided in the memory chip 112.

The photometry unit 503 detects the luminance distribution of the scene prior to a series of shooting sequences that generate image data. The photometry unit 503 includes an AE sensor with approximately 1 million pixels, for example. The calculation unit 512 of the system control unit 501 receives the output of the photometry unit 503 and calculates the luminance of each area of the scene. The calculation unit 512 also performs various calculations to operate the imaging device 500. The calculation unit 512 may also perform the functions of the setting unit 460 described above.

Next, the setting and correction of exposure conditions in the image sensor of this embodiment will be explained with reference to the figures.

Traditionally, cameras have a limited dynamic range that they can capture in one shot. For example, shooting with a short exposure time (sometimes called "short seconds") to match the bright areas of a scene results in crushed shadows in the dark areas of the image. Conversely, shooting with a long exposure time (sometimes called "long seconds") to match the dark areas of a scene results in blown-out highlights in the bright areas of the image.

In recent years, therefore, high dynamic range technology has been used to capture multiple images and combine them to obtain images with a wide dynamic range. High dynamic range technology is a technique in which multiple images are captured under different exposure conditions, and only the necessary areas of each image are extracted and combined. This effectively expands the dynamic range.

However, if the gap between the bright and dark areas of a scene is large, the dynamic range becomes too wide, causing a problem of memory overflow. For example, if the dynamic range is the difference in EV value, ΔEV, the number of shots required for composition is 2 ^ΔEV or more.

[Setting exposure conditions]
7 is a flow diagram showing an example of the exposure condition setting process. As described above, the setting unit 460 sets the exposure condition for each block 131 according to the luminance distribution of the scene acquired from the system control unit 501. The luminance distribution of the scene may be calculated in response to a pre-shooting instruction from the user. For example, when the system control unit 501 detects the pressing of the shutter switch, the photometry unit 503 executes a photometry process, and the calculation unit 512 calculates the luminance distribution of the scene based on the output from the photometry unit 503.

In process 710, the setting unit 460 calculates a representative value 1 from the luminance distribution. As an example, the representative value 1 is the average value (average luminance) of the luminance values corresponding to the pixels in the target block 131.

In process 720, the setting unit 460 calculates a representative value 2 from the luminance distribution. As an example, the representative value 2 is the maximum luminance value (maximum luminance) corresponding to the pixels in the target block 131.

In process 730, the setting unit 460 sets the exposure conditions of the target block 131 according to the representative values 1 and 2. As an example, the setting unit 460 judges whether the average brightness and the maximum brightness are equal. If the setting unit 460 judges that the average brightness and the maximum brightness are equal, it sets the exposure time corresponding to the average brightness as the exposure condition of the target block 131. If the setting unit 460 judges that the maximum brightness is greater than the average brightness, it judges whether the pixels in the target block 131 will be saturated at the exposure time corresponding to the average brightness. If it is judged that they will not be saturated, the setting unit 460 sets the exposure time corresponding to the average brightness as the exposure condition of the target block 131. Conversely, if it is judged that they will be saturated, the setting unit 460 sets the exposure time corresponding to the maximum brightness as the exposure condition of the target block 131.

In process 740, the drive control unit 420 controls the sensor control unit 441 to expose each pixel under the exposure conditions set for each block 131, and the image processing unit 511 synthesizes the generated multiple images. Note that, as described below, the setting unit 460 may correct the set exposure conditions before process 740 and transfer the corrected exposure conditions to the drive control unit 420.

The maximum luminance may be calculated from a predetermined range of luminance from the top in a luminance histogram of the pre-captured image. The exposure times corresponding to the maximum luminance and the average luminance are exposure times when the maximum and average luminance values in the pre-captured image are converted to target maximum and average values, respectively, and may be calculated according to the following formula.

Here, _I0,Max and I0 _,Ave are the maximum and average luminance values in the pre-captured image, respectively, and _t0 is the exposure time. _ITarget,Max and _ITarget,Ave are the target maximum and average values, respectively, and _tMax and _tAve are the exposure times corresponding to the target maximum and average values, respectively.

The setting section 460 may use the shorter of the exposure times corresponding to the two representative values, that is, the exposure time closer to the bright region, as shown in the following formula.

Here, t is the exposure time set as an exposure condition. However, if the pixels in the block 131 are saturated when the exposure time t _Ave is adopted, the setting unit 460 may adopt t _Max , which is an exposure time closer to the dark region.

Figure 8 is a diagram comparing an image taken under exposure conditions set according to the flow in Figure 7 with an image taken under exposure conditions set by another method. (A) in the top row shows an image taken when the exposure time was set using only the average brightness value, and the corresponding exposure time setting. (B) in the bottom row shows an image taken when the exposure time was set using the average and maximum brightness values, and the corresponding exposure time setting. Both images are of the same scene, that is, an outdoor view taken from indoors through a window. Note that the exposure time setting means that the brighter the color of the block (closer to white), the longer the exposure time (emphasis on dark areas), and the darker the color (closer to black), the shorter the exposure time (emphasis on bright areas).

In the captured image of (A), the block boundaries are noticeable near the window frame and in the area where the lattice attached to the window intersects (particularly the area indicated by the white arrow). This is because when a single block 131 contains an area with a large difference in brightness, such as the window frame and lattice and the window glass, the pixels corresponding to the bright areas become saturated when the exposure time is set using only the average brightness value, making it impossible to obtain sufficient information. On the other hand, in (B), the average value is not used for such blocks, and the exposure time corresponding to the maximum value is set, so saturation does not occur and the adverse effects of (A) are not seen.

As described above, if the exposure conditions for block 131 are set according to the average brightness, there is a risk of saturation occurring in pixels corresponding to brightness greater than the average value. Therefore, if saturation does not occur under the exposure conditions corresponding to the average brightness, those exposure conditions are adopted, and if saturation does occur, exposure conditions corresponding to another representative value are adopted. This makes it possible to prevent saturation within block 131 while achieving proper exposure.

The exposure condition setting process described above is executed when setting the exposure conditions that serve as the basis for the exposure condition correction process described next. Alternatively, the exposure condition setting process described above is executed to determine whether or not highlight blowout or blackout will occur under the exposure conditions set in the exposure condition correction process, and if it is determined that highlight blowout or blackout will occur, the correction process is executed repeatedly.

[Correction of Exposure Conditions]
9 is a flow chart showing an example of a correction process for the exposure conditions. First, in process 910, the setting unit 460 sets the exposure conditions for each block 131 as described above.

The setting unit 460 corrects the exposure conditions set for each block 131 so that the difference between the exposure conditions in each block 131 is equal to or less than a threshold value. Specifically, in process 920, the setting unit 460 creates a histogram of the exposure conditions in each block 131. In process 930, the setting unit 460 sets upper and lower limits according to the histogram. That is, the setting unit 460 corrects the exposure conditions set for each block 131 so that the difference between the maximum and minimum values in the histogram is equal to or less than a threshold value.

Figure 10 is a diagram showing a specific example of setting the upper and lower limits of the exposure conditions shown in Figure 9. Here, the exposure condition is the exposure time TV, and the threshold value TH (TV difference between maximum TV and minimum TV) is 5. Histogram H in (1) shows a histogram of the initial exposure conditions, where the maximum TV is 9 and the minimum TV is 2. Therefore, the TV difference is 7, which is greater than TH, so the exposure conditions need to be corrected.

The setting unit 460 compares the frequency of the maximum TV with the frequency of the minimum TV. Here, since the frequency of the maximum TV is smaller than the frequency of the minimum TV, the setting unit 460 corrects the maximum TV to the second largest TV. In other words, the frequency of TV9 is added to the second largest TV8. As a result of rounding the maximum TV, TV9, in this way, histogram H of (2) is obtained.

In histogram H of (2), the maximum TV is 8 and the minimum TV is 2. Therefore, the TV difference is 6, which is greater than TH, and so the exposure conditions need to be corrected. The setting unit 460 compares the frequency of the maximum TV with the frequency of the minimum TV. Here, since the frequency of the minimum TV is smaller than the frequency of the maximum TV, the setting unit 460 corrects the minimum TV to the second smallest TV. In other words, the frequency of TV2 is added to the second smallest TV3. As a result of rounding the minimum TV TV2 in this way, histogram H of (3) is obtained.

In histogram H of (3), the maximum TV is 7 and the minimum TV is 3. Therefore, the TV difference is 5, which is equal to TH, and processing ends without further correction of the exposure conditions. The setting unit 460 corrects the exposure conditions of the corresponding block 131 according to histogram H of (3), and passes the corrected exposure conditions to the drive control unit 420. The subsequent processing is as described above, so explanation is omitted.

Figure 11 is a diagram comparing images captured when the range of exposure conditions is restricted according to the example of Figure 10 with images captured when the range of exposure conditions is restricted by another method. (A) is an image captured when the range is restricted while maintaining maximum TV (emphasis on dark areas), (B) is an image captured when the range is restricted while maintaining minimum TV (emphasis on light areas), and (C) is an image captured when TV is restricted according to the example of Figure 10. All images are of the same scene, i.e., an outdoor view captured from indoors through a window.

Figure 12 shows histograms of the exposure conditions used for each captured image shown in Figure 11. In (A), (B), and (C), the TV range of 3 to 17 in the original setting (O) is limited by a tolerance (threshold TH) of 8 TV. The TV range of (A), which maintains the maximum TV, is 9 to 17 TV, with TVs below the lower limit of 9 TV being cut off. The TV range of (B), which maintains the minimum TV, is 3 to 11 TV, with TVs exceeding the upper limit of 11 TV being cut off. The TV range of (C), which is limited according to frequency, is 7 to 15, with TVs below the lower limit of 7 TV and TVs exceeding the upper limit of 15 TV being cut off.

Returning to Figure 11, we can see that (B), which emphasizes bright areas, is able to capture information about the view outside the window (buildings and trees), whereas (A), which emphasizes dark areas, is unable to capture the same information in the bright areas, resulting in blown-out highlights. On the other hand, (C) is able to capture a certain amount of information about the same bright areas. Conversely, although not shown, (B), which emphasizes bright areas, has a worsening S/N ratio in dark areas, which may result in crushed shadows.

In this way, simply limiting the range of exposure conditions would result in the sacrifice of either bright or dark areas, but by limiting the range according to the frequency of the exposure conditions, it is possible to minimize the sacrifice of bright and dark areas while preventing memory overflow.

The setting unit 460 also limits the range of exposure conditions so that the amount of pixel signal data is equal to or less than the memory capacity as a result of cutting the exposure conditions. The setting unit 460 may also preferentially cut exposure conditions that correspond to dark areas. Since information on dark areas can at least be obtained even with short exposure times, sufficient information can be obtained by adding together a large number of captured images. Furthermore, by cutting long exposure times, the shooting time can be shortened.

Figure 13 is a flow diagram showing another example of the exposure condition correction process. Note that the correction process of Figure 13 may be performed following the correction process of Figure 9.

In process 1310, the setting unit 460 sets exposure conditions for each block 131. Process 1310 is similar to process 910 in Fig. 9, and therefore description thereof will be omitted. When the correction process in Fig. 13 is executed following the correction process in Fig. 9, process 1320, which will be described next, is executed after process 930 in Fig. 9.

In process 1320, the setting unit 460 performs an equalization process of the exposure conditions for the target block 131. Here, the equalization process refers to correcting the exposure conditions set for each block 131 so that the difference in exposure conditions between adjacent blocks 131 is equal to or less than the boundary threshold value.

Figure 14 is a diagram showing a specific example of the exposure condition smoothing process shown in Figure 13. (1) shows the exposure conditions set in process 1310 for each block 131 arranged in a 3 x 4 matrix. Here, the exposure condition is the exposure time TV, and the threshold value (boundary threshold) of the TV difference between adjacent blocks is set to 3.

The setting unit 460 selects a target block to be subjected to the smoothing process from the arranged blocks 313, and of the nine blocks 131 adjacent to the target block on all four sides, sets four L-shaped blocks 131 consisting of three blocks 131 on the top and one block 131 on the left as comparison blocks. Note that if the target block is located at the end of the arrangement, the number of comparison blocks may be less than four.

The setting unit 460 sequentially selects target blocks from the block array in the forward direction and executes the first smoothing process. Here, the forward direction starts from the upper left side of the block array. That is, the forward direction proceeds from the leftmost block 131 in the top row to the rightmost block 131, then from the leftmost block 131 in the second row from the top to the rightmost block 131, and finally from the leftmost block 131 in the bottom row to the rightmost block 131.

The specific steps of the smoothing process are described below. The setting unit 460 compares the TV of the target block with the minimum TV value of the comparison block. If the TV of the target block is greater than the minimum TV value of the comparison block and the difference is greater than a threshold, the setting unit 460 corrects the TV of the target block so that the difference is equal to or less than the threshold.

For example, when performing forward smoothing on the block array of (1), first, the upper left block 131 (TV10) is selected as the target block. However, since this target block does not have a comparison block, the setting unit 460 does not perform smoothing on the target block, and moves on to the next target block. The next target block selected is the second block from the left in the top row, 131 (TV9). Since this target block has a comparison block (TV10) on its left, its TV becomes the minimum TV value of the comparison block. Since the TV of the target block (TV9) is less than the minimum TV value of the comparison block (TV10), the setting unit 460 does not perform smoothing on the target block, and moves on to the next target block. In this way, the setting unit 460 sequentially selects target blocks in the forward direction, and performs smoothing according to the TV difference.

Consider the case where the upper right block 131 (TV8) is selected as the target block, as shown in (2). This target block has a comparison block (TV3) on its left, so its TV becomes the minimum TV value of the comparison block. Since the TV of the target block (TV8) is greater than the minimum TV value of the comparison block (TV3), the setting unit 460 corrects the TV of the target block to 6 so that the difference with the minimum TV value of the comparison block (TV3) is less than or equal to the threshold value of 3.

(3) shows the block array resulting from the forward smoothing process, and the values shown in white are the corrected TVs. However, there are still some TVs where the TV difference between adjacent blocks exceeds the threshold, such as the second block 131 (TV9) and the third block 131 (TV3) from the left in the top row.

After performing the smoothing process in the forward direction, as shown in (4), the setting unit 460 resets the setting of the comparison blocks. The setting unit 460 sets, as the comparison blocks, four L-shaped blocks 131 consisting of three blocks 131 on the lower side and one block 131 on the right side, out of the nine blocks 131 adjacent to the target block on the top, bottom, left, and right sides. Note that if the target block is located at the end of the array, the number of comparison blocks may be less than four.

The setting unit 460 sequentially selects target blocks in the reverse direction from the block array, and executes a second smoothing process. Here, the reverse direction starts from the lower right side of the block array. That is, the reverse direction proceeds from the rightmost block 131 in the bottom row to the leftmost block 131, then from the rightmost block 131 in the second row from the bottom to the leftmost block 131, and finally from the rightmost block 131 in the top row to the leftmost block 131. As shown in (5), the setting unit 460 corrects the TV of the target block according to the difference with the minimum TV value of the comparison block, as in the forward smoothing process.

(6) is the block array resulting from performing the smoothing process in the reverse direction, and the values shown in white are the TVs corrected by the smoothing process in the reverse direction. As a result of performing the smoothing process in the reverse direction after the smoothing process in the forward direction, it can be seen that the TV differences between all adjacent blocks are below the threshold.

Because the S/N ratio is affected by the exposure time, if the difference in S/N ratio between adjacent blocks is large, the block boundaries become noticeable. Therefore, by averaging the TV difference between adjacent blocks, it is possible to obtain a natural image in which the block boundaries are not noticeable, although the S/N ratio will worsen.

The threshold value may be uniquely determined according to the characteristics of the image sensor. Alternatively, the relationship between the S/N ratio and the exposure time may be determined in advance, and an appropriate boundary threshold value may be determined based on the difference in the S/N ratio obtained from the noise calculation formula.

Returning to FIG. 13 again, in process 1330, the drive control unit 420 controls the sensor control unit 441 to expose each pixel under the corrected exposure conditions, and the image processing unit 511 synthesizes the generated multiple images. Here, the image processing unit 511 may delete noise to fill in the difference in S/N ratio between the blocks. Alternatively, the image processing unit 511 may add noise to the long-exposure block 131 or remove noise from the short-exposure block 131 to fill in the difference in S/N ratio between the blocks.

Furthermore, the setting unit 460 may set the exposure conditions for each block 131 so that the proportion of pixels in which whiteout or blackout occurs within the block 131 is a predetermined proportion. For example, the predetermined proportion is 10% or less for a block 131 of 16 x 16 pixels. In this way, by controlling specifically with numerical values, it is possible to reduce the probability that pixels in which whiteout or blackout occurs exist at block boundaries, and obtain a natural image in which the block boundaries are not noticeable.

Figure 15 is a diagram comparing the exposure conditions before and after performing the smoothing process according to the example of Figure 14. (A) is the exposure time setting before performing the smoothing process and the captured image. (B) is the exposure time setting after performing the smoothing process. The subject is a high-rise building at night. The exposure time setting means that the brighter (closer to white) the color of the block is, the longer the exposure time (emphasis on dark areas) and the darker (closer to black) the shorter the exposure time (emphasis on bright areas).

As shown by the arrow in image (A), the boundaries between adjacent blocks are conspicuous around the obstruction lights on the top floor of a high-rise building. This is because there is a large difference in the S/N ratio due to the large difference in brightness between the obstruction lights and the night sky in the background. Looking at the exposure time setting in (A), we can see that only the block corresponding to the position of the obstruction light is exposed for a short time due to the influence of the brightness of the obstruction light, and there is a large difference in exposure time between the adjacent blocks. Therefore, by performing an equalization process according to the example in Figure 14, the difference in exposure time between the block corresponding to the obstruction light and the surrounding blocks is equalized, as shown in (B), and a natural image with inconspicuous block boundaries can be obtained.

Figure 16 is a flow diagram showing a modified example of the exposure condition setting process. In process 1610, the setting unit 460 sets the exposure conditions according to the bright area. Specifically, the setting unit 460 obtains the exposure conditions corresponding to the bright area from the luminance distribution of the scene obtained from the system control unit 501, and sets the obtained exposure conditions to all blocks 131.

The exposure conditions corresponding to the bright regions may be calculated according to the method of obtaining the maximum brightness from the brightness distribution, as described above. When calculating the exposure conditions, the maximum exposure time that takes into account camera shake suppression may also be taken into account.

In process 1620, the setting unit 460 sets the number of shots depending on the dynamic range to be acquired. The dynamic range to be acquired may be arbitrarily set by a user or a designer, or may be automatically set by the system control unit 501 depending on the luminance distribution of the shooting scene. As described above, the required number of shots is 2 ^ΔEV or more, where ΔEV is the dynamic range.

In process 1630, the setting unit 460 performs shooting according to the set exposure conditions and number of shots, and in process 1640, the image processing unit 511 adds the shot images to synthesize the obtained image. Note that before process 1640, the image processing unit 511 may further perform detection and alignment processing of improper images caused by camera shake, etc. If the required number of shots is insufficient due to the elimination of improper images, feedback may be sent from the image processing unit 511 to the drive control unit 420 to add more shots.

Thus, in this example, unlike the examples in Figures 1 to 15 in which different exposure conditions are set for each block 131, a common exposure condition is set for all blocks 131. Because exposure conditions are set to match the bright areas, there is no risk of whiteout, and information on dark areas can also be obtained by adding a large number of images. Furthermore, compared to when exposure conditions are changed on a block-by-block basis, the shooting and synthesis process is simplified. Furthermore, because the same exposure conditions are set for all blocks 131, it is possible to suppress deterioration in image quality caused by misalignment of the exposure conditions due to camera shake or the like, which can lead to inability to properly acquire information.

In addition, because all acquired information is added together, there is no waste and a good S/N ratio can be obtained. Furthermore, because it is shot with a short exposure time, it is resistant to camera shake and the dynamic range can be expanded simply by increasing the number of shots.

Although the present invention has been described above using an embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms incorporating such modifications or improvements can also be included in the technical scope of the present invention.

In the above embodiment, the setting unit 460 and the mode switching unit 470 are provided in the memory chip 112 or the signal processing chip 111 of the image sensor 100, but the setting unit 460 and the mode switching unit 470 may be provided in an element, circuit, or board other than the image sensor 100. In this case, for example, information on the luminance of the pixels in each block 131 may be transmitted from the image sensor 100 to the setting unit 460 and the mode switching unit 470, respectively, and the setting unit 460 may set the exposure conditions or the mode switching unit 470 may switch the mode based on this, and the results may be transmitted from the setting unit 460 and the mode switching unit 470 to the image sensor 100.

The setting unit 460 and the mode switching unit 470 may be provided in the same element, circuit, or board, or may be provided in different elements, circuits, or boards. In addition, the element, circuit, or board on which the setting unit 460 and the mode switching unit 470 are provided may be provided in a device other than the imaging device 500.

It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before" or "prior to," and that the processes may be performed in any order, unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, this does not mean that it is essential to perform the processes in that order.

100 imaging element, 101 microlens, 102 color filter, 103 passivation film, 104 PD, 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 block, 302 transfer transistor, 303 reset transistor, 304 amplification transistor, 305 selection transistor, 306 reset wiring, 307 TX wiring, 308 decoder wiring, 309 output wiring, 310 Vdd wiring, 311 load current source, 411 multiplexer, 412 signal processing circuit, 413 demultiplexer, 414 pixel memory, 415 arithmetic circuit, 420 drive control unit, 441 sensor control unit, 443 synchronization control unit, 444 Signal control unit, 460 setting unit, 470 mode switching unit, 500 imaging device, 501 system control unit, 503 photometry unit, 504 work memory, 505 recording unit, 506 display unit, 511 image processing unit, 512 calculation unit

Claims (17)

A plurality of pixels that generate pixel signals in response to incident light;
a setting unit that sets an exposure condition for each of a plurality of blocks, each of which includes at least two of the pixels;
The setting unit sets exposure conditions for each block such that a difference between the exposure conditions for each block is equal to or smaller than a threshold value. The image sensor according to claim 1 , wherein the setting section sets the exposure condition for each block such that a difference between a maximum exposure condition and a minimum exposure condition is equal to or smaller than the threshold value. 3. The image sensor according to claim 2, wherein the setting unit compares the frequency of occurrence of the blocks under the maximum exposure condition with the frequency of occurrence of the blocks under the minimum exposure condition, and eliminates the maximum exposure condition if the frequency of occurrence of the blocks under the maximum exposure condition is low, and eliminates the minimum exposure condition if the frequency of occurrence of the blocks under the minimum exposure condition is low. The image sensor according to claim 3 , wherein the setting unit preferentially cuts exposure conditions corresponding to dark regions. A memory for storing the pixel signal is further provided,
The image sensor according to claim 2 , wherein the setting section sets the exposure conditions for each block so that an amount of data of the pixel signals is equal to or smaller than a capacity of the memory. The image sensor according to claim 1 , wherein the setting unit sets the exposure conditions for each block such that a difference between the exposure conditions for adjacent blocks is equal to or smaller than the threshold value. The image sensor according to claim 1 , wherein the setting unit sets an exposure condition for the block in accordance with at least two representative values of luminance corresponding to pixels in the block. the at least two representative values include a maximum luminance and an average luminance corresponding to pixels in the block;
The setting unit is
if the pixels in the block are saturated at the exposure time corresponding to the average luminance, an exposure time corresponding to the maximum luminance is set as an exposure condition for the block;
The image sensor according to claim 7 , wherein, if the pixels in the block are not saturated with the exposure time corresponding to the average luminance, the exposure time corresponding to the average luminance is set as an exposure condition for the block. 9. The imaging element according to claim 1 , further comprising a mode switching unit that switches between a first mode in which a difference between a maximum exposure condition and a minimum exposure condition in the plurality of blocks is a first value, and a second mode in which the difference is smaller than the first value. 9. The imaging element according to claim 1, further comprising a mode switching unit that switches between a first mode in which a maximum value of an absolute value of a difference between an exposure condition of a first block among the plurality of blocks and an exposure condition of each of a plurality of blocks adjacent to the first block is a first value, and a second mode in which the maximum value is smaller than the first value. The image sensor according to claim 1 , further comprising a mode switching unit that switches an image capturing mode between a standard mode using a first exposure condition and a correction mode using a second exposure condition obtained by correcting the first exposure condition. The imaging element according to claim 1 , comprising: an imaging chip on which the plurality of pixels are provided; and a chip on which the setting unit is provided, the chip being stacked on the imaging chip. The imaging chip;
a signal processing chip that is stacked on the imaging chip and processes the pixel signals;
The imaging element according to claim 12 , further comprising: a chip, the chip being stacked on the signal processing chip and including the setting unit. the imaging chip and the signal processing chip are joined by their respective opposing surfaces and connection portions provided on the respective opposing surfaces,
The imaging element according to claim 13 , wherein the signal processing chip and the chip on which the setting unit is provided are connected to each other by their respective opposing surfaces and at least one of a connection portion provided on each of the opposing surfaces and a through electrode provided on the signal processing chip. The image sensor according to claim 12 , further comprising a memory chip having a memory for storing the pixel signals stacked thereon. An imaging device comprising the imaging element according to claim 1 . an imaging element having a plurality of pixels that generate pixel signals in response to incident light;
a setting unit that sets an exposure condition for each of a plurality of blocks, each of which includes at least two of the pixels;
Equipped with
The setting unit is an apparatus that sets exposure conditions for each block such that a difference between the exposure conditions for each block is equal to or smaller than a threshold value.

Images