Patent Description:
In a conventional imaging device, a readout operation of signals of pixels of one imaging frame is performed at the same pixel resolution, so that when extracting a specific region (hereinafter, sometimes referred to as a "region of interest"), extraction of the region of interest is realized by detecting the region of interest and performing data calculation after reading out at high resolution.

<CIT> (Patent Document <NUM>) discloses a technology of using pixel signals of a unit group included in the region of interest (ROI) for detecting a focal point. In this conventional technology, after performing analog-digital conversion on signals of all the pixels, they are stored in an externally prepared memory, and thereafter, pixel data is added while leaving the region of interest designated by an external controller to create low resolution data.

<CIT> relates to a X-ray imaging system including a detector cassette, a computer and control system, a user interface, a fluoroscopic display, and a radiographic display.

<CIT> relates to a method for super resolution enhancement of infrared imaging data employing an image array having simultaneous, high speed, randomly addressable windows of pixels for small regions of interest (ROI) within a large imaging sensor field of view.

<CIT> relates to dynamically re-configurable CMOS imagers for an active vision system.

<CIT> relates to a spatial-temporal multi-resolution image sensor with adaptive frame rates for tracking movement in a region of interest.

<CIT> relates to a capturing element and a electronic camera.

By the way, in an imaging device equipped with an analog-digital conversion unit, it is the analog-digital conversion unit that consumes the power most. From this point of view, in the conventional technology disclosed in Patent Document <NUM>, since the signals of all the pixels are subjected to the analog-digital conversion, power consumption increases. Furthermore, the pixel data is added to create the low-resolution data, and large power is consumed at the time of this adding process, too.

Therefore, an object of the present disclosure is to provide an imaging device and a driving method of the imaging device capable of reducing power consumption.

The following disclosure may include some but not all features as literally defined in the claims and are present for illustration purposes only.

An imaging device of the present disclosure for achieving the above-described object is defined by claim <NUM>. Further solutions are the devices according to the dependent claims <NUM>-<NUM>.

A driving method of an imaging device of the present disclosure for achieving the above-described object is defined by claim <NUM>.

This object is solved by the claimed-subject-matter which defines the present invention.

Hereinafter, a mode for carrying out the technology of the present disclosure (hereinafter referred to as an "embodiment") is described in detail with reference to the drawings. The technology of the present disclosure is not limited to the embodiment, and various numerical values in the embodiment are illustrative. In the following description, the same reference sign is used for the same elements or elements having the same function, and the description thereof is not repeated. Note that, the description is given in the following order.

In an imaging device and a driving method thereof according to the present disclosure, it may be configured to detect a region with motion in a taken image as a region of interest. Then, it may be configured to, when detecting the region of interest, detect the region with motion in the taken image on the basis of a result of comparison between image information of a current imaging frame and image information of at least one imaging frame before.

In the imaging device according to the present disclosure including the above-described preferable configuration, a detection unit may include an image memory, a comparison unit, a motion amount memory, and a region of interest determination unit. The image memory holds the image information of at least one imaging frame before. The comparison unit obtains a difference absolute value between the image information of the current imaging frame and the image information held in the image memory. The motion amount memory stores the difference absolute value obtained by the comparison unit as a motion amount from a past image to a current image. The region of interest determination unit determines the region of interest on the basis of the motion amount stored in the motion amount memory.

In the imaging device and the driving method thereof according to the present disclosure including the above-described preferable configuration, it may be configured to, when detecting the region of interest, detect the region with motion in the taken image using image information at second pixel resolution.

Furthermore, in the imaging device and the driving method thereof according to the present disclosure including the above-described preferable configuration, it is configured to, when a plurality of pixels in a pixel array unit is made a pixel unit, selectively set a first operation mode to add a plurality of pixel signals in the pixel unit to supply to an analog-digital conversion unit and a second operation mode to independently supply the plurality of pixel signals to the analog-digital conversion unit. At that time, it sets the second operation mode for the region of interest and set the first operation mode for a region other than the region of interest.

Furthermore, in the imaging device and the driving method thereof according to the present disclosure including the above-described preferable configuration, the plurality of pixels in the pixel unit are configured to share one vertical signal line between the pixels and include a control switch which selectively connects the pixels to the vertical signal line. Then, it is configured to selectively set the first operation mode and the second operation mode by on/off control of each control switch of the plurality of pixels.

Furthermore, in the imaging device and the driving method thereof according to the present disclosure including the above-described preferable configuration, the plurality of pixels of the pixel unit may include pixels of the same color adjacent to each other. Alternatively, as for the plurality of pixels of the pixel unit, the plurality of pixels of the pixel unit may include the pixels of the same color separated from each other with a pixel of another color interposed therebetween.

A system configuration of the imaging device according to the embodiment of the present disclosure is described. In this embodiment, a complementary metal oxide semiconductor (CMOS) image sensor, which is one type of an X-Y address imaging device, is described as an example of the imaging device. The CMOS image sensor is an image sensor fabricated by applying or partially using a CMOS process.

<FIG> is a block diagram illustrating an outline of the system configuration of the imaging device according to the embodiment of the present disclosure. As illustrated in <FIG>, an imaging device <NUM> according to this embodiment includes a pixel array unit <NUM> and a peripheral circuit unit arranged around the pixel array unit <NUM>. As the peripheral circuit unit, for example, a row selection unit <NUM>, a constant current source unit <NUM>, an analog-digital conversion unit <NUM>, a horizontal transfer scan unit <NUM>, an image processing unit <NUM>, an output interface (I/F) <NUM>, a region of interest detection unit <NUM>, a control unit <NUM> and the like are provided.

In the pixel array unit <NUM>, pixels <NUM> each including a photoelectric conversion unit are two-dimensionally arranged in a row direction and in a column direction, that is, in a matrix. Here, the row direction is intended to mean an array direction of the pixels <NUM> in a pixel row (a so-called horizontal direction), and the column direction is intended to mean an array direction of the pixels <NUM> in a pixel column (a so-called vertical direction). The pixel <NUM> performs photoelectric conversion to generate and accumulate photocharges according to an amount of received light. A specific circuit configuration of the pixel <NUM> is described later.

In the pixel array unit <NUM>, pixel drive lines <NUM><NUM> to <NUM>m (hereinafter, they are sometimes collectively referred to as "pixel drive lines <NUM>") are wired in the row direction for the respective pixel rows in a pixel array in a matrix. Furthermore, vertical signal lines <NUM><NUM> to <NUM>n (hereinafter, they are sometimes collectively referred to as "vertical signal lines <NUM>") are wired in the column direction for the respective pixel columns. The pixel drive line <NUM> transfers a drive signal for driving when reading out a signal from the pixel <NUM>. In <FIG>, the pixel drive line <NUM> is illustrated as one wire, but this is not limited to one wire. One end of the pixel drive line <NUM> is connected to an output end corresponding to each row of the row selection unit <NUM>.

Each circuit unit of the peripheral circuit unit of the pixel array unit <NUM>, that is, the row selection unit <NUM>, the constant current source unit <NUM>, the analog-digital conversion unit <NUM>, the horizontal transfer scan unit <NUM>, the image processing unit <NUM>, the output I/F <NUM>, the region of interest detection unit <NUM>, and the control unit <NUM> are hereinafter described.

The row selection unit <NUM> includes a shift register, an address decoder and the like, and drives the pixels <NUM> of the pixel array unit <NUM> simultaneously for all the pixels, row by row and the like under the control of the control unit <NUM>. Each pixel <NUM> of the pixel array unit <NUM> is selected by the row selection unit <NUM> in units of pixel rows, so that a pixel signal is read out from each pixel <NUM> of the selected pixel row.

The constant current source unit <NUM> includes a set of current sources I including MOS transistors connected to the vertical signal lines <NUM><NUM> to <NUM>n, respectively, for each pixel column (refer to <FIG>), and supplies a bias current to each pixel <NUM> of the pixel row selectively scanned by the row selection unit <NUM> through each of the vertical signal lines <NUM><NUM> to <NUM>n. The pixel signals read out from the respective pixels <NUM> of the pixel array unit <NUM> in units of pixel rows are supplied to the analog-digital conversion unit <NUM> through the vertical signal lines <NUM><NUM> to <NUM>n, respectively.

The analog-digital conversion unit <NUM> includes a set of a plurality of analog-digital converters (ADCs) <NUM> (refer to <FIG>) provided corresponding to the vertical signal lines <NUM><NUM> to <NUM>n, respectively, and converts analog pixel signals output for each pixel column to digital signals. That is, the analog-digital conversion unit <NUM> is a column-parallel analog-digital conversion unit in which a plurality of analog-digital converters <NUM> is arranged in parallel corresponding to the pixel columns.

A well-known analog-digital converter may be used as the analog-digital converter <NUM>. Specifically, as the analog-digital converter <NUM>, a single slope analog-digital converter, a successive approximation analog-digital converter, or a delta-sigma modulation (ΔΣ modulation) analog-digital converter which are examples of a reference signal comparison analog-digital converter may be exemplified. However, the analog-digital converter is not limited to them.

In the analog-digital conversion unit <NUM>, the analog-digital converter <NUM> may be arranged in a one-to-one relationship with respect to the pixel column, that is, may be arranged for each pixel column, or one analog-digital converter may be arranged for a plurality of pixel columns. In this embodiment, one analog-digital converter <NUM> is arranged for every horizontal two pixels (two pixel columns) (refer to <FIG>). In this case, analog-digital conversion is performed twice for obtaining pixel data of one row.

The analog-digital converter <NUM> has a large gate size and large power consumption of the transistor forming the same. Here, power in a case where one analog-digital converter performs the analog-digital conversion once for one pixel, and power in a case where one analog-digital converter performs the analog-digital conversion twice for two pixels may be considered as equivalent. That is, in a case where the analog-digital conversion is performed for the same number of pixels, if the parallel number of the analog-digital converters is small, individual power consumption is small, but since the analog-digital conversions is performed plural times, total power consumption is equivalent.

The analog-digital conversion unit <NUM> includes a latch circuit which latches the pixel data after the analog-digital conversion in a readout period of the pixel signal from each pixel <NUM> of the pixel array unit <NUM> on an output stage of the analog-digital converter <NUM>.

The horizontal transfer scan unit <NUM> includes a shift register, an address decoder and the like, and controls scanning of the pixel column and an address of the pixel column when reading out the signal of each pixel <NUM> of the pixel array unit <NUM>. Under the control of the horizontal transfer scan unit <NUM>, the pixel data converted into the digital signals by the analog-digital conversion unit <NUM> and latched by the latch circuit is read out to a horizontal transfer line L in units of pixel columns.

The pixel data read out to the horizontal transfer line L is subjected to predetermined image processing by the image processing unit <NUM>, and then output through the output I/F <NUM>. The pixel data read out to the horizontal transfer line L is further directly supplied to the region of interest detection unit <NUM>.

The region of interest detection unit <NUM> is a detection unit which detects a specific region in the taken image from image contents as a region of interest (ROI) or a focused region on the basis of the pixel data supplied through the horizontal transfer line L. The region of interest detection unit <NUM> may detect the region with motion in the taken image as the region of interest (focused region) by using, for example, a well-known technology of detecting motion. However, the technology of detecting the region of interest is not limited to the technology of detecting motion.

In a case where the technology of detecting motion is used, it is necessary to hold the image information of at least one imaging frame before. Therefore, the region of interest detection unit <NUM> includes a built-in image memory which stores the image information of at least one imaging frame before. The region of interest detection unit <NUM> detects the region with motion in the taken image as the region of interest on the basis of the result of comparison between the image information of the current imaging frame and the image information of at least one imaging frame before held in the image memory, and provides region of interest information to the control unit <NUM>.

The control unit <NUM> generates various timing signals, clock signals, control signals and the like, and performs drive control of the row selection unit <NUM>, the analog-digital conversion unit <NUM>, the horizontal transfer scan unit <NUM> and the like on the basis of the generated signals. Furthermore, the control unit <NUM> controls the selected pixel row and the pixel resolution on the basis of the region of interest information provided by the region of interest detection unit <NUM>. The control of the pixel row and the pixel resolution is described later in detail.

The imaging device <NUM> having the above-described configuration may obtain an image through a lens (not illustrated). Then, under drive by the row selection unit <NUM>, the analog-digital conversion unit <NUM> performs the analog-digital conversion for each pixel row, and under drive by the horizontal transfer scan unit <NUM>, the pixel data of the row is sequentially scanned, so that an image of one screen may be obtained.

The pixel row from which the pixel signals are read out has the address, and this is a row address incremented from below upward in the drawing on the circuit. In general, a Kepler lens is used as the above-described lens, and an image is a mirror image. Therefore, assuming that the image is the mirror image, a lower portion on the circuit is located in a higher portion on the image, and the row address is incremented from above downward on the image.

In the imaging device <NUM> having the above-described configuration, a chip structure may be a so-called flat structure or a so-called stacked structure.

Here, the flat structure is the chip structure in which the peripheral circuit unit of the pixel array unit <NUM>, that is, the row selection unit <NUM>, the constant current source unit <NUM>, the analog-digital conversion unit <NUM>, the horizontal transfer scan unit <NUM>, the image processing unit <NUM>, the output I/F <NUM>, the region of interest detection unit <NUM>, and the control unit <NUM> are formed on the same semiconductor substrate (semiconductor chip) as the pixel array unit <NUM>.

Furthermore, the stacked structure is the chip structure in which the peripheral circuit unit of the pixel array unit <NUM> is formed on at least one semiconductor substrate different from the semiconductor substrate on which the pixel array unit <NUM> is formed. According to the imaging device <NUM> having this laminated structure, a size (area) of a first-layer semiconductor substrate on which the pixel array unit <NUM> may be formed is sufficient, so that the size (area) of the first-layer semiconductor substrate, and eventually, a size of an entire chip may be reduced. Moreover, since a process suitable for fabricating the pixel <NUM> may be applied to the first-layer semiconductor substrate and a process suitable for fabricating a circuit portion may be applied to other semiconductor substrates, there also is an advantage that the process may be optimized when manufacturing the imaging device <NUM>.

<FIG> is a circuit diagram illustrating an example of a circuit configuration of the pixel <NUM>. The pixel <NUM> includes, for example, a photodiode <NUM> as the photoelectric conversion unit, and has the circuit configuration including a transfer transistor <NUM>, a reset transistor <NUM>, an amplification transistor <NUM>, and a selection transistor <NUM> in addition to the photodiode <NUM>.

Note that, here, N-channel MOS field-effect transistors are used, for example, as four transistors of the transfer transistor <NUM>, the reset transistor <NUM>, the amplification transistor <NUM>, and the selection transistor <NUM>. However, a combination of conductivity types of the four transistors <NUM> to <NUM> herein exemplified is merely an example and the combination is not limited thereto.

Regarding the pixels <NUM>, as the above-described pixel drive lines <NUM>, a plurality of pixel drive lines is wired in common to the pixels <NUM> in the same pixel row. The plurality of pixel drive lines is connected to the output terminals corresponding to the respective pixel rows of the row selection unit <NUM> for each pixel row. The row selection unit <NUM> appropriately outputs a transfer signal TRG, a reset signal RST, and a selection signal SEL to the plurality of pixel drive lines.

The photodiode <NUM> an anode electrode of which is connected to a low potential side power supply (for example, ground) photoelectrically converts the received light into the photocharges (herein, photoelectrons) of a charge amount corresponding to the amount of light and accumulates the photocharges. A cathode electrode of the photodiode <NUM> is electrically connected to a gate electrode of the amplification transistor <NUM> via the transfer transistor <NUM>. Here, a region where the gate electrode of the amplification transistor <NUM> is electrically connected is a floating diffusion (floating diffusion region/impurity diffusion region) FD. The floating diffusion FD is a charge-voltage conversion unit which converts charges into a voltage.

To a gate electrode of the transfer transistor <NUM>, the transfer signal TRG in which a high level (for example, VDD level) is active is supplied from the row selection unit <NUM>. When the transfer transistor <NUM> is put into a conductive state in response to the transfer signal TRG, this transfers the photocharges photoelectrically converted by the photodiode <NUM> and accumulated in the photodiode <NUM> to the floating diffusion FD.

The reset transistor <NUM> is connected between a node of a high-potential side power supply VDD and the floating diffusion FD. To a gate electrode of the reset transistor <NUM>, the reset signal RST in which a high level is active is supplied from the row selection unit <NUM>. The reset transistor <NUM> is put into a conductive state in response to the reset signal RST, and resets the floating diffusion FD by discharging the charge of the floating diffusion FD to the node of the voltage VDD.

The amplification transistor <NUM> is such that the gate electrode is connected to the floating diffusion FD and a drain electrode is connected to the node of the high-potential side power supply VDD. The amplification transistor <NUM> serves as an input unit of a source follower which reads out a signal obtained by the photoelectric conversion in the photodiode <NUM>. That is, a source electrode of the amplification transistor <NUM> is connected to the vertical signal line <NUM> through the selection transistor <NUM>. Then, the amplification transistor <NUM> and the current source I connected to one end of the vertical signal line <NUM> form the source follower which converts the voltage of the floating diffusion FD into potential of the vertical signal line <NUM>.

A drain electrode and a source electrode of the selection transistor <NUM> are connected to the source electrode of the amplification transistor <NUM> and the vertical signal line <NUM>, respectively, for example. To a gate electrode of the selection transistor <NUM>, the selection signal SEL in which a high level is active is supplied from the row selection unit <NUM>. When the selection transistor <NUM> is put into a conductive state in response to the selection signal SEL, this puts the unit pixel <NUM> into a selected state and transfers the signal output from the amplification transistor <NUM> to the vertical signal line <NUM>.

Note that, as the pixel circuit of the pixel <NUM>, a 4Tr circuit configuration including the transfer transistor <NUM>, the reset transistor <NUM>, the amplification transistor <NUM>, and the selection transistor <NUM>, that is four transistors (Trs) is herein described as an example; however, this is not limited to the 4Tr circuit configuration. Furthermore, as the pixel structure, when a substrate surface on a side on which a wiring layer is provided is a front surface (front), it is also possible to use a back surface irradiation pixel structure which captures irradiation light from a back surface side opposite to the front surface, or may use a front surface irradiation pixel structure which captures irradiation light from a front surface side.

In the above description, the system configuration of a general imaging device in which one vertical signal line <NUM> is wired for each pixel column is described as an assumption, but the imaging device <NUM> according to this embodiment adopts a system configuration in which a plurality of pixels of the pixel array unit <NUM> is made a unit (hereinafter, referred to as a "pixel unit") and one vertical signal line <NUM> is shared by the plurality of pixels in the pixel unit.

Furthermore, the imaging device <NUM> according to this embodiment includes the region of interest detection unit <NUM> which detects the specific region in the taken image as the region of interest. Then, the imaging device <NUM> according to this embodiment reads out the pixel signals at first pixel resolution in the region including the region of interest detected by the region of interest detection unit <NUM>, and reads out the pixel signals at second pixel resolution lower than the first pixel resolution in the region not including the region of interest under the control of the control unit <NUM>.

Hereinafter, the first pixel resolution is referred to as high resolution, and the second pixel resolution is referred to as low resolution. Specific examples of this embodiment are described below.

An example <NUM> is an example in which a plurality of pixels of the same color adjacent to each other, for example, horizontal two pixels × vertical two pixels (pixels of two columns × two rows) is made one pixel unit <NUM>, and a plurality of pixels in the pixel unit <NUM> shares one vertical signal line <NUM>. <FIG> illustrates a configuration of a substantial part of an imaging device according to the example <NUM>. Here, a case where the pixel unit <NUM> including horizontal two pixels × vertical two pixels is made a color unit and a color array is a Bayer array of red R, green G, and blue B is illustrated.

<FIG> is a configuration diagram for selecting pixels in one pixel unit <NUM>, and <FIG> is a conceptual diagram of high-resolution readout and low-resolution readout by a control switch. In <FIG>, for example, four pixels 2R<NUM> to 2R<NUM> including horizontal two × vertical two red R pixels are illustrated.

As illustrated in <FIG>, in a pixel array unit in which the pixel units <NUM> each including the four pixels including horizontal two pixels × vertical two pixels are arranged in a Bayer array of red R, green G, and blue B, a row in units of the pixel units <NUM> is referred to as a unit row. Then, under the control of a control unit <NUM>, unit row selection signals V<NUM>, V<NUM>, V<NUM>,. are provided from a row selection unit <NUM> to the respective unit rows to select the unit row.

Furthermore, as illustrated in <FIG>, the four pixels 2R<NUM> to 2R<NUM> in the pixel unit <NUM> share one vertical signal line <NUM> among the pixels and include control switches SW<NUM> to SW<NUM> which selectively connect them to the vertical signal line <NUM>, respectively. The control switches SW<NUM> to SW<NUM> are connected between a selection transistor <NUM> and the vertical signal line <NUM> illustrated in <FIG> and are subjected to on/off control by switch control signal S<NUM> to S<NUM> appropriately provided from the row selection unit <NUM> under the control of the control unit <NUM>.

<FIG> illustrates a timing relationship of the unit row selection signals V<NUM>, V<NUM>, and V<NUM> and the switch control signals S<NUM> to S<NUM>.

In the imaging device according to the example <NUM> having the above-described configuration, an operation is performed in which signals of the four pixels 2R<NUM> to 2R<NUM> in the pixel unit <NUM> are simultaneously read out to the vertical signal line <NUM> to be added by turning on all of the control switches SW<NUM> to SW<NUM> under the control of the control unit <NUM> (first operation mode). According to this first operation mode, the signals of the four pixels 2R<NUM> to 2R<NUM> in the pixel unit <NUM> are added at an analog level, and the added signals are supplied to an analog-digital converter <NUM> arranged for every two pixel columns. That is, the first operation mode is a low-resolution readout mode in which signals of four pixels are read out as a signal of one pixel as illustrated on a right side in <FIG>.

Furthermore, an operation is performed in which the signals of the four pixels 2R<NUM> to 2R<NUM> are sequentially read out to the vertical signal line <NUM> to be supplied to the analog-digital converter <NUM> in units of pixels by sequentially turning on the control switches SW<NUM> to SW<NUM> by the switch control signals S<NUM> to S<NUM>, respectively, under the control of the control unit <NUM> (second operation mode). The second operation mode is a high-resolution readout mode in which the signals of the four pixels 2R<NUM> to 2R<NUM> are read out in units of pixels as illustrated on a left side in <FIG>.

In the high-resolution readout, the readout of the pixel signals is realized by performing the analog-digital conversion four times on the four pixels 2R<NUM> to 2R<NUM>. On the other hand, in the low-resolution readout, the readout of the pixel signals is realized by performing the analog-digital conversion once on the four pixels 2R<NUM> to 2R<NUM>. Therefore, in the first operation mode of the low-resolution readout, the pixel signals may be read out with one-quarter the readout time and one-quarter the power consumption as compared with those in the second operation mode of the high-resolution readout.

As illustrated in <FIG>, the analog-digital conversion is performed in units of one pixel unit row. At the time of low-resolution readout, the analog-digital conversion is performed on a signal obtained by adding the signals of the four pixels 2R<NUM> to 2R<NUM>, so that data of one pixel unit row may be obtained by one analog-digital conversion operation. In the low-resolution readout, the pixel signals are added, so that the switches SW<NUM> to SW<NUM> are simultaneously turned on and the signals of the four pixels 2R<NUM> to 2R<NUM> are read out simultaneously. On the other hand, in the high-resolution readout, in order to read out the signals of the four pixels 2R<NUM> to 2R<NUM> one pixel at a time, the switches SW<NUM> to SW<NUM> are individually turned on, and the analog-digital conversion is sequentially performed.

<FIG> illustrates a readout image of the pixel signals in a case where the low-resolution readout and the high-resolution readout are combined. By combining control of the low-resolution readout and control of the high-resolution readout, an image at high resolution by the high-resolution readout is obtained for a portion of a region of interest. Furthermore, as for a portion other than the region of interest, an operation of reading out at low resolution is realized.

An example <NUM> is an example of a circuit configuration of a region of interest detection unit <NUM> which uses a technology of detecting motion when detecting a region of interest. <FIG> illustrates an example of a circuit configuration of a region of interest detection unit according to the example <NUM>. Furthermore, <FIG>) is conceptual diagrams of detection of the region of interest using the technology of detecting motion.

The region of interest detection unit <NUM> includes an image memory <NUM>, a comparison unit <NUM>, a motion amount memory <NUM>, and a region of interest determination unit <NUM>.

In the region of interest detection unit <NUM> having the above-described configuration, the image memory <NUM> holds image information of at least one imaging frame before as past image information (<FIG>). The comparison unit <NUM> compares the past image information (<FIG>) held in the image memory <NUM> with current image information (<FIG>), takes a difference absolute value between the same pixel units, and obtains a difference absolute value image (<FIG>). The current image information is stored in the image memory <NUM> for a comparison operation in a next imaging frame.

The difference absolute value image (<FIG>) obtained by the comparison operation by the comparison unit <NUM> is stored in the motion amount memory <NUM> as a motion amount from a past image (<FIG>) to a current image (<FIG>). By using a reduced image as a unit of storage and comparison of the image information, the image memory <NUM> and the circuit may be significantly downsized.

The region of interest determination unit <NUM> determines that there is motion in a portion in which the motion amount is larger than a predetermined amount on the basis of the motion amount stored in the motion amount memory <NUM>, detects the portion as the region of interest, and supplies region of interest information to a control unit <NUM>.

The control unit <NUM> which receives the region of interest information from the region of interest detection unit <NUM> performs control to read out a pixel signal of a portion of the region of interest by high-resolution readout and performs control to read out a pixel signal of a portion other than the region of interest by low-resolution readout (<FIG>).

Here, it is preferable that the region of interest detection unit <NUM> detects a region with motion in a taken image by using image information at low resolution which is second pixel resolution. Specifically, at least, the image data is stored in the image memory <NUM> and compared by the comparison unit <NUM> using a reduction ratio corresponding to the low resolution which is the second resolution, or a reduction ratio higher than this. This makes it possible to match the high-resolution readout to the low-resolution readout. The difference absolute value image (<FIG>) may be stored at granularity of each pixel unit <NUM>, but in one embodiment, this is stored in the motion amount memory <NUM> for each pixel unit row.

Next, readout control adapted to the region of interest (ROI) is described. First, row address motion in a case where there is no region of interest is described with reference to <FIG>. In <FIG>, a view on a left side is a graph in which time is plotted along the abscissa and the row address is plotted along the ordinate.

The row address makes a transition from a small value to a large value in sequence, and since the pixel signals of all the pixels are obtained by high-resolution readout, it takes time at a constant rate. A shaded portion in the graph represents exposure for each row, a line on a left side of a parallelogram represents a pixel reset (reset) timing, and a line on a right side represents a pixel signal readout (readout) timing.

In <FIG>, a view on a right side is a view illustrating an image in which a black-painted portion represents an image obtained by high-resolution readout. Physical positions of the row address in the view on the left side and the image in the view on the right side are illustrated to match. The analog-digital conversion is performed when reading out the pixel signal, and a period thereof is represented by "AD conversion (high power)". Since power consumption is high in this AD conversion period, reducing this time leads to realization of power saving.

Next, the row address motion in a case where there is the region of interest is described with reference to <FIG>. In <FIG> also, a view on a left side is a graph in which time is plotted along the abscissa and the row address is plotted along the ordinate as in <FIG>.

As for the portion other than the region of interest, it is driven by the low-resolution readout, and an image is drawn as a white outline. In a case of a low-resolution readout operation, the pixel signals may be read out in one-quarter the time in this example, so that a slope of the graph is sharper than that of the graph in <FIG>. In response to this, the AD conversion period for one screen is shortened. Therefore, in the portion other than the region of interest, by performing the low-resolution readout, the power consumption may be significantly reduced as compared with a case where the pixel signals of all the pixels are obtained by the high-resolution readout in <FIG>.

Next, motion of a continuous operation that matches motion of a subject is described with reference to <FIG>. In <FIG>, from a top stage, there are a "scene" of an actual scene image, a "difference" from the image one imaging frame before, a "readout content" of the imaging device <NUM>, "row address motion" of the imaging device <NUM>, an "operation content" of the imaging device <NUM>, and a "power image" illustrating an outline of the power consumption.

In the "operation content", an AD conversion period by the analog-digital conversion unit <NUM> is represented as "ADC", and a period other than this is represented as "standby". The imaging device <NUM> consumes a large amount of power in the AD conversion by the analog-digital conversion unit <NUM>, and normally performs processing from image processing to data output in this AD conversion period. Then, the power consumption may be reduced by shortening the AD conversion period.

A graph of the power consumption is illustrated in the "power image". From this graph, it is understood that the power consumption may be reduced by shortening the AD conversion period. In the "power image", a high portion of the graph is a portion in which power consumption is high. A large amount of power is consumed in an "ADC" period, and very small power is consumed in a "standby" period.

In a case where the readout operation of the pixel signal is performed, data motion and the like do not occur and a large amount of power is not required, but this is larger than that in the "standby" period, so that this is represented by a small height. Since the circuit does not operate in the "standby" period, an analog circuit is controlled to shift to a mode in which the power consumption is extremely small, and a digital circuit may cut off the power.

<FIG> illustrates a scenario from operation start (frame <NUM>); a vehicle moves (frame <NUM> to frame <NUM>), thereafter the vehicle disappears from a screen, then a small bird appears on a bank of a pond (frame <NUM>).

The scene of the (frame <NUM>) is an initial operation and there is no previous imaging frame, so that there is no difference information. As a readout operation of the pixel signal, since there is no region of interest, it is driven by high-resolution readout. Since an entire screen is controlled by the high-resolution readout, the analog-digital conversion period (ADC) is the longest. Since a large amount of power is consumed at the time of analog-digital conversion, in the "power image", the high portion of the graph becomes longer and the total power consumption also increases.

In the (frame <NUM>), since it is driven as a normal operation (not the initial operation any more), the entire screen is driven by low-resolution readout. Therefore, a slope of a graph of the "row address motion" becomes sharp and the analog-digital conversion period becomes short. In a graph of the "power image" also, a portion of the high power becomes short, so that the power consumption becomes small. In this example, since the number of pixels becomes one-quarter, the power consumption is reduced to about one-quarter or smaller.

The motion of the vehicle is detected on the basis of a difference between image information of the (frame <NUM>) and image information of the (frame <NUM>). A position in the screen of this vehicle is reflected as the region of interest in an operation of the next imaging frame. A portion of high-resolution readout is generated, so that it becomes worse in terms of power than a case where it is entirely driven by the low-resolution readout, but an effect of power improvement is larger than that in a case where all the pixels are driven by high-resolution readout. Furthermore, since an external controller which receives this image data has received a high-resolution image in the past, it is possible to always obtain a high-resolution image by complementing by using the past image as for a portion without motion. This is a great advantage in a case of using the technology of detecting motion to detect the region of interest.

Furthermore, the imaging device <NUM> according to one embodiment includes the region of interest detection unit <NUM> which detects a specific region in the taken image as the region of interest, and the imaging device itself may detect the region of interest, so that it is easy to detect the region of interest and reflect the same to control. A change in image position of motion detection and a change in control corresponding to this are represented in the (frame <NUM>) to the (frame <NUM>). A situation is illustrated in which the vehicle disappears from the screen in the (frame <NUM>) and the small bird appears on the bank of the pond in the (frame <NUM>). It is illustrated that the motion is detected by the appearance of the small bird, the position of the region of interest changes accordingly, and the control changes in the (frame <NUM>).

An example <NUM> is a variation of the example <NUM> and is another pixel configuration example of one pixel unit <NUM>. In the example <NUM>, one pixel unit <NUM> includes four pixels of horizontal two pixels × vertical two pixels (pixels in two columns × two rows) (refer to <FIG>). A first specific example of the pixel unit <NUM> according to the example <NUM> is illustrated in <FIG>, a second specific example thereof is illustrated in <FIG>, and a third specific example thereof is illustrated in <FIG>.

The pixel unit <NUM> according to the first specific example includes a total of <NUM> pixels of horizontal four pixels × vertical four pixels (pixels of four columns × four rows) of the same color adjacent to each other as illustrated in <FIG>, and signals of the <NUM> pixels are added on a vertical signal line <NUM>. The pixel unit <NUM> according to the second specific example includes two pixels of the same color adjacent to each other in the same pixel row as illustrated in <FIG>, and signals of the two pixels are added on the vertical signal line <NUM>. The pixel unit <NUM> according to the third specific example includes two pixels of the same color adjacent to each other in the same pixel column as illustrated in <FIG>, and signals of the two pixels are added on the vertical signal line <NUM>.

Note that, three examples of the first specific example, the second specific example, and the third specific example are herein given as another pixel configuration example of one pixel unit <NUM>, but it is sufficient that the pixel unit <NUM> has a pixel configuration capable of realizing low-resolution readout by performing the pixel addition on the vertical signal line <NUM> before analog-digital conversion in addition to these three examples.

An example <NUM> is a variation of the example <NUM> and is another example of high-resolution readout. In the example <NUM>, in one pixel unit <NUM> including four pixels of horizontal two pixels × vertical two pixels, it is sequentially read out one pixel at a time at the time of high-resolution readout (refer to <FIG>). On the other hand, in the example <NUM>, it is also possible to configure to read out two pixels together as illustrated in <FIG>.

Note that, two types of combinations of the two pixels in <FIG> are herein illustrated, but this is not limited to these combinations, and another combination of two pixels may be used, and the combination is not limited to the combination of two pixels but may be a combination of three pixels.

An example <NUM> is an example in which a pixel unit <NUM> includes pixels of the same color separated from each other with a pixel of another color interposed therebetween. <FIG> illustrates a configuration of a substantial part of an imaging device according to the example <NUM>. A color array of pixels of an imaging device according to the example <NUM> is a color array of a general imaging device, specifically, a Bayer array of red R, green G, and blue B in units of pixels. That is, the color array of the pixels of the imaging device according to the example <NUM> is the color array in which the pixels of the same color are not adjacent to each other.

In the example <NUM>, pixel rows are selected by row selection signals SV1_1/SV1_2, SV2_1/SV2_2, SV3_1/SV3_2,. The row selection signals SV1_1/SV1_2, SV2_1/SV2_2, SV3_1/SV3_2,. drive pixel switches provided for each pixel to select a pixel row and a pixel. <FIG> illustrates pixel switches for a total of eight pixels in first to fourth columns in first and second rows surrounded by a dashed square A in <FIG>.

In the first row, a pixel switch SWR1_1 and a pixel switch SWG1_1 driven by the row selection signal SV1_1 are connected between an R pixel in the first column and a vertical signal line <NUM>, and between a G pixel in the second column and the vertical signal line <NUM>, respectively. Furthermore, a pixel switch SWR1_2 and a pixel switch SWG1_2 driven by the row selection signal SV1_2 are connected between an R pixel in the third column and the vertical signal line <NUM>, and between a G pixel in the fourth column and the vertical signal line <NUM>, respectively.

In the second row, a pixel switch SWG2_1 and a pixel switch SWB2_1 driven by the row selection signal SV2_1 are connected between a G pixel in the first column and the vertical signal line <NUM>, and between a B pixel in the second column and the vertical signal line <NUM>, respectively. Furthermore, a pixel switch SWG2_2 and a pixel switch SWB2_2 driven by the row selection signal SV2_2 are connected between a G pixel in the third column and the vertical signal line <NUM>, and between a B pixel in the fourth column and the vertical signal line <NUM>, respectively.

As illustrated in <FIG>, four pixel columns adjacent to each other are made a unit, and one ends of the selection switch SW1_1, the selection switch SW1_2, the selection switch SW2_1, and the selection switch SW2_2 are connected to the vertical signal lines <NUM> of the respective pixel columns. Furthermore, the other ends of the selection switch SW1_1 in the first column and the selection switch SW2_1 in the third column are commonly connected, and the other ends of the selection switch SW1_2 in the second column and the selection switch SW2_2 in the fourth column are commonly connected. For fifth and subsequent columns, a similar configuration as that of the first to fourth columns is repeated in units of four pixel columns.

The selection switch SW1_1 and the selection switch SW1_2 are driven by a selection signal SH<NUM>, and the selection switch SW2_1 and the selection switch SW2_2 are driven by a selection signal SH<NUM>. The imaging device according to the example <NUM> has the color array in which the pixels of the same color are not adjacent to each other, so that the selection switch SW1_1, the selection switch SW1_2, the selection switch SW2_1, and the selection switch SW2_2 form a mechanism of adding the pixel signals of the two columns on a stage before an input of an analog-digital converter (ADC) <NUM>.

One analog-digital converter <NUM> is arranged for every two pixel columns. Then, the other ends of the selection switches SW1_1 and SW2_1 commonly connected and the other ends of the selection switches SW1_2 and SW2_2 commonly connected are connected to the input end of the corresponding analog-digital converter <NUM>.

<FIG> illustrates a timing relationship between the selection signals SH<NUM> and SH<NUM> and the row selection signals SV1_1/SV1_2, SV2_1/SV2_2,. , and SV6_1/SV6_2. Low-resolution readout and high-resolution readout may be realized by a combination of these signals.

In the low-resolution readout, as illustrated in <FIG>, for example, the first and third pixel rows are selected by the row selection signals SV1_1/SV1_2 and SV3_1/SV3_2. Then, in order to select and add the same color, the selection signals SH<NUM> and SH<NUM> turn on the selection switches SW1_1, SW1_2, SW2_1, and SW2_2. Therefore, the signals of the four pixels of the same color are analog-added, so that they may be read out by one analog-digital conversion.

In the high-resolution readout, as illustrated in <FIG>, for example, the signals are sequentially read out one pixel at a time such that a signal of one pixel is read out while putting only the row selection signal SV5_1 and the selection signal SH<NUM> into an active state, and then a signal of one pixel is read out while putting only the row selection signal SV5_2 and the selection signal SH<NUM> into an active state.

Although the technology of the present disclosure is described above on the basis of the preferred embodiment, the technology of the present disclosure is not limited to the embodiment. The configuration and structure of the imaging element described in the above embodiment are illustrative, and may be changed as appropriate.

For example, although a case of applying to the CMOS image sensor in which the pixels <NUM> are arranged in a matrix is described as an example in the above-described embodiment, the technology of the present disclosure is not limited to the application to the CMOS image sensor. That is, the technology of the present disclosure may be applied to all X-Y address imaging devices in which the pixels <NUM> are two-dimensionally arranged in a matrix.

The imaging device according to this embodiment described above may be used in various devices which sense light such as visible light, infrared light, ultraviolet light, and X-rays, as illustrated in <FIG>, for example. Specific examples of the various devices are listed below.

The technology according to the present disclosure is applicable to various products. More specifically, the invention may be applied to an imaging system such as a digital still camera or a video camera, a mobile terminal device having an imaging function such as a mobile phone, or an electronic device such as a copying machine using an imaging element in an image read unit. Hereinafter, a case where the invention is applied to an imaging system such as a digital still camera or a video camera is described.

<FIG> is a block diagram illustrating a configuration of an imaging system which is an example of an electronic device. As illustrated in <FIG>, an imaging system <NUM> according to this example includes an imaging optical system <NUM> including a lens group and the like, an imaging unit <NUM>, a digital signal processor (DSP) circuit <NUM>, a frame memory <NUM>, a display device <NUM>, a recording device <NUM>, an operating system <NUM>, a power supply system <NUM> and the like. Then, the DSP circuit <NUM>, the frame memory <NUM>, the display device <NUM>, the recording device <NUM>, the operating system <NUM>, and the power supply system <NUM> are connected to each other via a bus line <NUM>.

The imaging optical system <NUM> captures incident light (image light) from a subject to form an image on an imaging surface of the imaging unit <NUM>. The imaging unit <NUM> converts a light amount of the incident light the image of which is formed on the imaging surface thereof by the optical system <NUM> to an electric signal in a pixel unit to output as a pixel signal. The DSP circuit <NUM> performs general camera signal processing such as white balance processing, demosaic processing, and gamma correction processing, for example.

The frame memory <NUM> is used to appropriately store data in the process of the signal processing in the DSP circuit <NUM>. The display device <NUM> including a panel display device such as a liquid crystal display device and an organic electro luminescence (EL) display device displays a moving image or a still image taken by the imaging unit <NUM>. The recording device <NUM> records the moving image or the still image taken by the imaging unit <NUM> on a recording medium such as a portable semiconductor memory, an optical disc, or a hard disk drive (HDD).

The operating system <NUM> issues an operation command regarding various functions of the imaging device <NUM> under an operation by a user. The power supply system <NUM> appropriately supplies various power supplies serving as operation power supplies of the DSP circuit <NUM>, the frame memory <NUM>, the display device <NUM>, the recording device <NUM>, and the operating system <NUM> to supply targets.

Claim 1:
An imaging device (<NUM>) comprising:
a pixel array unit (<NUM>);
a detection unit (<NUM>) that is configured to receive images taken by the pixel array unit (<NUM>) and to detect that a specific region in an image taken by the pixel array unit (<NUM>) is a region of interest;
a control unit (<NUM>) that is configured to perform control to read out a pixel signal at first pixel resolution in a region including the region of interest and read out a pixel signal at second pixel resolution lower than the first pixel resolution in a region not including the region of interest; and
a plurality of analog-digital conversion units (<NUM>, <NUM>) each of which being provided corresponding to one vertical signal line (<NUM>) of the pixel array unit (<NUM>), the plurality of analog-digital conversion units (<NUM>, <NUM>) converting pixel signals read out by the control unit (<NUM>) into digital signals,
wherein a plurality of pixels in the pixel array unit (<NUM>) is defined as a pixel unit (<NUM>),
wherein the plurality of pixels in the pixel unit (<NUM>) shares one vertical signal line (<NUM>) between the pixels and includes control switches (SW1, SW2, SW3, SW4) that selectively connect the pixels to the vertical signal line (<NUM>), and
and wherein
the control unit (<NUM>) is configured to selectively set a second operation mode in which signals of the plurality of pixels in the pixel unit (<NUM>) are sequentially read out and supplied via the vertical signal line (<NUM>) of the pixel unit (<NUM>) to the analog-digital conversion unit (<NUM>, <NUM>) corresponding to said vertical signal line (<NUM>) and a first operation mode in which signals of the plurality of pixels are added and read out as a signal of one pixel supplied via the vertical signal line (<NUM>) of the pixel unit (<NUM>) to the analog-digital conversion unit (<NUM>, <NUM>) corresponding to said vertical signal line (<NUM>), and
the control unit (<NUM>) sets the second operation mode for the region of interest and sets the first operation mode for a region other than the region of interest,
the control unit (<NUM>) selectively sets the first operation mode and the second operation mode by on/off controlling each of the control switches (SW<NUM>, SW<NUM>, SW<NUM>, SW<NUM>) of the plurality of pixels.