Image sensor and electronic camera

An image sensor includes: a plurality of filter units, transmission wavelengths of which can be adjusted; a plurality of photoelectric conversion units that receive light transmitted through the filter unit; and a control unit that alters a size of a first region containing a first filter unit, among the plurality of filter units, through which light at a first wavelength is transmitted before entering a photoelectric conversion unit.

TECHNICAL FIELD

The present invention relates to an image sensor and an electronic camera.

There is an image sensor known in the related art that includes pixels each having a variable filter the transmission wavelength of which can be adjusted (PTL 1). There is an issue yet to be addressed in the image sensor in the related art in that the resolution cannot be altered.

CITATION LIST

Patent Literature

PTL 1: Japanese Laid Open Patent Publication No. 2013-85028

SUMMARY OF INVENTION

According to the 1st aspect of the present invention, an image sensor comprises: a plurality of filter units, transmission wavelengths of which can be adjusted; a plurality of photoelectric conversion units that receive light transmitted through the filter unit; and a control unit that alters a size of a first region containing a first filter unit, among the plurality of filter units, through which light at a first wavelength is transmitted before entering a photoelectric conversion unit.

According to the 2nd aspect of the present invention, an electronic camera comprises: the image sensor according to the 1st aspect; and an image generation unit that generates image data based upon a signal provided by the image sensor.

FIRST EMBODIMENT

FIG.1is a block diagram showing the structure of the image capturing device in the first embodiment. The image-capturing device in the first embodiment may be an electronic camera1adopting a structure such as that shown inFIG.1. The electronic camera1comprises a photographic optical system2, an image sensor3and a control unit4. The photographic optical system2forms a subject image at the image sensor3. The image sensor3generates pixel signals by capturing the subject image formed by the photographic optical system2. The image sensor3may be, for instance, a CMOS image sensor. The control unit4outputs control signals to the image sensor3so as to control operations of the image sensor3. In addition, the control unit4functions as an image generation unit that generates image data by executing various types of image processing on the pixel signals output from the image sensor3. It is to be noted that the photographic optical system2may be an interchangeable system that can be mounted at and dismounted from the electronic camera1.

In reference toFIG.2andFIG.3, the structure of the image sensor3in the first embodiment will be explained.FIG.2is a block diagram showing the structure of part of the image sensor3in the first embodiment in an abridged presentation.FIG.3presents diagrams illustrating the image sensor3in the first embodiment.FIG.3(a)presents an example of a structure that may be adopted in the image sensor3in a sectional view, whereasFIG.3(b)illustrates how transparent electrodes may be laid out in the filter units at the image sensor3in a plan view. As shown inFIG.2, the image sensor3includes a plurality of pixels10, a filter vertical drive unit40, a filter horizontal drive unit50, a filter control unit60, a pixel vertical drive unit70, a column circuit unit80, a horizontal scanning unit90, an output unit100and a system control unit110. At the image sensor3, the pixels10are disposed in a two-dimensional pattern (e.g., along a row direction, i.e., along a first direction, and a column direction, i.e., a second direction intersecting the first direction). While only 16 pixels (across)×12 pixels (down) are shown as the pixels10so as to simplify the illustration in the example presented inFIG.2, the image sensor3actually includes, for instance, several million to several hundred million pixels, or an even greater number of pixels.

The image sensor3may be, for instance, a back-illuminated image sensor. As shown inFIG.3(a), the image sensor3includes a semiconductor substrate220, a wiring layer210laminated on the semiconductor substrate220, a support substrate200, microlenses31and filter units5. The semiconductor substrate220is constituted with, for instance, a silicon semiconductor substrate, whereas the support substrate200is constituted with a semiconductor substrate, a glass substrate or the like. The semiconductor substrate220is laminated on the support substrate200via the wiring layer210. In the wiring layer210, which includes a conductor film (metal film) and an insulating film, a plurality of wirings, vias and the like are disposed. The conductor film may be constituted of, for instance, copper or aluminum. The insulating film may be an oxide film, a nitride film or the like. As shown inFIG.3(a), incident light enters the image sensor primarily toward the + side of a Z axis. As the coordinate axes in the figure indicate, the direction running rightward on the drawing sheet perpendicular to the Z axis is designated as an X axis+direction and the direction running away from the viewer of the drawing, perpendicular to the Z axis and the X axis, is designated as a Y axis+direction.

The semiconductor substrate220has a first surface201aused as an entry surface at which light enters and a second surface201bdifferent from the first surface201a. The second surface201bis located on the side opposite from the first surface201a. The wiring layer210is laminated on the side at which the second surface201bof the semiconductor substrate220is located. Since light is radiated from the side opposite the wiring layer210, i.e., the side on which the first surface201ais located, the image sensor3functions as a back-illuminated image sensor. The semiconductor substrate220includes photoelectric conversion units34disposed in the area between the first surface201aand the second surface201b. At a photoelectric conversion unit34, which may be constituted with, for instance, a photodiode (PD), light having entered therein is converted to an electric charge. A signal generated based upon the electric charge resulting from the photoelectric conversion at the photoelectric conversion unit34is output to the wiring layer210. A plurality of pixels10, each having a photoelectric conversion unit34, are disposed along the X axis and along the Y axis. On the side where the first surface201aof the semiconductor substrate220is located, a filter unit5and a microlens31are disposed in correspondence to each pixel10.

A pixel10is structured so as to include a microlens31, a filter unit5, light shielding films32and a photoelectric conversion unit34. The microlens31condenses light having entered therein onto the photoelectric conversion unit34. The light shielding films32, each disposed at a boundary between pixels10disposed adjacent to each other, minimize light leakage from one pixel to another.

The filter unit5includes electro-chromic (hereafter will be referred to as EC) layers21,22and23and transparent electrodes11,12,13and14, laminated in sequence, starting on the side where the microlens31is present, toward the semiconductor substrate220. The EC layers21through23are formed by using an electro-chromic material such as a metal oxide. The transparent electrodes11through14may be constituted of, for instance, ITO (indium tin oxide). An insulating film33is disposed in the areas between the EC layer21and the transparent electrode12, between the EC layer22and the transparent electrode13, and between the EC layer23and the transparent electrode14. In addition, an electrolytic layer (electrolytic film) (not shown) is disposed in the filter unit5.

Transparent electrodes11are disposed, each in correspondence to a plurality of EC layers21that are disposed one after another along the X direction, i.e., the row direction, so as to cover one side of the surfaces of the plurality of EC layers21, as is clearly shown inFIG.3(b). In the example presented inFIG.2, the pixels10are arrayed over twelve rows and thus, twelve transparent electrodes11are disposed parallel to one another. Transparent electrodes12and transparent electrodes13are also disposed in much the same way as the transparent electrodes11, so as to cover one side of the surfaces of the plurality of EC layers22, disposed one after another along the X direction, or one side of the surfaces of the plurality of EC layers23disposed one after another along the X direction.

A transparent electrode14, which is a common electrode used in conjunction with three EC layers21,22and23, is disposed on the side where the other surface of the EC layer23is located. Common transparent electrodes14are disposed, each in correspondence to the plurality of EC layers23that are disposed one after another along the Y direction, i.e., the column direction, along the plurality of EC layers23disposed one after another along the column direction, as is clearly shown inFIG.3(b). In the example presented inFIG.2, the pixels10are arrayed over 16 columns, and thus, 16 common transparent electrodes14are disposed parallel to one another.

The transparent electrodes11through13and the common transparent electrodes14are electrodes disposed in a matrix pattern (mesh pattern) in relation to the EC layers21,22and23. The transparent electrodes11through13are connected to the filter vertical drive unit40, whereas the common transparent electrodes14are connected to the filter horizontal drive unit50. Thus, active matrix drive that enables drive control for the EC layers21,22and23can be executed by using the electrodes disposed in the matrix pattern in the embodiment.

An EC layer21produces Mg (magenta) color through an oxidation-reduction reaction induced as a drive signal is provided via the corresponding transparent electrode11and common transparent electrode14. This means that light in a wavelength range corresponding to Mg (magenta) in the incident light is transmitted through the EC layer21as a drive signal is provided thereto. An EC layer22produces Ye (yellow) color through an oxidation-reduction reaction induced as a drive signal is provided via the corresponding transparent electrode12and common transparent electrode14. This means that light in a wavelength range corresponding to Ye (yellow) in the incident light is transmitted through the EC layer22as a drive signal is provided thereto. An EC layer23produces Cy (cyan) color through an oxidation-reduction reaction induced as a drive signal is provided via the corresponding transparent electrode13and common transparent electrode14. This means that light in a wavelength range corresponding to Cy (cyan) in the incident light is transmitted through the EC layer23as a drive signal is provided thereto. At each EC layer among the EC layers21,22and23, the color produced as described above is sustained over a predetermined length of time even when the drive signal is no longer provided thereto, whereas the EC layers achieve a transparent (achromatic) state, in which light in the entire wavelength range in the light having entered the filter unit5is transmitted through them when a reset signal is provided thereto.

As described above, the plurality of filter units5are each configured with three filters, i.e., an EC layer21that produces Mg (magenta) color, an EC layer22that produces Ye (yellow) color and an EC layer23that produces Cy (cyan) color. This means that light primarily in a specific wavelength range among the wavelength ranges corresponding to Mg, Ye, Cy, W (white), BK (black), R (red), G (green) and B (blue) can be allowed to be transmitted through a filter unit5by selecting a specific combination of transmission wavelengths for the EC layers21through23.

The filter control unit60inFIG.2sets (adjusts) the transmission wavelength for each filter unit5by controlling signals input to the filter unit5from the filter vertical drive unit40and the filter horizontal drive unit50. The filter vertical drive unit40selects a specific row among a plurality of rows over which filter units5are disposed one after another i.e., it selects a specific transparent electrode among the plurality of transparent electrodes11through13, and provides a drive signal to the selected transparent electrode. The filter horizontal drive unit50selects a specific column among a plurality of columns in which filter units5are disposed side by side, i.e., it selects a specific common transparent electrode among the plurality of common transparent electrodes14, and provides a drive signal to the selected common transparent electrode. As a result, an EC layer corresponding to both the transparent electrode among the transparent electrodes11through13selected by the filter vertical drive unit40and the common transparent electrode14selected by the filter horizontal drive unit50produces a color.

For instance, the filter horizontal drive unit50may select the common transparent electrode14located at the right end, among the three common transparent electrodes14inFIG.3(b), and provide a drive signal to the selected common transparent electrode14, and the filter vertical drive unit40may select the transparent electrode11located at the upper end among the nine transparent electrodes11through13and provide a drive signal thereto. In such a case, the EC layer21located at the upper right end position will produce a color. In addition, if the filter horizontal drive unit50selects the same common transparent electrode14and provides a drive signal thereto and the filter vertical drive unit40selects the transparent electrode12located at the upper end and provides a drive signal thereto, the EC layer22at the upper right end will produce a color. If the filter horizontal drive unit50selects the same common transparent electrode14and provides a drive signal thereto and the filter vertical drive unit40selects the transparent electrode13located at the upper end and provides a drive signal thereto, the EC layer23at the upper right end will produce a color.

The pixel vertical drive unit70provides control signals such as a signal TX, a signal RST and a signal SEL which will be described in detail later, to the various pixels10, so as to control operations of the individual pixels10. The system control unit110controls the filter control unit60, the pixel vertical drive unit70, the column circuit unit80, the horizontal scanning unit90and the output unit100based upon control signals used to control operations of the image sensor3, which are output from the control unit4in the electronic camera1. The system control unit110, which includes, for instance, a pulse generation circuit and the like, controls the components listed above by outputting pulse signals and the like, generated based upon the control signals provided by the control unit4, to the filter control unit60and the like.

The column circuit unit80, configured so as to include a plurality of analog/digital conversion units (A/D conversion units), converts signals, which are output from the individual pixels10, to digital signals and outputs the digital signals resulting from the conversion to the horizontal scanning unit90. The horizontal scanning unit90sequentially outputs the signals, having been output from the column circuit unit80, to the output unit100based upon pulse signals or the like output from the system control unit110. The output unit100, which includes a signal processing unit (not shown), executes signal processing such as correlated double sampling and signal level correction processing and outputs the signals having undergone the signal processing to the control unit4in the electronic camera1. The output unit100, having an input/output circuit and the like supporting a high-speed interface such as LVDS and SLVS, is able to transmit the signals to the control unit4at high speed.

FIG.4shows how transmission wavelengths may be selected at the filter units in the first embodiment. In the example presented inFIG.4, the filter unit5is set in a state in which light in a wavelength range for W (white), BK (black), Mg (magenta), Ye (yellow), Cy (cyan), R (red), G (green) or B (blue) is primarily transmitted by selecting a specific combination of transmission wavelengths for the EC layers21through23.

InFIG.4, Mg inside a dash-line frame indicates a state in which light in the Mg wavelength range is transmitted through the EC layer21. Ye inside a dash-line frame indicates a state in which light in the Ye wavelength range is transmitted through the EC layer22. Cy inside a dash-line frame indicates a state in which light in the Cy wavelength range is transmitted through the EC layer23. In addition, a dotted-line frame indicates that the corresponding EC layer is in a transparent (achromatic) state in which light in the entire wavelength range is transmitted through the EC layer. W, BK, Mg, Ye, Cy, R, G or B inside a solid-line frame indicates the wavelength range of light transmitted through the three EC layers21,22and23(three-layer EC transmission wavelength range).

When a drive signal is provided to an EC layer21, the EC layer21enters a state in which it absorbs light in the G wavelength range and allows light in the R wavelength range and light in the B wavelength range to be transmitted, i.e., a state in which light in the Mg wavelength range is transmitted. In addition, when a drive signal is provided to an EC layer22, the EC layer22enters a state in which it absorbs light in the B wavelength range and allows light in the R wavelength range and light in the G wavelength range to be transmitted, i.e., a state in which light in the Ye wavelength range is transmitted. Moreover, when a drive signal is provided to an EC layer23, the EC layer23enters a state in which it absorbs light in the R wavelength range and allows light in the G wavelength range and light in the B wavelength range to be transmitted, i.e., a state in which light in the Cy wavelength range is transmitted.

When a drive signal is provided to the EC layer21alone, the EC layer22alone or the EC layer23alone among the three EC layers21,22and23, the three-layer EC transmission wavelength range for Mg (magenta), Ye (yellow) or Cy (cyan) is set. In addition, when drive signals are provided to both the EC layer21and the EC layer22, the three-layer EC transmission wavelength range for R (red) is set, when drive signals are provided to both the EC layer22and the EC layer23, the three-layer EC transmission wavelength range for G (green) is set, and when drive signals are provided to both the EC layer21and the EC layer23, the three-layer EC transmission wavelength range for B (blue) is set. When no drive signal is provided to any of the EC layers21,22and23, light in the full wavelength range is transmitted through all the EC layers21through23and thus, the three-layer EC transmission wavelength range for W (white) is set. When drive signals are provided to all three EC layers21,22and23, light in the G wavelength range is absorbed in the EC layer21, light in the B wavelength range is absorbed in the EC layer22and light in the R wavelength range is absorbed in the EC layer23, thereby setting the three-layer EC transmission wavelength range for BK (black).

FIG.5illustrates how the transmission wavelengths may be altered at the filter units5in the first embodiment. It is to be noted that for purposes of simplification, filter units5in only four pixels (across)×four pixels (down) taking positions at a coordinate point (1, 1) through a coordinate point (4, 4) are shown inFIG.5.FIGS.5(a) through5(g)illustrate in time sequence how the four×four pixels, initially all set in a W (white) state, shift into a state in which they form an RGB Bayer array pattern, as a voltage is sequentially applied to specific transparent electrodes among the transparent electrodes11through14in the individual filter units5.

In the initial state shown inFIG.5(a), all the filter units5are in a state in which the entering light is transmitted over its full wavelength range, i.e., all the filter units5function as W filter units5. The filter control unit60may supply a positive potential to the transparent electrodes11through13in all the filter units5and supply a negative potential to the common transparent electrodes14in all the filter units5so as to cause the EC layers21through23in a transparent (achromatic) state, in which light entering the filter units5is transmitted in its full wavelength range.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(b)by applying voltages, which are the opposite of those applied to cause the EC layers achromatic, to the common electrodes14at the filter units5in the first column and the third column and to the transparent electrodes11at the filter units5in the first row and the third row, i.e., it applies a positive potential to the common transparent electrodes14and a negative potential to the transparent electrodes11. As a result, the filter units5at the coordinate points (1, 1), (1, 3), (3, 1) and (3, 3) enter a state in which magenta color is produced at the EC layers21and thus, the filter units5at these four coordinate point positions function as Mg filter units5, through which light primarily in the magenta wavelength range is transmitted. In addition, while the voltage application to the filter units5at the coordinate points (1, 1), (1, 3), (3, 1) and (3, 3) stops after the voltage is applied over a predetermined length of time, the color will be sustained over a specific length of time due to the “memory effect” at the EC layers.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(c)by applying a positive potential to the common transparent electrodes14at the filter units5in the second column and the fourth column and applying a negative potential to the transparent electrodes11at the filter units5in the second row and the fourth row. As a result, the filter units5at the coordinate points (2, 2), (2, 4), (4, 2) and (4, 4) enter a state in which magenta color is produced at the EC layers21and thus, the filter units5at these coordinate point positions function as Mg filter units5.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(d)by applying a positive potential to the common transparent electrodes14at the filter units5in the first column and the third column and applying a negative potential to the transparent electrodes12at the filter units5in the first row through the fourth row. As a result, the filter units5at the coordinate points (2, 1), (2, 3), (4, 1) and (4, 3) enter a state in which yellow color is produced at the EC layers22and thus, the filter units5at these coordinate point positions function as Ye filter units5, through which light primarily in the yellow wavelength range is transmitted. In addition, the filter units5at the coordinate points (1, 1), (1, 3), (3, 1) and (3, 3), where the EC layers21enter a state of magenta color production and the EC layers22enter a state of yellow color production, are caused to function as R filter units5through which light primarily in the red wavelength range is transmitted.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(e)by applying a voltage to the common transparent electrodes14at the filter units in the second column and the fourth column and applying a voltage to the transparent electrodes12at the filter units5in the first row and the third row. As a result, the filter units5at the coordinate points (1, 2), (1, 4), (3, 2) and (3, 4) enter a state in which yellow color is produced at the EC layers22and thus, the filter units5at these coordinate point positions function as Ye filter units5.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(f)by applying a voltage to the common transparent electrodes14at the filter units5in the first column and the third column and applying a voltage to the transparent electrodes13at the filter units5in the second row and the fourth row. As a result, the filter units5at the coordinate points (2, 1), (2, 3), (4, 1) and (4, 3) enter a state in which yellow color is produced at the EC layers22and cyan color is produced at the EC layers23, thereby causing the filter units5to function as G filter units5through which light primarily in the green wavelength range is transmitted.

The filter control unit60executes control to achieve the condition illustrated inFIG.5(g)by applying a voltage to the common transparent electrodes14at the filter units in the second column and the fourth column and applying a voltage to the transparent electrodes13at the filter units5in the first row through the fourth row. As a result, the filter units5at the coordinate points (1, 2), (1, 4), (3, 2) and (3, 4) enter a state in which yellow color is produced at the EC layers23and cyan color is produced, thereby causing the filter units5to function as a G filter units5. In addition, the filter units5at the coordinate points (2, 2), (2, 4), (4, 2) and (4, 4), where the EC layers21enter a state of magenta color production and the EC layers23enter a state of cyan color production, are caused to function as B filter units5through which light primarily in the blue wavelength range is transmitted.

The filter control unit60is capable of controlling the filter units5in the pixels10so as to form a Bayer array pattern with R pixels having R filter units5, G pixels having G filter units5and B pixels having B filter units5as illustrated inFIG.5(g). As described above, the filter control unit60in the embodiment is able to alter the transmission wavelength at each filter unit5through sequential control of the transmission wavelength at the individual filter units5. In addition, the filter control unit60is able to simultaneously control the transmission wavelengths at the plurality of filter units5disposed along the row direction or the column direction by providing electric signals via the transparent electrodes11through14disposed in a matrix pattern and then and stopping the electric signals.

The image sensor3in the embodiment is capable of executing processing through which signals are individually read out from all the pixels10and processing through which signals, each representing the sum of signals generated at a plurality of pixels10, are read out, as will be explained in detail below. The image sensor3may execute the processing through which the signals generated at all the pixels10in the image sensor3are individually read out when photographing a still image, whereas it may execute the processing for reading out signals each representing the sum of signals generated at a plurality of pixels10when shooting movie. In addition, while the image sensor3may include an extremely large number of pixels (e.g., several hundred million pixels), it is rare that a display device capable of displaying a high-resolution image expressed with the extremely large number of pixels in the image sensor is used. Accordingly, addition processing for adding together signals generated at a plurality of pixels10will be executed so as to generate signals in a quantity corresponding to the number of pixels required to express an image brought up on display at the display device in use. The “addition processing” executed under such circumstances includes averaging processing through which a plurality of signals are added together and averaged, weighted addition processing through which a plurality of signals are first weighted and added together, and the like. It is to be noted that the method that may be adopted when generating a signal by using signals generated at a plurality of pixels is not limited to these examples.

FIG.6presents examples of control that may be executed on the filter units5in the first embodiment. As explained earlier, the filter control unit60is able to create R pixels having R filter units5, G pixels having G filter units5and B pixels having B filter units5by setting specific transmission wavelengths for the individual filter units5. In the example presented inFIG.6(a), a region41A corresponding to a single R pixel, a region42A and a region43A each corresponding to a single G pixel and a region44A corresponding to a single B pixel together constitute a Bayer array basic unit (41A,42A,43A and44A). At the image sensor3, the disposition of the 2 pixels×2 pixels basic unit (41A,42A,43A and44A) is reiterated.

In the example presented inFIG.6(b), a region41B that contains 2×2=4 R pixels, a region42B and a region43B each of which contains 2×2=4 G pixels, and a region44B that contains 2×2=4 B pixels are set in a Bayer array pattern. In the example presented inFIG.6(b), the 4×4 pixels present in the regions41B through44B form a Bayer array reiterating basic unit. In the example inFIG.6(c)a region41C that contains 3×3=9 R pixels, a region42C and a region43C each of which contains 3×3=9 G pixels, and a region44C that contains 3×3=9 B pixels are set in a Bayer array pattern. In the example inFIG.6(c), the 6×6 pixels present in the regions41C through44C together form a Bayer array reiterating basic unit. Namely, the filter control unit60in the embodiment is able to adjust the size of the Bayer array basic unit by controlling the filter units5so as to set the same transmission wavelength range for the filter units5in a plurality of pixels disposed adjacent to each other. In other words, the size of the Bayer array basic unit can be adjusted to that made up with the regions41A through44A, where 2×2 pixels are present, to that made up with regions41B through44B, where 4×4 pixels are present or to that made up with the regions44C through44C where 6×6 pixels are present.

When the regions41B,42B,43B and44B constituting the basic unit are each made up with 2×2=4 pixels, as shown inFIG.6(b), a sum pixel signal is generated through addition processing executed by adding together the pixel signals from the four pixels in each region. More specifically, the image sensor3generates sum pixel signals each by adding together the pixel signals generated at the 2×2=4 pixels in one of the plurality of regions41B through44B, as will be explained later. As a result, when sum pixel signals are output by controlling the transmission wavelength ranges at the filter units5, as shown inFIG.6(b), the resolution is lowered to ¼ that of an image expressed with signals individually output from the individual pixels, as shown inFIG.6(a). Likewise, when the regions41C,42C,43C and44C constituting the basic unit are each made up with 3×3=9 pixels, as shown inFIG.6(c), a sum pixel signal is generated through addition processing executed by adding together the pixel signals from the nine pixels in each region. As a result, when sum pixel signals are output by controlling the transmission wavelength ranges at the filter units5, as shown inFIG.6(c), the resolution is lowered to 1/9 that of an image expressed with signals individually output from the individual pixels, as shown inFIG.6(a).

It is to be noted that instead of adding together the pixel signals generated at the four pixels in each of the regions41B through44B or adding together the pixel signals generated at the nine pixels in each of the regions41C through44C through addition processing executed within the image sensor3, as will be explained later in reference toFIG.8, pixel signals originating from the image sensor3may undergo addition processing in the control unit4shown inFIG.1.

It is desirable that the electronic camera1capture an image at high resolution when the number of display pixels at the display device at which image data generated in the image sensor3are brought up on display is substantially equal to the number of pixels at the image sensor3and that it capture an image at a relatively low resolution if the number of display pixels is smaller than the number of pixels at the image sensor3. Likewise, it is desirable that the electronic camera1capture an image at high resolution when an image expressed with the image data is to be printed out in a large format and that it capture an image at low resolution if the image expressed with the image data is to be printed out in a small size.

Accordingly, if the electronic camera1in the embodiment is set in a high-resolution photographing mode via, for instance, an operation unit (not shown), the filter control unit60controls the filter units5in the individual pixels10, as shown inFIG.6(a). Likewise, if the electronic camera1is set in a lower-resolution photographing mode via, for instance, the operation unit (not shown), the filter control unit60controls the filter units5in the individual pixels10, as shown inFIG.6(b)or6(c).

In addition, if the electronic camera1is set in a still image photographing mode via the operation unit (not shown), the filter control unit60controls the filter units5at the individual pixels10, as shown inFIG.6(a)so as to obtain high-resolution image data. If, on the other hand, the electronic camera1is set in a movie shooting mode via the operation unit (not shown), the filter control unit60controls the filter units5in the individual pixels10, as shown inFIG.6(b)orFIG.6(c)so as to achieve a high frame rate.

An image sensor, having filter units with fixed transmission wavelengths disposed in a Bayer array, needs to add together signals generated at a plurality of same-color pixels corresponding to a given color, which are disposed at positions set apart from one another. In this situation, the signal generated at a pixel corresponding to a different color present between the same-color pixels will not be used and thus will be wasted. Furthermore, color mixing may occur in the same-color pixel signals to be added together, due to crosstalk from different-color pixels adjacent to the same-color pixels.

The regions41A through44A, the regions41B through44B or the regions41C through44C, constituting the Bayer array basic unit in the embodiment, are each invariably made up with same-color pixels. This means that the signals generated at the same-color pixels within each region41through44can be added together. Since the filter units5in adjacent pixels correspond to the same color, crosstalk from a pixel having a different-color filter unit can be limited.

In reference toFIG.7andFIG.8, the circuit structure adopted in the image sensor3in the first embodiment will be explained.FIG.7is a circuit diagram showing the structure adopted in a pixel10in the first embodiment.FIG.8is a circuit diagram showing the structure in part of the image sensor3in the first embodiment. The pixels10each include a photoelectric conversion unit34and a readout unit20. The photoelectric conversion unit34has a function of converting light having entered therein to an electric charge and accumulating the electric charge resulting from the photoelectric conversion. The readout unit20includes a transfer unit25, a reset unit26, a floating diffusion27, an amplifier unit28, a selection unit29, a first switch unit18and a second switch unit19.

The transfer unit25transfers the electric charge resulting from the photoelectric conversion executed at the photoelectric conversion unit34to the floating diffusion27under control executed based upon a signal TX. Namely, the transfer unit25forms an electric charge transfer path between the photoelectric conversion unit34and the floating diffusion27. The electric charge is accumulated (held) in a capacitance FD at the floating diffusion27. The amplifier unit28amplifies a signal generated based upon the electric charge held in the capacitance FD and outputs the amplified signal. In the example presented inFIG.7, the amplifier unit28is configured with a transistor M3, a drain terminal, a gate terminal and a source terminal of which are respectively connected to a source VDD, the floating diffusion27and the selection unit29. The source terminal of the amplifier unit28is connected to a vertical signal line101via the selection unit29. The amplifier unit28functions as part of a source follower circuit that uses a current source81shown inFIG.8as a load current source.

The reset unit26, which is controlled based upon a signal RST, resets the electric charge at the capacitance FD and resets the potential at the floating diffusion27to a reset potential (reference potential). The selection unit29, which is controlled based upon a signal SEL, outputs the signal provided from the amplifier unit28to the vertical signal line101. The transfer unit25, the reset unit26and the selection unit29may be respectively configured with, for instance, a transistor M1, a transistor M2and a transistor M4.

Via first switch units18, each controlled with a signal SW_X, the floating diffusions27in a plurality of pixels10disposed side-by-side along the row direction (the first direction) are connected as shown inFIG.8. Via second switch units19, each controlled with a signal SW_Y, the floating diffusions27in a plurality of pixels10disposed side-by-side along the column direction (the second direction) are connected as shown inFIG.8. A first switch unit18and a second switch unit19may be constituted with, for instance, a transistor M5and a transistor M6respectively.

The readout unit20reads out a signal (pixel signal) corresponding to an electric charge transferred by the transfer unit25from the photoelectric conversion unit34to the floating diffusion27and a signal (noise signal) generated when the potential at the floating diffusion27is reset to the reset potential, to the vertical signal line101.

As shown inFIG.8, the image sensor3includes a plurality of pixels10disposed in a matrix pattern, the pixel vertical drive unit70and the column circuit unit80. The column circuit unit80includes current sources81(current source81athrough current source81d) and A/D conversion units82(A/D conversion unit82athrough A/D conversion unit82d). The current sources81and the A/D conversion units82are each disposed in correspondence to one of the pixel columns each made up with a plurality of pixels disposed side-by-side along the column direction, i.e., along the longitudinal direction. In addition, vertical signal lines101(vertical signal line101athrough vertical signal line101d) are disposed each in correspondence to one of the columns made up with pixels10. It is to be noted that only a small number of pixels10, i.e., four pixels (across)×four pixels (down), are shown inFIG.8so as to simplify the illustration. Among the plurality of pixels10shown inFIG.8, the pixel10taking the lower left position is designated as a first row/first column pixel10(1,1), andFIG.8shows the pixel10(1,1) through the pixel10(4,4).

The pixel vertical drive unit70provides a signal TX, a signal RST, a signal SEL, a signal SW_X and a signal SW_Y to each pixel10. A current source81, which is connected via the corresponding vertical signal line101with the individual pixels10, generates a current to be used for reading out the pixel signal and the noise signal from each pixel10. The current source81supplies the electric current that it has generated to the corresponding vertical signal line101and pixels10. An A/D conversion unit82converts signals output to the corresponding vertical signal line101to digital signals.

In the embodiment, the pixel vertical drive unit70, the first switch units18, the second switch units19, and the capacitances FD together function as an adder unit that adds together signals provided from the photoelectric conversion units34. In more specific terms, the pixel vertical drive unit70outputs signals SW_X and signals SW_Y to the individual pixels10and executes ON/OFF control for the first switch units18and the second switch units19therein so as to execute addition processing for adding together signals originating in the plurality of photoelectric conversion units34.

FIG.9illustrates how an operation may be executed in the image sensor3in the first embodiment.FIG.9(a)shows a Bayer array reiterating basic unit made up with 2×2 pixels present in regions41A through44A.FIG.9(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.9(a). InFIG.9(b), time points are indicated along the horizontal axis. In the timing chart inFIG.9(b), a transistor to which a high-level control signal (e.g., at the source potential) is input, enters an ON state and a transistor to which a low-level control signal (e.g., at the ground potential) is input, enters an OFF state.

At a time point t1, a signal RST1shifts to high level, thereby setting the transistors M2constituting the reset units26in an ON state and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,4) in the first row. In addition, at the time point t1, signals SEL1athrough SEL1fshift to high level and, as a result, noise signals originating at the pixel10(1,1) through the pixel10(1,4) are respectively output to a vertical signal line101athrough a vertical signal line101dvia the transistors M3constituting the amplifier units28and the transistors M4constituting the selection units29. The noise signals from the pixels10in the first row, individually output to the vertical signal line101athrough the vertical signal line101d, are respectively input to the A/D conversion unit82athrough the A/D conversion unit82dwhere they are converted to digital signals.

At a time point t2, a signal TX1shifts to high level, thereby setting the transistors M1constituting the transfer units25in an ON state at the pixel10(1,1) through the pixel (1,4) in the first row. As a result, electric charges resulting from photoelectric conversion executed in a PD11through a PD14are respectively transferred to a capacitance FD11through a capacitance FD14at the individual floating diffusions27. The electric charges having been transferred are accumulated in the capacitances FD11through FD14at the floating diffusions27. In addition, since the signals SEL1athrough SEL1fare at high level at the time point t2, pixel signals at the pixel10(1,1) through the pixel10(1,4) are respectively output to the vertical signal line101athrough the vertical signal line101dvia the corresponding amplifier units28and selection units29. The pixel signals output from the pixels10in the first row to the vertical signal line101athrough the vertical signal line101dare respectively input to the A/D conversion unit82athrough the A/D conversion unit82dwhere they are converted to digital signals.

During a time period elapsing between a time point t3and a time point t5, noise signals and pixel signals originating at the pixels10(2,1) through10(2,4) in the second row are read out in the same way as the signals are read out over the time period elapsing between the time point t1and the time point t3. Likewise, noise signals and pixel signals originating at the pixels10(3,1) through10(3,4) in the third row are read out over a time period elapsing between the time point t5and a time point t7, and noise signals and pixel signals originating at the pixels10(4,1) through10(4,4) in the fourth row are read out over a time period elapsing between the time point t7and a time point t9. In addition, the noise signals and the pixel signals, converted to digital signals at the A/D conversion units82, are input to the output unit100via the horizontal scanning unit90shown inFIG.2. The output unit100executes differential processing with respect to the noise signals and the pixel signals having originated in the pixels10through correlated double sampling. Through the embodiment described above, pixel signals at the pixels can be individually read out when the regions41A through44A constituting the Bayer array basic unit are each made up with a single pixel.

FIG.10presents another example of an operation that may be executed in the image sensor3in the first embodiment.FIG.10(a)shows a Bayer array reiterating basic unit made up with 4×4 pixels present in regions41B through44B.FIG.10(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.10(a).

At a time point t1, a signal SW_X1a, a signal SW_X2aand a signal SW_Y1shift to high level, thereby electrically connecting the capacitances at four pixels10, i.e., the capacitance FD11at the pixel10(1,1), the capacitance FD12at the pixel10(1,2), the capacitance FD21at the pixel10(2,1) and the capacitance FD22at the pixel10(2,2), with one another. In addition, at the time point t1, a signal SW_X1c, a signal SW_X2cand the signal SW_Y1shift to high level, thereby electrically connecting the capacitances at four pixels10, i.e., the capacitance FD13at the pixel10(1,3), the capacitance FD14at the pixel10(1,4), the capacitance FD23at the pixel10(2,3) and the capacitance FD24at the pixel10(2,4), with one another.

Furthermore, at the time point t1, a signal RST1and a signal RST2shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through (1,4) and the pixels10(2,1) through10(2,4). In this situation, since the capacitances FD at the four pixels10are connected as explained earlier, the potentials at the floating diffusions27in the pixel10(1,1), the pixel10(1,2), the pixel10(2,1) and the pixel10(2,2) are averaged. In addition, the potentials at the floating diffusions27in the pixel10(1,3), the pixel10(1,4), the pixel10(2,3) and the pixel10(2,4) are averaged.

Additionally, as a signal SEL1ashifts to high level at the time point t1, a noise signal generated by averaging signals at the four pixels, i.e., the pixel10(1,1), the pixel (1,2), the pixel10(2,1) and the pixel10(2,2), is output to the vertical signal line101avia the amplifier unit28and the selection unit29at the pixel10(1,1). The noise signal output to the vertical signal line101ais input to the A/D conversion unit82a, which then converts it to a digital signal. Moreover, as a signal SEL1cshifts to high level at the time point t1, a noise signal generated by averaging signals at the four pixels, i.e., the pixel10(1,3), the pixel10(1,4), the pixel10(2,3) and the pixel10(2,4), is output to the vertical signal line101cvia the amplifier unit28and the selection unit29at the pixel (1,3). The noise signal output to the vertical signal line101cis input to the A/D conversion unit82c, which then converts it to a digital signal.

At a time point t2, a signal TX1and a signal TX2shift to high level thereby turning on the transistors M1constituting the transfer units25to transfer electric charges resulting from photoelectric conversion executed in the PDs11through14and the PDs21through PD24, to the corresponding floating diffusions27at the pixels10(1,1) through (1,4) and the pixels10(2,1) through10(2,4). Since the capacitances FD in the four pixels10are connected with one another as explained earlier, the electric charges transferred from the four corresponding PDs, i.e., the PD11, the PD12, the PD21and the PD22, are distributed among the four capacitances FD11, FD12, FD21and FD22. In addition, the electric charges transferred from the four PDs13,14,23and24are distributed among the four capacitances FD13, FD14, FD23and FD24.

At the time point t2, the signal SEL1ais at high level and thus, a sum pixel signal generated by averaging signals at the four pixels, i.e., the pixel10(1,1), the pixel10(1,2), the pixel10(2,1) and the pixel10(2,2), is output to the vertical signal line101avia the amplifier unit28and the selection unit29at the pixel10(1,1). The sum pixel signal output to the vertical signal line101ais input to the A/D conversion unit82awhich then converts it to a digital signal. Furthermore, at the time point t2, the signal SEL1cis at high level and thus, a sum pixel signal generated by averaging signals at the four pixels, i.e., the pixel10(1,3), the pixel10(1,4), the pixel10(2,3) and the pixel10(2,4), is output to the vertical signal line101cvia the amplifier unit28and the selection unit29at the pixel10(1,3). The sum pixel signal output to the vertical signal line101cis input to the A/D conversion unit82cwhich then converts it to a digital signal. The noise signals and the sum pixel signals having been converted to digital signals at the A/D conversion units82are input to the output unit100via the horizontal scanning unit90shown inFIG.2. The output unit100executes differential processing to determine the differences between the noise signals and the sum pixel signals originating at the pixels10through correlated double sampling.

During a time period elapsing between a time point t3and a time point t5, signals generated by adding together and averaging signals at the pixel10(3,1), the pixel10(3,2), the pixel10(4,1) and the pixel10(4,2) and signals generated by adding together and averaging signals generated at the pixel10(3,3), the pixel10(3,4), the pixel10(4,3) and the pixel10(4,4) are read out in the same way as signals are read out during the time period elapsing between the time point t1and the time point t3. During a time period elapsing between the time point t5and a time point t7, signals generated by adding together and averaging signals at the pixel10(5,1), the pixel10(5,2), the pixel10(6,1) and the pixel10(6,2) and signals generated by adding together and averaging signals generated at the pixel10(5,3), the pixel10(5,4), the pixel10(6,3) and the pixel10(6,4) are read out in the same way as signals are read out during the time period elapsing between the time point t1and the time point t3. In this embodiment, a signal can be read out by adding together the signals at the four pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41B through44B, each made up with 2×2=4 pixels.

In addition, a sum pixel signal obtained by adding together the signals generated at the four pixels is read out to the vertical signal line101aor the vertical signal line101cin the example presented inFIG.10. Since this allows current generation at the current sources81band81d, connected to the vertical signal lines101band101d, to which no sum pixel signals are read out, to be stopped, the level of current consumption in the image sensor3can be lowered.

FIG.11presents yet another example of an operation that may be executed in the image sensor3in the first embodiment.FIG.11(a)shows a Bayer array reiterating basic unit made up with 6×6 pixels present in regions41C through44C.FIG.11(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.11(a).

At a time point t1, a signal SW_X1a, a signal SW_X1b, a signal SW_X2a, a signal SW_X2b, a signal SW_X3a, a signal SW_X3b, a signal SW_Y1and a signal SW_Y2shift to high level, thereby electrically connecting the capacitances at nine pixels10, i.e., the capacitance FD11at the pixel10(1,1), the capacitance FD12at the pixel10(1,2), the capacitance FD13at the pixel10(1,3), the capacitance FD21at the pixel10(2,1), the capacitance FD22at the pixel10(2,2), the capacitance FD23at the pixel10(2,3), the capacitance FD31at the pixel10(3,1), the capacitance FD32at the pixel10(3,2) and the capacitance FD33at the pixel10(3,3) with one another.

In addition, at the time point t1, a signal RST1, a signal RST2and a signal RST3shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,3), the pixels10(2,1) through10(2,3) and the pixels10(3,1) through (3,3). In this case, the potentials at the floating diffusions27are averaged in the capacitances FD at the nine pixels10listed above.

Furthermore, as a signal SEL2bshifts to high level at the time point t1, a noise signal generated by averaging signals at the nine pixels is output to the vertical signal line101bvia the amplifier unit28and the selection unit29at the pixel10(2,2). The noise signal output to the vertical signal line101bis input to the A/D conversion unit82b, which then converts it to a digital signal.

At a time point t2, a signal TX1, a signal TX2and a signal TX3shift to high level, thereby turning on the transistors M1constituting the transfer units25to transfer electric charges resulting from photoelectric conversion executed at the PDs11through13, the PDs21through23and the PDs31through33to the corresponding floating diffusions27at the pixels10(1,1) through10(1,3), the pixels10(2,1) through10(2,3) and the pixels10(3,1) through10(3,3). The electric charges transferred from the nine PDs, i.e., the PD11through the PD13, the PD21through the PD23, and the PD31through the PD33, are distributed among the nine capacitances FD11, FD12, FD13, FD21, FD22, FD23, FD31, FD32and FD33.

In addition, at the time point t2, the signal SEL2bis at high level and thus, a sum pixel signal generated by averaging signals generated at the nine pixels is output to the vertical signal line101bvia the amplifier unit28and the selection unit29at the pixel10(2,2). The sum pixel signal output to the vertical signal line101bis input to the A/D conversion unit82bwhich then converts it to a digital signal. In this embodiment, a signal can be read out by adding together the signals at the nine pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41C through44C, each made up with 3×3=9 pixels.

In addition, a sum pixel signal obtained by adding together the signals generated at the nine pixels is read out to the vertical signal line101bin the example presented inFIG.11. Since this allows current generation at the current sources81aand81c, connected to the vertical signal lines101aand101c, to which no sum pixel signals are read out, to be stopped, the level of current consumption in the image sensor3can be lowered.

It is to be noted that while addition processing for adding together signals generated at the individual pixels is executed within the pixels10in the embodiment described above, the pixel signals generated at the pixels10may be individually output to the output unit100and addition processing may be executed in the output unit100, instead.

The power consumption and the length of time required for signal readout are bound to increase if the signals from all the pixels10are to be read out individually in an image sensor3having a very large number of pixels, to satisfy the requirements of, for instance, surveillance or industrial applications. In the embodiment, the size of the area that includes R, G and B filter units5is altered while sustaining the Bayer array pattern so as to make it possible to output a signal generated by adding together the signals generated at a plurality of pixels10adjacent to one another. Since the signals generated at adjacent pixels are added together, the level of noise in the signal and the current consumption can both be lowered in comparison to signal generation executed by adding together signals generated at pixels at positions set apart from one another. In addition, since the signals from adjacent pixels are added together, the length of time required for the addition processing can be reduced over the length of time required for addition processing executed by adding together signals at pixels disposed at positions set apart from one another, which makes it possible to reduce the length of time required for pixel signal readout.

The following advantages and operations are achieved through the embodiment described above.

(1) The image sensor3includes a plurality of filter units5, the transmission wavelength of which can be adjusted, a plurality of photoelectric conversion units34that receive light having been transmitted through the filter units5and a control unit (filter control unit60) that alters the size of a first region that contains a first filter unit5, among the plurality of filter units5, which allows light at a first wavelength to be transmitted and enter a photoelectric conversion unit34. This structure enables the filter control unit60to alter the size of a region41that includes an R pixel, a region42and a region43each of which includes a G pixel, and a region44that includes a B pixel, by controlling the individual filter units5. In addition, the filter control unit60is able to alter the size of a Bayer array basic unit by controlling the filter units5so as to set the same transmission wavelength range for the filter units5in a plurality of pixels adjacent to one another.

(2) The filter control unit60in the embodiment alters the size of the regions41through44while sustaining the Bayer array pattern. This means that a signal generated by adding together the signals generated at a plurality of pixels10adjacent to one another can be output. Since signals at same-color pixels adjacent to one another are added together, the level of noise in the signal and the level of current consumption can be lowered in comparison to levels of noise and current consumption in an image sensor that generates a signal by adding together signals generated at same-color pixels disposed at positions set apart from one another. In addition, the length of time required for pixel signal readout can be reduced in comparison to the length of time required to read out signals each generated by adding together signals generated at pixels disposed at positions set apart from one another.

SECOND EMBODIMENT

In reference toFIG.12, the image sensor in the second embodiment will be described. The image sensor3in the second embodiment adjusts the pixel signal readout area, to an area120A,120B or120C in correspondence the zoom magnification factor selected for the electronic zoom function of the electronic camera1, and adjusts the transmission wavelength ranges for the filter units5in the pixels10present in the readout areas120A through120C, as indicated inFIGS.6(a) through6(c).

FIG.12(a)shows the pixel signal readout area120A set when a relatively high magnification factor is set for the electronic zoom function and the array pattern with which R pixels, G pixels and B pixels are set within the readout area120A.FIG.12(b)shows the pixel signal readout area120B set when an intermediate magnification factor is set for the electronic zoom function and the array pattern with which R pixels, G pixels and B pixels are set within the readout area120B.FIG.12(c)shows the pixel signal readout area120C set when a relatively low magnification factor is set for the electronic zoom function and the array pattern with which R pixels, G pixels and B pixels are set within the readout area120C.

The readout area120A inFIG.12(a)includes a Bayer array reiterating basic unit made up with 2×2=4 pixels, i.e., one R pixel, two G pixels and one B pixel. Namely, in the readout area120A, a region41A where a single R pixel is present, a region42A and a region43A each containing a single G pixel, and a region44A where a single B pixel is present constitute the Bayer array basic unit, in the same manner as shown inFIG.6(a). Such regions41A,42A43A and44A are set by controlling the filter units5in the individual pixels10via the filter control unit5.

The readout area120A for high magnification zoom is selected by ensuring that the number of pixels10in the readout area120A substantially matches the number of display pixels disposed at an external display device with a relatively high resolution that is utilized by, for instance, the photographer when viewing photographic image data. It is to be noted that the selection may be made by the photographer as he enters the number of display pixels at the display device into the camera1by operating an operation member (not shown) at the electronic camera1and sets the readout area120A based upon the entered number of display pixels thus input. Pixel signals generated at the pixels10within the readout area120A are read out through processing similar to the readout processing described in reference toFIG.8.

For purposes of simplifying the illustration, the readout area120A in the example presented inFIG.12(a)contains 6×6 pixels. Namely, in the example presented inFIG.12(a), i.e., in high magnification zoom, the image sensor3outputs 36 pixel signals.

The readout area120B inFIG.12(b), selected for electronic zoom at an intermediate magnification factor, is set greater than the readout area120A corresponding to a high magnification factor shown inFIG.12(a). In more specific terms, it is set to take up an area four times the area of the readout area120A. In the readout area120B, a region41B, where 2×2=4 R pixels are present, a region42B and a region43B each containing 2×2=4 G pixels, and a region44B where 2×2=4 B pixels are present are set in a Bayer array pattern, in the same manner as shown inFIG.6(b). Such regions41B,42B,43B and44B are set by controlling the filter units5in the individual pixels10via the filter control unit5.

The image sensor3reads out a sum pixel signal generated by adding together pixel signals at the four R pixels in the region41B and reads out a sum pixel signal generated by adding together pixel signals at the four G pixels in the region42B in the readout area120B. Likewise, the image sensor3reads out a sum pixel signal generated by adding together pixel signals at the four G pixels in the region43B and reads out a sum pixel signal generated by adding together pixel signals at the four B pixels in the region44B in the readout area120B. Namely, in the example presented inFIG.12(b), i.e., in intermediate magnification zoom, the image sensor36outputs sum pixel signals just as it outputs 36 pixel signals for high magnification zoom.

The readout area120C inFIG.12(c), selected for electronic zoom at a low magnification factor, is set even greater than the readout area120B corresponding to an intermediate magnification factor shown inFIG.12(b). In more specific terms, it is set to take up an area nine times the area of the readout area120A for high magnification zoom. In the readout area120C, a region41C, where 3×3=9 R pixels are present, a region42C and a region43C each containing 3×3=9 G pixels, and a region44C where 3×3=9 B pixels are present are set in a Bayer array pattern, in the same manner as shown inFIG.6(c). Such regions41C,42C,43C and44C are set by controlling the filter units5in the individual pixels10via the filter control unit5.

The image sensor3reads out a sum pixel signal generated by adding together pixel signals at the nine R pixels in the region41C and reads out a sum pixel signal generated by adding together pixel signals at the nine G pixels in the region42C in the readout area120C. Likewise, the image sensor3reads out a sum pixel signal generated by adding together pixel signals at the nine G pixels in the region43C and reads out a sum pixel signal generated by adding together pixel signals at the nine B pixels in the region44C in the readout area120C. Namely, in the example presented inFIG.12(c), i.e., in low magnification zoom, the image sensor3outputs 36 sum pixel signals just as it outputs 36 signals for high magnification zoom and intermediate magnification zoom.

As described above, the filter control unit60in the second embodiment controls the filter units5in the individual pixels10so as to set a single R pixel in the region41A inFIG.12(a), set four R pixels in the region41B inFIG.12(b)and set nine R pixels in the region41C inFIG.12(c). Likewise, the filter control unit60sets a single G pixel in each of the regions42A and43A inFIG.12(a), sets four G pixels in each of the regions42B and43B inFIG.12(b)and sets nine G pixels in each of the regions42C and43C inFIG.12(c). Likewise, the filter control unit60sets a single B pixel in the region44A inFIG.12(a), sets four B pixels in the region44B inFIG.12(b)and sets nine B pixels in the region44C inFIG.12(c). Thus, the filter control unit60is able to set a fixed number of pixel signals or sum pixel signals to be output from the image sensor3regardless of the zoom magnification setting by adjusting the size of a filter unit5, which is controlled to assume a given transmission wavelength range, in correspondence to the electronic zoom magnification setting.

The image sensor3in the embodiment as described above is capable of outputting a fixed number of pixel signals or sum pixel signals in correspondence to all the zoom magnification settings that may be selected for electronic zooming, and is thus able to sustain a given level of resolution for images to be brought up at display devices.

In addition to advantages and operations similar to those of the first embodiment, the following advantage and operation are achieved through the embodiment described above.

(3) The total number of signals obtained via a plurality of photoelectric conversion units34having received light transmitted through a plurality of first filter units under first control and the total number of sum signals generated by adding together signals generated via a plurality of photoelectric conversion units34having received light transmitted through a first region under second control are substantially equal to each other. The total number of signals obtained through a plurality of photoelectric conversion units34having received light transmitted through a plurality of second filter units under the first control and the total number of sum signals generated by adding together signals generated via a plurality of photoelectric conversion units34having received light transmitted through a second region under the second control are substantially equal to each other. As a result, the same number of pixel signals or sum pixel signals can be output at all the zoom magnification settings that may be selected for electronic zooming. Ultimately, a uniform resolution can be sustained in images displayed at display devices.

The following variations are also within the scope of the present invention, and one of the variations or a plurality of variations may be adopted in combination with either of the embodiments described above.

In reference to drawings, the image sensor3in variation 1 will be explained. It is to be noted that in the figures, the same reference signs are assigned to elements identical to or equivalent to those in the first embodiment and that the following explanation will focus on features differentiating the image sensor in variation 1 from the image sensor3in the first embodiment.FIG.13is a circuit diagram showing the structure in part of the image sensor3in variation 1. The column circuit unit80includes switch units SW11(SW11athrough SW11f), switch units SW12(SW12athrough SW12f), switch units SW13(SW13athrough SW13f), arithmetic operation circuit units83(arithmetic operation circuit units83athrough83f), and a switch control unit84. A switch unit SW11, a switch unit SW12, a switch unit SW13and an arithmetic operation circuit unit83are disposed in correspondence to each pixel column made up with a plurality of pixels10disposed side-by-side along the column direction, i.e., along the longitudinal direction. In addition, the pixels10in variation 1 do not include first switch units18.

ON/OFF control of the switch unit SW11, the switch unit SW12and the switch unit SW13is executed by the switch control unit84. The arithmetic operation circuit unit83, which may be constituted with, for instance, an amplifier circuit, has a function of executing addition processing for adding together a plurality of signals input thereto. In the embodiment, the pixel vertical drive unit70, the second switch units19, the capacitances FD, the switch unit SW11, the switch unit SW12, the switch unit SW13and the arithmetic operation circuit unit83together function as an adder unit that adds together signals from the photoelectric conversion units34.

FIG.14illustrates how an operation may be executed in the image sensor3in variation 1.FIG.14(a)presents an example in which a Bayer array reiterating basic unit is made up with 2×2 pixels each present in one of regions41A through44A.FIG.14(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths are set for the filter units5as shown inFIG.14(a). InFIG.14(b), time points are indicated along the horizontal axis. In addition, SW11(SW11athrough SW11f), SW12(SW12athrough SW12f) and SW13(SW13athrough SW13f) respectively indicate control signals input to the switch units SW11(SW11athrough SW11f), the switch units SW12(SW12athrough SW12f) and the switch units SW13(SW13athrough SW13f). In the timing chart inFIG.14(b), a transistor, to which a high-level control signal (e.g., at the source potential) is input, enters an ON state and a transistor, to which a low-level control signal (e.g., at the ground potential) is input, enters an OFF state.

At a time point t1, a signal RST1shifts to high level, thereby setting the transistors M2constituting the reset units26in an ON state and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,4) in the first row. In addition, at the time point t1, a signal SEL1shifts to high level and, as a result, noise signals originating at the pixel10(1,1) through the pixel10(1,4) are respectively output to the vertical signal lines101athrough101dvia the transistor M3constituting the amplifier units28and the transistors M4constituting the selection units29. As signals SW11athrough SW11dshift to high level at the time point t1, the noise signals from the individual pixels10in the first row, having been output to the vertical signal lines101athrough101d, are respectively input to the arithmetic operation circuit unit83athrough the arithmetic operation circuit unit83d. The arithmetic operation circuit units83athrough83doutput the signals input thereto to the A/D conversion unit82athrough the A/D conversion unit82drespectively. The A/D conversion units82athrough82dconvert the signals input thereto to digital signals.

At a time point t2, a signal TX1shifts to high level, thereby setting the transistors M1constituting the transfer units25in an ON state at the pixel10(1,1) through the pixel (1,4) in the first row. As a result, electric charges, resulting from photoelectric conversion executed at the PD11through the PD14are respectively transferred to the capacitance FD11through the capacitance FD14at the individual floating diffusions27. In addition, since the signal SEL1is at high level at the time point t2, pixel signals generated at the pixel10(1,1) through the pixel10(1,4) are respectively output to the vertical signal lines101athrough101dvia the corresponding amplifier units28and selection units29. Moreover, since the signals SW11athrough SW11dare at high level at the time point t2, the pixel signals output from the pixels10in the first row to the vertical signal lines101athrough101dare respectively input, via the arithmetic operation circuit units83athrough83d, to the A/D conversion unit82athrough the A/D conversion unit82dwhere they are converted to digital signals.

During a time period elapsing between a time point t3and a time point t5, noise signals and pixel signals originating at the pixels10(2,1) through10(2,4) in the second row are read out in the same way as signals are read out over the time period elapsing between the time point t1and the time point t3. Likewise, noise signals and pixel signals originating at the pixels10(3,1) through10(3,4) in the third row are read out over a time period elapsing between the time point t5and a time point t7, and noise signals and pixel signals originating at the pixels10(4,1) through10(4,4) in the fourth row are read out over a time period elapsing between the time point t7and a time point t9. Through variation 1 described above, pixel signals generated at the pixels can be individually read out when the regions41A through44A constituting the Bayer array basic unit are each made up with a single pixel, as in the first embodiment.

FIG.15presents another example of an operation that may be executed in the image sensor3in variation 1.FIG.15(a)shows a Bayer array reiterating basic unit made up with 4×4 pixels present in regions41B through44B.FIG.15(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.15(a).

At a time point t1, a signal SW_Y1shifts to high level, thereby electrically connecting the capacitances at pixels10, i.e., the capacitance FD11and the capacitance FD21at the pixels10(1,1) and10(2,1), the capacitance FD12and the capacitance FD22at the pixels10(1,2) and10(2,2), the capacitance FD13and the capacitance FD23at the pixels10(1,3) and10(2,3) and the capacitance FD14and the capacitance FD24at the pixels10(1,4) and10(2,4) are electrically connected with each other.

In addition, at the time point t1, a signal RST1and a signal RST2shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through (1,4) and the pixels10(2,1) through10(2,4).

At the time point t1, as a signal SEL1shifts to high level, a noise signal generated by averaging signals at the two pixels10(1,1), and10(2,1) is output to the vertical signal line101avia the amplifier unit28and the selection unit29at the pixel10(1,1). In addition, as the signal SEL1shifts to high level at the time point t1, a noise signal generated by averaging signals at the two pixels10(1,2), and10(2,2), a noise signal generated by averaging signals at the two pixels10(1,3), and10(2,3) and a noise signal generated by averaging signals at the two pixels10(1,4), and10(2,4) are respectively output to the vertical signal line101bthrough the vertical signal line101d.

At the time point t1, a signal SW11a, a signal SW11c, a signal SW13aand a signal SW13calso shift to high level. It is to be noted that a signal SW11b, a signal SW11d, a signal SW13b, a signal SW13dand the signals SW12athrough SW12dare each set to low level. As a result, the noise signal generated by averaging the signals at the two pixels10(1,1) and10(2,1) output to the vertical signal line101aand the noise signal generated by averaging the signals at the two pixels10(1,2) and10(2,2) output to the vertical signal line101bare input to the arithmetic operation circuit unit83awhere they are added together and averaged. Namely, the arithmetic operation circuit unit83agenerates a noise signal representing the average of the signals at the four pixels, i.e., the pixel10(1,1), the pixel10(2,1), the pixel10(1,2) and the pixel10(2,2), and outputs the noise signal thus generated to the A/D conversion unit82a. The A/D conversion unit82athen converts the signal input thereto to a digital signal.

Likewise, the noise signal generated by averaging the signals at the two pixels10(1,3) and10(2,3) output to the vertical signal line101cand the noise signal generated by averaging the signals at the two pixels10(1,4) and10(2,4) output to the vertical signal line101dare input to the arithmetic operation circuit unit83cwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83cgenerates a noise signal representing the average of the signals at the four pixels, i.e., the pixel10(1,3), the pixel10(2,3), the pixel10(1,4) and the pixel10(2,4), and outputs the noise signal thus generated to the A/D conversion unit82c. The A/D conversion unit82cthen converts the signal input thereto to a digital signal.

At a time point t2, a signal TX1and a signal TX2shift to high level, thereby turning on the transistors M1constituting the transfer units25to transfer electric charges resulting from photoelectric conversion executed at the PD11through the PD14and at the PD21through the PD24to the corresponding floating diffusions at the pixels10(1,1) through10(1,4) and the pixels10(2,1) through10(2,4).

In addition, at the time point t2, a sum pixel signal generated by averaging signals at the two pixels10(1,1) and10(2,1) is output to the vertical signal line101a. Furthermore, at the time point t2, a sum pixel signal generated by averaging signals at the two pixels10(1,2) and10(2,2), a sum pixel signal generated by averaging signals at the two pixels10(1,3) and10(2,3) and a sum pixel signal generated by averaging signals at the two pixels10(1,4) and10(2,4) are respectively output to the vertical signal line101bthrough the vertical signal line101d.

Also at the time point t2, the sum pixel signal generated by averaging the signals at the two pixels10(1,1) and10(2,1) output to the vertical signal line101a, and the sum pixel signal generated by averaging the signals at the two pixels10(1,2) and10(2,2) output to the vertical signal line101b, are input to the arithmetic operation circuit unit83awhere they are added together and averaged. Namely, the arithmetic operation circuit unit83agenerates a sum pixel signal representing the average of the signals at the four pixels, i.e., the pixel10(1,1), the pixel10(2,1), the pixel10(1,2) and the pixel10(2,2), and outputs the sum pixel signal thus generated to the A/D conversion unit82a. The A/D conversion unit82athen converts the signal input thereto to a digital signal.

Likewise, the sum pixel signal generated by averaging the signals at the two pixels (1,3) and10(2,3) output to the vertical signal line101c, and the sum pixel signal generated by averaging the signals at the two pixels10(1,4) and10(2,4) output to the vertical signal line101d, are input to the arithmetic operation circuit unit83cwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83cgenerates a sum pixel signal representing the average of the signals at the four pixels, i.e., the pixel10(1,3), the pixel10(2,3), the pixel10(1,4) and the pixel10(2,4), and outputs the sum pixel signal thus generated to the A/D conversion unit82c. The A/D conversion unit82cthen converts the signal input thereto to a digital signal.

During a time period elapsing between a time point t3and a time point t5, signals generated by adding together and averaging signals generated at the pixel10(3,1), the pixel10(3,2), the pixel10(4,1) and the pixel10(4,2) and signals generated by adding together and averaging signals generated at the pixel10(3,3), the pixel10(3,4), the pixel (4,3) and the pixel10(4,4) are read out in the same way as signals are read out during the time period elapsing between the time point t1and the time point t3. During a time period elapsing between the time point t5and a time point t7, signals generated by adding together and averaging signals at the pixel10(5,1), the pixel10(5,2), the pixel10(6,1) and the pixel10(6,2) and signals generated by adding together and averaging signals generated at the pixel10(5,3), the pixel10(5,4), the pixel10(6,3) and the pixel10(6,4) are read out in the same way as signals read out during the time period elapsing between the time point t1and the time point t3. In the above described manner, a signal can be read out by adding together the signals at four pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41B through44B, each made up with 2×2=4 pixels.

FIG.16presents yet another example of an operation that may be executed in the image sensor3in variation 1.FIG.16(a)shows a Bayer array reiterating basic unit made up with 6×6 pixels present in regions41C through44C.FIG.16(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.16(a).

At a time point t1, a signal SW_Y1and a signal SW_Y2shift to high level, thereby electrically connecting capacitances, i.e., the capacitance FD11at the pixel10(1,1), the capacitance FD21at the pixel10(2,1) and the capacitance FD31at the pixel10(3,1), with one another. In addition, the capacitance FD12at the pixel10(1,2), the capacitance FD22at the pixel10(2,2) and the capacitance FD32at the pixel10(3,2), become electrically connected with one another. The capacitance FD13at the pixel10(1,3), the capacitance FD23at the pixel10(2,3) and the capacitance FD33at the pixel10(3,3), become electrically connected with one another.

In addition, at the time point t1, a signal RST1, a signal RST2and a signal RST3shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,3), the pixels10(2,1) through10(2,3) and the pixels10(3,1) through (3,3). In this situation, the potentials of the floating diffusions27are averaged among the capacitances FD electrically connected with one another.

Furthermore, as a signal SEL2shifts to high level at the time point t1, a noise signal generated by averaging signals at the three pixels10(1,1),10(2,1) and10(3,1), is output to the vertical signal line101avia the amplifier unit28and the selection unit29at the pixel10(2,1). As the signal SEL2shifts to high level at the time point t1, a noise signal generated by averaging signals at the three pixels10(1,2),10(2,2) and10(3,2), is output to the vertical signal line101bvia the amplifier unit28and the selection unit29at the pixel10(2,2). As the signal SEL2shifts to high level at the time point t1, a noise signal generated by averaging signals at the three pixels10(1,3),10(2,3) and10(3,3), is output to the vertical signal line101cvia the amplifier unit28and the selection unit29at the pixel10(2,3).

At the time point t1, a signal SW12a, a signal SW11band a signal SW13bshift to high level. It is to be noted that a signal SW11a, a signal SW13a, a signal SW12b, a signal SW11c, a signal SW12cand a signal SW13care all set to low level. As a result, the noise signals output to the vertical signal line101athrough the vertical signal line101care input to the arithmetic operation circuit unit83bwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83bgenerates a noise signal representing the average of the signals at the nine pixels, i.e., the pixel10(1,1), the pixel (1,2), the pixel10(1,3), the pixel10(2,1), the pixel10(2,2), the pixel10(2,3), the pixel10(3,1), the pixel10(3,2) and the pixel10(3,3), and outputs the noise signal thus generated to the A/D conversion unit82b. The A/D conversion unit83bthen converts the signal input thereto to a digital signal.

At a time point t2, a signal TX1, a signal TX2and a signal TX3shift to high level, thereby turning on the transistors M1constituting the transfer units25to transfer electric charges resulting from photoelectric conversion executed at the PD11through the PD13, the PD21through the PD23and the PD31through the PD33to the corresponding floating diffusions27at the pixels10(1,1) through10(1,3), the pixels10(2,1) through10(2,3) and the pixels10(3,1) through10(3,3).

In addition, at the time point t2, a sum pixel signal generated by averaging signals at the three pixels10(1,1),10(2,1) and10(3,1) is output to the vertical signal line101a. Furthermore, at the time point t2, a sum pixel signal generated by averaging signals at the three pixels10(1,2),10(2,2) and10(3,2), and a sum pixel signal generated by averaging signals at the three pixels10(1,3),10(2,3) and10(3,3) are respectively output to the vertical signal line101band the vertical signal line101c.

Also at the time point t2, the sum pixel signals output to the vertical signal line101athrough the vertical signal line101care input to the arithmetic operation circuit unit83bwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83bgenerates a sum pixel signal representing the average of the signals at the nine pixels, and outputs the sum pixel signal thus generated to the A/D conversion unit82b. The A/D conversion unit82bthen converts the signal input thereto to a digital signal. In the above described manner, the image sensor3is thus able to read out a signal by adding together the signals at nine pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41C through44C, each made up with 3×3=9 pixels.

In reference to drawings, the image sensor3in variation 2 will be explained. It is to be noted that in the figures, the same reference signs are assigned to elements identical to or equivalent to those in the first embodiment and variation 1, and that the following explanation will focus on features differentiating the image sensor in this variation from the image sensor3in the first embodiment and variation 1.FIG.17is a circuit diagram showing the structure in part of the image sensor3in variation 2. The pixels10in variation 2 adopt a structure that does not include the first switch unit18or the second switch unit19. In variation 2, the pixel vertical drive unit70, a switch unit SW11, a switch unit SW12, a switch unit SW13and an arithmetic operation circuit unit83together function as an adder unit that adds together signals from the photoelectric conversion units34.

FIG.18illustrates how an operation may be executed in the image sensor3in variation 2.FIG.18(a)presents an example in which a Bayer array reiterating basic unit is made up with 2×2 pixels each present in one of regions41A through44A.FIG.18(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths are set for the filter units5as shown inFIG.18(a). InFIG.18(b), time points are indicated along the horizontal axis.

At a time point t1, a signal RST1shifts to high level, thereby setting the transistors M2constituting the reset units26in an ON state and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,4) in the first row. In addition, at the time point t1, a signal SEL1shifts to high level and, as a result, noise signals originating at the pixel10(1,1) through the pixel10(1,4) are respectively output to the vertical signal line101athrough the vertical signal line101dvia the transistors M3constituting the amplifier units28and the transistors M4constituting the selection units29. As signals SW11athrough SW11fshift to high level at the time point t1, the noise signals from the individual pixels10in the first row, having been output to the vertical signal line101athrough the vertical signal line101d, are input to the A/D conversion unit82athrough the A/D conversion unit82drespectively via the arithmetic operation circuit unit83athrough the arithmetic operation circuit unit83d. The A/D conversion units82athrough82dconvert the signals input thereto to digital signals.

At a time point t2, a signal TX1shifts to high level, thereby setting the transistors M1constituting the transfer units25in an ON state at the pixels10(1,1) through10(1,4) in the first row. As a result, electric charges resulting from photoelectric conversion executed at the PDs11through14are respectively transferred to the capacitance FD11through the capacitance FD14. In addition, since the signal SEL1is at high level at the time point t2, pixel signals generated at the pixels10(1,1) through10(1,4) are respectively output to the vertical signal line101athrough the vertical signal line101dvia the corresponding amplifier units28and selection units29. Furthermore, since the signals SW11athrough SW11dare at high level at the time point t2, the pixel signals output from the pixels10in the first row to the vertical signal line101athrough the vertical signal line101dare respectively input via the arithmetic operation circuit units83athrough83d, to the A/D conversion unit82athrough the A/D conversion unit82dwhere they are converted to digital signals.

During a time period elapsing between a time point t3and a time point t5, noise signals and pixel signals originating at pixels10(2,1) through10(2,4) in the second row are read out in the same way as signals are read out over the time period elapsing between the time point t1and the time point t3. Likewise, noise signals and pixel signals originating at the pixels10(3,1) through10(3,4) in the third row are read out over a time period elapsing between the time point t5and a time point t7, and noise signals and pixel signals originating at the pixels10(4,1) through10(4,4) in the fourth row are read out over a time period elapsing between the time point t7and a time point t9. Through variation 2 described above, pixel signals generated at the pixels can be individually read out when the regions41A through44A constituting the Bayer array basic unit are each made up with a single pixel, as in the first embodiment and variation 1.

FIG.19presents another example of an operation that may be executed in the image sensor3in variation 2.FIG.19(a)shows a Bayer array reiterating basic unit made up with 4×4 pixels present in regions41B through44B.FIG.19(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.19(a).

At a time point t1, a signal RST1and a signal RST2shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through10(1,4) and the pixels10(2,1) through10(2,4).

As a signal SEL1and a signal SEL2shift to high level at the time point t1, the source terminals of the transistors M3constituting the amplifier units28at the pixel10(1,1) and the pixel10(2,1) become electrically connected with each other via the vertical signal line101a. Thus, a noise signal generated by adding together and averaging signals at the two pixels10(1,1) and10(2,1), is output to the vertical signal line101a. The noise signal output to the vertical signal line101ais a signal corresponding to the average (value) of the potentials at the floating diffusions27in the pixel10(1,1) and the pixel10(2,1).

In addition, as the signal SEL1and the signal SEL2shift to high level at the time point t1, the amplifier unit28in the pixel10(1,2) and the amplifier unit28in the pixel10(2,2) become electrically connected with each other via the vertical signal line101a. Thus, a noise signal generated by adding together and averaging signals at the two pixels (1,2) and10(2,2), is output to the vertical signal line101b. Likewise, as the signal SEL1and the signal SEL2shift to high level at the time point t1, a noise signal generated by averaging signals at two pixels10(1,3) and10(2,3), and a noise signal generated by averaging signals at the two pixels10(1,4) and10(2,4) are respectively output to the vertical signal line101cand the vertical signal line101d.

At the time point t1, a signal SW11a, a signal SW11c, a signal SW13aand a signal SW13calso shift to high levels. It is to be noted that a signal SW11b, a signal SW11d, a signal SW13b, a signal SW13dand the signals SW12athrough SW12dare each set to low level. As a result, the noise signal generated by averaging the signals at the two pixels10(1,1) and10(2,1) output to the vertical signal line101aand the noise signal generated by averaging the signals at the two pixels10(1,2) and10(2,2) output to the vertical signal line101bare input to the arithmetic operation circuit unit83awhere they are added together and averaged. Namely, the arithmetic operation circuit unit83agenerates a noise signal representing the average of the signals at the four pixels, i.e., the pixel10(1,1), the pixel10(2,1), the pixel10(1,2) and the pixel10(2,2), and outputs the noise signal thus generated to the A/D conversion unit82a. The A/D conversion unit82athen converts the signal input thereto to a digital signal.

Likewise, the noise signal generated by averaging the signals at the two pixels10(1,3) and10(2,3) output to the vertical signal line101cand the noise signal generated by averaging the signals at the two pixels10(1,4) and10(2,4) output to the vertical signal line101dare input to the arithmetic operation circuit unit83cwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83cgenerates a noise signal representing the average of the signals at the four pixels, i.e., the pixel10(1,3), the pixel10(2,3), the pixel10(1,4) and the pixel10(2,4), and outputs the noise signal thus generated to the A/D conversion unit82c. The A/D conversion unit82cthen converts the signal input thereto to a digital signal.

At a time point t2, a signal TX1and a signal TX2shift to high level, thereby turning on the transistors M1constituting the transfer units25to transfer electric charges resulting from photoelectric conversion executed at the PDs11through14and the PDs21through24to the corresponding floating diffusions27at the pixels10(1,1) through10(1,4) and the pixels10(2,1) through10(2,4).

In addition, at the time point t2, the amplifier units28and the pixel10(1,1) and the pixel10(2,1) are electrically connected with each other, and thus, a sum pixel signal generated by averaging signals at the two pixels10(1,1) and10(2,1) is output to the vertical signal line101a. The sum pixel signal output to the vertical signal line101ais a signal corresponding to the average of the potentials at the floating diffusions27in the pixel10(1,1) and the pixel10(2,1). Namely, a signal corresponds to the average of the potential based upon the electric charge resulting from photoelectric conversion executed at the PD11at the pixel10(1,1) and the potential based upon the electric charge resulting from photoelectric conversion executed at the PD21at the pixel10(2,1).

At the time point t2, a sum pixel signal generated by averaging signals at the two pixels10(1,2) and10(2,2), a sum pixel signal generated by averaging signals at the two pixels10(1,3) and10(2,3) and a sum pixel signal generated by averaging signals at the two pixels10(1,4) and10(2,4) are respectively output to the vertical signal line101bthrough the vertical signal line101d.

At the time point t2, the sum pixel signal generated by averaging the signals at the two pixels10(1,1) and10(2,1) output to the vertical signal line101a, and the sum pixel signal generated by averaging the signals at the two pixels10(1,2) and10(2,2) output to the vertical signal line101b, are input to the arithmetic operation circuit unit83awhere they are added together and averaged. Namely, the arithmetic operation circuit unit83agenerates a sum pixel signal representing the average of the signals at the four pixels, i.e., the pixel10(1,1), the pixel10(2,1), the pixel10(1,2) and the pixel10(2,2), and outputs the sum pixel signal thus generated to the A/D conversion unit82a. The A/D conversion unit82athen converts the signal input thereto to a digital signal.

Likewise, the sum pixel signal generated by averaging the signals at the two pixels (1,3) and10(2,3) output to the vertical signal line101c, and the sum pixel signal generated by averaging the signals at the two pixels10(1,4) and10(2,4) output to the vertical signal line101d, are input to the arithmetic operation circuit unit83cwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83cgenerates a sum pixel signal representing the average of the signals at the four pixels, i.e., the pixel10(1,3), the pixel10(2,3), the pixel10(1,4) and the pixel10(2,4), and outputs the sum pixel signal thus generated to the A/D conversion unit82c. The A/D conversion unit82cthen converts the signal input thereto to a digital signal.

During a time period elapsing between a time point t3and a time point t5, signals generated by adding together and averaging signals generated at the pixel10(3,1), the pixel10(3,2), the pixel10(4,1) and the pixel10(4,2) and signals generated by adding together and averaging signals generated at the pixel10(3,3), the pixel10(3,4), the pixel (4,3) and the pixel10(4,4) are read out in the same way as signals are read out during the time period elapsing between the time point t1and the time point t3. During a time period elapsing between the time point t5and a time point t7, signals generated by adding together and averaging signals at the pixel10(5,1), the pixel10(5,2), the pixel10(6,1) and the pixel10(6,2) and signals generated by adding together and averaging signals generated at the pixel10(5,3), the pixel10(5,4), the pixel10(6,3) and the pixel10(6,4) are read out in the same way as signals are read out during the time period elapsing between the time point t1and the time point t3. In the above described manner, a signal can be read out by adding together the signals at four pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41B through44B, each made up with 2×2=4 pixels.

FIG.20presents yet another example of an operation that may be executed in the image sensor3in variation 2.FIG.20(a)shows a Bayer array reiterating basic unit made up with 6×6 pixels present in regions41C through44C.FIG.20(b)is a timing chart of an operation that may be executed in the image sensor3when the transmission wavelengths at the filter units5are set as shown inFIG.20(c).

At a time point t1, a signal RST1, a signal RST2and a signal RST3shift to high level, thereby turning on the transistors M2constituting the reset units26and setting the potentials at the floating diffusions27to the reset potential at the pixels10(1,1) through (1,3), the pixels10(2,1) through10(2,3) and the pixels10(3,1) through10(3,3).

As a signal SEL1, a signal SEL2and a signal SEL3shift to high level at the time point t1, the source terminals of the transistors M3constituting the amplifier units28in the pixel10(1,1), the pixel10(2,1) and the pixel10(3,1) become electrically connected with one another via the vertical signal line101a. Thus, a noise signal generated by adding together and averaging signals at the three pixels10(1,1),10(2,1) and10(3,1) is output to the vertical signal line101a.

In addition, as the signal SEL1, the signal SEL2and the signal SEL3shift to high level at the time point t1, the amplifier units28in the pixel10(1,2), the pixel10(2,2) and the pixel10(3,2) become electrically connected with one another via the vertical signal line101a. Thus, a noise signal generated by adding together and averaging signals at the three pixels10(1,2),10(2,2) and10(3,2) is output to the vertical signal line101b. Likewise, as the signal SEL1, the signal SEL2and the signal SEL3shift to high level at the time point t1, a noise signal generated by averaging signals at the three pixels (1,3),10(2,3) and10(3,3) is output to the vertical signal line101c.

At the time point t1, a signal SW12a, a signal SW11band a signal SW13bshift to high levels. It is to be noted that s signal SW11a, a signal SW13a, a signal SW12b, a signal SW11c, a signal SW12cand a signal SW13care each set to low level. As a result, the noise signals output to the vertical signal line101athrough the vertical signal line101care input to the arithmetic operation circuit unit83bwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83bgenerates a noise signal representing the average of the signals at the nine pixels,10(1,1),10(1,2),10(1,3),10(2,1),10(2,2),10(2,3),10(3,1),10(3,2) and10(3,3), and outputs the noise signal thus generated to the A/D conversion unit82b. The A/D conversion unit83bthen converts the signal input thereto to a digital signal.

At a time point t2, a signal TX1, a signal T2X and a signal TX3shift to high level, thereby turning on the transistors M1constituting the transfer unit25, to transfer electric charges resulting from photoelectric conversion executed at the PDs11through13, the PDs21through23and the PDs31through33, to the corresponding floating diffusions27at the pixels10(1,1) through10(1,3) the pixels10(2,1) through10(2,3) and the pixels (3,1) through10(3,3).

In addition, at the time point t2, a sum pixel signal generated by averaging signals at the three pixels10(1,1),10(2,1) and10(3,1) is output to the vertical signal line101a. At the time point t2, a sum pixel signal generated by averaging signals at the three pixels (1,2),10(2,2) and10(2,3) and a sum pixel signal generated by averaging signals at the three pixels10(1,3),10(2,3) and10(3,3) are respectively output to the vertical signal line101band the vertical signal line101c.

At the time point t2, the sum pixel signals output to the vertical signal line101athrough the vertical signal line101care input to the arithmetic operation circuit unit83bwhere they are added together and averaged. Namely, the arithmetic operation circuit unit83bgenerates a sum pixel signal representing the average of the signals at the nine pixels, and outputs the sum pixel signal thus generated to the A/D conversion unit82b. The A/D conversion unit82bthen converts the signal input thereto to a digital signal. In the above described manner, the image sensor3is thus able to read out a signal by adding together the signals at nine pixels present in each region in conjunction with a Bayer array basic unit constituted with the regions41C through44C, each made up with 3×3=9 pixels.

In this variation, the amplifier units28in the plurality of pixels10disposed along the column direction are electrically connected with one another via a vertical signal line101so allow signals generated in the plurality of pixels10to be added together at the vertical signal line101. Thus, the need for the second switch units19via which the signals at a plurality of pixels10disposed along the column direction are added together and the wiring for connecting the second switch units19to the floating divisions27is eliminated. In addition, since the signals generated at the plurality of pixels10disposed along the row direction are added together in an arithmetic operation circuit unit83, the need for the first switch units18via which the signals in the plurality of pixels10disposed along the row direction are added together and the wiring for connecting the first switch units18to the floating divisions27, is eliminated. Consequently, the pixels can be miniaturized and the chip area of the image sensor can be reduced.

Furthermore, when signals generated at pixels are added together by connecting a plurality of amplifier units28with one another, an accurate sum cannot be calculated unless the difference among the signals at the individual pixels10, to be added together, i.e., the potential differences among the potentials at the floating diffusions27in the individual pixels, is small. For instance, if there is a significant difference between the potentials at the floating diffusions27in two addition-target pixels, almost all of the electric current from the current source81will flow to the amplifier unit28in the pixel with the higher level signal, and in such a case, a signal corresponding to the average of the potentials at the two floating diffusions27cannot be obtained. In contrast, the regions41A through44A,41B through44B and41C through44C in the variation each contain same-color pixels10and thus, the difference among the signals at the individual pixels10to be added together is expected to be small. As a result, accurate addition processing can be executed in this variation.

In variation 2, signals generated at a plurality of pixels10disposed along the column direction are added together at a vertical signal line101and signals generated at a plurality of pixels10disposed along the row direction are added together in an arithmetic operation circuit unit83. As an alternative, signals generated at a plurality of pixels10disposed along the column direction and signals generated at a plurality of pixels10disposed along the row direction may both be added together at a vertical signal line101.FIG.21is a circuit diagram showing the structure in part of the image sensor3in variation 3. The column circuit unit80in variation 3 does not include arithmetic operation circuit units83. Timing charts pertaining to operations that may be executed in the image sensor3in variation 3, which would be identical to the timing charts inFIGS.18through20, are not provided and these operations will not be explained in detail. The following explanation will focus on primary differences from the image sensor3in variation 2.

At the time point t1inFIG.19, a signal SEL1, a signal SEL2, a signal SW11aand a signal SW13ashift to high level, thereby electrically connecting the amplifier units28at the pixel10(1,1), the pixel10(1,2), the pixel10(2,1) and the pixel10(2,2) with one another via the vertical signal lines101aand101b. As a result, a noise signal generated by averaging signals at the four pixels10(1,1),10(1,2),10(2,1) and10(2,2) is output to the A/D conversion unit82awhere it is converted to a digital signal. Likewise, as a signal SW11cand a signal SW13cshift to high level at the time point t1, a noise signal generated by averaging signals at the four pixels10(1,3),10(2,3),10(1,4) and10(2,4) is output to the A/D conversion unit82cwhich then converts it to a digital signal.

At the time point t2inFIG.19, a signal TX1and a signal TX2shift to high level and a sum pixel signal generated by averaging signals at the four pixels10(1,1),10(1,2),10(2,1) and10(2,2) is output to the A/D conversion unit82awhere it is converted to a digital signal. Likewise, at the time point t2, a sum pixel signal generated by averaging signals at the four pixels10(1,3),10(2,3),10(1,4) and10(2,4) is output to the A/D conversion unit82cwhich then converts it to a digital signal.

During the period of time elapsing between the time point t3and the time point t5inFIG.19, signals generated by adding together and averaging signals generated at the pixel10(3,1), the pixel10(3,2), the pixel10(4,1) and the pixel10(4,2) and signals generated by adding together and averaging signals generated at the pixel10(3,3), the pixel10(3,4), the pixel10(4,3) and the pixel10(4,4) are read out in the same way as in the signal readout executed during the time period elapsing between the time point t1and the time point t3. During the period of time elapsing between the time point t5and the time point t7, signals generated by adding together and averaging signals generated at the pixel10(5,1), the pixel10(5,2), the pixel10(6,1) and the pixel10(6,2) and signals generated by adding together and averaging signals generated at the pixel10(5,3), the pixel10(5,4), the pixel10(6,3) and the pixel10(6,4) are read out in the same way as the signal readout executed during the time period elapsing between the time point t1and the time point t3.

At the time point t1inFIG.20, a signal SEL1, a signal SEL2, a signal SEL3, a signal SW12a, a signal SW11band a signal SW13bshift to high level. In response, the amplifier units28at the pixel10(1,1), the pixel10(1,2), the pixel10(1,3), the pixel10(2,1), the pixel10(2,2), the pixel10(2,3), the pixel10(3,1), the pixel10(3,2) and the pixel10(3,3) become electrically connected with one another via the vertical signal lines101a,101band101c. As a result, a noise signal generated by averaging signals at the nine pixels10(1,1),10(1,2),10(1,3),10(2,1),10(2,2),10(2,3),10(3,1),10(3,2) and (3,3) is output to the A/D conversion unit82bwhere it is converted to a digital signal.

At the time point t2inFIG.20, a signal TX1, a signal TX2and a signal TX3shift to high level. As a result, a sum pixel signal generated by averaging signals at the nine pixels10(1,1),10(1,2),10(1,3),10(2,1),10(2,2),10(2,3),10(3,1),10(3,2) and (3,3) is output to the A/D conversion unit82b, which then converts it to a digital signal.

In variation 3 described above, in conjunction with the Bayer array basic unit constituted with the regions41B through44B each containing 2×2=4 pixels, signals generated at the four pixels in each region are added together at a vertical signal line101. In variation 3 described above, in conjunction with the Bayer array basic unit constituted with the regions41C through44C each containing 3×3=9 pixels, signals generated at the nine pixels in each region are added together at a vertical signal line101. As a result, the need for arithmetic operation circuit units83used for adding together signals generated in a plurality of pixels10disposed along the row direction is eliminated. Consequently, the chip area of the image sensor can be reduced.

In the embodiments and the variations thereof described above, the filter units5each include three filters constituted with an EC layer21that produces Mg (magenta) color, an EC layer22that produces Ye (yellow) color and an EC layer23that produces Cy (cyan) color. As an alternative, the filter units5may be configured so that they each include three filters constituted with an EC layer that produces R (red) color, an EC layer that produces G (green) color and an EC layer that produces B (blue) color. In addition, the filter units5may be variable filters constituted of liquid crystal.

In the embodiments and the variations thereof described above, R pixels, G pixels and B pixels are formed by controlling the filter units5of the individual pixels10. As an alternative, the filter units5at the pixels10may be controlled so as to form W pixels, each having a W (white) filter unit5, and BK pixels each having a BK (black) filter unit5. In such a case, the size of a region where W pixels with W (white) filter units5are present and the size of a region where BK pixels with BK (black) filter units5are present may be individually altered.

In the embodiments and the variations thereof described above, the photoelectric conversion units are each constituted with a photodiode. As an alternative, photoelectric conversion units each constituted with a photoelectric conversion film may be used.

The image sensor3in the embodiments and the variations thereof is a back-illuminated image sensor. As an alternative, the image sensor3may be configured as a front-illuminated image sensor having a wiring layer210disposed on the entry surface side where light enters.

The image sensor3having been described in reference to the embodiments and the variations thereof may be adopted in a camera, a smart phone, a tablet, a built-in camera in a PC, an on-vehicle camera, a camera installed in an unmanned aircraft (such as a drone or a radio-controlled airplane) and the like.

While the present invention has been described in reference to various embodiments and variations thereof, the present invention is not limited to the particulars of these examples. Any other mode conceivable within the scope of the technical teaching of the present invention is within the scope of the present invention.

The disclosures of the following priority applications are herein incorporated by reference:Japanese Patent Application No. 2016-192249 filed Sep. 29, 2016Japanese Patent Application No. 2017-61131 filed Mar. 27, 2017

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