Imaging device including phase detection pixels arranged to perform capturing and to detect phase difference

An imaging device including phase difference detection pixels and, more particularly, an imaging device that comprises a plurality of pixels that are two-dimensionally arranged to capture an image and to detect phase difference, a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that circuits formed in every pixel for phase difference detection are arranged opposite to each other with respect to an opening of a photoelectric conversion pixel. In the imaging device, phase difference detection may be performed with respect to entire photographed screen areas. In addition, the imaging device including phase difference detection pixels may have no defect pixels and thus improved image quality is obtained. Photographing and AF of a subject may be performed in low luminance.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2011-0102658, filed on Oct. 7, 2011, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein in by reference.

BACKGROUND

1. Field of the Invention

The invention relates to an imaging device including phase difference detection pixels, and more particularly, to an imaging device including phase difference detection pixels arranged to detect phase difference and to capture images.

2. Description of the Related Art

Some image capturing devices use phase difference detection pixels to perform autofocus (AF). Phase difference detection works by adding phase difference detection pixels between imaging pixels. The signals output from the phase difference detection pixels are used to detect phase differences between signals generated by different phase difference detection pixels. The detected phase differences can be used to perform AF. Because the output of phase detection pixels may be different from the output of normal image capturing pixels, the phase difference detection pixels are often used only to detect phase differences and not to capture the image. This may reduce the quality of the captured image compared with an image captured from an image capturing device that does not use phase difference detection pixels.

Additionally, openings for phase difference detection pixels are small making it is difficult to perform AF in low luminance.

SUMMARY

Therefore, there is a need in the art for an imaging device that receives an image formed by an optical system and includes a plurality of pixels that are two-dimensionally arranged to perform capturing and detect phase difference, the imaging device including: a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that circuits formed for each of a plurality of pixels for phase difference detection are arranged opposite to each other with respect to an opening of a photoelectric conversion pixel.

All pixels of the imaging device may output a signal for obtaining phase difference.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row each may include a transistor circuit formed in each of a plurality of photoelectric conversion pixels, wherein the plurality of photoelectric conversion pixels share an amplification circuit or a reset circuit in the transistor circuit.

The circuits formed for each of a plurality of pixels for phase difference detection may include at least one selected from the group consisting of a transmission circuit, a reset circuit, an amplification circuit, and a wiring circuit.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a micro lens is formed on each of the plurality of photoelectric conversion pixels and an opening is formed between the micro lens and a photoelectric conversion unit, wherein the opening is eccentrically formed with respect to an optical axis of the micro lens, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are in directions opposite to each other.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a mask is formed in an area other than areas in which the plurality of photoelectric conversion pixels are formed.

Pixels constituting each of the first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be formed of color filters, wherein the pixels are configured in a Bayer pattern to form Bayer pattern pixel units, wherein the Bayer pattern pixel units constitute each of the first photoelectric conversion pixel row and the second photoelectric conversion pixel row.

According to another aspect of the invention, there is provided an imaging device that receives an image formed by an optical system and includes a plurality of pixels that are two-dimensionally arranged to perform capturing and detect phase difference, the imaging device including: a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that a circuit formed in every four pixels arranged in a Bayer pattern is positioned in a phase difference detection direction.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a mask is formed in an area other than areas in which the plurality of photoelectric conversion pixels are formed.

According to another aspect of the invention, there is provided an imaging device that receives an image formed by an optical system and includes a plurality of pixels that are two-dimensionally arranged to perform capturing and detect phase difference, the imaging device including: a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that circuits formed in every pixel for phase difference detection are arranged opposite to each other with respect to an opening of a photoelectric conversion pixel and a circuit formed in every four pixels arranged in a Bayer pattern is positioned in a phase difference detection direction.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a mask is formed in an area other than areas in which the plurality of photoelectric conversion pixels are formed.

According to another aspect of the invention, there is provided an imaging device that receives an image formed by an optical system and includes a plurality of pixels that are two-dimensionally arranged to perform capturing and detect phase difference, the imaging device including: a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that circuits formed in every pixel for phase difference detection are arranged opposite to each other with respect to an opening of a photoelectric conversion pixel and a plurality of the photoelectric conversion pixels share an amplification circuit or a reset circuit of a transistor circuit formed in each of the plurality of the photoelectric conversion pixel.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a mask is formed in an area other than areas in which the plurality of photoelectric conversion pixels are formed.

According to another aspect of the invention, there is provided an imaging device that receives an image formed by an optical system and includes a plurality of pixels that are two-dimensionally arranged to perform capturing and detect phase difference, the imaging device including: a first photoelectric conversion pixel row; and a second photoelectric conversion pixel row, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are each disposed such that circuits formed in every pixel for phase difference detection are arranged opposite to each other with respect to an opening of the pixel for phase difference detection and circuits formed in every pixel that does not perform phase difference detection are arranged in the same direction with respect to openings of the pixels.

The first photoelectric conversion pixel row and the second photoelectric conversion pixel row may be each disposed such that a micro lens is formed on each of the plurality of pixels, wherein an opening is formed between the micro lens and a photoelectric conversion unit, wherein the opening is eccentrically formed with respect to an optical axis of the micro lens, wherein the first photoelectric conversion pixel row and the second photoelectric conversion pixel row are in directions opposite to each other.

DETAILED DESCRIPTION

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the invention are encompassed in the invention. In the description of the invention, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention.

The invention will now be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, like reference numerals denote like elements, and thus a detailed description thereof is provided once. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

FIG. 1is a block diagram illustrating an example of a structure of a digital image processing device100including an imaging device according to an embodiment of the invention.

Referring toFIG. 1, a lens is separable from the digital image processing device100, but an imaging device108is configured in an integrated manner with the digital image processing device100. In addition, the digital image processing device100including the imaging device108may perform phase difference autofocus (AF) and contrast AF.

The digital image processing device100includes an imaging lens101including a focus lens102. The digital image processing device100has focus detection capability through operation of the focus lens102. The imaging lens101includes a lens operation unit103that operates the focus lens102, a lens position detection unit104that detects a position of the focus lens102, and a lens control unit105that controls the focus lens102. The lens control unit105transmits information on focus detection to a CPU106of the digital image processing device100.

The digital image processing device100includes the imaging device108and thus captures light that is incident on and transmitted through the imaging lens101, thereby generating an image signal. The imaging device108may include a plurality of photoelectric conversion units (not shown) arranged in a matrix form and a transfer path (not shown) that transfers charges from the photoelectric conversion units to read an image signal.

An imaging device control unit107generates a timing signal, thereby controlling the imaging device108to capture an image. In addition, the imaging device control unit107sequentially reads out image signals when accumulation of charges on each of a plurality of scan lines is terminated.

The read-out image signals are converted to digital image signals by an A/D conversion unit110via an analogue signal processing unit109, and then input to an image input controller111and processed therein.

The digital image signals input to the image input controller111are subjected to auto white balance (AWB), auto exposure (AE) and AF calculations respectively performed by an AWB detection unit116, an AE detection unit117, and an AF detection unit118. The AF detection unit118outputs a detection value with respect to a contrast value during AF and outputs pixel information to the CPU106during phase difference AF, thereby allowing phase difference calculation to be performed in the CPU106. The phase difference calculation performed by the CPU106may be obtained by calculating a correlation between a plurality of pixel row signals. As a result of the phase difference calculation, a position or direction of a focal point may be obtained.

The image signals may also be stored in a synchronous dynamic random access memory (SDRAM)119, that is, a temporary memory. A digital signal processing unit112performs a series of image signal processing operations such as gamma correction to create a displayable live view image or captured image. A compression/decompression unit113compresses an image signal in a JPEG compression format or an H.264 compression format or decompresses the image signal when image signal processing is performed. An image file including the image signal compressed in the compression/decompression unit113is transmitted to a memory card122via a media controller121to be stored therein.

Image information for display is stored in a video RAM (VRAM)120and an image is displayed on an LCD115via a video encoder114. The CPU106, which acts as a control unit, controls overall operations of each unit of the digital image processing device100. An electrically erasable programmable read-only memory (EEPROM)123stores and maintains information for correcting defects of pixels of the imaging device108or adjustment information on the pixel defects. A manipulation unit124is a unit through which various commands of a user are input to manipulate the digital image processing device100. The manipulation unit124may include various buttons such as a shutter-release button (not shown), a main button (not shown), a mode dial (not shown), a menu button (not shown), or the like.

FIG. 2is a diagram for explaining an example of an AF principle of phase difference pixels by using the imaging device108ofFIG. 1, according to an embodiment of the invention.

Referring toFIG. 2, light of a subject that has transmitted through an imaging lens11transmits through a micro lens array14to be incident on light receiving pixels R(15) and L(16). Masks17and18for restricting pupils12and13of the imaging lens11or restricted openings are respectively formed in portions of the light receiving pixels R(15) and L(16). Among the pupils12and13of the imaging lens11, light from the pupil12above an optical axis10of the imaging lens11is incident on the light receiving pixel L(16), and light from the pupil13below the optical axis10of the imaging lens11is incident on the light receiving pixel R(15). Light that is reverse transmitted to the pupils12and13by the micro lens array14is incident on the light receiving pixels R(15) and L(16), which is referred to as pupil division.

An example of continuous outputs of the light receiving pixels R(15) and L(16) by pupil division by the micro lens array14are illustrated inFIG. 3. InFIG. 3, a horizontal axis denotes positions of the light receiving pixels R(15) and L(16), and a vertical axis denotes output values of the light receiving pixels R(15) and L(16). Referring toFIG. 3, plots showing outputs of the light receiving pixels R(15) and L(16) exhibit the same shape, but exhibit different phases with respect to position. This is due to image formation positions of light from the eccentrically formed pupils12and13of the imaging lens11being different from each other. Thus, when focal points of light from the eccentrically formed pupils12and13are inconsistent with each other, the light receiving pixels R(15) and L(16) exhibit an output phase difference, as illustrated inFIG. 3A. On the other hand, when focal points of light from the eccentric pupils12and13are consistent with each other, images are formed at the same position as illustrated inFIG. 3B. In addition, a direction of focus may be determined from the focus difference. A front-focusing indicates that an object is in a front focus state and is illustrated inFIG. 3A. Referring toFIG. 3A, the phase of the output of the light receiving pixel R(15) is shifted further to the left than that in the focused state, and the phase of the output of the light receiving pixel L(16) is shifted further to the right than that in the focused state. In contrast, a back-focusing indicates that an object is in a back focus state. In this case, the phase of the output of the light receiving pixel R(15) is shifted further to the right than that in the focused state, and the phase of the output of the light receiving pixel L(16) is shifted further to the left than that in the focused state. The shift amount between the phases of the light receiving pixels R(15) and L(16) may be converted to a deviation amount between the focuses.

FIG. 4is a diagram illustrating an example of a structure of pixels constituting a general imaging device.

Referring toFIG. 4, two pixels are illustrated. The two pixels include micro lenses21, a surface layer22, a color filter layer23, a wire layer24, photodiode layers25, and a substrate layer26. The drawing is illustrated in a simplified manner.

Light from a subject enters the photodiode layer25of each pixel via the micro lenses21, and a photodiode in the photodiode layer25of each pixel generates charges that serve as pixel information. The generated charges are released through the wire layer24. Such incident light from a subject is all light that has transmitted through an exit pupil of an imaging lens, and luminance information corresponding to a subject position may be obtained corresponding to a pixel position. In general, the color filter layer23may be a layer including pixels of red (R), green (G), and blue (B). Also, the color filter layer23may include pixels of cyan (C), magenta (M), and yellow (Y).

FIG. 5illustrates an example of a vertical configuration of phase difference pixels for obtaining signals of the R and L pixels illustrated inFIG. 2, in which masks27and28are installed in openings of the imaging device108ofFIG. 4. The R and L pixels for phase difference detection are referred to as S1and S2, respectively. InFIG. 5, S1and S2include the mask27for the R pixel and the mask28for the L pixel, respectively, each interposed between the micro lenses21and the photodiode layers25. However, the positions of the masks27and28are not limited to the example illustrated inFIG. 5. For example, the masks27and28may be interposed somewhere between the micro lenses21and the photodiode layers25. InFIG. 5, optical axes of the micro lenses21are each represented by a dashed dotted line, and paths through which light is incident from the micro lenses21are each represented by a dotted line. The amounts of light incident on the photodiode layers25are restricted by 50% by the masks27and28with respect to the optical axes of the micro lenses21.

FIGS. 6A and 6Bare diagrams illustrating an example of a relationship between positions of pixels of the imaging device ofFIG. 5and imaging lenses, according to an embodiment of the invention.

FIG. 6Aillustrates an imaging lens31, an R pixel (S1)33of the imaging device ofFIG. 5, a top view of a mask34, and a pupil32.FIG. 6Billustrates an imaging lens36, an L pixel (S2)38of the imaging device ofFIG. 5, a top view of a mask39, and a pupil37. In this regard, the masks34and39each have an aperture ratio of 50% with respect to optical axes of the imaging lenses31and36.

The R pixel (S1)33and the L pixel (S2)38illustrated inFIGS. 6A and 6Bmay not necessarily be arranged adjacent to each other. In addition,FIGS. 6A and 6Billustrate a configuration of pixels arranged in vicinity of the optical axes of the imaging lenses31and36. If pixels are arranged further away from the optical axes of the imaging lenses31and36, to correct the cos4θ law, positions of the optical axes of the imaging lenses31and36and the masks34and39are shifted in an external direction of a screen.

FIG. 7illustrates an example of a general Bayer pattern pixel structure of an imaging device.

Referring toFIG. 7, color filters of three colors, i.e., red (R), green (G), and blue (B), are arranged and 4 pixels are configured as a single unit. In this regard, two G pixels are arranged in the unit. An arrangement of pixels for phase difference detection based on the Bayer pattern pixel structure ofFIG. 7is illustrated inFIG. 8.

Referring toFIG. 8, general Bayer pattern pixels BY1and BY2are arranged and PH1including R pixels (S1) for phase difference detection and PH2including L pixels (S2) for phase difference detection are arranged therebetween. Conventionally, phase difference pixels are arranged using G Bayer pattern pixels. However, it is difficult to perform interpolation computation for a general Bayer arrangement by using the G pixels and thus the S1and S2pixels are regarded as defect pixels so that they are not effectively used and the quality of image captured using the imaging device including the phase difference pixels is deteriorated compared to that of images captured using a general imaging device without phase difference pixels. In addition, compared to general pixels, it is necessary for phase difference pixels to have an aperture ratio of 50% or less and thus the amount of light incident on the phase difference pixels is 50% or less. The reduced aperture ratio may make it difficult to perform AF in low luminance, which may make photographing difficult.

Thus, in an imaging device according to an embodiment of the invention, a pixel circuit is configured such that phase difference detection is performed in all of pixels thereof, whereby good image quality without pixel defects is obtained and phase difference detection may be performed in all the pixels. In addition, an area of openings of phase difference pixels is not made small and AF may be performed even in low luminance. A configuration of only 16 pixels of an example of an imaging device is illustrated inFIGS. 9A and 9B.

FIGS. 9A and 9Billustrate phase difference pixels of an imaging device configured in a horizontal direction, according to an embodiment of the invention.FIG. 9Aillustrates a configuration of the color filters of R, G, and B in the R pixels (S1) and the color filters of R, G, and B in the L pixels (S2), andFIG. 9Billustrates arrangement of photoelectric conversion openings. InFIG. 9A, RLa denotes that an opening for an L pixel is formed in an R color filter.FIG. 9Billustrates the R and L pixels each having an aperture ratio of about 50% with respect to the optical axes of the imaging lenses31and36, each opening of which does not contact the optical axes or contacts but does not include the optical axes. The openings illustrated inFIG. 9Bare referred to as “A-type opening” for convenience of explanation, and thus a configuration of phase difference pixels in the horizontal direction is referred to as HA.

InFIG. 9A, the L pixels are arranged in a first row41and a second row42, and the R pixels are arranged in a third row43and a fourth row44. Pixel row signals of the pixels of the first row41and the second row42or a sum (binning output) of the pixel row signals of the L pixels of the first low41and the second row42, and pixel row signals of the pixels of the third row43and the fourth row44or a sum (binning output) of the pixel row signals of the pixels of the third row43and the fourth row44are obtained as illustrated inFIG. 3to calculate a phase difference between the R and L pixels. The pixel row signals are obtained as a line image in the horizontal direction. Thus, an image with a contrast change in the horizontal direction may be detected. The pixel rows in the HA configuration are composed of pixels each having an aperture ratio of about 50% with respect to the optical axes of the imaging lenses31and36(seeFIG. 6), each opening of which does not contact the optical axes or contacts but does not include the optical axes. Therefore, crosstalk between adjacent pixels does not occur and a position of a focal point in the horizontal direction of a subject may be obtained from information about the phase difference.

FIGS. 10A and 10Billustrate phase difference pixels of an imaging device configured in a vertical direction, according to an embodiment of the invention.

FIG. 10Aillustrates an example of a configuration of the color filters of R, G, and B in the R pixels (S1) and the color filters of R, G, and B in the L pixels (S2), andFIG. 10Billustrates arrangements of photoelectric conversion openings. InFIG. 10A, RLa denotes that an opening for an L pixel is formed in an R color filter.FIG. 10illustrates the R and L pixels each having an aperture ratio of about 50% with respect to the optical axes of the imaging lenses31and36(seeFIG. 6), each opening of which does not contact the optical axes or contacts but does not include the optical axes. A configuration of phase difference pixels in the vertical direction is referred to as VA.

InFIG. 10A, the L pixels are arranged in a first row51and a second row52, and the R pixels are arranged in a third row53and a fourth row54. The rows inFIG. 10Aare arranged vertically, and will be referred to rows rather than columns for consistency with other arrangements. Pixel row signals of the pixels of the first row51and the second row52or a sum (binning output) of the pixel row signals of the L pixels of the first row51and the second row52, and pixel row signals of the pixels of the third row53and the fourth row54or a sum (binning output) of the pixel row signals of the pixels of the third row53and the fourth row54are obtained as illustrated inFIG. 3to calculate a phase difference between the R and L pixels.

The pixel row signals are obtained as a line image in the vertical direction. The pixel row signals in the VA configuration may be used to detect an image with a contrast change in the vertical direction, and thus a position of a focal point in the vertical direction of a subject may be obtained from information about the phase difference.

FIGS. 11A and 11Billustrate examples of vertical configurations of RLa and GLa pixels and RRa and GRa pixels, respectively, of the HA configuration illustrated inFIG. 9, according to an embodiment of the invention.

Referring toFIGS. 11A and 11B, each of the RLa and RRa pixels and each of the GLa and GRa pixels include a color filter layer23, in which the color filter layer23in the RLa and RRa pixels is an R color filter and in which the color filter layer23in the GLa and GRa pixels is a G color filter, and the RLa and GLa pixels each include a mask28for an L pixel and the RRa and GRa pixels each include a mask27for an R pixel. While sizes of the masks27and28may be the same as those of pixels of a general imaging device, a position relationship between the masks27and28and micro lenses21is different from that in a general imaging device. Optical axes of the micro lenses21are eccentrically formed respectively from centers of openings and the openings contact but do not include the optical axes. InFIG. 11, the masks27and28are formed on non-opening sides with respect to the optical axes so that unnecessary light is not incident on the openings. Referring toFIG. 11, similar to the R and L pixels illustrated inFIG. 5, the RLa and GLa pixels and the RRa and GRa pixels each include a wire layer24, a photodiode layer25, and a substrate layer26; however, unlike the R and L pixels ofFIG. 5, the pixels ofFIG. 11include transistor circuits.

FIG. 12is a circuit diagram illustrating a basic pixel structure of an imaging device according to an embodiment of the invention.

Referring toFIG. 12, an example of the basic pixel structure of an imaging device includes a buried-type photodiode PD, a transistor Tr1having a source connected to an anode of the PD, a transistor Tr2having a source connected to a drain of the transistor Tr1, a transistor Tr3having a gate connected to an access node connected to the drain of the transistor Tr1and the source of the transistor Tr2, and a transistor Tr4having a drain connected to a source of the transistor Tr3. A direct voltage VPS is applied to a cathode of the photodiode PD and back gates of the transistors Tr1through Tr4and a direct voltage (VPD2, VPD) is applied to a drain of each of the transistors Tr2and Tr3, respectively. A φTX signal, a φRS signal, and a φV signal are respectively applied to gates of the transistors Tr1, Tr2, and Tr4. Unnecessary charges are initially reset by the transistor Tr2, charges generated by the photodiode PD are migrated into a floating diffusion layer FD of the transistor Tr1, the charges are amplified by the transistor Tr3, a pixel is selected by the transistor Tr4, and a signal of the pixel is output from a vertical output line (LV).

FIG. 13is a circuit diagram particularly illustrating an example of photoelectric conversion portions of a pixel illustrated inFIG. 12, arranged on a silicon substrate, according to an embodiment of the invention.

Referring toFIG. 13, an N-type layer61is buried in a P-type substrate or P-type well layer60and a P-type layer62is formed on the N-type layer61, thereby completing formation of a buried-type photodiode PD. A transmission gate TG including an insulating layer63and a gate electrode64is formed on a surface of a region that is adjacent to a region in which the buried-type photodiode PD is formed, an N-type floating diffusion layer FD is formed below a region that is adjacent to the region in which the transmission gate TG is formed, a reset gate RG including an insulating layer65and a gate electrode66is formed on a surface of a region that is adjacent to the N-type floating diffusion layer FD, and an N-type diffusion layer is formed below a region that is adjacent to the region in which the reset gate RG is formed. The buried-type photodiode PD is formed such that the P-type layer62, which is highly concentrated, is formed on a surface of the N-type layer61, which is a buried type layer. In addition, the N-type layer61, the N-type floating diffusion layer FD, and the transmission gate TG constitute the transistor Tr1, and the N-type floating diffusion layer FD, the N-type diffusion layer, and the reset gate RG constitute the transistor Tr2. The gate of the transistor Tr3is connected to the N-type floating diffusion layer FD. In other words, each of a plurality of pixels includes 4 transistors as well as photoelectric conversion portions. This is referred to as a pixel of a 4-Tr structure. Such a pixel structure needs a large area in semiconductor manufacturing processes and thus an area available for photoelectric conversion is restricted. In addition, it is necessary to fabricate a variety of transistors or wire circuits in addition to photoelectric conversion openings. Thus, a circuit is generally formed next to a photoelectric conversion unit in each pixel and arrangement of the circuit is the same in all the pixels. That is, in all the pixels, the circuit is formed next to the photoelectric conversion opening in the same direction. In embodiments of the invention, the arrangements of the photoelectric conversion openings and the circuits are optimized.

Meanwhile, as the number of pixels of an imaging device has recently increased and, accordingly, it is difficult to obtain areas of openings, there are many cases in which transistors are formed between pixels instead of in each pixel to obtain the areas of openings. For example,FIG. 14illustrates an example of a circuit in which four pixels share a reset transistor and an amplification transistor and a selection transistor selects transmission transistors.

Referring toFIG. 14, transistors Tr1, Tr2, Tr3, and Tr4are respectively formed for photodiodes PD1, PD2, PD3, and PD4and respectively connected to transmission timing signals TX1, TX2, TX3, and TX4. In addition, a reset transistor Tr5is connected to a reset signal RS. The four pixels share the reset transistor Tr5and an amplification transistor Tr6. InFIG. 14, the four pixels share6transistors and thus they may be referred to as pixels of a 1.5-Tr structure. For two pixel sharing, for example, a 2.5-Tr structure or a 2-Tr structure may be used. The case in which the four pixels arranged in a vertical direction share the reset transistor Tr5and the amplification transistor Tr6is illustrated inFIG. 14, but the invention is not limited to the above example. For example,FIG. 15illustrates a case in which four pixels arranged on top, bottom, left, and right sides share the reset transistor Tr5and the amplification transistor Tr6. Referring toFIG. 15, the number of components of a circuit is the same as that inFIG. 14. Conventionally, these pixels are repeatedly configured in vertical and horizontal directions in the same pattern, each pixel is in a square arrangement, and circuits of transistors are arranged in a certain direction.

FIG. 16is an example of a circuit plan view of a general imaging device. Referring toFIG. 16, two pixels share a reset transistor and an amplification transistor. In other words,FIG. 16illustrates a two-pixel unit in which photodiodes PD11and PD21share a reset transistor TrR11and an amplification transistor TrA11.FIG. 16only illustrates 8 units including 16 pixels, but the imaging device108actually includes more repeated configurations of the units, for example, 20 mega pixels. Four pixels including photodiodes PD11, PD12, PD21, and PD22are in a Bayer pattern and R, G, and B color filters are formed on the photodiodes. In addition, a mask having openings only on the photodiodes exists on the plan view. Micro lenses are formed on the mask. A timing signal is routed around each of the photodiodes. Signal lines TX1and TX2for transmission timing and reset signal lines RES for reset are wired in a horizontal direction and pixel signal readout lines LV1, LV2, LV3, and LV4are wired in a vertical direction, and such a configuration is repeatedly present.

Referring toFIG. 16, transmission transistors Tr11and Tr21are respectively positioned on left sides of the photodiodes PD11and PD21. A side of the transmission transistor Tr11is connected to the photodiode PD11by a vertical line and a side of the transmission transistor Tr21is connected to the photodiode PD21by the vertical line, and the reset transistor TrR11is positioned in front of the transmission transistors Tr11and Tr21. The transmission transistors Tr11and Tr21are simultaneously connected to the amplification transistor TrA11and an output side is connected to the pixel signal readout line LV1.

Outputs of the photodiodes PD11and PD21are switched by timing of the horizontal signals TX1and TX2. The transmission transistors Tr11and Tr21selectively transmit the outputs of the photodiodes PD11and PD21and the amplification transistor TrA11selectively amplifies the outputs of the photodiodes PD11and PD21. The reset transistor TrR11resets the photodiodes PD11and PD21. In the example illustrated, all the pixels, all the circuits and lines of transistors are positioned on a left side of photodiodes and the photodiodes are periodically arrayed at an equal interval both in horizontal and vertical directions.

FIG. 17is a circuit plan view of an example of an imaging device according to an embodiment of the invention.FIG. 17illustrates the HA configuration illustrated inFIG. 9and that two pixels share a reset transistor and an amplification transistor. Referring toFIG. 17, four pixels including photodiodes RLa41, GLa31, GLa42, and BLa32indicate a unit including R, G, G, and B pixels arranged in a Bayer pattern. The Bayer pattern pixel structure corresponds to phase difference pixels, i.e., L pixels, and constitutes a first pixel row in phase difference calculation. Four pixels including photodiodes RRa22, GRa12, GRa23, and BRa13indicate a unit including R, G, G, and B pixels in a Bayer pattern, and the Bayer pattern pixel unit structure corresponds to phase difference pixels, i.e., R pixels, and constitutes a second pixel row in phase difference calculation.

In phase difference detection, the pixels including the photodiodes RLa41and GLa31of the first pixel row correspond to the pixels including the photodiodes RRa22and GRa12of the second pixel row. Similarly, the pixels including the photodiodes GLa42and BLa32of the first pixel row correspond to the pixels including the photodiodes GRa23and BRa13of the second pixel row. Although readout lines for the first and second pixel rows are different from each other, a pixel signal that is temporarily stored in a memory is used in correlation calculation and thus this does not matter.

Transmission transistors Tr41and Tr31are respectively positioned on left sides of the photodiodes RLa41and GLa31of the L pixels. Outputs of the transmission transistors Tr41and Tr31are connected to each other by wiring and connected to a reset transistor TrR31. In addition, the transmission transistors Tr41and Tr31are connected to an amplification transistor TrA31therebetween. An output of the amplification transistor TrA31is connected to a signal readout line LV1.

Transmission transistors Tr21and Tr11are respectively positioned on right sides of photodiodes GRa21and Bra11of the R pixels. Outputs of the transmission transistors Tr21and Tr11are connected to each other by wiring. The transmission transistors Tr21and Tr11are connected to an amplification transistor TrA11therebetween. An output of the amplification transistor TrA11is connected to the signal readout line LV1. Each of the L pixels and the R pixels is repeatedly arranged to configure L pixel series and R pixel series. An operation of a circuit of each transistor is the same as that inFIG. 16.

In the L pixel series and the R pixel series, transmission transistors, reset transistors, amplification transistors, and lines, with photodiodes therebetween, are positioned on opposite sides. The L pixels and the R pixels are configured as described above, and thus do not have reduced areas of openings.

FIG. 18is a circuit plan view of an example of an imaging device according to another embodiment of the invention.FIG. 18illustrates the HA configuration illustrated inFIG. 9and that vertically arranged four pixels share a reset transistor and an amplification transistor. Referring toFIG. 18, as illustrated inFIG. 17, four pixels including photodiodes RLa41, GLa31, GLa42, and BLa32indicate a unit including R, G, G, and B pixels arranged in a Bayer pattern. The Bayer pattern pixel unit structure corresponds to phase difference pixels, i.e., L pixels, and constitutes a first pixel row in phase difference calculation. Four pixels including photodiodes RRa22, GRa12, GRa23, and BRa13indicate a unit including R, G, G, and B pixels in a Bayer pattern, and the Bayer pattern pixel unit structure corresponds to phase difference pixels, i.e., R pixels, and constitutes a second pixel row in phase difference calculation. In phase difference detection, the pixels including the photodiodes RLa41and GLa31of the first pixel row correspond to the pixels including photodiodes GRa21and BRa11of the second pixel row.

Transmission transistors Tr41and Tr31are respectively positioned on left sides of the photodiodes RLa41and GLa31of the L pixels. Outputs of the transmission transistors Tr41and Tr31are connected to each other by wiring. Transmission transistors Tr21and Tr11are respectively positioned on right sides of the photodiodes GRa21and Bra11of the R pixels. Outputs of the transmission transistors Tr21and Tr11are connected to each other by wiring. The transmission transistors Tr21and Tr11are also connected to output lines of the L pixels. The transmission transistors Tr41, Tr31, Tr21and Tr11selectively transfer charges according to timing of horizontal signals TX4, TX3, TX2and TX1, respectively. The transferred charges pass through an N-type floating diffusion layer, and a pixel signal is amplified in an amplification transistor TrA11and the amplified pixel signal passes through a vertical pixel readout line LV1to be output. The vertical pixel readout line LV1is also connected to a reset transistor TrR11and outputs of the photodiodes RLa41, GLa31, GRa21and Bra11are reset by an RES signal. As described above, in the L pixel series, transmission transistors and amplification transistors are positioned on left sides of photodiodes. On the other hand, in the R pixel series, transmission transistors and reset transistors are positioned on right sides of photodiodes. In both the L pixel series and the R pixel series, transmission transistors and lines, with photodiodes therebetween, are positioned on opposite sides.

FIG. 19is a circuit plan view of an example of an imaging device according to another embodiment of the invention.FIG. 19illustrates the HA configuration illustrated inFIG. 9and that four pixels arranged in horizontal and vertical directions share a reset transistor and an amplification transistor. Referring toFIG. 19, as illustrated inFIGS. 17 and 18, four pixels including photodiodes RLa41, GLa31, GLa42, and BLa32indicate a unit including R, G, G, and B pixels arranged in a Bayer pattern. The Bayer pattern pixel unit structure corresponds to phase difference pixels, i.e., L pixels, and constitutes a first pixel row in phase difference calculation. On the other hand, four pixels including photodiodes RRa21, GRa11, GRa22, and BRa12indicate a unit including R, G, G, and B pixels in a Bayer pattern, and the Bayer pattern pixel unit structure corresponds to phase difference pixels, i.e., R pixels, and constitutes a second pixel row in phase difference calculation. In phase difference detection, the pixels including the photodiodes RLa41and GLa31of the first pixel row correspond to the pixels including the photodiodes RRa21and GRa11of the second pixel row.

Transmission transistors Tr42and Tr32are respectively positioned on left sides of photodiodes GLa42and BLa32of the L pixels. Outputs of the transmission transistors Tr42and Tr32are connected to each other by wiring. A transmission transistor Tr41is positioned below the photodiode RLa41of the L pixels and a transmission transistor Tr31is positioned above the photodiode GLa31of the L pixels. In addition, outputs of the four pixels including photodiodes RLa41, GLa31, GLa42, and BLa32are connected to one another by wiring and also connected to an amplification transistor TrA31. Also, the outputs of the four pixels are connected to a reset transistor TrR31. The transmission transistors Tr41, Tr31, Tr42, and Tr32selectively transfer charges according to timing of horizontal signals TX4, TX3, TX2, and TX1. The transferred charges pass through an N-type floating diffusion layer, and a pixel signal is amplified by the amplification transistor TrA31and the amplified pixel signal passes through a vertical pixel readout line LV1to be output. The reset transistor TrR31is connected to the vertical pixel readout line LV1and outputs of the photodiodes RLa41, GLa31, GLa42, and BLa32are reset by an RES signal. On the other hand, the transmission transistors Tr21and Tr11are respectively positioned on right sides of the photodiodes RRa21and GRa11of the R pixels. Outputs of the transmission transistors Tr21and Tr11are connected to each other by wiring. A transmission transistor Tr22is positioned below the photodiode GRa22and a transmission transistor Tr12is positioned above the photodiode BRa12.

Outputs of the four photodiodes RRa21, GRa11, GRa22, and BRa12are connected to one another by wiring, to an amplification transistor TrA11, and to a reset transistor TrR11. The transmission transistors Tr21, Tr11, Tr22, and Tr12selectively transfer charges according to timing of the horizontal signals TX4, TX3, TX2and TX1. As described above, in L pixel series, transmission transistors, amplification transistors, and reset transistors are mainly positioned on left sides of four photodiodes, and, on the other hand, in R pixel series, transmission transistors, amplification transistors, and reset transistors are mainly positioned on right sides of four photodiodes. In the L and R pixel series, transistor circuits and lines, with photodiodes therebetween, are positioned on opposite sides.

FIG. 20is a circuit plan view of an imaging device according to another embodiment of the invention.FIG. 20illustrates the VA configuration illustrated inFIG. 10for detecting vertical phase difference. InFIG. 20, as illustrated inFIG. 19, four pixels arranged in horizontal and vertical directions share a reset transistor and an amplification transistor. A structure of each of a plurality of pixels is the same as that inFIG. 19, except that, in L and R pixel series, transistor circuits and lines are positioned in the same direction with respect to photodiodes. For pixels to be configured as phase difference pixels, the L pixel series and the R pixel series are alternately arranged with respect to each other in a plane direction and a plurality of wire lines are wired corresponding thereto. In this embodiment, the four pixels arranged in horizontal and vertical directions share the amplification transistor and the reset transistor and thus sufficient wiring intervals are obtainable for each of units including four pixels. Although not illustrated inFIG. 20, the VA configuration ofFIG. 20may be repeatedly arranged on left and right sides thereof. In other words, the configuration ofFIG. 10may be repeatedly arranged. The same design also applies to pixels arranged in a horizontal direction.

FIG. 21illustrates an example of an imaging device in which a plurality of different phase difference pixels are configured, according to an embodiment of the invention. Actually, an imaging device may be, for example, a 14.6 mega pixel imaging device having a pixel configuration in which 4670 pixels are arranged in a horizontal direction and 3100 pixels are arranged in a vertical direction. In this embodiment, however, smaller pixel dimensions are arranged for explanation in diagram form. Referring toFIG. 21, the imaging device includes HAs and VAs. Pixels in which horizontal phase difference is detectable, e.g., the pixels having the HA configuration ofFIG. 19, are arranged in the vicinity of an optical axis and pixels in which vertical phase difference is detectable, e.g., the pixels having the VA configuration ofFIG. 20, are arranged on left and right sides of an area in which the HAs are arranged. Focal point detection by phase difference may be performed with respect to an entire screen area. In addition, contrast AF may be performed with respect to an entire screen area by using pixel information.

FIG. 22illustrates an example of an imaging device in which general imaging pixels and phase difference pixels are configured, according to an embodiment of the invention.

In this embodiment, smaller pixel dimensions are arranged for explanation in diagram form as illustrated inFIG. 21. Referring toFIG. 22, HAs having the phase difference pixel configuration ofFIG. 17are arranged around a center area in three lines and the general imaging pixels ofFIG. 16are arranged in remaining areas. In this regard, the HAs are arranged only on the center area to enable phase difference detection by using a lens with a low F number, according to identical conditions for phase difference detection. Similar to this embodiment, a configuration other than a configuration for phase difference detection with respect to entire screen areas is possible. In the imaging device ofFIG. 22, arrangement of circuits is changed only for phase difference pixels.

As described above, according to the one or more embodiments of the invention, phase difference detection may be performed with respect to entire photographed screen areas. In addition, an imaging device including phase difference detection pixels has no defect pixels and thus it may obtain good image quality. Photographing and AF of a subject may be performed even in low luminance.

In embodiments, the invention provides an imaging device that maintains the same aperture ratio for all of pixels thereof, is capable of detecting phase difference from all the pixels by changing positions of openings through arrangement of circuits installed in pixels, and is capable of capturing an image of a subject and performing AF on a subject in low luminance.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) should be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Finally, the steps of all methods described herein are performable in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. Moreover, it is well understood by one of ordinary skill in the art that numerous modifications, adaptations, and changes may be made under design conditions and factors without departing from the spirit and scope of the invention as defined by the following claims and within the range of equivalents thereof.