Patent Description:
As one of the focus detection methods performed in an image capturing apparatus, a so-called on-imaging plane phase difference method in which a pair of pupil division signals are acquired using the focus detection pixels formed in an image sensor and focus detection of the phase difference method is performed using the pair of pupil division signals is known.

In such an image sensor, International Publication No. <CIT> discloses to suppress color mixing of a phase difference detection signal to an imaging signal by forming photoelectric conversion portions at different depths in order to photoelectrically convert visible light in different wavelength ranges. Further, it also discloses to obtain focus detection signals having phase differences in two different directions from one pixel by forming a pair of regions that mainly photoelectrically convert red light in a deep portion and a pair of regions that mainly photoelectrically convert blue light in a shallow portion, and arranging the pairs of regions in directions orthogonal to each other.

However, the image sensor disclosed in International Publication No. <CIT>uses a transfer transistor for transferring a signal from each of the photoelectric conversion portions formed at different depths, or a vertical transfer transistor that is commonly used for transferring signals from a plurality of the photoelectric conversion portions formed at different depths. When a transfer transistor is provided for each of the photoelectric conversion portions, the number of transfer transistors is large and the area of the light receiving region becomes small, in which case there is a problem that the manufacturing cost is high and the saturation charge amount that a photoelectric conversion portion can hold is small. Further, in a case where a vertical transfer transistor is used, there is a problem that the manufacturing cost of the image sensor will be increased because the process for forming the transistor is complicated.

In addition, document <CIT> describes an image sensor, a focus detection apparatus, and an electronic camera.

The present invention has been made in consideration of the above situation, and increases a saturation charge amount with a simple configuration while keeping the number of the pupil division directions of the phase difference signals for focus detection at two.

According to the present invention, provided is an image sensor as specified in claim <NUM>.

Further, according to the present invention, provided is an image capturing apparatus as specified in a further independent claim. Further advantageous modifications thereof are defined in the dependent claims.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.

Note, the following embodiments are not intended to limit the scope of the claimed invention, and limitation is not made an invention that requires a combination of all features described in the embodiments. Two or more of the multiple features described in the embodiments may be combined as appropriate. Furthermore, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.

<FIG> is a diagram schematically showing the overall configuration of an image sensor <NUM> according to a first embodiment of the present invention. The image sensor <NUM> includes a pixel array <NUM> (pixel section), a vertical selection circuit <NUM>, a column circuit <NUM>, and a horizontal selection circuit <NUM>.

A plurality of pixels <NUM> are arranged in a matrix in the pixel array <NUM>. The outputs of the vertical selection circuit <NUM> are input to the pixels <NUM> via pixel drive wiring groups <NUM>, and the pixel signals of the pixels <NUM> in a row selected by the vertical selection circuit <NUM> are read out to the column circuit <NUM> via output signal lines <NUM>. One output signal line <NUM> may be provided for each pixel column or for a plurality of pixel columns, or a plurality of the output signal lines <NUM> may be provided for each pixel column. Signals read out in parallel through the plurality of output signal lines <NUM> are input to the column circuit <NUM>, and the column circuit <NUM> performs processes, such as signal amplification, noise reduction, and A/D conversion, are performed, and holds the processed signals. The horizontal selection circuit <NUM> selects the signals held in the column circuit <NUM> sequentially, randomly, or simultaneously, so that the selected signals are output outside the image sensor <NUM> via a horizontal output line and an output section (not shown).

By sequentially performing the operation of outputting the pixel signals in the row selected by the vertical selection circuit <NUM> to the outside of the image sensor <NUM> while the vertical selection circuit <NUM> changes the row to select, two-dimensional imaging signals or focus detection signals can be read out from the image sensor <NUM>.

<FIG> is an equivalent circuit diagram of the pixel <NUM> of the present embodiment.

Each pixel <NUM> has two photodiodes <NUM> (PDA) and <NUM> (PDB), which are photoelectric conversion units. The signal charge which is photoelectrically converted by the PDA <NUM> corresponding to the amount of incident light and accumulated in the PDA <NUM> is transferred to a floating diffusion unit (FD) <NUM> that constitutes a charge storage unit via a transfer switch (TXA) <NUM>. Further, the signal charge which is photoelectrically converted by the PDB <NUM> and accumulated in the PDB <NUM> is transferred to the FD <NUM> via a transfer switch (TXB) <NUM>. A reset switch (RES) <NUM> is turned on to reset the FD <NUM> to the voltage of a constant voltage source VDD. Further, by turning on the RES <NUM>, TXA <NUM> and TXB <NUM> simultaneously, it is possible to reset the PDA <NUM> and PDB <NUM>.

When the selection switch (SEL) <NUM> for selecting a pixel is turned on, the amplification transistor (SF) <NUM> converts the signal charge accumulated in the FD <NUM> into a voltage, and the converted signal voltage is output from the pixel to the output signal line <NUM>. Further, the gates of the TXA203, TXB <NUM>, RES <NUM>, and SEL <NUM> are connected to the pixel drive wiring group <NUM>, and are controlled by the vertical selection circuit <NUM>.

In the following description, in the present embodiment, the signal charge accumulated in the photoelectric conversion unit is electrons, the photoelectric conversion unit is formed by an N-type semiconductor, and a P-type semiconductor is used to separate the N-type semiconductor. However, the signal charge may be holes, and the photoelectric conversion unit may be formed by a P-type semiconductor and an N-type semiconductor may be used to separate the P-type semiconductor.

Next, in the pixel having the above-described configuration, the operation of reading out the signal charge from the PDAs <NUM> and PDBs <NUM> after the predetermined charge accumulation period has elapsed since the PDAs <NUM> and PDBs <NUM> are reset will be described. First, when the SEL <NUM> of each of the pixels <NUM> in the row selected by the vertical selection circuit <NUM> is turned on and the source of the SF <NUM> and the output signal line <NUM> are connected, a voltage corresponding to the voltage of FD <NUM> can be read out to the output signal line <NUM>. Then, the RES <NUM> is turned on and then off, thereby the potential of the FD <NUM> is reset. After that, the process waits until the output signal line <NUM> affected by the voltage fluctuation of the FD <NUM> settles down, and the column circuit <NUM> takes the voltage of the settled output signal line <NUM> as a signal voltage N, processes it, and holds the processed signal voltage N.

After that, the TXA <NUM> is turned on and then off, thereby the signal charge stored in the PDA <NUM> is transferred to the FD <NUM>. The voltage of the FD <NUM> drops by the amount corresponding to the amount of signal charge stored in the PDA <NUM>. After that, the process waits until the output signal line <NUM> affected by the voltage fluctuation of the FD <NUM> settles down, and the column circuit <NUM> takes the voltage of the settled output signal lines <NUM> as a signal voltage A, processes it, and holds the processed signal voltage A.

After that, the TXB <NUM> is turned on and then off, thereby the signal charge stored in the PDB <NUM> is transferred to the FD <NUM>. The voltage of the FD <NUM> drops by the amount corresponding to the amount of signal charge stored in the PDB <NUM>. After that, the process waits until the output signal line <NUM> affected by the voltage fluctuation of the FD <NUM> settles down, and the column circuit <NUM> takes the voltage of the settled output signal lines <NUM> as a signal voltage (A+B), processes it, and holds the processed signal voltage (A+B).

From the difference between the signal voltage N and the signal voltage A taken in this way, a signal A corresponding to the amount of signal charge stored in the PDA <NUM> can be obtained. Further, from the difference between the signal voltage A and the signal voltage (A+B), a signal B corresponding to the amount of signal charge accumulated in the PDB <NUM> can be obtained. This difference calculation may be performed by the column circuit <NUM> or after those signals are output from the image sensor <NUM>. A phase difference signal can be obtained by using the signal A and the signal B, independently, and an imaging signal can be obtained by adding the signal A and the signal B. Alternatively, in a case where the difference calculation is performed after the signal voltages are output from the image sensor <NUM>, the imaging signal may be obtained by taking the difference between the signal voltage N and the signal voltage (A+B).

Next, with reference to <FIG>, the basic structure of the pixel <NUM> in the present embodiment will be described in detail.

<FIG> is a schematic diagram showing a basic layout of the elements constituting the pixel <NUM> according to the present embodiment. In <FIG>, the horizontal direction is the x direction, the vertical direction is the y direction, and the protruding direction is the z direction. Further, in the present embodiment, "plan view" means viewing from the z direction or the -z direction with respect to a plane (xy plane) substantially parallel to the surface of the semiconductor substrate on the side where the gates of the transistors are arranged. Further, in the present embodiment, the "horizontal" direction refers to the x direction, the "vertical" direction refers to the y direction, and the "depth" direction refers to the z direction.

In <FIG>, the same configurations as those in <FIG> are given the same reference numerals, and detailed description thereof will be omitted. In <FIG>, <NUM> denotes a microlens (ML); <NUM>, a gate electrode of the TXA <NUM>; <NUM>, a gate electrode of the TXB <NUM>; <NUM>, a gate electrode of the RES <NUM>; <NUM>, a gate electrode of the SEL <NUM>; <NUM>, a gate electrode of the SF <NUM>; and <NUM>, a voltage supply line.

The PDA <NUM> includes an accumulation region <NUM>, a sensitivity region <NUM>, and an N-type connecting region <NUM>, and the PDB <NUM> includes an accumulation region <NUM>, a sensitivity region <NUM>, and an N-type connecting region <NUM>. These accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, and N-type connecting regions <NUM> and <NUM> are made of N-type semiconductors. The sensitivity regions <NUM> and <NUM> have larger areas than the accumulation regions <NUM> and <NUM>, respectively. Further, as will be described in detail with reference to <FIG>, the accumulation regions <NUM> and <NUM> are formed at a first depth, and the sensitivity regions <NUM> and <NUM> are formed at a second depth different from the first depth. Further, for the sake of clarity, the region where the electric charge is mainly generated in response to the incident light is referred to as the "sensitivity region", and the region where the generated electric charge is mainly accumulated is referred to as the "accumulation region". However, there is no clear distinction between the charge generation region and the charge accumulation region. Charges are also generated in the accumulation regions <NUM> and <NUM> in response to the light that has arrived, and a part of the generated charges stays in the sensitivity regions <NUM> and <NUM> as well.

<FIG> are diagrams schematically showing a basic cross-sectional structure of the pixel <NUM>. <FIG> is a schematic view of an A-A' cross section of <FIG>, <FIG> is a schematic view of a B-B' cross section of <FIG>, and <FIG> is a schematic view of a C-C' cross section of <FIG>. The pixel <NUM> of the present embodiment is arranged on a semiconductor substrate <NUM>, and the semiconductor substrate <NUM> has a first surface and a second surface facing the first surface. The first surface is the front surface of the semiconductor substrate <NUM>, and the second surface is the back surface of the semiconductor substrate <NUM>. The direction from the second surface to the first surface is the positive direction in the Z direction. Transistor gate electrodes, a multilayer wiring structure, and the like are arranged on the first surface (front surface) side of the semiconductor substrate <NUM>. Further, on the second surface (back surface) side of the semiconductor substrate <NUM>, optical structures such as a color filter <NUM> and the ML <NUM> that collectively cover the two photodiodes of each pixel are arranged, and light is incident on the second surface (back surface) side.

As shown in <FIG>, in the semiconductor substrate <NUM>, a P-type semiconductor region <NUM>, and the accumulation regions <NUM> and <NUM> and sensitivity regions <NUM> and <NUM> surrounded by the P-type semiconductor region <NUM> are arranged. The accumulation region <NUM> and sensitivity region <NUM>, as well as the accumulation region <NUM> and sensitivity region <NUM> have different shapes in a plan view, and parts of their regions overlap in the plan view. Further, as described above, the accumulation regions <NUM> and <NUM> and the sensitivity regions <NUM> and <NUM> are formed at different depths, and the accumulation regions <NUM> and <NUM> are formed at a depth closer to the first surface side (first depth), and the sensitivity regions <NUM> and <NUM> are formed at a depth closer to the second surface side (second depth). Of the P-type semiconductor region <NUM>, an accumulation separation region <NUM> separates the accumulation region <NUM> and the accumulation region <NUM>, and a sensitivity separation region <NUM> separates the sensitivity region <NUM> and the sensitivity region <NUM>.

As shown in <FIG>, the accumulation region <NUM> and the sensitivity region <NUM> are connected in the depth direction via the N-type connecting region <NUM>. Further, as shown in <FIG>, the accumulation region <NUM> and the sensitivity region <NUM> are connected in the depth direction via the N-type connecting region <NUM>.

Further, in <FIG>, a region <NUM> in the accumulation region <NUM> has a shape recessed in the Z direction and filled with the P-type semiconductor, and the recessed region <NUM> suppresses the generation of charge accumulation in the region that overlaps with the N-type connecting region <NUM> in the plan view on the first surface side of the accumulation region <NUM>. As a result, when the signal charge accumulated in the accumulation region <NUM> in the PDA <NUM> is transferred to the FD <NUM>, the residue of the signal charge in the PDA <NUM> is suppressed. Note that the present invention is not limited to form the recessed region <NUM> in order to suppress the residue of the signal charge, and another method such as lowering the impurity concentration of a part of the accumulation region <NUM> may be used as long as the residue of the signal charge can be suppressed.

Further, as shown in <FIG>, the lengths of the accumulation regions <NUM> and <NUM> in the Z direction are shorter than the lengths of the accumulation regions <NUM> and <NUM> in the Z direction in the cross sections shown in <FIG>. Regions <NUM> corresponding to the length by which the accumulation regions <NUM> and <NUM> in the Z direction are shortened are filled with a P-type semiconductor. The reason for changing the length in this way will be described later in detail.

<FIG> are XY cross-sectional views of the PDA <NUM> and PDB <NUM> at different depths in the Z direction. <FIG> is a cross-sectional view taken along the line E-E' of <FIG>, <FIG> is a cross-sectional view taken along the line F-F' of <FIG>, and <FIG> is a cross-sectional view taken along the line G-G' of <FIG>, and <FIG> is a cross-sectional view taken along the line H-H' of <FIG>. As shown in <FIG>, in the partial regions of accumulation regions <NUM> and <NUM> located away from the gate electrodes <NUM> and <NUM>, as described with reference to <FIG>, the accumulation regions <NUM> and <NUM> are not formed and replaced by the notched region <NUM> of the P-type semiconductor.

<FIG> is a schematic cross-sectional view taken along the line D-D' of <FIG>. The accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, and N-type connecting regions <NUM> and <NUM> are shown in the same figure by expanding the XY plane along the line D-D' in <FIG>. When light is incident on the second surface of the semiconductor substrate <NUM> via the ML <NUM> during a charge accumulation period, electrons (signal charge) are generated mainly in the sensitivity regions <NUM> and <NUM> by photoelectric conversion. Most of the signal charge generated in the sensitivity region <NUM> moves to accumulation region <NUM> via the N-type connecting region <NUM> and is accumulated there. In addition, most of the signal charge generated in the sensitivity region <NUM> moves to the accumulation region <NUM> via the N-type connecting region <NUM> and is accumulated there. In order to realize signal charge transfer from the sensitivity region to the accumulation region, it is desirable that the potential that affects the electrons monotonically decreases on the charge transfer path from the sensitivity region to the accumulation region.

Since the accumulation regions and the sensitivity regions are arranged at different depths, it is possible to design the shapes of the accumulation regions and the sensitivity regions so as to extend in the different directions. Below, examples of arrangements of the accumulation regions and the sensitivity regions will be described with reference to <FIG>. The constituents having the same functions as the constituents shown in <FIG> and <FIG> described above are designated by the same reference numerals.

<FIG> are schematic views showing a first arrangement of the semiconductor regions according to the present embodiment. In the following description, the pixel <NUM> having the first arrangement is referred to as a pixel <NUM>.

<FIG> is an exploded perspective view of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the pixel <NUM>. In the first arrangement, all of the accumulation regions <NUM> and <NUM> and the sensitivity regions <NUM> and <NUM> extend in the y direction, that is, in the same direction.

<FIG> is a schematic plan view showing the positional relationship of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the plan view of the pixel <NUM>. In the first arrangement, since the sensitivity regions <NUM> and <NUM> where charges are generated by the photoelectric conversion are laid out in the x direction, it is possible to acquire phase difference signals whose pupil division direction is the x direction. A reference numeral <NUM> indicates the division direction of the phase difference signals.

<FIG> is a schematic plan view showing the positional relationship between the accumulation separation region <NUM> and the sensitivity separation region <NUM> in the plan view of the pixel <NUM>. In the first arrangement, both the accumulation separation region <NUM> and the sensitivity separation region <NUM> extend in the y direction.

<FIG> are schematic views showing a second arrangement of the semiconductor regions according to the present embodiment. In the following description, the pixel <NUM> having the second arrangement is referred to as a pixel <NUM>.

<FIG> is an exploded perspective view of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the pixel <NUM>. In the second arrangement, the accumulation regions <NUM> and <NUM> extend in the y direction and the sensitivity regions <NUM> and <NUM> extend in the x direction which is orthogonal to the y direction, that is, in the different direction.

<FIG> is a schematic plan view showing the positional relationship of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the plan view of the pixel <NUM>. In the second arrangement, since the sensitivity regions <NUM> and <NUM> where charges are generated by the photoelectric conversion are laid out in the y direction, it is possible to acquire phase difference signals whose pupil division direction is the y direction. A reference numeral <NUM> indicates the division direction of the phase difference signals.

<FIG> is a schematic plan view showing the positional relationship between the accumulation separation region <NUM> and the sensitivity separation region <NUM> in the plan view of the pixel <NUM>. In the second arrangement, the accumulation separation region <NUM> extends in the y direction, and the sensitivity separation region <NUM> extends in the x direction.

As described above, when the extending direction of the sensitivity regions <NUM> and <NUM> and the extending direction of the accumulation regions <NUM> and <NUM> are orthogonal to each other, the sensitivity separation region <NUM> overlaps with the accumulation regions <NUM> and <NUM> in a plan view. In the regions of the accumulation region <NUM> and the accumulation region <NUM> that overlap with the sensitivity separation region <NUM> in a plan view, the N-type concentration becomes thin due to the influence of injection of P-type impurities for forming the sensitivity separation region <NUM>. Therefore, by shortening the thickness of the accumulation regions <NUM> and <NUM> in the Z direction at locations away from the gate electrode <NUM> of TXA <NUM> and the gate electrode <NUM> of TXB <NUM>, the residue of the signal charge in the regions where the N-type concentration becomes low is suppressed. However, as long as the residue of the signal charge can be suppressed, another method such as lowering the concentration of impurities in parts of the accumulation regions <NUM> and <NUM> may be used.

<FIG> are schematic views showing a third arrangement of the semiconductor regions according to the present embodiment. In the following description, the pixel <NUM> having the third arrangement is referred to as a pixel <NUM>. In the third arrangement, the position of the recessed region <NUM> and the positions of the N-type connecting regions <NUM> and <NUM> are different from those of the first arrangement shown in <FIG>.

<FIG> is an exploded perspective view of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the pixel <NUM>. In the third arrangement, all of the accumulation regions <NUM> and <NUM> and the sensitivity regions <NUM> and <NUM> extend in the same direction (y direction) similarly to the first arrangement.

<FIG> is a schematic plan view showing the positional relationship of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the plan view of the pixel <NUM>. In the third arrangement, similarly to the first arrangement, since the sensitivity regions <NUM> and <NUM> are laid out in the x direction, it is possible to acquire phase difference signals whose pupil division direction is the x direction. A reference numeral <NUM> indicates the division direction of the phase difference signals.

<FIG> is a schematic plan view showing the positional relationship between the accumulation separation region <NUM> and the sensitivity separation region <NUM> in the plan view of the pixel <NUM>. In the third arrangement, similarly to the first arrangement, both the accumulation separation region <NUM> and the sensitivity separation region <NUM> extend in the y direction.

<FIG> are schematic views showing a fourth arrangement of the semiconductor regions according to the present embodiment. In the following description, the pixel <NUM> having the fourth arrangement is referred to as a pixel <NUM>. In the fourth arrangement, the position of the recessed region <NUM> and the positions of the N-type connecting regions <NUM> and <NUM> are different from those of the second arrangement shown in <FIG>, which causes different connection between the accumulation regions <NUM> and <NUM>, and the sensitivity regions <NUM> and <NUM>.

<FIG> is an exploded perspective view of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the pixel <NUM>. In the fourth arrangement, the accumulation regions <NUM> and <NUM> extend in the y direction and the sensitivity regions <NUM> and <NUM> extend in the x direction which is orthogonal to the y direction in the plan view.

<FIG> is a schematic plan view showing the positional relationship of the accumulation regions <NUM> and <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, and FD <NUM> in the plan view of the pixel <NUM>. In the fourth arrangement, since the sensitivity regions <NUM> and <NUM> where charges are generated by the photoelectric conversion are laid out in the y direction, it is possible to acquire phase difference signals whose pupil division direction is the y direction. A reference numeral <NUM> indicates the division direction of the phase difference signals.

<FIG> is a schematic plan view showing the positional relationship between the accumulation separation region <NUM> and the sensitivity separation region <NUM> in the plan view of the pixel <NUM>. In the fourth arrangement, the accumulation separation region <NUM> extends in the y direction, and the sensitivity separation region <NUM> extends in the x direction.

In the fourth arrangement, too, in the regions of the accumulation region <NUM> and the accumulation region <NUM> that overlap with the sensitivity separation region <NUM> in a plan view, the N-type concentration becomes thin due to the influence of injection of P-type impurities for forming the sensitivity separation region <NUM>. Therefore, by shortening the thickness of the accumulation regions <NUM> and <NUM> in the Z direction at locations away from the gate electrode <NUM> of TXA <NUM> and the gate electrode <NUM> of TXB <NUM>, the residue of the signal charge in the regions where the N-type concentration becomes low is suppressed. However, as long as the residue of the signal charge can be suppressed, another method such as lowering the concentration of impurities in parts of the accumulation regions <NUM> and <NUM> may be used.

As shown in <FIG>, in the first to fourth arrangements, the arrangements of the accumulation regions <NUM> and <NUM>, the gate electrode <NUM> of TXA <NUM>, the gate electrode <NUM> of TXB <NUM>, and the FD <NUM> are the same. Therefore, it is possible to make the layout of the RES <NUM>, SF <NUM>, SEL <NUM> and metal wiring the same in the first to fourth arrangements. As a result, the capacitance of the FD <NUM> can be made the same for all pixels, and a gain for converting the signal charge transferred to the FD <NUM> to the voltage and a gain for reading out the voltage of the SF <NUM> can be set equal for all pixels.

Next, an example of pixel layout of the pixels <NUM>, <NUM>, <NUM>, <NUM> having the above configurations will be described.

<FIG> is a schematic diagram showing the pixel layout of the pixel array <NUM> in the range of <NUM> rows × <NUM> columns. By laying out a large number of sets of pixels of <NUM> rows × <NUM> columns shown in <FIG> on a plane, the imaging signal and the phase difference signals can be acquired. In <FIG>, the ML <NUM>, sensitivity regions <NUM> and <NUM>, N-type connecting regions <NUM> and <NUM>, gate electrode <NUM> of the TXA <NUM>, gate electrode <NUM> of the TXB <NUM>, FD <NUM>, division directions of phase difference signals, and color filter <NUM> are shown.

A color filter (CFR) <NUM> having an R (red) spectral transmission characteristic, a color filter (CFG) <NUM> having a G (green) spectral transmission characteristic, and a color filter <NUM> having a B (blue) spectral transmission characteristic are used as the color filters <NUM>. These color filters <NUM> are arranged in a Bayer array. Further, in the example shown in <FIG>, pixels are arranged in the order of pixel <NUM>, pixel <NUM>, pixel <NUM>, and pixel <NUM> from the top to the bottom of the right column. Further, pixels are arranged in the order of pixel <NUM>, pixel <NUM>, pixel <NUM>, and pixel <NUM> from the top to the bottom of the left column.

By using the phase difference signals acquired from the pixels <NUM> and the pixels <NUM>, it is possible to acquire the phase difference signals whose pupil division direction is the x direction. Further, by using the phase difference signal acquired from the pixel <NUM> and the pixel <NUM>, it is possible to acquire the phase difference signals whose pupil division direction is the y direction. Phase difference signals whose pupil division direction is the x direction is more effective in a case where the contrast in the x direction is high, such as when the subject has a pattern close to a vertical stripe pattern. On the other hand, the phase difference signals whose pupil division direction is the y direction is more effective in a case where the contrast in the y direction is high, such as when the subject has a pattern close to a horizontal stripe pattern.

The accumulation regions of the pixels arranged as described above are divided into type <NUM> and type <NUM>. In the type <NUM>, the accumulation region is adjacent to both the recessed region <NUM> and the notched region <NUM> of the P-type semiconductor (accumulation region <NUM> of the pixel <NUM>, accumulation region <NUM> of the pixel <NUM>, accumulation region <NUM> of the pixel <NUM>, and accumulation region <NUM> of the pixel <NUM>). In the type <NUM>, the accumulation region is adjacent only to the notched region <NUM> of the P-type semiconductor (accumulation region <NUM> of the pixel <NUM>, accumulation region <NUM> of the pixel <NUM>, accumulation region <NUM> of the pixel <NUM>, accumulation region <NUM> of the pixel <NUM>). Since the volume of the N-type region of the accumulation region in the type <NUM> is smaller than that of the accumulation region in the type <NUM>, the amount of signal charge that can be stored in the accumulation region in the type <NUM> may be smaller.

Since the imaging signal is a signal obtained by adding the signal A and the signal B, the saturation charge amount of the imaging signal is uniform in all the pixels. On the other hand, since the phase difference signals use the signal A and the signal B independently, the saturation charge amounts of the phase difference signals are different between the first arrangement and the second arrangement, and between the third arrangement and the fourth arrangement. In consideration of the above feature, a large number of sets of the pixels arranged as shown in <FIG> are arranged on a plane to form the pixel array <NUM>, and by performing signal processing such as averaging or using only the signals of specific pixels in accordance with the arrangement of the pixels, the saturated charge amounts of the phase difference signals obtained in the entire region of the pixel array <NUM> can be made uniform.

For example, if the intensity distribution of the phase difference signals obtained only from the pixels <NUM> and the intensity distribution of the phase difference signals obtained only from the pixels <NUM> have shapes significantly different from each other, there is a high possibility that the phase difference signals of the either of the pixels <NUM> and <NUM> will be saturated. In such a case, of the phase difference signals only from the pixels <NUM> and the phase difference signals only from the pixels <NUM>, it is conceivable that the phase difference signals having a smaller signal intensity difference between the signal A and the signal B will include a saturated phase difference signal. Accordingly, the focus detection is performed using the phase difference signals from the pixels <NUM> or <NUM> having the larger signal intensity difference between the signal A and the signal B. By doing so, the phase difference signals from the pixels having a larger saturation charge amount can be used, and thereby it is possible to make the saturation charge amounts of the phase difference signals to be used uniform in the entire region of the pixel array.

Further, by arranging the pixels as in the present embodiment, even in cases where the mutual relationship between the accumulation regions <NUM> and <NUM>, the N-type connecting regions <NUM> and <NUM>, and the P-type regions <NUM> and <NUM> varies due to the alignment variation at the time of manufacturing and the amounts of charge that can be accumulated in accumulation regions <NUM> and <NUM> deviate from the designed structure, the saturated charge amounts of the phase difference signals can be made uniform by performing signal processing such as averaging or using only specific signals according to the arrangement of the semiconductor regions in each pixel.

As described above, according to the first embodiment, it is possible to make the capacitances of the FD and the saturated charge amounts uniform while making the pupil division directions to two, so that it is possible to acquire image data that does not require interpolation processing.

Next, a modification of the first embodiment will be described. The constituents having the same functions as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified as appropriate. In this modification, another example of pixel layout will be described.

<FIG> is a schematic view showing the pixel array <NUM> in the modification of the first embodiment, and a partial pixel array <NUM> on the left side and a partial pixel array <NUM> on the right side with respect to the center in the x direction in <FIG> have different pixel layouts.

<FIG> is a schematic diagram showing the pixel layout of the partial pixel array <NUM> in the range of <NUM> rows × <NUM> columns, and the partial pixel array <NUM> is configured by laying out a large number of sets of the pixels of the <NUM> rows × <NUM> columns shown in <FIG> on a plane. The color filter arrangement is CFG <NUM> and CFB <NUM> from the top to the bottom in the right column, and CFR <NUM> and CFG <NUM> from the top to the bottom in the left column. The arrangement of the semiconductor regions is shown by the pixel <NUM> and pixel <NUM> from the top to the bottom in the right column, and the pixel <NUM> and pixel <NUM> from the top to the bottom in the left column.

<FIG> is a schematic diagram showing the pixel layout of the partial pixel array <NUM> in the range of <NUM> rows × <NUM> columns, and the partial pixel array <NUM> is configured by arranging a large number of sets of the pixels of the <NUM> rows × <NUM> columns shown in <FIG> on a plane. The color filter arrangement is CFG <NUM> and CFB <NUM> from the top to the bottom in the right column, and CFR <NUM> and CFG <NUM> from the top to the bottom in the left column. The arrangement of the semiconductor region is shown by the pixel <NUM> and pixel <NUM> from the top to the bottom in the right column, and the pixel <NUM> and pixel <NUM> from the top to the bottom in the left column.

In the partial pixel array <NUM>, when detecting the phase difference in the x direction, the phase difference signals acquired from the pixels <NUM> are used. In the pixel <NUM>, the sensitivity region connected to the type <NUM> accumulation region, which has a larger saturation charge amount than the type <NUM> accumulation region, is arranged on the side in the pixel where the x-coordinate is relatively small. On the other hand, in the partial pixel array <NUM>, when performing the phase difference detection in the x direction, the phase difference signals acquired from the pixels <NUM> are used. In the pixel <NUM>, the sensitivity region connected to the type <NUM> accumulation region is arranged on the side in the pixel where the x-coordinate is relatively large. By laying out pixels in this way, the saturation charge amount of the phase difference signals can be increased in each pixel in a case where a larger amount of light is incident on the side away from the center of the pixel array.

In this modification, the microlens is optically designed to be formed by eccentricity toward the intersection of the pixel array and the optical axis according to the distance from the intersection, so that the center of pupil division intersects the optical axis at a fixed distance from the pixel array for all the pixels. This distance will be called a sensor pupil distance below. In a case where the exit pupil distance of the imaging lens is shorter than the sensor pupil distance, more light is incident on the side of each pixel far from the intersection with the optical axis than on the side of each pixel closer to the intersection. In this modification, since the sensitivity region connected to the accumulation region having a larger saturation charge amount is arranged on the side in each pixel far from the optical axis, the saturation charge amounts of the phase difference signals become large.

Thus, by adopting the pixel array layout as in the modification of the first embodiment, the saturation charge amount of the phase difference signal can be increased according to the relationship between the sensor pupil distance and the exit pupil distance of the imaging lens.

In the second embodiment, a configuration in which a pixel signal reading circuit constituted with the FD <NUM> and its subsequent elements is shared by two pixels will be described. The constituents having the same functions as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted or simplified.

<FIG> is an equivalent circuit diagram of two pixels in the second embodiment. In order to distinguish the photodiodes of the two pixels, the pixel on the upper side of the drawing is referred to as a pixel 105U and the two photodiodes of the pixel 105U are hereinafter referred to as PD1A <NUM> and PD1B <NUM>. Further, the pixel on the lower side of the drawing is referred to as a pixel 105D and the two photodiodes of the pixel 105D are referred to as PD2A <NUM> and PD2B <NUM>.

PD1A <NUM> and PD1B <NUM> share one microlens <NUM>, and PD2A <NUM> and PD2B <NUM> share one microlens. The two pixels, namely, the pixel 105U and the pixel 105D, share the pixel signal reading circuit constituted with FD <NUM>, RES <NUM>, SEL <NUM>, and SF <NUM>.

The signal charge obtained by photoelectric conversion according to the amount of incident light by the PD1A <NUM> and accumulated in the PD1A <NUM> is transferred to the FD <NUM> via a transfer switch (TX1A) <NUM>. Further, the signal charge obtained by photoelectric conversion and accumulated in the PD1B <NUM> is transferred to the FD <NUM> via a transfer switch (TX1B) <NUM>. Similarly, the signal charge obtained by photoelectric conversion and accumulated in the PD2A <NUM> is transferred to the FD <NUM> via a transfer switch (TX2A) <NUM>, and the signal charge obtained by photoelectric conversion and accumulated in the PD2B <NUM> is transferred to the FD <NUM> via a transfer switch (TX2B) <NUM>.

<FIG> are schematic views showing a fifth arrangement of the semiconductor regions of the two pixels according to the second embodiment. In the following description, the two pixels 105U and 105D having the fifth arrangement are referred to as a pixel set <NUM>.

<FIG> is an exploded perspective view of accumulation regions <NUM>, <NUM>, <NUM> and <NUM>, sensitivity regions <NUM>, <NUM>, <NUM> and <NUM>, N-type connecting regions <NUM>, <NUM>, <NUM> and <NUM>, gate electrode <NUM> of the TX1A <NUM>, gate electrode <NUM> of the TX1B <NUM>, gate electrode <NUM> of the TX2A <NUM>, gate electrode <NUM> of the TX2B <NUM>, and FD <NUM> in the pixel set <NUM>.

The PD1A <NUM> shown in <FIG> is composed of the accumulation region <NUM>, sensitivity region <NUM>, and N-type connecting region <NUM>, and the PD1B <NUM> is composed of the accumulation region <NUM>, sensitivity region <NUM>, and N-type connecting region <NUM>. The PD2A <NUM> is composed of the accumulation region <NUM>, sensitivity region <NUM>, and N-type connecting region <NUM>, and the PD2B <NUM> is composed of the accumulation region <NUM>, sensitivity region <NUM>, and N-type connecting region <NUM>. The PD1A <NUM> and PD1B <NUM> constituting the pixel 105U are arranged on the side having a relatively large y coordinate with respect to the FD <NUM>, and the PD2A <NUM> and PD2B <NUM> constituting the pixel 105D are arranged on the side have a relatively small y coordinate with respect to the FD <NUM>.

<FIG> is a schematic plan view showing the positional relationship of the accumulation regions <NUM>, <NUM>, <NUM> and <NUM>, sensitivity regions <NUM>, <NUM>, <NUM> and <NUM>, N-type connecting regions <NUM>, <NUM>, <NUM> and <NUM>, gate electrode <NUM> of the TX1A <NUM>, gate electrode <NUM> of the TX1B <NUM>, gate electrode <NUM> of the TX2A <NUM>, gate electrode <NUM> of the TX2B <NUM>, and FD <NUM> in the plan view of the pixel set <NUM>. Since all of the sensitivity regions <NUM> and <NUM> of the pixel 105U and the sensitivity regions <NUM> and <NUM> of the pixel 105D extend in the y direction, it is possible to acquire phase difference signals whose pupil division direction is the x direction from both of the pixels 105U and 105D. Arrows <NUM> indicate the division direction of the phase difference signals.

<FIG> are schematic views showing a sixth arrangement of the semiconductor regions of the two pixels according to the second embodiment. In the following description, the two pixels 105U and 105D having the sixth arrangement are referred to as a pixel set <NUM>.

<FIG> is an exploded perspective view of the accumulation regions <NUM>, <NUM>, <NUM> and <NUM>, sensitivity regions <NUM>, <NUM>, <NUM> and <NUM>, N-type connecting regions <NUM>, <NUM>, <NUM> and <NUM>, gate electrode <NUM> of the TX1A <NUM>, gate electrode <NUM> of the TX1B <NUM>, gate electrode <NUM> of the TX2A <NUM>, gate electrode <NUM> of the TX2B <NUM>, and FD <NUM> in the pixel set <NUM>. Further, <FIG> is a schematic plan view showing the positional relationship of constituents of the pixel set <NUM> in the plan view.

The pixel set <NUM> has the same configuration as that of the pixel set <NUM> except for the extending directions of the sensitivity regions <NUM> and <NUM> of the pixel 105D are different. Similarly to the pixel set <NUM>, the pixel 105U has the sensitivity regions <NUM> and <NUM> extending in the y direction, and can acquire phase difference signals whose pupil division direction is the x direction. On the other hand, in the pixel 105D, since the sensitivity regions <NUM> and <NUM> extend in the x direction, it is possible to acquire phase difference signals whose pupil division direction is the y direction. Arrows <NUM> and <NUM> indicate the division directions of the phase difference signals.

<FIG> are schematic views showing a seventh arrangement of the semiconductor regions of two pixels according to the second embodiment. In the following description, two pixels 105U and 105D having the seventh arrangement are referred to as a pixel set <NUM>.

The pixel set <NUM> has the same configuration as that of the pixel set <NUM> except for the extending directions of the sensitivity regions <NUM> and <NUM> of the pixel 105U are different. Similarly to the pixel set <NUM>, the pixel 105D has the sensitivity regions <NUM> and <NUM> extending in the y direction, and can acquire phase difference signals whose pupil division direction is the x direction. On the other hand, in the pixel 105U, since the sensitivity regions <NUM> and <NUM> extend in the x direction, it is possible to acquire phase difference signals whose pupil division direction is the y direction. Arrows <NUM> and <NUM> indicate the division directions of the phase difference signals.

Next, an example of pixel arrangement of the pixels <NUM>, <NUM> and <NUM> having the above configurations will be described.

<FIG> is a schematic diagram showing the pixel layout of the pixel array <NUM> in the range of <NUM> rows × <NUM> columns in the second embodiment. By laying out a large number of sets of pixels of <NUM> rows × <NUM> columns shown in <FIG> on a plane, the imaging signal and the phase difference signals can be acquired. In <FIG>, the ML <NUM>, sensitivity regions <NUM>, <NUM>, <NUM> and <NUM>, N-type connecting regions <NUM>, <NUM>, <NUM> and <NUM>, gate electrodes <NUM>, <NUM>, <NUM> and <NUM>, FD <NUM>, division directions of phase difference signals, and color filter <NUM> are shown. As the color filter <NUM>, CFR <NUM>, CFG <NUM> and CFB <NUM>, arranged in a Bayer array, are shown.

Further, in the example shown in <FIG>, the pixel sets <NUM> are laid out in the first column from the left, the pixel sets <NUM> are laid out in the second column, the pixel sets <NUM> are laid out in the third column, and the pixel sets <NUM> are laid out in the fourth column. Further, in the third and fourth columns, the pixel sets are laid out so as to be shifted by one pixel in the y direction with respect to the pixel sets in the first and second rows.

By laying out the pixel sets in this way, phase difference signals whose pupil division direction is the x direction can be acquired from pixels covered from the CFR <NUM> (R pixels), pixels covered by the CFB <NUM> (B pixels), and pixels covered by the CFG <NUM> (Gr pixels) which are laid out in the same row as the pixels covered by the CFR <NUM>. Further, from the pixels (Gb pixels) covered by the CFG <NUM> laid out in the same row as the pixels covered by the CFB <NUM> (B pixels), the phase difference signals whose pupil division direction is the y direction can be acquired.

Here, the characteristics of the Gb pixels laid out in the first column and the Gb pixels laid out in the third column will be described.

The Gb pixels laid out in the first column are the pixels 105D of the pixel sets <NUM>, and charge converted from the light incident on the sensitivity regions <NUM> having a larger y coordinate is accumulated in the accumulation regions <NUM> and charge converted from the light incident on the sensitivity regions <NUM> having a smaller y coordinate is accumulated in the accumulation regions <NUM>. Here, the accumulation region <NUM> in the pixel set <NUM> is type <NUM> and adjacent to both the recessed region <NUM> and the notched region <NUM> of the P-type semiconductor, and the accumulation region <NUM> is type <NUM> and adjacent only to the notched region <NUM> of the P-type semiconductor.

The Gb pixels laid out in the third column are the pixels 105U of the pixel sets <NUM>, and charge converted from the light incident on the sensitivity regions <NUM> having a larger y coordinate is accumulated in the accumulation regions <NUM> and charge converted from the light incident on the sensitivity regions <NUM> having a smaller y coordinate is accumulated in the accumulation regions <NUM>. Here, the accumulation region <NUM> in the pixel set <NUM> is type <NUM>, and the accumulation region <NUM> is type <NUM>.

Since the volume of the N-type region of the accumulation region of type <NUM> is smaller than that of the accumulation region of type <NUM>, the amount of signal charge that can be stored in the accumulation region of type <NUM> may be smaller. That is, in the Gb pixels laid out in the first column, the saturation charge amounts of the sensitivity regions whose y coordinates are smaller are larger than the saturation charge amounts of the sensitivity regions whose y coordinates are larger. On the other hand, in the Gb pixels laid out in the third column, the saturation charge amounts of the sensitivity regions whose y coordinates are larger are larger than the saturation charge amounts of the sensitivity regions whose y coordinates are smaller.

Therefore, as shown in <FIG>, by alternately laying out the Gb pixels (first column) in which saturation charge amounts of the sensitivity regions whose y coordinates are smaller are larger than the sensitivity regions whose y coordinates are larger, and the Gb pixels (third column) in which saturation charge amounts of the sensitivity regions whose y coordinates are larger are larger than the sensitivity regions whose y coordinates are smaller every two columns, it is possible to acquire non-saturated signals both in a case where a larger amount of light is incident on the sensitivity regions whose y coordinates are larger than the other sensitivity regions in the Gb pixels and in a case where a larger amount of light is incident on the sensitivity regions whose y coordinates are smaller than the other sensitivity regions in the Gb pixels. That is, the saturation charge amounts of the phase difference signals from the pupil division pixels divided in the vertical direction can be made even.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained even with the configuration in which the readout circuit is shared by two pixels.

Next, a third embodiment of the present invention will be described.

<FIG> is a block diagram showing a schematic configuration of an image capturing apparatus according to the third embodiment of the present invention. The image capturing apparatus of the present embodiment includes an image sensor <NUM> having the configuration as described above, an overall control/arithmetic unit <NUM>, an instruction unit <NUM>, a timing generation unit <NUM>, an imaging lens unit <NUM>, a lens drive unit <NUM>, a signal processing unit <NUM>, a display unit <NUM> and a recording unit <NUM>.

The imaging lens unit <NUM> forms an optical image of a subject on the image sensor <NUM>. Although it is represented by one lens in the figure, the imaging lens unit <NUM> may include a plurality of lenses including a focus lens, a zoom lens, and a diaphragm, and may be detachable from the main body of the image capturing apparatus or may be integrally configured with the main body.

The image sensor <NUM> has the configuration as described in the above embodiments, and converts the light incident through the imaging lens unit <NUM> into an electric signal and outputs it. Signals are read out from each pixel of the image sensor <NUM> so that pupil division signals that can be used in phase difference focus detection and an imaging signal that is a signal of each pixel can be acquired.

The signal processing unit <NUM> performs predetermined signal processing such as correction processing on the signals output from the image sensor <NUM>, and outputs the pupil division signals used for focus detection and the imaging signal used for recording.

The overall control/arithmetic unit <NUM> comprehensively drives and controls the entire image capturing apparatus. In addition, the overall control/arithmetic unit <NUM> also performs calculations for focus detection using the pupil division signals processed by signal processing unit <NUM>, and performs arithmetic processing for exposure control, and predetermined signal processing, such as development for generating images for recording/playback and compression, on the image signal.

The lens drive unit <NUM> drives the imaging lens unit <NUM>, and performs focus control, zoom control, aperture control, and the like on the imaging lens unit <NUM> according to control signals from the overall control/arithmetic unit <NUM>.

The instruction unit <NUM> accepts inputs such as shooting execution instructions, drive mode settings for the image capturing apparatus, and other various settings and selections that are input from the outside by the operation of the user, for example, and sends them to the overall control/arithmetic unit <NUM>.

The timing generation unit <NUM> generates a timing signal for driving the image sensor <NUM> and the signal processing unit <NUM> according to a control signal from the overall control/arithmetic unit <NUM>.

The display unit <NUM> displays a preview image, a playback image, and information such as the drive mode settings of the image capturing apparatus.

The recording unit <NUM> is provided with a recording medium (not shown), and an imaging signal for recording is recorded. Examples of the recording medium include semiconductor memories such as flash memory. The recording medium may be detachable from the recording unit <NUM> or may be built-in.

Next, an arithmetic method for calculating a defocus amount from the pupil division signals in the overall control/arithmetic unit <NUM> will be described.

First, the phase difference focus detection in the x direction in the present embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view of the pixel <NUM> or pixel <NUM> taken along the line A-A' shown in <FIG> whose pupil division direction is the x direction, and a pupil plane at the position separated from an imaging plane <NUM> of the image sensor <NUM> by a distance Ds in the negative direction of the z-axis. In <FIG>, x, y, and z indicate the coordinate axes on the imaging plane <NUM>, and xp, yp, and zp indicate the coordinate axes on the pupil plane.

The pupil plane and the light receiving surface (second surface) of the image sensor <NUM> have substantially conjugated relationship via the ML <NUM>. Therefore, the luminous flux that has passed through a partial pupil region <NUM> is received in the sensitivity region <NUM> or the accumulation region <NUM>. Further, the luminous flux that has passed through a partial pupil region <NUM> is received in the sensitivity region <NUM> or the accumulation region <NUM>. The signal charge photoelectrically converted near the boundary between the sensitivity region <NUM> and the sensitivity region <NUM> is stochastically transported to the accumulation region <NUM> or the accumulation region <NUM>. Therefore, at the boundary between the partial pupil region <NUM> and the partial pupil region <NUM>, the signals are gradually switched as the x coordinate becomes larger, and the x direction dependencies of the pupil intensity distributions have shapes as illustrated in <FIG>. Hereinafter, the pupil intensity distribution corresponding to the sensitivity region <NUM> and the accumulation region <NUM> is referred to as a first pupil intensity distribution <NUM>, and the pupil intensity distribution corresponding to the sensitivity region <NUM> and the accumulation region <NUM> is referred to as a second pupil intensity distribution <NUM>.

Next, with reference to <FIG>, a sensor entrance pupil of the image sensor <NUM> will be described. In the image sensor <NUM> of the present embodiment, the MLs <NUM> of respective pixels are continuously shifted toward the center of the image sensor <NUM> depending on the image height coordinates of the pixels on the two-dimensional plane. That is, each ML <NUM> is arranged so as to be more eccentric toward the center as the image height of the pixel becomes higher. The center of the image sensor <NUM> and the optical axis of the imaging optical system change depending on the mechanism that reduces the influence of blurring due to camera shake or the like by driving the imaging optical system or the image sensor <NUM>, but they are substantially the same. As a result, in the pupil plane located at a distance Ds from the image sensor <NUM>, the first pupil intensity distribution <NUM> and the second pupil intensity distribution <NUM> of each pixel <NUM> or pixel <NUM> arranged at each image height coordinate of the image sensor <NUM> substantially match. That is, in the pupil plane located at the distance Ds from the image sensor <NUM>, the first pupil intensity distribution <NUM> and the second pupil intensity distribution <NUM> of all the pixels of the image sensor <NUM> substantially match.

Hereinafter, the first pupil intensity distribution <NUM> and the second pupil intensity distribution <NUM> are referred to as the "sensor entrance pupil" of the image sensor <NUM>, and the distance Ds is referred to as the "sensor pupil distance" of the image sensor <NUM>. It is not necessary to configure all the pixels to have the same sensor pupil distance. For example, the sensor pupil distances of pixels up to <NUM>% of the image height may be substantially the same, or pixels may be configured to have different sensor pupil distances by each row or by each detection area.

<FIG> shows a schematic relationship diagram between an image shift amount and a defocus amount between parallax images. The image sensor <NUM> (not shown) of the present embodiment is aligned on the imaging plane <NUM>, and the exit pupil of the imaging optical system is divided into the partial pupil region <NUM> and the partial pupil region <NUM> as in <FIG>.

For a defocus amount d, the distance from the imaging position of the subject to the imaging plane is given by | d |, the front focused state in which the imaging position of the subject is closer to the subject than the imaging plane is expressed by negative (d < <NUM>), and the rear focused state in which the imaging position of the subject is on the opposite side of the subject with respect to the imaging plane is expressed by positive (d > <NUM>). The in-focus state in which the imaging position of the subject is on the imaging plane is expressed as d = <NUM>. <FIG> shows an example in which a subject on an object plane <NUM> is in the in-focus state (d = <NUM>) and a subject on an object plane <NUM> is in the front focused state (d < <NUM>). The front focused state (d < <NUM>) and the rear focused state (d > <NUM>) are both referred to as a defocus state (| d | > <NUM>).

In the front focused state (d <<NUM>), among the luminous fluxes from the subject on the object plane <NUM>, the luminous flux that has passed through the partial pupil region <NUM> (<NUM>) converges once and then diverges to have the radius Γ1 (Γ2) about the position G1 (G2) as the center of gravity of the luminous flux, and formed as a blurred image on the imaging plane <NUM>. The blurred image is received by the sensitivity region <NUM> and the accumulation region <NUM>, and the sensitivity region <NUM> and the accumulation region <NUM>, and parallax images are generated. Therefore, the generated parallax images are blurred images of the subject with the images of the subject on the object plane <NUM> is spread to have the radius Γ1 (Γ2) about the position G1 (G2) of the center of gravity.

The radius Γ1 (Γ2) of blur of the subject image generally increases proportionally as the magnitude | d | of the defocus amount d increases. Similarly, the magnitude | p <NUM> of an image shift amount p (= G2-G1) between the subject images of the parallax images also increases approximately proportionally as the magnitude | d | of the defocus amount d increases. The same relationship is held in the rear focused state (d> <NUM>), although the image shift direction of the subject images between the parallax images is opposite to that in the front focused state. In the in-focus state (d = <NUM>), the positions of the centers of gravity of the subject images in the parallax images are the same (p = <NUM>), and no image shift occurs.

Therefore, with regard to the two phase difference signals obtained by using the signals from the sensitivity region <NUM> and accumulation region <NUM>, and the signals from the sensitivity region <NUM> and accumulation region <NUM>, as the magnitude of the defocus amount of the parallax images increases, the magnitude of the image shift amount between the two phase difference signals in the x direction increases. Based on this relationship, the phase difference focus detection is performed by converting the image shift amount calculated by performing correlation operation on the image shift amount between the parallax images in the x-direction into the defocus amount. A conversion coefficient used at this time is referred to as a conversion coefficient Kx.

Next, the relationship between the conversion coefficient Kx and shift of pupil will be described. <FIG> show relationships between the partial pupil regions <NUM> and <NUM> in the pixels <NUM> or <NUM> located at a peripheral image height (R, <NUM>) of the image sensor <NUM> and the exit pupil <NUM> of the imaging optical system. Further, <FIG> show relationships of x-direction dependency between the exit pupil and the pupil intensity distribution. Of the x-direction dependency of the pupil intensity distribution, the region inside the exit pupil is shown by solid lines, and the region outside the exit pupil is shown by broken lines. The position (R, <NUM>) of the pixel <NUM> or the pixel <NUM> in the pixel array is a position shifted in the x-plus direction from the center of the optical axis, as shown in <FIG>.

<FIG> shows a case where an exit pupil distance D1 of the imaging optical system and the sensor pupil distance Ds of the image sensor <NUM> are the same. In this case, the pupil is divided into the first partial pupil region <NUM> and the second partial pupil region <NUM> near the center of an exit pupil <NUM> of the imaging optical system. In this case, the range of light flux to be received spreads to the same extent in the plus and minus directions from the x coordinate where the signal intensities of the first pupil intensity distribution <NUM> and the second pupil intensity distribution <NUM> intersect. As a result, the relationship between the pupil intensity distribution and the exit pupil is as shown in <FIG>.

On the other hand, as shown in <FIG>, when the exit pupil distance Dl of the imaging optical system is shorter than the sensor pupil distance Ds of the image sensor <NUM>, the pupil deviation occurs between the exit pupil of the imaging optical system and the entrance pupil of the sensor <NUM> at the peripheral image height of the image sensor <NUM>, and as a result, the exit pupil <NUM> of the imaging optical system is unevenly divided, and the relationship between the pupil intensity distribution and the exit pupil is as shown in <FIG>.

Similarly, as shown in <FIG>, when the exit pupil distance Dl of the imaging optical system is longer than the sensor pupil distance Ds of the image sensor <NUM>, the pupil deviation occurs between the exit pupil of the imaging optical system and the entrance pupil of the sensor <NUM> at the peripheral image height of the image sensor <NUM>, and as a result, the exit pupil <NUM> of the imaging optical system is unevenly divided, and the relationship between the pupil intensity distribution and the exit pupil is as shown in <FIG>.

As shown in <FIG>, the region of the pupil intensity distribution included in the exit pupil differs depending on the exit pupil distance D1. Therefore, the conversion coefficient Kx, which represents the relationship between the magnitude of the defocus amount and the magnitude of the image shift amount in the x direction between the phase difference signals, has different values depending on the exit pupil distance and the image height.

Next, with reference to <FIG>, the phase difference focus detection in a case where the pupil division direction is the y direction will be described. The description of the part which is the same as that of the phase difference focus detection in the x direction will be omitted, and the difference will be explained. In the phase difference focus detection in the y direction, the image shift amount in the y direction is calculated from the phase difference signals of the pixels <NUM> or pixels <NUM> whose pupil division direction is the y direction, and the image shift amount is converted into a defocus amount using a conversion coefficient Ky.

<FIG> shows a cross-sectional view of the pixel <NUM> or <NUM> in which the pupil division direction of the sensitivity region is the y direction, and a pupil plane at a position separated by the sensor pupil distance Ds in the negative z-axis direction from the imaging plane <NUM> of the image sensor <NUM>. In <FIG>, x, y, and z indicate the coordinate axes on the imaging plane <NUM>, and xp, yp, and zp indicate the coordinate axes on the pupil plane.

The pupil plane and the light receiving surface (second surface) of the image sensor <NUM> have a substantially conjugated relationship via the ML <NUM>. Therefore, the luminous flux that has passed through a partial pupil region <NUM> is received in the sensitivity region <NUM>, and the luminous flux that has passed through a partial pupil region <NUM> is received in the sensitivity region <NUM>. Further, the luminous flux that has passed through a partial pupil region <NUM> is received in the accumulation region <NUM>, and the luminous flux that has passed through a partial pupil region <NUM> is received in the accumulation region <NUM>. The proportion of the luminous flux received in the sensitivity regions <NUM> and <NUM> and the proportion of the luminous flux received in the accumulation regions <NUM> and <NUM> are determined mostly by the wavelength of the received light.

Next, the relationship between shift of pupil and the conversion coefficient Ky which represents the relationship between the image shift amount between parallax images at the time of detecting phase difference in the y direction and the defocus amount will be described. <FIG> show relationships between the partial pupil regions <NUM> to <NUM> in the pixel <NUM> or <NUM> located at a peripheral image height (<NUM>, U) of the image sensor <NUM> and the exit pupil <NUM> of the imaging optical system. Further, <FIG> show relationships of y-direction dependency between the exit pupil and the pupil intensity distribution. The position (<NUM>, U) of the pixel <NUM> or the pixel <NUM> in the pixel array is a position shifted in the y-plus direction from the center of the optical axis, as shown in <FIG>.

<FIG> shows a case where the exit pupil distance D1 of the imaging optical system and the sensor pupil distance Ds of the image sensor <NUM> are the same. In this case, the light flux to be received in the sensitivity regions <NUM> and <NUM> divides the exit pupil in the y direction near the center of the exit pupil <NUM> of the imaging optical system. Accordingly, the y direction dependency between the third pupil intensity distribution <NUM> that corresponds to the sensitivity region <NUM> and the fourth pupil intensity distribution <NUM> that corresponds to the sensitivity region <NUM> in a pixel whose pupil division direction is the y direction is as shown in <FIG>.

Further, the light received in the accumulation regions <NUM> and <NUM> is not divided in the y direction, which is the direction for calculating the image shift amount, and the light amounts are substantially the same. Accordingly, the y direction dependency between a third pupil intensity distribution <NUM> that corresponds to the sensitivity region <NUM> and a fourth pupil intensity distribution <NUM> that corresponds to the sensitivity region <NUM> in a pixel whose pupil division direction is the y direction is as shown in <FIG>.

In the pixel <NUM>, the sensitivity region <NUM> and the accumulation region <NUM>, and the sensitivity region <NUM> and the accumulation region <NUM> are respectively connected via the N-type connection regions, and in the pixel <NUM>, the sensitivity region <NUM> and the accumulation region <NUM>, and the sensitivity region <NUM> and the accumulation region <NUM> are respectively connected via the N-type connection regions. Therefore, in the pixel <NUM>, a signal corresponding to the combination of the third pupil intensity distribution <NUM> and the fifth pupil intensity distribution <NUM> and a signal corresponding to the combination of the fourth pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> are output as phase difference signals.

On the other hand, in the pixel <NUM>, a signal corresponding to the combination of the third pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> and a signal corresponding to the combination of the fourth pupil intensity distribution <NUM> and the fifth pupil intensity distribution <NUM> are output as phase difference signals. Since the fifth pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> are substantially constant with respect to the y direction and have substantially the same signal amount, the phase difference signals obtained from the pixel <NUM> and the pixel <NUM> are substantially the same. Therefore, the positions of the centers of gravity of the pixel <NUM> and the pixel <NUM> are equal in the y direction, and the conversion coefficients Ky, which represents the relationship between the magnitude of the defocus amount and the image shift amount in the y direction for the pixel <NUM> and the pixel <NUM> have approximately the same value. That is, the signals obtained from the accumulation regions <NUM> and <NUM> that do not divide the pupils in the y direction are added as offset components to the signals obtained from the sensitivity regions <NUM> and <NUM> that divide the exit pupils in the y direction, however, since the offset amounts are equal, the conversion coefficient Ky does not change even if the combinations of the signals to be added from the sensitivity regions and the accumulation regions whose signals are different between the pixels <NUM> and <NUM>.

<FIG> and <FIG> show cases where the exit pupil distance D1 of the imaging optical system is shorter or longer than the sensor pupil distance Ds in the pixel <NUM> or the pixel <NUM> at the position (<NUM>, U). In this case, the relationship between the third pupil intensity distribution <NUM> and the fourth pupil intensity distribution <NUM> and the exit pupil is the same as a case where the pupil division direction is the x direction. Further, the fifth pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> are the same as those in the cases of <FIG> and <FIG>, and the signal amounts are substantially constant with respect to the y direction and substantially equal. Therefore, the conversion coefficient Ky takes the same value for the pixel <NUM> and the pixel <NUM>.

Next, with reference to <FIG>, in the phase difference detection in a case where the pupil division direction is the y direction, the pixel position in the pixel array is at a position (R, U) that is shifted from the optical axis in the x-plus direction and the y-plus direction will be described. As shown in <FIG>, the pixel position (R, U) in the pixel array is the position shifted by R in the x-plus direction and by U in the y-plus direction from the optical axis.

<FIG> shows a case where the exit pupil distance D1 of the imaging optical system and the sensor pupil distance Ds of the image sensor are the same. In this case, as in the case of the pixel <NUM> or the pixel <NUM> at the position (<NUM>, U), since the third pupil intensity distribution <NUM> and the fourth pupil intensity distribution <NUM> divide the vicinity of the center of the exit pupil <NUM> of the imaging optical system and the fifth pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> are not divided in the y direction and have substantially the same amount of light, and distributions are as shown in <FIG>.

<FIG> shows a relationship between the partial pupil regions <NUM> to <NUM> and the exit pupil distance D1 of the imaging optical system in a case where the exit pupil distance D1 of the imaging optical system is shorter than the sensor pupil distance Ds of the image sensor <NUM>. Since the exit pupil <NUM> is divided to the partial pupil region <NUM> corresponding to the sensitivity region <NUM> and the partial pupil region <NUM> corresponding to the sensitivity region <NUM> in the same manner as in the case of the pixel <NUM> or the pixel <NUM> at the position (<NUM>, U), the y-direction dependency of the the third pupil intensity distribution <NUM> and the fourth pupil intensity distribution <NUM> is almost the same as that of the pixel <NUM> or the pixel <NUM> located at the position (<NUM>, U), and have characteristics as shown in <FIG>.

On the other hand, since the partial pupil region <NUM> and the partial pupil region <NUM> are not divided in the y direction, the fifth pupil intensity distribution <NUM> and the sixth pupil intensity distribution <NUM> do not have the y-direction dependency. However, since the amount of light passing through the the pupil region <NUM> is less than the pupil region <NUM>, the fifth pupil intensity distribution <NUM> is smaller than the sixth pupil intensity distribution <NUM>, and have characteristics as shown in <FIG>.

Similarly, the relationship between the partial pupil regions <NUM> to <NUM> and the exit pupil distance D1 of the imaging optical system in a case where the exit pupil distance D1 of the imaging optical system is longer than the sensor pupil distance Ds of the image sensor <NUM> is as shown in <FIG>. In this case, the y-direction dependency of the third pupil intensity distribution <NUM> and the fourth pupil intensity distribution <NUM> is almost the same as that of the pixel <NUM> or the pixel <NUM> located at the position (<NUM>, U).

On the other hand, since the amount of light passing through the partial pupil region <NUM> is less than that passing through the partial pupil region <NUM>, the sixth pupil intensity distribution <NUM> is smaller than the fifth pupil intensity distribution <NUM>, and have characteristics as shown in <FIG>. In this case, the offset components added to the sensitivity regions <NUM> and <NUM> that divide the exit pupil in the Y direction are different between the pixels <NUM> and the pixels <NUM>. Therefore, the conversion coefficient Ky takes different values between the pixel <NUM> and the pixel <NUM>.

Therefore, in the phase difference focus detection in the y direction, a more accurate defocus amount can be calculated by calculating the image shift amount from the phase difference signals obtained from the pixels <NUM> and the pixel <NUM>, and by calculating the defocus amount using different conversion coefficients Ky.

Claim 1:
An image sensor (<NUM>) comprising:
a plurality of microlenses (<NUM>); and
a pixel array (<NUM>) having, with respect to each of the microlenses (<NUM>),
a pair of first regions formed at a first depth from a surface on which light is incident,
a pair of second regions formed at a second depth deeper than the first depth, and
a plurality of connecting regions that connects the pair of first regions and the pair of second regions, respectively,
wherein a direction of arranging the pair of second regions corresponding to each microlens (<NUM>) is a first direction, and a direction of arranging the pair of first regions is either the first direction or a second direction which is orthogonal to the first direction,
wherein the first regions generate charge by performing photoelectric conversion on incident light, and the second regions accumulate the charge generated in the first regions via the connecting regions,
wherein the pixel array (<NUM>) further includes
conversion means configured to convert charge into voltage, and
transfer means, which is connected to each of the second regions, configured to transfer the charge accumulated in the second regions to the conversion means,
characterized in that
a length of each of the second regions in the depth direction in a first partial region of the second region is shorter than a length of said second region in the depth direction in a second partial region of the second region, or
an impurity concentration in the first partial region is lower than an impurity concentration in the second partial region,
wherein the first partial region is located farther from the transfer means than the second partial region.