JP4915126B2 - Solid-state imaging device and electronic camera - Google Patents

Description

  The present invention relates to a solid-state imaging device and an electronic camera.

Conventionally, a pupil division phase difference method is known as one of focus detection techniques. This method forms a pair of divided images by dividing the luminous flux passing through the photographing lens into pupils. The defocus amount of the photographing lens is detected by detecting the pattern shift between the pair of divided images.
Patent Documents 1 and 2 are known as solid-state imaging devices to which the principle of the pupil division phase difference method is applied. Patent Documents 1 and 2 disclose a configuration in which pupil division is performed by arranging two photoelectric conversion regions under a single-layer microlens to generate an electric signal of the pupil division method.
A solid-state imaging device in which microlenses of imaging pixels are formed in a multilayer is disclosed in Patent Document 3.
JP 2002-314062 A JP 2003-244712 A JP-A-6-163866

  In a normal solid-state imaging device, a microlens is provided on the imaging surface in order to improve the light receiving efficiency in pixel units. This microlens only has to collect the received light beam in the range of the photoelectric conversion region, and the required condensing power is relatively small. Therefore, it is not necessary to forcibly shorten the focal length of the microlens, and the lens curvature is accordingly small.

  On the other hand, the microlenses described in Patent Documents 1 and 2 need to form a real image of the exit pupil of the photographing lens at a short distance to the photoelectric conversion region. Therefore, the condensing power required for the microlens is large, and the lens curvature is accordingly increased.

For these reasons, the microlenses of Patent Documents 1 and 2 are very difficult to manufacture. Furthermore, increasing the lens curvature of the microlens tends to be adversely affected by spherical aberration and the like. This spherical aberration or the like disturbs the light beam after passing through the microlens, so that the light beam at the exit pupil cannot be clearly divided, resulting in a problem that the focus detection accuracy is lowered.
Accordingly, an object of the present invention is to provide a technique for generating a high-quality pupil division type electrical signal in a solid-state imaging device.

<< 1 >> The solid-state imaging device of the present invention includes, on the imaging surface, a group of focus detection pixels that generate pupil division type electric signals whose phase difference changes depending on the defocus amount of the photographing lens.
A group of imaging pixels that generate an image signal by performing photoelectric conversion on a pixel basis is provided on the imaging surface.
This focus detection pixel includes the following upper-layer microlens, lower-layer microlens, and photoelectric conversion region.
The upper microlens condenses the received light flux of the focus detection pixels.
The lower-layer microlens is formed below the upper-layer microlens and compensates for the condensing power of the upper-layer microlens to form a real image of the exit pupil of the photographing lens in units of focus detection pixels.
The photoelectric conversion area is arranged so as to be biased in a predetermined pupil division direction with respect to the real image of the exit pupil, and generates a pupil division type electric signal.
The focus detection pixel occupies a section having a size corresponding to a plurality of imaging pixels, and one upper layer microlens and one lower layer microlens are provided over the section.
<< 2 >> Preferably , the imaging pixel includes a microlens formed in the same layer as either the upper microlens or the lower microlens.
"3" Incidentally Preferably, the focus detection pixel includes a photoelectric conversion region of the real image of the exit pupil for each position symmetrically divided in the pupil division direction.
<< 4 >> Also preferably, the lower microlens is an inner lens formed in a layer between the upper microlens / photoelectric conversion region.
<< 5 >> An electronic camera of the present invention includes the solid-state imaging device according to any one of the above << 1 >> to << 4 >>, a focus calculation unit, and an imaging control unit.
Among these, the focus calculation unit reads the pupil division type electric signal from the solid-state imaging device, detects a pattern shift of the pupil division image obtained from the electric signal, and performs focus detection.
On the other hand, the imaging control unit reads the photoelectric conversion output from the solid-state imaging device to obtain an image signal.

  In the present invention, the condensing power of the upper microlens is supplemented by the lower microlens. For this reason, it is not necessary to forcibly shorten the focal length of each microlens, and it is possible to generate a high-quality pupil division type electric signal.

<< First Embodiment >>
[Description of electronic camera configuration]
FIG. 1 is a block diagram showing an electronic camera 10 of the present embodiment.
In FIG. 1, a photographing lens 12 is attached to the electronic camera 10. The photographing lens 12 is driven by a lens control unit 12a for focus and diaphragm. In the image space of the photographic lens 12, the imaging surface of the solid-state imaging device 11 is arranged. The solid-state imaging device 11 is driven by the imaging control unit 14. Image data output from the solid-state imaging device 11 is processed via the signal processing unit 15 and the A / D conversion unit 16 and then temporarily stored in the memory 17.
This memory 17 is connected to a bus 18. The bus 18 is also connected with a lens control unit 12a, an imaging control unit 14, a microprocessor 19, a focus calculation unit 20, a recording unit 22, an image compression unit 24, an image processing unit 25, and the like.
The microprocessor 19 is connected to an operation unit 19a such as a release button. A recording medium 22a is detachably attached to the recording unit 22.

[Description of pixel layout]
FIG. 2 is a diagram illustrating a focus detection area (arrangement area of the focus detection pixels 37) of the solid-state imaging device 11. Such focus detection areas are provided at a plurality of locations on the imaging surface.
FIG. 3 is a diagram illustrating a cross-section of the imaging surface of the solid-state imaging device 11.
Hereinafter, the pixel configuration of the solid-state imaging device 11 will be described with reference to FIGS. 2 and 3. First, a group of imaging pixels 31 is arranged on the imaging surface of the solid-state imaging device 11. Each imaging pixel 31 is provided with a photoelectric conversion area 32 that photoelectrically converts a received light beam in units of pixels. Above the photoelectric conversion region 32, a microlens 33 that collects the received light flux on the photoelectric conversion region 32 is provided via a planarization layer 38. The group of imaging pixels 31 generates an image signal by photoelectrically converting a subject image projected onto the imaging surface via the imaging lens 12 in units of pixels.
On the other hand, focus detection pixels 37 are arranged in the focus detection area so as to sew between groups of imaging pixels 31. The focus detection pixel 37 has an upper microlens 36 formed in the same layer as the microlens 33. Similar to the microlens 33, the upper microlens 36 condenses the received light beam from the photographing lens 12.
A lower layer microlens 35 is formed in the planarizing layer 38 below the upper layer microlens 36. The lower-layer microlens 35 supplements the light condensing power of the upper-layer microlens 36 and forms a real image of the exit pupil of the photographing lens 12 in units of pixels.
Further, the focus detection pixel 37 includes a set of photoelectric conversion areas 34 formed in the same layer as the photoelectric conversion area 32. This set of photoelectric conversion areas 34 is arranged so as to divide the real image of the exit pupil symmetrically in the pupil division direction (vertical, horizontal, diagonal, etc.).
The set of photoelectric conversion areas 34 photoelectrically convert a part of the real image of the exit pupil (pupil-divided light beams A and B shown in FIG. 2), thereby generating pupil division type electric signals.
As shown in FIG. 2, on the imaging surface, these focus detection pixels 37 are arranged at predetermined pitches so as to be aligned in the pupil division direction. Note that it is preferable to shift the arrangement of the focus detection pixels 37 in a staggered pattern so that they are not simply aligned.

[Circuit explanation]
FIG. 4 is a diagram illustrating an equivalent circuit of the solid-state imaging device 11.
The solid-state imaging device 11 is roughly composed of a vertical transfer circuit 3, a horizontal transfer circuit 4, a correlated double sampling circuit 5, a group of imaging pixels 31, and a group of focus detection pixels 37.
First, the circuit configuration of the imaging pixel 31 will be described. The imaging pixel 31 is provided with a floating diffusion FD. The floating diffusion FD is connected to a low impedance power supply line VDD via a reset transistor QR. A transfer transistor QT is disposed between the floating diffusion FD and the photoelectric conversion area 32. A control signal φTGa is supplied from the vertical transfer circuit 3 to the gate of the transfer transistor QT.
The voltage of the floating diffusion FD is applied to the gate of the amplifying element QA. The source of the amplifying element QA is connected to the vertical readout line 2 by turning on the row selection transistor QS. The current source Is is connected to the source of the amplification element QA via the row selection transistor QS, so that the amplification element QA constitutes a source follower circuit. As a result, a source follower voltage corresponding to the voltage of the floating diffusion FD is output to the vertical readout line 2.
Next, structural features of the focus detection pixel 37 will be described. The focus detection pixel 37 is provided with a set of photoelectric conversion areas 34 divided in the pupil division direction instead of the photoelectric conversion area 32 of the imaging pixel 31.
One of the photoelectric conversion areas 34 is connected to the floating diffusion FD via the transfer transistor QTa. A control signal φTGa is supplied from the vertical transfer circuit 3 to the gate of the transfer transistor QTa.
The other side of the photoelectric conversion area 34 is connected to the floating diffusion FD via the transfer transistor QTb. A control signal φTGb is supplied from the vertical transfer circuit 3 to the gate of the transfer transistor QTb.
Since the other circuit configuration of the focus detection pixel 37 is the same as that of the imaging pixel 31, the description thereof is omitted here.

[Eye signal readout operation of pupil division method]
Next, a pupil division type electric signal readout operation by the electronic camera 10 will be described.
The microprocessor 19 in the electronic camera 10 drives the imaging control unit 14 in synchronization with the half-pressing operation of the release button, and starts a pupil division type electric signal readout operation.
FIG. 5 is a timing chart for explaining the readout operation of the electric signal of the pupil division method.
First, the vertical transfer circuit 3 raises the control signal φRS (n) and the control signal φTGa (n) in the n-th row where the focus detection pixels 37 exist. As a result, the photoelectric conversion area 34 connected to the transfer transistor QTa is reset via the transfer transistor QTa, the floating diffusion FD, and the reset transistor QR.
Thereafter, the vertical transfer circuit 3 lowers the control signal φTGa (n) in the n-th row and changes the transfer transistor QTa to non-conduction. From this point, the photoelectric conversion region 34 connected to the transfer transistor QTa starts to accumulate signal charges.

In this state, the vertical transfer circuit 3 sets the control signal φL (n) to a high level during the period T1, and turns on the row selection transistor QS of the nth row. In synchronization with this, the vertical transfer circuit 3 maintains the conduction state of the reset transistor QR in the n-th row only for the period T2. By maintaining this conductive state, the potential of the floating diffusion FD in the n-th row is reset.
After the period T2, when the reset transistor QR changes to non-conduction, the floating diffusion FD returns to the floating state. The voltage at the moment of switching (reset voltage) is held in the floating diffusion FD. The reset voltage in the n-th row is output as a source follower to the vertical readout line 2 via the amplifying element QA.

As described above, the reset voltage of the nth row is output from the vertical read line 2 in units of columns. These reset voltages are held in the correlated double sampling circuit 5 (capacitor group in the circuit) in synchronization with the falling timing of the control signal φSH (at the end of the period T3).
Next, the vertical transfer circuit 3 makes the transfer transistor QTa in the n-th row conductive for the period T4 using the control signal φTGa (n). By this conduction, the signal charge accumulated in the photoelectric conversion area 34 connected to the transfer transistor QTa is transferred to the floating diffusion FD. Along with this transfer operation, the voltage of the floating diffusion FD changes relative to the reset voltage by the amount of signal charge transferred. The signal voltage of the nth row is output as a source follower to the vertical readout line 2 via the amplifying element QA.

Thus, the n-th row signal voltage output in units of columns via the vertical readout line 2 is applied to the correlated double sampling circuit 5. The correlated double sampling circuit 5 outputs a true signal voltage corresponding to the difference between the signal voltage and the reset voltage.
In this state, the horizontal transfer circuit 4 sequentially uses the control signals φH3, φH4 and the like of the column in which the focus detection pixels 37 are present to sequentially apply the true signal voltage of the photoelectric conversion area 34 connected to the transfer transistor QTa from Vout. Read to.

Subsequently, the true signal voltage of the photoelectric conversion region 34 connected to the transfer transistor QTb is also sequentially increased from Vout by repeating the above-described reading operation by replacing the control signal φTGa (n) with the control signal φTGb (n). Read to.
By repeating the above operation for only the focus detection pixels 37, it is possible to read out the pupil division type electric signal in a short time without reading out all the pixels.
The pupil division type electrical signal read in this way is digitized via the signal processing unit 15 and the A / D conversion unit 16 and then temporarily stored in the memory 17.

[Operation of the focus calculation unit 20]
The focus calculation unit 20 in the electronic camera 10 performs a focus detection calculation using the pupil division type electrical signal stored in the memory 17. Hereinafter, the optical principle of the focus detection and the calculation process will be described with reference to FIG.
First, the upper microlens 36 condenses the light beam that has passed through the exit pupil of the photographing lens 12. The lower layer microlens 35 supplements the condensing power of the upper layer microlens 36 and forms a real image of the exit pupil on the set of photoelectric conversion areas 34.

As a result, the pair of photoelectric conversion areas 34 individually photoelectrically convert light beams partially passing through the exit pupil of the photographing lens 12 (pupil divided light beams A and B shown in FIG. 3).
By the way, the light beam emitted from one point (including the close point) of the focused subject passes through different positions of the exit pupil of the photographing lens 12, and then converges again to form a point image on the imaging surface. Therefore, when in a focused state, the set of photoelectric conversion areas 34 receives pupil-divided light beams emitted from the same point on the subject. Therefore, a set of pupil-divided images obtained by photoelectric conversion has substantially the same image pattern and exhibits substantially no phase difference.

On the other hand, the light beam emitted from the subject in the front pin state passes through different portions of the exit pupil of the photographing lens 12 and then reaches a pixel position that intersects and deviates in front of the imaging surface. In this case, the pair of pupil division images shows a phase difference shifted in the pupil division direction.
On the other hand, the light beam emitted from the object in the rear pin state passes through different portions of the exit pupil of the photographing lens 12 and then reaches the pixel position where the imaging surface is shifted with insufficient focusing. In this case, a set of pupil-divided images shows a phase difference shifted in the opposite direction to the front pin state.

  As described above, the phase difference of the pupil-divided image changes according to the focusing state of the photographic lens 12. Therefore, the focus calculation unit 20 distributes the pupil division type electric signals in the memory 17 to obtain an image pattern of a set of pupil division images. The focus calculation unit 20 performs a pattern matching process on these image patterns to detect a phase difference (image shift). The focus calculation unit 20 detects the in-focus state and the defocus amount of the photographing lens 12 based on this phase difference.

[Explanation of shooting operation]
The defocus amount detected by the focus calculation unit 20 is transmitted to the lens control unit 12a. The lens control unit 12a drives the photographing lens 12 based on the transmitted defocus amount, and focuses the photographing lens 12 on the subject.
Thereafter, the microprocessor 19 in the electronic camera 10 starts an image signal reading operation using the imaging control unit 14 in synchronization with the full pressing operation of the release button.
This image signal readout operation is performed by repeating the signal readout procedure using the control signal φTGa described above for each imaging pixel 31.
It should be noted that image signals are missing at the locations where the focus detection pixels 37 are arranged. This missing image signal can be interpolated using surrounding image signals. Further, the image signal of the missing portion may be generated based on the signal of the photoelectric conversion area 34 of the focus detection pixel 37.

[Effects of First Embodiment]
In general, the microlens of the focus detection pixel 37 must image the exit pupil of the photographing lens 12 at a short distance to the photoelectric conversion area 34.
In order to solve this problem, as shown in FIG. 6A, a method of providing a step S in the microlenses 33 and 33a to compensate for the imaging distance of the focus detection pixels can be considered. However, with this measure, another problem arises that, as shown in FIG. 6B, vignetting occurs in obliquely incident light due to the step S on the imaging surface.

  The first embodiment solves the above-described problem of the imaging distance by multilayering the microlenses 35 and 36 of the focus detection pixel 37 to reduce the focal length. In this case, the condensing power of the upper microlens 36 can be easily supplemented by the lower microlens 35. Therefore, with respect to the individual microlenses 35 and 36, it is possible to appropriately reduce the condensing power and the lens curvature.

  As a result, in the first embodiment, adverse effects such as spherical aberration due to the lens curvature are small, and the luminous flux disturbance of the pupil splitting luminous fluxes A and B (see FIG. 3) is small. As a result, it is possible to generate a high-quality pupil division type electrical signal, and it is possible to improve the accuracy of focus detection.

  Furthermore, in the first embodiment, the image magnification of the real image of the exit pupil is reduced by reducing the imaging distance of the focus detection pixels. For this reason, it becomes easy to form an image of the large exit pupil of the large-diameter photographing lens 12 as much as possible within the focus detection pixel section. As a result, it is possible to improve the focus detection performance of the large-diameter lens.

  In the first embodiment, the upper microlens 36 of the focus detection pixel 37 is formed in the same layer as the microlens 33 of the imaging pixel 31. Therefore, the upper microlens 36 and the microlens 33 can be manufactured together, and the manufacturing process of the solid-state imaging device 11 can be simplified.

  Furthermore, in the first embodiment, the lower microlens 35 is formed as an inner lens in the planarization layer 38. Therefore, in spite of the multi-layering of the microlenses 35 and 36, an extra step is not generated on the imaging surface, and vignetting of oblique incident light due to the step can be prevented.

  The plurality of focus detection pixels 37 are staggered on the imaging surface along the pupil division direction. In this staggered arrangement, the imaging pixels 31 always exist adjacent to the individual focus detection pixels 37. Therefore, it is possible to interpolate an image signal lost by the focus detection pixel 37 with high quality using the adjacent imaging pixel 31.

<< Second Embodiment >>
FIG. 7 is a diagram illustrating a focus detection area (arrangement area of focus detection pixels 37a) of the solid-state imaging device 11a. FIG. 8 is a diagram showing a cross section of the imaging surface of the solid-state imaging device 11a. Since the configuration of the electronic camera is the same as that of the first embodiment (FIG. 1), description thereof is omitted here.
A feature of the second embodiment is that one focus detection pixel 37a is divided into a plurality of (two in this case) pixels 31 for imaging.
With this configuration, the size of the lower-layer microlens 35a and the upper-layer microlens 36a is increased as shown in FIG. Further, one photoelectric conversion area 34a corresponds to one section of the imaging pixel 31 as shown in FIG.

[Effects of Second Embodiment, etc.]
In the second embodiment described above, the same function and effect as in the first embodiment can be obtained.

  Furthermore, in the second embodiment, an electric signal of the pupil division method can be read from the focus detection pixel 37a in the same procedure as reading the pixel output from the imaging pixels 31 for two pixels.

  Furthermore, in the second embodiment, the light receiving efficiency is increased by the size expansion of the lower layer micro lens 35a and the upper layer micro lens 36a. For this reason, the signal level of the pupil division type electric signal becomes high, and accurate focus detection is possible even in a low illumination environment.

  In the second embodiment, the size of the focus detection pixel 37 a is made to match the size of a plurality of the imaging pixels 31. Therefore, even if the focus detection pixels 37a are arranged between the groups of the imaging pixels 31, no useless gap is generated, and the loss of received light amount is small.

<< Third Embodiment >>
FIG. 9 is a diagram for specifically explaining the inner lens structure of the focus detection pixel 37b.
Since other configurations are the same as those of the first embodiment and the second embodiment, description thereof is omitted here.
As shown in FIG. 9, the lower-layer microlens 35b has a refractive index of a lens-forming layer 38b in which a curved depression (or mountain) is formed in the lower layer of the upper-layer microlens 36b, and a planarization layer 39b formed thereon. Are formed differently. Note that, when the intermediate layer has a three-layer structure, the lower microlens 35b can be formed as a double inner lens as shown in the lower part of FIG. Also, such an inner lens can be realized in the form of a diffraction grating lens.

<< 4th Embodiment >>
FIG. 10 is a diagram illustrating the solid-state imaging device 11c. Since the configuration of the electronic camera is the same as that of the first embodiment (FIG. 1), description thereof is omitted here.
A feature of the fourth embodiment is that one focus detection pixel 37c is composed of a plurality of imaging pixels 31c arranged radially (here, 2 vertical pixels × 2 horizontal pixels). The lower-layer microlens 35c and the upper-layer microlens 36c are formed so as to cover the imaging pixels 31c arranged in a radiation manner. The center of this radiation arrangement is preferably located at the lens center of the upper microlens 36c or the image center of the real image of the exit pupil.
With such a radiation arrangement, the individual photoelectric conversion areas 34c individually photoelectrically convert pupil-divided light beams that are radially divided into pupils. As shown in FIG. 10, it is preferable to increase the light receiving efficiency of the pupil-divided light beam by arranging the individual photoelectric conversion areas 34c close to the arrangement center.
Further, a Bayer array color filter 40c is provided for each photoelectric conversion region 34c on the imaging surface of the solid-state imaging device 11c. One focus detection pixel 37c is provided for each minimum color array (R, Gr, Gb, B) of the Bayer array.
The lower microlens 35c is preferably an inner lens formed in the upper microlens 36c and the photoelectric conversion region 34c.

[Focus Detection in Fourth Embodiment]
The electronic camera 10 reads out the photoelectric conversion output of the photoelectric conversion area 34c limited to the focus detection area set in advance, and obtains the pupil division type electric signal.
The focus calculation unit 20 separates and extracts the photoelectric conversion output at the Gr position and the photoelectric conversion output at the Gb position from the electrical signal of the pupil division method, thereby obtaining a G-color divided image pattern that is pupil-divided obliquely. be able to.
The focus calculation unit 20 can detect the focus by shifting the G-color divided image pattern in an oblique direction and detecting a phase difference.

  In addition, the focus calculation unit 20 may add photoelectric conversion outputs radially divided into four to two vertical pixels and two horizontal pixels, respectively. By this processing, it is possible to simultaneously obtain a divided image pattern obtained by dividing the pupil in the vertical direction and a divided image pattern obtained by dividing the pupil in the horizontal direction.

  The focus calculation unit 20 detects the phase difference of the luminance distribution while shifting the divided image pattern obtained by dividing the pupil in the vertical direction in the vertical direction, thereby enabling accurate focus detection for a subject having a horizontal edge as a main pattern. . On the other hand, by detecting the phase difference of the luminance distribution while shifting the divided image pattern obtained by dividing the pupil in the horizontal direction in the horizontal direction, it is possible to accurately detect the focus on the subject whose main image is the vertical edge.

  It is also possible to select the one with higher reliability from the two focus detection results by comparing the vertical and horizontal phase difference detection errors (image matching errors).

[Reading Image Signal According to Fourth Embodiment]
The electronic camera 10 performs automatic focus adjustment based on the obtained focus detection result.
Thereafter, the microprocessor 19 in the electronic camera 10 starts an image signal reading operation in synchronization with the full pressing operation of the release button.
This image signal readout operation is performed by sequentially reading out the photoelectric conversion output of the photoelectric conversion region 34c for the entire effective pixel region.

[Effects of Fourth Embodiment, etc.]
In 4th Embodiment mentioned above, the effect similar to 1st Embodiment can be acquired.

  Furthermore, in the fourth embodiment, one focus detection pixel 37c is arranged for each minimum color arrangement. With this configuration, the lower-layer microlens 35c and the upper-layer microlens 36c can perform the same function as an optical low-pass filter for preventing moire. Therefore, it is possible to omit the optical low-pass filter from the solid-state imaging device 11c. In addition, the optical low-pass filter can be made thinner by reducing the blurring amount of the optical low-pass filter by the amount of the optical action of the microlenses 35c and 36c.

  Further, in the fourth embodiment, it is possible to change the pupil division direction instantly by adding four photoelectric conversion areas 34c arranged radially in the vertical and horizontal directions.

<< Additional items of embodiment >>
In the embodiment described above, the incident side of the upper microlens is formed in a convex shape. However, the embodiment is not limited to this. For example, the exit side of the upper microlens may be convex and the incident side may be made flat or close to flat. With this shape, obliquely incident light on adjacent pixels is less likely to be blocked by the upper microlens, and the light receiving efficiency of the solid-state imaging device can be increased.

  In the first to third embodiments described above, a color filter may be arranged in the imaging pixel. In this case, it is preferable to increase the light receiving efficiency of the focus detection pixel by omitting the color filter for the focus detection pixel.

  In the first to third embodiments described above, focus detection pixels are arranged only in a predetermined focus detection area. However, the embodiment is not limited to this. For example, focus detection pixels may be arranged at a predetermined pitch over the entire imaging surface. With this configuration, it is possible to flexibly select a desired region and read out the pupil division type electrical signal from the region.

  In the first to third embodiments described above, two photoelectric conversion areas are provided in the section of the focus detection pixel. However, the embodiment is not limited to this. A plurality (three or more) of photoelectric conversion areas may be arranged in the focus detection pixel section. By separating these photoelectric conversion areas symmetrically with a center line having an appropriate inclination and combining them, the pupil division direction of the focus detection pixels can be changed in various ways. Conversely, one photoelectric conversion area may be provided in the focus detection pixel section. In this case, it is possible to generate an electric signal of the pupil division method by performing pupil division with adjacent focus detection pixels as a set.

  In the fourth embodiment described above, focus detection pixels are arranged over the entire imaging surface. However, the embodiment is not limited to this. A focus detection pixel may be arranged every N pixels, and a dedicated pixel for imaging may be arranged at other pixel positions. Alternatively, focus detection pixels may be arranged in a checkered pattern, and pixels dedicated to imaging may be arranged at other pixel positions.

  In the above-described fourth embodiment, the case of the primary color Bayer arrangement has been described. However, the fourth embodiment is not limited to this. A minimum color arrangement may be determined according to an arbitrary color arrangement, and an upper layer microlens may be arranged for each area of the minimum color arrangement.

  Further, in the above-described embodiment, the case of an XY address type (CMOS type, etc.) solid-state imaging device has been described. However, the embodiment is not limited to this. The present invention may be applied to a CCD type solid-state imaging device or the like.

  In the embodiment described above, the microlens for the imaging pixel and the upper microlens for the focus detection pixel are formed in the same layer. However, the embodiment is not limited to this. For example, the microlens for the imaging pixel and the lower layer microlens for the focus detection pixel may be formed in the same layer.

  In the embodiment described above, a two-layer configuration of an upper microlens and a lower microlens is employed. However, the embodiment is not limited to this. For example, a lens configuration of three or more layers may be obtained by adding one or more middle-layer microlenses.

  As described above, the present invention is a technique that can be used for a solid-state imaging device having a pupil division type electric signal generation function.

1 is a block diagram showing an electronic camera 10. FIG. 3 is a diagram illustrating a focus detection area of the solid-state imaging device 11. FIG. 2 is a diagram illustrating a cross section of an imaging surface of the solid-state imaging device 11. FIG. 2 is a diagram illustrating an equivalent circuit of the solid-state imaging device 11. FIG. It is a timing chart explaining the read-out operation | movement of the electrical signal of a pupil division system. It is a figure explaining the malfunction of the policy which provides the level | step difference S in an imaging surface. It is a figure which shows the focus detection area of the solid-state imaging device 11a. It is a figure which shows the cross section of the imaging surface of the solid-state imaging device 11a. It is a figure explaining an inner lens structure. It is a figure which shows the solid-state imaging device 11c.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electronic camera, 11 ... Solid-state imaging device, 12 ... Shooting lens, 12a ... Lens control part, 14 ... Imaging control part, 15 ... Signal processing part, 16 ... A / D conversion part, 20 ... Focus calculation part, 31 ... Imaging pixels, 32... Photoelectric conversion area, 33... Microlens, 34... Photoelectric conversion area, 35 .. lower layer microlens, 36 ... upper layer microlens, 37 ... focus detection pixel, 38.

Claims (5)

A solid-state imaging device having a group of focus detection pixels for generating an electrical signal of a pupil division method in which a phase difference changes depending on a defocus amount of a photographing lens, on an imaging surface,
A group of imaging pixels that photoelectrically convert pixel by pixel to generate an image signal is provided on the imaging surface,
The focus detection pixel is:
An upper microlens that collects the received light flux of the focus detection pixels;
A lower-layer microlens that is formed in the lower layer of the upper-layer microlens, supplements the condensing power of the upper-layer microlens, and forms a real image of an exit pupil of the photographing lens in units of the focus detection pixels;
A photoelectric conversion region that is arranged in a predetermined pupil division direction with respect to the real image of the exit pupil and generates an electrical signal of the pupil division method ,
One focus detection pixel occupies a section corresponding to a plurality of the imaging pixels,
A solid-state imaging device , wherein the upper microlens and the lower microlens are provided one by one over the section . The solid-state imaging device according to claim 1 ,
The imaging pixels are
A solid-state imaging device comprising: a microlens formed in the same layer as any one of the upper layer microlens and the lower layer microlens. The solid-state imaging device according to claim 1,
Before Symbol focus detection pixels,
The solid-state imaging device, characterized in that Ru comprising the photoelectric conversion region a real image of the exit pupil for each position symmetrically divided into the pupil division direction. The solid-state imaging device according to claim 1,
The lower microlenses, a solid-state imaging device, wherein the Ru inner lens der formed in a layer between the upper layer microlens / the photoelectric conversion region. A solid-state imaging device according to any one of claims 1 to 4,
A focus calculation unit that reads out the electrical signal of the pupil division method from the solid-state imaging device, detects a pattern shift of the pupil division image obtained from the electrical signal, and performs focus detection;
An imaging control unit that reads out photoelectric conversion output from the solid-state imaging device and obtains an image signal;
Electronic camera comprising the.

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