JP2022180110A - Imaging apparatus - Google Patents

Abstract

To improve detection accuracy of image surface phase difference focal detection under low illuminance.SOLUTION: An imaging apparatus comprises: an image pickup device which has each focus state detection part including a plurality of image surface phase difference detection parts which are respectively arranged at different positions along a second direction crossing a first direction, the first direction being a detection direction, and are respectively different in design pupil distance; and an addition part which generates an addition signal by adding at least two of detection signals detected by the image surface phase difference detection parts included in the focus state detection part.SELECTED DRAWING: Figure 7

Description

The present invention relates to an imaging device.

2. Description of the Related Art An imaging device including focus detection pixels that receive a light beam that has passed through a partial area of an exit pupil of an imaging optical system is known (for example, Patent Document 1). Conventionally, there has been a demand for improving the accuracy of focus detection.

JP 2016-66051 A

According to the first aspect, the image pickup apparatus has a first direction as a detection direction, and a plurality of image plane positions each having a different design pupil distance DPD, which are arranged at different positions in a second direction that intersects the first direction. At least two of a plurality of detection signals detected by an image sensor having a focus state detection section including a phase difference detection section and the plurality of image plane phase difference detection sections included in the focus state detection section are added. and an addition unit configured to generate an addition signal.

1 is a cross-sectional view schematically showing the configuration of an imaging device according to an embodiment; FIG. FIG. 4 is a diagram showing an example of a light beam entering an image plane phase difference detection unit from an imaging optical system; FIG. 2 is a plan view of the imaging element of the embodiment as viewed from the imaging surface side; FIG. 4 is a diagram showing an electric circuit included in a pixel; FIG. 4 is an enlarged view of an image plane phase difference detection unit; FIG. 5 is a diagram showing a state in which a ray bundle that has passed through an exit pupil is incident on an image plane phase difference detection unit; FIG. 4 is a diagram showing an arrangement example of an image plane phase difference detection section in a focus state detection section; 4A and 4B are diagrams showing some examples of the position of the focus state detection unit on the image sensor; FIG. FIG. 10 is a diagram showing a modification of the arrangement of the image plane phase difference detection section in the in-focus state detection section;

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing the configuration of an imaging device 1 of the first embodiment and an imaging optical system 2 attached to the imaging device 1 for use.

The X, Y and Z directions indicated by arrows in FIG. 1 are directions perpendicular to each other. It should be noted that the X direction, Y direction and Z direction shown in subsequent drawings are the same directions as the X direction, Y direction and Z direction shown in FIG. 1, respectively. The directions of the arrows are +X direction, +Y direction and +Z direction, respectively.
Hereinafter, the position in the X direction is also referred to as the X position, the position in the Y direction as the Y position, and the position in the Z direction as the Z position.

FIG. 1 is a cross-sectional view of the imaging device 1 and the imaging optical system 2 as seen from the +X direction.
The imaging device 1 includes an imaging element 3 , an imaging control section 4 , a lens driving section 6 , a display section 7 , an operation section 8 and a first communication section 9 .
The imaging optical system 2 forms a subject image on the imaging surface 3 s of the imaging device 3 . The imaging optical system 2 includes a diaphragm 21 having an aperture 22, a front lens group 20a arranged closer to the subject than the diaphragm 21, a rear lens group 20b arranged closer to the image sensor 3 than the diaphragm 21, and a 2 communication unit 23 is included. Both the front lens group 20a and the rear lens group 20b may be composed of a plurality of lenses.

The diaphragm 21 may be an iris diaphragm or a light shielding member having an opening with a predetermined diameter. may be limited. One of the front lens group 20a and the rear lens group 20b may not be arranged.

The front lens group 20a or the rear lens group 20b, or at least one lens among the plurality of lenses constituting them, is movable in the optical axis AX direction (Z direction) to adjust the focus of the imaging optical system 2. It may be a focus adjustment lens.
Further, the front lens group 20a or the front lens group 20a, or at least one lens among a plurality of lenses constituting them, is arranged in the optical axis AX direction (Z direction) in order to change the focal length of the imaging optical system 2. It may be a lens for variable magnification (zooming) that can be moved to any position.

At least part of the focal length of the imaging optical system 2, the aperture value (F value), and the current position information of the lens movable in the optical axis AX direction is transmitted from the second communication unit 23 of the imaging optical system 2 to the imaging device 1. is transmitted to the first communication unit 9 and further transmitted to the imaging control unit 4 .

The image pickup device 3 picks up a subject image and outputs a signal. The imaging control unit 4 controls each unit such as the imaging element 3 . The imaging control unit 4 performs image processing and the like on the image signal output from the imaging element 3 to generate image data. The imaging control unit 4 performs processing such as recording image data in a recording medium (not shown) and displaying an image based on the image data on the display unit 7 . The display unit 7 is a display device having a display member such as a liquid crystal panel.

The imaging control unit 4 further performs focus detection processing necessary for automatic focus adjustment (AF) of the imaging optical system 2 by a known image plane phase difference detection method. Specifically, the imaging control unit 4 detects, from at least a pair of focus detection signals output from the imaging element 3, a phase difference, which is the amount of phase shift between the focus detection signals, as will be described later.

The imaging control unit 4 calculates the amount of deviation (defocus amount) between the imaging position of the object in the imaging optical system 2 and the imaging surface 3s of the imaging element 3 based on the detected phase difference. Then, according to the defocus amount, the driving amount in the optical axis AX direction for focusing the focus adjusting lens in the imaging optical system 2 is calculated. A signal corresponding to this drive amount is sent from the lens drive unit 6 through the first communication unit 9 and the second communication unit 23 to an actuator (not shown) in the imaging optical system 2, and the focus adjustment lens moves in the optical axis AX direction. Focus adjustment is automatically performed by moving to .

FIG. 2 is a cross-sectional view of the imaging device 1 and the imaging optical system 2 as seen from the -Y direction. It is a figure which shows an example of LRB.

The light beam LRB shown in FIG. 2 is refracted by the front lens group 20a and then has its diameter restricted by the diaphragm 21. As shown in FIG. After passing through the aperture 22 , the light beam LRB is refracted again by the rear lens group 20 b and enters the image-side focal point FP in the vicinity of the focus state detection portion FA of the image sensor 3 . Here, the incident side surface (+Z side surface) of the imaging device 3 is arranged so as to substantially coincide with the condensing point of the light beam LRB, that is, the image-side focal point FP of the imaging optical system 2 . In FIG. 2, the focus state detection unit FA of the imaging device 3 is arranged at a position separated by a distance X1 in the +X direction from the optical axis AX of the imaging optical system 2, as an example.

The exit pupil EP is a virtual image of the aperture 22 of the diaphragm 21 formed by the rear lens group 20b, viewed from the image-side focal point FP side. In other words, the exit pupil EP is the optical path between the rear lens group 20b and the imaging element of the chief ray LPR of the ray bundle LRB that passes through the intersection point PC between the XY plane on which the diaphragm 21 is arranged and the optical axis AX. coincides with the XY plane including the intersection point PCI between the linearly extended line segment PRI and the optical axis AX. The intersection point PCI can be said to be the center (center PCI) of the exit pupil EP.

In this specification, the distance in the Z direction from the exit pupil EP to the image-side focal point FP is also referred to as exit pupil distance LPD.
As described above, the exit pupil EP is a virtual image of the aperture 22 of the diaphragm 21 and is optically equivalent. It is also called LRB.

The exit pupil distance LPD of the imaging optical system 2 is transmitted from the second communication unit 23 of the imaging optical system 2 to the first communication unit 9 of the imaging device 1 in the same manner as the information such as the focal length of the imaging optical system 2 described above. , and further transmitted to the imaging control unit 4 .

(image sensor)
FIG. 3 is a view of the imaging element 3 as seen from the imaging surface 3s side, that is, from the +Z side. The imaging device 3 has a semiconductor substrate 30 and a plurality of pixels 40 arranged on the semiconductor substrate 30 in the X direction and the Y direction. The arrangement of the pixels 40 in the X direction is also called a "row", and the arrangement of the pixels 40 in the Y direction is also called a "column". Although some of the pixels 40 are omitted in FIG. 2, the pixels 40 may be arranged in large numbers, for example, 1000 or more in each of the X and Y directions.

Each of the plurality of pixels 40 has higher spectral sensitivity to any one of the three different wavelengths of light than to the other wavelengths. The pixels 40 marked with R (hereinafter also referred to as “R pixels”) have high spectral sensitivity to red light, and the pixels 40 marked with G (hereinafter also referred to as “G pixels”) have high spectral sensitivity to green light. Pixels 40 labeled B (hereinafter also referred to as “B pixels”) have high spectral sensitivity to blue light. These RGB pixels 40 are arranged, for example, in a Bayer array within the imaging area.
The above-described spectral sensitivities of the R pixel, G pixel, and B pixel are set by, for example, a color filter (described later) provided in each pixel 40 .

A horizontal control section 31H is provided at the left end in FIG. 3, and a vertical control section 31V is provided at the upper end in FIG. The horizontal control section 31H and the vertical control section 31V are also collectively or individually referred to as the control section 31 .

A plurality of control lines 32 extend in the X direction from the horizontal control section 31H, and each control line 32 is connected to a plurality of pixels 40 arranged in one row in the X direction among the plurality of pixels 40 . A signal line 33 is connected to each of a plurality of pixels 40 arranged in a row in the Y direction among the plurality of pixels 40 in the image sensor 3 .

Each pixel 40 produces a signal based on the amount of light incident on it during a given imaging period. A signal generated by a pixel 40 connected to one or a plurality of control lines 32 to which a predetermined control voltage is applied from the horizontal control section 31H is transmitted through the signal line 33 connected to the pixel 40. , are read out by a predetermined reading unit 34 . As an example, the signal output from each pixel 40 is an analog signal, and the reading unit 34 is an analog/digital converter that converts (A/D converts) the analog signal into a digital signal.
A signal from the pixel 40 that has undergone A/D conversion or the like by the reading unit 34 is output from the output unit 36 of the image sensor 3 to the imaging control unit 4 via the data lane 35 as an output signal Sg.

Some of the plurality of pixels 40 are a first AF pixel P and a second AF pixel for detecting each of a pair of detection signals used for focus detection processing necessary for AF of the imaging optical system 2 in the phase difference detection method described above. It has become M. The first AF pixel P is the pixel 40 marked with P, and the second AF pixel M is the pixel 40 marked with M.

A plurality of first AF pixels P are arranged side by side in the X direction at predetermined positions in the Y direction. A plurality of first AF pixels P arranged side by side in the X direction at the same Y position are also referred to as a first detection unit F1. The signal output from the first detection section F1 is one of the pair of detection signals described above, which is the first detection signal.

A plurality of second AF pixels M are also arranged side by side in the X direction at a predetermined position in the Y direction different from the first detection unit F1. A plurality of second AF pixels M arranged side by side in the X direction at the same Y position are also referred to as a second detection unit F2. The signal output from the second detection section F2 is the other second detection signal of the pair of detection signals described above.

In FIG. 2, for convenience of illustration, the G pixel G is included in the dashed frame indicating the first detection unit F1 and the second detection unit F2, but the first detection unit F1 and the second detection unit F2 may not include the G pixel G.
Also, in FIG. 2, the first detection unit F1 and the second detection unit F2 are arranged over the approximate end on the −X side of the effective imaging area IA to the approximate end on the +X side. , the first detection unit F1 and the second detection unit F2 may be arranged in a part of the effective imaging area IA in the X direction. Also, the first detection section F1 and the second detection section F2 may be arranged discretely in the X direction of the effective imaging area IA.

A pair of one first detection unit F1 and one second detection unit F2 is also called an image plane phase difference detection unit FS. The image plane phase difference detection unit FS detects the phase of the X-direction intensity distribution of the image of the imaging optical system 2 formed in the first detection unit F1 and the phase of the imaging optical system 2 formed in the second detection unit F2. A pair of detection signals is generated for detecting a phase difference between the phase of the X-direction intensity distribution of the image.

The X direction in which the first AF pixel P and the second AF pixel M are arranged side by side can be called the detection direction, and can also be called the first direction. Also, the Y direction can be called the second direction.
Together or individually, the first AF pixel P and the second AF pixel M are also called AF pixels.
On the other hand, pixels other than AF pixels (R pixels, G pixels, and B pixels) among the plurality of pixels 40 described above are also collectively or individually referred to as imaging pixels.

As an example, both the first AF pixel P and the second AF pixel M are arranged at positions where the B pixels should be arranged in the original Bayer array. However, both the first AF pixel P and the second AF pixel M may be arranged at the position where the R pixel should be arranged in the original Bayer array.

In FIG. 3, the interval in the Y direction between the first detection portion F1 and the second detection portion F2 is the interval at which five pixels 40 are arranged in the interval. may be an interval at which an odd number of pixels 40 are arranged.

FIG. 4 is a diagram showing an electrical circuit included in the pixel 40. As shown in FIG. The pixel 40 includes a photoelectric conversion section 41 and an amplifier circuit 42 . Note that the structure of the pixel 40 will be described later.
The photoelectric conversion unit 41 is composed of a photodiode or the like, and photoelectrically converts incident light. Charges generated by photoelectric conversion in the photoelectric conversion unit 41 are transferred to the storage unit FD by the transfer unit TX when a transfer signal is input to the transfer unit TX. A predetermined voltage VDD is supplied from the power supply to the amplifier section TA, and a signal corresponding to the charge transferred to the storage section FD is amplified and output to the selection section TS.

A control line 32 is connected to the selection section TS. When a predetermined signal is input to the control line 32 from the horizontal control section 31H, the signal output from the selection section TS is output to the signal line 33 .
A predetermined voltage VDD is supplied from the power supply to the reset unit TR, and when a reset signal is input to the reset unit at a predetermined timing, the reset unit becomes conductive and the storage unit FD is reset to the voltage VDD.

The transfer section TX, amplifier section TA, selection section TS, and reset section TR may be MOS transistors. An electric circuit that constitutes the pixel 40 may be, for example, the same as an electric circuit included in a pixel of a conventional so-called four-transistor CMOS imaging device.
The transfer signal and the reset signal described above may be supplied from the horizontal control section 31H via a control line extending in the X direction similar to the control line 32 .

The configuration of the pixel 40 including the first AF pixel P and the second AF pixel M will be described below with reference to FIGS. 5 and 6. FIG.
FIG. 5 is an enlarged view of the image plane phase difference detection section FS (see FIG. 3) included in the focus state detection section FA shown in FIG.
FIG. 5A is a diagram showing an XZ cross-sectional view of the pixel 40 (G pixel G and first AF pixel P) in the first detection unit F1 (see FIG. 3) included in the image plane phase difference detection unit FS. be.
FIG. 5B is a diagram showing an XZ cross-sectional view of the pixel 40 (G pixel G and second AF pixel M) in the second detection unit F2 (see FIG. 3) included in the image plane phase difference detection unit FS. be.

As shown in FIGS. 5A and 5B, the semiconductor substrate 30 includes, for example, an upper substrate 30a on which a photoelectric conversion unit 41 such as a photodiode and an amplifier circuit 42 are formed, and a wiring layer. It is laminated with the lower substrate 30b. The upper substrate 30a and the lower substrate 30b may be electrically connected via bumps.

A transparent protective film 43 is formed on the upper substrate 30a (+Z direction), and above the protective film 43, the above-described color filters 44 are formed. A microlens 45 is formed above the color filter 44 to condense the light to be imaged onto the photoelectric conversion section 41 .
Light irradiated to the pixels 40 from above (+Z direction) is refracted by the microlenses 45 and enters the photoelectric conversion unit 41 after the wavelength range of the transmitted light is roughly selected by the color filter 44 .

The color filters 44 arranged in the first AF pixels P and the second AF pixels M may be color filters that preferentially transmit any one of the blue light, the green light, and the red light described above. , a color filter that preferentially transmits two colors of green light and red light, a filter that transmits all visible light, or a filter that transmits infrared light.

The photoelectric conversion section 41 may be a photodiode formed in the upper substrate 30a, or may be a photoelectric conversion section formed of an organic film formed above (+z side) the upper substrate 30a.
Note that the color filter 44 may be omitted when the spectral sensitivity of the photoelectric conversion unit 41 is different for each of the plurality of pixels 40 .

As shown in FIG. 5A, the first AF pixel P has a first light shielding portion 46P on the upper end (+Z side end) side of the photoelectric conversion portion 41 for blocking light incident on the +X side of the photoelectric conversion portion 41. have. Further, as shown in FIG. 5B, the second AF pixel M is provided on the upper end (+Z side end) side of the photoelectric conversion unit 41 to block the light incident on the −X side of the photoelectric conversion unit 41. It has a portion 46M.

FIG. 6 shows a first AF pixel P and a second AF pixel in which the ray bundle LRB that has passed through the exit pupil EP of the imaging optical system 2 is included in the image plane phase difference detection unit FS in the focus state detection unit FA of the imaging device 3. FIG. 10 is a diagram showing a state in which light is incident on M and M, and shows an XZ cross section of the imaging device 3 as viewed from the -Y direction.
Note that in FIG. 6, the first AF pixel P and the second AF pixel M, which are arranged at the same X position in the image plane phase difference detection unit FS, that is, are arranged to overlap in the depth direction of the paper surface, are overlapped. is represented.

The distance in the Z direction between the vertex 45c of the microlens 45 and the first light shielding portion 46P or the second light shielding portion 46M is defined as a distance DML.
The first light shielding portion 46P and the second light shielding portion 46M are arranged at a Z position Z1 that is approximately conjugate (imaging relationship) via the microlens 45 with respect to the exit pupil EP of the imaging optical system 2 described above. In other words, the first light shielding portion 46P and the second light shielding portion 46M are located at a Z position Z1 that is approximately conjugate with the diaphragm 21 of the imaging optical system 2 via the microlens 45 and the rear lens group 20b (see FIG. 4). are placed in

Therefore, a large amount of light that has passed through the +X side of the optical axis AX in the exit pupil EP enters the photoelectric conversion unit 41 of the first AF pixel P. Further, a large amount of light that has passed through the -X side of the optical axis AX in the exit pupil EP is incident on the photoelectric conversion unit 41 of the second AF pixel M.
The photoelectric conversion unit 41 of the first AF pixel P converts the light passing through the exit pupil EP of the imaging optical system 2 on the + side (one side) in the X direction to the - side (the other side) in the X direction of the exit pupil. It can also be said that it is the first light receiving portion that detects more light than the light that passes through.
The photoelectric conversion unit 41 of the second AF pixel M converts the light passing through the exit pupil EP of the imaging optical system 2 to the - side in the X direction (the other side described above) of the exit pupil on the + side in the X direction (the one side described above). side) can be said to be the second light receiving portion that detects more light than the light passing through.

As an example, the focus state detection unit FA shown in FIGS. 2 and 6 is arranged at a position separated by a distance X1 in the +X direction from the center of the imaging device 3 in the X direction and the optical axis AX of the imaging optical system 2. ing. Therefore, the ray bundle LRB enters the focus state detection unit FA from a direction centered on a direction that is slightly tilted toward the −X direction with respect to the +Z direction.

Correspondingly, in order to increase the light receiving efficiency of the photoelectric conversion unit 41, in each pixel 40 of the focus state detection unit FA, the center position of the microlens 45 in the X direction is set to It is displaced in the -X direction with respect to the central position. Conversely, the center position of the photoelectric conversion unit 41 in the X direction is shifted in the +X direction with respect to the center position of the microlens 45 in the X direction.

Therefore, as shown in FIG. 5(a), the position of the −X side edge 46PE of the first light shielding portion 46P in the first AF pixel P is from the vertex 45c of the microlens 45 (the point on the most +Z side). It is arranged at a position shifted to the +X side by a distance XP. Further, as shown in FIG. 5B, the position of the +X side edge 46ME of the second light shielding portion 46M in the second AF pixel M is also shifted to the +X side by the distance XM from the vertex 45c of the microlens 45. are placed.

A vertex 45c of the microlens 45 is arranged at a distance X1 in the +X direction from the optical axis AX. Also, the distance in the Z direction between the exit pupil EP and the vertex 45c of the microlens 45 is the exit pupil distance LPD. Therefore, the principal ray LPR of the ray bundle LRB that passes through the center PCI of the exit pupil EP and is incident on the vertex 45c of the microlens 45 of the first AF pixel P and the second AF pixel M is expressed by the following formula (1 ) in a direction inclined in the +X direction by an angle θ determined by
tan(θ) = X1/LPD (1)

That is, the principal ray LPR travels in a direction inclined by an angle θ with respect to both the optical axis AX parallel to the Z direction and the normal NL to the imaging surface 3s of the imaging device 3 .
The principal ray LPR is refracted near the vertex 45c of the microlens 45, passes through the microlens 45, the color filter 44, and the protective film 43, and is shielded by the first light shielding portion 46P or the second light shielding portion 46M, Alternatively, the light enters the photoelectric conversion unit 41 .

Let XC be the distance in the X direction from the vertex 45c of the microlens 45 to the principal ray LPR at the Z position Z1 where the first light shielding part 46P or the second light shielding part 46M is arranged. From geometrical optics considerations, the distance XC is approximately determined by the following formula (2).
XC=tan(θ)×DML/n (2)

Here, the distance DML is the distance in the Z direction between the vertex 45c of the microlens 45 and the first light shielding portion 46P or the second light shielding portion 46M as described above, and n is the lens material of the microlens 45. is the refractive index.
Moreover, the following formula (3) can be derived from the formulas (1) and (2).
XC=X1×DML/(n×LPD) (3)

At this time, if the distance XC is equal to the average value of the distance XP and the distance XM described above, the amount of light incident on the photoelectric conversion unit 41 of the first AF pixel P and the amount of light incident on the photoelectric conversion unit 41 of the second AF pixel M are can be made approximately equal. That is, the amount of light that passes through the +X side of the exit pupil EP and enters the photoelectric conversion unit 41 without being blocked by the first light blocking portion 46P of the first AF pixel P, and the amount of light that passes through the −X side of the exit pupil EP and enters the second AF The amount of light incident on the photoelectric conversion section 41 without being blocked by the second light blocking section 46M of the pixel M can be substantially equalized. Therefore, at this time, the accuracy of focus position detection by the image plane phase difference detection unit FS can be improved.

Conversely, if the distance X1, the distance DML, the distance XP, the distance XM, and the refractive index n, which are the quantities related to the configuration of the image plane phase difference detection unit FS, are determined, the exit pupil distance LPD suitable for the in-focus state detection unit FA can be calculated. The exit pupil distance LPD suitable for a predetermined image plane phase difference detection unit FS is hereinafter also referred to as the design pupil distance DPD of the image plane phase difference detection unit FS.

The design pupil distance DPD is, for example, the following formula (4 ).
DPD=X1×DML/{n×(XP+XM)/2} (4)

In order to improve the accuracy of focal position detection by the image plane phase difference detector FS, it is desirable to match the design pupil distance DPD with the exit pupil distance LPD of the imaging optical system 2 . However, the exit pupil distance LPD varies depending on the image pickup optical system 2, and if the image pickup optical system 2 is a zoom lens, the exit pupil distance LPD also varies with zooming. Therefore, it is difficult to always match the design pupil distance DPD of one image plane phase difference detection unit FS with the exit pupil distance LPD of the imaging optical system 2 .

Therefore, in the image sensor 3 of the first embodiment, as shown in FIG. 7, a plurality of image plane phase difference detection units FS (FSA to FSE) is provided. Each of the image plane phase difference detection units FSA to FSE includes a first detection unit F1 (F1A to F1E) and a second detection unit F2 (F2A to F2E).

In the first AF pixels P respectively included in these first detection units F1A to F1E, the distances XP described above as an example are different from each other. Further, the distances XM described above as an example are different from each other in the second AF pixels M respectively included in these second detection units F2A to F2E. As a result, the design pupil distances DPD of the image plane phase difference detection units FSA to FSE have different values.

In the image pickup apparatus 1 of the first embodiment, the image pickup control unit 4 controls the image plane phase difference detection unit FS having the design pupil distance DPD close to the exit pupil distance LPD of the image pickup optical system 2 as the image plane phase difference detection unit FSA to the image plane phase difference detection unit FS. A focus position is detected using a detection signal from the selected image plane phase difference detection unit FS. As a result, even when the attached imaging optical system 2 is replaced or when the imaging optical system 2 is zoomed, the focal position can be detected with high accuracy.

The number of image plane phase difference detection units FSA to FSE provided in one focus state detection unit FA is not limited to five as described above, and may be arbitrary m (m is a natural number of 2 or more). can be For example, the exit pupil distance LPD of each of the image plane phase difference detection units FSA to FSE may be an arbitrary length between approximately 10 mm and approximately 150 mm. As a further example, the length may be any length between about 0.6 times and about 5 times the diagonal length of the effective imaging area IA of the image sensor 3 .

The exit pupil distance LPD of each of the plurality of image plane phase difference detection units FSA to FSE may be set so as to increase at approximately equal intervals between the minimum value and the maximum value among them. Alternatively, the inclination angle θ of the principal ray LPR incident on the first AF pixel P and the second AF pixel M from the exit pupil EP at each exit pupil distance LPD with respect to the normal line NL shown in FIG. may be set so as to increase at approximately equal intervals from to the maximum value.

In the first AF pixels P respectively included in the first detection units F1A to F1E, instead of or in addition to the distance XP described above, the values of the distance DML described above may differ from each other. Further, in the second AF pixels M included in the second detection units F2A to F2E, instead of or in addition to the distance XM, the distance DML may have different values.

The exit pupil distance LPD of each of the plurality of image plane phase difference detection units FSA to FSE may monotonously increase or decrease in accordance with the respective Y position. It may change randomly regardless.

In FIG. 7, in order to avoid complication of the drawing, imaging pixels (G pixels G, B pixels B and R pixels R) are omitted from the drawing. However, in one focus state detection unit FA, for example, three or more imaging pixels are arranged between the first detection units F1A to F1E and the second detection units F2A to F2E in the Y direction. Also good.

A distance in the Y direction between the first detection units F1A to F1E and the second detection units F2A to F2E in one image plane phase difference detection unit FSA to FSE can be called a first distance P1. Also, the distance in the Y direction between each of the plurality of image plane phase difference detection units FSA to FSE can be called a second distance P2. The second distance P2 may be longer than the first distance P1.
Conversely, the second distance P2 may be shorter than the first distance P1.

By the way, when the image pickup apparatus 1 is used to take an image, for example, under low illumination, the light amount of the light beam LRB from the object decreases, and as a result, any one of the image plane phase difference detection units FSA to FSE The S/N of the obtained detection signal is lowered. In this case, the accuracy of focus position detection by the image plane phase difference detectors FSA to FSE may decrease.

In the imaging device 1 and the imaging device 3 of the embodiment, some of the plurality of detection signals detected by the plurality of focus state detection units FA arranged at different positions in the Y direction are added to generate an addition signal. , the addition signal is used as a detection signal to improve the accuracy of focus position detection.

Specifically, generated by a plurality of first AF pixels P at the same X position and different Y positions in a plurality of image plane phase difference detection units FSA to FSE in one focus state detection unit FA. add the signals Similarly, in a plurality of image plane phase difference detection units FSA to FSE in one in-focus state detection unit FA, generated by a plurality of second AF pixels M at the same X position and different Y positions Add the signals.

Addition of a plurality of detection signals is performed by so-called source follower addition as one example. That is, signals generated by a plurality of first AF pixels P included in different focus state detection units FA and located at the same X position are output to the signal lines 33 connected to the first AF pixels P substantially simultaneously. . Similarly, signals generated by a plurality of second AF pixels M included in different focus state detection units FA and located at the same X position are output substantially simultaneously to the signal lines 33 connected to those second AF pixels M. Let Then, the readout section 34 reads out these added signals on the signal line 33 .

The horizontal control unit 31H sends a control signal to the first AF pixel P or the second AF pixel M whose signals are mutually added via the control line 32, and causes the signals from these pixels to be output to the signal line 33 substantially at the same time.
In this case, the signal line 33 and the readout section 34 constitute an addition section that adds at least two of the plurality of detection signals to generate an addition signal.

The addition of a plurality of detection signals may be performed by another configuration. For example, a memory for temporarily storing digital signals output from predetermined AF pixels (P, M) via the data lane 35 to the output unit 36 of the imaging device 3, and signals from a plurality of predetermined AF pixels. may be provided to add a plurality of detection signals.
In this case, the adder circuit provided in the output unit 36 of the imaging device 3 constitutes an adder unit that adds at least two of the plurality of detection signals to generate an addition signal.

Note that these memory and addition circuit may be provided as the addition circuit section 5 in the imaging control section 4 instead of in the imaging element 3 . In this case, the imaging control unit 4 includes an addition unit that adds at least two of the plurality of detection signals to generate an addition signal.

The addition signal is, for example, the detection signal from the image plane phase difference detection unit FS whose design pupil distance DPD is closest to the exit pupil distance LPD of the imaging optical system 2 from the first to the kth (k is a natural number equal to or less than m). Generated by addition. As an example, assume that the exit pupil distance LPD of the imaging optical system 2 is 100 mm, and the design pupil distances DPD of the plurality of image plane phase difference detection units FSA to FSE are 50 mm, 70 mm, 90 mm, 110 mm, and 130 mm, respectively. At this time, the adder adds the detection signals from two (k=2) image plane phase difference detectors FS whose design pupil distances DPD are 90 mm and 110 mm, for example.

As described above, it is desirable to match the design pupil distance DPD with the exit pupil distance LPD of the imaging optical system 2 in order to increase the accuracy of focus position detection by the image plane phase difference detector FS. Therefore, if the detection signal from the image plane phase difference detection unit FS having a design pupil distance DPD that is significantly different from the exit pupil distance LPD of the imaging optical system 2 is added to generate an addition signal, the accuracy of focus position detection is reduced. There is also the fear that

Therefore, when generating the addition signal, the number of detection signals to be added may be changed based on the light amount of the light beam LRB, that is, the magnitude of the detection signal from the image plane phase difference detection section FS. That is, when the amount of light incident on the imaging device 3 is small and the intensity of the imaging signal output from the imaging device 3 is low, the addition unit adds more detection signals than when the intensity of the imaging signal is high. can be Here, the imaging signal output by the imaging device 3 may be a detection signal output by an AF pixel, and an image forming signal output by an imaging pixel (G pixel G, B pixel B, R pixel R). can be

Note that the effect on the accuracy of focus position detection due to the mismatch between the exit pupil distance LPD of the imaging optical system 2 and the design pupil distance DPD of the image plane phase difference detection unit FS is the aperture value (F value) of the imaging optical system 2 The larger the value of , the larger. Therefore, when generating the addition signal, the addition unit may add more detection signals when the aperture value of the imaging optical system 2 is small than when the aperture value of the imaging optical system 2 is large.

By the way, the influence on the accuracy of focus position detection due to the mismatch between the exit pupil distance LPD of the imaging optical system 2 and the design pupil distance DPD of the image plane phase difference detection unit FS is due to the in-focus state detection unit FA in the image sensor 3. It also depends on the position. That is, when the in-focus state detection unit FA is near the center of the effective imaging area IA in the detection direction (X direction), that is, when it is near the detection direction from the optical axis AX of the imaging optical system 2, the effect is small. The influence is great when the state detection part FA is away from the optical axis AX in the detection direction.

Therefore, when the addition signal is generated, when the position of the focus state detection unit FA in the detection direction (X direction) is close to the center of the image sensor 3, the addition unit detects the position of the focus state detection unit FA in the first direction. is far from the center of the imaging element 3, more detection signals may be added.

FIG. 8 is a diagram showing some examples of the positions of the focus state detection units FA (FA1 to FA6) on the image sensor 3. FIG. For example, in the focus state detection units FA1 and FA2 where the distance in the X direction from the center CL in the X direction of the effective imaging area IA on the imaging surface 3s of the imaging element 3 is less than the distance D1, m image plane positions All the detection signals from the phase difference detector FS may be added.

On the other hand, the addition unit adds k1 detection signals in the focus state detection units FA5 and FA6 whose distance in the X direction from the center CL is the distance D2 or more, and the distance in the X direction from the center CL is the distance D1. As described above, k2 detection signals may be added in the focus state detection units FA3 and FA4 where the distance is less than D2. Here, both k1 and K2 are natural numbers, and 1≦k1<k2<m.

Note that when there are a plurality of focus state detection units FA (FA1 to FA6) in the effective imaging area IA, the addition unit determines the position of the selected focus state detection unit FA in the detection direction (X direction). , a method of adding the detection signals from all the focus state detection units FA may be determined. That is, when the position of the selected focus state detection unit FA in the X direction is close to the center of the image pickup device 3, the addition unit determines that the focus state detection units FA A large number of detection signals from the image plane phase difference detection section FS may be added.

Which focus state detection unit FA to select from among the plurality of focus state detection units FA may be input by the user through the operation unit 8, and the imaging control unit 4 may be determined.

In the above description, one in-focus state detection unit FA includes a plurality of image plane phase difference detection units FS with different design pupil distances DPD. Furthermore, it may include an image plane phase difference detector FS having the same design pupil distance DPD. In this case, the adder may add the detection signals from the image plane phase difference detectors FS having the same design pupil distance DPD.

As an example of such a focus state detection section FA, a plurality of focus state detection sections FA shown in FIG. 7 may be arranged close to each other in the Y direction at the same X position.
Alternatively, a plurality of image plane phase difference detection units FS having the same design pupil distance DPD are grouped and arranged close to each other in the Y direction, and a group of image plane phase difference detection units FS having different design pupil distances DPD. may be arranged at positions relatively separated from them in the Y direction.

Depending on the imaging device 1, the size of the effective imaging area IA on the imaging element 3 may be changeable. For example, it may be possible to switch the size of the effective imaging area IA between a so-called 35 mm full frame size and a smaller size. Then, the optimum detection condition of the image plane phase difference detection unit FS may change due to the change of the effective imaging area IA. Therefore, the adding section may change the number of detection signals to be added according to the size of the effective imaging area IA of the imaging device 3 .

(Modified Example of Arrangement of Image Plane Phase Difference Detector)
FIG. 9 is a diagram showing a modification of the arrangement of the image plane phase difference detection section FS in the focus state detection section FA.
In the first embodiment described above, in the focus state detection unit FA, the first AF pixel P and the second AF pixel M, which are AF pixels, are both B pixels B (or R pixels R) arranged in the original Bayer array. It is assumed that it is placed at the position where it should be. Therefore, the X positions of the AF pixels are arranged at intervals of two pixels 40 .

In the arrangement of the modification shown in FIG. 9, the AF pixels are arranged at the positions of the B pixels B in the original Bayer arrangement in the odd-numbered image plane phase difference detection units FSA, FSC, and FSE in the Y direction, and the even-numbered AF pixels in the Y direction. th image plane phase difference detection units FSBs and FSDs are arranged at the position of the R pixel R. Therefore, the X positions of the AF pixels are arranged at intervals of one pixel 40 inside the focus state detection unit FA.

Therefore, in the arrangement of this modified example, since the density of sampling by the first AF pixel P and the second AF pixel M, which are AF pixels for the image formed by the imaging optical system 2, is improved, a more accurate image plane phase difference can be obtained. Detection can be performed.

The example of FIG. 9 is just an example, and the AF pixels are arranged at the positions of the R pixels R in the original Bayer arrangement in the odd-numbered image plane phase difference detection units FSA, FSC, and FSE in the Y direction. The even-numbered image plane phase difference detection units FSBs and FSDs may be arranged at the positions of the B pixels.

In the above embodiments and modified examples, for example, as described above, when the addition section is configured by the signal line 33 and the readout section 34, or when the addition section is configured by the addition circuit provided in the output section 36 of the image sensor 3, In this case, the imaging device 3 can also be said to be an imaging device. The adder circuit may be stacked on the imaging section of the imaging device 3 .

(Effects of Embodiments and Modifications)
According to the embodiment described above, the following effects are obtained.
(1) The imaging device 1 of each of the above-described embodiments has a first direction (X direction) as a detection direction, and designed pupils arranged at different positions in a second direction (Y direction) that intersects with the first direction. The image sensor 3 having a focus state detection unit FA including a plurality of image plane phase difference detection units FS with different distances DPD, and a plurality of image plane phase difference detection units FS included in the focus state detection unit FA detected and an addition unit (readout unit 34 or the like, or imaging control unit 4) that adds at least two of the plurality of detection signals to generate an addition signal.
With this configuration, it is possible to improve the accuracy of focus position detection even for a subject under low illuminance.

(2) The image plane phase difference detection unit FS detects the light that has passed through one side of the exit pupil EP of the imaging optical system 2 in the first direction (X direction) to the side opposite to the one side of the exit pupil EP. A first detection unit F1 in which a plurality of first light receiving units (photoelectric conversion units 41 of the first AF pixels P) that detect more light than light passing through the other side are arranged in a first direction, and a first direction of the exit pupil EP A plurality of second light receiving units (photoelectric conversion units 41 of the second AF pixels M) that detect more light that has passed through the other side of the exit pupil EP than light that has passed through the one side of the exit pupil EP are arranged in the first direction. and a second detection unit F2. Then, the addition unit adds at least two of the plurality of detection signals from the first detection unit F1 included in the plurality of image plane phase difference detection units FS, and adds the signals to the image plane phase difference detection units FS. At least two of the plurality of detection signals from the second detection section F2 may be added.
With this configuration, it is possible to further improve the accuracy of focus position detection even for a subject under low illumination.

(3) When the amount of light incident on the imaging device 3 is small and the intensity of the imaging signal output by the imaging device 3 is low, the addition unit adds more detection signals than when the intensity of the imaging signal is high. Also good. In this case, when the amount of light incident on the imaging device 3 is small and the intensity of the imaging signal output by the imaging device 3 is small, the S/N of the detection signal can be improved by adding many detection signals. This makes it possible to perform highly accurate focus position detection. On the other hand, when the amount of light incident on the imaging device 3 is large and the intensity of the imaging signal output by the imaging device 3 is high, the detection signal with the highest detection accuracy, that is, the design pupil distance DPD is the exit pupil distance LPD of the imaging optical system 2. By preferentially using the detection signal from the image plane phase difference detector FS closest to , highly accurate focus position detection can be performed.

(4) The adder may add more detection signals when the aperture value (F value) of the imaging optical system 2 is small than when the aperture value of the imaging optical system 2 is large. When the aperture value (F value) of the imaging optical system 2 is small, the effect on the accuracy of focus position detection due to the mismatch between the exit pupil distance LPD of the imaging optical system 2 and the design pupil distance DPD of the image plane phase difference detection unit FS Less is. Therefore, when the aperture value of the imaging optical system 2 is small, the improvement in focus position detection accuracy due to the improvement in the detection signal S/N due to the addition of many detection signals is the exit pupil distance LPD and the design pupil distance DPD. is larger than the decrease in the accuracy of focus position detection due to the discrepancy with . Thereby, highly accurate focus position detection can be performed.

(5) The image pickup device 3 has a plurality of focus state detection units FA, and the adder unit adjusts the focus state detection unit FA when the position of the focus state detection unit FA is close to the center of the image pickup device 3 in the first direction. is far from the center of the imaging element 3 in the first direction, more detection signals may be added. When the position of the in-focus state detection unit FA in the first direction is close to the center of the image pickup device 3, the focus associated with the mismatch between the exit pupil distance LPD of the imaging optical system 2 and the design pupil distance DPD of the image plane phase difference detection unit FS Less impact on position detection accuracy. When the position of the in-focus state detection unit FA in the first direction is close to the center of the image pickup device 3, the improvement in focus position detection accuracy due to the improvement in the detection signal S/N due to the addition of many detection signals This is larger than the decrease in focus position detection accuracy caused by the discrepancy between the pupil distance LPD and the design pupil distance DPD. Thereby, highly accurate focus position detection can be performed.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Moreover, each embodiment and modification may be applied independently, respectively, and may be used in combination. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1: imaging device, 2: imaging optical system, 3: imaging device, 4: imaging control unit, 6: lens driving unit, 7: display unit, 8: operation unit, 30: semiconductor substrate, 31: control unit, 40: Pixel, P: first AF pixel, M: second AF pixel, F1: first detection unit, F2: second detection unit, FS: image plane phase difference detection unit, 32: control line, 33: signal line, 34: readout Section 36: Output Section 41: Photoelectric Conversion Section 42: Amplifier Circuit 44: Color Filter 45: Microlens 46P: First Light Blocking Section 46M: Second Light Blocking Section

Claims (10)

A focus state detection unit including a plurality of image plane phase difference detection units each having a different design pupil distance and arranged at different positions in a second direction intersecting the first direction with a first direction as a detection direction. an imaging device;
an addition unit that adds at least two of a plurality of detection signals detected by the plurality of image plane phase difference detection units included in the in-focus state detection unit to generate an addition signal;
An imaging device comprising: The imaging device according to claim 1,
The image plane phase difference detection unit is
A first light receiving unit that detects more light that has passed through one side of the exit pupil of the imaging optical system in the first direction than light that has passed through the other side of the exit pupil that is opposite to the one side of the exit pupil. a first detection unit in which a plurality of are arranged in the first direction;
A plurality of second light receiving units are arranged in the first direction for detecting more light that has passed through the other side of the exit pupil in the first direction than light that has passed through the one side of the exit pupil. a second detection unit;
An imaging device, comprising: In the imaging device according to claim 2,
The addition unit
adding at least two of the plurality of detection signals from the first detection unit included in the plurality of image plane phase difference detection units;
adding at least two of the plurality of detection signals from the second detection unit included in the plurality of image plane phase difference detection units;
Imaging device. In the imaging device according to claim 2 or 3,
The second detection unit is arranged apart from the first detection unit by a first distance in the second direction,
Each of the plurality of image plane phase difference detection units is arranged in the second direction at a distance of a second distance longer than the first distance,
Imaging device. In the imaging device according to any one of claims 1 to 4,
When the amount of light incident on the imaging element is small and the intensity of the imaging signal output by the imaging element is low, the addition unit adds more detection signals than when the intensity of the imaging signal is high. Imaging device. In the imaging device according to any one of claims 1 to 5,
The imaging device, wherein the adder adds more detection signals when the aperture value of the imaging optical system is small than when the aperture value of the imaging optical system is large. In the imaging device according to any one of claims 1 to 6,
The imaging device has a plurality of the focus state detection units,
When the position of the focus state detection unit in the first direction is close to the center of the image pickup device, the adder unit adjusts the position of the focus state detection unit in the first direction far from the center of the image pickup device. An imaging device that adds a larger number of the detection signals. In the imaging device according to any one of claims 1 to 7,
The imaging device has a plurality of the focus state detection units,
The adding section detects the selected focus state when the position of the focus state detection section selected from among the plurality of focus state detection sections in the first direction is close to the center of the imaging device. an image pickup apparatus, wherein more of the detection signals from the image plane phase difference detection section are added in the plurality of focus state detection sections than when the position of the section in the first direction is far from the center of the image pickup device. In the imaging device according to any one of claims 1 to 8,
The imaging device, wherein the adding section selects the plurality of detection signals to be added according to an exit pupil distance of an imaging optical system. In the imaging device according to any one of claims 1 to 9,
The imaging device, wherein the adding section changes the number of the detection signals to be added according to the size of the effective imaging area of the imaging element.

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