JP2015162562A - Imaging apparatus and digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform focus detection in a pupil division phase difference manner using infrared light and also to pick up a visible light image.SOLUTION: An imaging apparatus includes: a first imaging element which photoelectrically converts light made incident on a surface side of a semiconductor substrate; a second imaging element which is stacked and arranged on a surface side of the first imaging element, and photoelectrically converts infrared light by using an organic photoelectric film absorbing the infrared light and transmitting the visible light; and a microlens array which is stacked and arranged on the opposite side of the second imaging element from the first imaging element. The first imaging element has a plurality of first pixels which output a first photoelectric conversion signal, and the second imaging element has a plurality of first pixels which output a second photoelectric conversion signal. The second pixels are pixels for focus detection which output a focus detection signal for detecting a focus adjustment state of an imaging optical system in a pupil division phase difference manner, and a light guide which guides the visible light transmitted through the second pixels of the second imaging element to the first pixels of the first imaging element is formed between the second imaging element and first imaging element.

Description

  The present invention relates to an imaging apparatus and a digital camera.

  A photoelectric conversion film that absorbs infrared light and performs photoelectric conversion is disposed above a semiconductor substrate having a photoelectric conversion unit that photoelectrically converts visible light (RGB), and captures a visible light image and an infrared light image. There is known an image pickup device configured to be able to simultaneously perform (see Patent Document 1).

JP 2012-169676 A

  In the above prior art, focus detection by the pupil division phase difference method cannot be performed.

(1) The imaging device according to claim 1 photoelectrically converts light incident on the surface side of the semiconductor substrate to generate a first photoelectric conversion signal, and via a wiring layer formed on the surface side of the semiconductor substrate. Infrared light is photoelectrically converted using a first imaging element that outputs a first photoelectric conversion signal and an organic photoelectric film that is laminated on the surface side of the first imaging element and absorbs infrared light and transmits visible light. The second image sensor that generates the second photoelectric conversion signal and outputs the second photoelectric conversion signal via the wiring layer, and the second image sensor is stacked on the opposite side of the first image sensor, and a plurality of micro-elements are arranged. A microlens array in which lenses are two-dimensionally arranged, and the first imaging element is provided corresponding to each of the microlenses and includes a plurality of first pixels that output a first photoelectric conversion signal, The second image sensor is provided corresponding to each of the micro lenses, and the second light There are a plurality of second pixels that output conversion signals, and the second pixels are focus detection pixels that output focus detection signals for detecting the focus adjustment state of the imaging optical system by the pupil division phase difference method. An optical waveguide that guides visible light transmitted through the second pixel of the second image sensor to the first pixel of the first image sensor is formed between the second image sensor and the first image sensor. It is characterized by.
(2) The imaging device according to claim 3, photoelectrically converts light incident on the back surface side of the semiconductor substrate to generate a first photoelectric conversion signal, and via a wiring layer formed on the front surface side of the semiconductor substrate Infrared light using a back-illuminated first imaging element that outputs a first photoelectric conversion signal and an organic photoelectric film that is laminated on the back side of the first imaging element and absorbs infrared light and transmits visible light The second imaging element that photoelectrically converts the second imaging signal to generate the second photoelectric conversion signal and outputs the second photoelectric conversion signal via the wiring layer is stacked on the opposite side of the second imaging element from the first imaging element. A microlens array in which a plurality of microlenses are two-dimensionally arranged, and a first imaging element is provided corresponding to each of the microlenses and includes a first pixel that outputs a first photoelectric conversion signal. A plurality of second image sensors are provided corresponding to each of the micro lenses. And a second pixel that outputs a second photoelectric conversion signal, and the second pixel outputs a focus detection signal for detecting a focus adjustment state of the imaging optical system by a pupil division phase difference method. It is a pixel for use.
(3) A digital camera according to a seventh aspect generates an image signal based on the imaging device according to any one of the first to sixth aspects and a first photoelectric conversion signal output from the first imaging element. And a first focus detection unit that detects a focus adjustment state of the imaging optical system by a pupil division phase difference method based on a second photoelectric conversion signal output from the second image sensor. Features.

  ADVANTAGE OF THE INVENTION According to this invention, the focus detection of a pupil division | segmentation phase difference system using infrared light can be performed, and a visible light image can be imaged.

It is a block diagram explaining the structural example of a digital camera. It is a figure explaining the outline | summary of an imaging part. (A) is a figure explaining the example of arrangement | positioning of a color filter, (b) is a figure explaining the output of each pixel of a 2nd image sensor, (c) is the output of each pixel of a 1st image sensor. It is a figure explaining. In the first embodiment, (a) is a diagram for explaining an example of a semiconductor layout of an imaging unit, (b) is a cross-sectional view when the imaging unit is cut along a cutting line AB, and (c) ) Is a cross-sectional view when the imaging unit is cut along a cutting line CD. (A) is sectional drawing when an imaging part is cut | disconnected by cutting line AB, (b) is a figure explaining the pixel position of cutting line AB in a 2nd image pick-up element. (A) is sectional drawing when an imaging part is cut | disconnected by the cutting line CD, (b) is a figure explaining the pixel position of the cutting line CD in a 2nd image pick-up element. It is the figure which expanded a part of Fig.6 (a). It is a figure which illustrates the circuit structure of one pixel in an imaging part. It is a flowchart explaining the flow of a focus detection process. It is a flowchart explaining the flow of imaging | photography process. In 2nd Embodiment, (a) is a figure explaining an example of the semiconductor layout of an imaging part, (b) is sectional drawing when an imaging part is cut | disconnected by the cutting line AB, (c) ) Is a cross-sectional view when the imaging unit is cut along a cutting line CD. It is sectional drawing when the imaging part by a modification is cut | disconnected by the cutting line CD. It is a figure explaining the outline | summary of the imaging part by a modification.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of a digital camera 1 according to the first embodiment of the invention. The digital camera 1 includes a photographing optical system 10, a control unit 11, an imaging unit 12, an operation unit 13, a liquid crystal monitor 15, and a buffer memory 16. In addition, a memory card 17 is attached to the digital camera 1.

  The photographing optical system 10 is composed of a plurality of lenses, and forms a subject image on the imaging surface of the imaging unit 12. The plurality of lenses constituting the photographing optical system 10 include a focus lens that is driven in the optical axis direction in order to adjust the focus position. The focus lens is driven in the optical axis direction by a lens driving unit (not shown).

  The control unit 11 includes a microprocessor and its peripheral circuits, and performs various controls of the digital camera 1 by executing a control program stored in a ROM (not shown). The control unit 11 functionally includes a focus detection unit 11a and an image generation unit 11b. Each of these functional units is implemented in software by the control program described above. Each of these functional units can also be configured by an electronic circuit.

  The focus detection unit 11 a detects the focus adjustment state of the photographing optical system 10 based on the output signal from the imaging unit 12. The image generation unit 11b generates a color image signal based on the output signal from the imaging unit 12.

  The subject image formed on the imaging unit 12 by the imaging optical system 10 is photoelectrically converted by the imaging unit 12. An output signal from the imaging unit 12 is converted into a digital image signal by an A / D conversion unit (not shown) and stored in the buffer memory 16.

  The digital image signal stored in the buffer memory 16 is displayed on the liquid crystal monitor 15 or stored in the memory card 17 after various image processing is performed. The memory card 17 is composed of a non-volatile flash memory or the like and is detachable from the digital camera 1.

  The operation unit 13 includes various operation buttons such as a release button, a mode switching button, and a power button, and is operated by a photographer. The operation unit 13 outputs an operation signal corresponding to the operation of each operation button by the photographer to the control unit 11.

<Description of imaging unit>
FIG. 2 is a diagram illustrating an overview of the imaging unit 12 according to the present embodiment. FIG. 2 shows a state where the light incident side of the imaging unit 12 is the upper side. Therefore, in the following description, the direction on the light incident side of the imaging unit 12 is “upper” or “upper”, and the direction opposite to the light incident side is “lower” or “lower”. The imaging unit 12 includes a first imaging element 31 and a second imaging element 32 disposed on the same optical path on the light incident side (upper side) of the first imaging element 31. The second imaging element 32 is configured by an organic photoelectric film that absorbs infrared light (photoelectric conversion). Visible light that has not been absorbed (photoelectrically converted) by the second image sensor 32 passes through the second image sensor 32 and enters the first image sensor 31, and is photoelectrically converted by the first image sensor 31. The first image sensor 31 performs photoelectric conversion using a photodiode. The second image sensor 32 and the first image sensor 31 are formed on the same semiconductor substrate, and each pixel position corresponds to one to one. For example, the pixel in the first row and the first column of the second image sensor 32 corresponds to the pixel in the first row and the first column of the first image sensor 31.

  FIG. 3A shows the arrangement of the color filter CF provided above the second image sensor 32. FIG. 3B shows the output of each pixel of the second image sensor 32. FIG. 3C shows the output of each pixel of the first image sensor 31. 3A to 3C, the horizontal direction is the x axis, the vertical direction is the y axis, and the coordinates of the pixel P are represented as P (x, y).

  Above the second image sensor 32, as shown in FIG. 3A, a color filter CF that transmits red (R), green (G), and blue (B) is provided in a so-called Bayer array. It has been. The color filter CF is configured to transmit infrared light in addition to any of RGB light. Note that no infrared filter is provided above the color filter CF. Specifically, the color filter CF (1, 1) disposed above the pixel P (1, 1) transmits G light and infrared light. For this reason, G light and infrared light are incident on the pixel P (1,1) of the second image sensor. Similarly, the color filter CF (2, 1) disposed above the pixel P (2, 1) transmits B light and infrared light. For this reason, B light and infrared light are incident on the pixel P (2, 1) of the second image sensor.

  In the second image sensor 32 shown in FIG. 3B, each pixel P is an organic photoelectric film that photoelectrically converts infrared light. Therefore, each pixel P absorbs infrared light and transmits visible light. For example, the pixel P (1, 1) to which infrared light and G light are incident photoelectrically converts infrared light (IR) and transmits G light. Similarly, the pixel P (2,1) to which the infrared light and B light are incident photoelectrically converts the infrared light (IR) and transmits the B light. The pixels P (1, 2) on which the infrared light and R light are incident photoelectrically convert the infrared light (IR) and transmit the R light. Further, as will be described in detail later, each pixel P of the second image sensor 32 is composed of focus detection pixels corresponding to the pupil division phase difference method.

  In the first image sensor 31 shown in FIG. 3C, the visible light transmitted through the second image sensor 32 is photoelectrically converted in each pixel P. In the first image sensor 31, for example, an image signal of the G component is obtained at the pixel P (1, 1) on which G light is incident. Similarly, a B component image signal is obtained at the pixel P (2,1) where the B light is incident, and an R component image signal is obtained at the pixel P (1,2) where the R light is incident.

  As described above, in the imaging unit 12 according to the present embodiment, the second imaging element 32 formed of an organic photoelectric film serves as an infrared filter with respect to the first imaging element 31. Therefore, the infrared filter installed in front of the image sensor in the conventional digital camera can be omitted.

  Further, in the imaging unit 12 according to the present embodiment, imaging pixels are arranged on the first imaging element 31 and focus detection pixels are arranged uniformly on the entire surface of the second imaging element 32. Therefore, it is not necessary to perform complicated pixel interpolation processing as in the prior art in which focus detection pixels are arranged in a part of the image pickup pixels, and the focus detection signal from the second image pickup element 32, the first A color (RGB) image signal by visible light can be obtained independently from the image sensor 31. Note that the imaging unit 12 is configured such that the first imaging element 31 and the second imaging element 32 can be independently driven, so that accumulation time control with a high degree of freedom is possible.

  FIG. 4A is an example of a semiconductor layout of the imaging unit 12. 4A corresponds to each pixel P (1,1) to pixel P (2,2) in FIG. 3 described above. 4B and 5A are cross-sectional views when the pixel P (1,1) and the pixel (2,1) of FIG. 4A are cut along the cutting line AB in the horizontal direction. is there. FIG. 5B is a diagram depicting the pixel position of the cutting line AB in the second image sensor 32 so that it can be easily understood. The cutting line AB cuts portions of the photoelectric conversion units PC_A (1, 1) and PC_A (2, 1). 4C and 6A are cross-sectional views when the pixel P (2,1) and the pixel (2,2) of FIG. 4A are cut along the cutting line CD in the vertical direction. is there. FIG. 6B is a diagram depicting the pixel position of the cutting line CD in the second image sensor 32 so that it can be easily understood. The cutting line CD cuts the photoelectric conversion units PC_A (2,1), PC_B (2,1), PC_A (2,2), and PC_B (2,2). FIG. 7 is an enlarged view of a part of FIG.

  As shown in FIG. 5, the first image sensor 31 is a so-called surface irradiation type image sensor, and photoelectrically converts light incident on the surface side of the semiconductor substrate 50 by the photodiode PD and A photoelectric conversion signal is output through the formed wiring layer 51. The second image sensor 32 using the organic photoelectric film is stacked on the surface side of the first image sensor 31. A microlens array in which a plurality of microlenses ML are two-dimensionally arranged is stacked above the second imaging element 32 (that is, on the side opposite to the first imaging element 31). Each pixel of the first image sensor 31 and the second image sensor 32 is provided corresponding to each microlens ML. In addition, the above-described color filter CF is disposed between each pixel of the second image sensor 32 and each microlens ML.

  The photoelectric conversion signal output from the second image sensor 32 is taken out from the signal output end 52 via the wiring layer 51. Separation layers 53 and 54 are disposed on both sides of the signal output end 52. Further, the photodiodes PD (1,1) and PD (2,1) are arranged with the separation layers 53 and 54 therebetween. Each pixel P of the first imaging element 31 is an imaging pixel, and one photodiode PD is provided for one imaging pixel. 4 to 6, the wiring layer 51 has a three-layer structure, but may have a two-layer structure.

  Further, as shown in FIG. 6, each pixel P of the second image sensor 32 is a focus detection pixel, and one pixel P is divided into two in the vertical direction in the figure, and two photoelectric conversions per one pixel P are performed. Parts PC_A and PC_B are provided. For example, the pixel P (2, 1) is provided with a photoelectric conversion unit PC_A (2, 1) and a photoelectric conversion unit PC_B (2, 1). Specifically, as shown in FIG. 7, in the pixel P (2,1), the photoelectric conversion unit PC_A (2) with the organic photoelectric film m sandwiched between the common electrode u and the partial electrode d_A (2,1). , 1) is configured. In addition, the photoelectric conversion unit PC_B (2, 1) is configured by sandwiching the organic photoelectric film m between the common electrode u and the partial electrode d_B (2, 1). The common electrode u is disposed on the microlens ML side, and the partial electrodes d_A and d_B are disposed on the first imaging element 31 side. The common electrode u and the partial electrodes d_A and d_B are transparent electrodes. The partial electrode d_A (2,1) is provided on the upper side in the drawing with respect to the center O (2,1) of the microlens ML (2,1), and the partial electrode d_B (2,1) is provided on the microlens ML ( 2,1) with respect to the center O (2,1). The partial electrode d_A (2,1) and the partial electrode d_B (2,1) are spaced apart from the center O (2,1) of the microlens ML (2,1) so as not to contact each other. Provided. The other pixels P are similarly configured.

  Each pixel P of the second image sensor 32 receives a pair of light beams that have passed through a pair of pupil regions of the imaging optical system 10 by the photoelectric conversion unit PC_A and the photoelectric conversion unit PC_B, respectively, and images by the pupil division phase difference method. A focus detection signal for detecting the focus adjustment state of the optical system 10 is output. Here, the wiring layer 51 in FIG. 5A corresponds to the wiring layer 51A and the wiring layer 51B in FIG. 6A. The wiring layer 51A outputs the signal of the photoelectric conversion unit PC_A (2, 1) of the organic photoelectric film to the signal output terminal 52A, and the wiring layer 51B outputs the signal of the photoelectric conversion unit PC_B (2, 1) of the organic photoelectric film. Output to the end 52B. In the wiring layer 51 of FIG. 5A, only one is visible because the wiring layer 51A and the wiring layer 51B overlap.

  The pixels P at the same positions of the first image sensor 31 and the second image sensor 32 receive subject light incident from the same microlens ML. For example, as shown in FIG. 5, among the subject light incident from the microlens ML (1, 1) corresponding to the pixel P (1, 1), infrared light and G light are color filters CF (1, 1). 1) is transmitted, and R and B light is shielded by the color filter CF (1, 1). In the second image sensor 32, the photoelectric conversion unit PC_A (1,1) and the photoelectric conversion unit PC_B (1,1) by the organic photoelectric film constituting the photoelectric conversion unit of the pixel P (1,1) are color filters CF ( 1,1) is subjected to photoelectric conversion, and G light is transmitted. In the first image sensor 31, the photodiode PD (1, 1) constituting the pixel P (1, 1) receives G light transmitted through the photoelectric conversion unit PC (1, 1) and performs photoelectric conversion.

  Further, as shown in FIG. 5, between the second image sensor 32 and the first image sensor 31, the boundary portion between the adjacent pixels of the first image sensor 31 (the signal output end 52 and the separation layers 53 and 54). ), A planarization layer 55 including the wiring layer 51 therein is formed. Further, the second image sensor 32 and the first image sensor 31 are made of a material having a higher refractive index than the planarizing layer 55 on the photodiode PD of each pixel P of the first image sensor 31. An optical waveguide 56 is formed. The optical waveguide 56 totally reflects the visible light transmitted through each pixel P of the second image sensor 32 at the boundary surface 57 between the optical waveguide 56 and the planarization layer 55, and the photo of each pixel P of the first image sensor 31. The light is guided to the diode PD. Further, the dimension of the optical waveguide 56 on the second imaging element 32 side is larger than the dimension on the first imaging element 31 side (photodiode PD side). With the configuration described above, crosstalk occurs between the light beams transmitted through the pixels of the second image sensor 32, and a plurality of pixels of the second image sensor 32 pass through one pixel of the first image sensor 31. It is possible to prevent the light beam from entering. That is, the pixels at the same position of the second image sensor 32 and the first image sensor 31 can receive incident light from the same microlens ML.

  FIG. 8 is a diagram illustrating a circuit configuration of one pixel P (x, y) in the imaging unit 12. The pixel P (x, y) includes a photodiode PD, a transfer transistor Tx, a reset transistor R, an output transistor SF, and a selection transistor SEL as a circuit for configuring the first imaging element 31. The photodiode PD accumulates charges according to the amount of incident light. The transfer transistor Tx transfers the charge accumulated in the photodiode PD to the floating diffusion region (FD portion) on the output transistor SF side. The output transistor SF forms a current source PW and a source follower via the selection transistor SEL, and outputs an electric signal corresponding to the electric charge accumulated in the FD section as an output signal OUT to the vertical signal line VLINE. The reset transistor R resets the charge in the FD portion to the power supply voltage Vcc.

  The pixel P (x, y) includes, as a circuit for configuring the second imaging element 32, photoelectric conversion units PC_A and PC_B using organic photoelectric films, reset transistors R_A and R_B, output transistors SF_A and SF_B, It has selection transistors SEL_A and SEL_B. Photoelectric conversion units PC_A and PC_B using organic photoelectric films convert non-transmitted light into electrical signals according to the amount of light, and output transistors SF_A and SF_B constituting source followers with current sources PW_A and PW_B via selection transistors SEL_A and SEL_B, respectively. Are output to the vertical signal lines VLINE_A and VLINE_B as output signals OUT_A and OUT_B, respectively. Note that the reset transistors R_A and R_B reset the output signals of the photoelectric conversion units PC_A and PC_B to the reference voltage Vref. Further, a high voltage Vpc is applied for the operation of the organic photoelectric film. Each transistor is composed of a MOS_FET.

  Here, the operation of the circuit relating to the first image sensor 31 will be described. First, when the selection signal φSEL becomes “High”, the selection transistor SEL is turned on. Next, when the reset signal φR becomes “High”, the FD section resets the power supply voltage Vcc, and the output signal OUT also becomes the reset level. Then, after the reset signal φR becomes “Low”, the transfer signal φTx becomes “High”, the charge accumulated in the photodiode PD is transferred to the FD portion, and the output signal OUT changes according to the amount of charge. Start and stabilize. Then, the transfer signal φTx becomes “Low”, and the signal level of the output signal OUT read from the pixel to the vertical signal line VLINE is determined. The output signal OUT of each pixel read to the vertical signal line VLINE is temporarily held for each row in a horizontal output circuit (not shown) and then output from the imaging unit 12. In this way, a signal is read from each pixel of the first image sensor 31 of the imaging unit 12.

  The operation of the circuit relating to the second image sensor 32 will be described. First, when the selection signal φSEL_A (or φSEL_B) becomes “High”, the selection transistor SEL_A (or SEL_B) is turned on. Next, the reset signal φR_A (or φR_B) becomes “High”, and the output signal OUT_A (or φOUT_B) also becomes the reset level. Then, immediately after the reset signal φR_A (or φR_B) becomes “Low”, the charge accumulation of the photoelectric conversion unit PC_A (or PC_B) by the organic photoelectric film is started, and the output signal OUT_A (or the output signal OUT_B) according to the amount of charge. ) Will change. The output signal OUT_A (or the output signal OUT_B) is temporarily held for each row in a horizontal output circuit (not shown), and then output from the imaging unit 12. In this way, a signal is read from each pixel of the second image sensor 32 of the imaging unit 12.

<Focus detection processing>
Next, the flow of the focus detection process executed by the control unit 11 will be described using the flowchart shown in FIG. The focus detection process illustrated in FIG. 9 is included in a control program executed by the control unit 11. When a predetermined focus detection operation (for example, an operation of pressing the release button halfway) is performed by the photographer, the control unit 11 starts a focus detection process illustrated in FIG.

  First, in step S1, the imaging unit 12 is caused to capture a subject image. Thereby, a photoelectric conversion signal is output from each of the first image sensor 31 and the second image sensor 32.

  In step S <b> 2, the focus detection unit 11 a performs focus detection processing by the pupil division phase difference method based on the focus detection signal by infrared light output from the second image sensor 32, and adjusts the focus of the imaging optical system 10. A defocus amount indicating the state is calculated. Since focus detection processing by the pupil division phase difference method is a well-known technique, detailed description thereof is omitted.

  In step S3, the control unit 11 determines whether the defocus amount has been calculated by the focus detection process in step S2, that is, whether the focus has been detected. If the focus can be detected, the control unit 11 makes a positive determination in step S3 and proceeds to step S4. On the other hand, if the focus cannot be detected, the control unit 11 makes a negative determination in step S3 and proceeds to step S6.

  In step S4, the focus detection unit 11a controls a lens driving unit (not shown) based on the defocus amount calculated in step S2, drives the focus lens of the photographing optical system 10, and moves to the in-focus position. Let

  In step S5, the control unit 11 determines whether or not an instruction to end the focus detection process is given. When the end of the focus detection process is instructed, step S5 is affirmed and the control unit 11 ends the focus detection process. On the other hand, when the end of the focus detection process is not instructed, the determination in step S5 is negative, and the control unit 11 returns to step S1.

  In step S6 that proceeds when a negative determination is made in step S3, the focus detection unit 11a adds the photoelectric conversion signals output from the two adjacent photoelectric conversion units PC_A and PC_B in each pixel P of the second image sensor 32. Thus, one signal is generated for each pixel P. Thereby, the infrared light image imaged with the 2nd image sensor 32 is acquirable.

  In step S7, the focus detection unit 11a performs a focus detection process by a contrast method based on the infrared light image acquired in step S6. Specifically, the focus detection unit 11a calculates a focus evaluation value (contrast value) based on the acquired infrared light image. To briefly explain the contrast method, the subject lens is picked up periodically while driving the focus lens, the contrast amount of the subject image is examined for each focus lens position, and the position of the focus lens where the contrast amount is maximized is determined. This is a method for specifying the in-focus position.

  In step S8, the focus detection unit 11a determines whether the focus lens is in the focused position, that is, whether the focus is detected, based on the focus evaluation value calculated in step S7. If it is determined that the focus lens is in the in-focus position, the control unit 11 makes a positive determination in step S8 and proceeds to step S5. On the other hand, if it is determined that the focus lens is not in the in-focus position, or if it is determined that focus detection cannot be performed using an infrared light signal, the control unit 11 makes a negative determination in step S8 and performs step Proceed to S9.

  In step S9, the focus detection unit 11a determines whether focus detection using an infrared light signal is possible. When it is determined that the focus cannot be detected with the infrared light signal, or the accuracy is insufficient, or the focus detection with visible light is necessary, the control unit 11 makes a negative determination in step S9 and proceeds to step S11. . On the other hand, if it is determined that focus detection using an infrared light signal is possible, the control unit 11 makes an affirmative determination in step S9 and proceeds to step S10.

  In step S10, the focus detection unit 11a controls a lens driving unit (not shown) to drive the focus lens by a predetermined amount in a predetermined direction in order to search for a focus position by a so-called hill climbing operation, and then proceeds to step S6. Return. That is, the focus detection unit 11a repeats steps S6 to S10 to search for the position of the focus lens where the focus evaluation value is maximized, that is, the focus position, and drives the focus lens to the focus position.

  In step S <b> 11 that proceeds when a negative determination is made in step S <b> 9, the focus detection unit 11 a performs focus detection processing by a contrast method based on the visible light image captured by the first image sensor 31. Specifically, the focus detection unit 11a calculates a focus evaluation value (contrast value) based on the acquired visible light image.

  In step S12, the focus detection unit 11a determines whether the focus lens is in the focused position, that is, whether the focus is detected, based on the focus evaluation value calculated in step S11. If it is determined that the focus lens is in the in-focus position, the control unit 11 makes a positive determination in step S12 and proceeds to step S5. On the other hand, if it is determined that the focus lens is not at the in-focus position, the control unit 11 makes a negative determination in step S12 and proceeds to step S13.

  In step S13, the focus detection unit 11a controls a lens driving unit (not shown) to drive the focus lens by a predetermined amount in a predetermined direction in order to search for the in-focus position by so-called hill climbing operation, and then proceeds to step S11. Return. In other words, the focus detection unit 11a repeats steps S11 to S13, searches for the position of the focus lens where the focus evaluation value is maximized, that is, the focus position, and drives the focus lens to the focus position.

Thus, in the digital camera 1 of the present embodiment, the following three types of focus detection processing can be performed based on the output signal from the imaging unit 12, and the following three types of focus detection processing can be used appropriately. it can.
(1) Focus detection process based on the pupil division phase difference method based on the infrared light signal from the second image sensor 32 (2) Focus detection process based on the contrast method based on the infrared light signal from the second image sensor 32 (3) Focus detection processing by a contrast method based on a visible light signal from the first image sensor 31

<Shooting process>
FIG. 10 is a flowchart for explaining the flow of imaging processing executed by the control unit 11. When the main switch is turned on, the control unit 11 causes the imaging unit 12 to start photoelectric conversion at a predetermined frame rate, and sequentially reproduces and displays a through image based on the image signal on the liquid crystal monitor 15, as illustrated in FIG. 10. Start the program that executes the process. Note that the through image is a monitor image acquired before an imaging instruction.

  In step S <b> 21 of FIG. 10, the control unit 11 determines whether a shooting instruction has been issued. When the release button is pressed, the control unit 11 makes a positive determination in step S21 and proceeds to step S22. If the release button is not pressed, the control unit 11 makes a negative determination in step S21 and proceeds to step S28.

  In step S28, the control unit 11 determines whether the time is up. The control unit 11 makes an affirmative decision in step S28 when a predetermined time (for example, 5 seconds) is counted, and ends the process of FIG. If the timed time is less than the predetermined time, the control unit 11 makes a negative determination in step S28 and returns to step S21.

  In step S22, the control unit 11 performs AE processing and AF processing. In the AE process, an exposure calculation is performed based on the level of the image signal for the through image, and an aperture value AV and a shutter speed TV are determined so that an appropriate exposure can be obtained. In the AF process, the focus adjustment is performed by performing the above-described focus detection process based on the output signal string from the pixel string included in the set focus detection area. When the control unit 11 performs the above AE and AF processes, the process proceeds to step S23.

  In step S23, the control unit 11 performs a photographing process and proceeds to step S24. Specifically, a diaphragm (not shown) is controlled based on the AV, and the imaging unit 12 performs photoelectric conversion for recording in the accumulation time based on the TV.

  In step S <b> 24, the image generation unit 11 b of the control unit 11 generates an image signal using the output signal from the first image sensor 31. As described above, since a so-called Bayer array image signal can be acquired from the first image sensor 31, the image generation unit 11b uses a known color interpolation process to output RGB three colors from the output signal of the first image sensor 31. Color image signals can be generated. Further, the image generation unit 11b performs predetermined image processing (gradation conversion processing, contour enhancement processing, white balance adjustment processing, etc.) on the generated color image signal.

  In step S25, the control unit 11 displays the captured image after the image processing in step S24 on the liquid crystal monitor 15, and proceeds to step S26.

  In step S26, the control unit 11 generates an image file for recording the captured image after the image processing in step S24, and proceeds to step S27.

  In step S27, the control unit 11 records the image file generated in step S26 on the memory card 17, and ends the photographing process.

According to the embodiment described above, the following operational effects can be obtained.
The imaging unit 12 of the digital camera 1 photoelectrically converts light incident on the surface side of the semiconductor substrate 50 to generate a photoelectric conversion signal, and the photoelectric conversion signal via the wiring layer 51 formed on the surface side of the semiconductor substrate 50. Is provided. The imaging unit 12 is stacked on the surface side of the semiconductor substrate 50 of the first imaging element 31 and photoelectrically converts infrared light using an organic photoelectric film that absorbs infrared light and transmits visible light. A second imaging element 32 that generates a conversion signal and outputs a photoelectric conversion signal via the wiring layer 51 is provided. In addition, the imaging unit 12 includes a microlens array in which the second imaging element 32 is stacked on the opposite side of the first imaging element 31 and a plurality of microlenses ML are two-dimensionally arranged. The first imaging element 31 has a plurality of imaging pixels provided corresponding to each of the microlenses ML. The second imaging element 32 has a plurality of focus detection pixels provided corresponding to each of the microlenses ML. The focus detection pixel is a focus detection pixel that outputs a focus detection signal for detecting the focus adjustment state of the photographing optical system 10 by the pupil division phase difference method. Between the second image sensor 32 and the first image sensor 31, there is an optical waveguide 56 that guides visible light transmitted through the focus detection pixels of the second image sensor 32 to the image pixels of the first image sensor 31. Is formed. With such a configuration, it is possible to perform focus detection by the pupil division phase difference method with high speed and high accuracy based on the focus detection signal of the infrared light from the second image sensor 32. Since focus detection is performed using infrared light, focus detection accuracy can be increased even in dark fields and low luminance. Furthermore, it is possible to prevent crosstalk from occurring between the light fluxes transmitted through the focus detection pixels of the second image sensor 32, and a visible light image can be appropriately captured by the first image sensor 31.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, the imaging unit 112 in the second embodiment will be described mainly with respect to differences from the first embodiment, and the description of the same configuration as in the first embodiment will be omitted.

  The configuration of the imaging unit 112 according to the second embodiment will be described with reference to FIG. FIG. 11A is an example of a semiconductor layout of the imaging unit 112. FIG. 11A corresponds to each pixel P (1,1) to pixel P (2,2) in FIG. 3 described above. FIG. 11B is a cross-sectional view of the pixel P (1,1) and the pixel (2,1) in FIG. 11A when cut in the horizontal direction along the cutting line AB. FIG. 11C is a cross-sectional view of the pixel P (2,1) and the pixel (2,2) of FIG. 11A cut along the cutting line CD in the vertical direction.

  Unlike the first embodiment, the first image sensor 131 in the second embodiment is a so-called back-illuminated image sensor. Therefore, the first image sensor 131 photoelectrically converts light incident on the back surface side of the semiconductor substrate 150 by the photodiode PD to generate a photoelectric conversion signal, and passes through the wiring layer 151 formed on the front surface side of the semiconductor substrate 150. The photoelectric conversion signal is output. A second image sensor 132 using an organic photoelectric film similar to that of the first embodiment is stacked on the back side of the first image sensor 131. Similar to the first embodiment, a microlens array in which a plurality of microlenses ML are two-dimensionally arranged is stacked above the second imaging element 132 (that is, on the side opposite to the first imaging element 131). Has been placed. In addition, a color filter CF is disposed between each pixel of the second image sensor 132 and each microlens ML, as in the first embodiment.

  A through via (through silicon via (TSV)) 152 for connecting the second image sensor 132 and the wiring layer 151 is formed in the semiconductor substrate 150 of the first image sensor 131. The photoelectric conversion signal output from the second image sensor 132 is output from the wiring layer 151 through the through via 152. The through via 152 is provided for each photoelectric conversion unit PC_A, PC_B (partial electrode d_A, d_B) of each pixel P of the second imaging element 132.

  In the imaging unit 112 of the second embodiment, since the first imaging element 131 is configured as a back-illuminated type, unlike the first embodiment, the second imaging element 132 and the light receiving surfaces of the first imaging element 131 There is no wiring layer between them. Therefore, in the second embodiment, since the distance between the second image sensor 132 and the light receiving surface of the first image sensor 131 can be shortened compared to the first embodiment, each pixel of the second image sensor 132 can be reduced. It is possible to prevent crosstalk from occurring between the light fluxes that have passed through the first imaging element 31 and prevent the light fluxes that have passed through the plurality of pixels of the second imaging element 132 from entering one pixel of the first imaging element 31. That is, the pixels at the same position of the second image sensor 132 and the first image sensor 131 can receive incident light from the same microlens ML.

According to the embodiment described above, the following operational effects can be obtained.
The imaging unit 112 photoelectrically converts light incident on the back surface side of the semiconductor substrate 150 to generate a photoelectric conversion signal, and outputs the photoelectric conversion signal via the wiring layer 151 formed on the front surface side of the semiconductor substrate 150. An irradiation-type first imaging element 131 is provided. The imaging unit 112 is stacked on the back side of the semiconductor substrate 150 of the first imaging element 131 and photoelectrically converts infrared light using an organic photoelectric film that absorbs infrared light and transmits visible light. A second imaging element 132 that generates a conversion signal and outputs a photoelectric conversion signal via the wiring layer 151 is provided. The imaging unit 112 includes a microlens array in which the second imaging element 132 is stacked on the opposite side of the first imaging element 131 and a plurality of microlenses ML are two-dimensionally arranged. The first imaging element 131 has a plurality of imaging pixels provided corresponding to each of the microlenses ML. The second imaging element 132 has a plurality of focus detection pixels provided corresponding to each of the microlenses ML. The focus detection pixel is a focus detection pixel that outputs a focus detection signal for detecting the focus adjustment state of the photographing optical system 10 by the pupil division phase difference method. With such a configuration, it is possible to perform focus detection by the pupil division phase difference method with high speed and high accuracy based on the focus detection signal of the infrared light from the second image sensor 32. Furthermore, it is possible to prevent crosstalk from occurring between the light fluxes transmitted through the focus detection pixels of the second image sensor 32, and a visible light image can be appropriately captured by the first image sensor 31.

(Modification 1)
In the embodiment described above, each of the focus detection pixels of the second image sensor 32 has two photoelectric conversion units PC_A and PC_B, and the photoelectric conversion unit PC_A has passed through a pair of pupil regions of the imaging optical system 10, respectively. The example in which one of the pair of light beams is received and the photoelectric conversion unit PC_B receives the other of the pair of light beams has been described.

  However, the focus detection pixel is not limited to the above configuration. For example, as shown in FIG. 12, the focus detection pixel having only the photoelectric conversion unit PC_A and the focus detection pixel having only the photoelectric conversion unit PC_B. The pixels may be arranged alternately. For example, the pixel P (2,1) has only the photoelectric conversion unit PC_A (2,1) configured by sandwiching the organic photoelectric film m between the common electrode u and the partial electrode d_A (2,1). The partial electrode d_A (2, 1) is provided on the upper side in the drawing with respect to the center O (2, 1) of the microlens ML (2, 1). Further, the pixel P (2, 2) has only the photoelectric conversion unit PC_B (2, 2) configured by sandwiching the organic photoelectric film m between the common electrode u and the partial electrode d_B (2, 2). The partial electrode d_B (2, 2) is provided on the lower side in the drawing with respect to the center O (2, 2) of the microlens ML (2, 2). In the configuration shown in FIG. 12, the partial electrode d_A and the partial electrode d_B can be provided without being spaced from the center O of the microlens ML, respectively. The areas of the conversion unit PC_A and the photoelectric conversion unit PC_B can be increased.

  In the second image sensor 32, the pupil division direction in each focus detection pixel is not limited to the above-described direction, and may be any of the vertical direction, the horizontal direction, and the diagonal direction, and may be in various directions. Focus detection pixels may be mixed.

(Modification 2)
In the imaging unit 112 according to the second embodiment described above, the pupil detection phase difference type focus detection may be performed for the first imaging element 131 as well. That is, two photodiodes PD_A and PD_B are provided in each pixel P of the first image sensor 131, and the two photodiodes PD_A and PD_B respectively receive a pair of light beams that have passed through a pair of pupil regions of the imaging optical system 10, respectively. You may comprise as follows. Since the light beam from which the infrared light is cut is incident on the first image sensor 131, the pupil division phase difference type focus detection with visible light can be performed. In this case, for example, as shown in FIG. 13, in the second image sensor 132, the pupil division direction of each focus detection pixel is the vertical direction, and in the first image sensor 131, the pupil division of each focus detection pixel is set. The pupil division direction may be changed between the second image sensor 132 and the first image sensor 131, for example, the direction is the horizontal direction. In this way, for example, in the case of a subject whose focus is easier to detect when the pupil division direction is the vertical direction, focus detection can be performed using the output signal from the second image sensor 132. On the other hand, when the subject is easier to detect the focus when the pupil division direction is the horizontal direction, focus detection can be performed using the output signal from the first image sensor 131. As described above, the first image sensor 131 and the second image sensor 132 can be properly used, and the focus detection accuracy can be increased. Further, in the first image sensor 131, focus detection pixels whose pupil division direction is vertical and horizontal focus detection pixels may be mixed, and in the second image sensor 132, the pupil division direction is vertical. These focus detection pixels and horizontal focus detection pixels may be mixed.

(Modification 3)
You may make it provide the infrared projector in the digital camera 1 of embodiment mentioned above. By projecting infrared rays with an infrared projector, the focus detection accuracy can be further increased in the above-described focus detection processing using infrared light. The infrared projector may emit uniform infrared light, or the infrared light to be irradiated may have a pattern. When the infrared light to be irradiated has a pattern, it may be a projection image that assists in focus detection, or a multi-point image arranged in a grid shape may be projected. When projecting a multipoint image arranged in a grid, distance detection can be performed by calculating the amount of distortion of the projected grid.

(Modification 4)
In the above-described embodiment, an example in which an infrared light image is acquired by adding photoelectric conversion signals between adjacent photoelectric conversion units in each focus detection pixel of the second image sensor 32 and used for focus detection by a contrast method. However, infrared light images may be used for other purposes. For example, a visible light image captured by the first image sensor 31 is compared with an infrared light image captured by the second image sensor 32, and a person hidden by strong light such as a headlight is displayed on the visible light image. You may make it detect on an infrared-light image. In addition, since infrared light has a long wavelength and an image deeper than the outermost surface of an object is obtained, the inside of human skin is analyzed based on an infrared light image obtained by photographing a human face, for example, It can also detect stains hidden inside.

(Modification 5)
In the above-described embodiment, an example in which the color filter arrangement is a Bayer array and an image signal of the Bayer array can be obtained from the first image sensor 31 has been described, but the color filter arrangement may be another arrangement. Further, the example in which the color filters that respectively transmit R, G, and B light have been described has been described. However, the present invention is not limited to this. For example, color filters that respectively transmit Cy, Mg, and Ye light may be disposed. It may be.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Each embodiment and modification may be combined as appropriate. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Digital camera, 10 ... Imaging optical system, 11 ... Control part, 11a ... Focus detection part, 11b ... Image generation part, 12, 112 ... Imaging part, 31, 131 ... 1st image sensor, 32, 132 ... 2nd Image sensor

Claims (8)

First imaging that photoelectrically converts light incident on the surface side of the semiconductor substrate to generate a first photoelectric conversion signal, and outputs the first photoelectric conversion signal via a wiring layer formed on the surface side of the semiconductor substrate Elements,
A second photoelectric conversion signal is generated by photoelectrically converting infrared light using an organic photoelectric film that is laminated on the surface side of the first imaging element and absorbs infrared light and transmits visible light, and generates the second photoelectric conversion signal. A second imaging element that outputs the second photoelectric conversion signal through a layer;
A microlens array in which a plurality of microlenses are arranged in a two-dimensional manner and stacked on the opposite side of the second imaging element from the first imaging element;
With
The first imaging element is provided corresponding to each of the microlenses, and includes a plurality of first pixels that output the first photoelectric conversion signal,
The second imaging element is provided corresponding to each of the microlenses, and includes a plurality of second pixels that output the second photoelectric conversion signal,
The second pixel is a focus detection pixel that outputs a focus detection signal for detecting a focus adjustment state of the imaging optical system by a pupil division phase difference method,
Between the second image sensor and the first image sensor, there is an optical waveguide for guiding visible light transmitted through the second pixel of the second image sensor to the first pixel of the first image sensor. An imaging device characterized by being formed. The imaging device according to claim 1,
Between the second image sensor and the first image sensor, a planarization layer including the wiring layer inside is formed on a boundary portion between the adjacent first pixels,
The optical waveguide is formed on the photoelectric conversion portion of each of the first pixels, is made of a material having a refractive index higher than that of the planarization layer, and transmits the second pixel of the second imaging element. An image pickup apparatus, wherein the visible light is totally reflected at a boundary surface between the optical waveguide and the planarization layer, and guided to the first pixel of the first image pickup element. Back-illuminated type that photoelectrically converts light incident on the back side of the semiconductor substrate to generate a first photoelectric conversion signal and outputs the first photoelectric conversion signal through a wiring layer formed on the front side of the semiconductor substrate A first imaging device of
A second photoelectric conversion signal is generated by photoelectrically converting infrared light using an organic photoelectric film that is stacked on the back side of the first imaging element and absorbs infrared light and transmits visible light, and generates the second photoelectric conversion signal. A second imaging element that outputs the second photoelectric conversion signal through a layer;
A microlens array in which a plurality of microlenses are arranged in a two-dimensional manner and stacked on the opposite side of the second imaging element from the first imaging element;
With
The first imaging element is provided corresponding to each of the microlenses, and includes a plurality of first pixels that output the first photoelectric conversion signal,
The second imaging element is provided corresponding to each of the microlenses, and includes a plurality of second pixels that output the second photoelectric conversion signal,
2. The imaging apparatus according to claim 1, wherein the second pixel is a focus detection pixel that outputs a focus detection signal for detecting a focus adjustment state of the imaging optical system by a pupil division phase difference method. The imaging device according to claim 3.
An image pickup apparatus, wherein a connection portion for connecting the second image pickup element and the wiring layer is formed on the semiconductor substrate of the first image pickup element. In the imaging device according to any one of claims 1 to 4,
Each of the second pixels has a first photoelectric conversion unit and a second photoelectric conversion unit,
The first photoelectric conversion unit receives one of a pair of light beams that have passed through a pair of pupil regions of the imaging optical system, and the second photoelectric conversion unit receives the other of the pair of light beams. An imaging apparatus characterized by receiving light. In the imaging device according to any one of claims 1 to 4,
The plurality of second pixels receive a first focus detection pixel that receives one of a pair of light beams that have passed through a pair of pupil regions of the imaging optical system, and receives the other of the pair of light beams. And a second focus detection pixel.
In the second imaging element, the first focus detection pixels and the second focus detection pixels are alternately arranged. The imaging device according to any one of claims 1 to 6,
Image generating means for generating an image signal based on a first photoelectric conversion signal output from the first image sensor;
First focus detection means for detecting a focus adjustment state of the imaging optical system by a pupil division phase difference method based on a second photoelectric conversion signal output from the second image sensor;
A digital camera comprising: The digital camera according to claim 7, wherein
Based on a first photoelectric conversion signal output from the first image sensor or a second photoelectric conversion signal output from the second image sensor, a focus adjustment state of the imaging optical system is detected by a contrast method. A digital camera further comprising bifocal point detection means.

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