JP2011029932A - Imaging element and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy light reception characteristics required for both pixels of a standard pixel and a pixel obtained by making the center of gravity of sensitivity eccentric, even if on-chip lens shapes are made to be approximately identical. <P>SOLUTION: An imaging element comprises: imaging pixels for generating image generating signals; and focal point detecting pixels discretely disposed among a plurality of imaging pixels for generating phase difference detecting signals. Each imaging pixel includes: a photoelectric conversion part 61 for converting light into charge; an on-chip lens 69 for converging light to the photoelectric conversion part; and an optical waveguide 70 disposed between the photoelectric conversion part and the on-chip lens for guiding light to the photoelectric conversion part. Each focal point detecting pixel includes: a photoelectric conversion part 61 for converting light into charge; an on-chip lens 69 for converging light to the photoelectric conversion part; and a light shielding layer 51 disposed between the photoelectric conversion part and the on-chip lens for light-shielding a part of the photoelectric conversion part. Both the on-chip lens of the imaging pixel and the on-chip lens of the focal point detecting pixel have focus positions at a position of a height where the light shielding layer 51 is approximately disposed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for detecting a focus state of a photographic lens based on an image signal obtained from an image sensor for performing imaging.

  As one of the methods for detecting the focus state of the photographic lens, Patent Document 1 discloses an apparatus that performs pupil division type focus detection using a two-dimensional sensor in which an on-chip lens is formed in each pixel of the sensor. Yes. In the device of Patent Document 1, the photoelectric conversion unit of each pixel constituting the sensor is divided into a plurality of parts, and the divided photoelectric conversion unit transmits light that has passed through different areas of the pupil of the photographing lens via an on-chip lens. It is configured to receive light.

  In Patent Document 2, a pupil division function is given by decentering the sensitivity center of gravity of the light receiving unit with respect to the optical axis of the on-chip microlens in some light receiving elements (pixels) of the image sensor. These pixels are used as focus detection pixels, and are arranged at predetermined intervals between the imaging pixel groups, thereby performing phase difference focus detection. In addition, since the location where the focus detection pixels are arranged corresponds to a defective portion of the imaging pixel, image information is created by interpolation from surrounding imaging pixel information.

JP-A-58-24105 JP 2000-156823 A

  Patent Document 2 described above discloses a configuration in which a light-shielding layer having an opening whose opening is biased with respect to the optical axis of the on-chip microlens is provided in order to decenter the sensitivity center of gravity of the light receiving portion. If the light shielding layer is also used as the wiring layer, it can be said that it is a promising configuration with almost no change from the conventional manufacturing process.

  FIG. 16 is a diagram illustrating a configuration of an imaging element in which the light shielding layer also serves as a wiring layer. In FIG. 16, 60 is a silicon substrate, 61 is a light receiving region, 69a is an on-chip lens, 51 is a wiring layer that also serves as a light shielding layer, and 62 is an interlayer insulating film. The right side shows the configuration of the standard pixel, and the left side shows the configuration of the pixel in which the sensitivity center of gravity of the light receiving unit is decentered. In FIG. 16, the focal position of the on-chip lens substantially coincides with the surface portion of the light receiving region 61. FIG. 17 is a diagram illustrating a configuration of an image sensor in which the height of the on-chip lens is increased. The focal position of the on-chip lens 69b substantially coincides with the arrangement height of the wiring layer 51 which also serves as a light shielding layer, and other configurations are the same as those in FIG.

  Hereinafter, a difference in characteristics of each pixel due to a difference in on-chip lens height will be described. FIG. 18 is a diagram for explaining the oblique incidence of standard pixels. FIG. 18A shows an example of the on-chip lens 69 a in which the light beam shown in FIG. 16 is almost converged on the surface of the light receiving region 61, and it can be seen that the entire light beam is irradiated on the light receiving region 61. On the other hand, FIG. 18B shows an example of the on-chip lens 69 b in which the light beam shown in FIG. 17 converges substantially at the arrangement height of the wiring layer 51, and it can be seen that a part of the light beam protrudes from the light receiving region 61. FIG. 19 is a diagram for explaining a state in which the aperture of a pixel with the sensitivity center of gravity decentered is transmitted. FIG. 19A shows an example of the on-chip lens 69a in which the light beam shown in FIG. 16 is almost converged on the surface of the light receiving region 61. A part of the light beam is blocked by the wiring layer 51 which also serves as a light shielding layer, and the total light beam is blocked. It can be seen that the light receiving area 61 is not reached. On the other hand, FIG. 19B shows an example of the on-chip lens 69 b in which the light beam shown in FIG. 17 is almost converged to the arrangement height of the wiring layer 51, and the total light beam is transmitted through the opening of the wiring layer 51. You can see how it reaches.

  FIG. 20 is a diagram showing the incident angle characteristics of a standard pixel. The horizontal axis represents the incident angle, and the vertical axis represents the light receiving efficiency. 20A corresponds to the case of the on-chip lens 69a in which the light beam shown in FIG. 16 converges almost on the surface of the light receiving region 61, and FIG. 20B shows the light beam shown in FIG. This corresponds to the case of the on-chip lens 69b that almost converges to the arrangement height. From FIG. 20, it can be seen that in the standard pixel, as the on-chip lens in which the light beam almost converges on the surface of the light receiving region 61, the light capturing efficiency can be ensured even in a lens having a bright incident angle and a pixel having a high image height.

  FIG. 21 is a diagram showing the incident angle characteristics of a pixel in which the sensitivity center of gravity is decentered. The horizontal axis indicates the incident angle, and the vertical axis indicates the light receiving efficiency. 21A corresponds to the case of the on-chip lens 69a in which the light flux shown in FIG. 16 converges almost on the surface of the light receiving region 61, and FIG. 21B shows the arrangement of the wiring layer 51 in which the light flux shown in FIG. This corresponds to the case of the on-chip lens 69b that almost converges to the height. From FIG. 21, in the pixel in which the sensitivity center of gravity is decentered, the characteristic of the pupil intensity distribution that is decentered becomes sharper as the on-chip lens in which the light beam converges substantially on the arrangement height of the wiring layer 51. That is, it can be seen that a good image signal can be obtained when performing phase difference focus detection.

  In other words, the optimal on-chip lens shape of the standard pixel does not match the optimal on-chip lens shape of the pixel whose sensitivity center of gravity is decentered, and an on-chip suitable for either pixel in the same on-chip lens manufacturing process. It was necessary to select the lens shape.

  The present invention has been made in view of the above-described problems. The object of the present invention is to satisfy the required light receiving characteristics in both the standard pixel and the pixel whose sensitivity center of gravity is decentered even when the on-chip lens shape is substantially the same. Is to do so.

  In order to solve the above-described problems and achieve the object, an imaging device according to the present invention includes an imaging pixel that photoelectrically converts a subject image formed by a photographic lens to generate an image generation signal, and a plurality of imaging pixels. Focus detection that is discretely arranged between the imaging pixels, divides a pupil region of the photographing lens, and photoelectrically converts a subject image from the divided pupil region to generate a phase difference detection signal The imaging pixel includes a photoelectric conversion unit that converts light into an electric charge, an on-chip lens that collects light on the photoelectric conversion unit, and a gap between the photoelectric conversion unit and the on-chip lens. An optical waveguide for guiding light to the photoelectric conversion unit, and the focus detection pixel includes a photoelectric conversion unit that converts light into electric charge, and an on-chip lens that condenses light on the photoelectric conversion unit And between the photoelectric conversion unit and the on-chip lens And a light shielding layer for shielding a part of the photoelectric conversion unit, and the on-chip lens of the imaging pixel and the on-chip lens of the focus detection pixel are both substantially disposed of the light shielding layer. It is characterized by having a focal position at a height position.

  According to the present invention, even if the on-chip lens shapes are substantially the same, it is possible to satisfy the required light receiving characteristics in both the standard pixel and the pixel whose sensitivity center of gravity is decentered.

It is a block diagram of the camera which is an imaging device concerning the 1st Embodiment of this invention. It is the figure which showed the schematic circuit structure of the image pick-up element. It is sectional drawing of the pixel wiring part of an image pick-up element. It is a timing chart which shows operation of an image sensor. It is a partial top view of an image sensor. It is a horizontal sectional view of focus detection pixels α and β and their adjacent pixels. It is a figure explaining the mode of the oblique incidence of a standard pixel. It is a figure explaining a mode that light permeate | transmits the opening of the pixel for focus detection. It is explanatory drawing of the light reception distribution of a standard pixel. It is explanatory drawing of the light reception distribution of the pixel for focus detection. It is a flowchart which shows the operation | movement of a defocus detection. It is a horizontal sectional view of focus detection pixels α and β and their adjacent pixels in the second embodiment. It is explanatory drawing of the light reception distribution of the pixel in 2nd Embodiment. FIG. 10 is a horizontal sectional view of focus detection pixels α and β and their adjacent pixels in a third embodiment. It is explanatory drawing of the light reception distribution of the pixel in 3rd Embodiment. It is a detailed structure explanatory drawing of the pixel of the conventional image sensor. It is a detailed structure explanatory drawing of the pixel of the conventional image sensor. It is a figure explaining the mode of the oblique incidence of a standard pixel. It is a figure explaining a mode that light permeate | transmits the opening of the pixel which made the sensitivity gravity center eccentric. It is a light-receiving distribution explanatory drawing of a standard pixel by the difference in the height of an on-chip lens. It is light reception distribution explanatory drawing of the pixel for focus detection by the difference in the height of an on-chip lens.

(First embodiment)
FIG. 1 is a configuration diagram of a camera 200 that is an image pickup apparatus according to the first embodiment of the present invention. An electronic device in which a camera body having an image pickup element and a photographing lens 100 for forming a subject image are integrated. Shows the camera. In FIG. 1, reference numeral 101 denotes a first lens group disposed at the tip of the taking lens 100, which is held so as to be able to advance and retreat in the optical axis direction. Reference numeral 102 denotes an aperture / shutter that adjusts the light amount at the time of shooting by adjusting the aperture diameter, and also functions as an exposure time adjustment shutter at the time of still image shooting. Reference numeral 103 denotes a second lens group. The aperture / shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction, and perform a zooming function (zoom function) in conjunction with the forward and backward movement of the first lens group 101. Reference numeral 105 denotes a third lens group that performs focus adjustment by advancing and retracting in the optical axis direction. Reference numeral 106 denotes an optical low-pass filter, which is an optical element for reducing false colors and moire in a captured image. Reference numeral 107 denotes an image sensor composed of a C-MOS sensor and its peripheral circuits. In the imaging element, one photoelectric conversion element is arranged on each of a plurality of light receiving pixels of m pixels in the horizontal direction and n pixels in the vertical direction.

  Reference numeral 111 denotes a zoom actuator, which rotates a cam cylinder (not shown) to drive the first lens group 111 to the third lens group 103 forward and backward in the optical axis direction, thereby performing a zooming operation. Reference numeral 112 denotes an aperture shutter actuator that controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light, and controls the exposure time during still image photographing. Reference numeral 114 denotes a focus actuator, which performs focus adjustment by driving the third lens group 105 back and forth in the optical axis direction. Reference numeral 115 denotes an electronic flash for illuminating a subject at the time of photographing, and a flash illumination device using a xenon tube is suitable, but an illumination device including an LED that emits light continuously may be used.

  Reference numeral 121 denotes an in-camera CPU that controls various controls of the camera body, and includes a calculation unit, ROM, RAM, A / D converter, D / A converter, communication interface circuit, and the like, and a predetermined program stored in the ROM Based on this, various circuits of the camera are driven. Then, a series of operations such as AF, shooting, image processing, and recording are executed. The CPU 121 also has functions as a focus detection unit that detects the focus state of the photographing lens 100 and a defocus amount calculation unit.

  An electronic flash control circuit 122 controls lighting of the electronic flash 115 in synchronization with the photographing operation. An image sensor driving circuit 124 controls the image capturing operation of the image sensor 107 and A / D converts the acquired image signal and transmits the image signal to the CPU 121. An image processing circuit 125 performs processes such as γ conversion, color interpolation, and JPEG compression of the image acquired by the image sensor 107. A focus drive circuit 126 controls the focus actuator 114 based on the focus detection result, and adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction. Reference numeral 128 denotes an aperture shutter drive circuit which controls the aperture shutter actuator 112 to control the aperture of the aperture / shutter 102. Reference numeral 129 denotes a zoom drive circuit that drives the zoom actuator 111 in accordance with the zoom operation of the photographer.

  Reference numeral 131 denotes a display device such as an LCD, which displays information related to the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, a focus state display image when focus is detected, and the like. An operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. Reference numeral 133 denotes a detachable flash memory that records a photographed image.

  FIG. 2 is a diagram showing a schematic circuit configuration of the image sensor according to the first embodiment of the present invention, and a technique disclosed in Japanese Patent Application Laid-Open No. 09-046596 by the applicant of the present application is suitable. FIG. 2 shows the range of a photoelectric conversion unit of 2 columns × 4 rows of a two-dimensional C-MOS area sensor, and has a circuit configuration for 8 pixels.

  In FIG. 2, 1 is a photoelectric conversion unit comprising a MOS transistor gate and a depletion layer under the gate, 2 is a photogate, 3 is a transfer switch MOS transistor, 4 is a reset MOS transistor, and 5 is a source follower amplifier MOS transistor. 6 is a horizontal selection switch MOS transistor, 7 is a load MOS transistor of the source follower, 8 is a dark output transfer MOS transistor, 9 is a light output transfer MOS transistor, 10 is a dark output storage capacitor CTN, and 11 is a light output storage capacitor CTS. . 12 is a horizontal transfer MOS transistor, 13 is a horizontal output line reset MOS transistor, 14 is a differential output amplifier, 15 is a horizontal scanning circuit, and 16 is a vertical scanning circuit.

  FIG. 3 shows a cross-sectional view of the pixel wiring portion. In FIG. 3, 17 is a P-type well, 18 is a gate oxide film, 19 is a first-layer poly-Si, 20 is a second-layer poly-Si, and 21 is an n + floating diffusion portion (FD portion). The FD unit 21 is connected to another photoelectric conversion unit via another transfer MOS transistor. In FIG. 3, the drain of the two transfer MOS transistors 3 and the FD portion 21 are made common to improve the sensitivity by miniaturization and the capacity reduction of the FD portion 21, but the FD portion 21 may be connected by an Al wiring. .

  Next, the operation of the image sensor will be described using the timing chart of FIG. This timing chart is for the case of all pixel independent output. First, according to the timing output from the vertical scanning circuit 16, the control pulse φL is set to high to reset the vertical output line. Further, the control pulses φR0, φPG00, and φPGe0 are set high, the reset MOS transistor 4 is turned on, and the first-layer poly Si 19 of the photogate 2 is set high. At time T0, the control pulse φS0 is set high, the selection switch MOS transistor 6 is turned on, and the pixel portions of the first and second lines are selected. Next, the control pulse φR0 is set to low, the reset of the FD unit 21 is stopped, the FD unit 21 is set in a floating state, the source-follower amplifier MOS transistor 5 is set to the through state, and the control pulse φTN is set high at time T1. And Then, the dark voltage of the FD unit 21 is output to the storage capacitor CTN10 by the source follower operation.

  Next, in order to perform photoelectric conversion output of the pixels of the first line, the control pulse φTX00 of the first line is set high, the transfer switch MOS transistor 3 is turned on, and then the control pulse φPG00 is lowered low at time T2. At this time, a voltage relationship is preferable in which the potential well that has spread under the photogate 2 is raised so that photogenerated carriers are completely transferred to the FD portion 21. Therefore, if complete transfer is possible, the control pulse φTX may be a fixed potential instead of a pulse. The electric charge from the photoelectric conversion unit 1 of the photodiode is transferred to the FD unit 21 at time T2, so that the potential of the FD unit 21 changes according to light. At this time, since the source follower amplifier MOS transistor 5 is in a floating state, the potential of the FD portion 21 is output to the storage capacitor CTS11 with the control pulse φTs being high at time T3. At this time, the dark output and the light output of the pixels of the first line are stored in the storage capacitors CTN10 and CTS11, respectively, and the horizontal output line reset MOS transistor 13 is turned on by setting the control pulse φHC at time T4 to be temporarily high. To reset. In the horizontal transfer period, the dark output and light output of the pixel are output to the horizontal output line by the scanning timing signal of the horizontal scanning circuit 15. At this time, if the differential output VOUT is obtained by the differential amplifier 14 with respect to the storage capacitors CTN10 and CTS11, a signal with good S / N from which random noise and fixed pattern noise of the pixel are removed can be obtained. The photoelectric charges of the pixels 30-12 and 30-22 are accumulated in the respective storage capacitors CTN10 and CTS11 simultaneously with the pixels 30-11 and 30-21, but the timing is read from the horizontal scanning circuit 15 by one pixel. The data is read out to the horizontal output line after being delayed and output from the differential amplifier 14. In the present embodiment, a configuration in which the differential output VOUT is performed in the chip is shown, but the same effect can be obtained even if a conventional CDS (Correlated Double Sampling) circuit is used outside without being included in the chip. Is obtained.

  After a bright output is output to the storage capacitor CTS11, the control pulse φR0 is set high to turn on the reset MOS transistor 4 and reset the FD portion 21 to the power supply VDD. After the horizontal transfer of the first line is completed, the second line is read. In reading the second line, the control pulse φTXe0 and the control pulse φPGe0 are driven in the same manner, and high pulses are supplied to the control pulses φTN and φTS, respectively, and photocharges are accumulated in the storage capacitors CTN10 and CTS11, respectively. Take the output. With the above driving, the first and second lines can be read independently. Thereafter, by scanning the vertical scanning circuit and reading out the 2n + 1 line and the 2n + 2 line (n = 1, 2,...) In the same manner, all pixels can be independently output. That is, when n = 1, first, the control pulse φS1 is set high, then φR1 is set low, then the control pulses φTN and φTX01 are set high, the control pulse φPG01 is set low, the control pulse φTS is set high, and the control pulse φHC Is temporarily high to read out pixel signals of the pixels 30-31 and 30-32. Subsequently, the control pulses φTXe1, φPGe1 and the control pulse are applied in the same manner as described above, and the pixel signals of the pixels 30-41 and 30-42 are read out.

  FIG. 5 is a partial plan view of a C-MOS sensor which is an image sensor. In FIG. 5, 51 and 52 are electrodes. A region separated by the electrodes (wiring layers) 51 and 52 represents one pixel, and the letters “R”, “G”, and “B” written in one pixel represent the hue of the color filter of each pixel. Yes. Pixels with the letter “R” transmit red component light, pixels with the letter “G” transmit green component light, and pixels with the letter “B” written Transmits blue component light. In addition, each pixel on which the characters “R”, “G”, and “B” are written is an image generation pixel configured to receive light that has passed through the entire pupil region of the photographing lens 100.

  When the color filter array is a Bayer array, one picture element is composed of “R” and “B” pixels and two “G” pixels. On the other hand, in the imaging device of this embodiment, focus detection pixels that receive light that has passed through a part of the pupil region of the photographing lens 100 are assigned to some of the pixels that should be “R” or “B”. ing. In the figure, α and β are focus detection pixels for detecting the focus state of the photographic lens 100, and the opening in the horizontal direction is restricted by the electrode 51. The focus detection pixels are discretely arranged between the plurality of imaging pixels, divide the pupil region of the photographing lens 100, photoelectrically convert the subject image from the divided pupil region, and detect the phase difference. Generate a signal.

  Two types of focus detection pixels arranged in a part of the image sensor 107 of the present embodiment are set such that the aperture center position of the aperture limited by the electrode 51 is different from the pixel center. Yes. For example, an aperture determined by the electrode 51-1α and the electrode 51-2α is the same at a position adjacent to four pixels in the horizontal direction and the vertical direction with respect to the focus detection pixel α in which the opening is deviated in the horizontal left direction with respect to the pixel center. The focus detection pixels having the electrode openings are arranged. In addition, a focus detection pixel β in which an opening determined by the electrodes 51-3β and 51-4β is displaced in the horizontal right direction is disposed at a position obliquely adjacent to the focus detection pixel α. Further, focus detection pixels having similar electrode openings are disposed at positions adjacent to the focus detection pixel β in four horizontal and vertical directions.

  6 is a horizontal sectional view of the focus detection pixels α and β and the adjacent pixels of the image sensor 107 in FIG. 5, and FIG. 6A is a sectional view taken along the line CC in FIG. b) is a cross-sectional view taken along the line DD in FIG.

  The left pixel in FIG. 6A indicates the focus detection pixel α, and the right pixel indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographic lens 100. In the image sensor 107, the photoelectric conversion unit 61 is formed inside the silicon substrate 60. The signal charges generated in the photoelectric conversion unit 61 are output to the outside through a floating diffusion unit (not shown), the first electrode 51, and the second electrode 52 (not shown). An interlayer insulating film 62 is formed between the photoelectric conversion unit 61 and the electrode 51, and an interlayer insulating film 63 is formed between the electrode 51 and the electrode 52. On the light incident side of the interlayer insulating film 63, a color filter layer 67, a planarizing layer 64, and an on-chip lens 69 are formed. Here, the power of the on-chip lens 69 is set so that the pupil of the photographing lens 100 and the electrode 51 are substantially conjugate. In other words, the on-chip lens 69 has a focal position substantially at the arrangement height of the electrode 51 so that the light beam incident on the on-chip lens 69 is substantially converged to the arrangement height of the electrode 51. In the pixel located at the center of the image sensor 107, the on-chip lens 69 is arranged at the center of the pixel, and at the pixels located at the periphery, the on-chip lens 69 is arranged deviated toward the optical axis side of the photographing lens 100. Reference numeral 70 denotes an air gap layer formed below the electrode 51, and has a waveguide function of reflecting the light beam irradiated on the air gap layer 70 at an angle satisfying the total reflection condition.

  The subject light transmitted through the photographing lens 100 is collected near the image sensor 107. Further, the light reaching each pixel of the image sensor 107 is refracted by the on-chip lens 69 and collected at the position of the electrode 51. In the pixel on the right side in the drawing used for normal imaging, a first electrode 51 and a second electrode 52 are provided so as not to block incident light.

  On the other hand, in the pixel that performs focus detection of the photographic lens 100 on the left side in the drawing, a part of the electrode 51 is configured to cover the photoelectric conversion unit 61. As a result, the focus detection pixel on the left side in the drawing can receive a light beam that passes through a part of the pupil of the photographing lens 100. Further, in order to prevent the output of the photoelectric conversion unit 61 from becoming small because the electrode 51 blocks a part of the incident light beam, the color filter layer 67W of the focus detection pixel does not absorb light and has high transmittance. It is made of resin.

  Similarly, the pixel on the right side of FIG. 6B indicates the focus detection pixel β, and the pixel on the left side indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographic lens 100. As can be seen from FIG. 6, the focus detection pixels α and β are almost bilaterally symmetric, and the relative positions of the on-chip lens 69 and the center of the opening of the electrode 51 are made different from each other. The received light distribution is different.

  FIG. 7 is a diagram for explaining the oblique incidence of standard pixels. As shown in FIG. 7, the on-chip lens 69 causes the light flux to almost converge to the arrangement height of the wiring layer (electrode) 51 that also serves as a light shielding layer, but because of the total reflection configuration by the air gap layer 70. It can be seen that the entire light beam is irradiated onto the light receiving region 61.

  FIG. 8 is a diagram for explaining a state of passing through the opening of a pixel (focus detection pixel) in which the sensitivity center of gravity is decentered. As shown in FIG. 8, it can be seen that the on-chip lens 69 causes the light beam to substantially converge at the arrangement height of the electrode 51, and that the total light beam passes through the opening of the electrode 51 and reaches the light receiving region 61. At this time, since the air gap layer 70 does not function as a waveguide, the air gap layer 70 may be omitted. Here, an example in which the air gap layer 70 is provided is shown in order to make it possible to manufacture in the same process as the standard pixel and because there is no particular problem.

  FIG. 9 is a diagram illustrating the incident angle characteristics of the standard pixel according to the first embodiment. The horizontal axis represents the incident angle, and the vertical axis represents the light receiving efficiency. From FIG. 9, it can be seen that the luminous flux shown in FIG.

  FIG. 10 is a diagram showing the incident angle characteristics of a pixel (focus detection pixel) whose sensitivity center of gravity is decentered. The horizontal axis represents the incident angle, and the vertical axis represents the light receiving efficiency. FIG. 10A shows the incident angle characteristic of a pixel whose opening is decentered to the right side, and FIG. 10B shows the incident angle characteristic of a pixel whose opening is decentered to the left side.

  As can be seen from FIGS. 9 and 10, according to the present embodiment, even with the same on-chip lens height, the standard pixel (imaging pixel) and the pixel (sensitivity detection pixel) in which the sensitivity centroid is decentered can be used. An optimal configuration can be realized.

  The CPU 121 having a function as focus detection means for detecting the focus state of the photographic lens 100 generates a first focus detection image from the focus detection pixel group having the same electrode opening as the focus detection pixel α. Similarly, a second focus detection image is generated from a focus detection pixel group having the same electrode opening as that of the focus detection pixel β. Further, the CPU 121 having a function as a defocus amount calculation means performs an area calculation based on the first focus detection image and the second focus detection image, thereby positioning the focus detection pixels α and β. The focus state of the taking lens 100 at is detected. During normal image capturing, the focus detection pixels whose pixel electrode openings are limited are treated as defective pixels, and an image signal is generated by performing interpolation processing from pixels located around the focus detection pixels. .

  FIG. 11 is a diagram illustrating a flowchart relating to detection of a defocus amount (defocus amount) according to the present embodiment, which is a part of autofocus. The main flow is the same as a general camera flow, and is therefore omitted.

  When the autofocus function is selected, first, in order to perform focus detection, reading of the imaging pixels and focus detection pixels in step S1 is performed. In step S2, two types of pattern images formed in the phase difference direction are created from the two types of focus detection pixel groups. FIG. 11 shows an example of a pattern image on two bar charts having different widths. Next, in step S3, a correlation calculation is performed on the pair of focus detection pixel groups α and β.

  Next, in step S4, the reliability of the correlation calculation result in step S3 is determined. Here, the reliability refers to the degree of coincidence of the paired images and the contrast of the images. When the degree of coincidence of the paired images is good, the reliability of the focus detection result is generally high and the contrast is high. In this case, it can be determined that the subject is good at ranging. If it is determined that the reliability is low, the reliability of the focus detection signal itself is determined to be low, and the process returns to step S1 and starts again from the image reading. If it is determined in step S4 that the reliability is OK, the image correlation value is finally converted into a defocus amount in step S5, and the defocus amount is calculated.

  In step S6, it is determined whether or not the defocus amount calculated in step S5 is less than or equal to an allowable value. If the defocus amount is larger than the allowable value, it is determined that the subject is out of focus, and in step S7, the focus lens is driven so as to correct the defocus amount calculated in step S5, and then steps S1 to S7 are repeated. Execute. If it is determined in step S6 that the in-focus state has been reached, in-focus display is performed in step S8, and the process exits from the autofocus subroutine.

  As described above, in the first embodiment, an air gap layer is formed in each pixel to provide a waveguide function, so that light is received by the imaging pixel and the focus detection pixel even at the same on-chip lens height. It is possible to prevent the amount of light from decreasing.

(Second Embodiment)
In the second embodiment, the configuration of the imaging device is the same as that of the first embodiment shown in FIGS. 1 to 5, and the internal structure of the imaging device is different. 12 is a horizontal sectional view of the focus detection pixels α and β and the adjacent pixels of the image sensor 107 in FIG. 5, and FIG. 12A is a sectional view taken along the line CC in FIG. b) is a cross-sectional view taken along the line DD in FIG.

  The left pixel in FIG. 12A indicates the focus detection pixel α, and the right pixel indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographic lens 100. In FIG. 12, the same components as those in FIG.

  Reference numeral 71 denotes a metal reflecting member (for example, an aluminum material) formed below the electrode 51. Here, an air gap layer is formed first, and then a metal reflecting member is embedded to form a reflective film having the same shape as the air gap layer 70 shown in FIG. In addition, a stopper film (not shown) is formed between the silicon layer 60 and the wiring layer 52, or an electrical connection is prevented by arranging arrangements that do not overlap three-dimensionally. The light beam applied to the metal reflecting member 71 causes metal reflection and functions as a waveguide.

  Similarly, the pixel on the right side of FIG. 12B indicates the focus detection pixel β, and the pixel on the left side indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographing lens 100. As can be seen from FIG. 12, the focus detection pixels α and β are almost bilaterally symmetric, and the relative positions of the on-chip lens 69 and the center of the opening of the electrode 51 are made different from each other. The received light distribution is different.

  FIG. 13 shows the incident angle characteristics of the second embodiment, where the horizontal axis represents the incident angle and the vertical axis represents the light receiving efficiency. 13A shows the incident angle characteristic of the standard pixel, FIG. 13B shows the incident angle characteristic of the pixel whose opening is decentered to the right side, and FIG. 13C shows the incident angle characteristic of the pixel whose opening is decentered to the left side. . As can be seen from FIG. 13, according to this embodiment, it is possible to realize an optimum configuration for the standard pixel and the pixel whose sensitivity centroid is decentered even at the same on-chip lens height.

  As described above, in the second embodiment, a reflection member is embedded in the air gap layer of each pixel to provide a waveguide function, and even at the same on-chip lens height, the imaging pixel and the focus detection pixel can be used. It prevents the amount of received light from decreasing.

(Third embodiment)
In the third embodiment, the configuration of the imaging device is the same as that of the first embodiment shown in FIGS. 1 to 5, and the internal structure of the imaging device is different. FIG. 14 is a horizontal sectional view of the focus detection pixels α and β and the adjacent pixels of the image sensor 107 in FIG. 5, and FIG. 14A is a sectional view taken along the line CC in FIG. b) is a cross-sectional view taken along the line DD in FIG.

  The left pixel in FIG. 14A indicates the focus detection pixel α, and the right pixel indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographic lens 100. 14, the same components as those in FIG. 6 are denoted by the same reference numerals.

  Reference numeral 72 denotes a waveguide made of a high refractive index material, for example, SiN, formed below the electrode 51. Here, first, plasma etching is performed on the high refractive index material embedded portion using a photolithography process to form a high refractive index material embedded layer. Thereafter, HDP-SiN (high density plasma SiN) is embedded by high density plasma CVD. Thus, the waveguide-shaped high refractive index material 72 shown in FIG. 14 is formed. Since SiN has a refractive index of about 2 and higher than the refractive index of 1.43 of the insulating member SiO, the side surface of the high refractive index material 72 satisfies the total reflection condition at a certain angle or more, and functions as a waveguide.

  Similarly, the pixel on the right side of FIG. 14B indicates the focus detection pixel β, and the pixel on the left side indicates a pixel (imaging pixel) that can receive the entire pupil region of the photographic lens 100. As can be seen from FIG. 14, the focus detection pixels α and β are almost bilaterally symmetric, and the relative position of the on-chip lens 69 and the center of the opening of the electrode 51 is made different from each other. The received light distribution is different.

  FIG. 15 is a diagram showing the incident angle characteristics of the present embodiment, where the horizontal axis indicates the incident angle and the vertical axis indicates the light receiving efficiency. 15A shows the incident angle characteristics of a standard pixel, FIG. 15B shows the incident angle characteristics of a pixel whose opening is decentered to the right, and FIG. 15C shows the incident angle characteristics of a pixel whose opening is decentered to the left. . As can be seen from FIG. 15, according to the present embodiment, it is possible to realize an optimum configuration for the standard pixel and the pixel whose sensitivity centroid is decentered even at the same on-chip lens height.

  As described above, in the third embodiment, the high refractive index material 72 is disposed under the wiring layer 51 to provide a waveguide function, and the imaging pixels and the focus detection pixels can be used even at the same on-chip lens height. The amount of received light is prevented from decreasing at the pixel.

  In the first to third embodiments described above, the electrode (wiring layer) that also serves as the light shielding member has been described. However, as the light shielding member, not only the electrode but also a light shielding filter that absorbs light is disposed in the color filter portion. May be. In the above embodiment, the configuration in which the optical waveguide is arranged between the same stack position as the light shielding member and the photoelectric conversion unit has been described. However, the configuration in which the optical waveguide is extended in the on-chip lens direction from the light shielding member. It may be taken.

Claims (5)

An imaging pixel that photoelectrically converts an object image formed by the photographic lens to generate an image generation signal;
A focus that is discretely arranged between the plurality of imaging pixels, divides a pupil region of the photographing lens, and photoelectrically converts a subject image from the divided pupil region to generate a phase difference detection signal. A detection pixel,
The imaging pixel includes a photoelectric conversion unit that converts light into electric charge, an on-chip lens that collects light on the photoelectric conversion unit, and the photoelectric conversion unit that is disposed between the photoelectric conversion unit and the on-chip lens. And an optical waveguide for guiding light to
The focus detection pixel is disposed between the photoelectric conversion unit and the on-chip lens, a photoelectric conversion unit that converts light into electric charge, an on-chip lens that collects light on the photoelectric conversion unit, and the photoelectric conversion A light shielding layer for shielding a part of the part,
The on-chip lens of the imaging pixel and the on-chip lens of the focus detection pixel both have a focal position at a height position where the light shielding layer is disposed.   The image pickup device according to claim 1, wherein the optical waveguide includes an air gap.   The imaging device according to claim 1, wherein the optical waveguide is formed of a reflective member.   The imaging device according to claim 1, wherein the optical waveguide is made of a high refractive index material. A taking lens that forms a subject image;
The imaging device according to any one of claims 1 to 4,
An imaging apparatus comprising:

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