JP2012242717A - Imaging apparatus, camera system and focus detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which enables highly accurate focus detection of a phase difference system regardless of colors of a subject while keeping light receiving efficiency of a CMOS type imaging device.SOLUTION: An imaging apparatus comprises: an imaging device including first pixels which receive light passing through a region of an exit pupil of a photographic lens, second pixels which receive light passing through a partial region of the exit pupil of the photographic lens, an electrode part provided on a photoelectric conversion part so as to cover a partial region of a photoelectric conversion part of the second pixels, and a light shield part which has an opening and covers a region different from the region covered by the electrode part of the photoelectric conversion part; and focus detection means for detecting the focus state of the photographic lens on the basis of outputs of the second pixels. The imaging apparatus further comprises: determination means for determining colors of a subject; and storage means for storing light receiving characteristics of the imaging device corresponding to the colors of the subject. The focus detection means detects the focus state of the photographic lens on the basis of subject color information determined by the determination means and the light receiving characteristics of the imaging device.

Description

  The present invention relates to an image pickup apparatus, a camera system, and a focus detection method including an image pickup device capable of detecting a focus state of a photographing lens.

  Conventional focus detection methods used in digital cameras that are imaging devices include a contrast detection method and a phase difference detection method.

  The single-lens reflex camera has a flip-up mirror for guiding the subject light to the viewfinder optical system so that the photographer can observe the subject through the photographing lens. The flip-up mirror is composed of a half mirror that transmits a part of the light, and the light that has passed through the flip-up mirror is guided to a phase difference type focus detection device, thereby making it possible to detect the focus of the photographing lens. The focus detection device is composed of a set of lenses and a set of image sensors that re-image light beams passing through different pupil regions of the photographing lens. When photographing with a recording medium, the flip-up mirror is retracted from the photographing optical path. For this reason, it is not possible to perform focus detection using the conventional phase difference detection method while shooting with a recording medium such as a film or an image sensor.

  When a moving image is observed or recorded in a camera using an image sensor as a recording medium, a contrast detection focus adjustment method is generally used. The contrast detection focus adjustment method extracts the high-frequency component of the image picked up by the image sensor while moving the focus lens of the photographic lens in the optical axis direction, and detects the lens position where the contrast peak is detected to adjust the focus. Is what you do. In the same focus adjustment method, since the contrast of the images is compared while moving the focus lens, the focus adjustment cannot be performed at high speed.

  Therefore, in order to solve the above problem, the present applicant limits the pupil region of the photographing lens that can receive light by limiting the photoelectric conversion region of some focus detection pixels constituting the CMOS type image pickup device. Japanese Patent Application Laid-Open No. H10-228688 discloses a camera capable of detecting a phase difference type focus. In this publication, a microlens that constitutes a part of a focus detection pixel is configured such that a pupil of a photographing lens and a wiring electrode are in a conjugate relationship. As a result, the pupil region of the photographing lens that can receive light is limited by shielding the light beam incident on the photoelectric conversion unit with the wiring electrode.

  However, the microlens that constitutes the imaging element must have a substantially conjugate relationship between the pupil of the photographing lens and the photoelectric conversion unit. Therefore, the present applicant has patented an imaging device that limits the pupil region of a photographic lens that can receive light by providing a light-shielding portion on the photoelectric conversion portion instead of shielding light with a wiring electrode located at a position away from the photoelectric conversion portion. This is disclosed in Document 2. A metal material such as tungsten is used for the light shielding portion.

JP 2010-117679 A JP 2009-244854 A

  Incidentally, a transfer electrode made of polysilicon is formed in a partial region on the photoelectric conversion portion of the CMOS image sensor. Here, if the polysilicon which is the transfer electrode is covered with tungsten which is the light shielding portion, the sensor height becomes high, and the light receiving efficiency (light receiving angle characteristic or Fno proportionality) of the CMOS type image pickup device is increased. ).

  In order to reduce the distance from the microlens to the photoelectric conversion unit with respect to such a problem, the light shielding unit formed of tungsten or the like has substantially the same thickness so as not to overlap the transfer electrode in the optical axis direction. It is desirable to be formed.

  Therefore, the present inventor has devised a configuration in which the light shielding portion and the transfer electrode are formed side by side in the direction perpendicular to the optical axis on the photoelectric conversion portion. In this case, the light-shielding part and the transfer electrode can be arranged so as not to overlap in the optical axis direction, and the distance from the microlens to the photoelectric conversion part can be shortened, so that the light-receiving efficiency of the CMOS image sensor is increased. Can do.

  However, in this case, the polysilicon constituting the transfer electrode is exposed to light passing through the photographing lens without being covered with tungsten constituting the light shielding portion. The spectral transmission characteristic of the polysilicon constituting the transfer electrode shows a characteristic that the transmittance is increased as the wavelength becomes longer on the red side while hardly transmitting on the blue side where the wavelength is short. For this reason, the pupil region and the intensity that can be received by the image sensor change depending on the color of the subject, and there is a drawback in that accurate focus detection cannot be performed.

  Furthermore, as the number of pixels of the image sensor increases, the pixel size becomes smaller, and as a result, the light receiving characteristics of the image sensor are easily affected by chromatic aberration and diffraction of the microlens that constitutes the image sensor. Since the chromatic aberration of the microlens and the degree of diffraction by the microlens differ depending on the wavelength, the pupil region and intensity that can be received by the image sensor change depending on the color of the subject, and there is a drawback that high-precision focus detection cannot be performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus, a camera system, and a focus detection method capable of performing phase difference focus detection with high accuracy regardless of the color of a subject while ensuring the light receiving efficiency of a CMOS image sensor. That is.

  In order to achieve the above object, an imaging apparatus according to an aspect of the present invention includes a first pixel that receives light passing through an exit pupil area of a photographing lens, and a partial area of the exit pupil of the photographing lens. A second pixel that receives light passing therethrough, an electrode provided on the photoelectric conversion unit so as to cover a partial region of the photoelectric conversion unit of the second pixel, and the photoelectric conversion unit having an opening A light-shielding unit that covers a region different from the region covered by the electrode unit, and a focus detection unit that detects a focus state of the photographing lens based on an output of the second pixel. An image pickup apparatus comprising: a determination unit that determines a color of the subject; and a storage unit that stores a light receiving characteristic of the image sensor corresponding to the color of the subject. Subject color information determined by determination means and previous And detecting a focus state of the photographing lens based on the light receiving characteristic of the imaging device.

  According to the present invention, it is possible to provide an imaging apparatus, a camera system, and a focus detection method capable of performing phase difference type focus detection with high accuracy regardless of the color of a subject while ensuring the light receiving efficiency of a CMOS image sensor. it can.

It is a block diagram of the optical apparatus (camera system) of this invention. It is a partial top view of the image sensor of the present invention. Example 1 It is a partial cross section figure of the image sensor of the present invention. Example 1 It is explanatory drawing of the manufacturing process of the image pick-up element of this invention. Example 1 It is light reception distribution explanatory drawing of the pixel for focus detection arrange | positioned at the image pick-up element of this invention. Example 1 FIG. 6 is a projection explanatory view of the received light distribution of FIG. 5. Example 1 It is an electric circuit block diagram of the optical apparatus of the present invention. 3 is a flowchart of a photographing operation of the optical device according to the present invention. It is a partial top view of the image sensor of the present invention. (Modification of Example 1) It is a partial top view of the image sensor of the present invention. (Example 2) It is a top view of the focus detection pixel of the image sensor of the present invention. (Example 2) It is explanatory drawing of the manufacturing process of the image pick-up element of this invention. (Example 2) It is light reception distribution explanatory drawing of the pixel for focus detection arrange | positioned at the image pick-up element of this invention. (Example 2) It is projection explanatory drawing of the light reception distribution of FIG. (Example 2)

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  1 to 8 show a first embodiment of the present invention. FIG. 1 is a block diagram of a digital camera which is an optical apparatus having the image sensor of the present invention. FIG. 2 is a partial plan view of the image sensor. FIG. 4 is a partial cross-sectional view of the image sensor of the present invention, and FIG. 4 is an explanatory diagram of the manufacturing process of the image sensor of the present invention. FIG. 5 is an explanatory diagram of received light distribution of the focus detection pixels arranged in the image sensor of the present invention, FIG. 6 is an explanatory diagram of projection of the received light distribution of FIG. 5, and FIG. 7 is an electric circuit block diagram of the camera of the present invention. FIG. 8 is a flowchart of the camera operation of the present invention.

  1, a digital camera (camera system) of the present invention is a single-lens reflex digital camera in which a photographing lens (interchangeable lens) 200 can be attached to and detached from a camera body 100 via a camera side mount 111 and a lens side mount 201. Is shown.

  The photographing lens 200 includes a plurality of lens groups (for example, a lens 203) and a diaphragm 204, and subject light transmitted through the photographing lens 200 is reflected by the flip-up mirror 101 of the camera 100 and converges near the focusing plate 102. To do. Further, the subject light diffused and transmitted by the focus plate 102 is guided to the eyes of a photographer (not shown) via the penta roof prism 103 and the eyepiece lens 104.

  The flip-up mirror 101 is a half mirror, and a part of the subject light transmitted through the flip-up mirror 101 is reflected by the sub mirror 105 and guided to the focus detection device 106. The focus detection device 106 has a known configuration for detecting the focus state of the photographic lens 200 from an image generated by light transmitted through different pupil regions of the photographic lens 200.

  Further, an imaging element (image sensor, CMOS type imaging element) 108 is disposed on the planned imaging plane of the photographing lens 200.

  The camera of the present invention can shoot a moving image, and at the time of moving image shooting, the flip-up mirror 101 and the sub mirror 105 are retracted from the shooting optical path, and the shutter 107 is set to an open state. At this time, an image photographed by the image sensor 108 can be visually recognized by the liquid crystal display element 109.

  Next, the configuration of the image sensor 108 will be described.

  FIG. 2 is a partial plan view of the image sensor 108, and FIG. 3 is a partial cross-sectional view of the image sensor 108.

  FIG. 3 is a cross-sectional view of the A-A ′ plane shown in the partial plan view of the image sensor 108 of FIG. 2.

  In the image sensor 108, a photoelectric conversion unit 312 is formed inside a silicon substrate 310. The signal charge generated in the photoelectric conversion unit 312 is transferred to a floating diffusion unit (not shown) by a transfer electrode (electrode unit) 330 formed so as to partially cover the photoelectric conversion unit 312. The transfer electrode 330 is usually made of polysilicon. Further, on the photoelectric conversion unit 312 of the pixel on the left side in the drawing, light shielding units 360_1 and 360_2 (hereinafter, these pair of light shielding units are collectively referred to as a light shielding unit 360) for limiting incident light are formed. Yes. The light shielding portions 360_1 and 360_2 are made of tungsten, and the light shielding portions 360_2 are formed so as not to overlap the transfer electrode 330. The light shielding portion 360_0 is formed in the peripheral portion of each pixel for preventing stray light.

  The signal charge transferred to the floating diffusion portion is output to the outside through the electrode 331 and the electrode 332. An interlayer insulating film 321 is formed between the photoelectric conversion unit 312 and the electrode 331, but the light shielding unit 360_2 is formed so as not to overlap the transfer electrode 330, and the light shielding unit 360 and the transfer electrode 330 have substantially the same thickness. Therefore, the thickness of the interlayer insulating film 321 does not increase. As a result, it is possible to prevent the light receiving efficiency of the image sensor 108, in particular, the incidence angle characteristic from being lowered.

  An interlayer insulating film 322 is formed between the electrode 331 and the electrode 332. Further, an interlayer insulating film 323 is formed between the electrode 332 and the electrode 333.

  In addition, an interlayer insulating film 324 is formed on the light incident side of the electrode 333, and further a passivation film 340 and a planarizing layer 350 are formed. On the light incident side of the planarization layer 350, color filter layers 351_1 and 351_2 (hereinafter collectively referred to as a color filter layer 351), a planarization layer 352, and a microlens 353 are formed. Here, the power of the micro lens 353 is set so that the pupil of the photographing lens 200 and the photoelectric conversion unit 312 are substantially conjugate.

  In this embodiment, a cross-sectional view of a pixel located at the center of the image sensor 108 is shown, and the microlens 353 is disposed at the approximate center of the pixel.

  The subject light that has passed through the photographic lens 200 is condensed in the vicinity of the image sensor 108 disposed on the planned imaging plane of the camera 100. Further, the light that reaches each pixel of the image sensor 108 is refracted by the microlens 353 and collected on the photoelectric conversion unit 312. The electrodes 331, 332, and 333 stacked in the optical axis direction of the image sensor 108 are disposed so as not to block incident light as much as possible.

  The pixel on the right side in the figure is an imaging pixel (first pixel) used during normal imaging, and is configured to receive the entire pupil region of the imaging lens 200.

  On the other hand, the pixel on the left side in the figure is a focus detection pixel (second pixel) used when detecting the focus state of the photographic lens 200. This focus detection pixel receives light passing through a partial region of the exit pupil of the photographic lens 200. Since the light-shielding portions 360_1 and 360_2 are formed on the photoelectric conversion portion 312 of the pixel on the left side in the drawing, it is possible to receive a light beam that passes through a part of the pupil of the photographing lens 200. Further, in order to improve the light receiving efficiency in the focus detection pixel, the color filter 351_1 is formed of a colorless one that does not absorb light.

  Next, the pixel arrangement of the image sensor 108 will be described with reference to the plan view of FIG.

  A light blocking portion 360_0 for preventing stray light is disposed in the peripheral portion of each pixel constituting the image sensor 108. The characters “R”, “G”, and “B” written in each pixel represent the hue of the color filter of each pixel. 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.

  When the color filter array is a Bayer array, one picture element is composed of “R” and “B” pixels and two “G” pixels, but the image sensor 108 of the present invention is a pixel corresponding to “G”. In part of these, focus detection pixels capable of detecting the focus of the photographing lens 200 are allocated.

  In the figure, Pα 1, Pβ 1, Pα 2, Pβ 2, Pα 3, and Pβ 3 indicate the apertures of the pixel light shielding portion 360 for detecting the focus state of the taking lens 200. In the present embodiment, the transfer electrodes 330_o and 330_e (hereinafter referred to as “the transfer electrodes 330_o” and “330_e”) are located at positions shifted in a direction (so-called correlation calculation direction or pupil division direction) orthogonal to the longitudinal direction (y direction in the drawing) of the opening of the light shielding portion 360. Collectively referred to as transfer electrode 330). The transfer electrode 330 according to the present invention is provided at the end of the photoelectric conversion unit 312 so as to cover at least a part of the photoelectric conversion unit 312. In addition, the light shielding unit 360 according to the present invention covers a region different from at least a part of the photoelectric conversion unit 312 covered by the transfer electrode 330 so as to avoid the transfer electrode 330. In other words, the light shielding unit 360 is arranged on the photoelectric conversion unit 312 in a direction orthogonal to the transfer electrode 330 so as not to overlap the transfer electrode 330 in the optical axis direction. Further, the imaging element 108 is configured such that the arrangement of the transfer electrodes 330_o and 330_e is different according to the position of the opening of the light shielding portion 360. This is for reducing the gap between the light shielding unit 360 and the transfer electrodes 330_o and 330_e and the asymmetry of the focus detection image caused by the light leaking from the transfer electrode 330 to the photoelectric conversion unit 312 to reduce the decrease in focus detection accuracy. is there.

  FIG. 4 is an explanatory diagram of a part of the manufacturing process of the image sensor 108. The focus detection pixel in the first row and the first column of the plan view of the image sensor 108 shown in FIG. 2 will be described as an example.

  4A, a p-type well region 311 is formed on an n-type silicon substrate 310, and an n-type photoelectric conversion portion 312 is formed on the surface of the well region 311. Next, a silicon oxide film 361 is formed on the surface of the silicon substrate 310 by thermally oxidizing the silicon substrate 310. Further, polysilicon that is the transfer electrode 330_o is formed.

  In FIG. 4B, a silicon nitride film 362 that is a first transparent insulating film is formed on the entire surface of the image sensor 108. Here, the refractive index of the silicon nitride film 362 as the first transparent insulating film is about 1.8 and the thickness is about 11 nm.

  In FIG. 4C, a light shielding portion 360 made of tungsten is formed on the silicon nitride film 362. The thickness of the light shielding portion 360 is substantially the same as that of polysilicon as the transfer electrode 330_o, and is formed so as not to overlap the transfer electrode 330_o in the optical axis direction. Here, since the light shielding portion 360_2 and the transfer electrode 330_o are insulated by the silicon nitride film 362 that is the first transparent insulating film, the gap between the light shielding portion 360_2 and the transfer electrode 330_o can be reduced.

  In FIG. 4D, a silicon nitride film 363 that is a second transparent insulating film is formed on the entire surface of the image sensor 108 so as to cover the light shielding portion 360. Here, the silicon nitride film 363 which is the second transparent insulating film has a refractive index of about 2.0 and a thickness of about 50 nm.

  In FIG. 4E, an interlayer insulating film 321 made of a silicon oxide film is formed.

  After FIG. 4E, an electrode 331, an interlayer insulating film 322, an electrode 332, an interlayer insulating film 323, an electrode 333, an interlayer insulating film 324, a passivation film 340, a planarizing layer 350, a color filter layer (not shown) are illustrated. 351, a planarization layer 352, and a microlens 353 are formed.

  Here, since the thickness of the light shielding portion 360 is substantially the same as that of the polysilicon that is the transfer electrode 330_o and does not overlap with the transfer electrode 330_o, the thickness of the interlayer insulating film 321 is also minimized. Is possible.

  In this embodiment, the silicon nitride film 363 that is the second transparent insulating film formed on the light shielding portion 360 made of tungsten functions as an antireflection film for the light shielding portion 360. Similarly, the silicon nitride film 362 that is the first transparent insulating film and the silicon nitride film 363 that is the second transparent insulating film formed on the transfer electrode 330_o made of polysilicon correspond to the transfer electrode 330_o. It functions as an antireflection film. In addition, the silicon nitride film 362 that is the first transparent insulating film and the silicon nitride film 363 that is the second transparent insulating film formed on the photoelectric conversion unit 312 serve as antireflection films for the photoelectric conversion unit 312. It is supposed to function.

  In the plan view of the image sensor 108 of this embodiment in FIG. 2, the pair of focus detection pixels arranged in a part of the image sensor 108 is formed by the light shielding unit 360 in order to correspond to the F value of the photographing lens. Three types with different relative intervals of openings are set.

  Further, in this embodiment, in the focus detection pixel in the first row and the first column in the drawing, when the opening Pα1 by the light shielding portions 360_1 and 360_2 is disposed on the left side (−x direction) with respect to the center of the pixel, transfer is performed. The electrode 330_o is disposed on the right side (+ x direction) with respect to the center of the pixel. On the other hand, in the focus detection pixel in the second row and second column in the figure, when the opening Pβ1 by the light shielding portions 360_3 and 360_4 is disposed on the right side (+ x direction) with respect to the center of the pixel, the transfer electrode 330_e is It is arranged on the left side (−x direction) with respect to the center. Further, in this embodiment, the transfer electrodes 330_o and 330_e are located on the right side (+ x direction) with respect to the center of the pixel in the odd-numbered rows, and with respect to the center of the pixels in the even-numbered rows. On the left side (−x direction).

  Hereinafter, the light receiving characteristics of the focus detection pixels will be described with reference to the light reception distribution explanatory diagram of the focus detection pixels arranged in the image sensor 108 of FIG. 5 and the projection explanatory view of the light reception distribution of FIG. Here, the light reception distribution explanatory diagram of FIG. 5 shows an example in the case where there is no vignetting in the photographing lens 200. The projection of the light reception distribution shown in FIG. 6 is obtained by projecting the light reception distribution on the pupil of the photographing lens 200 of the focus detection pixel shown in FIG. A generated line image distribution function (so-called line image) L is shown.

  In the plan view of the image sensor 108 in FIG. 2, the aperture Pα1 formed by the light shielding portions 360_1 and 360_2 of the pixel capable of focus detection arranged in the first row and first column is a first deviation in the −x direction with respect to the pixel center. It is deviated by the amount.

  FIG. 5A is an explanatory diagram of light reception distribution of focus detection pixels arranged in the first row and first column of the image sensor 108. The light reception distribution explanatory diagram of FIG. 5 shows a light amount distribution that can be received on the pupil of the photographing lens 200 when there is no manufacturing error of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pα1 of the light-shielding portion of the pixel arranged in the first row and first column of the image sensor 108 can receive the region Sα1 on the pupil of the photographing lens 200. In the figure, a region Sγ in which the amount of received light at the position in the −x direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is high is leakage from the gap between the light shielding portion 360_2 and the transfer electrode 330_o. This is due to the light and the partially transmitted light of the transfer electrode 330_o.

  Further, in the plan view of the image sensor 108 in FIG. 2, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the first row and first column are adjacent to each other in the oblique direction (in the drawing). (2nd row, 2nd column). The pair of focus-detectable pixels are formed with light shielding portions 360_3 and 360_4, and the center of the opening Pβ1 formed by the light shielding portions 360_3 and 360_4 is displaced by a first displacement amount in the + x direction with respect to the pixel center. Yes.

  FIG. 5B is an explanatory diagram of the light reception distribution of the pixels arranged in the second row and second column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ1 formed by the light shielding portions 360_3 and 360_4 of the pixels arranged in the second row and second column of the image sensor 108 can receive the region Sβ1 on the pupil of the photographing lens 200. In the figure, a region Sγ where the amount of received light in the position in the + x direction from the optical axis of the photographing lens 200 (the intersection of the xy axes in the figure) is a leaked light from the gap between the light shielding portion 360_3 and the transfer electrode 330_e. This is due to the partially transmitted light of the transfer electrode 330_e.

  When there is no manufacturing error of the image sensor 108, the distance xα1 and the distance xβ1 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 are equal.

  In the plan view of the image sensor 108 in FIG. 2, focus-detectable pixels in which light-shielding portions 360_5 and 360_6 are formed in rows adjacent to four pixels in the −y direction from the first row and first column (the fifth row in the figure). Is arranged. In the pixel arranged in the fifth row and first column and capable of focus detection, the center of the opening Pα2 by the light shielding portions 360_5 and 360_6 is different from the first deviation amount in the −x direction with respect to the pixel center. It is displaced by the amount of displacement.

  FIG. 5C is an explanatory diagram of the light reception distribution of the pixel arranged in the fifth row and the first column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pα2 formed by the light shielding portions 360_5 and 360_6 of the pixel disposed in the fifth row and first column of the image sensor 108 can receive the region Sα2 on the pupil of the photographing lens 200. In the figure, a region Sγ where the amount of received light at the position in the −x direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is a gap between the light shielding portion 360_6 and the transfer electrode 330_o and the transfer electrode. This is due to leakage light from 330_o and partially transmitted light from the transfer electrode 330_o.

  Further, in the plan view of the image sensor 108 in FIG. 2, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the fifth row and first column are adjacent to each other in the oblique direction (in the drawing). (6th row, 2nd column). Similarly, light shielding portions 360_7 and 360_8 are formed in the pair of focus-detectable pixels, and the center of the opening Pβ2 by the light shielding portions 360_7 and 360_8 is deviated from the pixel center by the second displacement amount in the + x direction. Is ranked.

  FIG. 5D is an explanatory diagram of the light reception distribution of the pixel arranged in the sixth row and second column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ2 formed by the light shielding portions 360_7 and 360_8 of the pixel arranged in the sixth row and the second column of the image sensor 108 can receive the region Sβ2 on the pupil of the photographing lens 200. In the figure, a region Sγ where the amount of received light is high at the position in the + x direction from the optical axis of the photographing lens 200 (the intersection of the xy axes in the figure) is leakage light from the gap between the light shielding portion 360_7 and the transfer electrode 330_e. This is due to the partially transmitted light of the transfer electrode 330_e.

  When there is no manufacturing error of the image sensor 108, the distance xα2 and the distance xβ2 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 are equal.

  In the plan view of the image sensor 108 in FIG. 2, focus detection is possible in which light shielding portions 360_9 and 360_10 are formed in a row adjacent to four pixels in the −y direction from the fifth row and first column (the ninth row in the figure). Pixels are arranged. In the pixel arranged in the 9th row and the 1st column and capable of focus detection, the center of the opening Pα3 by the light shielding portions 360_9 and 360_10 is different from the first and second deviation amounts in the −x direction with respect to the pixel center. It is displaced by the third displacement amount.

  FIG. 5E is an explanatory diagram of the light reception distribution of the pixel arranged in the 9th row and the 1st column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pα3 formed by the light shielding portions 360_9 and 360_10 of the pixel disposed in the 9th row and the 1st column of the image sensor 108 can receive the region Sα3 on the pupil of the photographing lens 200. In the figure, a region Sγ where the amount of received light at the position in the −x direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is leaked from the gap between the light shielding portion 360_10 and the transfer electrode 330_o. This is due to the light and the partially transmitted light of the transfer electrode 330_o.

  Further, in the plan view of the image sensor 108 in FIG. 2, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the 9th row and the 1st column are adjacent to each other in the oblique direction (in the drawing). (10th row, second column). Similarly, the light-shielding portions 360_11 and 360_12 are formed in the pair of focus-detectable pixels, and the center of the opening Pβ3 by the light-shielding portions 360_11 and 360_12 is deviated with a third displacement amount in the + x direction with respect to the pixel center. Is ranked.

  FIG. 5F is an explanatory view of the light reception distribution of the pixel arranged in the 10th row and the 2nd column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ3 formed by the light shielding portions 360_11 and 360_12 of the pixel arranged in the 10th row and the 2nd column of the image sensor 108 can receive the region Sβ3 on the pupil of the photographing lens 200. In the drawing, a region Sγ where the amount of received light is high in the + x direction position from the optical axis of the photographing lens 200 (the intersection of the xy axes in the drawing) is leaked light from the gap between the light shielding portion 360_11 and the transfer electrode 330_e. This is due to the partially transmitted light of the transfer electrode 330_e.

  When there is no manufacturing error of the image sensor 108, the distance xα3 and the distance xβ3 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 are equal.

  Further, there is a focus-detectable pixel having a similar opening Pα1 at a position adjacent to the + x direction in the + x direction of the focus-detectable pixel having the opening Pα1 by the light-shielding portion (pixel in the first row and first column in FIG. 2). It is arranged.

  Similarly, a focus-detectable pixel having the same aperture Pβ1 is arranged at a position adjacent to the + x direction of the pixel having the aperture Pβ1 by the light-shielding portion (pixel in the second row and second column in the figure) in the + x direction. It is installed.

  When detecting the focus state of the photographic lens 200, signals of the focus detection pixel group having the aperture Pα1 and the focus detection pixel group having the aperture Pβ1 are output.

  Further, there is a focus-detectable pixel having a similar aperture Pα2 at a position adjacent to the + x direction in the + x direction of the focus-detectable pixel having the aperture Pα2 by the light-shielding portion (pixel in the fifth row and first column in FIG. 2). It is arranged.

  Similarly, a focus-detectable pixel having the same opening Pβ2 is arranged at a position adjacent to the + x-direction in the + x direction of the focus-detectable pixel having the opening Pβ2 by the light-shielding portion (pixel in the sixth row and second column in the figure). It is installed.

  FIG. 6 is a projection of the received light distribution of the focus detection pixel shown in FIG. 5 on the pupil of the photographing lens 200 in the y direction in the figure, and shows a line image L generated by the focus detection pixel group. ing.

  FIG. 6A shows a line image Lα generated by the focus detection pixel group having the opening Pα2 arranged in the fifth row in the plan view of the image sensor 108 of FIG. In the line image Lα, an image having a small intensity is generated at a position away from the position having the highest intensity in the −x direction in the figure. This image is an image generated by light leaked from the gap between the light shielding portion 360_6 and the transfer electrode 330_o and partially transmitted light of the transfer electrode 330_o.

  By the way, since the transfer electrode 330 is made of polysilicon, it absorbs light having a short wavelength but transmits light having a long wavelength. Therefore, the light reception distribution on the pupil of the photographing lens 200 changes depending on the wavelength of light. The line image Lα shown in FIG. 6A is substantially equivalent to the line image Lαg for green light shown in FIG.

  FIG. 6C shows lines for blue light, green light, and red light generated by the focus detection pixel group having the aperture Pα2 arranged in the fifth row in the plan view of the image sensor 108 of FIG. An image Lα is shown. The line image Lαb for blue light is indicated by a solid line. A line image Lαg for green light is indicated by a dotted line. In the line image Lαg, an image due to leakage light is generated at a position away from the position having the highest intensity in the −x direction in the figure. Since the image due to the leakage light includes a component that is transmitted by the polysilicon serving as the transfer electrode 330_o, the image due to the leakage light of green light is larger than the image due to the leakage light of blue light. The line image Lαr for red light is indicated by a broken line. In the line image Lαr, an image due to leakage light is generated at a position away from the position having the highest intensity in the −x direction in the figure. Since the image due to the leakage light includes a component that is transmitted by polysilicon as the transfer electrode 330_o, the image due to the leakage light of red light is larger than the image due to the leakage light of green light. Further, in the line images Lαb, Lαg, and Lαr, the position and the half-value width of the image having the highest intensity due to the aperture Pα2 of the image sensor 108 are different depending on the wavelength due to the influence of chromatic aberration and diffraction of the microlens constituting the image sensor. .

  FIG. 6B shows a line image Lβ generated by the focus detection pixel group having the aperture Pβ2 arranged in the sixth row in the plan view of the image sensor 108 of FIG. In the line image Lβ, an image having a small intensity is generated at a position away from the position having the highest intensity in the + x direction in the figure. This image is an image generated by light leaked from the gap between the light shielding portion 360_7 and the transfer electrode 330_e and partially transmitted light of the transfer electrode 330_e. Here, the line image Lβ is substantially equivalent to the line image Lβg for green light shown in FIG.

  FIG. 6D shows lines for blue light, green light, and red light generated by the focus detection pixel group having the aperture Pβ2 arranged in the sixth row in the plan view of the image sensor 108 of FIG. An image Lβ is shown. The line image Lβb for blue light is indicated by a solid line. In the line image for green light, Lβg is indicated by a dotted line. In the line image Lβg, an image due to leakage light is generated at a position away from the position having the highest intensity in the + x direction in the figure. Since the image due to the leakage light includes a component that is transmitted by polysilicon which is the transfer electrode 330_e, the image of the leakage light of green light is larger than the image of the leakage light of blue light. A line image Lβr for red light is indicated by a broken line. In the line image Lβr, an image due to leakage light is generated at a position away from the position with the highest intensity in the + x direction in the figure. Since the image due to the leakage light includes a component that is transmitted by the polysilicon that is the transfer electrode 330_e, the leakage light of the red light is larger than the image due to the leakage light of the green light. Further, in the line images Lβb, Lβg, and Lβr, the position and the half-value width of the image having the highest intensity due to the aperture Pβ2 of the image sensor 108 vary depending on the wavelength due to the influence of chromatic aberration and diffraction of the microlens constituting the image sensor. .

  When the focus state of the photographic lens 200 is detected, signals of the focus detection pixel group having the aperture Pα2 and the focus detection pixel group having the aperture Pβ2 are output.

  Further, a focus-detectable pixel having the same photoelectric conversion unit Pα3 is arranged at a position adjacent to the + x direction of the focus-detectable pixel having the photoelectric conversion unit Pα3 (9th row, first column in FIG. 2) in a 4-pixel cycle. It is installed.

  Similarly, a focus-detectable pixel having the same photoelectric conversion unit Pβ3 is disposed at a position adjacent to the + x direction of the focus-detectable pixel having the photoelectric conversion unit Pβ3 (10th row and second column in the figure) in a cycle of 4 pixels. Has been.

  When the focus state of the photographic lens 200 is detected, signals of the focus detection pixel group having the aperture Pα3 and the focus detection pixel group having the aperture Pβ3 are output.

  Here, as shown in the projection explanatory view of the light reception distribution in FIG. 6, since the line images of the focus detection pixel group having the aperture Pα2 and the focus detection pixel group having the aperture Pβ2 are asymmetric, the focus output from the image sensor 108 is not shown. The detection image signal is also asymmetric. When a known correlation calculation is performed using an asymmetric focus detection image signal, a calculation error occurs, and thus correction for eliminating the asymmetry of the focus detection image signal is necessary. A correction method for eliminating the asymmetry of the focus detection image signal will be described later.

  Hereinafter, with reference to the electric circuit block diagram of the camera in FIG. 7 and the flowchart in FIG. 8, the photographing operation of the camera, which is an optical device having the image sensor of the present invention, will be described.

  In the flowchart of FIG. 8A, when a power source (not shown) of the camera 100 is turned on (s100), the camera CPU 150 that controls the camera 100 confirms the state of the first operation switch 151 that instructs to capture a moving image ( s101). When the first operation switch 151 is turned on to instruct moving image shooting (s101), the camera CPU 150 causes the flip-up mirror 101 and the sub mirror 105 to be retracted from the shooting optical path, and the shutter 107 is opened via the shutter drive circuit 156. To.

  When the preparation for photographing is completed, the camera CPU 150 photographs the subject with the image sensor 108 via the image sensor driving circuit 153 (s102). The image photographed by the image sensor 108 is processed into a display image by the image processing circuit 154 and displayed on the liquid crystal display element 109 via the liquid crystal display element driving circuit 155 (s103). Further, the image subjected to image processing by the image processing circuit 154 is recorded in the memory circuit 157 (s104). Here, what records an image may be a recording medium.

  Further, the camera CPU 150 and the image processing circuit 154 also serve as focus detection means, and the focus state of the taking lens 200 is detected based on the image taken by the image sensor 108 (s200). A focus detection method using the image sensor 108 of the present invention will be described later.

  If the photographing lens 200 is not in focus (s106), the camera CPU 150 transmits the defocus amount of the photographing lens 200 detected by the image processing circuit 154 to the lens CPU 250. The lens CPU 250 converts the defocus amount of the photographing lens 200 into a step drive amount of the focus lens, and then transmits a signal to the focus lens drive circuit 251 to drive the focus lens (s107).

  Subsequently, the camera CPU 150 confirms the state of the first operation switch 151 for instructing moving image shooting. If the first operation switch 151 is in the ON state (s101), the moving image shooting is continued (s102).

  On the other hand, if the first operation switch 151 for instructing moving image shooting is in the OFF state (s101), the camera CPU 150 confirms the state of the second operation switch 152 for instructing still image shooting (s108). If the first operation (SW-1) for still image shooting is not executed by the second operation switch 152, the camera CPU 150 stands by.

  On the other hand, when the previous operation (SW-1) for still image shooting is executed by the second operation switch 152, the camera CPU 150 detects the focus state of the shooting lens 200 from the output of the focus detection device 106 (s109). . A focus detection method at the time of still image shooting is a known technique.

  If the taking lens 200 is in focus (s110), the camera CPU 150 checks the state of the second operation switch 152 that instructs to take a still image (s112). On the other hand, if the photographing lens 200 is not in focus (s110), the camera CPU 150 transmits the detected defocus amount of the photographing lens 200 to the lens CPU 250. The lens CPU 250 converts the defocus amount of the photographing lens 200 into a step drive amount of the focus lens, and then transmits a signal to the focus lens drive circuit 251 to drive the focus lens (s111).

  Furthermore, the camera CPU 150 confirms the state of the second operation switch 152 that instructs to capture a still image (s112). If the second operation switch 152 does not perform the subsequent operation (SW-2) for still image shooting, the camera CPU 150 stands by.

  On the other hand, when the subsequent operation (SW-2) is performed for still image shooting by the second operation switch 152 (s112), the camera CPU 150 retracts the flip-up mirror 101 and the sub mirror 105 from the imaging optical path. Further, the shutter 107 is opened through the shutter driving circuit 156 and the opening state of the diaphragm 204 is adjusted through the diaphragm driving circuit 252. When the preparation for taking a still image is completed, the camera CPU 150 takes an image of the subject with the image sensor 108 via the image sensor drive circuit 153 (s113). The image captured by the image sensor 108 is processed into a display image by the image processing circuit 154 and displayed on the liquid crystal display element 109 via the liquid crystal display element driving circuit 155 (s114). Further, the image processed into an image for recording by the image processing circuit 154 is recorded in the memory circuit 157 (s115). Here, what records an image may be a recording medium.

  When the image recording is finished (s115), a series of camera photographing operations is finished (s116).

  Next, the details of the focus detection flow of the camera having the image sensor 108 of the present invention will be described using the flowchart of FIG.

  First, the camera CPU 150 (acquisition means) acquires lens information via the lens CPU 250 or reads it from the memory circuit 157 in order to know the vignetting state of the light flux at the photographing lens 200 (s201). Next, the focus detection area set by the user is confirmed (s202). Further, the subject color in the confirmed focus detection area is determined by the image processing circuit 154 (determination means) (s203).

  Next, the CPU 150 reads the received light distribution of the focus detection pixels of the image sensor 108 stored in the memory circuit 157 (storage means). As the light reception distribution of the focus detection pixels, a plurality of types of light reception distributions corresponding to differences in the aperture and wavelength of the light shielding unit 360 that shields the photoelectric conversion unit 312 of the image sensor 108 are stored.

  Further, the CPU 150 calculates vignetting in the focus detection area set from the lens information of the photographing lens 200. Then, the image processing circuit 154 calculates a line image distribution function L from the subject color information in the set focus detection region, the light reception distribution corresponding to the subject color in the set focus detection region, and the vignetting of the photographing lens 200. Calculate (s204).

  Since the camera 100 which is the imaging apparatus of the present invention detects the focus state of the photographic lens 200 based on the light receiving characteristics of the imaging element 108 corresponding to the subject color as described below, it is highly accurate regardless of the subject color. Focus detection is possible.

  For example, the line image distribution function of the focus detection pixel group having the opening Pα2 of the light shielding portion 360 disposed in the fifth row in the plan view of the image sensor 108 in FIG. 2 is Lα, and the light shielding disposed in the sixth row. The line image distribution function of the focus detection pixel group having the opening Pβ2 of the part 360 is Lβ. Here, the line image distribution function L has different characteristics depending on the subject color, as shown in the projection explanatory diagrams of FIGS. 6C and 6D.

  When the focus state of the photographing lens 200 is detected using two images generated from light beams that pass through different pupil regions of the photographing lens 200, the focus detection accuracy is determined by the position of the center of gravity of the light beams that pass through the pupil region. The center-of-gravity interval of light beams passing through different pupil regions of the photographing lens 200 is called a base line length, and the base line length is a projection of the light reception distribution of the focus detection pixels that pass through the different pupil regions of the photographing lens 200 by the image processing circuit 154. It is calculated from the center of gravity interval of the line image distribution function.

  The center of gravity of the line image distribution function Lα of the focus detection pixel group line having the opening Pα2 of the light shielding unit 360 is

Is required. Similarly, the center of gravity of the line image distribution function Lβ of the focus detection pixel group having the opening Pβ2 of the light shielding portion 360 is

Asked. From these calculation results, the baseline length G is

(S205).

  Since the imaging element 108 of the present embodiment minimizes the gap between the light shielding portion 360 and the transfer electrode 330, the intensity of the image generated by the leaked light from the gap between the light shielding portion 360 and the transfer electrode 330 is small. As a result, the influence of the change in the baseline length due to the leaked light from the gap between the light shielding portion 360 and the transfer electrode 330 is minimized.

  Next, correction data for correcting the uniformity of the output image of the image sensor 108 is calculated based on the line image distribution functions Lα and Lβ previously obtained by the image processing circuit 154, and the bias of the output of the focus detection image is calculated. Correction (so-called shading correction) is performed (s206).

  Further, the image processing circuit 154 obtains an image shift amount by a known correlation calculation method using the focus detection image after the shading correction, and temporarily uses the baseline length calculated by the equations (1) to (3). A defocus amount is obtained (s207).

  The CPU 150 determines whether or not the calculated provisional defocus amount is within a predetermined range (s208). When it is determined that the provisional defocus amount is within the predetermined range (s208), image correction processing of the focus detection image is performed in order to calculate the defocus amount with higher accuracy. On the other hand, when it is determined that the provisional defocus amount is outside the predetermined range (s208), the process returns to the main routine (s213).

  The image correction process is not performed when the provisional defocus amount is outside the predetermined range. If the defocus amount is too large, the image for focus detection is further blurred by the image correction process, which makes the correlation calculation difficult. Because. On the other hand, when the defocus amount is small, the asymmetry of the two images is not so much collapsed, so it is not necessary to correct the image. For the above two reasons, it is more effective to perform image correction only within a predetermined defocus range.

  When the provisional defocus amount is determined to be within the predetermined range (s208), the CPU 150 first calculates a filter shape for correcting the output image of the image sensor 108 in order to perform image correction processing of the focus detection image. Filters Lα ′ and Lβ ′ are created (s209). The image correction filters Lα ′ and Lβ ′ are obtained based on the already obtained line image distribution functions Lα and Lβ and the calculated provisional defocus amount.

  When the image correction filters Lα ′ and Lβ ′ are created (s209), the image processing circuit 154 performs filter processing for eliminating asymmetry of the focus detection images Iα and Iβ output from the image sensor 108 ( s210). If the corrected focus detection images are Iα ′ and Iβ ′,

Is calculated.

  Since the filtering process is performed on the focus detection image, the filtering process is also performed on the line image distribution function for calculating the baseline length to recalculate the baseline length (s211).

  First, a corrected line image Lcα obtained by performing filtering on the line image distribution function Lα is obtained by an image processing circuit 154.

Is calculated. Therefore, if the center of gravity of the corrected line image Lcα is Gα ′,

Is required.

  Similarly, the corrected line image Lcβ obtained by performing the filtering process on the line image distribution function Lβ is obtained by the image processing circuit 154.

Is calculated. Therefore, if the center of gravity of the corrected line image Lcβ is Gβ ′,

Is required. Therefore, if the baseline length to be obtained is G ′,

(S211).

  Further, using the corrected focus detection image subject images Iα ′ and Iβ ′ obtained by the equations (4) and (5), the image shift amount between the two images is transferred to the image processing circuit 154 by a known correlation calculation method. To calculate the focus state. Further, the defocus amount is obtained using the corrected baseline length obtained by the equations (6) to (10) (s212). When the defocus amount is calculated, the process returns to the main routine (s213).

  According to the above configuration, the image can be restored according to the vignetting state of the light beam for focus detection, and the focusing accuracy can be improved.

  The image sensor 108 of the present embodiment shows a case where the compositions of the first transparent insulating film and the second transparent insulating film are different and the refractive index of the first transparent insulating film is smaller than the refractive index of the second transparent insulating film. However, the first transparent insulating film and the second transparent insulating film may have the same composition and the same refractive index.

  In order to obtain an antireflection effect at the photoelectric conversion unit 312 and the transfer electrode 330, the silicon nitride film 362 as the first transparent insulating film has a thickness of about 11 nm. The thickness may be increased.

  If the gap between the transfer electrode 330 and the light shielding portion 360 can be minimized, the side closer to the opening of the light shielding portion 360 (one row and one column) as shown in the plan view of the image sensor in FIG. It is also possible to arrange the transfer electrode 330 on the −x direction side of the eye pixel.

  10 to 14 show a second embodiment of the present invention. FIG. 10 is a partial plan view of the image sensor of the present invention. FIG. 11 is a plan view of a focus detection pixel of the image sensor of the present invention. It is manufacturing process explanatory drawing of the image pick-up element of invention. FIG. 13 is an explanatory diagram of light reception distribution of focus detection pixels arranged in the image sensor of the present invention, and FIG. 14 is an explanatory diagram of projection of the light reception distribution of FIG. Since the camera having the image sensor of the present invention is the same as that of the first embodiment, description thereof is omitted. Moreover, the same number is attached | subjected to the member same as a 1st Example.

  The pixel arrangement of the image sensor 108 of the present invention will be described with reference to the plan view of FIG.

  A light blocking portion 360_0 for preventing stray light is disposed in the peripheral portion of each pixel constituting the image sensor 108. The characters “R”, “G”, and “B” written in each pixel represent the hue of the color filter of each pixel. 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.

  When the color filter array is a Bayer array, one picture element is composed of “R” and “B” pixels and two “G” pixels, but the image sensor 108 of the present invention is a pixel corresponding to “G”. In part of these, focus detection pixels capable of detecting the focus of the photographing lens 200 are allocated.

  In the figure, Pα 1, Pβ 1, Pα 2, Pβ 2, Pα 3, and Pβ 3 indicate the apertures of the pixel light shielding portion 360 for detecting the focus state of the taking lens 200. In the present embodiment, the transfer electrode 330 is disposed at a position displaced in a direction parallel to the longitudinal direction (y direction in the drawing) of the light shielding portion 360 (so-called correlation calculation direction or a direction perpendicular to the pupil division direction). ing. Therefore, as will be described later, the asymmetry of the focus detection image caused by the gap between the light shielding unit 360 and the transfer electrode 330 and the light leaking from the transfer electrode 330 to the photoelectric conversion unit 312 is small.

  FIG. 11 is an explanatory diagram of the focus detection pixel in the first row and the first column in the plan view of the image sensor shown in FIG. FIG. 12 is a diagram for explaining a part of the manufacturing process of the image sensor 108 according to the present invention. The focus detection pixel EE ′ section shown in FIG. 11 will be described as an example.

  In FIG. 12A, a p-type well region 311 is formed on an n-type silicon substrate 310, and an n-type photoelectric conversion portion 312 is formed on the surface of the well region 311. Next, a silicon oxide film 361 is formed on the surface of the silicon substrate 310 by thermally oxidizing the silicon substrate 310. Further, polysilicon that is the transfer electrode 330 is formed.

  In FIG. 12B, a silicon nitride film 362 that is a first transparent insulating film is formed on the entire surface of the image sensor 108. Here, the silicon nitride film 362 as the first transparent insulating film has a refractive index of about 2.0 and a thickness of about 10 nm.

  In FIG. 12C, a light shielding portion 360 made of tungsten is formed on the silicon nitride film 362. The thickness of the light shielding portion 360 is substantially the same as that of polysilicon as the transfer electrode 330 and is formed so as not to overlap the transfer electrode 330 in the optical axis direction. Here, since the light shielding part 360_1 and the light shielding part 360_2 and the transfer electrode 330 are insulated by the silicon nitride film 362 which is the first transparent insulating film, the gap between the light shielding part 360_1 and the transfer electrode 330 and the light shielding part 360_2 The gap with the transfer electrode 330 can be reduced.

  In FIG. 12D, a silicon nitride film 363 that is a second transparent insulating film is formed on the entire surface of the image sensor 108 so as to cover the light shielding portion 360. Here, the silicon nitride film 363 which is the second transparent insulating film has a refractive index of about 2.0 and a thickness of about 50 nm.

  In FIG. 12E, an interlayer insulating film 321 made of a silicon oxide film is formed.

  After FIG. 12E, an electrode 331, an interlayer insulating film 322, an electrode 332, an interlayer insulating film 323, an electrode 333, an interlayer insulating film 324, a passivation film 340, a planarizing layer 350, a color filter layer (not shown) are provided. 351, a planarization layer 352, and a microlens 353 are formed.

  Here, since the film thickness of the light shielding portion 360 is substantially the same as that of the polysilicon that is the transfer electrode 330 and does not overlap the transfer electrode 330, the thickness of the interlayer insulating film 321 is also minimized. Is possible.

  In this embodiment, the silicon nitride film 363 that is the second transparent insulating film formed on the light shielding portion 360 made of tungsten functions as an antireflection film for the light shielding portion 360. Similarly, the silicon nitride film 362 that is the first transparent insulating film and the silicon nitride film 363 that is the second transparent insulating film formed on the transfer electrode 330 made of polysilicon are in contact with the transfer electrode 330. It functions as an antireflection film. In addition, the silicon nitride film 362 that is the first transparent insulating film and the silicon nitride film 363 that is the second transparent insulating film formed on the photoelectric conversion unit 312 serve as antireflection films for the photoelectric conversion unit 312. It is supposed to function.

  In the plan view of the image sensor 108 of this embodiment in FIG. 10, the pair of focus detection pixels arranged in a part of the image sensor 108 have the same relative distance between the apertures by the light-shielding portion 360 and the positions thereof are different. Three types are set. This is a countermeasure when the relative positional relationship between the aperture of the light shielding unit 360 and the microlens 353 cannot be achieved due to a manufacturing error of the image sensor 108.

  Hereinafter, the light reception characteristics of the focus detection pixels will be described with reference to the light reception distribution explanatory view of the focus detection pixels arranged in the image sensor 108 of FIG. 13 and the projection explanatory view of the light reception distribution of FIG. Here, the light receiving distribution explanatory diagram of FIG. 13 shows an example in the case where there is no vignetting in the photographing lens 200. Further, the projection of the light reception distribution shown in FIG. 14 is obtained by projecting the light reception distribution on the pupil of the photographing lens 200 of the focus detection pixel shown in FIG. 13 in the y direction in the figure, and depends on the focus detection pixel group. A generated line image distribution function (so-called line image) L is shown.

  In the plan view of the image sensor 108 in FIG. 10, the aperture Pα1 formed by the light shielding portions 360_1 and 360_2 of the pixel capable of focus detection arranged in the first row and first column has a first deviation in the −x direction with respect to the pixel center. It is deviated by the amount.

  FIG. 13A is an explanatory view of the light reception distribution of the focus detection pixels arranged in the first row and the first column of the image sensor 108. The light reception distribution explanatory diagram of FIG. 13 shows a light amount distribution that can be received on the pupil of the photographing lens 200 when there is no manufacturing error of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The light-shielding portion opening Pα1 of the pixel arranged in the first row and first column of the image sensor 108 can receive the region Sα1 on the pupil of the photographing lens 200. In the figure, the region Sγ where the amount of received light at the position in the + y direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is high is from the gap between the light shielding portions 360_1 and 360_2 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  Further, in the plan view of the image sensor 108 in FIG. 10, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the first row and first column are adjacent to each other in the oblique direction (in the drawing). (2nd row, 2nd column). The pair of focus-detectable pixels are formed with light shielding portions 360_3 and 360_4, and the center of the opening Pβ1 formed by the light shielding portions 360_3 and 360_4 is displaced by a third displacement amount in the + x direction with respect to the pixel center. Yes.

  FIG. 13B is an explanatory diagram of the light reception distribution of the pixels arranged in the second row and second column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ1 formed by the light shielding portions 360_3 and 360_4 of the pixels arranged in the second row and second column of the image sensor 108 can receive the region Sβ1 on the pupil of the photographing lens 200. In the figure, the region Sγ where the amount of received light in the + y direction position from the optical axis of the photographing lens 200 (the intersection of the xy axes in the figure) is high is from the gap between the light shielding portions 360_3, 360_4 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  When there is no manufacturing error of the image sensor 108, the sum of the distance xα1 and the distance xβ1 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 becomes a predetermined value.

  In the plan view of the image sensor 108 in FIG. 10, focus-detectable pixels in which light-shielding portions 360_5 and 360_6 are formed in rows adjacent to four pixels in the −y direction from the first row and first column (the fifth row in the figure). Is arranged. In the pixel arranged in the fifth row and first column and capable of focus detection, the center of the opening Pα2 by the light shielding portions 360_5 and 360_6 is different from the first deviation amount in the −x direction with respect to the pixel center. It is displaced by the amount of displacement.

  FIG. 13C is an explanatory view of the light reception distribution of the pixel arranged in the fifth row and first column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pα2 formed by the light shielding portions 360_5 and 360_6 of the pixel disposed in the fifth row and first column of the image sensor 108 can receive the region Sα2 on the pupil of the photographing lens 200. In the figure, the region Sγ where the amount of received light at the position in the + y direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is high is from the gap between the light shielding portions 360_5, 360_6 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  In addition, in the plan view of the image sensor 108 in FIG. 10, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the fifth row and first column are adjacent to each other in the oblique direction (in the drawing). (6th row, 2nd column). Similarly, light shielding portions 360_7 and 360_8 are formed in the pair of focus-detectable pixels, and the center of the opening Pβ2 by the light shielding portions 360_7 and 360_8 is deviated from the pixel center by the second displacement amount in the + x direction. Is ranked.

  FIG. 13D is an explanatory diagram of the light reception distribution of the pixel arranged in the sixth row and second column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ2 formed by the light shielding portions 360_7 and 360_8 of the pixel arranged in the sixth row and the second column of the image sensor 108 can receive the region Sβ2 on the pupil of the photographing lens 200. In the figure, the region Sγ where the amount of received light in the position in the + y direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is high is from the gap between the light shielding portions 360_7, 360_8 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  When there is no manufacturing error of the image sensor 108, the sum of the distance xα2 and the distance xβ2 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 becomes a predetermined value, and the distance xα1 It is equal to the sum of the distance xβ1.

  In the plan view of the image sensor 108 in FIG. 10, focus detection is possible in which light-shielding portions 360_9 and 360_10 are formed in a row adjacent to four pixels in the −y direction from the fifth row and first column (the ninth row in the figure). Pixels are arranged. In the pixel arranged in the 9th row and the 1st column and capable of focus detection, the center of the opening Pα3 by the light shielding portions 360_9 and 360_10 is different from the first and second deviation amounts in the −x direction with respect to the pixel center. It is displaced by the third displacement amount.

  FIG. 13E is an explanatory diagram of the light reception distribution of the pixel arranged in the 9th row and the 1st column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pα3 formed by the light shielding portions 360_9 and 360_10 of the pixel disposed in the 9th row and the 1st column of the image sensor 108 can receive the region Sα3 on the pupil of the photographing lens 200. In the figure, the region Sγ where the amount of received light at the position in the + y direction from the optical axis of the photographic lens 200 (the intersection of the xy axes in the figure) is increased from the gap between the light shielding portions 360_9, 360_10 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  Further, in the plan view of the image sensor 108 in FIG. 10, the focus-detectable pixels that are paired with the focus-detectable pixels arranged in the 9th row and the 1st column are adjacent to each other in the oblique direction (in the drawing). (10th row, second column). Similarly, the light-shielding portions 360_11 and 360_12 are formed in the pair of focus-detectable pixels, and the center of the opening Pβ3 by the light-shielding portions 360_11 and 360_12 is deviated by the first deviation amount in the + x direction with respect to the pixel center. Is ranked.

  FIG. 13F is an explanatory diagram of the light reception distribution of the pixel arranged in the 10th row and the 2nd column of the image sensor 108. In the drawing, black and white shades indicate the amount of light that can be received, and the white region has a high amount of received light.

  The aperture Pβ3 formed by the light shielding portions 360_11 and 360_12 of the pixel arranged in the 10th row and the 2nd column of the image sensor 108 can receive the region Sβ3 on the pupil of the photographing lens 200. In the figure, a region Sγ where the amount of received light at the position in the + y direction from the optical axis of the photographing lens 200 (the intersection of the xy axes in the figure) is increased from the gap between the light shielding portions 360_11, 360_12 and the transfer electrode 330. This is due to leakage light and partially transmitted light of the transfer electrode 330.

  When there is no manufacturing error of the image sensor 108, the sum of the distance xα3 and the distance xβ3 from the optical axis of the region where the amount of received light is high on the pupil of the photographing lens 200 becomes a predetermined value, and the distance xα1 and the distance It is equal to the sum of xβ1 and the sum of the distance xα2 and the distance xβ2.

  Further, a focus-detectable pixel having a similar opening Pα1 at a position adjacent to the + x direction in the + x direction of the focus-detectable pixel having the opening Pα1 by the light-shielding portion (pixel in the first row and first column in FIG. 10). It is arranged.

  Similarly, a focus-detectable pixel having the same aperture Pβ1 is arranged at a position adjacent to the + x direction of the pixel having the aperture Pβ1 by the light-shielding portion (pixel in the second row and second column in the figure) in the + x direction. It is installed.

  When detecting the focus state of the photographic lens 200, signals of the focus detection pixel group having the aperture Pα1 and the focus detection pixel group having the aperture Pβ1 are output.

  Further, a focus-detectable pixel having a similar opening Pα2 at a position adjacent to the + x direction in the + x direction of the focus-detectable pixel having the opening Pα2 by the light-shielding portion (the pixel in the fifth row and first column in FIG. 10). It is arranged.

  Similarly, a focus-detectable pixel having the same opening Pβ2 is arranged at a position adjacent to the + x-direction in the + x direction of the focus-detectable pixel having the opening Pβ2 by the light-shielding portion (pixel in the sixth row and second column in the figure). It is installed.

  FIG. 14 is a projection of the received light distribution of the focus detection pixel on the pupil of the photographing lens 200 shown in FIG. 13 in the y direction in the figure, and shows a line image L generated by the focus detection pixel group. ing.

  FIG. 14A shows a line image Lα generated by the focus detection pixel group having the opening Pα2 arranged in the fifth row in the plan view of the image sensor 108 of FIG. In the image sensor 108 of the present embodiment, the transfer electrode 330 is disposed at a position displaced in a direction parallel to the longitudinal direction of the opening of the light shielding portion 360 (so-called correlation calculation direction or a direction orthogonal to the pupil division direction). Therefore, the gap between the light shielding unit 360 and the transfer electrode 330 and the change in the line image Lα due to light leaking from the transfer electrode 330 to the photoelectric conversion unit 312 are small.

  By the way, since the transfer electrode 330 is made of polysilicon, it absorbs light having a short wavelength but transmits light having a long wavelength. Therefore, the light reception distribution on the pupil of the photographing lens 200 changes depending on the wavelength of light. The line image Lα shown in FIG. 14A is substantially equivalent to the line image Lαg for green light shown in FIG.

  FIG. 14C shows lines for blue light, green light, and red light generated by the focus detection pixel group having the aperture Pα2 arranged in the fifth row in the plan view of the image sensor 108 of FIG. An image Lα is shown. The line image Lαb for blue light is indicated by a solid line. A line image Lαg for green light is indicated by a dotted line. In the line image Lαg, a component that is transmitted by the polysilicon serving as the transfer electrode 330 is generated around the position having the highest intensity. The line image Lαr for red light is indicated by a broken line. In the vicinity of the position where the intensity is the highest in the line image Lαr, a component that is transmitted by the polysilicon serving as the transfer electrode 330 is generated. The transmission component of red light is larger than the transmission component of green light.

  FIG. 14B shows a line image Lβ generated by the focus detection pixel group having the aperture Pβ2 arranged in the sixth row in the plan view of the image sensor 108 of FIG. In the image sensor 108 of the present embodiment, the transfer electrode 330 is disposed at a position displaced in a direction parallel to the longitudinal direction of the opening of the light shielding portion 360 (so-called correlation calculation direction or a direction orthogonal to the pupil division direction). Therefore, the gap between the light shielding unit 360 and the transfer electrode 330 and the change in the line image Lβ due to light leaking from the transfer electrode 330 to the photoelectric conversion unit 312 are small. Here, the line image Lβ is substantially equivalent to the line image Lβg for green light shown in FIG.

  FIG. 14D shows lines for blue light, green light, and red light generated by the focus detection pixel group having the aperture Pβ2 arranged in the sixth row in the plan view of the image sensor 108 of FIG. An image Lβ is shown. The line image Lβb for blue light is indicated by a solid line. In the line image for green light, Lβg is indicated by a dotted line. A component that is transmitted by the polysilicon serving as the transfer electrode 330 is generated around the position having the highest intensity in the line image Lβg. A line image Lβr for red light is indicated by a broken line. In the line image Lβr, a component that is transmitted by the polysilicon serving as the transfer electrode 330 is generated around the position having the highest intensity. The transmission component of red light is larger than the transmission component of green light.

  A plurality of types of received light distributions of the focus detection pixels are stored in the memory circuit of the camera corresponding to the difference in the aperture and wavelength of the light shielding unit that shields the photoelectric conversion unit of the image sensor.

  When the focus state of the photographic lens 200 is detected, signals of the focus detection pixel group having the aperture Pα2 and the focus detection pixel group having the aperture Pβ2 are output.

  In addition, a focus-detectable pixel having a similar photoelectric conversion unit Pα3 at a position adjacent to the + x direction of the pixel having the photoelectric conversion unit Pα3 in the + x direction (pixel in the 9th row and the first column in FIG. 10). Is arranged.

  Similarly, a focus-detectable pixel having the same photoelectric conversion unit Pβ3 at a position adjacent to the + x direction of the pixel having the photoelectric conversion unit Pβ3 in the + x direction (pixel in the 10th row and the second column in the drawing). It is arranged.

  When the focus state of the photographic lens 200 is detected, signals of the focus detection pixel group having the aperture Pα3 and the focus detection pixel group having the aperture Pβ3 are output.

  When a focus detection image signal is output from the image sensor 108, the focus state of the photographic lens 200 is detected using a known correlation calculation method.

  In the present embodiment, the transfer electrode 330 is disposed at a position displaced in a direction parallel to the longitudinal direction (y direction in the drawing) of the light shielding portion 360 (so-called correlation calculation direction or a direction orthogonal to the pupil division direction). Yes. Therefore, the gap between the light shielding unit 360 and the transfer electrode 330 and the asymmetry of the focus detection image caused by the light leaking from the transfer electrode 330 to the photoelectric conversion unit 312 are small.

  The camera 100, which is the image pickup apparatus of the present invention, detects the focus state of the photographing lens 200 based on the light receiving characteristics of the image pickup element 108 corresponding to the subject color as in the first embodiment. Therefore, highly accurate focus detection is possible.

  The imaging apparatus of the present invention can be suitably used for optical equipment such as a video camera, a compact camera, or a single-lens reflex camera.

DESCRIPTION OF SYMBOLS 100 Camera 101 Bounce mirror 102 Focus plate 103 Penta roof prism 104 Eyepiece 105 Sub mirror 106 Focus detection apparatus 107 Focal plane shutter 108 Imaging element 109 Liquid crystal display element 200 Shooting lens

Claims (7)

A first pixel that receives light passing through an exit pupil region of the photographic lens;
A second pixel that receives light passing through a partial region of the exit pupil of the photographing lens;
An electrode unit provided on the photoelectric conversion unit so as to cover a partial region of the photoelectric conversion unit of the second pixel;
A light-shielding portion that has an opening and covers a region different from the region covered by the electrode portion of the photoelectric conversion unit;
An imaging device having:
A focus detection unit that detects a focus state of the photographic lens based on an output of the second pixel,
Determination means for determining the color of the subject;
Storage means for storing the light receiving characteristics of the image sensor corresponding to the color of the subject,
The image pickup apparatus, wherein the focus detection unit detects a focus state of the photographing lens based on subject color information determined by the determination unit and a light receiving characteristic of the image sensor. Obtaining means for obtaining lens information of the photographing lens;
The imaging apparatus according to claim 1, wherein the focus detection unit detects a focus state of the photographing lens based on the lens information, the subject color information, and a light receiving characteristic of the imaging element.   The imaging apparatus according to claim 2, wherein the focus detection unit calculates a baseline length based on the lens information, the subject color information, and a light receiving characteristic of the imaging element.   The said focus detection means calculates the filter shape which corrects the output image of the said image pick-up element based on the said lens information, the said object color information, and the light reception characteristic of the said image pick-up element. Imaging device.   The focus detection unit calculates correction data for correcting uniformity of an output image of the image sensor based on the lens information, the subject color information, and a light receiving characteristic of the image sensor. 2. The imaging device according to 2. The imaging apparatus according to any one of claims 1 to 5,
An interchangeable lens that can be attached to and detached from the imaging apparatus. A first pixel that receives light passing through an exit pupil area of the photographic lens, a second pixel that receives light passing through a partial area of the exit pupil of the photographic lens, and photoelectric conversion of the second pixel An electrode part provided on the photoelectric conversion part so as to cover a partial area of the part, a light shielding part that has an opening and covers an area different from the area covered by the electrode part of the photoelectric conversion part, A focus detection method for an image pickup apparatus, comprising: an image pickup device including: a focus detection unit configured to detect a focus state of the photographing lens based on an output of the second pixel;
A determination step for determining the color of the subject;
A focus detection step for detecting a focus state of the photographing lens based on the subject color information determined in the determination step and the light receiving characteristic of the image sensor corresponding to the color of the subject stored in the storage unit of the imaging device; And a focus detection method.