JP2014186338A - Imaging apparatus, imaging system, and method for controlling imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately perform focus detection, even if there is vignetting of a focus detection luminous flux due to manufacture errors in focus detection by a phase difference system.SOLUTION: An imaging apparatus comprises: an imaging device (107) comprising a plurality of focus detecting pixel pairs for outputting an image signal pair by respectively photoelectric converting a luminous flux pair passing through different areas of a taking lens (TL); a flash memory (133) for storing center axis misalignment information of the focus detecting pixel pair, relative to an optical axis of the taking lens; a correction part (170) for correcting a signal level of the image signal pair so as to compensate for imbalance in quantity of light incident on each of the focus detecting pixel pair, on the basis of the center axis misalignment information and exit pupil information of the taking lens; and focus detection means (171) for performing focus detection of the taking lens, by using the image signal pair corrected by the correction part.

Description

  The present invention relates to an imaging apparatus, an imaging system, and a focus detection method, and more particularly to an imaging apparatus such as a digital still camera, a video camera, and a silver salt camera, an imaging system, and a focus detection method.

  There are a contrast detection method and a phase difference detection method as a general method using a light beam that has passed through a photographing lens in a focus detection and adjustment method of an imaging apparatus. The contrast detection method is a method often used in video cameras and digital still cameras, and an image sensor is used as a focus detection sensor. Focusing on the output signal of the image sensor, particularly information on high-frequency components (contrast information), the position of the photographing lens with the largest evaluation value is used as the in-focus position. However, as it is said to be a hill-climbing method, it is necessary to obtain an evaluation value while moving the photographic lens by a small amount and move it until it is understood that the evaluation value is the maximum as a result. It is considered unsuitable.

  On the other hand, the phase difference detection method is often used in a single-lens reflex camera using a silver salt film, and is the technology that has contributed most to the practical application of an auto focus (AF) single-lens reflex camera. In the phase difference detection method, the light beam that has passed through the exit pupil of the photographing lens is divided into two, and the two divided light beams are received by a set of focus detection sensors. Then, the amount of deviation of the photographic lens in the focus direction is directly obtained by detecting the amount of deviation of the output signal according to the amount of received light, that is, the amount of relative positional deviation in the light beam splitting direction. Therefore, once the accumulation operation is performed by the focus detection sensor, the amount and direction of the focus shift can be obtained, and thus a high-speed focus adjustment operation is possible.

  Then, in order to obtain a signal corresponding to each of the light beams divided into two, an optical path splitting mechanism such as a half mirror or a reflecting mirror consisting of a quick return mechanism is provided in the imaging optical path, and a focus detection optical system and an AF are provided beyond that. It is common to provide a sensor.

  By the way, in order to perform focus detection by this phase difference detection method, focus detection optics is used so that the above-described two-divided light beams are not vignetted due to vignetting (vignetting) due to changes in the exit pupil, image height, and zoom position of the photographing lens. It is necessary to set the system. In particular, in a camera system in which a plurality of photographing lenses having different exit pupil positions and diameters and vignettings can be mounted, there are many restrictions on performing focus detection so as not to cause vignetting. For this reason, there is a problem that the focus detection area cannot be set in a wide range, and the accuracy cannot be improved by expanding the base length of the light beam divided into two.

  Therefore, Patent Document 1 discloses an example in which focus detection is performed by correcting a decrease in light amount of a focus detection signal due to vignetting of a focus detection light beam from information such as an exit pupil of a photographing lens. According to this example, since the phase difference type focus detection can be performed even if there is some vignetting, it is possible to perform focus detection in a wide range and highly accurate focus detection by expanding the base line length.

  In recent years, a technique for providing a phase difference detection function to an image sensor, eliminating the need for a dedicated AF sensor, and realizing high-speed phase difference AF has also been disclosed.

  For example, in Patent Document 2, in some of the light receiving elements (pixels) of the image sensor, the pupil division function is given by decentering the sensitivity region of the light receiving unit with respect to the optical axis of the on-chip microlens. 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. Further, since the location where the focus detection pixels are arranged corresponds to a defective portion of the imaging pixel, image information is generated by interpolation from surrounding imaging pixel information. According to this example, since it is possible to perform phase difference type focus detection on the imaging surface, high-speed and high-precision focus detection can be performed.

Japanese Patent Laid-Open No. 03-214133 JP 2000-156823 A

However, Patent Documents 1 and 2 have the following problems.
In Patent Document 1, correction of light amount reduction of a focus detection signal due to vignetting of a photographing lens is performed based on information on the photographing lens side. However, the degree of vignetting depends not only on the taking lens side but also on manufacturing errors on the camera side. In particular, since a single-lens reflex camera performs complicated optical path conversion and optical path separation in a focus detection optical system, a manufacturing error due to this is large. Therefore, even if the light amount reduction correction is performed only with information on the photographing lens side, an error occurs in the focus detection result.

  In Patent Document 2, since pupil division is performed based on the relative positional relationship between the on-chip microlens and the light receiving unit, there is a problem that the pupil division is greatly shifted due to a manufacturing error of the on-chip microlens. In the pupil division by the on-chip microlens, the light receiving part at a depth of several microns with respect to the microlens is back projected onto the exit pupil position of the taking lens several tens to several hundreds of millimeters, so the imaging magnification is Become very large. Therefore, since a slight manufacturing error of the on-chip microlens becomes a large deviation, a large amount of vignetting occurs in the focus detection light beam, and the focus cannot be detected.

  The present invention has been made in view of the above problems, and an object of the present invention is to perform focus detection with high accuracy even when there is vignetting of a focus detection light beam due to a manufacturing error in focus detection using a phase difference method.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a plurality of focus detection pixel pairs that photoelectrically convert pairs of light beams that pass through different regions of a photographing lens and output image signal pairs. Imaging devices each having a microlens corresponding to the above, a storage means for storing center axis deviation information relating to a manufacturing error including an alignment error at the time of forming the microlens, and the focus through the exit pupil of the photographing lens A function indicating the ratio of the amount of light that changes in accordance with the image height when there is no manufacturing error is changed based on the center axis deviation information so as to compensate for an unbalance of the amount of light incident on each detection pixel pair. Correction means for correcting the signal level of the image signal pair in accordance with the changed function and the image height of the focus detection pixel pair, and the image corrected by the correction means. Using the signal to, and a focus detection means for performing focus detection of the photographing lens.

  The imaging system of the present invention includes the imaging device and a lens unit that can be attached to and detached from the imaging device, stores the central axis deviation information in the imaging device, and information on the exit pupil in the lens unit. And information on the exit pupil is transmitted from the lens unit to the imaging device.

  Further, in the focus detection method of the present invention in the image pickup apparatus, the output means photoelectrically converts a pair of light fluxes passing through different regions of the photographing lens by a plurality of focus detection pixel pairs included in the image pickup device, respectively, to generate an image signal. An output step of outputting a pair; an acquisition unit that acquires center axis deviation information relating to a manufacturing error including an alignment error when forming a microlens formed corresponding to each pixel of the image sensor; and a correction Means for compensating for an unbalance of the amount of light incident on each of the focus detection pixel pairs via the exit pupil of the photographing lens, so that the amount of light that changes according to the image height when there is no manufacturing error. A function that changes the function indicating the ratio based on the center axis deviation information, and corrects the signal level of the image signal pair according to the changed function and the image height of the focus detection pixel pair. Comprising a degree, the focus detection means, using the image signal to which has been corrected by said correction step, and a focus detection step of performing focus detection of the photographing lens.

  According to the present invention, focus detection can be performed with high accuracy even when there is vignetting of a focus detection light beam due to manufacturing errors in phase difference type focus detection.

It is a block diagram which shows the structure of the camera in the 1st Embodiment of this invention. It is the top view which looked at the light reception pixel of the image sensor in the 1st Embodiment of this invention from the imaging lens side. It is a figure explaining the structure of the pixel for imaging in the 1st Embodiment of this invention. It is a figure explaining the structure of the pixel for focus detection in the 1st Embodiment of this invention. It is a figure explaining the structure of the pixel for a focus detection of the peripheral part of the image pick-up element in the 1st Embodiment of this invention. It is a figure explaining the structure of the pixel for a focus detection which performs pupil division in the orthogonal | vertical direction of the imaging lens in the 1st Embodiment of this invention. It is a figure which shows schematically the focus detection structure in the 1st Embodiment of this invention. It is a figure which shows the signal for focus detection in the 1st Embodiment of this invention. It is a figure which illustrates notionally the pupil division function by the pixel for a focus detection in the 1st Embodiment of this invention. It is a figure which represents typically the CMOS sensor chip of a layer layer structure. FIG. 5 is a diagram showing a case where an alignment error of a microlens occurs in the structure of FIG. It is a figure which shows the case where the alignment error of a micro lens has generate | occur | produced in the structure of FIG. It is the figure which looked at the exit pupil when the alignment error of a micro lens occurred from the image sensor side. It is the figure which looked at the exit pupil when the alignment error of a micro lens occurred from the image sensor side. It is a figure which shows the relationship between an entrance pupil and an exit pupil. It is the figure which matched the exit pupil shape in an image sensor and its image height. It is a block diagram which shows the structure for correct | amending the signal for focus detection in the 1st Embodiment of this invention. It is a flowchart which shows the correction | amendment procedure of the signal for focus detection in the 1st Embodiment of this invention. It is a graph which shows the relationship between the image height h of a focus detection pixel, and the light quantity ratio C. It is a figure explaining the structure of the pixel for focus detection in the 2nd Embodiment of this invention. It is the figure which looked at the exit pupil in the 2nd Embodiment of this invention from the image pick-up element side. It is a block diagram which shows the structure of the camera system in the 3rd Embodiment of this invention. It is a block diagram which shows the structure for correct | amending the signal for focus detection in the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the camera system in the 4th Embodiment of this invention. It is a conceptual diagram which shows the relationship between the focus detection part in the 4th Embodiment of this invention, and the exit pupil of various interchangeable lenses.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a camera according to the first embodiment of the present invention. As an example, a digital still camera in which a camera body having an image sensor and a photographing lens 100 are integrally configured is shown.

  In the figure, L is an optical axis of the taking lens 100, and 101 is a first lens group disposed at the tip of the taking lens 100, and is held so as to be able to advance and retreat in the optical axis direction. Reference numeral 102 denotes an aperture / shutter which adjusts the light amount during shooting by adjusting the aperture diameter, and also has a function of adjusting the exposure time during 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, which performs focus adjustment by moving back and forth 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 CMOS image sensor and its peripheral circuits. In this image sensor 107, a Bayer array primary color filter is formed on-chip on 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 101 to the second lens group 103 back and forth in the optical axis direction to perform 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 116 denotes an AF auxiliary light emitting unit that projects an image of a mask having a predetermined opening pattern onto a subject field via a light projecting lens, and improves focus detection capability for a dark subject or a low-contrast subject.

  Reference numeral 121 denotes a CPU which controls various controls of the camera body in the imaging apparatus. The CPU 121 includes, for example, a calculation unit, ROM, RAM, A / D converter, D / A converter, communication interface circuit, and the like. Then, the CPU 121 drives various circuits included in the imaging device based on a predetermined program stored in the ROM, and executes a series of operations such as AF, shooting, image processing, and recording.

  An electronic flash control circuit 122 controls lighting of the electronic flash 115 in synchronization with the photographing operation. Reference numeral 123 denotes an auxiliary light driving circuit that controls the lighting of the AF auxiliary light emitting unit 116 in synchronization with the focus detection operation. Reference numeral 124 denotes an image sensor driving circuit that controls the imaging operation of the image sensor 107 and A / D-converts the acquired image signal and transmits it to the CPU 121. An image processing circuit 125 performs processing such as γ conversion, color interpolation, and JPEG compression of an image acquired by the image sensor 107.

  A focus driving circuit 126 controls the focus actuator 114 based on the focus detection result, and performs focus adjustment 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 such as an LCD, which displays information related to the shooting mode of the imaging apparatus, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, 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 plan view of a light receiving pixel on which a subject image is formed in the image sensor 107 of FIG. Reference numeral 20 denotes an entire pixel formed of m pixels in the horizontal direction and n pixels in the vertical direction on the image sensor 107, and 21 denotes a pixel portion thereof. In each pixel portion, an on-chip Bayer array primary color filter is formed and arranged in a 4-pixel cycle of 2 rows × 2 columns. In FIG. 2, only the pixel portion of 10 pixels × 10 pixels on the upper left side is displayed and the other pixel portions are omitted for easy understanding of the drawing.

  3 and 4 are diagrams illustrating the structure of the imaging pixel and the focus detection pixel in the pixel portion in FIG. In the first embodiment, out of 4 pixels of 2 rows × 2 columns, pixels having G (green) spectral sensitivity are arranged in 2 diagonal pixels, and R (red) and B ( A Bayer arrangement in which one pixel each having a spectral sensitivity of (blue) is arranged is employed. A focus detection pixel having a structure to be described later is arranged between the Bayer arrays.

FIG. 3 shows the arrangement and structure of the imaging pixels. FIG. 3A is a plan view of 2 × 2 imaging pixels. FIG. 3B is a cross-sectional view taken along the line AA in FIG. ML denotes an on-chip microlens arranged in front of each pixel, CF _R is a color filter, CF _G of R (red), a G (green) color filter. PD (Photo Diode) schematically shows a photoelectric conversion element of the image sensor 107. CL (Contact Layer) is a wiring layer for forming signal lines for transmitting various signals in the image sensor 107. TL (Taking Lens) schematically shows the photographing lens 100, and L is an optical axis of the photographing lens TL. FIG. 3 is a diagram showing a pixel structure in the vicinity of the center of the image sensor 107, that is, a pixel structure in the vicinity of the photographing lens TL.

  Here, the on-chip microlens ML and the photoelectric conversion element PD of the imaging pixel are configured to capture the light beam that has passed through the photographing lens TL as effectively as possible. In other words, the exit pupil EP (Exit Pupil) of the photographic lens TL and the photoelectric conversion element PD are in a conjugate relationship by the microlens ML, and the effective area of the photoelectric conversion element is designed to be large. The light beam 30 shows the state, and the entire area of the exit pupil EP is taken into the photoelectric conversion element PD. In FIG. 3B, the incident light beam of the R pixel has been described, but the G pixel and the B (blue) pixel have the same structure.

FIG. 4 shows the arrangement and structure of focus detection pixels for performing pupil division in the horizontal direction (lateral direction) of the photographic lens TL. Here, the horizontal direction indicates the longitudinal direction of the image sensor 107 shown in FIG. FIG. 4A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When obtaining an image signal for recording or viewing, the main component of luminance information is acquired by G pixels. This is because human image recognition characteristics are sensitive to luminance information, and if G pixels are lost, image quality degradation is easily recognized. On the other hand, the R pixel or the B pixel is a pixel that acquires color information (color difference information). However, since human visual characteristics are insensitive to color information, the pixel that acquires color information has some defects. However, image quality degradation is difficult to recognize. Therefore, in the first embodiment, among the pixels in 2 rows × 2 columns, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are replaced with focus detection pixels. This focus detection pixel pair is denoted as S _HA and S _HB in FIG.

  FIG. 4B is a cross-sectional view taken along the line AA in FIG. The microlens ML and the photoelectric conversion element PD have the same structure as the imaging pixel shown in FIG. FIG. 4 is also a diagram showing the structure of a pixel near the center of the image sensor 107, that is, a pixel near the axis of the photographic lens TL.

In the first embodiment, since the signal of the focus detection pixel is not used for image generation, a transparent film CFW (white) is arranged instead of the color separation color filter. Further, since pupil division is performed by the image sensor 107, the opening of the wiring layer CL is eccentric in one direction with respect to the center line of the microlens ML. Specifically, since the opening OP _HA of the pixel S _HA is decentered by 41 _HA on the right side with respect to the center line of the microlens ML, the left exit pupil region EP _HA across the optical axis L of the photographing lens TL. The light beam 40 _HA that has passed through is received. Similarly, since the opening OP _HB of the pixel S _HB is decentered by 41 _HB on the left side with respect to the center line of the micro lens ML, it passes through the right exit pupil region EP _HB across the optical axis L of the photographing lens TL. The received light beam 40 _HB is received. As is apparent from the figure, the eccentric amount 41 _HA is equal to the eccentric amount 41 _HB .

The pixels _SHA having the above-described configuration are regularly arranged in the horizontal direction, and a subject image acquired by these pixel groups is defined as an A image. Also, the pixels _SHB are regularly arranged in the horizontal direction, and the subject image acquired by these pixel groups is a B image. By detecting the relative positions of the A image and the B image, the amount of focus deviation of the subject image is detected. (Defocus amount) can be detected.

On the other hand, FIG. 5 is a cross-sectional view taken along the line AA in FIG. 4A as in FIG. In the peripheral portion, pupil division is performed by decentering the openings OP _HA and OP _HB of the microlens ML and the wiring layer CL in a state different from that in FIG. When towards the opening OP _HA will be described as an example, in the peripheral portion by the eccentric to adjust the center and the sphere center of the microlens ML made of substantially spherical on a line connecting the exit pupil area EP _HA center of the opening OP _HA Can also perform pupil division substantially equivalent to that on the axis.

Specifically, since the opening OP _HA of the pixel S _HA is decentered by 51 _HA on the right side with respect to the center line of the microlens ML, the left exit pupil region EP _HA across the optical axis L of the photographing lens TL. The beam 50 _HA that has passed through is received. Similarly, since the opening OP _HB of the pixel S _HB is decentered by 51 _HB on the left side with respect to the center line of the microlens ML, it passes through the right exit pupil region EP _HB across the optical axis L of the photographing lens TL. The received light beam 50 _HB is received. As is apparent from the figure, the eccentric amount 51 _HB is set larger than the eccentric amount 51 _HA . Note that the eccentricity described above has been described by taking the peripheral portion in the horizontal direction as an example, but it is possible to perform pupil division in the same manner in the peripheral portion in the vertical direction and also in the peripheral portion where both horizontal and vertical are mixed. .

In the focus detection pixel pair S _HA and S _HB , focus detection is possible for an object having a luminance distribution in the horizontal direction of the photographing screen, for example, a vertical line, but a horizontal line having a luminance distribution in the vertical direction is a focus. It cannot be detected. For this purpose, it is only necessary to provide a pixel that performs pupil division in the vertical direction (longitudinal direction) of the photographing lens.

FIG. 6 shows the arrangement and structure of focus detection pixels for performing pupil division in the vertical direction of the photographing lens. Here, the vertical direction and the vertical direction indicate the short direction of the image sensor 107 shown in FIG. FIG. 6A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. As in FIG. 4A, G pixels are left as imaging pixels, and R pixels and B pixels are used. Focus detection pixels are used. The focus detection pixels are denoted as S _VC and S _VD in FIG.

FIG. 6B is a sectional view taken along the line AA in FIG. The pixel in FIG. 4B has a structure in which the pupil is separated in the horizontal direction, whereas the pixel in FIG. 6B has the vertical direction in the pupil separation direction. is there. Due to the decentered by _{61 VC} below the the center line of the opening _{OP VC} microlens ML of the pixel _{S VC,} the light flux passing through the upper exit pupil region _{EP VC} across the optical axis L of the taking lens TL 60 _VC is received. Similarly, since the opening OP _VD of the pixel S _VD is decentered by 61 _{VD on the} upper side with respect to the center line of the microlens ML, the lower exit pupil region EP _VD across the optical axis L of the photographing lens TL is defined. The _transmitted light beam 60 _VD is received. As is apparent from the figure, FIG. 6 shows the pixel structure near the axis of the image sensor 107 as in FIG. 4, and therefore the eccentricity 61 _VC and the eccentricity 61 _VD are equal.

The pixels _SVC having the above-described configuration are regularly arranged in the vertical direction, and a subject image acquired by these pixel groups is defined as a C image. Further, the pixels _SVD are also regularly arranged in the vertical direction, and the subject image acquired by these pixel groups is defined as a D image. Then, by detecting the relative positions of the C image and the D image, it is possible to detect the focus shift amount (defocus amount) of the subject image having the luminance distribution in the vertical direction. Even in the case where the pupil division is performed in the vertical direction, the pupil detection is performed on the peripheral focus detection pixels by the method described with reference to FIG.

By the way, since the focus detection pixel pairs S _HA and S _HB , S _VC and S _VD do not have original color information, a signal is created by performing interpolation calculation from pixel signals in the peripheral portion when forming a captured image. . Therefore, the image quality of the captured image is not reduced by arranging the focus detection pixel pairs on the image sensor 107 in a discrete manner rather than continuously.

  As described above with reference to FIGS. 3 to 6, the image sensor 107 serves not only as an image capturing function but also as a focus detection means of the present invention.

FIG. 7 is a diagram schematically showing the focus detection configuration of the present invention. The image sensor 107 includes a plurality of focus detection units 901 including first focus detection pixels 901a and second focus detection pixels 901b that are divided into pupils. Incidentally, the focus detection unit 901 has the configuration shown in FIG. 4 (a), the focus detection pixels 901a on the pixel _{S HA,} the focus detection pixel 901b corresponding to the pixel _{S HB.} The image sensor 107 includes a plurality of imaging pixels for photoelectrically converting the subject image formed by the photographing lens 100.

  The CPU 121 includes a synthesis unit 902, a connection unit 903, and a calculation unit 904. The CPU 121 also assigns a plurality of sections (regions) CST to the imaging surface of the imaging element 107 so as to include a plurality of focus detection units 901. The CPU 121 can appropriately change the size, arrangement, number, etc. of the section CST. In each of the plurality of sections CST assigned to the image sensor 107, the combining unit 902 performs a process of combining the output signals from the first focus detection pixels 901a to obtain a first combined signal of one pixel. In addition, in each section CST, the combining unit 902 performs a process of combining the output signals from the second focus detection pixels 901b to obtain a second combined signal of one pixel. In the plurality of sections CST, the connecting unit 903 connects the pixels that are the first combined signal to obtain the first connected signal, and connects the second combined signal to obtain the second connected signal. Process. In this way, a connection signal in which the number of sections of pixels are connected to each of the first focus detection pixel 901a and the first focus detection pixel 901b is obtained. The calculation unit 904 calculates a defocus amount of the imaging optical system based on the first connection signal and the second connection signal. In this way, since the output signals of the focus detection pixels in the same pupil division direction arranged in the section are synthesized, even if the brightness of each focus detection unit is small, the brightness distribution of the subject is Sufficient detection is possible.

  FIG. 7 shows an example in which the pupil is divided in the horizontal direction, but the same applies to the case where the pupil is divided in the vertical direction.

FIG. 8 shows an example of a focus detection signal pair (image signal pair) formed by the focus detection unit 901, the synthesis unit 902, and the connection unit 903 in FIG. 7 and input to the calculation unit 904. In the graph of FIG. 8, the horizontal axis indicates the pixel arrangement direction of the connected signals, and the vertical axis indicates the signal intensity. The focus detection signal shown in FIG. 8 is obtained when a single vertical line is detected. The focus detection signal IMG _A is formed by the focus detection pixel 901a, and the focus detection signal IMG _B is formed by the focus detection pixel 901b. Signal. Since the photographing lens 100 shown in FIG. 1 is shifted to the rear pin side with respect to the image sensor 107, the focus detection signal IMG _A is shifted to the left side and the focus detection signal IMG _B is shifted to the right side. It has become.

By calculating the deviation amount of the focus detection signals IMG _A and IMG _B by a known correlation calculation or the like, it is possible to know how much the photographing lens 100 is defocused, so that focusing can be performed. It becomes. Since the calculation of the deviation amount is known, the description is omitted. In FIG. 8, the case of shifting to the rear pin side is described as an example. However, when shifting to the front pin side, the shift directions of the focus detection signals IMG _A and IMG _B are reversed left and right.

  FIG. 9 is a diagram for conceptually explaining the pupil division function by the focus detection pixels of the image sensor 107. TL is a photographing lens, 107 is an image sensor, OBJ is a subject, and IMG is a subject image.

As described with reference to FIG. 3, the imaging pixels receive the light flux that has passed through the entire exit pupil EP of the photographing lens TL. On the other hand, the focus detection pixel has a pupil division function as described with reference to FIGS. Specifically, the pixel S _{HA in} FIG. 4 receives the light beam L _HA that has passed through the left pupil when viewed from the imaging surface, that is, the light beam that has passed through the pupil EP _HA in FIG. Similarly, the pixels S _HB , S _VC, and S _VD receive the light beams that have passed through the exit pupil regions EP _HB , EP _VC, and EP _VD , respectively. Since the focus detection pixels are distributed over the entire area of the image sensor 107, it is possible to detect the focus in the entire imaging area. With the configuration as described above, it is possible to perform phase difference type focus detection over a wide range of the image sensor 107.

In the above description, the focus detection system in an ideal state without considering the manufacturing error has been described. However, in reality, the exit pupil regions EP _HA , EP _HB , EP _VC for focus detection are caused by a variation factor such as a manufacturing error. A large deviation occurs in the EP _VD . Therefore, in the present invention, this shift information is stored in advance, and the focus detection signal is corrected to perform highly accurate focus detection. Details will be described below.

  In general, an image sensor such as a CMOS sensor is manufactured by stacking a plurality of layer layers on a silicon wafer. FIG. 10 is a diagram schematically showing a CMOS sensor chip having a layer layer structure included in the image sensor 107 in FIG. In the CMOS sensor chip, a unit pixel is formed by forming a pad insulating layer on a lower layer where a photodiode and a transistor are formed. Next, the pad insulating layer is selectively removed so that the metal wiring in the lower layer is exposed. The metal wiring is used to connect the transistor to an external element. A plurality of such wirings and insulating layers are formed according to the circuit scale, and are collectively shown as a wiring layer and an insulating layer 11 in FIG. That is, the wiring layer CL in FIGS.

  Then, a colored photoresist is applied, and this is processed by an exposure and development process to form the color filter layer 12. Next, the microlens flattening layer 13 is formed so that a uniform microlens can be formed. Then, a photoresist is applied on the microlens planarizing layer 13, and this is processed by exposure and development processes, thereby patterning the photoresist. Next, by processing the photoresist patterned by the heat treatment process, the photoresist is subjected to a reflow process to form a dome-shaped microlens 14 layer. As described above, since the CMOS sensor chip is manufactured for each layer layer, an error in manufacturing is interposed between the layer layers. Therefore, the positional accuracy of the microlens 14 with respect to the wiring layer and the insulating layer 11 is determined by the alignment accuracy of the semiconductor manufacturing apparatus for patterning the photoresist. That is, the microlens ML is displaced by this alignment accuracy with respect to the wiring layer CL shown in FIGS. In general, the distance between the microlens ML and the photodiode PD is several microns. On the other hand, since the distance from the microlens ML to the exit pupil of the photographing lens 100 is a unit of several tens of millimeters, the optical imaging magnification is several tens of thousands of times. In this case, an alignment error of 0.1 μm results in a very large deviation of several millimeters on the exit pupil, which is a factor that greatly reduces the focus detection accuracy.

FIG. 11 shows a case where an alignment error occurs in the microlens ML in the horizontal direction in the focus detection pixel for pupil division in the horizontal direction (lateral direction) of the photographing lens shown in FIG. In the figure, the microlens ML represents a case is shifted by D _ML amount to the left, the microlens ML shown by a dotted line is no error (Figure 4 (b)). That is, the deviation D _ML in FIG. 11 is added to or subtracted from the eccentric amounts 41 _HA and 41 _HB in FIG. 4B, and the opening OP _HA of the pixel S _HA is deviated by 111 _HA on the right side with respect to the center line of the microlens ML. I have a heart. The opening _{OP HB} of the pixel _{S HB} is offset by _{111 HB} to the left relative to the center line of the microlens ML. The pixels S _HA and S _HB receive the light beams 110 _HA and 110 _HB corresponding to the exit pupil regions EP _HA and EP _HB that are shifted by D _{EP with} respect to the optical axis L of the photographing lens TL.

FIG. 12 shows a case where an alignment error of the microlens ML occurs in the focus detection pixels in the peripheral portion of the image sensor 107 shown in FIG. As described with reference to FIG. 10, since the microlens is manufactured for each layer layer, the alignment error is constant regardless of the position on the image sensor 107. Therefore, when the alignment error occurs only D _ML in FIG. 11 are shifted by the same amount of DML as compared with the case where there is no error (Figure 5) to the microlens ML shown by a dotted line also in Fig. 12. That is, the deviation _{D ML} in FIG. 12 is added to or subtracted from the amount of eccentricity ₅₁ HA, _{51 HB} of FIG. 5, the opening _{OP HA} of the pixel _{S HA} is offset by _{121 HA} on the right side of the center line of the microlens ML. The opening _{OP HB} of the pixel _{S HB} is offset by _{121 HB} to the left relative to the center line of the microlens ML. The pixels S _HA and S _HB receive light beams 120 _HA and 120 _HB corresponding to the exit pupil regions EP _HA and EP _HB that are shifted by D _{EP with} respect to the optical axis L of the photographing lens TL.

On the other hand, in the focus detection pixel for performing pupil division in the vertical direction described with reference to FIG. 6B, the error generation direction is the vertical direction on the paper surface, and thus the pupil division state remains unchanged in this cross section. Therefore, detailed description using the drawings is omitted. Although described disengagement D _EP above description as an alignment error of the microlens ML, in an actual camera, also applied embedded adjustment error such as parallel eccentricity and inclination of the imaging element 107. However, in the displacement D _EP alignment error of the microlenses ML is the most dominant.

  FIGS. 13 and 14 are views of the exit pupil EP of the pixels in the vicinity of the axis of the image sensor 107 in FIG. 11 or FIGS. 4B and 6B as viewed from the image sensor 107 side. FIGS. 13 (a) and 14 (a) show the microlens ML with error, and FIGS. 13 (b) and 14 (b) show the state without error.

In FIG. 13A, the center L _AF of the exit pupil areas EP _HA , EP _HB , EP _VC , and EP _VD for focus detection is shifted by D _{EP with} respect to the optical axis L of the photographing lens TL. Here, L _AF becomes a central axis of the focus detection means in the present invention, D _EP corresponds to the central axis shift. A common area of the exit pupil EP and the exit pupil areas EP _HA and EP _HB for focus detection, that is, an area through which a light beam actually used for focus detection passes, as shown in the figure, is a hatched area 130 _{HA that} rises to the right. , 130 _HB . In this case, the hatched region ₁₃₀ HA, _{130 HB} has a horizontally asymmetrical a pupil division direction by the central axis shift _{D EP.}

On the other hand, as shown in FIG. 13B, when there is no error of the microlens ML, the optical axis L and the central axis _LAF of the focus detection means coincide. Accordingly, the diagonally upward slanting regions 131 _HA and 131 _HB through which the focus detection light beam passes are symmetrical in the horizontal direction about the central axis LAF.

FIG. 14 is a view similar to FIG. 13, focusing on the exit pupil regions EP _VC and EP _VD for focus detection that separate the exit pupil EP in the vertical direction. The common areas of the exit pupil EP of the photographic lens TL and the exit pupil areas EP _VC and EP _VD for focus detection are diagonally upward areas 140 _VC and 140 _VD that rise to the left. In this case, the hatched region 140 _VC, 140 _VD to the center axis shift D _EP is displaced laterally in the same manner, maintaining the vertical symmetry in the vertical direction is a pupil division direction about the optical axis L or the central axis L _AF It is laterally shifted.

In the above description, the center axis deviation _DEP has occurred in the horizontal direction. However, the focus detection light flux passes through the same way as described above when it occurs in the vertical direction or in both the horizontal and vertical directions. The shaded area can be derived.

13 and 14 illustrate the pixel near the center of the image sensor 107. In addition, the exit pupil EP of the photographic lens TL varies depending on the image height in the peripheral portion. FIG. 15 is a diagram for explaining this, and the photographic lens 100 is simplified by an entrance pupil E _NTP and an exit pupil EP. The entrance pupil E _NTP and the exit pupil EP have different distances and diameters from the image sensor 107, and the light beam incident on the image sensor 107 must pass through these two circles. Therefore, the light beam incident on the pixel portion other than the vicinity of the optical axis L of the imaging element 107 is affected by the entrance pupil E _{NT P} not only the exit pupil EP.

FIG. 16 is a diagram in which the imaging element 107 is associated with the exit pupil shape at the image height. In Figure 16, EP _C denotes an exit pupil shape of the on-axis shows subscript T, B, L, the image height of vertical and horizontal R, respectively. For example, the upper left diagonal is expressed as EP _TL together with _TL . As can be seen from the figure, the exit pupil shape decreases as the image height from the center of the image sensor 107 increases. Therefore, in the first embodiment, 160 indicated by a dotted line in the figure is set as a focus detection area, and an area where the change in the exit pupil shape is relatively small at all zoom and focus positions is used. If the photographic lens 100 is a telecentric optical system in which the shape change of the exit pupil is small up to the end of the image sensor 107, better focus detection can be performed to the end of the photographic screen.

From the above, the combination of the center axis deviation due to the microlens alignment error and the shape change of the exit pupil of the photographing lens due to the image height, the focus detection light beam on the exit pupil as shown by the hatched portion in FIGS. The exit pupil area is determined. In the phase difference type focus detection, when such an exit pupil region change occurs, there are mainly three adverse effects.
(1) Unbalance of light quantity incident on each focus detection pixel pair (2) Deformation of focus detection signal shape due to change in line image distribution in pupil separation direction (3) Defocus amount detection error due to change in baseline length, As for (2) and (3), the effect decreases as the focus position is approached, and the effect is completely eliminated at the focus position. Therefore, if the focus detection algorithm is devised and the focus time is somewhat longer, The influence on the final focusing accuracy can be reduced. However, (1) greatly affects the correlation calculation accuracy for calculating the defocus amount. Therefore, in the first embodiment, with respect to (1), highly accurate phase difference focus detection is realized by correcting the signal level of the focus adjustment signal pair so as to compensate for the light quantity imbalance.

  FIG. 17 is a block diagram showing the internal details of the calculation unit 904 provided in the CPU 121 of FIG. 7 for correcting the focus detection signal pair in the first embodiment. In FIG. 17, the focus detection signal formed by the connecting unit 903 in FIG. 7 is subjected to correction including (1) by the correction unit 170 inside the calculation unit 904 and then input to the correlation calculation unit 171.

  A flash memory 133 connected to the CPU 121 includes pixel sensitivity unevenness information 175 of each pixel forming a focus detection signal, exit pupil information 176 based on the image height of the photographing lens 100, and center axis deviation information 177 based on an alignment error of the microlens. . Here, the pixel sensitivity unevenness information 175 and the center axis deviation information 177 are information written during the manufacturing process of the camera. The exit pupil information 176 stores information based on design values without error in advance.

  FIG. 18 is a flowchart showing a procedure for correcting the focus detection signal according to the first embodiment. First, the correction unit 170 performs two-step correction on the input pair of focus detection signals in steps S181 and S182. And the correlation calculation part 171 performs the process of step S183-S186.

  In step S181, based on the pixel sensitivity unevenness information 175 of the flash memory 133, sensitivity unevenness correction specific to each pixel is performed by multiplying the output value data of each pixel by a coefficient for correcting the sensitivity unevenness.

  In step S182, for each pixel that forms a pair of focus detection signals, the hatched area as described with reference to FIGS. 13A and 14A is calculated from the exit pupil information 176 and the center axis deviation information 177. calculate. The light amount is corrected by multiplying the output value of each pixel by a coefficient corresponding to the area. Here, if the area calculation is performed for each pixel each time, the calculation amount is too large and it takes time to detect the focus. Therefore, the amount of calculation can be reduced by taking the following method.

FIG. 19 shows a graph in which the horizontal axis represents the image height h of the paired focus detection pixels, and the vertical axis represents the light amount ratio C thereof. Here, the light quantity ratio C represents the light quantity ratio of S _HB when the focus detection pixel unit S _HA of FIG. 4 is used as a reference. Reference numeral 190 denotes a light amount ratio when there is no manufacturing error as described in FIGS. 13B and 14B. When h = 0, the light amount ratio C is 1.0. When the light quantity ratio indicated by 190 is C0 and is expressed as a function of the image height h, it can be expressed as the following equation (1).
C0 = f (h) (1)

Reference numeral 191 denotes a light amount ratio in the case where a manufacturing error occurs due to a microlens alignment error _DML or the like, and the image heights at which the light amounts of the paired focus detection pixel portions are equal are shifted. When the shift amount is h _ERR , C = 1.0 when h = h _ERR . Since the entire curve changes depending on h _ERR , the light quantity ratio indicated by 191 is C _ERR , and the image height h and h _ERR are variables, and can be expressed by the following equation (2).
CERR = f (h−h _ERR ) · g (h _ERR ) (2)

In the camera of the first embodiment, the exit pupil change of the photographing lens 100 is rotationally symmetric about the optical axis L, but the focus detection pixel structure of the image sensor 107 is not rotationally symmetric. Therefore, when the distance from the axis of the focus detection pixel of the image sensor 107 instead of the image height h is replaced with (x, y) and the shift distance due to the manufacturing error is replaced with (x _ERR , y _ERR ), Expression (2) Can be rewritten as the following equation (3).
C (x _ERR , y _ERR ) = f (xx _ERR , _{yy ERR} ) · g (x _ERR , y _ERR ) (3)

With the above configuration, f (x, y) is stored in advance as exit pupil information 176, and (x _ERR , y _ERR ) and g (x _ERR , y _ERR ) are stored as center axis deviation information 177 in advance. Then, by multiplying the focus detection signal by a coefficient based on the light amount ratio C (x _ERR , y _ERR ) calculated by Expression (3), it is possible to perform correction with a small amount of calculation. Here, the manufacturing error (x _ERR , y _ERR ) is dominated by the alignment error of the microlens. According to the manufacturing method described with reference to FIG. 10, the alignment error is uniformly shifted for each wafer. Therefore, in the camera manufacturing process, if this alignment error is managed for each CMOS sensor chip, it is not necessary to check the alignment error for each unit, and therefore the process can be shortened. Other manufacturing errors (x _ERR , y _ERR ) include position adjustment errors such as parallel eccentricity and tilt when the image sensor 107 is incorporated into the camera.

  When the stored information differs depending on the zoom or focus position of the photographing lens, the zoom or focus position may be divided for convenience and stored for each divided position. Note that the photographing lens 100 according to the first embodiment is a photographing lens in which there is no change in the exit pupil due to zooming or focusing.

  In step S183, it is determined whether the focus detection signal corrected by the correction unit 170 is sufficiently reliable when the subsequent processing is performed. Specifically, the determination is performed by analyzing the contrast component of the image.

  Step S184 is a process performed when it is determined that the focus detection signal is reliable. A digital filter process is performed to remove frequency components unnecessary for the calculation. On the other hand, S185 is a process when it is determined that the focus detection signal is not reliable. In this case, an in-focus process such as notifying the user of the in-focus state is performed and the process ends.

  Finally, in step S186, an image shift amount is calculated by a known correlation calculation. Then, as shown in FIG. 17, the defocus amount, that is, the defocus amount of the photographing lens 100 is calculated based on the image shift amount.

  With the configuration as described above, even when the center axis deviation of the focus detection exit pupil region due to the microlens alignment error occurs, high-precision focus detection can be realized by correcting the focus detection signal by the correction unit. . The correction by the correction unit of the first embodiment is configured to correct only (1) among the above-described (1) to (3), but the first implementation is also performed for (2) and (3). It is possible to correct by the configuration of the form. By doing so, it is possible to perform focus detection with higher accuracy even during defocusing.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.

  The second embodiment is different from the first embodiment in that the photographing lens 100 corresponds to a case where the pupil distance greatly changes depending on the zoom or focus position.

FIG. 20 is a diagram for explaining this, and shows focus detection pixels corresponding to the focus detection pixels shown in FIG. 11 of the first embodiment. In FIG. 20, EP ₁ shows the exit pupil when the zoom position of the taking lens 100 is at the tele end, while EP ₂ shows the case when the zoom position of the taking lens 100 is at the wide end. And between tele and wide, an exit pupil changes in the range connected with a dotted line in a figure.

Thus, in the second embodiment, it can be seen that not only the exit pupil diameter but also the distance from the microlens to the exit pupil, that is, the exit pupil distance, changes according to the zoom position of the photographic lens 100. Therefore, the deviations D _EP1 and D _EP2 of the exit pupil regions EP _HA1 and EP _HB1 and EP _HA2 and EP _HB2 due to the alignment error D _ML of the microlens ML are different between the exit pupils EP ₁ and EP ₂ .

FIGS. 21A and 21B are views of the exit pupils of pixels near the axis of the image sensor 107 in FIG. 20 as viewed from the image sensor 107 side, where FIG. 21A shows the tele end side and FIG. 21B shows the wide end side. The centers L _AF1 and L _AF2 of the exit pupil areas EP _HA1 and EP _HB1 and EP _HA2 and EP _HB2 for focus detection are shifted from the optical axis L of the photographing lens TL by D _EP1 and D _EP2 , respectively. Here, L _AF1 and L _AF2 are the central axes of the focus detection means in the respective exit pupils EP1 and EP2, and D _EP1 and D _EP2 correspond to the center axis deviation. The exit pupil regions EP ₁ and EP 2 and the exit pupil regions EP _HA1 and EP _HB1 for focus detection, the common region of EP _HA2 and EP _HB2 , that is, the region through which the light beam used for actual focus detection passes is an oblique line region that rises to the right. 210 _HA1 and 210 _HB1 , 211 _HA2 and 211 _HB2 .

As is apparent from these hatched areas, it is understood that the light quantity ratio of the focus detection pixels that are paired differs between the tele end side and the wide end side. This in addition to variations from the exit pupil EP ₁ to EP _2, the central axis shift is due to changes from _{D EP1} to _{D EP2.} 20 and 21 illustrate the pixels in the vicinity of the axis of the image sensor 107. In the peripheral portion, the change degree of the center axis deviation is different from that on the axis. Therefore, it is necessary to store the center axis deviation in a format that can cope with the change in the exit pupil distance, instead of storing it as information on only one exit pupil as in the first embodiment.

Therefore, if the distance from the image sensor 107 to the exit pupil is 1, the center axis deviation (x _ERR , y _ERR ) at an arbitrary pixel position (x, y) of the image sensor 107 is the distance l and the pixel position (x, It can be expressed by the following formulas (4) and (5) as a function of y).
x _ERR = h (l, x) (4)
y _ERR = i (l, y) (5)

The h (l, x) and i (l, y) are stored in the camera in advance as center axis deviation information, and the calculated (x _ERR , y _ERR ) is substituted into the expression (3) of the first embodiment. By doing so, the amount of light can be corrected. By the way, when writing h (l, x) and i (l, y) during the manufacturing process of the camera, the center axis deviations D _EP1 and D at two exit pupil distances EP ₁ and EP ₂ as shown in FIG. _EP2 is measured at multiple image heights. In this way, h (l, x) and i (l, y) can be easily determined. In the second embodiment, since the exit pupil changes according to the zoom position, f (x, y) and g (x _ERR , y _ERR ) in Expression (3) are also stored for each zoom position. Have taken.

  As described above, in the second embodiment, since the center axis deviation information is stored in the camera as information in a form corresponding to the pupil distance change of the photographing lens 100, even in a camera equipped with a photographing lens having a large pupil distance variation. Focus detection can be performed with high accuracy. In the above description, the pupil distance variation due to the zoom of the photographing lens has been described as an example. However, the second embodiment can be applied to a camera system in which a plurality of photographing lenses having different exit pupils can be mounted.

<Third Embodiment>
Next, a third embodiment of the present invention will be described.

  The third embodiment shows an example in which the focus detection unit of the first embodiment is applied to a camera system.

  FIG. 22 is a block diagram illustrating a configuration of a camera system according to the third embodiment. In addition, what attached | subjected the code | symbol similar to 1st Embodiment plays the same role, and abbreviate | omits description. In FIG. 22, reference numeral 220 denotes a camera body, and 221 denotes an interchangeable lens that can be attached to and detached from the camera body 220. The interchangeable lens 221 includes a CPU 224 that performs various arithmetic processes, and is connected to a drive circuit 225 that drives zoom, focus, aperture shutter, and the like of the photographing lens 100, and each actuator 226 is connected to the drive circuit 225. Further, a flash memory 227 capable of rewriting various information is provided in the same manner as the camera body 220.

  FIG. 23 is a block diagram in which portions related to the present invention are extracted from the block diagram of FIG. 22 and shows more detailed contents. In the figure, the right side of the center dotted line is the camera body 220, and the left side is the interchangeable lens 221 (lens unit). The difference from the first embodiment is that the flash memory 133 of the camera body 220 has only pixel sensitivity unevenness information 175 and center axis deviation information 177, and the flash memory 227 of the interchangeable lens 221 has exit pupil information 176. is there. Therefore, even when another type of lens is attached as the interchangeable lens 221, the exit pupil information 176 unique to the lens can be acquired via the IF units 222 and 223.

  Since the third embodiment is premised on a camera system in which a plurality of photographing lenses having different exit pupil diameters and distances can be attached to individual lenses, the center axis deviation information 177 is the same as that of the second embodiment. It is preferable to store in the format. In order to reduce the capacity of the flash memory 133, it is effective to use the center axis deviation information 177 at typical exit pupil distances of various interchangeable lenses. However, the method according to the second embodiment is more accurate. Needless to say. With the above-described configuration, the correction unit 170 performs the correction described in the first embodiment or the second embodiment, so that highly accurate focus detection can be realized even in the camera system.

<Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described.

  Compared to the first embodiment, the fourth embodiment shows an example in which the present invention is applied to a camera system having a secondary imaging type and a phase difference type focus detection unit.

  FIG. 24 is a block diagram illustrating a configuration of a camera system according to the fourth embodiment. In addition, what attached | subjected the code | symbol similar to 1st-3rd embodiment played the same role, and abbreviate | omits description. In the figure, the camera body 220 includes a secondary imaging type and phase difference type focus detection unit 240. Therefore, unlike the first embodiment, the image sensor 107 is an image sensor dedicated to imaging, which includes only the pixels of FIG. A main mirror 241 and a sub mirror 242 are disposed between the photographing lens 100 of the interchangeable lens 221 and the image sensor 107 to split and polarize the light beam that has passed through the photographing lens 100.

  First, the main mirror 241 is formed of a half mirror, and reflects part of the light beam that has passed through the photographing lens 100 upward and transmits the rest. The light beam reflected by the main mirror 241 is incident on a finder optical system 243 including a focusing screen, a condenser lens, a pentaprism, and an eyepiece lens group so that a subject image can be observed by a user. On the other hand, the light beam transmitted through the main mirror 241 is reflected downward by the sub-mirror 242 and enters the focus detection unit 240. The main mirror 241 and the sub mirror 242 are configured by a known quick return mechanism, and can be retracted out of the optical path during photographing.

  The focus detection unit 240 uses a secondary imaging type phase difference method and has a known configuration including a field lens, a pair of secondary imaging lenses, a pair of light receiving sensors, and the like, and detailed description thereof is omitted. To do.

FIG. 25 is a conceptual diagram illustrating the relationship between the focus detection unit 240 and the exit pupils of various interchangeable lenses, and is a diagram in which the main mirror 241 and the sub mirror 242 in FIG. 24 are omitted. In FIG. 25, EP _L1 indicates an exit pupil of an interchangeable lens, and EP _L2 indicates an exit pupil of another interchangeable lens different from this. L1 and L2 indicate the optical axes of these interchangeable lenses, and are represented by one line here because the two optical axes overlap. Reference numeral 250 denotes a primary imaging plane which is a focal plane of the interchangeable lens, and is at a position optically equivalent to the imaging plane of the imaging element 107 in FIG. The focus detection unit 240 is disposed behind the primary imaging plane 250, and 251 indicated by a one-dot chain line is the central axis of the focus detection unit 240.

Central axis 251 deviation occurs with respect to the optical axis L1, L2 due to a manufacturing error, than on the exit pupil _{EP L1} central axis shift _{D EPL1} next, it is on the exit pupil _{EP L2} has a central axis shift _{D EPL2.} That is, when a deviation occurs in the central axis 251 of the focus detection unit 240, it indicates that the deviation of the central axis varies depending on the exit pupil distance in a camera system in which a photographing lens having various exit pupils can be attached. Therefore, if such center axis deviation information is stored in the camera in a format corresponding to the exit pupil distance in advance, high-precision focus detection can be performed by the method described in the second embodiment.

  The center axis deviation in the fourth embodiment may occur due to a position error of the main mirror 241 and the sub mirror 242 or a manufacturing error due to a field lens inside the focus detection unit 240. In view of this, some mechanisms for adjusting the center axis deviation of the focus detection unit 240 and performing adjustment at the time of assembling and manufacturing have been disclosed. If this fourth embodiment is applied, this mechanism itself is Since it can be eliminated, there is an effect of cost reduction.

  100: photographing lens 107: imaging device 170: correction unit 176: exit pupil information 177: center axis deviation information

In order to achieve the above object, an imaging apparatus of the present invention is an imaging apparatus capable of detecting a focal position of a lens from a pair of image signals, and outputs a pair of image signals corresponding to a set area in a screen. an imaging element capable, prior to compensate for the difference in signal level caused by the imbalance of the amount of light incident to the image signal capable of outputting the image pickup device of said pair through the exit pupil of sharp lens, is the set comprising areas and correcting means for correcting the signal level of the image signal of the pair in accordance with the correction information associated with misalignment during manufacture of the image height and the image sensor, a.

The imaging system of the present invention includes the imaging device and a lens unit that can be attached to and detached from the imaging device, stores the correction information in the imaging device, and stores information on the exit pupil in the lens unit. Then, information regarding the exit pupil is transmitted from the lens unit to the imaging device.

Further, the control method of the present invention for an imaging apparatus capable of detecting the focal position of a lens from a pair of image signals includes an output step of outputting a pair of image signals corresponding to a set area in a screen from the imaging device, In the correction step of correcting so as to compensate for the difference in signal level caused by the unbalance of the amount of light incident on the imaging device capable of outputting the pair of image signals via the exit pupil of the lens, the image of the set region The signal level of the pair of image signals is corrected according to the height and correction information related to an alignment error at the time of manufacturing the imaging device.

Claims (7)

An image sensor including a plurality of focus detection pixel pairs that photoelectrically convert a pair of light fluxes that pass through different areas of the photographing lens and output image signal pairs, each of which is formed with a microlens corresponding to each pixel;
Storage means for storing center axis deviation information relating to manufacturing errors including alignment errors at the time of forming the microlens;
The ratio of the amount of light that changes according to the image height when there is no manufacturing error so as to compensate for the unbalance of the amount of light incident on each of the focus detection pixel pairs via the exit pupil of the photographing lens. A function that changes a function based on the center axis deviation information, and corrects the signal level of the image signal pair according to the changed function and the image height of the focus detection pixel pair;
An imaging apparatus comprising: a focus detection unit that performs focus detection of the photographing lens using the image signal pair corrected by the correction unit.   The correction means further corrects the center axis deviation information of the focus detection pixel pair at each position of the imaging element based on the exit pupil distance to the exit pupil of the photographing lens, and the corrected center The imaging apparatus according to claim 1, wherein a signal level of the image signal pair is corrected based on axis deviation information.   The imaging device according to claim 1, wherein the imaging device is an imaging device used for taking an image, and a part of pixels of the imaging device is configured as the focus detection pixel pair.   The imaging apparatus according to claim 1, wherein the imaging element is an imaging element for focus detection that is configured separately from an imaging element used for capturing an image.   The imaging apparatus according to claim 1, wherein the center axis deviation information is information set at least for each imaging apparatus. The imaging apparatus according to any one of claims 1 to 5,
A lens unit detachable from the imaging device;
An imaging system comprising: storing the central axis deviation information in the imaging apparatus; storing information on the exit pupil in the lens unit; and transmitting information on the exit pupil from the lens unit to the imaging apparatus. A focus detection method in an imaging apparatus,
An output unit that outputs a pair of image signals by photoelectrically converting a pair of light beams that pass through different regions of the photographing lens by a plurality of focus detection pixel pairs included in the image sensor; and
An acquisition step in which an acquisition unit acquires center axis deviation information related to a manufacturing error including an alignment error when forming a microlens formed corresponding to each pixel of the image sensor;
The amount of light that changes in accordance with the image height when there is no manufacturing error so that the correction means compensates for an unbalance of the amount of light incident on each of the focus detection pixel pairs via the exit pupil of the photographing lens. A correction step for correcting the signal level of the image signal pair according to the changed function and the image height of the focus detection pixel pair,
A focus detection method, comprising: a focus detection step of performing focus detection of the photographing lens using the image signal pair corrected in the correction step.

Images