JP2008299184A - Imaging apparatus and focus detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a blurred image in a photographic optical system upon a non-focusing. <P>SOLUTION: The imaging apparatus is equipped with: an imaging device 4 where a first pixel 41 receiving one luminous flux out of a pair of luminous fluxes passing through different pupil areas of the photographic optical system by a first light receiving part 41a through a microlens 41b, and a second pixel 42 receiving the other by a second light receiving part 42a through a microlens 42b are arranged, and which receives an image formed by the photographic optical system; and an arithmetic means which adds output from the first pixel 41 to output from the second pixel 42. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device and a focus detection device.

The imaging element in which the pixels comprising the microlens and the light receiving unit are two-dimensionally arranged receives light from the subject that has passed through the imaging optical system, generates an image using the pixel signal of the imaging element, and the imaging optical system. There is known an imaging apparatus that detects the focus adjustment state of the camera (see, for example, Patent Document 1).
In the apparatus described above, focus detection by the pupil division type phase difference detection method is enabled by alternately shifting the optical axis of the microlens and the center of the light receiving unit.

Prior art documents related to the invention of this application include the following.
Patent No. 2959142

  However, in the conventional imaging device described above, the optical axis of the microlens and the center of the light receiving unit are alternately shifted. Therefore, when an image is generated by the output signal of each pixel of the imaging device, the imaging optical system is not focused. There is a problem that the blurred image in the state becomes “mottled” and “grainy”, resulting in an unnatural image.

(1) According to the first aspect of the present invention, a first pixel that receives one light beam by a first light receiving unit via a micro lens among a pair of light beams that have passed through different pupil regions of the photographing optical system, and a micro lens are provided. A second pixel that receives the other light beam by the second light receiving unit, and an image pickup device that receives an image formed by the photographing optical system, an output of the first pixel, and an output of the second pixel Arithmetic means for adding.
(2) In the imaging apparatus according to claim 2, the outputs of the first pixel and the second pixel that are targeted for the respective deviations of the first light receiving unit and the second light receiving unit with respect to the optical axis of the microlens are added by the calculation unit. It is what I did.
(3) In the imaging device according to claim 3, the first light receiving unit and the second light receiving unit are located inside each other with respect to the optical axis of each microlens in the arrangement of the first pixel and the second pixel by the calculating unit. An image is synthesized based on the addition result obtained by adding the output of the set and the addition result obtained by adding the output of the set in which the first light receiving unit and the second light receiving unit are outside each other with respect to the optical axis of each microlens. It is what you do.
(4) The invention of claim 4 is a first pixel having a first light receiving portion for receiving one of a pair of light beams that have passed through different pupil regions of the photographing optical system, and the other light beam of the pair of light beams. And a second pixel having a second light-receiving unit that receives the light, and an image sensor that receives an image formed by the photographing optical system, and an output corresponding to the other light beam incident on the first pixel. Calculation means for obtaining the output of the first pixel based on the output obtained by the second light receiving unit in the pixel and the output corresponding to the other light beam and the output obtained by the first light receiving unit.
(5) The imaging apparatus according to claim 5 is configured to obtain an output corresponding to the other light flux based on an output obtained by the second light receiving unit in the second pixel located in the vicinity of the first pixel by the arithmetic unit. It is a thing.
(6) In the imaging device of the imaging device according to the sixth aspect, the first pixels and the second pixels are alternately arranged.
(7) In the imaging device according to claim 7, when the shapes of the first light receiving unit and the second light receiving unit overlap the first pixel and the second pixel, the outer periphery of the first light receiving unit and the second light receiving unit. Is determined to be substantially circular.
(8) In the image pickup device of the image pickup apparatus according to the eighth aspect, the first pixel and the second pixel are two-dimensionally arranged.
(9) The image pickup apparatus according to claim 9 adds the outputs of the first pixel and the second pixel arranged in the dividing direction of the pupil region of the photographing optical system by the calculating means.
(10) The imaging device of the imaging device according to claim 10 is arranged so that the first pixel and the second pixel do not have translational symmetry in a direction orthogonal to the dividing direction of the pupil region.
(11) A focus detection apparatus according to an eleventh aspect is the imaging apparatus according to any one of the first to tenth aspects, and imaging optical by pupil division type phase difference detection based on outputs of the first pixel and the second pixel. Focus detection means for detecting the focus adjustment state of the system.

  According to the present invention, it is possible to suppress a blurred image in the out-of-focus state of the photographic optical system from becoming a mottled and rough state and obtain a smooth blurred image.

  FIG. 1 shows a main part configuration of an imaging apparatus 1 according to an embodiment. Light from the subject that has passed through the photographic lens 2 passes through the condenser lens 3 and enters the image sensor 4. The image pickup device 4 is integrally formed with a microlens array 4m in which a plurality of microlenses are arranged in a two-dimensional manner and a light receiving portion array 4j in which a plurality of photoelectric conversion elements (hereinafter referred to as light receiving portions) are arranged in a two-dimensional manner. And one light receiving portion is arranged under one microlens to constitute one pixel. The condenser lens 3 makes incident light to each microlens parallel to the optical axis of the photographing lens 2.

  The imaging device 1 includes a control device 5, a drive device 6, a memory 7, and the like. The control device 5 includes a microcomputer (not shown), a memory, an A / D converter, an image sensor driving circuit, and the like, and includes a focus detection unit 5a and an image synthesis unit 5b configured by a microcomputer software form. .

  The focus detection unit 5 a detects the defocus amount indicating the focus adjustment state of the photographing lens 2 based on the output signal of the image sensor 4, converts it into a lens drive amount, and outputs it to the drive device 6. The driving device 6 includes a lens driving motor (not shown), drives a focusing lens (not shown) of the photographing lens 2 according to the lens driving amount, and performs focus adjustment. The image synthesizing unit 5 b synthesizes the output signals of the image sensor 4, performs various processes on the synthesized image, generates a subject image, and records it in the memory 7.

  FIG. 2 is a front view of the image sensor 4 as viewed from the condenser lens 3 side. In FIG. 2, a part of the upper left corner of the image sensor 4 is enlarged. In the imaging device 4, two types of pixels 41 and 42 that receive a pair of light beams respectively passing through different pupil regions of the photographing lens 2 are alternately two-dimensionally in the division direction of the pupil region (column direction in FIG. 2). It is arranged. The first pixel 41 includes a light receiving unit 41a that receives a light beam that has passed through one of the pair of pupil regions of the photographing lens 2, and a micro lens 41b. The second pixel 42 includes a light receiving unit 42a that receives a light beam that has passed through the other pupil region of the pair of pupil regions of the photographing lens 2, and a micro lens 42b. The microlenses 41b and 42b are the same, but the light receiving portions 41a and 42a are different from each other. A pair of pixels 41 and 42 is composed of a pixel 41 having one light receiving portion 41a of the pair of light receiving portions 41a and 42a and a pixel 42 having the other light receiving portion 42a.

  In the imaging device 4, a pair of pixels 41 and 42 in which the optical axis of the microlens and the center of the light receiving unit are alternately shifted are alternately arranged in the dividing direction (column direction in FIG. 2) of the pupil region of the photographing lens 2. ing. In this embodiment, when the pair of pixels 41 and 42 are further overlapped, the shape of the pair of light receiving parts 41a and 42a is determined so that the outer periphery of each of the light receiving parts 41a and 42a is circular. . In other words, the shape when the pair of light receiving portions 41a and 42a are overlapped is determined so that the cross-section of the combined received light beam of the pair of light receiving portions 41a and 42a is substantially circular.

  As described above, when the light receiving part shape is determined so that the outer periphery when the light receiving parts 41a and 42a of the pair of pixels 41 and 42 are overlapped is substantially circular, the photographing lens 2 is not in focus. The blurred image becomes a smooth circle and does not give the viewer a sense of incongruity. On the other hand, if the shape of the pair of light receiving parts is a quadrangle as shown in FIG. 3, the blurred image also becomes a quadrangle, giving the viewer a sense of discomfort. In FIG. 3, the outer peripheral shape when the light receiving portions 51a and 52a of the pair of pixels 51 and 52 are superposed is a quadrangle, and the blurred image when the photographing lens is not in focus is also a quadrangle.

  Next, a method for synthesizing the outputs of the respective light receiving units according to the embodiment will be described. FIG. 4 shows the connection between points 0 to 9 on the object-side surface O that are conjugate to the photographing lens 2 and corresponding points (0) to (9) on the image plane Q of these points 0 to 9. FIG. 4 is a diagram showing an image relationship and a point P at a defocus position through which of a pair of pupil regions A and B of the photographing lens 2 reaches an image plane Q. 5 to 9 are diagrams for explaining the state of blurring of the image of the point P on the image plane Q. FIGS. 5 and 7 correspond to the corresponding points (0) to (9) on the image plane Q. 6, FIG. 8, and FIG. 9 show signal output states of the pixels at corresponding points (0) to (9) on the image plane Q. FIG. 5 and 7 represent positions where light emitted from the point P is received. 6, 8, and 9, pixels that receive light and output signals are hatched.

  As shown in FIG. 5, when the shape of the light receiving portion 53a of each microlens 53 is circular and the size is uniform, the pixels of the corresponding points (0) to (6) are emitted from the positions of the points P, respectively. Can receive light. Therefore, as shown in FIG. 6, the pixels at the corresponding points (0) to (6) output signals corresponding to the received light intensity. On the other hand, in the pixels of the corresponding points (7) to (9), the light emitted from the point P is not received, so that no light reception signal is output. Therefore, a blurred image of the point P with the pixel of the corresponding point (6) and the pixel of (7) as a boundary is obtained.

  On the other hand, the pair of pixels 41 and 42 (see FIG. 2) of the embodiment has a corresponding point (see FIG. 7) because the pair of semicircular light receiving portions 41a and 42a alternately change positions. The pixels 42, 41, 42,..., 41 in (0) to (9) receive light emitted from the point P or not. In FIG. 7, the pixel 42 at the corresponding point (0) receives light from the point P at the light receiving portion 42a, but the pixel 41 at the corresponding point (1) does not receive light from the point P at the light receiving portion 41a. .

  As a result, as shown in FIG. 8, the pixels (0, 2, 3, 5) receiving the light from the point P output a signal corresponding to the received light intensity, but the pixels (1, 4, 6) that do not receive the light. In the range of (0) to (6) where there is no light reception signal output and a blurred image should be formed at the corresponding points (6) and (7) which are the boundaries of the original blurred image. In this case, a pixel having no light receiving output is generated. Therefore, an image formed from all the pixel outputs of the image sensor 4 is a mottled and rough blurred image, and an image having a poor impression.

  In this embodiment, in order to solve such a problem, the outputs of the light receiving portions 41a and 42a of the pair of pixels 41 and 42 are added and combined by the image combining portion 5b of the control device 5. In other words, the output of a pair of pixels whose deviation between the optical axis of the microlens and the center of the light receiving unit is an object, in other words, the output of a pair of pixels whose outer periphery is substantially circular when the light receiving units are overlapped is added and combined. To do. As a result, the combined pixel uses the light of the entire pupil of the photographic lens 2.

  Specifically, the pixel outputs of corresponding points (0) and (1), (1) and (2), (2) and (3),... Shown in FIG. If each output is one pixel, each combined pixel receives light transmitted through the pupil region A of the photographing lens 2 and light transmitted through the pupil region B, and the output state of each pixel after combining. Is as shown in FIG. Therefore, it is possible to prevent a pixel having no light reception signal from being lost, and an uneven blur image.

  Next, in this embodiment, the pixels 41 and 42 are arranged so that the arrangement of the pixels 41 and 42 does not have translational symmetry in a direction orthogonal to the above-described division direction of the pupil region. In the pixel arrangement example shown in FIG. 2, a pair of pixels 41 and 42 whose outer periphery is substantially circular when the light receiving portions 41 a and 42 a are overlapped are arranged in the pupil region division direction (column direction), and the pupil region In the direction orthogonal to the division direction (the row direction of the image sensor 4 shown in FIG. 2), the pixel array is made not to have translational symmetry. Specifically, adjacent pixels in the row direction of the first column and the second column in FIG. 2 do not have translational symmetry. Similarly, the second column and the third column in the row direction, the third column and the fourth column, and all the adjacent pixel columns hereinafter have no translational symmetry.

  By adopting such a pixel arrangement, it is possible to suppress the occurrence of a mottled and blurred image due to the occurrence of pixel pitch shading in the image when the above-described pixel synthesis of one embodiment is performed. For example, in the pixel output after pixel synthesis shown in FIG. 9, the pixels at the corresponding points (2) and (3) shown in FIG. 8 both receive light from the point P and output a signal. The output of the point (2 + 3) becomes a level obtained by adding the signals for two pixels, resulting in a dark image. On the other hand, the pixel at the corresponding point (1) shown in FIG. 8 does not receive light, and the pixel at the corresponding point (2) receives light. Therefore, the output of the corresponding point (1 + 2) after combining has a signal level of one pixel and is light. It becomes an image. In this way, the pixel image can be shaded in the synthesized image, but the pixel array is arranged so that the arrangement of the pair of pixels 41 and 42 does not have translational symmetry in the direction orthogonal to the division direction of the pupil region. Therefore, it is possible to suppress the formation of a grainy, blurred image in which the pixel pitch band-like shade does not appear on the screen and the pixel pitch shade is appropriately dispersed over the entire screen.

  In the above embodiment, the output of the light receiving unit of a pair of pixels is added to synthesize the image signal. However, the image signal is synthesized by obtaining the virtual output of the light receiving unit that does not exist in one pixel. Will be explained.

  As described above, the imaging element shown in FIG. 2 is different from the first pixel 41 having the light receiving portion 41 a that receives one of a pair of light beams that have passed through different pupil regions of the photographing lens 2, and the photographing lens 2. Second pixels 42 having second light receiving parts 42a that receive the other of the pair of light beams that have passed through the pupil region are alternately arranged two-dimensionally. The first light beam 41 should be incident on the first pixel 41 at a position in the first pixel corresponding to the light receiving portion 42a of the second pixel 42. Since there is no light receiving part, no output can be obtained. Similarly, the second pixel 42 cannot obtain the output of the light beam incident on the position corresponding to the light receiving portion 41 a of the first pixel 41.

  Therefore, the output of the “other light flux” that should be obtained when the “virtual light receiving portion” of the first pixel 41 exists is obtained by substituting the output of the light receiving portion 42 a of the second pixel 42. . This may be obtained by directly using the output of the light receiving unit 42a as the output of the virtual light receiving unit or by interpolating from the output of the light receiving unit 42a. Then, the sum of the output of the light receiving unit 41a of the first pixel and the output of the virtual light receiving unit is used as the output of the first pixel, and the output of the pixel is similarly applied to other pixels including the second pixel 42. Try to ask.

  In addition to the second pixel 42, a third pixel 43 that receives “the other beam” is present around the first pixel 41, as in the second pixel. Therefore, the output of the light receiving unit 42a of the second pixel 42 and the output of the light receiving unit 43a of the third pixel 43 are averaged to obtain the output of the “virtual light receiving unit” in the first pixel 41. Also good. In this case, if the output obtained from the same pixel as the second pixel located on the opposite side of the second pixel 42 with respect to the first pixel is averaged with the output of the light receiving unit 42a, the virtual image is better. The output of the light receiving unit can be obtained.

  Furthermore, when the distance between the first pixel 41 and the second pixel 42 is different from the distance between the first pixel 41 and the third pixel 43, a large weight is given to the output of the pixel having the shorter distance. In this case, the weighted averaging may be performed.

《Pixel array modification》
FIG. 10 shows a modification of the pixel array. In the figure, reference numeral 40 denotes a normal imaging pixel, which has a circular light receiving portion under the microlens. In the imaging element 4A, an imaging pixel 40 is disposed between a pair of pixels 41 and 42. By combining the outputs of the pair of pixels 41 and 42 in such a pixel array, a mottled and rough image can be obtained.

<< Other variations of pixel arrangement >>
FIG. 11 shows another modification of the pixel array. In this image sensor 4B, pixels 43, 44, 45, 46 having light receiving portions 43a, 44a, 45a, 46a in the shape of (1/4) circles are arranged under each microlens. In this imaging device 4B, four pixels 43, 44, 45, and 46 form one set, and by adding and combining these four sets of pixel outputs, a mottled and rough image is obtained. be able to.

  Next, a focus detection method according to an embodiment will be described. The focus detection unit 5a of the control device 5 detects the focus adjustment state of the photographing lens 2 by a pupil division type phase difference detection method in a preset focus detection area in the photographing screen of the photographing lens 2. For example, the fourth column of the image sensor 4 shown in FIG. 2 corresponds to the focus detection area, and when focus detection is performed in this focus detection area, one of the plurality of pixels 41 and 42 belonging to the fourth column is selected. A first signal sequence (first image) is generated by arranging only the output signals of the pixels 41, and a second signal sequence (second image) is generated by arranging only the output signals of the other pixel 42. An image shift amount is calculated by performing a focus detection calculation of a detection method, and converted into a defocus amount of the photographing lens 2.

  Note that the imaging element 4 shown in FIG. 2 is not limited to the fourth column as long as it is in the pupil division direction of the pair of pixels 41 and 42, and the focus detection of the photographic lens 2 can be performed using another pixel arrangement. . For the image sensor 4B shown in FIG. 11, a pair of pixels used for focus detection are arranged in a pair of pixels (43, 46) arranged in a 45 ° upward diagonal direction and in a 45 ° upward diagonal direction. The defocus amount of the photographing lens 2 in the 45 degree direction in the photographing screen can be detected based on the output of the pair of pixels (44, 45).

  The focus detection unit 5 a of the control device 5 converts the defocus amount into a lens drive amount of a focusing lens (not shown) and outputs the lens drive amount to the drive device 6. The driving device 6 drives a focusing lens (not shown) of the photographic lens 2 according to the lens driving amount to adjust the focus of the photographic lens 2.

  In the above-described embodiment and its modification, the image pickup element in which the pixels used for focus detection are two-dimensionally developed has been described as an example. However, the embodiment is used only for image pickup such as the pixel 40 in FIG. The present invention can also be applied to a case where an image sensor is used in which pixels are developed two-dimensionally and a part of the array is used for focus detection, and focus detection and imaging are performed.

The figure which shows the principal part structure of the imaging device of one Embodiment Front view of the image sensor as seen from the condenser lens side Diagram when the image sensor is configured with a rectangular light receiving part The imaging relationship between the points 0 to 9 on the object-side surface O that are conjugate to the photographic lens and the corresponding points (0) to (9) on the image plane Q of these points 0 to 9 and A diagram showing which point P at the focus position passes through the pupils A and B of the photographing lens and reaches the image plane Q The figure for demonstrating the blurring state of the image on the image surface Q of the point P The figure for demonstrating the blurring state of the image on the image surface Q of the point P The figure for demonstrating the blurring state of the image on the image surface Q of the point P The figure for demonstrating the blurring state of the image on the image surface Q of the point P The figure for demonstrating the blurring state of the image on the image surface Q of the point P The figure which shows the image pick-up element of a modification The figure which shows the image pick-up element of another modification

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Shooting lens 4, 4A, 4B Image pick-up element 5 Control apparatus 5a Focus detection part 5b Image composition part 41-46 Pixel 41a-46a Light-receiving part (photoelectric conversion element)
41b, 42b Microlens

Claims (11)

Of the pair of light beams that have passed through different pupil regions of the photographing optical system, a first pixel that receives one light beam by the first light receiving unit through the micro lens, and the other light beam by the second light receiving unit through the micro lens. And an image sensor that receives an image formed by the imaging optical system,
An imaging apparatus comprising: an arithmetic unit that adds the output of the first pixel and the output of the second pixel. The imaging apparatus according to claim 1,
The computing means adds the outputs of the first pixel and the second pixel that are targeted for the respective deviations of the first light receiving unit and the second light receiving unit with respect to the optical axis of the microlens. Imaging device. The imaging device according to claim 2,
The calculation means outputs a set of outputs in which the first light receiving unit and the second light receiving unit are inside each other with respect to the optical axis of each microlens in the arrangement of the first pixel and the second pixel. An image is synthesized based on the addition result obtained by addition and the addition result obtained by adding the output of the pair in which the first light receiving unit and the second light receiving unit are outside each other with respect to the optical axis of each microlens. An imaging apparatus characterized by the above. A first pixel having a first light-receiving unit that receives one of a pair of light beams that have passed through different pupil regions of the imaging optical system; and a second light-receiving unit that receives the other light beam of the pair of light beams. An image sensor in which a second pixel is arranged and receives an image formed by the imaging optical system;
An output corresponding to the other light beam incident on the first pixel is obtained based on an output obtained by the second light receiving unit in the second pixel, and an output corresponding to the other light beam and the first light receiving unit And an arithmetic unit that obtains the output of the first pixel based on the output obtained in step (1). The imaging apparatus according to claim 4,
The imaging device is characterized in that an output corresponding to the other light beam is obtained based on an output obtained by the second light receiving unit in the second pixel located in the vicinity of the first pixel. In the imaging device according to any one of claims 1 to 5,
The imaging device is characterized in that the first pixel and the second pixel are alternately arranged. In the imaging device according to any one of claims 1 to 6,
The shapes of the first light receiving part and the second light receiving part are such that, when the first pixel and the second pixel are overlapped, the outer circumferences of the first light receiving part and the second light receiving part are substantially circular. An imaging apparatus characterized by being determined as follows. In the imaging device according to any one of claims 1 to 7,
In the imaging device, the first pixel and the second pixel are two-dimensionally arranged. The imaging device according to claim 8,
The imaging device is characterized in that the calculation means adds the outputs of the first pixel and the second pixel arranged in the dividing direction of the pupil region of the photographing optical system. In the imaging device according to claim 8 or 9,
The imaging device, wherein the first pixel and the second pixel are arranged so as not to have translational symmetry in a direction orthogonal to a division direction of the pupil region. The imaging device according to any one of claims 1 to 10,
A focus detection device comprising: focus detection means for detecting a focus adjustment state of the photographing optical system by pupil division type phase difference detection based on outputs of the first pixel and the second pixel.

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