JP6248417B2 - Image sensor and camera - Google Patents

Description

  The present invention relates to an image sensor and a camera.

  2. Description of the Related Art Conventionally, an imaging element that obtains digital image data of a subject by arranging a large number of imaging pixels two-dimensionally is known (for example, Patent Document 1).

JP 2009-267912 A

  The prior art has a problem that if the imaging pixel is made small in order to increase the resolving power, the light receiving area for each imaging pixel is reduced and the sensitivity is deteriorated.

Imaging device according to claim 1, each having a light receiving surface of the rectangular first layer having sensitivity to at least the blue color light, a second layer which is sensitive to at least the green light, the sensitivity to at least the red color light A plurality of imaging pixels having a third layer, and an imaging region in which a long side direction is the first direction. The imaging pixels include odd-numbered columns and even-numbered columns. The eyes are arranged so that the positions of the centers of gravity in the first direction are different from each other, and the ratio of the long side length to the short side length of the light receiving surface is greater than 1 and less than 2.
The camera of Claim 4 is provided with the image pick-up element as described in any one of Claims 1-3.

  According to the present invention, both improvement in sensitivity and improvement in resolution can be achieved.

It is sectional drawing which shows typically the structure of the imaging device which concerns on the 1st Embodiment of this invention. 2 is a cross-sectional view illustrating a configuration of an image sensor 3. FIG. 3 is a top view showing a pixel array of the image sensor 3. FIG. It is a top view which shows typically the image pick-up surface of a single plate type image pick-up element which has a color filter of a Bayer arrangement. It is a top view which shows typically the imaging surface of the image pick-up element of the structure which laminated | stacked the photodiode of 3 layers. It is the top view which showed typically the imaging surface of the image pick-up element 3 of this embodiment. It is a figure which shows the frequency resolution area of the image pick-up elements 3 and 5.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing the configuration of the imaging apparatus according to the first embodiment of the present invention. The imaging device 1 is a so-called single-lens reflex digital camera, and the subject image formed by the imaging optical system 2 is imaged by the imaging element 3 to create digital image data.

  The image sensor 3 is a CMOS image sensor. The image pickup surface of the image pickup device 3 is rectangular, and the long side direction substantially coincides with the horizontal direction (lateral direction). The aspect ratio of the imaging surface of the imaging device 3 is about 2 to 3. The control device 4 performs various image processing on the imaging signal output from the imaging device 3 to create digital image data.

  FIG. 2 is a cross-sectional view showing the configuration of the image sensor 3. The image sensor 3 has a configuration in which three layers of photodiodes are stacked. The first layer 31 located at the shallowest position on the imaging surface includes light in a wavelength region corresponding to blue (blue light), light in a wavelength region corresponding to green (green light), and light in a wavelength region corresponding to red. (Red light) is photoelectrically converted. Next, the second layer 32 at the shallowest position photoelectrically converts light in a wavelength range corresponding to green (green light) and light in a wavelength range corresponding to red (red light). The third layer 33 located at the deepest position photoelectrically converts only light in a wavelength region corresponding to red (red light). Since light having a longer wavelength enters the silicon substrate more deeply, the amount of light of each color can be individually detected by stacking photodiodes as described above.

  For example, the amount of green light can be detected by subtracting the amount of light detected by the third layer 33 from the amount of light detected by the second layer 32. Similarly, the amount of blue light can be detected by subtracting the amount of light detected by the second layer 32 from the amount of light detected by the first layer 31.

  FIG. 3 is a top view showing a pixel array of the image sensor 3. In FIG. 3, only a part of the imaging pixels arranged in the imaging region (imaging surface) is shown in an enlarged manner, and actually a larger number (for example, several million or more) of imaging pixels than shown in FIG. 3. Are arranged in the imaging region.

  Each of the plurality of imaging pixels 30 arranged on the imaging surface has a rectangular light receiving surface. The long side direction of the imaging pixel 30 is substantially the same as the long side direction of the imaging screen (that is, the long side direction of the imaging region of the imaging device 3). The long side of the light receiving surface of the imaging pixel 30 has a length of about √2 times the short side. The plurality of imaging pixels 30 have different positions of the center of gravity in the horizontal direction of the imaging pixels 30 in the odd-numbered rows 34 and the even-numbered rows 35. Specifically, the barycentric positions of the imaging pixels 30 arranged in the even-numbered columns 35 are shifted in the horizontal direction by 0.5 L from the barycentric positions of the imaging pixels 30 arranged in the odd-numbered columns 34. In other words, the imaging pixels 30 are arranged in a staggered manner.

  The imaging device 3 configured as described above has a higher resolution than a conventional imaging device. Hereinafter, this point will be described by comparing a conventional imaging element in which imaging pixels having a square light-receiving surface on the imaging surface are squarely arranged with the imaging element 3 of the present embodiment. In the following description, as a conventional image sensor, a single-plate image sensor having a Bayer color filter and an image sensor having a structure in which three layers of photodiodes are stacked in the same manner as the image sensor 3 of the present embodiment. I will give you. As for the size of the image pickup pixel, the length in the vertical direction of the image pickup pixel 30 included in the image pickup element 3 of the present embodiment is L, and the conventional image pickup element has an image pickup pixel whose length is L on each side. Will be described. That is, the image pickup pixel 30 included in the image pickup device 3 of the present embodiment will be described as having a shape obtained by extending the image pickup pixel included in the conventional image pickup device in the horizontal direction.

  FIG. 4 is a plan view schematically showing an imaging surface of a single-plate type imaging device having a Bayer array color filter. A plurality of red pixels 50R having a red color filter, green pixels 50G having a green color filter, and blue pixels 50B having a blue color filter are arranged on the imaging surface of the imaging element 5 illustrated in FIG. ing.

  As is well known, in the Bayer array, the number of green pixels 50G is larger than the number of red pixels 50R and the number of blue pixels 50B. Therefore, it is necessary to consider the resolution of the image pickup device 5 that employs the Bayer arrangement separately for green light, red light, and blue light.

  First, consider the resolution for green light. As shown in FIG. 4A, the green pixels 50G are arranged at intervals of L in the horizontal direction. Similarly in the vertical direction, the arrangement interval of the green pixels 50G is L. When viewed in a 45-degree direction, the green pixels 50G are arranged at an interval of (√2) × L (about 1.4 L). That is, the green pixel 50G can resolve a black and white straight line extending in the vertical direction and the horizontal direction if the distance between the white straight line and the black straight line is L or more. Also, a black and white straight line extending obliquely at 45 degrees can be resolved if the distance between the white straight line and the black straight line is about 1.4 L or more.

  Next, the resolution for red light will be examined. Since the red pixels 50R are arranged more sparsely than the green pixels 50G, the resolution for red light is lower than that for green light. As shown in FIG. 4B, the red pixels 50R are arranged at 2L intervals in the horizontal and vertical directions. Further, when viewed in a 45-degree direction, the red pixels 50R are arranged at an interval of (√2) × L (about 1.4L). In other words, the resolution of the image sensor 5 with respect to red light is half that of green light in the vertical and horizontal directions, and is equivalent to that of green light in the oblique 45-degree direction.

  Since the resolution for blue light is the same as that for red light, description thereof is omitted.

  FIG. 5 is a plan view schematically showing an imaging surface of an imaging device having a configuration in which three layers of photodiodes are stacked. A plurality of imaging pixels 60 having sensitivity to red light, green light, and blue light are arranged on the imaging surface of the imaging device 6 shown in FIG. If the size of each imaging pixel 60 is the same as that of the imaging device 5 shown in FIG. 4, the number of pixels of the image created from the imaging output of the imaging device 6 is the imaging device 5 shown in FIG. 4. More than

  The imaging pixels 60 are arranged at intervals of L in the horizontal direction and the vertical direction, and at intervals of (√2) / 2 × L (about 0.7 L) in a 45-degree direction. That is, the vertical and horizontal resolutions of the image sensor 6 are equivalent to the resolution of the image sensor 5 that employs the Bayer arrangement for green light, and higher than the resolution of the image sensor 5 for red light and blue light. Further, the resolution in the oblique 45-degree direction is higher than the resolution of the image sensor 5 that employs the Bayer arrangement for any color light.

  FIG. 6 is a plan view schematically showing the imaging surface of the imaging device 3 of the present embodiment. The light receiving surfaces of the plurality of imaging pixels 30 are rectangles each having a short side in the vertical direction and a long side in the horizontal direction, the length in the vertical direction is L, and the length in the horizontal direction is about (√2) × L. .

  The imaging pixels 30 are arranged at intervals of (√2) / 2 × L (about 0.7 L) in the horizontal direction. Further, they are arranged at intervals of L in the vertical direction and at intervals of ((√2) −1) / 2 × L (about 0.2 L) in the 45-degree direction. That is, the image sensor 3 can resolve a black and white straight line extending in the vertical direction if the distance between the white straight line and the black straight line is about 0.7 L or more. Also, if the black and white straight line extending in the horizontal direction has an interval of L or more between the white straight line and the black straight line, the black and white straight line extending diagonally at 45 degrees is about 0.2 L between the white straight line and the black straight line. If it is above, it can each be resolved.

  FIG. 7 is a diagram illustrating a frequency resolution region possessed by sampling signals of the image sensor 3 of the present embodiment and the conventional image sensor 5. The horizontal axis in FIG. 7 represents the frequency band in which the image sensor 3 and the image sensor 5 can be resolved in the horizontal direction, and the vertical axis in FIG. 7 represents the frequency band in which the image sensor 3 and the image sensor 5 can be resolved in the vertical direction. Each is shown. As shown in FIG. 7, the Nyquist frequency 71 of the conventional image sensor 5 is symmetrical in the horizontal and vertical directions, whereas the Nyquist frequency 72 of the image sensor 3 of the present embodiment The shape is extended horizontally. That is, the imaging device 3 of the present embodiment has higher resolution in the horizontal direction and the oblique direction than the conventional imaging device 5.

According to the image sensor according to the first embodiment described above, the following operational effects can be obtained.
(1) The imaging device 3 includes an imaging region in which a plurality of imaging pixels 30 each having a rectangular light receiving surface are two-dimensionally arranged so that the long side direction substantially coincides with the horizontal direction. The plurality of imaging pixels 30 are arranged so that the positions of the center of gravity in the horizontal direction are different between the odd-numbered columns and the even-numbered columns, and the ratio of the long side length to the short side length of the light receiving surface is greater than 1 and from 2 Small √2. Since it did in this way, the improvement of a sensitivity and the improvement of resolving power can be made compatible. The improvement in sensitivity is due to the fact that the light receiving surface for each imaging pixel is larger than the conventional imaging elements 5 and 6 shown in FIGS. Further, the improvement of the resolving power is due to the presence of the imaging pixels 30 at a finer pitch than in the past in the lateral direction and the oblique 45 degree direction, as shown in FIG.

(2) The imaging region of the imaging element 3 is rectangular, and the long side direction of the plurality of imaging pixels 30 substantially matches the long side direction of the imaging region. Since it did in this way, resolving power improves about the long side direction of an image pick-up field. In the present embodiment, the long side direction of the imaging region is the horizontal direction. Since two human eyes are arranged in the horizontal direction, it is more desirable that the resolution is higher in the horizontal direction when shooting or when viewing a shot image.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
An image sensor to which the present invention is applied may be an image sensor other than a CMOS image sensor. For example, an image sensor using an organic photoelectric conversion film may be used like the image sensor described in Patent Document 1. In addition, the image sensor may not be a single plate type. For example, the present invention can also be applied to a so-called three-plate type imaging device in which subject light is split into red light, green light, and blue light by a prism or the like and light of each color is received by a light receiving element corresponding to the light. .

(Modification 2)
The ratio of the short side to the long side of the imaging pixel 30 may not be 1: √2. More specifically, the length of the long side may be a length that is greater than 1 and less than 2 with respect to the short side. This ratio may be different from the ratio of the short side to the long side of the imaging region of the image sensor 3.

(Modification 3)
In the embodiment described above, the imaging pixel 30 has a light receiving surface that is long in the horizontal direction (lateral direction), but this may be elongated in the vertical direction (longitudinal direction). The imaging area of the imaging device 3 may be a rectangle that is long in the vertical direction (longitudinal direction) or may be a square. When the imaging region of the imaging device 3 is rectangular, the long side direction does not have to coincide with the long side direction of the imaging pixel 30.

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Imaging optical system 3, 5, 6 ... Imaging device, 4 ... Control apparatus, 30, 60 ... Imaging pixel, 50R ... Red pixel, 50G ... Green pixel, 50B ... Blue pixel

Claims (4)

Each having a light receiving surface of the rectangular first layer having sensitivity to at least the blue color light, a second layer which is sensitive to at least the green light, the plurality having a third layer which is sensitive to at least red color light The imaging pixel is provided with an imaging region arranged in a two-dimensional manner so that the long side direction is the first direction,
The plurality of imaging pixels are arranged so that the positions of the centers of gravity in the first direction are different between the odd-numbered columns and the even-numbered columns, and the ratio of the long side length to the short side length of the light receiving surface is greater than 1. Image sensor smaller than 2. The imaging device according to claim 1,
The first layer photoelectrically converts red light, green light, and blue light, the second layer photoelectrically converts red light and green light that has passed through the first layer, and the third layer An image sensor that photoelectrically converts red light that has passed through the second layer. The imaging device according to claim 1 or 2,
The image pickup area is an image pickup device having a rectangular shape whose long side direction is the first direction.   A camera provided with the image pick-up element as described in any one of Claims 1-3.

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