JP6084744B2 - Image pickup apparatus and manufacturing method thereof - Google Patents

Description

  This technique relates to an imaging device and a method for manufacturing the same.

  Conventionally, a solid-state imaging device provided with three imaging elements for red, green, and blue is known. In such an imaging apparatus, as in Patent Document 1, the imaging light is separated into imaging light of the three primary colors by the color separation prism of the imaging optical system. In addition, an imaging signal is generated and output for each color by causing each color of imaging light to enter a corresponding color imaging device and photoelectrically convert it.

JP 2008-103846 A

  By the way, in the imaging apparatus, the resolution of the imaging element is being increased so as to provide a high-definition and high-quality captured image. In addition, the imaging device size is configured to be equal to the conventional size in order to be able to use a number of lenses already provided. For this reason, the individual pixel size of the image sensor becomes smaller than that of the conventional one, and a decrease in contrast due to registration deviation becomes remarkable, making it difficult to acquire a high-quality captured image. In addition, when an imaging apparatus is manufactured so that there is no registration deviation, productivity is lowered and manufacturing cost is increased.

  Therefore, an object of this technology is to provide an imaging apparatus that can acquire a high-definition and high-quality captured image easily and inexpensively.

The first aspect of this technology is
It is assumed that there is no registration error when fixing an image sensor having 3840 or more horizontal pixels to the light separation unit that separates incident light into a plurality of wavelength regions, and the wavelength is set by the image sensor provided for each wavelength region. When the contrast of the test image indicated by the image signal generated by performing the photoelectric conversion using the light of the region is 100%, the contrast of the test image is reduced by using a lens having no aberration and a predetermined aperture value. determining a registration error amount to be 40% and the predetermined threshold value,
When fixing the image sensor provided for each wavelength region to the light separating unit, the center of the image sensor is generated due to a deviation amount in the horizontal direction and the vertical direction in the other image sensor and an error in the rotation direction with respect to the image sensor. The image pickup apparatus manufacturing method includes fixing the amount of deviation between the horizontal direction and the vertical direction of the pixel farthest from the pixel to a predetermined threshold value or less .

  According to this technique, incident light is separated into a plurality of wavelength regions by the light separation unit. In addition, for each wavelength region separated by the light separation unit, an image sensor that performs photoelectric conversion using light of the separated wavelength region to generate an image signal is provided. The size of the image sensor is 2.5 μm × 2.5 μm or less, and the registration error of the image sensor provided for each wavelength region is limited to a threshold value or less based on the pixel size. By limiting the registration error in this way, an imaging apparatus capable of acquiring a high-definition and high-quality captured image can be provided easily and inexpensively. Note that the effects described in the present specification are merely examples and are not limited, and may have additional effects.

It is the figure which illustrated the composition of the imaging device. It is the figure which showed the positional relationship of a color separation prism and an image pick-up element. It is the figure which illustrated the composition of the adhering device. It is a figure for demonstrating the relationship between contrast and a registration error. It is the figure which showed the relationship between the registration error in 4K resolution, and contrast. It is the figure which showed the relationship between the pixel size at the time of using an ideal lens and contrast for every aperture value. It is the figure which showed the relationship between the registration error of 4K resolution at the time of using an ideal lens, and contrast for every aperture value. It is the figure which showed typically the case where the positional deviation in a rotation direction produced the image pick-up element for red with respect to the image pick-up element for green.

Hereinafter, embodiments for carrying out the present technology will be described. The description will be given in the following order.
1. Configuration of imaging apparatus Configuration and operation of image sensor fixing device

<1. Configuration of Imaging Device>
Hereinafter, embodiments of this technique will be described. In the embodiment, a case where incident light is separated into, for example, red, green, and blue components, and an imaging signal corresponding to each color component is generated by an imaging device provided for each color is illustrated.

  FIG. 1 illustrates the configuration of the imaging apparatus. The imaging apparatus 10 includes a light separation unit that separates incident light into a plurality of wavelength regions, for example, a color separation prism 20 that separates subject light incident through a lens into red, green, and blue components. In the imaging device 10, an imaging element is provided for each wavelength region separated by the light separation unit. The imaging element performs photoelectric conversion using the light in the separated wavelength region and generates an imaging signal. For example, in the imaging device 10, imaging elements 31R, 31G, and 31B are provided.

  The image sensors 31R, 31G, and 31B are CMOS (Complementary Metal Oxide Semiconductor) image sensors, CCD (Charge Coupled Device) image sensors, and the like. The image pickup device 31R is fixed to the red light emission surface of the color separation prism 20 via a fixed glass plate (fixed plate) 42R while being sandwiched between the fixed glass (fixed member) 41R. Similarly, the image pickup element 31G (31B) is sandwiched by the fixed glass (fixed member) 41G (41B) and green light (in the color separation prism 20 through the fixed glass plate (fixed plate) 42G (42B)) ( (Blue light) is fixed to the emission surface. The image sensor 31R is mounted on the substrate 32R, and the image sensor 31G (31B) is mounted on the substrate 32G (32B).

  The image sensor 31R performs photoelectric conversion using the light in the red wavelength region separated by the color separation prism 20, and generates an image signal. Similarly, the image sensor 31G performs photoelectric conversion using the light in the green wavelength region separated by the color separation prism 20, and generates an image signal. The image sensor 31B performs photoelectric conversion using the light in the blue wavelength region separated by the color separation prism 20, and generates an image signal.

  FIG. 2 shows the positional relationship between the color separation prism and the image sensor. In FIG. 2, the fixing glass, the fixing glass plate, and the substrate are omitted for easy understanding.

  The subject light incident on the incident light surface 21 of the color separation prism 20 is separated into green components by the block 22G of the color separation prism 20, and the green component light is imaged on the light receiving surface of the image sensor 31G. Next, the blue component of the light that has passed through the block 22G of the color separation prism 20 is separated by the block 22B of the color separation prism 20, and the blue component light is imaged on the light receiving surface of the image sensor 31B. The light that has passed through the blocks 22G and 22B of the color separation prism 20, that is, the red component light, is imaged on the light receiving surface of the image sensor 31R through the block 22R.

  In the imaging apparatus 10 configured as described above, after positioning the imaging elements 31R, 31G, and 31B with respect to the color separation prism 20, the imaging elements 31R, 31G, and 31B are used as the color separation prism 20 by using an adhesive. Stick. As the adhesive, for example, an ultraviolet curable adhesive that cures in a short time with a small shrinkage of curing is used in order to increase the fixing accuracy between the members.

<2. Structure and operation of fixing device>
Figure 3 illustrates the configuration of a fixing device for fixing the imaging element in the color separation prism. The fixing device 50 includes a light source 51, position adjustment jigs 52R, 52G, and 52B for each color, element driving units 53R, 53G, and 53B, and amplifiers 54R, 54G, and 54B. The fixing device 50 includes a memory unit 55, a timing generator 56, a signal processing unit 57, a display unit 58, and a measurement unit 59.

  The light source unit 51 makes subject light such as a test image used when fixing the image pickup devices 31R, 31G, and 31B enter the color separation prism 20.

  The red position adjustment jig 52 </ b> R is a mechanism for adjusting the position of the red image sensor 31 </ b> R with respect to the color separation prism 20. The green position adjustment jig 52G is a mechanism for adjusting the position of the green image pickup element 31G with the color separation prism 20, and the blue position adjustment jig 52B is provided on the color separation prism 20. On the other hand, this is a mechanism for adjusting the position of the blue image sensor 31B.

  The red element driving unit 53R drives the red image pickup element 31R to generate a red component image pickup signal based on the red component light separated from the subject light incident on the color separation prism 20. The green element driving unit 53G drives the green imaging element 31G to generate a green component imaging signal based on the green component light separated from the subject light incident on the color separation prism 20. The blue element driving unit 53B drives the blue imaging element 31B to generate a blue component imaging signal based on the blue component light separated from the subject light incident on the color separation prism 20.

  The red amplifier 54R amplifies the red component imaging signal generated by the imaging element 31R with a predetermined gain and outputs the amplified signal to the memory unit 55. The green amplifier 54G amplifies the green component imaging signal generated by the imaging element 31G with a predetermined gain and outputs the amplified signal to the memory unit 55. Further, the blue amplifier 54B amplifies the blue component imaging signal generated by the imaging element 31B with a predetermined gain and outputs the amplified signal to the memory unit 55.

  The memory unit 55 stores the imaging signals supplied from the imaging elements 31R, 31G, and 31B, reads the stored imaging signals at a predetermined speed, and outputs the readout signals to the signal processing unit 57.

  The timing generator 56 generates timing signals and supplies them to the element driving units 53R, 53G, and 53B and the memory unit 55, thereby generating imaging signals in the imaging elements 31R, 31G, and 31B and storing the imaging signals in the memory unit 55. Can be synchronized. The timing generator 56 supplies the timing signal to the memory unit 55 so that the stored imaging signal can be read out at a predetermined speed and output to the signal processing unit 57.

  The signal processing unit 57 converts the imaging signal read from the memory unit 55 into an image signal corresponding to the display unit 58 and the measurement unit 59, and outputs the converted image signal to the display unit 58 and the measurement unit 59. Further, the signal processing unit 57 may supply, for example, a RAW signal of each image sensor to the measurement unit 59 so that the measurement error can be accurately detected by the measurement unit 59.

  The display unit 58 displays a test image or the like based on the image signal supplied from the signal processing unit 57. The measurement unit 59 measures registration errors of the image sensors 31R, 31G, and 31B based on the image signal supplied from the signal processing unit 57.

Next, the relationship between the contrast of the luminance signal and the registration error will be described. The luminance signal is based on ITU-R recommendation BT2020-1 that defines an ultra-high-definition video format such as 4K resolution, for example, and the luminance signal Y includes a red component imaging signal R and a green component imaging signal as shown in Equation (1). It is calculated from G and the blue component imaging signal B. The contrast Dct is calculated based on the equation (2).
Y = 0.2627R + 0.6780G + 0.0593B (1)
Dct = (Ymax−Ymin) / (Ymax + Ymin) (2)

  FIG. 4 is a diagram for explaining the relationship between contrast and registration error. FIG. 4 illustrates a case where a registration error occurs in the horizontal direction.

  FIG. 4A illustrates a test image incident on the color separation prism 20. The test image is a monochrome binary image in which white areas (for one pixel or a plurality of pixels) and black areas (for one pixel or a plurality of pixels) are alternately provided in the horizontal direction.

  FIG. 4B illustrates a state in which the horizontal positions of the pixels of each color also match. 4B and 4E, the pixels of the respective colors whose vertical positions are aligned are arranged in the vertical direction so that the positional relationship in the horizontal direction of the pixels of each color can be easily grasped. It is shown.

  FIG. 4C shows an image based on the luminance signal in a state where the positions of the pixels of each color match. In a state where the positions of the pixels of each color match, the test image is a binary image that is black and white. Therefore, the image based on the luminance signal is equal to the test image. FIG. 4D shows the relationship between the pixel position and the luminance signal at this time, and the image contrast Dct is high.

  FIG. 4E illustrates a case where a registration error occurs in the horizontal direction between the red and blue pixels with respect to the green pixel. In this case, since the red and blue pixels are misaligned with respect to the green pixels, as shown in FIG. 4F, the white pixels of the test image are not white but become chromatic and black pixels. Is not black and is chromatic. Therefore, the image based on the luminance signal is different from the test image, and the relationship between the pixel position and the luminance signal is (G) in FIG. That is, the contrast Dct is lower than that in the case where the positions of the pixels of the respective colors match.

  In the imaging apparatus 10, the resolution of the imaging elements 31R, 31G, and 31B is set to 4K so that a high-definition captured image can be provided. Further, in order to make it possible to use a large number of lenses that have already been provided, the sizes of the image pickup devices 31R, 31G, and 31B are set to 2/3 inch size, which is equal to the size of the conventional image pickup device. In such an image sensor, when the resolution is 4K (3840 pixels × 2160 pixels), the pixel size is “2.5 μm × 2.5 μm”. The 4K resolution includes the case of “4096 pixels × 2160 pixels”, and the pixel size at this time is smaller than “2.5 μm × 2.5 μm”.

  FIG. 5 shows the relationship between registration error and contrast at 4K resolution. FIG. 5 shows a case where the positional deviation of the red and blue pixels with respect to the green pixel is the same amount in the same direction and the pixel size is “2.5 μm × 2.5 μm”. The contrast when the registration error is “0” is 100%. Here, if the lower limit of the contrast reduction is approximately 90%, the registration error is in the range of “± 0.5 μm”.

  Further, when an ideal lens having no aberration is used, the contrast changes as shown in FIG. 6 according to the pixel size and the aperture value. FIG. 6 shows the relationship between the pixel size and contrast for each aperture value when using an ideal lens and e-line (546 nm). In FIG. 6, the contrast when the registration error is “0” with no ideal lens is 100%. Here, in the case of an aperture value “f / 4.0” that is often used when capturing moving images, when the pixel size is “5 μm × 5 μm”, the contrast is 70% or more, and the pixel size is “2. When it is “5 μm × 2.5 μm”, it is 50% or less.

  FIG. 7 shows the relationship between 4K resolution registration error and contrast for each aperture value when an ideal lens is used. In the imaging apparatus, the registration error is limited so that the contrast is equal to or higher than a desired level at an aperture value that is frequently used when capturing a moving image. Here, since the aperture value is often set to “f / 4.0”, for example, when the aperture value is “f / 4.0”, the contrast is 40% or more, which is a desired level. Set the error range of the registration error in. That is, the imaging apparatus limits the registration error within an error range of ± 0.5 μm. Here, when the 4K resolution is “3840 pixels × 2160 pixels”, the error range of ± 0.5 μm corresponds to a range of 20% or less of the pixel size in the image sensor. Therefore, the imaging apparatus limits the registration error within an error range of ± 0.5 μm, for example, within a range of 20% or less of the pixel size. Note that the desired level of contrast when the ideal lens is taken into consideration corresponds to an acceptable level even when the contrast is lowered due to a registration error in actual imaging.

  Also, the registration error may occur not only in the horizontal direction or the vertical direction but also in the rotation direction with the optical axis direction as the rotation axis. Therefore, even if a shift in the rotation direction occurs, the rotation is limited so that the registration error is within an error range of ± 0.5 μm, for example, a range of 20% or less of the pixel size.

  FIG. 8 schematically shows a case where the red image pickup device is displaced in the rotation direction with respect to the green image pickup device.

  As shown in FIG. 8A, when the image sensor rotates in the direction of the arrow FR about the center position CP, the movement amount of the outermost pixel Pa that is farthest from the center becomes the largest. Therefore, as shown in FIG. 8B, the positional deviation in the rotation direction is, for example, 20% or less of the pixel size where the movement amounts dH and dV of the outermost pixel Pa are both within an error range of ± 0.5 μm. Limit within the range.

  Here, when the size of the image sensor is 2/3 inch and the diagonal length is 11 mm, the outermost pixel Pa is 5.5 mm away from the center. Further, when the size of the image sensor is 2/3 inch and 4K resolution (3840 pixels × 2160 pixels), the registration error is limited within an error range of ± 0.5 μm. Therefore, the deviation in the rotation direction is limited to within the rotation angle θ at which the movement amounts dH and dV are both 0.5 μm. Here, the rotation angle θ at which the movement amount dH is 0.5 μm is θ = 0.011 degrees. The rotation angle θ at which the moving amount dV is 0.5 μm is θ = 0.006 degrees. Therefore, when there is no error in the center position of the image sensor, the positional deviation in the rotation direction is within “± 0.006 degrees”.

  The fixing device 50 is limited to a range of, for example, 20% or less of the pixel size, which is within an error range of a registration error of ± 0.5 μm of the image sensor provided for each wavelength region.

  The fixing device 50 fixes, for example, the green image sensor 31G to the color separation prism 20. Thereafter, the fixing device 50 adjusts the positions of the red image pickup element 31R and the blue image pickup element 31B with reference to the green image pickup element 31G. Specifically, the registration error of the red image sensor 31R (blue image sensor 31B) with respect to the green image sensor 31G is within an error range of ± 0.5 μm, for example, a range of 20% or less of the pixel size. The position of the red image sensor 31R (blue image sensor 31B) is adjusted so as to be within. The fixing device 50 fixes the image sensor 31 </ b> R and the image sensor 31 </ b> B whose positions have been adjusted to the color separation prism 20.

  Therefore, according to this technique, when a 2 / 3-inch image pickup device that has 4K resolution and can use a lens that has already been provided is used, the registration error is within an error range of ± 0.5 μm. It is limited to a range of 20% or less of the pixel size. Therefore, each image sensor is fixed to the color separation prism so that the adverse effect due to the registration error is within an allowable range, and thus it is easier and less expensive than the case where the image pickup apparatus is manufactured so that there is no registration error. An imaging device can be provided.

  In addition, as a method for compensating for registration errors, a method for electrically compensating an image pickup signal generated by an image pickup device has been proposed. However, this method requires a signal processing circuit for performing compensation, and may not be compensated depending on the direction of deviation. However, with this technique, the image sensor is fixed to the color separation prism so that the registration error is within an error range of ± 0.5 μm, for example, within 20% of the pixel size. Regardless, the adverse effects caused by registration errors can be suppressed to an allowable range. Therefore, the imaging device 10 can generate a high-definition and high-quality captured image. When the 4K resolution is “4096 pixels × 2160 pixels”, the pixel size is smaller than “3840 pixels × 2160 pixels”. Therefore, if the registration error is limited to an error range of ± 0.5 μm, for example, 20% or less of the pixel size, even if the resolution is “4096 pixels × 2160 pixels”, the adverse effect due to the registration error is allowed. Can be suppressed.

  In addition, the effect described in this specification is an illustration to the last, and is not limited, There may be an additional effect which is not described. Further, the present technology should not be construed as being limited to the embodiments of the technology described above. The embodiments of this technology disclose the present technology in the form of examples, and it is obvious that those skilled in the art can make modifications and substitutions of the embodiments without departing from the gist of the present technology. In other words, in order to determine the gist of the present technology, the claims should be taken into consideration.

  In the imaging device and the manufacturing method thereof according to this technique, incident light is separated into a plurality of wavelength regions by the light separation unit. In addition, for each wavelength region separated by the light separation unit, an image sensor that performs photoelectric conversion using light of the separated wavelength region to generate an image signal is provided. The size of the image sensor is 2.5 μm × 2.5 μm or less, and the registration error of the image sensor provided for each wavelength region is limited to a threshold value or less based on the pixel size. By limiting the registration error in this way, an imaging apparatus capable of acquiring a high-definition and high-quality captured image can be provided easily and inexpensively. Therefore, it is suitable for a video camera or the like that captures a desired subject with high definition and high image quality.

DESCRIPTION OF SYMBOLS 10 ... Imaging device 20 ... Color separation prism 21 ... Incident light surface 22R, 22G, 22B ... Block 31R, 31G, 31B ... Imaging element 32R, 32G, 32B ... Substrate 50. ··· Fixing device 51 ··· Light source portion 52R, 52G and 52B ··· Position adjustment jig 53R, 53G and 53B ··· Element drive portion 54R, 54G and 54B · · · Amplifier 55 · · · Memory portion 56 · · · ... The timing generator 57 ... signal processing unit 58 ... display unit 59 ... measurement unit

Claims (7)

It is assumed that there is no registration error when fixing an image sensor having 3840 or more horizontal pixels to the light separation unit that separates incident light into a plurality of wavelength regions, and the wavelength is set by the image sensor provided for each wavelength region. When the contrast of the test image indicated by the image signal generated by performing the photoelectric conversion using the light of the region is 100%, the contrast of the test image is reduced by using a lens having no aberration and a predetermined aperture value. Determining a registration error amount of 40% as a predetermined threshold;
When fixing the image sensor provided for each wavelength region to the light separating unit, the center of the image sensor is generated due to a deviation amount in the horizontal direction and the vertical direction in the other image sensor and an error in the rotation direction with respect to the image sensor. A method for manufacturing an imaging apparatus, comprising: fixing a pixel that is farthest from the pixel in a horizontal direction and a vertical direction by limiting an amount of shift to a predetermined threshold value or less . The first image sensor is fixed to the light separation unit, and then the other image sensor is set so that a registration error of the other image sensor with respect to the first image sensor is equal to or less than the threshold value. The method of manufacturing an imaging apparatus according to claim 1, further comprising fixing to the light separation unit. The method of manufacturing an imaging apparatus according to claim 1, wherein the contrast is calculated from a luminance signal generated using an imaging signal generated by an imaging element provided for each wavelength region. The method of manufacturing an imaging apparatus according to claim 1, wherein the imaging element has a pixel size of 2.5 μm × 2.5 μm, and the aperture value is f / 4.0. The method of manufacturing an imaging apparatus according to claim 4, wherein the predetermined threshold is 0.5 μm. The imaging device manufacturing method according to claim 1, wherein the imaging element provided for each wavelength region has a size of 2/3 inch. The method of manufacturing an image pickup apparatus according to claim 1, wherein the image pickup device is fixed to the light separation unit using an ultraviolet curable adhesive.

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