JP2014103597A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can obtain a multiband image where miniaturization and resolution are secured.SOLUTION: An imaging apparatus includes: an objective optical system 1 for image-forming a light flux from an object; a division element 2 which includes a first face 2a1 and a second face 2b1, divides a light flux made incident on the first face via the objective optical system into two light fluxes of a reflection light flux and a transmission light flux and reflects the transmission light flux on the second face; a first filter arrangement region 5a1 which includes an imaging element 5, and in which a normal line of an imaging face in the imaging element is arranged in a direction crossing a rotational symmetry axis of the objective optical system, a plurality of color filters are disposed and on which the reflection light flux in the two optical fluxes divided on the first face is made incident; and a second filter arrangement region 5a2 in which a plurality of color filters including at least one type of color filter whose transmission wavelength characteristic differs from the color filter arranged in the first filter arrangement region are disposed and on which the transmission light flux reflected on the second face is made incident.

Description

  The present invention relates to an imaging apparatus that acquires a multiband image suitable for, for example, endoscopic observation.

In an imaging apparatus that acquires a multi-band image in endoscopic observation, it is an important issue to achieve both miniaturization and ensuring of resolving power.
When acquiring a multi-band image in endoscopic observation, for example, when using a single-plate image pickup device including one image pickup element in which three types of color filters having transmission wavelength ranges of R, G, and B are arranged , Each type of color filter in the entire imaging region as compared to a three-plate type imaging device provided with three imaging elements in which one type of color filter having a transmission wavelength range corresponding to each of R, G, and B is arranged As the proportion of the color decreases and the amount of information of each color decreases, there is a problem that the resolution cannot be ensured accordingly. If a three-plate image sensor is used or the image sensor is enlarged in the two-dimensional direction, the resolving power can be ensured, but this will increase the size of the image pickup device and make it difficult to reduce the size of the endoscope tip insertion portion. Become.

Conventionally, as an imaging device that acquires a multiband image in endoscopic observation, for example, there are devices described in Patent Documents 1 and 2 below.
As disclosed in Patent Document 1, for example, as shown in FIG. 7, two image pickup devices 51 and 52 are arranged so as to face each other at 90 degrees, and wiring connection portions that connect to the substrates of the respective image pickup devices. The side surfaces not provided with 51a and 52a are brought close to each other so as to face each other, and the arrangement space in the endoscope insertion tip portion is efficiently utilized, thereby reducing the size of the endoscope insertion tip portion.

  In addition, the image sensor described in Patent Document 2 has a plurality of types of color filters having different spectral characteristics, for example, regularly arranged color filters C1 of predetermined colors as shown in FIG. Color filters C2 to C5, which are different in color from the color filter C1, are randomly arranged at pixel positions where C1 does not exist, thereby suppressing a reduction in resolution and reducing false colors.

Japanese Patent No. 4841391 JP 2011-135623 A

However, in the configuration using two imaging elements as in the imaging apparatus described in Patent Document 1, an arrangement space for wirings connected to the substrate is required for each of the two imaging elements, and the imaging apparatus becomes large. In the configuration in which the two image sensors are arranged close to each other at 90 degrees, the long side of one of the image sensors determines the size of the diameter of the endoscope insertion tip. It becomes difficult to make the diameter of the endoscope insertion tip smaller than the long side of the image sensor.
In addition, in the configuration using two image sensors, when image processing such as demosaicing or image composition is performed using information obtained by each image sensor, a detection value caused by individual differences between the image sensors. Due to the deviation, the accuracy of the processed image tends to be lowered. For this reason, a complicated display calibration process for eliminating the deviation of the detection value caused by the individual difference of each image sensor is required.

  Further, as described above, in the configuration in which a plurality of types of color filters are allocated and arranged at each pixel position in one image sensor as in the image sensor described in Patent Document 2, as described above, each type of color is used in the entire image capturing area. Since the proportion of the filter decreases and the information amount of each color decreases, it is difficult to ensure the resolution. In addition, narrow-band light observation is an important observation method in endoscopic observation, but it is photographed when narrow-band color filters are included in multiple types of color filters arranged in one image sensor. It is difficult to create a demosaic image with a narrow band from a single piece of information, and it is difficult to ensure resolution.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an imaging device capable of acquiring a multiband image while ensuring miniaturization and resolving power.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an objective optical system for forming an image of a light beam from an object, a first surface, and a second surface, and the objective surface is the first surface. A splitting element that splits a light flux incident through the optical system into two light fluxes, a reflected light flux and a transmitted light flux, and reflects the transmitted light flux on the second surface; and an image of the reflected light flux split by the splitting element; A plurality of color filters, each of which has an image pickup device for picking up an image of a transmitted light beam, the image pickup device being arranged in a direction in which a normal line of an image pickup surface intersects a rotation target axis of the objective optical system; Are arranged in the first filter arrangement region where the reflected light beam of the two light beams divided by the first surface of the dividing element is incident, and the first filter arrangement region Color filters with different transmission wavelength characteristics from color filters A plurality of color filters including at least one type of filter are arranged, and a second filter arrangement region on which the transmitted light beam reflected by the second surface is incident is provided.

  In the imaging apparatus of the present invention, light in each of the R, G, and B wavelength ranges is transmitted through one of the first filter placement region and the second filter placement region. The three types of color filters to be transmitted are arranged, and the other filter arrangement region has at least one type of transmission wavelength region different from any of the three types of color filters that transmit light in the wavelength regions of R, G, and B. It is preferable that the color filter is disposed.

  In the imaging apparatus of the present invention, the other filter arrangement region has a narrower band than the transmission wavelength regions of the three types of color filters that transmit light in the R, G, and B wavelength regions. The same type of color filter that transmits light is preferably disposed.

  In the imaging device of the present invention, a color filter having a transmission peak wavelength on the short wavelength side is arranged in one of the first filter arrangement area and the second filter arrangement area. In the other filter arrangement region, it is preferable that a color filter having a transmission peak wavelength on the longer wavelength side than any color filter arranged in the one filter arrangement region is arranged.

  In the imaging apparatus of the present invention, light in each of the R, G, and B wavelength ranges is transmitted through one of the first filter placement region and the second filter placement region. One or two of the three types of color filters are arranged, and the other filter arrangement region has three types of color filters that transmit light in the R, G, and B wavelength ranges. It is preferable that a color filter including at least the remaining types of color filters not disposed in the one filter region is disposed.

  In the imaging device of the present invention, the first surface of the dividing element reflects a part of the light beam incident through the objective optical system toward the first filter arrangement region of the imaging element. Is preferred.

  In the imaging apparatus of the present invention, the first surface of the splitting element reflects a part of the light beam incident through the objective optical system in a direction away from the first filter arrangement region of the imaging element. And a reflecting member that reflects the reflected light beam reflected in a direction away from the first filter arrangement area so as to be incident on the first filter arrangement area of the imaging device. preferable.

  In the imaging device of the present invention, the information output through the plurality of color filters arranged in the one filter arrangement region of the imaging element is used to arrange the one arranged in the other filter arrangement region. It is preferable to further include an image processing unit that performs demosaicing on information output through a plurality of color filters.

  According to the present invention, it is possible to obtain an imaging apparatus capable of obtaining a multiband image while ensuring miniaturization and resolving power.

It is explanatory drawing which shows typically the whole structure of the imaging device concerning 1st Embodiment of this invention. FIG. 2 is a plan view schematically showing an example of the arrangement of color filters provided in the first and second filter arrangement regions of the image sensor used in the imaging device of FIG. 1, (a) is a diagram showing an example, and (b). FIG. 8 is a diagram showing another example. FIG. 2A is a plan view schematically showing an arrangement example of color filters provided in a filter arrangement region of an imaging element used in a conventional imaging apparatus according to a comparative example of the imaging apparatus in FIG. 1, and FIG. The figure which shows the comparative example with respect to this example, (b) is a figure which shows the comparative example with respect to the example of FIG.2 (b). 3 is a table showing combinations of color filter arrangements provided in first and second filter arrangement regions of an image sensor used in the imaging apparatus of FIG. 1. It is explanatory drawing which shows the structure of the imaging device concerning 2nd Embodiment of this invention, (a) is a plane which shows typically the example of arrangement | positioning of the color filter with which the 1st and 2nd filter arrangement | positioning area | region of an image pick-up element is equipped. FIG. 4B is a graph schematically showing transmission peak bands of color filters provided in the first and second filter arrangement regions. It is explanatory drawing which shows typically the whole structure of the imaging device concerning 3rd Embodiment of this invention. FIG. 11 is a cross-sectional view illustrating an arrangement configuration example of image pickup elements in the image pickup apparatus described in Patent Literature 1. FIG. 10 is an explanatory diagram illustrating an example of an arrangement configuration of color filters in an image sensor described in Patent Literature 2.

Prior to the description of the embodiments, the effects of the present invention will be described.
An imaging apparatus according to the present invention includes an objective optical system for forming a light beam from an object, a first surface, and a second surface, and the light beam incident on the first surface via the objective optical system. Is divided into two light fluxes, a reflected light flux and a transmitted light flux, a splitting element that reflects the transmitted light flux on the second surface, and an image of the reflected light flux and an image of the transmitted light flux split by the splitting element are captured. The image pickup device is arranged in a direction in which a normal line of the image pickup surface intersects a rotation target axis of the objective optical system, and a plurality of color filters are arranged and the division is performed. The first filter arrangement region where the reflected light beam of the two light beams divided by the first surface of the element is incident and the color filter disposed in the first filter arrangement region are transmission wavelength characteristics. At least one color filter with different A plurality of color filters including comprises a second filter arrangement region in which the transmitted light beam reflected by the second surface be disposed is incident.
As in the present invention, two filter arrangement regions are provided in one image sensor, and the reflected light beam and the transmitted light beam divided by the division element are incident on the respective filter arrangement regions. If a plurality of color filters including at least one color filter having a transmission wavelength characteristic different from any of the color filters arranged in the filter arrangement region are arranged, for example, when demosaicing color information in one filter arrangement region In addition, more information can be used by using the color information in the other filter arrangement region, and the demosaic using only the color information obtained by arranging a plurality of color filters in one image sensor. Compared to this, it is possible to perform a demosaicing with high accuracy.

This point will be described in detail.
In general, an image sensor used in a single-plate imaging device that captures a color image has a set of photodetectors corresponding to pixels and a plurality of types of color filters arranged in a mosaic pattern above the photodetectors. doing. The photodetector itself detects luminance information but not color information. For this reason, in the imaging device, a plurality of types of color filters are arranged on the top of each photodetector, and light of the color that has passed through the plurality of types of color filters is received by each photodetector, so that each color is received. Get information about.
However, the information received by each photodetector is single-color information transmitted through a color filter arranged on the upper portion of the detector, and is collected for each pixel in the entire pixel region of the image sensor by the aggregate of photodetectors. However, information on the colors of all types of color filters is not detected. Therefore, even if the information picked up by the image pickup device is used as it is, a color image in which information of a plurality of types of colors is overlapped at the same pixel position cannot be obtained.
For this reason, in a single-plate imaging device that captures a color image, generally, the image processing device uses the single-color information obtained at each pixel position in the imaging device for each pixel of the color filter. Image processing that interpolates information on the same type of color as the color obtained at the pixel position at other pixel positions where a different type of color from the color obtained at the position is obtained, and creates information for all pixel areas Perform processing (demosaic). And the color image of all the pixel areas is obtained by superimposing the information of all the pixel areas for each color of the color filter that has been demosaiced.
The demosaic is performed by calculating using the luminance correlation value between the color information obtained at the pixel positions around the pixel position and the color information obtained at the pixel position.

By the way, if there is no restriction on the size of the pixel area of the image sensor, increasing the types of color filters arranged above the aggregate of photodetectors can increase the dynamic range while ensuring resolution, Reproducibility can be improved.
However, for example, in an imaging apparatus that is required to be miniaturized, such as that disposed in an endoscope distal end insertion portion, the size of the imaging element is limited, so that it is disposed above the aggregate of photodetectors. When the types of color filters are increased, the information amount of each color occupying the imaging area is reduced. Further, the color information obtained at the pixel positions around the pixel position used for the demosaic includes the color information obtained at the pixel position away from the pixel position. The light intensity at the pixel position is less likely to reflect the light intensity at the pixel position. For this reason, the accuracy of the information of all the pixel areas for each color of the demosaiced color filter is reduced, and even if the information of all the pixel areas for each color of the demosaiced color filter is superimposed, the color image of all the pixel areas The accuracy of the image quality decreases and the resolving power decreases.

  Accordingly, in the configuration in which a plurality of types of color filters are arranged in an imaging region where one image is formed as in the imaging device described in Patent Document 2, the above-described configuration is used when the imaging device is limited in size. As described above, the accuracy of the demosaic is lowered and the resolving power cannot be secured. Since it is difficult to increase the types of color filters, it is difficult to further expand the dynamic range and further improve color reproducibility.

  However, as in the image pickup apparatus of the present invention, if two image pickup regions are provided in one image pickup device and a filter region in which a plurality of color filters are arranged in each image pickup region is provided, in order to widen the dynamic range, Even if the number of types of color filters is increased in order to improve reproducibility, a decrease in the amount of information of each color occupying the imaging area can be suppressed as compared with the imaging element described in Patent Document 2, and a highly accurate demosaic can be achieved. Can be performed, and the resolving power can be secured.

  It is possible to increase the number of types of color filters while suppressing a decrease in the proportion of the color filter in the imaging region where one image is formed, even by providing two imaging elements as in the imaging device described in Patent Document 1. However, there are individual differences between the image sensors, and the detected values are shifted. When demosaic is performed, the detected values such as brightness and color are shifted due to individual differences between the two image sensors, and the accuracy of the demosaic is reduced. I will let you. For this reason, complicated calibration (display calibration processing) for eliminating the deviation of the detection value caused by the individual difference of each image sensor is required.

  However, as in the image pickup apparatus of the present invention, if two filter arrangement regions are provided in one image pickup element, each of the conventional image pickup apparatuses provided with two image pickup elements as described in Patent Document 1 is used. A complicated display calibration process for eliminating the deviation of the detection value caused by the individual difference between the image pickup elements is not required, so that more accurate demosaic can be performed and the resolving power can be secured. In addition, substrate wiring can be reduced as compared with the case where two imaging elements are used, and the corresponding arrangement space is not required, and the imaging apparatus can be reduced in size.

  Further, when two filter arrangement areas are provided as in the image pickup apparatus of the present invention, R, G, B color filters are arranged in one of the two filter arrangement areas, and a color filter of a specific wavelength is arranged in the other. For example, when a moving image is acquired and displayed on a display device, a color image obtained by demosaicing and combining information obtained from R, G, and B color filters during normal visible light observation is obtained. It is also possible to switch to display of an image in another filter arrangement area as necessary. In addition, it is possible to display a narrow band image while displaying R, G, B color images.

Further, as in the imaging device of the present invention, if the imaging element is arranged in a direction in which the normal of the imaging surface intersects the rotation target axis of the objective optical system, the long side of the imaging element is the endoscope insertion tip. Therefore, it is easy to reduce the size of the endoscope insertion tip. The shape of the image sensor in the image pickup apparatus of the present invention is a rectangle having an image pickup surface extending in a direction along the rotation target axis of the objective optical system and having two filter arrangement regions in the long side direction. Since the endoscope tip insertion portion is configured to extend long along the rotation target axis direction of the objective optical system, it does not hinder downsizing of the endoscope tip insertion portion.
Therefore, according to the imaging apparatus of the present invention, it is possible to realize an imaging apparatus capable of acquiring a multiband image with a small size and a high resolving power.

In the imaging apparatus of the present invention, light in each of the R, G, and B wavelength ranges is transmitted through one of the first filter placement region and the second filter placement region. The three types of color filters to be transmitted are arranged, and the other filter arrangement region has at least one type of transmission wavelength region different from any of the three types of color filters that transmit light in the wavelength regions of R, G, and B. It is preferable that the color filter is disposed.
If a color filter arranged in one of the first filter arrangement area and the second filter arrangement area is composed of R, G, and B color filters, a normal visible light image can be acquired. Become.

In the imaging apparatus of the present invention, the other filter arrangement region has a narrower band than the transmission wavelength regions of the three types of color filters that transmit light in the R, G, and B wavelength regions. The same type of color filter that transmits light is preferably disposed.
If the color filter arranged in the other filter arrangement region is composed of the same type of color filter that transmits narrow-band light, information of the same type of wavelength region can be obtained in the entire imaging region where one image is formed. Therefore, it is possible to acquire an image in a wavelength region important for an endoscope, such as NBI, without performing demosaicing, and it is possible to minimize the influence of noise when acquiring an image.

In the imaging device of the present invention, a color filter having a transmission peak wavelength on the short wavelength side is arranged in one of the first filter arrangement area and the second filter arrangement area. In the other filter arrangement region, it is preferable that a color filter having a transmission peak wavelength on the longer wavelength side than any color filter arranged in the one filter arrangement region is arranged.
The refractive index of the optical system varies depending on the wavelength, and the imaging position (image plane position) varies with the wavelength. However, if a color filter that transmits a relatively short wavelength is arranged in one filter arrangement area and a color filter that transmits a relatively long wavelength is arranged in the other filter arrangement area, one image is formed. It is possible to reduce the difference between the lengths of the wavelengths formed in the respective imaging regions, and to easily align the image planes in each imaging region where one image is formed, and to adjust the image planes. It can be simplified.

In the imaging apparatus of the present invention, light in each of the R, G, and B wavelength ranges is transmitted through one of the first filter placement region and the second filter placement region. One or two of the three types of color filters are arranged, and the other filter arrangement region has three types of color filters that transmit light in the R, G, and B wavelength ranges. It is preferable that a color filter including at least the remaining types of color filters not disposed in the one filter region is disposed.
In this way, it is possible to perform R, G, and B demosaicing on an image output via the other filter arrangement area using information output via either one of the two filter arrangement areas. In addition, if three types of color filters that transmit light in each wavelength region of R, G, and B are arranged separately in one of the two filter arrangement regions, they are arranged in the respective filter arrangement regions. Since the types of color filters can be reduced, the accuracy of the demosaic can be improved and high resolution can be ensured.

In the imaging device of the present invention, the first surface of the dividing element reflects a part of the light beam incident through the objective optical system toward the first filter arrangement region of the imaging element. Is preferred.
For example, if a half mirror is used for the first surface of the splitting element, it is possible to make the light beam split with a simple configuration enter each filter arrangement region.

In the imaging apparatus of the present invention, the first surface of the splitting element reflects a part of the light beam incident through the objective optical system in a direction away from the first filter arrangement region of the imaging element. And a reflecting member that reflects the reflected light beam reflected in a direction away from the first filter arrangement area so as to be incident on the first filter arrangement area of the imaging device. preferable.
For example, if a polarization beam splitter is used on the first surface of the splitting element, the optical path lengths to the first and second filter arrangement regions can be made the same through the reflecting member, and one image is formed. It is possible to simplify the adjustment of the imaging state in each imaging region.

In the imaging device of the present invention, the information output through the plurality of color filters arranged in the one filter arrangement region of the imaging element is used to arrange the one arranged in the other filter arrangement region. It is preferable to further include an image processing unit that performs demosaicing on information output through a plurality of color filters.
If the demosaic is performed on the information output via the color filter arranged in the other filter arrangement area using the information outputted via the color filter arranged in one filter arrangement area, a plurality of filters are provided in one filter arrangement area. Compared to a demosaic that uses only the information obtained with a single plate with a color filter, the type and amount of color information used in the demosaic can be increased, enabling highly accurate demosaic and ensuring resolution. It becomes easy to do.

First Embodiment FIG. 1 is an explanatory diagram schematically showing the overall configuration of an imaging apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view schematically showing an example of the arrangement of color filters provided in the first and second filter arrangement regions of the image sensor used in the imaging apparatus of FIG. 1, and FIG. (b) is a diagram showing another example. 3 is a plan view schematically showing an arrangement example of color filters provided in a filter arrangement region of an image sensor used in a conventional imaging apparatus according to a comparative example of the imaging apparatus in FIG. 1, and FIG. The figure which shows the comparative example with respect to the example of (a), (b) is a figure which shows the comparative example with respect to the example of FIG.2 (b). FIG. 4 is a table showing combinations of color filter arrangements provided in the first and second filter arrangement regions of the image sensor used in the imaging apparatus of FIG.

  The imaging apparatus according to the first embodiment includes an objective optical system 1, a dividing element 2, a λ / 4 plate 3, a mirror 4, an imaging element 5, and an image processing device 6. In FIG. 1, reference numeral 7 denotes a display device.

The objective optical system 1 forms an image of a light beam from an object.
The splitting element 2 includes a polarizing beam splitter 2a having a polarizing beam splitter surface 2a1 as a first surface and a mirror 2b having a mirror surface 2b1 as a second surface.
The polarization beam splitter 2a is disposed at a position where the light beam that has passed through the objective optical system 1 enters the polarization beam splitter surface 2a1. The polarization beam splitter surface 2a1 divides the light beam into two light beams, a reflected light beam and a transmitted light beam, according to the polarization components of the P wave and S wave in the incident light beam. Further, the polarization beam splitter surface 2a1 is disposed so that the reflected light beam is directed to the side opposite to the imaging element 5 (here, the mirror 4 side).
The polarization beam splitter 2a is configured to be movable in the direction of the arrow AB, and the optical path length of a light beam incident on a first filter arrangement region 5a1 (described later) of the image sensor 5 divided by the polarization beam splitter surface 2a1. The optical path length of a light beam incident on a second filter arrangement region 5a2 described later and the image formation position on the imaging surface can be finely adjusted.
In the example of FIG. 1, the splitting element 2 is composed of the polarization beam splitter 2 a and the mirror 2 b independent members, but the splitting element 2 is composed of a prism in which the polarization beam splitter 2 a and the mirror 2 b are integrated. May be.
The mirror 2b is disposed at a position where a transmitted light beam out of the light beam split by the polarization beam splitter surface 2a1 through the objective optical system 1 enters the mirror surface 2b1. The mirror surface 2b1 reflects the incident light beam so that it enters the second filter arrangement region 5a2 of the image sensor 5.
The λ / 4 plate 3 converts the phase of the light beam reflected by the polarization beam splitter surface 2a1 by 90 degrees and converts the phase of the light beam reflected by the mirror 4 by 90 degrees.
The mirror 4 reflects the light beam reflected by the polarization beam splitter surface 2a1 and having the phase converted by 90 ° by the λ / 4 plate 3 in the folding direction so as to enter the first filter arrangement region 5a1 of the image sensor 5. Let

The imaging element 5 has a color filter arrangement unit 5a and an imaging unit 5b composed of an aggregate of photodetectors corresponding to pixels, and is formed in an elongated shape. Further, the image sensor 5 is arranged in a direction (vertical in the example of FIG. 1) in which the normal line of the imaging surface intersects the rotation target axis of the objective optical system 1.
The color filter placement unit 5a has a first filter placement area 5a1 and a second filter placement area 5a2.
In the first filter arrangement region 5a1, as shown in FIG. 2 (a), as a plurality of color filters, three types of color filters that transmit light in each of the R, G, and B wavelength regions are, for example, Bayer. They are arranged in a mosaic pattern in a predetermined arrangement such as an arrangement.
In the second filter arrangement region 5a2, a plurality of color filters in which at least one type of color filter transmits light in a wavelength region other than R, G, and B are shown in FIG. ), Three types of color filters that transmit light in the respective wavelength regions of Cy (cyan), M (magenta), and Y (yellow), which are complementary to R, G, and B, are Bayer. They are arranged in a mosaic pattern in a predetermined arrangement such as an arrangement. The arrangement configuration of the plurality of filters in the second filter arrangement area 5a2 is the same as that in the second filter arrangement area 5a2, as shown in FIG. 2B. It may be arranged in the entire pixel area.

The image processing device 6 is provided in a central processing unit (not shown), has an image processing unit 6 a, and is connected to the image sensor 5. The image processing unit 6a uses the information output from the plurality of color filters arranged in the first filter arrangement region 5a1 of the image sensor 5 from the plurality of color filters arranged in the second filter arrangement region 5a2. It is configured to be able to perform image processing such as demosaicing or composition of the output information. Note that the image processing unit 6a uses information output from a plurality of types of color filters arranged in the same filter arrangement area in the image sensor 5, and outputs the information from the plurality of color filters arranged in the filter arrangement area. It is also possible to perform image processing such as demosaicing and synthesis of information.
The display device 7 displays information after image processing by the image processing device 6.

  In the imaging apparatus of the first embodiment configured as described above, the light beam from the object enters the polarization beam splitter 2a through the objective optical system 1. The light beam incident on the polarization beam splitter 2a is separated by the polarization beam splitter surface 2a1 into a reflected light beam of one of the linearly polarized S-polarized component and a P-polarized component and a transmitted light beam of the other component.

  The linearly polarized light beam of one polarization component reflected by the polarization beam splitter surface 2 a 1 passes through the λ / 4 plate 3, the polarization state is converted to circularly polarized light, and enters the mirror 4. The light beam reflected by the mirror 4 passes through the λ / 4 plate 3 again, the polarization state is converted from the circularly polarized light to the linearly polarized light of the other polarization component, enters the polarizing beam splitter 2a again, and passes through the polarizing beam splitter surface 2a1. Then, an image is formed on the first filter arrangement region 5a1 of the image sensor 5. At this time, in the first filter arrangement region 5a1, as the plurality of color filters, three types of color filters that transmit light in the R, G, and B wavelength regions are arranged in a mosaic arrangement. For this reason, a single-plate type in which each color of R, G, and B is scattered in a mosaic manner through a plurality of photodetectors arranged in the imaging region corresponding to the first filter arrangement region 5a1 in the imaging unit 5b. Information is acquired.

  On the other hand, the linearly polarized light beam of the other polarization component that has passed through the polarization beam splitter surface 2 a 1 when entering the polarization beam splitter 2 a via the objective optical system 1 is reflected by the mirror surface 2 b 1 of the mirror 2 b, and The image is formed on the second filter arrangement region 5a2. At this time, in the second filter arrangement region 5a2, as a plurality of color filters, a plurality of types of color filters that transmit light in wavelength bands other than R, G, and B (for example, complementary colors for R, G, and B). The color filters that transmit light in the wavelength bands of Cy (cyan), M (magenta), and Y (yellow), which are related, are arranged in a mosaic pattern. Alternatively, the same type of color filter that transmits light in the wavelength band of the narrow band N is disposed in the entire area. For this reason, single-plate information in which the colors of Cy, M, and Y are scattered in a mosaic manner through a plurality of photodetectors arranged at positions corresponding to the second filter arrangement region 5a2 in the imaging unit 5b, Alternatively, single-plate information consisting of a narrow band N color is acquired.

The image processing unit 6a of the image processing device 6 is arranged in the second filter arrangement area 5a2 using information output from the plurality of color filters arranged in the first filter arrangement area 5a1 of the imaging device 5. Demosaicing of information output from a plurality of color filters. Next, the information of all the coordinate areas for each color of the color filter that has been demosaiced is superimposed to synthesize a color image of all the coordinate areas.
The display device 7 displays a color image created through image processing such as demosaicing and synthesis by the image processing unit 6.

  According to the imaging apparatus of the first embodiment, two filter arrangement regions 5a1 and 5a2 are provided in one image pickup device 5, and the reflected light flux and the transmitted light beam divided by the division element 2 are respectively provided in the filter arrangement regions 5a1 and 5a2. A plurality of color filters including at least one color filter having a transmission wavelength characteristic different from any of the color filters arranged in the other filter arrangement region, in one of the filter arrangement regions 5a1 and 5a2. Since the color filter is arranged, when demosaicing the color information in one filter arrangement area, more information can be used by using the color information in the other filter arrangement area. High demosaicing is possible. Moreover, according to the imaging apparatus of the first embodiment, since the two filter arrangement regions 5a1 and 5a2 are provided on the imaging surface of one imaging element 5, two conventional imaging elements as described in Patent Document 1 are provided. Eliminates the need for complicated display calibration processing to eliminate deviations in detection values caused by individual differences in each image sensor in the type of imaging device provided, enabling more accurate demosaic processing and ensuring resolving power it can. In addition, substrate wiring can be reduced as compared with the case where two imaging elements are used, and the corresponding arrangement space is not required, and the imaging apparatus can be reduced in size.

  According to the imaging apparatus of the first embodiment, the plurality of color filters arranged in the first filter arrangement region 5a1 are configured by color filters that transmit light in the R, G, and B wavelength bands. Therefore, a normal visible light image can be acquired. Here, the plurality of color filters arranged in the second filter arrangement region 5a2 are configured by color filters that transmit light in the Cy, M, and Y wavelength regions that are complementary to R, G, and B. In this case, the accuracy of the demosaic is improved and the color reproducibility (color reproduction range) of the synthesized image is improved.

  Further, when the color filters arranged in the second filter arrangement area are configured by the same type of color filter that transmits the light of the narrow band N, the same type of color filter is formed in the entire imaging area where one image is formed. Since information on the wavelength range can be obtained, it is possible to acquire an image in the wavelength range important for an endoscope, such as NBI, without performing demosaicing, and minimize the influence of noise when acquiring the image. To the limit.

  On the other hand, in the configuration in which a plurality of types of color filters are allocated and arranged at each pixel position in one image sensor as in the image sensor described in Patent Document 2, the proportion of each color filter in the entire image area is Since the information amount of each color occupying in the imaging area is reduced, it is difficult to ensure the resolution.

FIG. 3A is a diagram illustrating an arrangement example of color filters according to a comparative example with respect to the example of FIG.
In the imaging device of the comparative example shown in FIG. 3A, each wavelength of R, G, B, Cy, M, and Y is in the same size as one filter arrangement region in the imaging device of the first embodiment. Six types of color filters that transmit light in the region are arranged.
In the image pickup device of the comparative example shown in FIG. 3A configured as described above, the information amount of each color in the image pickup region is halved compared to the example of FIG. Can not do. As a result, even if the information of all the pixel areas for each color of the color filter that has been demosaiced is superimposed, the accuracy of the color image in all the pixel areas is lowered, and the resolution is lowered.

FIG. 3B is a diagram illustrating an arrangement example of color filters according to a comparative example with respect to the example of FIG.
In the imaging device of the comparative example shown in FIG. 3B, light in each of the R, G, and B wavelength ranges is transmitted through a region having the same size as one filter arrangement region in the imaging device of the first embodiment. A total of four color filters, a color filter and a color filter that transmits light in a narrow band N, are arranged.
In the comparative example of the imaging device shown in FIG. 3B configured as described above, the amount of information of each color in the imaging region is reduced as compared with the example of FIG. It is difficult. In addition, since it is not a configuration that obtains information of the same type of wavelength region in the entire imaging region where one image is formed, a wavelength region (narrow, for example, NBI) that is important for an endoscope is used without demosaicing. An image in band N) cannot be acquired. In addition, when demosaicing information of each color is performed, information of the same type of wavelength region cannot be used in the entire imaging region where one image is formed, and therefore high-precision demosaicing cannot be performed. As a result, even if the information of all the coordinate areas for each color of the color filter that has been demosaiced is superimposed, the accuracy of the color image in all the coordinate areas is lowered, and the resolution is lowered.

  Note that the combination of the color filters arranged in the first and second filter arrangement regions 5a1 and 5a2 in the imaging device of the first embodiment is not limited to the combination shown in FIG. The combinations shown in the table may be used.

  For example, R, G, and B filters may be arranged in the first filter arrangement region 5a1, and infrared and / or ultraviolet filters may be arranged in the second filter arrangement region 5a2. In this way, in the medical field, it is possible to observe the affected area and the surgical site at a specific wavelength together with visible light.

  Further, for example, R, G, B filters are arranged in the first filter arrangement area 5a1, and LR (light red), LG (light green), LB (light blue) filters are arranged in the second filter arrangement area 5a2. May be. In this way, information obtained through filters having different transmission wavelength ranges for the same color can be obtained, so that the dynamic range can be expanded.

  Further, for example, R, G, B filters may be arranged in the first filter arrangement area 5a1, and W (white) filters may be arranged in the second filter arrangement area 5a2. In this way, R, G, B arranged in the first filter arrangement area 5a1 using the color information acquired through the W filter arranged in the second filter arrangement area 5a2 as a reference. When performing demosaicing of the color information acquired through the respective filters, it becomes easy to calculate the information of each color, and furthermore, information of the same type of wavelength region can be used in the entire imaging region. High-precision demosaic can be performed, and resolution can be secured.

  Also, one of the first filter arrangement area 5a1 and the second filter arrangement area 5a2 has three kinds of color filters that transmit light in the R, G, and B wavelength ranges. One type or two types of color filters are arranged, and the other filter arrangement region is arranged in one of the three types of color filters that transmit light in the R, G, and B wavelength ranges. A color filter including at least the remaining types of color filters that have not been performed may be arranged.

  For example, a G filter may be arranged in the first filter arrangement area 5a1, and an R, B, Cy, Or (orange) filter may be arranged in the second filter arrangement area 5a2. In this way, since the number of types of color filters increases, color reproducibility can be improved, and moreover, imaging in which one image is formed by arranging only the G filter in the first filter arrangement region 5a1. Since information of the same type of wavelength region can be obtained in the entire region, the information is obtained through a color filter that transmits light in each wavelength band of R, B, Cy, Or disposed in the second filter region 5a2. When performing demosaic of information of each color, it is possible to perform demosaic with high accuracy by using the information of G color in the entire imaging region.

  Further, for example, a G filter may be arranged in the first filter arrangement area 5a1, and an R and B filter may be arranged in the second filter arrangement area 5a2. In this way, the types of filters arranged in the filter arrangement area of each filter can be reduced, and one image is formed by arranging only the G filter in the first filter arrangement area 5a1. Since information of the same type of wavelength region can be obtained in the entire imaging region, high-accuracy demosaic can be performed and high resolution can be ensured.

  For example, G and W filters may be arranged in the first filter arrangement area 5a1, and R and B filters may be arranged in the second filter arrangement area 5a2. Even in this case, the types of filters arranged in the filter arrangement area of each filter can be reduced, and information on other colors can be obtained using the color information obtained through the W filter as a reference. By performing the demosaic, it is easy to calculate the information of each color, so it is possible to perform a highly accurate demosaic and secure a high resolution.

Note that the combination of the color filters arranged in the two filter arrangement regions 5a1 and 5a2 in the imaging device of the first embodiment may be replaced with each other.
Further, for example, as shown in FIG. 2A, the plurality of color filters arranged in one filter arrangement region 5a1 are configured by color filters that transmit light in the R, G, and B wavelength bands. When the plurality of color filters arranged in the other filter arrangement region 5a2 are configured by color filters that transmit light in the wavelength ranges of Cy, M, and Y that are complementary to R, G, and B. The color filter arranged in each filter arrangement area captures the color filter arranged in the corresponding pixel position in the other filter arrangement area with respect to the color filter arranged in the pixel position in one filter arrangement area. It is preferable to arrange each color filter so as to have a relationship. In this way, it becomes easy to calculate the information of each color for each corresponding pixel position, so that highly accurate demosaic can be performed and high resolution can be ensured.

Second Embodiment FIG. 5 is an explanatory view showing the configuration of an image pickup apparatus according to a second embodiment of the present invention. (A) is an arrangement of color filters provided in the first and second filter arrangement areas of the image pickup device. The top view which shows an example typically, (b) is a graph which shows typically the permeation | transmission peak zone | band of a color filter with which the 1st and 2nd filter arrangement | positioning area | region is equipped.
In the imaging device according to the second embodiment, all types of color filters λ _{1 to} λ ₃ arranged in the first filter arrangement region 5a1 are configured by color filters having transmission peak wavelengths on the short wavelength side. All types of color filters λ _{4 to} λ ₆ arranged in the filter arrangement region 5a2 are formed of color filters having a transmission peak wavelength on the long wavelength side. Here, the transmission peak wavelength λn is λ1 <λ2 <λ3 <λ4 <λ5 <λ6, as shown in FIG. 5B.
Other configurations are substantially the same as those of the imaging apparatus of the first embodiment.

According to the imaging device of the second embodiment, a color filter that transmits a relatively short wavelength is arranged in the first filter arrangement region 5a1, and a color that transmits a relatively long wavelength in the second filter arrangement region 5a2. Since the filter is arranged, the difference in length between the wavelengths formed in the respective imaging regions where one image is formed can be reduced, and the image plane can be reduced in each imaging region where one image is formed. And the adjustment for matching the image plane can be simplified.
Other functions and effects are substantially the same as those of the imaging device of the first embodiment.

Third Embodiment FIG. 6 is an explanatory diagram schematically showing the overall configuration of an imaging apparatus according to a third embodiment of the present invention.
In the imaging device of the third embodiment, the dividing element 2 includes a half mirror 2a ′ having a half mirror surface 2a1 ′ as a first surface and a mirror 2b having a mirror surface 2b1 as a second surface. It is configured.
The half mirror 2a ′ is arranged so that the light beam incident through the objective optical system 1 is incident on the half mirror surface 2a1 ′, and the half mirror surface 2a1 ′ splits the reflected light beam and the transmitted light beam into two light beams. . Further, the half mirror surface 2 a 1 ′ is arranged so that the reflected light beam is directed to the first filter arrangement region of the image sensor 5.
Further, in the imaging apparatus of the third embodiment, the λ / 4 plate 3 and the mirror 4 are not arranged.
Other configurations are substantially the same as those of the imaging apparatus of the first embodiment.

In the imaging apparatus according to the third embodiment configured as described above, the light beam from the object enters the half mirror 2a ′ via the objective optical system 1. The light incident on the half mirror 2a ′ is separated into a reflected light beam and a transmitted light beam by the half mirror surface 2a1 ′.
The light beam reflected by the half mirror surface 2 a 1 ′ forms an image on the first filter arrangement region 5 a 1 of the image sensor 5.
On the other hand, the light beam that has passed through the half mirror surface 2a1 ′ when entering the half mirror 2a ′ via the objective optical system 1 is reflected by the mirror surface 2b1 of the mirror 2b, and enters the second filter arrangement region 5a2 of the image sensor 5. Form an image.

According to the imaging apparatus of the third embodiment, the first surface of the splitting element 2 is configured by the half mirror surface 2a1 ′, and the light beam reflected by the half mirror surface 2a1 ′ is the first filter arrangement region 5a1 of the imaging device 5. Therefore, it is not necessary to provide the λ / 4 plate 3 and the mirror 4 for converting the phase of the linearly polarized light component in the imaging device of the first embodiment or the second embodiment, and the configuration is simplified. it can.
Other functions and effects are substantially the same as those of the imaging device of the first embodiment.

  The image pickup apparatus of the present invention is useful in a field where observation of a multiband image in which downsizing and resolving power are required is required.

DESCRIPTION OF SYMBOLS 1 Objective optical system 2 Split element 2a Polarization beam splitter 2a1 Polarization beam splitter surface 2a 'Half mirror 2a1' Half mirror surface 2b Mirror 2b1 Mirror surface 3 (lambda) / 4 board 4 Mirror 5 Image pick-up element 5a Color filter arrangement | positioning part 5a1 1st filter Arrangement area 5a2 Second filter arrangement area 5b Imaging section 6 Image processing apparatus 6a Image processing section 7 Image display apparatuses 51, 52 Imaging elements 51a, 52a Connection sections C1, C2, C3, C4, C5 Color filter

Claims (8)

An objective optical system for imaging the light flux from the object;
A first surface and a second surface, the light beam incident on the first surface via the objective optical system is divided into two light beams, a reflected light beam and a transmitted light beam; A splitting element that reflects the transmitted light beam;
One imaging element that captures an image of the reflected light beam and an image of the transmitted light beam divided by the dividing element;
The image pickup device is arranged in a direction in which a normal line of the image pickup surface intersects a rotation target axis of the objective optical system, and a plurality of color filters are arranged and divided by the first surface of the division device. The first filter arrangement region where the reflected light beam of the two light beams is incident and the color filter arranged in the first filter arrangement region include at least one color filter having different transmission wavelength characteristics. An image pickup apparatus comprising: a second filter arrangement region in which a plurality of color filters are arranged and the transmitted light flux reflected by the second surface is incident.   In one of the first filter arrangement region and the second filter arrangement region, three types of color filters that transmit light in the R, G, and B wavelength ranges are arranged, The other filter arrangement region is characterized in that at least one color filter having a transmission wavelength range different from any of the three types of color filters that transmit light in each of the RGB wavelength ranges is arranged. Item 2. The imaging device according to Item 1.   In the other filter arrangement region, the same type of color filter that transmits light in a narrow band as compared with the transmission wavelength regions of the three types of color filters that transmit light in the respective wavelength regions of R, G, and B is provided. The imaging apparatus according to claim 2, wherein the imaging apparatus is arranged.   A color filter having a transmission peak wavelength on the short wavelength side is arranged in one of the first filter arrangement region and the second filter arrangement region, and in the other filter arrangement region, The image pickup apparatus according to claim 1, wherein a color filter having a transmission peak wavelength on a longer wavelength side than any of the color filters arranged in one filter arrangement region is arranged.   One of the first filter arrangement area and the second filter arrangement area is one of three types of color filters that transmit light in the R, G, and B wavelength ranges. Two or more types of color filters are arranged, and the other filter arrangement region is arranged in the one filter region of the three types of color filters that transmit light in the R, G, and B wavelength regions. The image pickup apparatus according to claim 1, wherein a color filter including at least a remaining type of color filter is disposed.   The first surface of the splitting element reflects a part of a light beam incident through the objective optical system toward the first filter arrangement region of the imaging element. The imaging device according to any one of the above. The first surface of the splitting element reflects a part of the light beam incident through the objective optical system in a direction away from the first filter arrangement region of the imaging element, and
And a reflecting member configured to reflect the reflected light flux after being reflected in a direction deviating from the first filter arrangement area so as to enter the first filter arrangement area of the imaging device. The imaging device according to claim 2.   Information output through the plurality of color filters arranged in the other filter arrangement area using information outputted through the plurality of color filters arranged in the one filter arrangement area of the image sensor The imaging apparatus according to claim 2, further comprising an image processing unit that performs demosaicing on the image.

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