JP2021164042A - Luminous flux separation imaging device - Google Patents

Abstract

To capture a circular image of a medical camera or the like with high resolution by combining a relatively inexpensive imaging element which is inferior in resolution instead of an expensive high-resolution imaging element.SOLUTION: A luminous flux separation imaging device includes a luminous flux separation prism 10 including a first prism 11 having an incident surface 11a, a separation surface 11b on which a separation film 13 is formed, and an exit surface 11c, and an angle θ formed by the incident surface 11a and the separation surface 11b is smaller than 45 degrees, and a second prism 12 having an incident surface 12a and an exit surface 12b, a reflected light imaging element 1 that faces the exit surface 11c of the first prism 11 and captures at least half of the image of an object, a transmitted light imaging element 2 that faces the exit surface 12b of the second prism 12 and captures at least the other half of the image of the object, and a signal processing unit that synthesizes an image signal from the reflected light imaging element 1 and the transmitted light imaging element 2 into one image signal corresponding to the image of the object, and a normal image is acquired by the reflected light imaging element 1 and the transmitted light imaging element 2.SELECTED DRAWING: Figure 2

Description

The present invention relates to a luminous flux separation imaging device that divides an image of an object into a plurality of images using a luminous flux separation optical system and images the image.

In recent years, the image pickup element of a video camera corresponds to an image for a wide display having an aspect ratio of 16: 9, and has 1920 × 1080 pixels for high-definition, 2K, which is also called HD, 3840 × 2160 pixels for 4K, 7680 × 4320. The resolution is gradually increasing, such as for 8K, and many types of products are easily available as general-purpose products. These image pickup devices become more expensive as the resolution increases to 2K, 4K, and 8K.

Image sensors are also used to acquire images of objects in medical cameras used for endoscopes, dermoscopes, microscopes, etc., astronomical cameras used for telescopes, binoculars, and the like. Since these medical cameras acquire an image with a circular field of view, a conventional standard resolution image pickup device with an aspect ratio of 4: 3, also called SD, or an aspect ratio of 1: 1 is used to match the circular image. The almost dedicated imaging device of No. 1 is preferred and frequently used.

Attempts have also been made to acquire high-resolution images in medical cameras and the like. For example, as shown in FIG. 1A, a high-resolution image sensor with an aspect ratio of 16: 9 for a wide display, which is available as a general-purpose product, is used, and a portion corresponding to a circular image is used in the image pickup area. May be imaged. Further, as shown in FIG. 1 (b), an expensive high-resolution image sensor is replaced with two image sensors that are inferior in resolution but relatively inexpensive, and a circular image is converted into reflected light and transmitted light by a half mirror. It is also conceivable to divide and image the reflected light image and the transmitted light image with two image sensors, and combine the two captured images to acquire a circular image. The method of synthesizing the images divided and captured in this way is known as a method of converting the aspect ratio (see, for example, Patent Document 1). A technique for obtaining a high-resolution image by combining a standard-resolution image sensor is also provided (see Patent Document 2).

Japanese Unexamined Patent Publication No. 7-140954 Japanese Unexamined Patent Publication No. 6-269010

However, when a circular image is imaged using a part of the image pickup area of the high resolution image pickup element having an aspect ratio of 16: 9 for a wide display as shown in FIG. 1A, the central portion of the image pickup area is taken. Only used for imaging. Therefore, in an expensive high-resolution image sensor, a considerable part of the image pickup area is not used for image pickup and is wasted.

As shown in FIG. 1B, when the image is divided into reflected light and transmitted light by a half mirror, two image pickup elements are combined to take an image, and the captured images are combined, the half mirror depends on the angle. Due to the change in the reflection characteristics, the reflected light image and the transmitted light image may not have the same image quality. In addition, the reflected light image becomes a mirror image (back image) due to reflection by the half mirror and returns to a normal image (front image) similar to the transmitted light image, so it is necessary to add an optical member or perform signal processing. there were.

The present invention is provided in view of the above circumstances, and a circular image such as a medical camera can be obtained by combining an image sensor having a lower resolution but a relatively low cost in place of an expensive high-resolution image sensor. It is an object of the present invention to provide a luminous flux separation image pickup device capable of taking an image with high resolution.

In order to solve the above-mentioned problems, the light beam separation imaging device according to the present application is a light beam separation prism that captures an image of an object and separates incident light from the object into transmitted light and reflected light. An incident surface on which incident light traveling along the optical axis is incident and a separation film are formed, and the separation film reflects a part of the incident light toward the incident surface as reflected light and the rest as transmitted light. A first prism and a first prism whose angle formed by the incident surface and the separation surface is smaller than 45 °, including an exit surface from which the reflected light reflected by the separation film and totally reflected by the incident surface is emitted. A second prism that includes an incident surface that is in contact with the separation surface via a separation film and that is incident with transmitted light that has passed through the separation film of the separation surface of the first prism, and an exit surface that emits transmitted light that travels along the optical axis. A light beam separation prism including A transmitted light image pickup element that is installed and images at least the other half of the image of the object from the transmitted light, a reflected light image signal from the reflected light image pickup element, and a transmitted light image signal from the transmitted light image pickup element. A signal processing unit that synthesizes a single video signal corresponding to the image of the above is included, and a normal image is acquired by the reflected light imaging element and the transmitted light imaging element.

The reflected light image sensor may image at least the upper half of the image of the object from the reflected light, and the transmitted light image sensor may image at least the lower half of the image of the object from the transmitted light. The reflected light image sensor may image at least the lower half of the image of the object from the reflected light, and the transmitted light image sensor may image at least the upper half of the image of the object from the transmitted light.

The image of the object is circular, at least half of the image of the object imaged by the reflected light image sensor contains at least a semicircular image, and at least the other half of the image of the object imaged by the transmitted light image sensor is at least. Other semicircular images may be included.

The reflected light image sensor and the transmitted light image sensor may have an aspect ratio of 16: 9. The reflected light image sensor and the transmitted light image sensor may have 1920 × 1080 pixels or 3840 × 2160 pixels.

The luminous flux separation imaging device may have a flange back length suitable for the C mount adapter.

According to the present invention, it is possible to capture a circular image of a medical camera or the like with high resolution by combining an expensive high-resolution image sensor with an inferior but relatively inexpensive image sensor.

It is a figure explaining the conventional technique which image | image | image | image | image | image | image | image | image of a circular image with a high-resolution image sensor for a wide display. It is a figure which shows the schematic structure of the luminous flux separation image pickup apparatus of this embodiment. It is a schematic diagram which shows the relationship between the image pickup area of the transmitted light image sensor and the reflected light image sensor of the light flux separation image sensor of this embodiment, and the image image | formed. It is a figure which shows one aspect which displays the video signal output from the luminous flux separation image pickup apparatus of this embodiment on a display. It is a figure which shows the other aspect which displays the video signal output from the luminous flux separation image pickup apparatus of this embodiment on a display.

Hereinafter, the luminous flux separation imaging device of the present embodiment will be described in detail with reference to the drawings. In the present embodiment, a circular image provided by a medical camera or the like is assumed as an image of an object to be imaged. Further, the luminous flux separation imaging device of the present embodiment includes a luminous flux separation optical system that separates incident light into transmitted light and reflected light, and divides an image into transmitted light and reflected light separated by the luminous flux separation optical system. Each image is taken using an image pickup element of a general-purpose product. In the present specification, the optical image of the object to be imaged on the image sensor is referred to as an image, and the moving image acquired by photoelectric conversion of the optical image by the image sensor is referred to as an image.

The image sensor is a combination of two 4K image sensors with 3840 x 2160 pixels, which are inferior in resolution but relatively inexpensive, in place of the expensive 7680 x 4320 pixel image sensor for 8K, and each has a transmitted light image and reflected light. It is assumed that an image is imaged and a transmitted light image and a reflected light image are combined to obtain a circular image corresponding to a resolution of 8K.

FIG. 2 is a diagram showing a schematic configuration of the luminous flux separation imaging device of the present embodiment. The luminous flux separation imaging device has a luminous flux separation optical system that separates the incident light 100 into the reflected light 101 and the transmitted light 102. The luminous flux separation optical system is composed of a luminous flux separation prism 10 having a first prism 11 and a second prism 12. In the luminous flux separation prism 10, the first prism 11 and the second prism 12 are provided in the direction in which the incident light 100 travels along the optical axis L.

The first prism 11 is formed of a glass material, is orthogonal to the optical axis L, and has an incident surface 11a on which the incident light 100 is incident. Further, the first prism 11 has a separation surface 11b in which a separation film 13 is formed on the surface thereof, forms an angle θ smaller than 45 degrees with the incident surface 11a, and intersects at the lower part in the drawing. The separation film 13 reflects a part of the incident light 100 from the incident surface 11a as the reflected light 101, and transmits the rest as the transmitted light 102. The separation film 13 separates the incident light 100 so that the reflected light 101 and the transmitted light 102 have the same characteristics and are separated by a one-to-one amount of light.

The first prism 11 has an exit surface 11c that intersects the entrance surface 11a and the separation surface 11b at the upper part in the drawing. The reflected light 101 reflected by the separation film 13 of the separation surface 11b is totally reflected by the incident surface 11a and emitted from the emission surface 11c. The exit surface 11c is orthogonal to the emitted reflected light 101. The reflected light 101 emitted from the exit surface 11c is reflected twice by the separation film 13 of the separation surface 11b and the incident surface 11a to give a normal image (representation image).

The second prism 12 is made of a glass material, extends along the optical axis L, faces the incident surface 11b of the first prism 11, and faces the incident surface 12a and the incident surface 12a that are in contact with each other with the separation film 13 interposed therebetween. It has an exit surface 12b. The exit surface 12b is orthogonal to the optical axis L. The transmitted light 102 transmitted through the separation film 13 formed on the separation surface 11b of the first prism 11 is incident on the incident surface 12a, and the transmitted light 102 travels along the optical axis L and is emitted from the emission surface 12b. .. The transmitted light 102 emitted from the exit surface 12b gives a normal image because it is not reflected.

The luminous flux separation imaging device includes a reflected light imaging element 1 provided so as to face the emission surface 11c of the first prism 11 and a transmitted light imaging element 2 provided so as to face the emission surface 12b of the second prism 12. Have. Both the reflected light imaging element 1 and the transmitted light imaging element 2 are composed of a 4K image pickup element having an aspect ratio of 16: 9 for a wide display and 3840 × 2160 pixels. The reflected light imaging element 1 and the transmitted light imaging element 2 capture images of the reflected light 101 and the transmitted light 102, respectively, and provide them by photoelectrically converting them into a reflected light image signal and a transmitted light image signal.

The reflected light image sensor 1 sandwiches a predetermined gap in the emission surface 11c of the first prism 11 so that the upper half of the reflected light image is imaged in the imaging region and the upper half of the image by the reflected light 101 is imaged. Therefore, it is installed so as to face substantially the upper half surface of the exit surface 11c. The transmitted light image sensor 2 sandwiches a predetermined gap between the exit surface 12b of the second prism 12 so that the lower half of the transmitted light image is imaged in the imaging region and the lower half of the image by the transmitted light 102 is imaged. Therefore, it is installed so as to face substantially the lower half surface of the exit surface 12b.

In the schematic view A at the upper part of FIG. 2, when the image pickup areas of the reflected light image sensor 1 are stacked and arranged in parallel to each other in the image pickup area of the transmitted light image sensor 2, the reflected light image sensor 1 The positional relationship between the reflected light image PR imaged in 1 and the transmitted light image PT imaged on the transmitted light image sensor 2 is shown. FIG. 3 is a schematic diagram showing in more detail the positional relationship between the reflected light image PR imaged on the reflected light image sensor 1 and the transmitted light image PT imaged on the transmitted light image sensor 2 shown in the schematic diagram A. .. The reflected light image sensor 1 is formed with an upper semicircular reflected light image PR corresponding to the upper half of the circular image of the object. A lower semicircular transmitted light image PT corresponding to the lower half of the circular image of the object is formed on the transmitted light image sensor 2. Both the reflected light image PR and the transmitted light image PT are normal images.

As shown in FIG. 3, both the reflected light image sensor 1 and the transmitted light image sensor 2 have an aspect ratio of H1: V1 of 16: 9, and when these the reflected light image sensor 1 and the transmitted light image sensor 2 are combined, the aspect ratio is H1: V2 is 16:18. On the other hand, the circular image in which the upper semicircular reflected light image PR and the lower semicircular transmitted light image PT are combined has an aspect ratio of H1: H2 = 1: 1. The aspect ratio H1: V2 = 16:18 of the reflected light imaging element 1 and the transmitted light imaging element 2 combined is close to the aspect ratio H1: H2 = 1: 1 of the circular image, and the reflected light imaging element 1 and the transmitted light imaging element 1 and the transmitted light imaging element It can be said that most of the imaging region of No. 2 is effectively used for imaging a circular image.

The luminous flux separation imaging device includes a signal processing unit (not shown) that synthesizes an image of an object from the reflected light image PR imaged by the reflected light imaging element 1 and the transmitted light image PT imaged by the transmitted light imaging element 2. There is. The signal processing unit includes a reflected light image signal obtained by converting the reflected light image PR of the upper half circle of the circular image of the object from the reflected light imaging element 1 into an electric signal, and a circular image of the object from the transmitted light imaging element 2. The transmitted light image PT of the lower half circle of the image is combined with the transmitted light image signal converted into an electric signal, and the combined image signal corresponding to the circular image of the object is output. The signal processing unit can be implemented by a well-configured electronic circuit, including, for example, a digital signal processor (DSP).

The luminous flux separation imaging device may have a flange back length of 17.526 mm corresponding to the C mount adapter so that the lens 5 can be attached to the lens mount of the C mount 4. Further, various filters such as an ultraviolet cut filter or an infrared cut filter may be attached on the optical path of the luminous flux separation imaging device.

In the light beam separation imaging device, the incident light 100 from the object is separated into the reflected light 101 and the transmitted light 102 by the light beam separating prism 10, and the reflected light image and the transmitted light image are separated into the reflected light imaging element 1 and the transmitted light imaging element, respectively. It is imaged in 2 and combined into one image corresponding to the object. Here, in the reflected light image, the reflection characteristic changes depending on the angle such that the separation surface 11b increases with the incident surface 11a due to the reflection by the separation film 13, but the angle θ is changed. By making it smaller than 45 degrees, the change in the reflection characteristic is suppressed so that the image quality equivalent to that of the transmitted light image can be obtained. By synthesizing the reflected light image and the transmitted light image having the same image quality, an image of an object having a uniform image quality can be obtained.

On the other hand, the reflected light image sensor 1 is provided so as to face the exit surface 11c of the first prism 11, and the reflected light image sensor 1 images the upper half of the circular image from the reflected light 101 emitted from the emission surface 11c. It corresponds to the upper half of the image so that you can get it. In order to supply the reflected light 101 to the reflected light image sensor 1, it is necessary to secure an emission surface 11c having a certain size corresponding to the reflected light image sensor 1. Therefore, the angle θ formed by the incident surface 11a and the separating surface 11b of the first prism 11 may be such that the above-mentioned reflected light image sensor 1 can secure a range in which substantially half of the image of the object can be acquired. ..

In the luminous flux separation image sensor, the reflected light image sensor 1 and the transmitted light image sensor 2 are formed with the upper half and the lower half of a circular image in the imaging region, respectively, and the circular reflected light 101 and the transmitted light 102 are formed. The upper and lower halves of the image are imaged, but the configuration is not limited to this. The reflected light image sensor 1 and the transmitted light image sensor 2 are formed so that at least the lower half and at least the upper half of the circular image are imaged in the imaging region, respectively, and at least below the image of the circular reflected light 101 and the transmitted light 102. Half and at least the upper half may be imaged. In such a case, the reflected light image sensor 1 is installed so as to face substantially the lower half surface of the exit surface 11c of the first prism 11 so that the lower half of the circular reflected light image is formed in the imaging region. May be good. The transmitted light imaging element 2 may be installed so as to face substantially the upper half surface of the exit surface 12b of the second prism 12 so that the upper half of the circular transmitted light image is formed in the imaging region. The reflected light image signal and the transmitted light image signal from the reflected light image sensor 1 and the transmitted light image sensor 2 may overlap with each other including a portion exceeding the lower half or a portion exceeding the upper half of the image. , The overlapping part of the image may be removed by the signal processing unit.

The light beam separation image sensor of the present embodiment is more than using one expensive 7680 × 4320 pixel 8K image sensor for a circular image such as that obtained by a medical camera used for an endoscope or the like. A general-purpose product with inferior resolution but relatively inexpensive 3840 x 2160 pixel 4K image sensor is combined to capture a transmitted light image and a reflected light image, respectively, and the transmitted light image and the reflected light image are 8K by signal processing. It is combined with a circular image corresponding to the resolution of. Since the 8K image sensor is expensive, the cost required for the image sensor can be suppressed by using two relatively inexpensive 4K image sensors. Further, by synthesizing the images captured by the two 4K image sensors, an image corresponding to 8K is realized. In addition, instead of the two 4K image sensors, two 2K image sensors of 1920 × 1080 pixels are used, and the images captured by these image sensors are combined to realize an image equivalent to 4K. May be good.

The luminous flux separation prism 10 constituting the luminous flux separation optical system has the same image quality of each image acquired by separating the incident light 100 from the object into the reflected light 101 and the transmitted light 102 by the above-described configuration. It makes it possible to maintain it as a thing. Further, the luminous flux separation prism 10 gives both the reflected light image and the transmitted light image as normal images (front images) of the reflected light 101 and the transmitted light 102. Therefore, unlike the case where a half mirror is used to separate the luminous flux, it is not necessary to restore the mirror image (back image) to a normal image (front image) by optical members or signal processing, and the mirror image (back image) is a normal image. It is not necessary to provide an optical member to restore the (front image), or to convert the mirror image (back image) into a normal image (front image) by signal processing.

Further, the luminous flux separation prism 10 is less susceptible to blurring due to vibration or movement as compared with the configuration using a half mirror, and can be robust and miniaturized. For this reason, the luminous flux separation imaging device that uses the luminous flux separation prism for the luminous flux separation optical system also has such robustness and can be miniaturized, so that medical treatment that is sensitive to blurring that may occur due to vibration or movement. Suitable for use in applications.

The luminous flux separation imaging device of the present embodiment is expected to have a wide range of applications for medical cameras used in endoscopes, microscopes, dermoscopes, etc., for which miniaturization is desired. Therefore, the luminous flux separation imaging device may be miniaturized by using an interchangeable lens having a flange back of 17.526 mm, which is compatible with the C mount 4 and has a short flange back, which is compatible with the C mount 4.

FIG. 4 is a diagram showing one aspect of displaying a high-resolution circular image acquired by the luminous flux separation imaging device of the present embodiment on a display. This display displays a composite video signal output from the luminous flux separation imaging device of the present embodiment. The light beam separation image pickup device shall synthesize the image acquired by using two 4K image pickup elements into an image equivalent to 8K, and the display is a wide display with a high resolution and an aspect ratio of H3: V2 = 16: 9, which is 7680 ×. It is assumed that 4320 pixels of 8K will be used. In the display, the central display area having an aspect ratio of H1: V2 = 16:18, which is obtained by removing the display areas of width AB from both sides, is used for displaying a circular image.

FIG. 5 is a diagram showing another aspect of displaying a high-resolution circular image acquired by the luminous flux separation imaging device of the present embodiment on a display. This display displays a composite video signal output from the luminous flux separation imaging device of the present embodiment. The light beam separation imaging device synthesizes the image acquired by using two 4K imaging elements into an image equivalent to 8K, and the display is 8K with 7680 x 4320 pixels as a wide display with a high resolution and an aspect ratio of 16: 9. Is supposed to be used. The display area of the display can be horizontally divided into two equal parts, one on the right side and the other on the left side. The same circular image may be displayed on the right side and the left side of the display area, or the image to be comparatively analyzed may be displayed on the right side and the left side. Further, the shooting conditions and the text information for explaining the video may be displayed on one side.

The present invention can be applied to a medical camera or the like used for an endoscope having a circular field of view or the like.

1 Reflected light imaging element 2 Transmitted light imaging element 10 Light beam separation prism 11 First prism 12 Second prism 13 Separation film 100 Incident light 101 Reflected light 102 Transmitted light

Claims (7)

In a light beam separation imaging device that images an object
A luminous flux separation prism that separates incident light from an object into transmitted light and reflected light.
An incident surface on which incident light traveling along the optical axis is incident and a separation film are formed, and the separation film reflects a part of the incident light toward the incident surface as reflected light and the rest as transmitted light. The angle formed between the incident surface and the separated surface is smaller than 45 °. 1 prism and
An incident surface that is in contact with the separation surface of the first prism via the separation film and is incident with transmitted light transmitted through the separation film of the separation surface of the first prism, and the transmitted light traveling along the optical axis are emitted. A light beam separation prism including a second prism including an exit surface and
A reflected light image sensor that is installed facing the exit surface of the first prism and captures at least half of the image of the object from the reflected light.
A transmitted light image sensor which is installed facing the exit surface of the second prism and images at least the other half of the image of the object from the transmitted light.
The reflection includes a signal processing unit that synthesizes a reflected light image signal from the reflected light image sensor and a transmitted light image signal from the transmitted light image sensor into one image signal corresponding to an image of the object. A light beam separation image sensor in which a normal image is acquired by an optical image sensor and the transmitted light image sensor. The first aspect of claim 1, wherein the reflected light image sensor images at least the upper half of the image of the object from the reflected light, and the transmitted light image sensor images at least the lower half of the image of the object from the transmitted light. Luminous flux separation image sensor. The first aspect of claim 1, wherein the reflected light image sensor images at least the lower half of the image of the object from the reflected light, and the transmitted light image sensor images at least the upper half of the image of the object from the transmitted light. Luminous flux separation image sensor. The image of the object is circular, at least half of the image of the object imaged by the reflected light imaging element includes an image of at least a semicircle, and at least the image of the object imaged by the transmitted light imaging element. The luminous flux separation imaging device according to any one of claims 1 to 3, wherein the other half includes at least an image of another semicircle. The luminous flux separation imaging device according to any one of claims 1 to 4, wherein the reflected light imaging element and the transmitted light imaging element have an aspect ratio of 16: 9. The luminous flux separation imaging device according to claim 5, wherein the reflected light image sensor and the transmitted light image sensor have 1920 × 1080 pixels or 3840 × 2160 pixels. The luminous flux separation imaging device according to any one of claims 1 to 6, which has a flange back length suitable for a C-mount adapter.

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