JP2010194041A - Optical system for capsule type endoscope, and capsule type endoscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system for a capsule type endoscope, photographing a side around a capsule, and the capsule type endoscope. <P>SOLUTION: The optical system for the capsule type endoscope 11 is fixed and disposed within the capsule 12, and includes a panoramic lens 21, a diaphragm 22 and an imaging lens 23. The panoramic lens 21 is formed as rotationally symmetrical around the center axis L, and includes two reflection faces and two refraction faces. When light enters the panoramic lens 21 from a subject in the side around the capsule 12, the panoramic lens 21 reflects the light twice internally, and emits the light to the rear of the panoramic lens 21. The diaphragm 22 adjusts the quantity of the subject light from the panoramic lens 21. The imaging lens 23 forms the image of the subject light transmitted through the diaphragm 22 in an imaging element 18 disposed in the rear. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an endoscope that captures an image of the inside of a subject, and more particularly, to a capsule endoscope that is swallowed by a subject.

  Conventionally, insertion-type endoscopes have been widely used in the medical field. An insertion-type endoscope inserts a thin and flexible insertion portion into a subject's body, and images the subject's body with an imaging device provided at the distal end of the insertion portion. The insertion portion is curved in accordance with the shape of the body of the subject, and the orientation of the distal end of the insertion portion provided with the imaging device can be freely adjusted. For this reason, the insertion type endoscope can accurately capture an image of any part of the body of the subject as necessary.

  However, the examination with the insertion type endoscope requires a long insertion part to be inserted into the body for a long time, and therefore the load on the subject is very large. For this reason, in recent years, capsule endoscopes that reduce the load on the subject are known.

  A capsule endoscope includes an imaging device including an imaging lens and an imaging device, a lamp that illuminates a subject, a battery that drives these, an antenna for transmitting a captured image to an external processor device, and the like. It is housed in a capsule of a size that can be easily swallowed, and is swallowed by a subject. For this reason, the capsule endoscope sequentially captures the state of the digestive tract while naturally moving in the digestive tract of the subject.

  On the other hand, since the capsule endoscope is swallowed and used by the subject as described above, it is difficult to control the position and posture of the subject in the body. For this reason, the imaging device of the capsule endoscope is equipped with a wide-angle imaging lens so that a wide range can be photographed at once. For example, an example in which a wide-angle imaging lens having an angle of view close to 180 degrees is mounted is also known.

  In addition, the capsule of the capsule endoscope has a shape in which both ends of the cylinder are formed in a dome shape. When the capsule endoscope moves in the digestive tract, the dome-shaped distal end portion is in the direction of the digestive tract. Move along the line. For this reason, the imaging device mounted on the capsule endoscope is arranged so as to photograph the state of the digestive tract from one end of the capsule formed in a dome shape with the front front as a center.

  However, since the digestive tract photographed with a capsule endoscope is tubular, it is difficult to accurately examine from a distant image captured near the center of the acquired image, and it is copied to the peripheral part of the acquired image. Examination is performed using the image of the surrounding side of the capsule.

  As described above, in the capsule endoscope, the image around the capsule is more important than the image in front of the capsule. Therefore, the image pickup apparatus can be rotated around the center axis of the capsule. 2. Description of the Related Art A capsule endoscope is known that is provided so as to be rotatable about a central axis of a capsule toward the side of the capsule and that images the side of the capsule while rotating the capsule endoscope (Patent Document 1). ).

  Similar to the capsule endoscope, an example of an imaging device in which it is important to take an image of the surrounding side rather than the front front of the imaging device is a surveillance camera provided on a ceiling or the like. In such a surveillance camera, the front front along the central axis of the surveillance camera is the ground or the floor, so it is difficult to check the face of a person even if the front of the camera is photographed. On the other hand, it is important to photograph the surrounding side. In the case of a surveillance camera, it is necessary to capture 360 degrees around the surveillance camera without omission in order not to create a blind spot.

  In this way, a lens (hereinafter referred to as a panoramic lens) used when the subject is not the front front but 360 ° with respect to the central axis of the lens (hereinafter referred to as a panoramic lens) is generally formed in an abacus ball shape and has an annular shape facing each other. One of the surfaces is a refracting surface, the other is a reflecting surface, a circular refracting surface is provided at the center of the reflecting surface, and a circular reflecting surface is provided at the center of the refracting surface. A panoramic lens is known in which light is reflected twice inside and emitted from a circular refracting surface (Patent Document 2).

JP 2007-159642 A JP 2003-195170 A

  As described above, in the diagnosis using the capsule endoscope, it is required to capture the surrounding side of the capsule without omission from the front side of the capsule. At the same time, the capsule endoscope is required to be configured as small as possible in order to reduce the burden when the subject swallows.

  However, as in the capsule endoscope of Patent Document 1, when the built-in imaging device is provided so as to be rotatable toward the side of the capsule, the imaging device is fixed and provided in front of the front. Since a new mechanism for rotating the imaging device has to be provided, the size of the capsule increases accordingly.

  In addition, since the capsule endoscope cannot be supplied with electric power from the outside, it is supplied with power from a built-in battery with a limited capacity. High power consumption. Further, when the imaging device is rotated, the number of times of photographing necessary for photographing the periphery of the capsule without omission increases. As a result, the number of times the captured image is transmitted to the processor device increases, and the power consumption accordingly increases. For this reason, when rotating the imaging device, it is necessary to use a battery having a larger size than when the imaging device is fixedly provided, and the entire size of the capsule endoscope is enlarged.

  The present invention has been made in view of the above-described problems, and is a capsule-type internal endoscope that can shoot a peripheral side of a capsule without omission while fixing an imaging device and suppressing power consumption. An object is to provide an optical system for a mirror and a capsule endoscope.

  An optical system for a capsule endoscope of the present invention is formed in an annular shape that is curved so as to be convex outward, and has a first refractive surface that refracts light incident from a lateral subject and enters the inside. The light refracted by the first refracting surface is formed in an annular shape that is provided at a position facing the first refracting surface and is curved in the opposite direction to the first refracting surface so as to be convex outward. A first reflecting surface that reflects, a second reflecting surface that is provided at the center of the first refracting surface so as to be convex toward the inside, and that reflects light reflected by the first reflecting surface; A rotationally symmetric panorama having a second refracting surface provided at the central portion of the first reflecting surface so as to be convex toward the inside and refracting light incident from the second reflecting surface and exiting to the outside. Adjust the amount of light from the lens and the subject emitted from the panoramic lens A diaphragm that, the light from the subject having passed through the aperture, characterized in that it and a focusing lens for forming the image pickup element provided in the rear.

  The first refracting surface, the first reflecting surface, the second reflecting surface, and the second refracting surface are spherical surfaces.

  In addition, the first reflecting surface is formed as a mirror surface on the outer surface side of the panoramic lens, and includes an illuminating unit that reflects the first reflecting surface on the outer surface side of the panoramic lens and irradiates the subject with illumination light. It is characterized by.

  The capsule endoscope of the present invention is characterized in that the above-described capsule endoscope optical system and imaging optical system are provided in a capsule that can be swallowed.

  In addition, an opening is provided at one end of the capsule, and the first refractive surface and the first reflecting surface of the panoramic lens are exposed from the opening, and the capsule and the panoramic lens provided with the opening have an outer shape. Is formed.

  Advantageous Effects of Invention According to the present invention, an optical system for a capsule endoscope capable of photographing a peripheral side of a capsule without omission while arranging an imaging device fixed and suppressing power consumption, and the capsule type An object is to provide an endoscope.

It is explanatory drawing which shows the structure of a capsule type | mold endoscope. It is a perspective view which shows the external appearance of a panoramic lens. It is explanatory drawing which shows the imaging | photography range of a capsule type | mold endoscope, and the image acquired. It is explanatory drawing which shows the optical path in a panoramic lens. It is explanatory drawing which shows arrangement | positioning of LED for illumination. It is explanatory drawing which shows the capsule endoscope which exposed the panoramic lens from the capsule.

  As shown in FIG. 1, a capsule endoscope 11 is a capsule 12 in which a small imaging device 13 is stored in a watertight manner, and is swallowed by a subject. Further, the capsule endoscope 11 captures an image of the state of the inner wall of the digestive tract (hereinafter referred to as a subject) while moving naturally within the body of the subject.

  The capsule 12 has a shape in which both ends of the cylinder are formed in a dome shape, and has a size that can be easily swallowed by the subject. The capsule 12 is made of a transparent material so as not to hinder the photographing of the subject by the built-in imaging device 13. Further, in the capsule 12, in addition to the imaging device 13, a battery that supplies power to the imaging device 13, an antenna that transmits an image acquired by the imaging device 13 to an external processor device, and the like (both shown) Not stored).

  The imaging device 13 includes an imaging optical system 16, an LED 17 (illumination unit), and an imaging element 18, and images 360 degrees around the capsule 12. The imaging device 13 is arranged at the center of the capsule 12 so that the central axis L is parallel to the capsule 12.

  The imaging optical system 16 includes a panoramic lens 21, an aperture stop 22, and an imaging lens 23 in order from the subject side, and is fixedly disposed in the capsule 12. The panoramic lens 21 is provided in a rotationally symmetric shape around the central axis L. The panoramic lens 21 transmits light incident from the side of the capsule 12 (direction perpendicular to the central axis L) rather than the front (the tip side of the capsule 12 formed in a dome shape). ).

  The aperture stop 22 is a stop provided with an opening having a predetermined size in the center, and adjusts the amount of light from the panoramic lens 21. The imaging lens 23 forms an image of the light from the panoramic lens 23 on the imaging surface of the imaging element 18.

  The LED 17 is a light source that illuminates the subject, and is disposed behind the panoramic lens 21. A plurality of LEDs 17 are arranged around the central axis L, and irradiate illumination light substantially uniformly over the entire imaging range of the imaging device 13. The imaging element 18 photoelectrically converts the light imaged on the imaging surface by the imaging lens 23 for each pixel and outputs it as a digital image. An image acquired by the image sensor 18 is transmitted to a processor device provided outside by an antenna (not shown).

  As shown in FIG. 2, the panoramic lens 21 is generally formed into an abacus ball shape, but includes four optical surfaces. First, two optical surfaces, a reflecting surface 31 (second reflecting surface) and a refracting surface 32 (first refracting surface), are provided on the upper surface of the panoramic lens 21 facing the front of the capsule 12. In addition, two optical surfaces, a reflecting surface 33 (first reflecting surface) and a refracting surface 34 (second refracting surface), are provided on the lower surface of the panoramic lens 21 facing the capsule 12.

  The reflection surface 31 is provided in a circular shape at the center of the top surface of the panoramic lens 21 and is a spherical concave surface that is recessed toward the inside of the panoramic lens 21. Further, the reflection surface 31 is coated with a reflection film in which the inner surface side of the panoramic lens 21 is a mirror surface so as to reflect light inside the panorama lens 21. For this reason, light does not enter the inside of the panoramic lens 21 from the outside of the panoramic lens 21 through the reflecting surface 31. When light enters the reflecting surface 31 from the inside of the panoramic lens 21, the reflecting surface 31 Then, the light is guided to the refractive surface 34 behind the panoramic lens 21.

  The refracting surface 32 is provided on the upper surface of the panoramic lens 21 around the reflecting surface 31 so as to surround the reflecting surface 31, and is an annular curved surface that is curved so as to protrude forward as a whole. The refracting surface 32 is a convex surface that swells in a spherical shape toward the outside of the panoramic lens 21. Light enters the refracting surface 32 from a subject located on the side of the periphery of the capsule 12. Light from the subject (hereinafter referred to as subject light) enters the interior of the panoramic lens 21 and is refracted by the refracting surface 32 and guided to the reflecting surface 33 provided on the lower surface side of the panoramic lens 21.

  The reflecting surface 33 is provided around the refracting surface 34 so as to surround the refracting surface 34 so as to face the refracting surface 32 on the upper surface, and is a circular curved surface that is curved so as to protrude rearward as a whole. The reflection surface 33 is a convex surface that swells in a spherical shape toward the outside of the panoramic lens 21. Further, the reflection surface 33 is coated with a reflection film in which both the inner surface side and the outer surface side of the panoramic lens 21 are mirror surfaces. For this reason, when subject light is incident on the inner surface side of the reflecting surface 33 through the refracting surface 32, the reflecting surface 33 reflects this and enters the reflecting surface 31 on the upper surface side.

  On the other hand, illumination light is incident from the LED 17 on the outer surface side of the reflecting surface 33. Since the reflecting surface 33 is a convex mirror when viewed from the outer surface side of the panoramic lens 21 on which the LEDs 17 are arranged, the illumination light from the LED 17 is reflected at a wide angle by the reflecting surface 33 and irradiates the subject. Is done. As a result, illumination light is evenly applied to the entire imaging range of the imaging device 13.

  The refracting surface 34 is provided in a circular shape at the center of the lower surface of the panoramic lens 21 and is a spherical concave surface that is recessed toward the inside of the panoramic lens 21. Subject light is incident on the refracting surface 34 from a reflecting surface 31 at the center of the upper surface of the panoramic lens 21. At this time, the subject light is refracted in a direction to converge when passing through the refracting surface 34 and guided to the aperture stop 22.

  In the panoramic lens 21, the radius of curvature of the reflective surface 31 is 1.76 mm, the radius of curvature of the refractive surface 32 is 2.80 mm, the radius of curvature of the reflective surface 33 is 2.64 mm, and the radius of curvature of the refractive surface 34 is 5.20 mm. It has become. The distance between the reflecting surface 31 and the refractive surface 34 along the central axis is 2.40 mm, and the diameter of the panoramic lens 21 (the diameter in the direction perpendicular to the central axis) is 4.87 mm.

  As described above, since the imaging optical system 16 of the imaging device 13 includes the panoramic lens 21, the band-shaped portion around the capsule 12 is not the front front of the capsule 12 but the capsule endoscope 11. The shooting range.

  As shown in FIG. 3A, when the capsule endoscope 11 is swallowed by the subject, the capsule endoscope 11 naturally moves in the digestive tract 41 of the subject. Therefore, the inner wall of the subject's digestive tract becomes the subject 42 of the capsule endoscope 11. The digestive tract 41 through which the capsule endoscope 11 moves has a tubular structure. For this reason, when the capsule endoscope 11 moves in the digestive tract 41, the front and rear tip portions formed in a dome shape move in a state substantially along the direction of the digestive tract 41.

  Thus, when the capsule endoscope 11 moves in the digestive tract 41, the capsule endoscope 11 images the subject 42 almost continuously. At this time, since the capsule endoscope 11 includes the panorama lens 21 in the imaging optical system 16 of the built-in imaging device 13, the imaging range 43 of the capsule endoscope 11 is the front front (X Direction), not the direction.

  The panoramic lens 21 has a rotationally symmetric shape around the central axis L. For this reason, the imaging range 43 is a range that is continuous in a band around 360 degrees around the capsule endoscope 11, and the capsule endoscope 11 images the subject 42 in the imaging range 43 at a time. Further, the capsule endoscope 11 moves in the digestive tract 41 while photographing a photographing range 43 in a predetermined direction with respect to the capsule endoscope 11 substantially continuously. Therefore, the capsule endoscope 11 images the subject 42 without omission.

  In this way, in the image 44 acquired by the capsule endoscope 11, as shown in FIG. 3B, the imaging range 43 is projected as an annular image 46. At this time, if the front end direction of the capsule 12 on which the panoramic lens 21 is disposed is the front X, and the front end direction of the capsule 12 on which the image sensor 18 is disposed is the rear Y, the image 46 in the imaging range 43 has the front X on the inner side. It becomes an annular image with the rear Y positioned outside. In addition, the moving direction of the capsule endoscope 11 may not match the front and rear XY of the capsule endoscope 11, and the capsule endoscope 11 may move in the backward Y direction. Similarly, in such a case, an annular image 46 in which the front X corresponds to the inner side and the rear Y corresponds to the outer side is photographed regardless of the moving direction of the capsule endoscope 11.

  As described above, when the subject 42 is photographed by the capsule endoscope 11, the subject light from the photographing range 43 first enters the refracting surface 32 on the top surface of the panoramic lens 21, as shown in FIG. At this time, the subject light passes through the refracting surface 32 and enters the panoramic lens 21, and is refracted according to the incident angle and curvature on the refracting surface 32, and enters the reflecting surface 33 on the lower surface of the panoramic lens 21.

  Next, the subject light incident on the reflecting surface 33 is reflected inside the panoramic lens 21 in accordance with the incident angle and curvature on the reflecting surface 33 and enters the reflecting surface 31 at the center of the upper surface of the panoramic lens 21. Then, the subject light is reflected by the reflecting surface 31, reaches the refracting surface 34 at the center of the bottom surface of the panoramic lens 21, is refracted according to the incident angle and curvature to the refracting surface 34, and passes through the refracting surface 34 to pass through the panoramic lens 21 is emitted to the outside.

  Thus, when the subject light from the imaging range 43 is emitted from the peripheral side of the capsule endoscope 11 toward the panoramic lens 21 along the central axis L, the subject light passes through the aperture stop 22. Then, the light enters the imaging lens 23. Then, the subject light is imaged on the imaging surface of the imaging element 18 by the imaging lens 23. At this time, subject light from the front X side forms an image on the center side of the image sensor 18, and subject light from the rear Y side forms an image on the outside of the image sensor 18. Thereby, in the acquired image 44, the strip-shaped imaging range 43 along the cylindrical digestive tract 41 is projected in an annular shape.

  Further, as described above, the capsule endoscope 11 takes an image of the inner wall of the digestive tract 41 as a subject 42, but since the inside of the digestive tract 41 is a dark place, the capsule endoscope 11 has at least an imaging range. 43 must be illuminated in a state suitable for shooting. Therefore, as shown in FIG. 5, the capsule endoscope 11 is provided with the LED 17 at a position where the imaging range 43 can be illuminated without omission.

  The LED 17 is disposed between the panoramic lens 21 and the aperture stop 22. In addition, the LED 17 is not disposed toward the photographing range 43 but is disposed toward the reflecting surface 33 on the lower surface of the panoramic lens 21. Since the reflection surface 33 is also a mirror surface on the outer surface side of the panoramic lens 21 as described above, the illumination light emitted from the LED 17 is reflected toward the photographing range 43 by the reflection surface 33. At this time, since the reflecting surface 33 is a convex mirror surface when viewed from the outside of the panoramic lens 21 (on the LED 17 side), the illumination light from the LED 17 is magnified and reflected toward the photographing range 43. For this reason, similarly to a general LED, even if the orientation angle of the LED 17 is about 30 to 40 degrees, the LED 17 illuminates the entire imaging range 43 wider than this substantially uniformly.

  Here, for example, a case is considered in which the LED 51 having an orientation angle of about 30 to 40 degrees is arranged at substantially the same position as the LED 17 instead of the LED 17 to illuminate the photographing range 43. At this time, unlike the LED 17, the LED 51 is arranged so that the illumination light is directly irradiated in the direction of the photographing range 43 without passing through the reflection surface 33 of the panoramic lens 21. As described above, when the illumination light is irradiated toward the photographing range 43 by the LED 51 arranged in place of the LED 17, the orientation angle of the LED 51 is small and the distance from the LED 51 to the photographing range 43 is short. Light is applied only to a part of the imaging range 43.

  Further, for example, consider a case in which the LED 52 having an orientation angle of about 30 to 40 degrees is arranged at a position different from the LED 17 instead of the LED 17 and the photographing range 43 is directly illuminated. At this time, the LED 52 is disposed behind the LED 17 so that illumination light is irradiated from the front X side to the rear Y side of the imaging range 43. Further, the LED 52 is arranged in the direction in which the illumination light is directly irradiated in the direction of the photographing range 43 without using the reflecting surface 33 of the panoramic lens 21 like the LED 17.

  As described above, according to the LED 52 arranged instead of the LED 17, the illumination light is irradiated from the front X side to the rear Y side of the imaging range 43, but as shown in FIG. 5, compared with the position of the LED 17. It must be located far away from the shooting range 43, and an optical path of illumination light from the LED 52 to the shooting range 43 must be secured.

  However, since the capsule endoscope 11 is swallowed by the subject, the size of the capsule 12 needs to be made as small as possible, but the illumination light source is positioned at the position of the LED 52 that secures the optical path of the illumination light. In order to place the capsule 12, the size of the capsule 12 must be increased. In addition, since a battery or the like for driving the capsule endoscope 11 is disposed at the position of the LED 52, it is difficult to secure a space for disposing the LED 52.

  For this reason, when the peripheral side of the capsule endoscope 11 is photographed by providing the imaging optical system 16 with the panoramic lens 21, the reflection surface 33 on the lower surface of the panoramic lens 21 is set to the outer surface side as described above. It is also preferable that the light source for illumination is disposed at the position of the LED 17 and the illumination range is irradiated to the photographing range 43 via the reflection surface 33.

  As described above, since the capsule endoscope 11 includes the panoramic lens 21 in the imaging optical system 16, the peripheral side of the capsule endoscope 11 (capsule 12) can be imaged at once without omission. Can do. Further, since the capsule endoscope 11 is arranged with the imaging optical system 16 fixed in the capsule 12, the capsule endoscope that takes an image of the side of the capsule while rotating the built-in imaging device. Compared with the power consumption can be reduced.

  Further, the panoramic lens 21 provided in the capsule endoscope 11 has four optical surfaces and has a complicated shape. However, the reflecting surfaces 31 and 33 and the refracting surfaces 32 and 34 are all spherical. is doing. For this reason, the imaging optical system 16 of the capsule endoscope 11 can be designed and manufactured relatively easily.

  Further, in the capsule endoscope 11, the reflecting surface 33 on the lower surface of the panoramic lens 21 is a mirror surface on both the inner surface side and the outer surface side, and the illumination light from the LED 17 is reflected by the outer surface of the reflecting surface 33. LED17 is arrange | positioned so that 43 may be irradiated. For this reason, even if it is a light source with a small orientation angle like LED, illumination light can be appropriately irradiated to the whole wide imaging | photography range 43 of the capsule endoscope 11. FIG.

  Further, by irradiating the photographing range 43 with illumination light through the reflecting surface 33 on the lower surface of the panoramic lens 21 in this way, the LED 17 can be provided substantially integrally with the imaging optical system 16 in the vicinity of the panoramic lens 21. it can. Thereby, the imaging device 13 incorporated in the capsule endoscope can be configured to be small, and the size of the capsule endoscope 11 as a whole (size of the capsule 12) can be reduced.

  In the above-described embodiment, an example in which each optical surface (the reflecting surfaces 31 and 33 and the refracting surfaces 32 and 33) of the panoramic lens 21 is a spherical surface has been described. Some or all of them may be aspherical to suppress aberrations.

  In the above-described embodiment, an example in which the LED 17 is disposed between the panoramic lens 21 and the aperture stop 22 has been described. However, when the illumination range is irradiated onto the imaging range 43 via the reflecting surface 33 on the lower surface of the panoramic lens 21. The position where the LED for illumination is arranged is not limited to this. For example, it may be disposed behind the aperture stop 22 (on the image sensor 18 side), or may be disposed adjacent to the imaging lens 23. That is, the illumination light source is preferably arranged so that the entire imaging device 13 is configured as small as possible in accordance with the size of the panoramic lens 21 and the curvature of the reflecting surface 33.

  In the above-described embodiment, the capsule 12 and the imaging optical system 16 are provided independently, and the example in which the imaging optical system 16 is disposed in the capsule 12 has been described. However, the imaging optical system 16 is a capsule. 12 may be exposed to the outside. For example, as shown in FIG. 6, the imaging optical system 16 is arranged on a capsule 62 having an opening at one end so that the upper surface (the reflecting surface 31 and the refracting surface 32) of the panoramic lens 21 is exposed from this opening. Thus, the capsule endoscope 63 may be configured. Thus, the capsule endoscope is further reduced in size by exposing the upper surface of the panoramic lens 21 from the capsule 62 and forming the outer shape of the capsule endoscope with the capsule 61 and the upper surface of the panoramic lens 21. Can do.

  In the above-described embodiment, the entire capsule 12 is made of a transparent material. However, the entire capsule 12 is not necessarily made of a transparent material, and at least a range through which illumination light and subject light are transmitted is transparent. What is necessary is just to be comprised from the material.

DESCRIPTION OF SYMBOLS 11,63 Capsule type endoscope 12,62 Capsule 13 Imaging device 16 Imaging optical system 17 LED (illumination means)
18 Image sensor 21 Panoramic lens 22 Aperture stop 23 Imaging lens 31 Reflecting surface (second reflecting surface)
32 Refraction surface (first refraction surface)
33 Reflective surface (first reflective surface)
34 Refraction surface (second refraction surface)
41 Gastrointestinal tract 42 Subject 43 Shooting range

Claims (5)

A first refracting surface which is formed in an annular shape which is curved so as to protrude outward, refracts light incident from a lateral subject and enters the inside, and is provided at a position facing the first refracting surface. A first reflecting surface which is formed in an annular shape curved in the opposite direction to the first refracting surface so as to be convex outward, and reflects light refracted by the first refracting surface; and A central portion is provided so as to be convex toward the inside, a second reflective surface that reflects light reflected by the first reflective surface, and a central portion of the first reflective surface that is convex toward the inside. A rotationally symmetric panoramic lens having a second refractive surface that refracts light incident from the second reflecting surface and emits the light to the outside,
A diaphragm for adjusting the amount of light from the subject emitted from the panoramic lens;
An imaging lens that forms an image of light from the subject that has passed through the diaphragm on an image sensor provided behind;
An optical system for a capsule endoscope, comprising:   The optical system for a capsule endoscope according to claim 1, wherein the first refracting surface, the first reflecting surface, the second reflecting surface, and the second refracting surface are spherical surfaces. The first reflecting surface is also formed as a mirror surface on the outer surface side of the panoramic lens,
3. The optical system for a capsule endoscope according to claim 1, further comprising: an illuminating unit that reflects the first panoramic lens on the outer surface side of the panoramic lens and irradiates the subject with illumination light. 4. .   A capsule endoscope comprising the optical system according to any one of claims 1 to 3 in a capsule having a size allowing swallowing. An opening is provided at one end of the capsule, and the first refractive surface and the first reflecting surface of the panoramic lens are exposed from the opening,
The capsule endoscope according to claim 4, wherein an outer shape is formed by the capsule provided with the opening and the panoramic lens.

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