CN114869198A

CN114869198A - Imaging element and capsule endoscope

Info

Publication number: CN114869198A
Application number: CN202210347863.0A
Authority: CN
Inventors: 段晓东
Original assignee: Ankon Medical Technologies Shanghai Ltd
Current assignee: Ankon Medical Technologies Shanghai Ltd
Priority date: 2022-04-01
Filing date: 2022-04-01
Publication date: 2022-08-09
Also published as: WO2023186117A1

Abstract

The embodiment of the invention discloses an imaging element and a capsule endoscope. An imaging element for a capsule endoscope according to an embodiment of the present invention includes an intermediate portion providing an optical path for imaging; a peripheral portion forming a unitary structure with the intermediate portion; a connecting portion adjoining the peripheral portion for connecting with a housing of the capsule endoscope to form a closed cavity, wherein an outer surface and an inner surface of the intermediate portion have different radii of curvature from each other. According to the imaging element and the capsule endoscope disclosed by the embodiment of the invention, the imaging element is connected with the shell of the capsule endoscope to form a closed cavity to isolate devices inside the capsule endoscope from external liquid, so that the effectiveness of the devices and the safety of a human body are ensured; and the light transmittance and the imaging quality of the capsule endoscope are improved.

Description

Imaging element and capsule endoscope

Technical Field

The invention relates to the technical field of medical instruments, in particular to an imaging element and a capsule endoscope.

Background

At present, a subject can acquire images in a digestive tract by orally taking a capsule endoscope with a built-in image acquisition and wireless communication device, and a doctor receives the images shot by the capsule endoscope by using an external instrument to know the condition of the digestive tract of the subject, so that medical diagnosis is made.

As shown in fig. 1, the capsule endoscope according to the related art includes an imaging lens group 100 and a transparent dome 200. The imaging lens group 100 is used for image acquisition. The transparent dome 200 is used as an additional lens window and mainly has the function of separating electronic components in the capsule from liquid such as water and the like as a closed transparent body, so that the effectiveness of the electronic components and the safety of a human body are ensured. The use of transparent domes 200 tends to cause the following problems:

the transparent dome 200 is generally composed of concentric hemispheres with the same radius inside and outside. Thus, the power of the dome, phi, is 0, meaning that there is no converging or diverging effect on the light, the only optical effect being as an optical window. The transmittance of the transparent dome 200 cannot be 100%, which may result in a decrease in the light utilization efficiency of the illumination due to the dome.

The transparent dome 200 forms a hemispherical cavity structure. The light emitted by the light source in the capsule endoscope is irradiated to the inner surface and the outer surface of the transparent dome 200, and is reflected, and the reflected light is received by the imaging lens group 100, which is called as stray light, so that the imaging quality is deteriorated.

Thirdly, the transparent dome 200 is used as an additional material, which increases the additional cost.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide an imaging element and a capsule endoscope, thereby improving light transmittance and imaging quality of the capsule endoscope.

According to an aspect of the present invention, there is provided an imaging element for a capsule endoscope, comprising: an intermediate portion providing an optical path for imaging; a peripheral portion forming a unitary structure with the intermediate portion; a connecting portion adjoining the peripheral portion for connecting with a housing of the capsule endoscope to form a closed cavity, wherein an outer surface and an inner surface of the intermediate portion have different radii of curvature from each other.

Preferably, the outer surface of the intermediate portion and the outer surface of the peripheral portion form a smoothly curved first surface.

Preferably, an inner surface of the middle portion and an inner surface of the peripheral portion form a second surface conformal to a plurality of components inside the capsule endoscope.

Preferably, an inner surface of the peripheral portion is formed with a cavity that accommodates the plurality of components.

Preferably, the plurality of components includes a light source for illumination, the peripheral portion providing an optical path for illumination.

Preferably, one of the connecting part and the side wall of the housing is provided with a groove, and the other is provided with a flange, and the groove is engaged with the flange.

Preferably, the intermediate portion forms any one of a plano-convex lens, a plano-concave lens, a biconvex lens, a biconcave lens, and a meniscus lens.

Preferably, the material of the imaging element is a material having a refractive index close to that of water.

Preferably, the material of the imaging element is E48R.

According to another aspect of the present invention, there is provided a capsule endoscope comprising a housing in the form of a capsule having an open top end and a closed bottom end; an imaging element as described above, the imaging element closing the top end of the housing to form a closed cavity; and a plurality of components housed in the enclosed cavity.

Preferably, a flange is provided on one of the side wall of the housing and the imaging element connecting portion, and a groove is provided on the other, the flange engaging with the groove.

Preferably, the plurality of components comprises: a magnet located in the closed cavity for movement of the capsule endoscope; and a battery located in the closed cavity for powering the capsule endoscope.

According to the imaging element and the capsule endoscope provided by the embodiment of the invention, the imaging element is connected with the shell of the capsule endoscope to form a closed cavity to isolate internal devices of the capsule endoscope from external liquid, so that the effectiveness of the internal devices and the safety of a human body are ensured.

According to the imaging element and the capsule endoscope provided by the embodiment of the invention, the imaging element is connected with the shell of the capsule endoscope, and an additional dome is not needed, so that the light transmittance is improved, and materials and cost are saved.

According to the imaging element and the capsule endoscope provided by the embodiment of the invention, the imaging element is connected with the shell of the capsule endoscope, so that the reflection condition of light is reduced, and the imaging quality is improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic structural view of a capsule endoscope according to the prior art;

FIG. 2 shows a schematic structural view of an imaging element for a capsule endoscope according to a first embodiment of the present invention;

FIG. 3 shows a schematic structural view of an imaging element for a capsule endoscope according to a second embodiment of the present invention;

FIG. 4 shows a schematic structural view of an imaging lens group for a capsule endoscope according to a first embodiment of the present invention;

FIG. 5 shows a schematic structural view of an imaging lens group for a capsule endoscope according to a second embodiment of the present invention;

FIG. 6 shows a schematic structural diagram of a capsule endoscope according to an embodiment of the present invention;

FIG. 7 shows a schematic internal structural view of a capsule endoscope according to an embodiment of the present invention;

FIG. 8 is a two-dimensional layout of an imaging lens group of a capsule endoscope at a working distance of 0mm according to a third embodiment of the present invention;

FIG. 9 shows an MTF plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 0 mm;

FIG. 10 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention on a light ray tracing image plane at a working distance of 0 mm;

FIG. 11 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 0 mm;

FIG. 12 is a two-dimensional layout of an imaging lens group of a capsule endoscope at a working distance of 8mm according to a third embodiment of the present invention;

FIG. 13 shows an MTF plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 8 mm;

FIG. 14 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention at a working distance of 8mm on a ray tracing image plane;

FIG. 15 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 8 mm;

FIG. 16 is a two-dimensional layout view of the imaging lens group of the capsule endoscope at a working distance of 30mm according to the third embodiment of the present invention;

FIG. 17 shows an MTF plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 30 mm;

FIG. 18 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention on a ray tracing image plane at a working distance of 30 mm;

FIG. 19 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 30 mm.

Fig. 20 shows parameters of respective constituent elements of an imaging lens group according to a third embodiment of the present invention;

fig. 21 shows parameters of respective constituent elements of the imaging lens group according to the third embodiment of the present invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. In the following description, numerous specific details are set forth, such as configurations of components, materials, dimensions, processing techniques and techniques, in order to provide a more thorough understanding of the present invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

It will be understood that when a layer, region or layer is referred to as being "on" or "over" another layer, region or layer in describing the structure of the component, it can be directly on the other layer, region or layer or intervening layers or regions may also be present. Also, if the component is turned over, one layer or region may be "under" or "beneath" another layer or region.

Fig. 2 shows a schematic structural view of an imaging element for a capsule endoscope according to a first embodiment of the present invention. Fig. 2(a) shows a front view of the imaging element 101. Fig. 2(b) shows a top view of the imaging element 101. As shown in fig. 2, the imaging element 101 according to the first embodiment of the present invention includes a middle portion 1011, a connecting portion 1012, and a peripheral portion 1013.

Specifically, the imaging element 101 is used for imaging of the capsule endoscope and multiplexed as a separate cover of the capsule endoscope. The imaging element 101 is connected to the housing of the capsule endoscope to form a closed cavity, functioning as a cage. The imaging element 101 includes a middle portion 1011, a connecting portion 1012, and a peripheral portion 1013. The outer surface and the inner surface of the middle portion 1011 have different radii of curvature from each other. The intermediate portion 1011 is, for example, a concave lens, is located on the light receiving path of the capsule endoscope, and provides an optical path for imaging for the capsule endoscope. The peripheral portion 1013 and the intermediate portion 1011 form an integral structure. Connecting portion 1012 abuts peripheral portion 1013 for connection with a housing of a capsule endoscope to form a closed cavity. The imaging element 101 is connected to the housing of the capsule endoscope to form a closed cavity, which acts as a shield for the components inside the capsule endoscope from the external environment. The imaging element 101 is, for example, a closed cap that separates electronic components inside the capsule endoscope from a liquid such as water.

In an alternative embodiment of the present invention, the outer surface and the inner surface of the middle portion 1011 have different radii of curvature from each other. The intermediate portion 1011 forms any one of a plano-convex lens, a plano-concave lens, a biconvex lens, a biconcave lens, and a meniscus lens.

In the embodiment of the invention, a conventional dome structure is not provided, so that the light transmittance of the lens is improved, the reflection of light of the dome is reduced, the material of the dome is reduced, and the material utilization rate is improved.

Fig. 3 shows a schematic structural view of an imaging element for a capsule endoscope according to a second embodiment of the present invention. As shown in fig. 3, the imaging element 101 according to the second embodiment of the present invention includes a middle portion 1011, a connecting portion 1012, and a peripheral portion 1013.

Specifically, the imaging element 101 is used for imaging of the capsule endoscope and multiplexed as a separate cover of the capsule endoscope. The imaging element 101 includes a middle portion 1011, a connecting portion 1012, and a peripheral portion 1013. The middle portion 1011 is located on the receiving light path of the capsule endoscope for imaging of the capsule endoscope. The upper surface of the middle portion 1011 is, for example, convex, and the lower surface is irregularly shaped to match the rest of the capsule endoscope. The inner surface of the middle portion 1011 and the inner surface of the peripheral portion 1013 form, for example, a second surface that conforms to the various components inside the capsule endoscope.

In a preferred embodiment of the present invention, the outer surface of the middle portion 1011 and the outer surface of the peripheral portion 1013 form a first surface of a smooth curved surface.

In an alternative embodiment of the invention, one of the connecting portion 1012 and the side wall of the capsule endoscope housing is provided with a recess and the other is provided with a flange, the recess engaging with the flange so that the imaging element 101 and the capsule endoscope housing form a closed cavity.

In a preferred embodiment of the present invention, the imaging element 101 is selected from a material having a refractive index close to that of water. Alternatively, the imaging element 101 selects the E48R material with a refractive index of 1.53.

In the above-described embodiments of the present invention, the imaging element 101 is in direct contact with water, and the material having a refractive index closer to that of water is selected, which can reduce the reflection caused by the refractive index adaptation.

Fig. 4 shows a schematic structural view of an imaging lens group for a capsule endoscope according to a first embodiment of the present invention. As shown in fig. 4, an imaging mirror group 100 according to the first embodiment of the present invention includes an imaging element 101 and a second imaging element 102. The imaging element 101 and the second imaging element 102 are arranged in sequence along the light incoming path of the capsule endoscope. The direction of the light entering path is shown by the arrow in fig. 4. The imaging element 101 is used for imaging of the capsule endoscope. The second imaging element 102 is used for imaging of the capsule endoscope. Optionally, the imaging element 101 and the second imaging element 102 constitute an imaging lens group 100 of the capsule endoscope.

In an alternative embodiment of the present invention, the imaging lens group 100 comprises an imaging element 101, a second imaging element 102 and at least one other imaging component, which at least comprises a light source 103, arranged in sequence along the light incoming path of the capsule endoscope.

Fig. 5 shows a schematic structural view of an imaging lens group for a capsule endoscope according to a second embodiment of the present invention. As shown in fig. 5, an imaging optical group 100 according to a second embodiment of the present invention includes an imaging element 101, a second imaging element 102, and a light source 103.

The imaging element 101 and the second imaging element 102 are arranged in sequence along the light incoming path of the capsule endoscope. The direction of the light entering path is shown by the arrow in fig. 5. The side of the second imaging element 102 is provided with a light source 103. The light source 103 is used to provide illumination. The light emitted from the light source 103 is radiated through the imaging element 101 and reflected (for example, on the stomach wall and reflected). The reflected light passes through the imaging element 101 and the second imaging element 102 in sequence to be imaged.

The upper surface of the imaging element 101 is convex and the lower surface is shaped to match the shape of the second imaging element 102 and the light source 103. The imaging element 101 is in direct contact with the second imaging element 102 and the light source 103.

In an alternative embodiment of the invention, the inner surface of the peripheral portion 1013 is formed with a cavity that accommodates the plurality of components. The peripheral portion 1013 provides an optical path for illumination, for example. The light source 103 is located in the cavity formed by the peripheral portion 1013.

In an alternative embodiment of the present invention, the imaging lens group 100 includes an imaging element 101, a second imaging element 102 and at least one other imaging component disposed along the optical path, the imaging component including at least a light source 103.

In an alternative embodiment of the invention, the light source 103 is an LED (light emitting diode) or a fluorescent lamp or another light source.

In the above embodiments of the present invention, the light emitted from the light source 103 directly exits through the imaging element 101, and is not reflected (or is slightly reflected) on the surface of the imaging element, and the imaging element does not (or less) receive the reflected light, so as to avoid the influence of stray light and improve the imaging quality.

FIG. 6 shows a schematic structural diagram of a capsule endoscope according to an embodiment of the present invention. As shown in fig. 6, the capsule endoscope according to the embodiment of the present invention includes an imaging element 101 and a housing 300. The imaging element 101 is used for imaging of the capsule endoscope and multiplexed as a shielding cover of the capsule endoscope. The housing 300 is located at the outermost side of the capsule endoscope for housing the specific components of the capsule endoscope.

The imaging element 101 is connected to the housing 300 to form a closed cavity to separate components such as electronic components inside the capsule endoscope from liquids such as water.

In an alternative embodiment of the present invention, one of the connecting portion 1012 and the side wall of the housing 300 is provided with a groove, and the other is provided with a flange, and the groove and the flange are engaged with each other, so that the imaging element 101 and the housing 300 form a closed cavity.

In an alternative embodiment of the present invention, the imaging element 101 includes a middle portion 1011, a connecting portion 1012, and a peripheral portion 1013. The housing 300 is provided with a housing connecting portion 301 (e.g., a flange provided on a side wall of the housing 300). The shell connecting part 301 is matched with the connecting part 1012 and can be tightly connected, so that the inside of the capsule endoscope is a closed space (closed cavity). Alternatively, the attachment portion 1012 and the housing attachment portion 301 are bonded using glue.

In an alternative embodiment of the present invention, imaging element 101 and housing 300 are integrated by mechanical fit, gluing. It should be noted that the connection manner of the imaging element 101 and the housing 300 is not limited to this, and various connection manners may be adopted in the case of ensuring the sealing property and the integrity.

In the above-described embodiments of the present invention, the imaging element 101 and the housing 300 of the capsule endoscope are integrated by mechanical fitting and gluing, and the sealing performance and integrity of the capsule endoscope are ensured.

Fig. 7 shows an internal structural view of a capsule endoscope according to an embodiment of the present invention. As shown in fig. 7 in combination with fig. 6, the capsule endoscope according to the embodiment of the present invention includes an imaging lens group 100, a magnet 400, a battery 500, and a housing 300. Therein, the imaging lens group 100 includes an imaging element 101.

The imaging element 101 is coupled to the housing 300 to form a closed cavity to isolate the components inside the capsule endoscope from external fluids (e.g., water, gastric fluids, etc.). The magnet 400 is located within the enclosed cavity for induction with an external magnetic field to control movement of the capsule endoscope.

In an alternative embodiment of the invention, magnet 400 controls capsule endoscope movement under the influence of external magnetic force.

As shown in fig. 8, a capsule endoscope imaging lens group according to a third embodiment of the present invention includes: an imaging element 101, a second imaging element 102, a third imaging element 103, a fourth imaging element 104, a fifth imaging element 105, a photosensitive surface glass 106, and an image surface 107. Wherein the imaging element 101 is in direct contact with the ambient liquid 800. The external liquid 800 is, for example, water or gastric juice. A diaphragm (not shown) is further disposed between the third imaging element 103 and the fourth imaging element 104. Fig. 20 shows parameters of respective constituent elements of the imaging lens group according to the third embodiment of the present invention. The parameters of the individual components of the imaging optics may be as shown in fig. 20. Fig. 21 shows parameters of respective constituent elements of the imaging lens group according to the third embodiment of the present invention. The parameters of the individual components of the imaging optics may be as shown in fig. 21.

FIG. 8 shows a two-dimensional layout of a capsule endoscope according to a third embodiment of the present invention at a working distance of 0 mm. As shown in fig. 8, the capsule endoscope according to the third embodiment of the present invention has a sufficient observation field of view with a full field angle of 100 ° when the working distance is 0mm, and the imaging element 101 is in direct contact with water.

FIG. 9 shows MTF plots for a capsule endoscope according to a third embodiment of the present invention at a working distance of 0 mm. Wherein, the ordinate is the Modulation Transfer Function (MTF) value, which represents the attenuation degree of the contrast; the abscissa is the spatial frequency in lp/mm, representing the resolving power for the spatial size of the observed object. The curve 1 is a meridian curve of a 0-degree field angle; the curve 2 is a sagittal curve of a 0-degree field angle; the curve 3 is a meridian curve with a 15-degree field angle; curve 4 is a sagittal curve at a field angle of 15 °; the curve 5 is a meridian curve with a field angle of 35 degrees; curve 6 is a sagittal curve at a field angle of 35 °; the curve 7 is a meridional curve with a field angle of 50 degrees; curve 8 is a sagittal curve for a field angle of 50 °. Wherein curve 1 coincides with curve 2. As shown in FIG. 9, the capsule endoscope according to the third embodiment of the present invention has good MTF performance at a working distance of 0mm, especially the MTF of the central field is the best. As can be seen from the graph, when the MTF is 0.2, the spatial frequency of the curve 1 and the curve 2 is 225lp/mm, i.e., the MTF20 of the central field is 225 lp/mm.

It should be noted that the above is only the MTF graph of one embodiment of the present invention. The capsule endoscopes of different embodiments have different MTF curves, and the MTF curves of the respective embodiments can all illustrate that the capsule endoscope according to the present embodiment has good MTF curves.

FIG. 10 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention on a light ray tracing image plane at a working distance of 0 mm. The circles in FIG. 10 are diffraction Airy spots. As shown in FIG. 10, the capsule endoscope according to the third embodiment of the present invention has a relatively small circle of confusion, particularly a central field of view, at a working distance of 0mm, and the circle of confusion has a Root Mean Square (RMS) radius of 1.3 μm. In fig. 10, Image area dot columns at half field angles of 0 °, 15 °, 35 ° and 50 ° Object (OBJ, Object) are shown, which correspond to half heights of the Image plane (IMA, Image) of 0mm, 0.203mm, 0.487mm and 0.726mm, respectively.

FIG. 11 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 0 mm. Wherein the abscissa in the graph represents the relative distortion rate; the ordinate represents the normalized field of view. As shown in FIG. 11, the capsule endoscope according to the third embodiment of the present invention has a small distortion at a working distance of 0 mm. In the case where the angle of view is relatively small, the distortion is very small. When the full field angle is 70 degrees, the distortion is 10 percent, and the full field distortion is 21 percent.

FIG. 12 shows a two-dimensional layout of a capsule endoscope according to a third embodiment of the present invention at a working distance of 8 mm. As shown in fig. 12, the capsule endoscope according to the third embodiment of the present invention has a sufficient observation field of view with a full field angle of 100 ° when the working distance is 8mm, and the imaging element 101 is in direct contact with water.

FIG. 13 shows MTF plots for a capsule endoscope according to a third embodiment of the present invention at a working distance of 8 mm. Wherein, the ordinate is MTF value, which represents the attenuation degree of contrast; the abscissa is the spatial frequency in lp/mm, representing the resolving power for the spatial size of the observed object. The curve 1 is a meridian curve of a 0-degree field angle; the curve 2 is a sagittal curve of a 0-degree field angle; the curve 3 is a meridian curve with a 15-degree field angle; curve 4 is a sagittal curve at a field angle of 15 °; the curve 5 is a meridian curve with a field angle of 35 degrees; curve 6 is a sagittal curve at a field angle of 35 °; the curve 7 is a meridional curve with a field angle of 50 degrees; curve 8 is a sagittal curve for a field angle of 50 °. Wherein curve 1 coincides with curve 2. As shown in FIG. 13, the MTF of the lens center field is best for the capsule endoscope according to the third embodiment of the present invention at a working distance of 8 mm. As can be seen from the graph, the spatial frequency of the curves 1 and 2 is 155lp/mm when the MTF is 0.2, i.e., the central field MTF20 is 155 lp/mm.

The above is only the MTF graph of one embodiment of the present invention. The capsule endoscopes of different embodiments have different MTF curves, and the MTF curves of the respective embodiments can all illustrate that the capsule endoscope according to the present embodiment has good MTF curves.

FIG. 14 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention on a light ray tracing image plane at a working distance of 8 mm. The circles in fig. 14 are diffraction airy discs. As shown in FIG. 14, the capsule endoscope according to the third embodiment of the present invention has a circle of confusion in its central field of view at a working distance of 8mm, and the RMS radius of the circle of confusion is 3.4 μm. The image side dot diagrams at 0 °, 15 °, 35 ° and 50 ° object side (OBJ) half field angles are shown in fig. 14, which correspond to image plane (IMA) half heights of 0mm, 0.203mm, 0.483mm and 0.714mm, respectively.

FIG. 15 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 8 mm. Wherein the abscissa in the graph represents the relative distortion rate; the ordinate represents the normalized field of view. As shown in FIG. 15, the capsule endoscope according to the third embodiment of the present invention has a small distortion at a working distance of 8 mm. In the case where the angle of view is relatively small, the distortion is very small. At a full field angle of 70 °, the distortion is 11%, and the full field distortion is 22%.

FIG. 16 shows a two-dimensional layout of a capsule endoscope according to a third embodiment of the present invention at a working distance of 30 mm. As shown in fig. 16, the capsule endoscope according to the third embodiment of the present invention has a sufficient observation field of view with a full field angle of 100 ° when the working distance is 30mm, and the imaging element 101 is in direct contact with water.

Fig. 17 shows MTF plots for a capsule endoscope according to the third embodiment of the present invention at a working distance of 30 mm. Wherein, the ordinate is MTF value, which represents the attenuation degree of contrast; the abscissa is the spatial frequency in lp/mm, representing the resolving power for the spatial size of the observed object. The curve 1 is a meridian curve of a 0-degree field angle; the curve 2 is a sagittal curve of a 0-degree field angle; the curve 3 is a meridian curve with a 15-degree field angle; curve 4 is a sagittal curve at a field angle of 15 °; the curve 5 is a meridian curve with a field angle of 35 degrees; curve 6 is a sagittal curve at a field angle of 35 °; the curve 7 is a meridional curve with a field angle of 50 degrees; curve 8 is a sagittal curve for a field angle of 50 °. Wherein curve 1 coincides with curve 2. As shown in FIG. 17, the MTF of the lens is best at the central field of view for the capsule endoscope according to the third embodiment of the present invention at a working distance of 30 mm. As can be seen from the graph, the spatial frequency of the curves 1 and 2 is 105lp/mm when the MTF is 0.2, i.e., the central field MTF20 is 105 lp/mm.

FIG. 18 shows a stippling diagram of a capsule endoscope according to a third embodiment of the present invention on a ray tracing plane at a working distance of 30 mm. The circles in FIG. 18 are diffraction Airy spots. As shown in FIG. 18, the capsule endoscope according to the third embodiment of the present invention has a circle of confusion in the central field of view at a working distance of 30mm, and the RMS radius of the circle of confusion is 4.9 μm. Fig. 18 shows a plot of the dot columns at 0 °, 15 °, 35 ° and 50 ° object-side (OBJ) half field angles, which correspond to image plane (IMA) half heights of 0mm, 0.203mm, 0.482mm and 0.710mm, respectively.

FIG. 19 shows a relative distortion plot for a capsule endoscope according to a third embodiment of the present invention at a working distance of 30 mm. Wherein the abscissa in the graph represents the relative distortion rate; the ordinate represents the normalized field of view. As shown in FIG. 19, the capsule endoscope according to the third embodiment of the present invention has a small distortion at a working distance of 30 mm. In the case where the angle of view is relatively small, the distortion is very small. At a full field angle of 70 °, the distortion is 11%, and the full field distortion is 23%.

The third embodiment described above illustrates the applicability and the good imaging quality of the capsule endoscope according to the embodiment of the present invention.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In accordance with embodiments of the present invention, as set forth above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An imaging element for a capsule endoscope, comprising:

an intermediate portion providing an optical path for imaging;

a peripheral portion forming a unitary structure with the intermediate portion;

a connecting portion adjacent to the peripheral portion for connecting with a housing of the capsule endoscope to form a closed cavity,

wherein the outer surface and the inner surface of the intermediate portion have different radii of curvature from each other.

2. An imaging element according to claim 1, wherein an outer surface of the intermediate portion and an outer surface of the peripheral portion form a smoothly curved first surface.

3. An imaging element according to claim 1, wherein an inner surface of the intermediate portion and an inner surface of the peripheral portion form a second surface that conforms to a plurality of components inside the capsule endoscope.

4. An imaging element according to claim 3, wherein an inner surface of the peripheral portion is formed with a cavity that accommodates the plurality of components.

5. An imaging element according to claim 4, wherein the plurality of components include a light source for illumination, the peripheral portion providing an optical path for illumination.

6. An imaging element according to claim 1, wherein one of said connecting portion and said side wall of said housing is provided with a recess, and the other is provided with a flange, said recess engaging with said flange.

7. An imaging element according to claim 1, wherein the intermediate portion forms any one of a plano-convex lens, a plano-concave lens, a biconvex lens, a biconcave lens, and a meniscus lens.

8. The imaging element of claim 1, wherein the material of the imaging element is a material having a refractive index close to that of water.

9. The imaging element of claim 8, wherein the imaging element is of material E48R.

10. A capsule endoscope, comprising:

a housing in the form of a capsule having an open top end and a closed bottom end;

the imaging element of any one of claims 1 to 9, the imaging element closing a top end of the housing to form a closed cavity; and

a plurality of components housed in the enclosed cavity.

11. The capsule endoscope of claim 10, wherein one of the side wall of the housing and the imaging element attachment portion is provided with a flange, and the other is provided with a groove, the flange engaging with the groove.

12. The capsule endoscope of claim 10, wherein the plurality of components comprises:

a magnet located in the closed cavity for movement of the capsule endoscope; and

a battery located in the enclosed cavity for powering the capsule endoscope.