Imaging device for distal end portion of endoscope, objective lens system, and endoscope

Abstract

The invention relates to an imaging device for a distal end portion of an endoscope, an objective lens system and an endoscope. The invention relates to an imaging device for a distal end part of an endoscope, in which the imaging device comprises a pentaprism having a body and a prism wedge, and at least a first image sensor for capturing light of a first spectral region and a second image sensor for capturing light of a second spectral region can be assigned to the imaging device, and a dichroic beam splitting layer as a first internal reflection and transmission light splitting layer is arranged between the body of the pentaprism and the prism wedge such that an incident light beam comprising the first and second spectral regions is split by the dichroic beam splitting layer into a first light beam of the first spectral region and a second light beam of the second spectral region, wherein at least one separate optical element is arranged between the pentaprism and the first image sensor and / or the second image sensor for changing the properties of the light in the first spectral region and / or the second spectral region. The invention further relates to an objective lens system and an endoscope.

Description

Technical Field

[0001] The present invention relates to an imaging device for a distal end portion of an endoscope, wherein the imaging device includes a pentaprism having a body and a prism wedge and an optical axis, and an incident surface, a second internal reflection surface and a first exit surface are arranged on the body, the second exit surface is arranged on the prism wedge, the pentaprism further includes a dichroic beam splitting layer as a first internal reflection and transmission beam splitting layer, and at least a first image sensor for capturing light of a first spectral region and a second image sensor for capturing light of a second spectral region can be assigned to the imaging device, wherein the first spectral region and the second spectral region are at least partially different from each other, and the dichroic beam splitting layer is arranged between the body and the prism wedge of the pentaprism, so that an incident light beam including the first and second spectral regions is split by the dichroic beam splitting layer into a first light beam of the first spectral region and a second light beam of the second spectral region. In addition, the present invention relates to an objective lens system and an endoscope. Background Art

[0002] Endoscopes for medical and / or non-medical applications can utilize both white light imaging and fluorescence imaging. Endoscopic instruments intended for industrial use rather than medical use are often referred to as borescopes. Since the present invention relates to medical endoscopes and borescopes, the term "endoscope" is often used to include both instruments. Conventional endoscopes are able to capture white light and fluorescence images with a single optical path, and only a single image sensor is achieved by collecting alternating frames with staggered white light and excitation illumination. This system arrangement results in a frame rate that is significantly lower than the frame rate of a system using only visible white light, typically up to half the frame rate of a system using only white light. The low frame rate results in unwanted motion blur. In addition to the necessary shuttering between white light and fluorescence frames, the sensitivity of the fluorescence frame is also limited by the shared optical path, which often results in one signal being unable to attenuate relative to the other. Image processing then analyzes and combines the images from the alternating frames to form a fluorescence / white light overlay with a lower overall frame rate. This technique results in reduced sensitivity in the fluorescence range, as well as reduced brightness and resolution of the overlay image compared to white light images only.

[0003] An alternative to using only one image sensor, shuttering off the frame and superimposing the white light and fluorescence images is to place two complete objective systems in the endoscope for capturing the white light and fluorescence images separately. However, due to the space requirements of two objective systems in parallel, not to mention the increased positional complexity, increased expense and loss of image brightness, this is not a feasible solution for chip-on-the-tip (COTT) endoscopes, in which the corresponding one or more electronic image sensors are arranged in the distal part, such as the tip of the endoscope's narrow shaft.

[0004] Instead of using two complete objective systems, it is also possible to use only one objective system, then split the beam by a beam splitter and direct the split beams onto two different image sensors. However, it is not possible to miniaturize a conventional beam splitter and two image sensors into the small space provided by a COTT endoscope. For example, splitting the afocal beam path comprising both white light and fluorescence by a 45° beam splitter has the disadvantage that in addition to providing the necessary afocal beam path itself, subsequent focusing is required. Otherwise, when a conventional beam splitter is used in the converging beam path in front of the image sensor, aberrations occur on the sensor, resulting in a reduction in transmission and image quality. Overall, this results in a large imaging device due to the need for refocusing.

[0005] US2020 / 0088579 A1 discloses a hybrid spectral imager, which includes a multi-band filtering optical device having a light analyzer device for generating at least two replica images of a target image and an adjustable multi-band filtering device inserted into the imaging path and realizing adjustable multi-band pass filtering in the image replica. The light analyzer can be a pentaprism, one of the five surfaces of which is coated with a polychromatic mirror substrate, and the coated surface is bonded to a triangular prism so that the rear surface of the prism is parallel to the front surface of the pentaprism. In addition, the pentaprism includes a tilt actuator to adjust the tilt angle of the prism assembly and the direction of the imaging beam. The image of the target object is focused by the objective optical element and separated by the tilted prism assembly onto two image sensors, wherein, in each tilt step, a new set of images is simultaneously obtained in snapshot mode, so that in scanning mode, the entire spectrum can be scanned to create a complete spectral cube for the target object. Therefore, in order to accommodate sensor arrays of various sizes, the path lengths of the two separated beams must be substantially equal. Therefore, the placement of such hybrid spectral imagers in the narrow shaft of a COTT endoscope is limited.

[0006] In US2014 / 0225992 A1, a minimally invasive surgical system with an image capture unit is described, the image capture unit comprising a prism assembly and a sensor assembly. The image capture unit comprises a shared lens assembly and a sensor assembly behind it, wherein the sensor assembly comprises a prism assembly, a reflection unit and a coplanar image capture sensor. Thus, two image capture sensors with similar image sizes are symmetrical on a plane intersecting the longitudinal axis of the stereo endoscope, and only a small gap is arranged between the corresponding surface of the prism assembly and each coplanar image capture sensor. Summary of the invention

[0007] The object of the invention is to improve the known state of the art.

[0008] This problem is solved by an imaging device for a distal end portion of an endoscope, wherein the imaging device includes a pentaprism having a body and a prism wedge and an optical axis, and an incident surface, a second internal reflection surface and a first exit surface are arranged on the body, and the second exit surface is arranged on the prism wedge, the pentaprism further includes a dichroic beam splitting layer as a first internal reflection and transmission beam splitting layer, and at least a first image sensor for capturing light in a first spectral region and a second image sensor for capturing light in a second spectral region can be assigned to the imaging device, wherein the first spectral region and the second spectral region are at least partially different from each other, and the dichroic beam splitting layer is arranged between the body and the prism wedge of the pentaprism, so that an incident light beam including the first and second spectral regions is split by the dichroic beam splitting layer into a first light beam in the first spectral region and a second light beam in the second spectral region, wherein at least one separate optical element is arranged between the pentaprism and the first image sensor and / or the second image sensor for changing the characteristics of light in the first spectral region and / or the second spectral region, so that the first image sensor and the second image sensor can capture two optimized separate images for superimposed imaging of light in the first spectral region and the second spectral region.

[0009] Thus, an imaging device is provided for a chip-on-tip endoscope, which imaging device is able to achieve optimized simultaneous capture of images of two different spectral regions by two separate image sensors to meet the limited space available in the shaft of such an endoscope. Thus, an increase in the overall frame rate and an optimized image quality can be achieved within the small confined space in the shaft of the video endoscope. Due to the specific design of the pentaprism and at least one separate optical element arranged between the pentaprism and the corresponding one or more image sensors, the first and second separated light beams can be further optimized and / or corrected independently of each other for imaging the optical superposition of the two spectral regions with the best available imaging quality. Thus, in a miniaturized design of the imaging device, which can be arranged or arranged in the small space available in the shaft of a COTT endoscope, at least two optically well-corrected separate images can be captured.

[0010] Due to the specific pentaprism design, the afocal beam does not have to be provided by the objective lens system upstream of the imaging device, which is not possible due to the construction and space requirements in the narrow shaft of a COTT endoscope. Instead, the pentaprism can be arranged in the converging beam path and designed so that the two image sensors receive images from the object space simultaneously without aberrations.

[0011] Furthermore, due to the specific geometry and the space-saving design of the pentaprism, a further optimization of the relative beam paths can be achieved by at least one separate optical element arranged between the pentaprism and the respective sensor, wherein the respective separate optical element may be present in only one of the two respective paths, or similar or different optical elements may be arranged in both respective paths. Thus, the sensitivity, image brightness and / or resolution of a defined spectral region may be optimized without necessarily affecting the optical parameters of other spectral regions to be captured by the respective image sensor.

[0012] One of the main innovations of the present invention is the special design of a pentaprism with a prismatic wedge, in combination with at least one separate optical element arranged downstream between the pentaprism and at least one of the respective two image sensors, for providing simultaneous capture of two images at high frame rates and high sensitivity and enabling the imaging device to be arranged in a small, confined space of the shaft of a COTT endoscope. Thus, both image sensors can be used at full frame rate and with optimized and / or specially adjusted image sizes and / or characteristics. Thus, due to the special design of the pentaprism in combination with at least one separate optical element arranged downstream, a space-saving geometry of the imaging device is achieved, which allows the imaging device and / or the allocable image sensor to be easily mounted within the shaft of the endoscope in the longitudinal and radial directions of the shaft and enables simultaneous optimized capture of separate images in a first spectral region and a second spectral region, each image being captured by a separate dedicated image sensor, thereby achieving an adapted and / or improved image quality. Due to the design of the pentaprism in combination with the separate optical element, frame rates of 60 frames per second or even higher can be achieved.

[0013] As used in accordance with the present disclosure, the following terms shall be understood to have the following meanings, unless otherwise indicated.

[0014] An "endoscope", in particular a video endoscope, is an endoscope having a device for digital image acquisition in and / or at the distal end of an elongated shaft, from which data is transmitted (e.g. to the proximal end of the endoscope). The endoscope comprises an elongated shaft and a handle which can be connected to each other. In the present invention, at least two digital image sensors are located in or at the distal end of the elongated shaft for image acquisition. In particular, the video endoscope is any type of digital endoscope, such as in a 2D colonoscope, laparoscope or gastroenteroscope or in a 3D video endoscope. In particular, the endoscope is a chip-on-tip endoscope (COTT).

[0015] The "slender rod" is specifically a rigid, semi-flexible or flexible tube. In particular, the rod is configured to be inserted into a cavity to be observed through the endoscope, such as a cavity in the human or animal body. In industrial applications, the endoscope or borescope rod will be placed in an element such as a pipeline, or in another area that is difficult to directly access, such as behind a wall. Typically, the outer diameter of the rod can be in the range of 4mm to 10mm. In addition to the objective lens system, the imaging device and two or more image sensors, the rod can also include one or more channels (commonly referred to as "working channels") for flushing or passing through a working instrument in order to achieve the desired effect in the cavity or opening. The rod can be detachably connected to the handle at its proximal end, or permanently connected to the handle. The distal portion of the slender rod is the portion away from the user, while the proximal portion of the rod is closer to the user.

[0016] An "objective system" is an optical system that includes an objective lens system for receiving, forwarding and / or modifying image light from object space.

[0017] The "objective lens system" specifically includes, in order from the object side, a cover glass and / or a first lens, a second lens and optionally other lenses arranged along the optical axis of the lens system. Optionally, one or more filters may be located between any two lenses of the lens system.

[0018] A "lens" is specifically a transmissive optical body that focuses or disperses a beam (light) by refraction. The first lens, the second lens and any other lenses can be single lenses that are separated by air gaps or that are in contact with adjacent lenses at most points. In addition, the lens can be a combined lens, a compound lens and / or a rod lens. Preferably, the lens is made of glass and / or a crystalline material.

[0019] The "imaging device" is in particular a device which further modifies the image light forwarded by the objective system and splits the image light to at least two image sensors. The imaging device at least comprises a pentaprism, at least one separate optical element and at least two image sensors for capturing images are assignable or included. The imaging device does not necessarily have to be arranged in the distal part of the rod close to the objective system, but can be positioned relatively close to the objective system in the distal part.

[0020] A "pentaprism" is an optical component in the form of a geometric prism with five sides. The pentaprism specifically comprises a body and a prism wedge, which together form five reflective, transmissive and / or non-light beam passing sides of the pentaprism in a longitudinal cross-sectional view. The pentaprism can be used for different optical effects. The optical properties of the pentaprism specifically depend on the angles and / or positions of the optically effective prism surfaces relative to each other, and the refractive index of the body and the prism wedge materials. In particular, the body and the prism wedge comprise glass, and preferably, the glass of the body and the prism wedge is selected to have the same or almost the same refractive index. For example, the refractive index of both the body and the prism wedge can be 1.6. In a cross-sectional view parallel to the direction of propagation of the incident light, and in a longitudinal cross-section, the pentaprism has a substantially pentagonal shape. In particular, the length of the pentaprism in the longitudinal direction and along the optical axis is less than 5.0 mm. In particular, the diameter of the pentaprism perpendicular to the optical axis is less than 3.5 mm. The prism wedge is preferably arranged at the proximal end of the body and bonded to the body. The bonded prismatic wedge prevents in particular beam deviation errors on the second image sensor, which is in particular arranged in the proximal direction perpendicular to the optical axis.

[0021] The "incident surface" on the body of the pentaprism is specifically the surface of the pentaprism through which the incoming light beam (incident light beam) including the first and second spectral regions enters the pentaprism. An area of ​​the incident surface on the body can be used as an entrance aperture, and an area outside the effective diameter of the incoming light beam can be made opaque to the incoming light. Preferably, the incoming light beam enters the pentaprism only through the incident surface of the body. Therefore, the incident surface of the body and / or areas of the non-beam-passing surfaces of the body and the prism wedge can be coated with an opaque substance, such as black paint, to avoid any stray or unwanted light from passing therethrough.

[0022] The “second internal reflection surface” is in particular a surface of the pentaprism body on which the split first light beam split by the dichroic beam splitting layer arranged between the body and the prism wedge is reflected within the body and directed toward the first image sensor. The “second internal reflection surface” of the body in particular directs the split first light beam perpendicularly to the longitudinal axis of the pentaprism and to the image plane of the first image sensor. In particular, the second internal reflection surface is a mirror surface used as an internal reflection surface. Preferably, the second internal reflection surface is the only reflection surface of the body except the dichroic beam splitting layer.

[0023] A "first exit surface" is in particular a surface of the pentaprism body which is substantially parallel to the longitudinal axis of the pentaprism and / or the axis. In a cross-sectional view along the longitudinal axis, the first exit surface is in particular the longest side of the pentaprism. The first light beam split and reflected by the second internal reflection surface of the body specifically leaves the body through the first exit surface. In particular, this surface of the pentaprism body is arranged so that an angle of 90° is each set between the incoming light beam entering the body through the incident surface and the split and reflected first light beam leaving the body through the first exit surface and / or between the first light beam reflected by the dichroic beam splitting layer and the second reflected light beam leaving the second internal reflection surface of the body through the first exit surface.

[0024] A "dichroic beam splitting layer" is specifically a thin layer that selectively reflects and transmits light according to the wavelength of the light. The dichroic beam splitting layer is selected so that an incident light beam is split into a first light beam in a first spectral region and a second light beam in a second spectral region. The dichroic beam splitting layer is arranged between the body and the prism wedge of the pentaprism. In particular, the body incident surface through which the incoming light beam passes is arranged to be substantially opposite or adjacent to the body surface on which the dichroic beam splitting layer is arranged. The dichroic beam splitting layer is specifically directed to be inclined relative to the optical axis, the longitudinal axis and / or the rod of the pentaprism, and to be oriented perpendicular to the longitudinal axis and / or the optical axis. The dichroic beam splitting layer can be a coating applied to the corresponding surfaces of the body and / or the surface of the prism wedge adjacent to each other. The adjacent surfaces of the body and the prism wedge associated with the coating can be bonded by optical adhesive. Therefore, the combination of these coated surfaces and optical adhesive can act as a dichroic filter. By the term "a dichroic beam splitting layer is arranged between adjacent surfaces", it is to be understood that, in particular, a dichroic beam splitting layer and / or a coating is arranged on at least one of two adjacent surfaces of the body and the prismatic wedge.

[0025] The dichroic beam splitting layer can also be a dielectric coating or a dichroic mirror. The dichroic beam splitting layer is specifically formed as a first internal reflection and transmission beam splitting layer, so that the first light beam is reflected internally and directed to the second internal reflection surface of the body, and the second light beam passes toward the prism wedge. In particular, the dichroic beam splitting layer is arranged so that two spectral regions of any type can be separated and thus separated from each other. In particular, the dichroic beam splitting layer splits the incident light beam into a first light beam with a spectrum of 400 to 658 nm in the visible range and a second light beam with a wavelength of 800 to 950 nm in the near infrared range.

[0026] The “second exit surface” is specifically a surface on the prism wedge through which the transmitted second light beam of the second spectral region leaves the pentaprism. The second exit surface is specifically arranged parallel to the incident surface of the main body. The incident surface of the main body is specifically arranged on the distal side, and the second exit surface of the prism wedge is specifically arranged on the proximal side of the pentaprism, the incident surface of the main body and the second exit surface of the prism wedge being opposite to each other.

[0027] By "separate optical element" is meant in particular any type of optical element which modifies, controls and / or corrects the properties of the first light beam of the first spectral region or of the second light beam of the second spectral region. The separate optical element, or two or more optical elements, are in particular arranged downstream of the pentaprism. Thus, one separate optical element, or two or more separate optical elements, may be arranged between the outer surfaces of the pentaprism radially to the optical axis or along the optical axis and thereby the longitudinal axis of the pentaprism or of the rod. For a space-saving imaging device, at least one separate optical element is arranged between the second exit surface of the prism wedge and the image sensor, the image sensor being arranged with its image plane perpendicular to the optical axis and / or the longitudinal axis of the pentaprism and / or of the rod. Thus, preferably, one separate optical element, or two or more separate optical elements, are arranged on the proximal side of the pentaprism within the rod of the endoscope.

[0028] The term "separate" optical element is to be understood as meaning that the optical element is generally not an integral part of the pentaprism, nor is it an integral part of any image sensor. Thus, in most embodiments, the separate optical element is not bonded to the second exit side of the prismatic wedge, nor is it connected in direct contact to the pentaprism or image sensor, but this is not limiting and some embodiments are envisioned in which these elements may be connected and / or in direct contact. Furthermore, the term "separate" may also mean that the pentaprism and the continuous optical element have different optical functions within the imaging device.

[0029] An "optical axis" particularly refers to a line in an optical system that has some degree of rotational symmetry. The optical axis is particularly an imaginary line that defines the path of an incoming light beam that propagates through an objective system in front of the imaging device or enters the imaging device. Preferably, the optical axis passes through the center of curvature of each optical element within the lens system and / or the objective system and / or the first entrance surface of a pentaprism of the imaging device. However, the optical axis may also be bent and / or directed by at least one optical element downstream of the lens, the optical element, the imaging device and / or the pentaprism and / or the prismatic wedge.

[0030] An "image sensor" is in particular one whose sensor plane is located in the image plane of the imaging device. The sensor plane of the respective image sensor can be substantially at a distance from, parallel to or perpendicular to the longitudinal axis of the pentaprism and / or the rod. In general, the terms "first image sensor" and "second image sensor" are used only for distinction. Thus, the second image sensor can also be arranged instead of the first image sensor and vice versa. Preferably, the first image sensor is arranged parallel to a first exit surface arranged on the pentaprism body, the second image sensor is preferably arranged perpendicular to the longitudinal axis of the pentaprism and / or the rod and thus parallel to a second exit surface arranged on the prism wedge of the pentagonal prism. In a preferred embodiment, the image size at the respective image sensor is at least 1.6 mm or more. The image planes of the first image sensor and the second image sensor can have the same size and / or properties, or different sizes and / or properties. Preferably, the image sensor capturing fluorescent and / or infrared light has a smaller image size than the second image sensor capturing visible light. For example, the image sensor for capturing visible light may have an image size diameter of 3.01 mm and an F number of 6, and the image sensor for capturing infrared light may have an image size diameter of 1.65 mm and an F number of 2.8. The image sensor, in particular an electronic image sensor, may be, for example, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Preferably, the electronic image sensor is a high definition (HD) image sensor having, for example, a full HD resolution. Typically, the electronic image sensor is configured to convert the captured image into an electrical image signal, and thus into image data. In particular, the electronic image sensor is arranged on the rod and / or the distal portion, such as the tip of the rod, and transmits the electrical image signal from the rod or the distal end of the rod to its proximal end via a transmission line, such as a wire, a cable and / or a flexible printed circuit board. Preferably, the electrical image signal generated by the electronic image sensor is transmitted from the rod to the handle of the endoscope and / or a display system and / or a processing unit for displaying the captured image. Optionally, the electrical image signal may be wirelessly transmitted directly from the rod and / or the distal portion, or wirelessly transmitted after being relayed to a transmitter contained in the handle. In the case of a 3D video endoscope, four image sensors are arranged in parallel, each group of two image sensors providing visible and fluorescent images from given different viewing angles.

[0031] Regarding “the first spectral region and the second spectral region are at least partially different from each other”, it can be understood that the first spectral region and its first wavelength band and the second spectral region and its second wavelength band do not include exactly the same wavelength. However, the first spectral region may completely include the second spectral region, and vice versa. For example, the first spectral region may include a wavelength range of 400nm to 900nm, and the second spectral region may include a wavelength range of 700nm to 800nm.

[0032] "White light" (also called "visible light") is generally understood to refer to the combined wavelengths of light between 380 nm and 750 nm, ie, electromagnetic radiation between the ultraviolet and infrared regions, the portion of the spectrum perceived by the healthy human eye.

[0033] "Fluorescence" specifically refers to light emitted by a substance called a fluorophore that absorbs light or other magnetic radiation. Fluorophores are usually irradiated with a specific excitation wavelength or band, resulting in the emission of light with a specific emission wavelength or band. Typically, the emission wavelength is longer than the excitation wavelength. For example, in the case of the commonly used fluorophore indocyanine green (ICG), the excitation wavelength range is between 600nm and 900nm, and the emission wavelength range is between 750nm and 950nm in the infrared spectrum. In fluorescence imaging, which is often used to optically define tumor areas during surgery, biological materials such as tissues in body cavities are directly stained with fluorophores, or the body or microorganisms convert the administered substance into a fluorophore, which is then imaged with an endoscope. In addition, autofluorescence can also be observed without pre-coloring of fluorophores or dyes.

[0034] Thus, "fluorescence" can refer to the excitation and / or emission wavelengths or bands of a fluorophore. The radiation that causes a fluorophore to fluoresce is often referred to as "excitation light," while the light emitted by the fluorophore is referred to as "emission light" or "fluorescence." In fluorescence imaging, an optional fluorescence filter can block the excitation wavelength from reaching the detection image sensor, so that fluorescence includes only the light emitted by the fluorophore.

[0035] The "refractive index" of an optical medium is a dimensionless number that gives an indication of the medium's ability to bend light. The refractive index specifically determines the degree to which a light path is bent or refracted when it enters the optical medium. For example, for a pentaprism including a prismatic wedge, a refractive index of 1.6 or higher is preferred.

[0036] In another embodiment of the imaging device, the at least one individual optical element and / or the further individual optical element is a lens for narrowing light in the first spectral region and / or in the second spectral region.

[0037] Although each reduction lens can be arranged in both the first separated light beam of the first spectral region and the second separated light beam of the second spectral region downstream of the pentaprism, it is particularly advantageous to arrange the reduction lens between the pentaprism and the fluorescence image sensor, in this way, the relative intensity of the fluorescence image (per unit area of ​​the sensor) is increased at the expense of resolution. Although the overall resolution is not a limiting parameter in fluorescence imaging, the increased fluorescence intensity significantly improves the signal-to-noise ratio of the fluorescence image sensor, thereby improving the overall imaging quality. By reducing the imaging using a reduction element (such as a lens), the photosensitivity of the first and / or second spectral region can be selectively increased. Therefore, a smaller sensor can be used to provide more light intensity in the corresponding spectral region. Due to the size restrictions caused by the inner rod diameter, the ability to use a smaller image sensor is particularly advantageous for an image sensor arranged perpendicular to the longitudinal direction of the rod. In addition, due to the reduction element and / or lens, aberrations of the corresponding image sensor during image capture are suppressed.

[0038] In order to provide a variable focal length, at least one individual optical element and / or another individual optical element may be movable.

[0039] Thus, by means of the at least one movable optical element, the image details on the image plane of the respective image sensor can be varied and adapted to different image portions and / or different applications. For moving the at least one individual optical element, for example, a linear motor and / or a piezoelectric element can be used. Likewise, the movable optical element can be connected to an operator control at the handle of the endoscope via a tension line. The at least one individual optical element is specifically movable along the longitudinal axis of the rod.

[0040] In a further embodiment of the imaging device, at least one separate optical element and / or the further separate optical element comprises a mirror element for redirecting the first light beam in the first spectral region and / or the second light beam in the second spectral region.

[0041] By arranging a separate optical element comprising a mirror element after the pentaprism, in particular corresponding spectral regions which are not redirected by the pentaprism itself can be redirected by the mirror element. Thus, for example, both image sensors can be arranged with their image planes parallel to the longitudinal axis of the pentaprism and / or the rod. Thus, both image sensors do not have to be arranged in a cross section of the rod perpendicular to the longitudinal axis.

[0042] A "mirror element" is in particular any optical element which reflects light and / or redirects light. A mirror element in particular comprises at least one reflecting surface. A mirror element can be, for example, a plane mirror surface and / or an attached reflecting prism.

[0043] In order to enable fluorescence imaging and / or capture only certain wavelengths of the corresponding spectral regions, at least one separate optical element and / or the other separate optical element may be a filter for blocking the excitation wavelength or for further distinguishing the first spectral region and / or the second spectral region.

[0044] Thus, in fluorescence imaging, a filter acting as a fluorescence filter can block the excitation wavelength from reaching the corresponding detection image sensor, so that the captured fluorescence only includes the light emitted by the applied fluorophores in the object field. Likewise, the wavelength range of the separated first or second spectral regions can be further modified by filters such as edge or band filters for distinguishing certain wavelengths.

[0045] In a further embodiment of the imaging device, the dichroic beam splitting layer is arranged on a surface of the body adjacent to a surface of the prism wedge, or on a surface of the prism wedge adjacent to a surface of the body.

[0046] By arranging a dichroic beamsplitting layer on a respective surface of the body or prism wedge, a compact and space-saving beamsplitting pentaprism is provided which is small enough to be arranged in the shaft and / or the distal end portion of the shaft of a COTT endoscope.

[0047] In order to integrate image capture into the imaging device, the imaging device comprises a first image sensor and / or a second image sensor.

[0048] Thus, maintaining a compact design of the pentaprism and the imaging device, the first image sensor and / or the second image sensor can be arranged outside the pentaprism and / or behind at least one optical element radially from the longitudinal axis of the rod or perpendicular to the longitudinal axis. Thus, the first image sensor and / or the second image sensor can likewise be arranged in the rod and / or its distal end portion. Thus, the two image sensors for capturing the first light beam with the first spectral region and the second light beam with the second spectral region can be arranged at respective distances to the pentaprism and / or to the at least one optical element, so that the optical path lengths of the two paths have the same value or different values. With the same optical path length value, a focused image is acquired for the first and second light beams.

[0049] In a further embodiment, the first image sensor and the second image sensor are arranged perpendicular to each other or both parallel to the optical axis of the imaging device.

[0050] Therefore, the first image sensor and the second image sensor can be flexibly arranged according to each corresponding inner diameter of the endoscope shaft.

[0051] To enable fluorescence imaging, a light source may be assigned to the imaging device, and the light source comprises a first illumination spectral region comprising white light and a second excitation spectral region comprising excitation light, thereby causing fluorophores within the illumination scene to emit fluorescence.

[0052] Therefore, although only one optical path is used for the incoming light beam before the pentaprism, through the beam-splitting pentaprism and the imaging device, white light and fluorescence images can be collected simultaneously and separately by a first image sensor dedicated to white light imaging in the visible light range and a second image sensor dedicated to fluorescence imaging. Therefore, compared with a conventional endoscope in which a shutter is closed between white light and fluorescence frames, a high overall frame rate in the superposition mode and a higher sensitivity of fluorescence imaging can be obtained while maintaining white light brightness and high fluorescence intensity in the tip chip endoscope.

[0053] In a further embodiment of the imaging device, the second image sensor for capturing the second spectral region including fluorescence has a smaller image area than the first image sensor for capturing the first spectral region including white light.

[0054] Due to the at least one separate optical element arranged behind the pentaprism in the proximal direction, the sensitivity of the image on the second image sensor for capturing fluorescent light and / or infrared light can be increased by reducing the size of the image by means of the at least one separate optical element. For example, thereby, the image size can be reduced by 45%, so that the image size of the second sensor can be reduced from 3.01 mm to 1.65 mm. This therefore leads to different system F numbers, whereby the image size of the first image sensor for visible light has an image size diameter of 3.01 mm and an F number of 6, and the image size of the second image sensor is reduced to a diameter of 1.65 mm and an F number of 2.8. As a result, the light intensity of the second sensor capturing fluorescent light and / or infrared light is increased by a factor of 4.5 relative to the visible light beam path.

[0055]

[0056] When the fluorescence and IR image sizes are small, larger pixels are used, thus achieving higher sensitivity and higher resolution, respectively.

[0057] In a further aspect of the present invention, the problem is solved by an objective system for an endoscope, wherein the objective system can be arranged in a distal part of a slender shaft of the endoscope, and at least a first image sensor for capturing an image of a first spectral region and a second image sensor for capturing an image of a second spectral region can be arranged in the slender shaft, wherein the objective system comprises an objective lens system having at least a first lens, at least a second lens and optionally other lenses so as to receive image light from the objective side and transmit the image light to the first image sensor and the second image sensor, wherein the objective comprises the imaging device previously described, wherein the imaging device is arranged between the proximal lens of the objective lens system and the first image sensor and / or the second image sensor.

[0058] Therefore, the objective system of the endoscope provides only one optical path for two spectral regions, preferably for white light and fluorescence imaging, wherein, after the lens system, the one optical path is split by a pentaprism into a separate first optical path for the first light beam within the first spectral region and a separate second optical path for the second light beam separated within the second spectral region, which allows images associated with each of the first and second spectral regions to be captured simultaneously by separate dedicated image sensors.

[0059] Therefore, the objective lens system can be directly arranged at the far end of the rod and / or in the far end part of the rod, while the imaging device can be arranged at a farther distance from the proximal side of the rod or the proximal part. Thus, an intermediate image or two or more intermediate images can be provided along the optical axis in the proximal direction between the objective lens system and the imaging device providing a longer focal length. Therefore, for example, the distance between the nearest lens of the objective lens system and the corresponding image sensor arranged along the optical axis can be longer, i.e. 70mm, instead of the traditional 20mm. Therefore, there is no need to use a larger video objective lens and therefore a larger prism, which will limit the spatial arrangement of the two image sensors. By arranging the imaging device in the proximal direction, keeping a farther distance from the nearest lens of the objective lens system, a smaller and more compact design of a pentaprism and a flexible arrangement of two image sensors can be applied.

[0060] Therefore, the function of the pentaprism is integrated into the overall system by a special optical design of the video endoscope, in which at least one intermediate image after the closest lens allows better control of the image-side focal length for the entire distance reached by the pentaprism. In addition, the stray light behavior of the complete optical system is improved. For example, the optical design is arranged for the following optical parameters: diameter of the optical system is 3.1 mm, focal length is -0.8 mm, F number is 4.5 to 6.0, diameter of the entrance pupil is 0.19 to 0.14, achromatic in the wavelength range of 400 to 950 nm, image ratio is 0.018.

[0061] In a further embodiment of the objective system, the light beam entering and / or leaving the pentaprism is focused and / or converged.

[0062] Therefore, no afocal beam path is required in the objective system and no post-focusing has to be applied after passing through the pentaprism. Despite the use of a focusing and / or converging beam path, due to the design of the pentaprism and the at least one separate optical element arranged subsequently, the aberrations that are common in systems known from the prior art do not occur in the objective system according to the invention and an overall improved image quality is provided.

[0063] In another aspect of the invention, the problem is solved by an endoscope, in particular a medical or industrial video endoscope, having a handle, an elongated shaft, a light source, an objective system and / or an imaging processing unit and / or a display system, wherein the endoscope comprises an imaging device as previously described or the objective system is the objective system as previously described, so that an image of a first spectral region and an image of a second spectral region are captured in parallel by a first image sensor and a second image sensor, respectively, and / or can be displayed as a superimposed image by the display system. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The present invention is further explained by the following exemplary description of specific embodiments. The accompanying drawings show:

[0065] Figure 1 is a schematic partial three-dimensional view of the endoscope and display system,

[0066] Figure 2 is a schematic longitudinal cross-sectional view of a pentaprism,

[0067] Figure 3 Yes Figure 2 A schematic longitudinal cross-sectional view of an imaging device of a pentaprism shown in FIG.

[0068] Figure 4 is a schematic longitudinal cross-sectional view of an objective system with a lens system and a proximally arranged imaging device. DETAILED DESCRIPTION

[0069] The video endoscope 101 includes a handle 103 and an elongated shaft 105, which may be connected to each other at a proximal end 107 of the shaft 105. The handle 103 includes operator controls 115 in the form of buttons and levers, and is connected at its proximal end via a cable 113 to an external control and processing unit (not shown) - commonly referred to as a camera control unit (CCU), and / or Figure 1 Display system 201 is shown. Display system 201 includes a monitor 203 and operator controls 215 for displaying endoscopic images.

[0070] The video endoscope 101 is designed to provide video and image data from an object space (not shown) within a body cavity. To this end, the elongated shaft 105 comprises a distal portion 111 at its distal end 109. The distal portion 111 of the elongated shaft 105 comprises an objective system 301 having an objective system 303 followed by an imaging device 400 on the proximal side 329 (see FIG. Figure 4 ).

[0071] The imaging device 400 includes a pentaprism 401 having a prism body 403 and a prism wedge 405. The prism wedge 405 is bonded to the prism body 403. In addition, the imaging device 400 includes a fluorescence filter 419 and a combined reduction lens 421 after the pentaprism 401 along the optical axis 373. A first image sensor 423 for capturing white light is arranged parallel to the first exit surface 413 of the pentaprism 401, and thus parallel to the optical axis 373. On the proximal side of the reduction lens 421, a second image sensor 425 ( Figure 3 and Figure 4 ).

[0072] The pentaprism 401 includes an incident surface 407 on its prism body 403, which is arranged perpendicular to the incident light beam 311 and the optical axis 373. In addition, the prism body 403 includes a first exit surface 413 facing the first image sensor 423 and a second internal reflection surface 411. The prism wedge 405 is arranged and bonded obliquely relative to the prism body 403 on the proximal side of the prism body 403. The prism wedge 405 includes a second exit surface 415 perpendicular to the optical axis 373. A dichroic beam splitting layer 417 is arranged between the prism body 403 and the prism wedge 405, forming a first internal reflection and transmission surface 409.

[0073] In the objective lens system 301, the lens system 303 includes, from the distal side 327 toward the proximal side 329 along the optical axis 373, a cover glass 339, a first distalmost objective lens 340, then an attenuation and / or relay optical element 341, a second lens 343 formed as a combined lens, a third lens 345, and a fourth lens 347 arranged in the distal end portion 111 of the elongated rod 105. At a distance from the fourth lens 347 in the proximal direction along the optical axis 373 is a fifth lens 351 formed as a combined lens. At a distance from the fifth lens 351 is a sixth lens 353 formed as a combined lens, and at a distance therefrom is a seventh lens 355 also formed as a combined lens and being the most proximal lens of the lens system 303. After the seventh lens 355 as the most proximal lens, the imaging device 400 having the pentaprism 401 as described above is arranged on the proximal side 329.

[0074] The inner diameter of the elongated rod 105 is 4 mm, and the diameter of the objective lens system 301 is 3.1 mm. The length of the pentaprism 401 along the optical axis 373 is 5 mm, and the entire imaging device 400 including the pentaprism 401 is 10 mm.

[0075] When the video endoscope 101 is used, the object beam 309 from the object space at the distal side 327 is collected by the objective system 301 and conditioned in a single optical path with a converging beam by the objective system 303. After the last seventh lens 355 of the lens system 303, the incident beam 311 enters the pentaprism 401 through the incident surface 407 and enters the prism body 403. Since the refractive index of the prism body 403 and the prism wedge 405 are both 0.6, the incoming incident beam 311 is selectively split into a white beam 323 and a fluorescent beam 325 by the dichroic beam splitting layer 417. The reflected white beam 323 is directed toward the second internal reflection surface 411 at a first angle 431 of 70° relative to the first internal reflection and transmission surface 409. The split and redirected white light beam 323 is reflected by the second internal reflection surface 411 of the prism body 403 at a second angle 433 of 65° relative to the second internal reflection surface 411 and in the direction of the first image sensor 423. As a result, the second reflected white light beam 325 intersects the optical axis 373 at an angle of 90° and has a third angle 435 of 90° relative to the first exit surface 413 of the prism body 403, wherein the light beam passes through the first exit surface 413, the air gap, and then passes through the first sensor cover glass 427 to intersect the image plane of the first image sensor 423. The fluorescent light beam 325 passes through the dichroic beam splitter layer 417 along the optical axis 373 and exits the prism wedge 405 through the second exit surface 415 in the proximal direction (see FIG. 4 ). Figure 2 , Figure 3 and Figure 4 ).

[0076] The fluorescence filter 419 disposed separately on the proximal side of the second exit surface 415 is used to absorb the excitation wavelength of the fluorescence and pass only the emission band of the fluorophore used in the object space. Subsequently, the fluorescence beam 325 is further focused by the reduction lens 421 before the fluorescence beam 325 passes through the air gap, the second sensor cover glass 429 and intersects with the image plane of the second image sensor 425 to capture the fluorescence. As a result, a smaller image size diameter of 1.65 mm is used in the second image sensor 425 for capturing fluorescence, compared to the image size diameter of 3.01 mm of the first image sensor 423 for capturing white light. The F number of the first image sensor 423 is 6.0 and the F number of the second image sensor 425 is 2.8, respectively. Due to the reduction lens 421, such a reduced image size of the image captured by the second image sensor 425 can be achieved, the intensity of the image is increased relative to the image size of the fluorescence on the second image sensor 425, and the sensitivity of the image sensor 425 to the fluorescence image is improved by increasing the signal-to-noise ratio. At the same time, aberration is suppressed in image capturing by the second image sensor 425 by the reduction lens 421 .

[0077] Therefore, the video endoscope 101 is provided with a compact imaging system 400 and a compact pentaprism 401 (providing a light beam split into white light and fluorescence), which are arranged in a narrow rod 105, allowing the separate white light beam 323 and fluorescent light beam 325 to be captured simultaneously by separate first and second image sensors 423, 425, with high quality images and a high frame rate of 60 frames per second.

[0078] Reference Numbers

[0079] 101 Video Endoscope

[0080] 103 handle

[0081] 105 slender rod

[0082] 107 rod proximal end

[0083] 109 rod far end

[0084] 111 Distal part

[0085] 113 Cable

[0086] 115 Operator Controls

[0087] 201 Display System

[0088] 203 Monitor

[0089] 215 Operator Controls

[0090] 301 objective system

[0091] 303 lens system

[0092] 309 Object Beam

[0093] 311 Incident beam

[0094] 323 White Beam

[0095] 325 fluorescent beam

[0096] 327 distal side

[0097] 329 proximal side

[0098] 339 Cover Glass

[0099] 340 First most distant objective

[0100] 341 Attenuation and / or relay optical elements

[0101] 343 Second lens (combination)

[0102] 345 Third lens

[0103] 347 fourth lens (combination)

[0104] 351 fifth lens (combination)

[0105] 353 Sixth lens (combination)

[0106] 355 seventh lens (combination)

[0107] 373 optical axis

[0108] 400 Imaging Devices

[0109] 401 Pentaprism

[0110] 403 prism body

[0111] 405 Prism Wedge

[0112] 407 Incident Surface

[0113] 409 First Internal Reflection and Transmission Surface

[0114] 411 second internal reflection surface

[0115] 413 first exit surface

[0116] 415 second exit surface

[0117] 417 Dichroic beam splitter layer

[0118] 419 Fluorescence Filter

[0119] 421 Zooming lens

[0120] 423 First Image Sensor (White Light)

[0121] 425 Second image sensor (fluorescence)

[0122] 427 First sensor cover glass

[0123] 429 Second sensor cover glass

[0124] 431 First Angle

[0125] 433 Second Angle

[0126] 435 The third angle

Claims

1. An imaging device (400) for a distal end portion (111) of an endoscope (101), wherein the imaging device (400) comprises a pentaprism (401) having a body (403) and a prism wedge (405) and an optical axis (373), and an incident surface (407), a second internal reflection surface (411) and a first exit surface (413) are arranged on the body (403), and a second exit surface (415) is arranged on the prism wedge (405), and the pentaprism (401) further comprises a dichroic beam splitting layer (417) as a first internal reflection and transmission beam splitting layer (409), and is used to capture at least a first light A first image sensor (423) for capturing light of a spectral region and a second image sensor (425) for capturing light of a second spectral region can be assigned to an imaging device (400), wherein the first spectral region and the second spectral region are at least partially different from each other, and the dichroic beam splitting layer (417) is arranged between the body (403) and the prism wedge (405) of the pentaprism (401), so that an incident light beam (311) including the first spectral region and the second spectral region is split by the dichroic beam splitting layer (417) into a first light beam (323) of the first spectral region and a second light beam (325) of the second spectral region, characterized in that At least one separate optical element (419, 421) is arranged between the pentaprism (401) and the first image sensor (423) and / or the second image sensor (425) for changing the characteristics of light in the first spectral region and / or the second spectral region so that the first image sensor (423) and the second image sensor (425) can capture two optimized separate images for superimposed imaging of light in the first spectral region and the second spectral region.

2. The imaging device (400) according to claim 1, characterized in that: The at least one separate optical element and / or the further separate optical element (419, 421) is a lens (421) for reducing light in the first spectral region and / or the second spectral region.

3. The imaging device (400) according to claim 1 or 2, characterized in that: The at least one individual optical element and / or the other individual optical element (419, 421) is movable.

4. The imaging device (400) according to any one of the preceding claims, characterized in that The at least one separate optical element and / or the further separate optical element (419, 421) comprises a mirror element for redirecting the first light beam (323) of the first spectral region and / or the second light beam (325) of the second spectral region.

5. The imaging device (400) according to any one of the preceding claims, characterized in that The at least one separate optical element and / or the further separate optical element (419, 421) is a filter (419) for blocking the excitation wavelength or for further distinguishing the first spectral region and / or the second spectral region.

6. The imaging device (400) according to any one of the preceding claims, characterized in that The dichroic beam splitting layer (417) is arranged on a surface of the main body (403) adjacent to a surface of the prism wedge (405), or on a surface of the prism wedge (405) adjacent to a surface of the main body (403).

7. The imaging device (400) according to any one of the preceding claims, characterized in that The imaging device (401) includes the first image sensor (423) and / or the second image sensor (425).

8. The imaging device (400) according to any one of the preceding claims, characterized in that The first image sensor (423) and the second image sensor (425) are arranged to be perpendicular to each other or parallel to the optical axis (373) of the imaging device (40).

9. The imaging device (400) according to any one of the preceding claims, wherein: A light source can be assigned to the imaging device (40), characterized in that the light source includes a first illumination spectrum region and a second excitation spectrum region, the first illumination spectrum region includes white light, and the second excitation spectrum region includes excitation light, so that the fluorophores in the illumination scene emit fluorescence.

10. The imaging device (400) according to claim 9, characterized in that: The second image sensor (425) for capturing the second spectral region including fluorescence has a smaller image area than the first image sensor (423) for capturing the first spectral region including white light.

11. An objective system (301) for an endoscope (101), wherein the objective system (301) can be arranged in a distal end portion (111) of an elongated shaft (105) of the endoscope (101), and at least a first image sensor (423) for capturing an image of a first spectral region and a second image sensor (425) for capturing an image of a second spectral region can be arranged in the elongated shaft (105), wherein: The objective system (301) comprises an objective lens system (303) having at least a first lens (340), at least a second lens (343) and optionally other lenses (345, 347, 349, 351, 353, 355) so as to receive image light from the objective side and transmit the image light to the first image sensor (423) and the second image sensor (425), characterized in that the objective system (301) comprises an imaging device (400) according to any one of claims 1 to 10, wherein the imaging device (400) is arranged between the nearest lens (355) of the objective lens system (301) and the first image sensor and / or the second image sensor (423, 425).

12. The objective lens system (301) according to claim 10 or 11, characterized in that: The light beam entering and / or leaving the pentaprism (401) is focused and / or converged.

13. An endoscope (101), in particular a medical or industrial video endoscope, having a handle (103), an elongated shaft (105), a light source, an objective system and / or an image processing unit and / or a display system (201), characterized in that The endoscope (101) comprises an imaging device according to any one of claims 1 to 10, or the objective system is an objective system (301) according to claim 11 or 12, so that the image of the first spectral region and the image of the second spectral region are captured in parallel by the first image sensor (423) and the second image sensor (425), respectively, and / or can be displayed as a superimposed image by the display system (201).

Images