Imaging device for a distal end section of an endoscope, a lens system and endoscope

Abstract

The present invention relates to an imaging device for a distal end section of an endoscope, wherein the imaging device comprises a pentaprism with a main body and a prism wedge, and the imaging device is assigned at least one first image sensor for detecting light of a first spectral range and a second image sensor for detecting light of a second spectral range, and a dichroic beam splitter layer is arranged between the main body and the prism wedge of the pentaprism as a first internal reflective and transparent splitter layer, such that incident rays comprising the first and second spectral ranges are split by the dichroic beam splitter layer into first rays of the first spectral range and second rays of the second spectral range.wherein at least one separate optical element for modifying a property of the light in the first spectral range and / or the second spectral range is arranged between the pentaprism and the first image sensor and / or the second image sensor. The invention further relates to a lens system and an endoscope.

Description

[0001] The present invention relates to an imaging device for a distal end section of an endoscope, wherein the imaging device comprises a pentaprism with a main body, a prism wedge, and an optical axis, and wherein an entrance surface, a second inner reflective surface, and a first exit surface are arranged on the main body, and a second exit surface is arranged on the prism wedge, and wherein the pentaprism further comprises a dichroic beam splitter layer as a first inner reflective and transparent splitter layer, and wherein the imaging device can be assigned at least a first image sensor for detecting light of a first spectral range and a second image sensor for detecting light of a second spectral range, wherein the first spectral range and the second spectral range differ at least partially from each other.and the dichroic beam splitter layer is arranged between the main body and the prism wedge of the pentaprism, such that incident rays comprising the first and second spectral ranges are split by the dichroic beam splitter layer into first rays of the first spectral range and second rays of the second spectral range. The invention further relates to a lens system and an endoscope.

[0002] Endoscopes for use in medical and / or non-medical applications can utilize both white light and fluorescence imaging. Endoscopic instruments intended for industrial rather than medical use are often referred to as borescopes. Since this invention relates to both medical endoscopes and borescopes, the term "endoscope" is generally used to encompass both instruments. Conventional endoscopes can acquire both white light and fluorescence images using a single optical path and a single image sensor by capturing alternating frames with offset white light and excitation illumination.Such a system configuration results in a frame rate that is considerably lower than that of a system using only visible white light, typically reaching at most half the frame rate of a system using only white light. This low frame rate leads to undesirable motion blur. In addition to the necessary stopping down between white light and fluorescence frames, the sensitivity of the fluorescence frames is limited by the shared optical path, typically resulting in one signal not being able to be attenuated relative to the other. Image processing then analyzes and combines the images from alternating frames into a fluorescence / white light superposition, resulting in a low overall frame rate.This technique results in lower sensitivity in the fluorescence range as well as reduced brightness and resolution of the superimposed image compared to an image created using only white light.

[0003] An alternative to using only one image sensor, dimming the individual images, and superimposing the white light and fluorescence images would be to incorporate two complete lens systems into an endoscope to capture white light and fluorescence images separately. However, due to the space required for two parallel lens systems, not to mention the added complexity of alignment, increased costs, and loss of image brightness, this is not a practical solution for chip-on-the-tip (COTT) endoscopes, where the respective electronic image sensor(s) is / are located in the distal end section, for example, the tip of the narrow shaft of the endoscope.

[0004] Instead of two complete lens systems, it is also possible to use only one lens system and subsequently split the beams using a beam splitter to direct the split beams to two different image sensors. However, it is not possible to miniaturize the conventional beam splitter and the two image sensors within the small space provided by COTT endoscopes. For example, splitting an afocal beam path containing both white and fluorescent light using a 45° beam splitter has the disadvantage that, in addition to providing the necessary afocal beam path itself, subsequent focusing is required. Otherwise, using a conventional beam splitter in the converging beam path in front of the image sensors results in imaging errors on the sensor, leading to a deterioration of transmission and image quality.Overall, this necessitates large imaging devices due to the required refocusing.

[0005] US 2020 / 0088579 A1 discloses a hybrid spectral imager comprising a multiband filter optic with a beam splitter for generating at least two replica images of a target image and a tunable multiband filter inserted into the imaging path that provides tunable multiband pass filtering in the image replicas. The beam splitter can be a pentaprism, wherein one of its five surfaces is coated with a polychrome mirror substrate and this coated surface is cemented to a triangular prism to form the rear surface of the prism parallel to the front surface of the pentaprism. Furthermore, the pentaprism includes a tilt actuator for adjusting the tilt angle of the prism assembly and thus the direction of the imaging rays.Images of a target object are focused by a lens optic and split onto two image sensors by the tilting prism array. With each tilt in snapshot mode, a new set of images is simultaneously acquired, allowing the entire spectrum to be scanned in scan mode to create a complete spectral cube for the target object. To accommodate sensor arrays of varying sizes, the path lengths of the two split beams must be essentially equal. Consequently, the arrangement of this hybrid spectral imager is limited within the narrow shaft of a COTT endoscope. A similar imaging device is known from US 2012 / 0105594 A1 for a TOF 3D camera. This device features an optical system with a beam splitter in the form of a pentaprism consisting of a main body and a wedge prism. The main body has an entrance face, an internal reflective surface, and an exit face.The wedge prism is designed with a dichroic beam-splitter layer as an internal reflective and transmitting surface. From DE 10 2022 116 292 A1, an imaging device for the distal end of an endoscope is known, which uses a pentaprism consisting of a main body, a wedge prism, and a dichroic beam-splitter layer arranged between them. Optical filter coatings can be provided on the exit surfaces of the pentaprism, which are aligned with image sensors, to increase the optical density of the exiting beams in a spectral range. These designs are also only partially suitable for the structural requirements in the distal end region of a COTT endoscope.

[0006] US Patent 2014 / 0225992 A1 describes a minimally invasive surgical system comprising an image acquisition unit including a prism array and a sensor array. The image acquisition unit includes a common lens array followed by a sensor array, which in turn includes a prism array, a reflecting unit, and coplanar image acquisition sensors. The two image acquisition sensors, with similar image sizes, are arranged symmetrically about a plane intersecting the longitudinal axis of the stereoscopic endoscope, with only a small gap between the respective surfaces of the prism array and each coplanar image acquisition sensor.

[0007] The objective of the present invention is to improve upon the known state of the art.

[0008] The problem is solved by an imaging device for a distal end section of an endoscope, wherein the imaging device comprises a pentaprism with a main body and a prism wedge and an optical axis, and wherein an entrance surface, a second inner reflective surface and a first exit surface are arranged on the main body and a second exit surface is arranged on the prism wedge, and wherein the pentaprism further comprises a dichroic beam splitter layer as the first inner reflective and transparent splitter layer, and wherein the imaging device can be associated with at least a first image sensor for detecting light of a first spectral range and a second image sensor for detecting light of a second spectral range, wherein the first spectral range and the second spectral range differ at least partially from each other.and the dichroic beam splitter layer is arranged between the main body and the prism wedge of the pentaprism, such that incident rays comprising the first and second spectral ranges are split by the dichroic beam splitter layer into first rays of the first spectral range and second rays of the second spectral range, wherein at least one separate optical element is arranged between the pentaprism and the first image sensor and / or the second image sensor for modifying a property of the light of the first spectral range and / or the second spectral range, such that two optimized separate images for superimposing the light of the first spectral range and the second spectral range can be detected by the first image sensor and the second image sensor.

[0009] This provides an imaging device for a chip-on-the-tip endoscope that enables the optimized simultaneous acquisition of images from two different spectral ranges using two separate image sensors, thus accommodating the limited space available in the shaft of this type of endoscope. This allows for an increased overall frame rate and optimized image quality within the small, confined space of a video endoscope shaft. The special design of the pentaprism and the at least one separate optical element positioned between the pentaprism and the respective image sensor(s) allows the first and second split beams to be further optimized and / or corrected independently to enable superimposed imaging of the light from both spectral ranges with the best possible image quality.This allows at least two optically well-corrected, separate images to be captured in a miniaturized design of the imaging device, which can be arranged in the small space available in the shafts of COTT endoscopes.

[0010] Due to the special pentaprism design, there is no need to provide an afocal beam using an objective lens system upstream of the imaging device. An afocal beam cannot be achieved in the narrow shaft of COTT endoscopes due to design and space constraints. Instead, the pentaprism can be arranged in a converging beam path and is designed so that both image sensors simultaneously receive the image from the object space without aberrations.

[0011] Furthermore, due to the special geometric and space-saving design of the pentaprism, further optimization of the relative beam path is possible through at least one separate optical element arranged between the pentaprism and the respective sensor. This separate optical element can be present in only one of the two respective beam paths, or both beam paths can contain identical or different optical elements. This allows, for example, the optimization of the sensitivity, image brightness, and / or resolution of a specific spectral range without necessarily affecting the optical parameters of the other spectral range captured by the respective image sensor.

[0012] One of the key innovations of the invention lies in the specific design of the pentaprism with a prism wedge in combination with at least one downstream separate optical element, which is arranged between the pentaprism and at least one of the two image sensors. This enables the simultaneous acquisition of two images with a high frame rate and high sensitivity, and allows the imaging device to be positioned within the small, confined space of a COTT endoscope shaft. This allows both image sensors to be used at full frame rate with optimized and / or specially adapted image size and / or characteristics.This design achieves a space-saving geometry for the imaging device through the special configuration of the pentaprism in combination with at least one downstream separate optical element. This allows for easy mounting of the imaging device and / or the associated image sensors in the shaft of an endoscope in both the longitudinal and radial directions of the shaft. Simultaneously, optimized acquisition of separate images in the first and second spectral ranges is enabled by separate, dedicated image sensors, resulting in optimized and improved image quality. The design of the pentaprism in combination with the separate optical element allows for a frame rate of 60 frames per second or even higher.

[0013] Unless otherwise stated, the following terms have the following meanings within the context of this disclosure.

[0014] An “endoscope”, in particular a video endoscope, is an endoscope with a means for digital image acquisition in and / or at the distal end of the elongated shaft and for transmitting the data from there, for example, 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 the elongated shaft or at its distal end for image acquisition. The video endoscope is in particular any type of digital endoscope, for example, a 2D colonoscope, a laparoscope, a gastroenteroscope, or a 3D video endoscope. The endoscope is in particular a chip-on-the-tip (COTT) endoscope.

[0015] The "elongated shaft" is, in particular, a rigid, semi-flexible, or flexible tube. Specifically, the shaft is configured for insertion into a cavity to be examined endoscopically, such as a cavity within a human or animal body. In industrial applications, the shaft of the endoscope or borescope is inserted into an element such as a pipe or other area that is difficult to access directly, for example, behind a wall. Generally, the shaft can have an outer diameter ranging from 4 mm to 10 mm. In addition to the objective system, the imaging device, and two or more image sensors, the shaft may have one or more channels for irrigation or for inserting working instruments (generally referred to as "working channels") to achieve the desired effect within the cavity or opening.The shaft can be detachably or permanently attached to a handle at its proximal end. The distal end of the elongated shaft is the section furthest from the user, while the proximal end is closer to the user.

[0016] An “objective system” is an optical system that includes an objective lens system to receive, transmit and / or modify the image light from an object space.

[0017] An “objective lens system” comprises, in particular, in sequence from one side of the object, a coverslip and / or a first lens, a second lens, and optionally further lenses arranged along an optical axis of the lens system. Optionally, one or more optical filters may be located between any two lenses of the lens system.

[0018] A "lens" is, in particular, a transparent optical body that focuses or scatters light rays by refraction. The first lens, the second lens, and optionally further lenses can be single lenses separated by an air gap or in contact with neighboring lenses only at a few points. A lens can also be a combined lens, a compound lens, and / or a rod lens. Preferably, the lenses are made of glass and / or a crystalline material.

[0019] An "imaging device" is understood to mean, in particular, a device that further modifies the imaging light transmitted by the objective system and distributes it between at least two image sensors. The imaging device comprises at least the pentaprism, wherein at least one separate optical element and at least two image sensors for image acquisition are assignable to or included within it. The imaging device need not necessarily be located in the distal end section of the shaft near the objective system, but can also be situated further proximally at a distance from the objective system in the distal end section.

[0020] A pentaprism is an optical component in the form of a geometric prism with five sides. The pentaprism consists, in particular, of a main body and a prism wedge, which together form the five reflective, transparent, and / or opaque sides of the pentaprism in a longitudinal section view. The pentaprism can be used for various optical effects. The optical properties of the pentaprism depend, in particular, on the angles and / or the position of the optically effective prism faces relative to each other, as well as on the refractive indices of the material of the main body and the prism wedge. In particular, the main body and the prism wedge are made of glass, and preferably the glass of the main body and the prism wedge is selected such that they have the same or nearly the same refractive index. For example, the refractive indices of the main body and the prism wedge can both be 1.6.In a cross-sectional view parallel to the direction of propagation of the incident light, and thus in a longitudinal section, the pentaprism essentially has the shape of a pentagon. In particular, the pentaprism has a longitudinal length, and thus along the optical axis, of less than 5.0 mm. Specifically, the pentaprism has a diameter perpendicular to the optical axis of less than 3.5 mm. The prism wedge is preferably arranged proximal to the main body and cemented to it. The cemented prism wedge, in particular, prevents beam misalignment errors on the second image sensor, which is arranged, in particular, in the proximal direction perpendicular to the optical axis.

[0021] The term "entry surface" on the main body of the pentaprism refers specifically to the surface of the pentaprism through which the incoming rays (incident rays) encompassing the first and second spectral ranges enter the pentaprism. A portion of the entry surface on the main body can serve as an entrance aperture, and areas outside the effective diameter of the incident ray can be made opaque to incident light. Incident rays preferably enter the pentaprism only via the entry surface of the main body. Therefore, areas of the entry surface of the main body and / or the non-transmissive surface of the main body and the prism wedge can be coated with an opaque substance, such as black paint, to prevent the penetration of scattered or unwanted light.

[0022] The "second inner reflective surface" is, in particular, a surface of the main body of the pentaprism, at which the first rays, split by the dichroic beam splitter layer arranged between the main body and the prism wedge, are reflected internally within the main body and directed towards the first image sensor. Specifically, the "second inner reflective surface" of the main body directs the split first rays perpendicular to the longitudinal axis of the pentaprism and to the image plane of the first image sensor. In particular, the second inner reflective surface is a mirror surface that serves as the internal reflecting surface. Preferably, the second inner reflective surface, with the exception of the dichroic beam splitter layer, is the only reflective surface of the main body.

[0023] A "first exit surface" is understood to be, in particular, a surface on the main body of the pentaprism that is essentially parallel to the longitudinal axis of the pentaprism and / or the stem. The first exit surface is, in particular, the longest side of the pentaprism in the cross-sectional view along the longitudinal axis. Specifically, the first rays, split and reflected by the second inner reflecting surface of the main body, exit the main body through the first exit surface.In particular, the surfaces of the main body of the pentaprism are arranged such that there is an angle of 90° between the incident rays entering the main body through the entrance surface and the split and reflected first rays exiting the main body through the first exit surface and / or between the first rays reflected by the dichroic beam splitter layer and the second rays exiting the main body through the first exit surface.

[0024] A dichroic beam splitter layer is, in particular, a thin layer that selectively reflects or transmits light depending on its wavelength. The dichroic beam splitter layer is designed such that the incident rays are split into first rays of the first spectral range and second rays of the second spectral range. The dichroic beam splitter layer is positioned between the main body and the prism wedge of the pentaprism. Specifically, the entrance surface of the main body, through which the incident rays pass, is located substantially opposite the surface of the main body on or adjacent to which the dichroic beam splitter layer is positioned.The dichroic beam splitter layer is oriented obliquely to the optical axis, the longitudinal axis of the pentaprism and / or the shaft, and in a vertical direction perpendicular to the longitudinal axis and / or optical axis. The dichroic beam splitter layer can be a coating applied to the respective surfaces of the main body and / or the prism wedge that are adjacent to each other. The adjacent surfaces of the main body and the prism wedge with the associated coating(s) can be bonded with optical cement. The combination of these coated surfaces and the optical cement can thus act as a dichroic filter.The phrase "the dichroic beam splitter layer is arranged between the adjacent surfaces" means that, in particular, the dichroic beam splitter layer and / or coating is arranged on at least one surface of the two adjacent surfaces of the main body and the prism wedge.

[0025] A dichroic beam splitter layer can also be a dielectric coating or a dichroic mirror. The dichroic beam splitter layer is specifically designed as a first inner reflective and transparent splitter layer, which causes the first rays to be reflected internally and directed towards the second inner reflective surface of the main body, while the second rays are directed towards the prism wedge. In particular, the dichroic beam splitter layer is designed such that any two spectral ranges can be split and thus separated. Specifically, the dichroic beam splitter layer splits the incident rays into first rays with a spectrum of 400 to 658 nm in the visible range and second rays with a wavelength of 800 to 950 nm in the near-infrared range.

[0026] A "second exit surface" is understood to mean, in particular, a surface on the prism wedge through which the transmitted second rays of the second spectral range exit the pentaprism. The second exit surface is arranged, in particular, parallel to the entrance surface of the main body. The entrance surface of the main body is located, in particular, on the distal side, and the second exit surface of the prism wedge is located, in particular, on the proximal side of the pentaprism, with the entrance surface of the main body and the second exit surface of the prism wedge being opposite each other.

[0027] A "separate optical element" is understood to mean, in particular, any type of optical element that modifies, controls, and / or corrects a property of the first rays of the first spectral range or the second rays of the second spectral range. The separate optical element, or two or more optical elements, are specifically arranged downstream of the pentaprism. A single separate optical element, or two or more separate optical elements, can be positioned between an outer surface of the pentaprism in a radial direction from the optical axis, or along the optical axis and thus the longitudinal axis of the pentaprism or its stem.For a space-saving imaging device, the at least one separate optical element is arranged between the second exit face of the prism wedge and the image sensor, which is positioned with its image plane perpendicular to the optical axis and / or the longitudinal direction of the pentaprism and / or the shaft. Therefore, preferably the one separate optical element, or two or more separate optical elements, are arranged on the proximal side of the pentaprism within the shaft of the endoscope.

[0028] The term "separate" optical element means that this optical element is generally not an integral part of the pentaprism, nor is it an integral part of either of the image sensors. Therefore, in most embodiments, the separate optical element is not cemented to the second exit face of the prism wedge or in direct contact with the pentaprism or the image sensor. However, this is not a limitation, and some embodiments are provided in which these elements may be connected and / or in direct contact. Furthermore, the term "separate" can also mean that the pentaprism and the subsequent optical element have different optical functions within the imaging device.

[0029] The "optical axis" is, in particular, a line along which a certain degree of rotational symmetry exists in an optical system. The optical axis is, in particular, an imaginary line that defines the path along which the incident rays propagate through a lens system in front of the imaging device or enter the imaging device. Preferably, the optical axis passes through the center of curvature of each optical element within a lens system and / or objective system and / or the first entrance face of the pentaprism of the imaging device. However, the optical axis can also be bent and / or deflected by a lens, an optical element, the imaging device, and / or the at least one optical element downstream of the pentaprism and / or prism wedge.

[0030] An "image sensor" has its sensor plane located in an image plane of the imaging device. The sensor plane of each image sensor can be substantially spaced apart and arranged parallel or perpendicular to the longitudinal axis of the pentaprism and / or the shaft. Generally, the terms "first image sensor" and "second image sensor" serve only for differentiation. Thus, the second image sensor can be arranged instead of the first, and vice versa. Preferably, the first image sensor is arranged parallel to the first exit surface located on the main body of the pentaprism, and the second image sensor is preferably arranged perpendicular to the longitudinal axis of the pentaprism and / or the shaft, and thus parallel to the second exit surface located on the prism wedge of the pentaprism. In preferred embodiments, the image size at each image sensor is at least 1.6 mm or more.The image planes of the first and second image sensors can be of the same size and / or have different properties. Preferably, the image sensor that detects fluorescent and / or infrared light has a smaller image size than the second image sensor that detects visible light. For example, the image sensor that detects visible light can have an image diameter of 3.01 mm and an aperture of f / 6, and the image sensor that detects infrared light can have an image diameter of 1.65 mm and an aperture of f / 2.8. The image sensor, in particular an electronic image sensor, can 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, for example, one with full HD resolution.In general, the electronic image sensor is designed to convert the captured image into electrical image signals and thus image data. Specifically, the electronic image sensor is located in the shaft and / or the distal end section, for example, the shaft tip, and transmits the electrical image signals from the shaft or the distal end of the shaft to its proximal end via electrical transmission lines, such as wires, cables, and / or a flexible circuit board. Preferably, the electrical image signals generated by the electronic image sensor are transmitted from the shaft to the handle of the endoscope and / or to a display system and / or a processing unit for displaying the captured images. Alternatively, the electrical image signals can be transmitted wirelessly, either directly from the shaft and / or the distal end section or after being relayed to a transmitter located in the handle.In a 3D video endoscope, four image sensors are arranged in parallel, with two image sensors providing visible and fluorescent images from a specific perspective.

[0031] Regarding the statement "the first spectral range and the second spectral range differ at least partially from each other," it should be understood that the first spectral range, and thus a first wavelength band, and the second spectral range, and thus a second wavelength band, do not encompass exactly the same wavelengths. However, the first spectral range can completely encompass the second spectral range, or vice versa. For example, the first spectral range can cover the wavelength range from 400 nm to 900 nm, and the second spectral range can cover the wavelength range from 700 nm to 800 nm.

[0032] "White light" (also called "visible light") is usually understood to be a combination of light wavelengths in the range of 380 nm to 750 nm, i.e. between the ultraviolet and infrared range, i.e. electromagnetic radiation within the part of the spectrum that can be perceived by a healthy human eye.

[0033] Fluorescent light refers specifically to the light emission from a substance called a fluorophore, which has absorbed light or other magnetic radiation. The fluorophore is typically irradiated with a specific excitation wavelength or wavelength band, resulting in the emission of light with a specific emission wavelength or wavelength band. The emission wavelength is usually longer than the excitation wavelength. For example, the commonly used fluorophore indocyanine green (ICG) has an excitation wavelength range between 600 nm and 900 nm and an emission wavelength range between 750 nm and 950 nm in the infrared spectrum.Fluorescence imaging, frequently used to visually define a tumor area during surgery, involves directly staining biological material, such as tissue in a body cavity, with a fluorophore, or converting an administered substance into a fluorophore by the body or a microorganism before imaging with an endoscope. Autofluorescence can also be observed without prior staining with a fluorophore or dye.

[0034] Consequently, "fluorescence light" can refer to the excitation and / or emission wavelengths or wavelength bands of a fluorophore. Radiation that causes a fluorophore to emit fluorescent light is generally referred to as "excitation light," and the resulting light emitted by the fluorophore is referred to as "emission light" or "fluorescence light." In fluorescence imaging, an optional fluorescence filter can prevent the excitation wavelength from reaching the capturing image sensor, so that the fluorescent light consists only of the light emitted by the fluorophore.

[0035] The refractive index of an optical medium is a dimensionless number that indicates the medium's ability to refract light. Specifically, the refractive index determines how much the path of light is bent or refracted upon entering the optical medium. For example, a refractive index of 1.6 or higher is preferred for a pentaprism including its prism wedge.

[0036] In another embodiment of the imaging device, the at least one separate optical element and / or another separate optical element is a lens for reducing the size of the light of the first spectral range and / or the second spectral range.

[0037] Although a reducing lens can be used in both the first split beams of the first spectral range and the second split beams of the second spectral range behind the pentaprism, it is particularly advantageous to position the reducing lens between the pentaprism and a fluorescence imaging sensor. This increases the relative intensity (per unit area of ​​the sensor) of the fluorescence image at the expense of resolution. While overall resolution is not a limiting parameter in fluorescence imaging, the increased fluorescence intensity significantly improves the signal-to-noise ratio at the fluorescence imaging sensor, thus enhancing the overall image quality. By reducing the image size using a reducing element, such as a lens, the light sensitivity of the first and / or second spectral range can be selectively increased.Consequently, a smaller sensor can be used, providing higher light intensity in the respective spectral range. The possibility of using a reduced-size image sensor is particularly advantageous for sensors positioned perpendicular to the longitudinal direction of the shaft, as the size is limited by the inner shaft diameter. Furthermore, the reduction element and / or lens prevent aberrations during image acquisition by the respective image sensor.

[0038] To provide a variable focal length, at least one separate optical element and / or another separate optical element can be movable.

[0039] This allows the image area on the image plane of the respective image sensor to be changed by means of at least one movable optical element and adapted for different image sections and / or different applications. A linear motor and / or a piezoelectric element, for example, can be used to move the at least one separate optical element. The movable optical element can also be connected to the operator control on the handle of an endoscope via a tension wire. The at least one separate optical element is movable, in particular, along the longitudinal axis of the shaft.

[0040] In a further embodiment of the imaging device, the at least one separate optical element and / or another separate optical element comprises a mirror element for deflecting the first rays of the first spectral range and / or the second rays of the second spectral range.

[0041] By placing a separate optical element, comprising a mirror element, downstream of the pentaprism, the specific spectral range not deflected by the pentaprism itself can be deflected by the mirror element. For example, both image sensors can be positioned with their image planes parallel to the longitudinal axis of the pentaprism and / or the shaft. Thus, neither image sensor needs to be perpendicular to the longitudinal axis in the cross-section of the shaft.

[0042] A "mirror element" is understood to mean, in particular, any optical element that reflects and / or deflects light. The mirror element must have at least one reflective surface. For example, the mirror element could be a flat mirror surface and / or an additional reflective prism.

[0043] In order to enable fluorescence imaging and / or to detect only certain wavelengths of the respective spectral range, the at least one separate optical element and / or another separate optical element can be a filter to block an excitation wavelength or to further differentiate the first spectral range and / or the second spectral range.

[0044] Therefore, when used as a fluorescence filter in fluorescence imaging, the filter can prevent the excitation wavelength from reaching the respective detecting image sensor, and thus the detected fluorescence light comprises only the light emitted by a fluorophore placed in the object field. Likewise, the wavelength range of the split first or second spectral range can be further modified by a filter, for example an edge or bandpass filter, to distinguish specific wavelengths.

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

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

[0047] To integrate image acquisition into the imaging device, the imaging device includes the first image sensor and / or the second image sensor.

[0048] While maintaining the compact design of the pentaprism and the imaging device, the first image sensor and / or the second image sensor can therefore be arranged outside the pentaprism and / or downstream of the at least one optical element in a radial direction from the longitudinal axis of the shaft or perpendicular to the longitudinal axis. The first image sensor and / or the second image sensor can thus also be arranged within the shaft and / or its distal end section. This allows the two image sensors for capturing the first beams with the first spectral range and the second beams with the second spectral range to be positioned at a respective distance from the pentaprism and / or the at least one optical element, such that the optical path lengths of both paths are the same or different.With identical values ​​for the optical path lengths, a sharp image is captured for both the first and the second ray.

[0049] In another 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] This allows the first and second image sensors to be flexibly arranged depending on the respective inner diameter of an endoscope shaft.

[0051] To enable fluorescence imaging, a light source can be associated with the imaging device, and the light source comprises a first illumination spectral range which includes white light, and a second excitation spectral range which includes excitation light, so that a fluorophore within an illuminated scene is caused to emit fluorescence light.

[0052] This allows, despite using only one optical path for the incoming beams in front of the pentaprism, white light and fluorescence images to be acquired simultaneously and separately by the beam-splitting pentaprism and thus the imaging device. This is achieved by the first image sensor, which is dedicated to white light imaging in the visible light range, and the second image sensor, which is dedicated to fluorescence imaging. Consequently, in overlay mode, a high overall frame rate and increased sensitivity for fluorescence imaging can be achieved, while maintaining white light brightness and high fluorescence light intensity in a "chip-on-the-tip" endoscope, compared to conventional endoscopes that switch between white light and fluorescence imaging.

[0053] In another embodiment of the imaging device, the second image sensor for detecting the second spectral range, which includes fluorescence light, has a smaller image area than the first image sensor for detecting the first spectral range, which includes white light.

[0054] The sensitivity of the image on the second image sensor for detecting fluorescence and / or IR light can be increased by the at least one separate optical element positioned proximally behind the pentaprism, thereby reducing the image size. For example, the image size can be reduced by a factor of 45%, thus decreasing the image size of the second sensor from 3.01 mm to 1.65 mm. This results in different system aperture values, with the first image sensor for visible light having an image diameter of 3.01 mm and an aperture value of f / 6, and the second image sensor having a reduced image diameter of 1.65 mm and an aperture value of f / 2.8. This allows the light intensity of the second sensor, which detects fluorescence and / or IR light, to be increased by a factor of 4.5 relative to the visible light path. (F#VISF#IR)2=(62,8)2=4.5

[0055] Since the fluorescence and IR image size is smaller, correspondingly larger pixels are used, thus achieving higher sensitivity and higher resolution.

[0056] In a further aspect of the invention, the problem is solved by a lens system for an endoscope, wherein the lens system can be arranged in a distal end section of an elongated shaft of the endoscope, and wherein at least a first image sensor for capturing images of a first spectral range and a second image sensor for capturing images of a second spectral range can be arranged in the elongated shaft, wherein the lens system comprises a lens system with at least a first lens, at least a second lens and optionally further lenses to receive image light from one lens side and to direct the image light towards the first image sensor and the second image sensor, wherein the lens system comprises a previously described imaging device, wherein the imaging device is arranged between a most proximal lens of the lens system and the first image sensor and / or the second image sensor.

[0057] Thus, an objective system for an endoscope with only one optical path for the two spectral ranges is provided, preferably for white light and fluorescence light imaging, wherein the one optical path after the lens system is divided by the pentaprism into a separate first optical path for the first rays within the first spectral range and a separate second optical path for the second rays divided in the second spectral range, thereby enabling the simultaneous acquisition of images, each assigned to the first and second spectral ranges, by separate image sensors provided for this purpose.

[0058] This allows the objective lens system to be positioned directly at the distal tip of the shaft and / or in the distal end section of the shaft, while the imaging device can be located somewhat further away on the proximal side or in the proximal section of the shaft. This enables the provision of one or more intermediate images along the optical axis in the proximal direction between the objective lens system and the imaging device, resulting in a longer focal length. For example, the distance between the most proximal lens of the objective lens system and the image sensor positioned along the optical axis can be greater, such as 70 mm, instead of the usual 20 mm. Therefore, it is not necessary to use a larger video lens and thus a larger prism, which would restrict the spatial arrangement of the two image sensors.By arranging the imaging device further in a proximal direction at a distance from the most proximal lens of the objective lens system, a smaller and more compact design of the pentaprism as well as a flexible arrangement of the two image sensors is possible.

[0059] In this design, the pentaprism function is integrated into the overall system through a special optical configuration for video endoscopes. At least one intermediate image after the proximal lens allows for better control of the image-side focal length, enabling the pentaprism to cover the entire distance. Additionally, the stray light characteristics of the entire optical system are improved. For example, the optical configuration is designed for the following optical parameters: optical system diameter of 3.1 mm, focal length of -0.8 mm, f-number 4.5 to 6.0, entrance pupil diameter of 0.19 to 0.14, achromatic for a wavelength range of 400 to 950 nm, and an image scale of 0.018.

[0060] In another embodiment of the lens system, rays entering and / or exiting the pentaprism are focal and / or converging.

[0061] Consequently, an afocal beam path in the objective system is not required, and refocusing after passing through the pentaprism is also unnecessary. Despite the use of a focal and / or converging beam path, the objective system according to the invention, due to the design of the pentaprism and the downstream at least one separate optical element, avoids the aberrations common in systems known from the prior art and provides an overall improved image quality.

[0062] In a further aspect of the invention, the problem is solved by an endoscope, in particular a medical or industrial video endoscope, with a handle, an elongated shaft, a light source, a lens system and / or an image processing unit and / or a display system, wherein the endoscope comprises a previously described imaging device or the lens system is a previously described lens system, such that images of the first spectral range are captured separately in parallel by the first image sensor and of the second spectral range by the second image sensor and / or can be displayed as superimposed images by the display system.

[0063] The invention is further explained by the following exemplary descriptions of particular embodiments. The figures show: Fig. 1. A schematic, partially three-dimensional view of an endoscope and a display system. Fig. 2 a schematic longitudinal cross-sectional view of a pentaprism, Fig. 3 a schematic longitudinal cross-sectional view of an imaging device including the in Fig. 2 pentaprisms shown, and Fig. 4 A schematic longitudinal cross-sectional view of an objective system with a lens system and the proximally arranged imaging device.

[0064] A video endoscope 101 comprises a handle 103 and an elongated shaft 105, which can 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 knobs and a lever and is connected at its proximal end via a cable 113 to an external control and processing unit (not shown), often referred to as a camera control unit (CCU), and / or to an integrated Fig. The display system 201 shown in Figure 1 is connected. The display system 201 includes a monitor 203 for displaying endoscopic images and operator controls 215.

[0065] The video endoscope 101 is designed to provide video and image data from an object space within a body cavity (not shown). For this purpose, the elongated shaft 105 includes a distal end section 111 at its distal end 109. The distal end section 111 of the elongated shaft 105 comprises an objective system 301 with an objective lens system 303, followed by an imaging device 400 on a proximal side 329 (see Fig. 4).

[0066] The imaging device 400 comprises a pentaprism 401 with a prism main body 403 and a prism wedge 405. The prism wedge 405 is cemented to the prism main body 403. Furthermore, downstream of the pentaprism 401 along an optical axis 373, the imaging device 400 comprises a fluorescence filter 419 and a combined reducing lens 421. A first image sensor 423 for detecting white light is arranged parallel to a first exit surface 413 of the pentaprism 401 and thus parallel to the optical axis 373. A second image sensor 425 for detecting fluorescence light is arranged on the proximal side of the reducing lens 421. Fig. 3 and Fig. 4).

[0067] The pentaprism 401 comprises an entrance surface 407 on its main prism body 403, which is arranged perpendicular to the incident rays 311 and the optical axis 373. Furthermore, the main prism body 403 comprises a second inner reflective surface 411 and a first exit surface 413, which is directed towards the first image sensor 423. The prism wedge 405 is inclined to the main prism body 403 and is cemented to it on the proximal side of the main prism body 403. The prism wedge 405 comprises a second exit surface 415, which is perpendicular to the optical axis 373. A dichroic beam splitter layer 417 is arranged between the main prism body 403 and the prism wedge 405 and forms a first inner reflective and transparent surface 409.

[0068] In the objective system 301, the lens system 303, extending along the optical axis 373 from the distal side 327 towards the proximal side 329, comprises a cover glass 339, a first most distal objective lens 340, followed by a damping and / or mediating optical element 341, a second lens 343 configured as a combined lens, a third lens 345, and a fourth lens 347, which are arranged in the distal end section 111 of the elongated shaft 105. A fifth lens 351, configured as a combined lens, is located at a distance from the fourth lens 347 along the optical axis 373 in the proximal direction. At a distance from the fifth lens 351, a sixth lens 353 is formed as a combined lens, and at a distance from it, a seventh lens 355 is also formed as a combined lens, and which is the most proximal lens of the lens system 303.Following the seventh lens 355 as the most proximal lens, the imaging device 400 with the pentaprism 401 is arranged on the proximal side 329 as described.

[0069] The elongated shaft 105 has an inner diameter of 4 mm and the lens system 301 has a diameter of 3.1 mm. The pentaprism 401 has a length along the optical axis 373 of 5 mm and the entire imaging device 400 including the pentaprism 401 of 10 mm.

[0070] When using the video endoscope 101, object rays 309, which reach the distal side 327 from the object space, are collected by the objective system 301 and processed by the objective lens system 303 in a single optical path with converging rays. After the last, seventh lens 355 of the lens system 303, incident rays 311 enter the prism body 403 through the entrance surface 407 in the pentaprism 401. Since both the prism body 403 and the prism wedge 405 have a refractive index of 0.6, the incident rays 311 are selectively split into white light rays 323 and fluorescent rays 325 by the dichroic beam splitter layer 417. The reflected white light rays 323 are directed at a first angle 431 of 70° relative to the first inner reflective and transparent surface 409 towards the second inner reflective surface 411.The split and redirected white light rays 323 are reflected by the second inner reflecting surface 411 of the prism main body 403 at a second angle 433 of 65° relative to the second inner reflecting surface 411 and in the direction of the first image sensor 423. The second reflected white light rays 325 intersect the optical axis 373 at an angle of 90° and exhibit a third angle 435 of 90° relative to the first exit surface 413 of the prism main body 403, passing through the first exit surface 413 and an air gap, and then intersecting the image plane of the first image sensor 423 through a first sensor cover glass 427. The fluorescence rays 325 pass through the dichroic beam splitter layer 417 along the optical axis 373 and exit the prism wedge 405 through the second exit surface 415 in a proximal direction (see . Fig. 2, Fig. 3 and Fig. 4).

[0071] The fluorescence filter 419, arranged separately proximal to the second exit surface 415, serves to absorb the excitation wavelength of the fluorescence light and allows only the emission wavelength band of the fluorophore used in the object space to pass through. The reduction lens 421 then further focuses the fluorescence beams 325 before these beams pass through an air gap and a second sensor cover glass 429 and intersect the image plane of the second image sensor 425 to detect fluorescence light. Thus, the second image sensor 425 uses a smaller image size diameter of 1.65 mm for detecting fluorescence light, in contrast to the image size diameter of 3.01 mm of the first image sensor 423 for detecting white light. The first image sensor 423 has an aperture of f-number 6.0, and the second image sensor 425 has an aperture of f-number 2.8.This reduced image size of the image captured by the second image sensor 425 is made possible by the reduction lens 421, which increases the intensity of the image relative to the image size on the second image sensor 425 for fluorescence light and improves the sensitivity of the image sensor 425 to the fluorescence image by increasing the signal-to-noise ratio. At the same time, the reduction lens 421 prevents image aberrations during image acquisition by the second image sensor 425.

[0072] This provides a video endoscope 101 with a compact imaging system 400 and a compact pentaprism 401 for beam splitting into white light and fluorescence light in the narrow shaft 105, which enables the simultaneous acquisition of separate white light beams 323 and fluorescence beams 325 by separate first and second image sensors 423, 425 with high-quality images and a high frame rate of 60 frames per second. Reference numbers 101 Video endoscope 103 Handle 105 elongated shaft 107 proximal end of the shaft 109 distal end of the shaft 111 distal end section 113 cables 115 operator controls 201 Display system 203 Monitor 215 operator controls 301 lens system 303 Lens system 309 Object rays 311 incident rays 323 white light rays 325 Fluorescence rays 327 distal side 329 proximal side 339 Cover glass 340 first most distal objective lens 341 damping and / or transmitting optical elements 343 second lens (combined) 345 third lens 347 fourth lens (combined) 351 fifth lens (combined) 353 sixth lens (combined) 355 seventh lens (combined) 373 optical axis 400 Imaging device 401 Pentaprism 403 Prism main body 405 prism wedge 407 Entrance area 409 first inner reflective and permeable surface 411 second inner reflective surface 413 first exit surface 415 second exit surface 417 dichroic beam splitter layer 419 Fluorescence filters 421 Minifying lens 423 first image sensor (white light) 425 second image sensor (fluorescent light) 427 first sensor cover glass 429 second sensor cover glass 431 first angle 433 second angle 435 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 main body (403) and a prism wedge (405) and an optical axis (373), and wherein an entrance surface (407), a second inner reflective surface (411) and a first exit surface (413) are arranged on the main body (403) and a second exit surface (415) is arranged on the prism wedge (405), and the pentaprism (401) further comprises a dichroic beam splitter layer (417) as a first inner reflective and transmissive splitter layer (409), and the imaging device (400) comprises at least one first image sensor (423) for detecting light of a first spectral range and a second image sensor (425) for detecting light of a second spectral range, wherein the first spectral range and the second spectral range differ at least partially from each other,and the dichroic beam splitter layer (417) is arranged between the main body (403) and the prism wedge (405) of the pentaprism (401), so that incident rays (311) comprising the first and second spectral ranges are split by the dichroic beam splitter layer (417) into first rays (323) of the first spectral range and second rays (325) of the second spectral range, wherein at least one separate optical element (419, 421) for changing a property of the light of the first spectral range and / or the second spectral range is arranged between the pentaprism (401) and the first image sensor (423) and / or the second image sensor (425), so that two optimized separate images for the superimposed imaging of the light of the first spectral range and the second spectral range can be detected., [2] Imaging device (400) according to claim 1, characterized bythat the at least one separate optical element and / or a further separate optical element (419, 421) is or are a lens (421) for reducing the light of the first spectral range and / or the second spectral range. [3] Imaging device (400) according to claim 1 or 2, characterized by that the at least one separate optical element and / or a further separate optical element (419, 421) is or are movable. [4] Imaging device (400) according to one of the preceding claims, characterized by that the at least one separate optical element and / or a further separate optical element (419, 421) comprises a mirror element for deflecting the first beams (323) of the first spectral range and / or the second beams (325) of the second spectral range. [5] Imaging device (400) according to one of the preceding claims, characterized bythat the at least one separate optical element and / or a further separate optical element (419, 421) is or are a filter (419) for blocking an excitation wavelength or for further distinguishing the first spectral range and / or the second spectral range. [6] Imaging device (400) according to one of the preceding claims, characterized by that the dichroic beam splitter 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] Imaging device (400) according to one of the preceding claims, characterized by that the imaging device (400) comprises the first image sensor (423) and / or the second image sensor (425). [8] Imaging device (400) according to one of the preceding claims, characterized bythat the first image sensor (423) and the second image sensor (425) are arranged perpendicular to each other or both parallel to the optical axis (373) of the imaging device (400). [9] Imaging device (400) according to one of the preceding claims, wherein a light source can be assigned to the imaging device (400), characterized by that the light source comprises a first illumination spectral range comprising white light and a second excitation spectral range comprising excitation light, such that a fluorophore within an illuminated scene is caused to emit fluorescent light. [10] Imaging device (400) according to claim 9, characterized by that the second image sensor (425) for detecting the second spectral range comprising fluorescent light has a smaller image area than the first image sensor (423) for detecting the first spectral range comprising white light. [11] An objective system (301) for an endoscope (101), wherein the objective system (301) is arranged in a distal end section (111) of an elongated shaft (105) of the endoscope (101), and at least one first image sensor (423) for capturing images of a first spectral range and a second image sensor (425) for capturing images of a second spectral range are arranged in the elongated shaft (105), wherein the objective system (301) comprises an objective lens system (303) with at least one first lens (340), at least one second lens (343), and optionally further lenses (345, 347, 351, 353, 355) for receiving image light from one objective side and for transmitting the image light in the direction of the first image sensor (423) and the second image sensor (425), characterized bythat the objective system (301) comprises an imaging device (400) according to one of claims 1 to 10, wherein the imaging device (400) is arranged between a most proximal lens (355) of the objective lens system (301) and the first image sensor and / or the second image sensor (423, 425). [12] Lens system (301) according to claim 11, characterized by that rays entering and / or exiting the pentaprism (401) are focal and / or converging. [13] Endoscope (101), in particular a medical or industrial video endoscope, with a handle (103), an elongated shaft (105), a light source, a lens system and / or an image processing unit and / or a display system (201), characterized bythat the endoscope (101) comprises an imaging device (400) according to one of claims 1 to 10 or the objective system is an objective system (301) according to claim 11 or 12, so that images of the first spectral range by the first image sensor (423) and of the second spectral range by the second image sensor (425) are captured separately in parallel and / or can be displayed by the display system (201) as superimposed images.

Images