Patent Application
20240032778
This application claims priority to German Patent Application No. 102022119018.8, filed Jul. 28, 2022, and entitled, “Optical system for implementation in an endoscope and endoscope,” which is incorporated herein by reference.
The present invention relates to optical systems in endoscopes, and in particular to optical systems to be used preferably in the distal end of an endoscope as part of the objective optical image acquisition system.
Endoscopes are generally imaging systems with a long, thin shaft that are widely used for the inspection of narrow cavities and conduits. The term endoscope or medical endoscope usually refers to scopes of this nature that are used in the medical industry, such as for surgery or imaging of remote areas of a human or animal body. Endoscopes for use in industrial applications are usually referred to as borescopes. The term endoscope in this disclosure refers to endoscopes designed to be used in medical and/or industrial applications, that is medical endoscopes or borescopes. Depending on the application, the diameters of the distal head of an endoscope typically range from between 4-5 mm to one or more centimeters. As mentioned above, such devices are used most prominently for medical applications, however they also have applications in the testing and maintenance of industrial structures (e.g., pipes, conduits, difficult to reach spaces, etc.) in buildings and industrial facilities.
Endoscopy is one of the cornerstones of modern medical technology. For example, endoscopes are routinely used in laparoscopy, gastroenterology, and other minimally invasive surgical and observational interventions, affording access to human tissues through narrow human tracts, and thereby providing a tool for a thorough inspection of the human body, which can lead to early and accurate diagnoses of diseases and other anomalies without the need for the more invasive surgical methods.
Endoscopes are frequently endowed with multifunctional distal heads, where, besides exploration with illumination and associated camera systems, cleaning elements such as flushing nozzles and other tools such as cutting and cauterizing elements, brushes, and suction nozzles, can also be present. In some endoscopes, the distal head of an endoscope can also be employed with a working channel through which various tools may be introduced into the body to provide the necessary intervention.
One of the most important elements of an endoscope is the objective lens system within the distal head, which collects light from the illuminated scene, e.g., from human tissue within the body, and focuses it, in the case of video endoscopes, onto an image sensor unit, generally comprising one or more electronic image sensors. Image data collected by this sensor unit is transferred to a video processor, often referred to as a camera control unit (CCU), which processes the image signals such that they can be viewed on an external monitor, headset, projection screen, etc., and/or stored for later analysis. The ability to view externally displayed live video assists the operator of the endoscope to perform the inspection or intervention.
One of the directions in which improvements in endoscopy takes place is in the design endoscopes with distal tips of an ever smaller cross sectional diameter, preferably without compromising the quality of the images acquired through their optical systems. This desire to create endoscopes with ever smaller distal diameters affects the ability of the optical system to efficiently focus images on the sensor unit.
Different mechanisms to provide for image focusing within the distal heads of endoscopes have been proposed in the literature. In US 2017/0296042 A1, for instance, an endoscope is described with an observation optical system unit comprising a front-group lens unit on a distal end of the optical system, a rear-group lens unit on the proximal end of the optical system, and a moving lens unit that can be advanced or retracted along a guide frame. Through the movement of the moving lens unit, the optical system unit can focus the incoming light from an object to an image pickup device, which comprises an image sensor.
In endoscopes with very thin shafts and correspondingly desired small cross sectional distal heads, the size of the image sensor might be the limiting factor as to the size of the distal head of the endoscope. The size of the active surface of the image sensor may be comparable or bigger than the target diameter of the video objective of the endoscope. Reducing the size of the image sensor itself, with the corresponding reduction of resolution, due to a reduction in overall pixels on the sensor chip, can lead to a corresponding reduction in image resolution and quality. Furthermore, such a customization of the image sensor itself can result in increased production costs.
It is an object of the present invention to provide an optical system for the proximal lens of an endoscope, preferably for endoscopes with very thin shafts and corresponding distal heads with small cross sectional diameters (typically between 3 mm and 4 mm), where the image sensor can be placed at the optimal focal distance without having to reduce its size.
The purpose of this invention will be achieved through a device with the features disclosed in claim 1. Preferred embodiments of the invention with advantageous features are given in the dependent claims.
A first aspect of the invention provides an optical system for implementation in an endoscope, comprising a most proximal lens with a proximal portion and a distal portion aligned along an X direction, parallel to an optical axis of the most proximal lens, an image sensor with an active surface containing an array of light sensitive pixels, and a reflective prism. The system is characterized in that the image sensor is placed orthogonal to the optical axis of the most proximal lens, with the active surface facing the reflective prism along a Y direction perpendicular to the X direction. The proximal portion is smaller than the distal portion, wherein the proximal portion of the most proximal lens overlaps along a length of the image sensor along the X axis, wherein the distal portion of the most proximal lens overlaps with a height of the image sensor along a Y axis perpendicular to the X axis, and wherein the image sensor can be positioned at a focal position of the optical system.
A most proximal lens is broadly defined as an optical object whose sides do not have the same size and do not necessarily have the same curvature. A most proximal lens can be a compound lens, with different lenses attached to each other, or a simple lens cut in a way such that it is not mirror-symmetric. In the present invention, the most proximal lens is the one closest to the image sensor in the distal head of the endoscope, which is commonly referred to as the proximal lens group of the endoscope.
Here and in the following, the proximal part or proximal portion of a most proximal lens describes the part or portion of the most proximal lens closest to the person handling the endoscope. Correspondingly, the distal part or distal portion of a lens describes the part or portion of the lens closest to the object, for example, a patient.
The X direction is typically parallel to the optical axis of the distal portion of the most proximal lens. The distal portion and the proximal portion of the most proximal lens do not necessarily have the same optical axis; in some configurations there is, therefore, not a single optical axis for the entire most proximal lens. The X direction will also be referred to as the axial direction, the distal direction (if an orientation towards the distal end of the endoscope is implied) or the proximal direction (if an orientation towards the proximal end of the endoscope is implied).
The Y and Z directions are orthogonal directions to the X direction and will both be referred to as the radial direction, unless confusion can arise, in which case they will be distinguished. The Y direction is defined orthogonal to the orientation of the active surface of the image sensor, i.e., the side of the image sensor containing light sensitive pixels, such that the reflective prism mounted upon the image sensor has a larger value along the Y axis than the image sensor. With these conventions, we will understand, for instance, “A is under B” to mean that A has a smaller Y coordinate value than B. Likewise, additional relative positional terms like “below”, “on top of” or “over” will acquire a well-defined meaning and they will be used hereafter.
With the previous definitions of directions, the image sensor's active surface being orthogonal to the most proximal lens means that the plane of the image sensor is parallel to the XZ direction. In this configuration, the light rays that cross the most proximal lens can only reach the sensor chips if they are directed thereto by the reflective prism.
Cross-sectional areas perpendicular to the X direction are cuts parallel to the YZ plane. The distal portion and the proximal portion of the most proximal lens typically show an outer surface with curvature. By the cross-sectional area of the distal portion and the proximal portion, cuts well into the bulk of the volumes of the proximal and distal portions are meant, for example at a position where the cut does not intersect with the proximal or distal curved end surface. Cross-sectional areas perpendicular to the X direction will also be referred to as transverse cross-sectional areas. In turn, cross-sectional areas parallel to the X direction (or: surface cuts with an orientation vector pointing in a radial direction) will be referred to as longitudinal cross-sectional areas.
The transverse cross-sectional area of the image sensor overlaps with the transverse cross-sectional area of the proximal portion of the most proximal lens if the image sensor and the proximal portion share Y and Z coordinates. Conversely, the transverse cross-sectional area of the image sensor does not overlap with the transverse cross-sectional area of the proximal portion if the image sensor and the proximal portion do not share Y nor Z coordinates. In other words, the configuration described in the first aspect of the invention implies that if the image sensor would move towards the distal direction, it would fit under the proximal portion (or: it would share X coordinates with the proximal portion but not Y nor Z coordinates) but would contact the distal portion.
One of the main benefits underlying the present invention is the optimization of the space occupied by the image sensor in the optical system installed at the distal end of an endoscope, preferably in endoscopes with very thin shafts, i.e., with distal head diameters of the order of millimeters. This is achieved by first placing the image sensor such that it extends along the direction of the scope (the horizontal direction or the X direction). In this configuration, the active surface of the image sensor does not face the X direction.
A reflective prism is installed in order for the light rays to be diverted from the X direction to the Y direction. This reflective prism will preferably be attached to, abutted to, or simply placed in contact with the image sensor. In order to protect the light sensitive pixels from a direct contact with the reflective prism, the image sensor contains a protective layer, e.g., a cover glass. The image sensor may be attached to a guide, which allows the image sensor to be moved in the X direction, towards the proximal portion of the most proximal lens of the endoscope or away from it. The proximal portion of the most proximal lens is configured to have a transverse cross-sectional area smaller than the transverse cross-sectional area of its distal portion.
This is configured such that the image sensor, in its allowed movement along the X axis does not hit or contact the proximal portion of the most proximal lens, but it eventually can hit or contact the (proximal part of the) distal portion of the most proximal lens. In other words, the image sensor is arranged or is arrangeable in a position which would hit or contact the proximal portion of the most proximal lens if the proximal portion had the same size as the distal portion.
Therefore, by reducing the size of the proximal portion of the most proximal lens with respect to the distal portion of the most proximal lens, the image sensor can move under the proximal portion of the most proximal lens towards the distal end of the endoscope. This wider reach in the available positioning of the image sensor guarantees that an optimal focal position for the image sensor can be achieved.
One advantage of the present invention is that one can reduce the size of the video objectives in endoscopes while still using a standard image sensor. This is particularly useful in endoscopes that require a very thin shaft (e.g., in cystoscopes for the urinary tract). This benefit is also useful in general for endoscopes that have complex distal heads with many functionalities, where freed space, as a result of the smaller objective optical systems, can be used for other purposes, such as providing an opening of a working channel or light sources. In these cases, reducing the size of the video objectives without compromising the quality of the images is clearly a desired feature.
Advantageous embodiments and further developments follow from the dependent claims as well as from the description of the different preferred embodiments illustrated in the accompanying figures.
According to some of the embodiments, the most proximal lens is a simple lens (or: monolithic lens). In this case, the proximal portion is defined by a cut-out or recessed portion of this monolithic lens. Knowing the required focal positions of optical system in relation to the image sensor, one can determine how far this cut-out region should extend towards the distal direction of the most proximal lens.
According to some of the embodiments, the most proximal lens comprises a compound lens with two or more lenses attached to each other, usually with an optical cement. The two or more lenses have a common refractive index or different refractive indices. The lens can therefore have a common optical axis or different optical axes depending on physical geometry of the lens. The different combinations of optical properties are to be adjusted such that the light rays coming from the distal head of the endoscope can be focused on the image sensor.
According to some of the embodiments, the distal portion of the most proximal lens has a convex outer surface and/or the proximal portion of the most proximal lens has a concave or flat outer surface. As mentioned above, in all these embodiments the most proximal lens is arranged such that the light rays coming from an object space into the endoscope are focused onto the image sensor.
According to some of the embodiments, the proximal portion of the most proximal lens comprises an indentation. An indentation here refers to any recess, notch or cut that the proximal portion of the most proximal lens shows and reduces its longitudinal cross-sectional area compared to the longitudinal cross-sectional area of distal portion of the most proximal lens. In some applications, this indentation can be a carved-out portion of the most proximal lens on its proximal side. Such a carving could be e.g., a cut parallel to the XZ plane on the proximal side of the most proximal lens from a certain Y value down to the bottom of the most proximal lens.
According to some of the embodiments, the proximal portion of the most proximal lens and the distal portion of the most proximal lens have different, parallel optical axes. The optical axis of the proximal portion of the most proximal lens may preferably be arranged further away from the image sensor than the optical axis of the distal portion, thereby allocating more room for the image sensor to be moved along the distal direction. By displacing the optical axes of the proximal and distal portions from each other, the perpendicular cross-sectional area of the proximal portion can be larger than if the axes were aligned.
This configuration may be particularly advantageous if the most proximal lens comprises two different circular lenses attached to each other, with the proximal lens having a diameter which in a configuration where the proximal portion and the distal portion had a common optical axis would be too big to grant space to the image sensor.
According to some of the embodiments, the reflective prism is a triangular prism reflector. Such a prism receives the light entering the endoscope through the distal head and traversing the most proximal lens and directs it by reflection at a right angle, i.e., the light rays are diverted from the X direction to the Y direction, such that the light can be detected at the image sensor.
According to some of the embodiments, the diameter of the distal portion of the most proximal lens is between 1 mm and 10 mm, preferably between 2.5 mm and 4 mm. The latter diameters define very thin scopes for video objectives in endoscopes.
According to some of the embodiments, the proximal surface of the most proximal lens is concave.
According to some of the embodiments, the image sensor comprises a cover glass positioned between the active surface and the reflective prism.
According to some of the embodiments, the reflective prism is directly adhered to the cover glass.
According to some of the embodiments, the position of the image sensor may be adjusted along an axis parallel to the optical axis.
According to some of the embodiments, the invention also provides an endoscope containing the optical system of the invention.
According to some of the embodiments, an endoscopic system comprising an endoscope containing the optical system of the invention further comprising an image processor is provided.
According to some of the embodiments, an endoscopic system comprising an endoscope containing the optical system of the invention further comprising an illumination source is provided.
When the optical system of the invention is embedded in an endoscope, in some embodiments the image sensor is configured to send a signal to an external video-processing device. The processed images, which can be adjusted to enhance the contrast, exposure, color, etc., can be further displayed in real time or quasi-real time on a screen. In this way a correct differentiation of e.g., human tissues can be aided.
The above embodiments and implementations can be combined with each other as desired, in order to solve specific technical challenges.
Further applicability of the present optical system will become apparent from the following figures, detailed description and claims. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
Aspects of the present disclosure will be better understood with reference to the following figures. The components in the drawings are not necessarily to scale, emphasis being placed instead upon clearly illustrating the principles of the present disclosure. Parts in the different figures that correspond to the same elements have been indicated with the same reference numerals in the figures, in which:
The figures are not necessarily to scale, and certain components can be shown in generalized or schematic form in the interest of clarity and conciseness. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present invention.
The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
The distal head 10 is a multifunctional component of the endoscope 1000 that may comprise a plurality of sensors and tools for inspection and intervention. In
The shaft 30 can range in length between approximately 10 cm to a meter long or longer depending on the intended use of the endoscope 1000. The shaft 30 may be rigid or flexible. Within the shaft 30 there may be contained a plurality of communication and/or transport means, e.g., electronic cables to transfer electric signals and power to and from a camera control unit, and/or tubes to carry fluid from an external source to a nozzle 54. Additionally, the shaft 30 may contain a waveguide, e.g., made of optical fiber, to bring light from an external illumination source 43 to the light emitters 55.
The shaft 30 connects the distal head 10 with the rest the handle 50. The shaft 30 may additionally contain, in the region adjacent to the distal head 10, a mechanism (not shown) that allows the distal head 10 to be articulated. This articulation mechanism eases the maneuvering of the distal head 10 to its desired location and permits a visual change in orientation relative to the shaft 30.
The handle 50 is typically a rigid, e.g., a hard-plastic or metallic ergonomic structure, from where the different functions of the endoscope 1000 and/or endoscopic system can be controlled. It typically contains a number of buttons 51 and/or other control mechanisms. The maneuvering of the orientation of the distal head 10, the activation of the nozzle 54, control of the illumination system, and/or the focal adjustment of the optical system 100, to give only some examples, can be performed with the handle 50 through its controls 51.
The video processor 42 is an image-processing unit that receives image data acquired by the optical system 100 and transfer it to a display monitor 40. The video processor 42 may also perform various image processing procedures, such as image contrast and color tonality adjustment. This image-enhancement may provide enhanced differentiation of the tissues under inspection.
The cable 31 is a regular insulated cable for electrical communication between the endoscope handle 50 and the video processor 42. Optionally (not shown in the figure), cable 31 can also be connected to the illumination source 43. In some embodiments it may also be convenient to have the screen 40 and the video processor 42 and/or the illumination source 43 be contained in a single unit.
However, it should be noted that this simplified optical system 100 can be more sophisticated, in particular comprising further lenses and/or lens groups towards the distal end of the endoscope 1000. In this case, the embodiment depicted in
The most proximal lens 1 has a proximal portion 1A and a distal portion 1B. In the embodiment depicted in
The image sensor 2 is an image-acquiring structure which usually comprises a protective surface such as a cover glass 20 and an array of light sensitive pixels 21. Commonly used image sensors include CMOS or CCD sensors.
The optical system 100 of
The reflective prism 3 is an optical device configured to reflect the light that impinges on it coming from the most proximal lens and divert it to the image sensor 2.
For simplicity, the light ray L1 under consideration travels along the optical axis of the most proximal lens 1. The light ray L1 therefore traverses the most proximal lens 1 following a straight trajectory and exits the most proximal lens 1 at the proximal portion 1A. The light ray L1 then impinges on the reflective prism 3 and its trajectory is diverted towards the image sensor 2, where the light ray L1 is detected.
In the embodiment shown in
The Y and Z directions are orthogonal to the X direction. As explained above, the Y direction is orthogonal to the plane of the active surface 23 of the image sensor 2, such that the reflective prism 3 is located at a position farther along the Y axis than is the image sensor 2. The Z direction is therefore defined as orthogonal to the X and Y axes in a Cartesian reference frame.
The placement of the image sensor 2 as shown in the embodiment depicted in
With the arrangement of the image sensor 2 depicted in
The holding frame 4 covers and protects the optical components within the optical system 100. Its inner diameter is typically set by the size of the most proximal lens 1. In order to distinguish both elements more clearly, a small separation is shown between the holding frame 4 and the most proximal lens 1 in
The image sensor 2, together with the reflective prism 3, may be moved along the X direction, e.g., with the help of a guide rail (not shown in the figure), such that the image sensor 2 can be placed at an optimal focal position. In order to reach an optimal focal position with configurations such as the one depicted in
In this illustration, the most proximal lens 1 consists of a circular cross-sectional proximal portion 1A and a circular cross-sectional distal portion 1B, where the diameter of the proximal portion 1A is smaller than the diameter of the distal portion 1B because of the presence of a recess 150, which lies on a plane parallel to the YZ plane. In contrast to the embodiment of the most proximal lens 1 shown in
The illustration on the right-hand side of
The illustration on the left-hand side of
The illustration on the right-hand side of
In
The illustration on the left-hand side of
The illustration on the right-hand side of
In
In all embodiments described in
The previous description of the disclosed embodiments are merely examples of possible implementations, which are provided to enable any person skilled in the art to make or use the present invention. Various variations and modifications of these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the present disclosure.
Thus, the present invention is not intended to be limited to the embodiments shown herein but it is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Therefore, the present invention is not to be limited except in accordance with the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 119 018.8 | Jul 2022 | DE | national |
