# Patent

## Title
Optical coupler for optical imaging visualization device

## Abstract

An optical coupler for mounting at a distal end of an optical imaging device includes a visualization section and an attachment section. At least one surface of the visualization section has a roughness that does not interfere with a video capture system of an optical imaging device.

## Background
RELATED APPLICATIONS
This application is a Continuation Application of U.S. application Ser. No. 14/494,090 filed Sep. 23, 2014, the entire contents of which are incorporated herein by reference.


BACKGROUND
Field of the Invention
This disclosure relates to an optical coupler having one or more surfaces with a defined degree of roughness for improved optical imaging of target areas by an optical imaging visualization device, such as an endoscope, laparoscope, arthroscope, ophthalmoscope, borescope, or other remote imaging visualization technology.
Description of the Related Art
Remote optical visualization devices such as endoscopes and other optical imaging visualization devices illuminate surfaces and other objects a distance from the user of the visualization device, allowing a user to perform a diagnosis or procedure using images and signals generated and transmitted a distance from the observed object. This can include, for example, viewing tissue inside a body cavity or a lumen, inspecting a hydraulic line in an aircraft, inspecting an oil pipeline for leaks, or inspecting a sewer line for leaks and/or blockages. Remote optical visualization devices transmit these images to the viewer in a variety of ways, including, among others, through the use of (i) relay lenses between the objective lens at the distal end of the scope and an eyepiece, (ii) fiber optics, and (iii) charge coupled devices (CCD) and complementary metal oxide semiconductor (CMOS) sensors. Frequently, a video capture system is connected to the optical visualization device to display a video image on a display monitor that can be viewed by a user during use of the optical visualization device, including the ability to adjust the focus of the display through manual adjustments or autofocus capability in a video processor system used with the optical imaging device. To achieve video capture with a video processor system, an objective lens of an optical visualization device focuses light reflected from a target being observed on an image sensor. The image sensor outputs signals based on the detected reflected light. The signals from the image sensor are output to a signal processor, which typically includes imaging software that controls an autofocus feature connected to the objective lens to adjust the in-focus object plane position. A control signal generated by the signal processor activates an autofocus operation to automatically bring the target being observed into focus.
Optical couplers positioned over the objective image capturing element of an optical visualization device allow improved remote observation in areas of the body where visibility has been obstructed by blood, stomach content, bowel content, or other opaque fluids and/or solid particulate matter. Optical couplers also allow improved remote observation in non-medical applications where visibility has been obstructed by fluids and/or solid particulate matter. However, imperfections on the surface of the optical coupler may inhibit the visualization of the optical visualization device, including confusing the signal processor of an optical visualization device using a video capture system, causing the autofocus feature to focus the objective lens on a surface of the optical coupler, rather than on the intended target to be observed. Further, when an optical coupler is used with visualization systems that do not use image capture software, visualization may be hindered when the light from the visualization system passes through imperfections on the distal surface of the optical coupler resulting in increased light reflection and increased glare due to these imperfections. This may occur when light proceeds through the optical coupler and when light returns back through the optical coupler to the scope camera.
It would be advantageous to provide an optical couple that allows improved remote visualization while not interfering with the autofocus feature of a video capture system and not causing increased light reflectance and glare due to improved surface finish.
SUMMARY
Optical couplers in accordance with the present disclosure attach to the distal end of a remote visualization device, such as an endoscope, and the optical couplers have a surface with a defined degree of roughness. In embodiments, a surface of the optical coupler has a Root Mean Square (RMS) Roughness below about 20 nanometers, in embodiments from about 5 nanometers to about 18 nanometers. In embodiments, the surface roughness of the optical coupler surface is below about 0.5 nanometers, in embodiments from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has a Root Mean Square (RMS) Roughness below about 20 nanometers with spatial frequencies between 1×10−1 mm−1 to 1×103 mm−1, in embodiments Y from about 5 nanometers to about 18 nanometers for a similar spatial frequency range.
The “surface roughness of the optical coupler surface is below about 0.5 nanometers” means that one of the center-line mean roughness (Ra), the ten-point height irregularities (Rz), and the maximum height roughness (Rmax) is less than 0.5 nanometers, ±0.05 nanometers. In embodiments, a surface of the optical coupler has a center-line mean roughness (Ra) of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has a ten-point height irregularities (Rz) of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has a maximum height roughness (Rmax) of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has an average defect density of no more than about 100 defects per 10 μm2, in embodiments from about 10 defects per 10 μm2 to about 75 defects per 10 μm2. In embodiments, the distal surface of the optical coupler has a defined degree of roughness. In embodiments, the surface of the optical coupler closest to the objective lens of the endoscope has a defined degree of roughness.



BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which:
FIG. 1 is a side view of a first embodiment of an optical coupler according to the invention;
FIG. 2 is a cross-sectional view of the optical coupler of FIG. 1 taken along line 2-2 of FIG. 1; and
FIG. 3 is a cross-sectional view of the optical coupler of FIGS. 1 and 2 taken along line 3-3 of FIG. 2, the optical coupler being attached to an endoscope.



The figures depict specific embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the present disclosure described herein.
DETAILED DESCRIPTION
The present optical couplers provide for improved optical imaging of surfaces covered with opaque fluids, semisolid materials or particulate matter, without interfering with the autofocus feature and other image capture and transmission elements of the optical imaging visualization device and its related system elements. These advantages are provided by ensuring that one or more surface(s) of the optical coupler in the optical path has a defined degree of roughness, as described in more detail below.
Turning now to FIGS. 1-3, an embodiment of an optical coupler 10 is shown. The optical coupler 10 includes a visualization section 12 at a distal end 13 of optical coupler 10. Visualization section 12 has a generally slightly curved, convex outer surface 14 that extends from a first outer side boundary 15 to a second opposite outer side boundary 16 of optical coupler 10, and a proximal surface 18. In other embodiments, the visualization section may be non-curved and other embodiments may be concave. Outer surface 14 may be spaced apart from proximal surface 18 of optical coupler 10 by a length D (see FIG. 1). In some embodiments, a hollow instrument channel 19 extends from proximal surface 18 toward outer surface 14. Instrument channel 19 may not extend all the way through visualization section 12 to the outer surface 14. In such a case, a barrier section 20 of material is provided between a distal end 21 of instrument channel 19 and outer surface 14 of optical coupler 10.
Optical coupler 10 also includes an attachment section 22 connected to and extending away from visualization section 12. Attachment section 22 is at the proximal end 23 of optical coupler 10. In the embodiment shown, attachment section 22 is in the form of a cylindrical wall 24. Proximal surface 18 and cylindrical wall 24 of optical coupler 10 define a cylindrical opening 25 of optical coupler 10 within cylindrical wall 24. In other embodiments, the optical coupler may be attached in other manners, including using a gel or glue.
Referring to FIG. 3, optical coupler 10 can be mounted on an endoscope 30. Endoscope 30 has a distal end 31 that is inserted in cylindrical opening 25 of optical coupler 10. Endoscope 30 has a sheath 32 with an outer surface 33 that snugly engages cylindrical wall 24 of optical coupler 10. An end surface 34 of endoscope 30 sealingly engages proximal surface 18 of optical coupler 10. Endoscope 30 includes a first lumen 35, a second lumen 36 and a third lumen 37 that extend from end surface 34 of endoscope 30 to a proximal end (not shown) of endoscope 30. A light guide 39 positioned in the first lumen 35 transmits light toward a surface area at or beyond outer surface 14 of optical coupler 10. An objective lens 40 is optically connected to a distal end of image carrying fiber 42. Objective lens 40 receives light reflected from the surface area being viewed and image carrying fiber 42 transmits the reflected light to a video capture system (not shown) at a proximal end (not shown) of image carrying fiber 42. Objective lens 40 and image carrying fiber 42 are located in second lumen 36. Third lumen 37 aligns with hollow instrument channel 19 of optical coupler 10 when optical coupler 10 is mounted on endoscope 30. Optical coupler 10 can also include a Light Emitting Diode (LED) 11 near outer surface 14 of the coupler to provide illumination prior to optical coupler 10 contacting any fluids, tissue, or structure. LED 11 may be provided power via a wire (not shown) in endoscope 30 or from an external source. Additional details regarding the construction and alternative embodiments of suitable optical couplers can be found in Published U.S. Patent Application No. US2012/0209074A1, the entire content of which is incorporated herein by this reference.
Outer surface 14 and proximal surface 18 of optical coupler 10 lie within the optical path of objective lens 40. In accordance with the present disclosure, at least one of outer surface 14 or proximal surface 18 of optical coupler 10 is provided with a defined degree of roughness. The degree of roughness is the aggregate of any textural constituent elements present on the lens. The size of the textural constituent element is not particularly limited provided the overall degree of roughness does not interfere with the visualization of the image transmitted by the image capture system associated with the endoscope onto which the optical coupler has been mounted.
In embodiments, the outer surface of the coupler transmits both the light used for illumination and the returning light used for imaging simultaneously. This common-path illumination and imaging lens allows for uniform illumination of an object near or at the focal region of the optical imaging visualization device. However because of this, any surface defects may cause light to be refracted or reflected back toward the camera and cause glare or reduced contrast. Also, even a very smooth transmitting surface will reflect a small percentage of light due to Fresnel reflections; therefore, the figure and location of the lens surface must be controlled such that light emitted from the illumination source will not reflect as such angles as to cause unwanted glare along with the surface finish with a defined degree of roughness.
In embodiments, the length and the width of any given textural constituent element can both be 10 μm or less. In embodiments, the length of the textural constituent element (size of the textural constituent element in the longer direction) is 3 μm or less and the width (size of the textural constituent element in the shorter direction) 500 nm or less. In other embodiments, the length and the width of the textural constituent element are preferably in the range of 3 μm to 50 nm. In embodiments, the depth of the textural constituent element may be 15 nm to 200 nm.
In embodiments where outer surface 14 or proximal surface 18 of optical coupler 10 includes depressions, the depressions have an average diameter less than 100 nanometers, in embodiments, from about 15 to about 50 nanometers. The depressions may have an average depth less than about 100 nanometers, in embodiments from about 4 nanometers to about 50. The depressions may have a density or an average density, meaning the number of depressions per 100 square micrometers of surface or the average number of depressions per 100 square micrometers of surface, of less than about 100 depressions per 100 square micrometers of surface, in embodiments from about 15 to about 50 depressions per 100 square micrometers of surface.
In embodiments, a surface of the optical coupler has a Root Mean Square (RMS) Roughness below about 200 Angstroms; in embodiments, from about 50 Angstroms to about 180 Angstroms. In embodiments, the surface roughness of the optical coupler surface is below about 0.5 nanometers, in embodiments from about 0.1 nanometers to about 0.4 nanometers. The “surface roughness of the optical coupler surface is below about 0.5 nanometers” means that one of the center-line mean roughness (Ra), the ten-point height irregularities (Rz), and the maximum height roughness (Rmax) is less than 0.5 nanometers, ±0.05 nanometers. In embodiments, a surface of the optical coupler has a center-line mean roughness (Ra) of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has a ten-point height irregularities (Rz) of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has a maximum height roughness (Rmax of no more than about 0.5 nanometers, in embodiments, from about 0.1 nanometers to about 0.4 nanometers. In embodiments, a surface of the optical coupler has an average defect density of no more than about 100 defects per 10 μm2, in embodiments from about 10 defects per 10 μm2 to about 75 defects per 10 μm2. In embodiments, outer surface 14 of optical coupler 10 has a defined degree of roughness. In embodiments, proximal surface 18 of optical coupler 10 (i.e., the surface closest to the objective lens of the endoscope) has a defined degree of roughness.
The degree of roughness can be determined by using any technique within the purview of those skilled in the art, such as, for example, a laser surface analyzer or a stylus surface profiler, but it can also be determined, simply by direct observation of the surface and cross section under SEM.
A defined degree of roughness is provided on a surface of the optical coupler using techniques within the purview of those skilled in the art. The specific method chosen will depend on a number of factors including the material from which the optical coupler is made.
Optical coupler 10 can be formed from a variety of materials exhibiting transparency or translucency and biocompatibility in medical applications. In embodiments, an optical coupler for non-medical applications can be formed from a variety of materials exhibiting transparency or translucency.
In embodiments, a rigid material, e.g., a resin material such as cycloolefin polymer or polycarbonate, is used to form the optical coupler. When rigid materials are used, they are typically molded and then one or more surface is polished to impart a defined degree of roughness. Polishing techniques are within the purview of those skilled in the art and include, for example, chemical-mechanical polishing, mechanical polishing, CMP processes, reactive ion etching (e.g., with a substantially chemically etching component), physical etching, and wet etching.
In embodiments, a flexible material is used to form the optical coupler. Flexible materials are typically difficult to polish. Accordingly, where flexible materials are used, a defined degree of roughness is provided on the surface of a mold and imparted to the optical coupler when it is molded.
In embodiments, the mold is prepared by any technique within the purview of those skilled in the art, such as for example, the use of a series of micropolish compounds to prepare and refine the finish of the mold to the point there the mold can produce an optical coupler with the desired surface finish on the optical coupler, and, alternatively, creating the mold using single-point diamond turning to cut the surface of the mold with a level of refined surface that the mold produces an optical coupler with the desired surface finish on the optical coupler.
In embodiments, optical coupler 10 is molded from a material selected from glass, silicone gels, silicone elastomers, epoxies, polyurethanes, polycarbonates, acrylics, other elastic materials, and mixtures thereof. The silicone gels can be lightly cross-linked polysiloxane (e.g., polydimethylsiloxane) fluids, where the cross-link is introduced through a multifunctional silane. The silicone elastomers can be cross-linked fluids whose three-dimensional structure is much more intricate than a gel as there is very little free fluid in the matrix. In other embodiments, optical coupler 10 is made from a material selected from hydrogels, such as polyvinyl alcohol, poly(hydroxyethyl methacrylate), polyethylene glycol, poly(methacrylic acid), and mixtures thereof. The material for optical coupler 10 may also be selected from albumin based gels, mineral oil based gels, polyisoprene, or polybutadiene. In embodiments, the material is viscoelastic.
In embodiments, the optical coupler is a clear gel attached to the outer distal portion of any optical imaging or image capturing device, such as an endoscope or camera lens. When pressed in contact with the surface of an area to be viewed, the gel creates an offset that allows clear visualization by mechanically displacing the opaque liquid or soft semisolids.
The material used to form the optical coupler can be comprised of two or more compounds, for example an opaque compound attaches and holds two visualization portions of a coupler in position, the first visualization portion is an inner clear semi rigid compound shaped to match the field of view and minimum depth field of the imaging system, and the second portion is attached to the outer boundary of the first visualization portion and is composed of very soft gel providing additional area of fluid displacement for maneuvering and positioning instruments under direct vision. In embodiments, the two or more compounds each can be of materials that exhibit transparency or translucency. Methods described in U.S. Pat. Nos. 7,235,592 and 7,205,339 can be utilized to produce a coupler with portions or areas of the gel with different physical properties.
Referring back to FIGS. 1-3, in the optical coupler 10, the material is optically clear such that the light guide 39 can transmit light through the optical coupler 10 toward a surface area at or beyond the outer surface 14 of the optical coupler 10 and such that the optical coupler 10 is capable of transmitting an optical image of the surface area being viewed back to the lens 40. In embodiments, the material has a degree of light transmittance greater than 80% based on test standard ASTM D-1003 (Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics). In other embodiments, the material has a degree of light transmittance greater than 98% based on test standard ASTM D-1003. In embodiments, the raw material has an optical absorption of less than 0.1% in the visible light range, and, in embodiments, an optical absorption of less than 0.01% in the visible light range. In embodiments, the material has an index of refraction of about 1.3 to about 2.2, and in embodiments, the index of refraction of the material matches the index of refraction of the light guide 39, or is as low as possible.
The optical coupler 10 may also be coated. Coating may reduce the amount of adherence properties and/or reduce unwanted light reflections, and/or change and enhance the optical coupler by adding hydrophobic or hydrophilic properties. Suitable coatings that may be used on the optical coupler include, but are not limited to, polymers based on p-xylylene, such as for example, polymers that are commercially available under the trade name Parylene C, which is an optically clear biocompatible polymer having abrasion resistant and hydrophobic or hydrophilic properties.
EXAMPLES
The following Examples have been presented in order to further illustrate the invention and are not intended to limit the invention in any way.
Example 1
A series of optical couplers in a shape similar to that of FIG. 3 was molded from Nusil MED-6033 an optical grade liquid silicone elastomer available from Nusil Technologies, Carpinteria, Calif. This silicone has an index of refraction of 1.41, and a durometer of about 45 on the Shore OO scale. The surface of the mold forming the outer surface of the optical coupler was manufactured using a micropolishing methodology to impart a surface finish better than the Society of Plastic Industry (SPI) A1 finish on to the mold. The surface finish of the mold and the resulting lenses were measured using a Zygo interferometer to determine the surface finish on the distal surface of the optical coupler.
These optical couplers were then placed on a number of scopes, including an Olympus CF-Q160A/L colonoscope, a 10 mm rigid laparoscope and a Pentax EG-2990 gastroscope. The visual performance of these optical couplers was observed to determine the impact of surface finish on the visual performance of these scopes without an optical coupler and with an optical coupler and the following was noted: The lenses measured with this approach had the following attributes:











TABLE A






Optical 
Surface 
Surface 
Interfere With 



Coupler
Roughness (RMS)
Roughness (Ra)
Image (Yes/No)








1
21.1646 nm
10.2766 nm
Yes



2
40.3157 nm
18.0538 nm
Yes



3
32.9431 nm
13.8726 nm
Yes



4
25.1743 nm
11.4089 nm
Yes



5
12.0249 nm
 8.5337 nm
No



6
12.7432 nm
10.1406 nm
No









To further assess the variations in the surface finish of the optical couplers, assessments were performed by placing the couplers on the scopes mentioned above and moving various targets in close and away from the endoscope, at specific distances ranging from 3 mm out to several centimeters to assess how changes in light and object distance impact optical performance, relative to surface finish. In addition, the optical couplers were tested at these various distances in situations involving fluid and debris to determine the impact of various levels of surface finish and various distances and environments on visual performance. The performance of these optical couplers was compared to the performance of a scope without the optical coupler to determine an acceptable surface finish that did not interfere with the capture of the visual image through the optical coupler.

As can be seen from the data in Table A, a surface roughness of less than 12.7432 nm RMS did not interfere with the video capture and autofocus software, while surface roughness in excess of this level of surface roughness confused the software, and caused the image of target tissue displayed by the endoscope to be intermittently out of focus. Further, when lenses were tested on scopes without imaging software, the glare and reflection was unacceptably high, inhibiting performance, at the surface roughness greater than 12.7432 nm RMS.
Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the present disclosure based on the above-described embodiments. Accordingly, the present disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.
It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. For example, the coupler may be used in non-medical applications wherein the coupler is attached to the distal end of a borescope or attached to micro, conventional, or robotic video cameras, inspection scopes, or still cameras, thereby allowing viewing and/or making repairs inside pipes, holding tanks, containers, etc. without the need to empty the pipes or containers of static or moving opaque fluid, such as petroleum products, sewerage, food products, paint, etc. In non-medical, industrial applications, the coupler can be formed from materials that resist acid, alkalinity, high heat, or viscosity of fluid being displaced by the coupler and may be reusable. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications and variances. The embodiments described with reference to the attached drawing figures are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods and techniques that are insubstantially different from those described above and/or in the appended claims are also intended to be within the scope of the disclosure.

## Claims

1. An optical coupler for mounting at a distal end of an optical imaging device for visualizing a surface area, the coupler comprising:
a visualization section comprising a material having an index of refraction of about 1.3 to about 2.2, and including a proximal surface and an outer surface spaced apart from the proximal surface; and
an attachment section connected to and extending away from the visualization section, the attachment section dimensioned to be mounted at the distal end of an optical imaging device,
wherein at least one of the proximal surface or the outer surface of the visualization section has a Root Mean Square (RMS) Roughness below about 200 Angstroms.

2. The optical coupler of claim 1 wherein the index of refraction of the visualization section matches an index of refraction of a light guide with which the optical coupler is used.

3. The optical coupler of claim 1 wherein the visualization section comprises an elastomeric material.

4. The optical coupler of claim 1 wherein the visualization section comprises a silicone elastomer.

5. The optical coupler of claim 1 wherein at least one of the proximal surface or the outer surface of the visualization section has a plurality of depressions with an average diameter less than about 150 nanometers.

6. The optical coupler of claim 1 wherein at least one of the proximal surface or the outer surface of the visualization section has a plurality of depressions having an average density less than about 100 depressions per 100 square micrometer.

7. The optical coupler of claim 1 wherein at least one of the proximal surface or the outer surface of the visualization section has an average surface roughness of from about 5 to about 30 nanometers RMS measured at spatial frequencies between 1×10−1 mm−1 to 1×103 mm−1.

8. The optical coupler of claim 1 wherein the visualization section comprises a material having a degree of light transmittance greater than 80%.

9. The optical coupler of claim 1 wherein the visualization section comprises a material having material has an optical absorption of less than 0.1%.

10. The optical coupler of claim 1 wherein at least a portion of the visualization section is coated.

11. The optical coupler of claim 1 wherein at least a portion of the visualization section is coated with a p-xylylene-based polymer.

12. An optical coupler for mounting at a distal end of an optical imaging device for visualizing a surface area, the coupler comprising:
a visualization section at one end of the coupler, the visualization section including a proximal surface and an outer surface spaced apart from the proximal surface; and
an attachment section connected to and extending away from the visualization section, the attachment section being dimensioned to be mounted at the distal end of an optical imaging device,
wherein both the proximal surface and the outer surface of the visualization section have a Root Mean Square (RMS) Roughness below about 200 Angstroms.

13. The optical coupler of claim 12 wherein the visualization section comprises a material having an index of refraction of about 1.3 to about 2.2.

14. The optical coupler of claim 12 wherein an index of refraction of the visualization section matches an index of refraction of a light guide with which the optical coupler is used.