Patent Publication Number: US-11656450-B2

Title: Rod lens relay system with reduced chromatic aberration

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates generally to the field of medical image capture and more specifically to endoscope designs for improving performance fluorescent imaging and visible light imaging. 
     BACKGROUND OF THE INVENTION 
     Endoscopes and other medical scopes often use fluorescing agents or autofluorescence to better examine tissue. A fluorescing agent such as a dye may be injected or otherwise administered to tissue. Subsequently, an excitation light is directed toward the tissue. Responsive to the excitation light, the fluorescing agent fluoresces (emits light, typically at a longer wavelength than the excitation light), allowing a sensor to detect this emission light. Image data is collected by the sensor, and examining the collected images can indicate the concentration of fluorescing agent in the observed tissue. In addition, a phenomenon known as autofluorescence, in which tissue fluoresces under certain conditions without a fluorescing agent, may occur. Such autofluorescence can be detected as well. Imaging based on detected fluoresced light, known as “fluorescence imaging” (FI), is useful in medical diagnosis, testing, and many scientific fields, and may be combined with visible light imaging for many purposes including to enhance surgical precision. 
     A typical prior art endoscope  2 , as illustrated in  FIG.  1   , usually includes a first imaging lens (e.g., an objective) followed by a series of carrier lenses (e.g., relays) which capture and transmit an optical image from inside an enclosed area  1  to the outside. The proximal end of the endoscope  2  may be attached, via direct coupling or an adaptor, to a camera head  3  or an eye-piece for viewing. The camera head  3  usually includes lenses for receiving the optical image and forming a real optical image onto the image sensor. The digital image captured by the image sensor can then be transmitted to a camera control unit (CCU) or other similar module for analysis and display. 
     Frequently, endoscopes used for FI applications, and particularly for applications involving the dye indocyanine green (ICG) are primarily designed and deployed for visible light imagery. As such, they are not typically designed to maintain a constant focus between infrared light and visible light. To perform FI imaging, such scopes often employ an appropriate optical filter to block the excitation light and transmit the fluoresced light. However, as these endoscopes are generally optimized for conventional visible light observation, due to the properties of the optical elements of the scope, including the relay lens system, the infrared fluorescence is focused at a different plane than the visible light, due to chromatic aberration occurring throughout the optical system, and primarily in the image relay system. There are existing approaches to compensate for the resulting focal differences. Camera head solutions include those wherein multiple sensors are employed, with sensors, associated with particularly wavelength bands (for example one for visible light and one for infrared light) located at different focal planes, and directed to the sensors by dichroic beam splitter. The various spectral bands are detected on the multiple sensors, each an individually appropriate focal plane, resulting in two, independently captured, in-focus images. This approach is disadvantageous due, only in part, to the complexity and cost of the necessity for multiple image sensors. Another major concern is that each individual endoscope used with such a camera head includes optics which may be particular to that make, model and manufacture of scope. Each particular endoscope will have varying amounts of chromatic error, requiring any camera head used therewith to compensate specifically for the error associated with the coupled scope. It is very difficult to construct a single camera head capable of compensating for a variety of endoscope models. 
     Other efforts to compensate for focal differences, such as, for example, that found in U.S. Pat. No. 8,773,756 to Tesar, et al., involve using an optical coupler that splits the light into two paths, a visible spectrum path and a NIR spectrum path. Different optical elements are used in each of the two beam paths to compensate for the chromatic focal differences. However, as with camera head solutions, such systems fail to compensate for differences between various endoscopes or to compensate for the variety of chromatic aberrations across the entire desired spectrum. For example, there is chromatic aberration, in the same direction as IR light, in the deep blue range of the visible spectrum, not addressed by Tesar, resulting in the deep blue range of the visible image being not ideally focused at the same plane as the remainder of the visible light. The dispersive properties of the optical materials used in endoscopes, and long glass paths through such optical materials, make conventional correction of the entire spectrum from deep blue to infrared particularly difficult. Finally, the chromatic aberration includes both longitudinal chromatic aberration and lateral chromatic aberration due to obliquely incident light from the object space. Techniques that employ lenses or prisms to correct for longitudinal chromatic aberration often introduce unwanted lateral chromatic aberration. 
     What is needed are devices and methods to enable endoscope-side solutions to issues associated with chromatic aberration of the entire spectrum from deep blue to infrared, such that such an endoscope can be attached to a generic camera head and allow the capture of in-focus visible light and FI images. What is further needed are endoscopes for fluorescence imaging applications without expensive and slow optical elements such as autofocus mechanisms or adapters and processing systems for chromatic aberration correction. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to improve correction, in endoscopic devices, of the entire spectrum from deep blue to infrared. In order to achieve this objective, various aspects of the invention provide devices and systems to enhance endoscopes for use with both FI and visible light capabilities. Relay lens systems are disclosed that compensate for chromatic aberration from the deep blue through the infrared spectrum usually utilized in visible and fluorescent imaging in endoscopic procedures. In particular, relay lens systems are disclosed which utilize fewer optical elements than has heretofore been possible. Further, some embodiments enable the use of more economical parts than possible with other state-of-the-art systems, decreasing cost as well as simplifying construction of both the relay lens systems themselves as well as the endoscopic devices in which they may be used. 
     According to a first aspect of the invention, a relay system for an endoscope is provided. The relay system includes an opposing pair of rod lens assemblies positioned symmetrically with respect to a central airspace, wherein each rod lens assembly includes optical elements consisting essentially of a meniscus lens, a first lens, a rod lens, and an outer manipulating structure. The meniscus lens is positioned immediately adjacent to a central airspace and with the convex surface facing the airspace. The first lens has positive power with a convex face positioned adjacent to the inner face of the meniscus lens and is formed of a material having anomalous partial dispersion. The rod lens is adjacent to the first lens having positive power, and has a first face and a second face, both first and second faces being beam passing faces. The outer optical manipulating structure is selected from the group consisting of: the second face of the rod lens, being concave, positioned adjacent to a second lens having positive power and having a convex face facing the second concave face of the rod lens; the second convex face of the rod lens, being convex, positioned adjacent to an outer meniscus lens; the second face of the rod lens, being plano, positioned adjacent to a plano-convex aspherical lens; the second face of the rod lens, being plano, positioned adjacent to a positive powered lens having a convex face facing the second plano face of the rod lens with a separation gap; the second face of the rod lens, being plano, positioned adjacent to a second plano convex lens; and the second face of the rod lens, being convex. The meniscus lens, the first lens having positive power, the rod lens, and the outer optical manipulating structure together provide chromatic aberration correction by manipulating light from the blue region of the spectrum through the near IR region of the spectrum to follow the same sequence of optical surfaces and come to a common focus in a common image plane. 
     According to some implementations of first aspect, the first lens having positive power is plano-convex. 
     According to some implementations of first aspect, the first lens is manufactured from a material having an Abbe number equal to or greater than 80. 
     According to some implementations of first aspect, the outer optical manipulating structure is the second, concave face of the rod lens positioned adjacent to a second lens having positive power and having a convex face facing the second concave face of the rod lens. In some implementations, the second lens having positive power may be plano-convex. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of first aspect, the outer optical manipulating structure is the second convex face of the rod lens positioned adjacent to an outer meniscus lens. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of first aspect, the outer optical manipulating structure is the second plano face of the rod lens positioned adjacent to a plano-convex aspherical lens. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of first aspect, the outer optical manipulating structure is the second plano face of the rod lens positioned adjacent to a plano-convex lens having a convex face facing the second plano face of the rod lens with a separation gap. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of first aspect, the outer optical manipulating structure is the second plano face of the rod lens positioned adjacent to a second plano convex lens. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of the first aspect, the outer optical manipulating structure is the second convex face of the rod lens. In some implementations, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of the first aspect, the relay system is also corrected for astigmatism. 
     According to some implementations of the first aspect, the meniscus lens is constructed of a crown glass having a refractive index less than 1.65 and an Abbe number between 55 and 75 
     According to some implementations of the first aspect, the chromatic aberration correction is provided from approximately 400 nm to 900 nm. 
     According to some implementations of the first aspect, the pair of rod lens assemblies is arranged around an air space containing an aperture stop. 
     According to some implementations of the first aspect, the relay system also includes an endoscope containing the relay system. 
     According to some implementations of the first aspect, the first and second faces of the rod lens are plano. 
     According to a second aspect of the invention, a relay system for an endoscope includes an opposing pair of rod lens assemblies positioned symmetrically with respect a central air space, wherein each rod lens assembly includes a meniscus lens, a first lens, a rod lens, and a single outer lens. The meniscus lens is positioned adjacent to the opposing rod lens assembly. The first lens has positive optical power with a convex face positioned adjacent to an inner face of the meniscus lens. The rod lens positioned adjacent to the first plano-convex lens. The meniscus lens, the first lens having positive optical power, the rod lens, and the single outer lens together are sufficient to manipulate light to provide chromatic aberration correction by manipulating light from the blue region of the spectrum through the near IR region of the spectrum to follow the same sequence of optical surfaces through the relay system and come to a common focus in a common image plane. 
     According to some implementations of the second aspect, each rod lens assembly has no additional optical manipulating elements other than the those listed. 
     According to some implementations of the second aspect, the first lens having positive optical power is manufactured from a material having anomalous partial dispersion. 
     According to some implementations of the second aspect, the meniscus lens is constructed of a crown glass having a refractive index less than 1.65 and an Abbe number between 55 and 75 
     According to some implementations of the second aspect, the chromatic aberration correction is provided from approximately 400 nm to 900 nm. 
     According to some implementations of the second aspect, the relay system is also corrected for astigmatism. 
     According to some implementations of the second aspect, the relay system further includes an endoscope containing the relay system. 
     According to some implementations of the second aspect, the first and second faces of the rod lens are plano. 
     These and other features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG.  1    is diagram of a prior art endoscopic system; 
         FIG.  2    is a block diagram of an endoscope device including a scope and an attached camera head; 
         FIG.  3    is a partial cross section diagram of the optical relay system according to some embodiments of the invention for use in an endoscope device wherein all lenses are spherical, and each rod lens assembly may be fully cemented together; 
         FIG.  4    is a chart showing the wavelength versus focal shift achievable with the optical relay system of  FIG.  3    according to an example embodiment; 
         FIG.  5    is a partial cross section diagram of the optical relay system of the invention for use in an endoscope device wherein all lenses are spherical, and each rod lens assembly may be fully cemented together according to additional embodiments; 
         FIG.  6    is a chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  5    according to an example embodiment; 
         FIG.  7    is a partial cross section diagram showing an optical relay system according to an embodiment where the rod lens element is planar on both ends and the rod lens assembly may be completely cemented together; 
         FIG.  8    is a chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  7    according to an example embodiment; 
         FIG.  9    is a partial cross section diagram showing an optical relay system according to embodiments where the rod lens element is planar on both ends and all lens elements are spherical, including detached elements; 
         FIG.  10    is a chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  9    according to an example embodiment; 
         FIG.  11    is another chart showing the wavelength versus focal shift achievable by the optical relay system according to another embodiment of the arrangement of  FIG.  9   , using optical elements with different focal powers from the embodiment of  FIG.  10   ; 
         FIG.  12    is a partial cross section diagram of an optical relay system according to additional embodiments; 
         FIG.  13    is a chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  12    according to an example embodiment; 
         FIG.  14    is another chart showing the wavelength versus focal shift achievable by the optical relay system according to another embodiment of the arrangement of  FIG.  12    using optical elements with different focal powers from the embodiment of  FIG.  13   . 
         FIG.  15    is a partial cross section diagram of an optical relay system according to additional embodiments; 
         FIG.  16    is a chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  15    according to an example embodiment; 
         FIG.  17    is another chart showing the wavelength versus focal shift achievable by the optical relay system of  FIG.  15    using optical elements with different focal powers from the embodiment of  FIG.  16   ; and 
         FIG.  18    is a hardware block diagram of system including an example image capture device according to an example embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     As used herein, first elements (e.g., sensors and lenses) that are “optically arranged” in relation to other elements, refers to the first elements&#39; position along a common optical path that includes first and other elements. For example, a lens group optically arranged between an image sensor and an objective, means that the lens group occupies a portion of the optical path that light travels (e.g., from the objective to the image sensor) for capturing images or video. 
     Because digital cameras and FI sensors and related circuitry for signal capture and processing are well-known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, a method and apparatus in accordance with the invention. Elements not specifically shown or described herein are selected from those known in the art. Certain aspects of the embodiments to be described are provided in software. Given the system as shown and described according to the invention in the following materials, software not specifically shown, described or suggested herein that is useful for implementation of the invention is conventional and within the ordinary skill in such arts. 
       FIG.  2    is a block diagram of an endoscope device  100  according to an example embodiment of the invention. Endoscope device  100  (“device  100 ”, “endoscope  100 ”) includes a shaft  102  connected to a proximal element  101 . The proximal element  101  may be an eyecup including an eyepiece enabling the user to view visible light traversing the shaft  102 . The eyecup may also act as an attachment element to connect the scope to a camera head  216  containing one more image sensors, via a bayonet connection, or other connection system known in the art. Alternatively the camera head element may be integrated with the shaft via the proximal element  101 . Various structural components supporting the depicted elements are omitted in the diagrams herein, as well as other components such as illumination sources, fluorescent excitation sources, and controls which are known in the art and are not shown in order to avoid obscuring the relevant details of the example embodiments of the invention. At the left is shown the distal tip of the endoscope shaft  102  including a cover glass  202 , which in this version faces directly along the longitudinal axis of the shaft  102 , but may also be positioned at an angle relative to the longitudinal axis as is known in the art. Behind, or on the proximal side of, the cover glass  202  is shown a preferred position for the objective lens  204 , usually set against or very near cover glass  202  and preferably assembled together with the cover glass in construction. While a wide angle lens is preferred for objective lens  204 , this is not limiting, and any suitable lens may be used in various embodiments. Objective lens  204  may be part of an objective lens group  104  which may include one or more additional lenses  103 . The particular number and arrangement of lenses in the endoscope shaft  102  will vary widely depending on the application. Optically arranged or attached at the proximal side of objective lens  204  or objective lens group  104  is rod lens relay system  107 , which serves to pass the light down shaft  102  in the proximal direction. Rod lens relay system  107 , including rod lens pairs, is adapted to direct the image light to create a telecentric internal image space at the proximal end of the one or more rod lenses, where a second lens group  214  is positioned as further discussed below. Also, the shaft  102  is typically rigid but shaft design variations are also known to allow rod lenses to be used in a semi-flexible shaft in which flexible joints are present in one or more places along the shaft between the rod lenses, while the shaft is rigid along the portions containing a rod lens. Such a shaft design may be used in various embodiments of the invention. 
     Rod lens relay system  107  functions to compensate for the chromatic aberration of the endoscope&#39;s multiple lenses such that a first portion of light having a first wavelength spectrum and a second portion of light having a second wavelength spectrum different from the first are focused onto substantially the same image plane. Assembly  214  is positioned within a telecentric internal image space proximal to rod lens relay system  107 . Second lens group  214  is preferably positioned within the proximal element  101  of device  100 , but may partially span the volume of the shaft  102  and the proximal element  101  or may be an element of the camera head or eyepiece  216 . 
     Typically, rod lens relay system  107  is integrated with endoscope device  100 , and, in particular, the shaft  102 , and is designed to correct for chromatic aberrations. As further described below, some embodiments also provide astigmatism correction. The eyepiece, or the image sensor assembly and its associated electronics (together constituting a camera) may be integrated with the device or may be separate and detachable, such as a detachable eyepiece or a detachable camera head. In various embodiments the invention may therefore constitute an endoscopic device or an imaging system including an endoscopic device  100 . 
       FIG.  3    is a partial cross section diagram of an optical relay lens system  300  according to some embodiments to be used in an endoscope device  100 . The depicted relay system  300  may be employed, for example, as rod lens relay system  107  in the system of  FIG.  2   . Relay system  300  includes an opposing pair of rod lens assemblies  301  positioned symmetrically with respect to a central airspace. More than one such pair may be employed in series to provide an overall relay system with a greater length. The central airspace between rod lens assemblies  301  may contain an aperture stop. This embodiment has the advantages of consisting of only four optical elements per rod lens assembly, wherein each lens is spherical, and the rod lens assembly may be fully cemented together and may have a planar outer surface, which can simplify the design and assembly of the overall relay system within the shaft  102 . 
     Each rod lens assembly  301 , according to this embodiment, includes a meniscus lens  302  positioned adjacent to the opposing rod lens assembly. A first plano-convex lens  304  has a convex face positioned adjacent to an inner face of meniscus lens  302  and a planar face at the opposite side. Other lenses may be used instead of a plano-convex lens. A rod lens  306  has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . 
     At the opposing, outer end of rod lens  306  is an outer optical manipulating structure which in this embodiment includes a second concave face of rod lens  306  positioned adjacent to a second plano-convex lens  308  having a convex face facing the second concave face of rod lens  306 . 
     A light ray diagram is shown showing the path taken by light  310  passing from an object plane depicted on the left to an image plane depicted on the right. Meniscus lens  302 , first plano-convex lens  304 , rod lens  306 , and the outer optical manipulating structure together perform chromatic aberration correction by manipulating light  310  of a spectrum from the blue region through the near IR region to have substantially the same effective optical path length and thus come to a common focus at a common image plane, allowing for simultaneous imaging throughout the spectrum. Each rod lens assembly  301  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or sequential or separate imaging without refocusing adjustments for the visible and IR spectra. The amount of chromatic aberration correction may vary depending on the materials, sizes, and curvatures of the various optical manipulating elements. Depending on the f-number of the system, the amount of correction in focal position due to chromatic aberration sufficient to allow simultaneous imaging across the IR and visible spectrum may be less than about 15 micrometers shift across the spectral range of 400 nm to 900 nm. Additionally, depending on the number of relays in a system, this correction in focal position may vary, as associated errors accumulate over multiple relays. More preferably, a correction to a total aberration of 10 micrometers of focal shift across that range is achievable with certain embodiments employing the relay system of  FIG.  3   . 
     Meniscus lens  302  is preferably constructed with a crown glass having a refractive index less than 1.65 and an Abbe number between 55 and 75. Preferably, the first positive power lens  304 , which is typically a plano-convex lens but may be another positive power lens, is constructed of a material having anomalous partial dispersion. The material of the first positive power lens  304  preferably has a lower refractive index and higher Abbe number than the material of the rod lens. For example, various types of crown glass may be used such as phosphate glasses or fluorophosphate glasses. A relatively high Abbe number is preferably used such as 55 or over. For example, various versions may employ crown glass with an Abbe number of 65, 70, 75, 80, or 85. For example, first positive power lens  304  has an Abbe number of 81.54 in some embodiments. Optical properties of the surface elements of one possible implementation of the embodiment shown in  FIG.  3    are given in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment FIG. 3 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 3.302 
                 Air 
                   
                 4.20 
               
               
                 1 
                 Infinity 
                 2.0 
                 1.847 
                 23.78 
                 6.48 
               
               
                 2 
                 −7.2169 
                 43.532 
                 1.618 
                 49.82 
                 6.48 
               
               
                 3 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 4 
                 −6.0591 
                 1.4 
                 1.522 
                 59.48 
                 6.48 
               
               
                 5 
                 −15.8891  
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 4.5857 
               
               
                 7 
                 15.8891 
                 1.4 
                 1.522 
                 59.48 
                 6.48 
               
               
                 8 
                  6.0591 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 9 
                 Infinity 
                 43.532 
                 1.618 
                 49.82 
                 6.48 
               
               
                 10  
                  7.2169 
                 2.0 
                 1.847 
                 23.78 
                 6.48 
               
               
                 11  
                 Infinity 
                 3.302 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2217 
               
               
                   
               
            
           
         
       
     
     In this embodiment, as well as the embodiments described below with respect to  FIG.  5   ,  FIG.  7   , and  FIG.  9   , the relay system also provides correction for astigmatism. As endoscope systems with rod lenses often have astigmatism, the outer optical manipulating structure of these embodiments preferably performs an astigmatism correction function. 
       FIG.  4    is a chart showing chromatic aberration correction achievable with the relay system of  FIG.  3    according to an example implementation with the properties shown in Table 1. The vertical axis shows the light wavelength in micrometers from 0.4 to 0.9 (400 to 900 nanometers), and the horizontal axis shows the focal shift provided by the relay system using a single pair of rod lens assemblies  301  in an endoscope optical assembly. As can be seen on the chart, the focal shift is about 6 micrometers at the 405 nanometer wavelength and exhibits a curve to about negative 4 micrometers of focal shift at the 900 nanometer wavelength, for a total focal shift range of about 10 micrometers across the depicted spectrum. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
       FIG.  5    is a partial cross section diagram of an optical relay lens system  500  according to some additional embodiments to be used in an endoscope device  100 . A light ray diagram is overlaid on the diagram. Relay system  500  includes an opposing pair of rod lens assemblies  501  positioned symmetrically with respect to a central airspace. As with the embodiments of  FIG.  3   , more than one such pair may be employed in series to provide an overall relay system with a greater length. The central airspace between rod lens assemblies  501  may contain an aperture stop. This embodiment has the advantages of consisting of only four optical elements per rod lens assembly, wherein each lens is spherical, and the rod lens assembly may be fully cemented together, which can simplify the design and assembly of the overall relay system within the shaft  102 . 
     Each rod lens assembly  501  includes a meniscus lens  302  and a first plano-convex lens  304 , or other positive power lens, similar to those described with respect to  FIG.  3   . In this embodiment, a rod lens  506  is a plano-convex rod lens having has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . At the opposing, outer end of rod lens  506  is an outer optical manipulating structure which includes a second convex face of rod lens  506  positioned adjacent to an outer meniscus lens  508 . 
     Meniscus lens  302 , first plano-convex lens  304 , rod lens  506 , and the outer optical manipulating structure together perform chromatic aberration correction by manipulating light  510  in the blue region of the spectrum through the near IR region of the spectrum to have the same effective optical path length so as to come to a common focus at a common image plane. Each rod lens assembly  501  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or sequential or separate imaging without refocusing adjustments for the visible spectrum and IR. Optical properties of the surface elements of an implementation of the embodiment shown in  FIG.  5    are given in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment shown in FIG. 5 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 6.0 
                 Air 
                   
                 4.2 
               
               
                 1 
                  13.2864 
                 2.0 
                 1.847 
                 23.78 
                 6.48 
               
               
                 2 
                  6.5539 
                 44.835 
                 1.618 
                 49.82 
                 6.48 
               
               
                 3 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 4 
                  −5.8150 
                 1.4 
                 1.512 
                 70.86 
                 6.48 
               
               
                 5 
                 −17.8746 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 5.3157 
               
               
                 7 
                  17.8746 
                 1.4 
                 1.512 
                 70.86 
                 6.48 
               
               
                 8 
                  5.8150 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 9 
                 Infinity 
                 44.835 
                 1.618 
                 49.82 
                 6.48 
               
               
                 10  
                  −6.5539 
                 2.0 
                 1.847 
                 23.78 
                 6.48 
               
               
                 11  
                 −13.2864 
                 6.0 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2209 
               
               
                   
               
            
           
         
       
     
       FIG.  6    is a chart showing chromatic aberration correction achievable with the relay system of  FIG.  5    according to an example implementation with the properties shown in Table 2. As can be seen, the range of focal shift across the spectrum from 405 to 900 nanometers varies from a minus 8 micrometer shift to about 5 micrometers, for a total range of approximately 13 micrometers. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
       FIG.  7    is a partial cross section diagram of an optical relay lens system  700  according to additional embodiments to be used in an endoscope device  100 . In this embodiment, and that of  FIG.  9   , the rod lenses  706  are plano-plano rod lenses which provide lower construction costs compared to rod lenses having curved faces. Relay system  700  includes an opposing pair of rod lens assemblies  701  positioned symmetrically with respect to a central airspace. As with the embodiments of  FIG.  3   , more than one such pair may be employed in series to provide an overall relay system with a greater length. The central airspace between rod lens assemblies  301  may contain an aperture stop. This embodiment has the advantages, beyond that of the planar-planar rod lens element, of consisting of only four optical elements per rod lens assembly and the rod lens assembly may be fully cemented together, which can simplify the design and assembly of the overall relay system within the shaft  102 . 
     A light ray diagram is overlaid on the diagram showing light passing from the object plane depicted on the left to an image plane depicted on the right. As with the other embodiments herein, additional pairs rod lens assemblies  701  may be placed end to end with the depicted pair of assemblies, with the image plane at which an image is measured with a sensor positioned after the final pair of rod lens assemblies. 
     Each rod lens assembly  701  includes a meniscus lens  302  and a first plano-convex lens  304 , or other positive power lens, similar to those described with respect to  FIG.  3   . In this embodiment, a rod lens  706  is a plano-plano rod lens having has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . At the opposing, outer end of rod lens  706  is an outer optical manipulating structure which includes a second plano face of rod lens  706  positioned adjacent to a plano-convex aspherical lens  708 . The use of an aspheric lens in this embodiment provides ability to correct for astigmatism while using a lower cost plano-plano rod lens. 
     Meniscus lens  302 , first plano-convex lens  304 , rod lens  706 , and the outer optical manipulating structure together perform chromatic aberration correction by manipulating light  710  in the blue region of the spectrum through the near IR region of the spectrum to have the same effective optical path length, and thus come to a common focus at a common image plane. Each rod lens assembly  701  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or sequential or separate imaging without refocusing adjustments for the visible spectrum and IR. Optical properties of the surface elements of an implementation of the embodiment shown in  FIG.  7    are given in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment shown in FIG. 7 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Abbe 
                 Clear 
                   
               
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 no. 
                 Diam 
                 Conic 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 6.995 
                 Air 
                   
                 4.2 
                 0 
               
               
                 1 
                 20.8646 
                 2.0 
                 1.717 
                 29.52 
                 6.48 
                 −5.6347 
               
               
                 2 
                 Infinity 
                 41.805 
                 1.618 
                 49.82 
                 6.48 
                 0 
               
               
                 3 
                 Infinity 
                 2.5 
                 1.529 
                 76.98 
                 6.48 
                 0 
               
               
                 4 
                 −5.5174  
                 1.4 
                 1.540 
                 59.71 
                 6.48 
                 0 
               
               
                 5 
                 −19.4448   
                 0.3 
                 Air 
                   
                 6.48 
                 0 
               
               
                 STO 
                 Infinity 
                 0.3 
                 Air 
                   
                 4.5372 
                 0 
               
               
                 7 
                 19.4448 
                 1.4 
                 1.540 
                 59.71 
                 6.48 
               
               
                 8 
                  5.5174 
                 2.5 
                 1.529 
                 76.98 
                 6.48 
                 0 
               
               
                 9 
                 Infinity 
                 41.805 
                 1.618 
                 49.82 
                 6.48 
                 0 
               
               
                 10  
                 Infinity 
                 2.0 
                 1.717 
                 29.52 
                 6.48 
                 0 
               
               
                 11  
                 −20.8646   
                 6.995 
                 Air 
                   
                 6.48 
                 −5.6347 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2247 
                 0 
               
               
                   
               
            
           
         
       
     
       FIG.  8    is a chart showing chromatic aberration correction achievable with the relay system of  FIG.  7    according to an example implementation with the properties shown in Table 3. The focal shift ranges from slightly larger than negative 8 micrometers at the 405 nanometer wavelength, to about positive 3 micrometers around 700 nanometers, providing a total focal shift range of about 11 micrometers. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
       FIG.  9    is a partial cross section diagram of an optical relay lens system  900  according to additional embodiments to be used in an endoscope device  100 . Relay system  900  includes an opposing pair of rod lens assemblies  901  positioned symmetrically with respect to a central airspace. As with the embodiments discussed above, more than one such pair may be employed in series to provide an overall relay system with a greater length. The central airspace between rod lens assemblies  301  may contain an aperture stop. This embodiment has the advantages, beyond that of the planar-planar rod lens element, of consisting of only four optical elements per rod lens assembly and all of the lenses are spherical. 
     A light ray diagram is overlaid on the diagram showing light passing from the object plane depicted on the left to an image plane depicted on the right. Additional pairs rod lens assemblies  901  may be placed end to end with the depicted pair of assemblies, with the image plane at which an image is measured with a sensor positioned after the final pair of rod lens assemblies. 
     Each rod lens assembly  901  includes a meniscus lens  302  and a first plano-convex lens  304 , or other positive power lens, like those of  FIG.  3   . In this embodiment, a rod lens  906  is a plano-plano rod lens having has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . At the opposing, outer end of rod lens  906  is an outer optical manipulating structure which includes a second plano face of the rod lens positioned adjacent to a plano-convex lens  908  having a convex face facing the second plano face of the rod lens with a separation gap. Other lenses with a positive power may be used in place of plano-convex lens  908 . This embodiment also provides ability to correct for astigmatism while using a low cost plano-plano rod lens in the relay system. 
     Meniscus lens  302 , first plano-convex lens  304 , rod lens  906 , and the outer optical manipulating structure  908  together perform chromatic aberration correction by manipulating light  910  in the blue region of the spectrum through the near IR region of the spectrum to have the same effective optical path length, and thus and come to a common focus at a common image plane. Each rod lens assembly  901  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or sequential or separate imaging without refocusing adjustments for the visible spectrum and IR. Optical properties of the surface elements of an implementation of the embodiment shown in  FIG.  9    are given in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Surface data summary for one implementation 
               
               
                 of the embodiment shown in FIG. 9 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 4.553 
                 Air 
                   
                 4.2 
               
               
                 1 
                 Infinity 
                 2.0 
                 1.923 
                 18.90 
                 6.48 
               
               
                 2 
                 −27.8072 
                 2.284 
                 Air 
                   
                 6.48 
               
               
                 3 
                 Infinity 
                 39.966 
                 1.618 
                 49.82 
                 6.48 
               
               
                 4 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 5 
                  −6.2398 
                 1.4 
                 1.523 
                 59.48 
                 6.48 
               
               
                 6 
                 −16.6953 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 4.5853 
               
               
                 8 
                  16.6953 
                 1.4 
                 1.523 
                 59.48 
                 6.48 
               
               
                 9 
                  6.2398 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 10 
                 Infinity 
                 39.996 
                 1.618 
                 49.82 
                 6.48 
               
               
                 11 
                 Infinity 
                 2.284 
                 Air 
                   
                 6.48 
               
               
                 12 
                  27.8073 
                 2.0 
                 1.923 
                 18.90 
                 6.48 
               
               
                 13 
                 Infinity 
                 4.553 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2233 
               
               
                   
               
            
           
         
       
     
       FIG.  10    is a chart showing chromatic aberration correction achievable with the relay system of  FIG.  9    according to an example implementation with the properties shown in Table 3. The focal shift ranges from 12 micrometers at the 405 nanometer wavelength, to slightly under zero micrometers at 550 nanometers, providing a total focal shift range of about 12 micrometers. 
       FIG.  11    is another chart showing chromatic aberration achievable according to another implementation of the embodiment of  FIG.  9    using elements with different properties (shown in Table 5) from the embodiment of  FIG.  10   . In this version, the focal shift ranges from about negative 4 micrometers at 405 nanometers, to slightly over two micrometers at 900 nanometers, for a total focal shift range of slightly over 6 micrometers. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Alternative surface data summary for one implementation 
               
               
                 of the embodiment shown in FIG. 9 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 6.3133 
                 Air 
                   
                 4.2 
               
               
                 1 
                 102.5046 
                 2.0 
                 1.923 
                 18.90 
                 6.48 
               
               
                 2 
                 −34.8825 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 3 
                 Infinity 
                 40.2717 
                 1.620 
                 36.37 
                 6.48 
               
               
                 4 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 5 
                  −6.2200 
                 1.4 
                 1.522 
                 59.48 
                 6.48 
               
               
                 6 
                 −17.0677 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 4.3345 
               
               
                 8 
                  17.0677 
                 1.4 
                 1.522 
                 59.48 
                 6.48 
               
               
                 9 
                  6.2200 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 10 
                 Infinity 
                 40.2717 
                 1.620 
                 36.37 
                 6.48 
               
               
                 11 
                 Infinity 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 12 
                  34.8825 
                 2.0 
                 1.923 
                 18.90 
                 6.48 
               
               
                 13 
                 −102.5046  
                 6.3133 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2 
               
               
                   
               
            
           
         
       
     
       FIG.  12    is a partial cross section diagram of an optical relay lens system  1200  according to additional embodiments to be used in an endoscope device  100 . Relay system  1200  includes an opposing pair of rod lens assemblies  1201  positioned symmetrically with respect to a central airspace. As with the embodiments discussed above, more than one such pair may be employed in series to provide an overall relay system with a greater length. The central airspace between rod lens assemblies  1201  may contain an aperture stop. While, as opposed to the embodiments shown above, this embodiment does not explicitly correct for astigmatism, it offers a simplified design, employing a plano-plano rod lens, consists of only four optical elements per rod lens assembly, and all of the lenses are spherical and may be cemented together into a single unit. 
     A light ray diagram is overlaid on the diagram showing light passing from the object plane depicted on the left to an image plane depicted on the right. Additional pairs rod lens assemblies  1201  may be placed end to end with the depicted pair of assemblies, with the image plane at which an image is measured with a sensor positioned after the final pair of rod lens assemblies. 
     Each rod lens assembly  1201  includes a meniscus lens  302  and a positive power lens such as first plano-convex lens  304  like that of  FIG.  3   . In this embodiment, a rod lens  1206  is a plano-plano rod lens having has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . At the opposing, outer end of rod lens  1206  is an outer optical manipulating structure which includes a second plano face of the rod lens positioned adjacent to a plano-convex lens  1208  having a plano face adjacent to rod lens  1206  and a convex face directed outward. 
     Meniscus lens  302 , first plano-convex lens  304 , rod lens  1206 , and the outer optical manipulating structure together perform chromatic aberration correction by manipulating light  1210  in the blue region of the spectrum through the near IR region of the spectrum to have substantially the same effective optical path length, and therefore come to a common focus at a common image plane. Each rod lens assembly  1201  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or separate or sequential imaging without refocusing adjustments for the visible spectrum and IR. 
       FIGS.  13  and  14    are charts showing chromatic aberration correction achievable with implementations of the relay system of  FIG.  12   .  FIG.  13   , with corresponding surface properties given in Table 6, shows a focal shift range from about negative 9 micrometers at the 405 nanometer wavelength, to about 3 micrometers at 700 nanometers, providing a total focal shift range of about 12 micrometers.  FIG.  14   , with corresponding surface properties given in Table 7, shows a focal shift rang from about 14 micrometers at 405 nanometers, to about negative two micrometers at around 500 nanometers, for a total focal shift range of 16 micrometers. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment shown in FIG. 12 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 7.257 
                 Air 
                   
                 4.2 
               
               
                 1 
                 21.3368 
                 2.0 
                 1.717 
                 29.52 
                 6.48 
               
               
                 2 
                 Infinity 
                 41.543 
                 1.618 
                 49.82 
                 6.48 
               
               
                 3 
                 Infinity 
                 2.5 
                 1.529 
                 76.98 
                 6.48 
               
               
                 4 
                 −5.4641 
                 1.4 
                 1.540 
                 59.71 
                 6.48 
               
               
                 5 
                 −19.5366 
                 0.3 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.3 
                 Air 
                   
                 4.5429 
               
               
                 7 
                 19.5366 
                 1.4 
                 1.540 
                 59.71 
                 6.48 
               
               
                 8 
                 5.4641 
                 2.5 
                 1.529 
                 76.98 
                 6.48 
               
               
                 9 
                 Infinity 
                 41.543 
                 1.618 
                 49.82 
                 6.48 
               
               
                 10  
                 Infinity 
                 2.0 
                 1.718 
                 29.52 
                 6.48 
               
               
                 11  
                 −21.3368 
                 7.257 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2695 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Surface Data Summary for an alternative implementation 
               
               
                 of the embodiment shown in FIG. 12 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 4.716 
                 Air 
                   
                 4.2 
               
               
                 1 
                  25.0813 
                 2.0 
                 1.801 
                 34.97 
                 6.48 
               
               
                 2 
                 Infinity 
                 44.083 
                 1.618 
                 49.82 
                 6.48 
               
               
                 3 
                 Infinity 
                 2.5 
                 1.439 
                 94.66 
                 6.48 
               
               
                 4 
                  −7.6413 
                 1.4 
                 1.569 
                 63.10 
                 6.48 
               
               
                 5 
                 −13.1283 
                 0.3 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.3 
                 Air 
                   
                 4.8458 
               
               
                 7 
                  13.1283 
                 1.4 
                 1.569 
                 63.10 
                 6.48 
               
               
                 8 
                  7.6413 
                 2.5 
                 1.439 
                 94.66 
                 6.48 
               
               
                 9 
                 Infinity 
                 44.083 
                 1.618 
                 49.82 
                 6.48 
               
               
                 10  
                 Infinity 
                 2.0 
                 1.801 
                 34.97 
                 6.48 
               
               
                 11  
                 −25.0813 
                 4.716 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2545 
               
               
                   
               
            
           
         
       
     
       FIG.  15    is a partial cross section diagram of an optical relay lens system  1500  according to additional embodiments to be used in an endoscope device  100 . Relay system  1500  includes an opposing pair of rod lens assemblies  1501  positioned symmetrically with respect to a central airspace. As with the embodiments discussed above, more than one such pair may be employed in series to provide an overall relay system with a greater length. As with the embodiment shown in  FIG.  12   , this embodiment does not explicitly correct for astigmatism, however it offers a simplified design, employing only three optical elements per rod lens assembly, and all of the lenses may be cemented together into a single unit. 
     A light ray diagram is overlaid on the diagram showing light passing from the object plane depicted on the left to an image plane depicted on the right. Additional pairs rod lens assemblies  1501  may be placed end to end with the depicted pair of assemblies, with the image plane at which an image is measured with a sensor positioned after the final pair of rod lens assemblies. 
     Each rod lens assembly  1501  includes a meniscus lens  302  and a positive power lens such as first plano-convex lens  304  like that of  FIG.  3   . In this embodiment, a rod lens  1506  is a plano-convex rod lens having has a first plano surface positioned adjacent to the plano face of first plano-convex lens  304 . At the opposing, outer end of rod lens  1506  is an outer optical manipulating structure which includes a convex face of the rod lens directed outward. 
     Meniscus lens  302 , first plano-convex lens  304 , rod lens  1506 , and the outer optical manipulating structure together perform chromatic aberration correction by manipulating light  1510  in the blue region of the spectrum through the near IR region of the spectrum to have the same effective optical path length, and thus come to a common focus at a common image plane. Each rod lens assembly  1501  has no additional optical manipulating elements other than the those listed which together provide a chromatic aberration correction sufficient to allow simultaneous imaging of visible and IR spectrum light at the depicted common imaging plane, or separate or sequential imaging without refocusing adjustments for the visible spectrum and IR. 
       FIGS.  16  and  17    are charts showing chromatic aberration correction achievable with implementations of the relay system of  FIG.  15   .  FIG.  16   , with corresponding surface properties given in Table 8 shows a focal shift range from about negative 7 micrometers at the 475 nanometer wavelength, to about 3 micrometers at 900 nanometers, providing a total focal shift range of about 10 micrometers.  FIG.  17   , with corresponding surface properties given in Table 9, shows a focal shift range from about negative 10 micrometers at 475 nanometers, to about three micrometers at around 725 nanometers, for a total focal shift range of 13 micrometers. This focal shift provided by the inventive optical relay system minimizes the variance of focal position as a function of wavelength which would ordinarily be present due to chromatic aberration of a conventional rod lens relay pair. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment shown in FIG. 15 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 6.0 
                 Air 
                   
                 4.2 
               
               
                 1 
                  23.0368 
                 55.533 
                 1.618 
                 49.82 
                 6.48 
               
               
                 2 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 3 
                  −6.6931 
                 1.4 
                 1.512 
                 64.98 
                 6.48 
               
               
                 4 
                 −20.6228 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 5.7193 
               
               
                 6 
                  20.6228 
                 1.4 
                 1.512 
                 64.98 
                 6.48 
               
               
                 7 
                  6.6931 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 8 
                 Infinity 
                 55.533 
                 1.618 
                 49.82 
                 6.48 
               
               
                 9 
                 −23.0368 
                 6.0 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2557 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Surface Data Summary for one implementation 
               
               
                 of the embodiment shown in FIG. 15 
               
            
           
           
               
               
               
               
               
               
            
               
                 Surface 
                 Radius 
                 Thickness 
                 Index 
                 Abbe no. 
                 Clear Diam 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Obj 
                 Infinity 
                 6.0 
                 Air 
                   
                 4.2 
               
               
                 1 
                  18.2447 
                 42.835 
                 1.620 
                 36.37 
                 6.48 
               
               
                 2 
                 Infinity 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 3 
                  −6.2847 
                 1.4 
                 1.525 
                 64.67 
                 6.48 
               
               
                 4 
                 −16.6115 
                 0.25 
                 Air 
                   
                 6.48 
               
               
                 STO 
                 Infinity 
                 0.25 
                 Air 
                   
                 4.5273 
               
               
                 6 
                  16.6115 
                 1.4 
                 1.525 
                 64.67 
                 6.48 
               
               
                 7 
                  6.2847 
                 2.5 
                 1.497 
                 81.55 
                 6.48 
               
               
                 8 
                 Infinity 
                 42.835 
                 1.620 
                 36.37 
                 6.48 
               
               
                 9 
                 −18.2447 
                 6.0 
                 Air 
                   
                 6.48 
               
               
                 IMA 
                 Infinity 
                   
                   
                   
                 4.2720 
               
               
                   
               
            
           
         
       
     
     Referring to  FIG.  18   , a block diagram of system including an image capture device and an endoscope device having an improved correction of chromatic aberration as described above. The invention is applicable to more than one type of device enabled for image capture, such as FI-capable endoscopes, other FI medical imaging devices. The preferred version is an imaging scope system, such as an endoscope. 
     As shown in the diagram of an endoscope device system, a light source  8  illuminates subject scene  9  with visible light and/or fluorescent excitation light, which may be outside the visible spectrum in the ultra-violet range or the infra-red/near infrared range, or both. Light source  8  may include a single light emitting element configured to provide light throughout the desired spectrum, or a visible light emitting element and a one or more fluorescent excitation light emitting elements. Further, light source  8  may include fiber optics passing through the body of the scope, or other light emitting arrangements such as LEDs or laser diodes positioned at or near the front of the scope. 
     As shown in the drawing, light  10  reflected from (or, alternatively, as in the case of fluorescence, excitation light  8  absorbed and subsequently emitted by) the subject scene is input to an optical assembly  11 , where the light is focused to form an image at a solid-state image sensor(s)  222  and/or fluoresced light sensor(s)  223 . 
     Optical assembly  11  includes an optical relay system constructed according to the techniques provided herein. For example, the embodiments of  FIG.  3   ,  FIG.  5   , FIG.  7 ,  FIG.  9   ,  FIG.  12   , or  FIG.  15    may be used, or other embodiments. An additional lens group may be included at the camera head, as discussed with respect to  FIG.  2   . As discussed above, portions of the optical assembly may be embodied in a camera head or other first optical device, while other portions are in an endoscope or other scope device, or the optical assembly  11  may be contained in a single imaging device. Image sensor  222  (which may include separate R, G, and B sensor arrays) and fluoresced light sensor  223  convert the incident visible and invisible light to an electrical signal by integrating charge for each picture element (pixel). It is noted that fluoresced light sensor  223  is shown as an optional dotted box because embodiments may use the RGB image sensor  222  to detect only white light images or to also detect fluoresced light (e.g., NIR, ICG, FI). The latter scheme may be used when the fluoresced light is in a spectrum detectable by image sensor  222  that is in or near the visible light spectrum typically detected by a RGB sensor arrays. 
     Of course, alternate implementations of the present inventive relay lens systems are possible. For example, optical assembly  11  may include a dichroic beam splitting element and may direct one band of the spectra to one sensor for visual imaging and another band to another sensor for fluorescence imaging. As the present invention enables a scope side solution to the problems associated with chromatic aberration in relay systems, the camera head image sensor assembly  28  need not be adjusted to assure both visible and FI images are in focus. 
     The image sensor  222  and fluoresced light sensor  223  may be active pixel complementary metal oxide semiconductor sensor (CMOS APS) or a charge-coupled device (CCD). 
     The total amount of light  10  reaching the image sensor  222  and/or fluoresced light sensor  223  is regulated by the light source  8  intensity, the optical assembly  11  aperture, and the time for which the image sensor  222  and fluoresced light sensor  223  integrates charge. An exposure controller  40  responds to the amount of light available in the scene given the intensity and spatial distribution of digitized signals corresponding to the intensity and spatial distribution of the light focused on image sensor  222  and fluoresced light sensor  223 . 
     Exposure controller  40  also controls the emission of fluorescent excitation light from light source  8 , and may control the visible and fluorescent light emitting elements to be on at the same time, or to alternate to allow fluoresced light frames to be captured in the absence of visible light if such is required by the fluorescent imaging scheme employed. Exposure controller  40  may also control the optical assembly  11  aperture, and indirectly, the time for which the image sensor  222  and fluoresced light sensor  223  integrate charge. The control connection from exposure controller  40  to timing generator  26  is shown as a dotted line because the control is typically indirect. 
     Typically, exposure controller  40  has a different timing and exposure scheme for each of sensors  222  and  223 . Due to the different types of sensed data, the exposure controller  40  may control the integration time of the sensors  222  and  223  by integrating sensor  222  up to the maximum allowed within a fixed 60 Hz or 50 Hz frame rate (standard frame rates for USA versus European video, respectively), while the fluoresced light sensor  223  may be controlled to vary its integration time from a small fraction of sensor  222  frame time to many multiples of sensor  222  frame time. The frame rate of sensor  222  will typically govern the synchronization process such that images frames based on sensor  223  are repeated or interpolated to synchronize in time with the 50 or 60 fps rate of sensor  222 . 
     Analog signals from the image sensor  222  and fluoresced light sensor  223  are processed by analog signal processor  22  and applied to analog-to-digital (A/D) converter  24  for digitizing the analog sensor signals. The digitized signals each representing streams of images or image representations based on the data, are fed to image processor  30  as image signal  27 , and first fluorescent light signal  29 . For versions in which the image sensor  222  also functions to detect the fluoresced light, fluoresced light data is included in the image signal  27 , typically in one or more of the three color channels. 
     Image processing circuitry  30  includes circuitry performing digital image processing functions to process and filter the received images as is known in the art. Image processing circuitry may include separate, parallel pipelines for processing the visible light image data and the FI image data separately. Such circuitry is known in the art and will not be further described here. 
     Image processing circuitry  30  may provide algorithms, known in the art, for combining visible light imagery with FI imagery in a combined image display, and further highlighting or emphasizing the FI imagery for easily distinguishing the presence of fluorescing features in the image. 
     Timing generator  26  produces various clocking signals to select rows and pixels and synchronizes the operation of image sensor  222  and fluorescent sensor  223 , analog signal processor  22 , and A/D converter  24 . Image sensor assembly  28  includes the image sensor  222  and fluorescent sensor  223 , adjustment control  20 , the analog signal processor  22 , the A/D converter  24 , and the timing generator  26 . The functional elements of the image sensor assembly  28  can be fabricated as a single integrated circuit as is commonly done with CMOS image sensors or they can be separately-fabricated integrated circuits. 
     The system controller  50  controls the overall operation of the image capture device based on a software program stored in program memory  54 . This memory can also be used to store user setting selections and other data to be preserved when the camera is turned off. 
     System controller  50  controls the sequence of data capture by directing exposure controller  40  to set the light source  8  intensity, the optical assembly  11  aperture, and controlling various filters in optical assembly  11  and timing that may be necessary to obtain image streams based on the visible light and fluoresced light. In some versions, optical assembly  11  includes an optical filter configured to attenuate excitation light and transmit the fluoresced light. A data bus  52  includes a pathway for address, data, and control signals. 
     Processed image data are continuously sent to video encoder  80  to produce a video signal. This signal is processed by display controller  82  and presented on image display  88 . This display is typically a liquid crystal display backlit with light-emitting diodes (LED LCD), although other types of displays are used as well. The processed image data can also be stored in system memory  56  or other internal or external memory device. 
     The user interface  60 , including all or any combination of image display  88 , user inputs  64 , and status display  62 , is controlled by a combination of software programs executed on system controller  50 . User inputs typically include some combination of typing keyboards, computer pointing devices, buttons, rocker switches, joysticks, rotary dials, or touch screens. The system controller  50  manages the graphical user interface (GUI) presented on one or more of the displays (e.g. on image display  88 ). In particular, the system controller  50  will typically have a mode toggle user input (typically through a button on the endoscope or camera head itself, but possibly through a GUI interface), and in response transmit commands to adjust image processing circuitry  30  based on predetermined setting stored in system memory. Preferably a system employed with any of the device designs herein provides ability to toggle between at least two modes, visible light and FI modes, and more preferably a combined mode is included in which FI images are combined or overlaid with visible images in a suitable manner known in the art. Such settings may include different settings for different models of scopes that may be attached to a camera head or other imaging device containing image sensor assembly  28 . 
     Image processing circuitry  30  is one of three programmable logic devices, processors, or controllers in this embodiment, in addition to a system controller  50  and the exposure controller  40 . Image processing circuitry  30 , controller  50 , exposure controller  40 , system and program memories  56  and  54 , video encoder  80  and display controller  82  may be housed within camera control unit (CCU)  70 . 
     CCU  70  may be responsible for powering and controlling light source  8 , image sensor assembly  28 , and/or optical assembly  11 . In some versions, a separate front end camera module may perform some of the image processing functions of image processing circuitry  30 . 
     Although this distribution of imaging device functional control among multiple programmable logic devices, processors, and controllers is typical, these programmable logic devices, processors, or controllers can be combinable in various ways without affecting the functional operation of the imaging device and the application of the invention. These programmable logic devices, processors, or controllers can comprise one or more programmable logic devices, digital signal processor devices, microcontrollers, or other digital logic circuits. Although a combination of such programmable logic devices, processors, or controllers has been described, it should be apparent that one programmable logic device, digital signal processor, microcontroller, or other digital logic circuit can be designated to perform all of the needed functions. All of these variations can perform the same function and fall within the scope of this invention. 
     As used herein the terms “comprising,” “including,” “carrying,” “having” “containing,” “involving,” and the like are to be understood to be open-ended, that is, to mean including but not limited to. Any use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed. Rather, unless specifically stated otherwise, such ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term). 
     The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the invention as set forth in the appended claims. 
     Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the invention as defined by the appended claims. The combinations of features described herein should not be interpreted to be limiting, and the features herein may be used in any working combination or sub-combination according to the invention. This description should therefore be interpreted as providing written support, under U.S. patent law and any relevant foreign patent laws, for any working combination or some sub-combination of the features herein. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.