Abstract:
A solid immersion lens device and method of making. A solid immersion lens device is provided having a plurality of solid immersion lenses. The solid immersion lenses are provided in a predetermined pattern and secured so as to cause them to be in a fixed position with respect to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a divisional of application Serial No. 10/171,168, filed Jun. 13,2002, entitled SOLID IMMERSION LENS ARRAY AND METHODS FOR PRODUCING A SOLID IMMERSION LENS ARRAY, in the names of David L. Patton, et al. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to an article, system and method used for creating a solid immersion lens array.  
         BACKGROUND OF THE INVENTION  
         [0003]    Recent advances in optics provide for a method of image capture on a length scale much smaller than previously realized. Such near-field optical methods are realized by placing an aperture or a lens in close proximity to the surface of the sample to be imaged. Others (see, for example, the review by Q. Wu, L. Ghislain, and V. B. Elings, Proc. IEEE (2000), 88(9), pg. 1491-1498) have developed means of exposure by the use of the solid immersion lens (SIL).  
           [0004]    Typically special methods for positioning control of the aperture or lens are required, as the distance between the optical elements (aperture or lens) and the sample is extremely small. The SIL is positioned within approximately 0.5 micrometer of the target surface by the use of special nano-positioning technology. SIL technology offers the advantage that the lens provides a true image capture capability. For example, features in a real object can be faithfully captured in an image of reduced spatial extent. In the case of the SIL, features can be captured much smaller than the feature size achievable through the use of conventional or classical optics. Such conventional optics are said to be diffraction-limited because the size of the smallest discemable feature in an image is limited by the physical diffraction.  
           [0005]    Due to limitations on resolutions obtainable with conventional optical lenses for the application such as microscopy, techniques have been developed to decrease the Rayleigh limit on transverse resolution δ. The Rayleigh limit is given by (δ=0.82λ/(NA) where λ is the wavelength and NA is the numerical aperture of the focusing objective (NA=nsin (θ), where n is refractive index of the medium, and θ is the angle between the outer most rays focusing on the sample and the optical axis).  
           [0006]    Coherent light such as laser light can be used to precisely control the wavelength of the illumination λ. One way to decrease the transverse resolution is to increase the index of refraction of the optical medium, such as by the use of oil-immersion microscopy or use of a solid immersion lens (SIL).  
           [0007]    If an SIL is placed in contact with the sample under examination, illumination can be more readily focused on it, and use of the high NA of the system allows efficient collection of the excitation light with high optical transmission efficiency and observation of the sample with very high resolution.  
           [0008]    Methods for molding a single solid immersion lens as part of a cover slide are disclosed in U.S. Pat. No. 6,301,055. Illumination of a limited field of view within a single flow channel of sample material is described.  
           [0009]    The problem is that a single solid immersion lens mounted on a microscope or attached as an integral part of a slide cover limits the area of view of the sample to a single location, the area directly beneath the solid immersion lens.  
           [0010]    Guerra et al. discloses in U.S. Pat. No. 5,910,940 a storage medium having a layer of micro-optical lenses, each lens generating an evanescent field. They further describe in U.S. Pat. No. 6,094,413 optical recording systems that take advantage of near field optics. Though recording of data is possible, the type of lenticular arrays described produce an oblong or otherwise deformed or unsymmetrical pattern unsuitable for microscopy applications.  
         SUMMARY OF THE INVENTION  
         [0011]    In accordance with one aspect of the present invention there is provided a method of making a solid immersion lens device having a plurality of solid immersion lenses, comprising the steps of:  
           [0012]    providing the plurality of solid immersion lenses in a predetermined pattern; and  
           [0013]    securing the solid immersion lenses in the predetermined pattern so as to cause them to be in a fixed position with respect to each other.  
           [0014]    In accordance with yet another aspect of the present invention there is provided a solid immersion lens device comprising:  
           [0015]    a plurality of solid immersion lenses; and  
           [0016]    a body portion in which the plurality of solid immersion lenses are integrally secured, the body portion having a top surface designed to engage a sample for viewing of the sample through the plurality of solid immersion lenses.  
           [0017]    In accordance with yet another aspect of the present invention there is provided a cover slide having a plurality of solid immersion lenses integrally formed therein, the cover slide having a surface designed to engage a sample for viewing of the sample through the plurality of solid immersion lenses.  
           [0018]    In accordance with still another aspect of the present invention there is provided a cover slide having a plurality of solid immersion lenses integrally formed therein, the cover slide having a surface designed to engage a sample for viewing of the sample through the plurality of solid immersion lenses and an open viewing area designed to engage a sample for viewing of the sample using a microscope under normal magnification.  
           [0019]    These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims and by reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings in which:  
         [0021]    [0021]FIG. 1 illustrates a schematic cross-sectional view of a single solid immersion lens structure made in accordance with the present art;  
         [0022]    [0022]FIG. 2 is a schematic top view of a solid immersion lens array molded as part of a slide cover made in accordance with the present invention;  
         [0023]    [0023]FIG. 3 is a schematic side view of a solid immersion lens array of FIG. 2;  
         [0024]    [0024]FIGS. 4 a ,  4   b  and  4   c  are schematic cross-sectional views of a solid immersion lens array as taken along line  4 — 4  of FIG. 2 along with an associated lens;  
         [0025]    [0025]FIG. 5 a  illustrates a schematic cross-sectional view of yet another solid immersion lens array made in accordance with the present invention;  
         [0026]    [0026]FIG. 5 b  illustrates a schematic cross-sectional view of still another solid immersion lens array made in accordance with the present invention;  
         [0027]    [0027]FIG. 6 is a schematic top plan view of yet still another solid immersion lens array made in accordance with the present invention;  
         [0028]    [0028]FIG. 7 is a schematic side view of a solid immersion lens array of FIG. 6;  
         [0029]    [0029]FIG. 8 is a schematic top plan view of another configuration of a solid immersion lens array made in accordance with the present invention;  
         [0030]    [0030]FIG. 9 is a schematic side view of a solid immersion lens array of FIG. 8;  
         [0031]    [0031]FIG. 10 is a schematic top plan view of a combination of a solid immersion lens array and a conventional cover slide made in accordance with the present invention;  
         [0032]    [0032]FIGS. 11 a ,  11   b  and  11   c  are schematic cross-sectional views of a solid immersion lens array of another embodiment of a solid immersion lens made in accordance with the present invention;  
         [0033]    [0033]FIG. 12 a  is a schematic view of the eye piece/sensor of an apparatus that uses the SIL array of FIGS.  2 - 4 ;  
         [0034]    [0034]FIG. 12 b  is an enlarged top plan view of the apparatus of FIG. 12 a  as indicated by the arrow showing the sample being viewed;  
         [0035]    [0035]FIG. 13 a  is a schematic view of the eye piece/sensor of an apparatus of another embodiment of the present invention; and  
         [0036]    [0036]FIG. 13 b  is an enlarged top plan view of the apparatus of FIG. 13 a  as indicated by the arrow showing the sample being viewed.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention.  
         [0038]    Referring to FIG. 1, there is illustrated a cross-sectional view of a functioning solid immersion lens (SIL)  10  made in accordance with the present art, with indications of the parameters used to describe the structure and operation. A solid immersion lens portion  15  comprises a truncated sphere of radius r and an index of refraction n s . It is disposed at a highest height h above a surface  20  of a body portion  25  so that a boundary margin  30  is formed which is narrower in diameter than the diameter of the lens ( 2 r) portion  15 . An observation region  35  is provided at a distance h′ from the surface  20 . The constraint height h is given by the following relation: 
           r (1−cos φ)&lt; h&lt;r+r/n   s   
         [0039]    where  
         [0040]    r is the radius of the sphere,  
         [0041]    h is the height of the layer,  
         [0042]    φ is the polar angle from the center of the sphere to the edge of the orifice formed by the undercut margin,  
         [0043]    n s  is the index of refraction of the material, which forms the lens.  
         [0044]    The region  35  comprise the area between the top surface  40  of a slide  45  and the surface  47  which is h′ below surface  20 . The thickness h′ above the surface  20  is given by the relation: 
           h′=r +( r/n   s )− h.   
         [0045]    Samples  37  are placed in the region  35  between the top surface  40  of the slide  45  and the bottom surface  47  of the body portion  25  for observation according to the intended application, such as microscopy, spectroscopy, or cytometry as is well known to those skilled in the art. The body portion  25  can also serve as a slide cover  27 . Also shown with the SIL  10  is a collecting/collimating lens  50 . The spherical structure and collection configuration admits to construction of lens systems having a numerical aperture higher than unity, which is particularly useful for ultra sensitive spectroscopy, high lateral resolution imaging, and finite depth of field imaging. A method for producing a SIL is disclosed in U.S. Pat. No. 6,301,055.  
         [0046]    [0046]FIG. 2 illustrates a top view of a solid immersion lens array  55  formed by molding a plurality of solid immersion lens portion  15  of the SIL  10  in a fixed position to one another as part of the slide cover  27  made in accordance with the present invention. As previously discussed in FIG. 1 like numerals indicate like parts and operations. The number and spacing of the solid immersion lens portion  15  can be made to suit the type of sample, which is to be observed. The type of material used to form the solid immersion lens array  55  depends on various parameters. The method disclosed in U.S. Pat. No. 6,301,055 for molding a single SIL lists suitable materials as low temperature of formation polymers, room temperature vulcanization elastomers, low temperature of formation epoxies, polyimides, polycarbonates, and photo resists, or pliant silicone elastomers,  
         [0047]    Optical performance of the elements of the array is related to the index of refraction n s  of the material forming the lens. The ability of the lens to reduce spot size as noted above, is inversely proportional to n s ; therefore it is highly desirable to work with lens materials with large indices of refraction. Commonly used glasses for lens manufacture range in index of refraction from about 1.49 to 1.85. However there are specialty glasses with much higher indices. Plastic materials tend to have low indices of refraction, therefore they are less desirable for SIL manufacture. Thus it is desirable that the index of refraction be equal to or greater than 1.49 for the SIL array. Another consideration in lens material is the ability to withstand the temperatures required for molding and the ability to interact appropriately with the mold material. A method for creating SIL arrays using glass is described in FIG. 5 a.    
         [0048]    [0048]FIG. 3 illustrates a side view of a solid immersion lens array  55  formed by molding the solid immersion lens portion  15  of the SIL  10  as part of the slide cover  27  made in accordance with the present invention. As previously discussed in FIG. 1 like numerals indicate like parts and operations.  
         [0049]    Referring to FIG. 4 a , there is illustrated a cross-sectional view of a solid immersion lens array  55  as taken along line  4 — 4  of FIG. 2 along with an associated lens made in accordance with the present invention. As previously discussed in FIG. 1 like numerals indicate like parts and operations. In the embodiment shown in FIG. 4 a , a plurality of solid immersion lens portion  15  are molded with a body portion  25  to form an array as part of a slide cover  27 . The solid immersion lens array  55  allows the user to move a magnifying imaging device  60  (see FIG. 12 a ) collecting/collimating lens  50  in an x and z direction to different positions as shown in FIGS. 4 b  and  4   c  to observed different locations of the sample  35  shown in FIG. 1.  
         [0050]    The present embodiment describes a plurality of solid immersion lens portions  15  integrally formed with the body portion  25  to form the solid immersion lens array  55 . In another embodiment of the present invention referring to FIG. 5 a , there is illustrated a cross-sectional view of a solid immersion lens array  100  made in accordance with the present invention. The solid immersion lens array  100  is made by placing glass spheres  101  and  102  in a fixed position with their edges touching. The spheres  101  and  102  are rigidly attached to each other by via a connecting member  110 . The connecting member  110  can be formed using an adhesive such as OP 29  manufactured by the Dymax Corporation. The SIL array is completed by grinding a flat surface  115  on the connected spheres  101  and  102 . forming SIL  104  and SIL  105 . The method of grinding a flat on a glass sphere is well known to those skilled in the art. In another method shown in FIG. 5 b , the SIL array  100  is created by forming adjacent SIL&#39;s  104 ,  105  and a connecting member  113  as an integral part. In both methods an observation region  35  is provided at critical distance f; as is well known to those skilled in the art. The observation region  35  comprises the area at the distance f, for example 0.5 micrometers below surface  115  of the SIL and the top surface  40  of a slide  45 . Samples  37  to be observed are placed in the observation region  35  according to the intended application, such as microscopy, spectroscopy, or cytometry as is well known to those skilled in the art. Alternatively, individual spherical or truncated spherical lens elements may be bonded to the body portion  25  to create the array. In this case, the adhesive must be index matched to both the body and the spherical elements so as to not degrade the imaging properties of the array. The bonding can be performed using an index matching adhesive such as OP 29  manufactured by the Dymax Corporation. Spheres made of materials having different indices would allow for different magnifications.  
         [0051]    [0051]FIG. 6 illustrates a top view of the embodiment of the solid immersion lens array  100  shown in FIGS. 5 a  and  5   b . In this embodiment the solid immersion lens array  100  is formed by connecting adjacent SIL&#39;s  104 ,  105 ,  106 ,  107 ,  108 , and  109  by the connecting member  110  or  113  described in FIGS. 7 a  and  7   b  respectively made in accordance with the present invention. As previously discussed in FIGS. 5 a  and  5   b  like numerals indicate like parts and operations. Multiple columns  111  and rows  112  of SIL  104  can be created using this technique. The number and spacing of the solid immersion lens  104  can be made to suit the type of sample, which is to be observed.  
         [0052]    [0052]FIG. 7 illustrates a side view of the embodiment of the solid immersion lens array  100  shown in FIG. 6.  
         [0053]    [0053]FIG. 8 illustrates a top view of another configuration the solid immersion lens array  100  shown in FIG. 6 made in accordance with the present invention. As previously discussed in FIG. 6 like numerals indicate like parts and operations. Multiple columns  111  and rows  112  of SIL  104  can be created using this technique. The number and spacing of the solid immersion lens  104  can be made to suit the type of sample, which is to be observed. In this case, a close-packed array of spherical components is described.  
         [0054]    [0054]FIG. 9 illustrates a side view of the solid immersion lens array  100  configuration shown in FIG. 8.  
         [0055]    [0055]FIG. 10 illustrates a top plan view of a combination of a solid immersion lens array  55  and a conventional cover slide  27  made in accordance with the present invention. As previously discussed in FIG. 2 like numerals indicate like parts and operations. The number and spacing of the solid immersion lens portion  15  can be made to suit the type of sample, which is to be observed. An open viewing area  120  is provided, which permits the user to observe the sample  37  (see FIG. 1) using the imaging device  60  such as a microscope under normal magnification or through the solid immersion lens portion  15  at increased spatial resolution.  
         [0056]    Referring to FIG. 11 a , there is illustrated a cross-sectional view of a solid immersion lens array  130  made in accordance with the present invention. As previously discussed in FIG. 4 a  like numerals indicate like parts and operations. In the embodiment shown in FIG. 11 a  the solid immersion lens portions  15  are molded with the body portion  25 . A channel  132  is formed as part of the body portion  25  and connected to a pumping mechanism (not shown) via tubes  136  and  137 . The method for forming the channel  132  and for pumping a sample  135  through the channel  132  is described in U.S. Pat. No. 6,301,055. The solid immersion lens array  130  allows the user to move the magnifying imaging device  60  (see FIG. 12 a ) collecting/collimating lens  50  in an x and z direction to observe different locations along the channel  132  as shown in FIGS. 11 b  and  11   c  to observed different portions of the sample  135 , which has been pumped into the channel  132 . Referring now to FIG. 12 a , the sample  37  can be viewed and an image captured using the solid immersion lens array  55  and a magnifying imaging device  60  such as a microscope. A light beam  62  from a light source  64  reflects from a beam splitter  66  and passes through the collecting/collimating lens  50  of conventional design and impinges onto the solid immersion lens portion  15  of the solid immersion lens array  55 . Samples  37  to be observed are placed in the region  35  between the top surface  40  of the slide  45  and the bottom surface  47  of the body portion  25  of the solid immersion lens array  55  as is well known to those skilled in the art. The light beam  62  is reflected from the sample  37 , passes through the solid immersion lens array  55 , the lens  50 , and the beam splitter  66 , imaging the sample  37  onto a sensor/eye piece  78  by a lens system  80 . The sensor  78  can be a CCD or similar type device. The slide  45  with the solid immersion lens array  55  is located on an x, y, z, and θ translation device  68 . The x, y, z, and θ translation device  68  can also contain an additional light source  70  whose light beam  72  can be directed to illuminate the slide  45  and sample  37  from underneath. The collecting/collimating lens  50  is positioned in relation to the solid immersion lens array  55  by an x, y, z, and θ translation device  74 . Both translation (positioning) devices  68  and  74  and sensor  78  are connected to and controlled by a logic, control and memory unit  76 . The light source  72  can be used in place of or in addition to the light source  64 . The light sources  64  and  72  can be chosen and filters (not shown) can be added to the light path to provide illumination of a specific wavelength. The light sources  64  and  72  can be lasers or other types of illumination such as UV, IR etc can be used, as appropriate for the type of lens material used.  
         [0057]    Referring now to FIG. 12 b , an enlarged partial view of the image of the sample  37  captured by the device  60  is shown. Using the imaging device  60 , images of the sample  37  are displayed for viewing. In addition to observing the sample  37  via a sensor  78  and electronic display (not shown) the sample  37  can be viewed by the human eye  90  using a standard microscope eyepiece  85 .  
         [0058]    [0058]FIG. 13 a  illustrates another embodiment of the present invention. The sample  37  can be viewed and an image captured using the solid immersion lens array  100  using a magnifying imaging device  60  such as a microscope. A light beam  62  from a light source  64  reflects from a beam splitter  66  and passes through the collecting/collimating lens  50  of conventional design and impinges onto the solid immersion lens portions  104 ,  105 ,  106 ,  107 ,  108  and  109  which represent several of the solid immersion lens portions of the solid immersion lens array  100 . Samples  37  to be observed are placed between the top surface  40  of the slide  45  and the bottom surface  47  of the solid immersion lens portions  104 ,  105 ,  106 ,  107 ,  108  and  109  of the solid immersion lens array  100  as is well known to those skilled in the art. The light beam  62  is reflected from the sample  37 , passes through the solid immersion lens array  100 , the lens  50 , and the beam splitter  66 , imaging the sample  37  onto a sensor/eye piece  78  by a lens system  80 . The slide  45  is located on an x, y, z, and θ translation (positioning) device  68 . The x, y, z, and θ translation device  68  can also contain an additional light source  70  whose light beam  72  can be directed to illuminate the slide  45  and sample  37  from underneath. The collecting/collimating lens  50  and the solid immersion lens array  100  are positioned in relation to each other and to the slide  45  by an x, y, z, and θ translation devices  74 ,  77 ,  79  and x, y, z, and θ translation device  68 . The translation devices  68 ,  74 ,  77  and  79  and sensor/eye piece  78  are connected to and controlled by a logic, control and memory unit  76 . The light source  72  can be used in place of or in addition to the light source  64 . The light sources  64  and  72  can be chosen and filters (not shown) can be added to the light path to provide illumination of a specific wavelength. Lasers or other types of illumination such as UV, IR etc can be used for the light sources  64  and  72 . Again, the lens material must be appropriately transmissive for use in a particular region of the spectrum.  
         [0059]    Referring now to FIG. 13 b , an enlarged partial view of the image of the sample  37  captured by the device  60  is shown. Using the imaging device  60 , images of the sample  37  are displayed for viewing. In addition to observing the sample  37  via a sensor/eye piece  78  and electronic display (not shown) the sample  37  can be viewed via the human eye  90 .  
         [0060]    It is to be understood that various changes and modifications made be made without departing from the scope of the present invention, the present invention being defined by the claims that follow.  
                                         PARTS LIST                                10   solid immersion lens (SIL)       15   solid immersion lens portion       20   surface       25   body portion       27   cover slide       30   margin       35   observation region       37   sample       40   top surface       45   slide       47   bottom surface       50   collecting/collimating lens       55   solid immersion lens array       60   magnifying imaging device       62   light beam       64   light source       66   beam splitter       68   translation device       70   light source       72   light beam       74   translation device       76   logic, control and memory unit       77   translation device       78   sensor/eye piece       79   translation device       80   lens system       85   eyepiece       90   eye       100   solid immersion lens array(SIL)       101   sphere       102   sphere       104   solid immersion lens (SIL)       105   solid immersion lens (SIL)       106   solid immersion lens (SIL)       107   solid immersion lens (SIL)       108   solid immersion lens (SIL)       109   solid immersion lens (SIL)       110   connecting member       111   column       112   row       113   connecting member       115   flat surface       120   open viewing area       130   solid immersion lens array       132   channel       135   sample       136   tube       137   tube