Magnification viewer

Information

  • Patent Grant
  • 6201640
  • Patent Number
    6,201,640
  • Date Filed
    Monday, April 20, 1998
    26 years ago
  • Date Issued
    Tuesday, March 13, 2001
    23 years ago
Abstract
A housing for a magnification loupe is provided having a body portion for an eyepiece lens and a nose portion for an objective lens. The body portion for the eyepiece lens includes outer circumferential threads over which the objective nose portion fits. The objective nose portion includes a pin slot defining an arc across the body of the nose. The arc is configured such that a pin may be secured through the holes in the nose piece to co-act with the threads of the eyepiece body such that radial movement is prohibited.
Description




BACKGROUND OF TEE INVENTION




1. Field of the Invention




The present invention relates to magnification viewers worn by surgeons and dentists. In particular, the invention relates to an assembly for optical viewers or loupes which allow a user to adjust an objective lens at a predetermined distance from an eyepiece lens to vary the focal point.




2. Description of the Related Art




Magnification viewers generally including pairs of magnification loupes, are worn by dentists and surgeons for extended periods of time during clinical procedures, so as to provide clarity of view while avoiding a hunched-over position that can result in debilitating neck and back strain, which can have an adverse effect on the success of the operation. The viewers permit the clinician to operate at a greater working distance from the patient. Higher magnification viewers also reduce the clinician's exposure to aerosols. Because clinicians use magnification viewers during surgery and other procedures requiring manual precision, it is important that they be light-weight, comfortable and have good clarity and wide field of vision while providing high magnification and good depth of field.




Surgical telescopes may be attached to a spectacle frame in one of two manners: outside-the-carrier or prescription lens (“outside-the-lens”), on an adjustment mechanism that provides for adjustment of the interpupillary distance and convergent angle variability, or through-the-lens, permanently cemented and fixed in place. As noted above, magnification viewers used by surgeons and dentists typically have a predetermined magnification. Neither the working distance nor the magnification may be changed without a tedious process of replacing either individual lens elements or the entire optical loupes themselves. Accordingly, there is a need for a simple method for changing the magnification of viewers being worn by a surgeon or dentist, as well as for altering the working distance of viewers having a particular magnification.




SUMMARY OF THE INVENTION




In accordance with one embodiment of the invention, a housing for a magnification loupe is provided having an eyepiece portion for an eyepiece lens and a nose portion for an objective lens. The body portion for the eyepiece lens includes outer circumferential threads over which the objective nose portion fits to enable the distance between the lenses in the body and nose portions to be varied in order to vary the working distance of the loupe. The objective nose portion includes a pair of apertures for receiving a pin. The apertures are configured such that the pin forms a chord across the body of the nose portion and co-acts with the threads of the eyepiece body forming an axial mechanical stop to prevent the nose portion from being removed during adjustment.




Magnification loupes according to the present invention include a nose housing for an objective lens and a body housing for an eyepiece lens. The system is configured such that the magnification of the magnification loupe may be changed simply by removing the nose housing and replacing it with another. The working distance for a particular magnification level may be adjusted by threading or unthreading the nose housing.











BRIEF DESCRIPTION OF THE DRAWINGS




A better understanding of the present invention is obtained when the following detailed description is considered in conjunction with the following drawings in which:





FIGS. 1



a


-


1




c


are perspective views of a magnification loupe in accordance with the present invention illustrating the connection of a pair of magnification loupes according to an embodiment of the present invention secured through the lenses of a pair of spectacles forming a magnification viewer in accordance with the present invention;





FIG. 2

is a perspective view of magnification loupes according to the present invention secured to an adjustable nose piece for securing to a pair of spectacles;





FIG. 3



a


is an exploded perspective view of the magnification loupe assembly for the magnification loupes of

FIGS. 1 and 2

;





FIG. 3



b


is a side cross-sectional view of the magnification loupe of

FIG. 3



a;







FIG. 4

is a side-elevation view of a nose housing forming a portion of the magnification viewers of

FIGS. 1 and 2

;





FIGS. 5



a


and


5




b


are side-cross-sectional views and detail side-cross-sectional views, respectively, of the housing of

FIG. 4

;





FIG. 6

is a top plan view of the nose housing of

FIGS. 4 and 5

;





FIG. 7

is a side elevational view of the eyepiece housing of

FIGS. 1 and 2

;





FIGS. 8



a


-


8




c


are side cross-sectional views of the housing of

FIG. 7

, including details thereof;





FIG. 9

is a top plan view of the eyepiece housing of

FIGS. 7 and 8

;





FIG. 10

is side elevational view of a spacer for the magnification loupes of

FIGS. 1 and 2

;





FIG. 11

is a side cross-sectional view of the spacer of

FIG. 10

;





FIG. 12

is a top elevational view of the spacer of

FIGS. 10 and 11

;





FIG. 13

is a side elevational view of a field stop of the magnification viewer of

FIGS. 1



a


-


3




b;







FIG. 14

is a side cross-sectional view of the field stop of

FIG. 13

;

FIG. 15

is a top plan view of the field stop of

FIGS. 13 and 14

;





FIG. 16

is a side elevational view of an objective lens retainer ring of the magnification loupes of

FIGS. 1



a


-


3




b;







FIG. 17

is side cross-sectional view of the objective retainer of

FIG. 16

;





FIG. 18

is a top plan view of the objective retainer of

FIGS. 16 and 17

;





FIGS. 19



a


and


19




b


are exploded perspective views of a prism assembly for the magnification loupes of

FIGS. 1



a


-


3




b;







FIGS. 20



a


,


20




b


and


21


-


22


illustrate a prism for the prism assembly of

FIGS. 19



a


and


19




b;







FIGS. 23-26

illustrate the prism assembly of,

FIGS. 19



a


and


19




b;







FIGS. 27-29

illustrate the roof prism of the prism assembly of

FIGS. 19



a


and


19




b;







FIGS. 30-32

illustrate the second prism of the prism assembly of

FIGS. 19



a


and


19




b;







FIG. 33

is a diagram of the optical layout of the magnification loupe of

FIGS. 1



c


,


3




a


and


3




b


; and





FIG. 34

is an optical layout diagram of the optical loupe of

FIGS. 1



a


,


1




b


and


1




c


according to an alternate embodiment.











DETAILED DESCRIPTION OF THE INVENTION




Turning now to the drawings and with particular attention to

FIGS. 1



a


and


1




b


a magnification viewer


10


including a pair of spectacles


100


with through-the-lens magnification loupes


106




a


,


106




b


. As illustrated, the magnification loupes


106




a


,


106




b


are of the Keplerian design. The spectacles


100


include carrier lenses


102




a


,


102




b


. The carrier lenses


102




a


,


102




b


may be either plano lenses or prescription lenses. The magnification loupes


106




a


,


106




b


are fixed in the carrier lenses


102




a


,


102




b


to provide stereoscopic vision. The magnification loupes


106




a


,


106




b


are set at the user's interpupillary distance converging to a desired working distance, for example, anywhere from 12 to 24 or 13-21 inches. As will be discussed in greater detail below, from a selected working distance, the user has the option to vary the viewing distance by rotating the objective lens housing or nose housing


108




a


,


108




b


of each magnification loupe


106




a


,


106




b


to the desired focus. As will be discussed in more detail below, one of the objective lens housings


108




a


,


108




b


formed and the eyepiece housings


110




a


,


110




b


are formed with threads, which cooperate with a pin attached to the other housing to form a threaded coupling. The eyepiece housings,


110




a


,


110




b


, in turn, are secured to the carrier lenses


102




a


,


102




b


by various techniques, including a friction fit on with an adhesive, such as epoxy. Alternatively, the eyepiece housings


110




a


,


110




b


may be secured to the carrier lenses


102




a


,


102




b


by way of known threading on the outside of the eyepiece housings


110




a


,


110




b


matching threading on the carrier lenses


102




a


,


102




b.






As will be discussed in greater detail below, magnifications of 3.3×, 3.8×, 4.3× and 4.8× are possible according to one embodiment of the invention to provide a wide range of selection. For each magnification, working distances of about


12


″,


16


″ and


24


″ may be provided. The carrier lenses


102




a


,


102




b


normally enable a user to focus comfortably at 500 mm, about −2D, a typical reading distance. The magnification loupes


106




a


,


106




b


, as will be discussed in greater detail below, further include a prism system (FIGS.


19


-


32


). Each magnification loupe uses an identical prism and eyepiece lens system. For different magnifications, only the objective lenses are changed. The user may create depth of field by adjusting the focal distance of each eye depending upon the operation being performed. The focuses of each of the magnification loupes


106




a


,


106




b


may be changed independently. The aperture for the objective lens has been reduced in size to provide an increase in depth of field at high magnifications while still providing substantial light.




Turning now to

FIG. 2

, an alternative configuration of the magnification loupes


106




a


,


106




b


of

FIGS. 1



a


and


1




b


is illustrated. It is noted that for the lens system


20


of

FIG. 2

, the optical configurations of the magnification loupes


206




a


,


206




b


are different from the through-the-lens configuration of

FIG. 1

, but the barrels or housings are similar in that only the objective lens need be changed to provide different magnifications. The prism and eyepiece remain the same. The optical system


20


of

FIG. 2

includes a pair of spectacles


200


including a pair of carrier lenses


202




a


,


202




b


and a binocular magnification viewer


25


, including a pair of magnification loupes


206




a


,


206




b


. As discussed in U.S. Pat. No. 5,667,291, the binocular magnification viewer


25


may be attached to the spectacles


200


by a pivot member


250


. Alternatively, the magnification loupes


206




a


,


206




b


, may be mounted close to the spectacle lenses, for example, about 0.5 mm from the carrier lenses


202




a


,


202




b


. The pivot member


250


in turn, is attached to a bridge


258


which includes a bridge adjustment knob


252


for adjusting a pair of extension of arms


254


,


256


to enable the interpupillary distances of the loupes


206




a


,


206




b


to be adjusted. The interpupillary distance of the magnification loupes


206




a


,


206




b


may further be adjusted by knobs


260




a


,


260




b


. The binocular magnification viewer


25


may be secured to the spectacles


200


by way of a clip, screws, glue or other known methods.




MECHANICAL CHARACTERISTICS




Turning now to

FIG. 3



a


, an exploded perspective view of the magnification loupes


106


in accordance with the present invention are shown. The magnification loupes


106




a


,


106




b


include a nose or objective housing


108




a


and a body or eyepiece housing


110




a


. As illustrated, the objective housing


108




a


includes a frusto-conical front portion


350


and a generally cylindrical rear portion


352


. It is noted that the housing


108


may be of different shapes; thus,

FIG. 3

is exemplary only. The objective housing


108




a


includes a pair of apertures


304


. The apertures


304


are configured to receive a pin


302


such that the pin


302


defines a chord across the cylindrical rear portion


352


of the objective housing


108




a


. More particularly with reference to

FIG. 3B

, the objective housing


108




a


includes an interior surface


308


which,engages an exterior surface


307


of the eyepiece housing


10




a


. Spiral threads


306


re formed into the surface of the eyepiece housing.


111




a


. The apertures


304


are located in the objective housing


108




a


so that the pin


302


engage the spiral or threads


306


. The pin


302


enables a threaded coupling between the two housing


108




a


and


108




a


even though only one housing


110




a


is formed with threads. The threaded coupling between the housings


106




a


and


108




a


permits the working distance of the loupes


106




a


,


106




b


to be adjusted by relating the objective housing


108




a


relative to the eyepiece housing


110




a


, which in turn, varies the distance between the eyepiece and objective lenses which varies the working distance of the loupes


106




a


,


106




b.






Another important aspect of the invention, is that the configuration allows the magnification of the loupes


106




a


,


106




b


to be rather easily changed. More particularly, the pin


302


may be removably mounted relative to the objective housing


108




a


or fixedly mounted with the use of epoxy. Depending on the embodiment, the magnification of the loupe can be rather easily changed at the factory or by the user or both. In particular, as will be discussed in more detail below, the magnification of the loupe


106




a


,


106




b


is changed simply by changing the objective lens in the loupe


106




a


,


106




b


. The objective lenses are easily changed by removing the pin


302


which enables the objective housing


108




a


to be removed so that the objective lens


312


can be removed and replaced. As will be discussed in more detail below, an important aspect of the invention relates to the ability to vary the magnification of the loupe


106




a


,


106




b.






As best illustrated in

FIG. 3



b


, the objective lens


312


is configured to rest within a first interior portion


360


of the objective housing


108




a


. The interior portion


360


includes a circumferential slot


311


for seating an O-ring


310


therein. The objective lens


312


rests against the O-ring


310


and is engaged in place-by a threaded retainer ring


314


. The retainer ring


314


includes external threads to engage corresponding threads on the interior portion


360


of the objective housing


108




a.






Additional details concerning the objective housing


108




a


are illustrated in

FIGS. 4-6

. For example, the exterior of the objective housing


108




a


may include a knurled portion


109


for easy engagement of the objective housing


108




a


to the eyepiece housing


110




a.






The eyepiece housing


110




a


, illustrated in greater detail in

FIGS. 7-9

, includes a forward engagement portion


307


and a rear cylindrical portion


309


. As discussed above, the forward engagement portion


307


includes threads


306


for engagement with the pin


302


. It is noted that according to one embodiment of the invention, the threads


306


are circular threads rather than notched or V-shaped threads so as to more effectively engage the pin


302


. The eyepiece housing


110




a


includes internal threads


340


positioned where the engagement housing


307


meets the rear cylindrical portion


309


. The threads


340


are configured to engage the threads


341


of the field stop


318


(

FIGS. 3



a


,


3




b


). The rear cylindrical portion


309


of the eyepiece housing


110




a


further includes a circumferential platform


344


, configured to receive a lens


332


for example, a prescription lens. The lens


332


is held in place against the platform


344


in contact with a prescription lens O-ring


330


and a retainer ring


334


, which has external threads that engage the internal threads


342


of the eyepiece housing


110




a


. In the embodiment illustrated, the rear cylindrical portion


309


of the housing


110




a


is configured to be fastened to the carrier lens


102




a


by way of a suitable adhesive, such as epoxy. In an alternative embodiment, however, the rear cylindrical portion


309


may be provided with threads to engage similar threads in the carrier lens.




The forward engagement portion


307


of the eyepiece housing


110




a


is further configured to receive a prism assembly


316


(

FIGS. 19



a


,


19




b


). The prism assembly


316


includes a prism holder


317


including a pair of arms


319




a


,


319




b


, a base portion


321


, and is adapted to fit within the housing


110




a


. The forward portions of the arms


319




a


,


319




b


include circular cutout portions


323




a


,


323




b


respectively, to engage a holder ring


402


. The holder ring


402


is configured, when attached in place (such as by an adhesive), to secure the prism elements


404


,


406


,


408


. According to one embodiment, the prism elements (

FIGS. 20



a


-


22


) form a roof-pechan prism separated by a spacer


408


. The spacer


408


is formed, for example, of a blackened ridge metal with a six millimeter diameter hole centered on the optical axis. The prism surfaces on opposite sides of the spacer are generally parallel. The individual elements of the roof pechan prism


404


,


406


and


408


are illustrated in

FIGS. 25-27

and


28


-


30


, respectively. The prism elements are formed from Schott BAK4 or LAK10 glass.




Turning back to

FIGS. 3



a


-


3




b


, the base of the prism assembly


316


is configured to rest against a rear wall


351


of the forward engagement portion


307


at approximately the position where it engages the rear cylindrical portion


309


. A field stop


318


(

FIGS. 13-15

) having external threads


341


engages the corresponding internal threads


340


of the housing


110




a


. The field stop


318


further includes internal grooves


343


. The rear cylindrical portion


309


of the housing


110




a


further houses the eyepiece lens elements. As shown, in

FIG. 36

the eyepiece lens includes elements


320


and


324


, separated by a spacer


322


. The spacer


322


is illustrated in

FIGS. 10-12

and may include internal concentric grooves


329


which form a light baffle. Finally, the eyepiece lens


324


rests against the platform


344


.




As shown in

FIGS. 3



a


and


3




b


, the exterior of the engagement housing


307


includes a pair of concentric circumferential grooves


325


,


327


configured to receive the O-rings


326


,


328


respectively. The O-rings


326


,


328


additionally function to self-center the objective housing


108




a


and hence, the objective lens


312


relative to the eyepiece housing


110




a.






While the configuration described and shown with regard to

FIGS. 3



a


-


3




b


relates to a through-the-lens viewer, a similar configuration may-be used in the outside-the-lens system shown in FIG.


2


. Such a system may be used without a prescription lens and, as will be described in greater detail below, a different eyepiece system.




OPTICAL CHARACTERISTICS




Turning now to

FIG. 33

, a diagram illustrating the optical layout of the magnification loupe


106




a


,


106




b


of

FIGS. 1



a


,


1




b


,


3




a


and


3




b


is shown. The magnification loupe


106




a


,


106




b


as illustrated in

FIG. 33

includes a two-element objective lens including elements I-II and including a three-element eyepiece including elements III-V. R1, R2 etc., represent the radii of respective refractive surfaces; S1-S5 represent the thickness of the air spaces; and T1, T2, etc., represent the thicknesses of the lens elements. As discussed above, according to one embodiment of the invention, magnifications of 3.3×, 3.8×, 4.3× and 4.8× are provided. All magnifications use the same prism and eyepiece lens system. As shown in

FIGS. 28 and 32

, the prior angle α may be used in the range 45°-49°, preferably 48° to increase the optical performance of the device while the prism angle B (

FIG. 32

) may be selected to be 24°. Thus, a common eyepiece housing


110




a


and optical elements included therein may be used for all of the magnifications. As discussed above, only the objective lens needs to be changed in order to alter the magnification.




The user may create a depth of field by adjusting the focal distance of each eye differently depending on the operation being performed. For example, a heart surgeon may wish to view the entire depth of the heart at high magnification previously unattainable in conventional magnification systems where depth of field is limited. This can be accomplished by adjusting the focus of the left eye one-inch beyond the right. When both eyes are then opened, the heart can be viewed in its entirety. However, a dentist may only require the depth of the coronal portion of the tooth to be in focus and thus, would only separate the focus by a millimeter or two. Alternatively, both magnification loupes can be precisely focused at the same distance for procedures requiring the highest resolution. The following exemplary fields of view may be provided:




93 mm@3.3×@16″WD




82 mm@3.3×@16″WD




72 mm@3.3×@16″WD




65 mm@3.3×@16″WD




Exemplary construction data for a magnification loupe built according to the embodiment shown in

FIGS. 1



a


-


3




b


are given in Tables I-XII. The radii, thickness, and separation dimensions are given in millimeters. Roman numerals identify the lens elements in their respective order from the objective side to the eyepoint side; nd represents the refractive index of each element; ν


d


is the abbe dispersion number; R1, R1, etc., represent the radii of the respective refractive surfaces in order from the objective side to the eyepoint side; T1, T2, etc., represent the thicknesses of the lens elements from the objective side to the eyepoint side; S1, S2 represent the thicknesses of air spaces respectively from the objective side to the eyepoint side measured along the optical centerline. Again, it is noted that the prism/objective distance


51


, can differ by about 2.5 mm if BAK4 glass is used, rather than LAK10, as in the tables.





FIG. 34

illustrates an embodiment of the present invention having long eye relief characteristics. Again, the system shown in

FIG. 34

employs the same prism and eyepieces, but separate objective doublets for each level of magnification. The objective doublets and the prism, however, are the same as for the through-the-lens embodiment shown in FIG.


33


. Additionally, only the eyepiece lens is changed from the through-the-lens configuration. As compared the embodiment of

FIG. 33

, eye relief—the distance to exit pupil—has been improved from about 17.8 mm to about 22.8 mm.




In particular, the viewer according to

FIG. 34

includes the two-element or doublet objective including elements I-II and a four-element eyepiece lens including elements III-VI. R1, R2, etc., again represent the radii of respective refractive surfaces; S1 and S2 represent the thicknesses of the air spaces; and T1, T2, etc., represent the thicknesses of the lens elements.




Exemplary construction data for loupes according to the embodiment of

FIG. 34

are given in Tables XIII—XXIV.












TABLE I











3.3X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 6.96







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE II











3.3X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 5.01







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE III











3.3X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 3.63







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE IV











3.8X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.04




4.0




13.4








BAH 27






R


2


= 14.61






II




Ohara




1.8052




25.4




R


2


= 14.61




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 12.38







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE V











3.8X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




4.0




13.4








BAH 27






R


2


= 14.61






II




Ohara




1.8052




25.4




R


2


= 14.61




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 9.92







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE VI











3.8X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.04




4.0




13.4








BAH 27






R


2


= 14.61






II




Ohara




1.8052




25.4




R


2


= 14.61




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 8.02







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE VII











4.3X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 50.15




4.0




13.4








BAH 27






R


2


= 16.00






II




Ohara




1.8052




25.4




R


2


= 16.00




1.5




13.4







PBH6W






R


3


= 47.79






Prism A




BAK4




1.5688




56.13







S


1


= 18.07







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE VIII











4.3X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 50.15




4.0




13.4








BAH 27






R


2


= 16.00






II




Ohara




1.8052




25.4




R


2


= 16.00




1.5




13.4







PBH6W






R


3


= 47.79






Prism A




BAK4




1.5688




56.13







S


1


= 15.56







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE IX











4.3X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 50.15




4.0




13.4








BAH 27






R


2


= 16.00






II




Ohara




1.8052




25.4




R


2


= 16.00




1.5




13.4







PBH6W






R


3


= 47.79






Prism A




BAK4




1.5688




56.13







S


1


= 13.13







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15. 4







BAH10






R


8


= 94.04






















TABLE X











4.8X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




61.12




4.0




13.4








BAH 27






II




Ohara




1.8052




25.4




16.98




1.5




13.4







SFL6






Prism A




BAK4




1.5688




56.13







S


1


= 25.16







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE XI











4.8X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




61.12




4.0




13.4








BAH 27






II




Ohara




1.8052




25.4




16.98




1.5




13.4







SFL6






Prism A




BAK4




1.5688




56.13







S


1


= 21.23







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE XII











4.8X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




61.12




4.0




13.4








BAH 27






II




Oshara




1.8052




25.4




16.98




1.5




13.4







SFL6






Prism A




BAK4




1.5688




56.13







S


1


= 18.22







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 7.04






Prism B




BAK4




1.5688




56.13







S


4


= 0.05







LAK10




1.7200




50.41







S


5


= 17.86






III




Ohara




1.8052




25.4




R


3


= 44.00




2.0




15.4







PBH6W






R


4


= 13.00






IV




Ohara




1.4875




70.2




R


5


= 13.00




6.5




15.4







FSL5






R


6


= 13.00






V




Ohara




1.6700




47.3




R


7


= 15.59




3.0




15.4







BAH10






R


8


= 94.04






















TABLE XIII











3.3X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


3


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 6.96







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= 0.5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XIV











3.3X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 5.1







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XV











3.3X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


3


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 3.63







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XVI











3.8X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 12.38







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XVII











3.8X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 9.92







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XVIII











3.8X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 8.02







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XIX











4.3X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 18.7







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17 5







S-LAM2






R


9


= 25.11






















TABLE XX











4.3X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 15.56







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XXI











4.3X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 13.13







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XXII











4.8X






(12″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 25.16







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XXIII











4.8X






(16″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00






Prism A




BAK4




1.5688




56.13







S


1


= 21.23







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.541




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11






















TABLE XXIV











4.8X






(24″ WD)


















Element




Glass




nd




νd




Radius




Thickness




Diameter




Sep.









I




Ohara




1.7015




41.2




R


1


= 42.19




3.5




13.4








BAH 27






R


2


= 12.45






II




Ohara




1.8052




25.4




R


2


= 12.45




1.5




13.4







PBH6W






R


3


= 36.00









Prism A




BAK4




1.5688




56.13







S


1


= 18.22







LAK10




1.7200




50.41







S


2


= 3.41













S


3


= 2.33






Prism B




BAK4




1.5688




56.13







S


4


= .5







LAK10




1.7200




50.41







S


5


= 22.8






III




Ohara




1.5410




47.2




R


4


= PLANO




3.0




12.0







S-TIL2






R


5


= 12.61






IV




Ohara




1.923




21.3




R


5


= 12.61




1.5




15.4







PBH71






R


6


= 12.61






V




SCHOTT




1.5168




64.2




R


7


= 10.06




7.1




15.4







BK7






R


6


= 12.61






VI




SCHOTT




1.744




44.8




R


8


= 25.11




4.7




17.5







S-LAM2






R


9


= 25.11














The invention described in the above detailed description is not intended to be limited to the specific form set forth herein, but, on the contrary, is intended to cover such alternatives, modifications and equivalents as can reasonably be included within the spirit and scope of the appended claims.



Claims
  • 1. A magnification loupe carried by spectacles having a pair of lenses comprising:an eyepiece lens housing having at least one eyepiece lens mounted therein, said eyepiece lens housing being smaller than a lens of said spectacles and including threads thereon; an objective lens housing having at least one objective lens mounted therein and including a pin aperture and a pin received in said pin aperture engaging said threads such that said objective lens housing is rotatably adjustable relative to said eyepiece lens housing to enable a distance between said eyepiece lens housing and said objective lens housing to be varied.
  • 2. A magnification loupe according to claims, wherein said objective lens housing is removable to permit substitution by a second objective lens housing carrying an objective lens of different magnification.
  • 3. A magnification loupe carried by spectacles having a pair of lenses comprising:an eyepiece lens housing having at least one eyepiece lens mounted therein, said eyepiece lens housing being smaller than a lens of said spectacles and including threads thereon; an objective lens housing having at least one objective lens mounted therein and including a pin aperture; and adjustable means for moving said objective lens housing relative to said eyepiece lens housing to vary a distance between said objective lens housing and said eyepiece lens housing; an optic element disposed on said loupe for increasing a light path length between said at least one objective lens and said at least one eyepiece lens; wherein said adjustable means includes a pin aperture in said objective lens housing, threads on said eyepiece lens housing opposing said pin aperture, and a pin received in said pin aperture for engaging said threads.
  • 4. A magnification loupe carried by spectacles having a pair of lenses comprising:an eyepiece lens housing having at least one eyepiece lens mounted therein, said eyepiece lens housing being smaller than a lens of said spectacles and including threads thereon; an objective lens housing having at least one objective lens mounted therein and including a pin aperture; and adjustable means for moving said objective lens housing relative to said eyepiece lens housing to vary a distance between said objective lens housing and said eyepiece lens housing; an optic element disposed on said loupe for increasing a light path length between said at least one objective lens and said at least one eyepiece lens, wherein said optic element is a roof-penchan prism; and wherein said adjustable means includes a pin aperture in said objective lens housing, threads on said eyepiece lens housing opposing said pin aperture, and a pin received in said pin aperture for engaging said threads.
  • 5. A magnification loupe carried by spectacles having a pair of lenses comprising:an eyepiece lens housing having at least one eyepiece lens mounted therein, said eyepiece lens housing being smaller than a lens of said spectacles and including threads thereon; an objective lens housing having at least one objective lens mounted therein and including a pin aperture; and adjustable means for moving said objective lens housing relative to said eyepiece lens housing to vary a distance between said objective lens housing and said eyepiece lens housing; an optic element disposed on said loupe for increasing a light path length between said at least one objective lens and said at least one eyepiece lens wherein the optic element is a roof-penchan prism that includes two prisms separated by a spacer having an aperture centered on an optical axis of said loop; and wherein said adjustable means includes a pin aperture in said objective lens housing, threads on the surface of said eyepiece lens housing opposing said pin aperture, and a pin received in said pin aperture for engaging said threads.
CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority of Provisional Application Serial No. 60/069,496, filed Dec. 15, 1997.

US Referenced Citations (14)
Number Name Date Kind
1159233 Konig Nov 1915
1507111 Erfle Sep 1924
1688113 Bornkessel Oct 1928
2456521 Maxwell Dec 1948
2550962 Brandon May 1951
2986969 Muncheryan Jun 1961
3273456 Feinbloom Sep 1966
3865468 Holcomb Feb 1975
3877793 Nakagawa Apr 1975
4273423 Uesugi Jun 1981
5076682 Pasfield Dec 1991
5088809 Portney Feb 1992
5627690 Caplan et al. May 1997
5680195 Pekar et al. Oct 1997
Foreign Referenced Citations (1)
Number Date Country
1645925 Apr 1991 RU
Provisional Applications (1)
Number Date Country
60/069496 Dec 1997 US