A system for aligning an optical fiber termination to a light path is disclosed. Light coming through the fiber at its termination as well as light introduced into the light path from a laser are directed along the light path to a viewer. The placement of the fiber termination is adjustable, as is the direction of the light path, such that the image of light from the optical fiber termination can be adjusted to coincide at the viewer with the image of light from the laser. A long focal length lens is optionally placed in the input beam path and laterally positioned as a fine resolution control over the point of focus at the fiber core. If the laser radiation is ultraviolet or infrared, a flourescing surface may be positioned in the light path to return visible light along the light path to the viewer.

FIELD OF THE INVENTION 
The present invention relates to optical fiber alignment techniques and in 
particular to aligning a fiber termination with respect to a light beam. 
BACKGROUND OF THE INVENTION 
This application is a continuation in part of commonly owned application 
Ser. No. 057,730, filed June 2, 1987, now abandoned, which is a 
continuation in part of commonly owned application Ser. No. 027,152 filed 
Mar. 17, 1987, now abandoned. 
In many research and experimental facilities it is important to be able to 
align an optical fiber termination with a light path or another optical 
fiber termination for coupling radiation therebetween. While there exist 
various connector or coupler schemes for special applications and which 
provide for a preset alignment of fiber and light path or active devices, 
such special purpose elements do not lend themselves readily to the 
flexibility required in experimental and research applications. Alignment 
systems which have existed in the past for accomplishing flexible 
alignment of beams and fiber terminations have been awkward and required 
substantial time and effort to achieve a fiber alignment function. 
In addition, in experimental applications, fibers are typically processed 
on the bench and cleaved by experimenters in order to provide the 
termination. Often times the quality of the termination, particularly as 
it relates to being able to accept radiation from a path into the fiber, 
is not always adequate. In addition, in launching radiation into a fiber 
it is often optimally achieved by placing the fiber termination at a point 
of focus and thus minimum waste size of the radiation in order to launch 
the maximum energy into the fiber itself. Further, often experiments 
require nonvisible light, such as infrared or ultraviolet laser radiation, 
to be aligned with the optical fiber. Such alignments necessitate the use 
of special complex viewers for viewing nonvisible radiation in the visible 
light range. 
BRIEF SUMMARY OF THE INVENTION 
According to the present invention an alignment system is provided in which 
an optical fiber termination and a light path can be rapidly and 
accurately aligned so that the light path represents a continuum of light 
passage into and out of the optical fiber core. 
In a particular implementation, an optical fiber termination is placed into 
an X, Y, Z, .theta. positioner with its terminal end exposed in the 
direction of the light path. The light path is defined extending from the 
fiber termination to a viewing means, so that light traveling from the 
optical fiber passes along the light path to the viewing means where its 
image is visible. The light path is further defined by an objective lens 
to receive, for example, laser radiation of a large aperture and reduce it 
to a small aperture. The direction of the light path is optionally 
adjustable, to ease alignment with the fiber termination, by means of a 
long focal length lens adjustably positioned in the light path. Light 
introduced from the laser along the light path is selectively returned 
back through the lenses by, for example, a reflector and then directed by 
a beam splitter onto the viewing means, where its image is visible. The 
viewing means may be a screen typically having a targeting grid thereon or 
any eyepiece having a reticle within. The light representing the optical 
fiber termination is provided by a core illuminator placed at the opposite 
end of the optical fiber and the light exiting from the core similarly 
travels along the light path, through the objective lens and long focal 
length lens, and is projected by the beam splitter onto the viewing means. 
The beam splitter may have a dichroic coating to pass only infrared and 
ultraviolet light and reflect visible light. 
The long focal length lens is positionally adjustable to adjust the 
direction of a portion of the light path, such that a large change in 
position of the lens results in a small change in position of the light 
path at the termination of the optical fiber. The X, Y, Z, .theta. 
positioner allows the fiber termination to be adjusted in directions 
orthogonal to the light path as well as along the light path in order to 
cause the image of the core to be projected into the same position as the 
reflected image of the light previously obtained from the reflector on the 
light path, assuring alignment. In order to place the fiber termination at 
the focus for the light on the light path, the reflector is adjustable in 
axial direction parallel to the light path so that it can be used to 
identify the position of focus from which the reflected light will appear 
as a minimal diameter on the projection screen. The optical fiber can then 
be placed with its termination at the same location after the reflector is 
retracted, ensuring the fiber will be coupling light from and to the light 
path at optimal efficiency. 
In lieu of a selectively positioned reflector, a flourescing surface may be 
utilized along the beam path having a flourescing surface which returns 
lights of a visible wavelength along the light path in response to 
incident laser radiation of ultraviolet or infrared wavelength. The thus 
returned light is reflected out of the beam path by a dichroic mirror to a 
viewing screen or eye piece. 
The alignment system of the present invention thus provides a rapid and 
efficienty alignment of an optical fiber termination to a light path by 
adjusting both the optical fiber termination and the light path. In 
addition, nonvisible radiation can easily be aligned to the fiber 
termination with no need for a complex nonvisible light viewer.

DETAILED DESCRIPTION 
The present invention contemplates a system for aligning an optical fiber 
termination and light path quickly and efficiently to ensure that light 
projected along the beam path will couple at optimal efficiency with the 
fiber to its termination. 
FIG. 1 shows a diagrammatic and pictorial representation of the present 
invention in which a housing 10 is provided to encompass the alignment 
optics which comprise at one end an X, Y, Z, .theta. micrometer 
displacement positioner 12 in which a chuck 14 positions a termination 16 
of an optical fiber 18. The positioner 12 is mounted at one end 20 of the 
housing 10 containing an aperture through which the fiber 18 passes. 
Adjustment in angle .theta. is an angular adjustment about the optical 
axis of the fiber termination. 
The opposite end of the housing 10 contains a further aperture 22 adapted 
to receive a large aperture beam 24 of laser radiation, typically from a 
laser 26. In the modification shown in FIG. 5, the beam 24 enters the 
housing 10 and passes through long focal length lens 70 and objective lens 
28. Lenses 70 and 28 define a light path 30. Lens 70 is adjustable by 
means of positioner 72 in directions othogonal to beam 24. A large 
positioning change of lens 70 provides a relatively smaller change in the 
position of light path 30 without changing its angle significantly. Lens 
70 may be plano-concave or double concave. Beam 24 is reduced in waist 
size by an objective lens 28 to form a small aperture beam along light 
path 30. The resolution of adjustment of the light path is a function of 
the focal length of the long focal length lens and the objective lens. The 
objective lens 28 is supported within the housing 10 by any support means 
32 convenient. 
A means 34 for returning light along the light path is pivoted within the 
housing 10 by a hinge 36 on a bracket 38 which runs along an axial guide 
40 providing adjustment of its axial position i.e., the direction parallel 
to the path 30, by a control 42. In this manner the location of the 
returning means 34 may be adjusted to different positions along the light 
path 30. The returning means 34 may be a mirror. Alternatively the 
returning means could be a flourescing surface responsive to incident 
ultraviolet or infrared radiation from the laser. The laser radiation 
stimulates the flourescing surface to flouresce with light in a visible 
wavelength. Suitable surfaces include screens Q-31, Q-32, Q-16, and U-21 
manufactured by Quantex. By converting the returned radiation to visible 
light, the expense of a high cost ultraviolet or infrared viewing means 48 
is avoided. 
Light from the returning means 34 returns on the light path 30 and on the 
path of the beam 24 to projection optics, typically a beam splitter 44 
(where element 34 is a mirror) within a housing 46. The beam splitter 44 
redirects the returned light and projects it onto a viewing means 48, 
which may be a screen surface with a grid pattern 52 (with or without an 
ultraviolet or infrared sensitivity) or an eyepiece containing a reticle. 
The returned light typically forms a spot 50 within grid pattern 52 as 
shown in FIG. 2. The beam splitter 44 may have a dichroic coating to 
transmit only the infrared or ultraviolet radiation coming from source 26 
along path 24 and 30 and reflects converted visible light coming back from 
fluorescing surface 34 along path 30, 24 to viewing means 48. 
A core illuminator 54 is provided and applies light to the core of the 
fiber 18 from an opposite end 56 thereof causing the core at the 
termination 16 to be illuminated. With the mirror or flourescing screen 34 
placed out of the path 30, light from the core 16 is directed back along 
the light path 30 through the objective lens 28 to the beam splitter 44 
and is similarly projected onto the screen 48 as a spot 58. Adjustment of 
the X, Y, Z, .theta. positioner 12 allows the spots 50 and 58 to be 
aligned with each other, thereby ensuring alignment of the light path 30 
with the core of the fiber 18. An additional benefit from the system 
occurs from the fact that the quality of the cleavage from the fiber 
termination 16 can be determined by the appearance and the intensity of 
the projected spot 58. 
In actual usage it is typically preferable to utilize the positioning 
control 42 to locate the mirror or flourescing surface 34 of the point of 
minimal beam width along the optical path 30 for light from the laser 26. 
This effectively places the mirror 34 at the focus of the illumination and 
is easily detected by minimal size for the spot 50 projected on the screen 
48. The lens 70 is adjusted using positioner 72 to adjust the direction of 
the light path. The fiber termination 16, after the mirror or flourescing 
screen 34 is swung out of the beam path 30, is then typically positioned 
at the same location of focus in the beam path 30 using the X, Y, Z, 
.theta. positioner, and at the same time aligned for coincidence with the 
position of spot 50. Use of positioner 12 to align the fiber with the 
light path ensures not only that the fiber core at the termination 16 will 
be located and centered on the optical light path 30 but that the 
termination 16 will be placed at the focal point for light passing along 
the path of beam 24. This ensures optimal coupling efficiency between path 
30 and fiber 18. 
As illustrated in FIG. 3, the returning means 34 alternatively may be a 
lens 60 or thin piece of glass having a reflecting surface 62 serving the 
function of the mirror or flourescing screen 34 along the light path 30. 
The lens 60 will be transparent to the radiation from the core at the 
termination 16 and at the same time be at least partially reflective to 
light along the path 30 from the laser source 26, permitting the 
projection of both spots on the screen 48 as described above. 
In FIG. 4 there is illustrated the use of the termination 16 of the fiber 
18 itself as the reflector for light on the beam path 30 allowing it to be 
projected from the beam splitter 44 onto the screen 48. 
The thus described alignment system permits rapid and accurate alignment 
between a light source such as a laser and an optical fiber for optimal 
radiation transfer. The system can also be utilized, by duplication of 
parts on either end, for coupling fibers to each other. The particular 
structures illustrated above are intended as exemplary only, the scope of 
the invention being as defined solely in the following claims.