Method and apparatus for observing tip portion of optical fibers butting each other

The present invention relates to a method and apparatus for observing, before and after fusion-splicing of optical fibers such as ribbon fibers each including a plurality of optical fibers in particular, the butting state of the tip portion of each of fiber ribbons in a wide range with a high accuracy. In the observation method in accordance with the present invention, while the optical fibers to be fusion-spliced together are disposed on a predetermined reference surface such that their end faces butt each other, at least a pair of cameras are independently or synchronously moved along a direction perpendicular to the longitudinal direction of the optical fibers so as to change the shooting areas of the respective cameras, thereby realizing the collective observation or local observation of the observation area. The observation apparatus in accordance with the present invention comprises a driving system for moving the pair of cameras along a predetermined direction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method and apparatus for observing, 
before and after fusion-splicing of optical fibers such as ribbon fibers 
each including a plurality of optical fibers in particular, the butting 
state of the tip portion of each of fiber ribbons in a wide range with a 
high accuracy. Here, the fusion-splicing of the fiber ribbons is effected 
as optical fibers in one fiber ribbon are fusion-spliced with the 
respective optical fibers in the other fiber ribbon in a state where end 
faces of the corresponding optical fibers butt each other. 
2. Related Background Art 
As optical communication networks expand, high-density multifilament 
fiber-optic cables have been used, thereby necessitating a method for 
connecting them together with a low loss, a high reliability, and a 
rapidness. From this viewpoint, fusion-splicing machines for fiber ribbons 
(also known as ribbon type optical fibers) constituting the high-density 
multifilament fiber-optic cables have been developed. Here, "fiber ribbon" 
refers to a tape-shaped fiber cord in which a plurality of optical fibers 
are unitedly coated with a resin or the like. Also, each optical fiber 
comprises a core region having a predetermined refractive index and a 
cladding region which covers the outer periphery of the core region and 
has a lower refractive index than the core region. 
FIG. 14 shows a configuration of the conventional fusion-splicing machine 
(including an observation apparatus) for fiber ribbons disclosed, for 
example, in U.S. Pat. No. 4,978,201. Fiber ribbons 1a and 1b to be spliced 
together are respectively held by fiber holding members 15a and 15b at 
their tip portions. The respective tip portions of the fiber ribbons 1a 
and 1b, stripped of coatings, are fixed onto installation members 16a and 
16b, each having a plurality of V-shaped grooves. Disposed on both sides 
of the installation members 16a and 16b are electrodes 18a and 18b. After 
each of the butting tip portions of the fiber ribbons 1a and 1b is 
observed, the fiber ribbons 1a and 1b are fusion-spliced together by 
discharge between the electrodes 18a and 18b. A mirror 19, which is 
disposed between the electrodes 18a and 18b, is movable along directions 
indicated by arrow A in this drawing. A light source 5 and a microscope 
camera 20 are disposed such that irradiation light from the light source 5 
is reflected by a mirror 19 and then is made incident on the microscope 
camera 20. 
Further, the image data captured by the microscope camera 20 by way of the 
mirror is temporarily taken into an image processing unit 70. The image of 
the butting tip portions of the fiber ribbons 1a and 1b are displayed on a 
TV monitor 9 by the image processing unit 70. 
Here, as shown in FIG. 15, after being reflected by the mirror 19, a part 
of the irradiation light from the light source 5 is transmitted through 
each optical fiber from the direction indicated by 23a so as to enter the 
microscope camera that has not yet been moved from its initial position 
20a. On the other hand, a part of irradiation light from the moved light 
source 5 is transmitted through each optical fiber from the direction 
indicated by 23b in the drawing and then is reflected by the mirror 19 so 
as to enter the microscope camera that has been moved to a position 
denoted by 20b. In order to observe the butting state of the tip portions 
of the fiber ribbons 1a and 1b, the real images and virtual images of the 
tip portions of respective pairs of the optical fibers thus butting each 
other have been successively taken into the image processing unit 70 as 
image data while the microscope camera 20 is driven, or the real images 
and virtual images of the tip portions of a plurality of sets of optical 
fibers butting each other whose focal points do not considerably deviate 
from each other have been successively taken into the image processing 
unit 70 as image information. 
SUMMARY OF THE INVENTION 
The inventor has studied the above-mentioned prior art and, as a result, 
has found the problems explained in the following. As a recent tendency, 
the filament number (number of optical fibers included in a fiber ribbon) 
of each fiber ribbon (ribbon-type optical fiber) to be spliced has been 
doubling, e.g., from 8 to 16 and 12 to 24. In the case where the fiber 
ribbons each having such an increased filament number are to be observed, 
even when the observation and measurement accuracy can be maintained, a 
wide range of observation cannot be effected, thereby it takes a long time 
for the fiber ribbons to be completely spliced together. 
Also, when the whole image of the tip portions of the respective fiber 
ribbons to be spliced together or image of the spliced portions of the 
respective fiber ribbons is to be displayed, since the side width (width 
in the direction orthogonal to the longitudinal direction of each optical 
fiber included in the fiber ribbon) increases, it is necessary for the 
magnification of the microscope camera to be lowered, thereby the 
resolution may deteriorate. 
Further, as the side width of the fiber ribbon increases, the microscope 
camera has a larger field angle, thereby it is likely to become out of 
focus. 
Here, known as technologies relating to the present invention are those 
disclosed in Japanese Patent Application Laid-Open Nos. 1-107218 and 
7-84190, for example. 
The present invention relates to a method and apparatus for observing, 
before and after fusion-splicing of optical fibers such as ribbon fibers 
each including a plurality of optical fibers in particular, the butting 
state of the tip portion of each of fiber ribbons in a wide range with a 
high accuracy. In particular, it is an object of the present invention to 
provide an observation method and observation apparatus which can observe 
the butting state of each set of optical fibers in a short time without 
lowering the observation and measurement accuracy even when the filament 
number in the fiber ribbons to be spliced together increases. 
Here, the fusion-splicing of the fiber ribbons is effected as optical 
fibers in one fiber ribbon are fusion-spliced with the respective optical 
fibers in the other fiber ribbon in a state where end faces of the 
corresponding optical fibers butt each other. 
In order to achieve the above-mentioned object, a first embodiment of the 
observation method in accordance with the present invention comprises, at 
least, the steps of disposing, while a tip portion of a first optical 
fiber (included in one fiber ribbon) and a tip portion of a second optical 
fiber (included in the other fiber ribbon to be spliced with the one fiber 
ribbon) butt each other, the tip portions of the first and second optical 
fibers onto a predetermined reference surface; and shooting an observation 
area on the reference surface from directions different from each other 
while moving a pair of microscope cameras (first and second cameras) along 
a direction perpendicular to a longitudinal direction of the first and 
second optical fibers disposed on the reference surface. Here, each of the 
first and second cameras is a microscope camera having an optical system 
with a predetermined magnification. In this observation method in 
accordance with the present invention, the above-mentioned image pick up 
step includes a collective observation step for shooting the whole 
observation area and a local observation step for shooting a part of the 
observation area. 
In particular, in a first movement control operation (collective 
observation step) for the above-mentioned pair of microscope cameras, the 
first and second cameras are moved in directions opposite to each other, 
which are perpendicular to the longitudinal direction of the first and 
second optical fibers, thereby the first and second cameras divisionally 
shoot the whole observation area (see FIGS. 4 and 5). Here, the movement 
control operations for the first and second cameras are executed 
independently of each other. Accordingly, at the collective observation 
step in the first embodiment, a first shooting area on the reference 
surface shoot by the first camera and a second shooting area on the 
reference surface shoot by the second camera are respectively scanned on 
the reference surface in directions opposite to each other, which are 
perpendicular to the longitudinal direction of the first and second 
optical fibers. 
A second movement control operation (local observation step) for the 
above-mentioned pair of microscope cameras (first and second cameras) is 
executed such that the first and second cameras are moved in the same 
direction perpendicular to the longitudinal direction of the first and 
second optical fibers, while maintaining a state where the first shooting 
area on the reference surface shoot by the first camera and the second 
shooting area on the reference surface shoot by the second camera 
substantially coincide with each other (see FIGS. 7 and 8). Here, the 
first and second shooting areas are included in the observation area on 
the reference surface. Accordingly, at the local observation step in the 
first embodiment, the first and second shooting areas are scanned on the 
reference surface in the same direction. 
Preferably, the pair of microscope cameras (first and second cameras) are 
moved along a direction perpendicular to the longitudinal direction of the 
first and second optical fibers, while maintaining a state where the 
optical axes of their respective optical systems are orthogonal to each 
other (see FIGS. 4 and 7). 
An observation apparatus for realizing the above-mentioned first embodiment 
of the observation method in accordance with the present invention 
comprises, as shown in FIGS. 1 to 4 and 7 for example, at least, a pair of 
installation members 16a and 16b for holding, while a tip portion of a 
first optical fiber 50a (included in one fiber ribbon 1a) and a tip 
portion of a second optical fiber 50b (included in the other fiber ribbon 
1b to be spliced with the one fiber ribbon 1a) butt each other, the tip 
portions of the first and second optical fibers 50a and 50b such that the 
tip portions of first and second optical fibers 50a and 50b are disposed 
on a predetermined reference surface P1; a first camera 2a and a second 
camera 2b for shooting an observation area on the reference surface P1 
respectively from directions different from each other; and a driving 
system for moving the first camera 2a and second camera 2b along a 
direction perpendicular to a longitudinal direction of the first and 
second optical fibers 50a and 50b disposed on the reference surface P1. 
Here, the pair of installation members 16a and 16b respectively have faces 
160a and 160b facing each other and perpendicular to the longitudinal 
direction of the first and second optical fibers 50a and 50b, as well as 
V-shaped grooves 161a and 161b for defining positions at which the optical 
fibers 50a and 50b are disposed. The first and second cameras 2a and 2b 
respectively have optical systems 4a and 4b with a predetermined 
magnification. 
In particular, as shown in FIGS. 1 and 2, the above-mentioned driving 
system comprises, at least, a guide 8 extending along the faced surfaces 
160a and 160b of the pair of installation members 16a and 16b; first and 
second drivers 10a and 10b which are movable on the guide 8; and a driving 
unit 11 for moving the first and second drivers 10a and 10b along a 
direction in which the guide 8 extends. 
Here, the first driver 10a is loaded with the first camera 2a having the 
optical system 4a, whereas the second driver 10b is loaded with the second 
camera 2b having the optical system 4b. Preferably, the first and second 
cameras 2a and 2b are respectively mounted on the first and second drivers 
10a and 10b such that the optical axes of their optical systems 4a and 4b 
are orthogonal to each other. 
In the observation apparatus, in order to realize the above-mentioned first 
embodiment (including the collective observation step and the local 
observation step) of the observation method, the first and second cameras 
2a and 2b are disposed along a direction perpendicular to the longitudinal 
direction of the first and second optical fibers 50a and 50b. Further in 
the local observation step, the driving unit 11 moves and controls the 
first and second drivers 10a and 10b such that the first shooting area on 
the reference surface P1 shoot by the first camera 2a and the second 
shooting area on the reference surface P1 shoot by the second camera 2b 
substantially coincide with each other. Here, the first and second 
shooting areas are included in the observation area on the reference 
surface P1. 
The observation apparatus further comprises a first light source 5a 
disposed at a position opposing the first camera 2a with respect to the 
reference surface P1 and a second light source 5b disposed at a position 
opposing the second camera 2b with respect to the reference surface P1. 
The first and second cameras 2a and 2b are respectively equipped with 
light receiving sections 3a and 3b for taking out images of the 
observation area on the reference surface P1 as electric signals through 
the optical systems 4a and 4b with a predetermined magnification. 
Also, the observation apparatus comprises an image processing system 
including a monitor 9 for displaying, at least, an image of the 
observation area on the reference surface P1 and an image processing unit 
7 for, at least, receiving a first image data obtained by the light 
receiving section 3a of the first camera 2a and a second image data 
obtained by the light receiving section 3b of the second camera 2b and 
forming, from thus received first and second image data, a composite image 
to be displayed on the monitor 9. 
The next observation method (second embodiment) in accordance with the 
present invention comprises, at least, the steps of disposing, while a tip 
portion of a first optical fiber (included in one fiber ribbon) and a tip 
portion of a second optical fiber (included in the other fiber ribbon to 
be spliced with the one fiber ribbon) butt each other, the tip portions of 
the first and second optical fibers onto a predetermined reference 
surface; shooting an observation area on the reference surface, as a 
whole, including the tip portions of the first and second optical fibers 
by a collective observation microscope camera (first camera) having an 
optical system with a predetermined magnification (collective observation 
step); and shooting a predetermined area in the observation area from 
directions different from each other while moving a pair of microscope 
cameras (second and third cameras) having optical systems with a 
magnification greater than the magnification of the optical system of the 
collective observation microscope camera along a direction perpendicular 
to a longitudinal direction of the first and second optical fibers 
disposed on the reference surface. 
In particular, in this second embodiment, at least the second and third 
cameras are preferably moved in the same direction perpendicular to the 
longitudinal direction of the first and second optical fibers, while 
maintaining a state where the first shooting area (included in the 
observation area) on the reference surface shoot by the second camera and 
the second shooting area (included in the observation area) on the 
reference surface shoot by the third camera substantially coincide with 
each other. Also, the second and third cameras are moved along the 
longitudinal direction of the first and second optical fibers while 
maintaining a state where the optical axes of their optical systems are 
orthogonal to each other. 
The observation apparatus for realizing the above-mentioned observation 
method (second embodiment) characteristically comprises, in place of the 
pair of cameras 2a and 2b of the observation apparatus shown in FIGS. 1 to 
3, a collective observation microscope camera (first camera 2c) and a pair 
of microscope cameras (second camera 2d and third camera 2e), respectively 
having optical systems 4c to 4e, while the magnification of the optical 
system 4c differs from that of the optical systems 4d and 4e. 
Namely, the observation apparatus for realizing the above-mentioned 
observation method (second embodiment) in accordance with the present 
invention comprises, at least, the pair of installation members 16a and 
16b for holding, while the tip portion of the first optical fiber 50a 
(included in one fiber ribbon 1a) and the tip portion of the second 
optical fiber 50b (included in the other fiber ribbon 1b to be spliced 
with the one fiber ribbon 1a) butt each other, the tip portions of the 
first and second optical fibers 50a and 50b such that the tip portions of 
first and second optical fibers 50a and 50b are disposed on the 
predetermined reference surface P1; the first camera (collective 
observation microscope camera) 2c having the optical system 4c with a 
predetermined magnification for shooting, as a whole, an observation area 
on the reference surface P1 including the tip portions of the first and 
second optical fibers 50a and 50b disposed on the reference surface P1; a 
pair of microscope cameras (second camera 2d and third camera 2e) for 
shooting a predetermined area in the observation area on the reference 
surface P1 respectively from directions different from each other; and a 
driving system for moving at least the second camera 2d and third camera 
2e disposed on the reference surface P1 along a direction perpendicular to 
the longitudinal direction of the first and second optical fibers 50a and 
50b disposed on the reference surface P1. Here, the pair of the 
installation members 16a and 16b respectively have the faces 160a and 160b 
facing each other and perpendicular to the longitudinal direction of the 
first and second optical fibers 50a and 50b, as well as the V-shaped 
grooves 161 and 161b for defining positions at which the optical fibers 
50a and 50b are disposed. The second and third cameras 2d and 2e 
respectively have the optical systems 4d and 4e with a magnification 
greater than the that of the optical system 4c of the first camera 2c. 
The above-mentioned driving system comprises, at least, the guide 8 
extending along the faced surfaces 160a and 160b of the pair of 
installation members 16a and 16b; a driver 10 which is movable on the 
guide 8; and the driving unit 11 for moving the driver 10 along a 
direction in which the guide 8 extends. Here, in order to reduce the size 
of the observation apparatus, it is preferable that the first to third 
cameras 2c to 2e be unitedly mounted on the driving apparatus 10. In this 
configuration, at least the pair of cameras (second and third cameras 2d 
and 2e) are moved in synchronization with each other. 
Preferably, in the configuration, the first and second cameras 2a and 2b 
are mounted on the driver 10 such that the optical axes of their optical 
systems 4d and 4e are orthogonal to each other. Also, the second and third 
cameras 2d and 2e mounted on the driver 10 are disposed along a direction 
perpendicular to the longitudinal direction of the first and second 
optical fibers 50a and 50b, while the first shooting area (included in the 
observation area) on the reference surface P1 shoot by the second camera 
2d and the second shooting area (included in the observation area) on the 
reference surface P1 shoot by the third camera 2e substantially coincide 
with each other. 
The observation apparatus shown in FIG. 12 further comprises a first light 
source 5c disposed at a position opposing the first camera 2c with respect 
to the reference surface P1, a second light source 5d disposed at a 
position opposing the second camera 2d with respect to the reference 
surface P1, and a third light source 5e disposed at a position opposing 
the third camera 2e with respect to the reference surface P1. Also, the 
observation apparatus comprises a light receiving section 33 for 
selectively taking out, as electric signals, a collective observation 
image data corresponding to the whole observation area on the reference 
surface P1 obtained by way of the optical system 4c of the first camera 2c 
and first and second local observation image data of the first and second 
shooting areas included in the observation area on the reference surface 
P1 respectively obtained by way of the optical systems 4d and 4e of the 
second and third cameras 2d and 2e. 
Also, the observation apparatus comprises an image processing system 
including the monitor 9 for displaying, at least, an image of the 
observation area on the reference surface P1 and the image processing unit 
7 for, at least, receiving the first local observation image data obtained 
by the second camera 2d and the second local observation image data 
obtained by the third camera 2e and forming, from thus received first and 
second local observation image data, a composite image to be displayed on 
the monitor 9. 
The present invention will be more fully understood from the detailed 
description given hereinbelow and the accompanying drawings, which are 
given by way of illustration only and are not to be considered as limiting 
the present invention. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will be apparent to those skilled in the 
art from this detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following, the observation methods (first and second embodiments) 
and observation apparatus in accordance with the present invention will be 
explained with reference to FIGS. 1 to 13. 
FIG. 1 is a perspective view showing a configuration of a fiber ribbon 
fusion-splicing machine including an observation apparatus in accordance 
with the present invention. This fiber fusion-splicing machine comprises a 
first fiber holding member 15a for holding a first fiber ribbon 1a and a 
second fiber holding member 15b for holding a second fiber ribbon 1b which 
is to be fusion-spliced with the first fiber ribbon 1a. The first and 
second fiber holding members 15a and 15b are movable in directions 
indicated by arrows B1 and B2 by first and second motors 13a and 13b by 
way of rod screws 12a and 12b, respectively. Also, the tip portions of the 
fiber ribbons 1a and 1b are stripped of their coatings so as to expose 
first and second optical fibers 50a and 50b, respectively. Thus exposed 
tip portions of the first and second optical fibers 50a and 50b are 
positioned by first and second installation members 16a and 16b having 
V-shaped grooves 161a and 161b, respectively. The fiber fusion-splicing 
machine further comprises electrodes 18a and 18b opposing each other 
across the exposed optical fibers 50a and 50b, which are respectively 
disposed on the first and second installation members 16a and 16b, so as 
to fusion-splice together each set of the first and second optical fibers 
50a and 50b, whose end faces butt each other, by discharge. 
Further, the fiber fusion-splicing machine shown in FIG. 1 includes the 
observation apparatus in accordance with the present invention. The 
observation apparatus for realizing a first embodiment of the observation 
method (comprising a collective observation step and a local observation 
step) explained later comprises, as shown in FIG. 2 for example, at least, 
a guide 8 extending along faced surfaces 160a and 160b of the pair of 
installation members 16a and 16b; first and second drivers 10a and 10b 
which are movable on the guide 8; and a driving unit 11 for moving the 
first and second drivers 10a and 10b along directions in which the guide 8 
extends (directions indicated by arrows C1 and C2 in the drawing). Also, 
the first driver 10a is loaded with a first microscope camera 2a having an 
optical system 4a, whereas the second driver 10b is loaded with a second 
microscope camera 2b having an optical system 4b. An observation image of 
each pair of the first and second optical fibers 50a and 50b whose end 
faces butt each other is obtained by the above-mentioned pair of the 
microscope cameras 2a and 2b. 
Here, the respective optical systems 4a and 4b of the first and second 
microscope cameras 2a and 2b have a predetermined magnification. The first 
and second microscope cameras 2a and 2b are respectively mounted on the 
first and second drivers 10a and 10b such that the optical axes of their 
optical systems 4a and 4b are orthogonal to each other (see FIGS. 4 and 
7). 
Also, the first and second optical fibers 50a and 50b are respectively 
disposed on the V-shaped grooves 161a and 161b of the pair of installation 
members 16a and 16b so as to be placed on a predetermined reference 
surface P1 as shown in FIG. 3, while their end faces butt each other. 
Therefore, in the observation apparatus, a first light source 5a is 
disposed at a position opposing the first microscope camera 2a with 
respect to the reference surface P1, while a second light source 5b is 
disposed at a position opposing the second microscope camera 2b with 
respect to the reference surface P1. 
Further, the first and second microscope cameras 2a and 2b are respectively 
equipped with light receiving sections 3a and 3b for taking out images of 
an observation area on the reference surface P1 as electric signals 
through the optical systems 4a and 4b with a predetermined magnification. 
Also, the observation apparatus comprises an image processing system 
including a monitor 9 for displaying, at least, an image of the 
observation area on the reference surface P1 and an image processing unit 
7 for, at least, receiving a first image data obtained by the light 
receiving section 3a of the first microscope camera 2a and a second image 
data obtained by the light receiving section 3b of the second microscope 
camera 2b and forming, from thus received first and second image data, a 
composite image to be displayed on the monitor 9. 
Here, at least the above-mentioned driving unit 11 and image processing 
unit 7 are included in a controller 100, which controls the light sources 
5a and 5b during the observing operation and the electrodes 18a and 18b 
during the fusion-splicing operation. The driving unit 11 also drives and 
controls the motors 13a and 13b shown in FIG. 1. 
In the following, the first embodiment of the observation method in 
accordance with the present invention will be explained with reference to 
FIGS. 4 to 11. Here, FIG. 4 is a view showing a schematic configuration of 
the observation apparatus for realizing the collective observation step in 
the first embodiment, whereas FIG. 7 is a view showing a schematic 
configuration of the observation apparatus for realizing the local 
observation step in the first embodiment. In the first embodiment, the 
movement control operations for the first and second microscope cameras 2a 
and 2b (directions for moving the respective microscope cameras) and the 
respective shooting areas of the first and second microscope cameras 2a 
and 2b on the reference surface P1 in the collective observation step are 
different from those in the local observation step. 
FIG. 5 is a view for explaining the collective observation step in the 
first embodiment, showing the shooting areas of the first and second 
microscope cameras 2a and 2b on the reference surface P1 on which the 
first and second optical fibers 50a and 50b are disposed. FIG. 6 is a view 
showing a monitor screen displaying a composite image 6 (image of the 
whole observation area) on the reference surface P1. This composite image 
6 is combined by the image processing unit 7 from image data 6a and 6b of 
a predetermined shooting area of the reference surface P1 respectively 
captured by the first and second microscope cameras 2a and 2b. 
On the other hand, FIG. 8 is a view for explaining the local observation 
step in the first embodiment, showing the shooting areas of the first and 
second microscope cameras 2a and 2b on the reference surface P1 on which 
the first and second optical fibers 50a and 50b are disposed. FIGS. 9 to 
11 are views respectively showing monitor screens displaying the composite 
images 6 (local observation images) on the reference surface P1. These 
composite images 6 are also combined by the image processing unit 7 from 
image data 6-1a to 6-3a and 6-1b to 6-3b of predetermined shooting areas 
on the reference surface P1 respectively captured by the first and second 
microscope cameras 2a and 2b. 
Namely, while fiber ribbons with 16 optical fibers (1-1, . . . , 1-16) to 
be fusion-spliced are disposed on the reference surface P1 with their end 
faces butting each other, the observation apparatus shown in FIG. 4 
comprises the first and second microscope cameras 2a and 2b, which are 
disposed obliquely with respect to the reference surface P1 with optical 
axes 23a and 23b of their respective optical systems 4a and 4b 
intersecting (normally at right angles). As mentioned above, this 
observation apparatus (shown in FIGS. 4 and 7) comprises the light sources 
5a and 5b for illuminating the first and second optical fibers 50a and 50b 
butting each other; a pair of the microscope cameras 2a and 2b for picking 
up images of thus illuminated optical fibers 50a and 50b from two 
respective directions; the drivers 10a and 10b movable by the driving unit 
11 in the direction of arrows C1 and C2 (so as to move the first and 
second microscope cameras 2a and 2b independently or simultaneously from 
one side (1-1) of the aligned optical fibers 50a and 50b toward the other 
side (1-16) across each of the fiber ribbons 1a and 1b); the image 
processing unit 7 for processing thus captured two-component composite 
image 6 (see FIG. 6); and the TV monitor 9 such as liquid crystal display, 
cathode ray tube (CRT) or the like for displaying thus processed composite 
image. Here, the pair of microscope cameras 2a and 2b may be moved across 
each of the optical fibers 50a and 50b either in different directions 
independently of each other (at the collective observation step; see FIG. 
5) or in the same direction at the same speed (at the local observation 
step; see FIG. 8). 
On the other hand, of the irradiation light beams from the light sources 5a 
and 5b, the light components respectively transmitted through the core and 
cladding of each of the butted optical fibers 50a and 50b from the two 
directions of the optical axes 23a and 23b vary according to the 
difference in refractive index therebetween, thereby an image of each of 
the optical fibers 50a and 50b is picked up by the pair of microscope 
cameras 2a and 2b. 
At the collective observation step in the first embodiment, as shown in 
FIG. 5, one microscope camera 2a is controlled such that a shooting area 
110a on the reference surface P1 is moved in the direction of arrow D1 
indicated therein, so as to pick up at least an image of the half within 
the whole observation area. On the other hand, the other microscope camera 
2b is controlled such that a shooting area 110b on the reference surface 
P1 is moved in the direction of arrow D2 indicated therein, so as to pick 
up at least an image of the remaining half within the whole observation 
area. Thus, in the collective observation step in the first embodiment, 
the image of the whole observation area is divisionally picked up by the 
pair of microscope cameras 2a and 2b. Here, of the respective shooting 
areas 110a and 110b of the microscope cameras 2a and 2b, 111a and 111b 
denote the effective areas displayed on the TV monitor 9. Also, 6a and 6b 
refer to the local observation images (respectively corresponding to the 
half regions of the whole observation area) picked up by the respective 
microscope cameras 2a and 2b. 
At the local observation step in the first embodiment, on the other hand, 
as shown in FIG. 8, the microscope cameras 2a and 2b are simultaneously 
moved by the respective drivers 10a and 10b from the optical fiber 1-1 
toward the optical fiber 1-16 across each of the fiber ribbons 1a and 1b. 
Namely, the shooting areas 110a and 110b of the respective microscope 
cameras 2a and 2b are simultaneously scanned at the same speed in the 
directions of arrows D1 and D2 indicated therein. 
As mentioned above, at the collective observation step in the first 
embodiment, the whole observation area is divisionally shoot by the 
microscope cameras 2a and 2b, thereby each optical fiber is observed from 
only one direction. Accordingly, the position of each of the butted 
optical fibers cannot correctly be measured. When the images 6a and 6b 
respectively picked up by the microscope cameras 2a and 2b are combined 
together, however, the overall butting state (optical fibers 1-1 to 1-16) 
can be observed simultaneously (see FIG. 6). Accordingly, before a 
detailed position is measured, the overall state can be inspected so as to 
see, for example, whether or not there is a great obstacle such as loss in 
splicing ends which may cause poor splicing. 
At the local observation step in the first embodiment, on the other hand, 
the two microscope cameras 2a and 2b simultaneously observe each optical 
fiber from the orthogonal directions 23a and 23b, thereby the position of 
each of the butted optical fibers can accurately be measured. FIGS. 9 to 
11 are views showing states of this observation step. FIG. 9 shows the 
composite image 6 formed by the images 6-1a and 6-1b capturing the optical 
fibers 1-1 to 1-8 respectively from the orthogonal directions 23a and 23b. 
When the relative positions of the microscope cameras 2a and 2b with 
respect to the fiber ribbons 1a and 1b are moved toward the right side of 
the arrows C1 and C2 in FIG. 7, the composite image formed by the images 
6-2a and 6-2b shown in FIG. 10 and the composite image formed by the 
images 6-3a and 6-3b shown in FIG. 11 are successively obtained as the 
microscope cameras 2a and 2b move from the optical fiber 1-1 toward the 
optical fiber 1-16. Nevertheless, the overall state cannot simultaneously 
be observed. 
The light beams thus incident on the microscope cameras 2a and 2b are 
magnified by the optical systems 4a and 4b and then are photoelectrically 
converted into image data by the light receiving sections (image pick-up 
devices) 3a and 3b, respectively. Thus obtained analog image data are 
A/D-converted by the image processing unit 7 and then are stored in a 
memory. Based on these data, the controller 100 computes amounts of axial 
deviation and movement. Then, the controller 100 judges whether the amount 
of axial deviation is less than a tolerable level or not. When it is 
judged as less than the tolerable level, based on the above-mentioned 
amount of movement, the controller 100 controls the rotations of the 
motors 13a and 13b so as to actuate the optical fiber holding members 15a 
and 15b such that, while the optical fibers 50a and 50b advance, electric 
currents are supplied to the electrodes 18a and 18b so as to fusion-splice 
the optical fibers 50a and 50b together by discharge (see FIG. 1). 
In the actual observation before and after the fusion-splicing, the 
above-mentioned collective observation step and local observation step are 
effected in combination. Namely, in the case where the fusion-splicing 
machine equipped with the above-mentioned observation apparatus is used 
for fusion-splicing fiber ribbons, initially, the first and second 
microscope cameras 2a and 2b respectively observe the abutting state of 
the optical fibers 1-1 to 1-8 and the abutting state of the optical fibers 
1-9 to 1-16, thereby forming the image of the whole observation area (at 
the collective observation step; see FIG. 4). Then, the first and second 
microscope cameras 2a and 2b are simultaneously moved from the optical 
fiber 1-1 toward the optical fiber 1-16 across each of the fiber ribbons 
1a and 1b (at the local observation step; see FIG. 7). 
Thus, when the collective observation step and the local observation step 
are combined together, the abutting state of the optical fibers butting 
each other, as a whole, can initially be inspected, and then the pair of 
microscope cameras 2a and 2b can be used to accurately measure the 
relative positions of the individual optical fibers without changing the 
magnification of the optical system of each camera. 
In the following, a second embodiment of the observation method in 
accordance with the present invention will be explained with reference to 
FIGS. 12 and 13. Here, FIG. 12 is a view showing a schematic configuration 
of an observation apparatus for realizing the second embodiment. As in the 
case of the first embodiment (see FIGS. 5 and 8), the second embodiment 
performs a step (collective observation step) of collectively observing 
all the sets of the first and second optical fibers 50a and 50b whose end 
faces butt each other and a step (local observation step) of partially 
observing the reference surface P1. Accordingly, the observation apparatus 
shown in FIG. 12 comprises a collective observation microscope camera 2c 
having an optical system 4c with a predetermined magnification for picking 
up an image of the whole observation area on the reference surface P1, and 
a pair of microscope cameras 2d and 2e respectively having optical systems 
4d and 4e with a magnification greater than that of the optical system 4c 
of the collective observation microscope camera 2c. 
FIG. 13 is a view for explaining the collective observation step, showing 
the shooting area (corresponding to the whole observation area) of the 
collective observation microscope 2c on the reference surface P1. Here, 
the operation at the local observation step is similar to that in the 
above-mentioned first embodiment. Namely, the shooting areas and movement 
control operations of the pair of microscope cameras 2d and 2e are shown 
in FIG. 8. Also, the monitor screens in the local observation step in the 
second embodiment are shown in FIGS. 9 to 11. 
The second embodiment is applied to cases where the filament number of the 
fiber ribbons 1a and 1b is so large that an overall image and a detailed 
image cannot be picked up by a microscope camera with a single 
magnification. 
The observation apparatus shown in FIG. 12 comprises the microscope camera 
(collective observation microscope camera) 2c with a small magnification 
disposed in a direction perpendicular to the reference surface P1 in order 
to shoot all the butted optical fibers 50a and 50b, and the pair of 
microscope cameras 2d and 2e with a large magnification (respectively 
having the optical systems 4d and 4e with a magnification greater than 
that of the optical system 4c) obliquely disposed with respect to the 
reference surface P1 on both sides of the above-mentioned perpendicular 
direction. The microscope cameras 2c, 2d, and 2e are unitedly fixed to a 
lens barrel 30. The image formed through the optical system 4c with a 
small magnification is photoelectrically converted by an image pick-up 
device (light receiving section) 33 through two half mirrors 31a and 31b. 
Also, the images formed through the pair of optical systems 4d and 4e with 
a large magnification are combined together by the image pick-up device 33 
respectively by way of mirrors 32a and 32b and the half mirrors 31a and 
31b. Further, the microscope cameras 2c to 2e are disposed on a driver 10 
for moving them across the optical fibers 50a and 50b. 
Since the images picked up by the three microscope cameras 2c, 2d, and 2e 
are processed by the single image pick-up device 33, this observation 
apparatus is simple in configuration and is easy to handle. 
In the case where the fusion-splicing machine equipped with the 
above-mentioned observation apparatus of the second embodiment is used for 
fusion-splicing the fiber ribbons 1a and 1b together, as shown in FIG. 13, 
the microscope camera 2c with a small magnification is initially used for 
picking up an image of the whole observation area. Then, the microscope 
cameras 2d and 2e with a large magnification are simultaneously moved from 
the optical fiber 1-1 to the optical fiber 1-16 so as to respectively pick 
up images (see FIGS. 8 to 11). Thus picked up two images are combined 
together by the single image pick-up device 33 so as to be observed. 
The present invention is carried out in the modes explained in the 
foregoing and yields the following effects. 
In the observation method and apparatus in accordance with the first 
embodiment, the state of the whole observation area can be inspected by a 
plurality of microscope cameras, and the relative positions of the 
respective sets of butting individual optical fibers can accurately be 
measured by the microscope cameras having the same magnification as those 
used for inspecting the whole observation area (without changing the 
magnification). 
The observation method and apparatus in accordance with the second 
embodiment is simple in configuration and is easy to handle, since the 
images picked up by three microscope cameras are processed by a single 
image pick-up device. Further, even when the filament number of each of 
the fiber ribbons to be fusion-spliced increases, the time required for 
observation can be reduced. 
From the invention thus described, it will be obvious that the invention 
may be varied in many ways. Such variations are not to be regarded as a 
departure from the spirit and scope of the invention, and all such 
modifications as would be obvious to one skilled in the art are intended 
for inclusion within the scope of the following claims. 
The basic Japanese Application No. 101355/1996 filed on Apr. 23, 1996 is 
hereby incorporated by reference.