Optical waveguides – With splice – Fusion splicing
Reexamination Certificate
1998-10-15
2001-09-11
Font, Frank G. (Department: 2877)
Optical waveguides
With splice
Fusion splicing
C385S095000, C385S097000, C385S098000, C385S099000, C356S073100
Reexamination Certificate
active
06287020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an observation apparatus for observing positions of optical fibers and a fusion splicer using the same for optical fibers.
2. Related Background Art
A conventional observation apparatus for optical fibers is disclosed in Japanese Laid-open Patent Application No. 1-107218. The conventional observation apparatus for optical fibers described in this application is an apparatus for illuminating light from obliquely above to a plurality of optical fibers fixed in a row on a support frame and for picking up an image of the neighborhood of end faces at spliced portions of the optical fibers illuminated by the light, through a TV camera located obliquely below.
FIG. 9
is a drawing to show an optical system according to a conventional observation apparatus for optical fibers. As shown in
FIG. 9
, an image pickup plane
100
of a TV camera is located normally to the optical axis
102
of optical lens
101
and the optical system is adjusted so that the focus is achieved on the image pickup plane
100
intersecting with the optical axis
102
. Accordingly, the focus deviates with increasing distances from this position, causing the image to be blurred; therefore, the number of the optical fibers for which the image could be displayed in a screen was limited to four pairs if their outside diameter portions were to be measured with the accuracy of several &mgr;m or less.
Incidentally, the observation apparatus for optical fibers was often incorporated in the fusion splicer for optical fibers. In that case, observation was carried out prior to fusion splicing so as to check whether an offset of axis or the like occurred between optical fibers to be fused and spliced with each other. Recently, the number of pairs of optical fibers to be spliced at one time with an fusion splicer for optical fibers has been increased, in order to increase the efficiency of splicing of optical fibers. At present, the technology for fusion-splicing twelve fiber pairs at one time is established, and the technology for fusion-splicing sixteen fiber pairs or twenty four fiber pairs at one time is also under research and development.
SUMMARY OF THE INVENTION
In the above observation apparatus for optical fibers, however, only four fiber pairs were allowed to be observed in one screen; and, because the offset of axis had to be measured while observing each optical fiber perpendicularly thereto, the splicing time largely increased with increase in the number of pairs of optical fibers to be fusion-spliced at one time, as shown in Table 1 below.
TABLE 1
Number of
observations
(4 optical fiber
pairs are observed
Number of optical
in each
fiber pairs
observation)
Splicing time
4
2
45
sec
8
4
70
sec
12
6
95
sec
16
8
120
sec
24
12
145
sec
In the splicing time, the time necessary for actual fusion splicing was constant irrespective of the number of fibers, and most of the increase in the splacing time was due to the time necessary for observation of positions and end-face states of the optical fibers by the observation apparatus for optical fibers. Since the observation time of optical fibers increased with the increase in the number of optical fiber pairs as described, the increase in the numbers of pairs of optical fibers to be spliced at one time did not result in increasing the efficiency of splicing of optical fibers accordingly.
Japanese Laid-open Patent Application No. 2-304403 discloses a conventional observation apparatus for optical fibers. The conventional observation apparatus for optical fibers described in this application was designed to make an attempt to bring more optical fibers into focus by inclining the image pickup plane of the image pickup device relative to the optical axis. This observation apparatus for optical fibers, however, needed a device for driving a mirror, because it used the mirror as a means for observation in two directions. It was also difficult to determine an appropriate position and an appropriate angle of the image pickup plane, because the position of the virtual image (mirror image) changed depending upon adjustment upon mounting of the mirror. Further, the aforementioned application describes that in practical application of the apparatus multiple pairs of optical fibers must be observed in sections. It was thus eventually impossible to bring all of multiple pairs of optical fibers into focus.
Further, with either of the above observation apparatus for optical fibers, magnifications of obtained images were not constant but varied depending upon the positions of optical fibers, so that arithmetic procedure or image processing was necessary for correction for the magnifications of images to a common magnification. The time for observation of optical fibers was lengthened by this processing as well and it also posed a problem in terms of the size and cost of apparatus.
An object of the present invention is to solve the above-described problems, thereby providing an observation apparatus for optical fibers and an fusion splicer for optical fibers capable of accurately observing positions and end face states of all of even more optical fibers within a short time. Another object of the invention is to provide an observation unit suitable for use in these apparatus.
An observation apparatus for optical fibers according to the present invention comprises an imaging optical system located opposite to plural pairs of optical fibers, and an image pickup device for picking up images of the optical fibers formed by the imaging optical system, wherein the imaging optical system comprises, in order from the side of the optical fibers, a pre-lens system, an aperture stop having an aperture at a position of a rear focus of the pre-lens system, and a post-lens system having a front focus at the position of the rear focus of the pre-lens system.
A more preferred embodiment of the observation apparatus for optical fibers according to the present invention is an observation apparatus for optical fibers for observing a plurality of optical fibers, in which an imaging optical system and image pickup means (an image pickup device) are disposed in order from the side of the plural optical fibers on each of two different optical axes that are normal to the optical axes of the plural optical fibers located in parallel and in a flat shape and that are different from a direction of a normal line to a placement surface of the plural optical fibers, the image pickup means picking up images of the plural optical fibers formed by the imaging optical system, wherein the imaging optical system comprises, in order from the side of the plural optical fibers, a pre-lens system, an aperture stop having an aperture at a position of a rear focus of the pre-lens system, and a post-lens system having a front focus at the position of the rear focus of the pre-lens system, wherein the image pickup plane of the image pickup means is inclined relative to the optical axis of the imaging optical system such that the longer the object distance of an optical fiber is, the shorter its image distance becomes and wherein the image pickup plane of the image pickup means is positioned in parallel to the optical axes of the plural optical fibers.
With this observation apparatus for optical fibers, light, which emerges from the plural optical fibers as observed objects illuminated by a light source, is focused on the image pickup plane of the image pickup means and is picked up by the image pickup means.
In this apparatus the imaging optical system is disposed on each of the two different optical axes which are almost normal to the optical axes of the plural optical fibers and which are not normal to the placement surface of the plural optical fibers, and the image pickup means has the image pickup plane located substantially in parallel to the optical axes of the optical fibers and inclined relative to the optical axis of the imaging optical system such that the longer the object distance is, the shorter the image distance becomes. Co
Hattori Kazunari
Osaka Keiji
Tanabe Akira
Watanabe Tsutomu
Font Frank G.
Nguyen Sang H.
Pillsbury & Winthrop LLP
Sumitomo Electric Industries Ltd.
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