U.S. patent application number 11/443415 was filed with the patent office on 2010-09-09 for off-axis fiber optic slip ring.
This patent application is currently assigned to Princetel, Inc.. Invention is credited to Boying B. Zhang, Hong Zhang.
Application Number | 20100226607 11/443415 |
Document ID | / |
Family ID | 42669701 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100226607 |
Kind Code |
A1 |
Zhang; Hong ; et
al. |
September 9, 2010 |
OFF-AXIS FIBER OPTIC SLIP RING
Abstract
A multi-channel off-axis optic slip ring system is disclosed.
The invention eliminates the huge number of fiber bundles and
photodiodes in most published patents. A couple of conventional
optical components such as mirrors and prisms are used to transmit
optical signals with high quality and low optic losses. The optical
signal pick-up is realized through a pair of prisms mounted on gear
transmission systems. It is a true passive, bi-directional
rotational optical transmission device which could be used for both
multi-mode and single mode fibers without the limitation to the
through bore diameters.
Inventors: |
Zhang; Hong; (Plainsboro,
NJ) ; Zhang; Boying B.; (Lawrenceville, NJ) |
Correspondence
Address: |
Lu & Associates, P.C.
P.O. Box 1380
HAVERTOWN
PA
19083
US
|
Assignee: |
Princetel, Inc.
|
Family ID: |
42669701 |
Appl. No.: |
11/443415 |
Filed: |
May 11, 2006 |
Current U.S.
Class: |
385/26 |
Current CPC
Class: |
G02B 6/3604
20130101 |
Class at
Publication: |
385/26 |
International
Class: |
G02B 6/42 20060101
G02B006/42 |
Claims
1. An off-axis fiber optic slip ring assembly for use with single
mode and multi-mode optical fibers comprising: a stator with a
central through bore and a rotor with a central through bore, able
to rotate independently of each other on a common axis through a
pair of bearings; a first fiber optical collimator mounted on said
rotor and able to rotate with the said rotor around the said common
axis; a hollow mirror array, having a number of concentric
cylindrical members with central through bore, fixed in the said
stator, coaxially orientated with the said rotor at a specific
distance from the said first gear portion of the rotor; rotor means
having a concentric first gear on the inward end portion of the
rotor; a second gear engaging with the said first gear, having a
concentric shaft, able to rotate around the axis of said shaft in a
bore of said stator through bearings; a third gear concentrically
attached on the said second gear, able to rotate with the said
second gear; a fourth gear engaging with the said third gear,
having a concentric shaft with a through bore, able to rotate
around the axis of said shaft in a bore of said stator through
bearings; a first rhomboid prism attached on the inward end portion
of said fourth gear radially, with one end portion of the rhomboid
prism covering the said through bore of the said fourth gear on the
inward side of the said fourth gear; a first right angle prism
attached on the said stator, parallel located with the said first
rhomboid prism with one end portion of the rhomboid prism covering
the said through bore of the said fourth gear on the outward side;
a second fiber optical collimator fixed in a bore of said stator,
coaxially aligned with the said first right angle prismprism with a
specific axial distance; a fifth gear, sixth gear, and seventh gear
being exactly the same gear as the said second gear, third gear,
and fourth gear respectively, and mounted in the said stator in a
symmetrical position to the said common axis through bearings; a
second rhomboid prism and second right angle prism being exactly
the same as the said first rhomboid prism and first right angle
prism respectively, and mounted in the said stator in a symmetrical
position to the said common axis; a third fiber optical collimator
fixed in a bore of said stator, coaxially aligned with the said
second right angle prism with a specific axial distance; an optical
coupler, fixed on the said stator, connected with the said second
and said third fiber optical collimator on one side.
2. An off-axis fiber optic slip ring assembly according to claim 1,
wherein said hollow mirror array, including a first channel
cylindrical member, a second channel cylindrical member, . . . and
more channel cylindrical member, means each of the cylindrical
members having at least two flat surfaces means the two flat
surfaces perpendicular each other forming a sharp edge
perpendicular to the said common axis, and the said flat surfaces
being optically coated as optical mirrors, means the first optical
minor surface and second optical mirror surface.
3. An off-axis fiber optic slip ring assembly according to claim 1,
wherein the axis of said fourth gear, and said seventh gear being
perpendicular to the said common axis;
4. An off-axis fiber optic slip ring assembly according to claim 1,
wherein the axis of said second gear and said fifth gear being
either parallel to the said common axis, or perpendicular to the
said common axis.
5. An off-axis fiber optic slip ring assembly according to claim 1,
claim 2, claim 3, and claim 4, wherein the optical signal could be
emitted from the said first collimator, when the said rotor rotates
from 0.degree. to 180.degree., reflected by the first optical
mirror surface of said cylindrical member, then reflected by the
said first rhomboid prism, after passing through the through bore
of said fourth gear, reflected by the said first right angle prism
and get into the said second collimator; and when the said rotor
rotates from 180.degree. to 360.degree., the optical signal,
reflected by the said second optical mirror surface, then reflected
by the said second rhomboid prism, after passing through the
through bore of said seventh gear, reflected by the said second
right angle prism and getting into the said third collimator; each
of said second collimator and third collimator optically connected
to one side of the said optical coupler; and the said optical
signal also could be emitted from the said optical coupler, in an
inverse way, getting into the said first collimator.
6. An off-axis fiber optic slip ring assembly for use with single
mode and multi-mode optical fibers comprising: a stator with a
central through bore and a rotor with a central through bore, able
to rotate independently of each other on a common axis through a
pair of bearings; a first fiber optical collimator mounted on said
rotor and able to rotate with the said rotor around the said common
axis; a hollow mirror array, having a number of concentric
cylindrical members with central through bore, fixed in the said
stator, coaxially orientated with the said rotor at a specific
distance from the said first gear portion of the rotor; rotor means
having a concentric first gear on the inward end portion of the
rotor; a second gear engaging with the said first gear, having a
concentric shaft, able to rotate around the axis of said shaft in a
bore of said stator through bearings; a third gear concentrically
attached on the said second gear, able to rotate with the said
second gear; a fourth gear engaging with the said third gear,
having a concentric shaft with a through bore, able to rotate
around the axis of said shaft in a bore of said stator through
bearings; a first rhomboid prism attached on the inward end portion
of said fourth gear radially, with one end portion of the rhomboid
prism covering the said through bore of the said fourth gear on the
inward side of the said fourth gear; a second fiber optical
collimator fixed in a bore of said stator, coaxially aligned with
the axis of said fourth gear with a specific axial distance; a
fifth gear, sixth gear, and seventh gear being exactly the same
gear as the said second gear, third gear, and fourth gear
respectively, and mounted in the said stator in a symmetrical
position to the said common axis through bearings; a second
rhomboid prism being exactly the same as the said first rhomboid
prism, and attached on the inward end portion of said seventh gear
radially, with one end portion of the rhomboid prism covering the
said through bore of the said seventh gear on the inward side of
the said seventh gear; a third fiber optical collimator fixed in a
bore of said stator, coaxially aligned with the axis of said
seventh gear with a specific axial distance; an optical coupler,
fixed on the said stator, connected with the said second and said
third fiber optical collimator on one side.
7. An off-axis fiber optic slip ring assembly according to claim 6,
wherein said hollow mirror array, including a first channel
cylindrical member, a second channel cylindrical member, . . . and
more channel cylindrical member, means each of the cylindrical
members having at least two flat surfaces means the two flat
surfaces perpendicular each other forming a sharp edge
perpendicular to the said common axis, and the said flat surfaces
being optically coated as optical mirrors, means the first optical
mirror surface and second optical mirror surface.
8. An off-axis fiber optic slip ring assembly according to claim 6,
wherein the axis of said fourth gear, and said seventh gear being
perpendicular to the said common axis;
9. An off-axis fiber optic slip ring assembly according to claim 6,
wherein the axis of said second gear and said fifth gear being
either parallel to the said common axis, or perpendicular to the
said common axis.
10. An off-axis fiber optic slip ring assembly according to claim
6, claim 7 claim 8 and claim 9, wherein optical signal could be
emitted from the said first collimator, when the said rotor rotates
from 0.degree. to 180.degree., reflected by the first optical
mirror surface of said cylindrical member, then reflected by the
said first rhomboid prism, after passing through the through bore
of said fourth gear, get into the said second collimator; and when
the said rotor rotates from 180.degree. to 360.degree., the optical
signal, reflected by the said second optical mirror surface, then
reflected by the said second rhomboid prism, after passing through
the through bore of said seventh gear, getting into the said third
collimator; each of said second collimator and third collimator
optically connected to one side of the said optical coupler; and
the said optical signal also could be emitted from the said optical
coupler, in an inverse way, getting into the said first
collimator.
11. An off-axis fiber optic slip ring assembly for use with single
mode and multi-mode optical fibers comprising: a stator with a
central through bore and a rotor with a central through bore, able
to rotate independently of each other on a common axis through a
pair of bearings; a first fiber optical collimator array, including
multi-channel optical collimators, mounted on said rotor and able
to rotate with the said rotor around the said common axis; a hollow
cylindrical member, fixed in the said stator, coaxially orientated
with the said rotor at a specific distance from the said first gear
portion of the rotor; rotor means having a concentric first gear on
the inward end portion of the rotor; a second gear engaging with
the said first gear, having a concentric shaft, able to rotate
around the axis of said shaft in a bore of said stator through
bearings; a third gear concentrically attached on the said second
gear, able to rotate with the said second gear; a fourth gear
engaging with the said third gear, having a concentric shaft with a
through bore, able to rotate around the axis of said shaft in a
bore of said stator through bearings; a first rhomboid prism
attached on the inward end portion of said fourth gear radially,
with one end portion of the rhomboid prism covering the said
through bore of the said fourth gear on the inward side of the said
fourth gear; an first on-axis multi-channel fiber optical rotary
joint mounted on the said stator, coaxially aligned with the said
fourth gear and driven by the said fourth gear; a second fiber
optical collimator array, including multi-channel optical
collimators, coaxially fixed with the second on-axis multi-channel
fiber optical rotary joint; a fifth gear, sixth gear, and seventh
gear being exactly the same gear as the said second gear, third
gear, and fourth gear respectively, and mounted in the said stator
in a symmetrical position to the said common axis through bearings;
a second rhomboid prism being exactly the same as the said first
rhomboid prism, and attached on the inward end portion of said
seventh gear radially, with one end portion of the rhomboid prism
covering the said through bore of the said seventh gear on the
inward side of the said seventh gear; an second on-axis
multi-channel fiber optical rotary joint mounted on the said
stator, coaxially aligned with the said seventh gear and driven by
the said seventh gear; a third fiber optical collimator array,
including multi-channel optical collimators, coaxially fixed with
the second on-axis multi-channel fiber optical rotary joint; an
optical coupler array, including multi-channel optical couplers,
fixed on the said stator, connected with the said second and said
third fiber optical collimator on one side.
12. An off-axis fiber optic slip ring assembly according to claim
11, wherein said hollow cylindrical member having at least two flat
surfaces means the two flat surfaces perpendicular each other
forming a sharp edge perpendicular to the said common axis, and the
said flat surfaces being optically coated as optical mirrors, means
the first optical mirror surface and second optical mirror
surface.
13. An off-axis fiber optic slip ring assembly according to claim
11, wherein the axis of said second gear, said fourth gear, said
fifth gear, said seventh gear being perpendicular to the said
common axis.
14. An off-axis fiber optic slip ring assembly according to claim
11, wherein the axis of said second gear and said fifth gear being
parallel to the said common axis, while the axis of the said fourth
gear and said seventh gear being perpendicular to the said common
axis.
15. An off-axis fiber optic slip ring assembly according to claim
11, wherein said on-axis multi-channel fiber optical rotary joint
means an opto-mechanical device including at least a first member
and a concentric second member relatively rotatable each other
through bearings on a common axis forming a continuous rotary
interface, able to pass optical signals on multiple, single-mode or
multi-mode optical channels across the said continuous rotary
interface; the said on-axis multi-channel fiber optical rotary
joint concentrically orientated with the said fourth gear, or
seventh gear; one of said first member, or second member attached
to said fourth gear, or said seventh gear and driven by the said
fourth gear, or said seventh gear, while another said first member,
or second member attached to said stator.
16. An off-axis fiber optic slip ring assembly according to claim
11, claim 12, claim 13, claim 14 and claim 15 wherein multi-channel
optical signals could be emitted from the said first collimator
array, when the said rotor rotates from 0.degree. to 180.degree.,
reflected by the first optical mirror surface of said cylindrical
member, then reflected by the said first rhomboid prism, after
passing through the said on-axis multi-channel fiber optical rotary
joint concentrically orientated with the said fourth gear, getting
into the said second collimator array; and when the said rotor
rotates from 180.degree. to 360.degree., the multi-channel optical
signals, reflected by the said second optical mirror surface, then
reflected by the said second rhomboid prism, after passing through
the said on-axis multi-channel fiber optical rotary joint
concentrically orientated with the said seventh gear, getting into
the said third collimator array; each of said second collimator
array and third collimator array optically connected to one side of
the said optical coupler array; and the said optical signals also
could be emitted from the said optical coupler array, in an inverse
way, getting into the said first collimator array.
Description
REFERENCES CITED
TABLE-US-00001 [0001] U.S. PATENT DOCUMENTS 4,460,242 July 1984
Birch, et al. 4,492,427 January 1985 Lewis, et al. 4,943,137 July
1990 Speer 4,934,783 June 1990 Jacobson 6,907,161 July 2005
Bowman
OTHER PUBLICATIONS
[0002] "Fiber Optic Rotary Joints-A Review", by GLENN F. I. DORSEY.
IEEE Trans. Components, Hybrids, and Manufac. Technol., vol.
CHMT-5, NO. 1, 1982, PP 39. [0003] "Mechanism design, analysis and
synthesis, volume 1" by Arthur G. Erdman and George N. Sandor.
Third Edition. 1997.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The invention is related to off-axis multi-channel fiber
optic slip ring to provide transmission of data in optic form
between a mechanically rotational interface with a through
bore.
[0006] 2. Description of Related Art
[0007] It is well known that the devices to transmit optical data
between two independently rotational members are called fiber
optical rotary joints, or optical slip ring. There are single
channel, two channel and multi-channel fiber optical rotary joints.
However, most of them are categorized as on-axis fiber optical
rotary joint because the optical paths are located along the axis
of rotation, or occupy the central space along the axis of
rotation. If the central space along the rotational axis is not
accessible, the optical light paths would not be allowed to path
through the central area along the rotational axis. Such devices
are usually called off-axis optical slip ring.
[0008] The simplest, off-axis slip ring has been described in U.S.
Pat. No. 4,492,427, which comprises two opposed annular fiber
bundles and increasing the number of such concentric annular
bundles radially would make the device multi-channeled. The
concentric, annular fiber bundle fiber optic slip rings are
bi-directional but do have a modulated light loss dependent on the
rotational angle. For minimizing the importance of the modulation,
a digitized signal rather than an analog signal has to be used.
This off-axis slip ring only could be used for multi-mode fibers,
not single mode fibers.
[0009] U.S. Pat. No. 4,460,242 discloses an optical slip ring
employing optical fibers to allow light signals applied to any one
or all of a number of inputs to be reproduced at a corresponding
number of outputs of the slip ring in a continuous manner. It
includes a rotatable output member, a stationary input member and a
second rotatable member which is rotated at half the speed of the
output member like a de-rotator. The input member having a
plurality of equispaced light inputs and the output member having a
corresponding number of light outputs and the second rotatable
member having a coherent strip formed of a plurality of bundles of
optical fibers for transmitting light from the light inputs on the
input member to the light outputs.
[0010] Another U.S. Pat. No. 4,943,137 assume the similar idea,
where, a de-rotating, transmissive intermediate optical component
with an array of lensed optical transmitters and receivers
respectively mounted on the rotor and stator. The derotating,
intermediate optical component comprises an image conduit, image
transporter, or coherent optical fiber bundle of close-packed
monofibers or multifibers.
[0011] But actually, it is almost no way to handle and arrange so
many fibers on the said rotatable members, especially for large
diameter slip ring. The optical loss is very obvious for multi-mode
fibers. It is almost impossible to use single mode fibers. The
effect of damaged fibers, the presence of debris, separation
distances, component tolerances, or backlash in the gearing also
cause problems.
[0012] A more sophisticated approach can be found in U.S. Pat. No.
6,907,161. The patent uses multiple inputs and pick-ups to send and
receive data across members that have large diameters. The use of
multiple inputs and pick-ups is required to keep the optical
signals at a level that is sufficiently high to permit the
photodiode receivers to operate. Wave guides are employed. The
multiple inputs and pick-ups also cause a rapid rise and fall of
the signal because the signal reflects from one area of the
waveguide to another. The drawback is to use photodiode receivers
which is an electro-optical device, so that the output signal is
electrical and the power must be high. Besides, there is a time
jitter thus limiting the data rate.
SUMMARY OF THE INVENTION
[0013] The object of the present invention is to eliminate the huge
number of fiber bundles and photodiodes in most prior arts, to
provide a true passive, bidirectional, no time jitter, low-loss
off-axis optic slip ring which could be used for both multi-mode
and single mode fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is preferred embodiment of the invention.
[0015] FIG. 2 is an outline diagram of the off-axis slip ring in
FIG. 1.
[0016] FIG. 3 shows the mirror array in the invention.
[0017] FIG. 4 illustrates another arrangement of the mirror array
in the invention.
[0018] FIG. 5 represents the position changes for the collimators
on stator.
[0019] FIG. 6 shows another embodiment of the gear transmission in
the invention.
[0020] FIG. 7 demonstrates a different way to build a multi-channel
off-axis optic slip ring.
[0021] FIG. 8 is the enlarged view for an on-axis multi-channel
optic rotary joint used in FIG. 7.
DETAILED DESCRIPTION OF THE INVENTION
[0022] As shown in FIG. 1, a typical embodiment of a multi-channel
off-axis optic slip ring in the present invention comprises rotor
18, stator 30, mirror array 16, 26, 36, 46, rhomboid prisms 15, 45,
right angle prisms 25,35, gears 19,22, 23,24, collimators
10,20,11,12, and coupler 13. A pair of bearings 50 are mounted
between rotor 18 and stator 30 to provide the main rotational
interface. Other bearings 51, 52, 53, and 54 are used to
rotationally support the gears 22, 23, 24; 32, 33, and 34 in the
stator 30. Collimators 10, 20, and more (depends on how many
channel would be built), are mounted on rotor 18 in circumferential
direction at a different distances to the common rotational axis
70. The axis of the collimators 10, and 20 are parallel to the main
rotational axis 70. The rotor 18 and the mirror holder 60 are
hollow along the said common rotational axis so that a through bore
is provided, leaving the central part of the interface totally
free. That means all the optical signals would not be allowed to
pass through the through bore. On the inward end part of rotor 18
is a bevel gear 19, which is engaged with another bevel gear 32. A
spur gear 33 is fixed with the bevel gear 32 and rotatable through
the bearings 53, thus driving the next spur gear 34 to rotate
through the bearings 54. A rhomboid prism 45 is attached on the
gear 34 thus rotating with gear 34. A folded mirror 16 is co-axial
with the common rotational axis 70 with two flat mirror surfaces
161 and 162, which are perpendicular each other and symmetrical to
the common rotational axis (as shown in FIG. 3). The mirror array
16, 26, 36 and 46 are stationary by fixed to stator 30 through
holder 60 and cover 40. The gear ratio between gear 19 and 34 is
designed to 1:1. The rotation direction of the gear 34 is the same
as that of rotor 18. When the collimator 10 rotates within
180.degree. and 360.degree., the light beam emitted from collimator
10 will be reflected by the mirror surface 162 to rhomboid prism 45
and reflected two times by the paralleled surfaces of rhomboid
prism 45 to the central hole of gear 34. Another similar right
angle prism 35 fixed in the stator 30 would pickup the light beam
to the collimator 11, which is also fixed on stator 30. Because the
counterpart of the above described gears, rhomboid prisms, right
angle prisms, and collimators are also symmetrically arranged to
the common axis 70, when the collimator 10 rotates between
0.degree. and 180.degree., the light beam emitted from collimator
10 will be reflected by mirror surface 161, prism 15 and 25, then
coupled to collimator 12. Finally, the collimator 11 and 12 are
connected to an optical coupler 13, which is also fixed to stator
30 through cap 40.
[0023] FIG. 2 is an outline diagram of the off-axis slip ring in
FIG. 1, where, member 80 represents the opto-mechanical
transformer, including all the gears, rhomboid prisms, right angle
prisms, mirrors and bearings. In the first channel, light beam
would be transmitted from collimator 10 to coupler 13, vise versa.
In the second channel, light beam would be transmitted from
collimator 20 to coupler 63, vise versa, in the same way. Mirror 26
is for second channel (as shown FIG. 1., FIG. 3 and FIG. 4). The
gears and prisms for the second channel are not shown in the FIG.
1, but they have the same opto-mechanical structure as the first
channel. As illustrated in FIG. 2, if the power of optical signal
from collimator 10 is P.sub.r, and the power of optical signal
through collimator 11 and 12 are P.sub.1 and P.sub.2 respectively,
then the power of optical signal to coupler 13, P.sub.s,can be
expressed as follows:
P s = P 2 / 2 , -- -- -- ( 0 ~ 180 0 ) P 1 / 2 , -- -- - ( 180 0 ~
360 0 ) , ##EQU00001##
where, P.sub.2.apprxeq.P.sub.r, - - -
(0.about.180.degree.),P.sub.1.apprxeq.P.sub.r, - - -
(180.degree..about.360.degree.),
(Note: the Angle Refers to the Rotation Position of Rotor 18 in
FIG. 1)
[0024] Due to the opto-mechanical transmission error, usually,
P.sub.1.noteq.P.sub.2, and P.sub.1-P.sub.2.ltoreq.1 dB
[0025] Another embodiment of mirror array is illustrated in FIG. 4
if the gear systems for the even number of channel are arranged to
perpendicular to the odd number of channel. For example, mirror 16
is for channel one, mirror 36 for channel 3, mirror 26 and 46 for
channel 2 and channel 4 respectively. In this way, the axis of
gears for channel 1 and 3 would be perpendicular to the axis of
gears for channel 2 and 4 in order to save space.
[0026] In FIG. 5, the optical signals would be directly coupled to
collimator 11 and 12 respectively instead of using right angle
prisms 25 and 35 like in FIG. 1.
[0027] An alternative embodiment of the invention is illustrated in
FIG. 6, where the gear transmission is arranged in a different way
as in FIG. 1. The gear engagement between 19 and 24, (or between 19
and 34), is in such an order as from spur gear to bevel gear, while
in FIG. 1 it is from bevel gear to spur gear. The gear engagement
order would not change the light path and the performance of the
invention, but affect the mechanical dimensions of the
invention.
[0028] In FIG. 7, a preferred embodiment of the invention for
multi-channel off-axis fiber optic slip ring is illustrated, where,
two on-axis multi-channel fiber optic rotary joints 99 and 100 are
utilized. They are co-axially arranged with gear 34 and gear 24
respectively. To compare with FIG. 1 and FIG. 5, almost all the
opto-mechanical members are the same in FIG. 7 as in FIG. 1 and
FIG. 5, but only one mirror 16 is needed for this embodiment. The
collimator 10 in FIG. 1 and FIG. 5 becomes a multi-collimator
bundle 1000 in FIG. 7 in the same position on rotor 18. The
collimator 11, or 12 in FIG. 1 and FIG. 5 becomes a
multi-collimator bundle 111, or 112 in FIG. 7 in the similar
position on stator 30. The multi-collimator bundle 1000 could
transmit multi-channel optical signals. The light beams emitted
from multi-collimator bundle 1000 should be parallel one another.
For example, the paralleled light beams from the multi-collimator
bundle 1000 would be reflected by the flat mirror surface 162, or
161, and then reflected two times by the rhomboid prism 45, or 15,
to get into the central bore of the gear 34, or gear 24 along the
rotational axis of gear 34, or gear 24. When the multi-collimator
bundle 1000 rotates with the rotor 18 around the common rotational
axis 70, the paralleled light beams from the multi-collimator
bundle 1000 will rotate around the axis of gear 34, or gear 24, in
a stable pattern after transmitted by the mirror 16 and rhomboid
prism 45, or 15. The on-axis fiber optic rotary joint 99, or 100,
will allow the rotating paralleled light beams from the
multi-collimator bundle 1000 to be coupled with the
multi-collimator bundle 111, 112, which is fixed to the stator 30.
Like in FIG. 1 and FIG. 5, a coupler bundle 133 will couple the
corresponding fibers from collimator bundle 111 and 112.
[0029] To explain how the on-axis fiber optic rotary joint (FORJ)
99, or 100 works, the cross section view of a preferred on-axis
fiber optic rotary joint 99, or 100 is enlarged in FIG. 8. The gear
34, or 24, is also the rotor of FORJ. A sun gear 118 is fixed with
rotor 34, which is engaged with planet gear 119, while another
planet gear 120 is engaged with an internal gear 122, which is part
of stator 99 of the FORJ. A Dove prism 115 is co-axially fixed
inside the through bore of carrier 116. The planet gear system is
such designed so that the carrier 116 will rotate at the half speed
as that of the rotor 34 and in the same rotational direction. In
this way, the rotating paralleled light beams on the rotor 34 will
be coupled into corresponding collimators in the collimator bundle
111, or 112 after pass through the Dove prism.
[0030] The on-axis fiber optic rotary joint in FIG. 8 is only one
typical on-axis fiber optic rotary join. Any other types of on-axis
fiber optic rotary joint could be used in present invention in the
same manner as the on-axis fiber optic rotary joints in FIG. 7.
* * * * *