CA1264583A - Photoradiator - Google Patents

Abstract

ABSTRACT
A photoradiator includes a notch at an axial end or in the periphery thereof in order to radiate light which propagates therethrough. Light is radiated in a desired direction and in a desired quantity at the notch. Even the optical property of the light radiated from the photoradiator may be varied for a desired application.

Description

6~58~

The present invention is a division of the canadian patent application 442,243 filed on November 30, 1983.

The present invention relates to a photoradiator for effectively radiating light propagating therethrough in a desired direction and in a desired quantity to the ambience, while furnishing it with an optical property suitable for a desired application.
Effective use of solar energy is tne key to energy saving today and has been studied in various fields actively.
For the most effective use of solar energy, solar energy has to be availed as it is without being transformed into another kind of energy such as thermal energy or electrical energy. In light of this, I have made various proposals for an illumination system which utilizes solar energy. The illumination system employs a light conducting element such as a fiber optic cable through which the sunlight converged by a lens or the like is conducted to a desired location to stream out thereat to illuminate the ambience.
In the illumination system of tne type described, the light advancing through the light conductor has directivity. Therefore, if the light is output at a simple cut end of the light conductor, it becomes radiated over an angle ~ which is usually as small as about 46. The light streaming through the simple cut end of the light conductor would fail to evenly ill~minate a desired space such as a room. I have proposed in various forms a photoradiator which is designed to effectively diffuse ligh~ conducted by a J~

~64S83

- 2-fiber optic cable to provide even illumination over a wide range.
Another problem encountered with a light conducting element of the kind described is that when it is laid over a len~th sufficient for practical use, fringes develop in the light emanating from the light conductor which are undesirable for ordinary lighting applieations~
although some particular applications may rather prefer them. '~hexe the light propagating through the light ~uide is a laser or ~he like~ fringes appear therein even if the light eonductor is of a very small diameter such as an optieal fiber, rendering the light unfeasible or use with a laser microscope or the like.

SUMMARY OF THE INVENTION
It is therefore an objeet of the present invention to provide a photoradiator whieh is capable of effeetive-ly diffusing light transmitted therethrough to the outside by means of a simple construetion.
Z0 It is another objeet of the present invention to provide a photoradiator whieh allows light propagat-ing therethrough to be radiated to the outside in a desixed direction and in a desired quantity.
It is another object of the present invention to provide a photoradiator which radiates light having a desired optical property.
It is another object of the present invention to provide a generally improved photoradiator.
According to the present invention there is provided a serially arranged cylindrical light conducting rods for propagating light along the axial length of the cylin-drical light conducting rods and for reflecting the light laterally outwardly, comprising first and second cylin-drical light conducting rods each having a longitudinal ~Zf~aS83 ~ - 3 -axis and each having an outer cylindrical wall, the first cylindrical llght conducting rod having a first longitudinal end section, the second cylindrical light conducting rod having a second longitudinal end section, the first longitudinal end section having two i.nner diverginy flat walls and an inner flat end wall, the inner flat end wall having two sides and two ends, the two inner diverging flat walls each having an outer terminating end extending to the longitudinal end of the -first longitudinal end section, the two diverging walls diverging as the longitudinal end of the first longitudinal end section is approached, the second longitudinal end section having two outer converging flat walls and an outer flat end wall, the outer flat end wall having two sides and two ends, the two outer converging flat walls each having an outer terminating end which is coincident with the sides of the outer flat end wall, each of the two outer converging flat walls extending to the longitudinal end of the second longitudinal end section, the two converging flat walls each converging as the longitudi-nal end of the second longitudinal end section is approached, the first and second light conducting rods being disposed in a serial and axially aligned position with the two diverging inner flat walls along with the inner flat end wall being complementarily arranged respectively with the two converging outer flat walls along with the outer flat end wall such that the complementarily disposition of the two diverging inner flat walls with the converging outer flat walls facilitates the axial alignment, whereby light propagating through the first cylindrical light conducting rod is transmitted to the second cylindrical light conducting rod via the inner and outer flat end walls while the rest of the light being prvpagated is partly reflected laterally outwardly by the two diverging inner flat walls and the two converging outer flat walls and. partly transmit-~4S~3 ~ 3a -ted through the two diverging inner flat walls and the two converging ou-ter flat walls into the second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light axially and reflecting the light laterally outwardly thereof.
The area of each of the two diverging flat walls may be equal, or it may be different such that one of the two diverging flat walls reflects more light laterally out-wardly than the other diverging f]at wall.
The area of each of the two converging flat walls may be equal, or it may be different such that one of the two converging flat walls reflects more light laterally outwardly than the other converging flat wall.
According to the present invention, there is also provided a serially arranged cylindrical light conducting rods for propagating light along the axial length of the cylindrical light conducting rods and for reflecting the light laterally outwardly, comprising first and second cylindrical light conducting rods each having a longitudinal axis and each having an outer cylindrical wall, the first cylindrical light conducting rod having a first longitudinal end section, the second cylindrical light conducting rod having a second longitudinal end section, the first longitudinal end section having two inner diverging flat walls and an inner flat end wall, the inner flat end wall having two sides and two ends, the two inner diverging flat walls each having an outer terminating end extending to the longitudinal end of the first longitudinal end section, the two diverging walls diverging as the longitudinal end of the first longitudinal end section is approached, the second longitudinal end section having two outer converging Elat walls and an outer flat end wall, the outer flat end wall having two sides and two ends, the two outer converging flat walls each having an outer terminating end which is coinci-lZ6gL~33 ~ - 3b -dent with the sides of -the outer flat end wall, each of the two outer converging flat walls extending to the longitudi-nal end of the second longitudinal end section, the two converging flat walls each converging as the longitudinal end of the second longitudinal end section i5 approached,the ~irst and second light conducting rods being disposed in a serial and axially aligned position with the two diverging inner flat walls along with the inner flat end wall being complementarily arranged and aligned respectively with the two converging outer flat walls along with the outer flat end wall and with an air space between the two diverging inner flat walls and the two convergir,g outer flat walls, whereby light propagating through the first cylindrical light conducting rod is transmitted to the second cylindrical light conducting rod via the inner and outer flat end walls while the rest of the light being propagated is partly reflected laterally outwardly by the two diverging inner flat walls and the two converging outer flat walls via the air space and partly transmitted through the two diverging inner flat walls and the two converging outer flat walls via the air space into the second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light axially and reflecting the light laterally outwardly thereof.
According to the present invention there is also provided a serially arranged cylindrical light conducting rods for propagating light along the axial length of the cylindrical light conducting rods and fo.r reflecting the light laterally outwardly, comprising first and second cylindrical light conducting rods each having a longitudinal axis and each having an outer cylindrical wall, the first cylindrical light conducting rod having a first longitudinal end section, the second cylindrical light conducting rod having a second longitudinal end section, the first ~Z69LS83 ~- 3c -longitudinal end section having two inner diverging flat walls and an inner flat end wall, the inner flat end wall having two sides and two ends, the two inner diverging flat walls each having an outer termina-ting end extending to the longitudinal end of the first longitudinal end section, the two diverging walls diverging as the longitudinal end of the first longitudinal end section is approached, the second longitudinal end section having two outer converging flat walls and an outer flat end wall, the outer flat end wall having two sides and two ends, the two outer converging flat walls each having an outer terminating end which is coincident with the sides of the outer flat end wall, each of the two outer converging flat walls extending to the longitudinal end of the second longitudinal end section, the two converging flat walls each converging as the longitudi-nal end of the second longitudinal end section is approached, the first and second light conducting rods being disposed in a serial and axially aligned position with the two diverging inner flat walls along with the inner flat end wall being complementarily arranged and aligned respectively with the two converging outer flat walls along with the outer flat end wall,a semitransparent layer disposed between the two diverging inner flat walls and the two converging outer flat walls, whereby light propagating through the first cylindrical light conducting rod is transmitted to the second cylindrical light conducting rod via the inner and outer flat end walls while the rest of the light being propagated is partly reflected laterally outwardly by the two diverging inner flat walls and -the two converging outer flat walls via the transparent layer and partly transmitted through the two diverging inner flat wall and the two converging outer flat walls via the transparent layer into the second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light ~IL2~S83

3~ -axially and reflecting the light laterally outwardly thereof.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying~drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures lA and lB to 4A and 4B are views of various embodiments of a photoradiator in accordance with the present invention, suffix "A" indicating a sectional side elevation and suffix "B", a cross-section;
Figures 5-9 are views of other embodiments of the present invention;
Figures 10-15 are perspective views of other embodiments of the present invention;
Figure 16 is a perspective view of a modification to a transparent control member included in the photoradiator of Figure 15;
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~264S83 Figure 17 is a side elevation of the control member of Figure 16 which is positioned to reflect incoming light;
Figures 18 and 19 are views of a prior art simple cylindrical light conducting element; and Figures 20A and 20B to 22A and 22B are views of other embodiments of the present invention.

DESCRIPTIOl~ OF THE PREFERRED EMBODIMENTS
While the photoradiator of the present invention is susceptible of numerous physica~ embodiments, depending upon the environment and requirements of use, substantial numbers of the herein shown and described embodiments have been made, tested and used, and all nave performed in an eminently satisfactory manner.
Referring to Figures lA and lB, a photoradiator em~odying the present invention is snown and comprises a light conducting element in the form of a rod 10. The light conductor 10 optically connects at one end thereof (not shown) to a source of converged light supply (not shown). The other end of the light conductor L0 is formed with a single conical notch lOa in order to efectively diffuse light as will be described.
Light such as sunlight L is converged by a lens or the like into the light conductor 10 at the source.
The light L propagates through the light conductor 10 while being repeatedly reflected by the rod wall. At the notch lOa in the end of the rod 10, the light L
is partly transmitted through the conical surface to the outside and partly reflected tnereby to change its course before being radiated. Stated another way, the light L propagating through the rod 10 is diffused to the outside at the conical end lOa over a substantial radiation angle.
A modification to the structure of Figures lA and and lB is shown in Figures 2A and 2B. As shown, the light conducting element 10' is formed with a number of conical notches lO'a at the light outlet end tnereof.
The effect attainable with such a multi-notch structure is essentially common to that achieved with the single notch s~ructure.
In both the structures shown in Figures lA and lB
and 2A and 2B, the conical notch configuration is only illustrative and may be replaced by a polygonal pyramid such as triangular pyramid or quadrangular pyramid.
If desixed, the notched surface or surfaces may be finished for diffusion in order ~o effectively scatter the light to make tne illumination tender to the eyes.
The principle described above is similarly applicable t4 a light conducting element in the form of a pipe. In Figures 3A and 3B, a light conducting pipe 20 comprises an annular wall 22 the light outlet end of which is cut aslant to define a radially outwardly flared opening 20a. In Figures 4A an~ 4B, a light conducting pipe 20' comprises an annular wall 22' the light outlet end of which is formed with a number of recesses or notches 20'a at spaced locations along the circumference of the pipe.
In the photoradiator shown in Figures 3A and 3B
or 4A and 4~, the converged light L such as sunlight propagates through the pipe wall 22 or 22' while being repeatedly reflected by the other peripheral surface thereof. The notch 20a or notches 20~a serve to e~fectively diffuse the light L to thereby radiate it to the ambience~
If desired, the embodiment shown in Figures 3A and 3B ana that shown in Figures 4A and 4B may be combined, that is, the light outlet end of a light conducting pipe may be cut to have a flared opening and formed with a number of recesses along the circumference lZ64583 thereof. Again, the light outlet end may be finished to serve as a light scattering surface and the illustrated notch configuration is only illustrative.
Referring to Figure 5, another ernbodiment of the S present invention is shown which is applied to a light conducting rod. The light conductor 30 in Figure 5 is formed with a plurality of spaced notches 30a along the circumference thereof and in a selected position between axially opposite ends. Part of light L
propagating through the rod 30 is partly diffused radially outwardly by the walls of the notches 30a.
This type of circumferential notch arrangement is also applicable to a light conducting pipe, as shown in Figure 6. The pipe 32 in Figure 6 is formed with notches 32a at spaced locations along the circumference thereof and in a selected position between axially oppoiste ends. The photoradiator in Figure 6 functions in the same manner as the photoradiator shown in Figure S, except that it reflects the light at both the 2~ inner and outer walls thereof.
In the photoradiator shown in Figure 5 or 6, a lower end wall 30al or 32al of each notch may be inclined radially outwardly with its associated upper end wall 3a2 or 32a2 formed perpendicular to the direction of light propagation as illustrated (to the axis of the light conductor 30 or 32). Alternatively, the upper end wall 3a2 or 32a2 may be oriented substantially parallel to the inclined lower end wall, as indicated by a phantom line in the drawing. Such a set of notches may be located at a nurnber of spaced locations along the direction of light propagation, or the axis of the light conductor. In this case, the radial depth d of the notches may be sequentially increased in the direction of light propayation in order to set up substantially uniform radiation of ~Z64583 lignt along the axis of the light conductor.
Referring to Figure 7, another embodiment of the present invention is shown which has a plurality of light conducting rods (34-38 in the drawing) interconnect~
ed end-to-end in the illustrated order a-ong the direction of light propagation. As sho~n, the rod 36 is ormed with notches 36a so that the inclined walls 36al thereof may effectively diffuse light coming out from the bottom of the rod 34. Likewise, the rod 38 below the rod 36 is formed with notches 38a to diffuse li~ht at the inclined walls 38al thereof. Such a serial inter-connection scheme is applicable to light conducting pipes as well. As shown in Fig~re 8, pipes 40-44 are interconnected sequentially along the direction of light propagation. The pipe 42 has notches 42a with inclined walls 42a1 and the pipe 44, notches 44a with inclined walls 44al.
It will be seen that the diffusion of light attainable with the photoradiator shown in Figure 7 or 8 is as effective as that attainable with the photo-radiator of Figure 5 or 6. NeVertheless, the photo-radiator of Figure 7 or ~ is distinguishable over the photoradiator of Figure 5 or 6 by the easier and more accurate production due to the serial connection of a plurality of light conducting elements which have been individually machined to have the notches.
A modification to the photoradiator of Figure 8 is illustrated in Figure 9~ As shown, the pipe 40 is connected to the pipe 42 by a light conducting rod 46 whose refractive index is larger than that of the pipe 40. Likewise, the pipe 42 is connected to the pipe 44 by another light conducting rod 46. The photoradiator ha~ing such a construction attains efficient transmission of light, since the light transmitted through the bore of any pipe is introduced ~26~5~3 into the annular wall of the adjacent pipe by the rod 46; the pipe walls have a higher light transmission efficiency than air.
Referring to Figures 10-13, other embodiments of the present invention are shown which are commonly designed to diffuse light raidally outwardly to the ambience. In Figure 10, the photoradiator comprises light conducting elements 50 and 52 which are connected end-to-end to each other. The end of the element 50 adjacent to the other element 52 comprises a flat surface 50a, while the end of the element 52 comprises a frustoconical inclined surface 52a which terminates at a flat top 52b. When the light conductors 50 and 52 are assembled together, light propagating through the light conductor S0 will be partly introduced into the follow-ing light conductor 52 and the rest is diffused effectively to the outside by refelection at the inclined surface 5Za while being partly routed into the element 52.
In the photoradiator shown in Figure 10, the inclination angle 0 of the inclinecl surface 52a is variable to steer the light in a desired direction out of the photoradiator. Where the angle ~ is 45 degrees, for example, the light will be radiated perpendicular to the axis of the pilotoradiator if it is parallellight, and over a substantial radiation angle if it is converged light. Also, the ratio in area between the inclined surface 52a and the flat top 52b may be varied to set up any desired ratio between the quantity of light steered to the outside and the quantity of light transmitted to the subsequent light conductor.
In Figure 11, a light conducting element 50' is formed with a frustoconical recess 50'a and a flat surface 50'b which are generally complementary to the contiguous frustoconical surface 52a and flat surface ~Z6~S~3 _9_ 52b of the light condueting element 52, whieh is the same as the element 52 of Figure 10. In this construe-tion, light propagating through the element 50' is partly transmitted to the element 52 via the aligned flat surfaees 50'b and 52b, while tne rest is partly refeleeted outwardly by the inclined surfaces 50'a and 52b and partly transmitted into the element 22. The photoradiator eonstruction shown in Figure 11 is advantageous in that i~ allows the two elements 50' and 52 to be aligned with ease to eaeh other.
In Figure 11, should the interconneeting surfaees of the rods 50' and 52 be eonfigured fully eomplementary to eaeh other, no light would be refelected by the inelined surfaees. It is preferable, therefore, to desposite a semitransparent layer on the inclined surfaee of either one of the rods 50' and 52. Generally, however, it will suffiee to form them approximately complementary so that an air spaee may be defined therebetween to refleet part of the propagatins light at the inelined surfaees.
In Figure 13, the photoradiator comprises a eylindrieal light eondueting element 54 having a flat end 54a, and a light eondueting elemeht 56 having two inelined surfaees 56a and 56b whieh eonverge to a flat top 56e. In this ease, light transmitted through the light conductor 54 will be diffused outwardly in two directions by the inclined surfaces 56a and 56b.
Again, the light eonductor 54 may have its end formed complementary to that of the light conductor 56 as shown in Figure 13. In Figure 13, the element 54' has a recess defined by opposite inelined surfaces 54'a and 54'b and a flat surface 54'c. The construction shown in ~igure 13, like that shown in Figure 11, will promote easy alignment between the two coaetive light conductors 54' and 56.

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While in the embodiment shown in Figure 12 or 13 the opposite inclined surfaces 56a and 56b are assumed to be equal in area to each other, they may be provided with different areas such that a larger quantity of light is reflected by one of them than by the other.
In the extreme case, the configuration may be such that the light is reflected by one inclined surface 60a of a light conducting element 60 as indicated by an arrow A. In this case, light may be supplied from the light conductor 60 into an upper light conductor 58 as indicated by an arrow ~.
Referring to Figure lS, another embodiment of the present invention is shown which is furnished with means for controlling a quantity of light radiation. The photoradiator in Figure 15 comprises a first light conducting element 62, a second light conducting element 64 and a transparent control member 68. Either one of the elements 62 and 64 (64 in this particular e~bodiment) is formed with a recess 64a at an end thereof which connects to the other element. The transparent control member 68 is removably disposed in the recess 64a. As shown, the control member 64 includes a flat surface 68a and an inclined surface 68b.
In this photoradiator construction, light propagating through the light conductox 62 is partly transmitted to the light conductor 64 via the flat surface 68a of the control member 68 and the rest is partly reflected outwardly by the inclined surface 68b while being partly routed into the light conductor 64.
A characteristic feature of the photoradiator shown in Figure 15 is that the quantity of light steered by the inclined surface 68b of tne control member 68 is adjustable by controlling the position of the control member 68 in the recess 64a. Light from the li~ht conductor 62 will be partly reflected by the ~LZ64S~33 inclined surface 68b of the control member 68 as indicated by an arrow A, while light from the light conductor 64 will be reflected by the inclined surface 86b as indicated by an arrow B. Therefore, light may be supplied in either one of the opposite directions as desired.
Another example of the transparent control member is shown in Figure 16. As shown, the alternative transparent control member 70 comprises two inclined surfaces 70al and 7a2 which reflect light from the light conductor 62 (Figure 15) in two different directions, as indicated by arrows A. The position of such a control member is adjustable in the recess 64a (Figure 15) to vary the pro~ortions of the light reflected by the opposite inclined surfaces 70al and 70a2 to each other. Again, only one inclined surface may be formed on the member 70 in the extreme case.
The control member 70, different from the control me~ber 68 of Figure 15, is incapable of reflecting light coming in from the light conductor 64 (Figure lS), since it would reflect it back thereinto at the inclined surfaces 70al and 7a2 as indicated by arrows ~.
It will be apparent that a number of interconnec-tion surfaces each including an inclined surace or surfaces as described may be defined sequentially along the axis of the photoradiator. In such a case, the control member 70 shown in Figure 16 may be installed in the photoradiator in the position shown in Figure 17 to return light reached the last light conductor n, thereby causing more effective radiation of light.
It is necessary then to treat a flat surface 70b between the inclined surfaces 70al and 7a2 to reflect incident light.
Now, assume a simple cylindrical light conducting element 80 as shown in Figures 18 and 19. When parallel ~;4S~3 light Ll is introduced into one end A of the light conductor 80 as shown in Figure 18, it will be radiated from the other end B without any divergenee. When the incident light is converged light as indicated by L2 5 in Figure lg, it will be radiated over a divergence angle a of about 46 degrees. However, sueh a simple eylindrieal light eonduetor suffers from the drawbacks previously discussed. Farther embodiments of the present invention will be deseribe whieh are elaborated 10 to radiate light after varying its optieal property to suit a desired applieation.
~ eferring to Figures 20A and 20Bt the photoradiator ~omprises a light eondueting element 90 whieh is made up of a eylindrieal portion 90a and a frustoconieal lS portion- 90b whieh -extends tapered from the eylindrieal portion 90a. When eonverged light L2 is ineident on an end A of the eylindrieal portion 90a, it will propagate through the light eonduetor 90 while being refleeted by the wall of the eontinuous portions 9Oa and 9Ob.
20 The light output from an end B of the frustoeonieal portion 90b has a substantial divergenee angle due to the N.A whieh has increased during tl~e travel of the light through the frustoeonieal portion 90b. Fringes whieh develop in the light output from the photo-25 radiator 90 will be feasible to speeial decorativeapplications. For more general lighting applications, parallel light Ll may be introdueed into the light conductor 90 as shown in Figure 20B. The light outgoing the light conduetor shown in Figure 20B is substantially 30 identical in optieal property with the incoming light.
Referring to Figure 21A, the photoradiator comprises a light condueting element 92 having a cylindrical portion 92a and a frustoconical portion 92b, and a second light eonducting element 94 having a 35 cylindrical portion 94a and a frustoconical portion 94b.

~Z~;4583 The light conductors 92 and 94 are interconnected at the ends of their frustoconical portions 92b and 94b as illustrated. This type of co~struction eliminates fringes in the light radiated from the photoradiator, since the fringes developed in the light conductor 92 is cancelled in the second light conductor 94. If desired, use may be made of a single piece light conductor 96 as shown in Figure 21B, which is identical in configura-tion with the interconnected light conductors 92 and 94.
Another embodiment of the present invention is shown in Figure 22A which comprises a light conducting element g8 having a cylindrical portion 98a and a frustoconical portion 9~b contiguous with the cylindrical portion 98a, and a second light conducting element 100 having a frustoconical portion lOOa, a cylindrical portion lOOb and a frustoconical portion lOOc~ This is similar to the construction shown in Figure 21A except for the additional conical portion lOOc which, as in the construction of Figure 20A, serves to increase the radiation angle of output light by reflection. Again, the two light conductors 93 and 100 may be replaced with a single light conductor 102 configured generally identical thereto.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Serially arranged cylindrical light conducting rods for propagating light along the axial length of the cylindrical light conducting rods and for reflecting the light laterally outwardly, comprising first and second cylindrical light conducting rods each having a longitudinal axis and each having an outer cylindrical wall, said first cylindrical light conducting rod having a first longitudinal end section, said second cylindrical light conducting rod having a second longitudinal end section, said first longitudinal end section having two inner diverging flat walls and an inner flat end wall, said inner flat end wall having two sides and two ends, said two inner diverging flat walls each having an outer terminating end extending to the longitudinal end of said first longitudinal end section, said two diverging walls diverging as said longitudinal end of said first longitudinal end section is approached, said second longitudinal end section having two outer converging flat walls and an outer flat end wall, said outer flat end wall having two sides and two ends, said two outer converging flat walls each having an outer terminating end which is coincident with said sides of said outer flat end wall, each of said two outer converging flat walls extending to the longitudinal end of said second longitudinal end section, said two converging flat walls each converging as said longitudinal end of said second longitudinal end section is approached, said first and second light conducting rods being disposed in a serial and axially aligned position with said two diverging inner flat walls along with said inner flat end wall being complementarily arranged respectively with said two converging outer flat walls along with said outer flat end wall such that said complementarily disposition of said two diverging inner flat walls with said converging outer flat walls facilitates said axial alignment, whereby light propagating through said first cylindrical light conducting rod is transmitted to said second cylindrical light conducting rod via said inner and outer flat end walls while the rest of the light being propagated is partly reflected laterally outwardly by said two diverging inner flat walls and said two converging outer flat walls and partly transmitted through said two diverging inner flat walls and said two converging outer flat walls into said second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light axially and reflecting the light laterally outwardly thereof.

2. Serially arranged light conducting rods according to claim 1, wherein the area of each of said two diverging flat walls is equal.

3. Serially arranged light conducting rods according to claim 1, wherein the area of each of said two diverging flat walls is different such that one of said two diverging flat walls reflects more light laterally outwardly than the other diverging flat wall.

4. Serially arranged light conducting rods according to claim 1, wherein the area of each of said two converging flat walls is equal.

5. Serially arranged light conducting rods according to claim 1, wherein the area of each of said two converging flat walls is different such that one of said two converging flat walls reflects more light laterally outwardly than the other converging flat wall.

6. Serially arranged cylindrical light conducting rods for propagating light along the axial length of the cylindrical light conducting rods and for reflecting the light laterally outwardly, comprising first and second cylindrical light conducting rods each having a longitudinal axis and each having an outer cylindrical wall, said first cylindrical light conducting rod having a first longitudinal end section, said second cylindrical light conducting rod having a second longitudinal end section, said first longitudinal end section having two inner diverging flat walls and an inner flat end wall, said inner flat end wall having two sides and two ends, said two inner diverging flat walls each having an outer terminating end extending to the longitudinal end of said first longitudinal end section, said two diverging walls diverging as said longitudinal end of said first longitudinal end section is approached, said second longitudinal end section having two outer converging flat walls and an outer flat end wall, said outer flat end wall having two sides and two ends, said two outer converging flat walls each having an outer terminating end which is coincident with said sides of said outer flat end wall, each of said two outer converging flat walls extending to the longitudinal end of said second longitudinal end section, said two converging flat walls each converging as said longitudinal end of said second longitudinal end section is approached, said first and second light conducting rods being disposed in a serial and axially aligned position with said two diverging inner flat walls along with said inner flat end wall being complementarily arranged and aligned respectively with said two converging outer flat walls along with said outer flat end wall and with an air space between the two diverging inner flat walls and said two converging outer flat walls, whereby light propagating through said first cylindrical light conducting rod is transmitted to said second cylindrical light conducting rod via said inner and outer flat end walls while the rest of the light being propagated is partly reflected laterally outwardly by said two diverging inner flat walls and said two converging outer flat walls via said air space and partly transmitted through said two diverging inner flat walls and said two converging outer flat walls via said air space into said second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light axially and reflecting the light laterally outwardly thereof.

7. Serially arranged cylindrical light conducting rods for propagating light along'the axial length of the cylindrical light conducting rods and for reflecting the light laterally outwardly, comprising first and second cylindrical light conducting rods each having a longitudinal axis and each having an outer cylindrical wall, said first cylindrical light conducting rod having a first longitudinal end section, said second cylindrical light conducting rod having a second longitudinal end section, said first longitudinal end section having two inner diverging flat walls and an inner flat end wall, said inner flat end wall having two sides and two ends, said two inner diverging flat walls each having an outer terminating end extending to the longitudinal end of said first longitudinal end section, said two diverging walls diverging as said longitudinal end of said first longitudinal end section is approached, said second longitudinal end section having two outer converging flat walls and an outer flat end wall, said outer flat end wall having two sides and two ends, said two outer converging flat walls each having an outer terminating end which is coincident with said sides of said outer flat end wall, each of said two outer converging flat walls extending to the longitudinal end of said second longitudinal end section, said two converging flat walls each converging as said longitudinal end of said second longitudinal end section is approached, said first and second light conducting rods being disposed in a serial and axially aligned position with said two diverging inner flat walls along with said inner flat end wall being complementarily arranged and aligned respectively with said two converging outer flat walls along with said outer flat end wall, a semitransparent layer disposed between said two diverging inner flat walls and said two converging outer flat walls, whereby light propagating through said first cylindrical light conducting rod is transmitted to said second cylindrical light conducting rod via said inner and outer flat end walls while the rest of the light being propagated is partly reflected laterally outwardly by said two diverging inner flat walls and said two converging outer flat walls via said transparent layer and partly transmitted through said two diverging inner flat wall and said two converging outer flat walls via said transparent layer into said second cylindrical light conducting rod, the serially arranged conducting rods thereby propagating the light axially and reflecting the light laterally outwardly thereof.