Title: Optical element having total reflection
Abstract: An optical element (1) for reflecting and/or redirecting light rays (L1) entering therein and again emerging therefrom consists of a transparent base body (2) which is so structured and/or formed that, with the formation of reflection surfaces (8) bounding the base body (2), at least a part of the light rays (L1) impinging upon the reflection surfaces (8) upon emergence from the transparent base body (2) are totally reflected, and at least one cover body (9) arranged behind the reflection surfaces (8). The reflection surfaces (8), and the surfaces of the cover body or bodies (9) towards the reflection surfaces, are adapted to one another such that between them there remains a thin gap (10) or only point contacts exist.
Patent Number: 6,980,728 Issued on 12/27/2005 to Ladstätter, et al.
| Inventors:
|
Ladstätter; Gerald (Klaus, AT);
Bohle; Markus (Dornbirn, AT)
|
| Assignee:
|
Zumtobel Staff GmbH (Dornbirn, AT)
|
| Appl. No.:
|
714874 |
| Filed:
|
November 18, 2003 |
Foreign Application Priority Data
| May 18, 2001[DE] | 101 24 370 |
| Current U.S. Class: |
385/146; 385/147; 385/901; 362/31; 362/339; 359/592; 359/597; 359/833; 359/837 |
| Intern'l Class: |
G02B 006/10; F21S 011/00 |
| Field of Search: |
359/591,592,597,833,837
385/146,147,901
362/26,31,337,339
|
References Cited [Referenced By]
U.S. Patent Documents
| 3712713 | Jan., 1973 | Appledorn.
| |
| 4519675 | May., 1985 | Bar-Yonah.
| |
| 5839823 | Nov., 1998 | Hou et al.
| |
| 5880886 | Mar., 1999 | Milner.
| |
| 6078426 | Jun., 2000 | Siegfried.
| |
| 6092904 | Jul., 2000 | Tai et al.
| |
| 6169594 | Jan., 2001 | Aye et al.
| |
| 6222689 | Apr., 2001 | Higuchi et al.
| |
| 6224223 | May., 2001 | Higuchi et al.
| |
| 6523980 | Feb., 2003 | Sejkora et al.
| |
| Foreign Patent Documents |
| 19622670 | Dec., 1997 | DE.
| |
| 19637199 | Mar., 1998 | DE.
| |
| 19923225 | Nov., 2000 | DE.
| |
| 0800035 | Oct., 1997 | EP.
| |
Primary Examiner: Ullah; Akm Enayet
Assistant Examiner: Petkovsek; Daniel
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This is a Continuation of International Application PCT/EP02/05491 filed May
17, 2002, which in turn claims priority of German Application No. 101 24 370.7
filed May 18, 2001, the priorities of which are hereby claimed, said International
Application having been published in German, but not in English, as WO 02/095290
A1 on Nov. 28, 2002. The disclosure of that International Application PCT/EP02/05491
is hereby incorporated by reference in its entirety, as if fully set forth herein.
Claims
1. An optical element for reflecting and/or redirecting light rays entering therein
and again emerging therefrom, said optical element comprising:
a transparent base body which is so structured and/or formed that, with the formation
of reflection surfaces bounding the base body, at least a part of the light rays
impinging upon the reflection surfaces upon emergence from the transparent base
body are totally reflected; and
at least one cover body having cover body surfaces arranged behind the reflection
surfaces,
said base body and said at least one cover body being of materials which do not
react with each other and,
the reflection surfaces and the corresponding cover body surfaces providing between
them a microscopic gap which results from applying, while in the liquid state,
one of said base body and said at least one cover body to the other while in the
liquid state.
2. An optical element according to claim 1 wherein,
the base body comprises a plate-like base part, one side of which is occupied
by microprisms which taper, starting from their roots, with the formation of depressions,
whereby the side surfaces of the microprisms form the reflection surfaces and the
cover bodies fill the depressions between the microprisms.
3. An optical element according to claim 2 wherein,
said microprisms have upper sides which are covered by a transparent plate which
is of the same material as the base body and which is connected to the base body
to form one piece.
4. An optical element according to claim 2 wherein,
said one side of the base body is completely covered over by the cover body.
5. An optical element according to claim 2 wherein,
said body is plate-like.
6. An optical element according to claim 2 wherein,
said body is curved.
7. An optical element according to claim 1 wherein
at least one light emitting diode is arranged within the transparent base body.
8. An optical element according to claim 1 wherein,
said at least one cover body is reflective.
9. An optical element according to claim 1 wherein,
said at least one cover body applied to said base body by means of casting or
injection molding or injection compressing.
10. An optical element according to claim 1 wherein,
said transparent base body and said at least one cover body are of different
materials.
11. An optical element according to claim 10 wherein,
said base body and said at least one cover body are of materials which do not
connect said bodies but instead define an air gap between them.
12. An optical element according to claim 1 wherein,
the transparent base body and/or said at least one cover body are of plastic.
13. An optical element according to claim 12 wherein,
the transparent base body is of polymethylmethacrylate (PMMA).
14. An optical element according to claim 12 wherein,
said at least one cover body is of polyoxymethylene (POM).
15. An optical element according to claim 12 wherein,
said at least one cover body is of polypropylene (PP).
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element for reflecting and/or redirecting
light rays entering into it and then exiting from it, wherein the redirection or
reflection is effected by means of a total reflection.
2. Description of the Related Art
Such an optical element is described for example in DE 199 23 255 A1 and illustrated
in FIG.
7. This known optical element
100 consists of a plate-like
base part
101 which at its upper side is occupied by a plurality of microprisms
102, which taper from their roots forming notches
103. The form of
these microprisms
102 is such that light rays which enter into them from
the upper side are totally reflected at the side walls
104, which has the
consequence that the light rays leave the substantially flat light exit surface
105 of the optical element
100 only in a certain angular range. Due
to this restriction of the light exit angle, light passing through this optical
element
100 is perceived by an observer as dazzle-free.
However, an anti-dazzle effect takes place only for such light rays as enter
via the upper side into the microprisms
102. In contrast, light which initially
enters into the notches
103 and some time later enters info the optical
element
101 is not rendered dazzle-free through the total reflection and
is therefore undesired. For this reason, with the illustrated known optical element
there is provided an additional cover element in the form of a grid
106
which is applied to the upper side of the optical element
100 and has light
permeable regions
107 and light absorbing or reflecting regions
108.
The arrangement of the light permeable and light absorbing regions
107 and
108 thereby corresponds to the arrangement of the microprisms
102
and notches
103, so that a light entry into the notches is prevented. In
this way it is ensured that solely dazzle-free light leaves optical element
100
at its light exit side
105.
The production and arrangement of such a grid
106 is possible when the
spacings between the microprisms
102 are sufficiently large, that is for
example in the millimeter or centimeter range. However, the tendency is towards
size reduction of the microprisms themselves and therewith also the spacings between
them. Through this, however, it is ever more difficult to produce and arrange an
exactly fitting cover grid in particular because, through heating, tolerances can
become effective to such a degree that the functioning of the cover is prevented.
A similar problem arises with the light guide element known from U.S. Pat. No.
6,092,904. This consists of a flat transparent light guide body which has on one
flat side a prism-like structure which is supposed to couple light rays out of
the light guide element using total reflection. In order to make the total reflection
possible, on its side having the prism structure the light guide body is covered
over by a so-called compensation body which has a form complementary to the structure
of the prisms and, with the aid of spacers, is slightly offset to the light guide
body. Through this a thin gap is formed between the light guide body and the compensation
body, which makes possible the total reflection at the side surfaces of the prisms.
Thereby, the spacers are either separate elements which are applied before the
light guide body and the compensation body are brought together, or are already
formed on the compensation body, which can for example be produced in an injection
molding process, in the production of the compensation body.
Also in the case of this known light guide element, for maintaining the total
reflection it is of substantial significance that the light guide body and the
compensation body are matched exactly to one another. If this is not the case,
the provision of the gap necessary for the total reflection can no longer be ensured
and the optical properties of the light guide element deteriorate. There again
arises, however, the problem that the exactly matching production of light guide
body and compensation body is ever more difficult and complex the smaller are the
prism structures chosen to be.
From DE 196 37 199 A1 it is further known to fill the free space located between
two totally reflecting surfaces of a light redirecting element with a powdery separation
material. Although this separation material prevents the two reflecting surfaces
coming directly into mutual contact during the production of the light redirecting
element, it is problematic for the later employment of the light redirecting element.
The free space filled by the separation material must later still be covered in
order to prevent that the separation material later falls out again. Further, the
powdery separation material does not form a homogeneous light-impermeable body
which would completely prevent light entry at the notches of the light redirecting element.
SUMMARY OF THE INVENTION
It is thus the object of the present invention to provide a simpler and more
economical
possibility to prevent light entry into the notches. In particular is should be
ensured that the free space next to the reflection surfaces, necessary for total
reflection, is reliably maintained. At the same time there should be provided a
certain protection for the sensitive outer surfaces of the microprisms.
The object is achieved by means of an optical element which distinguishes itself
in that it is of a transparent base body which, with the formation of reflection
surfaces, is so structured or formed that at least a part of the light rays incident
upon the reflection surfaces on exiting from the transparent base body are totally
reflected. Further, there is provided at least one cover body arranged behind the
reflection surfaces, whereby the reflection surfaces and surfaces of the cover
body or bodies towards the reflection surfaces are so adapted to one another that
there remains between them a thin gap or only point contacts arise, wherein the
cover body or bodies are applied to the base body, in accordance with the invention,
in the liquid state
The solution in accordance with the invention thus consists, analogously to U.S.
Pat. No. 6,092,904, first not in covering the notch openings with a grid but instead
to cover over at least those surfaces which are employed for total reflection and
this in such a manner that in substance a thin gap remains. Due to this thin gap
between the reflection surfaces and the cover body it remains ensured that also
the desired total reflection continues to occur. Beyond this, the cover offers
a protection which prevents a scratching or contamination of the reflection surfaces.
However, in accordance with the present invention, the covering over of
the reflection surfaces is effected in a substantially simpler manner in that the
cover body or bodies are applied to the base body in the liquid state. Thereby
it is to be taken into consideration that the material of the transparent base
body should not react with the cover material, since otherwise wide area connections
between the transparent body and the cover material could arise at the reflection
surfaces, with the consequence that the total reflection capability is lost. If,
in contrast, suitable materials are employed there arises automatically a microscopic
gap which gives rise to the total reflection. For example, for the case that the
transparent base body is of polymethylmethacrylate (PMMA), there can be employed
as cover material polyoxymethylene (POM) or polypropylene (PP).
The invention also relates to a method to which the advantages likewise apply.
Further developments of the invention are also disclosed and claimed herein.
Thus, for the case that the base body is formed by means of a plate-like base
part with microprisms, it can be provided to cover not only the reflection surfaces
but in general to completely fill the notches arranged between the microprisms
with a cover body, in order through this to prevent light entry. This is in particular
simple to carry out when at least the cover material is of plastics, since in this
case the application can be effected in the liquid state, for example by means
of injection molding.
In accordance with a further development or a further embodiment of the invention
the upper side of the microprisms may be covered with a further transparent plate,
which is of the same material as the base body and connected in one piece with
the latter. This can be achieved in that after-the filling of the notches with
the cover material a further layer of the material of the transparent base body
is applied, which enters into a connection with the microprisms but not, however,
with the cover bodies. An optical element configured in this way is preferentially
suitable, when it has the form of a plate or pane, for a lateral or narrow side
light entry and a light exit directed transversely thereto, in particular offset
by in substance 90°, which in the case of a pane or plate is arranged on the
broad side.
The known optical element illustrated in FIG. 7 serves as a so-called light guide
element with which the light of a light source enters into the element via a light
entry surface and leaves it again via a light exit surface. Further, with a suitable
configuration of the microprisms such an element can also be employed as a reflector,
wherein the light entry surface and the light exit surface are identical and a
total reflection takes place at the oppositely lying microprisms. Also for this
case, the covering over of the reflection surfaces with a cover material in accordance
with the invention is of advantage, since the sensitive reflection surfaces are
protected from external influences. There arises here the possibility of covering
over the entire side of the transparent base body which has the microprisms with
the cover material.
Beyond this, the cover material can also be employed to lend the reflector
the necessary stability, insofar as the transparent base body itself does not manifest
sufficient stability. There is for example the possibility of forming the transparent
base body by means of a flexible foil which on one side has a microprism structure.
If the foil is brought into a form corresponding to the reflector and then covered
with the cover material, after the setting of the cover material the reflector
has a sufficient stability. Through this the possibility is provided of producing
even complex reflector forms in a simple and rapid manner.
Finally, the optical element in accordance with the invention can also be
so configured that there is arranged within the transparent base body a light source,
for example a light emitting diode. Through the transparent base body there is
then formed a reflector which bundles the light emitted from the light source exclusively
by means of total reflection.
BRIEF DESCRIPTION OF THE DRAWINGS
Below, the invention will be described in more detail with reference to the
accompanying drawings.
FIG. 1 depicts a first exemplary embodiment of an optical element in accordance
with the invention;
FIG. 2 depicts a further development of the optical element illustrated in FIG.
1 or a second embodiment of the optical element;
FIG. 2
a depicts an end face of the optical element according to FIG.
2, which is supplemented to become a luminaire;
FIG. 3 depicts a further exemplary embodiment of an optical element in accordance
with the invention, which serves as reflector;
FIGS. 4
a-d depict the individual steps of a method for the production
of a reflector in accordance with the invention;
FIG. 5 depicts a further exemplary embodiment of an optical element in accordance
with the invention, for forming a light emitting diode arrangement;
FIG. 6 depicts a further exemplary embodiment of an optical element in accordance
with the invention, for bundling the light of a light emitting diode; and
FIG. 7 depicts a known optical element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first embodiment of an optical element
1 in accordance with the invention
illustrated in FIG. 1 corresponds to the optical element known from FIG.
7.
It is likewise of a transparent base body
2, which is formed by means of
a plate-like base part
3 the underside
4 of which forms the light
exit surface of the optical element
1. On the side of the base part
3
opposite to the light exit side
4 there are a plurality of microprisms
5
which taper starting from their roots, so that there arise notches
6 between
the microprisms
5.
The function of the microprisms
5 consists in that a light ray entering
into the transparent base body
2 at their upper side
7 exits the
light exit surface
4 within a predetermined angular range. The directing
of the light is thereby effected by means of total reflection at the side surfaces
of the microprisms, as is illustrated by the example of light ray L
1. For
this purpose the transparent base body
2 consists of a material having a
refractive index which is greater than the refractive index of air. The two refractive
indices determine a total refraction angle, whereby light rays which wish to leave
the base body
2 at an angle which is greater than the total reflection angle
are reflected.
Total reflection of the desired kind for the functioning of the optical element
1 takes place, however, only for light rays which enter into the base body
2 via the upper, sides
7 of the microprisms
5. For this reason
it must be prevented that light rays can also enter the base body
2 via
the notches
6 lying between the microprisms
5. In contrast to the
known optical element illustrated in FIG. 7, no cover network is provided; instead
in the case of the exemplary embodiment according to the invention illustrated
in FIG. 1 the notches
6 are completely filled by cover bodies
9.
The material of the cover bodies
9 is in the illustrated example formed
to be reflecting, so that light rays incident on this are reflected, as is the
case for example with the light ray L
2.
Beyond this, the cover bodies
9 offer protection for the reflection
surfaces
8 of the microprisms
5 so that the danger does not arise
that these could be contaminated or scratched. In accordance with the invention,
however, the cover bodies
9 are of a material which does not contact with
the material of the base body
2 or only forms point contacts. Preferably,
the base body
2 on the one hand and the cover bodies
9 on the other
hand are of different materials or of materials with different refractive indices.
Through this there arises a microscopic gap
10 between the side walls of
the base body
2 and of the cover bodies
9, which ensures that the
total reflection angle arising between the base body
2 and air remains unchanged.
This thus means that through the filling of the notches
6 with the cover
bodies
9 the desired effect of total reflection is not affected.
The base body
2 is preferably of plastics, for example of polymethylmethacrylate
(PMMA) and thus can be produced in a simple manner for example by means of injection
molding. Also for the cover material there is preferably employed a plastics, for
example polyoxymethylene (POM) or polypropylene (PP). These two materials make
no connection—as desired—with the polymethylmethacrylate (PMMA) of
the base body
2, so that the gap
10 in accordance with the invention
arises. Beyond this, these materials can be liquefied and thus likewise applied
into the notches by means of injection molding.
A method for the production of the optical element illustrated in FIG. 1 may
for
example consist in first producing the transparent base body
2 by means
of injection molding and then, as soon as the base body
2 has sufficiently
hardened, filling the notches
6 with the cover material. The filling of
the notches
6 or the production of the cover bodies
9 can be effected
by means of liquid application of the material of the cover bodies
9, in
particular plastics, for example by means of casting on, injection molding or injection
compressing. A two-component injection molding or injection compressing is likewise
advantageous. In the case of injection compressing, after the injection of the
material in a manner known per se, the pressure in the mold chamber of the associated
mold is increased, for example by means of a slight reduction of the mold volume,
through which the material is pressed into the notches
6 with everywhere
uniform pressure. This method of producing the optical element
1 is substantially
more simple to carry out than the covering of the notches
6 with a cover grid.
FIG. 2 shows a further development of the exemplary embodiment shown in FIG.
1 or a further exemplary embodiment and is concerned with a problem that occurs
likewise with the optical element described in DE 199 23 225 A1. With the known
optical element there is provided an additional transparent covering of the upper
side of the microprisms, which is applied with the aid of a transparent adhesive
medium. The difficulty here lies in the attainment of a homogenous connection between
the upper sides of the microprisms and the covering. Through the employment of
the adhesive medium inhomogeneities and gaps can arise, through which the optical
properties of the overall element are impaired.
With the exemplary embodiment illustrated in FIG. 2 the upper sides of the microprisms
5 are likewise provided with a transparent covering
11 in particular
in the form of a plate, whereby however, this covering
11 is of the same
material as the base body
2 and is connected with this in one piece. This
is attained in that, as already described above with reference to FIG. 1, first
the base body
2 consisting of the base part
3 and the microprisms
5 is formed, for example by means of injection molding. In a second step
the notches
6 located between the microprisms
5 are then filled with
the cover material in order to form the cover bodies
9. In a subsequent
step, the upper side is in turn then covered with the material of the base body
2, whereby the transparent plate
11 formed in this manner homogeneously
connects with the microprisms
5, whilst on the other hand no connection
occurs between the transparent plate
11 and the cover material. The cover
bodies
9 are thus completely enclosed by the transparent material of the
base body
2 and of the covering
11 with the formation of microscopic
gaps
10. The application of the plate
11 or covering can likewise
be effected by means of casting, injection molding or injection compressing.
With this, the present invention offers the possibility of producing such optical
elements in a simple and rapid manner. In comparison with the known elements the
optical properties can further be significantly improved, since no interfaces arise
at which undesired light scattering can occur. Without the employment of a glue
or the like there can be attained here a one-piece and homogenous connection between
the base body
2 and transparent plate
11. The chain line illustrated
in FIG. 2 is intended merely to make more clear that the material for the transparent
plate
11 is first applied at a later point in time.
Such an optical element
1 is suitable in particular also for applications
in which light is introduced laterally or at the narrow side into the transparent
covering
11 and in substance so redirected by means of total reflection
in the optical element that it emerges at the underside, in particular the broad underside.
FIG. 2
a shows by example the left end region of a luminaire in the case
of which the optical element
1 is a so called light guide plate. Before
the narrow side end face
11a of the transparent covering
11
there is arranged a light source
11b which irradiates the light into
the face
11a. For improved exploitation of the light source
11b
there may be arranged on the side of the light source
11d away
from the covering
11a reflector
11c which reflects
the light into the end face
11a. The end face
11a thus
forms a light entrance
11d. The end surface region
2a of
the body
2 can; if appropriate, be light permeably covered over so that
the light of the light source
11b is irradiated only into the light
entrance
11d. As covering
2b there may serve for example
a light non-permeable layer or a frame, which may be constituted as holder for
the optical element
1. The frame may have, for example on the inside and
preferably on the underside, a carrier limb
2c on which the optical
element
1 may lie. The light source
11b and/or the reflector
11c may also, if appropriate, be held on the frame. The frame can
also serve for the mounting of the thus formed luminaire, for example as a surface-mounted
luminaire or as a suspended luminaire. The light source
11b is preferably
a tube, in particular a fluorescent tube, extending longitudinally of the end face
11a.
The opposite end region of the light may be formed correspondingly to the above-described
end region.
The narrow sides of the transparent covering
11 which do not serve for
light entry can be covered over in a light non-permeable manner, for example by
means of a corresponding coating. Correspondingly, also the upper side of the transparent
covering
11 and the narrow side of the base body
2 may be covered.
The optical element
1 is not restricted to the functional disposition
described above and illustrated in the drawings according to FIGS. 1,
2
and
2a, in which the light is emitted at the underside. Within the
scope of the invention it is also possible to arrange the optical element
1
on edge, so that it can for example serve as an emission element for a wall luminaire
or serve as another kind of light display.
With regard to the two exemplary embodiments illustrated in FIGS. 1 and 2 it
is to be noted that the microprisms
5 can in principle take any form suitable
for attaining the desired directing of light. The covering of the reflection sides
with the cover material in accordance with the invention has no influence on the
form of the microprisms
5 since the total reflection takes place at the
transition between the material of the transparent base body and the air located
in the gap. The optical properties of the cover material are of no significance
for this. Correspondingly there arises the possibility to employ as cover material
a material which is reflecting, absorbing or even colored. The optical element
can also be employed as a light guide element, whereby the light is coupled into
the light guide element laterally and coupled out perpendicularly thereto.
FIG. 3 shows a further exemplary embodiment of the optical element in accordance
with the invention which is now, however, employed as a reflector. The optical
element
21 again is of a transparent base body
12 in the form of
a plate-like base part
13 with microprisms
15 arranged thereon. The
underside
14 of the base part
13 now, however, forms the light entry
and light exit surface. A light ray L
3 entering the transparent base body
12 from the underside is twice reflected at the side surfaces of the saw-tooth
like microprisms
15 so that it again leaves the base body
2 at its
underside
14.
The upper side of the transparent body
12 is completely covered over with
a cover body
19, which again enters into no connection or only point connection
with the material of the base body
12, so that between the cover body
19
and the microprisms
15 there arises a microscopically thin air gap
20.
This means that also in this exemplary embodiment the reflection at the side walls
18 of the microprisms
15 arises through total reflection. The function
of the cover body
19 consists in this case primarily in protecting the outer
surface of the microprisms
15 from external influences. The reflection occurs
solely through the form of the transparent base body
12 which is for example
employable as a so-called retro-reflector such as is put to use for example in
a cat's eyes.
Beyond this, through the selection of the cover material also the optics of
the reflector can, however, be altered. For example the cover material may be constituted
to be reflecting, in order to again increase the reflection properties. This is
possible because total reflection only arises when the angle between the light
ray and the totally reflecting surface fulfils certain conditions. Outside this
angular range the light can, as before, leave the transparent body
12 at
its upper side. On the other hand, there arises the possibility that light incident
on the microprisms
15 from the upper side can again emerge at the underside
14 of the base body
12. In order to prevent this, the cover body
19 may for example be of a white material and thus diffusely return the
light. On the other side there can also purposively be employed a transparent material
as cover material, if a reflector with through-light characteristics is to be attained.
The production of the reflector can be effected in the same manner as the production
of the optical element illustrated in FIG.
1. Alternatively thereto, there
arises however also the possibility of first forming the cover body
19,
for example again by means of injection molding, and then applying the transparent
material for the base body
12. Finally, it would also be conceivable to
produce the base body and the cover body initially separately from one another
and only subsequently to bring them together to the illustrated arrangement.
The cover body in accordance with the invention can beyond this also provide
for the necessary stability of the optical element, as will be explained with reference
to FIGS. 4
a-d. These Figures show a plurality of steps of a particularly
simple method for producing a reflector.
As starting material for the reflector there is employed a transparent flexible
foil
32, which later forms the transparent base body. This foil has a flat
light entry and light exit side
34, and a structured surface lying opposite
thereto with microprisms
35. The microprisms
35 have the same form
as the microprisms illustrated in FIG.
3 and are again intended to provide
for a total reflection of light rays which enter into the foil from the underside
34.
The foil
32 has no self-stability and is thus in a first step, illustrated
in FIG. 4
b, applied onto a shaping body
41, the outer contour of
which corresponds to the desired reflector shape. The smooth underside
34
of the foil
32 thereby comes to bear against the upper side of the shaping
body
41.
In a following step (FIG. 4
c) the upper side of the foil
32 is
then
covered with a cover material
39, which in accordance with the invention
enters into no chemical connection with the foil
32, so that at the upper
sides of the microprisms
35 again the microscopically thin gap
40
arises. The settable cover material may be for example sprayed on or cast on.
In a final step (FIG. 4
d), after the hardening of the cover material to
a cover body
39, the total arrangement is then removed from the shaping
body
41, so that a reflector
31 is formed which is constituted like
the reflector described in FIG.
3. The solidified cover body
39 hereby
provides for a sufficient stability.
With the method just described, complicated reflector shapes can also be produced
in a simple and rapid manner. In particular it is substantially simpler to produce
a flexible foil and then bring it to the desired shape, than to form from the start
a curved transparent base body, which has a microprism structure on its upper surface.
A further field of application for the optical element in accordance with the
invention
is illustrated in FIG.
5. This FIG. 5 shows a light emitting diode arrangement
62 which is of a plurality of LED chips
63 arranged on a board
61.
If a plurality of such LEDs
63 are arranged on a board
61, overall
a sufficiently high light intensity can be attained so that such a light emitting
diode arrangement
62 can also be put to use for illumination purposes. For
reasons of process economy, however, the light emitting diodes
63 are preferably
arranged without housings; that is, only the light emitting chip (the so-called
die) is attached to the board
61. Despite this it is desired to bundle the
light rays emitted from the light emitting diodes
63, whereby the application
of individual reflectors for this purposes would however be extremely complex.
The exemplary embodiment of the optical element in accordance with the invention
illustrated in FIG. 5 is suitable for bundling the radiation of the light emitting
diodes
63. For this purpose, the light emitting diodes are arranged within
a bell-shaped transparent body
55, the form of which corresponds to the
form of a suitable reflector. In order thus to attain the same effect as with a
reflector it is necessary again to so configure the transparent base body
55
that light rays incident on its side walls
58 are reflected, as is illustrated
by way of example by the light ray L
4.
As also in the exemplary embodiments of FIGS. 1-4 the reflection is effected
thus
by means of total reflection which is ensured in that the transparent base body
55 is surrounded by air—more precisely is again surrounded by an air
gap
60. This is achieved in that the free space
56 between the bell-like
transparent base bodies
55 is filled with cover material which enters into
no connection with the material of transparent bodies
55, so that again
a microscopic gap
60 arises for ensuring total reflection.
The production of the light emitting diode arrangement
62 occurs preferably
in the following manner. After the arrangement of the LEDs
63 on the board
61, there are first applied to the board
61 the pyramid-like elevations
59 which are of the cover material, for example by means of gluing or the
like. In a subsequent step, the overall arrangement is then covered over with the
transparent material, so that this provides the illustrated arrangement. This process
also distinguishes itself in that a per se relatively complicated structure can
be produced through few and simple process steps. In particular the method in accordance
with the invention offers the possibility of forming undercuts.
The last exemplary embodiment, illustrated in FIG. 6, is concerned likewise with
the problem of the, arrangement of light emitting diodes for illumination purposes.
Here, a light emitting diode
83 is first cast into an again bell-shaped
transparent plastics body
72, which at the same time is to serve as reflector
for the light rays L
5 emitted from the light emitting diode. At its underside
the plastics body
72 further has an oblique extension part
76 through
which the exiting light is again laterally deflected so that through this the rays
can be purposively directed into a desired direction.
The holding of the plastics block
72 is effected by means of a carrier
layer
79 of the cover material, into which the transparent plastics block
79 is cast. Again, the transparent block
72 and the holder
79
are of materials which enter into no intimate connection so that correspondingly
a thin air gap
80 forms between the plastics block and the holder
79.
This has on the one hand the consequence that the light rays emitted from the LED
83 and incident on the wall of the plastics block
72 are totally
reflected, beyond this, the plastics block
72 and therewith the extension
part
76 can be subsequently rotated with respect to the holder
79.
Through this, there arises the possibility of subsequently making a change of the
direction in which the light is to be emitted.
The present invention distinguishes itself in that optical elements with excellent
optical properties can be achieved which are suitable for a plurality of possible
applications. Beyond this, these optical elements can be produced in a simple and
economical manner. Even complicated structures, which would be difficult to achieve
with conventional methods, are possible without great effort.
*
