U.S. patent application number 09/136995 was filed with the patent office on 2001-07-19 for non-lambertian glass diffuser and method of making.
Invention is credited to SAVANT, GAJENDRA D..
Application Number | 20010008681 09/136995 |
Document ID | / |
Family ID | 22475352 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008681 |
Kind Code |
A1 |
SAVANT, GAJENDRA D. |
July 19, 2001 |
NON-LAMBERTIAN GLASS DIFFUSER AND METHOD OF MAKING
Abstract
A glass diffuser is fabricated by first producing a metal shim
submaster or other high temperature resistant diffuser having a
surface relief structure on one surface. A glass substrate material
is heated to a suitable temperature and at least one exposed
surface is thereby softened to a desired degree. The submaster
diffuser, and particularly the surface relief structure, is then
placed in contact with the exposed and softened glass substrate
material in order to replicate the surface relief structure in the
glass material. The submaster diffuser and the glass substrate are
separated and then the glass is allowed to cool to form a glass
diffuser.
Inventors: |
SAVANT, GAJENDRA D.;
(TORRANCE, CA) |
Correspondence
Address: |
ANDREW J NILLES
NILLES & NILLES
777 EAST WISCONSIN AVENUE
SUITE 2000
MILWAUKEE
WI
532025345
|
Family ID: |
22475352 |
Appl. No.: |
09/136995 |
Filed: |
August 20, 1998 |
Current U.S.
Class: |
428/156 ;
65/102 |
Current CPC
Class: |
C03B 23/0302 20130101;
Y10S 428/913 20130101; C03B 2215/44 20130101; G02B 5/0268 20130101;
Y10T 428/24479 20150115; C03B 2215/41 20130101; G02B 5/0278
20130101; G02B 5/021 20130101; C03B 11/06 20130101; C03B 11/082
20130101 |
Class at
Publication: |
428/156 ;
65/102 |
International
Class: |
B32B 003/26; C03B
023/00 |
Claims
What is claimed is:
1. A method of making a glass optical element, the method
comprising the steps of: providing a optical element having an
optical surface relief structure on one side; preparing a heated
glass substrate material having an exposed first surface, the glass
substrate material heated to a temperature sufficient to soften at
least the first surface; contacting the first surface of the glass
substrate material with the surface relief structure of the optical
element for a predetermined time period; applying a pressure
forcing the optical element and the glass substrate material
against one another for at least a portion of the predetermined
time period to substantially replicate the surface relief structure
in the first surface of the glass substrate material; releasing the
pressure; separating the optical element and the glass substrate
material; and cooling the glass substrate material.
2. The method according to claim 1, wherein the step of providing
further comprises the step of: forming a holographic surface
structure as the surface relief structure on the one side of the
optical element.
3. The method according to claim 1, wherein the step of providing
further comprises the steps of: creating a holographic surface
structure in a photoresist medium carried on a substrate body;
coating the photoresist medium with a layer of silver material
replicating the holographic surface structure in the silver
material layer; electroplating the silver material layer with a
nickel material layer; and removing the nickel and silver layers
from the photoresist medium to form a metal shim as the optical
element having the holographic surface structure as the surface
relief structure.
4. The method according to claim 1, wherein the step of preparing
further comprises the steps of: preparing a softened glass material
from a molten glass during its manufacture as the glass substrate
material; and exposing a surface of the softened glass material to
define the exposed first surface.
5. The method according to claim 1, further comprising the steps
of: preparing a softened glass material from a molten glass during
its manufacture as the glass substrate material; contacting an
exposed surface of the softened glass material with the master
optical element; and separating the optical element from the
softened glass material prior to cooling the softened glass.
6. The method according to claim 1, wherein the step of preparing
further comprises the steps of: providing a glass plate substrate;
and placing the glass plate substrate in a heated furnace.
7. The method according to claim 1, wherein the step of preparing
further comprises the steps of: providing a direct heat source; and
exposing at least the exposed first surface of the glass material
substrate to the heat source.
8. The method according to claim 1, wherein the step of preparing
further comprises the step of: providing a glass plate substrate;
and heating at least the exposed first surface with an oxyacetylene
flame.
9. The method according to claim 1, further comprising the step of:
placing the glass substrate material on the surface relief
structure of the optical element prior to the step of
contacting.
10. The method according to claim 1, further comprising the steps
of: placing the optical element on a support surface; and placing
the glass substrate material on the surface relief structure of the
optical element prior to the step of contacting.
11. The method according to claim 1, wherein the step of contacting
further comprises the steps of: positioning the glass substrate
material over the surface relief structure of the optical element;
and lowering the glass substrate material into contact with the
optical element.
12. The method according to claim 1, wherein the step of contacting
further comprises the steps of: positioning the glass substrate
material over the surface relief structure of the optical element;
and raising the optical element into contact with the glass
substrate material.
13. The method according to claim 1, wherein the step of contacting
further comprises the steps of: positioning the optical element
over the glass substrate material; and lowering the optical element
into contact with the glass substrate material.
14. The method according to claim 1, wherein the step of applying
pressure further comprises the steps of: providing a pressure plate
connected to a drive cylinder; placing the optical element and the
glass substrate material adjacent one another beneath the pressure
plate; and operating the drive cylinder to force the pressure plate
against one of the optical element and the glass substrate
material.
15. A glass light diffuser produced by a process comprising the
steps of: providing an optical diffuser having an optical surface
relief structure on one side; preparing a heated glass substrate
material having an exposed first surface, the glass substrate
material heated to a temperature sufficient to soften at least the
first surface; contacting the first surface of the glass substrate
material with the surface relief structure of the optical diffuser
for a predetermined time period; applying a pressure forcing the
optical diffuser and the glass substrate material against one
another for at least a portion of the predetermined time period to
substantially replicate the surface relief structure in the first
surface of the glass substrate material; releasing the pressure;
separating the optical diffuser and the glass substrate material;
and cooling the glass substrate material.
16. A glass optical element comprising: a unitary body structure
made from a glass material having at least one optical surface; and
an optical surface relief structure replicated onto the at least
one optical surface from a optical element.
17. The glass optical element according to claim 16, wherein the
glass material is selected from a group of glass materials
comprising borosilicate, light flint, brown flint, brown, flint,
light barium brown and fused glass.
18. The glass optical element according to claim 16, wherein the
glass material is comprised of a composite glass.
19. The glass optical element according to claim 16, wherein the
glass material is a semi-transparent glass material.
20. The glass optical element according to claim 16, wherein the
surface relief structure is a holographic surface structure.
21. The glass optical element according to claim 16, wherein the
surface relief structure is a light diffusing surface capable of
producing a light output of a desired characteristic.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to optical elements,
and more particularly to a non-Lambertian glass diffuser replicated
from a master diffuser for use in active lighting applications.
[0003] 2. Description of the Related Art
[0004] Methods for manufacturing and replicating optical components
utilizing a master and one or more submasters to achieve a final
diffuser product having desired light diffusing characteristics are
well known. In many of these methods, the creation of the first
generation submaster from the master destroys the master rendering
it unavailable for later use. There are also other methods of
making a replica of a master which contains optical features
identical to that of the master without destroying the master.
These other methods are described in one or more pending U.S.
applications, referenced below, which are assigned to the assignee
of the present invention. However, with each of these methods, the
submasters are each made from materials which are not significantly
durable or suitable for use under high temperature conditions.
[0005] The specific embodiments described below regarding the
rubber submaster and the silver and nickel submaster are disclosed
in co-pending U.S. application Ser. No. 09/052,586 entitled "Method
of Making Replicas While Preserving Master," commonly assigned to
the assignee of the present invention.
[0006] One such method involves recording optical features on a
photosensitive medium using coherent or incoherent light. The
photosensitive medium is then further processed to create a master
optical product. A layer of two part silicone epoxy is poured over
the master to replicate the optical surface features of the master
photosensitive medium in the silicone material. The silicone epoxy
layer gets cured at room temperature and becomes rubber. The
silicone material is then cured further and separated from the
master to obtain a silicone submaster. The soft silicone submaster
is then used to make successive generations of submasters or final
optical products by covering the soft submaster with a layer of
epoxy, covering the layer of epoxy with a plastic substrate, curing
the epoxy and separating the epoxy and plastic substrate from the
submaster.
[0007] Another method of creating a submaster for an optical
product involves coating the recorded and developed photosensitive
medium master discussed above with a layer of silver instead of
silicone. A layer of nickel is electroplated onto the silver layer
and then the silver layer and layer of nickel are removed from the
photosensitive material or medium to form the submaster. The
combined silver and nickel backing form a metal shim submaster
which is then used to create final optical products by embossing
the surface features of the submaster into epoxies, plastics or
polycarbonate materials, or by injection molding such materials
into a mold carrying the submaster.
[0008] One significant shortcoming with each of these methods is
that the final optical products created from the submasters are
made from relatively non-durable materials such as plastics,
epoxies, or polycarbonate composites. These materials are not
suited for use near extremely high temperature light sources and
are also not well suited for use outdoors under exposure to
cyclical or extreme environmental conditions.
[0009] Other commonly assigned U.S. patents and pending
applications disclose somewhat related methods for making and
recording optical products and replicating those products so that
they may be mass produced. For example, U.S. Pat. No. 5,365,354
entitled "Grin Type Diffuser Based on Volume Holographic Material",
U.S. Pat. No. 5,534,386 entitled "Homogenizer Formed Using Coherent
Light and a Holographic Diffuser", and U.S. Pat. No. 5,609,939
entitled "Viewing Screen Formed Using Coherent Light", all owned by
the present assignee relate to methods for recording and
replicating optical products. Each of these U.S. patents is
incorporated herein by reference for purposes including, but not
limited to, indicating the background of the present invention and
illustrating the state of the art.
[0010] Related U.S. patent applications include Ser. No. 08/595,307
entitled "LCD With Light Source Destructuring and Shaping Device",
Ser. No. 08/601,133 entitled "Liquid Crystal Display System with
Collimated Backlighting and Non-Lambertian Diffusing", Ser. No.
08/618,539 entitled "Method of Making Liquid Crystal Display
System", Ser. No. 08/800,872 entitled "Method of Making Replicas
and Compositions for Use Therewith", and Ser. No. 09/075,023
entitled "Method and Apparatus for Making Optical Masters Using
Incoherent Light." All the above applications are owned by the
present assignee and are hereby incorporated by reference for
purposes including, but not limited to, indicating the background
of the present invention and illustrating the state of the art.
SUMMARY OF THE INVENTION
[0011] A primary object of the present invention is to provide a
method for making a replica of a master diffuser containing optical
features of the diffuser in an extremely durable material such as
glass. It is another object of the invention to provide a diffuser
made from a material such as glass which is highly durable and
suitable for use under extreme conditions such as adjacent a high
temperature active light source such as for liquid crystal displays
and the like.
[0012] In accordance with the present invention, these objects are
achieved by a glass optical element having a unitary body structure
made from a glass material and at least one optical surface. A
surface relief structure is replicated onto the at least one
optical surface from a metal submaster optical element. The glass
material is first heated to a suitable temperature in order that
the glass be softened to a predetermined level of softness. The
softened glass is supported on a sturdy support such as a flat
metal surface with at least one surface of the glass substrate
exposed. The exposed surface is contacted with the surface relief
structure of the metal shim submaster optical element for a length
of time while pressure is applied to force the metal submaster
optical element and softened glass substrate material against one
another during at least a portion of the length of time of contact.
By the combination of the softness of the glass, the pressure
applied between the master optical element, the glass substrate and
the sturdy support surface, and the duration of time of such
contact and applied pressure, the surface relief structure is
replicated in the glass material. The pressure is then released and
the master optical element or metal shim and glass material are
separated from one another. The glass is then cooled to produce the
glass diffuser according to the invention.
[0013] The master optical element may in one embodiment be a metal
shim having a silver layer backed by a chromium or nickel layer.
The silver layer includes a surface relief structure recorded from
a photoresist medium by any one of many conventional means. Other
master optical elements may be utilized depending upon the
particular glass and process characteristics necessary for
production of a desired glass diffuser.
[0014] The glass substrate material may also be heated utilizing a
number of means. For example, the glass substrate material may be
placed within a furnace to elevate the temperature of the glass
prior to the application of pressure between the glass material and
the master optical element. Alternatively, the glass substrate
material may be exposed to a direct heat source such as an
oxyacetylene flame in order to sufficiently soften an exposed
surface of the glass material. In another alternative, a molten
glass material may be slightly cooled to a softened state and then
contacted with the master optical element during initial
manufacture of a glass substrate thereby replicating the surface
relief structure directly into the original glass object.
[0015] Using this methodology, the assignee has demonstrated the
fabrication of glass diffusers in the laboratory. Different types
of metals can be used in place of silver, and or nickel-chromium.
One alternative choice of such a metal is steel having a higher
percentage of carbon. One can also effectively replicate the glass
diffuser using a graphite based diffuser master. For example, a
diffuser master structure can be ion milled onto the steel metal
and/or graphite materials which have thermal expansion coefficients
closer to the glass. The use of graphite is critical when a more
softened or liquified glass is used.
[0016] These and other aspects and objects of the present invention
will be better appreciated and understood when considered in
conjunction with the following description and accompanying
drawings. It should be understood, however, that the following
description, while indicating preferred embodiments of the present
invention, is given by way of illustration and not of limitation.
Many changes and modifications may be made within the scope of the
present invention without departing from the spirit thereof and the
invention includes all such modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] A clear conception of the advantages and features of the
present invention, and of the construction and operation of typical
mechanisms provided with the present invention, will become more
readily apparent by referring to the exemplary and therefore
non-limiting embodiments illustrated in the drawings accompanying
and forming a part of this specification, and in which:
[0018] FIG. 1 illustrates a perspective elevational view of a glass
diffuser constructed in accordance with one embodiment of the
present invention;
[0019] FIGS. 2A-2D illustrate a schematic representation of the
steps for forming a metal shim submaster diffuser which is then
utilized to produced the glass diffuser shown in FIG. 1;
[0020] FIG. 3 illustrates one embodiment of the process and
apparatus for forming the glass diffuser shown in FIG. 1;
[0021] FIG. 4 illustrates an alternative embodiment of a process
and apparatus for forming the glass diffuser shown in FIG. 1;
[0022] FIG. 5 illustrates a second alternative embodiment of a
process and apparatus for producing the glass diffuser shown in
FIG. 1;
[0023] FIG. 6 illustrates a glass substrate undergoing a polishing
or lapping process in order to form the glass diffuser shown in
FIG. 1;
[0024] FIGS. 7A and 7B illustrate a plot of, respectively, vertical
and horizontal spread of light output against the light input power
for a metal master shim diffuser; and
[0025] FIGS. 8A and 8B illustrate a plot of, respectively, vertical
and horizontal spread of light output against light input power for
a glass diffuser as shown in FIG. 1.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0026] FIG. 1 illustrates an elevational perspective view of a
transparent glass diffuser 20 constructed and fabricated in
accordance with one embodiment of the present invention. The glass
diffuser 20 is generally fabricated according to the invention by
first creating a master diffuser from a durable material such as a
metal. A silver layer having a nickel backing may, for example, be
created as a submaster diffuser. The submaster is then used for
compression molding under high pressure and high temperature the
diffuser surface from the submaster into a glass substrate. The
resulting glass diffuser 20 is extremely scratch resistant, high
temperature resistant and also resistant to breaking.
[0027] FIGS. 2A-2D illustrate schematically one method for
manufacturing a metal shim submaster diffuser 30. FIG. 2A
illustrates first providing a substrate of a planar material such
as a glass substrate 32 having a layer of photoresist material 34
thereon. The thickness of the photoresist may be, for example,
approximately 20 microns although other thicknesses may
advantageously be used, depending upon the particular application.
A surface relief structure capable of producing desired optical
characteristics is recorded in the photoresist by any means such as
those disclosed in the aforementioned patent applications and
patents. A layer of silver 36 is then vacuum coated onto the
photoresist layer 34 using standard procedures and processes and
may, for example, have a thickness in a range of about 500-1000
.ANG.. The silver layer 36 replicates the master diffuser surface
structure formed in the photoresist material layer 34.
[0028] FIG. 2B illustrates that this composite structure including
the substrate 32, photoresist layer 34, and silver layer 36 is then
placed in a solution or bath 38. An anode 40 is connected to the
silver layer 36 and a cathode 42 attached to a nickel plate 44
submersed in the same bath 38. The resulting electrochemical
reaction deposits a layer of nickel 46 onto the silver layer 36 as
is further illustrated in FIG. 2C. This backing layer, for example,
may be in a range anywhere from approximately about 0.005 inches to
about 0.5 inches thick, or more or less. The layer of silver 36 and
the layer of nickel 46 in combination define the metal shim 30
which is then separated as is illustrated in FIG. 2D from the
photoresist layer 34. This separation may destroy the photoresist
layer 34 and glass substrate 32.
[0029] The resulting metal shim 30 includes both the silver layer
36 and the nickel layer 46 wherein the exterior surface of the
silver layer 36 includes the surface structure or image replicated
from the photoresist layer 34 of master substrate 32. Once this
metal shim submaster 30 is created, it may then be used as a tool
or submaster shim to replicate the same surface structure into a
plate of glass as described below in order to form the glass
diffuser 20. The nickel plate 44 may be substituted, for example,
by a chromium plate or a chromium nickel plate to form either a
chromium backing or chromium nickel backing, respectively, on the
silver layer.
[0030] FIG. 3 illustrates one embodiment of a process for
manufacturing the glass diffuser 20 using the metal shim master 30.
The process includes providing a rigid or sturdy support surface 50
manufactured from a metal or some other high temperature resistant
material. The support surface 50 is housed within a high
temperature furnace 52 having a heating element 54 capable of
heating the interior of the furnace to a suitable elevated
temperature as described below. The metal shim master 30 is then
placed on the support surface 50 with the silver layer 36 facing
upward exposing the surface relief structure.
[0031] A glass substrate 56, which in this embodiment is
prefabricated, is selected according to principals described in
more detail below and placed in the furnace on top of the silver
layer 36 of the master shim 30. A suitable pressure plate 58 which
is also preferably constructed from a metal or other high
temperature resistant and substantially rigid or sturdy material is
positioned over an exposed surface 59 of the glass substrate 56
within the furnace 52.
[0032] Heat is then supplied to the interior of the furnace 52 via
the heating element 54 to increase the temperature to a suitably
high temperature in order to soften at least the exposed surface 59
of the glass substrate 56. The heating element may be of any type
such as, for example, a gas burner or an electric coil or burner.
The suitable temperature is primarily determined by the glass
characteristics as described in more detail below. Once the furnace
52 reaches the desired or suitable temperature and the exposed
surface 59 of the glass substrate 56 reaches the desired softness,
the pressure plate 58 is lowered to apply pressure to the glass
substrate 56 which in turn presses against the surface relief
structure of the silver layer 36 and against the metal shim master
30.
[0033] By heating the glass substrate to the appropriate
temperature and applying the appropriate amount of pressure via the
pressure plate 58, the exposed surface 59 of the glass substrate 56
will permanently receive and replicate the surface relief structure
of the silver layer 36.
[0034] The glass substrate 56 is then removed from the furnace 52
and cooled in order to re-harden the substrate. As illustrated in
FIG. 6, the side opposite the exposed surface 59 of the glass
substrate 56 which does not carry the replicated surface relief
structure may then be worked or further processed accordingly to
achieve a particular thickness, critical smoothness or other
surface condition. The glass substrate may be polished or lapped or
ground down to achieve the desired thickness and smoothness. Thus,
FIGS. 3 and 6 illustrate one embodiment of forming the glass
diffuser 20 utilizing a high temperature press or stamping
process.
[0035] FIG. 4 illustrates one alternative embodiment for producing
the glass diffuser 20 utilizing the metal shim master diffuser 30.
In this embodiment, the glass substrate 56 is passed through or
otherwise subjected to a direct heat source, and particularly
preferred is an oxyacetylene flame 60 while supported on a support
surface 62. The flame 60 softens at least the exposed surface of
the glass substrate 56 to a suitable degree. The metal shim master
30 is then pressed as described above by the plate 58 against the
exposed side of the glass substrate 56 with the surface relief side
of the silver layer 36 facing the glass substrate.
[0036] FIG. 5 illustrates another alternative embodiment for
manufacturing the glass diffuser 20 of the invention. The process
disclosed in FIG. 5 involves embossing or otherwise replicating the
surface relief structure or image of the silver layer 36 from the
metal shim master 30 into a liquified and/or softened glass
material 70 during the initial manufacture of the glass. In the
other two embodiments described above, the glass had already been
produced and hardened as a plate of glass. In this embodiment, the
glass material is slightly cooled from the initial molten glass
state to a softened state without first achieving a hardened glass
state.
[0037] The metal shim master 30 is disposed adjacent the liquified
and/or softened glass material 70. As the glass material 70 is
being manufactured and has achieved a predetermined consistency
which is not yet fully solidified or hardened, the metal shim
master 30 is brought into contact with the glass material 70. The
softened glass preferably has somewhat solidified or slightly
cooled from a molten state in order to retain the surface relief
structure from the silver layer 36, and so that the master shim is
not destroyed. The glass material is then further permitted to
solidify or harden to a desired consistency prior to separating the
metal shim master 30 from the softened glass material. The softened
glass material 70 must, however, achieve a certain level of
solidification prior to separation from the metal shim master 30 in
order that the surface relief structure on the silver layer 36 is
replicated and retained in the exposed surface of the softened
glass material.
[0038] One example of conventional technology for manufacturing
glass is briefly described for illustrative purposes although other
technologies may be utilized without departing from the scope and
the spirit of the present invention. Furnaces are available that
can accept particular types of glass beads which are ground into a
powder and then melted within the furnace. Once melted and
homogenized into a liquid or fluid described as molten glass, the
molten glass is used to fill a mold cavity. The mold may be
produced including a particular shape, dimensional characteristics,
and surface characteristics for any particular application. Once
the mold is filled with the molten glass, it may be cooled to
produce a glass object of a particular desired shape and size. Such
a glass forming mold may include one or more surfaces which carry
an optical surface relief structure formed thereon or may include
the metal shim diffuser 30 as described above as a mold insert.
[0039] A mold of this type may be utilized to mass produce glass
objects having the desired surface relief structure. One such
non-diffuser use would be for microscope sample slide plates. The
relief surface assists in retaining a sample on the slide plate and
yet permits light to pass through the plate and sample. By creating
slide plates using this technology, each slide plate will have an
identical surface structure thus producing highly consistent
analysis results from one sample to the next.
[0040] A glass micro-slide plate having the surface relief
structure can be used for many applications where micro-slide
plates are used, such as in the biological field, for example. The
mold may be manufactured to produce surface relief features which
correspond to a particular biological sample feature which also in
turn enhances growth, sample adhesion, and sample analysis. Any of
the standard glass manufacturing techniques can be applied to
fabricate a glass diffuser. A cast iron or graphite material can be
used to make a mold and/or diffuser master shim. This process can
be described as an analogous process of injection molding. The only
difference is that the bulk material in this patent application is
glass instead of plastic.
[0041] The temperature at which the glass substrate 56 or the
softened or molten glass material 70 is maintained during the above
replication or molding processes is determined and selected
primarily according to the glass composition desired for a
particular application. Table 1 lists a number of different glass
compositions and the softening temperature of each glass
composition at which the glass becomes deformable or moldable.
1 TABLE 1 Softening Glass Temperature .degree. C. (.degree. F.)
Borosilicate 716 (1321) Light flint 585 (1085) Brown flint 661
(1222) Light barium brown 731 (1348) Flint 593 (1100) Fused 1000
(1832) Brown 720 (1328)
[0042] As can be seen from Table 1, the softening temperatures for
most types of glass are relatively high in comparison to the
softening or melting temperatures of the conventional diffuser
materials such as plastics, polycarbonates, and epoxies. The
temperatures range from the conventional glass such as flint glass
which softens at just under 600.degree. C. or 1100.degree. F. to a
special glass such as fused glass which softens at a much higher
temperature of 1000.degree. C. or 1832.degree. F. Other relatively
common glass materials fall somewhere in this range of softening
temperatures and may include conventional brown glass, light barium
brown glass, brown flint glass, light flint glass, or borosilicate
glass. Table 1 is merely a representative sample of various glass
types which may be utilized in practicing the present invention. It
will be evident to those skilled in the art that other glass
compositions and composites may also be utilized without departing
from the spirit and scope of the invention.
[0043] Glass selection will essentially depend upon what wavelength
of light transmission is desired for a particular application. Some
glass transmits light at wavelengths in the ultra violet range,
such as about 148 to 400 nm, which may be desired. Some glasses are
more transparent for a given or desired wavelength than others. A
glass diffuser can be constructed according to the invention using
virtually any glass, depending upon the application.
[0044] It is imperative that the metal shim master 30 not be
destroyed during the process of replicating the surface relief
structure from the silver layer 36 into the glass substrate 56 or
the softened or molten glass 70. To this end, the metal shim 30
including the nickel and silver layers is a preferred embodiment
for forming the glass diffuser of the invention. A typical glass
material must be significantly softened in order to be pressed or
stamped to replicate the surface relief structure from the metal
shim master 30. The glass material therefore must be elevated to a
very high temperature.
[0045] A typical grade of glass softens at about 600.degree. to
700.degree. C. or about 1100.degree. to 1300.degree. F. Therefore,
conventional methods of forming master and sub-master diffusers
from plastics and epoxies are not sufficient where a glass material
is desired for the diffuser 20 as the final product. For example, a
conventional compression molding process for manufacturing plastic
and epoxy diffusers is typically conducted at temperatures of about
150.degree. C. or about 300.degree. F. The molding or stamping of
glass must be conducted at much higher temperatures, on the order
of 4-5 times higher, than for conventional materials. Therefore,
one preferred diffuser is a metal shim diffuser as described above
because the melting points of such a metal shim are significantly
higher than for the conventional plastic and epoxy materials.
[0046] However, composite glass materials which exhibit many of the
durability and high temperature resistance characteristics of
conventional glass may be utilized to form the glass diffuser 20 of
the invention. Such composite glass materials may have a somewhat
lower melting point and/or softening temperature than for
conventional glass. However, the softening or melting point will be
significantly higher than for the conventional plastic and epoxy
materials. It is therefore contemplated that other lower
temperature submasters may be utilized when forming the surface
relief into the composite glass diffuser. The type of suitable
submaster diffuser will depend upon the softening and/or melting
temperature of the composite glass substrate as well as the
necessary time duration for contact between the submaster diffuser
and the glass material. If the contact times are relatively short,
the submaster diffuser may not even necessarily need to withstand
temperatures at which the selected composite glass material melts
or softens. If the required contact times are longer, heat
conduction from the glass material to the master may necessitate
that the submaster be capable of withstanding such temperatures. In
such situations, a submaster may be fabricated in cast iron or
graphite material which withstands high temperatures.
[0047] However, if products are to be mass produced, it is
preferred that the submaster diffuser material be capable of
withstanding at least the temperature at which the glass material
substrate is to be maintained during manufacture of the glass
diffusers. This is so that as the submaster diffuser temperature
slowly elevates during repetitive and cyclical contact with
successive heated glass substrate materials, the submaster
maintains the surface relief structure, and does not become damaged
or destroyed over time.
[0048] As with the formation of conventional master diffusers and
sub-master diffusers, each successive generation of replication of
the original master or submaster surface relief may less accurately
replicate the actual original surface relief. Therefore, for a
particular glass material, it may be necessary to go through a
step-by-step or trial and error process in order to achieve a
desired light diffusion angle in a finished glass diffuser 20. For
example, if a 10.degree. output angle is desired from the glass
diffuser 20, it may be necessary to manufacture the original metal
shim submaster 30 having a smaller diffusion angle in order that
the glass diffuser produces the desired light output
characteristics.
[0049] For example, FIGS. 7A and 7B illustrate, respectively, a
light output plot of the vertical and horizontal spread of light
from a metal shim manufactured as described above. FIGS. 8A and 8B
represent, respectively, the vertical and horizontal spread of
light from a glass diffuser replicated from the metal shim and
fabricated by the process illustrated in and described with regard
to FIG. 4. The vertical and horizontal spreads are plotted against
light input power. As can be seen, the glass diffuser 20
characteristically has a somewhat wider vertical and horizontal
spread for a given light input power than the metal diffuser.
Therefore, when fabricating a glass diffuser 20 intended to have
particular light diffusion characteristics, the metal shim master
30 must be fabricated having a particular surface structure
generating a somewhat narrower vertical and horizontal spread of
light output. Each prior generation of the surface relief structure
from an original master diffuser to the metal shim submaster may
therefore also need to have a successively narrower light output
angle as well.
[0050] Though the invention was described referring to particular
embodiments, many other changes and modifications may be made to
the invention as described without departing from the spirit and
scope thereof. The scope and spirit of these changes and
modifications will become apparent from the appended claims. The
scope of the invention is therefore intended only to be limited by
the appended claims.
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