U.S. patent number 3,743,382 [Application Number 05/133,205] was granted by the patent office on 1973-07-03 for method, material and apparatus for increasing and decreasing the transmission of radiation.
This patent grant is currently assigned to Research Frontiers Incorporated. Invention is credited to Paul Rosenberg.
United States Patent |
3,743,382 |
Rosenberg |
July 3, 1973 |
METHOD, MATERIAL AND APPARATUS FOR INCREASING AND DECREASING THE
TRANSMISSION OF RADIATION
Abstract
A light control valve is disclosed having certain fluid
suspensions therein which when activated increase the transmission
of radiation through the valve in one part of the electromagnetic
spectrum and decrease the transmission in another part of the
spectrum.
Inventors: |
Rosenberg; Paul (Larchmont,
NY) |
Assignee: |
Research Frontiers Incorporated
(Plainview, NY)
|
Family
ID: |
22457478 |
Appl.
No.: |
05/133,205 |
Filed: |
April 12, 1971 |
Current U.S.
Class: |
359/296 |
Current CPC
Class: |
G02F
1/172 (20130101) |
Current International
Class: |
G02F
1/01 (20060101); G02F 1/17 (20060101); G02f
001/28 () |
Field of
Search: |
;350/160,161,267,266 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sikes; William L.
Claims
I claim:
1. A light valve for controlling the transmission of radiation in
the electromagnetic spectrum comprising:
a cell having front and rear wall sections spaced apart a distance
which is small compared to the lateral dimensions of the
sections
a fluid suspension in said cell of minute particles dispersed
therein capable of having their orientation changed by the
application of an electric field to the suspension to change the
transmission of radiation through the suspension
means for applying an electric field to the suspension between said
wall sections in a direction substantially parallel to the
direction of transmission of radiation through the suspension and
substantially perpendicular to said wall sections, and
said suspension being characterized in that it is responsive to
said field applied in said direction to decrease the level of
transmission of radiation therethrough, in part of the
electromagnetic spectrum, below the level of transmission of
radiation in this part of the spectrum when said field is not
applied to the suspension and to simultaneously increase the level
of transmission of radiation therethrough, in another part of the
electromagnetic spectrum, above the level of transmission of
radiation in this other part of the spectrum when said field is not
applied to the suspension.
2. The light valve of claim 1 wherein the minute particles comprise
titanium dioxide.
3. The light valve of claim 1 wherein the minute particles comprise
iron oxide.
4. The light valve of claim 1 wherein the minute particles comprise
cobalt aluminate.
5. The light valve of claim 1 wherein the part of the
electromagnetic spectrum where the level of transmission is
decreased and the part of the electromagnetic spectrum where the
level of transmission is increased are both in the visible section
of the electromagnetic spectrum.
6. The light valve of claim 1 wherein filter means are provided to
attenuate the light transmitted through the light valve in that
portion of the visible spectrum where the level of transmission of
radiation is increased in response to an applied electric
field.
7. The light valve of claim 1 wherein filter means are provided to
attenuate the light transmitted through the light valve in that
portion of the visible spectrum where the level of transmission of
radiation is decreased in response to an applied electric
field.
8. A material for controlling the transmission of radiation in the
electromagnetic spectrum comprising
a fluid suspension including:
a suspending medium and
a plurality of minute particles dispersed therein capable of having
their orientation changed by the application of an electric field
to the suspension to change the transmission of radiation through
the suspension,
said suspension being characterized in that it is responsive to
said field applied in a direction substantially parallel to the
direction of transmission of radiation through the suspension to
decrease the level of transmission of radiation therethrough, in
part of the electromagnetic spectrum, below the level of
transmission of radiation in this part of the spectrum, when said
field is not applied to the suspension, and to simultaneously
increase the level of transmission of radiation therethrough, in
another part of the electromagnetic spectrum, above the level of
transmission of radiation in this other part of the spectrum when
the field is not applied to the suspension.
9. The material of claim 8 wherein the minute particles comprise
titanium dioxide.
10. The material of claim 8 wherein the minute particles comprise
iron oxide.
11. The material of claim 8 wherein the minute particles comprise
cobalt aluminate.
12. The material of claim 8 wherein the part of the electromagnetic
spectrum where the level of transmission is decreased and the part
of the electromagnetic spectrum where the level of transmission is
increased are both in the visible section of the electromagnetic
spectrum.
Description
BACKGROUND OF THE INVENTION
Variable density light control devices, shutters, and filters of
many kinds have been developed to control and vary the intensity of
radiation, especially electromagnetic radiation in the region that
includes ultraviolet, visible, and infrared radiation. These
devices include mechanical shutters, iris diaphrams of variable
opening, wedge shaped filters of variable thickness, liquid crystal
light valves, Kerr cells and variable density light valves of the
kind which use suspensions of particles in a fluid. When the
last-mentioned control devices are opened or partially opened, or
operated to increase the transmission of radiation, the
transmission is increased simultaneously for all wavelengths,
frequencies, and colors, even though the amount of the increase is
different for different wavelengths, frequencies or colors.
Likewise, when these control devices are closed or partially
closed, or otherwise operated to decrease the transmission of
radiation, the transmission is decreased simultaneously for all
wavelengths, frequencies or colors, even though the amount of
decrease is different for different wavelengths, frequencies or
colors. Thus, these control devices have the effect of either
increasing the transmission at all wavelengths or decreasing the
transmission at all wavelengths. They cannot be used to decrease
the transmission at some wavelengths and to increase the
transmission at other wavelengths. These devices cannot
substantially attenuate one color while letting another one pass
through, but can only be used to substantially block out all colors
(all wavelengths) or none at all.
Such a valve that can selectively filter certain wavelengths and
transmit others would have substantial use in many industries. For
example, in the photographic and related industries, a filtering
valve such as this can be used in film printing and developing to
surpress certain colors while enhancing others. Thus, there is a
need for a light valve which acts as an inexpensive filter to
filter out certain colors while increasing the transmission of
others.
SUMMARY OF THE INVENTION
A light valve having a fluid suspension therein, which, when
activated can reduce the light transmission in one part of the
electromagnetic spectrum while simultaneously increasing the
transmission in another part of the spectrum over the amounts of
transmission in these same parts of the spectrum when the valve is
not activated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph plotting transmission vs. wavelength for a device
of the PRIOR ART.
FIG. 2 is a graph plotting transmission vs. wavelengths for the
device of this invention.
FIG. 3 is a perspective view of the light valve of FIG. 1.
FIG. 4 is a cross-sectional view of the valve of FIG. 1.
PREFERRED EMBODIMENT OF THE INVENTION
This invention is concerned with light control devices more
commonly known as light valves of the type which consist of cells
containing a substance therein which changes the transmission of
radiation through the cell when a field is applied across the
substance. A typical example of such a light valve is described in
co-pending U.S. Application, Ser. No. 25,541, filed Apr. 1, 1970,
Light Valve With Flowing Fluid Suspension, which is assigned to the
assignee of the present Application. The aforesaid Application
discloses light valves having thin, transparent walls constructed
of flat glass or similar material and separated by a small gap
which is filled with a fluid suspension containing small particles
distributed therein. These particles will align themselves when a
field is placed across the suspension. To place the field across
the suspension, a thin layer of transparent, conductive material is
coated on the inner side of each sheet of glass, either in contact
with the substance, or spaced from the substance by a thin,
transparent, non-conducting layer. The conductive layers are
connected to an energy source by suitable wiring. Upon the
application of a voltage across the suspension, the particles in
the suspension are oriented so as to cause the suspension to be
transparent; whereas, before the application of the voltage, the
particles in the suspension were disoriented and therefore, the
suspension was opaque. Light valves that operate such as these have
been described in the above-identified Application and are well
known in the prior art.
FIG. 1 is a graph showing wavelength vs. transmission for a valve
of the prior art, a valve containing a suspension where increasing
voltage causes increasing transmission, such as the valves
discussed in the above Patent Application. In this graph,
wavelength in Angstrom units is plotted along the X axis, and
increasing transmission is plotted along the Y axis. The straight
line 1 on the graph represents the transmission of radiation
through the valve when no activating voltage is applied to the
conductive surfaces. For ease in description, this line has been
normalized to the same level of transmission for all wavelengths
(20 percent transmission). It will be appreciated that the
transmission through the valve in the off condition is not
necessarily zero and that is the reason why straight line 1 is not
shown at the position of zero transmission.
The curves 2, 3 and 4 represent transmission through the above
prior art valves with applied voltages. Curve 2 in FIG. 1
represents the transmission of radiation through the valve at one
activating voltage and frequency. Curve 3 represents the
transmission of radiation at another voltage and frequency, and
curve 4 represents the transmission and still another activating
voltage and frequency. As the activating voltage and frequency are
varied, the transmission varies from one to another of the family
of curves 2, 3 and 4. The curves are such that when the voltages
are increased or decreased, the transmission of radiation at all
wavelengths are either all increased simultaneously or decreased
simultaneously. These curves uniformly increase and decrease; they
never cross each other and they never go below the straight line
(representing the inactivated condition of the valve). The
transmission at any wavelength increases as the voltage increases.
For example, if we take a wavelength of 6,000 Angstroms, which is
in the orange color region, the transmission of light at that
wavelength is greater with a greater applied voltage. The dotted
line at 6,000 Angstroms intersects line 4 at a greater transmission
value than where it intersects line 2. Thus, the transmission is
always greater as the applied voltage is increased and the
transmission is always greater when a voltage is applied then when
no voltage is applied at all (the straight line).
When these prior art valves are activated by any applied voltage,
the valve becomes optically less dense (transmits more light
through it) than when no voltage is applied and this occurs
throughout all wavelengths. Still another way of starting this
would be to say that density ratio of the prior art valves is
always greater than unity. The density ratio is the ratio of the
optical density of the light valve in the inactivated condition, to
the optical density in the activated condition. Thus, with these
prior art valves there is no possibility of increasing the
transmission of one range of wavelengths while decreasing the
transmission of another range of wavelengths. With these prior art
valves the transmissions of all wavelengths are either all
decreased or all increased. Thus, for example, with these valves, a
filter could not be produced which would increase the transmission
of blue light while decreasing the transmission of red light, or
vice versa. However, with the valve of the present invention, this
can be accomplished.
FIG. 2 is a graph showing the transmission of a typical light valve
in accordance with the present invention; a light valve, which when
it is activated, increases the transmission of radiation through it
in one part of the spectrum and decreases the transmission through
it in another part of the spectrum. In the graph percent
transmission of radiation is plotted along the Y axis and the
wavelength in Angstrom units is plotted along the X axis. This
curve is for Example I, which is discussed hereinafter. The
straight line 12 in the figure represents the transmission of the
inactivated valve normalized to the same transmission for all
wavelengths (20 percent). It is not actually the same for all
wavelengths in the inactivated state, but for ease in illustration
transmission for all wavelengths has been normalized to the same
value and transmission in the activated state has been
correspondingly changed. The curve represents light transmission of
a light valve with an applied voltage of 1,000 volts at a frequency
of 125 kilohertz as discussed in Example I. It will be seen from
this graph that when voltage is applied, the transmission in one
part of the spectrum (below 4,900 Angstroms) increases above the
transmission for the inactivated valve and in another part of the
spectrum (above 4,900 Angstroms) decreases below the transmission
for the inactivated valve. There is also a point at about 4,900
Angstroms (for this example) where transmission is the same in both
the activated and inactivated states. At this point, which is
referred to as the crossing point, activating the valve will have
no effect on transmission through the valve. From the graph, it
will be seen with this particular valve (the valve of Example I)
the transmission with the valve activated reaches a maximum at
about 4,000 Angstroms and reaches two minimums, one about 5,750 and
one about 6,500 Angstroms. It should be noted, however, that this
is just one example of the valves of this invention. It will be
appreciated that even though graphs of the valves of this invention
have the general shape of the graph of FIG. 2, the maximums,
minimums and crossing points will vary substantially. The Examples
mentioned hereinafter will point this out in more detail. One
significant point to be noted is that because of the increase in
transmission in one area and the decrease in another area, when a
white light is seen through the valve, of the above example before
the valve is activated, it would appear white, however, when the
valve is activated, the intensities of the longer length
wavelengths will be decreased, whereas, the intensities of the
shorter ones will be increased; this will cause the color to change
from white to a blue-white color. In other words, basically, the
transmission curve for the activated light valve of this Example
rises above the straight line 12 in the blue-purple part of the
spectrum and falls below the level of transmission for the
inactivated valve in the red-orange-yellow-green part of the
spectrum. This can be expressed in still another way in accordance
with the aforementioned density ratio, namely, the density ratio is
greater than unity in one portion of the spectrum (e.g. the
blue-violet region) and is less than unity in another portion of
the spectrum, (e.g. the green-yellow-orange and red region). The
valve then transmits more light in one region when it is activated
than when it is inactivated, and transmits less light in another
region when it is activated than when it is inactivated.
It also will be appreciated that by varying and changing the
voltage and its frequency, a variety of filter and transmission
effects can be produced to control the transmission of radiation in
various wavelengths, including controlling color, color balance,
color hue and color tone. As the transmission of one color of the
spectrum is increased, another can be decreased and so on.
Now, describing the suspension itself: As aforementioned, this
suspension is placed in the valve between its two transparent
plates. On the inside of each of these plates is a conductive
coating which may be in contact with the suspension (it can also be
separated from the coating by a thin layer of insulating material).
The cell is more clearly shown in FIGS. 3 and 4 where the plates
are designated 2 and 3, the conductive coatings 4 and 5, and the
suspension therebetween, 6. A suitable sealant 7 is also provided
to prevent the suspension from escaping from the valve.
The suspension may be a liquid or a gas, however, better results
seem to be achieved with a liquid because its specific gravity
makes it easier to keep the particles in suspension for longer
periods of time. It also appears to be preferrable for the fluid
and the suspended particles to have specific gravities that are as
close to each other as practical. When the specific gravities are
close to each other, there is less chance of the suspended
particles coming out of suspension. For example, if the suspended
particles and the fluid have the same specific gravity (i.e.
density) then there are no net forces acting on the particles to
cause them to settle out of the suspension. The particles may be of
any shape. One preferred shape is an elongated rod with a ratio of
length to cross-sectional diameter of about 25 to 1.
It is desirable that the ratio of the dielectic constant of the
particle to dielectic constant of the suspending fluid be large in
order that the electric forces on the particle be large. For
example, ratios may vary from 3 or 4 to 1 to 50 to 100 or 200 to 1.
Titanium dioxide which is used for the particles has a dielectic
constant of approximately 170 and two commonly used suspending
fluids for titanium dioxide, toluene and isopentyl acetate have
dielectic constants of approximately 2 and 5, to result in ratios
of about 85 to 1, or 34 to 1.
Also, suspending fluids of high viscosity cause the particles to
remain suspended for a longer time. At the same time, suspensions
in high viscosity fluids seem to be slower to react to an
activating electric voltage, i.e. a high viscosity suspension is
slower to act when an electric field is applied than a lower
viscosity suspension. However, this is not a problem in most
applications since light valves of the kind described in the
invention can act in times less than 2 milliseconds. It is also
desirable that the particles and fluid of the suspension be
chemically stable and inert and that they do not react chemically
with one another or with the walls, conductive layers or sealant of
the cell in which they are contained or the effective life of the
light valve will be substantially diminished.
Some materials that might be useful as the suspended particles
include metal oxides, metal salts, alkali halides, and alkali
oxides. Some of these materials that are particularly useful are:
an oxide of titanium, TiO.sub.2 ; an oxide of iron, Fe.sub.2
O.sub.3.sup.. H.sub.2 O; and the salt of cobalt, CoAl.sub.2
O.sub.4, cobalt aluminate.
The amounts of particles in suspension may vary on a part by weight
basis within wide ranges depending on the size of the particles,
the viscosity of the suspending medium (as aformentioned) and the
amount of particles desired per volume of suspending fluid. For
example, a suspension of 400-800 parts per weight of suspending
medium to 1 part of suspending particles yields good results.
However, if desired, these proportions can be increased to 1000 to
one or greater or decreased below the 400 figure if desired. If a
very dilute suspension is desired, one where it is only slightly
tinted in the inactivated condition, the amount of particles to
suspending medium will be substantially lessened. Conversely, if a
very dark suspension were desired, then the ratio of suspending
fluid to particles would be decreased from the 400 to 1 figure
aforementioned. A figure of 200 or 100 to 1 might be desirable.
The following examples are illustrative of various embodiments of
the practice of the present invention. However, it will be
understood that they are not to be construed as limiting the
invention in any way.
EXAMPLE I
Titanium dioxide (Titanox RA10) manufactured by Titanium Pigment
Corporation, New York, New York (average particle size of
approximately less than about 1 micron) was added to a mixture of
isopentyl acetate and nitrocellulose with the latter added to
minimize the tendencies of the particles to agglomerate or settle
out. The mixture was ground with a mortar and pestle and then left
to settle for one-half minute. More isopentyl acetate was added. An
eye dropper was then used to draw out the top part of the
suspension leaving the settled part of the mixture remaining. The
part in the eye dropper had a composition of approximately 1 part
of TiO.sub.2 to 800 parts of isopentyl acetate to 3 parts of
nitrocellulose by weight. This suspension was then placed in a
cell. The cell was composed of two sheets of glass, each coated
with a thin layer of conductive material, and spaced 33 millimeters
apart and held together by a sealant in the same manner as
previously described and as shown in FIG. 3. After the suspension
was placed in the cell, 1000 volts at the frequency of 125
kilohertz was applied across the suspension and a tungston filament
lamp was placed on one side of the cell. Readings were then taken
with a spectrophotometer positioned on the opposite side of the
cell from the light source. The results were tabulated as follows
and are plotted as previously discussed in FIG. 2. ##SPC1##
From this data and the graph it will be seen that the transmission
through the cell when it is activated (on) is less in one region
(between 4900 and 7000 Angstroms) than when the cell is inactivated
(off); and the transmission is greater when activated than when
inactivated in another region (3500 to 4900 Angstroms.
EXAMPLE II
Yellow iron oxide Fe.sub.2 O.sub.3.sup.. H.sub.2 O, sold under the
tradename 2288 high oil, manufactured by Chas. Pfizer & Co.,
New York, New York, was added to a mixture of toluene and Ganex
V220. Ganex V220, manufactured by GAF Corp., New York, N.Y. is a
modified type polyvinyl pyrrolidone which tends to minimize the
tendency of the particles of Fe.sub.2 O.sub.3.sup.. H.sub.2 O to
settle out of suspension. The mixture was ground with a mortar and
pestle. More toluene was then added. The suspension was then left
to settle for about one-half minute. Also, as before, an eye
dropper was used to remove the top part of the mixture. The
suspension at this point consisted of about the same proportions as
the previous example. The suspension was then placed in the same
cell as in the previous example, comprising two conductive coated
glass sheets separated by 33 mills. A tungsten filament was then
placed on one side of the cell and the effect was observed from the
opposite side of tthe cell by a spectrophotometer. A voltage of 500
volts at a frequency of 10 kilohertz was applied across the
suspension in the first of the two groups of results stated below,
and a voltage of 1000 volts still at a frequency of 10 kilohertz
was used in the second group of results. The data is expressed in
optical density instead of transmission. (As a substance becomes
optically more dense, it transmits less radiation through it.)
##SPC2##
In each of these cases the same results as with the previous
example showed up, that is, the density increased (transmission
decreased) with the application of voltage over one part of the
visible spectrum, while the density decreased (transmission
increased) with the application of voltage in another part of the
spectrum.
EXAMPLE III
Cobalt aluminate was added to a mixture of nitrocellulose and
isopentyl acetate in the same manner as with Examples I and II with
cobalt aluminate being substituted for titanium dioxide and iron
oxide in those examples. The entire procedure was the same as that
of Examples I and II, with the same proportions and the same cell
being used with the following results (with the readings in optical
density). ##SPC3##
Then the mixture was diluted by the addition of about 30 grams of
isopentyl acetate, 500 volts at a frequency of 10 kilohertz was
then applied with the following results (with the readings in
transmission). ##SPC4##
From both these results it will be seen that as before, the
transmission decreased in one part of the spectrum (density
increased) when voltage was applied instead of increasing as with
the prior art cells.
Up until this point this invention has been discussed with regard
to having a single type of particle in suspension. However, it will
be appreciated that suspensions of two or more types of particles
having different results can be used in the same suspending fluid.
They can also be used in mixtures or solutions of two or more
fluids. This will produce light valves that have combinations and
modifications of the control effects of each individual suspension.
An example of this is to mix TiO.sub.2 with Fe.sub.2 O.sub.3.sup..
H.sub.2 O to form the suspension. This mixture is then suspended in
isopentyl acetate with a protective colloid such as the
aforementioned nitrocellulose. The effect of this is to produce a
light valve which has a curve of transmission vs. wavelength such
as to combine the separate effects of TiO.sub.2 and Fe.sub.2
O.sub.3.sup.. H.sub.2 O and produce results which fall between the
curves of each of the two individual ingrediants.
Moreover, one or more suspensions of the above substances can be
combined, mixed, or dispersed into one or more of the suspensions
of the conventional substances, such as herapathite, as described
in the aforesaid application, Ser. No. 25,541, to make light valves
that produce combinations of the effect of the light valve of this
invention and the light valves using conventional suspensions. For
example, titanium dioxide can be mixed with herapathite, or iron
oxide can be combined with herapathite.
The valves of this invention can also be used in combination with
conventional filters, as for example, the Wratten filters,
manufactured by Eastman Kodak Company of Rochester, New York, to
create other filtering effects.
By the use of a filter or filters, part of the spectrum can be
attenuated while the remainder acts in its normal way in this
invention. For example, in FIG. 4, a filter 8 can be inserted in
front of the light valve to filter out all wavelengths shorter than
those of the crossing point (namely, all wavelengths to the left of
the wavelengths at which the curve crosses the horizontal straight
line) as shown in FIG. 2. When this is done, only the wavelengths
longer than 4900 will be able to pass through the valve. However,
those wavelengths are ones where the transmission decreases when a
voltage is applied. The light valve then has an optical density
ratio less than one since it is only operating in this decreasing
region. The valve now operates in the reverse manner to
conventional light valves of this type. The light valve will be
darker when activated than when not activated. This is the reverse
of the effect of the previously mentioned prior art valves which
are lighter when activated than when not activated.
Also, a filter can also be used to attenuate the portion of the
spectrum to the right of the crossing point in FIG. 2 (i.e.
wavelengths longer than those of the crossing point). The part of
the spectrum remaining will then act in a fashion similar to a
conventional prior art light valve - increasing transmission with
increasing voltage. This will have the advantage of a high optical
density ratio which gives the advantage of a more complete valve
operation.
Also, a filter can be used to attenuate only a portion or portions
of either or both the decreasing or increasing parts of the
spectrum aforementioned to create still different effects.
Further, two or more light valves with different suspensions, each
with its own characteristic transmission curves, such as those
shown in FIG. 2 can be combined in series with the light passing
successively through each of them. This will result in a still
further variety of color control and color effects. Also, one or
more of these valves can be combined with one or more of the
conventionally reacting valves such as mentioned in the
aformentioned Patent Application to produce a still further variety
of color control and color effects.
The voltage applied to activate the light valves can either be a DC
voltage or an AC voltage, or a pulsed voltage. An alternating type
voltage is preferred for most applications because this type of
voltage is less likely to produce undesirable side effects such as
coagulation, agglomeration, precipitation, or electrochemical
destruction of the particles, or migration or plating of the
particles on to the electrodes. Any of these will substantially
impair the proper operation of the valves.
Magnetic fields can also be used either alone or in combination
with electric fields to activate the light valve of this
invention.
It is noted that if the transmission of a light valve of this
invention is integrated over the full spectrum, the increased
transmission in one portion of the spectrum is partially or fully
compensated by the decreased transmission in another portion of the
spectrum. By suitably selecting the frequency and voltage of the
electric field applied to the suspension, and/or by using filters
to attenuate portions of the spectrum, the aforesaid compensation
can be made such that the integrated radiation energy transmitted
by the valves over the entire spectrum remains practically constant
as the valve is operated. For example, in the visible portion of
the spectrum, the total transmitted light energy can be kept
constant as the effective color and color balance are varied. In
such a case, the optical density ratio of the valve for white light
could be unity or close to unity while the density ratios for
certain wavelengths and certain portions of the spectrum could be
greater or less than unity.
The light valve of this invention can be used to control or modify
color, color balance, color tones, color values, and color hues in
the exposure, processing and printing of color photographic
materials. For example, if a color photographic print is too
redish, i.e. if red predominates at the expense of blue, the
photograph can be printed through the light valve of this invention
with the valve adjusted to transmit more of the blue portion of the
visible spectrum and less of the red portion of the visible
spectrum. Thus, tthe amounts of the blue and red transmissions can
be controlled by the valve to modify the color balance of the print
as desired.
The light valve of this invention can also be used to modify and
control color and color balance in duplicating or printing motion
picture films from the master or negative film on which the picture
was originally made. In this duplicating or printing operation it
is usually necessary or desirable to modify the color balance in a
different way from scene to scene in order to achieve color realism
or for dramatic or artistic effects. The light valve of this
invention is highly suited to the Application because it operates
rapidly so that a desired change in color balance can be made in
the time between the individual frames of the motion picture film.
The operation and construction of the valve, which is entirely
electrical with no mechanical moving parts, is simple compared to
the complicated sets of rotatable and adjustable mirrors, color
filters, and lenses that are usual in this application; and
further, it is easier to control or program the light valve of this
invention than it is to program and control the usual system of
mirrors, lenses and filters. The latter is true because the light
valve of this invention is controlled and operated by a direct
electrical input to the valve with no electromechanical or
mechanical moving parts.
Light valves according to this invention can also be used to
produce illuminated displays which change color. For example, a
displayed word can be made to change the color of each of its
letters independently as well as flash each letter on and off in
any desired sequence of pattern. Likewise, a pattern or diagram or
picture or illustration can have its displayed components or parts
or individual symbols changed at will in color, color hue and color
intensity. These effects are useful for purposes of advertising,
amusement, artistic display, psychological testing and as aids in
teaching instruction and education.
Thus, it will be appreciated that a highly efficient light valve is
provided which selectively controls radiation transmission in
different parts of the spectrum.
While specific embodiments of the invention have been described, it
will be appreciated that the invention is not limited thereto since
many modifications may be made by ones skilled in the art and fall
within the true spirit and scope of this invention.
* * * * *