Color combiner and separator and implementations

The trichromatic beamsplitter consists of composited dichroic beamsplitter plates that separate a projected image into its three color components with spatial as well as spectral precision. The three linear array photosensor comprises a monolithic sensor having three parallel photodiode arrays spaced precisely to accept the color component images of the trichromatic beamsplitter. The present invention also employs a spectral and spatial combiner that is capable of maintaining equal optical path lengths of each spectral beam so that a single combined beam can be produced and can be employed in a number of different applications such as a color camera device, a color recording device, a graphics presentation device, an electronic color filter device, a color projector device and a multi-channel optical communication device.

BACKGROUND OF THE INVENTION 
A. Field of Invention 
The present invention pertains generally to optics and more specifically to 
color separators, color combiners and inventions utilizing color 
separators and color combiners. 
B. Description Of The Background 
Color imagers include color video cameras and color scanners for commercial 
printing. Color imagers transform color pictures into machine readable 
data. This is accomplished by dividing a color image into many small 
portions called pixels. The color imager separates light from each pixel 
into red, blue or green light. Numbers assigned to each pixel of the color 
image represent the red, blue, and green light. A fast, high resolution, 
accurate color imager would enhance the usefulness of computers and 
automate numerous tasks. For example, computers can print and display 
color images. However, the lack of fast, accurate, and high resolution 
means for transferring color images into a computer limits the use of this 
capability. In the early prior art, discrete optical components, such as 
beamsplitters and color filters, separate the color components of an 
image. Dichroic beamsplitters have been widely used due to the combined 
functions of these devices as both beamsplitters and filters. Dichroic 
beamsplitters employ selected multilayer dielectric interference optical 
filter coatings, hereinafter referred to as dichroic coatings. Typically, 
color separation is achieved by placing two discrete dichroic 
beamsplitters in the optical pathway between the projection lens of the 
imager and its photosensors. The first dichroic beamsplitter reflects a 
first spectral band (e.g., green) to the first photosensor while 
transmitting the remaining spectral bands to the second dichroic 
beamsplitter. The second dichroic beamsplitter reflects a second band 
(e.g., red) to a second photosensor while transmitting the remaining 
spectral band (e.g., blue) to the third photosensor. The disadvantage of 
this approach is that the respective dichroic beamsplitters and 
photosensors must be precisely aligned; otherwise, the color components 
will not have the proper optical coincidence. The costly alignment process 
limits the use of this prior art color separator. Dichroic beamsplitters 
(dichroic prism), as well as other prior art techniques of color scanning 
are described more fully in a Japanese article entitled 
"Image Scanners," OEP November 1986, pp. 18-22. As disclosed therein, the 
dichroic prism requires each sensor to be placed on a different plane. 
With the advent of low-cost, solid-state photodiode array photosensors, 
various attempts have been made to develop low cost color separation 
techniques for color scanners and video cameras. 
Solid-state, photodiode arrays with integral color filters have been 
commercialized by Hitachi, Toshiba, Sony and RCA. These devices employ a 
two-dimensional array of photodiodes on a single silicon substrate. The 
array is coated with a gelatin layer, into which color dyes are 
selectively impregnated, using standard masking techniques. Each 
photodiode is, thus, given an integral color filter, e.g., red, green or 
blue, according to a color pattern which is repeated throughout the array. 
The same technology has been applied to one-dimensional photodiode array 
sensors for line scanners. The latter devices have been commercialized by 
Toshiba and Fairchild. 
A prior art color imager using photodiode arrays is shown in FIG. 1. The 
single linear photodiode array 23 has individual organic dye filters 
impregnated over each photodiode in a repetitive red, blue and green 
pattern. Color separation, the breaking down of a color image into red, 
blue and green light, is achieved by focusing the light beam on the array, 
as shown in FIG. 1. One red, green and blue photodiode grouping 25 
provides information to one color pixel. This prior art technique has 
several disadvantages. Since three photodiodes supply information to one 
pixel, the pixel resolution is reduced to one-third. For accurate color 
imaging, the luminance detail and chroma of a given color pixel from the 
original image must be resolved by three optically coincidental 
photosensor elements. However, the prior art photodiode arrays do not have 
color-coincidence. The red light is detected from one location, green from 
another, and blue from a third location. In addition, two-thirds of the 
light incident on each photodiode is lost by filler absorption (e.g., a 
red filter absorbs green and blue spectral bands). In order to increase 
the resolution, the array 23 must be lengthened or the photodiode area 
must be decreased. However, either of these approaches to increase the 
resolution will proportionately decrease scan speed. Also, the dye filters 
have less color band purity than dichroic filters. The prior art approach 
desaturates color sensitivity and is otherwise spectrally inaccurate. 
Another prior art color imager using photodiode arrays has a rotating color 
wheel composed of colored filter segments. The lens focuses a line image 
of the original object on a linear photodiode array. The rotating color 
wheel filters the projected line image in a repeating color sequence, 
e.g., red, green, blue. The signal for each color component of a given 
line image is stored digitally until all three color components have been 
detected. The signals ar then reordered in memory to assign three color 
values to each pixel in the line image. 
The color wheel color separation technique has the advantages of utilizing 
the full resolution of the photodiode array as well as utilizing dichroic 
filters. However, it has several disadvantages. The scan speed is 
one-third of the integral sensor/filter scan speed, since only one of 
three colors is detected at a time. Also, further speed reduction results 
from transitions between filter segments during rotation of the wheel. 
When the color wheel and scan line are continuously driven, as opposed to 
synchronously "stepped", the effective resolution of the photodiode array 
is diminished in the scan direction by the movement of the scan line 
through the color cycle of the color wheel. Another disadvantage is the 
size of the color wheel which limits device extensibility. Page-width 
"contact" or "traversing head" type scanner embodiments become impossible 
or unwieldy. Further, this prior art device is burdened with a large 
moving mechanism and the control of this mechanism. 
The Sharp Corporation of Japan has introduced a third prior art color 
separation technique for color document scanning. The Sharp scanner 
employs a single photodiode array with three sequentially-fired colored 
fluorescent lamps (e.g., red, green, blue), as the imaging light source. 
The sequence of signals obtained by the photodiode array is directly 
analogous to the color wheel color separator. That is, the input to the 
photodiode array is a sequential input of the red, green and blue 
components of a given original line image. Likewise, the photodiode 
signals for each color component are digitally stored and reordered in 
memory at the end of each color cycle. 
Like the color wheel color separator, the tricolored lamp approach provides 
imaging means that utilize the full resolution of the photodiode array. 
Several shortcomings, however, limit the speed and color integrity of the 
imager. In order to obtain correct color separation, the light output from 
each lamp should be extinguised before the firing of the next lamp in 
sequence; blended lamp output produces undersaturated color detection. 
Scanning speed, as a result, is limited by the persistence time of the 
phosphors utilized in each fluorescent lamp or the ability to dynamically 
subtract out the signal produced by the decaying light output of a 
previously fired lamp. Color integrity is further limited by the selection 
of phosphors having persistence values sufficiently low to meet commercial 
scan speed specifications. Typically, external absorption filtering of the 
lamps is required to obtain the desired spectral characteristics or each 
lamp output. As with the color wheel color separator, when the scan line 
is continuously driven, as is desirable for scan speed, the effective 
resolution of the photodiode array is diminished in the scan direction by 
the movement of the can line through the color cycle of the 
sequentially-fired lamps. The size and bulk of the optical system 
comprising the three lamps likewise restricts device extensibility toward 
"contact" or "traversing head" type scanner applications. 
Color combiner devices suffer from many of the same disadvantages and 
limitations as the color separators set forth above. A color combiner, as 
defined herein, comprises an optical device for taking individual color 
components and spatially and spectrally combining each of the individual 
beams into a single optical beam wherein each of the individual color 
component beams have coincident optical axes. The prior art does not 
disclose any device that is capable of combining individual spectral 
beams, as described, in a simple and easy manner. 
SUMMARY OF THE INVENTION 
The present invention overcomes the disadvantages and limitations of the 
prior art by providing an optical device for spatially and spectrally 
combining a plurality of substantially parallel optical beams such that 
the optical axes of each of the plurality of optical beams are coincident 
and form a single combined beam and the optical path lengths of each of 
the individual optical beams is substantially equal. The present invention 
is also capable of spatially and spectrally combining beams that allows 
imaging from a single object plane to a single image plane. 
The present invention also comprises a optical color imaging device for 
generating a color image on an image plane in response to an electronic 
imaging signal using an optical device for spatially and spectrally 
combining a plurality of optical beams having different spectral ranges 
and spatially separated optical axes to form a single combined beam with 
coincident optical axes. The optical color imaging device can be utilized 
for projecting a video image, recording a document scan signal, or other 
similar applications of an imaging device. 
The present invention can also comprise a color image detector device for 
generating a color electronic image signal representative of a color image 
formed from an image beam focused on an image plane by using a spectral 
separator for spatially and spectrally separating the color image beam 
into a plurality of optical beams that have predetermined spectral ranges 
and substantially equal optical path lengths. 
The present invention may also comprise an electronic color filter device 
that uses a spectral separator for spatially and spectrally separating an 
input optical beam into a plurality of individual color beams that are 
spectrally and spatially separated. An aperture device can be used to 
control the intensity of each of the color beams. 
The present invention may also comprise an electronic color filter that 
uses a spectral combiner to combine a plurality of color beams from a 
spectral separator, or a plurality of sources of color beams, into a 
single combined output beam. The combiner can be designed such that the 
optical axes of each of the color beams have substantially equal optical 
path lengths and are substantially aligned with a single optical axis. 
The present invention may also comprise a multiple channel fiber optic 
communication device that is capable of transmitting multiple channels on 
a single fiber optic by using a plurality of optical beams having 
different spectral ranges that are combined for transmission through the 
fiber optic and are separated after transmission through the fiber optic. 
An advantage of the present invention is that the spectral separator and 
combiner optical components are compact, inexpensive and easy to 
manufacture. Another advantage of the present invention is that the 
optical components produce color coincidence within a pixel. That is, each 
portion of a pixel generates all three color components so as to provide 
exact color convergence and line acuity. The invention also provides 
accurate spectral and spatial separation as well as accurate spectral and 
spatial combination. 
The optical combiner and optical separator components of the present 
invention are also extremely efficient in comparison to conventional 
filtration techniques since dichroic reflective layers are used. 
Essentially all of the incident light striking the components is 
transmitted with very little absorption. A conventional filter typically 
absorbs two spectral bands to transmit one. Since essentially all of the 
visible light is utilized, maximum speed is achievable for a given optical 
system. 
Additionally, the optical components of the present invention do not 
require costly optical alignment. The dichroic coatings are precisely 
separated by glass plates and/or precise separator devices in the 
manufacturing process. This separation is determined by considering the 
refractive indices of the substances used in the optical separator and 
combiner components as well as the angles of incidence to provide a very 
precise alignment. The optical separator and combiner components provide 
equal optical path lengths for each of the individual beams with minimal 
alignment problems. 
Also, since the present invention uses substantially parallel, spatially 
separated, spectral beams for both the combiner and separator optical 
components, a single object and image plane are employed in accordance 
with the present invention.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 2 illustrates a single layer dichroic optical component that comprises 
a substantially transparent optical support medium 60, such as a glass 
plate, that is optically flat and a dichroic layer 50 that is deposited on 
one side of the glass plate 60. As shown in FIG. 2, an input optical beam 
51 is split into two spatially and spectrally separated optical beams 53 
and 55. Dichroic layer 50 reflects optical radiation having a 
predetermined wavelength and transmits all other radiation along optical 
beam 55. Because the index of refraction of air is different than the 
index of refraction of glass, the portion 57 of optical beam 55 is 
refracted at a different angle through the glass plate 60. 
FIG. 3 illustrates the manner in which a glass plate 62 can be coated on 
two sides with two dichroic layers 52 and 54 to split an incoming beam 59 
into three spatially and spectrally separated beams 61, 63, 65. Optical 
beams 61 and 63 are transmitted in parallel directions as a result of the 
parallel faces of substantially transparent optical support medium 62. 
FIG. 4 illustrates the manner in which two optically flat transparent 
optical support media 60 and 62 can be attached to provide three 
substantially equally spaced dichroic layers to produce three 
substantially parallel optical beams 8, 9, 10 that are both spatially and 
spectrally separated. In accordance with the present invention, precise 
spectral and spatial separation of a projected line image is achieved 
through composited dichroic beamsplitters, as shown in FIG. 4. The optical 
separator 56 consists of precisely ground and polished glass plates 60 and 
62 coated on one or both faces with dichroic coatings 50, 52, and 54. At 
each dichroic coating 50, 52, and 54, incident light is either reflected 
or transmitted according to wavelength with negligible absorption loss. 
The composition of the dichroic coatings 50, 52, and 54 can be designed 
for accurate bandpass filtration. 
Dichroic coatings are well known in the art of optics. Dichroic coatings 
typically consist of 20 or more alternating high and low refractive index 
optical layers vacuum-deposited to an accumulative thickness of, 
typically, about one to three microns on a glass surface. The material 
composition and method of deposition can be designed for very accurate 
spectral bandpass filtration. A variety of dichroic filters, consisting of 
a single glass plate front surface coated with a dichroic coating, are 
commercially available from a variety of sources (e.g., Optical Coating 
Laboratory, Inc., located in Santa Rosa, Calif.). 
The plate 2, shown in FIG. 4, is designed such that incident light striking 
dichroic coating 50 at 45 degrees reflects blue light (approximately 
400-500 nm.) while transmitting red light and green light. 
Plate 3, shown in FIG. 4, is coated on both faces with dichroic coatings 52 
and 54 such that incident light striking a first dichroic coating 52 at 
nominally 45 degree reflects the red spectral band (e.g., 600-700 nm.) 
while transmitting the green band. The green light striking a second 
dichroic coating 54 and having an optical axis oriented nominally 45 
degrees from the dichroic coating is reflected. The reflected green light 
is caused to pass back through the glass plate 62 and through the other 
dichroic coatings 52 and 50 at a 45 degrees angle. As shown in FIG. 4, 
each of the components 8, 9 and 10 of the incident light are reflected at 
90 degrees to incoming beam 67. The reflected red and green components 9 
and 8 are parallel and separated from each other by a distance determined 
by the glass plate 62 and dichroic coating thickness 54, the plate 62, and 
the angle of incidence. Similarly, the blue and red components 10 and 9 
are separated by a distance determined by the thickness of glass plate 60, 
dichroic coating 50, the index of refraction of the plate 60 and the angle 
of incidence. 
A trichromatic separation of an incident light beam can be achieved through 
a composite of beamsplitter plates 2 and 3, as shown in FIG. 4. Each of 
the three spectrally-tailored dichroic coatings 50, 52, and 54, are 
separated by the thickness of glass plates 60, 62. Incident light striking 
the first dichroic coating, and having, for example, an angle of incidence 
of 45 degrees from the dichroic coating, is filtered such that the blue 
spectral band is reflected. The unreflected bands (red and green) are 
transmitted to a second dichroic coating 52 located between the glass 
plates 60 and 62. Coating 52 reflects the red spectral band. The remaining 
band, i.e., the green spectral band, is reflected from the third dichroic 
coating 54. The red and green spectral components exit the composite 
beamsplitter 56 through the glass plates 60 and 62 and dichroic coatings 
50 and 52, essentially unperturbed. Thus separated, red, green, and blue 
components of the incident light beam are reflected at 90 degrees to the 
principal incident beam with a parallel spatial separation which is solely 
determined by the thickness of the glass plates 60, 62, and dichroic 
coatings 50, 52, and 54, and the refractive indices thereof. The order in 
which the reflected color bands have been presented is by example only. It 
is further obvious that a mirror coating could be substituted for the 
third dichroic coating 54, since only the third remaining color component 
reaches that coating interface. 
A suitable photosensor for use with this invention is shown in FIG. 5. 
Photosensor 11 is preferably a single chip, single package solid state 
device having three linear photosensor arrays, 12, 13 and 14, precisely 
aligned and spaced to coincide with the focused line images 8, 9 and 10, 
respectively, shown in FIGS. 4 and 7. Such devices can be made using known 
technologies. For example, numerous photosensor array devices are now 
commercially available. Most prominent are photodiode arrays with 
charge-coupled shift registers (CCD photosensors). Such single line CCD 
photodiode array devices are commercially available from Fairchild 
Semiconductor, located in Palo Alto, Calif., Toshiba, located in Japan, 
and other companies. The photosensor array devices have commercial 
resolutions ranging from 128 to over 5000 photoelements per line. The 
spacing between photoelements typically ranges from 10 to 62 microns. 
Thus, the design and manufacture of a photodiode array shown in FIG. 5 
uses known technologies to produce the three parallel photosensor arrays 
12, 13 and 14. 
As illustrated in FIG. 6, a distance "D" separates the photosensor arrays 
12, 13, and 14. As shown in FIG. 7, the distance "D" is related to the 
separation of the dichroic coatings 50, 52, and 54, and angle theta of the 
photosensor 11. The distance between photosensors 12 and 13 does not have 
to be equal to the distance between photosensors 13 and 14. The three 
photosensor arrays 12, 13, and 14 have common clock inputs for 
synchronization. As is well known in the art, integrated circuit 
photolithography processes are capable of aligning and spacing the three 
linear photosensor arrays 12, 13 and 14 to submicron precision. The 
combined spatial precision of the described trichromatic beamsplitter 56 
and three photosensor array detectors, 12, 13 and 14, allows accurate 
coincidence of the detected images with the single line image of the 
original. 
The preferred arrangement of trichromatic beamsplitter 56 and photosensor 
11 is shown in an end view in FIG. 7. Due to the variations in 
path-length-through-glass between the three separated color components, 
beamsplitter 56 and photosensor 11 are mounted to have an inclusive angle 
less than 90 degrees, typically 80 degrees for nominal glass refractive 
index. The inclusive angle is independent of the focal distance between 
the lens and photosensor. At the inclusive angle, the three separated 
color components will properly focus on each respective linear photosensor 
array 12, 13 and 14. The spatial separation of arrays 12, 13, and 14 is 
directly determined by the thickness of the glass plates 60 and 62, 
dichroic coatings 50, 52, and 54, and the refractive indexes of the 
optical support medium 60 and 62. (Standard lens formulas are used to 
calculate the angle and separation distances.) Trichromatic beamsplitter 
56 and photosensor 11 are preferably assembled in a housing that maintains 
the desired angles and distances, and that consolidates the parts into a 
single package. 
As is well known in optics, a focused light beam transmitted through as 
glass plate at an angle of incidence other than 90 degrees is subject to 
oblique spherical aberration. This causes astigmatism. Increasing glass 
thickness and angle of incidence exacerbate the astigmatism. The red, 
blue, and green spectral components experience different degrees of 
degradation due to their different path length through the glass and the 
high angle of incidence (45 degrees). This compromises the focus and 
resolution of the color separation technique to the extent that the 
chromatic foci through the trichromatic beamsplitter occur beyond the 
depth of focus provided by the imaging lens. 
In the preferred embodiment, the thickness of the glass plates 60 and 62 
and dichroic coatings 50, 52, and 54, and the spatial separation of the 
three photosensor arrays 12, 13, and 14, in photosensor 11 are 
collectively minimized to render negligible the otherwise optical 
deficiencies and minimize cost. Since thin glass plates (on the order of 
0.1 to 0.2 millimeter) are difficult to grind and coat without substantial 
warpage, a preferred method of beamsplitter manufacture will include a 
thick glass substrate 70, shown in FIG. 8, from which the trichromatic 
beamsplitter 56 is built up. In this preferred method, the thick glass 
substrate 70 is ground flat, polished and coated with dichroic coating 54. 
Glass plate 62 is bonded using an optical cement. The exposed surface of 
glass plate 62 is then ground flat and polished to provide the desired 
thickness of coating, cement and glass as measured through the composite. 
In a like manner, glass plate 62 is coated with dichroic coating 52, then 
bonded to glass plate 60, at which point the surface of plate 60 is ground 
and polished to the desired thickness. Finally, dichroic coating 50 is 
deposited on the exposed surface of plate 60. Using said fabrication 
method, trichromatic beamsplitter 56 can be manufactured from relatively 
large glass sheets from which many beamsplitters may be cut at minimum 
part cost. 
An alternate embodiment utilizes a single pair of beamsplitter plates and a 
single prism. As shown in FIG. 9, the incident light beam is aligned to 
impinge a first base side 30 of right-angle prism 1 at a normal angle and 
transmit therein to the hypotenuse face 32 of the prism 1 which the light 
beam impinges at 45 degrees. The composite beamsplitter 56 of FIG. 4, 
consisting of beamsplitters 2 and 3, is attached thereto. A trichromatic 
separation of the red, green and blue spectral components of the incident 
light beam occurs as previously described. The three reflected component 
beams re-enter the prism 1 and are directed toward the second base side 34 
of the prism. The component beams exit the prism at 90 degrees to its base 
side 34 and with an optical axis spatial separation (SQRT 2)x where x is 
the thickness of the glass, optical cement and dichroic coating between 
two adjacent dichroic coatings. Irrespective of the lens used to focus 
through beamsplitter 56, the three component light beams will focus on a 
plane oriented at an angle theta=arctan 2 (n-1/n) to the second base side 
34 of prism 1, where n is the refractive index of the glass prism 1 and 
beamsplitter plates (for n=1.517, theta=34.28 degrees). The three linear 
array photosensors 12, 13, and 14, as previously described, are aligned on 
said plane at angle theta at the location of foci of the three component 
beams. Trichromatic beamsplitter 56 with the prism 1 allows a 90 degree 
angle of incidence to glass and chromatic focusing to each sensor array 
12, 13, and 14. 
In order to align photosensor 11 to be perpendicular to the optical axes of 
the color-separated beams, the dual trichromatic beamsplitter with prism 
59 shown in FIG. 10 is adopted. In this embodiment, the 
path-lengths-through-glass of the color-separated beams are made equal by 
the reciprocal arrangement of the trichromatic beamsplitters 56 and 58. 
As shown in FIG. 10, the incident light beam is aligned to impinge the 
hypotenuse face 32 of right angle prism 1 at a normal angle and transmit 
therein to a first base side 30 of the prism 1 which the light beam 
impinges at 45 degrees. The composite beamsplitter 56 of FIG. 4 is 
attached thereto. A trichromatic separation of the red, green and blue 
spectral components of the incident light beam occurs as previously 
described. The three reflected component beams re-enter the prism 1 and 
are directed toward the second base side 34 of prism 1, each separated 
beam impinging the second base side 34 at 45 degrees incidence. A second 
composite beamsplitter 58 is attached to the second base side 34 of prism 
1. The plates 60 and 62 and the dichroic coatings 50, 52, and 54, in 
beamsplitters 56 and 58 are identical. However, the orientation of the 
composite beamsplitters 56 and 58, and the multilayer dielectric coatings 
50, 52, and 54, on each base side 30 and 34 of the prism 1 are reversed so 
that the path lengths of each component color beam entering and exiting 
the trichromatic prism beamsplitter 59 are identical. That is, a component 
color beam, such as blue, reflects off the dichroic coating 50 on plate 60 
located on base side 30. Next, the blue component reflects off the 
dichroic coating 50 on plate 60 located adjacent to base side 34. In a 
like manner, a red component color beam goes from middle filter 52 on base 
side 30 to middle filter 52 on base side 34, and the green component 
reflects off a backside filter 54 to a front side filter 54 as shown in 
FIG. 10 Reflected beams from the trichromatic beamsplitter 58 adjacent to 
base side 34 are directed out of prism 1. The beams are perpendicular to 
the hypotenuse side 32 and parallel to the incident light beam. The 
thickness of the beamsplitter glass plates, 60 and 62, and the dichroic 
coatings 50, 52, and 54, determine the separation of the reflected beams. 
Thus, the dual trichromatic beamsplitter 59 provides an equal path length 
through the glass for all color components. Also, the light enters and 
leaves the prism at a normal angle of incidence. 
An alternative embodiment of trichromatic beamsplitter 59 could omit prism 
1. Without the prism 1, incident light impinges the beamsplitter 56 and 58 
at 45 degrees, creating astigmatic foci at the focal point of photosensor 
11. The degree of effect due to the astigmatism is a function of the depth 
of focus of the projection lens in the accompanying optical system, the 
spatial separation of the various dichroic coatings composing the 
trichromatic beamsplitter and the angle of incidence of the beams. The 
primary advantage of such an alternative embodiment is the removal of 
glass in the optical path for which a lens must correct. 
By way of example only, an optical system employing the trichromatic 
beamsplitter 59 of FIG. 10 is shown in FIGS. 12 and 13. A similar optical 
system can be employed with the beamsplitters 56 and 58, and prismless 
beamsplitter 59, in FIGS. 7, 9 and 10, respectively, or a beamsplitter 
that separates an incident light beam into more than three spectral bands 
through the compositing of multiple beamsplitter plates. A line image 7 of 
an original object is projected through an aperture 75, as shown in FIG. 
12, by a lens 6 through the hypotenuse face of prism 1 such that the 
optical axis of the incident beam is normal to said face. Aperture 75 is 
constructed to block images from far away adjacent object lines about the 
principal object line 7 which would otherwise allow multiple separated 
images to strike the photosensors. The incident beam is separated into its 
three color components as previously described. The blue, red and green 
components emerge from the prism 1 as line images 8, 9 and 10, 
respectively. Since the individual path lengths of the color component 
beams through the beamsplitter 58 are identical, the said line images 8, 9 
and 10 reside on a single plane which is perpendicular to the hypotenuse 
face of prism 1. The spatial separation of the three line images 8, 9 and 
10, is determined by the glass plate spacing of the six dichroic coatings, 
50, 52, and 54, on the beamsplitter plates 60 and 62. By carefully 
tolerancing the individual thicknesses of beamsplitter plates 60 and 62, 
the spatial separation of focused line images 8, 9 and 10 can be very 
accurately determined and maintained. This feature is particularly suited 
for trichromatic photo detection on said monolithic solid state 
photosensor 11 shown in FIG. 12 and 5. Each line image, 8, 9 and 10, is 
electronically detected by one of three parallel spaced photosensors, 12, 
13 and 14. 
An assembly view of the described trichromatic beamsplitter 59 is shown in 
FIG. 11. The four beamsplitter plates 2, 3, 4, and 5 are oriented about 
prism 1 as shown and secured together with optical cement according to 
standard practice. Said optical cement is selected to have matching 
refractive index with the glass. Typical optical cements are polyester or 
acrylic bases. In the assembly process it is important to minimize glue 
line thickness, preferably micron to submicron glue films, to minimize 
random variation in the spacing of the dichroic coatings on the 
beamsplitter plates. This is typically accomplished by the application of 
heat and pressure to the composite structure during the adhesive process. 
Referring now to the beamsplitter dimensioning shown in FIG. 10, assuming 
the dichroic coatings 50, 52, and 54 are separated by a distance X, the 
incurred separation of the three focus line images 8, 9 and 10, will be 
(SQRT 2)(2x). The separation of the dielectric optical filters, 50, 52 and 
54, is dominated by the glass plate thickness (the filter 50, 52 and 54 
thickness is typically 3 micrometer for standard dichroic coatings). Thus, 
the glass plate thickness principally determines the separation between 
image lines 8, 9 and 10. Variations in image lines 8, 9 and 10 separation 
are determined by variations in glass plate separation. For example, to 
maintain image lines 8, 9 and 10, a spacing tolerance of 7 microns 
(one-half of standard 13 micron photoelement) a glass plate thickness 
tolerance of 2.5 microns (0.0001 inch) is required. Such glass thickness 
accuracy is available using conventional grinding and polishing procedures 
and equipment. 
The color component's path length through the trichromatic beamsplitter 59 
is (2).sup.1/2 A+2(2).sup.1/2 X where A is the dimension of a base side of 
prism 1, as shown in FIG. 7A. Reasonable small variations in the base and 
plate dimension can usually be handled by normal depth of focus 
characteristics of most lenses. 
As previously indicated, the line images 8, 9 and 10 and photosensor arrays 
12, 13, and 14 preferably have matched spacing. Thus, the spacing between 
photosensor arrays 12, 13, and 14 should be (SQRT 2)(2x) when the spacing 
between the dichroic coatings 50, 52 and 54 is x in beamsplitter 59 as 
shown in FIG. 10. Thus, an array spacing of 1.0 mm required a beamsplitter 
plate 60 and 62, thickness of 0.35 mm. for beamsplitter 59. Under normal 
conditions, dichroic coatings 50, 52, and 54, applied to glass plates of 
such small thickness will cause a mild bowing of the glass plate. During 
assembly of beamsplitter 59, however, the bow can be removed by the 
plate's adherence and conformity to the rigid flat surface of the prism 1. 
Reasonable minimum array spacings for CCD photodiode arrays are about 0.2 
to 0.3. Such minimum spacings dictate beamsplitter plates 60 and 62, on 
the order of 0.07 to 0.2 mm. thick, depending on the beamsplitter 
embodiment utilized. To achieve these dimensions in manufacture, the 
previously described fabrication technique of FIG. 8 is recommended. It is 
obvious that this technique is applicable to all of the aforementioned 
trichromatic beamsplitter embodiments. 
The profile view of FIG. 12, has the appearance of a "projection" imaging 
apparatus. That is, a relatively long object line 7 is projected into 
smaller image lines 8, 9 and 10 via lens 6. In such a system, the 
photoelements 80 shown in FIG. 6 in the photosensor arrays 12, 13 and 14 
must be proportionately smaller than the desired scanning resolution of 
the original. The advantages of such a "projection" type scanning device 
is the use of a small photosensor arrays 12, 13 and 14. 
The present invention is not limited to "projection" optics and, in fact, 
is quite extensible into other product and application forms. In 
particular, the present trichromatic beamsplitter 59 and three linear 
array photosensor 11 can be packaged with a fiber array lens 15 to produce 
a "contact" type scan head 57, shown in FIG. 14. "Contact" type scan heads 
57 principally use lenses with unity magnification. As such, the lens and 
sensor can be compacted in close proximity to the original. (The scan head 
does not actually contact the original as the name would imply.) 
Fiber array lenses 15 are well known in the imaging field and are a product 
of Nippon Sheet Glass (Japan) under the name SelFoc Lens. The fiber array 
lenses 15 are available in small and long length such as page width. The 
fiber array lenses 15 are made of glass fibers of given length. Each fiber 
acts as an individual lens since chemical treatment varies the refractive 
index as a function of its radius. In this instance, the lens array 15 
projects the line image of an original 7 through the trichromatic 
beamsplitter 59 to three linear array sensor 11. The length of the lens 
array 15, beamsplitter 59 (or other previously described beamsplitter 
embodiment) and photosensor 11, as it moves into the page in FIG. 14, is 
determined by the application: relatively long lengths for page width 
scanning (e.g., 8.5 inches long) or short lengths for "traversing" type 
scanning in which the scan head 57 is caused to traverse back and forth 
over the original object by an external mechanism. For equivalent scanning 
resolution, the contact (unity magnification) type scan head 57 shown in 
FIG. 14 requires proportionately less stringent tolerance on beamsplitter 
plates 2, 3, 4 and 5 thickness in comparison to the projection type 
scanner shown in FIGS. 12 and 13. On the other hand, for equivalent scan 
width, the contact scanner 57 must be proportionately longer as measured 
by the ratio of the lens magnifications, unless the scan head 57 is 
traversed across the original. 
A significant advantage of dichroic coatings 50, 52 and 54 over other 
filtration techniques is design versatility with respect to bandpass 
wavelengths and the slope and crossover characteristics of the band pass. 
Very sharp step function bandpass as well as controlled slope crossover 
with adjacent color bands is controller by a number of layers, material 
type, and coating layer thicknesses in a given filter. In the visible 
spectrum very clean bandpass discrimination can be achieved between red, 
green and blue or cyan, magenta and yellow. By contrast, conventional 
organic dye filters, as used in the prior art, are typically not as 
well-defined and usually have close band or multiple band filtration 
characteristics which ultimately prevents accurate color separation, 
usually due to undersaturation of a given detected trichromatic color. 
The teachings of the present invention have been principally applied to 
color document scanning. Scanned document images, in this instance, are 
displayed on a color monitor. The accuracy of the color separation is 
judged by the likeness of the displayed image colors to that of the 
original document. To obtain color fidelity, the color separation must 
match the spectral characteristics of the individual red, green and blue 
phosphorus in the monitor display screen. This was successfully achieved 
by using dichroic beamsplitters 16 and 17 and a phosphor-tailored 
fluorescent lamp 22 in a test apparatus, depicted in FIG. 15. The test 
apparatus utilizes three single linear array CCD photosensor 18, 19 and 20 
(Toshiba TCD 102C-1) with a 2048 element array. 
Referring to FIG. 15, a fluorescent light source 22 illuminates the surface 
of an original document 21. A line image of the original seven is 
projected onto a beamsplitter assembly, consisting of dichroic 
beamsplitters 16 and 17, by lens 6. Beamsplitters 16 and 17 are flat glass 
plates coated on one side with dichroic coatings 50 and 52, respectively. 
Beamsplitter 16 is designed to reflect blue light while transmitting red 
and green spectral bands. The blue light is reflected to a first CCD 
linear-array photosensor 18, with beamsplitter 16 tilted at 45 degrees to 
the incident light beam. Beamsplitter 17 reflects red light to a second 
CCD photodiode array sensor 20. The beamsplitter plates are Optical 
Coating Lab commercial blue and red 45 degrees Dichroic Color Separation 
Filters. The green line image passing through both beamsplitter plates is 
captured by the third CCD photodiode array sensor 19. Beamsplitter plate 
17 is also aligned at 45 degrees, as shown. 
The band pass characteristics of the collective beamsplitter assembly of 
FIG. 15 is shown in FIG. 16. Although the crossover wavelengths between 
color bands is clean and spectrally accurate for separation, the reflected 
bands do not share the spectral shape and balance of the output device's 
color palette. Output devices include monitors and hard copy devices. 
Spectral accuracy, in this case, is most easily provided by spectrally 
tailoring the light source 22. Fluorescent lamp phosphors can be blended 
to achieve a wide variety of spectra. The spectral bandpass 
characteristics of the dichroic coatings 50 and 52, can be used to choose 
phosphors of the lamp 22 so that the color separation of the coatings 50 
and 52, will match the monitor's display phosphors. The result of the HP 
Color Model study was a lamp specification used by Sylvania Lamp to 
prototype a scanner lamp source 22. The prescribed phosphor recipe (from 
Hewlett-Packard Company) and the spectra of the prototype lamp, as made 
and measured by Sylvania, is shown in FIG. 17. 
The spectra of the spectrally-tailored fluorescent lamp as separated by the 
dichroic beamsplitters 16 and 17 and detected by CCD photodiode arrays 18, 
19 and 20, produce a color gamut nearly equivalent t standard monitor 
phosphor output. 
FIG. 18 is a schematic diagram showing a cut away view of the optical 
component 100 of the present invention employed as a trichromatic 
beamsplitter device. As shown in FIG. 18, an input beam 102 is focused by 
a lens 104 which is held by a lens holder 106 capable of focusing the lens 
very precisely on the detector surface of the three line CCD array 108. 
Input beam 102 impinges upon the optical surfaces of the optical separator 
100 and is separated into three predetermined colors to form three optical 
beams having predetermined spectral ranges that are carefully selected by 
the dichroic layers placed on the optical surfaces of the optical 
separator 100. As shown on FIG. 18, the first dichroic layer device 110 is 
disposed such that the angle of incidence of the optical axes of input 
beam 102 is approximately 22.5 degrees. Input beam 102 is then split into 
three spatially and spectrally separated beams that are transmitted to a 
second dichroic layer device 112 which is also disposed at approximately 
22.5 degrees to the optical axes of each of the spatially and spectrally 
separated optical beams. The second dichroic layer device 112 is normally 
constructed in the same manner as the first dichroic layer device 110 so 
that the three separate optical beams that are transmitted from the second 
dichroic layer device have equal optical path lengths to a predetermined 
image plane. As shown in FIG. 18, the detector device 108 is disposed on 
the image plane that is substantially normal to the optical axis of input 
beam 102. Each of the three spatially and spectrally separated optical 
beams is focused on a separate line detector array on detector 108 so that 
a line scan of, for example, a document, results in each of the colors 
from the line scan being detected simultaneously on the detector surface 
of detector 108 as a result of the equal optical path lengths of each of 
the individual spectrally separated beams. The dichroic layer devices 110 
and 112 are precisely held in the positions illustrated by a mounting 
device 114 that includes arm support structures 116, 118 and 120 that 
extend between two side portions. The support structure 114 is open in the 
central portions to allow light to be transmitted to the optical component 
100 and subsequently to detector 108. Detector 108 is also precisely 
located in the mounting device 114 by way of interface surfaces 122 and 
124. Signals derived from detector 108 are fed directly to circuit board 
126 via connectors 128 and 130 that comprise a plurality of connectors. 
FIG. 19 illustrates an alternative manner in which the optical component of 
the present invention can be constructed and utilized. As shown in FIG. 
19, the optical component 132 can be used to separate an input beam 134 
into three separate spatially and spectrally separated beams 136, 138 and 
140. Alternatively, the optical component 132 can be used to combine three 
spatially and spectrally separated input beams 142, 144, and 146, into a 
single combined output beam 148 that spectrally and spatially combines 
each of the input beams such that each optical axes of the input beams 
142, 144 and 146, are coincident as shown by output beam 148. Of course, 
all of the optical devices illustrated and described herein can be used in 
this manner as an optical combiner as long as the optical axes of each of 
the spatially and spectrally beams is aligned properly with the optical 
component, such as optical component 132. 
FIG. 19 also illustrates the manner in which each of the dichroic layer 
devices 150 and 152 can be constructed. As illustrated in FIG. 19, 
dichroic layer devices 150 comprises a substantially transparent optical 
support medium 154 that is coated on both sides with dichroic layers 156 
and 158. The substantially transparent optical support medium 154 is 
supported by spacers 160 and 162, that are attached to a substrate device 
164 having either a totally reflective surface 166, or a surface coated 
with another dichroic layer to provide a specified spectral range to be 
reflected from surface 166. The space between the surface 166 and the 
dichroic layer 158 can comprise an air gap or can be filled with an 
optically transparent medium or can be evacuated, depending upon the 
application of the optical component 132. As shown in FIG. 19, the 
optically transparent support medium 154 can comprise a glass plate that 
has a higher refractive index in the surrounding air, causing the 
individual optical beams to be refracted at different angles. Since the 
optical surfaces are reversed in dichroic layer device 152, the optical 
path lengths are adjusted so that they are equal in length to a plane that 
is substantially normal to the optical axes of each of the individual 
beams. Of course, the same is true whether the optical component 132 is 
being used as a color separator or color combiner. The difference in the 
refractive index of the glass plate versus the air gap does not cause a 
change in optical path lengths due to the fact that the surfaces from 
which the beams are reflected is reversed on the subsequent dichroic layer 
device as long as the glass plate has an air equivalent path length of the 
air gap. More specifically, a first and second dichroic plane may be 
separated by a distance X.sub.1 by material having an index of refraction 
of N.sub.1, and the second and a third dichroic layer are separated by a 
distance X.sub.2, by material having an index of refraction of N.sub.2. To 
have equal optical path lengths through the dichroic layers, the following 
must be true: 
EQU X.sub.1 /X.sub.2 =N.sub.1 /N.sub.2 
Hence, to maintain an air equivalent path length that is the same through 
each medium, the spacing between any two planes is directly proportional 
to the spacing between the other planes times the index of refraction of 
the material between the other two planes, and inversely proportional to 
the index of refraction of the material occupying the space between the 
other two planes. This is easily discernable when considering an air gap 
spacing since air has an index of refraction equal to 1. 
As illustrated in both FIGS. 18 and 19, the angle of incidence is 
approximately 22.5 degrees for each of the dichroic layer devices. The low 
angle of incidence and the very small plate size that is used in many 
applications results in minimal astigmatism so that more expensive optical 
prisms can be eliminated without noticeable degradation of optical 
quality. 
FIG. 20 illustrates an optical component 168 that can be constructed in an 
alternative manner. Optical component 168 can comprise first and second 
dichroic layer devices 170 and 172, that can be used for either spectrally 
and spatially combining or separating optical beams. As shown, dichroic 
layer device 170 has a substantially transparent optical support medium 
174 that has dichroic layers 176 and 178 disposed on two substantially 
flat sides. The substantially optically transparent support medium 174 is 
attached to a substrate 180 having either a totally reflective surface 
182, or a surface coated with another dichroic layer to provide a 
specified spectral range to be reflected from surface 166 by way of an 
optical glue 184 that is capable of transmitting substantially all optical 
radiation. The optical glue, such as previously disclosed above, can have 
an index of refraction that closely matches the optically transparent 
support medium 174 to prevent a change in the angle of refraction within 
the dichroic layer device 170. As mentioned previously, the optical 
transparent support medium 174, for many applications, must be very thin 
to produce the desired spacing between the beams. Coating of the dichroic 
layers 176 and 178 on the glass plates 174 may result in a bending or 
warpage of the optical transparent support medium 174. However, substrate 
180 has sufficient thickness to prevent warpage and has a substantially 
flat reflective surface 182 to which the optical transparent support 
medium 174 can be attached by way of the optically transparent glue 184. 
Proper attachment of the optical transparent support medium 174 to the 
substantially flat reflective surface 182 can provide sufficient support 
to maintain a substantially flat surface on optical transparent support 
medium 174. Of course, the thinner the glue layer is between optical 
transparent support medium 174 and the substantially flat reflective 
surface 182, the stiffer the glue line becomes which, in turn, further 
restricts relative movement. To provide even additional support, a glass 
plate with a thin layer of adhesive on both sides can be used in place of 
the optical glue 184. Again, dichroic layer device 172 would typically be 
constructed in the same manner as dichroic layer device 170 to simplify 
the overall optical component 168. 
FIG. 21 illustrates an alternative manner of constructing a dichroic layer 
device 186. Again, FIG. 21 illustrates that the dichroic layer device 186 
can be used either as a beam splitter or a beam combiner. Additionally, 
only one composite dichroic component 186 is illustrated, although 
additional composite dichroic component devices can certainly be utilized 
to equalize optical path lengths and direct the optical beams to different 
locations. 
FIG. 21 also illustrates that a plurality of optical transparent support 
media 188, 190, 192, 194, and 196, can be used to either separate or 
combine a plurality of beams. Of course, any number of beams can be 
combined or separated using the techniques of the present invention. As 
shown in FIG. 21, each of the optically transparent support medium 188, 
190, 192, 194, and 196, have dichroic layers 198, 200, 202, 204, and 206, 
disposed on its front layer. Spacers 208, 210, 212, 214, 216, 218, 220 and 
222, support and separate each of the optically transparent support media 
188, 190, 192, 194, and 196. Where large separation of the individual 
spectral beams occurs or is desired, the dichroic layer device 186 
illustrated in FIG. 21 is ideally suited. The spacing provided by spacers 
208, 210, 212, 214, 216, 218, 220 and 222, can be varied to account for 
the increased thickness such as the increased glass thickness of each of 
the optical transparent support media 188, 190, 192, 194, and 196, as the 
beam is transmitted through the dichroic layer device 186 to insure proper 
alignment of each of the individual spectral beams. Of course, optical 
glues, angles of incidence, plate thicknesses, use of prisms and other 
techniques, such as described herein, can be used in any of the devices 
shown, to reduce the effects of astigmatism and prevent other possible 
problems. Of course, it should be understood that any manner of supporting 
and separating substantially parallel dichroic planes can be used in 
addition to the glass plates, glue layers, spacers, etc., disclosed 
herein. The method of support and separation of a plurality of dichroic 
planes is secondary to the primary invention disclosed herein which 
comprises the use of a plurality of dichroic planes disposed at an angle 
to the optical beams for either spatially and spectrally combining or 
separating the beams. Additionally, the last optical transparent support 
medium 196 can be replaced with a totally reflective surface as described 
above. 
FIG. 22 illustrates other implementations of the optical component 224 of 
the present invention. As illustrated in FIG. 22, the spacing of the 
dichroic layer devices 226 and 228 can be changed as well as the angles of 
impingement, Theta One and Theta Two of the optical beams with the 
dichroic layers devices 226 and 228, respectively. Additionally, the total 
included angle theta three can also be varied to direct the optical beams 
to a predetermined plane. It is possible to maintain equal optical path 
lengths as well as vary the spacing between the optical axes of each of 
the individual spectral beams by varying both the angle of impingement and 
the plate thicknesses. As mentioned previously, the materials utilized in 
the dichroic layers devices 226, 228 can also be different to change the 
index of refraction as well as the path length of the optical beams within 
the dichroic layer devices to provide an additional manner of adjusting 
the optical component 224 of the present invention. For the purposes of 
simplicity, FIG. 22, as well as other drawings disclosed herein, have been 
drawn without the angles of refraction illustrated. 
FIG. 23 is a schematic side view of a color imaging device 230 that 
generates a color image on a recording medium 232 located on an image 
plane. As illustrated in FIG. 23, an illumination source 234 provides a 
source of white light which is filtered by filters 236 to provide three 
separate color beams that have predetermined spectral ranges and function 
as three separate sources of illumination. The color filters 236 are 
located adjacent to a liquid crystal display (LCD) device 238 that is 
further illustrated in FIG. 24. 
Referring to FIG. 24, the liquid crystal display device 238 has three 
linear arrays 240, 242, 244 of liquid crystal display shutters that are 
capable of transmitting light on a continuously variable gray scale from 
essentially a total throughput level to approximately opaque in response 
to an electrical control signal. A resolution of approximately 1000 
elements per inch can be obtained in LCD arrays, such as illustrated in 
FIG. 24. As a means of comparison, fine grain film may typically have a 
range of resolution of 600 to 800 line pairs per inch. Hence, a very high 
resolution can be obtained using LCD shutters. LCD shutters are available 
through several manufacturers including Epson Corporation and Sharp 
Corporation in Japan. 
Referring again to FIG. 23, the three optical beams 246, 248, and 250, that 
are transmitted from LCD shutter 238 have been adjusted in intensity to 
represent the color intensity of a single line of information to be 
recorded on recording medium 232 in accordance with the image information 
provided by the control signal. Optical beams 246, 248, and 250, are 
directed through optical component 252, which can comprise any of the 
optical components disclosed herein, and are focused by lens 254 onto the 
recording media 232. As illustrated, the three separate lines of 
information provided by each of the line matrices 240, 242 and 244 (FIG. 
24), is combined into a single beam having coincident optical axes such 
that each pixel element comprises a combination of the three primary 
colors from each of the optical beams 246, 248 and 250. This results in 
very high convergence and line acuity that is not possible using other 
techniques. For example, one method that has been contemplated for 
recording documents in this manner utilizes a CRT color monitor that is 
focused on a recording document with each of the colors sequentially 
exposed on the recording media. Not only does this technique require three 
separate exposures of the recording media, which is expensive and time 
consuming, line acuity and convergence are extremely low because of the 
triad of colors that are required in CRT color monitors. 
The recording media 232 of FIG. 23 can comprise a wide range of recording 
media. For example, the present invention could be used for presentation 
graphics by using a special color exposure paper available from Mead 
Company. The Mead paper is coated such that, when it is exposed to light, 
it changes chemically. The paper is then run through a roller which 
crushes the chemically altered coating to produce a color print. 
Additionally, recording medium 232 can comprise photographic film or any 
other recording medium capable of recording optical radiation, including 
non-visible radiation. Rollers 256 function to advance the recording 
medium 232 and can be driven continuously or in a step fashion using a 
stepping motor to correspond to the manner in which the control signal is 
applied to LCD shutter device 238. Alternatively, LCD shutter device 238 
can comprise three arrays of light emitting diodes (LEDs) that produce 
three different spectra of light in response to a control signal. In that 
case, the illumination source 234 and filters 236 can be eliminated. 
FIG. 25 is a schematic side view of a projection device using the optical 
component 260 of the present invention. As illustrated in FIG. 25, the 
optical component 260 is constructed in a manner similar to optical 
component 186 illustrated in FIG. 21 but can comprise any of the 
implementations of the optical component of the present invention. As 
mentioned previously, the spacing between the glass plates can be adjusted 
for the refraction produced in the glass plates. For example, if the angle 
of incidence is 22.5 degrees, as schematically illustrated in FIG. 25, the 
angle of the beam within the glass plate changes to approximately 14.61 
degrees for glass. To account for added glass thickness, each of the 
spacers must provide additional space for subsequently deeper layers in 
the optical component 260. Of course, the advantage of the spaced plate 
optical component 260, illustrated in FIG. 25, and optical component 186, 
illustrated in FIG. 1, is that as long as the glass plates are thick 
enough to provide an optically flat surface without warpage, the spacers 
provide automatic alignment of the glass plates to an accuracy of 
approximately two microns. 
FIG. 25 illustrates a two-dimensional projection device in which an optical 
source 262 produces white light that is filtered by color filters 264 
which each project a different spectral range of frequencies. Each of 
these filters 264 has a two dimensional surface that overlays the LCD 
matrixes 266. LCD matrixes 266 are also illustrated in FIG. 26. LCD 
matrixes 266 comprise three individual matrix arrays 268, 270 and 272, 
which are individually controlled by a control signal schematically 
illustrated by contacts 274, to provide an image for each separate color 
of the three primary colors. Of course, any number of matrixes can be used 
to provide any number of colors desired, although, only the three primary 
colors are necessary to provide a full color display. Each LCD matrix 
display is capable of transmitting a pre-determined amount of radiation of 
each spectral band at each spatial location of each individual matrix 
element in a continuously variable fashion that is controlled by the image 
control signal 274. The LCD matrices act as light shutters and are 
deposited using photolithography deposition precision that allows for very 
high resolution images. Additionally, they can be deposited on a 
monolithic substrate which allows the matrices to be aligned with the 
optical beams very easily, provides a very uniform electrical responsivity 
across each matrix, as well as between different colors (different 
matrices), and is easy and inexpensive to manufacture. The three 
two-dimensional beams are precisely combined in the optical component 260 
so that each of the optical beams 274, 276 and 278, has an equal optical 
path length. The single spectrally and spatially combined beam 280 is then 
focused by lens 282 on a projection screen 284 which can be designed for 
viewing either from the front or back sides. Lens 282 is schematic in 
nature and most likely will comprise at least a two element lens for 
projection onto screen 284. 
An advantage of the projection device illustrated in FIG. 25 is that each 
pixel element is a superimposition of each of the three colors. In other 
words, each pixel is a color composite of all three colors. This differs 
significantly from typical color CRT screens wherein each pixel is a 
separate color that the eye optically integrates into a single combined 
color pixel. In accordance with the present invention, a much sharper 
image is produced since there is a convergence of all three colors in each 
pixel element. Furthermore, typical color CRT screens require a shadow 
mask to separate each individual color pixel. Since the present invention 
has complete color convergence of each pixel, shadow masks are not 
necessary and much greater picture clarity can be obtained. Most 
importantly, the projection device of the present invention does not 
produce the harmful X-rays that are produced by CRTs. 
Alternatively, the device of FIG. 25 can be used as a projection device for 
projecting an image on a recording medium. In other words, projection 
screen 284 can comprise a recording medium rather than a projection screen 
so that images can be recorded in both dimensions simultaneously rather 
than in a single dimension in a serial fashion such as is illustrated in 
FIG. 23. Moreover, the LCD matrix 266 can be replaced by a series of light 
emitting diode matrixes such that the filters 264 and illumination source 
262 can be eliminated. In this case, each LED matrix 268, 270 and 272, 
would produce a different spectral range of frequencies. 
FIG. 27 is a schematic isometric view of an implementation of the optical 
component 286 of the present invention employed as a two dimensional color 
optical component system that could be employed, for example, in a color 
camera. As illustrated in FIG. 27, lens 288 focuses an image from an 
object plane 290 through an aperture device 292 that determines the field 
of view of the color camera device illustrated in FIG. 27. The image from 
the object plane 290 is focused onto an image plane on which three 
matrixes of detectors 294, 296, and 298, are disposed to detect the 
individual color beams that are separated by optical component 286. 
Optical component 286 is shown constructed as a prism 310 having optical 
spacer plates 300, 302, 304, and 306 attached thereto. Of course, any of 
the optical component devices disclosed herein can be used in place of 
optical component 286, illustrated in FIG. 27, depending upon the 
precision and expense desired. A clear advantage of the implementation of 
the present invention illustrated in FIG. 27 is that each of the detector 
matrixes 294, 296, and 298, can be located in the same plane and adjacent 
to each other so that they can be constructed on a monolithic substrate. 
This eliminates many alignment problems that are associated with standard 
prior art dichroic prism devices and provides a uniform output so that 
each color intensity need not be individually adjusted for each use or 
during the course of use of the camera. Because each of the matrices of 
detectors 294, 296, and 298, are located on the same substrate, nearly 
uniform temperature gradient provides for nearly identical variations in 
output intensity of the signals from the detectors. 
FIG. 28 comprises a schematic side view of a color camera device, such as 
illustrated in FIG. 27, that uses the spaced plate implementation, such as 
illustrated in FIG. 21 and FIG. 25, for the optical component 312. As 
illustrated in FIG. 28, an aperture device 314 restricts the field of view 
of an image that is focused by lens 316 onto the three matrix detector 
318, 320, and 322. Optical components 312 split the single optical beam 
324 into three separate color beams 326, 328, and 330, having equal 
optical path lengths, in the manner described previously. 
FIG. 29 illustrates the three matrix detector 318, 320, and 322 that are 
mounted on a monolithic substrate 332 to provide a uniform color output 
signal. 
FIG. 30 illustrates an electronic colored filter device for filtering an 
input optical beam 334 produced by an illumination source 336 that is 
imaged through a pinhole or line aperture 351 in an aperture plate 338 to 
form a filtered output optical beam 336. Input optical beam 334 is focused 
by lens 340 through the spectral beam splitter 342 onto an aperture plane 
344 on which a number of aperture devices, such as LCD shutters 346, 348, 
and 350, are disposed to vary the throughput of light in response to an 
electrical control signal. LCD shutters 346, 348, and 350, can comprise 
either single pinhole apertures or can comprise a linear array depending 
upon whether aperture 351 comprises a pinhole aperture or a line aperture. 
The resultant beams that are projected through the LCD shutters 346, 348, 
and 350, have an intensity that is adjusted by the electrical control 
signal that controls the opacity of the LCD shutter devices. These beams 
are then precisely combined by spectral combiner 352 and focused by lens 
354 to produce the single combined output beam 336 that is both spatially 
and spectrally combined and adjusted in spectral content in accordance 
with the electronic control signal. Again, any number of color beams can 
be produced in the device illustrated in FIG. 30 together with a 
corresponding number of shutter devices to provide additional control of 
the spectral content of output beam 336. Also, any type of shutter device 
can be used in place of the LCD shutters 346, 348, and 350. Additionally, 
the individual spectral beams can be produced in any desired manner and it 
is not necessary that the beamsplitter 342 be employed. 
FIG. 31 comprises a schematic side view of a multiple channel fiber optic 
communication device 360. Fiber optic communication devices allow 
transmission of high bandwidth information across a fiber optic such as 
fiber optic 362. This allows for high frequency modulation of an optical 
source such as laser diode. Laser diodes can be switched in the megahertz 
frequency range. However, the demodulated signal at the receiving end 
constitutes a single station signal since only one carrier frequency is 
transmitted through the fiber optic. 
The present invention, as disclosed in FIG. 31, overcomes these 
disadvantages and limitations by providing multiple carrier signals in the 
form of plurality of spatially and spectrally separated beams that have 
been combined into a single combined beam. As illustrated in FIG. 31, an 
optical generator 364 contains a plurality of individual and spatially 
separated optical generators 366, 368, and 370, each having a different 
spectral range. Each of the individual optical generators 366, 368, and 
370, is modulated separately by a separate communication signal via 
electrical connectors schematically illustrated as connectors 372. The 
optical component 374 of the present invention is aligned to combine the 
individual beams produced by optical generators 366, 368, and 370, into a 
single combined beam 376. The single combined beam is then focused by way 
of lens 378 into a beam 380 onto the end of a fiber optic 362 for 
transmission to a remote location. 
At the remote location, as illustrated in FIG. 31, the combined spectral 
beam is transmitted as shown at 382 from fiber optic 362 and focused by 
lens 384 through the optical component 386 of the present invention onto a 
plurality of photo detectors 388, 390, and 392. The optical component 386 
spatially and spectrally separates the combined beam 382 into its spectral 
components that are individually focused on photo detectors 388, 390, and 
392. Alignment of the optical component 386 and selection of the dichroic 
filter layers allows for accurate separation of each of these spectral 
bands that is produced by optical generators 366, 368, and 370, onto photo 
detectors 388, 390, 392. 
The device of FIG. 31 allows for transmission of multiple channels on a 
single fiber optic 362 by virtue of the ability to spatially combine a 
plurality of individual beams having different spectral ranges for 
transmission across fiber optic 362 and subsequently separate the optical 
beam into its spectral components at the receiving end. In this manner, 
the present invention provides the ability to transmit multiple carrier 
bands on a single fiber optic. Of course, as many spectral bands as 
desired can be transmitted and the present invention is ideally suited for 
transmitting multiple spectral bands since the dichroic layers can be 
designed as notch filters to reflect and transmit very narrow spectral 
bands. Additionally, the optical signal can be generated by any desired 
optical source including the aperture device 344 illustrated in the 
electronic filter disclosed in FIG. 30. Also, the optical source 364 can 
comprise a series of line generators or a matrix of generators that can be 
focused by lens 378 onto an array of fiber optic cables to facilitate 
transmission over multiple fiber optic cables in a simple and easy manner. 
FIG. 32 schematically illustrates the use of multiple laser sources 394, 
396 and 398, which can comprise solid state lasers or gaseous lasers 
depending upon the application of the optical source. As illustrated in 
FIG. 32, laser 394 is capable of generating a red beam 400 while laser 396 
generates a blue beam 402 and laser 398 generates a green beam 404. Again, 
as many different optical sources can be used as desired to produce as 
many beams as required. Laser sources can be used in any of the 
applications of the present invention illustrated herein. For example, 
gaseous lasers may be required to produce sufficient power for 
transmission over extended distances over a fiber optic 362, as 
illustrated in FIG. 31. Additionally, it may be advantageous to use 
gaseous lasers in the various projection systems, such as the projection 
system illustrated in FIG. 25, to produce sufficient illumination of the 
projection source. Also, color holographic projection or recording may be 
implemented using lasers. 
FIG. 33 shows an alternative implementation of the device illustrated in 
FIG. 31. As illustrated in FIG. 33, an optical generator 406 capable of 
generating a plurality of spectral beams is combined into a single beam 
408 by lens 410. Lens 410 combines the individual spectral beams into the 
single combined beam 408 and focuses the single combined beam 408 on the 
end of fiber optic 412. The invention is then implemented in substantially 
the same manner as described in FIG. 31 at the receiving end to spatially 
separate the combined beam 414 by way of optical component 416. Each of 
the individual spectral beams is focused onto a photo detector 418 by way 
of lens 420. Because the optical path lengths of each of the individual 
beams is not critical, due to the fact that each spectral beam comprises 
an individual carrier band, it is not essential that both composite 
dichroic devices 422 and 424 be employed to separate the combined beam 
414. Hence, only a single composite dichroic device, such as dichroic 
device 424, is necessary in accordance with the invention illustrated in 
FIG. 33. 
The present invention therefore provides both an optical separator device 
as well as an optical combiner device which can be employed in a number of 
unique implementations. The composite dichroic layer devices of the 
present invention can be employed in a number of different ways with a 
wide range of variables to produce the desired results and optical 
quality. The present invention is capable of inexpensively combining or 
separating individual substantially parallel spectral beams which 
eliminates many of the problems involved with alignment of components. 
Additionally, construction techniques of the optical component are greatly 
simplified over prior art devices, such as dichroic prisms, allowing for 
an optical component capable of producing comparable or better optical 
quality at only a fraction of the cost of dichroic prisms. 
The foregoing description of the invention has been presented for purposes 
of illustration and description. It is not intended to be exhaustive or to 
limit the invention to precise form disclosed, and other modifications and 
variations may be possible in light of the above teachings. The embodiment 
was chosen and described in order to best explain the principles of the 
invention and its practical application to thereby enable others skilled 
in the art to best utilize the invention in various embodiments and 
various modifications as are suited to the particular use contemplated. It 
is intended that the appended claims be construed to include other 
alternative embodiments of the invention except insofar as limited by the 
prior art.