Imaging system using tellurium-based energy sensitive sheet and variable image displaying means

A system is disclosed which includes a transmissive liquid crystal display of the type which may display a line of characters or symbols at a time, or which may display only a raster line in combination with an energy source and a controllable and transportable medium. The medium is exposed by energy from the source of energy passing through the liquid crystal display which acts as a mask for the source of energy. The liquid crystal display may be set by electrical signals manually generated such as by a keyboard or by signals automatically generated by use of other electronic equipment. In one alternate embodiment of the invention a large area two-dimensional liquid crystal display is used as a mask. In another embodiment of the invention a liquid crystal display is used as a mask for the purpose of exposing a photoconductive drum of the type used in xerography. A reflective liquid crystal display is disclosed in yet another embodiment of the invention.

FIELD OF THE INVENTION 
The present invention generally relates to a system for creating images, 
such as letter characters, on a medium such as paper. The present 
invention more particularly relates to such a system which includes an 
electronically controlled image forming means, such as a liquid crystal 
display, to enable the formation of the images on a light sensitive 
medium. The invention further relates to such a system capable of making 
multiple copies of an image without the need for first forming an 
intermediate or original copy of the image. 
BACKGROUND OF THE INVENTION 
Various types of impact printers or impact mechanisms are known in the 
prior art to create images, such as letter characters, on paper. Impact 
printers while widely used exhibit certain deficiencies. For example, 
impact printers require inking. Typically, the inking is accomplished by 
an ink carrying ribbon which must be periodically replaced. The ribbon not 
only must be properly inserted into the printer but, in addition, 
represents an additional cost in operating the printer. Impact printers 
further are noisy and because they are electro-mechanical devices 
incorporating many moving parts, they are always subject to wear. The 
electro-mechanical nature of such printers also limits their operating 
speed as well. Further, because they are electrochemical in nature and 
have become fairly complex, they require periodic servicing to minimize 
break downs, are bulky and heavy, and as a result, are difficult to move. 
Such printers are therefore essentially not portable. 
Xerographic systems are also known in the prior art for creating multiple 
copies of images, such as letter characters, on paper. Such systems rely 
heavily on complex optical systems and require an intermediate medium such 
as an original copy on which the images are recorded prior to the making 
of the multiple copies. Further, conventional xerographic machines include 
mechanical scanning systems which provide scanning movement of the 
original with the image formed thereon relative to a light source. These 
scanning systems are complex and subject to break down. As a result, they 
require periodic maintenance and service. 
Laser based non-impact systems are also known in the prior art for forming 
images, such as letter characters on paper. They generally require complex 
electronics to precisely control the deflection of the laser. Further, 
such systems require adequate power to properly drive the laser as well as 
the related control circuitry. These systems are also rather expensive due 
to the cost of the laser and the control circuitry. 
It has also been known from the prior art to use electromechanical plotters 
or ink jet technology to apply ink in a nonimpact fashion to a medium to 
form images thereon. The electromechanical plotter technology is very 
speed limited. The ink jet technology relies on controllably applying a 
stream of ink to a medium and exhibits the disadvantage of being a wet 
process. Further, the ink jet technology is limited by the speed at which 
a jet can apply particles of ink to a medium. 
There is therefore a need in the art for a light-weight, essentially silent 
image creation system that can inexpensively create high quality images. 
There is further a need in the art for a light-weight, essentially silent 
image creation system which can also create multiple copies of an image 
without the need for an intermediate or original copy. 
SUMMARY OF THE INVENTION 
The invention provides for a display system having a source of radiant 
energy, an energy sensitive medium, means for displaying an image and 
means for providing an electrical control signal connected to the means 
for displaying an image with the means for displaying an image adapted to 
display an image in response to the electrical control signal and further 
adapted to control the spatial impingement of radiant energy generated by 
the source of radiant energy onto the energy sensitive medium whereby an 
image corresponding to the image displayed on said means for displaying an 
image is formed on the energy sensitive medium. 
An embodiment of the invention includes a transmissive liquid crystal 
display positioned between a light sensitive medium such as a tellurium 
imaging film or paper coated with tellurium imaging material and a light 
source. The liquid crystal display acts as a passive valve or mask which 
is electronically controlled from a keyboard or other source of electrical 
signals. The image formed on the display in response to the electrical 
signals, determines which regions of the film or coated paper will be 
exposed by radiant energy from the source of light. The image is 
permanently formed on the film or coated paper. A transport mechanism 
adapted to move the film or coated paper permits a liquid crystal display 
that displays only a line of characters at a time or a raster line display 
that displays only a single raster line at a time to be used to generate a 
larger image. 
An alternate embodiment of the invention includes either a transmissive or 
a reflective liquid crystal display which is electronically controlled. 
The display can be used to control the impingement of radiant energy upon 
a photosensitive drum such as used in a standard xerographic reproduction 
process. 
The invention also provides for a method of forming a permanent image in an 
energy sensitive medium comprising the steps of: providing a selected 
electrical signal corresponding to the image to be formed, sensing the 
electrical signal and forming a spatial representation thereof, modulating 
radiant energy from a source of energy by means of the formed spectral 
representation of the image, and exposing a region of the energy sensitive 
medium with the modulated radiant energy to form the image permanently 
thereon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With respect to the figures, FIG. 1 discloses a block diagram 5 of an 
embodiment of the present invention. The imaging system of block diagram 5 
includes a keyboard 10 connected a register 15 having a display unit 20 
attached thereto. Keyboard 10 is a standard electronic or 
electromechanical typewriter-like keyboard which when a key thereon is 
depressed causes a character code to be loaded into register 15. The 
display unit 20 displays the last line of characters that have been 
entered using the keyboard 10. The register unit 15 generates electrical 
signals corresponding to the stored characters and these signals are 
connected to a liquid crystal display 25. The liquid crystal display 25 is 
of the transmissive type and is adapted to display a line of perhaps 
eighty alphanumeric characters with each character being formed of a 
selected matrix size such as 9.times.12. The display 25 displays the 
characters whose codes have been loaded into the register unit 15. 
The liquid crystal display 25 is positioned in a housing 30 along with a 
source of illumination or energy 35 positioned above the liquid crystal 
display 25. Liquid crystal displays of a suitable type are known in the 
art and such displays are disclosed, for example, in U.S. patent 
application Ser. No. 573,004 filed Jan. 23, 1984 and entitled Liquid 
Crystal Displays Operated by Amorphous Silicon Alloy Diodes, assigned to 
the assignee of the present application Ser. No. 573,004 is incorporated 
herein by reference. The display 25 is positioned between the source of 
energy 35 and an energy sensitive medium 40. The energy sensitive medium 
40 can be a selected film or coated paper. 
The display 20 can be electrically connected to the register 15 such that 
the display 20 will display the line of characters loaded into the 
register 15 by means of the keyboard 10. The display unit 20 alternately 
can be optically connected to the liquid crystal display 25 and provide a 
way for an operator to directly view the image on the liquid crystal 
display 25. 
Since the display 25 is of the transmissive type, each of the displayed 
characters is displayed transparently so that energy from the source 35 
passes through the displayed character and falls upon the medium 40. The 
medium 40 may be any variety of energy sensitive film adapted for use with 
the source of energy 35. In the block diagram 5 of FIG. 1, the liquid 
crystal display 25 functions as an electrically controlled mask positioned 
between the source of energy 35 and the energy sensitive medium 40. The 
liquid crystal display 25 by means of the image formed therein in response 
to the electrical signals from the register 15 controls the spatial 
impingement of energy generated by the source 35 onto the medium 40. The 
liquid crystal display 25 thus acts as a spatial modulator of the radiant 
energy generated by the source 35. The control unit 17 causes the source 
of energy 35 to flash or generate bursts of energy in synchronism with the 
entry of a line of characters from the keyboard 10 into the register 15. 
The source of energy 35 might generate visible light or some other 
selected form of radiant energy. 
One type of film usable as the medium 40 is a class of tellurium based 
imaging films. Energy sensitive tellurium based films are disclosed in the 
prior art. Such films are disclosed, for example, in U.S. Pat. No. 
4,340,662, issued July 20, 1982, U.S. Pat. No. 4,066,460, issued Jan. 3, 
1978 and also in pending U.S. patent applications Ser. No. 392,586 filed 
June 28, 1982 as well as Ser. No. 392,576 filed June 28, 1982. Both of 
said patent applications being assigned to the assignee of the present 
application. The disclosures of said two patent applications and said two 
issued patents are incorporated herein by reference. 
Tellurium based films of the type disclosed in the '460 and the '662 
patents may be developed after exposure to radiant energy such as light by 
the application of heat. A heat generating developer 45 also positioned in 
the housing 30 and can be used to develop the exposed portions of the film 
40. A medium control unit 50 connected through the register unit 15 to the 
control unit 17 can be used to actuate a pair of medium moving rollers 55, 
60. The medium control unit 50 moves the film 40 a line of characters at a 
time in the direction of an arrow 65 once each line of characters has been 
exposed through the display 25 in combination with the source of energy or 
illumination 35. 
While the liquid crystal display 25 has been described in terms of a 
character line at a time display, it will also be understood to those 
skilled in the art that the liquid crystal display 25 could be implemented 
as a raster line display with one or more raster lines with as many pixels 
along each line as desired. For example, pixel sizes on the order of 1 to 
10 microns are possible in current liquid crystal displays. In such an 
implementation, one or more raster lines may be displayed by setting a 
plurality of control bits in a register corresponding to the register 15. 
Alphanumeric characters or any other image could then be created by 
repeatedly setting the raster line display by means of a control register 
and then exposing the film 40 by means of the source of illumination 35. 
As an alternate to the tellurium based films referred to previously, 
dispersion imaging films might be used. Such films are known in the art 
and disclosed in U.S. Pat. No. 4,332,880 which issued June 1, 1982 and is 
assigned to the assignee of the present application. The disclosure of the 
'880 patent is incorporated herein by reference. Other types of light 
sensitive films known to those skilled in the art might also be used. 
Alternately, instead of a film, a coated paper could be used as the medium 
40. In such an embodiment a positive coating could be used on the paper 
which upon exposure to the source of illumination 35 and then development 
by the developer 45, develops dark. 
It will be understood that while a keyboard 10 is shown in FIG. 1 as the 
source of the symbols to be displayed, alternate sources could be used. 
For example, keyboard 10 could be replaced with a connection to a computer 
or other electronic unit adapted to generate sequences of symbols or 
images to be displayed. 
FIG. 2 discloses a front planar view of the imaging system of block diagram 
5. The same identification numerals are used in FIG. 2 in connection with 
corresponding components as are used in FIG. 1. As can be seen from FIG. 
2, the liquid crystal display 25 is positioned against the film or coated 
paper 40. A shield 70 blocks the source of energy 35 from the medium 40 
except in a region 73 which is exposed by the image formed on the liquid 
crystal display 25. 
FIG. 3 discloses an alternative embodiment of the present invention. In 
FIG. 3, an imaging system 75 is disclosed having a large area liquid 
crystal display 77 positioned adjacent a medium member 80. The large area 
liquid crystal display 77 is adapted to be of the transmissive type and 
includes a large number of display pixels, perhaps 1024.times.1024 or 
larger, arranged in a two-dimensional array so as to display either a 
portion of an entire image or an entire image at one time. A source of 
energy is positioned above the liquid crystal display 77 such that the 
display 77 can act as a mask with respect to the medium 80. A plurality of 
control signals 83 is indicated in FIG. 3 as setting the display 77. The 
control signals 83 can be generated electronically, perhaps by a computer, 
and might correspond to alphanumeric characters or other graphical 
symbols. The medium control signals 85 could also be generated 
electronically so as to move the medium 80 in synchronism with the liquid 
crystal display signals 83. 
The imaging system 5 of FIG. 1 or the imaging system 75 of FIG. 3 can 
create multiple copies of an image without any need to first create an 
original document having the image formed thereon. 
Yet another embodiment of the present invention is shown in FIG. 4. A 
system 90 as disclosed in FIG. 4 includes a source of illumination 100, a 
liquid crystal display 105 positioned between the source of illumination 
100 and a photoresponsive drum 110 such as those used in the xerography 
process. As the drum 110 rotates in the indicated direction 115 the liquid 
crystal display 105, either the raster line type or the character line at 
a time type acts as an electronically controlled mask for the source of 
illumination 100 so as to form either a display of graphical information 
or a display of characters or both on the photosensitive drum 110. Once 
the display is formed on the drum 110 the xerographic process is completed 
in a standard fashion. As a result, the system of FIG. 4 is adapted for 
use with plain papers as is any other xerographic process. 
FIG. 5 discloses yet another embodiment of the invention. In FIG. 5, a 
system 120 includes a source of energy or illumination 130, a focusing 
system indicated schematically at 140, a liquid crystal display 150, a 
second focusing mechanism indicated schematically at 160 an energy or 
light sensitive medium 170, a control unit 180, a medium position control 
190 and a medium movement mechanism 200. 
In the system 120 of FIG. 5, the liquid crystal display 150 is of the 
reflective type. Light generated by the source 130 and focused through the 
focusing mechanism 140 reflects off of the display set in the liquid 
crystal display 150. The reflected light passes through the focusing 
mechanism 160 and falls upon the energy or light sensitive medium 170. The 
control unit 180 in response to display data provided thereto creates the 
electrical signals necessary to generate the image on the liquid crystal 
display 150. The display 150 might be a raster line display or alternately 
could be a character line display. The control unit 180 is electrically 
connected to the medium position control 190 so as to be able to move the 
medium 170 during the process of creating the desired image. 
The energy or light sensitive medium 170 could be a tellurium imaging film, 
a paper coated with a tellurium imaging material, or any other energy or 
light sensitive medium. 
While various modifications and changes might be proposed by those skilled 
in the art, it will be understood that the broader aspects of the 
invention include all variety of light or energy sensitive films, light or 
energy sensitive coated papers or variations on the type or 
characteristics of the liquid crystal displays.