Integrated image-input type display unit

An integrated image-input type display unit employs a conventional liquid crystal display panel and is capable of optically writing an original image directly at a high resolution into liquid crystal display panel and electrically reading the image. This unit has an image input/output device comprising a liquid crystal cell which contains light-sensitive molecules. The light-sensitive molecules are capable of changing their structure to a first molecular structure when being irradiated with light of a first wavelength range and to a second molecular structure when being irradiated with light of a second wavelength range, and are further capable of changing their alignment in accordance with the structural change of the light-sensitive molecules.

BACKGROUND OF THE INVENTION 
There have been image-input type display units which can serve both as an 
image input terminal and an image display each by combining a 
liquid-crystal display (LCD) panel with a two-dimensional image sensor and 
which are, for example, disclosed in Japanese Laid-open Patent 
Publications No. 4-282609 (TOKKAI HEI) and No. 6-186585 (TOKKAI HEI). The 
display unit described in Japanese Laid-open Patent Publication (TOKKAI 
HEI) No. 4-282609 comprises a color liquid-crystal display panel, a 
two-dimensional image sensor mounted on the reverse surface of the color 
LCD-panel and a light-source. When an original placed on the top surface 
of the color LCD-panel is illuminated by light emitted from the light 
source trough the LCD-panel, light reflected from the original through 
again the LCD-panel is received by the image sensor for reading an image 
of the original. 
The display unit disclosed in Japanese Laid-open Patent Publication (TOKKAI 
HEI) No. 6-186585 is composed of a LCD panel, an image sensor composed of 
a photo-diodes formed at grid points of a non-display portion of the 
LCD-panel and a light-source. This display unit in a similar way as 
described above reads an image of an original placed on a top surface of 
the color LCD-panel by illuminating with light emitted from the light 
source through the panel and by receiving light reflected from the 
original by a photo-diode. 
In the above-mentioned device, the image sensor is formed on another 
surface than a surface of the color LCD panel where a liquid-crystal 
driving electrode or a TFT (thin film transistor). In other words, 
elements different in function are merely laid on each other. 
On the other hand, Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
4-251824 discloses another display unit wherein a LCD panel and an image 
sensor are combined with each other more effectively. 
This device is constructed of an upper substrate with a non-linear 
resistive element formed thereon, a lower substrate, liquid-crystals held 
between the upper substrate and the lower substrate, a polarizer stuck to 
a top surface of the upper substrate, a polarizer stuck to a bottom 
surface of the lower substrate, a light-source for a back light and a 
light-guide plate for leading the light from the light source into the 
liquid-crystal layer. 
The non-linear resistive element sandwiched between a pixel electrode and a 
signal electrode is in contact with the signal electrode. The lower 
substrate has a scanning electrode through which it is in contact with the 
liquid crystal. 
The above-mentioned device construction is the same as that of a 
two-terminal matrix type LCD panel which is represented by a MIM 
(metal-insulator-metal) diode excepting the former adopting non-linear 
resistive elements having light-sensitivity. 
The optical writing operation of the device is as follows: 
The liquid crystal is put into a transparent state and a desired voltage is 
applied across the pixel electrode and the scanning electrode, then an 
original is illuminated. Light reflected from the original falls on 
non-linear resistive elements, those of which received light reflected 
from white portions of the original reduce its resistance, causing 
reduction of an effective voltage applied to the liquid crystal molecules 
which in this case are aligned parallel to the substrates. As light is 
absorbed by black parts of the original, no light falls on corresponding 
non-linear resistive elements which have no change in its resistance and 
therefore keep the liquid crystals as be aligned perpendicular to the 
substrates. Thus, an image of the original is written directly into the 
liquid crystal display panel by light. 
The electrical image-reading method is as follows: 
The non-linear resistive elements are classified into resistive components 
and capacitive components, which are connected in parallel to each other. 
The liquid crystals are also classified into resistive components and 
capacitive components, which are connected in parallel to each other. The 
non-linear resistive elements are connected in series to the liquid 
crystals. When reflected light rays from the original image fall on 
non-linear resistive elements and liquid crystals, resistive components of 
the resistive elements and capacitive components of the liquid crystals 
decrease. With a voltage being applied across the pixel electrodes and 
scanning electrodes, current flowing illuminated pixels may differ in 
value from current flowing not-illuminated pixels. The written image can 
be read by detecting differential currents of pixels. 
As described above, both the prior art display units provided with an image 
input facility, which are disclosed in Japanese Laid-open Patent 
Publications No. 4-282609 (TOKKAI HEI) and No. 6-186585 (TOKKAI HEI), are 
manufactured each by merely laminating an image sensor on a liquid-crystal 
display panel. Each device is complicated in structure because of forming 
a LCD layer (display electrodes) and an image inputting sensor layer 
(image-inputting electrodes) on different surfaces. 
To read an original image and display it on a LCD panel, each device has to 
convert the optical image into electrical signals through processes of 
reading the original image by the image sensor, converting electrical 
signals of the read image into electrical signals for display, displaying 
the image by electrical signals on the display panel. The device may have 
errors in the processes resulting in lowering the displayed image quality. 
An image displayed on the LCD panel can be restricted in its resolution by 
either lower one of resolution powers of the image sensor and the LCD 
panel. 
On the other hand, the conventional device with an image input facility, 
which described in Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
4-251824, is constructed on the base of a two-terminal element matrix type 
LCD panel. This can not be adapted to a TFT-type LCD panel or a simple 
matrix type LCD panel. 
Non-linear resistive elements used for displaying and inputting an original 
image can not transmit light, so an increase of an area of these elements 
may darken the display image whilst a decrease of an area of the elements 
decreases a light-receiving surface area, causing a problem not to obtain 
large signals of high signal to noise ratio. 
The device can optically write an original image into the LCD panel to 
directly display the image thereon. However, the resolution of the 
displayed image is restricted by the density of the non-linear resistive 
elements. In other words, it is limited to the resolution of the LCD 
panel. 
The discrete arrangement of the small-surface non-linear resistive elements 
may cause a decreased density of input image sampling resulting in 
increasing an error of the image signal. 
SUMMARY OF THE INVENTION 
The present invention relates to integrated image-input type display units 
which is used for personal computers, word processors, pocket-type 
electronic computers, portable information terminals or other information 
devices. 
This invention is directed to provide an integrated image-input type 
display unit which is capable of directly writing an original image at a 
high resolution with light into a liquid crystal display panel which may 
be a TFT type LCD panel, a simple matrix type LCD panel or two-terminal 
element matrix type LCD panel and which light-receiving portion is divided 
into many widely dispersed divisions assuring a high-quality of an input 
image and a high signal to noise ratio of image signals, attaining an 
accurate image input with a sufficiently increased sampling density and 
realizing simple design inexpensive to manufacture. 
(1) An object of the present invention is to provide an image-input and 
display unit which comprises: an image input/output device composed of a 
liquid-crystal cell, the cell containing light-sensitive molecules capable 
of changing their structure to a first molecular structure by irradiation 
with light of a first wavelength and to a second molecular structure by 
irradiation with light of a second wavelength and liquid crystal molecules 
capable of changing their alignment in accordance with the structural 
change of the light-sensitive molecules, both kinds of molecules 
hermetically sandwiched between two transparent substrates, a first group 
of electrodes and a second group of electrodes; first electrode-driving 
means for driving the first group of electrodes; second electrode-driving 
means for driving the second group of electrodes; illuminating means for 
irradiating the image input/output device with light of the first 
wavelength and light of the second wavelength; reading means for reading 
capacities produced at places corresponding to intersection points formed 
between the first-group electrodes and the second-group electrodes in 
accordance with a pulse voltage applied to the first-group electrodes; and 
control means for controlling the first electrode driving means, the 
second electrode driving means, the illuminating means and the reading 
means in such a manner that, when displaying an image, the alignment of 
the liquid crystal molecules corresponding to intersection points between 
the first group electrodes and the second group electrodes is changed by 
irradiating the image input/output device with light of the first 
wavelength to display a first image on the input/output device and, when 
inputting an image, a second image is inputted into the input/output 
device by irradiating with light of the second wavelength, a pulse voltage 
is applied to the first group of electrodes and capacities at places 
corresponding to intersection points between the first-group electrodes 
and the second-group electrodes are read to read the second image. 
(2) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the light-sensitive molecules are fixed to at least one of 
two transparent substrates. 
(3) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the liquid crystal molecules are a mixture of 
high-molecular liquid crystals and low-molecular liquid crystals and said 
mixture and the light-sensitive molecules are dispersed in the liquid 
crystal cell. 
(4) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the first group electrodes are formed on one of the 
transparent substrates and the second group electrodes are formed on the 
other transparent substrate. 
(5) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the first group electrodes and the second group electrodes 
are formed on one of the transparent substrates, switching elements are 
formed one at each of intersection points formed between the first group 
electrodes and the second group electrodes and a common electrode is 
formed on the other transparent substrate. 
(6) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the reading means is composed of voltage detecting means 
for detecting from the capacity a voltage after the elapse of a certain 
time and voltage comparing means for comparing the detected voltage value 
with a specified voltage value. 
(7) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the reading means is composed of voltage detecting means 
for detecting a voltage from the capacity and time measuring means for 
measuring a time until the detected voltage reaches a specified voltage 
value. 
(8) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the illuminating means is capable of irradiating the 
input/output device with light of a third wavelength not to change a state 
of the light-sensitive molecules when displaying a second image inputted 
into the input/output device. 
(9) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the illuminating means uses a common light source capable 
of generating the first-wavelength light and the second-wavelength light 
and is provided with light wavelength separating means for separating the 
first-wavelength light from the second-wavelength light. 
(10) Another object of the present invention is to provide an integrated 
image-input type display unit which is constructed as mentioned item (1) 
above, wherein the illuminating means uses a common light source capable 
of generating the first-wavelength light and the second-wavelength light 
and is provided with light-guide means for irradiating with the 
first-wavelength light through one of the transparent substrate and with 
the second-wavelength light through the other transparent substrate.

PREFERRED EMBODIMENTS OF THE INVENTION 
Several integrated image-input type display units according to prior arts 
will be described first for reference as follows: 
There have been image-input type display units which can serve both as an 
image input terminal and an image display each by combining a 
liquid-crystal display (LCD) panel with a two-dimensional image sensor and 
which are, for example, disclosed in Japanese Laid-open Patent 
Publications No. 4-282609 (TOKKAI HEI) and No. 6-186585 (TOKKAI HEI). The 
display unit (Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
4-282609) comprises a color liquid-crystal display panel, a 
two-dimensional image sensor mounted on the reverse surface of the color 
LCD-panel and a light-source. When an original placed on the top surface 
of the color LCD-panel is illuminated by light emitted from the light 
source trough the LCD-panel, light reflected from the original through 
again the LCD-panel is received by the image sensor for reading an image 
of the original. 
The display unit (Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
6-186585) comprises a LCD panel, an image sensor composed of a 
photo-diodes formed at grid points of a non-display portion of the 
LCD-panel and a light-source. This device in a similar way as described 
above reads an image of an original placed on a top surface of the color 
LCD-panel by illuminating with light emitted from the light source through 
the panel and by receiving light reflected from the original by a 
photo-diode. 
In the above-mentioned device, the image sensor is formed on another 
surface than a surface of the color LCD panel where a liquid-crystal 
driving electrode or a TFT (thin film transistor). In other words, 
elements different in function are merely laid on each other. 
On the other hand, Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
4-251824 discloses another display unit wherein a LCD panel and an image 
sensor are combined with each other more effectively. 
This device is constructed of an upper substrate 510 with a non-linear 
resistive element 521 formed thereon, a lower substrate 511, 
liquid-crystal 520 held between the upper substrate 510 and the lower 
substrate 511, a polarizer 512 stuck to a top surface of the upper 
substrate 510, a polarizer 513 stuck to a bottom surface of the lower 
substrate 511, a light-source 528 for a back light and a light-guide plate 
527 for leading the light from the light source 528 into the 
liquid-crystal 520. 
The non-linear resistive element 521 sandwiched between a pixel electrode 
and a signal electrode is in contact with the signal electrode. The lower 
substrate 511 has a scanning electrode through which it is in contact with 
the liquid-crystal 520. 
The above-mentioned device construction is the same as that of a 
two-terminal matrix type LCD panel which is represented by a MIM 
(metal-insulator-metal) diode excepting the former adopting non-linear 
resistive elements having light-sensitivity. 
The optical writing operation of the device is as follows: 
The liquid crystal is put into a transparent state and a desired voltage is 
applied across the pixel electrode and the scanning electrode, then an 
original 526 is illuminated. Light reflected from the original 526 falls 
on non-linear resistive elements 521b, those of which received light 
reflected from white portions 526b of the original 526 reduce its 
resistance, causing reduction of an effective voltage applied to the 
liquid crystal molecules which in this case are aligned parallel to the 
substrates. As light is absorbed by black parts 526a of the original 526, 
no light falls on corresponding non-linear resistive elements 521a which 
have no change in its resistance and therefore keep the liquid crystals as 
be aligned perpendicular to the substrates. Thus, an image of the original 
is written directly into the liquid crystal by light. 
The electrical image-reading method is as follows: The non-linear resistive 
elements are classified into resistive components and capacitive 
components, which are connected in parallel to each other. The liquid 
crystals are also classified into resistive components and capacitive 
components, which are connected in parallel to each other. The non-linear 
resistive elements are connected in series to the liquid crystals. When 
reflected light rays from the original image fall on non-linear resistive 
elements and liquid crystals, resistive components of the resistive 
elements and capacitive components of the liquid crystals decrease. With a 
voltage being applied across the pixel electrodes and scanning electrodes, 
current flowing illuminated pixels differs in value from current flowing 
not-illuminated pixels. The written image can be read by detecting 
differential currents of pixels. 
As described above, both the prior art display units provided with an image 
input facility, which are disclosed in Japanese Laid-open Patent 
Publications No. 4-282609 (TOKKAI HEI) and No. 6-186585 (TOKKAI HEI), are 
manufactured each by merely laminating an image sensor on a liquid-crystal 
display panel. Each device is complicated in structure because of forming 
a LCD layer (display electrodes) and an image inputting sensor layer 
(image-inputting electrodes) on different surfaces. 
To read an original image and display it on a LCD panel, each device has to 
convert the optical image into electrical signals through processes of 
reading the original image by the image sensor, converting electrical 
signals of the read image into electrical signals for display, displaying 
the image by electrical signals on the display panel. The device may have 
errors in the processes resulting in lowering the displayed image quality. 
An image displayed on the LCD panel can be restricted in its resolution by 
either lower one of resolution powers of the image sensor and the LCD 
panel. 
On the other hand, the conventional device with an image input facility, 
which described in Japanese Laid-open Patent Publication (TOKKAI HEI) No. 
4-251824, is constructed on the base of a two-terminal element matrix type 
LCD panel. This can not be adapted to a TFT-type LCD panel or a simple 
matrix type LCD panel. 
Non-linear resistive elements used for displaying and inputting an original 
image can not transmit light, so an increase of an area of these elements 
may darken the display image whilst a decrease of an area of the elements 
decreases a light-receiving surface area, causing a problem not to obtain 
large signals of high signal-to-noise ratio. 
The device can optically write an original image into the LCD panel to 
directly display the image thereon. The resolution of the displayed image 
is, however, restricted by the density of the non-linear resistive 
elements. Namely, it is limited to the resolution of the LCD panel. 
The discrete arrangement of the small-surface non-linear resistive elements 
may cause a decreased density of input image sampling resulting in 
increasing an error of th e image signal. 
Referring now to the accompanying drawings, integrated image-input type 
display units which are preferred embodiments of the present invention 
will be described below in detail. 
Referring to FIG. 2, a construction of an embodiment system for realizing 
the present invention is first described as follows: 
The system is composed mainly of following two basic units--an image 
input/output panel 101 and illuminating portion comprising an illuminating 
light generating portion 110, an illuminating light control portion 111 
and an illuminating light diffusing portion 112. 
The image input/output panel 101 is divided into a device portion composed 
of an image input/output device 102, a segment electrode driving circuit 
103 and a common electrode driving circuit 104; a reading portion composed 
of a reading circuit 108; and a system control portion composed of a 
control circuit 105, a drive control circuit 106, a display control 
circuit 107 and an illuminating light control circuit 109. 
The above-mentioned classification is only applied for explaining 
embodiments of the present invention and can not always be applied 
strictly to practical implementations which may have a variety of partial 
modifications. 
The system control portion controls the operation of a whole system of an 
integrated image-input type display unit shown in FIG. 2. 
The control circuit 105 receives signals from the external circuit or the 
drive control circuit 106, the display control circuit 107, an 
illuminating light control circuit 109 and reading circuit 108 and gives 
respective control signals to respective circuits in order to realize an 
object operation of a whole system by coordinating and controlling the 
activities of all other blocks. 
The display control circuit 107 is used for controlling the display 
operation of the image input/output device 102 and performs the display 
data control in a mode designated by the control circuit 105, to hold 
display data from the external circuit, image data read from the reading 
circuit 108 or image data read in the image input/output panel 101. 
The drive control circuit 106 gives necessary control signals and display 
information to the segment electrode driving circuit 103 and the common 
electrode driving circuit 104 according to a control signal from the 
control circuit 105 to display an image on the image input/output device 
102, write an original image information into the image input/output 
device 102 or read-out the written image information from the image 
input/output device 102. 
Similarly, the illuminating light control circuit 109 gives necessary 
control signals to the illuminating light generating portion 110 and 
illuminating light control portion 111 according to a control signal from 
the control circuit 105 to display an image on the image input/output 
device 102, write an original image information into the image 
input/output device 102 or read-out the written image information from the 
image input/output device 102. 
The device portion of the display unit is described below. This portion 
performs image input-output operations. 
The image input/output portion 102 is composed of liquid-crystal cells 
containing therein liquid crystal molecules and light-sensitive molecules 
capable of changing their molecular structure by the effect of 
illumination of specified wavelengths. 
An image based on displaying data supplied by the display control circuit 
107 through the drive control circuit 106 is displayed, in the same way as 
in the conventional liquid-crystal panel, with light supplied from the 
illuminating light diffusing portion 112 in accordance with driving 
signals from the segment electrode driving circuit 103 and the common 
electrode driving circuit 104. 
On the other hand, a desired image information from an original can also be 
written into the image input/output device 102 in terms of a change in 
structural state of light-sensitive molecules by the effect of light 
supplied by the illuminating light diffusing portion 112 through the 
original according to driving signals from the segment electrode driving 
circuit 103 and the common electrode driving circuit 104. 
The segment electrode driving circuit 103 and the common electrode driving 
circuit 104 are based on conventional driving circuits for a duty type 
liquid crystal panel and prepared with some necessary modifications made 
thereto. In designing the image input/output device 102 on the basis of 
the construction of a TFT liquid crystal panel, it is also possible to 
design the segment electrode driving circuit 103 and the common electrode 
driving circuit 104 on the basis of a source electrode driving circuit and 
a gate electrode driving circuit. 
The illuminating portion is described as follows: 
This portion is intended to supply the image input/output device 102 with 
light that is used as back light for displaying an image on the image 
input/output device 102 and is used as light for illuminating an original 
when writing an original image into the image input/output device 102. 
The illuminating light generating portion 110 generates light of specified 
wavelengths necessary for displaying an image on the image input/output 
device 102 and light of specified wavelengths necessary for writing an 
original image into the image input/output device 102. The illuminating 
light control portion 111 cuts off unnecessary light or prevents light 
from leaking into unnecessary blocks and other necessary operations on 
light emitted from the illuminating light generating portion 110 according 
to a specified operation mode. The illuminating light generating portion 
110 and the illuminating light control portion 111 may have a variety of 
construction in combination with each other as described later in 
preferred embodiments of the present invention. 
The illuminating light diffusing portion 112 is intended to evenly 
illuminate a whole surface of the image input/output device 102 by 
diffusing light from the illuminating light generating portion 110 through 
the illuminating light control portion 111. 
The reading portion is described as follows: 
This portion is composed of the reading circuit 108 which control signal 
effecting on the segment electrode driving circuit 103 and common 
electrode driving circuit 104 through the control circuit 105 and the 
drive control circuit 106 in such a way that an image information written 
in terms of a change in state of the light-sensitive molecules in the 
image input/output device 102 is read out in terms of electric signals 
obtained by conversion of detected differential capacities representing 
the variation of alignment of liquid crystal molecules, which was caused 
by the change in the state of the light-sensitive molecules. 
Referring to FIGS. 2 (system construction) and 4 (flowchart), operation 
modes of the system are described as follows: 
The system works in any one of three following modes: 
In FIGS. 3A and 3B, the flowchart describes the sequential control 
operation of the system, wherein respective modes are indicated by 
dividing the chart by dotted lines. The flowchart of the operation of the 
system in each operation mode may be described on the basis of the shown 
flowchart. 
The operation mode 1 is the mode in which the system displays information, 
e.g., data supplied from the external circuit on the image input/output 
device 102 in the same way in the conventional liquid crystal panel. 
The operation of the system in the mode 1 is described according to the 
flow chart of FIGS. 3A and 3B. 
By switching ON an electric power supply of the system, a display content 
selecting routine is called for judging which one of images is displayed, 
an image based on the image data supplied from the external circuit, an 
image based on image data read by the reading circuit 108 or an image 
based on image data written from an original into the image input/output 
device 102 (with no modification). A control signal based on the judgment 
made by the routine is given from the control circuit 105 (FIG. 2) to the 
display control circuit 107, the drive control circuit 106 and 
illuminating light control circuit 109. 
The display control circuit 107 receives display image data together with 
the control signal from the control circuit 105 and supplies the data to 
the drive control circuit 106 in due timing suitable for displaying a new 
image on the image input/output device 102. The drive control circuit 106 
gives drive control signals and display image data to the segment 
electrode driving circuit 103 and the common electrode driving circuit 104 
to display the image on the image input/output device 102. 
On the other hand, the illuminating light control circuit 109 is instructed 
to supply light for illuminating the image input/output device 102. In the 
mode 1, the illuminating light control circuit 109 controls the 
illuminating light generating portion 110 and the illuminating light 
control portion 111 to supply light as back light through the illuminating 
light diffusing portion 112. 
After displaying the image by a frame or several frames, it is determined 
whether or not image input is performed. If not, the selection of a 
display content is made and then the display operation is performed. If an 
image is input, the system operates in mode 2. In this operation mode, an 
image information of an original is read in the image input/output device 
102 to be followed by the same display operation as made in mode 1. 
The following operation steps will be performed in mode 2 if it was judged 
in mode 1 that an image input is required. In this case, the control 
circuit 105 gives a control signal by which image information of an 
original placed on the specified place of the image input/output device 
102 is optically written therein. 
Following the operation in mode 1, the control circuit 105 gives a control 
signal to initialize the display by using the segment electrode driving 
circuit 103 and the common electrode driving circuit 104 through drive 
control circuit 106. By doing this, the image input/output device 102 is 
set in its initial state allowing further image inputting operation. 
After this, the segment electrode driving circuit 103 and the common 
electrode driving circuit 104 are ready to conduct the image input 
operation by the drive control circuit 106 and, in addition, the 
illuminating light control circuit 109 under the control of the control 
circuit 105 controls the illuminating light diffusing portion 112 to 
supply light of a specified wavelength necessary for writing an image into 
the image input/output device 102. Thus, the necessary light transmits the 
original and enters into the image input/output device 102. 
By the effect of the above-mentioned control, the original image 
information is written in terms of variation of state of the 
light-sensitive molecules in the image input/output device after the 
elapse of a specified time and then the segment electrode driving circuit 
103 and the common electrode driving circuit 104 turned into a state to 
hold the written image information. The illuminating light generating 
portion 110 and illuminating light control portion 111 are turned by the 
illuminating light control circuit 109 to a state for image display. The 
image input operation in the mode 2 is now completed. 
The mode 3 is applied if it was judged in mode 2 that reading the image 
written in the image input/output device is requested. In this case, steps 
including a step following the image input operation are performed. 
According to the instruction given by the control circuit 105, the image 
written in the image input/output device 102 is read in terms of electric 
signals by the reading circuit 108. 
By the effect of a control signal from the control circuit 105, the reading 
circuit 108 gives necessary control signal to the drive control circuit 
106 which in turn through segment driving circuit 103 and the common 
electrode driving circuit 104 reads by scanning the image in the image 
input/output device 102. 
Scanned signals from the image input/output device 102 through the segment 
driving circuit 103 and the common electrode driving circuit 104 are 
output to the reading circuit 108. The processed signals from the reading 
circuit transfer to the control circuit 105 which in turn outputs the 
signals to the external circuit and supplies the signals as display 
information to the display control circuit 107. Thus, the image written in 
the image input/output device 102 is read out therefrom and displayed 
thereon. 
The processing made on the scanned signals by the reading circuit 108 will 
be described later in detail with an example of the reading circuit 108. 
The whole system of the embodiment, the summary of its operation and the 
activities of system control portion have been described above. The 
illuminating portion, the device portion and the reading portion of the 
system will be described below in detail in regard with their 
implementations. 
FIGS. 4A and 4B show an external appearance of an integrated image-input 
type display unit, when displaying and reading image in FIG. 4A, when 
inserting an original to be read in FIG. 4B respectively. 
A body 100 is composed mainly of an upper half 170 and a lower half 171. 
The upper half 170 is provided with an image input/output portion 102, 
switch 130 (FIG. 4A) and a flapper cover 131 (FIG. 4A). The lower half 171 
is provided with a first lamp 121 (FIG. 4B) for emitting visible light, a 
second lamp 123 (FIG. 4B) for emitting ultraviolet light, a diffuser plate 
125 (FIG. 4B) and a filter 132 (FIG. 4B). The upper half 170 and the lower 
half 171 of the body 100 can be turned open and close (laid on each other) 
about the connector portion 172. 
The image input/output device 102 is a liquid crystal display. Three kinds 
of light for illuminating the image input/output device 102 through the 
diffuser plate 125 (FIG. 4B) can be generated by using the first lamp 121 
(FIG. 4B), the second lamp 123 (FIG. 4B) and the filter 132 (FIG. 4B) as 
described later in detail. The first light is white light having visible 
range wavelength, which contains light of a specified wavelength 
.lambda.1. The second light is ultraviolet light having an ultraviolet 
range wavelength, which contains light of another specified wavelength 
.lambda.2. The filter 132 (FIG. 4B) is divided into two light-passing 
portions (not shown) (a) for transmitting the first light and (b) for 
absorbing only light of wavelength .lambda.1. When the first lamp 121 
(FIG. 4B) lights, either one of two light-passing portions (a) and (b) is 
selected to use and inserted between the first lamp 121 and the diffuser 
plate 125 (FIG. 4B). While the light-passing portion (a) of the filter 132 
(FIG. 4B) is used, the first light enters the diffuser plate 125 (FIG. 
4B). While the light-passing portion (b) is used, the third light, which 
is obtained by eliminating light of wavelength .lambda.1 from the first 
light, enters the diffuser plate 125 (FIG. 4B). The third light does not 
cause the change in the state of light-sensitive molecules in the image 
input/output device since it contains no light of wavelengths .lambda.1 
and .lambda.2 to which said molecules react. 
This display unit can be used as a simple display device when the selector 
switch 130 (FIG. 4A) is set in Display Mode. In this case, light from the 
diffuser plate 125 (FIG. 4B) is controlled to be the first light. The 
image input/output device 102 is supplied with a display signal and 
displays thereon an image as shown in FIG. 4A. The first light serves as 
back light, allowing a user to see the image on the display screen of the 
image input/output device 102. 
An image is input to the image input/output device 102 in the following 
manner: 
As shown in FIG. 4B, the upper half 170 is swung up to expose the diffuser 
plate 125. An original 129 desired to be read is placed at an adequate 
position on the diffuser plate 125 and then the upper half 170 is swung 
down to close as seen in FIG. 4A. The selector switch 130 (FIG. 4A) is set 
in Input Mode to start the image inputting operation. In this instance, 
light from the diffuser plate 125 is controlled to be the second light by 
which the original image is input to the image input/output device 102. 
Upon completion of the image input operation, the light is switched over 
to the third light by which the input image is displayed on the display 
screen of the image input/output device 102. The original 129 can be 
removed from the display unit if no need be. 
With the selector switch set in Read Mode, the image written into the image 
input/output device 102 can be read therefrom in form of electric signals. 
The above-mentioned display unit may be used for wide field of application 
by building a variety of functions therein. For example, it may be used as 
a personal computer (PC) which is capable of inputting a variety of data 
from paper documents, putting titles or keywords to respective data by 
using a keyboard or a mouse connected to the display unit and storing the 
input data into a memory or other storing medium. Each of such stored data 
can be quickly called to the display unit by searching a keyword. 
Furthermore, any input image can be converted immediately into coded 
information suitable for further edition by using a character recognizing 
technique and an image recognizing technique for the personal computer. 
The coded character and image information can be edited by using a word 
processing software and a computer-aided designing software. The display 
unit provided with a radio or wire communication facility can transmit and 
receive an input image to and from another terminal. The display unit may 
be used as a facsimile using a public telecommunication network. For this 
purpose, a modem may be attached to or built in the display unit. The use 
of this embodiment with a variety of functions is effective to create a 
pocket computer or portable information terminal. The unit may serve as an 
effective information tool for personal use. The above-mentioned 
multi-functional display units are shown by way of examples and do not 
restrict the scope of multi-functioning of the unit. 
The device portion is described in detail as follows: 
FIG. 5 is a sectional view of the image input/output device 102 of the 
first embodiment of the present invention. 
The image input/output device 102 is composed of liquid crystal cells each 
containing light-sensitive molecules 300 and liquid-crystal molecules 301 
hermetically held between two transparent substrates 302 and 303. This 
device is basically similar in construction to a duty type liquid crystal 
panel. 
The transparent substrates 302 and 303 are usually made of transparent 
plate glass, which are used for hermetically holding liquid-crystal 
molecules 301. Accordingly, they may also be made of transparent plastic, 
transparent ceramics or transparent synthetic rubber. These substrates may 
be not only plates but also be flexible films. Polarizers 304 and 305 made 
of transparent film are stuck on the substrates 302 and 303 respectively. 
The polarizers 304 and 305 are used for converting input light into 
linearly polarized light and arranged with their crystal axes being 
substantially normal to each other. 
Light-sensitive molecules 300 form a thin layer attached to a surface of 
the transparent substrate 302, which may function as an orientation film 
for controlling the orientation direction of liquid crystal molecules 301. 
The light-sensitive molecules 300 are photochromic molecules capable of 
reversibly changing molecular structure when exposed to light of specified 
wavelengths (e.g., stilbene, azobenzene derivative and so on). 
A method of manufacturing the image input/output device 102 is shortly 
described. It is basically the same as a method of manufacturing a liquid 
crystal panel. A thin film containing the light-sensitive molecules 300 is 
formed by chemical adsorption or application or LB-film adhesion on the 
substrate 302 with a driving transparent electrode formed thereon. The 
transparent substrate 302 with the thin film of the light-sensitive 
molecules 300 formed thereon and the transparent substrate 303 with a 
transparent electrode formed thereon are opposed to each other through a 
spacer and hermetized at the periphery with hermetic material. Liquid 
crystal is pored into the space between the transparent substrates through 
an open port that is then sealed with hermetic material. 
The function of the light-sensitive molecules 300 is mimically shown in 
FIGS. 6A and 6B. The light-sensitive molecules 300 change their molecular 
structure into linear trans-form 300a (FIG. 6A) when exposed to light of a 
specified wavelength .lambda.1 and change their molecular structure into 
V-shaped cis-form 300b (FIG. 6B) when exposed to light of a specified 
waveform .lambda.2. These reactions are reversible and repeatable. Namely, 
the light-sensitive molecules 300 undergo change of their molecular 
structure when exposed to light of specified wavelengths .lambda.1 and 
.lambda.2. The molecules 300 maintain the changed structure until they are 
exposed to light of different specified wavelength .lambda.1 or .lambda.2. 
In short, the trans-form molecules remain unchanged until they are exposed 
to light of the wavelength .lambda.2 and the cis-form molecules remain 
unchanged until they are exposed to light of the wavelength .lambda.1. 
The molecular structures of compounds usable as the light-sensitive 
molecules 300 are shown by way of example in FIGS. 8A and 8B. In FIG. 8A, 
there is shown a molecular structure of a compound of polyvinyl alcohole 
(PVA) with azobenzene. This molecular compound changes its form from 
trans-form into cis-form when exposed to ultraviolet light of 363 nm 
(.lambda.2). The compound alters its form from cis-form into trans-form 
when exposed to visible light of 436 nm (.lambda.1). FIG. 8B shows the 
molecular structure of a 4,4'-dinonylazobenzene that changes from 
trans-form into cis-form when exposed to ultraviolet light (.lambda.2) and 
from cis-form into trans-form when exposed to visible light (.lambda.1). 
The light-sensitive compound 300 containing the above-mentioned 
photochromic molecules substantially changes the molecular structure from 
cis-form into trans-form when exposed to visible light having a specified 
wavelength and from trans-form into cis-form when exposed to ultraviolet 
light of a specified wavelength. 
The liquid crystal molecules 301 are liquid crystal molecules usually used 
for displays, for example, twisted nematic (TN) liquid crystal or 
super-twist nematic liquid crystal. ON-OFF control of transmission of 
light is realized by changing the alignment of the liquid crystal 
molecules in the image input/output device by the effect of two polarizers 
304 and 305. 
The effect of the light-sensitive molecules 300 on the liquid crystal 
molecules 301 is described as follows: 
As shown in FIG. 5, the light-sensitive molecules 300 takes the linear 
trans-form (300a) while the image input/output device 102 is illuminated 
by visible light 307 containing light of a wavelength (.lambda.1) (the 
first light). The light-sensitive molecules 300 acts as an aligning film 
of the liquid crystal molecules 301. Consequently, the liquid crystal 
molecules 301 under the influence of the light-sensitive molecules 300 
have homeotropic alignment in the direction perpendicular to the 
transparent substrates 302 and 303. 
On the other hand, as shown in FIG. 7, the light-sensitive molecules 300 
takes the V-shape cis-form (300b) while the image input/output device 102 
is illuminated by ultraviolet light 308 containing light of a wavelength 
(.lambda.2) (the second light). The liquid crystal molecules 301 under the 
influence of the molecule-shape of the light-sensitive molecules 300 have 
planer orientation in the direction parallel to the transparent substrates 
302 and 303. The control of transmission light by aligning the liquid 
crystal molecules is the same as in the usual liquid crystal display. The 
light transmits when the liquid crystal molecules are in homeotropic 
alignment whilst light is shut off when the liquid crystal molecules are 
in planer alignment. The above-mentioned change may occur with no voltage 
applied on the liquid crystal molecules 301. However, it is possible to 
apply a voltage lower than a threshold value to the liquid crystal 
molecules to increase a response characteristic. 
The light-sensitive molecules 300 takes either one of cis-form and 
trans-form. However, the change in form of the light-sensitive molecules 
occurs at a probability. Accordingly, the number of changeable molecules 
300 depend on an intensity of visible or ultraviolet light. Namely, an 
input image may be written with gradation as the intensity of the incident 
light. 
Although the described embodiment uses a combination of visible light (as 
the first light) and ultraviolet light (as the second light), it may adopt 
another combination, e.g., of visible light (as the first light) and 
infrared light (as the second light) with no change in the essence of the 
invention. 
The light-sensitive molecules 300 are much smaller than the segment 
electrode and the common electrode. A vast number of the light-sensitive 
molecules 300 (beyond the comparison with that of electrodes) are formed 
in the transparent substrate 302, so an optically written image can have a 
greater resolution than that of an electrically written image. 
Referring to FIGS. 9A, 9B, 9C and 9D, the actions of writing an optical 
image (in Image-Input Mode), electrically reading a written image and 
electrically writing an image in the image input/output device 102 is 
described below: 
The image input/output device 102 shown in FIGS. 9A, 9B, 9C and 9D differ 
in construction from that of FIG. 5 by adding segment electrodes 310 and a 
common electrode 311 for realizing electrical writing and reading 
functions. Polarizers 304 and 305 are not shown in FIGS. 9A, 9B, 9C and 
9D. In this case, three kinds of light are applied: The first light is 
visible light 307 (FIG. 9A) containing light of a wavelength .lambda.1 
causing the light-sensitive molecules 300 to change their molecular 
structure from cis-form into trans-form. The first light is desired to 
contain all wavelength components since it is commonly used as back light 
for the display. It does not contain light of wavelength .lambda.2. The 
second light is ultraviolet light 308 (FIG. 9B) containing light of 
wavelength .lambda.2 which can cause the light-sensitive molecules 300 to 
change their molecular structure from the trans-form into the cis-form. It 
does not contain light of wavelength .lambda.1. The third light is visible 
light (not shown) which does not contain light of wavelength .lambda.1. It 
does not contain, of course, light of wavelength .lambda.2. 
The Image-input Mode operation is described first as follows: 
A liquid crystal cell is set into an initialized state (FIG. 9A) in which 
its whole surface is transparent with the homeotropically aligned 
liquid-crystal molecules uniformly arranged therein. Visible light 307 is 
applied from one side to a whole surface of the liquid crystal cell to 
cause the light-sensitive molecules to change into trans-form. The 
incident light may enter the crystal cell from any side but preferably in 
view of effectiveness from the transparent substrate 302 whereon 
light-sensitive molecules 300 are formed. Since most of the 
light-sensitive molecules 300 change into trans-form 300a, the liquid 
crystal molecules 301 are aligned homeotropically, bringing the liquid 
cell into transparent state. In this case, no voltage is applied across 
the segment electrodes 310 and the common electrode 311. 
According to an illumination method shown in FIGS. 4A and 4B using 
ultraviolet light, a transmitted ultraviolet-light image of an original is 
projected to the image input/output device (FIG. 9B). Ultraviolet light 
transmitted through white portion of the original enters into the image 
input/output device 102. Light-sensitive molecules exposed to ultraviolet 
rays 308 change their structure from trans-form 300a into cisform 300b. 
Accordingly, liquid crystal molecules 301 in the neighborhood of the 
cis-form light-sensitive molecules are planarly aligned. Light-sensitive 
molecules not exposed to ultraviolet rays are left as be of trans-form 
300a and, therefore, liquid crystal molecules in the neighborhood of these 
light-sensitive molecules remain homeotropically aligned. Namely, areas 
exposed to the second light 308 become opaque while areas not exposed to 
the second light remain transparent. Namely, an inverse image of the 
original is written into the image input/output device 102. In this case, 
no voltage is applied across the segment electrodes 310 and the common 
electrode 311. The written image can be held unless light of wavelengths 
.lambda.1 and .lambda.2 is entered into the image input/output device 102 
or a voltage higher than a threshold value is applied across the segment 
electrodes 310 and the common electrode 311. 
An image optically written into the image input/output device 102 can be 
displayed thereon by using the third light as back light. The third light 
can not erase the written image since it does not is., change the form of 
the light-sensitive molecules. The optically written image has a high 
resolution as mentioned before. Therefore, it can be displayed at a high 
resolution independent of the sizes of segment and common electrode. 
Referring to FIG. 9C, the operation of the image input/output device 102 is 
described now in Image-reading Mode for electrically reading an image 
written in the image input/output device 102. 
The liquid-crystal molecules possess dielectric anisotropy. In other words, 
a change in alignment of the liquid-crystal molecules causes a dielectric 
constant across the segment electrodes 310 and common electrode 311. This 
means that alignment of the liquid-crystal molecules can be determined by 
detecting a dielectric constant for each pixel. When the written image is 
held in the image input/output device 102, a voltage is applied across the 
segment electrodes 310 and the common electrode 311 to detect the 
alignment of the liquid-crystal molecules. The applied voltage is lower 
than the threshold value at which the alignment of the liquid crystals can 
not be changed. This voltage may be a direct-current voltage or 
alternating-current voltage. Thus, the optically written image can be read 
out by converting it into electric signals. 
Referring to FIG. 9D, the operation of the image input/output device 102 is 
described in Display Mode for inputting an electric signal therein and 
displaying corresponding input image thereon (by a method of usual use of 
a liquid-crystal panel). 
In the Display Mode, a whole surface of the liquid crystal cell (panel) is 
always illuminated with visible light 309 as back light. The visible light 
309 contains light of wavelength .lambda.1 and therefore causes the 
light-sensitive molecules 300 to change their structure into trans-form 
300a. Namely, the panel is initialized with all liquid-crystal molecules 
being homeotropically aligned. In this state, each pixel is given an 
electric signal. When a voltage higher than a threshold is applied a 
pixel, homeotropical alignment of liquid crystal molecules of the pixel is 
altered into planar alignment. Thus, the image input/output device 102 
works in the same way as the conventional liquid crystal panel. The 
visible light 307 and the back light (for display) does not necessarily 
have the same wavelength components in principle. However, the visible 
light 309 can be used in common as back light. This makes the panel be 
much simple. There is no need for use a separate back light of different 
wavelengths. The shown embodiment uses twisted nematic liquid-crystals or 
supper-twisted nematic liquid-crystals as liquid crystal display panel 
which can, therefore, be driven at a low voltage. 
FIG. 10 shows sectional view of image input/output device 102 of a second 
embodiment of the present invention. The image input/output device 102 
comprises light-sensitive molecules 400, low-molecular liquid crystals 
401, high-molecular liquid crystals 402, ions 403, a transparent substrate 
404, a transparent substrate 405, a common electrode 406 and segment 
electrodes 407. The transparent substrates 304 and 405 hermetically hold 
therein the light-sensitive molecules 400, the low-molecular liquid 
crystals 401 and high-molecular liquid crystals 402. 
The light-sensitive molecules 400 together with the low-molecular liquid 
crystals 401 and high-molecular liquid crystals 402 compose a complex. The 
light-sensitive molecules 400 controls transmission and diffusion of light 
in the complex. The light-sensitive molecules 400 contain photochromic 
molecules that can be photoisomerized at a certain temperature in electric 
field of a certain frequency. The embodiment uses, as light-sensitive 
molecules 400, azo-compounds that can reversibly change its structure from 
trans-form into cis-form when exposed to ultraviolet light and from 
cis-form into trans-form when exposed to visible light. 
FIG. 11 mimically shows how the light-sensitive compound 400 functions. 
This compound 400 alters its molecular structure into a linear trans-form 
400a when exposed to visible light of wavelength .lambda.1. It further 
changes the molecular structure into a V-shape cis-form 400b when exposed 
to ultraviolet light of wavelength .lambda.2. These reactions are 
reversible and repeatable. 
An exemplified molecular structure of a light-sensitive compound 400 that 
is 4,4'-dinonylazobenzene that undergoes a reversible change in molecular 
structure from the trans-form into the cis-form by ultraviolet radiation 
and from the cis-form into the trans-form by visible-light radiation. 
The low-molecular liquid crystals 401 and the high-molecular liquid 
crystals 402 are selected so that the complex they compose together with 
the light-sensitive compound may possess a high-speed memory switching 
function by alterring the molecular alignment by the effect of controlled 
electric field. The lower-molecular liquid-crystal 401 is selected so as 
to make the complex have an adequate viscosity at which it possesses an 
improved response at the minimal sacrifice of the memorizing property. The 
high-molecular liquid-crystal 402 is selected so as to make the complex 
have a suitable memorizing property at the minimal sacrifice of the 
response characteristic. They can undergo a reversible change in alignment 
under the influence of the controlled electric field. 
The image input/output device 102 is constructed in such a way that the 
complex prepared of the light-sensitive molecules 400, the low-molecular 
liquid-crystal 401 and the high-molecular liquid-crystal 402 are 
sandwiched between the transparent substrate 404 with the internally 
mounted common electrode 406 and the transparent substrate 405 with the 
internally mounted segment electrodes 407. 
The operation principle of the image input/output device 102 is as follows: 
The complex is composed of the light-sensitive molecules 400, the 
low-molecular liquid-crystal 401 and the high-molecular liquid-crystal 402 
and contains ions 403. These ions travel in the complex when a certain 
low-frequency electric field at a voltage not lower than a threshold value 
is applied across the common electrode 406 and the segment electrodes 407. 
These moving ions disturb molecular alignment of high-molecular 
liquid-crystals 402, producing a large number of micro-domains (areas) in 
the complex. Namely, the complex becomes optically very heterogeneous, 
scattering incident light by a large number of refractivity boundaries of 
the produced domains. 
The ion movement ceases when a frequency of the applied electric field is 
increased to and over a certain frequency (a first critical frequency 
fc1), so the electric field is applied to liquid crystal molecules which 
are homeotropically aligned by their dielectric anisotropy. The complex 
becomes a large optical domain having a uniform refractive index. It 
appears transparent. 
A second critical frequency fc2 is used when the light-sensitive molecules 
400 have the cis-form by the effect of ultraviolet radiation. This 
frequency fc2 is higher than the first critical frequency fcl. In other 
words, a higher frequency electric field is required to make the 
light-sensitive molecules 400 of the cis-form be homeotropically aligned 
because the cis-formed molecules can easily scatter light. 
Referring to FIG. 12, the operation modes of the image input/output device 
102 are explained below: 
The Image-input Mode operation is described first as follows: 
A complex composed of light-sensitive molecules 400, low-molecular 
liquid-crystals 401 and high-molecular liquid-crystals 402 is set into an 
initialized entirely transparent state (FIG. 12A). A high-frequency 
electric field of a voltage higher than a certain threshold value and a 
frequency higher than the first critical frequency fc1 is applied from an 
electric supply source 408 to a circuit between a common electrode 406 and 
segment electrodes 407. At the same time, visible light 411 containing 
light of a frequency .lambda.1 is applied from one side to a whole surface 
of the complex. 
The light-sensitive molecules 400 change their form into trans-form 400a by 
light radiation of the frequency .lambda.1. Under the influence of the 
high-frequency electric field (at a frequency higher than the first 
critical frequency fc1), the high-molecular liquid-crystals 402 becomes 
homeotropically aligned to be entirely transparent. 
Ultraviolet light 409 containing light of a frequency .lambda.2 transmitted 
through an original is projected to the image input/output device 102 
(FIG. 12B) wherein the transmitted ultraviolet light image is written. 
A high-frequency electric field which has a voltage higher than the 
threshold value and a frequency higher than the first critical frequency 
fc1 and lower than the second critical frequency fc2 is applied from the 
electric supply source 408 to a circuit between the common electrode 406 
and the segment electrodes 407. At the same time, the transmitted 
ultraviolet light 409 carrying the original image is applied to the 
complex. 
Light-sensitive molecules exposed to ultraviolet rays 409 change their 
structure from trans-form 400a into cis-form 400b. Under the influence of 
the applied high-frequency electric field having the frequency lower than 
the second critical frequency cf2, the high-molecular liquid-crystals 402 
are in scattering state. 
Light-sensitive molecules 400 not exposed to ultraviolet radiation remain 
as be of trans-form. Under the influence of the applied high-frequency 
electric field having the frequency higher than first critical frequency 
cf1, the high-molecular liquid-crystals 402 are homeotropically aligned to 
be transparent. In short, the complex has the opaque areas exposed to the 
ultraviolet light and the transparent areas not exposed to the ultraviolet 
light. Namely, an inverse image of the original is written into the image 
input/output device 102. 
The written image can be held unless an electric field having a voltage not 
less than the threshold value applied to or light of wavelength .lambda.1 
or .lambda.2 is entered into the image input/output device 102. 
An image optically written into the image input/output device 102 can be 
displayed thereon by using third light that is visible light not 
containing light of the frequency .lambda.1 and, of course, light of the 
frequency .lambda.2. The third light can not erase the written image since 
it does not change the form of the light-sensitive molecules 400. 
Referring to FIG. 12C, the operation of the image input/output device 102 
is described in Image-reading Mode for electrically reading an image 
written in the device 102. 
A high-frequency electric field which has a voltage lower than the 
threshold value and a frequency higher than the first critical frequency 
fc1 is supplied from the power supply source 408 to the circuit between 
the common electrode 406 and the segment electrode 407. No light is 
applied in this instance. 
The high-molecular liquid-crystals possess dielectric anisotropy. In other 
words, a change in alignment of the liquid-crystal molecules causes a 
change in dielectric constant across the common electrode 406 and segment 
electrodes 407. This means that alignment of the liquid-crystal molecules 
can be determined by detecting a dielectric constant for each pixel. 
The written image is held in the image input/output device 102 since the 
applied voltage is smaller than the threshold value and no light is 
applied to the light-sensitive molecules 400. 
Referring to FIG. 12D, the operation of the image input/output device 102 
is described in Display Mode for displaying an input image by applying a 
low-frequency high-voltage to each electrically selected pixel (by a usual 
method of using a liquid crystal display panel). 
In the Display Mode, a whole surface of the image input/output device 102 
is always illuminated with back light 410. This back light 410 is visible 
light that contains light of wavelength .lambda.1 and therefore can be 
used commonly as visible light 411. 
I this mode, the light-sensitive molecules 400 have trans-form 400a under 
the influence of light of a frequency .lambda.1. 
A low-frequency electric field or a high-frequency electric field is 
selectively applied to each of pixels according to input image 
information. The electric supply source 408 generates a low-frequency 
field having a voltage greater than the threshold and a frequency lower 
than a first critical frequency (fc1) and a high-frequency field having a 
voltage greater than the threshold and a frequency higher than the first 
critical frequency (fc1) and selectively applies the electric field across 
the common electrode 406 and the segment electrodes 407 in such a way that 
the low-frequency electric field is applied to turned ON pixels and the 
high-frequency electric field is applied to turned OFF pixels of the input 
image according to the input image information. The ON pixels to which the 
low-frequency electric field of a frequency lower than the critical 
frequency (cf1) have a disturbed molecular alignment of high-molecular 
liquid-crystals 402 with large movements of ions 403. The OFF pixels 
whereto the high-frequency electric field of a frequency higher than the 
first critical frequency (fc1) is applied become transparent because the 
high-molecular liquid crystals 402 are aligned in the direction of the 
electric field due to their dielectric anisotropy with a small movement of 
ions 403. 
Thus, an image can be written in the image input/output device 102 
according to electrical signals of the input image information. 
The device portion of the second embodiment is featured by the fact that it 
can work without polarizing plates. This enables the image input/output 
device 102 to effectively use a transmitted light of an input original 
image to be written therein. 
In the first embodiment, the second-wavelength light transmitted through an 
original enters the image input/output device 102 through a polarizer. The 
light-sensitive molecules do not require polarization of light to which 
they react, but the polarizer is used for such reasons that frequently 
removing the polarizer every time before Display Mode operation is 
troublesome and requires a complicated mechanism. The transmission loss of 
light having passed the polarizer amounts 50%. There is a loss of light 
through the polarizer in the usual Display Mode. 
On the other hands, the second embodiment in itself does not require any 
polarizer and can effectively use the transmitted image light to be 
written in the image input/output device 102. This enables use of a lamp 
having a smaller power, realizing reduction of the power consumption. With 
the same power lamp, this embodiment can write therein pixels of an 
original of a small light transmittance. 
Referring to FIG. 13, an image input/output device 102 in a device portion 
according to a third embodiment of the present invention will be described 
below: 
The image input/output device 102 is composed of light-sensitive molecules 
300 and liquid crystal molecules 301, which are hermetically held between 
two transparent substrates 302 and 303. The transparent substrate 302 has 
a formed thereon thin-film transistor (TFF) 450 which is composed of a 
gate 451, a source 453, drain 454, a semi-conductor 452 and an insulating 
film 455. 
The gate 451 can be made of chromium (Cr) or tantalum (Ta) metal. The 
insulating film 455 is made of tantalum oxide. The semi-conductor 452, the 
source 453 and the drain 454 are made of amorphous silicone (a-Si). 
One pixel is formed for a TFT which turns on and off said pixel. The 
above-described liquid crystal panel is the same as an active matrix type 
liquid-crystal panel. 
The other transparent substrate 303 has a formed thereon common electrode 
456 which is a transparent electrode such as ITO. The transparent 
substrate 303 has a thin layer of light-sensitive molecules 300, which is 
evenly formed thereon in the same way as shown in the first embodiment. 
This light-sensitive molecular layer acts as aligning film for the 
liquid-crystal molecules 301. The working principle of the light-sensitive 
molecules 300 acting on the molecular alignment of the liquid crystals 301 
according to frequencies of light radiation is the same as described 
before. The construction of the light-sensitive molecules 300 and 
liquid-crystals 301 is not limited to that shown in FIG. 13. The mixture 
of light-sensitive molecules, high-molecular liquid crystals and 
low-molecular liquid crystals, like as shown in FIG. 10, is also 
applicable. 
In the third embodiment, an active matrix type liquid-crystal cell based on 
TFTs can be used for optically writing an optical image directly into an 
image input/output device, electrically reading the written image and 
electrically reading an image. The use of the active matrix type liquid 
crystals creates an integrated image-input type display unit which is 
capable of displaying a high-contrast and highly fine image with a high 
response. 
The construction and operation of the illumination light portion of the 
embodiment are now described in detail as follows: 
FIG. 14 shows a section of the illuminating device according to the first 
embodiment of the present invention. The illuminating light generating 
portion 110 (FIG. 2) is composed of a first lamp 121, a second lamp 123, a 
first reflecting plate 122 and a second reflecting plate 124. The light 
control portion 111 (FIG. 2) is composed of a filter 132 and a light 
diffusing portion 112 (FIG. 2) is composed of a diffusing plate 125. 
A first light emitted from the first lamp 121 is white light of a visible 
wavelength range. The first light contains light of a specified wavelength 
.lambda.1. Light emitted from the second lamp 123 is light of an 
ultraviolet wavelength range that contains light having a specified 
wavelength .lambda.2. The first lamp 121 is provided with the first 
reflecting plate 122 and the second lamp 123 is provided with the second 
reflecting plate 124. These reflecting plates assure effective light 
radiation of the diffusing plate 125. The diffusing plate 125 is provided 
at its bottom surface with a scattering light reflecting plate 127 to 
effectively return back the scattering light. The filter 132 is divided 
into two transmittal areas (a) (for allowing the first light to pass 
therethrough) and (b) (for absorbing the first light). The filter 125 
having flexibility are fixed at its upper and lower edges to paired upper 
and lower rollers, respectively, of a light-filter lifting mechanism 141 
with a driving micro-motor. The upper and lower rollers rotate from the 
micro-motor to set the filter so that light from the first lamp 121 can 
fall on the filtering area (a) or (b). When the first lamp 121 is turned 
ON, either one of the areas (a) and (b) is selected and set between the 
first lamp 121 and the diffusing plate 125. 
The diffusing plate 125 has a transparent original holder 128 thereon. When 
observing an image displayed on a display screen of the image input/output 
device 102, only the first lamp 121 is turned ON and the 
light-transmitting area (a) of the filter 132 is selected in advance to 
allow the white light from the first lamp 121 to pass the image 
input/output device 102. Accordingly, the image input/output device 102 is 
supplied with the white light as back light and, at the same time, is 
given an image signal to be displayed. A user can see a sharp image 
displayed on the display screen of the image input/output device 102 as 
shown in FIGS. 3A and 3B. 
In inputting an image, an original 129 is placed on the transparent 
original holder 129 and only the second lamp 123 is turned on to apply 
ultraviolet radiation to the image input/output device 102. The selector 
switch 130 is used for selectively switching on the necessary lamp. 
Before observing the image thus written in the image input/output device 
102, only the first lamp 121 is turned ON and the light-transmitting area 
(b) of the filter 132 is selected in advance to apply the third light 
(back light) to the image input/output device 102. In this case, the 
original 129 can be removed in advance if no need be. 
The cover 131 is put on the image input/output device 102 to protect a user 
against ultraviolet radiation when inputting an image into the image 
input/output device 102. It is also possible to cover the viewing surface 
of the image input/output device 102 with a film allowing visible light 
but not allowing ultraviolet light instead of the cover 131. 
The illuminating portion of the first embodiment is featured by the 
provision of the specially usable lamps 121 and 123 which can be simply 
switched over to the first visible light or the second ultraviolet light. 
The third light can be also obtained by filtering the first light from the 
first lamp 121 without using any additional lamp. An original 129 can be 
easily placed in the correct position on the image input/output device 
since the image input/output device 102 is initialized to transparent 
state before placing the original 129 thereon. 
An illuminating portion of the second embodiment of the present invention 
is illustrated in section in FIG. 15. 
In FIG. 15, components similar to those shown in FIG. 14 are given the same 
numerals. The description is focused at the different points of the 
illuminating portion from that of the first embodiment. 
A lamp 142 is a light source that can emit light of a wide wavelength range 
from ultraviolet light to infrared light. The light radiation contains 
light of wavelengths .lambda.1 and .lambda.2. Light emitted from the lamp 
142 together with light reflected from a reflecting plate 122 passes 
through a light filter 150 and enters a diffusing plate 125. 
The light filter 150 is a flexible film having three filtering divisions 
(bands)--a first division 151, a second division 152 and a third division 
153 as shown in FIG. 16. Characteristics of the light filter 150 is shown 
in FIG. 17. The first division 151 of the light filter has such a property 
that it rejects almost short-wavelength light of the second wavelength 
range but transmits almost all light of the first wavelength range as 
shown (a) in FIG. 17. This division is used for supplying visible white 
light as back light when displaying an image on the image input/output 
device 102 by applying a voltage thereto according to a display signal. 
The second division 152 possesses such a property that it rejects almost 
short-wavelength light of the first wavelength range but transmits almost 
all light of the second wavelength range as shown (c) in FIG. 17. This 
division is used for supplying the second wavelength-range light when 
reading therein an original image. The third division 153 possesses such a 
property that it rejects almost short-wavelength light of the second 
wavelength range but transmits almost all light of the first 
wavelength-range light excepting light of the wavelength .lambda.1 as 
shown (b) in FIG. 17. This division is used for supplying back light that 
can not cause the light-sensitive molecules to change their structure when 
reading out an original image written therein. 
The light filter 150 is fixed at its upper edge and lower edge to an upper 
roller and a lower roller, respectively, of a filter winding mechanism 141 
to expose one of three divisions of the filter to transmit a pass band of 
light from the lamp 142. 
As describe before, the image input/output device 102 displays an image 
thereon in a usual mode by controlling the molecular alignment of liquid 
crystals under the influence of a voltage applied across the display 
electrodes. For this purpose, it is suitable to supply white light as back 
light of the liquid crystal display. Accordingly, the first division 151 
of the filter 150 is set in advance to cover a whole surface of the light 
passage by using the filter winding mechanism 141. By doing so, the white 
light enters the image input/output device 102, making it easy to see the 
image displayed thereon. In this case, all light-sensitive molecules are 
exposed to light of the wavelength .lambda.1 contained in the white light 
and change their state into trans-form (first state). This itself has no 
influence to an image electrically displayed on the image input/output 
device 102. However, an image to be displayed on the image input/output 
device 102 may be erased all or partially if all or a part of the image 
relates to the cis-form (second state) of the light-sensitive molecules. 
Therefore, the first light is limited to illumination when electrically 
displaying an image. 
In case of writing an original image into the image input/output device 
102, the second division 152 of the filter 150 is set in advance to cover 
a whole surface of the light passage by using the filter winding mechanism 
141. Consequently, only ultraviolet light (the second light) through the 
filter 150 enters the diffusing plate 125 which causes the second light to 
be evenly diffused and directed up to the original 129 placed on the image 
input/output device 102. The second light transmitted with the image 
representing the original 129 through it enters the image input/output 
device 102 wherein the light acts on the light-sensitive molecules which 
changes their structure into cis-form and causes the liquid-crystals to 
change their molecular alignment. Thus, the original image is written in 
the image input/output device 102. 
The third division 153 of the filter 150 is then set to cover a whole 
surface of the light passage by using the filter winding mechanism 141 
when the original image written by the second light is further displayed 
on the image input/output device. Light having passed through the third 
division of the filter 150 is white light (the first light) wherefrom 
light of the wavelength .lambda.1 is eliminated by the filter 150. The 
light enters the diffusing plate 125 through which it is evenly diffused 
and directed up. In this case, there is no original between the diffusing 
plate 125 and the image input/output device 102 and, therefore, the 
diffused light directly transmits through the image input/output device 
102. Thus, the image can be observed on the screen of the display unit. In 
this case, the original image can be observed as be written since the 
light does not contains wavelengths .lambda.1 and .lambda.2 and, 
therefore, does not cause any change in the state of the light-sensitive 
molecules. 
Although the described filter has the second division having the property 
shown (c) in FIG. 17, it may have the second division that has a peak 
transmittance of light having the wavelength .lambda.2 changing the 
light-sensitive molecules into the second state and has a very small 
transmittance of light having other wavelengths than the wavelength 
.lambda.2. 
A cover is put on the image input/output device 102 to protect a user 
against ultraviolet radiation when inputting an image into the image 
input/output device 102. It is also possible to cover the viewing surface 
of the image input/output device 102 with a film allowing visible light 
but not allowing ultraviolet light instead of the cover. 
The illuminating portion of the second embodiment is featured by using one 
lamp 142 in combination with the light filter 150 to easily obtain three 
kinds of light, i.e., the first light, the second light and the third 
light. The use of a single lamp enables saving in size of the device body 
and saving in manufacturing cost. An original 129 can be easily placed in 
the correct position on the image input/output device 102 since the device 
102 is initialized to transparent state before placing the original 
thereon. 
An illuminating portion of the third embodiment of the present invention is 
shown in FIGS. 18A and 18B. Components similar to those shown in drawings 
of the first and second embodiments are given the same numerals. The 
description relates to the different points of the illuminating portion 
from those of the first and second embodiments. 
FIG. 18A is illustrative of the illuminating portion of the third 
embodiment working when displaying an image thereon. 
A lamp 142 shown in FIGS. 18A and 18B is equivalent to the lamp 142 shown 
in FIG. 15. A first light filter 155 has a light-transmitting portion [a] 
having the property shown (a) in FIG. 17 and a light-transmitting portion 
[b] having the property shown (b) in FIG. 17. These two portions can be 
switched over to each other. Light emitted from the lamp 142 together with 
light reflected from a reflecting plate 122 passes through the first light 
filter 155 and enters a diffusing plate 125. Light having passed the first 
light-transmitting portion [a] of the first light-filter 155 is first 
light that contains light having a wavelength Al and is used as back light 
for displaying an image on an image input/output device 102. Light having 
passed the second light-transmitting portion [b] of the first light-filter 
155 is third light that does not contain light having a wavelength Al and 
is used as back light when displaying an optically written image on the 
image input/output device. 
The first light or the third light is evenly diffused upward over a whole 
surface of the diffusing plate 125. The diffused light from the diffusing 
plate 125 directly passes through the image input/output device 102 to 
display an image thereon. 
FIG. 18B shows the operation of the third embodiment when reading (writing) 
an original image into the image input/output device 102. In this case, an 
original 129 is placed on the image input/output device 102 and a cover 
131 is laid thereon. The cover 131 is provided with an upper diffusing 
plate 161, a second light filter 156 and a mirror 162 for reflecting light 
from the lamp 142 toward the upper diffusing plate 161. 
The lamp (light source) 142 and the reflecting plate 122 can change the 
direction of light radiation upward. This can be realized by rotating the 
lamp 142 united with the reflecting plate 122 by 90.degree. about an axis 
of the lamp 142. Upward light is reflected from the mirror 162 of the 
cover 131 and enters through the second light filter 156 into an upper 
diffusing plate 161 of the cover 131. The second filter possesses the 
output characteristic shown (c) in FIG. 17. Accordingly, the light 
entering the upper diffusing plate 161 is the second light that is then 
evenly diffused downward over the whole bottom surface thereof. The second 
light from the upper diffusing plate 161 passes an original 129 inserted 
between the upper diffusing plate 161 and the image input/output device 
102. The transmitted light then enters the image input/output device 102 
wherein the second light representing an original image is written. 
The illuminating portion of the third embodiment is featured in that its 
body is made in a single piece (without dividing upper and lower parts) 
allowing accommodation therein connection wirings with the image 
input/output panel and thus simplifies the construction of the whole 
system. The cover 131 has only optical parts and does not contain any 
electrical circuit, eliminating the need for wiring between the body and 
the cover. There is no fear of exposing observer's eyes to ultraviolet 
radiation since the latter directed downward when inputting an image into 
the image input/output device. 
The reading portion of the embodiment will be described below in detail: 
FIG. 19 shows a reading portion that is an extraction of components 
directly relating to image reading-out operations from the wholesystem 
shown in FIG. 2. A control circuit 105 controls a drive control circuit 
106 and readout circuit 108 according to a signal of judgment what 
operation mode (display, image-input or read-out) is selected. The 
read-out circuit 108 controls drive control circuit 106 to apply an 
adequate voltage waveform across segment electrodes and a common electrode 
only when reading-out an image written in the image input/output device. 
The principle of electrically reading a written image is as follows: 
According to the present invention, an optically written information is 
recorded in terms of a change in relative permittivity .epsilon. per 
pixel. Accordingly, the information can be read-out by determining a 
change of the permittivity .epsilon. of each pixel. As shown in FIGS. 20A 
and 20B, a pixel of liquid crystal is supposed to be a capacitor and 
composes a capacitor in an electric circuit including a detecting 
resistance R and an electric source. The resistance of the liquid crystal 
itself is very small to be negligible. An electrode including its wiring 
has a resistance but is omitted for simplicity of explanation. FIG. 20A 
shows the so-called "charging" state of a capacity detection circuit in 
which a voltage is applied to the liquid crystal. FIG. 20B shows the 
so-called "discharging" state of the circuit in which a charge accumulated 
in the liquid crystal is discharging. 
Capacity of a liquid crystal can be expressed as follows: 
EQU C=.epsilon.S/d (1) 
where S is a surface of an electrode and d is a distance between 
electrodes. As the expression (1) indicates, a change of C is proportional 
to a change of .epsilon.. Accordingly, a change of value C is detected. 
The pixel is now charged by applying a voltage Vo thereto (FIG. 20A). At a 
moment t=0 after the pixel was charged to the steady-state, switch SW is 
open to discharge (FIG. 20B). The voltage Vo is selected so that it may 
not change the information that the liquid crystal has. In this instance, 
a voltage VR(t) applied across a resistance R is determined by solving the 
following equation of the circuit: 
EQU VR(t)=Vo exp(-t/RC) (2) 
A relationship between the voltage VR(t) and the time moment (t) is shown 
in FIG. 21. The capacity Con of a pixel bearing an image information is 
more than the capacity Coff of a pixel not bearing image information. 
Accordingly, a change of the voltage VR(t) in the state of Con differs 
from that of the voltage VR(t) in the state Coff. 
A value of VR at a moment t=t0 is determined and the determined value is 
then compared with a preset threshold voltage Vth. It may be judged that 
there is information if VR is larger than Vth or there is no information 
if VR smaller than Vth. 
The above-described operation relates to one pixel of the liquid crystal 
display. However, the reading portion must act as a scanner for reading 
all pixels information. Accordingly, the reading portion reads information 
by line by line-sequential scanning just like in displaying an image. If 
one line consists of m pixels, the reading portion is provided with 
switches, A-D converters and comparators for m pixels respectively to 
treat with data for m pixels at a time. As electrodes including its wiring 
have respective resistance values depending on pixels' locations, which 
were omitted for simplicity of explanation, the pixels must have 
respectively preset threshold voltage values Vth. 
A practical reading method is described as follows: 
It is supposed that an image shown in FIG. 22, by way of example, have been 
recorded in the image input/output device. In FIG. 22, white-circles 
(.largecircle.)-marks indicate pixels having information recorded thereon 
(capacity Con) and x-marks indicate pixels having no information recorded 
thereon (capacity Coff). Segment electrodes are designated by Xi-Xi+4 
respectively and common electrodes are designated by Yj-Yj+4 respectively. 
In reading the written image, a voltage is applied across a common 
electrode in line-sequence. At this time, a voltage applied across each 
segment electrode is kept at 0 V. The charging period is followed by the 
discharging period. For the discharging period, a detected voltage on each 
segment electrode varies as shown in FIG. 23. However, a change of the 
voltage for each pixel Con quite differs from a change of the voltage for 
each pixel Coff. Accordingly, a voltage is detected on respective segment 
electrodes in a line at a certain moment of time after the beginning of 
the discharge period and converted from analog to digital values which are 
then compared by the comparator with corresponding threshold voltage 
values preset for the respective pixels to determine whether each of the 
pixels has information or not. In the case of FIG. 21, the pixel Con is 
judged to have image information since its voltage V1 detected at t=t0 is 
grater than its threshold voltage Vth whilst the pixel Coff is judged to 
have no-information since its detected voltage V2 is smaller than its 
threshold value Vth. FIG. 24 is a flow chart describing the 
above-mentioned reading operation procedure, where the liquid crystal 
panel is composed of m.times.n pixels. 
Although the above-mentioned process treats with binary recorded 
information (ON or OFF), the display unit according to the present 
invention can treat with multi-valued records of an image information. 
FIG. 25 is a view for explaining the principle of detecting 4-valued 
information. The capacity of pixels of a liquid-crystal panel after 
optically writing an original image therein changes to Coff, C1, C2 and C3 
(Coff&lt;C1&lt;C2&lt;C3) according to gradation of the original image. In this 
case, it is possible to determine the capacity state of each pixel by 
presetting three thresholds (Vth1, Vth2 and Vth3) for discriminating 4 
states of pixel capacities. Namely, the number of thresholds is determined 
by subtracting one from the number of gradation steps to be detected. This 
enables reading an image information with gradation steps. 
To avoid impairment of a liquid crystal panel by applying a DC voltage 
thereto, the polarity of the applied voltage is usually inverted at a 
certain interval of time when displaying an image on the panel. This is 
also realized in reading written information by the embodiment according 
to the present invention. Namely, one scan is performed with a negative 
voltage (-Vo) applied and next scan is performed with a positive voltage 
(Vo) applied, as shown in FIG. 26. These cycles are then repeated. By 
doing so, the impairment of liquid crystals can be prevented. 
A method of reading an information in an active matrix type TFT 
liquid-crystal panel is described as follows: 
An equivalent circuit of one pixel for the TFT liquid-crystal panel is 
illustrated in FIG. 27. A thin film transistor (TFT) is placed at an 
intersection in matrix of signal lines and scanning lines. A gate is 
connected to a scanning line, a source is connected to a signal line and a 
drain is connected to a capacity of a liquid crystal. The TFT acts as a 
switch which maintains ON while reading information written in the liquid 
crystal whose capacity is therefore connected to the signal line. In this 
instance, a resistance value of the TFT being in ON position is omitted 
for simplicity of explanation as the resistance of the electrode including 
its wiring was omitted when explaining the embodiment with the duty type 
liquid crystal panel. Thus, the reading circuit may be considered to be 
the same as those shown in FIGS. 20A and 20B. In this instance, the 
circuit being charged is as shown in FIG. 20A whilst the circuit being 
discharged is as shown in FIG. 20B. Accordingly, the reading method may be 
the same as in duty type liquid crystal panel. 
Next, another method of judging whether a pixel has information or not is 
described below: 
The before-described method (FIG. 21) is such that a voltage detected for a 
pixel at a specified time is compared with a preset threshold voltage Vth 
to determine the pixel has information if the detected value is grater 
than the threshold. Another method shown in FIG. 28 is such that a pixel 
is judged to have information by determining a time for which the detected 
voltage of the pixel reached a certain voltage Vf (&lt;V0) and comparing the 
determined time with a preset threshold time Tth. In FIG. 28, a pixel Con 
is judged to have information since a time T1 for which a detected voltage 
VR becomes equal to the voltage Vf is longer than the preset threshold 
time Tth whilst a pixel is judged to have no information since a time T2 
for which VR becomes equal to Vf is shorter than Tth. Time is measured by 
a counter. 
The detection of multi-valued records of an image information was described 
before with reference to FIG. 25. This is also realized by using threshold 
time values. Namely, 4-value information, for example, can be detected by 
providing three thresholds of time duration (Tth1, Tth2, Tth3) as shown in 
FIG. 29. In this instance, the state of each pixel is discriminated as one 
of 4 states. The number of thresholds is determined by subtracting one 
from the number of gradation steps to be detected. This enables reading an 
image information with gradation steps. 
(1) The integrated image-input type display unit according to the present 
invention has a single unit capable of realizing both functions of 
displaying an image thereon and writing/reading an image therein and 
therefrom by using a liquid-crystal cell liquid-tightly holding therein 
liquid-crystal molecules together with light-sensitive molecules and by 
commonly using electrodes for image displaying and image inputting. This 
enables the display unit to be simple, small and inexpensive to 
manufacture. 
This display unit can optically inputting a multi-gradational image and 
electrically reading the inputted image since the liquid crystal cell 
contains very small light-sensitive molecules. The liquid crystal cell 
exhibits high input-light sensitivity since it contains a vast number of 
light-sensitive molecules dispersed therein and can obtain sufficiently 
large signals of a high signal-to-noise ratio to be electrically read-out. 
The resolution of electrically read image is defined by the density of 
first-group electrodes and second-group electrodes. In the display unit 
according to the present invention, an electric signal of each pixel 
reflects an average density of pixels (not discretely sampled density) 
since there are a large number of dispersed light-sensitive molecules 
therein. The signal is free from moire pattern thanks to the effect of a 
low-pass filter used. 
Furthermore, this display unit according to the present invention has such 
a function that temporarily stores an input image in the image 
input/output device by keeping the molecular alignment of liquid crystals 
therein. This enables the display unit to sequentially input an image in 
the image input/output device and electrically reading the input image 
stored therein. The flexibility of the system is thus increased. 
Accordingly, the image input/output device can display a still picture 
without being always supplied with electric signals for display image. 
This can save the power consumption of the display unit. 
(2) Another integrated image-input type display unit according to the 
present invention offers, in addition to the features of the 
above-mentioned item (1), a wide selection of liquid crystals to be used 
in the liquid crystal cell. Namely, it may use twisted nematic liquid 
crystals or supper-twisted nematic liquid crystals that can be used with a 
low voltage and at a low power consumption. Accordingly, this display unit 
is suitable for use in driven personal computers or potable information 
terminals. 
(3) Another integrated image-input type display unit according to the 
present invention offers, in addition to the features of item (1), the 
following advantageous features: 
It uses a liquid crystal cell containing therein high-molecular liquid 
crystals, low-molecular liquid crystals and light-sensitive molecules, 
which liquid crystal cell does not require polarizers and which, 
therefore, can effectively use light for inputting an image therein and 
light for displaying an image thereon. This enables the use of a lamp 
having a reduced illuminating power and lower power consumption. 
(4) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured by using an image input/output device which is 
similar in construction to a duty-type liquid-crystal panel and which can 
be manufactured at a low cost by relatively simple method. 
(5) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured by using an image input/output device which is 
similar in construction to a TFT type liquid-crystal panel and which can 
display a video image having a high contrast and fine resolution in 
display mode. 
(6) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured by using simplified detection means and has a 
plurality of threshold voltages to read the gradation of an original 
image. 
(7) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured in that a voltage value detected by detection 
means is converted into time value. This enables the device to be 
digitalized: a digitized circuit can be easily prepared at a low cost. 
The resolution can be easily improved by changing a clock of a counter. The 
gradation of an original can be read out by detecting multi-value 
information. This does not requires the provision of a plurality of 
reference voltages. The inexpensive detecting means can detect information 
at a high accuracy. 
(8) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured in that an image input/output device can directly 
display thereon an input image which was optically input therein. The 
image input/output device contains a vast number of very fine 
light-sensitive molecules. Accordingly, an optically input image has a 
very high resolution. Namely, the very-high resolution image can be 
displayed in case displaying an optically input image. 
(9) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured by using simplified illuminating means. The body 
of the display unit can be thus miniaturized and manufactured at a low 
cost. 
(10) Another integrated image-input type display unit according to the 
present invention, in addition to the features of the above-mentioned item 
(1), is further featured in that it assures safety operation: there is no 
fear of exposing observer's eyes to ultraviolet radiation since the latter 
directed downward when inputting an image into the image input/output 
device.