U.S. patent application number 09/264896 was filed with the patent office on 2002-06-06 for image display device, semiconductor device and optical equipment.
Invention is credited to HOSHI, JUNICHI, INOUE, SHUNSUKE, KOHCHI, TETSUNOBU, MIYAWAKI, MAMORU.
Application Number | 20020067419 09/264896 |
Document ID | / |
Family ID | 27310626 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020067419 |
Kind Code |
A1 |
INOUE, SHUNSUKE ; et
al. |
June 6, 2002 |
IMAGE DISPLAY DEVICE, SEMICONDUCTOR DEVICE AND OPTICAL
EQUIPMENT
Abstract
An optical apparatus comprises at least image display device, a
light source for illuminating the image display device,
light-receiving device for receiving the light reflected from the
eye of an observer, and calculation device for calculating the line
of sight of the observer based on the output of the light-receiving
means. At least, a part of the illuminating light from the light
source is utilized as the illuminating light for illuminating the
eye of the observer.
Inventors: |
INOUE, SHUNSUKE;
(YOKOHAMA-SHI, JP) ; MIYAWAKI, MAMORU;
(ISEHARA-SHI, JP) ; HOSHI, JUNICHI; (HADANO-SHI,
JP) ; KOHCHI, TETSUNOBU; (HIRATSUKA-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
27310626 |
Appl. No.: |
09/264896 |
Filed: |
March 9, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09264896 |
Mar 9, 1999 |
|
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|
08833116 |
Apr 4, 1997 |
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Current U.S.
Class: |
348/333.03 ;
348/333.01 |
Current CPC
Class: |
G03B 13/02 20130101;
G03B 2213/025 20130101; G03B 17/20 20130101; G02F 1/133509
20130101; H01L 27/14647 20130101; G02B 27/16 20130101; G02B 27/108
20130101; H01L 27/14621 20130101 |
Class at
Publication: |
348/333.03 ;
348/333.01 |
International
Class: |
H04N 005/222 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 1992 |
JP |
4-352365 |
Apr 9, 1993 |
JP |
5-105987 |
Nov 29, 1993 |
JP |
5-320893 |
Claims
What is claimed is:
1. An optical equipment comprising at least image display means, a
light source for illuminating said image display means,
light-receiving means for receiving the reflected light from the
eye of an observer, and calculation means for calculating the line
of sight of said observer based on the output of said
light-receiving means, wherein at least a part of the illuminating
light from said light source is utilized as the illuminating light
for illuminating the eye of said observer.
2. An optical equipment according to claim 1, wherein said light
source is a rear light source for illuminating said image display
means from the rear side thereof.
3. An optical equipment according to claim 1 or 2, wherein the
illuminating light for illuminating the eye of said observer
includes infrared or near-infrared light.
4. An optical equipment according to claim 3, wherein said infrared
or near-infrared light is obtained through a filter.
5. An optical equipment according to claim 1, wherein the
illuminating light for illuminating the eye of said observer is
obtained through a filter provided in said image display means.
6. An optical equipment according to claim 5, wherein said filter
is provided in an area, other than the pixel portions, of said
image display device.
7. An optical equipment according to claim 6, wherein said area
other than the pixel portions is an area including space between
the pixels.
8. An optical equipment according to claim 5, wherein said filter
is adapted to transmit a desired visible light region and the
infrared or near-infrared light.
9. An optical equipment according to claim 8, wherein said desired
visible light region is at least a visible light region selected
from a group consisting of red light, green light and blue
light.
10. An optical equipment according to claim 5, wherein said area
other than the pixel portions has a configuration substantially
same as that of the pixel said image display device.
11. An optical equipment according to claim 5, wherein said area
other than the pixel portions is included in an image display area
of said image display device.
12. An optical equipment according to claim 11, wherein said area
other than the pixel portions is divided into plural areas.
13. An optical equipment according to claim 1, wherein said light
source includes a visible light region component and a wavelength
component longer than said visible light region component.
14. An optical equipment according to claim 13, wherein said longer
wavelength component includes the infrared or near-infrared
light.
15. An optical equipment according to claim 13, wherein said light
source at least includes a lst light source for emitting light
principally containing a visible light region component, and a 2nd
light source for emitting light principally containing a component
longer in wavelength than said visible light region component.
16. An optical equipment according to claim 1, wherein said light
source is at least one selected from the group consisting of a
fluorescent lamp, a photodiode, a light source by the electron beam
of the cathode ray tube, a plasma display tube and an
electroluminescent tube.
17. An optical equipment according to claim 1, wherein said light
source is a fluorescent lamp having fluorescent materials emitting
red light, green light, blue light and infrared and/or
near-infrared light.
18. An optical equipment according to claim 17, wherein said red
light, green light, blue light and infrared and/or near-infrared
light are generated by at least a fluorescent lamp.
19. An optical equipment according to claim 2, wherein said
infrared or near-infrared light contains light of a wavelength of
850-950 nm.
20. An optical equipment according to claim 13, wherein said longer
wavelength component contains a component of a wavelength of
850-950 nm.
21. An optical equipment according to claim 1, wherein said image
display means includes a liquid crystal display device.
22. An optical equipment according to claim 1, wherein said
light-receiving means is a photoelectric converting element.
23. An optical equipment according to claim 1, wherein said
light-receiving means is included in said image display means.
24. An optical equipment according to claim 23, wherein said
light-receiving means is included in an image display area of said
image display means.
25. An optical equipment according to claim 23, wherein said
light-receiving means includes plural photoelectric converting
elements.
26. An optical equipment according to any of claims 22 to 25,
wherein said image display means includes a liquid crystal display
device.
27. An optical equipment according to claim 1, further comprising
an optical system for condensing the reflected light from the eye
of said observer.
28. An optical equipment according to claim 1, wherein said image
display means is driven by a shift register.
29. An optical equipment according to claim 1, wherein said
light-receiving means is driven by a shift register.
30. An optical equipment according to claim 1, wherein said image
display means and said light-receiving means are driven by a common
shift register.
31. An image display device provided with a rear light source, and
image display means for effecting display by passing the light of
said rear light source through plural pixels, wherein the light
from said light source includes a visible region component and a
longer wavelength component outside the visible region.
32. An image display device according to claim 31, wherein the
longer wavelength component outside the visible region contains a
component of 850-950 nm.
33. An image display device according to claim 31, further
comprising a filter transmitting at least said longer wavelength
component outside the visible region.
34. An image display device according to claim 33, wherein said
filter substantially does not transmit the visible region
component.
35. An image display device according to claim 33, wherein said
filter further transmits light of a wavelength of the visible
region component.
36. An image display device according to claim 31, wherein said
visible region component is colored light selected from red light,
green light and blue light.
37. An image display device according to claim 31, wherein said
light source includes a 1st light source principally emitting said
visible region component and a 2nd light source principally
emitting said longer wavelength component outside the visible
region.
38. An image display device according to claim 31, wherein said
visible region component and said longer wavelength component
outside the visible region are generated by at least a fluorescent
lamp.
39. An image display device according to claim 38, wherein said
fluorescent lamp includes fluorescent materials emitting red light,
green light, blue light and infrared and/or near-infrared
light.
40. An image display device according to claim 31, wherein said
light source includes a semiconductor.
41. An image display device according to claim 33, wherein said
filter is provided at least in an area between the pixels.
42. An image display device according to claim 33, wherein said
filter is provided at least within an image display area of the
image display means.
43. An image display device according to claim 32, wherein said
filter has a configuration substantially same as that of the
pixel.
44. An image display device according to claim 31, wherein said
image display means further includes a light-receiving unit.
45. An image display device according to claim 31, further
comprising a light-receiving unit.
46. An image display device according to claim 31, wherein said
image display means is liquid crystal display means.
47. An image display device provided with a rear light source and
image display means for effecting display by passing the light from
said rear light source through plural pixels, wherein said image
display means includes a light-receiving unit.
48. An image display device according to claim 47, wherein said
light-receiving unit is a photoelectric converting element.
49. An image display device according to claim 47, wherein said
light-receiving unit is provided in an area between the pixels of
said image display means.
50. An image display device according to claim 47, wherein said
image display means is liquid crystal display means.
51. A semiconductor device, wherein a Si-containing light-emitting
element and a light-receiving element are formed on a same silicon
chip.
52. A semiconductor device according to claim 51, wherein said
Si-containing light-emitting is an element utilizing the
light-emitting phenomenon in the crystal defects in monocrystalline
silicon, in amorphous silicon, at the polysilicon-monocrystalline
silicon interface or in porous silicon.
53. A semiconductor device according to claim 51, wherein plural
light-emitting elements and/or plural light-receiving elements are
arranged in an array.
54. A semiconductor device according to claim 51, wherein an
on-chip lens are provided on the light-emitting element and/or the
light-receiving element.
55. An optical equipment provided with a semiconductor device
according to claim 51.
56. An image display device provided with a semiconductor device
according to claim 51.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image display device
adapted for use as display means in an electronic still camera, a
video camera or the like, a semiconductor device adapted for use in
various optical sensors, and an optical equipment equipped with the
image display device and/or the semiconductor device mentioned
above, and more particularly to an image display device and/or a
semiconductor device adapted for use in detection of line of sight
or optical detection, and an optical equipment having such function
of detection of line of sight or optical detection.
[0003] 2. Related Background Art
[0004] The image display devices are available in different sizes,
and are being used in various applications such as television,
monitors for office equipment, monitors (view finders) of
electronic still cameras or video cameras etc.
[0005] Also the image display devices are known in various types,
such as liquid crystal display device, CRT (cathode ray tube),
plasma display, EL (electro-luminescence) display etc. Among these,
the liquid crystal display device is being utilized in various
applications because of various advantages such as light weight,
possibility of compactization, ease of full-color display and low
electric power consumption.
[0006] On the other hand, the apparatus for recording images on a
silver halide-based film, namely the camera, has recently shown
remarkable progress particularly in the automatic focusing
technology. Within this field there is already known a technology
for detecting the direction of the line of sight of the observer
(photographer) and automatically focusing the phototaking lens to
such observed position, as disclosed in the Japanese Patent
Laid-open Application Nos. 1-241511 and 4-240438.
[0007] This invention aim at achieving, for example, convenient
auto focusing function of larger freedom "by providing a finder
device for observing an object, illumination means for illuminating
the eye of the observer looking into the finder device, a
condensing optical system for condensing the reflected light from
the eye of the observer, photoelectric conversion means for
receiving the condensed reflected light, and calculation means for
calculating the direction of the line of sight of the observer from
the output of the photoelectric conversion means, and controlling
at least one of the phototaking condition setting means of the
camera according to the result of calculation of the calculation
means".
[0008] An example of the sight line detecting device will be
schematically explained with reference to FIG. 1. An infrared light
source 2901 constituting a point light source illuminates an
eyeball 105 through a condensing lens 2902 and a half mirror 2903.
The human eye can be considered as an adhered lens, with the front
face 106a of the cornea, the rear face 106b thereof, the front face
108a of the lens and the rear face 108b thereof as the adhering
faces or the interfaces, and the iris 107 is positioned close to
the front face of the lens. The variations in the refractive index
are different at these adhering faces, and the reflection occurs in
the descending order of the front face of the cornea, the front
face of the lens, the rear face thereof, and the rear face of of
the cornea. Also the paraxial tracking indicates that the reflected
images at the different interfaces, in response to a parallel
incident light beam, are positioned as shown in FIG. 2, when the
eyeball is seen from the front.
[0009] As shown in FIG. 2, the reflected images of the interfaces
are focused at positions, measured from the front face 106a of the
cornea, of 3.990, 4.017, 4.251 and 10.452 mm in the order of the
1st, 2nd, . . . faces. These values correspond to the standard
shape and values, shown in the following, of the human eye.
[0010] standard radius of curvature of 106a=7.98 mm
[0011] standard radius of curvature of 106b=6.22 mm
[0012] standard radius of curvature of 108a=10.20 mm
[0013] standard radius of curvature of 108b=61.7 mm
[0014] refractive index between 106a-106b: n.sub.1=1.376
[0015] refractive index between 106b-108a: n.sub.2=1.336
[0016] refractive index between 108a-108b: n.sub.3=1.406
[0017] refractive index to the right of 108b: n.sub.4=1.336
[0018] These images are called Purkinje'3 s images. The reflected
images by the eye of the observer are guided by the inverse path,
then reflected by the half mirror 2904, and enter a photoelectric
converter 2905, on which the Purkinje's images reflected at
different interfaces are focused. The Purkinje's images appear as
point images arranged linearly on the optical axis of the eyeball,
but, if the line of sight is directed to either direction by the
rotation of the eyeball, the illuminating light enters obliquely to
the optical axis of the eyeball, so that the Purkinje's images move
to positions deviated from the center of the pupil. Thus there can
be observed plural Purkinje's images, because the amount and
direction of movement of the Purkinje's image depend on the
interface where the Purkinje's image is formed. The direction of
the line of sight can be detected by electrically finding the
movement of these Purkinje's images, and, if necessary, the centers
of the pupil and the iris.
[0019] This principle will be briefly explained with reference to
FIGS. 3 and 4. Referring to FIG. 3, when the iris 3102, pupil 3103,
Purkinje's 1st image 3104 and Purkinje's 2nd image 3105 are
detected as illustrated on a device consisting of a two-dimensional
array of photoelectric converting elements 3101, the elements for
example of the 7th row and the 5th column provide the illustrated
outputs. Thus a position (x.sub.5, y.sub.7) providing a 1st peak
and a position (x.sub.10, y.sub.7) providing a 2nd peak are
respectively detected as 1st and 2nd images, and the rotation angle
of the eyeball can be calculated, according to FIG. 4, from the
amount of positional aberration of the two images, or the amount of
displacement of the Purkinje's images.
[0020] FIG. 1 shows a conventional configuration of a sight line
detecting device for auto focusing control by the feedback of thus
detected information of the watching point of the observer.
[0021] As shown in FIG. 1, the sight line detecting device includes
a light-emitting device used for the light source 2901 and a
photosensor used for the photoelectric converter 2905. Also apart
from the detection of the line of sight, there are already known
various light-emitting devices and photosensors, usable for the
purpose of projecting light to an object and detecting the
reflected light thereby detecting the image or position of the
object.
[0022] In a signal processing system for reading the coordinates of
an optical image by light irradiation, as shown in FIG. 5, the
light source 3301 need not be an array but can be a point light
source as long as it can uniformly illuminate the entire object
3302 which randomly reflect the light at the surface. For this
reason there is generally used an inexpensive light-emitting
element such as LED. By uniform illumination on the object 3302,
the light containing positional information enters a photosensor
3304 through an optical system 3303 of the system.
[0023] The photosensor 3304 requires at least one-dimensional array
unless it is not equipped with a geometrical scanning mechanism.
The photosensor 3304 is generally composed of a photodiode array or
the like for simple positional detection, and a CCD for more
complex image recognition.
[0024] Attention is now being attracted to a recently discovered
light-emitting phenomenon in Si which is an indirect transition
semiconductor material. For example, monocrystalline silicon emits
light at discontinuity of the crystal, such as a defect, when a
large current of the order of 1 mA is given. Also at the interface
of polysilicon and monocrystalline silicon, the light emission is
possible by the current force. A similar light-emitting phenomenon
is also known in amorphous silicon. The most famous light-emitting
phenomenon is reported by Axel Richter et al. in "Current-Induced
Light Emission from a Porous Silicon Device", 1EEE Electron Device
Letters, Vol. 12, No. 12, December 1991, pp. 691-692.
[0025] The porous silicon emits red light with a good efficiency,
and is attracting attention as the future light source.
[0026] However, for applying the aforementioned detection of the
line of sight of the observer to an image display device such as a
view finder, there are required a new light source for such sight
line detection, and an optical system for condensing the light in a
predetermined position in the view finder. Stated differently,
independently from the light coming for example from the light,
there is required light of a desired intensity, preferably
invisible to the human eyes.
[0027] Consequently there is required a space for the light source
for the sight line detection, the photoelectric converting device,
and the optical system if necessary, leading often to the drawbacks
of increased size and cost of the equipment.
[0028] More specifically there are required anew an LED light
source 2901 for obtaining infrared or near-infrared light for the
detection of the line of sight, and a light-splitting half mirror
2904, and these components not only increase the dimension of the
equipment in optical designing but also the number of component
parts, thus raising the cost.
[0029] Besides, if the light emission intensity of the LED light
source is increased in order to improve the sensitivity of
detection, increases will result in the power consumption and in
heat generation, hindering the compactization and power saving of
the equipment. Furthermore, there is requirement for avoiding entry
of unnecessary light amount into the eyeball.
[0030] As expalined above, when the photoelectric conversion means
and the driving means therefor, for the detection of the line of
sight, are provided independently from the main image display
device, there are required additional space and components for such
detecting function, leading to an increased cost of the
product.
[0031] On the other hand, in an optical signal processing system as
shown in FIG. 5, the light source and the photosensor are generally
constructed independently, and the light source 3301 is usually
composed of a semiconductor device capable of providing a high
intensity such as a Ga-As device, or a small lamp such as an
incandescent or fluorescent lamp. It will be easily understood that
the integration of such light source and the aforementioned
photosensor 3304 on a same chip is extremely difficult.
[0032] Also there is required an additional optical system for
guiding the light from the above-mentioned light source 3301 to the
object 3302, and this increases the volume of the entire
system.
[0033] Also the system including the optical system 3303, generally
involving the imaging process, requires a dimension several times
as large as the focal length of the lens contained in the optical
system 3303. Such increase in the dimension of the system is never
desirable, though the extent of such increase is dependent on the
system.
[0034] Also in terms of the cost, the III-V semiconductor device,
such as Ga-As device, is more expensive in comparison with the
Si-based semiconductor device. Besides the cost increase of the
system, resulting from the presence of a non-essential additional
optical system should be avoided.
SUMMARY OF THE INVENTION
[0035] An object of the present invention is to provide an optical
equipment including a sight line detecting mechanism while
attaining compactization, weight reduction and cost reduction, and
an image display device and a semiconductor device usable
advantageously therein.
[0036] Another object of the present invention is to provide an
image display device enabling power saving, suppression of
unnecessary heat generation, compactization of the entire device
and designing with electric power saving, and an optical equipment
including such image display device.
[0037] Still another object of the present invention is to provide
an optical equipment not requiring additional light source and/or
photosensor for the detection of the line of sight, and an image
display device advantageously usable therein.
[0038] Still another object of the present invention is to provide
an image display device capable of detecting the line of sight
without additional drive means and/or optical system.
[0039] Still another object of the present invention is to provide
a semiconductor device enabling compactization and cost
reduction.
[0040] Still another object of the present invention is to provide
an optical equipment, provided at least with image display means, a
light source for illuminating said image display means,
light-receiving means for receiving the light, reflected by the eye
of the observer, of said image display means, and calculation means
for calculating the line of sight of said eye of the observer based
on the output of said light-receiving means, wherein at least a
part of the illuminating light from said light source is utilized
as the illuminating light for illuminating said eye of the
observer.
[0041] Still another object of the present invention is to provide
an image display device provided with a rear light source and image
display means for effecting display by passing the light from said
rear light source through plural pixels, wherein the light from
said light source contains a visible spectral component and a
longer wavelength component outside the visible spectral
region.
[0042] Still another object of the present invention is to provide
an image display device provided with a rear light source and image
display means for effecting display by passing the light from said
rear light source through plural pixels, wherein said image display
means includes a light-receiving unit.
[0043] Still another object of the present invention is to provide
a semiconductor device in which a Si-containing light-emitting
element and a light-receiving element are formed on a same chip,
and an image display device and an optical equipment including such
semiconductor device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a schematic view showing a sight line detecting
mechanism;
[0045] FIG. 2 is a view showing reflected images (Purkinje's
images) at differnt interfaces of the eyeball;
[0046] FIG. 3 is a view showing an example of the method for
detecting the line of sight;
[0047] FIG. 4 is a chart showing the relationship between the
amount of displacement of the Purkinje's image of a human eye and
the rotation angle of the eyeball in a sight line detecting
system;
[0048] FIG. 5 is a view showing a signal processing system for the
optical image;
[0049] FIG. 6 is a schematic view showing an example of the optical
equipment of the present invention;
[0050] FIG. 7 is a schematic perspective view of an example of the
image display means applicable in the present invention;
[0051] FIGS. 8A, 10, 12 and 13A are schematic cross-sectional views
of image display means;
[0052] FIGS. 8B and 13B are schematic plan views of image display
means;
[0053] FIGS. 9, 11, 14, 15, 18, 19, 21 and 23 are circuit diagrams
showing examples of the driving circuit of the present
invention;
[0054] FIGS. 16, 20 and 22 are timing charts showing the timings of
functions;
[0055] FIGS. 17, 24 and 25 are schematic partial cross-sectional
views of image display means;
[0056] FIG. 26 is a spectral chart showing an example of the
spectral distribution of the rear light source;
[0057] FIGS. 27A and 29A are schematic perspective views showing
examples of the light source;
[0058] FIGS. 27B, 29B, 30 and 31 are schematic cross-sectional
views showing examples of the light source;
[0059] FIG. 28 is a schematic cross-sectional view showing the
light-emitting source of the light source;
[0060] FIG. 32 is a spectral chart showing an example of the
transmission characteristics of the filters;
[0061] FIGS. 33, 36 and 37 are schematic cross-sectional views
showing examples of the semiconductor device of the present
invention;
[0062] FIGS. 34A to 34G are schematic views showing an example of
the preparation method of the semiconductor device of the present
invention;
[0063] FIG. 35 is a circuit diagram showing an example of the
driving circuit for the semiconductor device of the present
invention;
[0064] FIGS. 38 and 39 are schematic plan views showing examples of
the arrangement of the light-receiving part and the light-emitting
part; and
[0065] FIG. 40 is a schematic view showing an example of the
optical equipment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0066] In short, the above-mentioned drawbacks can be resolved and
the above-mentioned objects can be attained by using the light
source for the image display means also as the light source for the
detection of the line of sight, and/or forming a light-receiving
unit for the detection of the line of sight within the image
display means.
[0067] Also the above-mentioned drawbacks can be resolved and the
above-mentioned objects can be attained by forming the
light-emitting unit and the light-receiving unit within a chip.
[0068] In the following, the present invention will be clarified in
detail by preferred embodiments thereof, with reference to the
attached drawings.
[0069] It is to be noted, however, that the present invention is
naturally not limited to the following embodiments but is subject
to various modifications and combinations of the following
embodiments, within the scope and spirit of the present
invention.
[0070] Embodiment 1
[0071] At first there will be explained the function of detection
of the line of sight in the image device of the present invention,
with reference to the schematic view of the optical equipment shown
in FIG. 6.
[0072] The light beam from a rear light source 101 of a liquid
crystal display panel 102 enters an eyeball 105, through an
eyepiece lens 103. A part of the light reflected by the front face
106a and rear face 106b of the cornea, and the front face 108a and
rear face 108b of the lens of the human eye proceed close to the
original optical axis, then partly separated by a light splitter
104, and is focused by a condenser lens 109 onto a photoelectric
converting device 110. The electric output thereof is supplied
through an output line 111 to a control circuit 112 constituting
calculation means for detecting the line of sight, which is used as
an auto focusing signal or a trigger signal for other functions. As
will be understood from the foregoing, the common use of the rear
light source also for the light source for sight line detection
dispenses with the additional components such as LED.
[0073] FIG. 7 is a schematic view showing an example of the
preferred configuration of a liquid crystal display panel 102,
constituting the active-matrix image display means usable in the
optical equipment shown in FIG. 6. On a translucent glass substrate
or a semiconductor substrate 207, there is formed a switching
element layer 206 having thin film transistors (TFT) and a lower
electrode. By on/off operation of the above-mentioned transistor of
each pixel, in response to the image signal, there is generated a
variation in the voltage applied to liquid crystal 205 sandwiched
between the upper electrode 204 and the lower electrode. The liquid
crystal twists the optical path depending on the applied voltage,
thus generating a light-transmitting state and a light-intercepting
state. White and black states can be distinguished to the human
eyes, by means of polarizing filters 201, 208 adhered on both sides
of the panel. Recently, color liquid crystal display devices,
having a color filter layer 203 utilizing dyes, are also rapidly
becoming popular.
[0074] FIGS. 8A and 8B are respectively a schematic cross-sectional
view and a schematic plan view of the color filter layer 203 in
magnified manner. In the present embodiment, so-called additive
color filters 301a, 301b, 301c of R (red), G (green) and B (blue)
are formed in chequer-board pattern, with the element isolation
area formed with a black matrix 302. In addition, one in every four
pixels is composed of an IR (infrared or near-infrared
transmitting) filter 303, for transmitting the illuminating light
for the detection of the line of sight. Such IR pixel is formed in
every four pixels in the present embodiment, but such configuration
is merely for the convenience of illustration, and the desired
function can be sufficiently attained by one pixel in a larger
number of pixels, for example in every 20 to 100 pixels.
[0075] FIG. 9 is an example of the equivalent circuit of the
switching element layer 206, for driving 4 pixels among the pixels
shown in FIG. 8B. Since the IR pixel preferably transmits the light
constantly regardless whether the image information is white or
black, in the normally-white liquid crystal display panel which
transmits the light when a zero voltage is applied to liquid
crystal R.sub.1 between the pixel electrode and the counter
electrode, as in the present embodiment, there is adopted, for
example, a condition V.sub.C.congruent.V.sub.COM. However, Vc and
V.sub.COM may be selected at different levels within an extent that
the liquid crystal shows a high transmittance and does not change
this state.
[0076] The cross section of a pixel is shown, in larger details, in
FIG. 10. Within an effective pixel 501 for display, there is
provided a transparent pixel electrode 514, connected to a drain
area 505 of a transistor having a source area 503, an n-type active
area 504, a drain area 505 and a gate electrode 506, in opposed
manner to an upper electrode 204 thereby applying a voltage to the
liquid crystal 205. Also an auxiliary capacitance for improving the
image rendition and eliminating the flicker is formed by the
capacitative coupling between another transparent electrode 512 and
the transparent pixel electrode 514. On the other hand, the
infrared transmitting pixel 502 does not have the transistor. In
this area 502, a transparent electrode 512 and a counter electrode
204 are mutually opposed across the liquid crystal 205 and
interlayer insulation films 513, 515 whereby the light is always
transmitted. In relation to the equivalent circuit diagram shown in
FIG. 9, V.sub.C is the potential of the upper (counter) electrode
204, and V.sub.COM is that of the transparent electrode 512.
[0077] It is desirable to select the gap thickness of the liquid
crystal layer in the infrared transmitting area larger than that in
the display area with the visible light, in order to suppress the
reflection in the former thereby increasing the light
transmittance. In this manner there can be achieved further
improvement in the performance.
[0078] In summary, the sight line detecting system in this
embodiment functions in the following manner. Among the light
components emitted from the rear light source 101, the visible
component displays an image according to the voltages controlled by
the switching elements. At the same time, through the infrared
transmitting filters of the IR pixels provided in a part of the
image display means, the infrared or near-infrared light for the
detection of the line of sight, of a constant intensity, enters the
human eye from the liquid crystal display device. The light
reflected by the eye is guided to the photoelectric converting
device as explained before to effect the detection of the line of
sight.
[0079] The sight line detection is executed according to the
principle and method explained before in relation to FIGS. 3 and
4.
[0080] In the present embodiment shown in FIG. 6, the photoelectric
converting device, the control circuit etc. constituting the sight
line detecting system are not essential, and, for example, the
configuration as shown in FIG. 1 may be adopted for this
purpose.
[0081] Also the IR filter shown in FIGS. 8A and 8B may be replaced
by visible-light cutting filter.
[0082] The present embodiment can achieve reduction in the size and
weight of the entire equipment, since the additional light source
for the sight line detection can be dispensed with. As a result, it
contributes to the realization of an optical equipment, such as a
video camera, provided with the sight line detecting function and
featured with a low cost and compactness.
[0083] Embodiment 2
[0084] This embodiment shows the configuration employing a normally
black liquid crystal display panel which is black when without
voltage application.
[0085] The configuration of the optical system of the sight line
detecting system and the schematic structure of the liquid crystal
display panel will not be explained as they can be same as those
shown in FIGS. 6 and 7. In circuit structure, as shown in FIG. 11,
there is additionally required a potential line of V.sub.SS side in
order to obtain a voltage .linevert split.V.sub.SS-
V.sub.COM.linevert split.>0 to be applied to the liquid crystal
of the infrared transmitting pixels (IR pixels).
[0086] FIG. 12 is a cross-sectional view of the pixel. An effective
pixel 501 for display is provided, as in the embodiment 1, with a
transistor having a source area 503, an n-type active area 504, a
drain area 505 and a gate electrode 506, an auxiliary capacitance
formed by capacitative coupling between said drain area 505 and a
polysilicon capacitor electrode 701, and a transparent electrode
514 electrically connected with said drain area 505. On the other
hand, in an infrared transmitting pixel 502, a transparent
electrode 703 receiving a potential V.sub.SS is connected to a rear
electrode 704 through a P.sup.+-silicon layer 702. The IR pixels
are given a common potential V.sub.SS electrical connection of the
rear electrodes 704 of all the infrared transmitting pixels. This
connection is preferably achieved by transparent electrodes or
relatively thin silicon or polysilicon, not hindering the
transmission of the infrared light, but there may be employed metal
wirings suitably positioned in superposing manner with the
over-lying element isolation areas. For the application of the
potential V.sub.SS, there is preferably employed an AC voltage, in
consideration of the deterioration of the liquid crystal. For
example, there can be employed a voltage V.sub.SS=V.sub.COM+5 (V)
in a half of the time for image display operation and a voltage
V.sub.SS=V.sub.COM-5 (V) in the remaining half, so that .linevert
split.V.sub.SS-V.sub.COM .linevert split. becomes always
constant.
[0087] Besides the present embodiment provides an advantage of
arbitrarily selecting the light transmittance of the liquid
crystal, by suitable selection of the potential of the rear
electrode 704. Consequently there can be constructed a system of
increased freedom, capable of independently adjusting the amount of
light for the rear illumination and that for the sight line
detection. Also the sight line detection can be stably achieved,
irrespective of the displayed image, since the transmittance of the
IR transmitting pixels can be controlled independently from the
luminance of the displayed image.
[0088] In the present embodiment, the auxiliary capacitance is
composed of the capacitative coupling between the polysilicon
capacitor electrode 701 and the P.sup.+ drain area 505, it may also
be formed by the capacitative coupling between the transparent
electrodes as in the embodiment 1.
[0089] Also the switching transistors are of p-MOS type, but n-type
ones may also be employed without impairing the advantages of the
present embodiment.
[0090] Embodiment 3
[0091] In the present embodiment there will be explained image
display means in which the R, G, B color filters provided in
so-called delta arrangement where the three color are positioned at
the corners of a regular triangle, and the element isolation area
is utilized for transmitting the illuminating light for the
detection of the line of sight.
[0092] FIGS. 13A and 13B are respectively a schematic
cross-sectional view and a schematic plan view of the color filter
layer portion of the image display device of the present
embodiment. As illustrated therein, the areas separating the R, G,
B pixels for color display are covered with an infrared
transmitting filter 801. On the other hand, the color pixels are
positioned in the delta arrangement as explained above. In this
arrangement, as shown in the schematic plan view in FIG. 13B, the
pixels are displaced by 0.5 pixels every row, and the color of each
filter is made different those of the closest positioned filters,
in order to avoid the appearance of a particular colored line in
the diagonal direction. This delta arrangement can improve the
image sharpness.
[0093] FIG. 14 is an equivalent circuit diagram of the switching
element layer 206, for driving 4 pixels among those shown in FIG.
13B. As shown in FIG. 14, all the pixels can be utilized as
effective pixels for image information display. In usual case there
is required a black matrix 302 for mutually separating the pixels
as shown in FIG. 8B, but, in this embodiment, this black matrix is
intentionally eliminated and the light is intentionally transmitted
through the infrared transmitting filter in the element isolation
area. This infrared transmitting filters, appear, to the human
eyes, as opaque area. This configuration dispenses with the black
matrix and provides the light for sight line detection, without
sacrificing the image information even by a bit. As a result, the
inexpensive image display device of high definition can be given
the component for the sight line detecting function, without the
addition of a new illuminating light source.
[0094] This embodiment is not limited to the liquid crystal device
but is applicable also to any display device in which the pixel
separating area can be made to transmit the infrared or
near-infrared light. Also it is naturally applicable to any
non-delta arrangement, without any variation in the configuration
or characteristics.
[0095] In the following there will be explained preferred examples
of the light source applicable to the present invention.
[0096] FIG. 26 shows an example of the light emission spectrum of
the rear light source 101. This light source is for color display,
including the blue (B) light having a peak around a wavelength 450
nm, the green (G) light having a peak around 550 nm and the red (R)
light having a peak around 670 nm, and also emits infrared (IR)
light having a peak in a region of 850-900 nm. The peak width of
each of B, G or R color is selected narrower than that of each
color in the spectral characteristics of the color filter of the
liquid crystal display panel 102, whereby the displayed colors are
determined by the characteristics of the light source, and there
can be obtained stable and excellent color reproduction. In the
present invention, the peak wavelength of the IR light is
preferably longer than 850 nm so as to be insensible to the human
eyes, and shorter than 950 nm so as to have a sufficient
sensitivity when the detector is composed of silicon
semiconductor.
[0097] FIGS. 27A and 27B are schematic views of the rear light
source 101.
[0098] The light source can be, for example, a fluorescent lamp, a
light-emitting diode, a cathode ray tube emitting light by an
electron beam, a plasma display tube or an EL (electroluminescence)
tube. The present embodiment employs a fluorescent lamp capable of
emitting the R, G, B and IR lights by a single tube.
[0099] FIGS. 27A and 27B are respectively a schematic perspective
view and a schematic transversal cross-sectional view. The light
emitted in all direction from a fluorescent lamp 404 is collected,
by a reflector 403 to a light curtain 402, which is a
semi-translucent reflector having aluminum deposition in such a
manner that the reflectance is larger in areas close to the
fluorescent lamp 404 constituting the light source and receiving a
larger amount of light, and smaller in areas farther from the light
source and receiving a smaller amount of light. The light reflected
by the light curtain 402 is reflected by the reflector 403, then
transmitted by the light curtain and scattered by a diffusing plate
401, thus being converted in uniform planar light and entering the
liquid crystal display panel 102.
[0100] FIG. 28 shows the detailed structure of the fluorescent lamp
404. An anode 602, a grid 603 and a filament 604 sealed in a vacuum
tube 601 are maintained at desired potentials by a bias source 605,
a bias resistor 605, a bias resistor 606, an AC filament power
source 607 and a cut-off bias source 608 provided outside. The
circuit functions in the following manner. The filament 604 heated
by the AC filament power source 607 emits thermal electrons, which
are attracted by the grid 603 when a grid selecting switch 609 is
turned on, and which pass through the gaps of the grid and collide
with the anode 602. The anode 602 is coated with a fluorescent
material which emits light when excited by the electron beam, and
thus emits light.
[0101] In the present embodiment, there is employed a blend of four
fluorescent materials of R, G, B and IR, in order to obtain a
light-emission spectrum as shown in FIG. 26. The cut-off bias
source 608 is provided to always maintain the filament 604 at a
higher potential than the grid 603 when the grid selecting switch
609 is turned off, thereby suppressing unnecessary light emission
in the off state.
[0102] In the following there will be explained another example of
the light source applicable in the present embodiment, with
reference to FIGS. 29A and 29B. FIG. 29A shows a planar light
source having a light condensing unit 405 at a side, wherein the
light emitted from a fluorescent lamp 404 is guided by a reflector
407a to a light guide plate 406. The light scattered in the light
guide plate is emitted uniformly upwards. A reflector 407b is
provided in order to effectively utilize the downward leaking
light. The reflectors 406a, 407b are made of a material reflecting
not only the visible light but also the IR light almost completely.
For improving the uniformity, there is preferably provided another
set of the fluorescent lamp and the reflector at the other
side.
[0103] Such configuration allows to compactize the light source and
the entire equipment, in comparison with the aforementioned
structure.
[0104] In the following there will be explained another example of
the light source applicable in the present invention, with
reference to schematic cross-sectional views shown in FIGS. 30 and
31.
[0105] The light source of this embodiment is featured by
incorporating a visible light emitting lamp 904 and an infrared
light emitting lamp 905 in the light source unit, in independently
controllable manner. FIGS. 30 and 31 are schematic cross-sectional
views, respectively showing a case applied to the light source of a
form explained in FIGS. 27A and 27B and a case applied to that
explained in FIGS. 29A and 29B, and the functions of the components
are same as already explained. The lamps are naturally so
positioned that the entire area of the liquid crystal panel 102 can
be uniformly illuminated both by the visible light and by the
infrared light.
[0106] The configurations shown in FIGS. 30 and 31 provide the
advantage that the amount of light of the visible light source for
image display and that of the infrared light source for sight line
detection can be independently controlled and can therefore be
respectively optimized. More specifically, the amount of light of
the visible light source can be regulated according to the
intention of the observer or according to the intensity of the
external light, while the amount of infrared light can be selected
in optimum manner according to the sensitivity of the sight line
detecting sensor, the optical designating etc. Consequently freedom
in designing and practicality are increased in the entire
equipment.
[0107] Naturally the range of the adjustment of the amount of light
can be further extended by the combination of the transmittance
control of the IR pixels of the image display device.
[0108] Also the configurations shown in FIGS. 30 and 31, not
necessarily requiring to vary the transmittance in the IR pixels or
in the IR transmitting area, allow to simplify the structure
including the control system.
[0109] Furthermore, the present invention can be exploited without
forming the IR filters anew, by suitably selecting the transmission
characteristics of the R, G and B color filters.
[0110] More specifically, the filter configuration of the present
embodiment may employ the IR filter shown in FIGS. 13A and 13B as
the black matrix, and color filters of the transmission
characteristics as shown in FIG. 32, representing the spectral
transmittances of the R, G and B filters suitable for this example.
In this example, the space between the color filters is covered
with the black matrix 702, while each of all the pixels is covered
with R, G or B filter and all the pixels are utilized for image
display. However, the spectral characteristics of such filters
transmits the light of infrared region (>80 nm) in any color, so
that the infrared light for the detection of the line of sight is
transmitted through all the pixels.
[0111] This embodiment is featured by a fact that the infrared
light for the detection of the line of sight can be transmitted
with a sufficient intensity, without any deterioration in the image
quality, since all the pixels are used for image display.
[0112] In the present invention, there can be conceived the light
sources of various forms and structures other than those shown in
the foregoing embodiments, but such light sources are
satisfactorily usable in the present invention as long as the light
thereof contains sufficiently the wavelength component usable for
the detection of the line of sight.
[0113] Also there can be conceived various arrangements of the R,
G, B and IR filters, but any arrangement is acceptable as long as
an area for effectively transmitting the IR light is secured on the
display panel.
[0114] Embodiment 4
[0115] In the following there will be explained an embodiment in
which the light-receiving device for the sight line detection is
integrated with the liquid crystal display panel. FIG. 40
schematically shows an optical equipment of the present embodiment,
including a liquid crystal display panel 4001 integrated with the
light-receiving device. Components equivalent to those in FIG. 6
are represented by same numbers.
[0116] FIG. 15 shows an example of the preferred circuit structure
of the image display device of the present embodiment, wherein
shown are a capacitance 1001 formed by the liquid crystal cell; a
switching TFT (pixel TFT) 1002 for applying a signal potential to
said liquid crystal cell or for connecting a photo-electric
converting element 1018 such as a photodiode with a signal line
1003; a 1st transfer gate 1004; a 1st buffer capacitance 1005; a
switching TFT 1006 for accumulating an external signal pulse in the
corresponding 1st buffer capacitance 1005; a 1st horizontal shift
register 1007 for driving the switching TFT's 1006; a vertical
shift register 1008 for driving the switching TFT's 1002; an
external signal input terminal 1009; a 2nd buffer capacitance 1010;
a 2nd transfer gate 1011 for accumulating the sensor output of a
photoelectric converting element 1018 in the corresponding 2nd
buffer capacitance 1010; a switching TFT 1012 for releasing the
sensor output signal of the photoelectric converting element,
retained in the 2nd buffer capacitance 1010, in successive manner
to an output line 1013; a 2nd horizontal shift register 1014 for
driving the switching TFT's 1012; an output terminal 1015 for the
sensor output signal; a resetting TFT 1016 for resetting the 2nd
buffer capacitance 1010; a resetting signal line 1017; a selecting
transistor 1019; a 2nd reset signal input terminal 1020; an image
signal input terminal 1021; a sampling capacitor 1022; and a
sampling transistor 1023.
[0117] Though not illustrated, an auxiliary capacitance may be
provided to each pixel for improving the image quality of the
panel.
[0118] As a specific example of the functions of this circuit,
there will be explained the drive of an active matrix device
employing TN liquid crystal and provided with photodiodes, with
reference to a timing chart shown (A) to (H) in FIG. 16.
[0119] At first, image signals of a line are entered in succession
from the external signal input terminal 1009 (A) in FIG. 16). The
1st horizontal shift register 1007, driven by the pulses
synchronized with the image signals, turns on the switching TFT's
1006, thereby transferring the image signals of the pixels to the
buffer capacitors 1005. In this operation, in the image signal of
the buffer capacitor 1005 corresponding to the pixel having the
photoelectric converting element 1018, a bit signal, corresponding
to the reset signal of the photoelectric converting element, is
transferred from the reset signal input terminal 1021, by the
switching of the selecting transistor 1019. In the so-called
blanking period after the signal transfer of the last bit of a line
to the buffer capacitor 1005 and before the entry of the image
signals of the next line to the buffer capacitors 1005, the pixel
TFT's 1002 of a desired row are turned on (cf. (B) in FIG. 16). The
resetting TFT's 1016 are turned on, thereby resetting the
potentials of the 2nd buffer capacitors 1010 (cf. (C) in FIG. 16).
Subsequently the resetting TFT's 1016 are turned off, and the 2nd
transfer gates 1011 are turned on, thereby transferring the sensor
outputs of the photoelectric converting elements 1018, detecting
the reflected light from the eye of the observer, to the 2nd buffer
capacitors 1010 (cf. (D) in FIG. 16).
[0120] In these operations, if the photoelectric converting
elements are non-amplifying elements such as photodiodes, the
signal amplitude transferred to the 2nd buffer capacitor 1010 is
determined by the ratio of the capacitance of the photodiode
accumulating the signal charge and the buffer capacitance 1010,
becoming larger as the buffer capacitance 1010 is smaller in
comparison with the photodiode capacitance. Also the signal
amplitude at the sensor signal output terminal 1015 is determined
by the ratio of the buffer capacitance 1010 and the capacitance
attached to the signal line 1013, becoming larger as the buffer
capacitance increases in comparison with the capacitance associated
with the signal line 1013. Consequently, the buffer capacitance
1015 is preferably so determined as to maximize the signal
amplitude given at the sensor signal output terminal 1015. The
buffer capacitance 1010 may be provided by an independent capacitor
as illustrated, or may be composed of a parasite capacitance of the
wirings.
[0121] After the transfer of the sensor output signals, the 2nd
transfer gates 1011 are turned off, while the 1st transfer gates
1004 are turned on, thereby transferring the image signals,
transferred to the 1st buffer capacitors 1005, to the respective
pixels. At the same time a reset signal is supplied to the
photoelectric converting elements 1018, thereby resetting the
sensor potentials (cf. (E) in FIG. 16). These operations of sensor
output signal read-out, image signal transfer to the pixels and
resetting of the photoelectric converting elements, are executed
during the blanking period.
[0122] (F) in FIG. 16 shows an example of the variation in the
potential of the photoelectric converting element 1018 in the
above-explained operations. From the resetting operation in the
blanking period at a timing shown in (E) in FIG. 16 to the
turning-on of the switching TFT of the same pixel after a frame
period, the photoelectric converting element 1018 accumulates
carriers generated by light. When the pixel TFT 1002 and the 2nd
transfer gate 1011 are turned on at the timing shown in (D) in FIG.
16, the accumulated signal charge is transferred to the 2nd buffer
capacitor 1010, whereupon the potential of the photoelectric
converting element 1018 reaches a value determined by the
capacitance division ratio with the 2nd buffer capacitor 1010. Then
the photoelectric converting element 1018 is reset and start the
accumulation of the signal corresponding to the next frame.
[0123] Also (G) in FIG. 16 shows the variation in potential of a
display pixel in the liquid crystal display device. The image
signal voltages are transferred by every line at the timing shown
in (E) in FIG. 16, and are retained for a frame period. According
to these signal voltages, the transmittance of the liquid crystal
cells varies, thus displaying an image of desired density.
[0124] The application method of the image signals has been
proposed in various manners, such as frame-inverted drive,
1H-inverted drive, dot-inverted drive in order to prevent
deterioration of the liquid crystal by the DC current component,
but the present invention is not limited to any of such signal
application methods. The sensor out signals, transferred to the 2nd
buffer capacitors 1010 during the blanking period, are released to
the signal output terminal 1015 by the switching TFT's 1012 turned
on by the 2nd horizontal shift register 1014 within a horizontal
scanning period. Depending on the arrangement of the photoelectric
converting elements, the image signal retained in the adjacent
display element may also be read in the buffer capacitor 1016. In
such case, it is possible to obtain the sensor output signal only,
by sampling of the sampling capacitor 1022 in synchronization with
the timing of signal transfer from the photoelectric converting
element. Otherwise the sensor output signal alone may be taken out
by a switch turned on and off by the shift register 1014.
[0125] The operation of the shift register 1014 may be synchronized
or not with that of the shift register 1007. It is also possible to
synchronize the shift registers 1014 and 1007, and to drive them
with same clock signals. Also the sensor output signal read-out
unit 1010-1017 may be connected alone to the signal lines 1003
connected to the photoelectric converting elements 1018, or to all
the signal lines to read the sensor output signals and to extract
the sensor signals by the signal processing after the signal output
terminal 1015.
[0126] FIG. 17 is a schematic cross-sectional view of an image
display pixel and a photoelectric converting element employed in
the present embodiment, wherein shown are a transparent insulating
substrate 1201; a gate electrode 1202 of the switching TFT 1002,
connected to the horizontal line for driving this device; a source
area 1203 of the switching TFT 1002, connected to the vertical line
(signal line 1003); a channel area 1204 of the switching TFT; a
drain area 1205 of the switching TFT 1002; an interlayer insulation
film 1206; and an insulation layer 1210, partly functioning as a
gate insulation layer for electrical insulation between the gate
electrode 1202 and the semiconductor layers (1203, 1204, 1205). The
semiconductor layers 1203, 1204, 1205, 1208 constituting the TFT
and the photoelectric converting unit are preferably masked from
the light, in order that the light entering from the substrate side
does not reach these semiconductor layers.
[0127] In the image display pixel, the drain area 1205 is
connected, through a contact hole formed thereon, a transparent
pixel electrode 1207 composed for example of ITO (indium tin
oxide). In response to the signal applied to the transparent pixel
electrode 1207, the liquid crystal thereon varies in transmittance,
thereby displaying a desired image.
[0128] The light masking means should be provided at an optimum
position, in consideration of the incident direction of the light.
For example the masking means may be so positioned as to cover the
lateral walls of the semiconductor layers, for achieving further
effective light masking.
[0129] Also in the photoelectric converting element, the drain area
1205 contains therein a semiconductor area 1208 of the opposite
conductive type, which is connected, through a contact hole formed
thereon, to an electrode 1209.
[0130] At first, in the blanking period, a reset voltage is applied
in such a manner that the drain area 1205 of the photoelectric
converting element and the semiconductor area 1208 of the opposite
conductive type are inversely biased. Then the switching TFT 1002
is turned off to maintain the drain area in the electrically
floating state. A depletion layer is spread between the drain area
1205 and the semiconductor area 1208, and the photoexcited
electron-hole pair, once caught in the depletion layer, is
attracted by the electric field thereof, whereby either of the
electron and the positive hole is dissipated at the electrode 1209
while the other is accumulated in the capacitance of the depletion
layer to constitute the photo signal.
[0131] The structure of the photoelectric converting element is not
limited to that explained above, but can be, for example, that
utilizing a Schottky junction or employing a SiGe layer in one of
the semiconductor layer, or a structure having a highly reflective
film at the back of the device for improving the light utilizing
efficiency. Also the photoelectric converting element need not
necessarily be provided on a transparent substrate.
[0132] The structure and the driving method explained above:
[0133] (1) do not require the photoelectric converting elements,
constituting the sensor for the sight line detection, separately
from the image display device, thereby achieving compactization and
cost reduction of the system; and
[0134] (2) do not newly require the driving circuit for the sight
line detecting sensor or enable significant simplification thereof,
since the driving circuit for the image display device itself is
used also for that of the sight line detecting sensor.
[0135] Naturally the photoelectric converting elements can be
determined in number and in distribution within an extent not
influencing the image quality, but such number and arrangement
should be so determined to provide necessary and sufficient
information on the line of sight, as the sensor for sight line
detection.
[0136] Embodiment 5
[0137] FIG. 18 shows an example of another preferred circuit
structure of the image display device, wherein components same as
those in FIG. 15 are represented by same numbers and will not be
explained further.
[0138] In this embodiment, switching TFT's 1006 for accumulating
the external signal pulses shown in FIG. 15 into the 1st buffer
capacitors 1005 and switching TFT's 1012 for releasing the sensor
output signals, coming from the photoelectric converting elements
1018 and accumulated in the 2nd buffer capacitors 1010, in
successive manner to the output line 1013 are driven by a single
horizontal shift register 1007, with timings as shown (A) to (H) in
FIG. 16. Within a horizontal scanning period, there are executed
the read-out of the sensor output signals, photosignal accumulation
of the next frame and image signal transfer to the 1st buffer
capacitors 1005, and, within the blanking period, there are
executed to the transfer of the sensor output signals to the 2nd
buffer capacitors 1010, resetting of the photoelectric converting
elements 1018 and image signal transfer to the liquid crystal cells
1001.
[0139] Also in this embodiment, the read-out unit 1010-1017 of the
sensor output signals may be connected only to the signal lines
connected to the photoelectric converting elements 1018, or may be
connected to all the signal lines to read the sensor output signals
and to extract the sensor signals by the signal processing after
the sensor signal output terminal 1015.
[0140] The present embodiment enables, in addition to the
advantages of the embodiment 4, further reduction of the panel
size, simplification of the driving circuit and improvement in
process yield, since there is required only one horizontal shift
register.
[0141] Embodiment 6
[0142] FIG. 19 shows an example of still another preferred circuit
structure of the image display device, wherein components same as
those in FIG. 15 are represented by same numbers and will not be
explained further.
[0143] In this embodiment, the image signals are not collectively
transferred by every line, but are transferred in succession to the
pixels during the horizontal scanning period.
[0144] The functions of the present embodiment will be explained in
the following, with reference to a timing chart shown (A) to (G) in
FIG. 20, wherein a switching TFT connected to the n-th line is
represented by 1002, and that connected to the (n+1)th line is
represented by 11002'.
[0145] At first the image signals of a line are entered in
succession from the external signal input terminal (cf. (A) in FIG.
20). The image signals are transferred, in succession, to the
pixels of a line, by the switching TFT's 1006 and the switching
TFT's 1002 (cf. (B) in FIG. 20), respectively turned by the 1st
horizontal shift register 1007 and the vertical shift register
1008, driven by pulse signals synchronized with the frequency of
the image signals. In this operation, a resetting signal is given
to the pixels where the photoelectric converting elements are
provided. After the signal transfer to the pixel of the last bit of
a line, the switching TFT's 1002 are turned off (cf. (B) in FIG.
20). Then the resetting TFT's 1016 are turned on to reset the
potential in the buffer capacitors 1010 (cf. (C) in FIG. 20). Then
the resetting TFT's 1016 are turned off, while the switching TFT's
1002' and the 2nd transfer gates 1011 are turned on to transfer the
sensor output singals from the photoelectric converting elements
1018 to the buffer capacitors 1010 ((D) in FIG. 20). After the
sensor output signals are read and the transfer gates 1011 are
turned off, the image signals of a next frame are transferred
through the switching TFT's 1006 and 1002'.
[0146] (E) in FIG. 20 shows the variation in potential of the
photoelectric converting element 1018 in these operations. The
element accumulates the photogenerated carriers, from the resetting
thereof at a timing shown (A) in FIG. 20 to the turning-on of the
switching TFT's 1002 and 1011 of the same pixel after a frame
period. The accumulating time of the pixels may become different by
a horizontal scanning period at maximum within a line, but this
difference is uniquely determined by the number of pixels and the
drive timing, and can be compensated externally. The accumulated
carriers are transferred to the buffer capacitor 1010 at the timing
shown (D) in FIG. 20.
[0147] Also (F) in FIG. 20 shows the variation in potential of a
display pixel in the liquid crystal display device. After the
switching TFT 1002 is turned on, the image signals are transferred
in succession as shown (A) in FIG. 20 and retained for a frame
period. In response to the voltage of the image signal, the liquid
crystal cell varies the transmittance, thereby displaying a desired
image. The sensor output signals, transferred to the buffer
capacitors 1010, are released in succession to the signal output
terminal 1015, by means of the switching TFT's 1012 turned on by
the 2nd horizontal shift register 1014. The present embodiment
enables further reduction in panel size and simplification of the
driving circuit, in addition to the advantages of the embodiment
4.
[0148] It is also naturally possible to combine this embodiment
with the embodiment 5, thereby achieving the driving operation with
a single horizontal shift register.
[0149] Embodiment 7
[0150] FIG. 21 shows an example of still another preferred circuit
structure of the image display device, wherein components same as
those in FIG. 15 are represented by same numbers and will not be
explained further.
[0151] In this embodiment, the image signals are not collectively
transferred by every line, but are transferred in succession to the
pixels during the horizontal scanning period, and the output
signals of the photoelectric converting elements 1018 are not
collectively transferred by every line, but are read from the
pixels in successive manner during a horizontal scanning
period.
[0152] The detailed functions of the present embodiment will be
explained in the following, with reference to a timing chart shown
in (A) to (F) in FIG. 22.
[0153] At first, during the blanking period, the resetting TFT 1016
is turned on to reset the signal output line 1013 connected to the
signal output terminal 1015 (cf. (A) in FIG. 22). Then the
resetting TFT 1016 is turned off, and the switching TFT 1002 of a
line is turned on. Then, within a horizontal scanning period, the
horizontal shift registers 1014 and 1007 are alternately activated,
thereby alternately turning on and off the switching TFT's 1012,
1006 connected to the signal lines 1003. Also the 2nd horizontal
shift register 1014 turns on the switching TFT 1012 connected to a
signal line 1003, whereby the sensor output signals of the
photoelectric converting elements 1018 are released to the signal
output terminal 1015 (cf. (B) in FIG. 22). Then, after the
switching TFT 1012 is turned off, the horizontal shift register
1007 turns on the switching TFT 1006 connected to a signal line
1003, whereby the image signals from the external signal input
terminal 1009 are transferred to the pixels through the switching
TFT's 1006 and 1002. At the same time, as already explained in
relation to FIG. 15, a signal corresponding to the reset signal is
supplied to the pixels where the photoelectric converting elements
are provided (cf. (C) in FIG. 22). Subsequently the switching TFT's
1012, 1006 connected to the signal lines are turned on and off in
succession, thereby achieving the read-out of the sensor output
signals and the writing of the image signals.
[0154] In these operations, the variations in potential of the
photoelectric converting element and of the display pixel in the
liquid crystal display device are respectively shown (D) and (E) in
FIG. 22.
[0155] In comparison with the embodiment 6, the present embodiment
enables further reduction in panel size and further simplification
of the driving circuit.
[0156] Embodiment 8
[0157] FIG. 23 schematically shows another circuit structure of the
image display device. The driving operations of the present
embodiment are similar to those of the embodiment 7, and the on/off
signals for the switching TFT's 1012 for the sensor output read-out
and for the switching TFT's 1006 for the external image signal
transfer are generated by a shift register 1007, AND gates 1803,
and two control signals 1801, 1802.
[0158] In this configuration, a single shift register can attain
the second effect of the present invention. The above-explained
control in the present embodiment is achieved by the combination of
the AND logic gates and two control signals, but such combination
is not limitative and a similar function can naturally be attained
in other configurations.
[0159] Embodiment 9
[0160] This embodiment shows another example of the structure of
the image display pixel and the photoelectric converting element,
usable in the image display devices of the circuit structures shown
in the embodiments 5 to 8.
[0161] FIG. 24 is a schematic cross-sectional view of the device of
the present embodiment, wherein a transparent insulating substrate
1901 for supporting the device is fixed, by an adhesive layer 1902,
to a device substrate 1905. Through a contact hole formed in the
transparent insulating substrate 1201 under a drain area 1205,
there is formed a rear collecting electrode 1903, by which a
transparent pixel electrode 1207 is connected to the drain area
1205 of the TFT. A light masking layer 1904, for preventing the
light leaking to the TFT of the photoelectric converting unit, is
formed, in the present embodiment, simultaneously with the
formation of the rear collecting electrode 1903. It is preferably
so formed as to cover the entire semiconductor area generating the
photocarriers. The configuration of the present embodiment allows
flatter formation of the pixel electrodes 1207 thereby reducing
distortion in the orientation of the liquid crystal and improving
the displayed image quality, and also enables to mask the
photoelectric converting elements at the rear side, thereby
reducing the light leaking, for example from the rear light source
for liquid crystal display and enabling light detection with a high
S/N ratio.
[0162] It is naturally possible also, as shown in FIG. 25, to form
the semiconductor area 1208 of the opposite conductive type closer
to the substrate and to take out the electrode 1209 from the rear
side. Also in this case it is desirable to sufficiently mask the
entire TFT area from the light.
[0163] In the foregoing embodiments 4-9 there are employed
PN-photodiodes as the photoelectric converting means, but such
means is not limited to such example. For example, amplifying
photoelectric converting elements can reduce the gain loss at the
read-out of the sensor output signals, thereby enabling to effect
the detection of the line of sight of the observer with a higher
sensitivity.
[0164] The illumination for the detection of the line of sight is
usually conducted with the light outside the visible region,
principally the infrared light, so as to be unnoticeable to the
observer. For this reason, a visible-light cut-off filter is
provided in front of the photoelectric converting means in order to
reduce the stray light, but such filter can be dispensed with if
there is employed photoelectric conversion means principally
sensitive to the infrared light region, such as those utilizing the
Schottky junction (IEEE ED May 1991, p. 1094) or those based on
HgCdTe (IEEE ED May 1991, p. 1104).
[0165] In the foregoing embodiments, the photoelectric converting
elements are distributed within the image display area but they may
also be arranged around the image display area.
[0166] Embodiment 10
[0167] The present embodiment relates to a semiconductor
device.
[0168] FIG. 33 is a cross-sectional view of the semiconductor
device of the present embodiment. The method of preparation thereof
will be explained in the following with reference to FIGS. 34A to
34G.
[0169] This embodiment provides an example of the semiconductor
device integrating the light-emitting source usable for the
detection of the line of sight and the light-receiving device for
receiving the reflected light for example from a human eye.
[0170] The light source may also be used as the illumination means
for example for a display panel. Also the light source may also be
shaped in a desired form such as a character or a pattern, as a
display directly observable by the observer.
[0171] At first, on an N-Si (100) substrate 2101 of a resistivity
of 1 .OMEGA..cndot.cm, a field oxide film 2102 is formed with a
thickness of 1 .mu.m. Then a buffer oxide film 2103 is formed with
a thickness of 500 .ANG., and boron ions as P-type impurity are
implanted with said field oxide film 2102 as the mask, followed by
heat treatment, to form a P-diffusion layer 2104 of a depth of 1
.mu.m (cf. FIG. 34A).
[0172] Then arsine as N-type impurity is implanted, utilizing a
photoresist mask 2100, to form an N-diffusion layer 2105 of a depth
of 0.3 .mu.m in the above-mentioned P-diffusion layer 2104 (FIG.
34B). These two layers constitute a diode functioning as a
photodiode.
[0173] Then an aperture of about 4 .mu.m square is opened in a part
of the buffer oxide film 2103 on the other part of the P-diffusion
layer 2104, and Si is epitaxially grown for a thickness of 0.5
.mu.m. Silicon on the above-mentioned aperture becomes
monocrystalline silicon 2106 by the influence of the underlying
silicon, but that on the oxide film 2103 becomes polycrystalline
silicon 2107 (cf. FIG. 34C).
[0174] Subsequently the polysilicon 2107 is removed by etching
solution capable of selectively etching polysilicon, such as
potassium iodide, then a nitride film 2108 capable of withstanding
the anodizing is deposited with a thickness of 1500 .ANG., and an
aperture is formed on the monocrystalline silicon 2106 to be
subjected to anodizing. Then the monocrystalline silicon 2106 is
made porous, by anodizing with 35% alcoholic solution of HF and
with a current of about 25 mA/cm.sup.2 (cf. FIG. 34D).
[0175] Subsequently contact holes for the electrodes are opened to
expose Si surface. Also in a portion corresponding to the
light-emitting unit, a pillar 2109 is formed for example of
heat-resistant polyimide resin, in order to form a light masking
portion for preventing light leakage to the outside (cf. FIG.
34E).
[0176] Then a metal 2110 of good step coverage, such as aluminum,
is deposited, and a thick resist layer 2111, as a planarization
material is coated over the entire surface. Subsequently the resist
2111 is etched back until the aluminum 2110 alone of the
above-mentioned pillar becomes exposed (cf. FIG. 34F).
[0177] Finally the aluminum on top of the pillar 2109 is etched
off, then the planarizing resist 2111 is removed, and the pillar
2109 of polyimide resin is removed. Subsequently the Al electrodes
are patterned in the ordinary method to form a light-emitting
portion 2112 and a light-receiving portion 2113 (cf. FIG. 34G). In
this operation, it is necessary to pay attention to the coverage of
the light masking portion 2110a. If the light masking portion 2110a
cannot be well protected by the resist, it is also possible to
separate the light masking portion 2110a and the electrode 2110b in
different layers, and to separately form the light masking portion
2110a after the formation of the electrode 2110b.
[0178] Now reference is made to FIG. 33 for explaining the
functions of the light-emitting portion 2112 and the
light-receiving portion 2113, formed with porous silicon
simultaneously on the semiconductor substrate. A voltage of several
volts, applied between the light masking portion 2110a, serving
also as the electrode of the light-emitting portion 2112, and the
electrode 2110b of the P-diffusion layer 2104, induces a current
between both electrodes, whereby the light-emitting portion of the
porous layer emits light. The emitted light is guided without
diffusion, by the light masking portion 2110a, and is addressed to
an object 2114 through an unrepresented optical system. The light
directed into the Si substrate is rapidly absorbed by the Si
substrate itself or by the depletion layer between the inversely
biased Si substrate 2101 and the P-diffusion layer 2104, so that it
does not constitute stray light transmitted far within the Si
substrate.
[0179] The light scattered by the object 2114 passes a path 2115
and enters the photodiode of the light-receiving portion. Since the
light is sufficiently focused by the optical system, the adjacent
light-receiving portion receives only very little light.
[0180] Since the incident position of the light is uniquely
determined by the light-emitting portion, optical system, object
etc., there can be achieved the detection of the object position by
the scanning operation with the light-emitting portions, the
optical system or the light-receiving portions.
[0181] FIG. 35 illustrates a part of the driving circuit for the
semiconductor device of the present embodiment, wherein the
light-emitting portion 2112 and the light-receiving portion 2113,
consisting of a photodiode, are positioned optically symmetrical,
with respect to an unrepresented optical system. The light-emitting
portion 2112 emits light by the application of an ON voltage to
terminals .phi.V.sub.1 and .phi.H.sub.1.
[0182] Said photodiode 2113 induces a photocurrent only in the
presence of an object reflecting the emitted light, and the
photocurrent is amplified and supplied to an output terminal 2401.
In the present embodiment, the above-explained circuit is arranged
in an m.times.n matrix, with terminals .phi.V.sub.1- .phi.V.sub.m
and .phi.H.sub.1-.phi.H.sub.n, whereby the position of the object
can be two-dimensionally detected.
[0183] The light-receiving element to be employed in this
embodiment is not limited photodiode, but can also be other known
photosensors such as CCD or phototransistor.
[0184] The semiconductor device of the present invention,
integrating the light-emitting source and the light-receiving
element within a same chip as explained above, can simplify the
system and reduce the cost thereof, when employed as a sensor for
detecting the position or image of an object. Particularly, when it
is utilized as a contact sensor in which the object is positioned
close to the device, there can be constructed an optical equipment
not requiring the optical system involving lens etc., thereby
significantly reducing the number of component parts, also
drastically reduce to volume of the entire equipment and further
reducing the manufacturing cost.
[0185] Embodiment 11
[0186] In the present embodiment, the light-emitting portion is
composed of a polysilicon or monocrystalline silicon interface
instead of porous silicon in the embodiment 10.
[0187] FIG. 36 is a cross-sectional view of the light-emitting
portion of the present embodiment, containing N polysilicon 2501.
As in case of porous silicon in the embodiment 10, the unnecessary
portion of polysilicon is removed or oxidized. When a voltage is
applied between electrodes 2110a and 2110b, a current is induced
therebetween whereby the light is emitted at the interface between
the N.sup.+ polysilicon 2501 and the N-diffusion layer 2502
consisting of monocrystalline silicon. Similarly amorphous silicon
is usable as the light source.
[0188] Embodiment 12
[0189] This embodiment utilizes crystal defects in monocrystalline
silicon as the light-emitting portion, instead of porous silicon in
the embodiment 10.
[0190] FIG. 37 is a cross-sectional view of the light-emitting
portion in the present embodiment, including the above-mentioned
crystal defects 2601. The crystal defects in silicon can be formed,
for example by oxygen ion implantation in the course of process.
The N-diffusion layer 2602 for the electric isolation has to be
made deeper than the defects 2601, because the junction leak
increases if the crystal defects cross the P-N junction. In the
present embodiment, sufficient light emission can be obtained only
with a relatively high voltage. Consequently, for the purpose of
reducing the unnecessary electric power consumption, the sheet
resistance of the diffusion layer 2602 should preferably be
higher.
[0191] Because of such nature, the present embodiment is suitable
for combination with a device of high voltage and high output.
[0192] Embodiment 13
[0193] This embodiment is to arrange the lightemitting elements, as
shown in the embodiments 10 to 12, in an array and to modify the
driving method, thereby intensifying the output for positional
detection. More specifically, all the light sources contained in a
single cell are emit light at the same time, and the
light-receiving portions only effect the scanning operation.
[0194] This embodiment can intensity the detected signal, since the
amount of light entering the object increases drastically.
[0195] In FIG. 38, there are shown a substrate 2701, an x-y matrix
2702 of the light-receiving elements, and light-emitting portions
2703 arranged in uniform arrays. However the optical system has to
be separated in the light-emitting portion and the light-receiving
portion in order to condens the light onto the object. The present
embodiment is suitable for a system in which the object is dark or
low in reflectance and requires a large amount of light for
illumination.
[0196] Embodiment 14
[0197] This embodiment is to arrange the light-receiving elements,
as shown in the embodiment 10, in an array as shown in FIG. 39 and
to modify the driving method, thereby intensifying the output for
positional detection. In FIG. 39 there are shown a substrate 2801,
a one-dimensional matrix 2802 of the lightemitting elements, and a
uniform array 2803 of the light-receiving elements. Contrary to the
embodiment 13, the detection of position is executed by the
scanning operation of the light-emitting elements only. This
embodiment is suitable for a system in which the object causes
random scattering.
[0198] The arrangements of the light-emitting portion and the
light-receiving portion are not limited to those in this embodiment
or in the embodiment 13, but can be optimized according to the
system.
[0199] Besides, on-chip lenses may be provided, by the already
known technology, on the light-emitting portion or on the
light-receiving portion to further improve the efficiency of light
emission and reception, thereby elevating the sensitivity and S/N
ratio of the positional detection.
[0200] Also there can be easily conceived examples employing other
known silicon processes, so that various designing can be assured
according to the desired system.
[0201] Also the LED 2901 and the photoelectric converter 2905,
shown in FIG. 1, may be replaced by the semiconductor device shown
in the foregoing embodiments 10-14 to dispense with the half mirror
2904, whereby there can be provided with an optical equipment
excellent in space and cost.
[0202] In addition, further compactization and cost reduction can
be achieved in the optical equipment by incorporating the concept
of the semiconductor device of the embodiments 10-12 into the image
display device shown in the embodiments 4-9, namely by forming the
pixel portion for image display, the photoelectric converting
elements (light-receiving portion) and the light-emitting portion
within the image display device.
[0203] In such case, the light-emitting portion may continuously
emits light, or intermittently in synchronization with the timing
of the detection of the line of sight. The latter case, capable of
further reducing the electric power consumption, is preferable
particularly in the application to a small-sized optical equipment
such as a video camera, as the battery of a large capacity can be
dispensed with.
[0204] Such configuration is naturally preferable also in case of
utilizing the illuminating light source of the image display means
for the light source for the detection of the line of sight, since
the drive with the battery of a smaller capacity becomes
possible.
[0205] Furthermore, in case the porous silicon is used for the
light-emitting portion, the light of a desired wavelength can be
emitted by the control of the pore diameter and pore density of the
porous material. It is therefore rendered possible to display
various colors on a single semiconductor chip, thereby broadening
the colors and applications of the display.
[0206] As detailedly explained in the foregoing, the present
invention provides the following advantages:
[0207] (1) The rear light source associated with the image display
device is utilized also as the illuminating light source for the
detection of the line of sight, thereby adding the sight line
detecting function without the addition of a new illuminating light
source, also reducing the size and weight of the entire equipment,
and contributing to the realization of an inexpensive and compact
optical equipment, such as a video camera, with the sight line
detecting function. In addition, there can be achieved reduction in
the number of component parts, enabling further reduction in cost.
Furthermore, there is achieved reduction of the electric power
consumption and heat generation of the infrared light source,
thereby contributing to the designing of an equipment with
compactor size and reduced power consumption.
[0208] (2) The common use of the driving circuit for image display
and that for the photoelectric converting means avoids, in an image
display device having additional sight line detecting function, the
necessity for the addition of the independent photoelectric
converting means or the drive means therefor, thus enabling
compactization, simplification and cost reduction of the entire
equipment.
[0209] (3) The light-emitting unit and the light-receiving unit can
be integrated on a same silicon chip, so that, in case of use of
such chip as a sensor of various optical equipment for detecting
the image or position of an object, such system can be realized
extremely compactly and very inexpensively.
[0210] Particularly in case of use in a contact sensor in which the
object is positioned in the vicinity of the device, there can be
constructed an optical device not requiring the optical system
involving lens etc., thereby significantly reducing the number of
component parts and drastically reducing the volume of the entire
equipment.
[0211] Also its simplicity in the configuration, the
above-mentioned device can be adopted in various applications, such
as a contact sensor for the copying machine, an optical sensor for
various handy equipment, and an optical sensor for small-sized
equipment to be used in an attached state to the human body.
[0212] In these cases there can naturally be attained various
advantages mentioned in the foregoing embodiments.
* * * * *