Stereoscopic display

A left eye image is projected from a projector 1L, and a right eye image is projected from a projector 1R. The images projected from the projectors 1L and 1R pass through light transmitting portions 21 in light shading means 2a. Consequently, pairs of right and left eye images are formed on a dispersion panel 2b. The light shading means 2a is composed of a liquid crystal display panel, for example. The width of each of the light transmitting portions 21 is made so small that two or more pairs of right and left eye images can exist in each of predetermined regions of the dispersion panel 2b. Further, the position of each of the light shading portions 21 can be shifted in the transverse direction. Each of the pairs of right and left eye images formed on the dispersion panel 2b is introduced into the right and left eyes of a viewer upon being separated by a lens portion of a lenticular lens 2c. A sensor 10 detects the position of the viewer. A driving and control unit 12 changes the positions of the light transmitting portions 21 in the light shading means 2a on the basis of an output of the sensor 10.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a stereoscopic display capable of viewing 
a stereoscopic image without using special glasses. 
2. Description of the Prior Art 
As a method of realizing display of a stereoscopic image without requiring 
special glasses, a method of a double lenticular system using two liquid 
crystal display (LCD) projectors as well as using a double lenticular 
screen as a screen has been proposed. This system is a system of 
respectively displaying a left eye image and a right eye image from one 
LCD projector 1a and the other LCD projector 1b, and projecting the images 
on a double lenticular screen 200 arranged ahead of the projectors, as 
shown in FIG. 10. The double lenticular screen 200 is so constructed that 
lenticular screens 200a and 200c are arranged ahead of and behind a 
dispersion panel 200b on which the images are formed such that the 
dispersion panel 200b is interposed therebetween. 
The left eye image and the right eye image are respectively changed into 
vertically striped images 200bL and 200bR by the function of the 
lenticular screen 200a on the side of the LCD projectors 1a and 1b (on the 
incidence side), and are alternately formed on the dispersion panel 200b. 
The right eye striped image and the left eye striped image out of the 
vertically striped images formed on the dispersion panel 200b are 
introduced upon being respectively separated into the right eye (3R) and 
the left eye (3L) of a viewer 3 by the function of the lenticular screen 
200c arranged on the light emission side of the dispersion panel 200b (on 
the side of the viewer). The viewer who views the left and right eye 
striped images with his or her respective eyes can view a stereoscopic 
image without wearing special glasses by the function of binocular 
parallax. 
In this type of stereoscopic display, regions where a right eye image or a 
left eye image can be viewed alternately exist at the optimum viewing 
distance (D) from a screen 200, as shown in FIG. 11. In FIG. 11, a range 
indicated by an arrow R is a right eye image viewing region, and a region 
indicated by an arrow L is a left eye image viewing region. When the right 
eye 3R and the left eye 3L of the viewer 3 are respectively in the R 
region and the L region (a position indicated by A), a stereoscopic image 
can be viewed. On the other hand, in the reverse case (a position 
indicated by B), a stereoscopic image cannot be viewed due to reversed 
view. 
As a method of preventing a reversed view state created by the shift in the 
position of the head of the viewer, a method of detecting the position of 
the head of a viewer 3 by a sensor 100 for detecting the position of the 
head of the viewer 3, and replacing the right and left images displayed by 
the LCD projectors 1a and 1b (which are not illustrated in FIGS. 12 and 
13) when it is judged that the head of the viewer 3 is in a reversed 
viewing position, for example, has been conventionally known, as shown in 
FIGS. 12 and 13. That is, when the position of the viewer 3 is changed 
from a just image viewing position as shown in FIG. 12 to a reversed 
viewing position, the right and left eye images displayed are replaced 
with each other, as shown in FIG. 13. Consequently, an image viewing 
region R indicated by a rhombus is positioned in the position of the right 
eye of the viewer, and an image viewing region L indicated by a rhombus is 
positioned in the position of the left eye of the viewer. 
In the above-mentioned prior art, however, means for replacing the right 
and left images with each other is required. A large screen display is 
viewed by a plurality of viewers in many cases. In this case, when only 
one of the viewers moves, and the right and left images are replaced with 
each other by its head tracking, the other viewers in just image viewing 
positions cannot view a proper image. 
The present invention has been made in view of the above-mentioned 
circumstances, and has for its object to provide a stereoscopic display 
requiring no means for replacing right and left images with each other and 
capable of properly viewing, even when it is viewed by a lot of viewers, a 
stereoscopic image by each of the viewers. 
SUMMARY OF THE INVENTION 
A stereoscopic display according to the present invention is characterized 
by comprising a first projector for projecting a left eye image, a second 
projector for projecting a right eye image, a dispersion panel on which 
the images projected from the projectors are formed, light shading means 
having a plurality of light transmitting portions for transmitting image 
light beams from the projectors to form pairs of right and left eye images 
on the dispersion panel, and being so constructed that the width of each 
of the light transmitting portions is so small that two or more pairs of 
right and left eye images can exist in each of predetermined regions of 
the dispersion panel, and the position of each of the light transmitting 
portions can be shifted in the transverse direction, separating means 
comprising separating function portions respectively corresponding to the 
predetermined regions for introducing the pair of right and left eye 
images formed on the dispersion panel into the right and left eyes of a 
viewer upon separating the images in each of the separating function 
portions, a sensor for detecting the position of the viewer, and light 
transmitting portion controlling means for changing the positions of the 
light transmitting portions in the light shading means on the basis of an 
output of the sensor. 
Consequently, the position of the light transmitting portion in the light 
shading means is changed depending on the position of the viewer, the pair 
of right and left eye images formed on the dispersion panel is shifted in 
the predetermined region by the change in the position, and it is possible 
for the viewer which moved to properly view the stereoscopic image by the 
shift in positions where the images are formed (hereinafter referred to as 
image forming positions). 
The light shading means may be so constructed that two or more light 
transmitting portions can exist with respect to each of the predetermined 
regions of the dispersion panel in order that two or more pairs of right 
and left eye images exist in the predetermined region, and the light 
transmitting portion controlling means may be so constructed that the 
positions of the light transmitting portions are individually changed 
depending on the position of each of two or more viewers. Consequently, 
the stereoscopic image can be viewed by two or more viewers. Even when the 
stereoscopic image is thus viewed by two or more viewers, the positions of 
the light transmitting portions are individually changed depending on the 
position of each of the viewers, whereby the respective viewers can 
properly view the stereoscopic image. 
The light transmitting portion controlling means carries out such control 
that two or more light transmitting portions provided with respect to each 
of the predetermined regions of the dispersion panel are not adjacent to 
each other. Consequently, it is possible to prevent the opening widths of 
the light transmitting portions from being undesirably increased by 
causing the light transmitting portions to be adjacent to each other. 
Further, one or two or more viewers are detected by the sensor, so that 
the number of light transmitting portions in the light shading means which 
correspond to each of the predetermined regions may be set in conformity 
with the number of viewers. 
The foregoing and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
(Embodiment 1) 
Embodiments of the present invention will be described on the basis of the 
drawings. 
FIG. 1 is a schematic diagram showing the construction of a stereoscopic 
display according to the present embodiment. The stereoscopic display 
comprises a screen 2, a first projector 1L, a second projector 1R, a 
sensor 10 for detecting the position of the head of a viewer (the 
positions of the eyes of the viewer), and a driving and control unit 12 
for driving and controlling light shading means 2a in the screen 2 
depending on the detected value of the sensor 10. 
The first projector 1L projects a left eye image, and the second projector 
1R projects a right eye image. A liquid crystal display (LCD) projector, 
for example, is used as the projectors 1L and 1R. 
The screen 2 comprises a dispersion panel 2b serving as an image display 
surface, light shading means 2a arranged on the incidence side of the 
dispersion panel 2b, and a lenticular lens 2c which is separating means 
arranged on the emission side of the dispersion panel 2b. The light 
shading means 2a has light transmitting portions 21 for forming the right 
and left eye images projected from the respective projectors 1L and 1R in 
a vertical stripe shape on the dispersion panel 2b. In the present 
embodiment, the light shading means 2a is composed of a TN-type (Twisted 
Nematic) LC panel. The type of the LC panel is not limited to the TN type. 
An LC panel of the other type may be used. Further, a dispersion type LC 
panel can be also used. The lenticular lens 2c introduces the vertically 
striped images formed on the dispersion panel 2b into the right and left 
eyes of the viewer upon separating the images. 
The width of the light transmitting portion 21 is so set that two or more 
pairs of right and left eye images can be formed in an image forming 
region (a predetermined region) on the dispersion panel 2b corresponding 
to one lens portion (a separating function portion) in the lenticular lens 
2c. In the embodiment, in the image forming region (reference numerals 31 
to 40 are assigned to respective positions obtained by subdividing the 
region) on the dispersion panel 2b corresponding to one lens portion, 
striped images are respectively formed, so that a maximum of five pairs of 
right and left eye images can be simultaneously formed. Consequently, 10 
(n=10) portions to be the light transmitting portions 21 are provided with 
respect to one lens portion in the lenticular lens 2c. The details thereof 
will be described later. The magnification of each of the lens portions is 
increased, as compared with that in a case where one pair of right and 
left eye images is formed. 
The light shading means 2a composed of the LC panel is driven and 
controlled by the above-mentioned driving and control unit 12. The LC 
panel composing the light shading means 2a comprises a liquid crystal 
layer 201, a pair of transparent glass plates 202 and 203 provided with 
the liquid crystal layer 201 interposed therebetween, a stripe pattern 
portion 204 composed of ITO (indium tin oxide) provided on a surface, on 
the side of the liquid crystal layer, of the transparent glass plate 202 
and constituting one transparent electrode, a solid pattern portion 205 
composed of ITO provided on a surface, on the side of the liquid crystal 
layer, of the transparent glass plate 203 and constituting the other 
transparent electrode, and polarizing plates 206 and 207 respectively 
provided on surfaces, on the opposite side of the liquid crystal layer, of 
the transparent glass plates, as shown in a cross-sectional view of FIG. 
2A. The stripe pattern portion 204 is so adapted that a lot of vertically 
striped ITO films are arranged at a predetermined pitch, and the width of 
a stripe of the ITO films corresponds to the width of (the pitch between) 
the light transmitting portions 21. 
FIG. 2B is a diagram showing a system for driving the LC panel composing 
the light shading means 2a. The driving and control unit 12 comprises a 
control unit 12a composed of a microcomputer and liquid crystal driving 
circuits 12b. The control unit 12a feeds signals to the liquid crystal 
driving circuits 12b depending on the position of the viewer 3 on the 
basis of an output of the sensor 10. Each of the liquid crystal driving 
circuits 12b forms a light transmitting state or a light shading state in 
a liquid crystal layer portion corresponding to arbitrary vertically 
striped ITO films in the stripe pattern portion 204 by applying (or not 
applying) a voltage to the vertically striped ITO films depending on the 
signal, to change the positions of the light transmitting portions 21. The 
one liquid crystal driving circuit 12b takes charge of the driving of the 
10 (n=10) vertically striped ITO films. The 10 vertically striped ITO 
films correspond to the one lens portion. The respective images from the 
projectors 1L and 1R can be formed in the positions (31 to 40) on the 
dispersion panel 2b corresponding to the one lens portion, as shown in 
FIG. 1, by turning the 10 vertically striped ITO films on and off. 
FIG. 3 is a diagram in which the dimensions and the like of respective 
portions of elements constituting the stereoscopic display according to 
the present embodiment are given. In FIG. 3, the following are defined: 
A: the distance between a light emitting point of the first projector 1L 
and a light emitting point of the second projector 1R 
G: the distance between each of the projectors 1L and 1R and the light 
shading means 2a 
g: the distance between the light shading means 2a and the dispersion panel 
2b 
k: the pitch between vertically striped images on the dispersion panel 2b 
E: the distance between the eyes of the viewer 3 
d: the distance between the dispersion panel 2b and the lens center of the 
lenticular lens 2c 
D: the distance between the lens center of the lenticular lens 2c and the 
viewer 3 
p: the pitch between the lens portions (the separating function portions) 
in the lenticular lens 2c 
b: the unit quantity of movement of the light transmitting portion 21 in 
the light shading means 2a 
In the stereoscopic display of such construction, the following conditions 
are satisfied: 
______________________________________ 
g:k = G:A . . . first equation 
k:(G + g) = b:G . . . second equation 
E:D = k:d . . . third equation 
p:D = nk:(D + d) . . . fourth equation 
where n = 10 
nk:(G + g) = nb:G . . . fifth equation 
1/d + 1/D = 1/f . . . sixth equation 
______________________________________ 
The following seventh to eleventh equations are derived from the foregoing 
equations: 
______________________________________ 
k = gA/G . . . seventh equation 
b = gA/(g + G) . . . eighth equation 
A = EdG/Dg . . . ninth equation 
p = nkD/(d + D) . . . tenth equation 
where n = 10 
f = kD/(k + E) . . . eleventh equation 
______________________________________ 
Description is now made of operations performed by the above-mentioned 
stereoscopic display. In the stereoscopic display shown in FIG. 1, the 
width of (that is, the pitch b between) the light transmitting portions 21 
is so set that a maximum of five pairs of right and left eye images can be 
simultaneously formed in an image forming region on the dispersion panel 
2b which corresponds to the one lens portion in the lenticular lens 2c. 
When five pairs of right and left eye images are formed, therefore, a 
maximum of five viewers 3 can view a stereoscopic image by respectively 
positioning their right and left eyes in predetermined positions (51, 52), 
(53, 54), (55, 56), (57, 58), and (59, 60). 
In the state shown in FIG. 1, it is assumed that the number of light 
transmitting portions 21 in the light shading means 2a which correspond to 
one lens portion is two. One of the light transmitting portions 21a is 
formed in correspondence to the positions 33 and 34 on the dispersion 
panel 2b, while the other light transmitting portion 21b is formed in 
correspondence to the positions 37 and 38 on the dispersion panel 2b. 
Therefore, two viewers, that is, a viewer whose eyes are positioned in 57 
and 58 and a viewer whose eyes are positioned in 53 and 54 recognize a 
stereoscopic image. 
Suppose only the viewer 3 whose eyes are positioned in 57 and 58 moves 
rightward in FIG. 1, so that both the eyes are positioned in 58 and 59, as 
shown in FIG. 4. Consequently, the sensor 10 detects the movement of the 
viewer 3, and the driving and control unit 12 changes only the light 
transmitting portion 21a (see FIG. 1) leftward by the width of one stripe, 
that is, one pitch b depending on the position of the viewer 3 on the 
basis of an output of the sensor 10. 
Description is made of the change in the position of the light transmitting 
portion 21a using FIG. 2. A liquid crystal layer portion on the ITO films 
corresponding to the light transmitting portion 21a out of the 10 ITO 
films shall be brought into a light shading state (this state is 
represented by crosshatching in FIG. 4), and a liquid crystal layer 
portion on the adjacent ITO film on the left side shall be brought into a 
light transmitting state. 
Since the position of the light transmitting portion 21 in the light 
shading means 2a is thus changed depending on the position of the viewer 
3, image forming positions (33, 34) of the pair of right and left eye 
images on the dispersion panel 2b are changed into the positions (32, 33) 
by the change, and it is possible for the viewer 3 which moved to properly 
view a stereoscopic image by the change in the image forming positions. 
Even when the stereoscopic display is viewed by a lot of viewers, the 
positions of the two light transmitting portions 21a and 21b are 
individually changed depending on the position of each of the viewers 3, 
as described above, so that the respective viewers can properly view a 
stereoscopic image. 
When the plurality of light transmitting portions 21 are adjacent to each 
other, a right eye image and a left eye image are simultaneously projected 
on the same position on the dispersion panel 2b, whereby the right and 
left images cannot be separated from each other with respect to the 
viewer. In the present embodiment, therefore, such control is carried out 
that the plurality of light transmitting portions 21 are not adjacent to 
each other in the driving and control unit 12. 
In the state shown in FIG. 1, in the case of only the viewer 3 whose eyes 
are positioned in 57 and 58, if the light transmitting portion 21b whose 
need is eliminated remains opened, right and left images are overlapped 
with each other when the one viewer positions his or her eyes in portions 
near 58 and 59, whereby the right and left images cannot be separated from 
each other with respect to the viewer. Therefore, the above-mentioned 
problem can be avoided by detecting each of the viewers by the sensor 10, 
setting the number of light transmitting portions 21 in the light shading 
means 2a which correspond to the one lens portion in the lenticular lens 
2c in conformity with the number of viewers, that is, bringing the light 
transmitting portion 21b whose need is eliminated into a light shading 
state. 
(Embodiment 2) 
Description is now made of another embodiment of the present invention on 
the basis of drawings. 
FIG. 5 is a schematic diagram showing the construction of a stereoscopic 
display according to the present embodiment. The difference from the 
embodiment 1 is that a parallax barrier 2c' is used as separating means. 
In the parallax barrier 2c', one slit constitutes one separating function 
portion. 
FIG. 6 is a diagram in which in the stereoscopic display according to the 
second embodiment, the dimensions and the like of respective portions of 
elements constituting the stereoscopic display are given, which are 
defined as follows: 
d: the distance between a dispersion panel 2b and the center of the 
parallax barrier 2c' which is the separating means 
p: the pitch between the slits (the separating function portions) in the 
parallax barrier 2c' 
h: the maximum value of the width of the slit in the parallax barrier 2c' 
D: the distance between the parallax barrier 2c' and a viewer 3 
Also in this construction, the first equation to the fifth equation shown 
in the embodiment 1 are satisfied. Further, the following relationship 
expressed by a twelfth equation is also satisfied: 
EQU D:h=(D+d):k twelfth equation 
The following thirteenth equation is derived by the foregoing twelfth 
equation: 
EQU h=kD/(D+d) thirteenth 
equation 
In the above-mentioned construction, when the viewer 3 moves rightward, 
from the position shown in FIG. 5 to the position shown in FIG. 7, so that 
his or her eyes are positioned in 58 and 59, a sensor 10 detects the 
movement of the viewer 3, and a driving and control unit 12 changes the 
light transmitting portion 21a leftward by the width of one stripe 
depending on the position of the viewer 3 on the basis of an output of the 
sensor 10. Image forming positions (33, 34) of right and left eye striped 
images on the dispersion panel 2b are changed into positions (32, 33) by 
the change in the position of the light transmitting portion 21a, and it 
is possible for the viewer 3 which moved to properly view a stereoscopic 
image by the change in the image forming positions. Even when the 
stereoscopic display is viewed by a lot of viewers 3, the positions of the 
two light transmitting portions 21a and 21b are individually changed 
depending on the position of each of the viewers 3, whereby the respective 
viewers can properly view a stereoscopic image. 
It is desirable that image information corresponding to not more than one 
pixel are respectively supplied from the two projectors to one separating 
function portion in the lenticular lens 2c or the parallax barrier 2c'. 
The reason for this is that when the image information corresponding to 
more than one pixels are supplied, pixels which cannot be seen depending 
on the viewing position are produced, resulting in reduced resolution. 
FIG. 8 illustrates a case where image information corresponding to two 
pixels (a pixel I and a pixel II) is supplied to one separating function 
portion in the lenticular lens 2c which is separating means, and FIG. 9 
illustrates a case where image information corresponding to not more than 
one pixel (a pixel I) is supplied to one separating function portion in 
the lenticular lens 2c. As can be seen from FIGS. 8 and 9, when the viewer 
moves to be positioned in X in FIG. 8, the pixel II is not seen, whereby 
the resolution is reduced. On the other hand, even if the viewer positions 
his or her eyes in any of 10 positions in FIG. 9, there is no possibility 
that the pixel I is not seen, whereby the resolution is prevented from 
being reduced. 
As described in the foregoing, according to the present invention, the 
position of the light transmitting portion in the light shading means is 
changed depending on the position of the viewer, and the stereoscopic 
image can be properly viewed by the viewer which moved. Even when a lot of 
viewers view the stereoscopic display, the positions of the light 
transmitting portions are individually changed depending on each of the 
positions of the viewers. Therefore, several effects are produced. For 
example, the respective viewers can properly view the stereoscopic image. 
Although the present invention has been described and illustrated in 
detail, it is clearly understood that the same is by way of illustration 
and example only and is not to be taken by way of limitation, the spirit 
and scope of the present invention being limited only by the terms of the 
appended claims.