Stereoscopic image display method, and stereoscopic image display apparatus using the method

A stereoscopic display apparatus and method performs and includes, respectively, steps of dividing each of a plurality of parallax images supplied from a parallax image source having parallax image information into stripe pixels, displaying, on a display, a single stripe image by arranging and synthesizing some of the stripe pixels in a predetermined order, displaying a slit pattern consisting of a light-transmission portion and a light-shielding portion arranged at a predetermined pitch on a spatial light modulation element arranged at a predetermined position on the front or rear side of the display, inputting light transmitted through the stripe pixels, corresponding to the right and left eyes of an observer, of the stripe image to the right and left eyes of the observer via the spatial light modulation element and synchronously displaying the stripe pattern and the slit pattern in units of pixels or scan lines on corresponding scan lines of the display and the spatial light modulation element.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a stereoscopic image display method and a 
stereoscopic image display apparatus using the same and, more 
particularly, to a stereoscopic image display method using a spatial light 
modulation element as a parallax barrier or a slit pattern for controlling 
the directivity of light coming from backlight, and a stereoscopic image 
display apparatus using the method. 
2. Related Background Art 
The technique of a stereoscopic image display method using a parallax 
barrier method is disclosed by S. H. Kaplan ("Theory of Parallax 
Barriers", J.SMPTE, Vol. 59, No. 7, pp. 11-21, 1952). In this method, each 
of a plurality of parallax images is divided into stripe pixels, the 
stripe pixels constituting the right and left parallax images are 
alternately arranged on a single screen to form and display a stripe 
image, and the corresponding parallax images are observed by the right and 
left eyes of an observer via a slit (called a parallax barrier) which is 
arranged at a position separated by a predetermined distance from the 
stripe image and has predetermined light-transmission portions, thereby 
obtaining a stereoscopic view. 
However, such conventional apparatus cannot be used as a two-dimensional 
image display apparatus such as a normal television apparatus. 
In view of this problem, Japanese Patent Application Laid-Open Nos. 
3-119889 and 5-122733 disclose a stereoscopic image display apparatus, 
which electronically forms a parallax barrier using, e.g., a transmission 
type liquid crystal element, and electronically controls to change the 
shape and positions of barrier stripes. 
FIG. 34 is a schematic diagram of a stereoscopic image display apparatus 
disclosed in Japanese Patent Application Laid-Open No. 3-119889. In this 
apparatus, an electronic parallax barrier 103 comprising a transmission 
type liquid crystal display element is arranged on an image display 
surface (panoramagram or stereogram) 101 via a transparent glass/acrylic 
spacer 102 having a thickness d. A plurality of parallax images obtained 
by picking up an image from two or more directions are displayed on the 
image display surface 101 as a stripe image obtained by dividing each of 
the parallax images into vertical stripe pixels, and alternately arranging 
the stripe pixels of the plurality of parallax images in a predetermined 
order. On the other hand, vertically elongated barrier stripes are formed 
at arbitrary positions on the display surface of the electronic parallax 
barrier 103 by designating the X and Y addresses of the parallax barrier 
103 using a control means such as a microcomputer 104, thus allowing a 
stereoscopic view according to the principle of the parallax barrier 
method. 
In order to display a two-dimensional image (non-stereoscopic image) on 
this apparatus, the entire image display region of the electronic parallax 
barrier 103 is set in a transparent state without forming any barrier 
stripes thereon. In this manner, both stereoscopic and two-dimensional 
images can be displayed unlike in the stereoscopic image display method 
using the conventional parallax barrier method. 
FIG. 35 is a schematic sectional view showing principal part of a 
stereoscopic image display apparatus constituted by a liquid crystal 
display panel and an electronic barrier disclosed in Japanese Patent 
Application Laid-Open No. 5-122733. In this stereoscopic image display 
apparatus, two liquid crystal layers (TN) 115 and 125 are respectively 
sandwiched between two pairs of polarizing plates 111 and 118, and 121 and 
128, so that the liquid crystal layer 115 serves as an image display 
means, and the liquid crystal layer 125 serves as an electronic barrier 
forming means. Note that the apparatus shown in FIG. 35 also comprises a 
glass (spacer) 102, upper glass substrates 112 and 122, lower glass 
substrates 117 and 127, common electrodes 113 and 123, spacers 114 and 
124, and pixel electrodes 116 and 126. In this apparatus as well, in order 
to display a two-dimensional image (non-stereoscopic image), the entire 
image display region of the electronic parallax barrier 125 is set in a 
transparent state without forming any barrier stripes thereon. In this 
manner, both stereoscopic and two-dimensional images can be displayed. 
In the prior art disclosed in Japanese Patent Application Laid-Open No. 
3-119889, the image display surface 101 displays a single stripe image 
obtained by dividing at least two parallax images into stripe pixels and 
alternately arranging the stripe pixels of these two parallax images. 
Therefore, the stereoscopic resolution of the image display apparatus is 
reduced to at least 1/2 that of original parallax images. 
Furthermore, in the above-mentioned prior art, since the stripe image 
constituted by the vertical stripe pixels displayed on the image display 
surface 101 is not synchronized with the parallax barrier pattern formed 
on the electronic parallax barrier 103, crosstalk between the right and 
left images is generated, and flicker noise is often generated, resulting 
in an eyesore. 
On the other hand, since the display positions of the barrier stripes 
remain the same unless the view point position of the observer moves, the 
luminance decreases in a localized stripe pattern. 
Furthermore, when the image display means comprises, e.g., a liquid 
crystal, the image display surface has a stripe-shaped pixel structure, 
and such image must be observed via similar barrier stripes, thus easily 
causing Moire fringes. 
Furthermore, in the prior art disclosed in Japanese Patent Application 
Laid-Open No. 5-122733, since the apparatus uses a total of four 
polarizing plates, the luminance lowers due to absorption by these plates. 
In addition, in these prior arts, when the observer horizontally moves by 
only the interval between his or her eyes (inter-ocular distance), a 
pseudoscopic view is prevented by replacing the display positions of the 
right and left eye images of the stripe image. However, the apparatus 
cannot cope with a change in view point position in the back-and-forth 
direction with respect to the apparatus. 
Furthermore, in order to prevent the pseudoscopic view, a change in view 
point position of the observer is followed so that normal parallax images 
are always incident on the eyes, and the observed stereoscopic image 
always remains the same. Thus, a "roundabout or wraparound stereoscopic 
view effect" that can obtain smooth stereoscopic feeling cannot be 
obtained. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a stereoscopic image 
display method and a stereoscopic image display apparatus using the 
method, which can reduce crosstalk between the right and left parallax 
images and can eliminate flicker noise and Moire fringes by synchronizing 
an image displayed on a display and a slit pattern displayed on a spatial 
light modulation element in units of corresponding pixels or corresponding 
scan lines using the parallax barrier method. 
It is another object of the present invention to provide a stereoscopic 
image display method and a stereoscopic image display apparatus using the 
method, which can obtain at least one of the following effects: 
(1-1) since the switching operation between the first and second stripe 
images and the switching operation between the first and second parallax 
barrier patterns are performed in synchronism with corresponding pixels or 
scan lines to display such images and patterns at high speed, crosstalk 
can be minimized, and the respective parallax images can be recognized on 
the entire display surface of a display at high resolution without any 
omission; 
(1-2) since the conventional apparatus uses four polarizing plates, the 
luminance lowers due to absorption by these polarizing plates, while since 
the number of polarizing plates can be reduced by one in the present 
invention, the display luminance can be improved; 
(1-3) since the width of stripe pixels to be displayed on the display, the 
width of light-transmission and light-shielding portions to be formed on 
the spatial light modulation element, the interval between the display and 
the spatial light modulation element, or the relative positional 
relationship between the stripe images and the light-transmission portions 
is controlled in accordance with a signal from an observation condition 
detection means for automatically detecting the view point position of the 
observer or an observation condition inputting means input by the 
observer, a satisfactory stereoscopic view can always be attained even 
when the observer moves; 
(1-4) since two out of three or more original parallax images constituting 
parallax image information of a parallax image source are selected and 
used, two parallax images are generated based on data constituting the 
parallax image information, or two parallax images are generated by 
interpolation or re-construction based on at least two original parallax 
images constituting the parallax image information, in accordance with a 
signal from the observation condition detection means for automatically 
detecting the view point position of the observer or the observation 
condition inputting means input by the observer, when the observer moves, 
parallax images with different view point positions are appropriately 
generated accordingly, and a stereoscopic image that can give a so-called 
smooth "roundabout effect" can be displayed; 
(1-5) a high-resolution stereoscopic image free from any crosstalk can be 
locally displayed in a two-dimensional image displayed on the display; 
(1-6) since an interlace driving operation is adopted, even when the 
display or the spatial light modulation element comprises, e.g., a liquid 
crystal element having a relatively low response speed, a high-definition 
stereoscopic image free from any flicker can be displayed; 
(1-7) since the display and the spatial light modulation element are 
designed to display an image by scanning scan lines in the vertical 
direction, driving circuits for their display screens can have a simple 
arrangement; 
(1-8) since the display surfaces of the display and the spatial light 
modulation element are divided into a plurality of areas having the same 
size along the scan lines, and the scan lines at the same relative 
positions are simultaneously selected from the plurality of areas so as to 
be synchronously driven, a display operation for one frame can be 
performed within a shorter period of time, and a stereoscopic image from 
which flicker noise is further eliminated can be displayed; 
(1-9) when the stripe image and the slit pattern are synchronously 
displayed on the display and the spatial light modulation element in units 
of pixels or scan lines, since a plurality of pixels preceding to the 
pixel to be synchronously displayed on the spatial light modulation 
element or a plurality of scan lines preceding to the scan line to be 
synchronously displayed are displayed precedently as light-shielding 
portions, crosstalk between the right and left parallax images can be 
further eliminated, and even when liquid crystal panels with different 
characteristics are used, crosstalk can be eliminated, thus assuring large 
driving margins of the respective panels; and 
(1-10) since a linear Fresnel lens is used, the display and the spatial 
light modulation elements can be constituted by liquid crystal elements 
having the same specifications, and a low-cost stereoscopic image display 
apparatus can be attained. 
In order to achieve the above objects, according to one aspect of the 
present invention, there is provided a stereoscopic image display method 
comprising the steps of: 
dividing each of a plurality of parallax images supplied from a parallax 
image source having parallax image information into stripe pixels; 
displaying, on a display, a single stripe image by arranging and 
synthesizing some of the stripe pixels in a predetermined order; 
displaying a slit pattern consisting of a light-transmission portion and a 
light-shielding portion arranged at a predetermined pitch on a spatial 
light modulation element arranged at a predetermined position on the front 
or rear side of the display; 
inputting light transmitted through the stripe pixels, corresponding to the 
right and left eyes of an observer, of the stripe image to the right and 
left eyes of the observer via the spatial light modulation element; and 
synchronously displaying the stripe pattern and the slit pattern in units 
of pixels or scan lines on corresponding scan lines of the display and the 
spatial light modulation element. 
The method further comprises the step of interlace-scanning the 
corresponding scan lines of the display and the spatial light modulation 
element. 
The method further comprises the step of scanning the corresponding scan 
lines of the display and the spatial light modulation element in a 
vertical direction. 
The plurality of parallax images are right and left parallax images, the 
stripe image is one of a first stripe image obtained by alternately 
arranging and synthesizing odd stripe pixels of the stripe pixels obtained 
by dividing the right parallax image and even stripe pixels of the stripe 
pixels obtained by dividing the left parallax image, and a second stripe 
image obtained by alternately arranging and synthesizing even stripe 
pixels of the stripe pixels obtained by dividing the right parallax image 
and odd stripe pixels of the stripe pixels obtained by dividing the left 
parallax image, one of the two stripe images is displayed on the display, 
the other stripe image is subsequently displayed, and the slit pattern in 
which the positions of the light-transmission portion and the 
light-shielding portion replace each other is displayed on the spatial 
light modulation element. 
The stripe image is displayed on a portion of a display surface of the 
display, a non-stripe image is displayed on the remaining portion of the 
display surface, the slit pattern is displayed on a portion, corresponding 
to the stripe image displayed on the display, of a display surface of the 
spatial light modulation element, and the remaining portion of the display 
surface of the spatial light modulation element is set in a 
light-transmission state. 
The stripe image is displayed on a portion of a display surface of the 
display, a non-stripe image is displayed on the remaining portion of the 
display surface, and the slit pattern is displayed on the entire display 
surface of the spatial light modulation element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display and/or the display width of each of 
the light-transmission portion and the light-shielding portion of the slit 
pattern to be displayed on the spatial light modulation element are/is set 
to be equal to the total width of a plurality of pixels constituting 
display surfaces of the display and the spatial light modulation element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display is set to be equal to the width of 
one pixel constituting a display surface of the display, and the display 
width of each of the light-transmission portion and the light-shielding 
portion of the slit pattern to be displayed on the spatial light 
modulation element is set to be equal to the total width of a plurality of 
pixels constituting a display surface of the spatial light modulation 
element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display is set to be equal to the total width 
of a plurality of pixels constituting a display surface of the display, 
and the display width of each of the light-transmission portion and the 
light-shielding portion of the slit pattern to be displayed on the spatial 
light modulation element is set to be equal to the width of one pixel 
constituting a display surface of the spatial light modulation element. 
Each of display surfaces of the display and the spatial light modulation 
element has pixels in a matrix structure. 
The method further comprises the step of outputting predetermined polarized 
light from the display. 
The spatial light modulation element comprises a liquid crystal element. 
The method further comprises the step of controlling at least one of 
constituting elements of the stripe image and constituting elements of the 
slit pattern in accordance with a signal from one of observation condition 
detecting means for automatically detecting a view point position of the 
observer and observation condition inputting means used by the operator to 
input an observation condition. 
The method further comprises the step of controlling a distance between the 
display and the spatial light modulation element on the basis of a signal 
from one of observation condition detecting means for automatically 
detecting a view point position of the observer and observation condition 
inputting means used by the operator to input an observation condition. 
The method further comprises the step of selecting and using the parallax 
images from at least three original parallax images constituting the 
parallax image information on the basis of a signal from one of 
observation condition detecting means for automatically detecting a view 
point position of the observer and observation condition inputting means 
used by the operator to input an observation condition. 
The method further comprises the step of generating the parallax images on 
the basis of data constituting the parallax image information or 
generating the parallax images on the basis of at least two original 
parallax images constituting the parallax image information by 
interpolation or re-construction in correspondence with a view point 
position of the observer, in accordance with a signal from one of 
observation condition detecting means for automatically detecting the view 
point position of the observer and observation condition inputting means 
used by the operator to input an observation condition. 
The method further comprises the step of precedently displaying, as the 
light-shielding portion, a plurality of pixels preceding to a pixel to be 
synchronously displayed or a plurality of scan lines preceding to a scan 
line to be synchronously displayed on the spatial light modulation element 
when the stripe image and the slit pattern are synchronously displayed on 
the display and the spatial light modulation element in units of pixels or 
scan lines. 
The method further comprises the step of dividing each of display surfaces 
of the display and the spatial light modulation element into a plurality 
of regions having the same size along a scan line, simultaneously 
selecting and scanning scan lines at the same relative positions of the 
plurality of regions, and synchronously displaying the stripe image and 
the slit pattern on the display and the spatial light modulation element 
in units of pixels on the plurality of scan lines or in units of 
corresponding scan lines of the plurality of scan lines. 
According to one aspect of the present invention, there is provided a 
stereoscopic image display apparatus comprising: 
a display for displaying a single stripe image obtained by arranging and 
synthesizing some of a plurality of stripe pixels which are obtained by 
dividing each of a plurality of parallax images supplied from a parallax 
image source having parallax image information; 
a spatial light modulation element arranged at a predetermined position on 
a front or rear side of the display, the spatial light modulation element 
displaying a slit pattern consisting of a light-transmission portion and a 
light-shielding portion arranged at a predetermined pitch, and light 
transmitted through the stripe pixels, corresponding to right and left 
eyes of an observer, of the stripe image being input to the right and left 
eyes of the observer via the spatial light modulation element so as to 
attain a stereoscopic view; and 
means for synchronously displaying the stripe image and the slit pattern on 
corresponding scan lines of the display and the spatial light modulation 
element in units of pixels or scan lines. 
The corresponding scan lines of the display and the spatial light 
modulation element are interlace-scanned. 
The corresponding scan lines of the display and the spatial light 
modulation element are scanned in a vertical direction. 
The plurality of parallax images are right and left parallax images, the 
stripe image is one of a first stripe image obtained by alternately 
arranging and synthesizing odd stripe pixels of the stripe pixels obtained 
by dividing the right parallax image and even stripe pixels of the stripe 
pixels obtained by dividing the left parallax image, and a second stripe 
image obtained by alternately arranging and synthesizing even stripe 
pixels of the stripe pixels obtained by dividing the right parallax image 
and odd stripe pixels of the stripe pixels obtained by dividing the left 
parallax image, the slit pattern to be displayed upon display of the first 
stripe image and the slit pattern to be displayed upon display of the 
second stripe image have opposite positional relationships of the 
light-transmission portion and the light-shielding portion, and the two 
stripe images are successively displayed. 
The stripe image is displayed on a portion of a display surface of the 
display, a non-stripe image is displayed on the remaining portion of the 
display surface, the slit pattern is displayed on a portion, corresponding 
to the stripe image displayed on the display, of a display surface of the 
spatial light modulation element, and the remaining portion of the display 
surface of the spatial light modulation element is set in a 
light-transmission state. 
The stripe image is displayed on a portion of a display surface of the 
display, a non-stripe image is displayed on the remaining portion of the 
display surface, and the slit pattern is displayed on the entire display 
surface of the spatial light modulation element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display and/or the display width of each of 
the light-transmission portion and the light-shielding portion of the slit 
pattern to be displayed on the spatial light modulation element are/is set 
to be equal to the total width of a plurality of pixels constituting 
display surfaces of the display and the spatial light modulation element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display is set to be equal to the width of 
one pixel constituting a display surface of the display, and the display 
width of each of the light-transmission portion and the light-shielding 
portion of the slit pattern to be displayed on the spatial light 
modulation element is set to be equal to the total width of a plurality of 
pixels constituting a display surface of the spatial light modulation 
element. 
The display width of each of the stripe pixels constituting the stripe 
image to be displayed on the display is set to be equal to the total width 
of a plurality of pixels constituting a display surface of the display, 
and the display width of each of the light-transmission portion and the 
light-shielding portion of the slit pattern to be displayed on the spatial 
light modulation element is set to be equal to the width of one pixel 
constituting a display surface of the spatial light modulation element. 
Each of display surfaces of the display and the spatial light modulation 
element has pixels in a matrix structure. 
The spatial light modulation element comprises a liquid crystal element. 
The spatial light modulation element comprises a ferroelectric liquid 
crystal element. 
The display comprises a liquid crystal element. 
The display comprises a ferroelectric liquid crystal element. 
The display comprises a self-emission type display and a single polarizing 
plate. 
Predetermined polarized light is output from the stripe image to be 
displayed on the display, and the spatial light modulation element 
comprises a liquid crystal element and a single polarizing plate. 
At least one of constituting elements of the stripe image and constituting 
elements of the slit pattern is controlled in accordance with a signal 
from one of observation condition detecting means for automatically 
detecting a view point position of the observer and observation condition 
inputting means used by the operator to input an observation condition. 
The distance between the display and the spatial light modulation element 
is controlled by distance controlling means on the basis of a signal from 
one of observation condition detecting means for automatically detecting a 
view point position of the observer and observation condition inputting 
means used by the operator to input an observation condition. 
The parallax images to be used are selected from at least three original 
parallax images constituting the parallax image information on the basis 
of a signal from one of observation condition detecting means for 
automatically detecting a view point position of the observer and 
observation condition inputting means used by the operator to input an 
observation condition. 
The parallax images are generated on the basis of data constituting the 
parallax image information or the parallax images are generated on the 
basis of at least two original parallax images constituting the parallax 
image information by interpolation or re-construction in correspondence 
with a view point position of the observer, in accordance with a signal 
from one of observation condition detecting means for automatically 
detecting the view point position of the observer and observation 
condition inputting means used by the operator to input an observation 
condition. 
A plurality of pixels preceding to a pixel to be synchronously displayed or 
a plurality of scan lines preceding to a scan line to be synchronously 
displayed on the spatial light modulation element are precedently 
displayed as the light-shielding portion when the stripe image and the 
slit pattern are synchronously displayed on the display and the spatial 
light modulation element in units of pixels or scan lines. 
Each of display surfaces of the display and the spatial light modulation 
element is divided into a plurality of regions having the same size along 
a scan line, scan lines at the same relative positions of the plurality of 
regions are simultaneously selected and scanned, and the stripe image and 
the slit pattern are synchronously displayed on the display and the 
spatial light modulation element in units of pixels on the plurality of 
scan lines or in units of corresponding scan lines of the plurality of 
scan lines. 
According to another aspect of the present invention, there is provided a 
stereoscopic image display apparatus comprising: 
a display for sequentially forming a single stripe image obtained by 
arranging and synthesizing some of a plurality of stripe pixels which are 
obtained by dividing each of right- and left-eye parallax images supplied 
from a parallax image source having parallax image information, while 
performing a scanning operation; and 
a spatial light modulation element located on the front or rear side of the 
display, the spatial light modulation element sequentially forming a slit 
pattern consisting of a light-transmission portion and a light-shielding 
portion arranged at a predetermined pitch in synchronism with the scanning 
operation, and light transmitted through the stripe pixels, corresponding 
to the right and left eyes of an observer, of the stripe image displayed 
on the display being input to the right and left eyes of the observer via 
the slit pattern. 
The spatial light modulation element is arranged on the front side of the 
display, and the apparatus further comprises a linear Fresnel lens having 
a power only in a horizontal direction and arranged on the front side of 
the spatial light modulation element or arranged between the display and 
the spatial light modulation element. 
A spatial light modulation element illuminated with light emitted by light 
source means is arranged on the rear side of the display, and the 
apparatus further comprises a linear Fresnel lens having a power only in a 
horizontal direction and arranged on the front side of the display or 
arranged between the display and the spatial light modulation element. 
According to another aspect of the present invention, there is provided a 
stereoscopic image display method comprising the steps of: 
sequentially forming, on a display, a single stripe image obtained by 
arranging and synthesizing some of a plurality of stripe pixels which are 
obtained by dividing each of right- and left-eye parallax images supplied 
from a parallax image source having parallax image information, while 
performing a scanning operation; and 
inputting light transmitted through the stripe pixels, corresponding to the 
right and left eyes of an observer, of the stripe image displayed on the 
display to the right and left eyes of the observer via a slit pattern, 
which is obtained by sequentially forming a light-transmission portion and 
a light-shielding portion at a predetermined pitch on a spatial light 
modulation element, in synchronism with the scanning operation. 
Examples of the present invention will become apparent from the following 
description of the embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the first embodiment of the present 
invention. FIGS. 2A and 2B are explanatory views of the stereoscopic image 
display method of the first embodiment, FIG. 3 is an explanatory view of 
the driving method of the first embodiment, and FIGS. 4A and 4B are 
explanatory views of the display states of the first embodiment. In these 
drawings, an image display portion is expressed by a horizontal sectional 
view. Referring to FIG. 1, a display 1 comprises, e.g., a liquid crystal 
element (LCD) having a backlight light source, and its display surface is 
constituted by a large number of pixels having a matrix structure. The 
display 1 displays an image by non-interlace scanning scan lines. A stripe 
image (to be described later) 11 (11.sub.A) is displayed on the image 
display surface of the display 1. 
A spatial light modulation element 2 comprises, e.g., a transmission type 
liquid crystal element, and its display surface is constituted by a large 
number of pixels having a matrix structure. When a stereoscopic image is 
displayed on the display 1, light-transmission portions (slit portions) 
and light-shielding portions are horizontally arranged on the display 
surface of the element 2 at a predetermined pitch to form (or display) a 
parallax barrier pattern (slit pattern) 2.sub.A or 2.sub.B. A.sub.R and 
A.sub.L respectively indicate the right and left eyes of an observer. 
In this specification, the observer side of the display 1 or the spatial 
light modulation element 2 is called a "front side", and the opposite side 
is called a "rear side". Therefore, in this embodiment, the spatial light 
modulation element 2 is arranged on the front side of the display 1. 
A parallax image source 15 comprises, e.g., a multi-channel VTR or a 
multi-channel image pickup device having multi-channel cameras, or 
three-dimensional data of an object. A plurality of images output from 
such device and three-dimensional data will be referred to as parallax 
image information hereinafter. Note that the multi-channel VTR, the 
multi-channel image pickup device, or the like has a plurality of images. 
Since parallax images (images with a parallax) are selected from these 
images, these plurality of images will be referred to as original parallax 
images hereinafter. 
An observation condition inputting means 9 inputs information such as 
observation position information of the observer, a display region of a 
stereoscopic image to be displayed on the display 1, and the like. An 
image processing means 3 extracts right- and left-eye parallax images 
R.sub.S and L.sub.S from the parallax image information of the parallax 
image source 15, divides these parallax images R.sub.S and L.sub.S in the 
horizontal direction to generate vertically elongated stripe pixels, and 
alternately arranges these stripe pixels to synthesize them to obtain a 
single stripe image. Stripe pixels based on the parallax image R.sub.S are 
represented by R.sub.i (i=1, 2, 3, 4, . . . ), and stripe pixels based on 
the parallax image L.sub.S are represented by L.sub.i (i=1, 2, 3, 4, . . . 
). 
A display driving circuit 4 displays the stripe image, which is synthesized 
by and output from the image processing means 3, on the display surface of 
the display 1. A barrier driving circuit 5 drives the spatial light 
modulation element 2 in accordance with a signal from the image processing 
means 3 to form a parallax barrier pattern thereon. 
The relationship between the stripe image 11 and the parallax barrier 
pattern of this embodiment will be explained below. In FIG. 1, let O be 
the interval (base length) between the two eyes of the observer, C be the 
observation distance from the displayed image (stripe image) 11 (11.sub.A) 
on the image display surface to the eyes of the observer, D be the 
distance between the display 1 and the spatial light modulation element 
(parallax barrier) 2, B' be the width of each slit portion of the parallax 
barrier pattern formed on the spatial light modulation element 2, and P be 
the pixel interval (width) of stripe pixels constituting the stripe image 
displayed on the display 1. Then, in order to obtain a stereoscopic view, 
these parameters must satisfy the following relations: 
EQU D=P.multidot.C/(O+P) (1) 
EQU B'=P.multidot.(C-D)/C (2) 
Note that the observation width has a finite divergence at the observation 
position in practice, and these quantities are set after they are slightly 
modified. These relationships have been described in detail in the 
above-mentioned S. H. Kaplan's reference. 
In this embodiment, since the display 1 uses a liquid crystal display 
having a pixel size of 0.110 mm (horizontal).times.0.330 mm (vertical), 
and one pixel size is set to be the width of one stripe pixel of each 
parallax image, the pixel interval is P=0.110 mm. On the other hand, since 
the base length and the observation distance are respectively set to be 
O=65 mm and C=1,000 mm as the observation conditions, the constituting 
data of the spatial light modulation element 2 are D=1.69 mm and B'=0.1098 
mm. Note that slight fine adjustment is made in consideration of the 
divergence of the observation width. 
The stereoscopic image display method of the present invention will be 
explained below with reference to FIG. 1, FIGS. 2A and 2B, FIG. 3, and 
FIGS. 4A and 4B. 
That is, at a certain time (at the time of the display state shown in FIG. 
2A), the image processing means 3 extracts two parallax images R.sub.S and 
L.sub.S from the parallax image source 15, divides these images into 
elongated stripe pixels R.sub.i and L.sub.i, and alternately arranges 
these stripe pixels from, e.g., the left end of the display surface in 
FIG. 1 in the order of R.sub.1, L.sub.2, R.sub.3, L.sub.4, R.sub.5, 
L.sub.6, . . . to synthesize them to obtain a first stripe image 11.sub.A. 
The data of the first stripe image 11.sub.A is input to the display 
driving circuit 4, which displays the first stripe image 11.sub.A on the 
image display surface of the display 1. 
At the same time, the image processing means 3 inputs image data of the 
parallax barrier pattern to the barrier driving circuit 3 in synchronism 
with the output data of the stripe image, and the barrier driving circuit 
5 displays a first parallax barrier pattern 2.sub.A on which 
light-transmission portions and light-shielding portions each having the 
width B' are alternately formed in the order of close, open, close, open, 
close, open, . . . from a point G on the spatial light modulation element 
2. 
The formation region of the parallax barrier corresponds to the image 
region (the entire surface in FIG. 1), where the stripe image 11 is 
displayed, of the display 1. 
At this time, only the right-eye parallax image constituted by the stripe 
pixels R.sub.1, R.sub.3, R.sub.5, . . . is incident on the right eye 
A.sub.R via the first parallax barrier pattern 2.sub.A, and only the 
left-eye parallax image constituted by the stripe pixels L.sub.2, L.sub.4, 
L.sub.6, . . . is incident on the left eye A.sub.L via the first parallax 
barrier pattern 2.sub.A. As a result, the observer can stereoscopically 
observe the first stripe image 11.sub.A by the same principle as that of 
the conventional parallax barrier method. 
At a time at which one frame has been scanned and the same scan line as 
described above is being scanned (at the time of the display state shown 
in FIG. 2B), the display 11 displays, as the stripe image 11, a second 
stripe image 11.sub.B constituted by arranging stripe pixels L.sub.1, 
R.sub.2, L.sub.3, R.sub.4, L.sub.5, R.sub.6, . . . in the opposite order 
to that of the image 11.sub.A, and the spatial light modulation element 2 
displays a second parallax barrier pattern 2.sub.B on which the 
light-transmission portions and light-shielding portions are alternately 
formed in the order of open, close, open, close, open, close, . . . 
opposite to that of the first parallax barrier pattern from the point G. 
At this time, only the right-eye parallax image constituted by the stripe 
pixels R.sub.2, R.sub.4, R.sub.6, . . . is incident on the right eye 
A.sub.R via the second parallax barrier pattern 2.sub.B, and only the 
left-eye parallax image constituted by the stripe pixels L.sub.1, L.sub.3, 
L.sub.5, . . . is incident on the left eye A.sub.L via the second parallax 
barrier pattern 2.sub.B. As a result, the observer can stereoscopically 
observe the second stripe image 11.sub.B by the same principle as that of 
the conventional parallax barrier method. 
The display 1 and the spatial light modulation element 2 are synchronously 
scanned in units of pixels to alternately attain these two display states 
so as to display the stripe images and the parallax barrier patterns. As a 
result, the right eye can observe the entire parallax image R.sub.S 
constituted by the stripe pixels R.sub.1, R.sub.2, R.sub.3, R.sub.4, . . . 
, and the left eye can observe the entire parallax image L.sub.S 
constituted by the stripe pixels L.sub.1, L.sub.2, L.sub.3, L.sub.4, . . . 
in a flicker-less state. 
The operation of the first embodiment will be described in more detail 
below with reference to FIG. 3. 
As described above, for example, when the first stripe image 11.sub.A and 
the first parallax barrier pattern 2.sub.A are displayed, scan lines (Y1, 
Y2, Y3, Y4, . . . ) of the display 1 and the spatial light modulation 
element 2 are respectively driven by Y drivers 6 and 6' via synchronizing 
signals from the image processing means 3, and at the same time, X drivers 
7 and 8 synchronously input a display driving signal and a barrier driving 
signal, as shown in FIG. 3. More specifically, the first scan line Y1 of 
the display 1 and the first scan line Y1 of the spatial light modulation 
element 2 are simultaneously driven, and pixels X.sub.i on the first scan 
line Y1 of the display 1 and pixels X.sub.i on the first scan line Y1 (the 
corresponding scan line to be scanned) of the spatial light modulation 
element 2 are synchronously driven to display images on these pixels. 
Assume that the second stripe image 11.sub.B is displayed on the entire 
display surface of the display 1, and the second parallax barrier pattern 
2.sub.B is displayed on the spatial light modulation element 2. As shown 
in FIG. 4A, the corresponding portion of the first stripe image 11.sub.A 
obtained by synthesizing the stripe pixels R, L, R, L, R, L, . . . (the 
stripe pixels will be simply abbreviated as above although they are, 
strictly speaking, R.sub.1, L.sub.2, R.sub.3, L.sub.4, R.sub.5, L.sub.6, . 
. . ) of the right and left parallax images is sequentially displayed on 
the pixels on the first scan line Y1 of the display 1 from the 
above-mentioned state. At the same time, as shown in FIG. 4B, the first 
parallax barrier pattern 2.sub.A constituted by alternately arranging the 
light-shielding portions and light-transmission portions in the order of 
close, open, close, open, close, open, . . . is sequentially displayed on 
the pixels on the first scan line Y1 of the spatial light modulation 
element 2 in units of pixels in synchronism with the display 1. 
Next, the second scan line Y2 is selected, and the corresponding portion of 
the first stripe image 11.sub.A and the corresponding portion of the first 
parallax barrier pattern 2A are synchronously displayed on the second scan 
lines Y2 of the display 1 and the spatial light modulation element 2 in 
the same manner as described above. 
FIGS. 4A and 4B illustrate the state at the instance when the fifth scan 
line Y5 is selected before completion of all the scan operations, the 
pixel data of the stripe pixel R.sub.7 is displayed on the seventh pixel 
X.sub.7 of the display 1 (FIG. 4A), and the light-shielding portion is 
synchronously formed on the seventh pixel X.sub.7 of the spatial light 
modulation element 2 (FIG. 4B). Therefore, the first stripe image 11.sub.A 
is displayed on the upper portion of the display 1, and the second stripe 
image 11.sub.B is displayed on the lower portion of the display 1. Also, 
the first parallax barrier pattern 2.sub.A is displayed on the upper 
portion of the spatial light modulation element 2, and the second parallax 
barrier pattern 2.sub.B is displayed on the lower portion thereof. 
When the above-mentioned operation is sequentially repeated, and the scan 
operation of the last scan line is completed, the first stripe image 
11.sub.A is displayed on the entire display screen. When the observer 
observes this first stripe image 11.sub.A via the spatial light modulation 
element 2 on which the first parallax barrier pattern 2.sub.A is formed, 
he or she can observe the first stripe image 11.sub.A as a stereoscopic 
image. 
Subsequently, the scan operation is started in turn from the first scan 
line, and in this case, the display 1 displays, as the stripe image 11, 
the corresponding portion of the second stripe image 11.sub.B obtained by 
arranging the stripe images L, R, L, R, L, R, . . . (the stripe pixels 
will be simply abbreviated as above although they are, strictly speaking, 
L.sub.1, R.sub.2, L.sub.3, R.sub.4, L.sub.5, R.sub.6, . . . ) in the 
opposite order. At the same time, the spatial light modulation element 2 
alternately forms and displays the light-transmission portions and the 
light-shielding portions in the opposite order of open, close, open, 
close, open, close, . . . as the second parallax barrier pattern 2. When 
the image displayed on the display 1 is observed via the spatial light 
modulation element 2, the second stripe image 11.sub.B can be observed as 
a stereoscopic image. 
Therefore, in this embodiment, since the observer alternately 
stereoscopically observes the stripe images 11.sub.A and 11.sub.B, the 
respective parallax images R.sub.S and L.sub.S are displayed on the eyes 
A.sub.R and A.sub.L of the observer without any omission, and the observer 
can observe a high-quality stereoscopic image without the resolution of 
the parallax images being reduced. Since the resolution lowers to 1/2 that 
of the display to be used in the stereoscopic image display apparatus 
using the conventional parallax barrier method, an image displayed in this 
embodiment can have a resolution twice that of the image obtained by the 
conventional apparatus. 
In addition, in this embodiment, since the display 1 and the spatial light 
modulation element 2 are synchronously driven in units of pixels on their 
scan lines, the stripe pixels and the slit portions of the corresponding 
parallax barrier pattern synchronously change at any timing during the 
display operation of the stripe images so as to maintain a relationship 
therebetween that allows the observer to normally observe a stereoscopic 
image. Therefore, in this embodiment, crosstalk between the right and left 
parallax images can be remarkably reduced. 
Furthermore, in this embodiment, since the light-transmission portions and 
the light-shielding portions of the parallax barrier pattern to be formed 
on the spatial light modulation element 2 alternately replace each other, 
a decrease in contrast in a Moire pattern, i.e., the repetitive structure 
of the light-transmission portions and the light-shielding portions of the 
parallax barrier pattern, is not conspicuous. 
Moreover, it is ideal to use the display 1 and the spatial light modulation 
element 2 having a high-speed frame rate in this embodiment. However, in 
this embodiment, since the stripe pattern and the parallax barrier pattern 
are synchronously displayed, the right and left parallax images are always 
incident on the right and left eyes of the observer without crosstalk 
therebetween, and the observer does not experience any flicker noise. For 
this reason, the display and the spatial light modulation element having a 
frame rate of 60 Hz to 120 Hz can be used. 
The spatial light modulation element 2 must have a high contrast and must 
realize a high-speed driving operation since it separates the right- and 
left-eye parallax images by means of the parallax barrier pattern formed 
thereon. In view of these situations, a ferroelectric liquid crystal 
element (FLC) is preferably used as the display 1 and the spatial light 
modulation element 2 of this embodiment. 
When the display 1 and the spatial light modulation element 2 comprise 
liquid crystal elements, they preferably use the same type of liquid 
crystal elements since it is easy to assure synchronization due to the 
same display speed (response speed) and identical driving circuits can be 
used. 
In this embodiment, the display 1 and the spatial light modulation element 
2 are driven in accordance with synchronizing signals supplied from the 
image processing means 3. However, various other driving methods may be 
used. For example, the display driving circuit 4 may generate a 
synchronizing signal to determine the driving timing of the barrier 
driving circuit 5, or the Y drivers may attain synchronization. 
This embodiment has exemplified a case wherein one pixel size of the 
display 1 is equal to the interval P of the stripe images, i.e., each of 
the stripe pixels R.sub.1, L.sub.2, . . . corresponds to one pixel of the 
display 1. However, the pixel width of each of the stripe pixels R.sub.i 
and L.sub.i may correspond to the width of a plurality of pixels of the 
display 1. For example, the interval P may equal the total width of R, G, 
and B pixels upon execution of a color display operation. 
Also, this embodiment has exemplified a case wherein two parallax images 
are displayed. In addition, the method of this embodiment may be applied 
to a "parallax panoramagram" in which a stripe image is generated by 
synthesizing a plurality of parallax images and is observed via an 
appropriate parallax barrier. 
The spatial light modulation element 2 of this embodiment need not have a 
matrix-shaped pixel structure but may have a vertical-line-shaped pixel 
structure since it forms vertically elongated, rectangular slit portions. 
Note that the width P of each stripe pixel, the number of stripe pixels, 
and the like are constituting elements of the stripe image, and the width 
B' of each of the slit and light-shielding portions of the parallax 
barrier pattern and the like are constituting elements of a slit pattern 
(parallax barrier pattern). 
In this embodiment, as described above, at least one of the constituting 
elements of the stripe image and the slit pattern is controlled in 
accordance with a signal from the observation condition inputting means 9. 
FIG. 5 is a schematic sectional view showing principal part of a 
stereoscopic image display apparatus according to the second embodiment of 
the present invention. In this embodiment, the display 1 and the spatial 
light modulation element 2 in the arrangement of the first embodiment 
specifically comprise TN liquid crystal elements (TN liquid crystal 
cells). Other arrangements are the same as those in the first embodiment. 
The display 1 for displaying the stripe image 11 is arranged so that a TN 
liquid crystal cell 23 (a glass substrate, electrodes, and the like are 
not shown) sandwiched between two polarizing plates 22 and 24 is 
illuminated with light emitted by a backlight 21 having a reflection plate 
and a light guide plate. Therefore, linearly polarized light emanates from 
an image displayed on the display 1. The spatial light modulation element 
2 is constituted by arranging a TN liquid crystal cell 25 on the side of 
the display 1, and a single polarizing plate 26 on the side of the 
observer, and displays a stripe-shaped parallax barrier pattern. 
In this embodiment as well, since the stripe images 11.sub.A and 11.sub.B 
on the display 1 and the parallax barrier patterns 2.sub.A and 2.sub.B on 
the spatial light modulation element 2 are synchronously switched and 
displayed, the observer can observe a high-quality stereoscopic image free 
from a decrease in resolution of parallax images. 
FIG. 6 is an explanatory view of the relationship between the directions of 
polarization axes of the polarizing plate and the observation image in 
this embodiment. For example, a case will be examined wherein the display 
1 of this embodiment uses a normally white mode liquid crystal display, 
and the polarization axis of the polarizing plate 22 is perpendicular to 
the plane of the drawing of FIG. 6. At this time, the polarizing plates 22 
and 24 are set to attain a crossed Nicols state. In this state, the 
polarization axis of only light components of the light, which are emitted 
by the backlight 21 and are incident on portions (OFF portions) applied 
with no voltage of the TN liquid crystal cell 23, is rotated by 
90.degree., and these light components are transmitted through the 
polarizing plate 24. 
On the other hand, the spatial light modulation element 2 is also 
constituted by the TN liquid crystal cell 25 and the single polarizing 
plate 26, and a voltage is applied to only the slit portions (ON portions) 
of the parallax barrier pattern. Therefore, the plane of polarization of 
the display image light (the polarization axis is parallel to the plane of 
the drawing) transmitted through the display 1 is not modulated by the 
slit portions (ON portions) of the parallax barrier pattern, and the 
display image light is directly transmitted through the polarizing plate 
26 (the polarization axis is parallel to the plane of the drawing). A 
left-eye image (L image) is transmitted in the direction of a left eye 
A.sub.L. A right-eye image (R image) is transmitted in the direction of a 
right eye A.sub.R, and a stereoscopic image is observed. The relationship 
between the polarization axes of the polarizing plates and the observation 
image has been described. 
Since the conventional apparatus disclosed in Japanese Patent Application 
Laid-Open No. 3-119889 uses four polarizing plates, the luminance of the 
displayed image lowers due to absorption by these polarizing plates. 
However, in this embodiment, Since the number of polarizing plates is 
decreased by one, the luminance of the displayed image can be improved. 
The polarization axis of the polarizing plate constituting the spatial 
light modulation element 2 can be set to have a direction other than that 
described above. For example, as shown in FIG. 7, the polarization axis of 
a polarizing plate 26' may be perpendicular to the plane of the drawing of 
FIG. 7, and at that time, no voltage is applied to the slit portions of 
the parallax barrier pattern displayed on the spatial light modulation 
element 2. In this case, the plane of polarization of the image display 
light (the polarization axis is parallel to the plane of the drawing) 
transmitted through the display 1 is rotated by 90.degree. by these slit 
portions (OFF portions), and the image display light is transmitted 
through the polarizing plate 26', whose polarization axis is set to be 
perpendicular to the plane of the drawing, so as to become incident on the 
corresponding eyes. That is, in this case, the direction of polarization 
of image light incident on the corresponding eyes is perpendicular to that 
shown in FIG. 6. 
Such change similarly occurs on the display mode of the liquid crystal 
panel used as the display 1. In such case, the polarization axes of the 
three polarizing plates used in the stereoscopic image display apparatus 
of the present invention can be set in correspondence with the respective 
states. 
Note that the display 1 may be constituted by a self-emission type display 
and a single polarizing plate, as shown in FIG. 8. 
FIG. 9 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the third embodiment of the present 
invention. In this embodiment, the view point position of the observer is 
automatically detected, and the operation of the stereoscopic image 
display apparatus is controlled in accordance with the detection result so 
as to allow a satisfactory stereoscopic view over a wide range. 
Referring to FIG. 9, an observer image inputting means 36 inputs an image 
of the observer who is observing this apparatus. The observer image 
inputting means 36 of this embodiment is constituted by a single camera. A 
camera controller 37 controls the observer image inputting means 36. A 
view point position/visual axis direction detecting circuit 38 detects the 
view point position and visual axis direction of the observer by 
performing image processing of the signal supplied from the observer image 
inputting means 36. The observer image inputting means 36, the camera 
controller 37, the view point position/visual axis direction detecting 
circuit 38, and the like constitute an observation condition detecting 
means 30. 
The operation of this embodiment will be described below. The image of the 
observer picked up by the observer image inputting means 36 is input to 
the view point position/visual axis direction detecting circuit 38 via the 
camera controller 37. The view point position/visual axis direction 
detecting circuit 38 extracts the images of the eyes of the observer by 
performing image processing of the input image, thereby detecting the view 
point position and visual axis direction of the observer. 
As has been described in the first embodiment, since the display operation 
of the stereoscopic image display apparatus of this embodiment is 
performed based on parallax barrier conditional formulas (1) and (2) 
above, if the observer moves backward or forward, it is preferable to 
change, in correspondence with the position (observation position) of the 
observer, the pixel interval (width) P of the stripe pixels displayed on 
the display 1 and the width B' of each slit portion of the parallax 
barrier pattern formed on the spatial light modulation element 2. 
In this case, since the display 1 uses a liquid crystal display having a 
pixel size of 0.110 mm (horizontal).times.0.330 mm (vertical) and three 
pixels correspond to the stripe width (the width of each stripe pixel) of 
the parallax image, the pixel interval is P=0.110.times.3=0.330 mm. 
As the first observation conditions, the base length and the observation 
distance are respectively set to be O=65 mm and C=1,000 mm. With these 
conditions, the conditions for the spatial light modulation element 2 are 
set to be D=5.05 mm and B'=0.3283 mm. Note that slight fine adjustment is 
preferably performed in consideration of the divergence of the observation 
width. If the observer moves from this position to a position at an 
observation distance of about 1,500 mm, the observation distance in the 
observation conditions changes to C=1,500 mm. In this case, if the 
interval D remains the same, conditional formulas (1) and (2) hold when 
the width P of each stripe pixel on the display 1 is set to be P=0.220 mm 
and the width B' of each slit portion of the parallax barrier pattern on 
the spatial light modulation element 2 is set to be B'=0.2192 mm. In this 
case, each stripe pixel of the stripe image can be displayed to have a 
width P corresponding to two pixels, and each slit portion of the parallax 
barrier pattern can be formed to have a width B' corresponding to two 
pixels. 
As described above, in this embodiment, the observation condition detecting 
means 30 detects the view point position of the observer, and the 
observation distance C is calculated in accordance with the detection 
result. Then, the width P of each stripe pixel constituting the stripe 
image and the width B' of each slit portion of the parallax barrier 
pattern to be displayed on the spatial light modulation element 2 are 
appropriately controlled in accordance with the calculated distance C, 
thus allowing a satisfactory stereoscopic view at the observation position 
over a wide range. 
Note that the observation condition detecting means 30 of this embodiment 
may use two cameras, an output from a magnetic sensor which is attached to 
the head portion of the observer and detects a magnetic field formed 
around the observer, or a visual axis detecting means such as a known eye 
mark camera. 
In this embodiment as well, the observer himself or herself may input the 
view point position using the observation condition inputting means 9 or 
may control an adjustment switch while observing the displayed image, thus 
controlling at least one of the constituting elements of the stripe image 
and the slit pattern, that display a stereoscopic image on the display 1. 
FIG. 10 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the fourth embodiment of the present 
invention. The difference between the fourth and third embodiments is as 
follows. That is, in the third embodiment, when the observation distance C 
changes, the width P of each stripe pixel and the width B' of each slit 
portion of the parallax barrier pattern are changed to display a 
stereoscopic image to be observed. However, in this embodiment, the 
distance D between the display 1 and the spatial light modulation element 
2 is changed to display a stereoscopic image to be observed. Other 
arrangements are the same as those in the third embodiment. 
Referring to FIG. 10, variable spacers 33 control the interval D between 
the display 1 and the spatial light modulation element 2, and their 
lengths change in accordance with a signal. A spacer driving means 34 
controls the variable spacers 33 in accordance with a signal from the 
image processing means 3. The variable spacers 33, the spacer driving 
means 34, and the like constitute an interval control means. 
The operation of this embodiment will be described below. In this 
embodiment, the observation condition detecting means 30 detects the view 
point position of the observer, and the observation distance C is 
calculated in accordance with the detection result. Then, the variable 
spacers 33 are controlled via the spacer driving means 34 in accordance 
with the calculated distance C so as to change the interval D between the 
display 1 and the spatial light modulation element 2. With this control, 
the observer can observe a stereoscopic image. 
The principle will be explained below. Formulas (1) and (2) are rewritten 
as follows: 
EQU C=D.multidot.(O+P)/P.ident.k.multidot.D (3) 
EQU B'=P.multidot.(k-1)/k (4) 
for k.ident.(O+P)/P 
With these formulas, when the width P of each stripe pixel of the stripe 
image 11 to be displayed on the display 1 and the base length O are 
determined, k is determined, and the width B' of each slit portion of the 
parallax barrier pattern is uniquely determined. Also, the interval D is 
proportional to the observation distance C. 
Therefore, when the interval D between the display 1 and the spatial light 
modulation element 2 that forms the parallax barrier pattern is controlled 
in correspondence with the observation distance C, the above-mentioned 
conditional formulas hold. 
For example, if the width P of each stripe image is set to be P=0.330 mm 
and the base length O is set to be O=65 mm, k=197.97, the interval D=5.05 
mm and the width B'=0.3283 mm of each slit portion can be set at the 
position of an observation distance C=1,000 mm as one first observation 
condition. When the observer moves to the position at an observation 
distance C=1,500 mm as one second observation condition, the 
above-mentioned conditional formulas hold if the interval D=7.58 mm and 
the width B'=0.3283 mm of each slit portion are set. 
In the apparatus for displaying a stereoscopic image to follow the view 
point position like in this embodiment, when the observer moves in the 
right-and-left direction, the formation positions of the slit portions of 
the parallax barrier pattern can be appropriately shifted in the 
right-and-left direction in correspondence with the view point position of 
the observer, as shown in FIGS. 11A and 11B, thus satisfactorily 
displaying a stereoscopic image even in such case. 
Assuming that each slit portion of the parallax barrier pattern is formed 
to have a width B' corresponding to three pixels of the spatial light 
modulation element 2, as indicated by 51 in FIG. 11A, when the view points 
move laterally to the position of A'.sub.R and A'.sub.L, as shown in FIG. 
11B, the slit portions of the parallax barrier pattern can be formed while 
shifting by one pixel relative to the stripe image 11.sub.A, as indicated 
by 51' in FIG. 11B. Thus, in such case, the observer can satisfactorily 
stereoscopically observe the stripe image 11.sub.A. Note that 52 or 52' 
indicates the position serving as a slit portion of a time-sequential 
parallax barrier pattern, as described above. 
Alternatively, the observer can also satisfactorily recognize a 
stereoscopic image when the position of the stripe image 11 displayed on 
the display 11 shifts in the right-and-left direction while the positions 
of the slit portions of the parallax barrier pattern remain the same. 
The 11th embodiment to be described later adopts the above-mentioned 
method. 
FIGS. 12 to 14D are explanatory views of a stereoscopic image display 
apparatus according to the fifth embodiment of the present invention. In 
the above embodiments, the parallax images R.sub.S and L.sub.S used for 
synthesizing a stripe image to be displayed on the display 1 are always 
the same. In other words, the above-mentioned stereoscopic image display 
method/apparatus allows the observer to always satisfactorily observe the 
same stereoscopic image that remains the same even when the observer 
changes the view point position. 
However, in this embodiment, this embodiment adopts the display method that 
gives a wraparound display effect to an image in correspondence with the 
change in view point position of the observer, and the parallax images 
R.sub.S and L.sub.S to be displayed on the display 1 are changed in 
accordance with the view point position of the observer. 
FIG. 12 shows, as a display apparatus 20, only a portion consisting of the 
display 1 and the spatial light modulation element 2 of the stereoscopic 
image display apparatus of the third or fourth embodiment. 
Assume that the observer observes an image from a position separated from 
the display apparatus 20 by the observation distance C. Note that the 
image processing means, the observation condition detecting means, and the 
like are not shown. 
On the other hand, FIG. 13 is a schematic view showing principal part of 
the parallax image source 15 of this embodiment. Referring to FIG. 13, 
cameras K.sub.A, K.sub.B, K.sub.C and K.sub.D are aligned at positions 
separated from objects 12 by the distance C to be separated by intervals 
equal to the interval (base length) O between the two eyes of the observer 
so as to pick up images of the objects. Note that A to D respectively 
indicate the object-side principal points of the optical systems of the 
cameras. Therefore, in this embodiment, the parallax image source 15 
always has four original parallax images. 
The operation of this embodiment will be described below. A case will be 
examined below wherein the observer moves from a position 17 (the right 
eye position A.sub.R, the left eye position A.sub.L) to a position 19 (the 
right eye position A.sub.R "=the left eye position A.sub.L ' at a position 
18, the left eye position A.sub.L ") via the position 18 (the right eye 
position A.sub.R '=the left eye position A.sub.L at the position 17, the 
left eye position A.sub.L '), as shown in FIG. 12. 
When the observer is located at the position 17, an original parallax image 
(FIG. 14A) picked up from the point A by the camera K.sub.A is input to 
the display apparatus 20 as an image R.sub.S to be observed by the right 
eye A.sub.R of the observer on the display apparatus 20. At the same time, 
an original parallax image (FIG. 14B) picked up at the point B by the 
camera K.sub.B is input to the display apparatus 20 as an image L.sub.S to 
be observed by the left eye A.sub.L of the observer. 
The display apparatus 20 uses the two original parallax images shown in 
FIGS. 14A and 14B as those used for synthesizing a stripe image to be 
displayed on the display 1, and synthesizes and displays the stripe image 
using the image shown in FIG. 14A as the right-eye image and the image 
shown in FIG. 14B as the left-eye image. In this manner, the observer can 
observe a stereoscopic image when he or she observes the objects from the 
positions of the cameras K.sub.A and K.sub.B. 
When the observer moves to the position 18, the original parallax image 
(FIG. 14B) picked up at the point B by the camera K.sub.B is input to the 
display apparatus 20 as an image R.sub.S to be observed by the right eye 
A.sub.R ' of the observer. At the same time, an original parallax image 
(FIG. 14C) picked up at the point B by the camera K.sub.C is input to the 
display apparatus 20 as an image L.sub.S to be observed by the left eye 
A.sub.L ' of the observer. 
The display apparatus 20 uses the two original parallax images shown in 
FIGS. 14B and 14C as those used for synthesizing a stripe image to be 
displayed on the display 1, and synthesizes and displays the stripe image 
using the image shown in FIG. 14B as the right-eye image and the image 
shown in FIG. 14C as the left-eye image. In this manner, the observer can 
observe a stereoscopic image when he or she observes the objects from the 
positions of the cameras K.sub.B and K.sub.C. 
When the observer moves to the position 19, the original parallax image 
(FIG. 14C) picked up at the point B by the camera K.sub.C is input to the 
display apparatus 20 as an image R.sub.S to be observed by the right eye 
A.sub.R " of the observer. At the same time, an original parallax image 
(FIG. 14D) picked up at the point B by the camera K.sub.D is input to the 
display apparatus 20 as an image L.sub.S to be observed by the left eye 
A.sub.L " of the observer. 
The display apparatus 20 uses the two original parallax images shown in 
FIGS. 14C and 14D as those used for synthesizing a stripe image to be 
displayed on the display 1, and synthesizes and displays the stripe image 
using the image shown in FIG. 14C as the right-eye image and the image 
shown in FIG. 14D as the left-eye image. In this manner, the observer can 
observe a stereoscopic image when he or she observes the objects from the 
positions of the cameras K.sub.C and K.sub.D. 
With the above-mentioned operations, when the observer moves and changes 
his or her view point position, a stereoscopic image to be observed is 
constituted by parallax images obtained by viewing the objects from 
different directions, and a "wraparound" stereoscopic image of the objects 
12 can be observed. 
In this embodiment, the parallax image source 15 has parallax image 
information consisting of four original parallax images. Two out of four 
original parallax images are selected and used in accordance with a signal 
from the observation condition detecting means 30 so as to display a 
stereoscopic image. 
In this embodiment, the object-side principal point positions A, B, C, and 
D of the cameras constituting the parallax image source 15 agree with the 
eye positions A.sub.R, A.sub.L (=A.sub.R '), A.sub.L ' (=A.sub.R "), and 
A.sub.L " at the respective observation positions. However, when the right 
eye of the observer is located between A.sub.R and A.sub.L of the position 
17, and the left eye is located between A.sub.R ' and A.sub.L ' of the 
position 18, a single right-eye image (parallax image) R.sub.S is 
synthesized by performing "image interpolation" of two original parallax 
images shown in FIGS. 14A and 14B, and a single right-eye image (parallax 
image) L.sub.S is synthesized by performing image interpolation of two 
original parallax images shown in FIGS. 14B and 14C. Using these two 
parallax images R.sub.S and L.sub.S obtained by synthesizing the original 
parallax images, a stripe image to be displayed on the display 1 can be 
synthesized and displayed, thus realizing a more smoothly continuous image 
wraparound effect. 
As the image interpolation method, a known method using an epipolar plane 
image (EPI), i.e., a method of creating an interpolated image by exploring 
corresponding points on an EPI (e.g., R. C. Bolles et. al: Int. J. 
Computer Vision, Vol. 1, No. 1, pp. 7-55, 1987) may be used. 
When the image interpolation method is used, the images of the objects 12 
need not be picked up by the four camera systems shown in FIG. 13. For 
example, using two original parallax images picked up by the cameras at 
the positions A and D, image interpolation is repeated to form desired 
parallax images, and a stripe image can be synthesized using the formed 
parallax images. (Note that forming parallax images by interpolation using 
those formed by interpolation will be referred to as "image 
re-construction" in the present invention.) 
When the observer moves forward or backward, parallax images corresponding 
to the view point position may be formed by image interpolation, and a 
stripe image can be synthesized using these images. As the method of 
processing these images, a method disclosed in Japanese Patent Application 
Laid-Open No. 7-129792 is effective. 
In the fifth embodiment, as images to be displayed, natural images picked 
up by four cameras are used. Alternatively, three-dimensional images such 
as so-called CG images created by a computer (e.g., a CAD) may be used. In 
this case, since "data" of an object is already three-dimensional data, 
parallax images viewed from arbitrary positions can be freely "generated". 
Therefore, a plurality of parallax images corresponding to the respective 
view point positions can be generated, and a stripe image can be 
synthesized and displayed based on these images. 
Conventionally, when a multi-parallax image display (called parallax 
panoramagram) is performed using the parallax barrier method so as to 
broaden the view range or to give the "wraparound effect", the display 
resolution lowers to 1/n (where n is the number of parallax images used at 
that time). 
However, in this embodiment, the decrease in resolution is at most 1/2. 
Furthermore, since this embodiment uses the arrangement of the third or 
fourth embodiment, a decrease in resolution can be prevented, and when the 
arrangement of the second embodiment is adopted, the image luminance can 
be improved. 
FIGS. 15A and 15B are explanatory view of the stereoscopic image display 
method of a stereoscopic image display apparatus according to the sixth 
embodiment of the present invention. In the first embodiment, the image 
display operation on the display 1 and the display operation of the 
parallax barrier pattern on the spatial light modulation element 2 are 
synchronously performed in units of pixels on the scan lines. However, in 
this embodiment, these display operations are synchronously performed in 
units of scan lines. 
FIG. 15A shows the same display state as that shown in FIG. 2A of the first 
embodiment. In this state, when the observer observes the first stripe 
image 11.sub.A via the first parallax barrier pattern 2.sub.A formed on 
the spatial light modulation element 2, his or her right and left eyes can 
observe the corresponding parallax images, thus attaining a stereoscopic 
view. 
In this embodiment, when the observer observes the second stripe image 
11.sub.B via the second parallax barrier pattern 2.sub.B in the state 
shown in FIG. 15B, a stereoscopic view can be attained. In this 
embodiment, the stripe image 11 to be displayed on the display 1 and the 
light-transmission portions of the parallax barrier pattern formed on the 
spatial light modulation element 2 are synchronously displayed in units of 
scan lines, and the two display states shown in FIGS. 15A and 15B are 
alternately and repetitively displayed. 
That is, at a certain time (at the time of the display state shown in FIG. 
15A), the corresponding portion of the first stripe image 11.sub.A 
obtained by arranging the stripe pixels R.sub.i and L.sub.i of the 
parallax images R.sub.S and L.sub.S in the order of R.sub.1, L.sub.2, 
R.sub.3, L.sub.4, . . . is displayed on a given scan line of the display 
1. At the same time, the first parallax barrier pattern 2.sub.A is formed 
by repetitively displaying the light-transmission portions and the 
light-shielding portions in the order of close (light-shielding portion), 
open (light-transmission portion), close, open, . . . from the point G on 
the corresponding scan line of the spatial light modulation element 2. At 
this time, only the right-eye image constituted by the stripe pixels 
R.sub.1, R.sub.3, R.sub.5, . . . is incident on the right eye A.sub.R, and 
only the left-eye image constituted by the stripe pixels L.sub.2, L.sub.4, 
L.sub.6, . .. is incident on the left eye A.sub.L, thus attaining a 
stereoscopic view. (Note that the right- and left-eye images have a 
resolution 1/2 that of the display surface of the display 1.) 
At a time at which one frame has been scanned and the same scan line as 
described above is being scanned (at the time of the display state shown 
in FIG. 15B), the second stripe image 11.sub.B obtained by arranging the 
stripe pixels R.sub.i and L.sub.i of the parallax images R.sub.S and 
L.sub.S in the order of L.sub.1, R.sub.2, L.sub.3, R.sub.4, . . . is 
displayed on the scan line of the display 1. At the same time, the second 
parallax barrier pattern 2.sub.B is formed by repetitively displaying the 
light-transmission portions and light-shielding portions in the order of 
open, close, open, close, open, close, . . . from the point G on the 
corresponding scan line of the spatial light modulation element 2 (the 
second and first parallax barrier patterns 2.sub.B and 2.sub.A have 
opposite arrangements of the light-transmission portions and the 
light-shielding portions). At this time, only the right-eye parallax image 
constituted by the stripe pixels R.sub.2, R.sub.4, R.sub.6, . . . is 
incident on the right eye A.sub.R, and only the left-eye parallax image 
constituted by the stripe pixels L.sub.1, L.sub.3, L.sub.5, . . . is 
incident on the left eye A.sub.L, thus similarly attaining a stereoscopic 
view. 
When these two display states are alternately and time-sequentially 
displayed at a high-speed frame rate, the right eye can observe the entire 
parallax image R.sub.S constituted by the stripe pixels R.sub.1, R.sub.2, 
R.sub.3, R.sub.4, . . . , and the left eye can observe the entire parallax 
image L.sub.S constituted by the stripe pixels L.sub.1, L.sub.2, L.sub.3, 
L.sub.4, . . . . As a result, the observer can observe a high-quality 
stereoscopic image without the display resolution of the display 1 being 
reduced. 
In the conventional stereoscopic image display method, the resolutions of 
images to be observed by the right and left eyes lower to 1/2 the display 
resolution of the display to be used. However, in this embodiment, an 
image having a resolution twice that of the image displayed by the 
conventional method can be displayed. 
The display switching operations of the display 1 and the spatial light 
modulation element 2 of this embodiment will be described in more detail 
below with reference to FIGS. 16A to 16C. FIGS. 16A to 16C show a case 
wherein the display 1 and the spatial light modulation element 2 are 
driven in a non-interlace manner using the circuit arrangement shown in 
FIG. 3. In each of FIGS. 16A to 16C, the left drawing indicates the 
display state of the display 1, and the right drawing indicates the 
parallax barrier pattern to be displayed on the spatial light modulation 
element 2. 
FIGS. 16A and 16C respectively show states wherein the images to be 
displayed on the display 1 have been completely switched to the first and 
second stripe images 11.sub.A and 11.sub.B, and FIG. 16B shows the 
intermediate scanning state between FIGS. 16A and 16C, i.e., the display 
state at the time upon completion of scanning of the fifth scan line Y5. 
As shown in FIG. 16A, at a certain time (at the time upon completion of 
scanning of the entire screen), the first stripe image 11.sub.A obtained 
by arranging the stripe pixels in the order of R.sub.1, L.sub.2, R.sub.3, 
L.sub.4, . . . is displayed on the entire screen of the display 1, and the 
first parallax barrier pattern 2.sub.A obtained by arranging stripe 
patterns in the order of close, open, close, open, . . . is displayed on 
the spatial light modulation element 2. 
From this state, the first scan line Y1 is selected, the corresponding 
portion of the second stripe image 11.sub.B obtained by arranging stripe 
pixels in the order of L.sub.1, R.sub.2, L.sub.3, R.sub.4, . . . is 
displayed on the scan line Y1 of the display 1, and the corresponding 
portion of the second parallax barrier pattern 2.sub.B obtained by 
arranging stripe patterns in the order of open, close, open, close, . . . 
is displayed on the scan line Y1 of the spatial light modulation element 2 
in synchronism with the scan line Y1 of the display 1. FIG. 16B shows the 
display state at the time upon completion of scanning of the fifth scan 
line Y5 after the above-mentioned operation is repeated in turn in the 
order of scan lines Y1, Y2, . . . . 
In this embodiment, the display driving operations of the display 1 and the 
spatial light modulation element 2 are synchronously performed in units of 
scan lines. FIG. 16C shows the state upon completion of scanning of all 
the scan lines. In this state, the display 1 displays the second stripe 
image 11.sub.B, which complements the first stripe image 11.sub.A shown in 
FIG. 16A. In FIG. 16A, the odd stripe pixels R.sub.1, R.sub.3, R.sub.5, . 
. . of the right parallax image R.sub.S are displayed, while in FIG. 16C, 
the even stripe pixels R.sub.2, R.sub.4, R.sub.6, . . . of the right 
parallax image R.sub.S are displayed. On the other hand, in FIG. 16A, the 
even stripe pixels L.sub.2, L.sub.4, L.sub.6, . . . of the left parallax 
image L.sub.S are displayed, while in FIG. 16C, the odd stripe pixels 
L.sub.1, L.sub.3, L.sub.5, . . . of the left parallax image L.sub.S are 
displayed. 
Upon completion of a series of scanning operations (the rewrite display 
operations of all the scan lines), the right and left parallax images 
R.sub.S and L.sub.S are displayed on all the pixels constituting the 
display 1. 
At this time, since the parallax barrier pattern to be formed on the 
spatial light modulation element 2 is synchronously switched and displayed 
in units of scan lines, even when a stripe image which is being rewritten 
or has been rewritten is observed via the spatial light modulation element 
2, a stereoscopic view can be attained on the basis of the principle of 
the parallax barrier method with almost no crosstalk. Therefore, the 
observer can observe a high-resolution stereoscopic image displayed on all 
the pixels of the display. 
In this embodiment, the display width P of each stripe pixel constituting 
the right and left parallax images matches one pixel of the display 1, and 
the display width of each of the light-transmission portions and the 
light-shielding portions of the parallax barrier pattern matches one pixel 
on the display surface of the spatial light modulation element 2. However, 
the present invention is not limited to this formation method of the 
parallax barrier pattern. For example, as shown in FIG. 17, the display 
width P of each stripe pixel may correspond to a plurality of pixels of 
the display 1, and the display width B' of each of the light-transmission 
portions and the light-shielding portions of the parallax barrier pattern 
may correspond to a plurality of pixels of the spatial light modulation 
element 2. These display widths can be independently selected. For 
example, the display width P of each stripe pixel may correspond to one 
pixel width of the display 1, and the display width B' of each of the 
light-transmission portions and the light-shielding portions of the 
parallax barrier pattern may correspond to a plurality of pixels of the 
spatial light modulation element 2. This applies to all the embodiments of 
the present invention. 
FIG. 18 is an explanatory view of the stereoscopic image display method of 
a stereoscopic image display apparatus according to the seventh embodiment 
of the present invention. The arrangement of the apparatus of this 
embodiment is basically same as that of the sixth embodiment. In the sixth 
embodiment, the stripe image 11.sub.A or 11.sub.B is displayed on the 
entire surface of the display 1, and the parallax barrier pattern 2.sub.A 
or 2.sub.B is synchronously formed on the entire display surface of the 
spatial light modulation element 2 in units of scan lines, thereby 
displaying a stereoscopic image on the entire display surface of the 
display 1. However, in this embodiment, a stereoscopic image can be 
displayed on only a portion of the display surface of the display 1 as if 
a window of a computer were opened. This point is different from the sixth 
embodiment. 
In this embodiment, at the beginning of the operation of the stereoscopic 
image display apparatus, the observation condition inputting means 9 
inputs a display range (region) 41 of a stereoscopic image on the display 
surface of the display 1, as shown in the left drawing in FIG. 18. A 
stripe image is displayed only on the designated region, and a 
two-dimensional image (non-stripe image) is displayed on the remaining 
region. At the same time, the parallax barrier pattern is formed on only a 
region 42, corresponding to the region 41 of the display 1, on the spatial 
light modulation element 2, and the remaining region is set in a 
light-transmission state. With this operation, a stereoscopic image can be 
observed only on the desired region 41 on the basis of the stripe image, 
and the two-dimensional image can be observed on a portion where the 
stripe image is not displayed. 
In this embodiment, when a stereoscopic image is to be displayed on the 
region 41, the display operations of the display 1 and the spatial light 
modulation element 2 are synchronously performed in units of scan lines, 
as has been described in the sixth embodiment. FIG. 18 illustrates a state 
at the instance upon completion of scanning of the fifth scan line Y5 
after the next image display operation is started from the state wherein 
the second stripe image 11.sub.B obtained by arranging stripe pixels in 
the order of L.sub.1, R.sub.2, L.sub.3, R.sub.4, L.sub.5, R.sub.6, . . . 
is displayed on the entire region 41, so that the first stripe image 
11.sub.A obtained by arranging stripe pixels in the order of R.sub.1, 
L.sub.2, R.sub.3, L.sub.4, R.sub.5, L.sub.6, . . . is switched and 
displayed on the region 41 from the fourth scan line, and at the same 
time, the light-transmission portions and the light-shielding portions of 
the corresponding portion of the spatial light modulation element 2 are 
switched in synchronism with the scan lines. 
In this embodiment, a stereoscopic image can be displayed on a portion of 
the display 1, so as to display both the stereoscopic image and a 
non-stereoscopic image, and the stripe image 11 to be displayed on the 
region 41 of the display 1 and the parallax barrier pattern to be formed 
on the region 42 of the spatial light modulation element 2 are 
synchronously displayed in units of scan lines. Therefore, even when the 
observer observes a locally displayed stripe image, he or she can attain a 
stereoscopic view based on the principle of the parallax barrier method 
without any crosstalk. 
In this embodiment, the size of the display region 41 of the locally 
displayed stereoscopic image can be selected within the display screen 
size of the display 1, and the two-dimensional display position of the 
display region can also be appropriately selected within the display 
screen. 
Note that the width P of each stripe pixel, the number of stripe pixels, 
the display region of the stripe image on the display 1, and the like are 
the constituting elements of the stripe image, and the width B' of each of 
the slit portions and the light-shielding portions of the parallax barrier 
pattern, the formation region of the parallax barrier pattern on the 
spatial light modulation element 2, and the like are the constituting 
elements of the slit pattern. 
In this case, the display driving operations of the display 1 and the 
spatial light modulation element 2 may be synchronously performed in units 
of pixels like in the first embodiment. 
FIGS. 19A to 19C are explanatory views of the stereoscopic image display 
method of a stereoscopic image display apparatus according to the eighth 
embodiment of the present invention. The arrangement of the apparatus of 
this embodiment is basically same as that of the seventh embodiment. The 
difference between this embodiment and the seventh embodiment is as 
follows. That is, in this embodiment, the parallax barrier pattern is 
always formed on the display region of a two-dimensional image (non-stripe 
image), i.e., on a region other than the region 41 of the display 1. A 
case will be explained below wherein a stereoscopic image is displayed 
only on the region 41 on the display surface of the display 1 as in the 
seventh embodiment. 
The state shown in FIG. 19A will be explained below. In this embodiment, as 
shown in the left drawing of FIG. 19A, a normal two-dimensional image is 
displayed on a region from the first scan line Y1 to the third scan line 
Y3 of the display 1. At this time, as shown in the right drawing of FIG. 
19A, the stripe-shaped first parallax barrier pattern 2.sub.A (close, 
open, close, open, . . . ) is displayed on the pixels on the respective 
scan lines on the entire display surface of the spatial light modulation 
element 2 in synchronism with the scanning timings of the scan lines of 
the display 1. 
Upon scanning of the fourth scan line Y4, the display 1 displays stripe 
pixels R, L, R, L, R, L, . . . (the stripe pixels will be simply 
abbreviated as above although they are R.sub.1, L.sub.2, R.sub.3, L.sub.4, 
R.sub.5, L.sub.6, . . . in practice) in the range from the first pixel 
X.sub.1 to the sixth pixel X.sub.6, and displays an image portion, 
corresponding to the seventh pixel X.sub.7 to the 12th pixel X.sub.12, of 
the two-dimensional image in the range of these pixels. 
The spatial light modulation element 2 displays the first parallax barrier 
pattern 2.sub.A (close, open, close, open, . . . ) on all the pixels from 
the first pixel X.sub.1 to the 12th pixel X.sub.12 on the fourth scan line 
Y4 in synchronism with the timing of the corresponding scan line of the 
display 1. FIG. 19A shows the state after similar scanning/display 
operations are performed from the fifth scan line Y5 to the eighth scan 
line Y8. 
The state shown in FIG. 19B will be explained below. Upon completion of 
scanning up to the eighth scan line Y8 in FIG. 19A, the scanning operation 
is restarted from the first scan line Y1. At this time, a normal 
two-dimensional image is displayed on the display 1 in the scanning 
operation from the first scan line Y1 to the third scan line Y3 as in the 
above-mentioned operation, but the second parallax barrier pattern 2.sub.B 
(open, close, open, close, . . . ) is displayed on all the scan lines of 
the spatial light modulation element 2. Upon scanning of the fourth scan 
line Y4, the display 1 displays stripe pixels L, R, L, R, L, R, . . . (the 
stripe pixels will be simply abbreviated as above although they are 
L.sub.1, R.sub.2, L.sub.3, R.sub.4, L.sub.5, R.sub.6, . . . in practice) 
in the range from the first pixel X.sub.1 to the sixth pixel X.sub.6, and 
displays an image portion, corresponding to the seventh pixel X.sub.7 to 
the 12th pixel X.sub.12, of the two-dimensional image in the range of 
these pixels, as in the above-mentioned operation. 
The spatial light modulation element 2 displays the second parallax barrier 
pattern 2.sub.B (open, close, open, close, . . . ) on all the pixels from 
the first pixel X.sub.1 to the 12th pixel X.sub.12 on the fourth scan line 
Y4 in synchronism with the timing of the corresponding scan line of the 
display 1. FIG. 19B shows the state after similar scanning/display 
operations are performed up to the fifth scan line Y5. 
FIG. 19C shows the state upon completion of the above-mentioned 
scanning/display operations up to the last scan line Y8. 
On the region 41 for displaying a stereoscopic image, upon completion of a 
series of scanning operations (the rewrite display operations of all the 
scan lines) as in the first embodiment, the right and left parallax images 
R.sub.S and L.sub.S are displayed on all the pixels in the region 41. 
Therefore, this embodiment can realize the display operations of both a 
stereoscopic image and a non-stereoscopic image, and a high-resolution 
stereoscopic image free from crosstalk between the right and left images 
can be displayed in the stereoscopic display region 41. 
Furthermore, since the parallax barrier pattern is displayed on the entire 
surface of the spatial light modulation element 2 in this embodiment, the 
arrangement of the barrier driving circuit can be simplified as compared 
to the seventh embodiment. 
The above embodiments have exemplified the stereoscopic image display 
apparatuses based on the non-interlace driving method. However, a 
stereoscopic image display apparatus of the present invention can be 
constituted using an interlace driving method. 
FIGS. 20A to 20D are explanatory views of the stereoscopic image display 
method of a stereoscopic image display apparatus according to the ninth 
embodiment of the present invention. The left drawing of each of FIGS. 20A 
to 20D shows the display state of the display 1, and the right drawing 
thereof shows the parallax barrier pattern to be formed on the spatial 
light modulation element 2. The arrangement of this embodiment is 
basically the same as that of the sixth embodiment. The difference between 
this embodiment and the sixth embodiment is that a stereoscopic image is 
displayed using an interlace scanning method in this embodiment. Other 
arrangements are the same as those in the sixth embodiment. 
FIGS. 20A and 20D respectively show the same states as those shown in FIGS. 
16A and 16C of the sixth embodiment. FIG. 20B shows the state upon 
completion of scanning of the odd scan lines of the display 1 and the 
spatial light modulation element 2 in this embodiment, and FIG. 20C shows 
the state upon completion of scanning of two lines (scan lines Y2 and Y4) 
of the even scan lines. 
As shown in FIG. 20A, at a certain time (at the time of completion of 
scanning of the entire screen), the first stripe image 11.sub.A obtained 
by arranging stripe pixels in the order of R, L, R, L, . . . (the stripe 
pixels will be simply abbreviated as above although they are R.sub.1, 
L.sub.2, R.sub.3, L.sub.4, . . . in practice) is displayed on the entire 
surface of the display 1, and the stripe-shaped first parallax barrier 
pattern 2.sub.A (close, open, close, open, . . . ) is displayed on the 
spatial light modulation element 2. 
Then, an odd scan line, e.g., the first scan line Y1, is selected, and the 
corresponding portion of the second stripe image 11.sub.B obtained by 
arranging stripe pixels in the order of L, R, L, R, . . . (the stripe 
pixels will be simply abbreviated as above although they are L.sub.1, 
R.sub.2, L.sub.3, R.sub.4, ... in practice) is displayed on the portion of 
the first scan line Y1 on the display 1. At the same time, the 
corresponding portion of the stripe-shaped parallax barrier pattern 
2.sub.B (open, close, open, close, . . . ) is displayed on the portion of 
the first scan line Y1 of the spatial light modulation element 2. In this 
manner, the display driving operations of the display 1 and the spatial 
light modulation element 2 are synchronously performed in units of scan 
lines. FIG. 20B shows the display state at the time upon completion of 
scanning of all the odd scan lines after the above-mentioned operation is 
sequentially repeated for the scan lines. 
Subsequently, an even scan line, e.g., the second scan line Y2, is 
selected, and the corresponding portion of the second stripe image 
11.sub.B obtained by arranging stripe pixels in the order of L, R, L, R, . 
. . is displayed on the portion of the second scan line Y2 on the display 
1. At the same time, the corresponding portion of the second parallax 
barrier pattern 2.sub.B (open, close, open, close, . . . ) is displayed on 
the portion of the second scan line Y2 of the spatial light modulation 
element 2. FIG. 20C shows the display state at the time upon completion of 
scanning of the fourth scan line Y4 after the above-mentioned operation is 
sequentially repeated for even scan lines. 
FIG. 20D shows the state upon completion of the scanning/display operations 
of all the even scan lines. In this state, the display 1 displays the 
second stripe pattern 11.sub.B which complements the first stripe image 
11.sub.A shown in FIG. 20A. On the other hand, the spatial light 
modulation element 2 displays the second parallax barrier pattern 2.sub.B. 
Upon completion of a series of scanning operations (the rewrite display 
operations of all the scan lines), the right and left parallax images 
R.sub.S and L.sub.S are displayed on all the pixels of the display 1. 
At this time, since the parallax barrier pattern is displayed in 
synchronism with a stripe image in units of scan lines, even when the 
observer observes the stripe image which is being rewritten or has been 
rewritten via the parallax barrier pattern, he or she can enjoy a 
stereoscopic view based on the principle of the parallax barrier method 
without causing any crosstalk, and can observe a stereoscopic image 
displayed on all the pixels of the display 1. 
When the display operation is performed using the interlace driving method, 
odd and even scan lines can be alternately displayed in units of fields. 
For this reason, even when the display 1 and the spatial light modulation 
element 2 comprise liquid crystal elements with a slightly low display 
speed, a high-resolution stereoscopic image free from any flicker can be 
displayed. 
This display method can be applied to the method for displaying a 
stereoscopic image on a portion on the screen of the display apparatus 
described in the seventh and eighth embodiments. 
The interlace driving method can also be applied to the method of 
synchronously displaying a stripe image and a parallax barrier pattern in 
units of pixels in the first embodiment. 
FIG. 21 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the 10th embodiment of the present 
invention. FIGS. 22A and 22B are explanatory views of the stereoscopic 
image display method of this embodiment. Note that the layout of the 
display 1 and the spatial light modulation element 2 of this embodiment is 
the same as that in the sixth embodiment. This embodiment comprises the 
observation condition inputting means 9 and the parallax image source 15 
as in the first embodiment although they are not shown. In this 
embodiment, the directions of the scan lines and data lines of the display 
1 and the spatial light modulation element 2 are rotated by 90.degree. as 
compared to the above embodiments. That is, in this embodiment, the 
scanning operation is performed in the vertical direction. 
The display method will be explained below. As shown in FIG. 22A, the first 
scan line Y1 is selected at a certain time, and the display 1 displays 
stripe pixels R.sub.1 of the right parallax image R.sub.S on all the 
pixels from the first pixel X.sub.1 to the last pixel X.sub.8 on its first 
scan line Y1. At this time, as shown in FIG. 22B, the spatial light 
modulation element 2 forms a light-shielding portion from the first pixel 
X.sub.1 to the last pixel X.sub.8 on its first scan line Y1. Then, the 
second scan line Y2 is selected, and the display 1 displays stripe pixels 
L.sub.2 of the left parallax image L.sub.S on all the pixels from the 
first pixel X.sub.1 to the last pixel X.sub.8 on its second scan line Y2. 
In synchronism with this display operation, the spatial light modulation 
element 2 forms a light-transmission portion on all the pixels on it s 
second scan line Y2. 
A similar driving operation is sequentially performed to display all the 
pixels. FIGS. 22A and 22B show the state upon completion of scanning of 
the seventh scan line Y7. 
In this embodiment, as described above, since the stripe image 11.sub.A or 
11.sub.B and the parallax barrier pattern 2.sub.A or 2.sub.B are formed in 
synchronism with each other in units of scan lines Yi of the display 1 and 
the spatial light modulation element 2, the observer can observe a 
stereoscopic image free from any crosstalk. 
As can be seen from FIGS. 22A and 22B, when the scan lines are set in the 
vertical direction as in this embodiment, a stripe image portion or a 
parallax barrier pattern portion to be displayed on each scan line can be 
defined by only stripe pixels R.sub.i or L.sub.i of one of the right and 
left parallax images R.sub.S and L.sub.S, or the light-transmission 
portion or the light-shielding portion. For this reason, unlike in the 
above embodiments, stripe pixels need not be alternately arranged and 
displayed like R, L, R, L, R, L, . . . along one scan line, nor the 
light-shielding portions and the light-transmission portions need be 
alternately formed and displayed, thus simplifying the display circuit. 
In this embodiment, the display 1 and the spatial light modulation element 
2 are driven in accordance with synchronizing signals supplied from the 
image processing means 3. However, various other driving methods may be 
used. For example, the display driving circuit 4 may generate a 
synchronizing signal to determine the driving timing of the barrier 
driving circuit 5, or the Y drivers may attain synchronization. 
This embodiment adopts a driving method similar to the non-interlace 
driving method for sequentially performing scanning from the first scan 
line Y1. However, an interlace driving method for displaying odd scan 
lines, and then displaying even scan lines may be used. 
FIG. 23 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the 11th embodiment of the present 
invention. This embodiment presents a developed form of the sixth 
embodiment. That is, in this embodiment, the view point position of the 
observer is detected, and the relative positional relationship between the 
parallax barrier pattern and the stripe image to be displayed on the 
display 1 is controlled in accordance with the view point position of the 
observer, thus allowing a stereoscopic view over a broad range. 
Referring to FIG. 23, the observation condition detecting means 30 
(described above in the third embodiment) picks up an image of the 
observer using a camera, extracts the images of the eyes of the observer 
by performing image processing of the input images, and detects the view 
point position of the observer. The observation condition inputting means 
9 is used for manually inputting the view point position of the observer 
as needed. An image and barrier positions calculating means 44 calculates 
an optimal relative positional relationship between the parallax barrier 
pattern and the stripe image to be displayed on the display 1 on the basis 
of the view point position information input from the observation 
condition detecting means 30 or the observation condition inputting means 
9, and outputs a signal to a barrier position controlling circuit 45 and 
the image processing means 3. The barrier position controlling circuit 45 
controls the barrier driving circuit 5 on the basis of the input signal so 
as to form an optimal parallax barrier pattern on the spatial light 
modulation element 2. 
The spatial light modulation element 2 is driven by X drivers 81 and 82. 
The X driver 81 drives odd pixels, and the X driver 82 drives even pixels. 
The operation of this embodiment will be described below. Referring to FIG. 
23, the observation condition detecting means 30 or the observation 
condition inputting means 9 inputs the view point position information of 
the observer to the image and barrier positions calculating means 44. The 
image and barrier positions calculating means 44 calculates an optimal 
relative positional relationship between the stripe image 11 to be 
displayed on the display 1 and, for example, the light-transmission 
portions of the parallax barrier pattern to be formed on the spatial light 
modulation element 2 on the basis of the input view point position 
information, and outputs a signal to the barrier position controlling 
circuit 45 and the image processing means 3. The barrier position 
controlling circuit 45 controls the barrier driving circuit 5 on the basis 
of the input signal to form the parallax barrier pattern at an optimal 
position on the spatial light modulation element 2. 
At the same time, the image processing means 3 displays the stripe image at 
an optimal position on the display 1 on the basis of the signal input form 
the image and barrier positions calculating means 44. 
FIGS. 24A to 24C show the display state (FIG. 24A) of the display 1 when 
the display is driven by the non-interlace method, and the parallax 
barrier pattern (FIG. 24B) formed on the spatial light modulation element 
2. 
FIG. 24C shows the driving state wherein when the observer moves in the 
right-and-left direction, the view point position after the movement is 
detected, and the position of the parallax barrier pattern to be formed on 
the spatial light modulation element 2 is shifted by one pixel in the 
right-and-left direction. Note that FIGS. 24A to 24C show the display 
states at the time upon completion of scanning of the fifth scan line Y5. 
In this embodiment, the width P of each stripe pixel to be displayed on the 
display 1 is set to be equal to the one-pixel width of the display 1, and 
the width B' of the light-transmission portion or the light-shielding 
portion of the parallax barrier pattern to be formed on the spatial light 
modulation element 2 is set to be equal to the two-pixel width of the 
spatial light modulation element 2. 
FIGS. 25A and 25B are explanatory views of the movement of the parallax 
barrier pattern in correspondence with the movement of the view point 
position in this embodiment. FIGS. 25A and 25B show the relationship among 
the stripe image, the parallax barrier pattern, and the view point 
position of the observer in a certain portion along the first scan line 
Y1. 
A case will be explained below wherein the stripe image to be displayed on 
the display 1 is fixed in position, and the positions of the 
light-transmission portions of the parallax barrier pattern to be formed 
on the spatial light modulation element 2 are controlled to optimal 
positions, upon movement of the observer. As shown in FIG. 25A, the 
observer observes a right stripe pixel R.sub.3 via a light-transmission 
portion 51 with his or her eight eye A.sub.R, and observes a left stripe 
pixel L.sub.2 via the light-transmission portion 51 with his or her left 
eye A.sub.L, thus observing a stereoscopic image. 
Assume that the eyes of the observer move from this state to positions 
A'.sub.R and A'.sub.L in the right-and-left direction, as shown in FIG. 
25B. A light-transmission portion 51' of the parallax barrier pattern is 
formed on the spatial light modulation element 2 upon being moved in the 
right-and-left direction by a width Pb of one pixel of the spatial light 
modulation element 2. The driving operation of the scan line is performed 
in synchronism with the scanning operation of the display 1, as described 
in the above embodiments. With this operation, the observer observes the 
right stripe pixel R.sub.3 via the light-transmission portion 51' with his 
or her right eye A'.sub.R, and observes the left stripe pixel L.sub.2 via 
the light-transmission portion 51' with his or her left eye A'.sub.L, thus 
observing a stereoscopic image. 
At this time, the light-transmission portion or light-shielding portion of 
the parallax barrier pattern to be formed on the spatial light modulation 
element 2 is preferably constituted by a plurality of pixels of the 
spatial light modulation element 2, since the parallax barrier pattern can 
then be moved at a fine pitch. 
In contrast to the above description, when the view point position moves, 
the positions of the light-transmission portions of the parallax barrier 
pattern may remain the same, and the position of the stripe image to be 
displayed on the display 1 may be shifted in the right-and-left direction. 
At this time, the width of each stripe pixel to be displayed on the 
display 1 is preferably constituted by a plurality of pixels of the 
display 1. That is, the display width P of each stripe pixel to be 
displayed on the display 1 is set to be equal to the total width of a 
plurality of pixels of the display 1. 
As described above, in this embodiment, even when the view point of the 
observer moves, the observation condition detecting means automatically 
detects the view point position of the observer to control the display 
position of the stripe image and the formation position of the parallax 
barrier pattern, so that the right and left parallax images can always be 
normally observed from the view point position of the observer. For this 
reason, the observation range of a stereoscopic image can be broadened 
very much. That is, in this embodiment, at least one of the constituting 
elements of the stripe image and the parallax barrier pattern is 
controlled in accordance with the signal from the observation condition 
detecting means or the observation condition inputting means so as to move 
the observation range of a stereoscopic image in correspondence with the 
movement of the view point position of the observer. 
Note that the observation condition detecting means 30 may use a method for 
obtaining distance information on the basis of the principle of 
trigonometrical measurement using a plurality of cameras, and detecting 
the view point position of the observer. 
Alternatively, a magnetic field may be formed around the observer, a 
magnetic sensor may be attached to the head portion of the observer, and 
the output from this sensor may be used. In addition to the 
above-mentioned observation condition detecting means, the observer 
himself or herself may control, e.g., an adjustment switch while observing 
the displayed image. 
FIG. 26 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the 12th embodiment of the present 
invention. The arrangement of this apparatus is substantially the same as 
that of the sixth embodiment, except for the driving circuits for the 
display 1 and the spatial light modulation element 2. Note that the 
observation condition inputting means 9 and the parallax image source 15 
are not shown. This embodiment is different from the sixth embodiment in 
that two X drivers and two Y drivers are arranged for each of the display 
1 and the spatial light modulation element 2, and each display screen is 
two-divisionally driven. For example, when VGA (640.times.480 pixels) 
liquid crystal displays are used as the display 1 and the spatial light 
modulation element 2, each of these liquid crystal displays is divided 
into two portions (each having 320 scan lines) to be driven by Y drivers 
71a and 71b or 72a and 72b. In this embodiment, the non-interlace driving 
method is used, and FIGS. 27A and 27B show the display states of the 
display 1 and the spatial light modulation element 2 of this embodiment. 
At a certain scan time, the display 1 receives an image signal on the basis 
of a synchronizing signal from the image processing means 3, and displays 
a stripe image generated based on the right and left parallax images. FIG. 
27A shows the state upon completion of scanning of the second scan lines 
Ya2 and Yb2 of the Y drivers 71a and 71b. 
The display method will be described below. Assume that the first stripe 
image 11.sub.A obtained by arranging stripe pixels in the order of 
R.sub.1, L.sub.2, R.sub.3, L.sub.4, . . . is displayed on the entire 
surface of the display 1 at a certain time (at the time of completion of 
scanning of the entire screen). When first scan lines Ya1 and Yb1 of the Y 
drivers 71a and 71b are selected and scanned again, the corresponding 
portions of the second stripe image 11.sub.B obtained by arranging stripe 
pixels in the order of L.sub.1, R.sub.2, L.sub.3, R.sub.4, . . . are 
displayed on these scan lines. Subsequently, second scan lines Ya2 and Yb2 
are selected, and the corresponding portions of the second stripe image 
11.sub.B are displayed on these scan lines. FIG. 27A shows the state at 
that time. 
A parallax barrier pattern is similarly formed on the spatial light 
modulation element 2. That is, at a certain time (at the time of 
completion of scanning of the entire screen), the stripe-shaped first 
parallax barrier pattern 2.sub.A obtained by arranging the 
light-transmission portions and the light-shielding portions in the order 
of close, open, close, open, . . . is displayed on the spatial light 
modulation element 2. When first scan lines Ya1 and Yb1 of the Y drivers 
72a and 72b are selected and scanned again, the corresponding portions of 
the stripe-shaped second parallax barrier pattern 11.sub.B obtained by 
arranging the light-transmission portions and the light-shielding portions 
in the order of open, close, open, close, . . . are displayed on these 
scan lines. Subsequently, second scan lines Ya2 and Yb2 are selected and 
scanned, and the corresponding portions of the second parallax barrier 
pattern 11.sub.B are displayed on these scan lines. FIG. 27B shows the 
state at that time. 
At this time, the second scan lines Ya2 and Yb2 of the Y drivers 71a and 
71b, and 72a and 72b of the display 1 and the spatial light modulation 
element 2 are synchronously driven by the image processing means 3. That 
is, in this embodiment, four scan lines are scanned at the same time. For 
this reason, two each data lines (X drivers) are provided in 
correspondence with the Y drivers. 
As described above, when the display screens of the display 1 and the 
spatial light modulation element 2 are two-divisionally driven, the 
display operation can be attained at a doubled driving speed, and a 
stereoscopic image from which flicker noise can be further eliminated as 
compared to the sixth embodiment and the like can be displayed. 
In this embodiment, the display 1 and the spatial light modulation element 
2 are synchronously driven in units of scan lines but may be synchronously 
driven in units of pixels as in the first embodiment. 
FIGS. 28A and 28B are explanatory views of the display states of a 
stereoscopic image display apparatus according to the 13th embodiment of 
the present invention. FIGS. 28A and 28B respectively show the display 
states of the display 1 and the spatial light modulation element 2. The 
arrangement of this embodiment is basically the same as that of the first 
embodiment. However, in this embodiment, when the display 1 and the 
spatial light modulation element 2 are synchronously driven in units of 
pixels, the light-shielding portion (close) is precedently displayed 
across several pixels on the spatial light modulation element 2. 
As shown in FIG. 28A, the display 1 displays the corresponding portion of 
the first stripe image 11.sub.A obtained by arranging stripe pixels in the 
order of R.sub.1, L.sub.2, R.sub.3, L.sub.4, R.sub.5, L.sub.6, . . . (R, 
L, R, L, R, L, . . . in FIG. 28A) on the first scan line Y1. At the same 
time, as shown in FIG. 28B, the spatial light modulation element 2 
displays the corresponding portion of the first parallax barrier pattern 
2.sub.A obtained by alternately arranging the light-shielding portions and 
the light-transmission portions in the order of close, open, close, open, 
close, open, . . . on the first scan line Y1. In the case of the 
non-interlace driving method, the second scan line Y2 is selected, and the 
corresponding portions of the first stripe image 11.sub.A and the first 
parallax barrier pattern 2.sub.A are displayed as in the first scan line. 
This operation is sequentially repeated to display the first stripe image 
11.sub.A on the entire display surface. When this image is observed via 
the first parallax barrier pattern 2.sub.A, a stereoscopic image can be 
observed. 
FIGS. 28A and 28B illustrate the display state wherein the fifth scan line 
Y5 is selected before completing all the scanning operations, pixel data 
of the seventh pixel X.sub.7 is displayed on the display 1 (FIG. 28A), and 
the parallax barrier pattern is formed on the spatial light modulation 
element 2 (FIG. 28B). 
In this embodiment, at this time, as shown in FIG. 28B, the light-shielding 
portion (close) is precedently displayed across several pixels (three 
pixels, i.e., the eighth pixel X.sub.8 to the 10th pixel X.sub.10 on the 
fifth scan line Y5) preceding to the seventh pixel X.sub.7 on the fifth 
scan line Y5 of the spatial light modulation element 2, and pixel data up 
to the 10th pixel X.sub.10 on the fifth scan line Y5 of the spatial light 
modulation element 2 are displayed as a light-shielding portion. 
As described above, when the stripe image and the corresponding parallax 
barrier pattern are synchronously displayed in units of pixels, the 
light-shielding portion (close) is precedently displayed across several 
pixels (in this case, three pixels), thus further reducing crosstalk 
between the right and left stripe pixels. 
In particular, when the display 1 and the spatial light modulation element 
2 use liquid crystal panels with different characteristics, even when they 
have different driving speeds for one scan line, crosstalk between the 
right and left images can be reduced. Conversely, in terms of the driving 
operations of the liquid crystal panels, a large driving margin for 
synchronously driving the two panels can be assured. 
Of course, this method can be applied to the sixth embodiment and the like 
for synchronously performing the driving operations in units of scan 
lines, in addition to this embodiment. In this case, a light-shielding 
portion (close) can be precedently displayed across several scan lines. 
FIG. 29 is a schematic diagram showing principal part of a stereoscopic 
image display apparatus according to the 14th embodiment of the present 
invention. In the above embodiments, the spatial light modulation element 
2 on which the parallax barrier pattern is formed is arranged on the front 
side (the observer side) of the display 1 to observe a stereoscopic image. 
However, in this embodiment, the spatial light modulation element 2 is 
arranged on the rear side of the display 1 to form a slit pattern having 
predetermined light-transmission portions (slit portions) and 
light-shielding portions, and a stereoscopic image is observed by 
controlling the transmission portions of light emitted by the backlight 
(light source means) 21. 
The arrangement of this apparatus will be explained below. Let O be the 
interval (base length) between the two eyes of the observer, C be the 
observation distance, D be the interval between the display 1 and the 
spatial light modulation element 2 for forming the parallax barrier 
pattern, B.sub.ap be the width of each slit portion of the slit pattern, 
and P.sub.rea be the pixel interval (pixel width) of the stripe image to 
be displayed on the display 1. In this case, in formulas (1) and (2) 
described in the first embodiment, P.sub.rea replaces B', and B.sub.ap 
replaces P. Thus, when these parameters satisfy the following relations, a 
stereoscopic view can be attained. 
EQU D=B.sub.ap .multidot.C/(O+B.sub.ap) (5) 
EQU P.sub.rea =B.sub.ap .multidot.(C-D)/C (6) 
Note that the observation width has a finite divergence at the observation 
position in practice, and these quantities are set after they are slightly 
modified. 
The stereoscopic image display method of this embodiment will be described 
below. The stripe image 11.sub.A or 11.sub.B is formed based on images 
from the parallax image source 15 shown in FIG. 29 and is displayed on the 
display 1 by the same method as in the first embodiment. On the other 
hand, the image processing means 3 inputs pixel data of the slit pattern 
2.sub.A or 2.sub.B to a slit pattern drive circuit 46 in synchronism with 
the output stripe image data, thereby displaying the stripe-shaped slit 
pattern 2.sub.A or 2.sub.B by alternately forming light-shielding portions 
and light-transmission portions each having the slit width B.sub.ap on the 
spatial light modulation element 2. 
Light emitted by the backlight 21 is transmitted through the 
light-transmission portions of the spatial light modulation element 2, 
illuminates stripe pixels R.sub.i on the display 1, and then becomes 
incident on the right eye A.sub.R of the observer. Similarly, light 
emitted by the backlight 21 and transmitted through the light-transmission 
portions of the spatial light modulation element 2 illuminates stripe 
pixels L.sub.i on the display 1, and becomes incident on the left eye 
A.sub.L of the observer. Thus, the observer observes the corresponding 
parallax images by his or her right and left eyes, and can 
stereoscopically observe the stripe image 11. 
At this time, as the driving circuits for the display 1 and the spatial 
light modulation element 2, the circuit arrangement shown in FIG. 3 is 
used. With this arrangement, the display 1 and the spatial light 
modulation element 2 can be synchronously driven in units of pixels. In 
addition, since the stripe image and the corresponding slit pattern are 
always synchronously displayed, crosstalk between the right and left 
parallax images can be reduced. 
Of course, the synchronous driving operation in units of scan lines may be 
used in addition to the method of this embodiment, and the display methods 
described in the embodiments described so far may be used. 
FIG. 30 is a perspective view of the stereoscopic image display apparatus 
of this embodiment. In this embodiment, the display apparatus performs a 
color display operation. In order to perform a color display operation in 
this embodiment, each of stripe pixels R.sub.i and L.sub.i can be 
controlled to correspond to one color pixel. However, when a known liquid 
crystal element having a vertical stripe type color filter layout is used, 
red, green, and blue colors deviate at the observation position, resulting 
in poor color reproducibility. In view of this problem, as indicated by an 
enlarged portion 47 in FIG. 30, red (r), green (g), and blue (b) color 
filters having a horizontal stripe structure are formed on the surface of 
a transmission type liquid crystal element used as the display 1, thus 
obtaining good color reproducibility. 
FIGS. 31A and 31B are schematic views showing principal part of a 
stereoscopic image display apparatus according to the 15th embodiment of 
the present invention. In this embodiment, the apparatus is arranged by 
adding a linear Fresnel lens 48 to the above-mentioned embodiments. As 
shown in FIGS. 31A and 31B, the positional relationship between the 
display 1 and the spatial light modulation element 2 is not particularly 
limited, and the operation and the display principle of this apparatus are 
as described above. 
The arrangement of this embodiment will be described below. In the above 
embodiments, the respective elements of the display 1 and the spatial 
light modulation element 2 are associated with each other to satisfy 
formulas (1) and (2) or (5) and (6), and the pixel width of the display 1 
is different from that of the spatial light modulation element 2. 
In this embodiment, the pixel pitch is adjusted using a linear Fresnel lens 
(cylindrical Fresnel lens) having a power in only the horizontal 
direction, and the display 1 and the spatial light modulation element 2 
can use liquid crystal elements having the same specifications. Since the 
principle of stereoscopic view and the driving methods are the same as 
those in the above embodiments, a detailed description thereof will be 
omitted. 
In FIGS. 31A and 31B, the linear Fresnel lens (cylindrical Fresnel lens) 
has a power in only the horizontal direction. A case will be exemplified 
below wherein the linear Fresnel lens 48 is arranged on the front side 
(the observer side) of the spatial light modulation element 2 for forming 
the parallax barrier pattern, as shown in FIG. 31A. 
Let f be the focal length of the linear Fresnel lens 48, O be the interval 
(base length) between the two eyes of the observer, and P.sub.LCD be the 
pixel interval (pixel width) of the stripe image 11 displayed on the 
display 1 (this width is equal to that of each of the light-transmission 
portions and light-shielding portions formed on the spatial light 
modulation element 2). When the interval, d.sub.1, between the display 1 
and the spatial light modulation element 2 satisfies the following 
relation, a stereoscopic view can be obtained: 
EQU d.sub.i =P.sub.LCD /(O/f) (7) 
In this embodiment, since the display 1 and the spatial light modulation 
element 2 use identical liquid crystal elements each having a pixel size 
of 0.110 mm (horizontal).times.0.330 mm (vertical), and one color pixel 
size is set to be the width of each stripe pixel and the width of each of 
the light-transmission portion and the light-shielding portion, P.sub.LCD 
=0.110 mm. If the base length and the observation distance are 
respectively set to be O=65 mm and C=f=500 mm, a value d.sub.1 =2.5385 mm 
is obtained. Note that this value is finely adjusted in consideration of 
divergence of the observation width. 
In this embodiment, when the display 1 and the spatial light modulation 
element 2 are synchronously driven in units of pixels or scan lines, since 
the stripe image and the corresponding slit pattern can always be 
synchronously displayed at any timing, the same display method as in the 
above embodiments can be adopted, and crosstalk between the right and left 
parallax images can be reduced. 
FIGS. 32A and 32B are schematic views showing principal part of another 
arrangement of the 15th embodiment. In this modification, the linear 
Fresnel lens 48 is arranged between the display 1 and the spatial light 
modulation element 2. 
FIG. 33 shows the optical layout of this modification. The operation of 
this modification will be explained below with reference to FIG. 33. Let S 
be the distance from the principal point of the linear Fresnel lens 48 to 
the first conjugate point (where the right or left eye A.sub.R or A.sub.L 
of the observer is located), S' be the distance from the principal point 
of the linear Fresnel lens 48 to the second conjugate point, d be the 
distance from the principal point of the linear Fresnel lens 48 to the 
display surface of the display 1 (or the spatial light modulation element 
2), and d' be the distance from the principal point of the linear Fresnel 
lens 48 to the display surface of the spatial light modulation element 2 
(or the display 1). Assuming that S=C (observation distance)=500 mm, if 
d=d' is set when f=250, the display 1 and the spatial light modulation 
element 2 can be constituted by liquid crystal elements having the same 
pixel widths. 
However, the thickness of a cover glass of the liquid crystal element used 
in this modification is about 1.35 mm (including the polarizing plate), 
and the thickness of the linear Fresnel lens is 2 mm. If the refractive 
index of these elements is assumed to be 1.5, at least 2.23 mm (air 
conversion) are required as the interval between the principal point of 
the linear Fresnel lens and the display surface of the liquid crystal 
display. Thus, in this modification as well, when liquid crystal elements 
having a pixel size of 0.11 mm.times.0.33 mm are used, and C=500 mm is 
set, d=d'=2.5385/2=1.2693 mm is obtained from the required panel interval 
d.sub.1 =2.5385 mm. As a result, an equal-magnification layout cannot be 
adopted. 
In this case, since the conditions that d.sub.1 =d.rarw.d', d'=S'/S d and 
1/f=1/S+1/S' are satisfied, the equation that 
##EQU1## 
is obtained. 
Namely, by the conditions that S=500 mm, d=2.23 mm, S'=69.5 mm and d'=0.31 
mm, the condition that f=60.76 mm can be used as the focal length of a 
Fresnel lens. 
Since this modification uses the above-mentioned arrangement, the display 1 
and the spatial light modulation element 2 can use liquid crystal elements 
having the same specifications, and the cost of the stereoscopic image 
display apparatus can be reduced. 
Furthermore, in this case, as compared to the case wherein the Fresnel lens 
is arranged on the front surface of the apparatus, as shown in FIGS. 31A 
and 31B, dazzling or the like of the Fresnel lens can be eliminated.