Image display device with plural planar microlens arrays

A reflective or transmissive image display device having a light-transmissive panel to which illuminating light for illuminating pixels is applied. The light-transmissive panel has laminated glass substrates having respective first and second planar microlens arrays. The glass substrates have their thicknesses adjusted by grinding to equalize focal lengths and other parameters of the first and second planar microlens arrays to preset values. Lenses of the first and second planar microlens arrays are formed by etching recesses in fire-finished surfaces of the glass substrates and filling the recesses with a synthetic resin having a high refractive index.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a reflective or transmissive image display 
device for use in a liquid-crystal projector or a projection television 
set (PTV) for displaying television or computer images at an enlarged 
scale. 
2. Description of the Prior Art 
More and more projectors which employ liquid crystal display devices 
capable of increasing image brightness depending on the brightness of 
illuminating light sources are finding use in place of projectors which 
employ cathode-ray tubes (CRTs). 
Liquid crystal display devices are roughly classified into reflective and 
transmissive liquid crystal display devices. In the transmissive liquid 
crystal display device, illuminating light is applied to a liquid crystal 
layer on which an image is formed, and the illuminating light which has 
passed through the liquid crystal layer is projected onto a projection 
screen by an optical system. In the reflective liquid crystal display 
device, illuminating light is applied to a liquid crystal layer on which 
an image is formed, and the illuminating light which has been reflected by 
the liquid crystal layer is projected onto a projection screen by an 
optical system. 
A color projector using such reflective liquid crystal display devices will 
be described below with reference to FIG. 11 of the accompanying drawings. 
As shown in FIG. 11, illuminating white light emitted from a white light 
source 100 is applied through a beam splitter 101 to a dichroic prism 102, 
which divides the white light into red light, blue light, and green light 
that are applied to corresponding reflective liquid crystal display 
devices 103. Images displayed by respective CRTs 104 are formed on the 
respective reflective liquid crystal display devices 103, and read as 
reflections of the applied red light, blue light, and green light. The 
read light passes through the beam splitter 101, and is projected as a 
combined image of the three colors onto a projection screen 105. 
As shown in FIG. 12 of the accompanying drawings, each of the reflective 
liquid crystal display devices 103 comprises a pair of glass substrates 
111, 118 with transparent electrodes 112, 117 disposed respectively on 
their confronting surfaces. A photoconductor layer 113 of Si, CdS, or the 
like, a light shield layer 114, and a mirror layer 115 are successively 
deposited on the transparent layer 112. A liquid crystal layer 116 is 
sealed between the transparent layer 117 and the mirror layer 115, thereby 
assembling a liquid crystal display cell as shown in FIG. 12. A voltage is 
applied between the transparent electrodes 112, 117. 
The image displayed by the CRT 104 is focused onto the photoconductor layer 
113 through a focusing lens. 
Since the resistance of the photoconductor layer 113 varies depending on 
the intensity of the light of the displayed image, an electric field 
applied to the liquid crystal layer 116 also varies depending on the 
intensity of the light of the displayed image. When illuminating light is 
applied from the glass substrate 1 18 to the liquid crystal layer 116, an 
image written in the liquid crystal layer 116 by the focused CRT image is 
read as reflections of the applied illuminating light. 
The color projector shown in FIGS. 11 and 12 requires the three sets of 
liquid crystal display devices 103 and CRTs 104 corresponding to the three 
primaries, and is necessarily large in size. 
If a color projector has only one liquid crystal display device 103, then 
the color projector may be reduced in size. One conventional color 
projector with a single liquid crystal display device uses a mosaic 
three-primary color filter. However, this conventional color projector 
utilizes only one-third of the illuminating light. Japanese laid-open 
patent publication No. 4-60538 discloses a color projector which solves 
such a problem. 
According to Japanese laid-open patent publication No. 4-60538, it is 
proposed to reduce the size of the color projector without reducing the 
brightness of illuminating light, using only one liquid crystal display 
device. In the disclosed color projector, as shown in FIGS. 13 and 14 of 
the accompanying drawings, illuminating light emitted from a white light 
source 150 is divided by dichroic mirrors 151 into light rays of three 
primaries, red (R), blue (B), and green (G), which are applied to a liquid 
crystal display device 152 at different angles thereto. Light emitted from 
the liquid crystal display device 152 is projected through a field lens 
153 and a projection lens 154 onto a projection screen 155. As shown in 
FIG. 14, the liquid crystal display device 152 comprises a pair of glass 
substrates 171, 172 with scanning and signal electrodes 171a, 172a mounted 
on respective confronting surfaces thereof. A liquid crystal layer 174 is 
filled in a gap which is defined between the glass substrates 171, 172 by 
a spacer 173. A planar microlens array 175 is joined to a surface of the 
glass substrate 171 to which the three-primary light rays are applied. The 
planar microlens array 175 serves to converge the three-primary light rays 
onto the signal electrodes 172a (pixel openings). 
If the liquid crystal display device shown in FIG. 14 is directly used as a 
reflective liquid crystal display device, then reflected light does not 
pass through the centers of the lenses of the planar microlens array 175, 
as shown in FIG. 15 of the accompanying drawings, so that the illuminating 
light cannot effectively be utilized. 
The lenses and pixels may be arrayed as shown in FIG. 17 of the 
accompanying drawings for effective utilization of the illuminating light. 
With the lenses and pixels thus arrayed, the reflected light passes 
through the centers of the lenses of the planar microlens array 175 as 
shown in FIG. 18 of the accompanying drawings. 
However, as can be seen from FIG. 17, in order for the reflected light to 
pass through the centers of the lenses, pixel electrodes cannot be arrayed 
linearly, but must be arrayed in an irregular pattern, which imposes undue 
limitations on the design of other components, resulting in disadvantages 
in total design. 
The planar microlens array 175 which is employed in the transmissive liquid 
crystal display device shown in FIGS. 13 and 14 allows almost all 
illuminating light to pass therethrough. Therefore, it can increase the 
brightness of images projected onto the projection screen 155. However, 
because the illuminating light which leaves the liquid crystal display 15 
device 152 spreads through a large angle, it is necessary that the 
projection lens 154 have a large diameter, as shown in FIG. 16 of the 
accompanying drawings. As a consequence, the entire optical system of the 
color projector is large in size. 
Proposals for reducing the diameter of the projection lens used in 
combination with the planar microlens array are disclosed in Japanese 
laid-open patent publications Nos. 5-341283and 7-181487. According to the 
disclosure of Japanese laid-open patent publication No. 5-341283, as shown 
in FIG. 19 of the accompanying drawings, a microlens array has two lens 
arrays 175a, 175b on opposite surfaces of a single glass substrate. The 
lens array 175a serves to converge illuminating light onto pixel openings, 
whereas the lens array 175b serves to make principal rays of exiting light 
parallel to the optical axis thereof. Japanese laid-open patent 
publication No. 7-181487 reveals two microlens arrays joined respectively 
to opposite surfaces of a single glass substrate. 
If the double-sided microlens array shown in FIG. 19 is incorporated in the 
optical system shown in FIGS. 13 and 14, then it is necessary that the 
thickness of the glass substrate 171 be set to such a value as to cause 
principal arrays of the colors R, B, which are inclined at certain 
respective angles to the optical axis, to be applied to pixel electrodes 
172a corresponding to the colors R, B on the liquid crystal panel. In many 
cases, pixel pitches are given by liquid crystal panels that are used, and 
angles at which the light rays of R, G, B are inclined are given by the 
aperture of the projection lens and the layout of the illuminating optical 
system, after which the thickness of the glass substrate 171 is determined 
based on the pixel pitch and the angles. Stated otherwise, the glass 
substrate 171 may have any of various thicknesses depending on the liquid 
crystal panel and the illuminating optical system which are used. 
The double-sided microlens array shown in FIG. 19 may be fabricated by a 
process shown in FIG. 20 of the accompanying drawings. According to the 
illustrated process, a mask 163 is placed over one side of a glass 
substrate 175 (such as of #7059 or #1737 manufactured by Corning 
Incorporated or NA45 or NA35 manufactured by NH Technoglass Co. Ltd.), and 
the glass substrate 175 is etched by isotropic etching to form 
substantially hemispherical recesses 164 therein. Then, the recesses 164 
are filled with a synthetic resin having a high refractive index, 
producing a microlens array 175a as shown in FIG. 21 of the accompanying 
drawings. Thereafter, the glass substrate 175 is ground to a desired 
thickness by a grinding wheel on its surface opposite to the microlens 
array 175a. The ground surface is then etched by isotropic etching to form 
substantially hemispherical recesses therein, which are then filled with a 
synthetic resin having a high refractive index, producing a microlens 
array 175b (see FIG. 19). 
If the ground surface of the glass substrate 175 is not sufficiently smooth 
but contains a minute flaw, then an etched recess 164 tends to be 
distorted in shape, as shown in FIG. 22 of the accompanying drawings. The 
double-sided microlens array with such a distortion has a poor light 
converging capability. Though the finished glass substrate needs to have 
any of various thicknesses, as described above, commercially available 
glass substrates in reality have only certain thicknesses such as of 1.1 
mm and 0.7 mm. To process such a commercially available glass substrate 
into a desired thickness, it is often necessary to grind the glass 
substrate to a considerable extent, possibly with the need to adjust its 
thickness according to a rough grinding process, known as lapping, using a 
loose abrasive material and a hard pad. After the glass substrate has been 
lapped, it is polished to such an accurate surface finish that any 
recesses etched in the polished surface will not be distorted. This 
grinding process is, however, so complex that the manufacturing cost of 
the double-sided microlens array is high. 
The same problem also arises if both surfaces of the glass substrate are 
initially ground and polished to a desired thickness. As a result the 
double-sided microlens array shown in FIG. 19 is actually very expensive 
to manufacture. 
The structure disclosed in Japanese laid-open patent publication No. 
7-181487, i.e., the microlens array assembly which has two microlens 
arrays joined respectively to opposite surfaces of a single glass 
substrate, is also disadvantageous in that its overall thickness is unduly 
large. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an image 
display device of the reflective or transmissive type which includes a 
planar microlens array to achieve a desired degree of brightness and 
reduce the aperture of a projection lens for use therewith. 
According to an aspect of the present invention, there is provided a 
reflective image display device for controlling a reflectivity with 
respect to illuminating light applied to pixels depending on an image to 
be displayed, comprising reflecting means for reflecting illuminating 
light toward a readout side thereof, and a light-transmissive panel 
positioned on the readout side of the reflecting means, the 
light-transmissive panel comprising a first planar microlens array having 
lenses for converging the illuminating light and a second planar microlens 
array having lenses for refracting the illuminating light, which has 
passed through the first planar microlens array, so as to be applied 
substantially perpendicularly to the reflecting means. 
The light-transmissive panel may comprise a first substrate with the first 
planar microlens array disposed thereon and a second substrate with the 
second planar microlens array disposed thereon, the first substrate and 
the second substrate being laminated to each other. Alternatively, the 
light-transmissive panel may comprise a substrate with the first and 
second planar microlens arrays disposed on respective opposite surfaces 
thereof. 
The reflective image display device may further comprise a pair of panels, 
at least one of which is the light-transmissive panel, and a liquid 
crystal layer disposed between the panels, the reflecting means comprising 
a reflecting surface disposed on a surface of the liquid crystal layer 
remotely from the light-transmissive panel, for reflecting the 
illuminating light applied to the liquid crystal layer thereby to read an 
image displayed by the liquid crystal layer as reflected light. 
The reflecting means may comprise a micromirror array (a digital mirror 
device) having minute mirrors corresponding respectively to the pixels, 
the light-transmissive panel being disposed on the readout side of the 
micromirror array, and means for controlling angles of the minute mirrors 
respectively with respect to the pixels, for thereby controlling a pattern 
of reflections of the illuminating light applied to the micromirror array 
to display the pattern of reflections as an image. 
According to the present invention, there is also provided a transmissive 
image display device comprising a pair of light-transmissive panels, a 
liquid crystal layer disposed between the light-transmissive panels, and a 
plurality of pixel electrodes disposed adjacent to the liquid crystal 
layer and defining pixel openings, respectively, one of the 
light-transmissive panels being disposed on a readout side of the liquid 
crystal layer and comprising a first microlens array and a second 
microlens array which are laminated to each other, the first microlens 
array being positioned remotely from the liquid crystal layer and having 
lenses on a first surface thereof for receiving rays of illuminating light 
applied thereto in respective different wavelength ranges and converging 
the rays of illuminating light onto the pixel electrodes, the second 
microlens array being positioned closer to the liquid crystal layer and 
having lenses on a first surface thereof for refracting principal rays of 
illuminating light substantially parallel to optical axes thereof for 
passage through the pixel openings, each of the first and second planar 
microlens arrays having a second surface opposite to the first surface 
thereof which is ground to adjust a thickness thereof, the first surface 
of the first planar microlens array being joined to the second surface of 
the second planar microlens array. 
The rays of illuminating light applied in the respective different 
wavelength ranges may comprise rays of illuminating light in primary 
colors, the pixel electrodes being linearly arrayed in a repetitive 
pattern and divided into groups each comprising pixel electrodes 
corresponding respectively to the three primaries, the pixel electrodes in 
each of the groups having respective centers disposed in a region of one 
of the lenses. 
Each of the first microlens array and the second microlens array comprises 
a glass substrate having a fire-finished surface etched to define recesses 
therein, the recesses being filled with a synthetic resin having a high 
refractive index thereby to form the lenses. 
The above and further objects, details and advantages of the present 
invention will become apparent from the following detailed description of 
preferred embodiments thereof, when read in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show a reflective liquid crystal display device as an image 
display device according to a first embodiment of the present invention. 
As shown in FIGS. 1 and 2, the reflective liquid crystal display device, 
generally designated by the reference numeral 1, comprises a pair of two 
light-transmissive panels 2, 3, a pair of transparent electrodes 2a, 3a 
disposed on respective confronting surfaces of the light-transmissive 
panels 2, 3, a photoconductor layer 4 disposed on the transparent 
electrode 3a, a light shield layer 5 disposed on the photoconductor layer 
4, a reflective film 6 disposed on the light shield layer 5, and a liquid 
crystal layer 7 filled in a gap between the reflective film 6 and the 
light-transmissive panel 2. Pixel electrodes 8 are disposed on the surface 
of the reflective film 6 which is held in contact with the liquid crystal 
layer 7. 
According to the first embodiment, the light-transmissive panel 2 comprises 
first and second planar microlens arrays 11, 12 that are laminated to each 
other. The first planar microlens array 11, which is positioned remotely 
from the liquid crystal layer 7, has lenses 15 that are formed by filling 
a synthetic resin having a high refractive index (1.58 to 1.63) in 
respective recesses 14 defined in one surface of a glass substrate 13 
which is held against the second planar microlens array 12. The lenses 15 
serve to converge light that is applied to the first planar microlens 
array 11. The second planar microlens array 12, which is positioned closer 
to the liquid crystal layer 7, has lenses 18 that are formed by filling a 
synthetic resin having a high refractive index (1.58 to 1.63) in 
respective recesses 17 defined in one surface of a glass substrate 16 
which is held against the transparent electrode 2a. The lenses 18 serve to 
refract the light that has passed through the lenses 15 of the first 
planar microlens array 11 so as to be applied perpendicularly to the 
reflective film 6. 
The lenses 15, 18 are aligned with each other such that they have common 
optical axes. As shown in FIG. 2, three pixel electrodes 8, which serve as 
a triad, have respective centers positioned respectively at the equally 
spaced vertexes of a triangle within the region of each of the lenses 15, 
18, which have a hexagonal profile. According to the pixel electrode 
pattern shown in FIG. 2, the centers of pixels of red (R), blue (B), green 
(G) are linearly arrayed across a plurality of lens regions. 
According to a first alternative shown in FIG. 3, pixels of red (R), blue 
(B), green (G) are linearly arrayed within the hexagonal region of each of 
the lenses 15, 18. FIG. 4 shows a second alternative in which each of the 
lenses 15, 18 has a rectangular profile and pixels of red (R), blue (B), 
green (G) are linearly arrayed within the rectangular region of each of 
the lenses 15, 18. Further alternatively, each of the lenses 15, 18 may 
have a circular profile, an elliptical profile, an oval profile, or the 
like. 
The glass substrates 13, 16 have their thicknesses adjusted by grinding to 
equalize focal lengths and other parameters of the planar microlens arrays 
11, 12 to preset values. 
The lenses 15, 18 of the planar microlens arrays 11, 12 are fabricated as 
follows: Smooth surfaces of the glass substrates 13, 16 which have not 
been ground are etched to form the recesses 14, 17. Then, a synthetic 
resin having a high refractive index are filled in the recesses 14, 17, 
forming the lenses 15, 18. Since the smooth surfaces of the glass 
substrates 13, 16 are etched, the etchant does not flow along minute flaws 
which would otherwise be produced by a grinding process. As a consequence, 
the recesses 14, 17 that are formed by the etching process have a shape 
that is not distorted when viewed in plan. The other surfaces of the glass 
substrates 13, 16 which have been ground contain minute flaws. Such minute 
flaws are filled up with an adhesive which comprises a synthetic resin 
having high refractive index, and hence will not pose any significant 
optical problems. 
An image displayed on a CRT that is positioned adjacent to the reflective 
liquid crystal display device 1 is applied to the reflective liquid 
crystal display device 1, and converted by the photoconductor layer 4 into 
electric charges that form the same image as the image displayed on the 
CRT on the liquid crystal layer 7. 
Rays of illuminating light that have been divided into three primaries are 
applied to each of the lenses 15 at respective different angles, as shown 
in FIG. 5. The rays of illuminating light are converged by the lens 15, 
and then refracted by the lens 18 so as to be applied perpendicularly to 
the reflective film 6. Readout light which is reflected by the reflective 
film 6 as a result of the application of the rays of illuminating light to 
the reflective film 6 travels back along the same path as the path of the 
rays of illuminating light, and exits from the reflective liquid crystal 
display device 1. 
Therefore, when the illuminating light is applied through the center of the 
lens 15, the reflected light which is produced by the illuminating light 
exits through the center of the lens 15. The illuminating light is thus 
effectively utilized. 
FIG. 6 shows a reflective liquid crystal display device according to a 
first modification which includes a modified microlens array in place of 
the microlens array of the reflective image display device shown in FIG. 
1. According to the first modification, a light-transmissive panel 2' 
comprises a single planar microlens array. The planar microlens array 
comprises a glass substrate 20 having recesses 21, 22 defined in opposite 
surfaces thereof and filled with a synthetic resin having a high 
refractive index (1.58 to 1.63), forming lenses 23, 24. The reflective 
liquid crystal display device shown in FIG. 6 operates in the same manner 
as the reflective liquid crystal display device shown in FIG. 1. 
FIG. 7 shows a reflective image display device according to a second 
modification which includes a micromirror array (digital mirror device) in 
place of the liquid crystal layer of the reflective image display device 
according to the first modification. 
According to the second modification, an Si substrate 30 is etched to leave 
a portion thereof as a micromirror 31. Specifically, a rear surface of the 
Si substrate 30 which faces the glass substrate 20 (see also FIG. 6) is 
etched by isotropic etching to form the micromirror 31 which is partially 
joined to the Si substrate 30. A micromirror actuating system 32 is 
disposed on the etched rear surface of the Si substrate 30 for tilting the 
micromirror 31. 
The glass substrate 20 is mounted on the etched rear surface of the Si 
substrate 30 by a spacer 33 which is interposed between the glass 
substrate 20 and the Si substrate 30. The glass substrate 20 has lenses 
23, 24 on their opposite surfaces which are made of a synthetic resin 
having a high refractive index. A space 34 for the micromirror 31 to be 
able to be tilted therein is defined between the glass substrate 20 and 
the Si substrate 30. 
When the micromirror 31 is not tilted, reflected light is returned, 
substantially 100%, from the reflective image display device to a 
projection screen. When the micromirror 31 is tilted, since reflected 
light is also tilted with respect to the reflective image display device, 
it is vignetted by a projection lens after having passed through the 
lenses 23, 24, so that the intensity of light on the projection screen is 
reduced. 
An electric drive (video) signal is applied to the micromirror actuating 
system 32, which tilts the micromirror 31 to a degree depending on the 
electric drive signal. In this manner, an image represented by the 
electric drive signal can be displayed on the projection screen by the 
reflective image display device. 
The lenses of the planar microlens array or arrays described above may be 
fabricated as lenses whose refractive index gradually varies, by an ion 
exchange process, rather than the above process of filling a synthetic 
resin having a high refractive index in recesses defined in a glass 
substrate by etching. 
The reflective image display device shown in FIG. 6 is used in a 
single-panel projector. However, the reflective image display device 
according to the first embodiment may be applicable to any of various 
projectors. 
With the first embodiment, as described above, the light-transmissive panel 
on the readout side of the two light-transmissive panels which hold the 
liquid crystal layer therebetween has the first and second planar 
microlens arrays that are laminated to each other, and the first planar 
microlens array has lenses for converging illuminating light and the 
second planar microlens array has lenses for refracting the illuminating 
light, which has passed through the first planar microlens array, so as to 
be applied perpendicularly to the reflective film. Therefore, it is 
possible to converge the illuminating light onto the pixel electrodes, and 
to read the reflected light that has passed through the same path as the 
illuminating light. 
The lenses of the planar microlens arrays are fabricated by etching the 
recesses in the smooth surfaces of the glass substrates which are not 
ground and filling a synthetic resin having a high refractive index in the 
recesses. Since the smooth surfaces of the glass substrates can uniformly 
be etched, the microlens arrays have excellent optical properties. 
With the first and second modifications, the light-transmissive panel on 
the readout side of the two light-transmissive panels which hold the 
liquid crystal layer or the micromirror array therebetween has the planar 
microlens array, and the planar microlens array has lenses on opposite 
surfaces of the glass substrate. The lenses positioned remotely from the 
liquid crystal layer or the micromirror array serves to converge 
illuminating light and the lenses positioned closer to the liquid crystal 
layer or the micromirror array serves to refract the illuminating light so 
as to be applied perpendicularly to the reflective film. The first and 
second modifications thus offer the same advantages as the first 
embodiment. 
Since the lenses of the planar microlens array are formed on the opposite 
surfaces of the single glass substrate in the first or second 
modification, the total number of parts used is reduced. 
An image display device (transmissive liquid crystal display device) 
according to a second embodiment of the present invention will be 
described below. 
FIG. 8 shows in cross section the transmissive liquid crystal display 
device according to the second embodiment of the present invention. As 
shown in FIG. 8, the transmissive liquid crystal display device, generally 
designated by the reference numeral 201, has a liquid crystal layer 205 
filled in a gap 204 defined between light-transmissive panels 202, 203. 
Specifically, the light-transmissive panel 202 which is positioned for the 
application of illuminating light thereto comprises first and second 
planar microlens arrays 206, 207 that are laminated to each other. A black 
matrix layer of Cr or the like and a transparent conductive film of ITO or 
the like are formed on the surface of the second planar microlens array 
207 which confronts the light-transmissive panel 203, and an alignment 
film is formed thereon. TFT5 (thin-film transistors) and pixel electrodes 
203a are formed on the surface of the light-transmissive panel 203 which 
faces the light-transmissive panel 202. These light-transmissive panels 
202, 203 are combined into a cell, and the liquid crystal layer 205 is 
introduced into the gap 204, thereby completing the transmissive liquid 
crystal display device 201. 
The first planar microlens array 206 positioned remotely from the liquid 
crystal layer 205 comprises a glass substrate 208 having recesses 209 
etched in a surface thereof, which faces the second planar microlens array 
206, and filled with a synthetic resin having a high refractive index, 
forming lenses 210. The second planar microlens array 206 positioned 
closer to the liquid crystal layer 205 also comprises a glass substrate 
207 having recesses 212 etched in a surface thereof, which faces the 
liquid crystal layer 205, and filled with a synthetic resin having a high 
refractive index, forming lenses 213. 
The synthetic resin having a high refractive index should be selected to 
clear the weather resistance of a general home electric appliance level 
and also to withstand temperatures, ranging from about 150 to 200.degree. 
C., of a liquid crystal display device fabrication process, e.g., steps of 
forming the transparent conductive film, forming the alignment film, and 
combining the light-transmissive panels into a cell. 
As with the first embodiment, the lenses 210, 213 of the first and second 
planar microlens arrays 206, 207 are aligned with each other, and three 
pixel electrodes 203a, which serve as a triad, have respective centers 
positioned respectively at the equally spaced vertexes of a triangle 
within the region of each of the lenses 210, 213, as shown in FIG. 2. 
According to the pixel electrode pattern shown in FIG. 2, the centers of 
pixels of red (R), blue (B), green (G) are linearly arrayed across a 
plurality of hexagonal lens regions., Furthermore, as with the first 
embodiment, pixels of red (R), blue (B), green (G) may be linearly arrayed 
within the hexagonal region of each of the lenses 210, 213. Alternatively, 
each of the lenses 210, 213 may have a rectangular profile and pixels of 
red (R), blue (B), green (G) may be linearly arrayed within the 
rectangular region of each of the lenses 210, 213, as shown in FIG. 4. 
Further alternatively, each of the lenses 210, 213 may have a circular 
profile, an elliptical profile, an oval profile, or the like. 
The glass substrates 208, 211 have their thicknesses adjusted by grinding 
to equalize focal lengths and other parameters of the planar microlens 
arrays 206, 207 to preset values. 
The lenses 210, 213 of the planar microlens arrays 206, 207 are fabricated 
as follows: Fire-finished (smooth) surfaces of the glass substrates 208, 
211 which have not been ground are etched to form the recesses 209, 212. 
Then, a synthetic resin having a high refractive index is filled in the 
recesses 209, 212, forming the lenses 210, 213. 
If outer peripheral grooves are defined by etching in the glass substrates 
208, 211 at the same time that the recesses 209, 212 are formed, then an 
excessive amount of the synthetic resin supplied to the recesses 209, 212 
will be collected by those outer peripheral grooves, leaving almost no 
excessive resin layer on the lenses 210, 213. Therefore, the surfaces of 
the lenses 210, 213 are made much flatter than the conventional 
double-layer planar microlens array structure. The formation of these 
outer peripheral grooves is highly effective in fabricating liquid crystal 
display devices of high quality. 
Since the fire-finished (smooth) surfaces of the glass substrates 208, 211 
are etched to form the recesses 209, 212, the recesses 209, 212 are shaped 
exactly complementarily to the mask openings. However, the surfaces of the 
glass substrates 208, 211 which are not etched are ground and hence suffer 
minute flaws (surface irregularities) 214 as shown in FIG. 9. When each of 
the recesses 209 is filled with the synthetic resin having a high 
refractive index, the synthetic resin also fills up those minute flaws, 
making them invisible to the extent that is permissible in the user of 
liquid crystal projectors. Therefore, the surfaces of the glass substrates 
208, 211 which are not etched may be ground to an inexpensive grinding 
level that is much lower than the surface finish level of the other 
surfaces which are etched. 
Specific dimensions of examples of the transmissive liquid crystal display 
device according to the second embodiment will be described below. 
Example 1 
LCD pixel pitch: 30.times.90 .mu.m (90.times.90 .mu.m for three pixels of 
R, G, B); 
Number of LCD pixels: 2400.times.600 (arranged in a square matrix); 
Effective LCD area: 72.times.54 mm; 
Microlens pixel pitch: 90.times.90 .mu.m (square dense array); 
Glass substrate (208, 211): alkali-free glass, n=1.51; 
Glass substrate (208) thickness: 0.7 mm; 
Glass substrate (211) thickness: 0.66 mm; 
Radius of curvature of the etched recesses: 66 .mu.m (for both the first 
and second lenses); 
Refractive index of the synthetic resin: n=1.66 (for both the first and 
second lenses); and Focal length of the microlenses: f=440 (for both the 
first and second lenses). 
Example 2 
LCD pixel pitch: 20.times.60 .mu.m (60.times.60 .mu.m for three pixels of 
R, G, B); 
Number of LCD pixels: 2400.times.600 (arranged in a square matrix); 
Effective LCD area: 48.times.36 mm; 
Microlens pixel pitch: 60.times.60 .mu.m (square dense array); 
Glass substrate (208, 211): alkali-free glass, n=1.51; 
Glass substrate (208) thickness: 0.7 mm; 
Glass substrate (211) thickness: 0.44 mm; 
Radius of curvature of the etched recesses: 44 .mu.m (for both the first 
and second lenses); 
Refractive index of the synthetic resin: n=1.66 (for both the first and 
second lenses); and 
Focal length of the microlenses: f=296 (for both the first and second 
lenses). 
With the second embodiment, as described above, the light-transmissive 
panel to which the illuminating light is applied has the first and second 
planar microlens arrays that are laminated to each other, and the first 
planar microlens array which is positioned remotely from the liquid 
crystal layer serves to converge illuminating light onto the pixels and 
the second planar microlens array which is positioned closer to the liquid 
crystal layer serves to direct the principal arrays of light substantially 
parallel to the optical axis thereof. Therefore, it is possible to 
effectively utilize the illuminating light and reduce the diameter of the 
projection lens. It is also possible to adjust the substrate thickness 
between the first and second microlens arrays easily to a value for better 
mass-production. As a result, a low-cost double-layer microlens array 
structure can be achieved. 
A transmissive liquid crystal display device for use in a single-panel 
color projector, where light rays of three primaries are applied at 
different angles, requires that the illuminating light be applied at an 
angle to the optical axis, and hence necessarily results in a large angle 
through which light leaving the transmissive liquid crystal display device 
spreads. However, as shown in FIG. 10, the transmissive liquid crystal 
display device according to the second embodiment causes light rays of R, 
G, B to converge at one point (shown as being separate points in FIG. 10 
for illustrative purpose), and can reduce the diameter of the projection 
lens and is highly effective in projector use. 
In the second embodiment, the fire-finished surfaces of the glass 
substrates are etched to form recesses and the recesses are filled with a 
synthetic resin having a high refractive index, forming the lenses. 
Furthermore, the surface of the first planar microlens array which has the 
lenses and the surface of the second planar microlens array which has been 
ground are joined to each other. These features are also applicable to the 
reflective image display device according 10 to the first embodiment of 
the present invention. 
In a functional equivalent to the first and second embodiments, recesses 
are not defined in the fire-finished surface of the glass substrate. 
Rather, a material 303' of synthetic resin is applied over a concaved 
surface of a stamper 311 as shown in FIG. 23, and then the microlens array 
is created by molding the resin layer under pressure due to a glass 
substrate 302 H pressurizing the stamper 311 to form symmetrically 
opposite to the situation illustrated in FIGS. 1, 5 and 6 (or as shown in 
FIG. 24, so as to protrude each microlens convexly away from the surface 
of the glass substrate 302). Conversely, the synthetic resin can be 
firstly applied to the glass substrate 302 and then stamper 311 placed 
thereon to pressurize and form the microlens array. In any case, a sheet 
of cover-glass 304 is then applied on the convex surface of the glass 20 
substrate 302 through a layer 305 of synthetic resin of a low refractive 
index (1.45 to 1.53) therebetween. The resultant microlens array (or a 
pair thereof) includes a plurality of microlenses convexly away from the 
glass substrate as oppositely to those of FIGS. 1, 5 and 6 but 
functionally equivalent. 
Although there have been described what are at present considered to be the 
preferred embodiments of the invention, it will be understood that the 
invention may be embodied in other specific forms without departing from 
the essential characteristics thereof. The present embodiments are 
therefore to be considered in all respects as illustrative, and not 
restrictive. The scope of the invention is indicated by the appended 
claims rather than by the foregoing description.