Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2001-03-26
2003-08-12
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
Reexamination Certificate
active
06606198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a lens array used in, for instance, a solid-state imaging element or a panel display element. The present invention further relates to a solid-state imaging element and a panel display element, each of which is provided with a lens array.
2. Related Background Art
The following description will depict a typical conventional solid-state imaging element.
FIG. 6
is a cross-sectional view illustrating a schematic configuration of a typical solid-state imaging element.
Generally, a solid-state imaging element includes, as shown in
FIG. 6
, an n-type semiconductor substrate
312
, a p-type well layer
311
, light receiving sections
310
, charge transfer sections
309
, a film
307
made of either silicon oxide or silicon nitride, polysilicon electrodes
308
, metal light-shielding layers
306
, an element-surface protective layer
305
, a flattening film
304
, a color filter layer
303
, an intermediate transparent film
302
, and a lens array (on-chip lens)
301
. Incidentally, the color filter layer
303
is unnecessary in the case of a three-plate-type imaging element or a monochrome imaging element, or in the case where incident light has already been subjected to color segmentation by another wavelength selecting means.
In a typical solid-state imaging element, light is received by only the light receiving sections
310
, while light incident on the other parts makes no contribution to sensitivity. In view of this, a method has been well known, as one of techniques for providing higher sensitivity, in which a lens array
301
is formed on the light receiving sections
310
to condense beams of light and direct them to the light receiving sections
310
.
Lenses of the lens array
301
are disposed at positions corresponding to the light receiving sections
310
, respectively, and by utilizing the light collecting effect of each lens, the light entering the same is efficiently guided toward each light receiving section
310
.
FIGS. 7A and 7B
illustrate a configuration of a conventional lens array.
FIG. 7A
is a plan view of the lens array
301
viewed from above, and
FIG. 7B
is a cross-sectional view taken on line VIIB—VIIB in
FIG. 7A
, viewed from the arrow direction. A region corresponding to one pixel (hereinafter occasionally referred to as a “pixel region”) is a region defined by vertical sides
355
and horizontal sides
354
. The lens
301
is provided substantially at the center of the foregoing region to contribute to the improvement in sensitivity. Here, spaces
353
are provided between adjacent lenses from the viewpoint of manufacture. Incidentally, though only four pixels are shown in
FIGS. 7A and 7B
for simplification of the drawings, predetermined numbers of pixels shown in
FIG. 7A
actually are aligned in the vertical and horizontal directions, respectively.
In the foregoing lens array, each lens is substantially round or elliptic in planar shape and has a diameter not exceeding a length of one side of the pixel-corresponding region. Therefore, the spaces
353
produced in the manufacturing process are present in each of the lens-alignment directions. Further, in each tetragonal pixel region, there also are spaces at corners where the lens
301
is not formed. Light incident on these portions hardly enters the light receiving sections, hence making substantially no contribution to the sensitivity.
Likewise, a lens array having spaces as shown in
FIGS. 7A and 7B
is laminated in a fashion such that each lens should correspond to each pixel, in a panel display element used in a transparent-type liquid crystal display as well. However, light entering the foregoing spaces does not contribute to the luminance of a screen of the liquid crystal display.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide a lens array arranged, for example, so as to include lenses each having a greater aperture and a sufficient curvature for collecting light, so that the lens array, for instance, can achieve improvements in sensitivity when used in a solid-state imaging element, and improvements in luminance of a screen when used in a panel display element.
In order to achieve the aforementioned object, a lens array of the present invention has the following configuration.
Namely, a lens array according to a first configuration of the present invention includes a plurality of condenser lenses arrayed in vertical and horizontal directions so that the condenser lenses and pixels arrayed in a two-dimensional plane have one-to-one correspondence. The lens array is characterized in that each of the condenser lenses, when viewed from a direction perpendicular to a condenser lens-arrayed plane, has a planar shape formed with four straight sides and four approximate circular arcs extending between the respective straight sides, and the center of the four approximate circular arcs substantially coincides with the center of a region corresponding to the pixel.
The lens array according to the first configuration ensures efficient utilization of each pixel region, thereby increasing the aperture of the condenser lens and reducing the loss of light passing through the pixel regions. This results in, for instance, improvement of sensitivity when the lens array is used in a solid-state imaging element, and improvement of luminance of a screen when the lens array is used in a panel display element. In addition, it is relatively easy to manufacture lenses in the aforementioned shape.
In the first configuration, it is preferable that the pixel-corresponding region be rectangular (either rectangular or square) in shape, and that a diameter of the approximate circular arcs be shorter than a diagonal of the region while being longer than a short side of the region (a vertical or horizontal side of the region in case it is square). The foregoing preferable configuration allows a proportion of a condenser-lens-provided area in the pixel region to increase, thereby causing the condenser lens to have a larger aperture.
Furthermore, in the first configuration, it is preferable that the pixel-corresponding region be rectangular (either rectangular or square) in shape, and that the condenser lens has a substantially equal curvature in diagonal and side directions in the region. The foregoing preferable configuration allows a lens array having a multiplicity of condenser lenses arrayed in the vertical and horizontal directions to be formed through a simple process described later.
Furthermore, in the first configuration, it is preferable that the pixel-corresponding region be rectangular (either rectangular or square) in shape, and that a radius of curvature R of the condenser lens satisfies:
X/
2
≦R
≦(½)×(
X
2
+Y
2
)
½
(1)
where X and Y represent a length of a short side and a length of a long side of the region, respectively (X=Y when the foregoing region is square), in either a vertical or horizontal direction in the region.
The foregoing preferable configuration allows a proportion of a condenser-lens-provided area in the pixel region to increase, thereby causing the condenser lens to have a larger aperture.
A lens array according to a second configuration of the present invention includes a plurality of condenser lenses arrayed in vertical and horizontal directions so that the condenser lenses and pixels arrayed in a two-dimensional plane have one-to-one correspondence. The lens array is characterized in that each of regions corresponding to the pixels, respectively, is rectangular in shape, and a short side of the region is not longer than ½ of a long side of the same, that each of the condenser lenses, when viewed from a direction perpendicular to a condenser lens-arrayed plane, has a planar shape formed with two straight sides opposing each other substantially in parallel and two approximate circular arcs extending between the straight sides, and further, that a center of the two a
Aoki Hiromitu
Ichikawa Michiyo
Komatsu Tomoko
Sano Yoshikazu
Sasano Tomohiko
Epps Georgia
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
O'Neill Gary
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