Optical waveguides – Optical fiber bundle – Fiber bundle plate
Reexamination Certificate
2002-04-19
2004-06-22
Ullah, Akm Enayet (Department: 2874)
Optical waveguides
Optical fiber bundle
Fiber bundle plate
C385S147000, C345S030000
Reexamination Certificate
active
06754419
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a discrete pattern. More particularly, the present invention relates to a discrete pattern having low discrepancy and including a pattern of dots arranged so there is no overlapping, an optical member, a light guide plate, a side light device and a light-transmitting liquid crystal display device that uses the discrete pattern, and to a method and a program for generating the discrete pattern, a computer-readable storage medium on which a computer-readable program is stored for generating the discrete pattern, and a discrete pattern generation system.
BACKGROUND ART
Various techniques using discrete pattern are known. These techniques are used for a light guide plate, for example, of light-transmitting liquid crystal display device or a diffuser sheet, and the discrete pattern can be, for example, a dithering pattern, a lithography photomask pattern or a pattern for stopper. Recently, the application of a discrete pattern for a DNA arrangement on a DNA chip has also been discussed.
Conventionally, a discrete pattern is formed so that dots are arranged at random by using a so-called random-number generator, or the dots are arranged on a regular orthogonal lattice, such as plotting paper. However, with the conventional methods, the following problems have arisen for the random pattern that is generated merely by a common random-number generator. Specifically, even when dots are arranged at random, the overlapping of dots and uneven dot densities, which occur because each dot has a definite size, can adversely affect the appearance of a dot pattern, and an optical malfunction, such as uneven luminance, can occur. Further, when the dots are regularly arranged, an undesirable optical pattern, such as moire, can occur due to an interference between dots or with an external regular pattern.
To resolve the problem, a method is proposed in Japanese Unexamined Patent Publication No. Hei 10-153779 whereby an irregular pattern is generated without an excessive approach between the dots. According to this method, first, as an “absolute random number arrangement method”, (1) the initial position (x, y) is provided for all the dots by a random-number generator; and (2) a random number is again generated for the overlapping dots and their positions are corrected. However, as for the calculation method disclosed in Japanese Unexamined Patent Publication No. Hei 10-153779, it is well known that the calculation performed to eliminate the overlapping of dots can not be convergent in an area having a dot filling rate of more than 50%. Specifically, when the method described in Japanese Unexamined Patent Publication No. Hei 10-153779 is used, it is quite difficult for an irregular pattern having no abnormal approach between dots to be generated, while maintaining randomness. Further, according to this method, which is based on the generation of multiple pseudo random numbers, it is also difficult to remove an uneven portion from a dot pattern, even if overlapping of dots can be removed from an area having a low dot filling rate.
FIG. 1
is a diagram showing an example dot pattern that is formed by the method described in Japanese Unexamined Patent Publication No. Hei 10-153779. The dot pattern in
FIG. 1
is generated using a process whereby (1) dots are arranged at two-dimensional regular lattice points formed by linear lines or curves, and these positions are defined as initial positions; (2) the displacement of each initial position is provided by a random-number generator; and (3) a random number is again generated for the overlapping dots and their positions are corrected. As is shown in
FIG. 1
, according to this method, the dots can be arranged without overlapping, so long as only small displacements of the lattice points are maintained. However, according to a method for generating a random position as a perturbation from a lattice point, in an area having a comparatively high dot filling rate, such as a ratio exceeding 50%, it is difficult to generate a satisfactory irregular pattern while avoiding the occurrence of moire. Further, according to this method, which is based on the multiplex generation of pseudo random numbers, many aggregations of dots appear even if dot overlapping is removed, and it is difficult to generate a uniform random pattern.
The reasons for this will be explained. For the conventional example using random dots, assume that the size of the dots being arranged is about 100 &mgr;m and that the filling rate is 70%. As is shown in
FIG. 1
, the shape of a dot is assumed to be a square. With this dot size and the filling rate described above, an interval of merely 20 &mgr;m is generated between the dots. In
FIG. 1
, dot
100
and intervals
102
between the dot
100
are shown at an exact reduced scale. When random perturbation is provided for the regular lattice, dots
104
, indicated by broken lines in
FIG. 1
, are obtained. It is understood that these dot
104
can only generate a pattern having an extremely limited irregularity (hereinafter referred to as randomness in this invention), as is shown in FIG.
1
. Because the adjacent dots do not jump over each other, and because the filling rate is high, the positions of these dots are corrected only within a limited range.
A square lattice is employed in the conventional art in FIG.
1
. However, under a condition wherein dots should not be arranged too closely together, the randomness of the dot pattern is more or less limited, even for other types of regular lattices. That is, according to the method whereby a predetermined dot is provided at an initial position and perturbation is employed to generate a random arrangement, in principle, as the filling rate increases, the possibility that a random dot pattern will be obtained that closely resembles a truly random arrangement decreases. Therefore, regardless of the filling rate, this method is not satisfactory for the generation of random patterns.
In addition, relative to the optical characteristic of a dot pattern generated by the above method, another problem has arisen in that a moire pattern will occur when a light beam is transmitted through or reflected from a dot pattern. Conventionally, in the printing field, many studies and proposals have been made to devise methods for removing moire. For example, in Japanese Unexamined Patent Publication No. 2000-94756, for a halftone process performed by a printer, a printing technique is disclosed for avoiding the occurrence of moire (so-called uneven feeding and uneven lines) caused by regular printing fluctuations, produced by the rotation of a paper feed drum, and printing dot patterns.
Therefore, in Japanese Unexamined Patent Publication No. 2000-94756, printing dots are arranged at random. That is, perturbation is provided at random for printing dots arranged on a regular lattice, an improvement that satisfactorily precludes the occurrence of the uneven dot densities that accompany the appearance of moire. However, for the above mentioned reasons, it is difficult for the randomness of this method to be directly applied for uniform discrete patterns.
The above problems, including the generation of random dot patterns and the occurrence and removal of moire, arise not only in the printing field, wherein printing techniques for printers are affected, but also in various other fields, such as the production of display devices that include rear lighting devices (hereinafter referred to as backlights).
As a specific example, since light, compact light-transmitting liquid crystal display devices can be made that consume little power, the production and use of these display devices have become ever more important as a core technique affecting the selection of hardware for use in the so-called IT revolution. However, since unlike conventional display devices, i.e., CRTs, liquid crystal devices do not emit light, backlight units must be provided that light all the liquid crystal cells in these devices. This is especially true today, since
Ide Tsuyoshi
Mizuta Hideyuki
Nishikai Akiko
Taira Yoichi
Dougherty Anne V.
Jennings Derek S.
Ullah Akm Enayet
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