Katsuya Fujisawa

Edge-Light Backlight Unit Using Optically Patterned Film

A novel edge-light backlight unit using an optically patterned film (OPF backlight unit) for liquid crystal displays (LCDs) is composed of a light guide plate bonded to the top of fine lenses formed on the OPF, a diffusive sheet, a reflective sheet and a light source. A viewing-angle-dependent luminance distribution of the OPF backlight unit was controllable by changing the shape of a fine lens used for the extraction of light propagating through a light guide plate and the direction control of radiating light, and a luminance distribution in a radiation plane suitable for LCDs was realized by adjusting the interval between lenses. Moreover, the extraction efficiency of the OPF backlight unit was greater than that of a conventional backlight unit. Thus, the OPF backlight unit was shown to be promising for the realization of a brighter, lower power consumption, slimmer and lighter LCD than conventional LCDs.

Grating-Type Soft-Focus Filter for Improving Picture Quality of Liquid Crystal Displays

A grating-type soft-focus filter was fabricated from a polymer film to transform the discontinuous picture of a liquid crystal display (LCD) into a continuous one. The soft-focus filter having a two-dimensional grating pattern with a sinusoidal cross section was photochemically formed on the film by proximity exposure through a photomask to ultraviolet light. When the LCD surface was covered with the soft-focus filter, the output light beam from the LCD was transformed into mainly nine beams as a result of (0, 0)- to (±1, ±1)-order diffractions with nearly equivalent intensities. Thereby, the picture discontinuity caused by the black matrix of the LCD was removed at a small expense of picture contrast.

Grating Optical Low-Pass Filter.

The spurious signals appearing in the picture image from a charge-coupled semiconductor device (CCD) camera were removed by means of a novel grating optical low-pass filter (GOLF). By placing the GOLF near the imaging plane of the CCD and adjusting the effective grating period projected onto the imaging plane with respect to the array period, or its integral multiplicative inverse of the picture elements formed in the imaging plane, it was verified that the GOLF eliminated the grating image superimposed on the picture image, which had been a long-standing problem. Photochemical reaction was useful for forming a sinusoidal grating crosssection which increased the MTF value in the region of low spatial frequencies to realize a clear-cut picture image. The GOLF fabricated in the form of a thin plate was promising to realize a new CCD with a built-in optical low-pass filter applicable for downsizing of camera optics.

Edge-Light Backlight Unit Using Optically Patterned Film with Plural Light-Emitting Diodes Placed on Side as Light Source

In an edge-light backlight unit using an optically patterned film (OPF backlight unit) with plural light-emitting diodes (LEDs) placed on the side as a light source, dark areas are easily generated between LEDs, because the OPF backlight unit mainly uses the total reflection induced by optical patterns formed on the OPF. Such dark areas were eliminated by narrowing the interval between optical patterns between LEDs and widening it near LEDs. By adjusting the interval between optical patterns across the entire area additionally, a luminance distribution in a radiation plane suitable for liquid crystal displays (LCDs) was realized. Moreover, viewing-angle-dependent luminance distribution can be narrowed by adjusting the shape of the lens-shaped optical pattern. Thus, the OPF backlight unit using plural LEDs was shown to be suitable for small-area LCDs.