JPH063624A - Image display device - Google Patents

Abstract

PURPOSE:To reduce the rate of deterioration of picture quality caused when picture elements appear as discontinuous dots by disposing an optical low-pass filter within a display optical path. CONSTITUTION:An optical low-pass filter 4 comprising a phase lattice is disposed perpendicular to an optical axis 3 within the display optical path of an LED display element 1 comprising an LED dot matrix panel or the like having a number of LEDs 2 two-dimensionally periodically arranged. The optical low-pass filter 4 comprising the phase grating has a cross section in the form of rectangular, trapezoidal or sine waves and can be fabricated by photolithography, injection molding or 2P molding method in which photosensitive resin is cured using molding dies. The optical low-pass filter 4 is preferably such a type as having a cut-off frequency between the Nyquist rate and sampling frequency. A shadow casted by a nonluminous part such as the substrate portion of the LED display element is thereby reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device by lighting an LED.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic plan view of a general LED display device. The LED display element 6 has a large number of LEDs 7
Characters, figures, etc. are displayed by periodically arranging them in the dimension direction and individually turning on the LEDs 7.

[0003]

In the LED display element 6 described above, only the portion of the LED 7 shown in FIG. 3 emits light, and the substrate portion 8 does not emit light. Therefore, such LE
When the D display element is directly viewed or magnified and viewed, each pixel (LED 7) looks like dots and discontinuity, and thus the image quality is low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image display device in which the deterioration of image quality due to the dots appearing discontinuously is reduced.

[0005]

In order to solve the above problems, according to the present invention, a large number of LEDs are periodically arranged in a two-dimensional direction, and an image can be displayed by selectively emitting each LED. In the image display device, an optical low-pass filter is arranged in the display optical path.

[0006]

In the image display device of the present invention, the above-mentioned deterioration in image quality is improved by "blurring" the lighting of the LEDs arranged periodically in the two-dimensional direction by an optical low-pass filter.

[0007]

1 is a schematic perspective view of an example of an image display device of the present invention. In the image display device shown in FIG. 1, an optical low-pass filter 4 including a phase grating is provided in a display optical path of an LED display element 1 including an LED dot matrix panel in which a large number of LEDs 2 are periodically arranged in a two-dimensional direction.
Are installed perpendicular to the optical axis 3. The optical low-pass filter 4 including this phase grating has a cross-sectional shape such as a rectangular wave shape, a trapezoidal wave shape, and a sine wave shape, and is a photolithography method, an injection molding method, or a 2P molding method in which a photosensitive resin is cured using a molding die. And the like. Further, FIG. 2 shows a schematic perspective view of an example of the optical low-pass filter 4 described above. The optical low-pass filter shown in FIG. 2 has a two-dimensional array in which a large number of protrusions 5 are arranged in the horizontal direction and the vertical direction. The arrangement direction of the above-mentioned protrusions 5 is
It may be in the same direction as the arrangement of the LEDs 2 of the LED display element 1 or in an oblique direction. The projections 5 of the optical low pass filter 4 may be arranged in a one-dimensional array.

When the horizontal interval of the LEDs 2 is represented by Ph and the vertical direction is represented by Pv, the sampling frequency is (1 / Ph,
1 / Pv), Nyquist frequency is (1 / 2Ph, 1/2
It is represented by Pv). The optical low-pass filter 4 is preferably of a form having a cutoff frequency between the Nyquist frequency and the sampling frequency.

As the optical low-pass filter 4 in the present invention, a birefringent plate such as quartz can be used in addition to the phase diffraction grating.

[0010]

As described above, in the image display device of the present invention, the optical low-pass filter is arranged in the display optical path of the LED display element, and the shadow caused by the non-light emitting portion such as the substrate portion of the LED display element. Is reduced, and a good image without deterioration of image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an example of an image display device of the present invention.

FIG. 2 is a schematic perspective view of an example of an optical low-pass filter according to the present invention.

FIG. 3 is a schematic plan view of an LED display element.

[Explanation of symbols]

 1 LED display element 2 LED 3 Optical axis 4 Optical low-pass filter 5 Protrusion 6 LED display element 7 LED 8 Board part

Claims (1)

[Claims] 1. An image display device capable of displaying an image by arranging a large number of LEDs periodically in a two-dimensional direction and selectively emitting each LED, wherein an optical low-pass filter is provided in a display optical path. An image display device, in which is arranged.