KR100842598B1 - Screen and display device using micro lens array - Google Patents

Abstract

The present invention relates to a screen and display device that can eliminate speckle generated when using a laser as a light source by using two arrays of opposing micro lenses in a projection system using a laser as a light source.

A rear projection screen according to an embodiment of the present invention includes a first micro lens array and a second micro lens array which form a micro pitch corresponding to the pixel and smaller than or equal to the pixel size of the projected image at a pattern pitch. The first microlens array and the second microlens array are spaced apart from each other by a focal length to face each other, thereby projecting an image to the rear surface.

Laser, Projection, Projection, Rear, Micro Lens Array

Description

Screen and display device using micro lens array

1A and 1B show a rear projection system and a front projection system each using a conventional laser as a light source.

2A is a schematic diagram of a projection system according to an embodiment of the present invention.

Fig. 2B shows a cross section of the micro lens array of Fig. 2A.

FIG. 3A shows a cross section of a single micro lens array, and FIG. 3B shows the intensity according to the wavelength of light passing through the single micro lens array of FIG. 3A.

FIG. 4A shows a cross section of the dual micro lens array according to the invention, and FIG. 4B shows the intensity according to the wavelength of light passing through the dual micro lens array of FIG. 4A.

5 shows a front projection system according to another embodiment of the present invention.

※ Description of main part of drawing ※

21: first micro lens array 22: second micro lens array

23 condenser lens 24 projector

25 lens pattern

51: Micro Lens Array 52: Mirror

53: projector

The present invention relates to speckle-free screens and display devices used in laser-based projection systems.

More specifically, the present invention relates to a screen and display apparatus that can eliminate speckles generated when using a laser as a light source by using two arrays of opposing micro lenses in a projection system using a laser as a light source.

Conventional projection apparatuses use a mercury lamp as a light source, but recently, a projection apparatus using a laser as a light source has been studied. The laser light source has a much longer life and a smaller volume than a conventional mercury lamp, and thus has many advantages when used in a recent thin TV.

When using a laser as a light source, a screen consisting of Fresnel and Lenticular lenses used as screens in a conventional rear projection system, or using a regular screen, induces irregular scattering of light. Will cause speckle.

1A and 1B show a rear projection system and a front projection system each using a conventional laser as a light source.

When the image is projected onto the general screen 12 using the laser light source 11, the speckle 13 having a granular shape is formed on the screen due to the characteristics of the laser, which causes a significant deterioration in image quality. Because of the coherence, the laser passes through irregular planes, causing interference and creating speckles 13 on the screen 12.

In display systems that use a laser as a light source, several methods have been tried to eliminate speckle on these screens.

First, to eliminate spatial coherence, laser light was placed in a fiber and shaken, or a diffuser was used to uniformly mix the beams. This method is effective in reducing speckle but cannot be eliminated completely.

The second method is to use pulses to eliminate temporal coherence, which is impossible to attempt because of product safety. Another method is to remove speckle by physically shaking the screen to randomize the phase of the beam incident on the screen. This can completely eliminate speckle, but it's hard to apply to mass production.

The speckle reduction method described above is a method of adding components to a conventional laser display system or shaking a screen, and since the laser is formed to have a structure that must pass through a rough surface, coherence is achieved. Due to this long laser characteristic, speckle phenomenon due to offset constructive interference necessarily occurs.

In the case of the rear projection system shown in FIG. 1A, a method of inserting diffuser grains to scatter light on the screen has also been attempted to prevent speckle. However, even at this time, since the diffuser grains are irregularly distributed, the surface to which the laser is irradiated is roughened to provide an environment in which the laser causes interference.

As a result, a system using a conventional laser as a light source is a structure in which speckles are inevitably formed due to offset complementary interference due to irregular scattering on the screen surface of the laser and irregular slit structure due to roughness on the surface.

There is a need for a fundamental solution to the speckle problem in projection systems using lasers as light sources.

An object of the present invention is to provide a screen or device for displaying a uniform and speckle-free image using a screen including two micro lens arrays in a display device or system using a laser as a light source.

SUMMARY OF THE INVENTION An object of the present invention is to provide a screen or display device that can solve the speckle problem in a display device or system using a laser as a light source and make the most of the advantages of the laser light source.

A rear projection screen according to an embodiment of the present invention includes a first micro lens array and a second micro lens array which form a micro pitch corresponding to the pixel and smaller than or equal to the pixel size of the projected image at a pattern pitch. The first micro lens array and the second micro lens array may be spaced apart from each other by a focal length to face each other to project an image on the rear surface.

According to an embodiment of the present invention, a front projection screen may include: a microlens array having a pattern pitch of a microlens equal to or smaller than a pixel size of a projected image and corresponding to the pixel; And a mirror for reflecting the image passing through the micro lens array, wherein the micro lens array and the mirror are disposed to be spaced apart by 1/2 of a focal length to project the image to the front.

A display apparatus according to an embodiment of the present invention, an image projector using a laser light source; And a first display configured to display an image projected from the image projector, and to form a micro pitch corresponding to the pixel, the microlenses having a pattern pitch that is equal to or smaller than the pixel size of the projected image and is spaced apart from each other by a focal length. And a rear projection screen including a micro lens array and a second micro array.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A is a schematic diagram of a projection system according to an embodiment of the present invention.

The image is projected from the projector 24 using the laser as a light source. The projected light passes through the first micro lens array 21 and the second micro lens array 22 and is projected to the user. The first micro lens array 21 and the second micro lens array 22 constitute a speckle free screen according to the present invention.

Preferably, according to the embodiment, after the second micro lens array 22, a condenser lens 23 serving as a condensing lens, such as a Fresnel lens of a conventional screen, is disposed to condense light exiting the screen area into a viewing angle range. Can give As the condenser lens 23, a convex lens may be used in addition to the Fresnel lens.

Further, according to an embodiment, the viewing angle of the projected image is magnified and transmitted to the viewer's eyes together with the condenser lens 23 after the second micro lens array 22 or instead of the condenser lens 23. Wide-angle lenses (not shown) that serve as lenticular lenses may be used.

Fig. 2B shows a cross section of the micro lens arrays 21 and 22 in Fig. 2A. Convex lens-shaped patterns 25 are arranged at regular intervals.

Each of the micro lenses of the micro lens arrays 21 and 22 corresponds to each pixel of the projected image. The pitch of the pattern 25 should be less than or equal to the pixel size of the projected image. If the size is larger than the pixel size of the image, the images overlap and the resolution decreases. Preferably, the pitch of the pattern 25 can be formed on the order of several hundred nm to several micrometers.

The dual micro lens arrays 21 and 22 according to the present invention scatter the incident beam in place of the diffuser grains used for conventional speckle removal to form an image. The image formed by the micro lens arrays 21 and 22 is transmitted to the viewer's eyes.

However, the dual microlens arrays 21 and 22 according to the present invention are arranged at a constant shape and interval, unlike conventional diffuser grains, which are non-uniformly distributed to induce light scattering. This causes the beam to be uniformly refracted and does not cause speckle.

The micro lens arrays 21 and 22 may be formed of a transparent material, and preferably, may be made of a transparent plastic.

The patterns 25 of the microlens arrays 21 and 22 are micro units such as etching through laser beam direct photolithography, an imprint method, and patterning using an E-beam on a transparent substrate. It can be patterned by applying a process method that can be patterned. Most preferably, patterning is possible using a laser beam direct drawing method.

In the display device of FIG. 2A according to the present invention, each of the micro lenses of the first micro lens array 21 and the second micro lens array 22 is disposed to face each other by a focal length f. As described above, the focus of the first micro lens array 21 is made to be bound to the second micro lens array 22.

By arranging the two micro lens arrays to face each other as described above, there is no dependence on the wavelength of the projected light, and uniformity can be ensured by allowing the 2,3,4..order orders due to diffraction to be ignored.

FIG. 3A shows a cross section of a single micro lens array, and FIG. 3B shows the intensity according to the wavelength of light passing through the single micro lens array of FIG. 3A.

FIG. 4A shows a cross section of the dual micro lens array according to the invention, and FIG. 4B shows the intensity according to the wavelength of light passing through the dual micro lens array of FIG. 4A.

In FIGS. 3B and 4B, the x-axis represents the major axis direction of the microlens arrays of FIGS. 3A and 4A, respectively, and the y-axis represents the intensity of the light to be measured. The maximum light intensity measured when the same laser is irradiated is 1; It is a graph of its relative size.

Comparing FIG. 3B and FIG. 4B, it can be seen that the light passing through the dual micro lens array according to the present invention exhibits a constant intensity regardless of the wavelength and ensures uniformity according to the wavelength.

The patterns 25 of the micro lens arrays 21 and 22 are designed such that the beams incident on the respective patterns do not overlap each other. The screen including the dual micro lens array according to the present invention thus designed can be used as a rear screen.

5 shows a front projection system according to another embodiment of the present invention.

In the embodiment shown in Fig. 5, instead of two micro lens arrays, one micro lens array 51 and a mirror 52 are used.

An image is projected from the projector 53 which uses a laser as a light source. The projected light passes through the micro lens array 51, is reflected by the mirror 52, and then passes through the micro lens array 51 to the viewer's eyes. The micro lens array 51 and the mirror 52 constitute a speckle free screen according to the present invention.

In order to achieve the same effect as the embodiment shown in Fig. 2A, the distance between the micro lens array 51 and the mirror 52 is formed by 1/2 of the focal length f of the micro lenses constituting the micro lens array 51. .

The image passing through the micro lens array 51 is reflected by the mirror 52 and moved by the focal length f of the micro lens array 51 to form an image on the micro lens array 51.

Preferably, before the microlens array 51, a condensing lens serving as a condensing lens, such as a Fresnel lens of a conventional screen, or a lenticular lens which enlarges the viewing angle of the projected image and delivers it to the viewer's eyes. A wide angle lens (not shown) can be disposed and used.

By using a screen or display device composed of a dual micro lens array according to the present invention, it is possible to prevent speckle generation in a system using a laser light source.

In addition, the screen or display device according to the present invention can display the image uniformly without depending on the wavelength.

In addition, the screen including the dual micro lens array according to the present invention can be applied to a mass production method such as an imprint, molding process even during manufacturing.

Claims (9)

A first microlens array and a second microlens array, wherein the first microlens array and the second microlens array form a microlens at a pattern pitch which is smaller than or equal to the pixel size of the projected image The first microlens array and the second microlens array are arranged so as to face each other by a focal length to project the image on the rear surface. The method of claim 1, And a condenser lens configured to condense and output light emitted from the second micro lens array. The method of claim 1, And a wide angle lens for enlarging a wide viewing angle of light emitted from the second micro lens array. A micro lens array having a pattern pitch of a micro lens equal to or smaller than a pixel size of the projected image and corresponding to the pixel; And And a mirror that reflects the image passing through the micro lens array. The micro lens array and the mirror is arranged to be spaced apart by 1/2 of the focal length screen to project the image to the front. The method of claim 4, wherein And a condenser lens for vertically projecting light emitted from the micro lens array. The method of claim 4, wherein And a wide angle lens for expanding a wide viewing angle of light emitted from the micro lens array. An image projector using a laser light source; And A first micro to display an image projected from the image projector, and to be spaced apart from each other by a focal length and to face each other, and to form a micro pitch corresponding to the pixel with a pattern size smaller than or equal to the pixel size of the projected image; And a rear projection screen comprising a lens array and a second micro array. The method of claim 7, wherein And a condenser lens for condensing and emitting light emitted from the second micro lens array. The method of claim 7, wherein And a wide angle lens for enlarging a wide viewing angle of light emitted from the second micro lens array.

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