JP2007140248A - Image display screen and image display device - Google Patents

Abstract

An object of the present invention is to provide an image display screen and an image display device that can eliminate speckle noise and can display natural and vivid colors even under external light illumination, for a projector using a light source with a narrow spectrum width.
A screen for displaying an image obtained by modulating light from a light source having a narrow spectrum width has a main diffusion layer and sub-diffusion layers separated from the main diffusion layer on both sides of the light entering and exiting, and the main diffusion layer And the sub-diffusion layer have a relationship of d × Δλ> λ ² and d <5 mm with respect to the output peak wavelength λ and the output wavelength half width Δλ of the light source. Further, a selective light absorption layer having an absorption peak at 550 to 610 nm is provided on the viewer side from the main diffusion layer. According to this configuration, speckle noise generated when a light source having a narrow spectrum width is used can be removed, and a high-quality image that does not fade can be displayed.
[Selection] Figure 1

Description

  The present invention relates to an apparatus for displaying an image by modulating light from a light source and a screen of the display apparatus.

  As an image display device, a projection display (projector) that projects an image on a screen has become widespread. The projector modulates light from a light source with a modulation element such as a liquid crystal panel, and projects the modulated image onto a screen. Conventionally, a lamp light source is used as a light source of a projector. However, the lamp light source has a short life, a limited color reproduction region, and low light use efficiency.

  In order to solve the problem of the lamp light source, an attempt has been made to use a laser light source as the light source of the projector. A laser light source has a longer life than a lamp and has high directivity, so that it is easy to improve the light utilization efficiency. Further, since the laser light source exhibits monochromaticity, the color reproduction area is large and a vivid image can be displayed.

  However, in a projector using a laser light source, speckle noise caused by the high coherence of the laser becomes a problem. Speckle noise is fine uneven noise generated by interference of scattered light when laser light is scattered on a screen.

  Screens for displaying projection images of a projector are roughly classified into a reflection type and a transmission type. The reflective screen projects light from the front of the screen, and displays an image by the reflected light from the reflective diffusion surface of the screen. The transmissive screen projects light from the back of the screen, and displays an image by the diffuse transmitted light of the screen.

  In the image display screen, reflection of external light becomes a problem. As the transmissive screen, a screen provided with a light-shielding portion composed of a lenticular lens sheet and a black stripe has been proposed and put into practical use.

In the transmissive screen, in order to obtain preferable light diffusion characteristics while using the Fresnel lens sheet, the lenticular lens sheet and the black stripe, Japanese Patent No. 3606862 discloses separation of the diffusion portion for each sheet, Japanese Patent Laid-Open No. 2002-236319 Has proposed the lamination of diffusion layers.
Japanese Patent No. 3606862 JP 2002-236319 A

  Many projection-type image display screens and image display devices have been proposed for the light shielding and light diffusion characteristics optimized for the lamp light source. However, a light source with a narrow spectral width such as a laser light source has been proposed. There are few proposals for speckle noise countermeasures and color display for external light when used.

  An object of the present invention is to provide an image display screen and an image display device that can remove speckle noise and can display natural and vivid colors even under external light illumination, with respect to a projector using a light source with a narrow spectrum width. It is said.

In order to solve the above problems, a screen for displaying an image obtained by modulating light from a light source having a narrow spectral width has a main diffusion layer and sub-diffusion layers separated from the main diffusion layer on both sides of the light entering and exiting. The distance d between the main diffusion layer and the sub-diffusion layer has a relationship of d × Δλ> λ ² and d <5 mm with respect to the output peak wavelength λ and the output wavelength half width Δλ of the light source.

  According to this configuration, speckle noise generated when a light source having a narrow spectrum width is used can be removed, and a high-quality image can be displayed.

  According to the image display screen and the image display device of the present invention, it is possible to always display a colorful high-quality image from which speckle noise has been removed.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic sectional view of an image display screen according to Embodiment 1 of the present invention. The transmissive image display screen 1 includes a sub-diffusion layer 11, a separation layer 21, a main diffusion layer 10, a separation layer 22, and a sub-diffusion layer 12 from the image light incident side. The separation layer 22 includes the light absorption layer 16. Image light obtained by modulating light from a light source having a narrow spectral width is projected on the screen from the image projection device 2, and the viewer observes the image on the screen from the right side of the figure.

  The image light of the present invention consists of three colors of RGB, and light from at least one color light source forms a colorful image. Therefore, when the output peak wavelength is λ, the output wavelength half-value width Δλ is less than 10 nm. . In order to form a colorful image, the output wavelength half-value width Δλ of light sources of all colors is preferably less than 10 nm.

The distance d1 between the sub-diffusion layer 11 and the main diffusion layer 10 separated by the separation layer and the distance d2 between the sub-diffusion layer 12 and the main diffusion layer 10 are less than 5 mm, and the light source output wavelength λ and the output of at least one color For the half-wave width Δλ, d × Δλ> λ ² is satisfied (both d1 and d2).

  The diffusion effect of the main diffusion layer and the sub-diffusion layer is obtained from the dispersion of the light diffusing agent and the surface irregularity shape. In the present invention, the diffusion of the main diffusion layer is the largest, and the viewer mainly focuses on the diffusion light of the main diffusion layer. Observe the image. Speckle noise is randomly scattered when coherent light such as laser light passes through and reflects the diffuser, and the scattered wave overlaps on the surface to be observed (retina), and a bright and dark speckled pattern is observed. It occurs in. In the screen of the present invention, by separating the diffusion layers, the coherence of scattered waves generated in each layer is lowered, and the sub-diffusion layer works so as to reduce the largest speckle noise due to the diffusion of the main diffusion layer.

  The incident side sub-diffusion layer diversifies the angular distribution of image light that illuminates the main diffusion layer, diversifies the speckle pattern of the main diffusion layer, and reduces noise. The emission side sub-diffusion layer reduces noise by superimposing the speckle pattern by superimposing the diffused light from the main diffusion layer.

In order to reduce the coherence of scattered waves generated in the main and sub-diffusion layers, in the present invention, the distance d (d1, d2) between the diffusion layers satisfies d × Δλ> λ ² and is larger than the coherence length. As a result, speckle noise generated by the synthesis of scattered waves from the respective diffusion layers is reduced.

  When the diffusion layer is separated, the focus and multiplexing of the image becomes a problem. However, in the present invention, the main diffusion layer is located between the sub-diffusion layers, so that the main image is focused by adjusting the focus of the image light to the main diffusion layer. By forming and observing together with the images of the sub-diffusion layers on both sides, the image quality can be maintained. Even when the main image is formed on the main diffusion layer, if the distance d between the diffusion layers is 5 mm or more, the image is blurred, so d is less than 5 mm.

  The image display screen of the present invention can provide a colorful and high-quality image from which speckle noise has been removed by adopting the above-described configuration.

  The haze values Hm and Hs representing the diffusivities of the main diffusion layer and the sub-diffusion layer are preferably 40% <Hs <Hm. The haze value is a value obtained by dividing the diffuse transmittance by the total light transmittance. The main diffusion layer has the highest diffusion effect and the haze value is larger than that of the sub-diffusion layer. When the haze value of the diffusion layer is 40% or less, the diffusivity is low and a sufficient image cannot be displayed. Therefore, the haze value of the sub-diffusion layer is also required to be 40% or more.

  The haze value of the diffusion layer of the transmissive screen 1 was 85% for the main diffusion layer and 64% for the sub-diffusion layer (both 11 and 12), and a high-quality image could be detected. In the transmission screen 1, a diffusion plate having a thickness of 1.5 mm, in which a sub-diffusion layer is coated with a diffusing agent on one side and a diffusion film having irregularities is used so that the coating surface becomes the surface, and the main diffusing layer is filled with the diffusing agent. Was used.

  The separation layer is formed of a transparent resin material or the like, and keeps the distance between the main and sub-diffusion layers. The separation layer is bonded to the diffusion layer with an adhesive or the like. Further, an air layer may be used as long as the interval is maintained. Further, as in the first embodiment, a dye or pigment that has a function of a light absorption layer and absorbs light of a specific wavelength may be included.

  Three or more sub-diffusion layers may be used, and in the case of three or more layers, the sub-diffusion layers are also separated by a separation layer.

  The image display screen preferably has a selective light absorption layer having a visible light absorption wavelength peak of 550 to 610 nm on the observer side of the main diffusion layer. In the screen 1, a dye having a visible light absorption wavelength peak of 550 to 610 nm is diffused in the light absorption layer 16 and functions as a selective light absorption layer. The selective light absorption layer prevents external light from being reflected on the screen and lowering the image quality. In particular, it is possible to prevent an image faded by the illumination light of a fluorescent lamp or a light bulb. When the illumination light is mixed, the color of the image is whitened by the mixed color and the color temperature is lowered. The selective light absorption layer absorbs light having a high visibility of 550 to 610 nm, thereby preventing a black image from becoming bright and making it possible to maintain the color temperature. When there is illumination light, the color temperature decreases and the image turns yellow. However, the selective light absorption layer selectively absorbs yellow to orange light, so that this yellowing can be prevented.

  The image display screen preferably has a visible short wave to ultraviolet absorption layer on the observer side of the main diffusion layer. In the screen 1, the resin material constituting the light absorption layer 16 absorbs light having a wavelength shorter than 430 nm, and functions as a visible short wave to ultraviolet absorption layer. Specifically, visible shortwave to ultraviolet light refers to light having a visibility of less than 0.02 and a wavelength of 300 nm or more, and the visible shortwave to ultraviolet absorption layer absorbs the wavelength. The visible short wave to ultraviolet absorption layer has low visibility and prevents harmful light from reaching the viewer from the projection light and external light, and prevents color shift due to external light.

  The image display screen preferably has a visible long wave to near infrared absorption layer on the viewer side of the main diffusion layer. In the screen 1, a dye that absorbs light having a wavelength longer than 670 nm is diffused in the light absorption layer 16, and functions as a visible long wave to near infrared absorption layer. Specifically, visible long wave to near-infrared light is light having a wavelength of around 700 to 1300 nm, and is often contained in incandescent bulbs and the like. The visible long wave to near-infrared absorbing layer absorbs the wavelength and prevents a decrease in color temperature of a particularly large image under illumination of an incandescent bulb. In particular, when an SHG laser light source is used as the light source of the image display device, it plays a role of blocking near infrared light, which is a fundamental wave, by the visible long wave to near infrared absorbing layer and reaching the viewer.

  In the transmissive image display screen 1, the light absorption layer 16 serves as the selective light absorption layer, the visible short wave to ultraviolet absorption layer, and the visible long wave to near infrared absorption layer. A three-layer structure may be used. In the first embodiment, the light absorption layer is provided between the main diffusion layer and the incident side sub-diffusion layer. However, the light absorption layer may be provided closer to the observer than the main diffusion layer, and may be provided on the outermost surface. Further, the incident side sub-diffusion layer may be provided with functions of a selective light absorption layer, a visible short wave to ultraviolet absorption layer, and a visible long wave to near infrared absorption layer.

  In order to reduce the influence of external light on the viewer, it is preferable to provide an AR coat on the viewer-side surface of the image display screen.

(Embodiment 2)
FIG. 2 is a schematic diagram of a cross section of an image display screen and a configuration of an image display device according to Embodiment 2 of the present invention. The same components as those in FIG. 1 will be described using the same reference numerals.

  After being waved, the light is guided to the modulation element 33 through the beam deflecting means 31 and the optical integrator 32. The modulation element 33 performs modulation for image display, and the modulated image light is projected on the transmissive image display screen 100 by the projection lens 34.

  The beam deflection means controls the beam angle temporally to give a change in angle, and in combination with the optical integrator, makes the beam intensity distribution rectangular and reduces speckle noise. The laser light sources r, g, and b are sequentially emitted and used by dividing the modulation element 33 in time, and display a color image by time-average additive color mixing on the screen. The modulation element 33 of the second embodiment uses a reflection type two-dimensional modulation element made of a digital micromirror device (DMD).

  In order to display a colorful image, the output wavelength half-value width Δλ of the independent light sources r, g, and b of RGB three colors is less than 10 nm, and various colors are displayed by additive color mixing. The output peak wavelengths λr, λg, and λb are characterized by 620 nm <λr <670 nm, 500 nm <λg <550 nm, and 430 nm <λb <480 nm. Since the image display apparatus of the present invention has the above-described independent light sources of three colors of RGB, it can display a vivid and wide color range.

  In particular, since the light source of the image display apparatus according to the second embodiment is a laser light source, it has excellent monochromaticity and can display three primary colors with very high saturation.

  More preferably, the output peak wavelengths of the RGB light sources are 625 nm <λr <660 nm, 510 nm <λg545 nm, 435 nm <λb <470 nm, and the half-value width Δλ of each light source wavelength is less than 5 nm. At this time, most of the object colors seen by humans can be displayed, and the visibility of each light source can be prevented from being lowered. The laser light source wavelengths of the respective colors in the second embodiment are λr: 639 nm, λg: 532 nm, and λb: 454 nm, and the half-value widths are Δλr: 1.4 nm, Δλg: 0.2 nm, and Δλb: 3.6 nm. there were. The laser light sources r and b are semiconductor lasers, and the laser light source g is an SHG laser having a fundamental wave of 1064 nm. FIG. 3 is a chromaticity diagram showing the color display range of the image display apparatus A. A color range of the sRGB standard, which is a display color range of a CRT that is a typical image display device, is shown for comparison. It can be seen that the image display apparatus A can display a very wide color range compared to the CRT. Further, it is possible to avoid energy loss when displaying the same brightness without lowering the visibility (stimulus value) by the three color light sources.

  As the laser light source of the present invention, a semiconductor laser, a solid-state laser, a gas laser, and an SHG laser obtained by converting these wavelengths can be used. In particular, the SHG laser is preferable as a light source for an image display device because it can oscillate various wavelengths by converting the wavelength of near-infrared light and can display various colors.

  The transmissive image display screen 100 includes a sub-diffusion layer 13, a Fresnel lens sheet 23, a lenticular lens sheet 24, a black stripe layer 25, a main diffusion layer 10, a separation layer 21, a sub-diffusion layer 14, and a light absorption layer 16 from the light incident side. Consists of. The viewer observes the transmitted diffused light from the transmissive image display screen from the right side of the figure.

  In the screen 100, the image light is made substantially parallel by the Fresnel lens sheet 23 and diverged in the horizontal direction by the lenticular lens sheets arranged in the horizontal direction. The black stripe layer is provided in the vicinity of the focal plane of the lenticular lens, and is a stripe-shaped light shielding layer that absorbs external light and allows only projection light to pass therethrough, and improves contrast in bright places. In the screen of the present invention, the lenticular lens sheet and the black stripe layer have the effects of separating the incident side sub-diffusion layer and the main diffusion layer, and improving the bright place contrast. In order to enhance the external light absorption effect of the black stripe layer and increase the area of the light shielding portion, in the present invention, the black stripe layer is provided closer to the incident light side of the image light than the main diffusion layer.

The distance d1 between the incident side sub-diffusion layer and the main diffusion layer and the distance d2 between the main diffusion layer and the emission side sub-diffusion layer of the screen 100 are d1 = d2 = 3 mm, d <5 mm, and all the wavelengths of RGB. meet the d × Δλ> λ ² in contrast, it was possible to display a high-quality image without speckle noise.

  The haze value of the diffusion layer of the screen 100 is 85% of the main diffusion layer, 65% of the incident-side sub-diffusion layer, and 75% of the emission-side sub-diffusion layer. The main diffusion layer is a diffusion plate having a thickness of 1.5 mm and each sub-diffusion layer. Used a diffusion plate having a thickness of 0.5 mm. The haze value of all the diffusion layers is 40% or more, the haze value of the main diffusion layer is the highest, the speckle noise is removed from the sufficient diffusion effect, and the wide vertical viewing angle and the main diffusion layer are the center. The image could be displayed.

  As in the first embodiment, the light absorption layer 16 has the effects of a selective light absorption layer, a visible shortwave to ultraviolet absorption layer, and a visible longwave to infrared absorption layer. In the image display device A, Δλ is less than 5 nm, 510 nm <λg <545 nm, 625 nm <λr <660 nm are satisfied, G and R spectra are separated, and the interval is wide, so that the absorption wavelength range of the selective light absorption layer is Absorption of projection light does not occur even if it is wide, and good selective light absorption can be achieved. When the light source wavelength of Blue is 435 nm <λb <470 nm, a layer that absorbs light of 470 nm to 510 nm may be added.

  By using the light absorption layer 16 together with the black stripe layer 25, it is possible to provide an image that has high contrast and does not fade under any illumination.

(Embodiment 3)
FIG. 4 is a sectional view of an image display screen according to Embodiment 3 of the present invention. The same components as those in FIG. 1 will be described using the same reference numerals. The reflective image display screen 200 includes a light absorption layer 16, a sub-diffusion layer 11, a separation layer 21, and a reflective main diffusion layer 15 from the surface. The image projection device 2 projects image light obtained by modulating light of a light source having a narrow wavelength width and a colorful half-wave width Δλ = less than 10 nm onto the screen, and the viewer mainly receives light reflected by the main diffusion layer. Observe the image from the right. The image light is diffused by the sub-diffusion layer, then reflected by the main diffusion layer, passes through the sub-diffusion layer again, receives the diffusion action, reaches the viewer, and one sub-diffusion layer is incident side sub-diffusion layer And also serves as an exit side sub-diffusion layer.

  The reflection type main diffusion layer 15 is formed of a reflection diffusion surface and reflects and diffuses light. For the reflective main diffusion layer, a beaded or matte screen material used in a front projector of a lamp light source can be used. The sub-diffusion layer 11 is made of a transmission type diffusion plate or a diffusion film and has an effect of mainly transmitting and diffusing, but it may reflect and diffuse a part of image light.

Specifically, in the reflective image display screen 200, the sub-diffusion layer is made of a resin diffusion plate (0.5 mmt) having a haze value of 65%, the reflective main diffusion layer is a bead-shaped screen, and the separation layer is a transparent resin of 2 mmt. It is made of a plate and is adhered to the main diffusion layer and the sub-diffusion layer to keep a distance d (2 mm). The haze value of the reflective main diffusion layer was 93% as a result of obtaining using the ratio between the reflected diffused light and the total light reflectance. The relative output wavelength half-width [Delta] [lambda] of the image light, satisfies the d × Δλ> λ ^2.

The reflection type image display screen has a large diffusion effect of each diffusion layer and satisfies d × Δλ> λ ² , so that speckle noise generated by a light beam having a bright and narrow spectral width can be removed. As in Embodiment 2, when a laser light source is used, the screen of the present invention is very suitable because it can remove speckle noise. Further, since d <5 mm and the haze value of the main diffusion layer is higher than that of the sub-diffusion layer, a high-quality image can be provided.

  Similar to the transmissive image display screen 1, the light absorption layer 16 has the effects of a selective light absorption layer, a visible short wave to ultraviolet absorption layer, and a visible long wave to infrared absorption layer, and is capable of fading the image color by illumination light. Can be prevented. As the material used for the light absorption layer, organic and inorganic materials can be used as long as they can absorb wavelengths in a specific region.

  The image display screen of the present invention only needs to allow the viewer to observe the image light of the image projection device, and may not be flat but curved, and the shape is not limited to a rectangle.

  The modulation means of the image display apparatus of the present invention is not particularly limited to the embodiment, and may be a transmission type modulation element, or a modulation element may be provided for each of the three colors of RGB. Further, the output of the light source may be modulated as image light modulating means. The optical system of the image projection apparatus is not particularly limited to the embodiment.

  The image display screen and the image display device of the present invention can be used as a display and display device for moving images and still images.

Screen schematic sectional drawing in Embodiment 1 of this invention Schematic cross-sectional view and image display device configuration diagram in Embodiment 2 of the present invention The figure which shows the display color range of the image display apparatus in Embodiment 2 of this invention. Screen schematic sectional drawing in Embodiment 3 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Transmission-type image display screen 2 Image display apparatus 10 Main diffusion layer 11, 12, 13, 14 Sub-diffusion layer 15 Reflection type main diffusion layer 16 Light absorption layer 21, 22 Separation layer 23 Fresnel lens sheet 24 Lenticular lens sheet 25 Black stripe layer 31 Beam deflecting means 32 Optical integrator 33 Modulating element 34 Projection lens 200 Reflective image display screen A Image display device r Red laser light source g Green laser light source b Blue laser light source d Spacing between main diffusion layer and sub-diffusion layer

Claims (11)

In an image display screen that projects an image obtained by modulating light from a light source,
A main diffusion layer, and a sub-diffusion layer separated from the main diffusion layer on both sides of light entering and exiting the main diffusion layer;
The distance d between the main diffusion layer and the sub-diffusion layer is d <5 mm,
For the output peak wavelength λ and the output wavelength half width Δλ of the light source of at least one color,
d × Δλ> λ ² , Δλ <10 nm
An image display screen characterized by satisfying The haze values Hm and Hs of the main diffusion layer and the sub-diffusion layer are
The image display screen according to claim 1, wherein 40% <Hs <Hm. The image display screen according to claim 1 or 2,
It has a selective light absorption layer on the viewer side from the main diffusion layer,
An image display screen, wherein the selective light absorption layer has a visible light absorption wavelength peak of 550 to 610 nm. In the image display screen as described in any one of Claims 1-3,
An image display screen having a visible short wave to ultraviolet absorption layer closer to the viewer than the main diffusion layer. In the image display screen as described in any one of Claims 1-4,
An image display screen having a visible long wave to near-infrared absorbing layer closer to the viewer than the main diffusion layer. In the image display screen as described in any one of Claims 1-5,
A transmissive image display screen comprising a lenticular lens sheet and a black stripe layer between a light incident side sub-diffusion layer of a main diffusion layer. In the image display screen as described in any one of Claims 1-5,
A reflection-type image display screen in which a main diffusion layer is a reflection diffusion surface, and one sub-diffusion layer serves as both an incident-side sub-diffusion layer and an emission-side sub-diffusion layer. The image display screen according to any one of claims 1 to 7 and an independent light source of at least three colors of RGB,
In an image display device that displays an image obtained by modulating light from each light source,
The output peak wavelengths λr, λg, λb of each light source are
620 nm <λr <670 nm, 500 nm <λg <550 nm, 430 nm <λb <480 nm
An image display device characterized by that. The image display device according to claim 8.
An image display device, wherein each of the RGB light sources is a laser light source. The output peak wavelength of each RGB light source is
625 nm <λr <660 nm, 510 nm <λg <545 nm, 435 nm <λb <470 nm,
The image display device according to claim 8, wherein a half-value width Δλ of each light source wavelength is less than 5 nm. The image display device according to claim 8, wherein at least one of the RGB light sources is
An image display device characterized by being an SHG laser light source.

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