WO2007043135A1

WO2007043135A1 - Micro mirror screen

Info

Publication number: WO2007043135A1
Application number: PCT/JP2005/018344
Authority: WO
Inventors: Kazunori Miwa
Original assignee: Kazunori Miwa
Priority date: 2005-10-04
Filing date: 2005-10-04
Publication date: 2007-04-19

Abstract

It is possible to improve a reflection-type and a transmission-type projection screen. By preventing reflection of an external light applied to a projection screen toward an observer in a visual range, it is possible to improve a display contrast under the external light. An optimally designed micro mirror is repeatedly arranged on a projection screen so as to effectively arrange a video light in a predetermined visual range and absorb or introduce external light out of the visual range, thereby improving the visibility under the external light and reducing power consumption. It is possible to manufacture, at a low cost, a reflection-type and a transmission-type projection screen visible under the external light. This can be applied to a display requiring visibility under the external light and saving power consumption.

Description

Specification

Micro mirror screen technology

[0001] The present invention relates to a reflective or transmissive projection screen with good visibility even in the outdoors or in a bright room where the display contrast is extremely high under external light. Background art

There are two types of projection screens: a front projection screen (reflection type) that emits image light from the viewer side, and a rear projection screen (transmission type) that emits image light from the opposite side of the viewer. Both types have a structure in which the image light from the projector is scattered and displayed by fine irregularities on the screen surface and diffusing material, so external light other than the image light is also scattered at the same time, resulting in a decrease in display contrast. There are structural problems such as ease.

[0003] Reflection-type projection screens include a mat type having an irregular surface and a bead type in which minute beads are spread to give retroreflective properties. These reflection type projection screens display the image with specular reflection component or retroreflective component and diffuse reflection component that reflects the image light from the projector on the screen surface, but if there are too many specular reflection components and retroreflective components Although it is easy to maintain contrast with external light, the viewing angle range is limited and hot spots are likely to occur in the image. On the other hand, when the diffuse reflection component is increased, the gain is low and the contrast with respect to the external light is maintained, but a good display quality can be realized.

[0004] A transmissive projection screen collimates the light flux from a projector with a Fresnel lens, expands the horizontal viewing angle characteristics with a lenticular lens, and further disperses a diffusing material in the lens medium to achieve a vertical viewing angle. There are many cases to get. The transmissive projection screen having such a structure has a problem that the contrast of the display is lowered due to scattering of external light by the diffusing material. In addition, the viewing angle range in the vertical direction by the diffusing material is about ± 20 to 30 ° at the maximum, and there is a problem that the characteristics are clearly inferior in the horizontal direction. When the concentration of the diffusing material is increased to improve the viewing angle characteristics, There is a problem in that the light extraction efficiency is lowered by diffusing light widely and increasing the components exceeding the critical angle in the lens medium and confining them in the medium.

[0005] In any case, because the projector displays the image by diffusing the projected image light, the off-brightness of the display is increased by the diffuse reflection of the external light, resulting in a contrast ratio. (ONZOFF ratio) decreases. Now, if the diffuse reflectance on the display surface is :, the display brightness is B (cdZm ² ), and the illuminance of outside light is L (lux), the contrast ratio C on the screen under outside light is

C = (rL + B) / rL

It can be expressed. Here, the display brightness of the non-display portion is assumed to be zero. The diffuse reflectance r varies depending on the external light incident angle and the direction of the observer. In addition, surface reflection (regular reflection) on the display surface and diffuse reflection are in a trade-off relationship. Roughening the surface reduces specular reflection but increases diffuse reflection.

[0006] A conventional reflective projection screen uses, for example, white salt vinyl, aluminum, cloth or the like as a screen base material, and a white ink containing a pearl pigment or an aluminum paste pigment is printed thereon as a reflective layer. Reflective screens are used that are coated and finely textured as required. In such a conventional reflective projection screen, when projecting in a bright room, it can be seen by increasing the overall brightness with a projector with a large amount of light, but the brightness in the bright part is improved, but the brightness in the dark part is not improved. Rather, the light emitted from the bright part in the screen is reflected on the wall surface etc. and is incident again as external light, which increases the brightness of the dark part and lowers the contrast. Therefore, it is common to project with the room lighting dimmed.

[0007] As a method for improving the visibility, there are a method for reducing the diffuse reflectance r and a method for making it difficult to reflect external light. The former method is a reflective type that improves the contrast ratio by forming a light-absorbing layer such as halftone dots, honeycombs, stripes, and grain with black ink on the display surface by printing. A screen has been proposed. As an example of the latter, in Patent Document 1, a louver composed of a light-shielding layer and a light diffusion layer is repeatedly arranged to diffuse and reflect the image light of the projection from below to the front of the screen, while outside light from above is A structure that is absorbed by the light shielding layer is proposed. As another example of the latter, Patent Document 2 describes a scan. By providing a reflective layer that selectively reflects the wavelength of the image light on the clean surface, the contrast to external light is improved.

[0008] In addition to this, a bead screen has been put into practical use, in which fine beads are spread over the entire display surface and the direction of the reflected light is returned to the incident direction so that it does not enter the viewer's eyes. A reflection type screen provided with a bead screen and a light absorption layer has also been proposed. In addition, by using a metal reflective layer, although the viewing angle range is narrowed, a proposal has been made to improve the contrast and brightness by lowering the diffuse reflectance and increasing the regular reflectance.

[0009] However, these conventional technologies require a projector with a large amount of light to reduce the screen reflectivity, and those using light-shielding objects such as louvers have a limited viewing angle range and are effective. There is a problem that the external light irradiation angle is limited. In addition, screens using a metal reflective layer have a very narrow viewing angle range, limiting the field of use. With these conventional techniques, the display contrast is insufficiently improved because these diffuse reflections are not completely removed.

Patent Document 1: Japanese Patent Laid-Open No. 51-44186

Patent Document 2: Japanese Patent Laid-Open No. 2003-344951

Disclosure of the invention

Problems to be solved by the invention

[0010] In display using light such as video display and illumination display, the problem of contrast reduction caused by scattering of external light is called washout, which is an inseparable problem for self-luminous display devices. Especially for projection screens, the display is originally due to light scattering, so this problem is large. Not only the visibility is deteriorated, but also an excessive light source output is required, and the viewpoint of energy saving is solved. Was desired.

Means for solving the problem

[0011] The light incident / reflection profile of the micro mirror composed of minute curved mirrors does not reflect the external light from the main external light incident angle within the light distribution range of the screen, and at least the light flux from the light source It has been clarified that it is possible to solve the above problems by realizing a micromirror screen that also has a micromirror group power set so as to satisfy the conditions for reflection within the light distribution range of the screen. The invention's effect

[0012] According to the present invention, it is possible to realize a projection screen with good visibility without reducing display contrast under strong external light even when a light source having a relatively low output is used. Such projection screens can be applied to the power of reflection-type front projection screens and transmission-type rear projection screens, super-power-saving picto-sign display devices and traffic signals.

Brief Description of Drawings

FIG. 1 is a layout view of a reflective micromirror screen. (Example 1)

FIG. 2 is a layout diagram of micromirrors in the vertical direction.

[FIG. 3] FIG. 3 is a layout diagram of micromirrors in the horizontal direction.

FIG. 4 is a cross-sectional view of a continuously formed micromirror array.

FIG. 5 is a cross-sectional view of a micromirror array embedded in a transparent body.

[FIG. 6] FIG. 6 is a sectional view of a see-through screen.

FIG. 7 is a cross-sectional view of a reflective curved screen.

FIG. 8 is a cross-sectional view of a reflective screen using a Fresnel lens.

FIG. 9 is a perspective view of a reflective screen on which strip-shaped micromirror arrays are arranged.

FIG. 10 is a perspective view of a reflective screen in which sub-micromirror rows are arranged.

FIG. 11 is a layout diagram of a transmission type micromirror screen. (Example 2)

FIG. 12 is a cross-sectional view of a transmission type macro mirror screen.

FIG. 13 is a sectional view of a transmissive curved screen.

FIG. 14 is a cross-sectional view for explaining a leakage light preventing structure.

FIG. 15 is a perspective view of a transmission type microscreen.

FIG. 16 is a perspective view of a display body formed by a set of micromirror screens. (Example 3)

Explanation of symbols

[0014] 1 Micro mirror screen

2 Projector

3 Observer 4 External light source

5 Farthest screen point

6 screen latest

7 Micromirror

8 Transparent body

9 Aspheric reflection mirror

10 Semi-permeable membrane

11 Statue behind the screen

12 Fure ^ Norenz

13 Resin base material

14 Strip-shaped micromirror array

15 Sub-micromirror

16 Transmission type micro mirror screen

17 Light incident part

18 Light absorption film

19 Display (A collection of micromirror screens)

20 Reflector or shading plate

21 LED light source

22 Enclosure

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] By repeatedly arranging a group of micromirrors that have been carefully optically designed, image light can be distributed within a predetermined range, and external light can be efficiently absorbed or guided outside the visual range. Can be solved.

Example 1

FIG. 1 is a layout view of a first embodiment according to the present invention. The arrangement of the reflective micromirror screen 1 and projector 2, observer 3, and external light source 4 is shown. The incident angle range in the vertical direction from the projector 2 with respect to the reflective micromirror screen 1 is a to a, and the viewing range is j8 to β. The outside light incident angle range is γ to γ. Micromi In order to reflect the image light of the incident angle from the projector to the viewing range j8 to β by the micromirror arranged at the farthest point 5, the micromirror screen 1 is constituted by a set of mirrors. Is normal (α + β) Ζ2 to + j8)

2 1 1 1 2

It should be in the range of Z2. By forming a micromirror corresponding to one pixel by the curved surface continuously changing in the normal direction, the image light can be evenly distributed in the set observation range. At this time, the center axis of the micromirror is arranged in the middle of the light distribution center (β + β) 2 of the screen and the light source direction _α of the micromirror force.

1 2 1

[0017] In addition, in order to reflect the image light having the incident angle α from the projector to the viewing range j8 to β by the micromirror disposed at the nearest point 6 of the screen, the micromirror method is used.

2 1 2

It suffices if the line is in the range of (ひ + β) Ζ2 to (ひ + β) Ζ2. At this time

2 1 2 2

The center axis of the light is the light distribution center of the screen (j8 + β) Ζ2 and the light source from this micromirror

1 2

Place it in the middle of direction α. Micromirror placed between the farthest point and the nearest point

2

Are similarly arranged.

[0018] The farthest point force can be simply arranged. Micromirrors having the same curved surface can be arranged up to the nearest point. When the minimum value Θ and the maximum value Θ of the normal of the micromirror are obtained,

mm max

It becomes. Therefore, when the screen is constructed by repeatedly arranging micromirrors with the same curved surface up to the nearest point, the curve that continuously changes to Θ force 0

min max

By configuring a micromirror corresponding to one pixel depending on the surface, the image light can be distributed evenly within the set observation range.

FIG. 2 shows a vertical arrangement of the micromirrors 7 of the reflective micromirror screen.

As shown in Fig. 2, the space between the upper and lower micromirrors is arranged so that the image light irradiates the micromirrors at the shortest point of the screen. The minimum distance between the micromirrors is _α when the upper end of the micromirror is looking up at the lower end of the adjacent micromirror. This time outside

2

The minimum external light irradiation angle at which light does not reflect from the screen to the viewer side is j8, and external light of upward force exceeding γ = β is not reflected in the observation range. The image light source is also unable to reflect the image light to the observer side above j8. Same profile in vertical direction When arraying micromirrors with a mirror, it is necessary to set the distance between the micromirrors wider in order to effectively enter the micromirror at the farthest point. Therefore, the image light source is arranged in an oblique direction with respect to the micro screen, and all the microphone mirrors are positioned at positions where the image light incident on the nearest point and the farthest point where the image light reaches at least the effective part of the micromirror And has a profile that does not overlap the external light irradiation angle range and the visual recognition range at least at the most recent micromirror, so that it can be visually recognized without causing a decrease in contrast due to external light.

[0020] Actually, diffuse reflected light of external light may travel to the observer side due to dirt or distortion of the micromirror. In addition, external light reflected by the micromirror may be reflected on the back surface of the micromirror and travel through the transparent body supporting the micromirror, or may be reflected at the support interface and return to the visible range. In order to prevent this, external light can be absorbed without reflecting to the viewer side by using one surface of the micromirror as a reflective layer and the back surface as an absorption layer. The same effect can be obtained by arranging a light absorption film behind the micromirror group.

[0021] In addition, the horizontal image light incident range, the visible range, and the external light incident range can be set in the same manner. FIG. 3 is a diagram showing the arrangement of the micromirror groups in the horizontal direction when the projector is placed at the center of the screen for projection. Each micromirror 7 constitutes one unit or less of pixels.

[0022] A micromirror that satisfies the curvatures in the vertical and horizontal directions can be formed of a part of a spheroid. By offsetting the arrangement of the individual micromirrors by a half pitch with respect to the top and bottom or left and right micromirrors, it is possible to suppress moiré that occurs during image light irradiation. In addition, the effect can be improved by setting the offset amount according to a specific rule or making it irregular.

[0023] When the arrangement in the vertical direction can sufficiently take measures against external light, it is possible to continuously form the gap portion of the micromirror with the reflecting mirror member in the horizontal direction. Fig. 4 shows an example of a micromirror array when a projector is projected at the center of the screen. By making each micromirror 7 symmetrical, 0 = — Θ, it is continuous in the horizontal direction.

mm max

It can be manufactured as a micromirror array. More simply, the above mirror angle It may be constituted by a series of fine wavy concave mirrors and convex mirrors satisfying the degree. In addition, when the red, green, and blue pixels of the image light source are spatially arranged, a color shift may occur in the projected image. For example, when the pixels are arranged in the horizontal direction, the diffusibility can be improved and the color shift can be reduced by setting the horizontal micromirror pitch to a fraction of the pixel size of the image light. .

[0024] In addition, by arranging the micromirror group so as to be embedded in a transparent body such as transparent resin, it is possible to widen the reflection range and increase the incident angle of the image light. FIG. 5 is a diagram for explaining the visible range of the group of micromirrors embedded in the transparent body. The image light from the projector 2 enters the micromirror 7 through the interface of the transparent body 8. Further, by adopting a configuration in which the light is reflected and projected by the aspherical reflecting mirror 9, the entire apparatus can be reduced in size.

[0025] The individual micromirrors constituting the micromirror group can be displayed without affecting the resolution of the image light as long as the size of the image light projected by the projector is one pixel or less. . However, moire occurs when the spatial frequency of the image light and the repetition frequency of the micromirror group are close, so it is necessary to determine the arrangement pitch of the micromirror group in consideration of the upper limit of the spatial frequency of the image light.

[0026] The micromirror screen, which is a group of micromirrors having such a configuration, reflects the image light incident from the image light source to the viewer side, provides good visibility in the viewing range, and allows outside light to be viewed in the viewing range. It is possible to prevent an observer from being reflected by reflecting outside, transmitting through a gap, or absorbing the absorption layer.

[0027] FIG. 6 is a cross-sectional view of a see-through screen in which a semi-transmissive film 10 is placed behind the micromirror screen 1 so that an image 11 behind the screen can be visually recognized, and an image projected on the screen. In this example, the effect of reducing the influence of the background on the light is provided. A device capable of adjusting the transparent state and the non-transparent state instead of the semi-transparent film may be used.

FIG. 7 is an example in which the screen is arranged in a curved shape so that the elevation angle of the image light source as seen from the micromirror array force is within a certain range. By adopting such a configuration, the micromirrors can be optimally arranged, and the light distribution range can be set effectively without waste.

FIG. 8 shows a configuration in which the image light from the projector 2 is collimated by the Fresnel lens 12 and then incident on the micromirror screen. With this configuration, the screen The optimal light distribution range can be realized with a group of micromirrors with a single profile while keeping the surface flat. The Fresnel lens 11 may be an aspheric lens or an aspheric mirror. It can also be arranged parallel to the screen.

FIG. 9 is a perspective view of a micro mirror screen in which a plurality of strip-shaped micro mirror rows 14 each having a micro mirror formed thereon are juxtaposed on a resin base material 13. The micromirror array 14 and the resin base material 13 can be produced by simultaneously molding by a synthetic resin molding method such as an injection molding method or a compression molding method using a resin material in which a black pigment or the like is dispersed as a molding material. The thickness of the macro mirror array is ΙΟΟηπ! Form a metal thin film such as Ag film or A1 film of ~ 1 μm. The metal thin film can be formed by electroless partial plating of Ag or vacuum deposition from the oblique direction of A1. A protective film such as transparent resin is formed on the metal thin film thus formed.

[0031] When the micromirror screen manufactured in this way is installed on the wall surface of a building and the screen is obliquely downwardly irradiated with image light from the projector, good visibility can be obtained despite direct sunlight. In addition, by including anatase type titanium oxide or the like in the protective film, an antifouling effect can be provided by a photocatalytic reaction. It is also possible to form the resin base material 13 with a transparent resin. In this case, a light absorption layer can be formed by forming a black layer or the like on the back surface of the metal thin film. Even if a metal thin film is not formed, a certain reflectance can be secured by making the surface roughness of the molded product equivalent to a mirror finish, and it can be used as a micromirror screen.

FIG. 10 is a perspective view of a macro mirror stain which also has a force with the main micro mirror 7 and the sub micro mirror 15. By forming the sub-micromirror 15, the image light from the image light source can be effectively distributed to the observation range regardless of the incident angle.

Example 2

FIG. 11 is a layout view of a second embodiment according to the present invention. This shows the arrangement of the transmissive micromirror stationary 16 and the projector 2, the observer 3, and the external light source 4. The incident angle range in the vertical direction from the projector 2 with respect to the transmission type microphone mouth mirror screen 16 is defined as a;

1 2 and the viewing range is j8 to β

1 2 The external light incident angle range is γ to γ

1 2 The design method of the micromirror is basically the same for the transmission type micromirror screen. In other words, the incident angle from the projector is reduced by the micromirror placed at the farthest point 5. In order to reflect the image light of a to the visible range j8 to β, the normal of the micromirror is (α

1 1 2

+ β

1 1) From Ζ2 (H + β

1 2) It should be in the range of Ζ2. At this time, the center axis of the micromirror is the light distribution center (j8 + β) +2 of the screen and the direction of the light source from this micromirror.

1 2 1 Place in the middle direction.

In addition, in order to reflect the image light having the incident angle α from the projector to the viewing range j8 to β by the micromirror disposed at the nearest point 6 of the screen, the micromirror method is used.

2 1 2

2 1 2 2

1 2

2

Are similarly arranged.

[0035] When the minimum value Θ and the maximum value Θ of the normal of the micromirror in the case where the micromirror having the same curved surface is arranged up to the nearest point are calculated as follows:

mm max

It becomes.

[0036] In a transmissive screen, the area from the projection engine (projector) to the back of the screen is usually covered with a light-shielded enclosure, so that the external light irradiation range and the image light irradiation range do not overlap and maintain good visibility. it can. Even if it is not covered with an enclosure, the range in which external light is emitted to the visible range due to the reflection of the macro mirror is extremely limited.

FIG. 12 is an example of a cross-sectional view of a transmissive micromirror screen. Here, an arrangement of only the force micromirror 7 composed of the main micromirror 7 and the submicromirror 15 is also possible. By arranging the sub-micromirror 15, leakage light from the microscreen can be prevented and display with high luminance can be achieved. In addition, as shown in Fig. 13, by arranging the screen in a curved shape so that the elevation angle of the image light source seen from a row of micromirrors is in a certain range, the light distribution range can be set effectively and without waste. Can be prevented. Further, as shown in FIG. 14, when the micromirror group is embedded in a transparent body, leakage light is prevented by making the incident angle of the leakage light with respect to the emission side interface equal to or greater than the critical angle. Can be stopped.

FIG. 15 is a perspective view of a strip-shaped transmissive micromirror screen formed of a transparent resin. The micromirror 7 is formed at the interface of the transparent resin, and the image light incident surface 17 and the light absorption film 18 are also formed at the other interface of the transparent resin. As the transparent resin, an acrylic or polyester thermosetting or ultraviolet curable resin can be used. It can also be molded by injection molding or hot pressing using a thermoplastic resin such as polycarbonate. The micromirror part formed at the resin interface can be used as a micromirror by forming a metal thin film by electroless selective plating or vacuum deposition. Moreover, it can be set as a light absorption layer by forming a black film etc. in the back surface of a metal thin film. Even if a metal thin film is not formed, it can be used as a micromirror by total reflection of light at the transparent resin interface. The light absorbing film 18 can be formed by allowing a resin containing black pigment or the like to flow down.

Example 3

FIG. 16 is a perspective view showing a third embodiment. Reference numeral 19 represents the shape of a set of micromirrors as a display body, here a pictogram. 20 is a white painted plate from the observer side, but the inner surface is a reflecting plate or a light shielding plate. Reference numeral 21 denotes an LED light source, which can select an emission color suitable for display. Reference numeral 22 denotes a housing having a reflecting plate or the like on the inner surface.

[0040] The internal illumination sign having such a structure can perform display with extremely low power consumption, and can maintain good visibility even under external light. A part of the light emitted from the LED light source 21 is directly incident on the micromirror screen and is distributed to a predetermined viewing range. A part of the light is reflected by the reflecting plate 20 or the reflecting plate on the inner surface of the housing 22 and enters the micromirror screen. In addition, a color filter that transmits the light from the LED light source according to the shape of the display body can be placed side by side to function as a reflective display device in the daytime.

[0041] In addition, a display body represented by a set of micromirrors is layered, or a reflective micromirror, a transmission micromirror, and a single or multiple light sources are combined to produce a multicolor display body or selective light emission. It is also possible to make a display for performing. It can also be used for power-saving traffic signal lights with strictly defined light distribution ranges. Industrial applicability

Good visibility can be ensured even under external light, and power-saving reflective and transparent projection screens can be manufactured at low cost. It can also be applied to displays and other applications that require visibility and power saving under external light.

Claims

The scope of the claims

[I] Consists of a micromirror force reflecting area composed of minute curved mirrors and a non-reflective area consisting of a transparent body, absorber, or air gap. A micromirror screen characterized by having a micromirror group power that does not reflect within the light range and has a profile that satisfies at least the condition of reflecting the luminous flux of light source within the light distribution range of the screen.

[2] The micromirror is composed of an interface between a transparent body constituting the micromirror screen and a gap, and incident light from the light source power is reflected to the light distribution range of the screen by total reflection at the interface. The micromirror screen according to claim 1, wherein:

3. The micromirror screen according to claim 1, wherein the micromirror is composed of a composite material of a reflective layer and a light absorbing layer or a light absorbing material having surface reflection.

4. The micromirror screen according to claim 1, wherein a light absorption film is disposed adjacent to the micromirror group.

5. The microphone mirror screen according to claim 1, wherein the micro mirror is formed of a metal thin film.

6. The micro mirror screen according to claim 1, wherein the micro mirror group is arranged in a curved shape.

7. The micromirror screen according to claim 1, wherein the image light from the projector is collimated and then incident on the micromirror group.

8. The reflective region comprising the micromirrors comprises a micromirror array arranged in a horizontal direction, and the reflective regions and the non-reflective regions are alternately arranged. Micro mirror screen.

9. The micromirror screen according to claim 1, wherein the group of micromirrors is composed of a group of micromirrors having a plurality of incident / reflecting angle profiles.

10. The micromirror screen according to claim 1, wherein the set of micromirror groups has a structure representing a shape as a display body or a part thereof.

[II] The micromirror screen according to claim 1, wherein a light shielding plate is juxtaposed so that the set of micromirror groups represents a shape as a display body or a part thereof.

[12] The display body expressed by the set of micromirror groups is expressed by combining light beams incident on a single or plural light sources or by combining light beams from a set of stacked micromirror groups. The micromirror screen according to claim 1, wherein:

[13] The micromirrors constituting the group of micromirrors also include a display reflection region that reflects incident light at a specific display light emission angle, and a progressive reflection region and force that causes the incident light to travel to other macromirrors. The micromirror screen according to claim 1, wherein: