Surface shape diffusing sheet for reducing blackening, reflective screen, image display system, and image display method

Abstract

Provided are a surface shape diffusing sheet, a reflective screen, an image display system, and an image display method that reduce blackening. A surface shape diffusion sheet (1) is provided with a surface shape anisotropic diffusion layer (2) and a substrate (3) as the base thereof, the diffusion angle in the in-plane up-down direction of the surface shape anisotropic diffusion layer (3) is within the range of + / -14 DEG (half width), and the transmittance (T) of the visible light wavelength band within or on the surface of the substrate (3) is within the range of 0.5 or more and less than 1. The image display system calculates the blackening amount (Lb) of the image (= 255 * brightness of black / brightness of white), and corrects the brightness range Lb < = Llt of the brightness (L) of each element of the image. The lightness observed within 2Lb is reduced.

Description

Technical Field

[0001] The present invention relates to a surface shape diffusion sheet for reducing blackening applied to a reflective screen, a reflective screen having the diffusion sheet, an image display system having the reflective screen, and an image display method using the reflective screen (hereinafter also referred to as the screen) and an image projection device.

[0002] The reflective screen mentioned here is a screen that diffuses / reflects the image light of the image projection device (also called a projector) from the front side (observer side) of the screen toward the front side and emits it. It refers to a type that diffuses / reflects the image light incident from the surface of the screen on the surface of the screen, and a type that diffuses the image light incident from the surface of the screen on the surface of the screen and reflects it from the internal reflective layer. Background Art

[0003] In reflective screens, there is a phenomenon called hot spot, in which the incident image light becomes a bright spot on the screen surface, and a phenomenon called reflection, in which the brightness of the ceiling light and the window near the screen is reflected on the screen surface and is visible.

[0004] In order to prevent these phenomena, a surface shape diffusion layer having a concave-convex shape with a pitch of several μm to several tens of μm is conventionally provided on the surface of the screen, so that the hot spot and the reflected light are diffused on the surface of the screen and are not noticeable (see Patent Document 1). In addition, the composition of the surface shape diffusion layer and the substrate as the base thereof is called a surface shape diffusion sheet.

[0005] However, when the surface of the surface shape diffusion layer becomes the screen surface, not only the image light from the projector, but also the external light (unnecessary light other than the image light) from the ceiling light, the floor, and the wall and window on the front side of the screen is diffused on the surface of the screen. Moreover, a part of it is reflected to the front side on the surface of the screen, and the rest reaches the reflection layer inside the screen and is reflected and emitted to the front side. These so-called external light diffuse reflection lights are superimposed on the image light, so as to generate so-called noise light, which deteriorates the image quality of the image of the observed object.

[0006] This phenomenon particularly causes the brightness of black in the image to increase, so it is called "blackening".

[0007] If blackening is caused by external light, the contrast, grayscale expression and color reproduction of the image will be greatly damaged. The image will not look three-dimensional, the black will not be tight but gray, and the image as a whole will not be bright in color. It will look thin and blurry, making it difficult to reproduce the image clearly.

[0008] This blackening depends on the intensity of external light, so it can be prevented by turning off the ceiling light in the room, using curtains to block the windows, and preventing external light from entering the screen. However, in school classrooms and corporate meeting rooms, it is also important to watch large displays, confirm each other's expressions, check documents in hand, and take notes. If these actions become impossible due to darkening the room, the efficiency of teaching and meeting operations will be significantly reduced.

[0009] On the other hand, as large displays used in lectures and meetings, there are also methods of using liquid crystals, OLEDs, or micro LEDs with less black, but these require large displays of 80 inches or more. In order to mass-produce these displays, a large amount of medicines, water, electricity, etc. are consumed in large-scale manufacturing equipment and manufacturing processes, which has an excessive environmental load from the perspective of SDGs (Sustainable Development Goals). In addition, due to the large size, weight, and power consumption of the display body, it is difficult to transport and install, and the price is also expensive, making it difficult to widely popularize. Due to the above situation, there is an increasing need to develop an image display system using a reflective screen that can reproduce high-quality images even in a bright environment affected by external light.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent No. 5971742 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] As described above, when blackening occurs due to external light, the contrast, grayscale expression, and color reproducibility of the image projected on the reflective screen are greatly affected. Since contrast is expressed by the ratio of the brightness of white to the brightness of black, the contrast deteriorates by the amount by which the brightness of black increases due to blackening. Similarly, grayscale expression is determined by the difference between the brightness of white and the brightness of black, so the brightness range of grayscale expression is narrowed by the amount by which the brightness of black increases.

[0015] Regarding the above-mentioned contrast and grayscale expression problems, the conventional measure is to increase the brightness of white by an amount corresponding to the blackening on the projector side. Currently, the image light output of the projector for schools and offices sold on the market is a high output of about 4000 lumens at maximum.

[0016] On the other hand, the current situation is that almost no measures have been taken to address the deterioration of color reproducibility due to blackening. Even in reflective projection displays using high-output projectors, there is still the following problem: in a bright environment affected by external light, the original color cannot be reproduced, and the color reproducibility deteriorates in proportion to the brightness of the blackening.

[0017] Therefore, the present invention provides a surface shape diffusion sheet that reduces the image quality degradation caused by external light from the ceiling light, which has the greatest influence on the above-mentioned blackening, and further all external light, in a bright environment of a reflective screen, and a reflective screen having the surface shape diffusion sheet. Also provided is an image display system and an image display method that can reduce the deterioration of the color reproducibility of the image in the reflective screen and can correct the deteriorated color reproducibility of the image.

[0018] Solutions for solving problems

[0019] In order to solve the above-mentioned problem, the inventors of the present invention have conducted intensive research and obtained the following knowledge: it is effective to set the surface shape diffusion layer of the surface shape diffusion sheet as a surface shape anisotropic diffusion layer that limits the diffusion angle in the vertical direction, and to reduce the transmittance of the substrate that is the base of the surface shape anisotropic diffusion layer in the visible light wavelength band as a solution. In addition, the inventors of the present invention have obtained the following knowledge: by expressing the blackening with the numerical value of the RGB color model, the deterioration of the color reproducibility of the image can be quantified.

[0020] The present inventors have completed the present invention through further research based on the above findings. That is, the present invention is as follows.

[0021] [1] A surface shape diffusion sheet provided on the surface of a reflective screen for diffusing and emitting image light from an image projection device, wherein the surface shape diffusion sheet reduces blackening and is characterized by comprising:

[0022] a surface anisotropic diffuser layer; and

[0023] a flat substrate, which is the base of the surface anisotropic diffusion layer,

[0024] wherein the diffusion angle in the vertical direction of the surface of the surface anisotropic diffusion layer is within the range of ±14° (half value width),

[0025] The transmittance T of the visible light wavelength band inside or on the surface of the substrate is within a range of 0.5 or more and less than 1.

[0026] [2] A reflective screen having a diffusion sheet on its surface, wherein:

[0027] The diffusion sheet is a diffusion sheet having a surface shape according to [1],

[0028] The reflective screen includes a reflective layer, a protective film, and a retaining plate which are sequentially arranged and bonded from the substrate toward the back side.

[0029] The bonding surface between the reflective layer and the substrate becomes a surface for reflecting the image light.

[0030] The protective film is a film covering the reflective layer,

[0031] The holding plate is a plate for maintaining the flatness of the substrate.

[0032] [3] The reflective screen according to [2], characterized in that:

[0033] It also has a lens layer, which is arranged and bonded between the substrate and the reflective layer.

[0034] The lens layer is composed of a Fresnel lens having a reflective surface shape on the back side.

[0035] The bonding surface between the reflection layer and the lens layer serves as a surface for reflecting the image light.

[0036] [4] The reflective screen according to [3], characterized in that:

[0037] The image light is reflected from the aperture surface of the projection lens of the image projection device, which is separated from the surface reflecting the image light by a distance a with respect to the focal length f of the Fresnel lens, thereby forming a spatial imaging aperture surface at a position separated by a distance b, wherein b satisfies the relationship (1 / a)+(1 / b)=1 / f.

[0038] [5] An image display system comprising the reflective screen according to any one of [2] to [4], an image projection device, a brightness meter, a black flooding calculation unit, and a brightness adjustment unit, wherein:

[0039] The image projection device projects image light,

[0040] The luminance meter measures the luminance of black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model projected from the image projection device onto the reflective screen under external light to obtain respective measurement values ​​Kmin and Kw.

[0041] The black flooding amount calculation unit calculates the black flooding amount Lb as the integer part of the value of the formula: 255×Kmin / Kw,

[0042] The brightness adjustment unit corrects the brightness reduction observed within the brightness range Lb≤L<2Lb of the brightness L of each element in the image that is faded from black (R=Lb, G=Lb, B=Lb).

[0043] [6] The image display system according to [5], characterized in that:

[0044] An image light output adjustment unit is provided in place of the brightness adjustment unit or in addition to the brightness adjustment unit.

[0045] The image light output adjustment unit increases the brightness of the white color from Kw to Kw×(1+2Lb / 255) to reduce black cast.

[0046] [7] An image display method using the reflective screen according to any one of [2] to [4] and an image projection device for projecting image light, the image display method comprising the following steps:

[0047] Projecting black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model from the image projection device to the reflective screen;

[0048] Measuring the brightness of the black and white colors under external light to obtain respective measurement values ​​Kmin and Kw;

[0049] The blackening amount Lb is calculated as the integer part of the value of the formula: 255×Kmin / Kw; and

[0050] The brightness adjustment step corrects the brightness reduction observed within the brightness range Lb≤L<2Lb of the brightness L of each element in the image that is blackened (R=Lb, G=Lb, B=Lb).

[0051] [8] The image display method according to [7] is characterized in that it has an image light output adjustment process instead of the brightness adjustment process or in addition to the brightness adjustment process, and in the image light output adjustment process, the brightness of the white color is increased from Kw to Kw×(1+2Lb / 255) to reduce black cast.

[0052] Effects of the Invention

[0053] According to the present invention, it is possible to reduce the blackening of a reflective screen in a bright environment due to external light, which has the greatest impact from the ceiling light, and all other external light. Furthermore, the following excellent effects are achieved: even if the color reproducibility of an image deteriorates due to the blackening, the deterioration can be corrected, and the deterioration of the color reproducibility can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram showing an example of the surface shape diffusion sheet according to the present invention.

[0055] Figure 2 It shows that Figure 1 An example of a reflective screen having a surface shape of a diffusion sheet and a schematic diagram of the configuration of an image projection device.

[0056] Figure 3 (a) is a schematic diagram showing the positional relationship between the reflective screen and the ceiling light, and (b) is a schematic diagram showing the positional relationship between the ceiling light, the reflective screen, the projector, and the measuring device (luminance meter) in the blackout measurement.

[0057] Figure 4 (a) is a schematic diagram showing an example of a reflective screen according to the present invention, and (b) is a cross-sectional view of (a) in the screen thickness direction.

[0058] Figure 5 (a) is a schematic diagram showing another example of the reflective screen according to the present invention, and (b) is a cross-sectional view of (a) in the screen thickness direction.

[0059] Figure 6 (a) is a schematic diagram showing another example of the reflective screen according to the present invention, and (b) is a cross-sectional view of (a) in the screen thickness direction.

[0060] Figure 7 This is a schematic diagram showing ray tracing of incident light and reflected light of external light by the Fresnel lens of the spatial imaging aperture surface method / reflective screen according to the present invention.

[0061] Figure 8 It is a schematic diagram showing an example of an internal optical system of the image projection device.

[0062] Fig. 9 : is a figure which shows the visual object display pattern used for studying the relationship between black bleeding and color reproducibility.

[0063] Fig.10 The figures show the visual object display patterns used in the measurement of the brightness reduction amount, (a) shows an example of the case where the brightness of the visual object = 230 and the blackening amount = 215, and (b) shows an example of the case where the brightness of the visual object = 230 and the blackening amount = 115.

[0064] Fig.11 This is a line graph showing the relationship between the amount of blackening and the amount of reduction in the brightness of the visual object, using the brightness of the visual object as a parameter.

[0065] Fig.12This is a line graph showing the relationship between the brightness of a visual object and the amount of brightness reduction, using the amount of blackening as a parameter.

[0066] Fig.13 The figures are diagrams showing visual object display patterns for confirming the brightness range that does not cause a decrease in the brightness of the visual object when the black level is set to 100, (a) is a pattern in which the brightness of the visual object is set to be the same on the left side (black level = 0) and the right side (black level = 100), and (b) is a pattern in which the brightness of the visual object on the right side is increased in order to make the visual object appear to have the same brightness on the left and right sides.

[0067] Fig.14 The figures show display patterns of visual objects for confirming a decrease in brightness, with the amount of blackening set to 255, the visual object set to white in (a), and the visual object set to green in (b).

[0068] Fig.15 1 is an explanatory diagram showing a correction method for the brightness reduction in the color non-reproducible brightness range when the amount of black cast=78.

[0069] Fig.16 This is an explanatory diagram showing that the change in the brightness reduction amount in the color non-reproducible brightness range with respect to the brightness of the visual object can be represented by, for example, a curve having the same shape as the curve A in the figure.

[0070] Fig.17 1 is a flowchart showing a process of obtaining a value of the amount of black cast in the RGB color model.

[0071] Fig.18 It is a diagram showing the blackening lightness range, the color non-reproducible lightness range, and the color reproducible lightness range when the blackening amount = 78. DETAILED DESCRIPTION

[0072] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0073] (Surface shape diffusion sheet according to the present invention: [1] of the present invention)

[0074] First, the surface shape diffusion sheet according to the present invention will be described.

[0075] Figure 1 1 is a schematic diagram showing a surface shape diffusion sheet 1 according to the present invention. Figure 2 As shown in FIG. 1 , the image light from the image projection device 5 is reflected and diffused. Figure 8As shown in the figure, the image light from the three primary color light source 130 composed of, for example, LED chips passes through the diffusion film laminate 122, relay lenses 120a, 120b, and digital mirror device 134 in sequence, and then passes through the projection optical system 138 composed of a plurality of lenses and is reflected in sequence by the concave reflector 140 and the convex reflector 142 to be sent to the reflective screen 4. In addition, the light that does not go to the screen is shielded by the light shielding plate 136. The projection optical system 138 has an aperture, and the space inside the aperture is called the aperture surface 18.

[0076] like Figure 1 As shown, the surface shape diffusion sheet 1 includes a surface shape anisotropic diffusion layer 2 and a flat substrate 3 located as a base of the surface shape anisotropic diffusion layer 2 .

[0077] The material of the anisotropic surface shape diffusion layer 2 is ultraviolet curing resin such as urethane acrylate and epoxy acrylate, or other ionizing radiation curing resin such as electron beam curing resin, and the anisotropic surface shape diffusion layer 2 has flexibility.

[0078] The surface shape anisotropic diffusion layer 2 has a surface shape in which a large number of convex strips of irregular length extending in approximately one direction are arranged laterally at irregular intervals in a direction orthogonal to the extending direction. The height of the convex strips is preferably greater than 0 μm and less than 10 μm. Here, the extending direction of the convex strips is set to the up-down direction, and the arrangement direction of the convex strips is set to the left-right direction. According to such a surface shape, the diffusion angle in the left-right direction is greater than the diffusion angle in the up-down direction. The diffusion angle in the up-down direction and the diffusion angle in the left-right direction can be set to various values ​​by changing the manufacturing conditions.

[0079] The substrate 3 is made of, for example, a transparent resin material and has flexibility. From the viewpoint of achieving both strength and weight reduction, the substrate thickness is preferably 50 μm or more and 250 μm or less.

[0080] The reflective screen 4 having the anisotropic diffusion layer 2 on the surface has a reflective layer 8 inside the screen and a retaining plate 10 for maintaining the flatness of the substrate 2 on the back side of the screen. Figure 2 In the reflective screen 4, as a preferred embodiment, the reflective layer 8 has a Fresnel lens surface shape so that the incident image light is deflected in the normal direction of the screen surface.

[0081] In the present invention, it is defined that the diffusion angle in the vertical direction of the surface of the surface anisotropic diffusion layer 2 is within the range of ±14° (half-value width), and the transmittance T of the visible light wavelength band inside or on the surface of the substrate is within the range of 0.5 or more and less than 1. Before explaining the reasons for these limitations, Figure 2Let's explain blackening in more detail.

[0082] like Figure 2 In this way, in the reflective screen 4 that makes the image light from the image projection device 5 on the front side reflected by the reflective layer 8 and diffusely emitted toward the front side again, in addition to the image light, external light from the ceiling light 11 and other places (floor, front wall, window) is also incident on the screen surface. These external lights are diffused on the screen surface (the surface of the surface-shaped diffusion layer 2), part of them are reflected toward the front side on the screen surface, and the rest reaches the reflective layer 8 inside the screen and is reflected by the reflective layer 8, and is emitted from the screen surface to the front side. The diffuse reflected light caused by these external lights (hereinafter referred to as the diffuse reflected light caused by external light) is superimposed on the image light, causing the image to be blackened. In addition, in Figure 2 In the figure, only the incident image light and the main light of the external light are shown, and the diffuse light is not shown.

[0083] (Diffusion angle of surface anisotropic diffusion layer)

[0084] In order to reduce the blackening caused by the external light from the ceiling light 11 which has the greatest influence, in the present invention, Figure 1 The diffusion angle of the surface anisotropic diffusion layer 2 in the vertical direction of the surface shape diffusion sheet 1 shown is set within the range of ±14° (half-value width). In addition, the range of the diffusion angle is an angle range in which the angle of either clockwise or counterclockwise is positive and the angle of the other is negative in a vertical plane orthogonal to the reflective screen surface in the vertical direction when the normal direction is set to 0° with respect to the screen surface.

[0085] In the present invention, use Figure 3 (a) is used to explain the reason for setting the diffusion angle in the vertical direction to within the range of ±14° (half-value width). Figure 3 (a) shows the general positional relationship between the reflective screen 4A and the ceiling light 11 for the diffusion angle study. The reflective screen 4A is not shown except for the surface shape diffusion layer 2A provided on the screen surface. The surface shape diffusion layer 2A is provided to be able to obtain various diffusion angles θ in the vertical direction in order to study the diffusion angle.

[0086] When Figure 3When the longitudinal dimension of the reflective screen 4A is set to 1H, it is assumed that: the observation position 60 of the reflective screen 4A is 2H to 3H away from the center of the screen, and the ceiling light 11 is located at about 0.5H above the reflective screen 4A and at positions 0.5H, 1H, 1.5H, and 2H away in the front direction. In addition, the diffuse reflected light of the external light caused by the ceiling light 11 is easy to reach the observation position when it is incident on the uppermost part of the reflective screen 4A. In addition, the brightness of the external light incident on the uppermost part is inversely proportional to the square of the distance r from the ceiling light, so the position of 0.5H is the brightest. On the other hand, the observation position is easy to reach at 1.5H and 2H. Therefore, the position of the ceiling light 11 where the influence of external light is the worst is determined by the interaction between the brightness of the external light and the reflection angle of the diffuse reflected light of the external light. Figure 3 In the case of the top light 11 at 1H, it is almost the worst condition. Under this worst condition, the diffuse reflected light of the external light reaches the observation position 2H to 3H as follows Figure 3 As shown in FIG. 1 , the diffusion angle θ of the main light ray 61 of the diffusely reflected light from the external light from the ceiling light 11 at the position 1H is 14.6° or more (greater than 14°). This is also true even if the surface shape diffusion layer 2A is replaced by the surface shape anisotropic diffusion layer 2. Therefore, in the present invention, the diffusion angle of the surface shape anisotropic diffusion layer 2 in the vertical direction is set within the range of ±14° (half value width).

[0087] Thereby, the diffusely reflected light of the external light diffusely reflected on the screen surface does not reach the vicinity of the eyes of the observer located in the front. In addition, it is preferable that the diffusion angle in the left-right direction is as large as possible.

[0088] (Determination of blackening)

[0089] Next, in order to evaluate the blackening reduction effect of setting the diffusion angle of the surface anisotropic diffusion layer to a range of ±14° (half value width), the Figure 1 The blackening caused by external light from the ceiling light was measured by using a surface anisotropic diffusion layer 2. As the diffusion sheet for measurement, a layer having a surface anisotropic diffusion layer 2 formed on a transparent substrate was used. Figure 1The diffusion sheet of the surface shape anisotropic diffusion layer 2 of the surface shape. The diffusion angle of the diffusion sheet for measurement is ±5° (half-value width) when measured as the diffusion angle of the transmitted light incident vertically from the shape side (front side). The aluminum reflection layer is provided on the back of the substrate. The diffusion angle of the diffusion sheet for measurement is ±10° (half-value width) when measured as the diffusion angle of the reflected light reflected by the reflection layer. Therefore, the value of the surface shape diffusion (the diffusion angle of the surface shape anisotropic diffusion layer of the diffusion sheet for measurement) is considered to be within the range of ±14° (half-value width). However, the diffuse reflection light of the external light from the ceiling light also includes light that reaches the reflection layer inside the screen and is reflected by the reflection layer and emitted from the screen surface.

[0090] replace Figure 2 The surface shape of the diffuse sheet 1 is prepared as the above-mentioned diffuse sheet for measurement, and a reflective screen (referred to as SHL screen 82) is prepared, and Figure 2 The measurement was performed using the arrangement shown in the figure. In addition, as a comparison, the same measurement was performed using a commercially available magnetic blackboard screen (referred to as white matte screen 81).

[0091] exist Figure 3 (b) shows the positional relationship between the ceiling light 11, the SHL screen 82 (or the white matte screen 81), the projector 5, and the measuring device (brightness meter 30). Figure 3 (b) The positional relationship between the ceiling light 11 and the SHL screen 82 and Figure 3 The positional relationship between the ceiling light 11 and the reflective screen 4A in (a) is substantially the same. The measurement was performed only when the observation position was 2H, which is a more stringent condition than 3H.

[0092] The device categories shown in Table 1 were used in the measurement. The illuminance of the ceiling light 11 at the center of each screen is shown in Table 2. In addition, although the measured value of the illuminance of the table directly below the ceiling light (illuminometer not shown) is also shown in Table 2 as a reference value, it can be seen from this that the lighting in the room used in the measurement is relatively bright.

[0093] The results of the blackening measurement are shown in Table 3. According to Table 3, it can be confirmed that the blackening (brightness when displaying in full black) of the SHL screen is reduced by about 60% (= (1-35 / 88) × 100) compared with the white matte screen used as a comparison. In addition, since the brightness when displaying in full black and when the projector is turned off is roughly the same, the blackening can also be set to the brightness when the projector is turned off.

[0094] [Table 1]

[0095] Measurement conditions

[0096] Projector EH-LS500 Projector Configuration Figure 3 (b) Displaying images Media player HDMI output (full white, front black image) indoor lighting Full Brightness Brightness meter LS-110

[0097] [Table 2]

[0098] Ceiling light illumination measurement results (unit: lx)

[0099] Center of screen The tabletop directly below the ceiling light Illuminance 410 750

[0100] [Table 3]

[0101] Blackening test results (unit: cd / m 2 )

[0102]

[0103] (Transmittance T of substrate)

[0104] Next, the reason why the transmittance T of the visible light wavelength band inside or on the surface of the substrate 3 is set to be within the range of 0.5 or more and less than 1 in the present invention is described. Here, the transmittance T refers to the ratio of incident light of a specific wavelength passing through the substrate, T = I / I0, I0 is the radiation divergence of the incident light, I is the radiation divergence of the light passing through the substrate (unit: W / m 2 ), since I0≥I, therefore T≤1.

[0105] The diffuse reflected light of the external light from the ceiling light includes light that reaches the reflective layer inside the screen and is reflected by the reflective layer and emitted from the screen surface, so this measure is also necessary. As a measure against the external light that passes through the substrate 3 twice like this, in the present invention, a transparent to black color tone is given to the inside or surface of the substrate 3 in order to reduce the transmittance T of the visible light wavelength band. In addition, reducing the transmittance T of the visible light wavelength band inside or on the surface of the substrate 3 is called transparent blackening. Thus, blackening reduces the amount of darkening of the external light that passes through the substrate 3 twice. Regardless of whether the part of the substrate 3 where the transmittance T is reduced is the inside or the surface of the substrate 3, blackening is reduced.

[0106] In the past, in order to make the image light as bright as possible, the transmittance T was usually increased. In the present invention, although there is also a disadvantage of darkening the image light, the deterioration of the image quality caused by the blackening is preferentially reduced. This is because, in this context, with the development of the light source of the projector from lamps to LEDs and further to lasers, it has become possible to make the image light bright. However, even if the image light can be made bright in this way, if the transmittance T is less than 0.5, the image becomes too dark, so 0.5 is set as the lower limit for the transmittance T. It is preferred to set 0.7 as the lower limit.

[0107] Here, a method for achieving the above-mentioned transparent blackening is described. As this method, a method of uniformly mixing an appropriate amount of UV (ultraviolet rays, the same below) black transmission dispersion into a resin as a material of the substrate 3 is cited (transparent blackening inside the substrate). Since the surface shape anisotropic diffusion layer 2 of the surface shape diffusion sheet 4 is formed on the substrate 3 by UV polymerization, the substrate 3 used in the UV polymerization needs to have the characteristics of allowing UV light to pass through and uniformly reducing the transmittance of visible light. The UV black transmission dispersion is a dispersion obtained by finely granulating a pigment with the characteristics of being black (uniformly absorbing visible light) and allowing UV to pass through, and is compatible with resins such as polyurethane resins, acrylic resins, ester resins, etc., which are the materials of the substrate 3. Therefore, the inside of the substrate can be transparently blackened by uniformly mixing an appropriate amount of the dispersion into the resin as the material of the substrate.

[0108] In addition, as a method of transparent blackening, in addition to the method of mixing the black dispersion into the substrate material, a method of applying the black dispersion to a resin plate of the substrate material (transparent blackening of the substrate surface) or a method of vapor-depositing metal onto the resin plate like an ND filter (transparent blackening of the substrate surface) can also be adopted.

[0109] Furthermore, the substrate 3 has flexibility, and in order to achieve both strength and weight reduction, the substrate thickness is preferably 50 μm or more and 250 μm or less.

[0110] (Confirmation of the blackening reduction effect of the surface shape diffusion sheet according to the present invention)

[0111] In the above-mentioned blackening measurement, the same measurement was performed using a sample screen having the surface-shaped diffusion sheet 1 according to the present invention on the surface. This sample screen was the same as the SHL screen 82 except that the transmittance T inside the substrate was reduced to 0.9 by the transparent blackening described above. As a result, it was confirmed that in this sample screen, the blackening (brightness when displaying completely black) was about 30 cd / m 2 , which is reduced by about 66% (= (1-30 / 88) × 100) compared to the white matte screen. In this sample screen, by reducing the transmittance of the substrate, the blackening is better than the blackening of the SHL screen 82 (about 35 cd / m 2 ) has been reduced.

[0112] (Reflective screen according to the present invention: [2] of the present invention)

[0113] Next, the reflective screen according to the present invention will be described. The reflective screen is a reflective screen having a surface shape diffusion sheet 1 according to the present invention. Figure 4In the illustrated embodiment, a reflective layer 8 , a protective film 9 , and a holding plate 10 are provided, which are sequentially arranged and bonded from the substrate 3 toward the back surface side.

[0114] The bonding surface between the reflective layer 8 and the substrate 3 is a surface for reflecting image light. The protective film 9 is a film covering the reflective layer 8 from the back side. The holding plate 10 is a plate for maintaining the flatness of the front substrate 3 .

[0115] (Reflective layer)

[0116] The reflective layer 8 is preferably formed by thinly depositing a layer of a metal with a high reflectivity (reflectivity of 70% or more) such as aluminum, silver, nickel, etc. so as to have flexibility, or by coating thin small pieces of aluminum called aluminum flakes so that their surfaces are aligned in parallel. The thickness of the reflective layer 8 is set to 0.5 μm to 0.9 μm in the case of vapor deposition and 10 μm to 50 μm in the case of coating, and is determined from the viewpoints of peelability, reflectivity, bending strength, etc.

[0117] (Protective film)

[0118] The protective film 9 is flexible and has the function of protecting the reflective layer 8 by suppressing degradation, peeling, and damage of the reflective layer 8. In addition, the protective film 9 has the function of absorbing light. As the material of the protective film 9, a material obtained by using a mixed resin such as a polyurethane resin, an epoxy resin, and an acrylic resin as a base material, adding a dark-colored paint such as black, a dark-colored dye, a pigment, or a bead containing them as a light absorbing material, and adding various additives having the function of protecting the reflective layer 8 from degradation such as oxidation. In addition, from the viewpoint of fully exerting the protective function and the light absorbing function, the thickness of the protective film 9 is preferably 5 μm to 100 μm at the thinnest part.

[0119] (Retaining plate)

[0120] The holding plate 10 is used to maintain the flatness of the substrate 3 (more specifically, the flatness of the components from the surface shape diffusion sheet 1 to the protective film 9). From the perspective of ensuring rigidity and light weight, it is preferably made of MDF obtained by compressing wood fibers with a thickness of 1.0 mm to 3.0 mm and fixing them with an adhesive. The holding plate 10 is attached to the protective film 9 via a bonding layer (not shown) made of an adhesive material such as a double-sided tape. By having the holding plate 10, deformation during transportation can be prevented, and installation operations such as hanging on a wall surface using a hook or the like can be easily performed.

[0121] Alternatively, a structure in which a magnet sheet (not shown) having a thickness of 300 μm to 400 μm is adhered may be adopted instead of the holding plate 10 .

[0122] exist Figure 4In the example of , the thickness of the anisotropic surface diffusion layer 2 is 40 μm, and the thickness of the substrate 3 is 250 μm. In this embodiment, since there is no Fresnel lens for deflecting image light, it is difficult for image light from the left and right ends to reach the observation position, so the diffusion in the left and right directions at the anisotropic surface diffusion layer 2 is preferably diffused in all directions like complete diffusion.

[0123] (Fresnel lens as lens layer: [3] of the present invention)

[0124] Next, one embodiment of using a Fresnel lens in a reflective screen according to the present invention is described. Figure 4 The images on the left and right sides of the screen are darkened, and it is preferred to use a Fresnel lens. Figure 5 As shown, in one embodiment using a Fresnel lens, the reflective screen is as follows: it has a lens layer 6 arranged and bonded between a substrate 3 and a reflective layer 8, the lens layer 6 is composed of a Fresnel lens having a reflective surface shape on the back side, and the bonding surface between the reflective layer 8 and the lens layer 6 becomes a surface that reflects the image light.

[0125] The lens layer 6 is made of ultraviolet curing resins such as polyurethane acrylate and epoxy acrylate, or other ionizing radiation curing resins such as electron beam curing resins, and is flexible. Its thickness direction boundary surface is a Fresnel lens surface that is arranged alternately in a concentric arc shape, with a plane on the front side and a lens surface 6a and a non-lens surface 6b on the back side. The layer thickness of the lens layer 6 is designed to be suppressed to a maximum of about 50μm. In addition, the radial dimension of the Fresnel lens of the lens surface 6a is about 100μm to 150μm, and the radial dimension of the Fresnel lens of the non-lens surface 6b is about 10μm at most. The ideal Fresnel lens is set to 0μm.

[0126] form Figure 5 The Fresnel lens of the lens layer 6 of the reflective screen 4 shown in the figure is a Fresnel lens with a focal length f, which deflects the image light from the image projection device 5 in the normal direction of the screen surface. Therefore, the focal length f is proportional to the distance from the screen surface to the image projection device 5, and more specifically, the space inside the aperture of the projection optical system 138 of the image projection device 5, that is, the aperture surface 18 (see Figure 8 However, the “consistent” here allows an error within ±10%.

[0127] Therefore, since the main light direction of the image light emitted from the left and right ends of the screen is also the normal direction of the screen surface, the image light is diffused twice by the surface anisotropic diffusion layer 2 and is Figure 4 Easier to reach the observation position.

[0128] exist Figure 5In (b), the lens layer 6 composed of Fresnel lenses can be directly formed on the back side of the substrate 3 of the surface-shaped diffuser sheet 1 by UV polymerization, but the sheet-like Fresnel lens can also be pasted to the back side of the substrate 3. In order to make the Fresnel lens reflective, it is covered with a reflective layer 8 formed by aligning thin small pieces of aluminum called aluminum sheets parallel to the transparent surface, and a protective film 9 is applied on its surface for protection. Since the thickness of the reflective screen is about 400μm excluding the retaining plate 10, in order to make it a flat screen without bumps, it is preferably adhered to the retaining plate 10 with a thickness of 1.0mm to 3.0mm. In addition, instead of the retaining plate 10, a screen with a magnetic sheet (not shown) attached thereto can be directly adhered to a plate or wall with a magnet.

[0129] (Spatial imaging aperture surface method: [4] of the present invention)

[0130] Next, another embodiment in which a Fresnel lens is used in the reflective screen according to the present invention will be described.

[0131] In this embodiment, if Figure 6 As shown, the reflective screen 4 reflects the image light from the projection lens of the image projection device 4 separated from the reflection image light by a distance a with respect to the focal length f of the Fresnel lens (see Figure 8 ) of the image light, thereby forming a spatial imaging aperture surface 20 at a position separated by a distance b, where b satisfies the relationship (1 / a)+(1 / b)=1 / f. In addition, the distances a and b are allowed to have an error within ±10% relative to the values ​​satisfying the above relationship.

[0132] Should Figure 6 The implementation method and Figure 5 The embodiment of the invention is different from the Fresnel lens in that only the lens layer 6 is formed. Figure 5 The lens layer 6 (Fresnel lens) shown in FIG. 1 deflects the image light from the image projection device 5 toward the normal direction of the screen. Figure 6 In the embodiment, the image light is focused to a position separated from the front of the screen by b. Optically, the focal lengths f are different from each other. Figure 6 Such an optical method is called a spatial imaging aperture surface method. Therefore, the reflective screen of this embodiment is also called a spatial imaging aperture surface method reflective screen.

[0133] (Behavior of external light on a spatial imaging aperture-type reflective screen)

[0134] Figure 7This is a ray tracing diagram of incident and reflected light of the external light of the Fresnel lens of the reflective screen using the spatial imaging aperture surface method. Since the external light 51 from the floor 13 is incident on the lens surface 6a of the Fresnel lens of the reflective screen 4 from the same direction as the image light 50 from the image projection device 5, it becomes the cause of the blackening.

[0135] In addition to the external light 51, the external light 52 incident on the lens surface 6a from the ceiling light 11 and the front window 12 is deflected by the lens surface 6a so as not to reach the spatial imaging aperture surface 20, and thus does not cause the blackening. On the other hand, a part of the external light 53 and 54 incident on the non-lens surface 6b from the ceiling light 11 and the front window 12 respectively reaches the spatial imaging aperture surface 20, and thus causes the blackening.

[0136] According to the surface shape diffusion sheet 1 involved in the present invention, it is possible to reduce the blackening caused by external light 51 to 54. However, in order to further reduce the blackening caused by external light 53 and 54, it is preferred to make the inclination of the non-lens surface 6b of the Fresnel lens perpendicular to the screen surface in the same direction as the screen normal, or exclude the non-lens surface 6b from the coverage of the reflective layer (such as a metal film) so that the non-lens surface 6b does not become a reflective surface, or cover it with an absorption film that absorbs light instead of the reflective layer.

[0137] (Image display system according to the present invention: [5] and [6] of the present invention)

[0138] Next, the image display system according to the present invention is described. The image display system comprises the reflective screen 4 according to the present invention and an image projection device 5 for projecting image light (in Figure 8 In addition, the image projection device 5 is not limited to Figure 8 The image projection device exemplified in the figure may include various projectors available on the market.

[0139] Under the above premise, there is a problem that in a bright environment affected by external light, as the brightness of black due to blackout increases, the image is covered with gray, the vividness of the color is damaged, and the original color cannot be reproduced. In order to solve this problem, the inventors of the present invention have repeatedly studied the relationship between blackout and color reproducibility. As a result, the following insight was obtained: by using the numerical value of the RGB color model to express the brightness of the blackout as the blackout amount, the deterioration of color reproducibility can be quantified. The process of the above research is described below.

[0140] (Amount of blackening)

[0141] In the RGB color model, each element of RGB is represented by R=0-255, G=0-255, and B=0-255. The values ​​0-255 are integers, called brightness (brightness), and indicate the relative intensity of brightness. The minimum value is 0, and the maximum value is 255. Therefore, the absolute black is R=0, G=0, B=0, and the brightest white is R=255, G=255, and B=255.

[0142] On the other hand, the brightness of the black color measured by the brightness meter (cd / m 2 ) is the minimum brightness measured on the screen when absolute black (R=0, G=0, B=0) is projected under external light. Therefore, it can be expressed relative to the maximum brightness (cd / m 2 ) ratio, that is, relative brightness (0 to 1), to express blackness.

[0143] However, the color of the image observed in the blackout state is also represented by the brightness (0 to 255) of each element of the RGB color model, similarly to the color of the projection light from the image projection device 5. Therefore, when quantifying the influence of blackout on the color reproducibility of the color of the image observed on the screen, it is considered easier to organize the relationship between the color of the image and the blackout state by representing the blackout state with the brightness of each element of the blackout = 255×(relative brightness of black) than by the relative brightness of the black. Therefore, below, the blackout state is represented by the brightness of each element of the blackout, and the value of this brightness (the brightness of each element of black is set to be the same) is called the "blackout amount". The symbol of the blackout amount is Lb. That is, the definition of the blackout amount Lb is Lb=255×(relative brightness of black).

[0144] However, since the brightness is an integer as described above, the integer part of the value of the formula is used. Here, although the integer part may be a value obtained by rounding off, discarding, or carrying up the decimal point of the calculated value, the rounded value is used below.

[0145] For example, in the case of the SHL screen in Table 3, the brightness of the black is 35.59 cd / m 2 The white brightness is 994.3cd / m 2 Therefore, the amount of blackening is Lb=255×35.59 / 994.3=9.

[0146] Therefore, in the above study, red (R), green (G), blue (B) and white obtained by mixing them in the RGB color model of the colors constituting the image are selected as visual objects. Then, various changes are made to the brightness of the visual object, and the black equivalent to the black that has been blackened is used as the background. Various changes are also made to the blackening amount, and the visual object is observed. As a result, in the range where the brightness of the visual object is greater than Lb and less than 2Lb, a "brightness reduction" occurs in which the brightness of the visual object decreases relative to the reference value in appearance. In addition, the reference value here refers to the brightness of the visual object when the background is black without blackening (RGB is all 0, that is, the blackening amount = 0). In addition, when the brightness of the visual object is less than Lb, it is a so-called blackened state in which the grayscale representation of black cannot be performed.

[0147] (Visual experiment of brightness reduction)

[0148] The following describes a visual experiment of brightness reduction for finding the relationship between the amount of blackening and the amount of brightness reduction of a visual object. Fig. 9 As shown, in the screen of the liquid crystal display, the brightness (0 to 255) of each element of the RGB color model is used to compare the black rectangle with no blackening (blackening amount = 0) on the right with the arbitrary blackening amount (in Fig. 9 In the image, black rectangles with a black level of 2.15 (i.e., RGB are both 2.15) are connected and displayed. Next, circles are used to represent the colors of the visual object in each rectangle. The diameter of the circle is 1.2 cm, and the observation distance is set to about 30 cm. The colors on the left and right are viewed from the front, and the difference in brightness of each color is visually observed. From the results, it can be seen that when the black level is 2.15, each color of the visual object can be seen to be darker than the basic color when the black level is 0. When blackening occurs, the image is covered with gray, and the vividness of the color is impaired. It is believed that this is because the brightness of each color in appearance is lower than the reference value (brightness when blackening level = 0) due to blackening, resulting in impaired color reproducibility.

[0149] exist Fig. 9 In the experiment, the image (the visual object and the background) displayed on the liquid crystal screen is visually observed, but when the brightness of the image is measured, the black (R = 0, G = 0, B = 0) is 1.5 cd / m 2 , white (R=255, G=255, B=255) is 85cd / m 2 .

[0150] And, even if it is Fig. 9 The same image as the image on the LCD screen Figure 3The image projection device 5 projects (b) onto the SHL screen 82 and the aforementioned sample screen, and it can be seen that the phenomenon that each color with a blackening amount = 215 is darker than each color with a blackening amount = 0 (basic color) is also observed in the same way as the situation displayed on the screen of the LCD display.

[0151] Next, in order to quantitatively measure the brightness reduction of each color as a visual object relative to the reference value, as shown in FIG. Fig.10 As shown in (a), in the right rectangle, the brightness of each color is recorded on the right side of the circle of the visual object. Fig. 9 The same is true for the rectangle on the left. In the upper part of each visual object, a circle is added to compensate for the lower brightness of the lower part, which makes it look the same as the colors on the right (colors with the same brightness as the reference value). On the left side of each visual object, the brightness is recorded in the same way as on the right. Fig.10 In (a), it is shown that when the amount of blackening is set to 215, the lightness of each color is reduced by about 18 from the reference value. This value is considered to depend on individual vision and was determined by observation by 5 people. Fig.10 (b) is a graph in which the amount of blackening is changed and the amount of blackening is obtained to obtain the same brightness on the right and left sides. It can be seen from this that when the brightness of the visual object = 230, if the amount of blackening is set to 115 or less, the brightness of the visual object will not be reduced. Fig.10 The same method is used to measure the brightness of visual objects (in Fig.10 In the example, the brightness of the visual object = 230) is used as a parameter to find the brightness reduction amount of the visual object corresponding to the amount of blackening. Fig.11 As can be seen from the figure, the amount of blackening that starts when the brightness of the visual object decreases is equal to the brightness of the visual object / 2.

[0152] then, Fig.12 This is a graph that uses the amount of blackening as a parameter to investigate the relationship between the brightness of a visual object and the amount of brightness reduction. According to this graph, when the brightness of a visual object becomes more than twice the amount of blackening, the brightness of the visual object will not be reduced. Fig.13 (a) and (b) show visual object patterns prepared to confirm the range of brightness of the visual object that does not cause a decrease in brightness of the visual object when white of various brightnesses (brightness is set to L, R=L, G=L, B=L, L=255, 230, 200, 170, 135, 115) is used as the visual object and the black level is set to 100 as the background. It can be confirmed that the brightness of the visual object is not reduced when the brightness is 200 or more, which is more than twice the black level of 100. In addition, Fig.13 As can be seen from (b), the amount of brightness reduction of the visual object is calculated. When the brightness is increased by the amount of brightness reduction, the brightness of the left and right visual objects becomes the same.

[0153] Based on the above research, the color reproducibility of the visual object does not deteriorate within the brightness range where the brightness of the visual object is more than twice the amount of blackening. In the conventional reflective screen, like the white matte screen in Table 3, in a bright environment with the ceiling light on, the brightness of blackening (minimum brightness) is about 88 cd / m 2 as large, and the all-white (maximum brightness) is 289 cd / m 2 , so the amount of blackening is 255×88 / 289 = 78.

[0154] Therefore, when the amount of blackening = 78, within the brightness range of the amount of blackening × 2 (= 156) to 255, the brightness of the visual object is not reduced. However, as shown in the curve graph of the amount of blackening = 78 as Fig.12 , the brightness of the visual object is reduced within a large range of the amount of blackening (= 78) to 2 × the amount of blackening (= 155).

[0155] (Color reproduction brightness range, color non-reproduction brightness range, and blackening brightness range)

[0156] By calculating the amount of blackening in this way, it is possible to determine the brightness range that causes the brightness reduction of the visual object (referred to as the color non-reproduction brightness range) and the brightness range that does not cause the brightness reduction of the visual object (referred to as the color reproduction brightness range). When setting Lb as the amount of blackening, 2Lb as 2 × the amount of blackening, and L as the brightness of each element of the visual object, the color non-reproduction brightness range is expressed as Lb ≤ L < 2Lb, and the color reproduction brightness range is expressed as 2Lb ≤ L ≤ 255.

[0157] In addition, the brightness range of 0 ≤ L < Lb is the brightness range that causes blackening (inability to perform black gray scale display due to blackening) as described above, referred to as the blackening brightness range.

[0158] (Expanding the color reproduction brightness range by adjusting the transmittance T and the brightness of white)

[0159] In the SHL screen of Table 3, the amount of blackening is 9 (=255×36 / 994), and 18 (=2×9) to 255 are the color reproduction brightness range. In such a color reproduction brightness range, the minimum value of the brightness range is determined by the minimum brightness as the basis of the blackening amount, and the maximum value is expanded by increasing the brightness of full white (white) as the maximum brightness. Therefore, by adjusting the transmittance T of the substrate 3 of the surface shape diffusion sheet 1 and the brightness Kw of the white color that is the maximum brightness of the image light from the image projection device 5, the color reproduction brightness range can be expanded. For example, the relationship between the amount of blackening Lb and Lmax (maximum value of brightness ≤255) is defined as Lb≤Lmax / 4, and in order to satisfy this relationship, the transmittance T of the substrate 3 of the surface shape diffusion sheet 1 is reduced to the range of 0.25≤T2<1 by the aforementioned transparent blackening, thereby reducing the amount of blackening Lb and increasing the output of the image light from the image projection device 5 to 1 / T2 times in order to compensate for the reduction in Lmax. Here, T2 is used because the image light passes through the substrate 3 twice in the reflective screen 4. As a result, Lb can be reduced without reducing Lmax, and the color reproduction brightness range can be expanded to 2Lb×T2≤color reproduction brightness range≤Lmax. It is assumed that the external light reflected on the screen surface is sufficiently small compared to the external light reflected by the reflective layer 8 inside the screen.

[0160] For example, if the transmittance T of the substrate 3 of the reflective screen 4 is set to about 0.9 and the output of the image light from the image projection device 5 is set to 1.24 times (1 / T2 times), the lower limit of the color reproduction brightness range becomes 2Lb×0.81, and the color reproduction brightness range can be expanded to the low brightness side by 2Lb×(1-0.81).

[0161] Furthermore, when the amount of blackening Lb becomes the brightness 255 of the maximum brightness white (R=255, G=255, B=255), the lower limit 2Lb of the color reproduction brightness range becomes 510 and exceeds the upper limit 255, so there is no color reproduction brightness range, causing brightness reduction in the entire area of ​​the brightness range (0 to 255) of the visual object. Fig.14 (a) shows a decrease in the brightness of the visual object when the black level is set to 255 and white is used as the visual object. Fig.14 (b) is the case where green (G) is used instead of white. Therefore, when the background becomes the maximum brightness, that is, white, it means that the brightness of the visual object relative to the black background without blackening (reference value) is reduced in the entire area of ​​the brightness range of the visual object. In order to make the visual object bright and look like a bright color, it is reasonable to set the background to black instead of white.

[0162] (Correction of brightness reduction: [5] of the present invention)

[0163] Based on the above research results, the image display system involved in [5] of the present invention is set to a structure that corrects the brightness reduction in the brightness range Lb≤L<2Lb (color non-reproduction brightness range). That is, the image display system has a reflective screen and an image display device as the above premise, and also has a brightness meter, a black flooding amount calculation unit, and a brightness adjustment unit.

[0164] (Brightness meter)

[0165] The luminance meter measures the luminance of black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model projected from the image projection device onto the reflective screen under external light, and obtains respective measurement values ​​Kmin and Kw.

[0166] The image and the black under external light correspond to the visual object and the darkened black (background) in the aforementioned visual experiment with reduced brightness, respectively.

[0167] The luminance meter can be formed of common commercially available products.

[0168] (Black amount calculation unit)

[0169] The blackening amount calculation unit calculates the blackening amount Lb as the integer part of the value of the formula: 255×Kmin / Kw. This formula corresponds to the above-mentioned definition formula of the blackening amount "Lb=255×(relative brightness of black)".

[0170] (Brightness adjustment unit)

[0171] The brightness adjustment unit corrects the brightness reduction observed within the brightness range Lb≤L<2Lb of the brightness L of the image.

[0172] As described in the above study, the brightness range Lb≤L<2Lb is a color non-reproduction brightness range in which the brightness reduction of the visual object is observed. Therefore, it is assumed that the brightness adjustment unit corrects the brightness reduction. The results of the aforementioned visual experiment of brightness reduction (e.g. Fig.12 ).

[0173] Fig.15 Shows Fig.12The color non-reproducible brightness range and the color reproduction brightness range when the amount of blackening in the image is 78. This figure is used as an example to illustrate the method of correcting the brightness reduction. As shown in the figure, in the color reproduction brightness range (156-255), the brightness reduction of the visual object is 0, so no brightness reduction occurs, and therefore each RGB color having the brightness of the horizontal axis is output as image light. On the other hand, in the color non-reproducible brightness range (78-155), the brightness reduction of the visual object is set to a negative value, so when each RGB color having the brightness of the horizontal axis is output as image light, a brightness reduction occurs. In order to prevent this brightness reduction, when the brightness of each RGB color to be output as image light enters the color non-reproducible brightness range, as shown in the figure, the brightness is corrected by adding the absolute value of the brightness reduction amount on the vertical axis corresponding to the value of the brightness on the horizontal axis, and each RGB color having the corrected brightness is output as image light.

[0174] As a result, it is possible to project an image without brightness reduction not only in the color reproduction brightness range of the visual object but also in the color non-reproduction brightness range.

[0175] Next, the above-mentioned method of correcting the brightness reduction will be described in more detail.

[0176] like Fig.16 As shown, the relationship between the lightness and the amount of lightness reduction of the visual object represented by the RGB color model changes as shown by the curve A in the figure. In addition, in the curve A of the figure, as an example, a curve obtained by extrapolating the relationship curve between the lightness and the amount of lightness reduction of the visual object in the case of the amount of blackening = 50 to the range of lightness less than 50 is shown, and the color non-reproduction range is greater than 50 and less than 100. The change of curve A (curve shape) is not only established when RGB is a primary color (only red R, only green G, only blue B are non-zero values, and the others are 0), but also established when the primary colors such as white (RGB are all the same non-zero values) are mixed (becoming a curve shape roughly the same as curve A). Therefore, even in the general color (R = Lr, G = Lg, B = Lbl) of the RGB color model, Lb ≤ Lr, Lg, Lbl < 2Lb is established, that is, Lb or more and less than 2Lb is the color non-reproduction lightness range.

[0177] Then, in Fig.17 The process of finding the value of the amount of blackening is shown in FIG. The amount of blackening varies depending on the external light in the setting environment of the image display system, so the amount of blackening must be found for each setting environment. The brightness and brightness reduction of the visual object are determined in accordance with the same principle whether in the RGB primary colors or in the general colors obtained by mixing them. Fig.16 The relationship curve changes in a shape roughly similar to curve A in , so if the amount of blackening in each setting environment is known, correction can be easily performed.

[0178] like Fig.17 As shown in the figure, black (RGB is 0) and white (RGB is 255) are projected in a bright environment with external light, the brightness of each image is measured, and the black level Lb is calculated based on the measured values ​​Kmin and Kw by the formula: Lb = 255 × Kmin / Kw. When calculating the black level Lb, Fig.16 A is moved parallel to the horizontal axis so that A matches the change in the brightness reduction in the brightness range Lb to 2Lb, and the brightness reduction in the color non-reproducible brightness range (above Lb and less than 2Lb) is obtained. The general color (R=Lr, G=Lg, B=Lbl) of the RGB color model is corrected separately for each primary color.

[0179] When Lr, Lg, and Lbl enter a color non-reproducible brightness range that is greater than Lb and less than 2Lb, Lr, Lg, and Lbl are corrected individually using Curve A.

[0180] The brightness adjustment unit that performs such correction can be realized by installing software describing the correction process in the image projection device.

[0181] (Adjustment of image light output: [6] of the present invention)

[0182] By the correction of the brightness reduction described above, the color non-reproduction brightness range can be converted into the color reproduction brightness range. However, in the blackening brightness range where the residual brightness is less than Lb, the detailed grayscale representation of black cannot be performed because the black display becomes the same brightness in this range. Therefore, the image display system involved in [6] of the present invention eliminates the blackening brightness range and the color non-reproduction brightness range, and sets the entire area of ​​the brightness range of the visual object to the color reproduction brightness range, thereby reducing blackening.

[0183] Therefore, the present invention [6] is characterized in that in the present invention [5], instead of the brightness adjustment unit, or in addition to the brightness adjustment unit, an image light output adjustment unit is provided, which increases the brightness of the white color from Kw to Kw×(1+2Lb / 255) to reduce blackening.

[0184] When the brightness of the white color is increased from Kw to Kw×(1+2Lb / 255), brightness exceeding 255 and below 255+2Lb outside the brightness (0-255) range of the RGB color model is newly added to the color reproduction brightness range of 2Lb to 255, thereby obtaining an extended color reproduction brightness range of 2Lb to 255+2Lb. An image having brightness within this color reproduction brightness range does not cause blackening or brightness reduction.

[0185] Then, by converting the extended color reproduction brightness range of more than 2Lb and less than 255+2Lb into a brightness range of more than 0 and less than 255, an image without blackening and brightness reduction can be observed in the entire brightness range (0 to 255) of the RGB color model.

[0186] use Fig.18 The example of [6] is used to illustrate the implementation method of the present invention. Fig.18 The diagram shows the blackening brightness range before blackening is reduced (above 0 and below 78), the color non-reproduction brightness range (above 78 and below 156), the color reproduction brightness range (above 156 and below 255), and the color reproduction brightness range after blackening is reduced (above 0 and below 255) when the blackening amount Lb = 78.

[0187] The image light output adjustment unit increases the brightness of white by (1+156 (=2×78) / 255) times. As a result, the color reproduction brightness range becomes greater than 156 and less than 411 (=255+156). Therefore, the transformation is performed as follows: the brightness (0 to 255) of each element of the visual object represented by the RGB color model is shifted by (brightness+156 (=2×78)) and 156 and projected by the image projection device.

[0188] In addition, the function of deriving the expanded color reproduction brightness range and converting the color of the RGB color model can be realized by installing software describing the derivation and conversion process in the image light output adjustment unit. In addition, the image light output adjustment unit can also be built into the image projection device.

[0189] Therefore, after the black cast is reduced, the entire area of ​​the brightness range of the RGB color model (0 or more and 255 or less) becomes the color reproduction brightness range, and an image without black cast and brightness reduction can be observed.

[0190] Absolute black (RGB is 0, image brightness = 0cd / m 2 ) can only be achieved in a dark room without external light. Therefore, the present invention is useful as a method of expressing various blacks by grayscale expression by taking the black with the minimum brightness under external light as absolute black. In [6] of the present invention, the black (2Lb) obtained by multiplying the brightness of white by (1+2Lb / 255) is set as the absolute black.

[0191] (Image display method according to the present invention: [7] of the present invention)

[0192] Next, the image display method of the present invention [7] is described. This method is based on the use of the reflective screen according to any one of the present invention [2] to [4] and an image projection device for projecting image light.

[0193] In [7] of the present invention, first, black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model are projected from the image projection device onto the reflective screen.

[0194] Next, the brightness of the black and white colors is measured under external light to obtain respective measurement values ​​Kmin and Kw. Various commercially available brightness meters can be used for the brightness measurement.

[0195] Next, the blackening amount Lb is calculated as the integer part of the value of the formula: 255×Kmin / Kw. For this calculation, a commercially available personal computer or a function calculator can be used.

[0196] Finally, the brightness reduction observed in the brightness range Lb≤L<2Lb of the brightness L of the image is corrected. This is called the brightness adjustment process. The brightness adjustment unit can be used in the implementation of this process.

[0197] (The image display method involved in the present invention: [8] of the present invention)

[0198] Next, the image display method of the present invention [8] is described. In this method, in the present invention [7], there is an image light output adjustment step instead of the brightness adjustment step, or in addition to the brightness adjustment step, in which the brightness of the white is increased from Kw to Kw×(1+2Lb / 255) to reduce black cast. The image light output adjustment unit can be used in the implementation of this step.

[0199] Explanation of symbols

[0200] 1: surface shape diffusion sheet (present invention); 2: surface shape anisotropic diffusion layer; 2A: surface shape diffusion layer (for diffusion angle research); 3: substrate; 4: reflective screen (present invention); 4A: reflective screen (for diffusion angle research); 5: image projection device (projector); 6: lens layer; 6a: lens surface; 6b: non-lens surface; 8: reflection layer; 9: protective film; 10: retaining plate; 11: ceiling light; 12: front window (window on the front of the screen); 13: floor; 18: aperture surface; 20: spatial imaging aperture surface; 30: brightness meter; 50: image light; 51 : External light from the floor to the lens surface; 52: External light from outside the floor to the lens surface; 53: External light from the ceiling light to the non-lens surface; 54: External light from the front window to the non-lens surface; 60: Observation position; 61: Main light of the diffused reflected light of external light caused by the ceiling light; 81: White matte screen; 82: SHL screen; 120a: Relay lens; 120b: Relay lens; 122: Diffusing film stack; 130: Three primary color light source; 134: Digital mirror device; 136: Shading plate; 138: Projection optical system; 140: Concave reflector; 142: Convex reflector.

Claims

1. A surface shape diffusion sheet, arranged on the surface of a reflective screen for diffusing image light from an image projection device, wherein the surface shape diffusion sheet reduces blackening, characterized in that have: a surface anisotropic diffuser layer; and a flat substrate, which is the base of the surface anisotropic diffusion layer, wherein the diffusion angle in the vertical direction of the surface of the surface anisotropic diffusion layer is within the range of ±14° (half value width), The transmittance T of the visible light wavelength band inside or on the surface of the substrate is within a range of 0.5 or more and less than 1.

2. A reflective screen having a diffuser sheet on its surface, wherein: The diffusion sheet is the surface shape diffusion sheet according to claim 1, The reflective screen includes a reflective layer, a protective film, and a retaining plate which are sequentially arranged and bonded from the substrate toward the back side. The bonding surface between the reflective layer and the substrate becomes a surface for reflecting the image light. The protective film is a film covering the reflective layer, The holding plate is a plate for maintaining the flatness of the substrate.

3. The reflective screen according to claim 2, characterized in that: It also has a lens layer, which is arranged and bonded between the substrate and the reflective layer. The lens layer is composed of a Fresnel lens having a reflective surface shape on the back side. The bonding surface between the reflection layer and the lens layer serves as a surface for reflecting the image light.

4. The reflective screen according to claim 3, characterized in that: The image light is reflected from the aperture surface of the projection lens of the image projection device, which is separated from the surface reflecting the image light by a distance a with respect to the focal length f of the Fresnel lens, thereby forming a spatial imaging aperture surface at a position separated by a distance b, wherein b satisfies the relationship (1 / a)+(1 / b)=1 / f.

5. An image display system comprising the reflective screen according to any one of claims 2 to 4, an image projection device, a brightness meter, a black flooding amount calculation unit, and a brightness adjustment unit, wherein: The image projection device projects image light, The luminance meter measures the luminance of black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model projected from the image projection device onto the reflective screen under external light to obtain respective measurement values ​​Kmin and Kw. The black flooding amount calculation unit calculates the black flooding amount Lb as the integer part of the value of the formula: 255×Kmin / Kw, The brightness adjustment unit corrects the brightness reduction observed within the brightness range Lb≤L<2Lb of the brightness L of each element in the image that is faded from black (R=Lb, G=Lb, B=Lb).

6. The image display system according to claim 5, characterized in that: An image light output adjustment unit is provided in place of the brightness adjustment unit or in addition to the brightness adjustment unit. The image light output adjustment unit increases the brightness of the white color from Kw to Kw×(1+2Lb / 255) to reduce black cast.

7. An image display method, using the reflective screen according to any one of claims 2 to 4 and an image projection device for projecting image light, the image display method comprising the following steps: Projecting black (R=0, G=0, B=0) and white (R=255, G=255, B=255) in the RGB color model from the image projection device to the reflective screen; Measuring the brightness of the black and white colors under external light to obtain respective measurement values ​​Kmin and Kw; The blackening amount Lb is calculated as the integer part of the value of the formula: 255×Kmin / Kw; and The brightness adjustment step corrects the brightness reduction observed within the brightness range Lb≤L<2Lb of the brightness L of each element in the image that is blackened (R=Lb, G=Lb, B=Lb).

8. The image display method according to claim 7, characterized in that: Instead of the brightness adjustment step, or in addition to the brightness adjustment step, there is an image light output adjustment step, in which the brightness of the white is increased from Kw to Kw×(1+2Lb / 255) to reduce black cast.

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