JP4285572B2 - Rear projection type image display device - Google Patents

Description

  The present invention relates to an image display device that performs display output of a large screen, and more particularly to a projection-type image display device that displays and outputs a large screen by projecting the screen onto a screen using a projector.

  More specifically, the present invention relates to a rear projection type image display device that forms an observable image by diffusing high-intensity projection light from a projector with a transmission type screen installed on its imaging surface. In particular, the present invention relates to a rear projection image display device, a screen, and a projection device that have a larger half-value angle and shield direct light from a projector from an observer.

  In addition to TV receivers, image display devices such as CRT (Cathode Ray Tube) displays and LCDs (Liquid Crystal Displays) are already widely used. Recently, there is an increasing demand for large screens such as home theater monitors and large-screen TVs.

  As a typical means for forming a large screen, a projection-type image display apparatus that projects an image by forming an irradiation light from a projector on a screen is widely known. In addition, the projection type image display device includes a front projection type that projects the irradiation light from the projector onto the front of the screen facing the observer, and a rear projection that projects the projection onto the transmission type screen and observes its image formation from the back. There are two types of molds.

  The rear projection type image display apparatus has a basic structure of enlarging and projecting a small, high-brightness image on the back side of a transmissive screen viewed by an observer. As an image source, a CRT (Cathode Ray Tube) projector can be used. In recent years, a projector using a spatial modulation element such as a liquid crystal projector has been developed. Further, it is possible to form a color image by superimposing the images of the three primary color single color projectors on the back of the transmissive screen.

  In a rear projection type image display device, in order to increase the brightness from the front and attract the eyes of the observer, one of the main design guidelines is to increase the front gain and project it onto the screen. ing. In addition, in order to suppress the “hot spot” phenomenon in which the light source becomes apparent in the projected image on the screen, it is common to construct a transmissive screen with a diffusing plate and diffuse the imaged light in various directions. The light distribution is performed so that a good image is formed and supplied to the observer.

  For example, a lenticular lens with the horizontal direction as the longitudinal direction is formed on the light incident surface, and a black stripe with the horizontal direction as the longitudinal direction is provided with a light non-transparent portion located near the focal point of the lenticular lens, and the vertical direction Proposal has been made for a rear projection screen that forms a lenticular lens with a longitudinal direction on the light exit surface, realizes a fine lenticular lens pitch that does not cause moiré interference, and reduces external light reflection. (For example, refer to Patent Document 1).

  In addition, a light transmission sheet and a rear projection screen with good diffusion characteristics are proposed by providing a light transmission layer made of polycarbonate or MS resin with low hygroscopicity on both sides of the diffusion layer based on PMMA, and preventing warping due to moisture absorption. (For example, see Patent Document 2).

  In addition, a diffusing structure plate for rear projection screens has been proposed, in which a plurality of reflecting mirrors having a parabolic column shape are formed in parallel between the entrance surface and the exit surface of the diffusion sheet to contribute to image sharpening. (For example, see Patent Document 3).

  In addition, a plurality of microlenses that collect incident light, a black matrix having an opening on the light path of the transmitted light on the exit side of the microlens, and a transmitted light of a microlens having a recess at a portion with respect to the opening A transmissive screen that can be used in a rear transmissive image display device that includes a diffusing unit that diffuses and has good viewing angle characteristics and light utilization efficiency has been proposed (see, for example, Patent Document 4).

  Recently, as one of attempts to further expand the projection area and increase the resolution, projectors are arranged in an array, for example, and a large image is projected onto a screen by overlapping a part of a plurality of images. A multi-projection system (see FIG. 16) is known.

  For example, the optical axis of the projection image from each image projection unit is set so as to be substantially parallel to the projection screen, and the image is reflected on the projection screen close to the projection screen to display the image on the projection screen. A proposal has been made for a liquid crystal display multi-projection apparatus configured (see, for example, Patent Document 5).

In addition, the brightness of a portion where each image signal corresponding to each image is overlapped with the adjacent image is electrically finely adjusted to project an image corresponding to the plurality of image signals, and the adjacent image by the smoothness of the brightness of the brightness optically attenuates at a predetermined smooth distribution the superimposed portion of the overlapping portion, of the multi-projection type that unobtrusively overlapping portions of adjacent images display A device has been proposed (see, for example, Patent Document 6).

  In addition, an upper projector that projects video signals at an acute angle with respect to the upper surface area of the screen is installed at the upper front of the screen, and a lower projector that projects video signals at an acute angle with respect to the lower surface area of the screen is installed at the lower front of the screen. Thus, a proposal has been made for a large-screen display device in which a human enters between a screen and a projector so as not to get in the way when viewing an image on the screen (see, for example, Patent Document 7). ).

  In the case of the front projection type, there is a problem that the shadow of the observer easily falls on the screen when the screen is enlarged. From such a point of view, the present inventors consider that the rear projection type is advantageous when the projectors are arranged in an array and multi-projected to increase the area.

  By the way, the projection light from a projector such as an LCD (Liquid Crystal Display) or CRT is basically divergent from the central part to the peripheral part, and in part, light with extremely high directivity is applied to the transmissive screen. Incident. As described above, an image that can be observed can be obtained on the screen by performing appropriate light distribution using the diffusion plate. However, since the incident light is divergently incident and the peripheral portion has outward directivity, there is a problem that the peripheral luminance becomes darker than the central luminance when observed from the front of the screen. For example, when observed from an oblique direction, the brightness of the screen is uneven, such that the near end is bright and the far end is dark.

  Even if a diffusion plate is interposed in the path of the projection light, or the projection screen itself is made of a diffusion plate to diffuse the imaged light rays in various directions to make the brightness uniform, It is difficult to avoid the phenomenon of having the maximum gain and decreasing the gain as the angle is increased with respect to the direction of the light beam from which the maximum gain can be obtained. As a general index of the screen gain change, an angle that is half the maximum gain, that is, a “half-value angle” is used. The larger the half-value angle, the wider the viewing angle and the better large screen can be obtained.

  In the case of a front projection type image display device, this half-value angle reaches 80 deg, and a wide range of diffusion can be obtained. On the other hand, in the case of a rear projection type image display device, the half-value angle is only about 45 deg at the maximum even when a high diffusion screen is used because of the design guideline (described above) of increasing the luminance from the front. Absent. Alternatively, in rear projection, even if a diffusion plate that performs simple diffusion is used, complete diffusion is difficult and the front gain becomes high.

  A small half-value angle means that the intensity of attenuation when the image is viewed from other than the front (that is, when the angle between the axis perpendicular to the screen and the line of sight is large) becomes severe. Depending on the location of the image to be reflected, the color may change, unevenness may occur, or uneven brightness may become severe. For this reason, even when constructing a multi-projection system in which projectors are arranged in an array, if a rear projection projector with a small half-value angle is used, the front gain of each emitted light on the screen is higher than the peripheral gain. In addition, it can be a factor of image quality degradation.

  It is known in the art to use a Fresnel lens as a means for solving the half-value angle problem in a rear projection type image display apparatus.

  For example, from the display light projection side, a first lenticular sheet in which a Fresnel lens sheet and a convex cylindrical lens are juxtaposed in a first direction, and a convex cylindrical lens that is orthogonal to the first direction. Proposals have been made for a projection screen having a configuration in which second lenticular sheets arranged in parallel in two directions are arranged in this order (see, for example, Patent Document 8). The viewing area can be expanded in two directions (vertical), and the emission range and contrast of the display video light can be strictly controlled.

  However, when projected onto a screen through a Fresnel lens, the brightness in the “blending area” (see FIG. 16) where the projection surfaces of the projectors overlap can be made uniform with other areas, but Since the corresponding incident angle of the lens is limited, the directionality of the emitted light cannot be eliminated. In addition, due to the limit of the corresponding incident angle, the installation position of the projector with respect to the Fresnel lens is significantly restricted. In addition, when a Fresnel lens is used, it is difficult to form a large screen and the production cost becomes high.

  Another problem with the rear projection type image display device is that the light emitted from the projector is directed to the observer through the transmission screen, so that the direct light is transmitted and observed.

Japanese Patent Laid-Open No. 11-344769 JP 2002-207253 A Japanese Patent Laid-Open No. 2005-24828 JP 2005-128352 A JP-A-9-265132 JP 2001-34304 A JP 2004-247868 A JP 2004-215715 A

  An object of the present invention is to diffuse a high-intensity projection light from a projector with a transmission screen installed on the image plane thereof, and to suitably form an observable image with reduced luminance spots. Another object of the present invention is to provide a rear projection image display device, a screen, and a projection device.

  A further object of the present invention is that the half-value angle of the gain at the time of transmission through the back surface is large, diffusion is obtained in a wider range, and brightness spots or images depending on the location of the image displayed on the transmission screen are viewed from other than the front surface. It is an object of the present invention to provide an excellent rear projection type image display device, a screen, and a projection device that can suppress luminance attenuation.

  A further object of the present invention is to provide an excellent rear projection type image display device, rear projection type image display device, screen, which has a larger half-value angle and can suitably shield direct light from a projector from an observer, and It is to provide a projection device.

  A further object of the present invention is to provide an excellent rear projection capable of presenting a uniform image over the entire screen by reducing the change in color tone and unevenness of brightness depending on the viewing angle when expanding the projection area by multi-projection. TYPE IMAGE DISPLAY DEVICE A rear projection image display device, a screen, and a projection device are provided.

  A further object of the present invention is to suppress a change in color and luminance unevenness due to a viewing angle while following a design guideline for rear projection in which the luminance from the front is increased when the projection area is enlarged by multi-projection. It is an object of the present invention to provide an excellent rear projection image display device, a screen, and a projection device that can present a uniform video throughout.

  The present invention has been made in consideration of the above problems, and a first aspect of the present invention is a projector that projects a relatively high-luminance image, and a fabric that is installed on an imaging surface of light projected by the projector. A rear projection type image display apparatus comprising: a transmissive screen made of light; and direct light blocking means for blocking direct light from the projector that is transmitted without being diffused by the transmissive screen.

  As a typical means for forming a large screen, a projection-type image display apparatus that projects an image by forming an irradiation light from a projector on a screen is widely known. This type of image display apparatus is roughly divided into a front projection type and a rear projection type. According to the latter, the projection area is expanded by arranging the projectors in an array or the resolution of the projection image is increased. It can be raised.

  However, since the rear projection type image display device has a smaller half-value angle of diffusion than the front projection type, there is a problem of luminance attenuation according to the location of the image reflected on the screen or luminance attenuation when viewed from other than the front. There is.

  Therefore, in the rear projection type image display device according to the present invention, a cloth such as cotton, silk, or artificial fiber (tetron = tetronponge) is installed as a transmission type screen that is installed on the image plane of the projection light of the projector and diffuses the light. By using it, the half-value angle of diffusion was improved. By projecting the back image of the image from the projector using the cloth as a screen, a fine image can be projected.

  In addition, when the projection light from the projector is rear-projected, there is a problem that the direct light that reaches the observer directly is observed without being sufficiently diffused by the screen. In particular, when a fabric screen is used, the direct light is diffracted and the light spreads in the direction of the fabric seam, which is serious.

  Therefore, the rear projection type image display apparatus according to the present invention is provided with a direct light blocking means for blocking direct light from the projector that passes through the transmissive screen so that direct light is not observed by an observer. did.

  Specifically, the direct light blocking means is disposed in the vicinity of the first polarizing plate disposed in front of the exit pupil of the projector and the rear surface (that is, the surface on the observer side) of the transmissive screen. The first polarizing axis of the first polarizing plate and the second main optical axis of the second polarizing plate have a second polarizing axis that is substantially orthogonal. Has been. Since the polarization axes of the pair of polarizing plates are thus orthogonal, only the scattered light diffused by the transmissive screen passes through the second polarizing plate and is observed from the back side of the screen, that is, the observer. The direct light from the projector is removed by the second polarizing plate.

  Further, by arranging the first polarizing plate in the vicinity of the front of the exit pupil of the projector, the size of the first polarizing plate can be reduced. However, in this case, since it is affected by heat generation from the light source, it is necessary to use a heat-resistant polarizing plate. For example, use a polarizing plate with high heat resistance, such as a glass polarizing filter sandwiched between glass plates or a filter using quartz after stretching a thin plate that has absorbed iodine in one direction to align molecules in parallel. be able to.

  Examples of projectors that generate high-luminance images include 3LCD projectors, reflective liquid crystal (LCOS) projectors, DLP projectors, CRT projectors GLV projectors, and the like.

  Of these, the 3LCD projector first separates the light emitted from a single high-intensity light source into components for each of the three primary colors of RGB using a mirror that transmits only a specific wavelength, such as a dichroic mirror. The control light is synthesized again by a prism and then projected. In LCOS (Liquid Crystal on Silicon), light is sequentially driven by a rotating prism mechanism that decomposes and projects light into RGB. Since the reflected light is polarized, in these methods, the transmitted light is polarized whenever it is separated into color components using a mirror. For example, the R and B polarization axes are aligned, and the G polarization axis is orthogonal to this. It has a specific polarization state. In such a case, when the polarization axis of any one of the light components is arranged so as to be parallel to either the first or second polarization axis, the light component does not pass through the second polarizing plate at all. Therefore, it is necessary to configure the first and second polarization axes to be non-parallel to the polarization axis of any component of the projection light.

  Specifically, when using a projector in which the polarization axis of the LCD in charge of R and B and the polarization axis of the LCD in charge of G make 90 degrees, the polarization axis of the second polarizing plate is By arranging so as to form approximately 45 deg with the polarization axis, it is possible to attenuate the R, B, and G components equally.

Further, the second aspect of the present invention normalizes incident light from one or more projectors that project a relatively high-brightness image, and the respective incident angles of the emitted light with a front gain. And a rear projection screen that diffuses so that the gain characteristics do not depend on the incident angle.

  The rear projection screen referred to here may be configured by arranging two different types of screens in parallel, a mat screen disposed on the viewer side and a screen made of fiber fabric disposed on the projector side. it can. The mat-type screen referred to here is, for example, formed by kneading diffusing particles in a vinyl chloride resin, and can use a tetronpong or the like for the fiber fabric.

  Such a rear projection screen has no restriction on the corresponding incident angle, and the incident light from the projector disposed at any place is output as the emitted light that uniformly increases the front gain. Therefore, when multi-projection is applied, even if the arrangement of the individual projectors is not particularly limited, it is predicted that any incident light will have a high front gain when passing through the screen. The installation locations of the projectors are not restricted to one fixed location, but can be arranged at any location. Then, each exit light is superimposed on the screen surface on the viewing side, and the change in luminance gain is small on the entire screen, that is, the half-value angle becomes large, and a wide viewing angle can be realized.

  When projecting the irradiation light from the projector onto the rear projection screen of the above two-layer structure, the optical axis center of the incident light from the projector does not coincide with the axis perpendicular to the screen surface, and various incident angles are obtained. Even when a plurality of projectors are installed, it is possible to reduce changes in color and brightness at the viewing position.

  When a multi-projection system is configured by using such a two-layer rear projection screen, even when different colors are superimposed on a plurality of projectors, the irradiation light from each projector is not dependent on the observation position. Since the light is received equally, the same color can be displayed at an arbitrary observation position. On the other hand, in a conventional screen such as a simple diffusion type, in the blending area, the intensity of light coming from each projector changes according to the viewing angle, so that it is observed as a change in color and brightness.

  According to the present invention, the half-value angle of the gain at the time of transmission through the back surface is large, diffusion is obtained in a wider range, luminance unevenness depending on the location of the image displayed on the transmission screen, and the image is viewed from other than the front surface It is possible to provide an excellent rear projection image display device, a rear projection image display device, a screen, and a projection device that can suppress the attenuation of luminance.

  Further, according to the present invention, an excellent rear projection type image display device, rear screen type image display device, screen, which has a larger half-value angle and can suitably shield direct light from a projector from an observer, In addition, a projection device can be provided.

  In addition, according to the present invention, by using a screen having a large half-value angle, a high diffusion, and a wide field of view as a rear projection screen, it is possible to suppress color change and luminance unevenness when multi-projection is applied. An excellent rear projection type image display device capable of enlarging the projection area, a rear projection type image display device, a screen, and a projection device can be provided.

  According to the rear image display device of the present invention, the incident light from each projector is diffused on the screen so as to obtain a gain pattern that increases the front gain without depending on the installation position of the projector. Screening can be realized, and a uniform video can be presented regardless of the viewing position.

  In the conventional rear projection type image display apparatus, it is preferable to arrange the optical axis of the incident light from the projector so as to be perpendicular to the projection screen surface. On the other hand, in the rear projection type image display apparatus according to the present invention, the incident light from any incident angle is diffused on the screen so that the front gain is increased, thereby causing a change in the color of the projected image and occurrence of uneven brightness. Therefore, the constraint condition regarding the arrangement of the projector is reduced. For example, it can be arranged such that the incident angle of incident light from the projector is close to parallel to the screen surface.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  FIG. 1 schematically shows the configuration of an image display apparatus according to the first embodiment of the present invention. The image display apparatus shown in the figure is a rear projection type image display apparatus that forms an image by projecting light emitted from a projector on a screen, and more specifically, a small high-intensity image emitted from the projector. This is a rear projection type image display device that magnifies and projects on the rear side of a transmissive screen viewed by an observer, and can be enlarged by arranging projectors in an array.

  The rear projection image display device 10 blocks a direct light from a projector 11 that projects a relatively high-brightness image, a transmissive screen 12 that is installed on an imaging surface of light projected by the projector 11, and the projector. For this purpose, there is provided a direct light blocking unit including a first polarizing plate 13 and a second polarizing plate 14 provided for the purpose.

  The transmissive screen 12 is generally composed of a diffusing plate that performs appropriate light distribution so that a good image free from luminance spots can be obtained from light projected from the projector 11. In the present embodiment, as the transmission screen 12, a cloth such as cotton, silk, or artificial fiber (tetron = tetronponge) is used. As a result, the half-value angle of diffusion can be increased.

  For example, tetronponge is a material for artificial fibers used for shop banners and the like, and is a fabric that can be obtained at a very low price. FIG. 2 shows a state in which this fabric is used as the transmission screen 12 and an image (taken by a dog) from the projector 11 is projected rearward. In this case, although a fine image can be projected, direct light (light that reaches the observer directly without being diffused) is observed around the nose of the dog. This direct light is accompanied by diffraction, and it can be confirmed that the direct light spreads in the direction of the seam of the fabric.

  3 to 4 show a state where the transmissive screen 12 is photographed from an angle other than the front. In FIG. 3, an angle of about 30 deg is given, and in FIG. 4, an angle of about 60 deg is given. Even when an angle of 60 deg or more is formed with respect to the image plane, that is, the transmission screen 12, a decrease in gain is suppressed. Further, it can be confirmed that the luminance unevenness of the entire image is relatively small. When the angle from the front exceeds a certain value, direct light does not reach the observer geometrically. Thus, it can be said that the transmissive screen 12 made of cloth, silk, tetronpong or the like is a diffusion material having a relatively large half-value angle other than direct light.

  Next, direct light shielding will be described. In the case of a rear projection type image display device, the irradiation light from the projector is directed to the observer through the transmission type screen, so that the direct light is transmitted and observed. In particular, when a fabric screen is used, the direct light is diffracted and directly spreads in the direction of the fabric seam (described above), which is serious.

  The rear projection image display device 10 according to the present embodiment is configured to block direct light from the projector by a direct light blocking unit including the first polarizing plate 13 and the second polarizing plate 14. The first polarizing plate 13 is disposed in front of the exit pupil of the projector, and the second polarizing plate 14 is disposed in the vicinity of the back surface (that is, the surface on the observer side) of the transmission screen. The first polarizing axis of the first polarizing plate and the second main optical axis of the second polarizing plate are arranged so as to be substantially orthogonal so that only the scattered light diffused by the transmission screen can be obtained. The light passes through the second polarizing plate 14 and can be observed from the back side of the transmissive screen 12, that is, an observer. Direct light from the projector is removed by the second polarizing plate 14.

  In addition, by arranging the first polarizing plate 13 in the vicinity of the front of the exit pupil of the projector 11, the size of the first polarizing plate 13 can be further reduced. However, in this case, since it is affected by heat generation from the light source, it is necessary to use a heat-resistant polarizing plate.

  A normal polarizing film has a structure in which a thin plate that has absorbed iodine is stretched in one direction so that molecules are aligned in parallel and sandwiched between acetylbutyl celluloses, and the use temperature is −50 ° C. to 80 ° C. For example, using a polarizing plate with higher heat resistance, such as a glass polarizing filter sandwiched between glass plates or a quartz-based filter after molecules are aligned in parallel by stretching a thin plate that has absorbed iodine in one direction can do.

  Examples of the projector 11 that generates a high-brightness image include a 3LCD projector, a reflective liquid crystal (LCOS) projector, a DLP projector, and a CRT projector GLV projector.

  Of these, the 3LCD projector first separates the light emitted from a single high-intensity light source into components for each of the three primary colors of RGB using a mirror that transmits only a specific wavelength, such as a dichroic mirror. The control light is synthesized again by a prism and then projected. In LCOS (Liquid Crystal on Silicon), light is sequentially driven by a rotating prism mechanism that decomposes and projects light into RGB.

  Since the reflected light is polarized, in these methods, the transmitted light is polarized whenever it is separated into color components using a mirror. For example, the R and B polarization axes are aligned, and the G polarization axis is orthogonal to this. It has a specific polarization state. In such a case, if the polarization axis of one of the light components is arranged so as to be substantially parallel to the polarization axis of either the first polarizing plate 13 or the second polarizing plate 14, the light component is completely transmitted. Disappear. Therefore, it is necessary to configure the first and second polarization axes to be non-parallel to the polarization axis of any component of the projection light.

  Specifically, when using a projector in which the polarization axis of the LCD in charge of R and B and the polarization axis of the LCD in charge of G make 90 degrees, as shown in FIG. By arranging the polarization axis of the plate 14 to be approximately 45 degrees with the polarization axis of both LCDs, the R, B, and G components can be attenuated equally. As a result, the gain of each wavelength of the light emitted from the projector 11 does not depend on the direction of the vibration surface of the electric field vector of the light beam.

  6 and 7 show the relationship between the angle between the polarization axes of the first polarizing plate 13 and the second polarizing plate 14 and the influence of direct light. Here, it is assumed that the second polarizing plate 14 is rotated with respect to the first polarizing plate 13.

  In FIG. 6, the polarization axes of both polarizing plates 13 to 14 are almost parallel, and a component having a vibration direction orthogonal to these polarization axes in the direct light passes through the second polarizing plate 14. Therefore, the effect of direct light is remarkable when viewed from the front.

  Then, when the second polarizing plate 14 is rotated with respect to the first polarizing plate 13 and the polarization axes of the two polarizing plates 13 to 14 are substantially orthogonal, only the scattered light diffused by the transmission screen 12 is the second. Because the light passes through the polarizing plate 14, direct light is blocked to a considerable extent.

  FIG. 7 shows a state where the back surface of the transmission screen 12 is observed from a direction other than the front surface in a state where direct light is blocked. When the polarizing plates 13 to 14 are used, the gain of the entire projected image is reduced, but the direct light that becomes a hindrance when viewed from the front is reduced, and when viewed from an angle other than the front It can be confirmed that the luminance reduction and the luminance unevenness of the entire screen are suppressed.

  8 and 9 show a state in which direct light is shielded by a polarizing plate and the back surface of the transmission screen 12 is observed from an angle other than the front surface. In FIG. 8, an angle of about 30 deg is given, and in FIG. 9, an angle of about 60 deg is given.

  Subsequently, a second embodiment of the present invention will be described. The second embodiment relates to a rear projection type image display device to which multi-projection is applied.

  Projection-type image display devices can form a large screen by projecting an image of light emitted from a projector on a screen, and according to a multi-projection system, each of a plurality of projectors By projecting a part of the displayed image on the screen while overlapping each other, the projection area can be further enlarged and the resolution can be increased.

  The present inventors consider that the rear projection type image display device is suitable for enlargement from the viewpoint that the shadow of the observer does not fall on the screen (described above). However, it is disadvantageous to use a projector with a small half-value angle in constructing a multi-projection system.

  If the emitted light that passes through the screen that also serves as the diffusion plate is completely diffused (see FIG. 17A), the screen gain does not depend on the angle between the incident light and the emitted light. In this case, even if multi-projection is used, it is considered that a change in color and luminance unevenness hardly occur in the projected image.

  However, in the rear projection, there is a main design guideline (described above) for increasing the luminance from the front, and the emitted light transmitted through the diffusion screen has a high gain in the front direction (FIG. 17B). Alternatively, in the rear projection, even when a diffuser plate that performs simple diffusion is used, complete diffusion as shown in FIG. 17A is difficult and the front gain becomes high. FIG. 18 shows a state in which the irradiation light from the projector is projected rearward. The emitted light has the maximum gain at a position that is collinear with the incident light on the central axis coming from the projector (at 0 ° in FIG. 18), and the gain decreases as the angle between the incident light and the emitted light increases. I will do it.

  Here, when a plurality of incident lights having a maximum gain in the traveling direction of light are simply diffused on the diffusing screen, each incident light has a high gain in a direction according to the exit angle as shown in FIG. (That is, since each emitted light does not align with a diffusion pattern having a high front gain), nonuniform brightness of the screen is observed. As described above, the degree of diffusion varies depending on the incident angle to the screen, and a change in color and unevenness in luminance occur depending on the observation location. Therefore, the present inventors consider that it is necessary to solve such a problem in order to construct a multi-projection system using rear projection.

  It is known in the art to use a Fresnel lens in a diffusing screen as one means to solve the half-value angle problem of the emitted light. In a projection system consisting of a single projector, a Fresnel lens can be an effective solution. However, because the incident angle of the Fresnel lens has a limit, the diffusion pattern is not guaranteed when the irradiation light from the projector enters the Fresnel lens from an angle other than assumed, and the direction of the emitted light, that is, The direction in which the gain is high cannot be predicted (see FIG. 20). That is, it is difficult to eliminate the directionality of the emitted light that has passed through the Fresnel lens, and it is difficult to achieve a wide viewing angle that is necessary for increasing the screen size by multi-projection.

  For example, by defining the relative positions of each projector and Fresnel lens, such as arranging the projectors that make up a multi-projection array, the light emitted from the projector does not enter the Fresnel lens at an unexpected incident angle. In this way, it is conceivable to guarantee a diffusion pattern of high front gain. In this case, emission light with a high front gain is obtained from the individual projectors, and the emission light is superposed to reduce the change in luminance gain of the entire screen. However, when a Fresnel lens is used, it is difficult to form a large screen, and the production cost becomes high. In addition, significant restrictions are imposed on the arrangement of a plurality of projectors.

  Further, in the multi-rear projector system arranged in an array, even when the signal processing is performed so that the luminance of the projection surface becomes uniform when the screen is viewed from a certain position, as shown in FIG. Since the incident angle of light or the combination of multiple incident angles differs depending on the location, when the screen is observed at a location outside the specific position where the entire image appears homogeneous, there is a change in color and uneven brightness. There is a problem that it appears prominently.

  Therefore, in this embodiment, a wide viewing angle of the rear projection type image display device is realized by using the diffusion screen that diffuses any incident light into the emitted light having a high front gain regardless of the incident angle. I tried to do it. Such a rear projection screen has no restriction on the arrangement of the projector, and as shown in FIG. 22, the incident light from the projector arranged at any place is output as the emitted light having a uniform front gain. When multi-projection is applied, it is predicted that the front gain will be high if it passes through the screen even if the arrangement of the individual projectors is not particularly limited. Therefore, each emission light is superimposed on the screen surface on the viewing side, and the change in luminance gain is small for the entire screen, that is, the half-value angle is large, and a wide viewing angle can be realized.

  A rear projection screen with wide diffusion characteristics is composed of two different types of screens arranged in parallel: a mat-type screen placed on the viewer side and a screen made of fiber fabric placed on the projector side. The The mat-type screen mentioned here can be constituted by mixing a diffusing agent in a resin film. For example, the mat-type screen is formed by kneading diffusing particles in a vinyl chloride resin. Moreover, a tetron ponge etc. can be utilized for a textile fabric. Tetron Ponji is an artificial fiber material that is used for shop banners and the like, and is a fabric that can be obtained at a very low price (described above).

  FIG. 10 schematically shows the configuration of an image display apparatus according to the second embodiment of the present invention. The illustrated image display device 20 is a rear projection type, and includes a projector 21 that projects an image with relatively high brightness, and a rear projection screen 22 that is installed on an imaging surface of light projected by the projector 21.

  As described above, the rear projection screen 22 has a two-layer screen configuration of a mat-type screen 22A disposed on the viewing side and a screen 22B made of a textile fabric disposed on the projector 21 side, so that a wide viewing angle is obtained. Has been achieved. By sufficiently bringing two screens into close contact, it is possible to project an image without blurring. Further, by separating the two screens by an appropriate distance, it is possible to further reduce the color difference of the projector 21 and blur the image.

  The mat screen 22A diffuses incident light. Further, the screen 22B made of a fiber fabric diffracts incident light according to the roughness of the fiber. That is, the incident light is irregularly reflected, so that the output light can have a gain characteristic of high front gain regardless of the incident angle.

  The rear projection screen 22 having such a two-layer structure has a wide viewing angle, and the incident light from any incident angle is output as the emitted light having a uniform front gain. There are no restrictions. In addition, when multi-projection (not shown) is applied, it is predicted that the luminance gain of any emitted light will be high front gain when passing through the screen, even if the arrangement of the individual projectors is not particularly limited ( See FIG.

  As described above, in the conventional rear projection, the degree of diffusion varies depending on the angle of incidence on the diffusion screen (see FIG. 19), and changes in color and uneven brightness occur depending on the projected location. Therefore, it is difficult to assume the application of multi-projection. On the other hand, in the present embodiment, the rear projection screen 22 has a wide diffusion characteristic, and by changing the degree of diffusion of the emitted light in each incident direction as much as possible, changes in color tone and uneven brightness are obtained. Can be suppressed. Therefore, each emission light is superimposed on the screen surface on the viewing side, and the change in luminance gain is small for the entire screen, that is, the half-value angle is large, and a wide viewing angle can be realized. (Here, “broad diffusion” refers to weakening the direction of the diffusion pattern of the emitted light for each projector across the screen)

  When the two-layer rear projection screen 22 is used, direct light may not be sufficiently blocked, but the direct light blocking unit according to the first embodiment described above can be used in combination. Although the brightness gain of the emitted light with respect to the incident light is expected to decrease due to the light shielding, the polarization of the irregularly reflected light generated when passing through the mat-type screen 22A is not preserved (the polarization characteristics of the projector irradiation are The light is lost due to a diffuse reflection effect when passing through the system screen 22A), so that the light is not shielded.

  12A to 12D show viewing angles (on the basis of 0 degrees in FIG. 18) when the projector 21 is projected directly on the screen 22 (the center of the optical axis of the projector 21 is perpendicular to the screen 22 surface). The change in luminance due to changing the viewing angle) and the state of luminance unevenness in the projection plane are used when using a normal simple diffusion screen conventionally used and the rear projection screen 22 according to the present embodiment. These cases are shown in comparison. The two-layer screen configuration shown in the figure is a case where two screens are brought into close contact with each other. 12A and 12B are projection images when viewing angles are 0 degrees and 80 degrees, respectively, when a screen consisting only of a mat screen that simply diffuses transmitted light is used. 12C and 12D are projection images when the viewing angles are 0 degrees and 80 degrees, respectively, when the rear projection screen 22 having a two-layer structure according to this embodiment is used.

  FIG. 13 shows screen gain characteristics obtained by rear projection using a conventional mat-type screen as a diffusion screen and the rear projection screen according to the present embodiment. In the figure, however, the brightness of the image projected on the screen by the projector is measured with an angle of 15 degrees with a two-dimensional color luminance meter. As can be seen from the figure, when the rear projection screen 22 according to the present embodiment is used, the incident light from the projector is incident on the screen as compared with the case where the conventional simple diffusion type screen is used. The change of the luminance level becomes gentle with respect to the change of the angle (the attenuation becomes small), the half-value angle becomes large, and a high luminance level can be obtained over the entire incident angle.

  As described above, since the rear projection screen 22 having a two-layer structure has a wide viewing angle, there is no restriction on the arrangement of the projector, and the incident light from the projector arranged at any location has a uniform front gain. Can be output as emitted light. As shown in FIG. 14, even when the projectors are installed so as to have various incident angles, the effect of widening the viewing angle can be expected because each emitted light has a high front gain. In other words, even when the projector projects the image onto the screen, even if the center of the optical axis of the incident light from the projector does not coincide with the axis perpendicular to the screen surface, the color and brightness change at the viewing position. Can be small.

  Therefore, when multi-projection (see FIG. 16) is applied to the image display apparatus shown in FIG. 10, the installation locations of the projectors are restricted to one fixed place regardless of the number of projectors. The effect can be obtained at any place.

  In a multi-projection system of the type that superimposes and projects light emitted from a plurality of projectors arranged in an array on a screen, in a “blending area” (see FIG. 16) where the projection surfaces of the projectors overlap. Color differences and luminance differences due to individual differences among individual projectors are often problematic. FIG. 15 shows a state in which light emitted from a plurality of projectors arranged in an array is superimposed and projected onto a conventional simple diffusion type screen and the rear projection screen 22 having a two-layer structure according to the present embodiment. Each is shown.

  As can be seen from FIG. 15A, in the conventional simple diffusing screen, the incident light from each projector becomes a diffusing pattern in which the gain increases in the direction of the emitted light after passing through the screen. Since there are a portion where the light appears to be an equally mixed color and a portion where the color of the incident light from some projectors appears strong, the problem of the difference in color and the difference in luminance becomes apparent.

  On the other hand, when the projection is performed on the rear projection screen having the two-layer structure according to the present embodiment, since all incident light is uniformly diffused in all directions, the luminance is not affected by the observation position even in the blending region. It is possible to obtain a projected image with little decrease in color and little change in color. That is, as can be seen from FIG. 15B, tile-like degradation or the like can be reduced regardless of the brightness of the blending region regardless of the observation position.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  The fabric used as the transmission screen is preferably a material that directly transmits light, such as cotton, silk, or artificial fibers such as tetron pongee.

  When a large-scale screen exceeding 300 inches is constructed using the rear projection type image display device according to the present invention, the fabric used as the screen may be used by bonding a roll fabric having a width of 2 meters. Moreover, since a polarizing plate having a large size and having a size of about 1 meter × 0.5 meter can be used, these may be bonded together.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram schematically showing a configuration of an image display apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing a state in which a dough is used as the transmission screen 12 and a video image (taken by a dog) from the projector 11 is projected rearward. FIG. 3 is a diagram showing a state where the transmission screen 12 is photographed from an angle other than the front. FIG. 4 is a diagram illustrating a state where the transmissive screen 12 is photographed from an angle other than the front. FIG. 5 shows a case where a projector in which the polarization axis of the LCD in charge of R and B and the polarization axis of the LCD in charge of G make a 90 deg. It is the figure which showed a mode that it arrange | positioned so that a polarization axis may be made about 45deg. FIG. 6 is a diagram showing the influence of direct light and the angle formed between the polarization axes of the first polarizing plate 13 and the second polarizing plate 14. FIG. 7 is a diagram showing the influence of direct light and the angle formed between the polarization axes of the polarizing plate 13 and the second polarizing plate 14. FIG. 8 is a diagram showing a state in which the rear surface of the transmission screen 12 is observed from an angle other than the front surface with direct light blocked by a polarizing plate. FIG. 9 is a diagram showing a state in which the rear surface of the transmission screen 12 is observed from an angle other than the front surface with direct light blocked by a polarizing plate. FIG. 10 is a diagram schematically showing a configuration of an image display apparatus according to the second embodiment of the present invention. FIG. 11 is a diagram illustrating a state in which the luminance gain of each emitted light that has passed through the rear projection screen becomes a high front gain. FIG. 12A is a projected image when the viewing angle is 0 degrees when a screen consisting only of a mat screen is used. FIG. 12B is a projected image when the viewing angle is 80 degrees when a screen consisting only of a mat screen is used. FIG. 12C is a projection image when the viewing angle is 0 degree when a rear projection screen having a two-layer structure is used. FIG. 12D is a projection image when the viewing angle is 80 degrees when a two-layer structure rear projection screen is used. FIG. 13 is a diagram showing characteristics of screen gain obtained by rear projection using a conventional mat-type screen as a diffusion screen and a rear projection screen according to the present embodiment. FIG. 14 is a diagram showing the state of the emitted light when the projector is installed so as to have various incident angles. FIG. 15A is a diagram showing a state in which light emitted from a plurality of projectors arranged in an array is superimposed and projected onto a simple diffusion screen. FIG. 15B is a diagram illustrating a state in which light emitted from a plurality of projectors arranged in an array is projected onto the rear projection screen 22 having a two-layer structure. FIG. 16 is a diagram illustrating a configuration example of a multi-projection system. FIG. 17A is a diagram showing a state in which emitted light passing through a screen that also serves as a diffusion plate is completely diffused. FIG. 17B is a diagram illustrating a state in which emitted light that passes through a screen that also serves as a diffusion plate is diffused so as to have a high front gain. FIG. 18 is a diagram showing a state in which the irradiation light from the projector is projected rearward. FIG. 19 is a diagram showing a state in which a plurality of incident lights whose light traveling direction has a maximum gain are each simply diffused on a diffusion screen. FIG. 20 is a diagram showing how incident light from a projector is diffused by a Fresnel lens. FIG. 21 is a diagram illustrating a state in which a change in color or luminance unevenness appears depending on the observation location on the screen due to a difference in incident angle of incident light or a combination of a plurality of incident angles. FIG. 22 is a diagram showing a state in which incident light from a projector arranged at any location using the rear projection screen according to the present invention is output as emitted light having a uniform front gain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Rear projection type image display apparatus 11 ... Projector 12 ... Transmission type screen 13 ... 1st polarizing plate 14 ... 2nd polarizing plate 20 ... Image display apparatus 21 ... Screen for projection 22 ... Screen for rear projection 22A ... Textile fabric Screen 22B ... Matte screen

Claims (2)

One or more projectors that project high brightness images;
A mat-type screen arranged on the viewer side and a screen made of fiber fabric arranged on the projector side are arranged in parallel, and the incident light from each projector is gained with respect to the respective emission angles of the emitted light. A rear projection screen that diffuses so that the gain characteristic normalized by the front gain does not depend on the incident angle;
A first polarizing plate having a first polarization direction disposed in front of an exit pupil of the projector, and the first polarizing plate disposed in the vicinity of a back surface (observer) side with respect to an irradiation surface of the transmissive screen. A direct light blocking means comprising a second polarizing plate having a second polarization direction substantially orthogonal to the polarization direction of the first;
A rear projection type image display device comprising: Among the rear projection screens, the mat screen disposed on the viewer side is formed by kneading diffusion particles into vinyl chloride resin, and the fiber dough screen disposed on the projector side is the Tetron. Made of Ponzi,
The rear projection image display apparatus according to claim 1, wherein