JP2005242378A - Rear projection television and projection method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection television which has a large screen but has a size reduced by eliminating externally excess space, and to provide a projection method thereof. <P>SOLUTION: A planar mirror 2 for folding an optical path is not arranged on the side of a screen 4 but rather is arranged on the rear surface or the upper surface side of an enclosure inside surface. A plurality of imaging mirror groups 5a to 5d, which allow a luminous flux to be emitted at a high launch angle to the normal of the screen and allows an image to be formed at a distance shorter than a conventional projection lens, are used in order to direct the optical path of image projection to a planar mirror 3 on the rear surface and upper surface sides of the enclosure. Since luminous flux is launched at a high angle and is reflected by the planar mirror 2 on the rear surface or upper surface side in the enclosure, the luminous flux is imaged on a screen 4 in front of the enclosure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rear projection television and a projection method thereof, and more particularly, to a rear projection television and an projection method thereof for enlarging and projecting an image on an image display element onto a screen.

  A conventional rear projection television will be described below with reference to FIGS. FIG. 9 shows an internal configuration of a rear projection television as the first conventional example. As shown in FIG. 9, the rear projection television of Conventional Example 1 includes a first flat mirror 102 in which a light beam emitted from a projector main body 101 disposed at a lower rear part in a casing is provided at a lower front part in the casing, a rear surface in the casing. The projection is performed through the second flat mirror 103 provided on the screen, and the screen is displayed by forming an image on the transmission screen 104 provided on the front surface of the casing.

  FIG. 10 shows an internal configuration of a rear projection television as the second conventional example. As shown in FIG. 10, in the rear projection television of Conventional Example 2, the light emitted from the projector main body 101 provided in the upper part of the housing is converted into the first plane mirror 102, the second plane mirror 103, and the third plane mirror. The screen is displayed by performing folding projection through 109 and forming an image on a transmission screen 104 provided on the front surface of the housing. In this conventional example 2, the thickness of the rear projection television main body is made thinner by increasing the number of mirrors for performing the folding projection and increasing the number of times the projection light beam emitted from the projector 101 is folded. For example, as such a rear projection television, there is an “oblique projection display device” disclosed in Patent Document 1.

  FIG. 11 is a diagram for explaining generation of stray light in the internal configuration of a conventional rear projection television. In FIG. 11, when a light beam emitted from the projector main body 101 is incident on the transmission screen 104 at an angle, some of the components are reflected on the surface of the transmission screen 104. The light beam 111 reflected by the transmissive screen 104 is incident on the transmissive screen 104 again via the second flat mirror 103 provided on the rear surface of the housing. The re-incident light beam 112 appears on the screen and becomes stray light, and a ghost image that does not exist in the original image is displayed on the screen.

  Similarly, a light beam (interior illumination light, etc.) that has entered from the outside is also reflected by the second flat mirror 103 provided on the back surface inside the housing after passing through the transmissive screen 104, and stray light caused by entering the transmissive screen 104 again. (Ghost image) may be copied.

JP-A-4-107521 JP-A-5-88264

  The conventional rear projection television as described above has the following problems.

  The first problem is that a storage space is required under the screen in order to store one of the plane mirrors. The storage space becomes an extra portion (skirt) in appearance, which hinders the miniaturization of the rear projection television.

  The second problem is the depth due to the projection distance of the rear projection television. In the projection by the conventional projection lens, the projection distance becomes longer due to the design of the lens, and even if the optical path is folded by the folding mirror, the projection distance becomes the same as that of the CRT monitor.

  The third problem is that stray light (ghost image) reflected on the screen is generated by reflection of the light flux on the screen incident surface and external light incident from outside the rear projection television main body.

  A fourth problem is that when the number of reflection mirrors used is large, the brightness of the image is deteriorated due to the problem of the reflectance of each reflection mirror.

  A fifth problem is that a multi-rear projection television in which a large number of rear projection televisions are arranged vertically and horizontally cannot be produced due to the presence of the skirt portion in the rear projection television body.

  In order to create a multi-rear projection television as described above, it is necessary that the joint between the screens is not noticeable. Therefore, if the rear projection television main body has a skirt portion, a multi-rear projection television cannot be manufactured. For this reason, in the conventional multi-rear projection television, a form in which the light flux of the projector is projected without folding the mirror is employed. Accordingly, the installation is a large-scale construction, and there is a problem that a room with a large depth is required to obtain a projection distance because the cost cannot be increased and mass production cannot be handled, and the projection projection cannot be performed.

  As means for solving some of these problems, Patent Document 2 discloses that a screen is provided on the entire front surface of the housing so that the emitted light of the projector is directed directly to the top plate side, and a large reflecting mirror is provided from the top plate side. Is disposed obliquely to reflect the emitted light toward the screen. This configuration eliminates the skirt, but a large reflecting mirror is provided with a large inclination from the top so that the incident angle on the screen does not increase. The size can be reduced only to about 1/2 to 1/3 of (dimension). In addition, since the projector is unnaturally arranged such that the projector is installed upward, maintenance management is troublesome.

  SUMMARY OF THE INVENTION A first object of the present invention is to provide a rear projection television and a projection method thereof that can reduce the size of the entire apparatus by eliminating the skirt portion and further reducing the depth of the rear projection television.

  A second object of the present invention is to provide a rear projection television and a projection method thereof that improve image quality by eliminating stray light (ghost images) displayed on a screen.

  It is a third object of the present invention to provide a rear projection television and a projection method thereof that improve the brightness by reducing the number of planar reflecting mirrors.

  The rear projection television of the present invention includes a transmissive screen, a projector that emits a light beam including image information, an imaging optical component that includes a plurality of imaging mirrors, and a light beam from the imaging optical component. A plane reflecting mirror that reflects the light toward the back surface of the transmissive screen, and other than the one plane reflecting mirror in the optical path between the imaging optical component and the transmissive screen. There is no mirror, and the front surface thereof is substantially composed of the transmission screen.

Alternatively, the rear projection television of the present invention includes a transmissive screen, a projector that emits a light beam including image information, an imaging optical component including a plurality of imaging mirrors, and the imaging optical component. A plane reflection mirror that reflects the light beam toward the rear surface of the transmission screen, and the one plane reflection mirror is disposed in an optical path between the imaging optical component and the transmission screen. There is no other mirror, and the imaging optical component is located behind the transmissive screen and above the lower end of the transmissive screen.
Alternatively, in the projection method of the rear projection television of the present invention, the light including the image information emitted from the projector is projected by the imaging optical component including a plurality of imaging mirrors, and the projected image information Is reflected toward the back surface of the screen by one plane reflecting mirror provided in an optical path between the imaging optical component and a screen that substantially constitutes the front surface. Further, the image information is imaged.
Alternatively, the rear projection television projection method of the present invention is configured to include light including image information emitted from the projector from a plurality of imaging mirrors located behind the screen and above the lower end of the screen. The image forming optical component projects light, and the light including the projected image information is reflected on the screen by a single plane reflection mirror provided in an optical path between the image forming optical component and the screen. The image information is imaged on the screen by reflecting toward the back.

  According to the rear projection television and the projection method of the present invention, it is not necessary to create a storage space only for a flat mirror as in the prior art, and the front surface of the housing can be only a screen. Further, the apparatus main body can be reduced in size.

  Further, according to the rear projection television and the projection method of the present invention, the projection distance of the projector is significantly shortened by using the imaging mirror, compared with the case of using the conventional projection lens, so that the entire optical path is shortened. In addition, the depth of the apparatus main body can be made smaller than before by using the imaging mirror and the folded projection.

  In addition, according to the rear projection television and the projection method of the present invention, the launch angle of the light beam becomes larger than that of the conventional rear projection television, so that stray light (ghost) on the screen can be prevented.

  In addition, according to the rear projection television and the projection method of the present invention, the number of reflecting mirrors is reduced, so that the total reflectance of the mirror can be kept small, and the brightness can be improved.

  Furthermore, according to the rear projection television and the projection method of the present invention, it is possible to eliminate the skirt of the main body of the apparatus and to use only the screen on the front surface of the housing, so that conventionally dedicated modification or large-scale construction is required. A large-screen multi-rear projection TV can be easily manufactured.

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

Referring to FIG. 1, an embodiment of the present invention will be described. A transmissive screen 4 is disposed on the entire front surface of a housing 10. A projector 1 that uses a plurality of imaging mirror groups 5a to 5d as imaging optical components is arranged on the bottom plate side in the housing 10 of the rear projection television. A flat mirror 3 is disposed on the top plate side of the housing 10.
The light beam emitted from the projector 1 is projected and projected at a high angle of 45 degrees or more with respect to the normal line of the screen by the plurality of imaging mirror groups 5d, 5c, 5b, and 5a. Reflected on the front surface of the housing by the plane mirror 3 arranged on the upper surface side in the housing in a positional relationship orthogonal to the screen 4, a projection image from the projector 1 is formed on the screen 4 on the front surface of the housing.

  The feature of the present invention is such that the center (optical axis) of a light beam projected and projected at a high angle toward the flat mirror 3 on the top plate side approaches the screen 4 as it approaches the flat mirror 3. That is, as shown in the figure, the distance between the projection optical axis and the screen is arranged so as to become smaller as it approaches the top-plate-side reflecting mirror.

  Since the main surface of the flat mirror 3 is orthogonal to the main surface of the screen 4, the launch angle of the projected light beam onto the flat mirror 3 is the same as the incident angle of the imaging light beam onto the screen 4. In other words, in the present invention, the casing is made thinner by arranging the optical system so that the incident angle is 45 degrees or more, contrary to the conventionally known technical idea of keeping the incident angle on the screen small. It is characterized by that. Further, by making the incident angle on the screen larger than that of the conventional rear projection television, an effect of preventing stray light (ghost) on the screen is also exhibited as will be described later.

  As the screen 4, it is desirable to employ a total reflection type Fresnel lens 41 having irregularities on the inner surface of the screen as shown in the enlarged view. More preferably, the screen is configured to overlap the lenticular lens.

  Next, a reference example of the present invention will be described with reference to FIGS. In this reference example, the plane mirror 2 is added on the back side in the housing 10. Since the mirror 2 is newly added, the projector 1 that uses the plurality of imaging mirrors 5a to 5d as imaging optical components is installed in a direction to project on the back side in the housing 10.

  Further, the light flux projected from the projector 1 is arranged so as to form an image on the screen 4 on the front surface of the housing via the housing rear surface side and the housing upper surface side. That is, the plane mirror 2 is disposed on the back side in the housing so that the main surface of the plane mirror 2 is in a positional relationship parallel to the main surface of the screen 4. Further, the plane mirror 3 is arranged on the upper surface side in the housing so as to be in a positional relationship orthogonal to the screen 4.

  A projector using a liquid crystal panel as an image display element will be described with reference to FIG. This is the case of a so-called liquid crystal projector in which red (R), green (G), and blue (B) image light beams formed by the liquid crystal panel are combined and emitted by the cross prism 1b. A projection imaging mirror 5d is installed in front of the projector 1, and the projection imaging mirrors 5c to 5a are sequentially moved upward and downward so that the optical path is zigzag above the projection imaging mirror 5d. Are alternately arranged to form a projection imaging optical system. The four projection imaging mirrors reflect and fold the image light and proceed upward. The folding plane mirror 2 is installed on the rear surface in the housing obliquely forward of the final projection imaging mirror 5d, and the folding plane mirror 3 is installed on the top plate surface in the housing. The light beam emitted from the projector 1 is reflected and folded by the projection imaging mirror and the folding plane mirrors 2 and 3, proceeds zigzag, and is projected and imaged on the screen 4.

  In the rear projection television of the present invention, for the purpose of reducing the depth of the main body, a plurality of projection imaging mirrors composed of an aspherical mirror as an image projection component and one folding plane mirror between the projector 1 and the screen 4. 2 is arranged. Since the launch angle of the aspherical mirror can be made larger than that of a lens, flat mirror, etc., the projection imaging mirrors 5a to 5d can be used to form a high-magnification screen with a short projection distance. ) (See FIG. 2) is larger than when a normal projection lens is used. As a result, the angle of incidence on the screen 4 also increases, and the flat mirror and other components interfere with and are not shielded from the reflected reflection of the projected light, so that the depth of the rear projection television can be significantly reduced.

  A screen 4 composed of a Fresnel lens 7 and a lenticular lens 8 is installed on the front surface of the housing, and the light beam reflected by the flat mirror 3 on the upper surface side in the housing is imaged on the screen 4.

  Next, a rear projection television that is another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4, the top mirror 3 on the top plate side is disposed on the upper surface side in the housing with a positional relationship of 95 degrees with respect to the main surface of the screen 4. A projector 1 that uses a plurality of imaging mirror groups 5a to 5d as imaging optical components is arranged in a housing of a rear projection television, as in the embodiment shown in FIG.

  The light beam projected from the projector 1 is launched and projected at a high angle of 45 degrees or more with respect to the normal line of the screen by the plurality of imaging mirror groups 5d, 5c, 5b, and 5a. The projected light beam is reflected by the flat mirror 3 to the front surface of the housing, whereby an image from the projector 1 is formed on the screen 4 on the front surface of the housing. In the figure, the case where the installation angle of the plane mirror 3 is set to 95 degrees with respect to the screen surface is shown, but the intention of the present invention can be realized even when this angle is changed from 70 degrees to 120 degrees.

  FIG. 5 is a schematic diagram showing an arrangement state of a plurality of imaging mirror groups as imaging optical components used in each embodiment of the present invention. As shown in FIG. 5, a light beam emitted from a projector (not shown) passes through an image display element 6 constituted by a liquid crystal panel, DMD (Digital Micromirror Device), or the like, to provide a mirror 5d, a mirror 5c, a mirror 5b, and a mirror. Reflected in the order of 5a. The light beam reflected by the mirror 5a is projected onto the screen via a flat mirror provided on the rear surface of the casing (not shown) or on the casing top plate.

  FIG. 6A and FIG. 6B are a top view and a front view showing a schematic configuration of a suitable screen in each embodiment of the present invention. The screen is configured by overlapping a total reflection type Fresnel lens 7 and a lenticular lens 8. The total reflection type Fresnel lens 7 is a thin lens in which only the curvature of the lens is formed in a step shape on a plane so as to have the optical properties of a thick lens. When this total reflection type Fresnel lens is used, a focal length shorter than the aperture can be achieved, which is not possible with a spherical lens. The lenticular lens 8 is a lens in which cylindrical lenses are arranged on a plane, and improves the efficiency of splitting and condensing light rays.

  FIG. 7 is an optical path tracking diagram of stray light in the reference example shown in FIG. As shown in FIG. 7, the luminous flux is launched at a high angle with respect to the normal line of the screen. Therefore, a part of the light beam reflected on the surface of the screen 4 is re-reflected by the plane mirror 3, but the incident angle of the original light beam on the plane mirror 3 is large, so that after being reflected again by the plane mirror 3, Head outside the screen 4. Therefore, it cannot enter the screen 4.

  Similarly, the light beam 13 incident from the outside is re-reflected by the plane mirror 2 because of the internal structure that launches the projected light beam at a high angle. However, depending on the position of the plane mirror 2, the re-reflected light 12 is reflected on the screen. 4 cannot enter. For this reason, stray light on the screen does not occur.

  In any of the above-described embodiments, the projection imaging mirrors 5a to 5d including aspherical lenses are used as the imaging optical system. However, the imaging optical system is configured by a combination of the projection imaging mirror and the projection lens. It may be configured.

  Further, as the projector, an example in which a transmissive image projection apparatus using a liquid crystal panel is used has been shown. However, as shown in FIGS. 8A and 8B, a micro mirror 32 is mounted on a silicon substrate 31. You may use the mirror array comprised by the micromirror aggregate | assembly which arrange | positions in the matrix form on the surface. In this mirror array, as shown in FIG. 8B, a minute mirror 32 is supported by a torsion beam 33 and installed on a silicon substrate, and one minute mirror 32 forms one pixel. The micro mirror 32 is rotated by electrostatic attraction between the micro mirror 32 and the address electrode 34 provided on the silicon substrate surface on the back side of the micro mirror. In this way, the attitude of each micromirror 32 is changed by turning on and off the voltage applied to the address electrode 34, the reflection direction of the light L from the light source lamp 30 is changed, and an image is generated to generate a projection lens 37. Thus, an image is projected (FIG. 8A).

  Each of the above-described embodiments is a preferred embodiment of the present invention, and various modifications can be made without departing from the spirit of the present invention.

1 is a side perspective view showing an internal structure of a rear projection television that is a first embodiment of the present invention; FIG. It is a side perspective view which shows the internal structure of the rear projection television which is a reference example. FIG. 3 is a perspective view showing the internal configuration of the rear projection television shown in FIG. 2. It is a side perspective view which shows the internal structure of the rear projection television which is the 2nd Example of this invention. It is a schematic explanatory drawing which shows the some imaging mirror group as an imaging optical component in each Example of this invention. It is the top view and front view which show schematic structure of the transmissive screen suitable for each Example of this invention. FIG. 3 is an optical path tracking diagram of stray light in the rear projection television shown in FIG. 2. It is the schematic of the image projection apparatus using the mirror array which consists of many micromirrors, and a structure schematic perspective view of micromirrors. It is a side see-through | perspective view which shows the internal structure of the rear projection television of the prior art example 1. FIG. It is a see-through | perspective perspective view which shows the internal structure of the rear projection television of the prior art example 2. FIG. It is a side perspective diagram explaining the stray light generation in the internal structure of the conventional rear projection television.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projector body 2 Plane mirror 3 Plane mirror 4 Screen 5a-5d Image formation mirror

Claims (4)

A transmissive screen,
A projector that emits a light beam including image information;
An imaging optical component composed of a plurality of imaging mirrors;
A plane reflection mirror that reflects the light beam from the imaging optical component toward the back surface of the transmission screen;
In the optical path between the imaging optical component and the transmission screen, there is no mirror other than the one plane reflection mirror,
The front surface is substantially composed of the transmissive screen,
Rear projection TV. A transmissive screen,
A projector that emits a light beam including image information;
An imaging optical component composed of a plurality of imaging mirrors;
A plane reflection mirror that reflects the light beam from the imaging optical component toward the back surface of the transmission screen;
In the optical path between the imaging optical component and the transmission screen, there is no mirror other than the one plane reflection mirror,
The imaging optical component is located behind the transmissive screen and above the lower end of the transmissive screen,
Rear projection TV.   Light including image information emitted from the projector is projected by an imaging optical component including a plurality of imaging mirrors, and the light including the projected image information is substantially the same as the imaging optical component. The image information is imaged on the screen by being reflected toward the back of the screen by a single plane reflecting mirror provided in the optical path between the screen and the screen constituting the front surface. Projection method for rear projection television. The light including image information emitted from the projector is projected by an imaging optical component composed of a plurality of imaging mirrors located behind the screen and above the lower end of the screen. The reflected light including the image information is reflected toward the back surface of the screen by a single plane reflection mirror provided in the optical path between the imaging optical component and the screen. A projection method for a rear projection television, wherein the image information is imaged.

Images