JP2002207190A - Rear projection television and its projection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear projection television which has a big screen but has a size reduced by removing an externally excessive space, and to provide its projection method. SOLUTION: A plane mirror 2 for folding an optical path is arranged in the easing on not the side of a screen 4, but the rear or upper side of the easing. A plurality of focusing mirrors 5a to 5d which enable luminous flux to form an image at a high launch angle to the normal of the screen through a shorter distance compared with a conventional projection lens, are used in order to direct the optical path of an image projection to a plane mirror 3 on the rear or upper side of the easing. Because the luminous flux projected by the focusing mirrors 5a to 5d is launched at a high angle and reflected by the plane mirror 2 at the rear or upper side in the easing, the luminous flux is imaged on the screen 4 provided on the front side of the easing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection television and a projection method therefor, and more particularly to a rear projection television for enlarging and projecting an image on an image display device onto a screen and a projection method therefor.

[0002]

2. Description of the Related Art A conventional rear projection television will be described below with reference to FIGS. FIG. 9 shows the internal configuration of a rear projection television as Conventional Example 1. 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 portion inside a housing is provided at a lower front portion inside the housing, and a rear surface inside the housing. Is projected through the second flat mirror 103 provided on the front panel, and the transmission screen 104 provided on the front surface of the housing.
The image is displayed on the screen.

FIG. 10 shows an internal configuration of a rear projection television as a second conventional example. As shown in FIG. 10, a rear projection television of Conventional Example 2 includes a projector main body 101 provided at an upper part in a housing.
Are reflected and projected through the first plane mirror 102, the second plane mirror 103, and the third plane mirror 109, and the transmission screen 1 provided on the front surface of the housing.
The image is displayed on the screen 04 to display the screen. In the second conventional example, the thickness of the rear projection television body is further reduced by increasing the number of mirrors for performing the return projection and increasing the number of times the projection light beam emitted from the projector 101 is returned. For example, such a rear projection television is disclosed in
There is an "oblique projection display device" disclosed in Japanese Patent Application Laid-Open No. 107521/1990.

FIG. 11 is a diagram for explaining the generation of stray light in the internal structure 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 its components are changed to the transmission screen 10.
4 is reflected on the surface. The light beam 111 reflected by the transmissive screen 104 passes through the second flat mirror 103 provided on the rear surface of the housing, and the light beam 112 enters the transmissive screen 104 again. The re-entered light beam 112 appears on the screen and becomes stray light, and a ghost image which is not present in the original image is projected on the screen.

Similarly, a luminous flux (such as room illumination light) that has entered from outside is transmitted through a transmissive screen 104 and then reflected by a second plane mirror 103 provided on the back surface of the inside of the housing.
In some cases, stray light (ghost image) due to re-entering the transmissive screen 104 may be displayed.

[0006]

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

[0007] The first problem is that a storage space is required below the screen to store one of the plane mirrors. The storage space becomes an extra part (skirt) in appearance, which hinders downsizing of the rear projection television.

[0008] 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 long due to the design of the lens, and even if the optical path is turned by the turning mirror, the depth becomes the same as that of the CRT monitor.

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

A fourth problem is that when the number of used mirrors is large, the brightness of an image is deteriorated due to the problem of the reflectance of each reflecting 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 manufactured due to the presence of a skirt portion in the rear projection television main body.

In order to create a multi-rear projection television as described above, it is necessary that the joint between the screens is inconspicuous. Therefore, if the rear projection television body has a skirt portion, a multi-rear projection television cannot be manufactured. Therefore, in a conventional multi-rear projection television, a mode in which a light beam of a projector is projected without folding back a mirror has been adopted. Therefore, the installation is a large-scale construction, and there is a problem that the cost increases and mass production cannot be performed, and that a room with a large depth is required to obtain a projection distance due to the inability to perform return projection.

As means for solving some of these problems, Japanese Patent Laid-Open Publication No. Hei 5-88264 discloses a screen provided on the entire front surface of a housing, which is installed so that light emitted from a projector is directly directed to a top plate. A configuration is disclosed in which a large reflecting mirror is installed obliquely from the top plate side to reflect the emitted light toward the screen. In this configuration, the skirt is eliminated, but a large reflecting mirror is provided at a large angle from the top plate side so that the angle of incidence on the screen does not increase. This is a configuration that can be reduced only to about ２〜 to ３ of the dimension). In addition, since the projector is placed in an unnatural arrangement in which the projector is installed upward, maintenance management is troublesome.

A first object of the present invention is to provide a rear projection television and a method of projecting the rear projection television in which the entire apparatus is downsized by eliminating a 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 image) reflected on a screen.

A third object of the present invention is to provide a rear projection television which improves brightness by reducing the number of plane reflecting mirrors, and a projection method therefor.

[0017]

In a rear projection television according to the present invention, an end-side reflecting mirror is arranged near an inner end of a transmissive screen, and a light beam from a projector is screened by the end-side reflecting mirror. Has a configuration in which the light is reflected toward the entire rear surface side of the. The present invention is characterized in that the distance between the optical axis of the incident light beam incident on the end-side reflection mirror and the screen becomes smaller as approaching the end-side reflection mirror.

Further, in such a rear projection television, an image forming optical component including a plurality of image forming mirrors for magnifying and projecting an image is arranged between the end side reflection mirror and the projector. Is also characterized. As such an imaging optical component, a first mirror that reflects light emitted from an image display element that forms image information, and a second mirror that receives and reflects light reflected from the first mirror And a third mirror that receives and reflects reflected light from the second mirror, and a fourth mirror that receives and reflects reflected light from the third mirror. In this case, it is desirable to dispose the first to fourth mirrors so that the reflected light from the fourth mirror becomes a light flux incident on the end-side reflecting mirror.

Furthermore, a rear-side reflection mirror is arranged on the rear side in the housing, so that a light beam from the projector is received and then incident on the end-side reflection mirror. I do. The angle between the end side reflection mirror surface and the screen surface is from 70 degrees to 120 degrees.
It is desirable to be within the range of degrees. Further, it is desirable that the angle between the optical axis of the incident light beam entering the center of the screen from the center of the end-side reflection mirror and the normal line of the center of the screen be 45 degrees or more.

According to the present invention, the depth of the housing can be set to 1/5 or less of the diagonal dimension of the screen.

The transmission type screen of the present invention preferably has a laminated structure of a total reflection type Fresnel lens and a Lentuchler lens, and it is particularly desirable that the optical axis of the Fresnel lens is located outside the screen.

In the rear projection television according to the present invention, a mirror for turning the optical path at the final stage is disposed on the top plate side or the floor plate side in the housing, and the optical component for imaging may be constituted by a plurality of lenses. Good. Further, as the image display element, a liquid crystal panel that expresses an image by reflecting and blocking an illumination light beam from a light source may be used.

As another example of the image display element, an assembly DMD (digital micromirror device) of microreflectors for expressing an image by reflecting an illumination light beam emitted from a light source in an arbitrary direction may be used. .

Further, as a projection method for a rear projection television according to the present invention, there is provided a method of projecting an image on an image display device by using an imaging optical component in an enlarged manner to form an incident light on a final-stage reflecting mirror for forming an image on a transmission screen. However, the imaging optical components and the reflection mirror are combined and arranged so that the distance between the optical axis of the light beam and the screen becomes smaller as the light beam of the incident light approaches the reflection mirror.

In particular, the angle of incidence of the incident light on the screen is set to 45 degrees or more. Also, the center of the formed image is located at a position different from the optical axis of the imaging optical component. Further, the distance between the optical axis of the light beam and the screen is reduced as the light beam reflected from the reflection mirror at the preceding stage of the last-stage reflection mirror approaches the last-stage reflection mirror.

[0026]

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. Plural imaging mirror groups 5a to 5d
Is disposed on the bottom plate side in the housing 10 of the rear projection television. The plane mirror 3 is arranged on the top plate side of the housing 10.

The light beam emitted from the projector 1 is launched and projected by a plurality of imaging mirror groups 5d, 5c, 5b and 5a at a high angle of 45 degrees or more with respect to the screen normal. The light is reflected on the front surface of the housing by the flat mirror 3 disposed on the upper surface side of the housing in a positional relationship orthogonal to the screen 4, and an image projected from the projector 1 is formed on the screen 4 on the front surface of the housing.

The feature of the present invention resides in that the center (optical axis) of a light beam projected and launched at a high angle toward the plane mirror 3 on the top plate side.
Is configured so as to approach the screen 4 as it approaches the plane mirror 3. That is, as shown in the drawing, the distance between the projection optical axis and the screen is arranged to be smaller as approaching the top plate side reflection mirror.

Since the main surface of the plane mirror 3 is orthogonal to the main surface of the screen 4, the launch angle of the projection light beam on the plane mirror 3 is the same as the incident angle of the imaging light beam on the screen 4. In other words, in the present invention, the housing 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 suppressing the incident angle to the screen. It is characterized by doing. Further, by making the angle of incidence on the screen larger than that of the conventional rear projection television, an effect of preventing stray light (ghost) on the screen as described later is also exerted.

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 an enlarged view. More desirably, the screen may be configured to overlap the lenticular lens.

Next, another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the plane mirror 2 is added to the rear side in the housing 10. Since the mirror 2 is newly added, the projector 1 using the plurality of imaging mirrors 5a to 5d as imaging optical components is installed in a direction in which the projector 1 projects on the rear side in the housing 10.

The luminous 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 rear surface of the housing and the upper surface of the housing. That is, the plane mirror 2 is arranged on the rear side in the housing such 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 have a positional relationship orthogonal to the screen 4.

A projector in which a liquid crystal panel is used as an image display device will be described with reference to FIG. This is a so-called liquid crystal projector in which red (R), green (G), and blue (B) image light rays formed by a liquid crystal panel are combined by the cross prism 1b and emitted. In front of the projector 1, a projection imaging mirror 5d is installed.
Above the projection imaging mirror 5d, the projection imaging mirrors 5c to 5a are sequentially arranged alternately back and forth upward so as to form a zigzag optical path, thereby forming a projection imaging optical system. The image light rays are reflected and turned back by these four mirrors for projection and imaging, and sequentially advance upward. A folding flat mirror 2 is installed on the inner rear surface of the housing obliquely in front of the final stage projection imaging mirror 5d, and a folding flat mirror 3 is installed on the top plate surface in the housing. The light beam emitted from the projector 1 is reflected / turned by the projection / imaging mirror and the folding plane mirrors 2 and 3, zigzag, and projected and imaged on the screen 4.

As described above, in the rear projection television of the present invention, in order to shorten the depth of the main body, a plurality of projection / imaging mirrors each including an aspherical mirror as an image projection component between the projector 1 and the screen 4. And folding flat mirrors 2 and 3 are arranged. Since the aspherical mirror can increase the launch angle as compared with a lens, a plane mirror, or the like, by using the projection imaging mirrors 5a to 5d, a screen with a short projection distance and a high magnification is obtained.
The launch angle ζ (see FIG. 2) of the projection light beam (incident light beam Li) becomes larger than in the case where a normal projection lens is used. As a result, the angle of incidence on the screen 4 increases, and the plane mirror and other components do not interfere with the reflected reflection of the projected light beam and are not blocked, so that the depth of the rear projection television can be greatly reduced.

A screen 4 composed of a Fresnel lens 7, a lenticular lens 8 and the like is provided on the front surface of the housing, and a light beam reflected by the plane mirror 3 on the upper surface side inside the housing is imaged on the screen 4. I have.

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

The light beam projected from the projector 1 is launched and projected by a plurality of imaging mirror groups 5d, 5c, 5b, 5a at a high angle of 45 degrees or more with respect to the screen normal. The projection light flux is reflected by the plane mirror 3 to the front surface of the housing, so that an image from the projector 1 is formed on the screen 4 on the front surface of the housing.
Although FIG. 1 shows a case where the plane mirror 3 is set at an angle of 95 degrees with respect to the screen surface, the present invention can be realized even if the angle is changed from 70 degrees to 120 degrees.

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

FIGS. 6A and 6B are a top view and a front view, respectively, showing a schematic structure of a screen suitable for each embodiment of the present invention. The screen is formed by stacking 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 in a plane so as to have the optical properties of a thick lens. The use of this total reflection Fresnel lens enables a focal length shorter than the aperture, which cannot be achieved 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 split light collection and scattering of light rays.

FIG. 7 is an optical path tracing diagram of stray light in the embodiment shown in FIG. As shown in FIG. 7, in the rear projection television according to each embodiment of the present invention, a light beam is launched at a high angle with respect to the normal 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. However, since the incident angle of the original light beam on the plane mirror 3 is large, the light beam is re-reflected by the plane mirror 3. Go outside screen 4. Therefore, the light cannot enter the screen 4.

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

In each of the above embodiments, the imaging optical system uses the projection imaging mirrors 5a to 5d each formed of an aspherical lens. However, the imaging is performed by a combination of the projection imaging mirror and the projection lens. An optical system may be configured.

Also, an example has been shown in which a transmissive image projection device using a liquid crystal panel is used as the projector.
As shown in FIGS. 8A and 8B, a mirror array composed of a group of micromirrors in which micromirrors 32 are arranged in a matrix on the surface of a silicon substrate 31 may be used. In this mirror array, as shown in FIG. 8B, a micromirror 32 is supported on a torsion beam 33 and installed on a silicon substrate, and one pixel is formed by one micromirror 32. The micromirror 32 is rotated by electrostatic attraction between the micromirror 32 and an address electrode 34 provided on the silicon substrate surface on the back side of the micromirror. As described above, by turning on / off the voltage applied to the address electrode 34, the attitude of each micro mirror 32 is changed, and the light source lamp 30
An image is generated by changing the reflection direction of the light L from the camera, and the image is projected by the projection lens 37 (FIG. 8A).

The embodiments described above are preferred embodiments of the present invention, and can be variously modified and implemented without departing from the gist of the present invention.

[0046]

As is apparent from the above description, according to the rear projection television and the projection method thereof of the present invention, the plane mirror for reflecting the light beam emitted from the projector is provided at least on the rear side and the upper side in the housing. By arranging it on the side, it is not necessary to create a storage space only for a conventional flat mirror, and the front surface of the housing becomes only the screen, so that the apparatus main body can be downsized.

Further, according to the rear projection television and the projection method of the present invention, the projection distance of the projector is greatly shortened by using the imaging mirror as compared with the case where the conventional projection lens is used. The optical path can be shortened, and the depth of the apparatus main body can be made smaller than before by using the imaging mirror and the folded projection.

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

Further, according to the rear projection television and the projection method of the present invention, since the number of reflecting mirrors is reduced, the total reflectance of the mirrors can be kept at a small reduction rate, so that the brightness can be improved. Can be.

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

[Brief description of the drawings]

FIG. 1 is a side perspective view showing the internal structure of a rear projection television according to a first embodiment of the present invention.

FIG. 2 is a side perspective view showing the internal configuration of a rear projection television according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing the internal configuration of a rear projection television according to a second embodiment of the present invention.

FIG. 4 is a side perspective view showing an internal configuration of a rear projection television according to a third embodiment of the present invention.

FIG. 5 is a schematic explanatory view showing a plurality of imaging mirror groups as imaging optical components in each embodiment of the present invention.

FIG. 6 is a plan view and a front view showing a schematic configuration of a transmission screen suitable for each embodiment of the present invention.

FIG. 7 is an optical path tracing diagram of stray light in a rear projection television according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of an image projection device using a mirror array including a large number of micromirrors, and a schematic perspective view of the configuration of the micromirrors.

FIG. 9 is a side perspective view showing an internal configuration of a rear projection television of Conventional Example 1.

FIG. 10 is a perspective view showing the internal configuration of a rear projection television of Conventional Example 2.

FIG. 11 is a side perspective view illustrating generation of stray light in the internal configuration of a conventional rear projection television.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projector main body 2 Flat mirror 3 Flat mirror 4 Screen 5a-5d Imaging mirror

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/74 H04N 5/74 A F

Claims (19)

[Claims] 1. A housing having a transmission screen on the front side, a projector disposed in the housing and emitting a light beam including image information, and a projector disposed in the housing near an end of the screen. And an end-side reflection mirror for reflecting the light beam from the projector toward the entire rear surface of the screen, wherein the end-side reflection mirror is a light beam of an incident light beam incident toward the end-side reflection mirror. A rear projection television, wherein a distance between an axis and the screen is reduced as approaching the end-side reflection mirror. 2. An image forming optical component comprising a plurality of image forming mirrors for magnifying and projecting an image is arranged between the end-side reflection mirror and the projector. 1. The rear projection television according to 1. 3. A rear-surface reflecting mirror disposed on the rear side of the housing and configured to receive the light beam from the projector and reflect the light so as to generate the incident light beam incident on the end-side reflecting mirror. The rear projection television according to claim 1, wherein: 4. The rear projection television according to claim 1, wherein an angle between the end-side reflection mirror surface and the screen surface is in a range of 70 degrees to 120 degrees. 5. An angle between an optical axis of an incident light beam entering the center of the screen from the center of the end-side reflection mirror and a center normal of the screen is 45 degrees or more. 1. The rear projection television according to 1. 6. The rear projection television according to claim 1, wherein a normal line of the end-side reflection mirror is parallel to the screen surface. 7. The apparatus according to claim 1, wherein a depth of the housing is not more than 1/5 of a diagonal dimension of the screen.
Rear projection television as described. 8. The rear projection television according to claim 1, wherein the screen has a laminated structure of a total reflection type Fresnel lens and a Lentuchler lens. 9. The rear projection television according to claim 8, wherein an optical axis of the Fresnel lens is separated from a center of the screen. 10. The rear projection television according to claim 9, wherein an optical axis of the Fresnel lens is located outside the screen. 11. The image forming optical component includes a first mirror that reflects light emitted from an image display element that forms the image information, and a first mirror that reflects and reflects light reflected from the first mirror. A second mirror, a third mirror that receives and reflects reflected light from the second mirror, and a fourth mirror that receives and reflects reflected light from the third mirror. 3. The rear projection television according to claim 2, wherein: 12. The first to fourth mirrors are arranged so that the reflected light from the fourth mirror becomes the incident light beam to the end-side reflecting mirror. 12. The rear projection television according to claim 11, wherein 13. The rear projection television according to claim 1, wherein an assembly of minute reflecting mirrors for expressing an image by reflecting an illumination light beam emitted from the light source in an arbitrary direction is used. 14. An image on an image display element is enlarged and projected by an imaging optical component to form an image on a transmissive screen. A projection method for a rear projection television, comprising: arranging the imaging optical component and a reflection mirror in combination such that a distance between an optical axis of the light beam and a screen becomes smaller as approaching. 15. The projection method according to claim 14, wherein an incident angle of the incident light on the screen is 45 degrees or more. 16. The projection method for a rear projection television according to claim 14, wherein a center of the formed image is located at a position different from an optical axis of the imaging optical component. 17. The rear projection television,
15. The projection method for a rear projection television according to claim 14, wherein a mirror for turning back an optical path is arranged on a top plate side or a floor plate side in the housing. 18. The distance between the optical axis of the light beam and the screen decreases as the light beam reflected from the reflection mirror preceding the last-stage reflection mirror approaches the last-stage reflection mirror. The projection method of the rear projection television described in the above. 19. The projection method for a rear projection television according to claim 14, wherein said imaging optical component is constituted by a plurality of mirrors.