JPH0296738A - Back-projection type screen and back-projection type display device - Google Patents

Abstract

PURPOSE:To allow a user to observe a full bright picture and to prevent moires and multiple pictures by refracting and deflecting the obliquely incident light forming a picture and leading it in the horizontal direction. CONSTITUTION:A screen 1 is triple-layered, and an eccentric Fresnel lens 11, an eccentric Fresnel lens 12 and a double lenticular sheet 13 are arranged in that order on the picture light incident side, that is, on the back side. With respect to oblique incidence at a large angle, the two eccentric Fresnel lenses 11 and 12 comparatively steadily and smoothly deflect and correct the picture light with less loss of light quantity. Consequently, the incident light is led with less reflection loss one each face. Thus, the moire phenomenon arising the repeated peripheral configuration of two or more prism groups, which is caused by the vignetting of a non-lens part, and multiple pictures can be prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rear projection type screen and a rear projection type display device using the same, and particularly to a rear projection type display device using the same. The present invention relates to an oblique incidence rear projection screen suitable for use in a projection device such as a video projector, which is viewed from a space opposite to the projection means, and a rear projection display device using the same. [Prior Art] Conventionally, a rear projection display device or screen of an oblique incidence type in which an image from a display device is projected obliquely onto a screen at an angle has been constructed as shown in FIG. In the figure, 31 is a screen, 32 is a projection lens, 33 is a CRT, 34a, 34b are mirrors, 3
5 is a cabinet, and the image displayed on the tube surface of the CRT 33 (the elephant is mirrors 34a and 34b from the lens 321);
The angle of incidence θ is incident on the screen 31 through the angle θ. is projected diagonally. With this configuration, the incident angle θ. 20 In other words, the depth 1 of the cabinet 35 can be made considerably smaller than that of a vertical incidence system that projects vertically onto the screen 31. [Problem to be solved by the invention] However, in the case of an oblique incidence system, the screen The projected image light emitted from the screen 31 to the viewer's side on the left side of FIG. , Therefore, in order to correct the deflection of the image light and emit the image light from the screen 31 in the horizontal direction, the inside of the screen 3] (
A single-sided eccentric Fresnel lens 41a and a double-sided eccentric Fresnel lens 41b as shown in FIGS. 7 and 8 are arranged or superimposed on the right side of FIG. 6 to brighten the image. However, even in such conventional examples, there is a limit to reducing the depth of the cabinet. In other words, in order to make the depth smaller, the angle of incidence θ shown in Figure 6 must be
. However, in the conventional example using the decentered Fresnel lens, there is a limit to increasing this angle θ.If the incident angle θ is increased (then the power of the decentered Fresnel lenses 41a, 41b must be increased;
This increases the loss in light transmission due to surface reflection and vignetting of the light beam. Particularly, the peripheral part of the screen 31 (particularly the lower part in FIG. 6)
The incident angle θ at is the incident angle θ at the center of the screen. This loss also increases as the A more detailed explanation is as follows. Comparing the eccentric Fresnel lens 41a of the type shown in FIG. 7 and the eccentric Fresnel lens 41b of the type shown in FIG. 8, the former requires one prism surface to be particularly steeply sloped to increase power; As shown in the figure, this is disadvantageous compared to the latter in terms of reflection loss at the prism surface 42. On the other hand, the one in Figure 8 can distribute the power to the prisms on both sides, so it can be said that it can handle a larger angle of incidence.
On the other hand, since there is a prism or Fresnel lens surface on the incident side, vignetting (light!jA b ) in the ineffective part or non-lens part 44 and reflection loss (light #il) in the effective part 45 occur as shown in FIG. a), and the incident angle θ is slightly larger than that in Fig. 7. It will stop at being able to respond. As an example, the size of the screen 31 is 50 inches (1
100100mm x 600, and when the projection distance from the projection lens 32 to the screen 31 is 1°5m, θ0
= 30 degrees, it becomes 01 to 40 degrees, and the above loss at the lower end of the screen 31 cannot be ignored (in other words,
When the incident angle is around 00230 degrees or more, a good projected image cannot be observed using the above conventional method. Furthermore, the double-sided eccentric Fresnel lens 41b shown in FIG.
What is the vignetting of the light flux at the non-lens part? This not only causes a decrease in brightness, but also causes problems such as moiré phenomena and multiple images that occur between the repeating periodic structures of the micro prism groups on both Fresnel lens surfaces. Therefore, the present invention provides a rear projection type that achieves brightness over the entire surface of one image and prevention of moiré and multiple images while emitting projected image light in the horizontal direction in an oblique incidence system that enables thinning. The purpose of this invention is to obtain a screen and a rear projection display device using the same. [Means for Solving the Problems] In order to achieve the above object, in the rear projection screen of the present invention, a plurality of sheets are provided facing each other, and at least two of these sheets have a Each of these is formed with a large number of concentric prisms with their centers offset from the center of the screen. Further, in order to achieve the above object, a rear projection type display device of the present invention is provided with a rear projection type screen and a display device configured as described above, and an image is projected onto the screen at an angle from the rear side. A display device is arranged to project. [Function] In a rear projection screen configured as described above, power is dispersed by multiple prism-forming surfaces, so even if the light beam has a large incident angle to the screen surface, each prism-forming surface has a relatively small incident angle. This allows the prism to be kept small, reducing light loss on each surface.In addition, since these prism forming surfaces are decentered Fresnel lens surfaces, the projected image light can be emitted well in the horizontal direction. [Embodiment] Figures 1 to 3 show an embodiment of the present invention, where l is a rear projection screen, 2 is a projection lens, 3 is a CRT, 4a and 4b are reflective mirrors, 5 is a cabinet, and 6 is a This is a light shielding plate.An enlarged side view of the screen 1 in FIG. 1 is shown in FIG. 2, and FIG. 3 shows the appearance of the screen 1 seen from above in FIG. CRT3 has red, green,
Blue-specific ones are arranged side by side (in-line 3-tube type),
Similarly, one lens 2 is placed in front of each CRT 3. The image displayed on the CRT 3 is projected through the lens 2, reflected by mirrors 4a and 4b, and then projected onto the screen l.
In this embodiment, the CRT 3 is a high-brightness CRT for projection by Finch, and the lens 2 has an aperture of 1.20φ.
F1 and F2 are used. The projection distance from the front of lens 2 to screen 1 is 1.5 m, and the screen size is 50 inches diagonally with an aspect ratio of 16:9.At this time, the incident angle θ0 is set to 30 degrees, and the depth L::4.
5cm, as shown in FIGS. 2 and 3, the screen 1 is composed of three lenses: an eccentric Fresnel lens 11, an eccentric Fresnel lens 12, and a double lenticular lens from the image light incident side, that is, from the back side. The sheets 13 are arranged in this order. [Eccentric Fresnel lens]] 12 has a large number of concentric prisms with the center centered on the screen 1 in Figure 1.
It is formed eccentrically above. Furthermore, both Fresnel lenses 1] and 2 have prism forming surfaces 11.
a, 12a toward the image light emission side, that is, the observation surface side,
The flat surfaces 11b and 12b are directed toward the back side. The double lenticular sheet 13 has a black stripe 13a, which widens the left and right viewing angles, prevents color shift and reflection of external light due to the in-line arrangement of the CRT 3, and provides better image and viewing characteristics. . With the above configuration, as shown in Fig. 2 (incidence angle (θ0) 3
Even for oblique incidence at a large angle of 0 degrees, the image light is corrected for deflection in the horizontal direction by the two decentered Fresnel lenses 11 and 12, relatively gradually and effortlessly with little light loss. In particular, the incident angle θ2 at the left and right ends of the bottom of the screen 1 is considerably larger than that at the center (θ0), reaching about 45 degrees under the above conditions. Even for such peripheral incident image light, a two-element decentered Fresnel lens 11.
12, deflection correction in the traveling direction is performed with less loss of light amount. This situation is shown in diagram t144. 45 degree angle of incidence θ2
The incident light beam is refracted and deflected at the prism forming surfaces 11a and +2a of the two Fresnel lenses 11. The incident light is guided with less reflection loss.Furthermore, since the flat surfaces 1tb12b of the Fresnel lenses 11 and 12 are on the incident side, vignetting of the light beam at the non-lens parts 11c and 12c is prevented as shown in FIG. As a result, the moiré phenomenon and the generation of multiple images between the repeating periodic structures of two or more prism groups caused by vignetting in the non-lens area are effectively prevented. A good, bright image can be observed over the entire surface without any reduction in brightness, moiré, or multiple images.By the way, in the case of the oblique incidence method, there are problems such as trapezoidal distortion of the projected image and inappropriate focus. In order to correct these, distortion correction using inverted trapezoidal display on the CRT screen and CRT
Take appropriate measures such as tilt correction for the lens. In addition, although CRT3 is used in the above embodiment, LC
(liquid crystal), PDP, EL (electroluminescence)
A display device such as the following may also be used. Furthermore, the mirror arrangement, lens and CR adopted in the above example
Although an optical layout such as a T arrangement is very effective for thinning the device, it is not limited to this layout. FIG. 5(a) shows another embodiment of the screen 1. Here, a diffusion plate 14 having a diffusion layer 14a is used instead of the lenticular sheet. By using the diffusion plate 14, resolution is improved, although color shift is slightly worsened compared to the above embodiment. . In this way, for the screen configuration sheet closest to the observation side,
It can be selected as appropriate depending on the desired image characteristics. FIG. 5(b) shows yet another embodiment of the screen 1.
Here, three eccentric Fresnel lenses 15.1617 are used. In this way, the eccentric Fresnel lens 15.1 is placed on the incident side.
6.17, it is possible to cope with oblique incidence at a larger angle of incidence θ. In this case, oblique incidence up to about θ0=45 degrees (center portion representative value) is possible, and further thinning can be achieved. However, the transmittance decreases as the number of decentered Fresnel lenses increases, so even if the number of decentered Fresnel lenses for power dispersion is increased in order to reduce the thickness, it is practically appropriate to use about 2 to 3 decentered Fresnel lenses. In the above embodiments, the plane side of the decentered Fresnel lens is placed on the light incident side to reduce vignetting, but this is not necessarily essential to the present invention.6 Key points of the present invention are as follows:
A rear projection screen is constructed by including a plurality of decentered Fresnel lenses. [Effects of the Invention J With the above configuration, in the present invention, the obliquely incident image light can be refracted and deflected easily and efficiently, guided in the horizontal direction, and emitted to the observation side, so that a bright image can be observed over the entire image area. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the oblique incidence type rear projection display device of the present invention, FIG. 2 is a partially enlarged view of the embodiment of the rear projection type screen of the present invention, and FIG. 3 is the screen of FIG. 2. FIG. 4 is a diagram showing the optical path of incident light in the screen of the present invention, FIGS. 5(a) and (b) are diagrams showing other embodiments of the screen of the present invention, and FIG. Figures 7 and 8 are schematic diagrams of conventional eccentric Fresnel lenses, and Figures 9 and 10 are diagrams of the eccentric Fresnel lenses of Figures 7 and 8. It is a figure explaining performance. 1... Rear projection screen, 2... Projection lens, 3... CRT, 4a, 4b... Reflection mirror, 11.12.15.16.17... Eccentric Fresnel Lens, 13...Double lenticular sheet, 1
4... Engraving of the diffuser board drawing (no changes to the content)

Claims (1)

[Claims] 1. A rear projection screen for projecting and observing an image at an angle from the back side, which is composed of a plurality of sheets arranged oppositely, of which at least A rear projection screen in which two sheets each have a large number of concentric prisms with their centers offset from the center of the screen. 2. The rear projection screen according to claim 1, wherein a large number of concentric prisms are formed on the viewing side of the at least two sheets, and the back sides of the prisms are flat. 3. The rear projection screen according to claim 1 or 2, wherein at least one side of the sheet closest to the viewing side is a surface having a light diffusion function. 4. A rear projection type comprising the rear projection type screen according to claim 1, 2 or 3 and a display device, the display device being arranged so as to project an image onto the screen at an angle from the rear side. Display device.