JP3004399B2 - Rear projection screen device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to red, green and blue TVs which are arranged next to each other and which are located behind a screen.
A rear projection screen device mainly used in a projection device including three TV projectors for projecting an image, comprising a rearwardly and vertically arranged lens element for horizontally refracting light incident on the backside from behind. A rear projection screen device having a vertically arranged masking stripe having a stripe forming portion positioned opposite to the backward facing lens element on the entire surface and further including a screen mixed with light diffusing particles. .

[0002]

2. Description of the Prior Art Screening devices such as those described above having light diffusing particles uniformly distributed in the screen material are known. These particles are used to refract light rays entering from behind so that the screen acquires the imaging properties, so that the image can be seen from the front of the screen.

[0003]

In these known screens, light rays penetrating vertically through the screen through the apex of the rearward facing lens element suffers an energy loss. Such rays pass through the screen as is,
Energy loss of the emitted light beam occurs under various circumstances. That is, some reflection occurs when the light ray enters the screen, some of the light ray is diffused as a result of the light ray passing between the particles, and some reflection occurs when the light ray exits from the front of the screen. Such as when it happens. Since such rays must pass through the thickest part of the screen, the energy loss of the outgoing ray is considered to be greater than the energy loss resulting from passing the shorter part of the screen as other rays pass through the screen. In practice, however, it turned out to be another cause. Light rays that strike perpendicular to the back of the screen and penetrate the surface side of the rearward facing lens element closest to the screen center do not impinge perpendicularly to that surface portion, and are therefore far more than rays that strike the rearward facing lens element apex. Large and partially reflected.
Such rays refract when passing through the screen,
It hits the stripe forming part at the front of the screen. Since the distance that these rays travel through the interior of the screen is quite short, the energy loss of the rays is much smaller compared to the rays passing through the apex of the rearward facing lens element. However, when a light ray passing through one of the surface sides passes through the stripe formation, it must pass from a high index material or screen material to a low index material or air. This means that most of such light rays are reflected when they strike the inside of the stripe formation, so that when the light rays leave the front of the screen, they pass through the vertex portion of the rearward facing lens element. The overall energy loss is greater than the energy loss. As a result, the energy of the light beam exiting the front of the screen is greatest for light exiting the screen plane at right angles, whereas the energy of light exiting obliquely to the screen surface is weakened. In other words, this means that a viewer who looks at the screen obliquely from the front in the horizontal direction with respect to the screen surface feels that the sharpness is lower than when the image is viewed from the front in the vertical direction.

Here, in order to compensate for this, it is conceivable to increase the energy density of light diffusing particles on the screen, thereby increasing the energy loss of light rays that pass through the screen over a long distance. In this case, light rays striking the vertex portion of the rearward lens element at right angles to the center plane of the screen are considered to be much weaker than the light rays striking the above-mentioned surface side, which is incorrect. If the concentration of light diffusing particles in the screen is too high, the light diffusing performance of the screen will increase at the same time,
As a result, the light intensity of the projected image is unacceptably low.

An object of the present invention is to improve the light transmission in the horizontal direction so that an image can be viewed from the front right angle to the screen surface or obliquely from the front, so that the rear projection of the above-described type can be seen with almost the same illuminance. To provide a screen device.

[0006]

The above object is achieved by the following objects.
This is achieved as follows. That is, the concentration of the light diffusing particles is much higher in the rear part of the screen than in the front part. The energy loss of the light ray that enters the vertex portion of the rearward facing lens element and passes through the screen is equal to the light ray that enters the rear surface of the screen perpendicularly and passes through the surface side of the rearward facing lens element closest to the center plane of the screen. Energy loss. As a result, light rays incident perpendicular to the back of the screen and passing through the surface side of the rearward facing lens element closest to the center plane of the screen pass through the portion of the screen where there are few light diffusing particles, thus minimizing energy loss. Just receive. When these lights exit the screen, they naturally undergo the same degree of reflection as if the particles are uniformly distributed, but the above-mentioned energy loss inside the screen is slight. However, the energy loss of light rays that pass vertically through the screen through the vertex portion of the backward-facing lens element is greater because the light rays must pass through the screen portion where the particle concentration is highest. . By taking this concentration sufficiently high and choosing the appropriate particle size and material, the light beam can achieve an energy loss comparable to that caused by reflection when other light beams exit the screen. As a result, even when the screen is viewed from the front right angle direction or obliquely from the front, it is felt as almost uniform illuminance.

[0007] The concentration distribution recommended by the present invention is such that during curing of the screen, the back side is placed face down, the starting viscosity of the screen material is properly selected, and the particle size with curing time is properly selected. Can be obtained. Thereby, particles can be deposited during the shaping of the screen and the concentration at the rear of the screen can be greater than at the front. However, since the task of selecting and observing each element that determines the deposition is considerably complicated, the screen device according to the embodiment of the present invention is composed of two parts, and the light diffusion particles are mixed only in the rear part thereof. .

Further, in the embodiment of the screen device according to the present invention, the stripe forming portion at the front of the screen is formed as a forward-facing lens that diffuses light incident from behind in the horizontal direction. This embodiment is more preferred because the forward facing lens has less internal reflection of light incident on the surface side of the rearward facing lens element than, for example, a planar stripe forming section or a concave stripe forming section. As the reflection of these rays is reduced, the need to compensate for the energy loss of the rays striking the apex of the rearward facing lens element is also reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a rear projection screen device (hereinafter, referred to as “screen device”).
4 shows three projectors 1, 2, and 3 that project a TV image to the rear of the screen device 4). Each projector projects a black and white TV image. Projector 1
In front of the projector 2, a filter is provided so that the color of the image projected by the projector on the screen device 4 is red, and in front of the projector 2, the color of the image projected by the projector on the screen device 4 is green. A filter is provided, and a filter is provided before the projector 3 so that the color of an image projected by the projector on the screen device 4 is blue. These three colors are labeled R, G, and B, respectively. The three projectors 1, 2, and 3 have an optical axis 7 of the central projector 9
Install side by side so as to form an angle of 0 °. Since the projectors 1, 2, and 3 are arranged in the horizontal direction, the optical axes 6 and 8 do not overlap with the optical axis 7, and the three optical axes form an angle of 7 ° with the adjacent optical axis. I have. Considering the size of the projector, it is difficult to make the angle of 7 ° smaller than that. On the other hand, as the projector has been improved and its output has been increased and the projection range can be widened in the horizontal direction, the angle of 7 ° described above can be sufficiently increased to 10 °. The optical axis is gathered at the center of the screen device 4, and each projector is further configured so that the images projected on the back surface of the screen device 4 overlap.
As a result, an image corresponding to a high-quality enlarged image formed by the color TV picture tube can be seen from the front of the screen device 4. The curved frame in FIG. 1 represents the position of the viewer.

The screen device 4 shown in FIG. 1 comprises two screens, a front screen A and a rear screen B. "Front" means closest to the viewer's position, and when the terms "front" and "rear" are used on the screen surface, mean the viewer's side and its opposite, respectively. I do.

The front part of the front screen A has a masking
The stripe 22 and the screen device 4 located therebetween
Has a stripe forming portion 23 extending in the vertical direction at the use position. In the embodiment of the screen device 4 shown in FIG. 1, the stripe forming part 23 is formed as a forward-facing convex lens, at an angle of about 90 ° to the screen plane along its side and the side of the masking stripe 22. Adjacent to the edge 24 that forms the boundary. The front screen A has a rearward, vertically placed lens element 25 behind it, each lens element 25 being located directly behind each stripe forming section 23. These lens elements 25 are mainly used to refract light incident from the rear so as to pass through the stripe forming section 23 at the front of the screen device 4. At the same time, the refraction of the emitted light is performed in the horizontal direction.

The rear screen B has a front surface formed as a Fresnel lens 27 and collimates light incident from behind. The three projectors 1, 2, and 3 having the optical axes 6, 7, and 8 face the center of the screen, and the optical axis of the projector 2 is at an angle of 90 ° with respect to the screen. Light rays from the projectors impinge on the screen device 4 so that the incident angle increases as the distance from the central optical axis 7 increases. However, this is mostly compensated for by the correction via the Fresnel lens 27.

The screen device 4 shown in FIG. 1 forms an image on the front screen A into which light diffusing particles are mixed. The present invention mainly relates to this screen A, and only the screen A is shown in the following figures. The screen A is generally used on the basis of the description according to FIG. 1, but in the following figures, light rays incident on the screen A vertically from behind,
That is, only the direction of the light beam from the projector 2 is shown. The same applies to the light rays from the projectors 1 and 3, which is the same even if the angle of, for example, the above-mentioned 7 ° is maintained for the green light rays which strike the back surface of the screen A at right angles after the collimation by the Fresnel lens B. I can say that.

FIG. 2 shows a partial horizontal sectional view of a known embodiment of a screen A having no light diffusing particles, as described above. Light ray 30 is incident on vertex portion 31 of rearward facing lens element 25 perpendicular to the center of the screen and passes through screen A as it is. The energy of the outgoing ray is slightly reduced as compared to that of the incident ray. If screen A is made of acrylic, the reflection results in a loss of light energy of about 7% when passing from air to acrylic and from acrylic to air. The rays 33 and 34 which are perpendicularly incident on the rear of the screen A are the rearward facing lens elements 25 which are arranged closest to the center of the screen.
After passing through the front side of the screen and passing through screen A, it will incur much greater energy loss than ray 30. This is due to the fact that the rays 33 and 34 impinge on the front side 35 at a very large angle of incidence, so that the reflection from said front side is relatively large. Here, the screen A is formed so that the light rays striking the surface side portion do not cause total reflection.

Further, partial reflection also occurs when the light rays 33 and 34 are incident on the inside of the stripe forming section 23. The angle of incidence is again relatively large, so that a correspondingly large reflection occurs. Regarding ray 33, when it strikes the deepest part of the surface side located approximately in the center of the two lens elements 25, the total energy loss is 30 to 50%, most of which ray 33 is striped. Due to the large refraction when exiting section 23. The corresponding loss when the light ray 33 enters the lens element 25 is calculated to be 15 to 20%, depending on the magnitude of the refraction at the time of incidence or the magnitude of the angle of incidence.

The respective losses of rays 30, 33 and 34 are shown in FIG. 2, where the arrows indicate the outgoing rays as well as their vectors. The exit vector of ray 30 is longer than the exit vector of ray 34, and the vector of ray 34 is ray 3
3 outgoing vectors.

FIG. 3 shows the distribution of this light energy in the horizontal direction.
Is shown in the graph. The energy of the ray 30 is maximum,
In the graph, it is represented as “25”. In this context, the screen A shown in FIG. 2 does not contain light-diffusing particles, so no vertical diffusion is seen and the exit vector can also completely represent the ray.

From the illustrated vectors and graphs, a viewer looking at the screen at a right angle from the front can receive much more light energy due to the aforementioned loss of reflection than when looking at the screen diagonally from the front.

FIG. 4 shows a screen similar to that of FIG.
Light diffusing particles 40 indicated by triangles are mixed. The light diffusing particles 40 are evenly distributed throughout the thickness of the screen in a known manner. FIG. 4 shows the same ray direction as FIG. 2, but it can be seen that the emission vector of the ray here is shorter than in FIG. This is due to the loss of energy that occurs as the light beam passes through the particles. However,
Again, the exit vector of ray 30 is ray 3
4, the output vector of this ray vector 34 is larger than that of the ray 33. This is also reflected in FIG. 5, and it can be seen that the maximum light energy is 6. This graph is somewhat flatter, because the length of the abscissa at half the maximum ordinate is longer than that shown in FIG.

The cause of this flattening is that the light beam 30 is
30 and 34, the energy loss due to the diffusion is greater for ray 30 than for rays 33 and 34. However, the loss due to reflection remains unchanged.

In FIG. 4, b3 denotes the highest point of the lens element 25 and the stripe forming portion 23 formed as a convex lens.
Indicates the distance to the highest point. Distance b3 represents the distance that ray 30 must pass through the screen, e represents the height of lens element 25, and d represents the difference between b3 and e.
From computer calculations and test results, the best ratio between d and e is e = 2: 3d or e according to FIG. 3b.
<D. According to FIG. 3, ray 30 is (e + d) =
0.55 + 0.80 = 1.35mm = b3

[0023]

(Equation 1) You only need to go the distance of. Assuming that the screen is made of acrylic, when the ray 33 travels from the air to the screen, ignoring about 15 to 20% of the loss of the ray 33, the ray 30 is 1.35 times as large as 33. You will travel a distance.

This means that, ignoring the energy loss of the two rays at lens 23, ray 33 has more energy than ray 30 when exiting the screen. When ray 30 exits the screen perpendicular to the surface, the loss is about 3-4%. However, in ray 33, the loss is 30-40%, due to the high refraction and consequent reflection loss. This allows the energy of the light beam 33 to be significantly smaller on exit than that of the light beam 30, even though the light beam 30 must travel a longer distance through the screen. Calculations and test results show that if the diffusing particles are evenly distributed throughout the thickness of the screen, it is unlikely that light ray 33 will acquire the same amount of reflected energy as light ray 30. This means that the light energy decreases as a function of the horizontal angle, as can be seen in FIG.

FIG. 7 shows a partial cross-sectional view of an embodiment of the screen according to the invention, in which the above-mentioned disadvantage of dispersing energy in the horizontal direction is compensated. In the embodiment of the screen according to the invention shown in FIG. 7, the diffusing particles 40 are located on the side of the screen where the light rays are incident,
That is, it is mixed only in the rear part of the screen. Broken line 36
Thereby, the portion having the light diffusion particles 40 is separated from the portion not including the light diffusion particles 40. The distance from the highest point of the rearward facing lens element 25 to this line is indicated by “i” in FIG. 7, and the distance between the broken line 36 and the upper point of the frontward lens 23 is indicated by “h”. In FIG. 7, the ray paths are the same as in FIGS. 2 and 3, and by appropriately selecting "h" and "i", the two exit vectors 30 and 33 can have the same length. . Thereby, the light energy distribution curve is represented as shown in FIG. As you can see, viewers can be at right angles to the screen,
Alternatively, even at a position forming an angle of 45 ° with respect to the perpendicular direction, the same light intensity can be obtained.

In the embodiment shown in FIG. 9, light diffusing particles are distributed only on the rearward facing lens element 25. Furthermore,
A light trail similar to that described above is shown. This causes the light beam 30 to be refracted as much as possible through the lens element 25, while the light beam 33 travels through the additive-free screen material. Thereby, the reflection vector of the ray 33 has a length of nxz (where n> 1), and the ray 30
Is longer than the length z of the reflection vector.

FIG. 10 shows an example of light distribution. The distribution curve has a saddle shape, and FIG. 9 shows the limit of the present invention.

As can be seen from FIG. 8, the maximum value of the energy of the emitted light beam is 8.

FIG. 11 shows another embodiment of the screen according to the present invention. As can be seen, the rearward facing lens element 25 is here formed as a cylindrical cross section with a radius of 0.56 mm. In this case, as shown in FIG. 12, the maximum value of the transmitted radiant energy is 10, which is superior to that of the embodiment shown in FIG. In this regard, when the height "i" is reduced as shown in FIG. 13, the energy distribution curve again becomes saddle-shaped as shown in FIG. As a result, the embodiment of the screen according to the invention can be formed in two parts, a rear part corresponding to the height "i" in FIGS. 7 and 11, and a front part corresponding to the rest of the screen. it can. Then, only the rear portion is formed of the screen material including the light diffusing particles 40, and then the two portions are joined. In the above, only the embodiment of the screen according to the invention is illustrated, the particles only being distributed at the rear of the screen. It will be appreciated, however, that even if the particles are distributed over the entire width of the screen, similar results can be achieved as long as the concentration of the particles is greatest at the rear of the screen.

As particles, that is, light diffusion particles, for example, S
iO, glass, BaSO, CaCO, or other finely divided translucent inorganic materials can be used.

Organic starch materials are also available. Although the particle size varies depending on the refractive index, the size of the light diffusion particles is preferably 5 to 100 μm.

As mentioned above, the screen can be composed of two parts, but the preferred dispersion of the light-diffusing particles can be achieved in other ways. This is mixed with a material such as, for example, transparent acrylic (PMMA), and then the screen is formed by a mold. The mold is placed horizontally with the back of the plate facing downward, and after a certain time, particles larger than the molding material are deposited.

If the light diffusing particles have different particle sizes, the deposition method described above is used, with the largest particles depositing in the portion of the rearward facing lens element 25, the particle size decreasing on the opposite side of the screen. . If some of the particles are too small, for example 0.01 to 0.3, and the viscosity of the base material of the screen is relatively large, those particles will not deposit and the effect on the dispersion of light will be small. Therefore, it is extremely small. Light is consequently only refracted by irregularities and particles larger than 0.3 to 0.9 um, the wavelength of the light.

The basic material of the screen further comprises transparent acrylic (PMMA), vinyl chloride, polyester, polycarbonate or similar substances.

FIG. 15 shows another embodiment of the screen according to the invention, which largely corresponds to the embodiment according to FIG. FIG. 15 shows particularly preferred dimensions of the screen, where the dimension "i" described above is 0.9 mm;
“H” is 0.5 mm. The radius of curvature of the rearward facing lens element 25, which is formed here as a cylindrical flat surface, is 0.7 mm, and the radius of curvature of the stripe forming portion 23 formed as a forward facing convex lens is 0.5 mm. In general, as seen in the upper right corner of FIG. 15, these lenses are 0.8 mm wide, with a central portion having a radius of curvature of 0.5 mm and a width of 0.4 mm as described above, and a central portion having a width of 0.2 mm and 0.2 mm. And a planar side portion joined tangentially to Thereby, the curved portion of the lens 23 covers the 130 ° top corner as seen in the upper left corner of FIG. Fig. 1
In this case, furthermore, the rays of red R, green G and blue B are shown, and how they are refracted. However, it should be noted that the dimensions shown in FIG. 15 are variable, especially with respect to the dimensions of the heights "i" and "h", i.e. due to the nature of the particulate material used. FIG. 16 shows a preferred embodiment of the dimensions when the screen is manufactured as shown in FIG.
In this case, the screen pitch is 1.2 mm as shown in FIG. 15, and the heights corresponding to "i" and "h" are 0.75 mm and 0.6 mm, respectively. The forward-facing lens 23 has a radius of curvature of 0.45 mm and the rearward-facing lens element 25 consists of three parts: a central part having a radius of curvature of 0.45 mm and covering a 90 ° apex, and this part. And a side portion having a radius of curvature of 1.0 located on both sides. The rearward facing lens element 25 has a vertex angle of 38 °, which is 0.36 mm with respect to the central axis of the rearward facing lens element 25 and 0.3 mm with respect to the intersection of two adjacent rearward facing lens elements 25. It corresponds to the center point of the displaced side bend. Further, the portion provided with the masking stripe has a width of 0.5 mm. Again, the given dimensions are variable within the range of obtaining the favorable results described above.

The permissible errors for the embodiment according to FIG.

Lens 25: 0.65 mm <R <0.8 mm, preferably 0.7 mm Lens 23: 0.40 mm <R <0.8 mm, preferably 0.50 mm Lens 23: Apex angle: 110 ° << 135 °, preferably 130 ° Lens 23: Difference between flat portion and curved portion = “K” 0.6 mm> K> 0.30 mm, preferably 0.4 mm Lens 23: Flat portion “F” 0.30 mm> F> 0 0.1 mm, preferably 0.2 mm Thickness: 0.4 mm <i <1.2 mm, proportional to thickness 0.2 mm <h <1.0 mm, proportional to thickness Acceptable for the embodiment of FIG. The error is as follows. "I": 0.55 mm <i <1.0 mm, preferably 0.75 mm "h": 0.35 mm <h <0.8 mm, preferably 0.6 mm The relationship between h and i is Is proportional to

[0038]

According to the present invention, there is provided a rear projection screen device which has almost the same brightness when viewed from any direction in front.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating a preferred use example of an embodiment of a rear projection screen device according to the present invention.

FIG. 2 is a horizontal cross-sectional partial view of a screen when light diffusing particles are not mixed.

FIG. 3 is a graph showing an energy distribution of light passing through the screen of FIG. 2;

FIG. 4 is a view similar to FIG. 2 of a known screen in which light diffusing particles are uniformly distributed.

FIG. 5 is a graph showing an energy distribution of light passing through the screen of FIG. 4;

FIG. 6 is a dimensional view of the screen of FIG.

FIG. 7 is a partial horizontal cross-sectional view through a part of an embodiment of the screen according to the present invention.

FIG. 8 is a graph showing the energy distribution of the emitted light beam in the embodiment of FIG.

FIG. 9 is a partial horizontal sectional view of another embodiment of the screen according to the present invention.

FIG. 10 is a graph showing an energy distribution of light emitted from the screen of FIG. 9;

FIG. 11 is a partial horizontal sectional view of still another embodiment of the screen according to the present invention.

FIG. 12 is a graph showing an energy distribution of a light beam emitted from the screen of FIG. 11;

FIG. 13 is a partial horizontal sectional view of still another embodiment of the screen according to the present invention.

FIG. 14 is a graph showing the energy distribution of light rays emitted from the screen of FIG.

FIG. 15 is a partial horizontal sectional view of still another embodiment of the screen according to the present invention, which does not include particles.

FIG. 16 is a partial horizontal sectional view of still another embodiment of the screen according to the present invention, showing preferred dimensions.

[Explanation of symbols]

 A Screen 1 TV Projector 2 TV Projector 3 TV Projector 4 Rear Projection Screen Device 22 Masking Stripe 23 Stripe Forming Section 25 Backward Lens Element 30 Ray 33 Ray 34 Light Diffusion Particle

Claims (2)

(57) [Claims] 1. A projection apparatus comprising three TV projectors (1, 2, 3,) arranged adjacent to each other and projecting red, green, and blue TV images on the back of a screen, respectively. Rear-projection screen device, wherein light (30, 33, 34,) incident on the rear surface from behind is provided.
And a vertically arranged lens element (25) for horizontally refracting the lens element, and a stripe forming portion (23) positioned opposite the rearwardly directed lens element on the entire surface. In a rear projection screen device provided with a screen (A) having a masking stripe and further mixed with light diffusing particles, the concentration of the light diffusing particles is much higher in the rear part than in the front part of the screen (A). Thereby, the energy loss of the light beam (30) passing vertically through the screen (A) through the vertex portion of the rearward facing lens element (25), and vertically incident on the back surface of the screen (A), The energy loss of the light rays (33, 34) passing through the surface side of the rearward facing lens element (25) closest to the center of the screen (A) and Rear projection screen device, characterized in that equally the. 2. A rear projection screen device according to claim 1, wherein said screen (A) comprises two joined portions, and light diffusing particles (40) are mixed only in a rear portion therein. .