JPH0514881B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a projection television apparatus.

BACKGROUND ART AND PROBLEMS A projection television receiver using a color cathode ray tube is basically constructed as shown in FIG.

In the figure, reference numeral 1 denotes a color cathode ray tube whose phosphor surface 1a has a striped color phosphor pattern, for example.
The image light from above a is projected onto a screen 4 via a projection lens 3, and an enlarged image 5 is obtained on this screen 4. In this case, an enlarged image 5 is obtained on the screen 4, and at the same time, as shown in FIG. The enlarged image 5 on the screen 4 becomes difficult to see.

Conventionally, in order to make the color stripe pattern less noticeable on the screen 4, a prism plate 6 having a predetermined inclination angle α is disposed between the projection lens 3 and the color cathode ray tube 1, as shown in FIG. It is proposed to do so. In this case, the image light from the point P on the fluorescent surface 1a of the color cathode ray tube 1 is transmitted to one prism surface 6a of the prism plate 6 and the other prism surface 6a of the prism plate 6.
and 6b, the optical path is divided into two and projected onto two points Pa and Pb on the screen 4. Therefore,
As shown in FIG. 4, two enlarged images 5a and 5b are formed on the screen 4, which are slightly translated in the horizontal direction, for example within a range less than the pitch Lc of one set of color stripes, and as a result, On the screen 4, an enlarged image 5 is obtained by combining these enlarged images 5a and 5b. In the end, the number of color stripes in enlarged image 5 is doubled, so
The color stripe pattern becomes less noticeable on the screen 4.

However, in this example in FIG.
There was a drawback that the amount of deviation between a and 5b changed, making it impossible to obtain the sufficient effect of arranging the prism plate 6 described above.

OBJECTS OF THE INVENTION The present invention has been made in view of these points, and aims to propose a prism whose separation angle hardly changes even with temperature changes.

Summary of the Invention In order to achieve the above object, the present invention includes: a first transparent material having a first refractive index and a first temperature coefficient;
A second transparent material having a second refractive index and a second temperature coefficient is laminated together, the interface thereof is a prism surface, and the ratio of the first refractive index and the second refractive index to the first refractive index is The ratio of the temperature coefficient and the second temperature coefficient is selected to be approximately equal.

Since the present invention is configured in this manner, even if the refractive index changes due to temperature changes, the separation angle hardly changes.

Embodiment Hereinafter, an example of the projection television apparatus of the present invention will be described with reference to FIG. 5 and subsequent figures.

In FIG. 5, 10 is a color cathode ray tube whose phosphor screen 10a has a striped color phosphor pattern, and 10b is a face plate.

Further, 11 is a fixed frame on the color cathode ray tube 10 side, and is made of aluminum, for example. On the outside of the fixed frame 11, an uneven heat dissipating portion 11a and a flange portion 11b are formed. A convex fixing portion 11c is formed inside the fixing frame 11, and the tip of the fixing portion 11c is designed to increase the contact area with the liquid to be injected as described later, thereby increasing the cooling effect. A contact portion 11d is formed. Moreover, the inside of this fixed frame 11 is processed to be black. This fixed frame 11 is adhesively fixed to the face plate 10b of the color cathode ray tube 10 using an adhesive 12 such as silicone resin. Further, adhesive 1 is applied to the fixing portion 11c of the fixing frame 11.
2, a glass plate 13 for absorbing X-rays is adhesively fixed.

Further, 14 is a fixed frame on the projection lens side, and is made of aluminum, for example. A flange portion 14a is formed on the outside of the fixed frame 14, and a convex fixed portion 14b is formed on the inside thereof. This fixed frame 14
The interior is painted black.

This fixed frame 14 is fixed to the above-mentioned fixed frame 11 via a packing 15 made of an elastic material such as rubber. For example, the flanges 11b and 14a formed on the outside of the fixed frames 11 and 14, respectively, are used and are screwed together with bolts 16a and nuts 16b with the packing 15 interposed therebetween.
Note that 17 is a spacer made of aluminum, for example.

Further, a prism plate 18 on which a plurality of prisms each having a predetermined inclination angle α is formed is adhesively fixed to the color cathode ray tube 10 side of the fixing portion 14b of the fixing frame 14 using an adhesive 12. Further, a lens barrel 20 to which a concave lens 19a constituting the projection lens 19 is fixed is fixed to the fixed frame 14 with an adhesive 12. This lens barrel 20 is made of plastic, for example, and its interior is painted black. Furthermore, a lens barrel 21 to which convex lenses 19b and 19c constituting the projection lens 19 are fixed is fitted inside the lens barrel 20. This lens barrel 21 is also made of plastic, for example, and its interior is painted black.

Further, in this example, between the color cathode ray tube 10 and the glass plate 13, the glass plate 13 and the prism plate 1
8 and between the prism plate 18 and the concave lens 19a, a transparent liquid 22, for example ethylene glycol, is injected. In this case, for example, a through hole is formed at a predetermined position of the aluminum spacer 17,
For example, an injection needle is inserted through this through hole and further through the packing 15, and the transparent liquid 22 is injected with this. In this case, for example, through holes are formed at the ends of the prism plate 18 and the glass plate 13, so that the transparent liquid 22 is evenly injected into the respective spaces.

Further, as shown in FIG. 6B, the prism plate 18 has a structure in which two transparent materials 18a and 18b are glued together, and the interface thereof forms a prism surface. Then, the refractive index of the transparent material 18a is n ₁ and the temperature coefficient is Δn ₁ , and the refractive index of the transparent material 18b is n ₂ ,
The transparent materials 18a and 18b are selected so that when the temperature coefficient is Δn ₂ , n ₂ /n ₁ ≈Δn ₂ /Δn ₁ . For example, as the transparent material 18a, the refractive index n ₁ (25°C) =
1.543, temperature coefficient Δn ₁ =-1.35×10 ^-4 /°C, and refractive index n ₂ as the transparent material 18b.
(25℃) = 1.508, temperature coefficient Δn ₂ = -1.30×10 ^-4 /℃
epoxy resin is selected. The reason for such a structure is that, as shown in FIG. 6A, in a structure made of a single transparent material 18c, the separation angle changes due to changes in the refractive index due to temperature changes, and the magnification on the screen changes. This is to avoid the drawback that the amount of image shift changes, making it impossible to obtain the above-mentioned effects by arranging the prism plate. That is, as shown in FIG. 7, the solid line A
When is the prism surface, the incident angle is α, and the separation angle is θ, the relationship n ₂ sin α=n ₁ sin (α−θ) …(1) is satisfied, and the separation angle θ is θ=α−sin ^{- 1} (n ₂ /n ₁ sinα) ...(2) The separation angle θ is determined by n ₂ /n ₁ . Here, the respective refractive indexes when the temperature changes by Δt are
If n ₁ (t) and n ₂ (t), then n ₂ (t)/n ₁ (t) = n ₂ +Δn ₂ Δt/n ₁ +Δn ₁ Δt...
It can be expressed as (3). Here, if Δn ₂ /Δn ₁ ≒n ₂ /n ₁ is selected, then n ₂ (t) / n ₁ (t) = n ₂ (1+Δ
n ₂ / n ₂ Δt) / n ₁ (1 + Δn ₁ / n ₁ Δt) ≒ n ₂ / n ₁ = constant...
(4) becomes. Therefore, when the prism plate 18 is configured as in this example, there is almost no change in the separation angle θ due to temperature changes.

Further, this prism plate 18 is manufactured, for example, by a process as shown in FIG. First, as shown in Figure A, a mold 2 is used to obtain a predetermined prism surface.
3 will be prepared. Next, as shown in Figure B, a spacer 25 is placed between the mold 23 and the glass plate 24.
A space is formed using the transparent material 18 in this space.
A is injected and hardened, and molded as shown in Figure C. Next, as shown in Figure D, a space is formed between the molded transparent material 18a and the glass plate 24 using a spacer 25, and the transparent material 18b is injected into this space and hardened. Then, by releasing the mold, a prism plate 18 made by gluing the transparent materials 18a and 18b together is obtained, as shown in FIG.

Thus, according to this example, the prism plate 18 has a structure in which the two transparent materials 18a and 18b are glued together as described above, and there is almost no change in the separation angle θ due to temperature changes. The effect of doing so can be fully demonstrated. In addition, the transparent liquid 22 is injected between the color cathode ray tube 10 and the glass plate 13, between the glass plate 13 and the prism plate 18, and between the prism plate 18 and the concave lens 19a, so that there is no air between them. Compared to other cases, reflection at the interface due to the difference in refractive index can be reduced. Therefore, it is possible to prevent the occurrence of multiple reflection images and a large loss in the amount of light. Further, since the transparent liquid 22 is injected, the thermal expansion of each part can be suppressed to a small level due to the liquid cooling effect, and the influence of optical path changes etc. due to this can be reduced.

In the above-described embodiment, it has been described that, for example, ethylene glycol is injected as the transparent liquid 22 between the glass plate 13 and the prism plate 18 and between the prism plate 18 and the concave lens 19a. , there is a fear that it will be absorbed into the resin forming the prism plate 18 and deteriorate the optical characteristics of the prism plate 18. Therefore, it is conceivable to use, for example, silicone oil instead of ethylene glycol. In this case, apart from the above embodiment, the spaces on both sides of the glass plate 13 are isolated from each other.

Further, in the above embodiment, the prism plate 18
As shown in FIG. 8, an example has been described in which it is obtained by a casting method, but it can also be obtained by the following method.

First, the transparent material 18 that constitutes the prism plate 18
Figure 9A and Figure 10A are methods for molding a.
Also, the method shown in FIG. 11A is conceivable.

The method shown in FIG. 9A is an injection molding method in which a pellet-like transparent material is plasticized and injected into a mold 30 for molding. After the mold is released, a transparent material 18a is obtained as shown in FIG.

Furthermore, the method shown in FIG. 10A is a transfer molding method, in which a tablet-shaped transparent material 18a' is heated to soften it, then transferred and filled into a mold 31, and heated and hardened to be molded. . After the mold is released, a transparent material 18a is obtained as shown in FIG.

The method shown in FIG. 11A is a compression molding method in which a transparent plate-like material 18a'' is pressed onto a heated mold 30 and molded by transferring the shape of the mold. As shown in B, transparent material 18a
is obtained.

Next, the transparent material 18a obtained in this way
The methods shown in FIG. 12A and FIGS. 13A, B, and C are conceivable as methods for molding the transparent material 18b and gluing them together.

What is shown in FIG. 12A is an injection molding method,
The transparent material 18a is inserted into the mold 33, and the transparent material is injected into the space formed by the transparent material 18a and the mold 33 to form the mold. After the mold is released, a prism plate 18 is obtained in which the transparent materials 18a and 18b are glued together, as shown in FIG.

The method shown in FIGS. 13A, B, and C is a casting method, in which a transparent material 18b' that is hardened by heat, infrared rays, ultraviolet rays, or other electron beams is prepared, and the transparent material 18b' is
It is injected (as shown in Figure A) or sprayed onto the prism surface of Figure A, molded as shown in Figure B, and further cured by irradiation with infrared rays 34 as shown in Figure C. In the end, as shown in Figure D, the transparent material 1
A prism plate 18 is obtained by gluing 8a and 18b together. In FIG. 13, 35 is a spacer and 36 is a glass plate.

Effects of the Invention According to the present invention described above, the first transparent material has a first refractive index and a first temperature coefficient, and the second transparent material has a second refractive index and a second temperature coefficient. and the interface is set as a prism surface, and the ratio of the first refractive index and the second refractive index and the ratio of the first temperature coefficient and the second temperature coefficient are selected to be approximately equal. Therefore, the separation angle hardly changes even with temperature changes. Therefore, as described above, according to the projection television apparatus of the present invention, the amount of deviation of the enlarged projected image due to the phosphor pattern can be made substantially constant, and this can be made less noticeable on the screen. Furthermore, in this case, the enlarged image itself will be projected with an approximately constant amount of deviation, and a so-called non-interlaced image structure can be obtained using only optical elements without using any electrical means. .

[Brief explanation of the drawing]

1 and 3 are block diagrams showing an example of a conventional projection television receiver, respectively, FIG. 2 is a diagram for explaining the example in FIG. 1, and FIG. 4 is a diagram for explaining the example in FIG. 3. FIG. 5 is a configuration diagram showing an embodiment of the present invention, FIGS. 6 to 8 are diagrams for explaining the prism plate, and FIGS. 9 to 13 are diagrams showing the manufacturing of the prism plate. FIG. 2 is a diagram used to explain the method. 10 is a color cathode ray tube, 18 is a prism plate, 1
8a and 18b are transparent materials, 19 is a projection lens, and 22 is a transparent liquid.

Claims (1)

[Scope of Claims] 1. A cathode ray tube that emits an image, a lens for projecting the image of the cathode ray tube onto a screen, a transparent liquid filled between the cathode ray tube and the lens, and a cathode ray tube that emits an image. and a prism positioned between the lens and the transparent liquid, the prism having a first refractive index and a first temperature coefficient. A transparent material and a second transparent material having a second refractive index and a second temperature coefficient are bonded together, the interface thereof is a prism surface, and the ratio of the first refractive index and the second refractive index is and a ratio of the first temperature coefficient and the second temperature coefficient are selected to be approximately equal.