JPH0576834B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television image projection device that enlarges and projects an image projected on a picture tube onto a screen using a projection lens.

Conventional configuration and its problems In order to obtain a large-screen television image, the method of projecting the television image onto a relatively small picture tube and enlarging it onto the screen using a projection lens is well known. . Furthermore, the refractive index of each medium existing in the space between the phosphor surface of the picture tube and the projection lens is made as similar as possible to reduce unnecessary reflection of light due to the difference in refractive index at the boundary of each medium, thereby reducing the projected image. It has been proposed to improve the contrast of

One such conventional example is shown in FIG. A metal plate 3 with a window is fixed on the face plate 2 of the picture tube 1 with an adhesive 4, a flat glass plate 5 is further fixed on the metal plate 3 with an adhesive 6, and a liquid 7 is poured into a sealed space inside. It is enclosed. A gel-like substance 10 is filled between the closing glass 5 and the single lens 9 of the projection lens 8 which is closest to the picture tube 1. In this way, when the refractive indexes of the face plate 2, liquid 7, flat glass 5, gel material 10, and single lens 9 are made the same,
Unnecessary reflection of light caused by the difference in refractive index at the boundaries between the respective media can be reduced, and as a result, the contrast of the projected image can be improved. Note that the liquid 7 shown in FIG.
It has a cooling effect. In other words, the heat generated from the face plate 2 is transferred to the metal plate 3 by the convection of the liquid 7, and the heat is dissipated from the surface of the metal plate 3 to the outside. Temperature can be reduced. As a result, implosion of the picture tube 1 can be prevented.

By the way, in the currently mainstream television image projection device, in order to obtain a color image,
Three sets of optical systems, red, green, and blue, are used to synthesize a color image on the screen. Therefore,
Three sets of red, green, and blue configurations as shown in FIG. 1 are required, resulting in a configuration as shown in FIG. 2. Optical axes 14, 1 of three projection lenses 11, 12, 13
The video tubes 18, 19, 20 and the projection lens 11,
12 and 13 are arranged inline. The optical axis 21 of the central green picture tube 19 is the optical axis 1 of the projection lens 12.
However, the optical axes 22 and 23 of the outer red and blue picture tubes 18 and 20 need to be tilted with respect to the optical axes 14 and 16 of the projection lenses 11 and 13, respectively. This is because the red and blue images are projected onto the screen 17 from an oblique direction, so tilt adjustment is required for the red and blue optical systems. Therefore, the optical axes 2 of the red and blue video tubes 18, 20
The aperture angles of the projection lenses 2 and 23 are larger than the aperture angles of the optical axes 14 and 16 of the projection lenses 11 and 13. This is not a big problem if the video tube and projection lens are separated, but as shown in Figure 1,
Video tubes 18, 19, 20 and projection lenses 11, 1
In the case of a configuration in which 2 and 13 cannot be separated from each other, a big problem arises. In other words, a component whose end surfaces are not parallel is required between the video tubes 18, 20 and the projection lenses 11, 13, and such components are troublesome to process and cannot be shared with components of the green optical system. The cost will be high. Furthermore, when gel-like substances 24, 25, and 26 are used as shown in FIG. 2, the troublesome work of filling the gel-like substances 24, 25, and 26 is required. In addition, video tubes 18, 19, 20
Also when replacing the gel material 24, 25, 2
6 needs to be refilled, which is a much more troublesome task than in the past. In any case, there was a problem of high costs.

OBJECTS OF THE INVENTION The present invention is intended to essentially solve the above-mentioned problems, and it is an object of the present invention to provide a television image projection device with good contrast without incurring a significant increase in cost.

Structure of the Invention A television image projection device according to the present invention includes three video tubes each projecting monochromatic images of red, green, and blue, and three video tubes arranged in front of the face plates of each of the three video tubes. Each projection lens consists of two groups: a rear group placed on the side of the picture tube and a front group placed on the opposite side, and there is a space between the three rear groups and the corresponding picture tube. Transparent bodies are arranged so that there is no air space, and 3
By aligning the optical axes of the two rear groups and the corresponding picture tubes, it is possible to share parts, thereby reducing costs and improving the contrast of projected images.

DESCRIPTION OF EMBODIMENTS An embodiment of a television image projection apparatus according to the present invention will be described with reference to the accompanying drawings.

An embodiment of the present invention is shown in FIG. Each,
Video tubes 27, 2 that project monochromatic images of red, green, and blue
Metal plates 33, 34, 35 having a window in the center on the face plates 30, 31, 32 of 8, 29
are fixed with adhesive, and concave lenses 36, 37, 38 whose concave surfaces face opposite to the picture tubes 27, 28, 29 are fixed with adhesive on the metal plates 33, 34, 35. Face plate 30, 31, 32
Transparent liquids 39, 40, 41 are placed in the respective sealed spaces between the plano-concave lenses 36, 37, and 38.
is filled. The picture tubes 27, 28, 29 are arranged in-line so that their optical axes 42, 43, 44 intersect with each other in front of the face plates 30, 31, 32, respectively. concave lens 36,3
In front of lenses 7 and 38, front groups 45, 46, and 47 each composed of two lenses are arranged. Plano-concave lenses 36, 37, and 38 form the rear group,
By combining the front group and the rear group, it functions as one projection lens. Front group 45, 46, 47
The optical axes 48, 49, and 50 are arranged inline on the screen 51 so as to intersect with each other.

The optical axes of the plano-concave lenses 36, 37, 38 are the optical axes 42, 4 of the corresponding video tubes 27, 28, 29, respectively.
3.44. The optical axis 43 of the green picture tube 28 and the corresponding optical axis 49 of the front group 46 coincide, but the optical axes 42 and 4 of the red and blue picture tubes 27 and 29 coincide.
4 is the optical axis 4 of each corresponding front group 45, 47
8, 50 and one point 52, 53, but they do not match. The opening angle between the optical axes 42 and 44 is the optical axis 4
The opening angle is larger than that of 8.50.

The imaging effect of the blue optical system having the configuration shown in FIG. 3 will be explained using FIG. 4. Note that the red optical system is the same as the blue optical system, so a description thereof will be omitted. For simplicity, the concave lens 3 shown in FIG.
8, the liquid 41 and the face plate 32 are collectively shown as one concave lens 54. The concave lens 54 forms a virtual image 57 of the object image 56 on the plane 55 of the concave lens 54 at a position slightly away from the plane 55. The object image 56 is the concave lens 5
4, the virtual image 57
is also perpendicular to the optical axis 44. The front group 47 forms a real image 58 relative to the virtual image 57, but since the virtual image 57 is inclined with respect to the optical axis 50 of the front group 47,
The real image 58 is also tilted with respect to the optical axis 50. In this way, with the configuration shown in FIG.
The image is projected over the entire surface of the screen without shifting focus.

In FIG. 4, a virtual image 57 is shown for ease of explanation.
Although shown as a straight line, in reality it becomes an arc-shaped virtual image 59 due to the field curvature correction effect of the concave lens 54.
Therefore, the positional relationship between the front group 47 and the concave lens 31,
Strictly speaking, the position of the intersection 53 of the two optical axes 50 and 44 of the front group 47 and the concave lens 31 matters. When the concave surface of the concave lens 38 is a spherical surface, the intersection point 53 is preferably aligned with the center of curvature of the concave surface. however,
Depending on the depth of focus of the optical system, it seems that there is no practical problem even if the intersection point 53 is shifted from the center of curvature of the concave surface. Therefore, even when the concave surface of the concave lens 31 is an aspherical surface, a projected image of practically acceptable image quality can be obtained with the configuration shown in FIG. Two optical axes 5 of front group 47 and concave lens 38
The distance from the intersection 53 of 0 and 44 to the apex of the concave lens 38 is l, and the radius of curvature of the apex of the concave surface of the concave lens 31 is r, and it is preferable to select it so as to satisfy the following condition: 0<l<5r (1). If the range of the above conditions is exceeded, the focus shift at the left and right ends of the projected image becomes too large to be of practical use.

In the configuration shown in FIG. 3, the opening angles of the optical axes 42 and 44 of the video tubes 27 and 29 of the outer red and blue optical systems may be determined as follows. However, it is assumed that the central green picture tube 28 and the optical axes 43 and 49 of the front group 46 both coincide with the normal line of the screen 51. The angles formed by the outer red and blue optical axes 48, 50 and the green optical axis 49 are both θ, and the optical axes 42, 4
4 and the optical axes 48 and 50 are both θ', and both the projection magnifications of the front group are m, it is preferable to satisfy θ'=θ/m (2). In addition, in reality,
It seems to be acceptable in practice as long as θ' is within ±10% of the value determined by equation (2).

Focus adjustment of the optical system is performed using front groups 45, 46, and 4.
7 along the optical axes 48, 49, 50.

As explained above, by using the configuration shown in FIG.
The optical axes 42 and 44 of the lenses 7 and 29 can be made to coincide with each other. Therefore, the metal plates 33, 34, and 35 can all have parallel cross sections and have a common shape, which can reduce costs compared to the configuration shown in FIG. . Furthermore, it is possible to improve the contrast, which is the aim of the present invention.

Next, other embodiments of the present invention will be described.
The parts related to the picture tubes 27, 28, 29 and concave lenses 36, 37, 38 shown in FIG. 3 can also be replaced with the configuration shown in FIG. 5 or 6. Figure 5 shows the face plate 6 of the video tube 59.
0, a metal plate 61 having a window in the center is fixed with an adhesive 62, a flat glass 63 is fixed on the metal plate 62 with an adhesive 64, and the flat glass 6
A concave lens 65 is bonded onto the glass plate 3 using a transparent adhesive 66, and a transparent liquid 67 is filled in the sealed space between the flat glass 63 and the face plate 60. FIG. 6 shows the face plate 6 of the picture tube 59.
0, a concave lens 65 is bonded with a transparent adhesive 66.

In either configuration, contrast can be improved without increasing cost or deteriorating performance.

Effects of the Invention As explained above, according to the present invention, it is possible to provide a television image with good contrast without causing an increase in cost or deterioration of imaging performance, and therefore has a great effect.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic cross-sectional configuration diagrams showing the configuration of a conventional television image projection device, respectively;
FIG. 3 is a schematic cross-sectional configuration diagram showing the configuration of a television image projection device according to an embodiment of the present invention, FIG. 4 is an explanatory diagram for explaining the image forming function of the present invention, and FIGS. 5 and 6 2A and 2B are schematic cross-sectional configuration diagrams showing configurations of other embodiments, respectively. 27, 28, 29...Picture tube, 36, 37, 3
8...Concave lens, 39,40,41...Transparent liquid, 45,46,47...Front group, 51...Screen, 59...Picture tube, 63...Flat glass, 6
5...Concave lens.

Claims (1)

[Claims] 1. 3 for projecting monochromatic images of red, green, and blue, respectively.
a picture tube; and three projection lenses each disposed in front of a face plate of the three picture tubes, each of the projection lenses having a rear group disposed on the side of the picture tube and a rear group disposed on the opposite side thereof. A transparent body is arranged between the rear group of the projection lens and the face plate of the picture tube so that no air region is interposed, and the light of the rear group is A television image projection device, wherein the axis is parallel to the optical axis of the corresponding picture tube, and the optical axis of the front group and the optical axis of the rear group are different for at least two projection lenses. 2. The television image projection apparatus according to claim 1, wherein each front group of the three projection lenses is arranged such that their respective optical axes intersect with each other at one point. 3. The television image projection device according to claim 1, wherein the optical axis of the rear group of the three projection lenses coincides with the optical axis of the corresponding picture tube. 4. The television image projection device according to claim 1, wherein the rear group of the projection lens is composed of one single lens. 5. The television image projection device according to claim 1, wherein the lens surface of the rear group of the projection lens closest to the front group is a concave surface. 6. The television image projection device according to claim 1, wherein the lens surface of the rear group of the projection lens closest to the front group is an aspherical concave surface. 7. The television image projection device according to claim 1, wherein the optical axis of the front group and the optical axis of the rear group of at least two projection lenses intersect at only one point. 8 The distance from the intersection of the optical axis of the front group and the optical axis of the rear group of the projection lens to the apex of the lens surface of the rear group closest to the front group is 1, and the distance of the lens closest to the front group of the rear group is 1. 8. The television image projection device according to claim 7, wherein the relationship 0<1<5r is satisfied, where r is the radius of curvature of the apex of the surface. 9 The angle between the optical axis of the front group and the normal to the screen is θ, the angle between the optical axis of the rear group and the optical axis of the front group is θ′,
2. The television image projection apparatus according to claim 1, wherein θ' is within ±10% of a value given by θ/m, where m is the projection magnification of the front group.