JPH0750938B2 - Optical system for projection TV - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical system of a projection television, and more particularly to residual distortion,
The present invention relates to an optical system for a projection television equipped with an assembly bracket of a projection tube and a lens, which is suitable for projecting a high-quality image with little color shift on a screen.

[Conventional technology]

A projection television is a television that obtains a large screen by enlarging an image on a relatively small projection tube with a lens and projecting it on a screen.

FIG. 2 is a vertical cross section thereof. In the figure, 1 is a projection tube, 2
Is a lens, 3 is a bracket for connecting the projection tube 1 and the lens 2, 4 is a mirror, 5 is a screen, and 6 is a cabinet for fixing and storing the above parts therein.

Next, the operation will be described. An image (not shown) projected on a fluorescent surface (not shown) of the projection tube 1 which is a small CRT is magnified by the lens 2 and projected from the rear surface of the screen 5 to obtain a large screen. In the figure, the depth of the cabinet 6 is made thin by inserting the mirror 4 in the middle of the projection optical path and bending the optical path.

In such a device, the projection tube 1 and the lens 3 are usually one each.
Instead of one set of books, three sets of three colors of red, green and blue are used.
The reason for this is that enlarging the image of one color CRT not only causes the dots of the three colors on the screen to be enlarged and becomes unnatural at a short distance, but also darkens the brightness.
As shown in FIG. 3, the projection tube and the lens used in three sets are installed so that their optical axes intersect at one point in the vicinity of the screen 5. At this time, the angle formed by the optical axes of the projection tube 1 and the lens 2 at the center and the optical axes of the projection tube 1 and the lens 2 at both ends is called a concentration angle A. The concentration angle A is an angle in the left-right direction with respect to the screen 5, but may be angled in the vertical direction as well. This is called the elevation angle (not shown) and is usually attached about 3 ° upward. Here, the elevation angle is set to zero for the sake of simplicity, but the same applies to the case where the elevation angle is attached.

In an actual set, the bracket 3 has an angle in order to realize the concentrated angle A. FIG. 4 shows an example generally performed by the conventional technique. In the figure, the same numbers as in FIG. 2 represent the same parts. For simplicity, only the projection tube 1, the lens 2, the bracket 3 and the mounting base 7 for fixing them are shown in the figure, and the screen 5 and other parts are omitted. Normally, a green projection tube 1G is centered, and a blue projection tube 1B and a red projection tube 1R are arranged on the left and right respectively. As for the lens, there is an example in which the transmittance is optimized for each projection tube, but generally three lenses are commonly used in common. It is not particularly divided in this explanation. The bracket 3 is a component for connecting the projection tube 1 and the lens 2 and fixing them to the mount 7. The bracket 3G for the green projection tube 1G has a zero convergence angle when the elevation angle is zero, so
The projection tube 1G and the lens 2 are fixed vertically to the mount 7.
On the other hand, in the bracket 3B for the blue projection tube 1B, the lens is fixed by rotating the lens in the clockwise direction with respect to the mount 7 by the concentration angle A. At the same time, center the blue projection tube 1B around the fluorescing surface (not shown) with respect to the optical axis of the lens, around 15% of the concentration angle (this angle is called the correction angle, and is on a screen that is not perpendicular to the optical axis. It is an angle that is indispensable for making the Just Focus on the whole area) and further fixed in the clockwise direction.

The red projection tube 1R bracket 3R is symmetrical to the blue projection tube 1B bracket 3B, and the rotation direction is counterclockwise.

As described above, the left and right brackets 3B and 3R have complicated angles, but in the prior art, as shown in the figure, each bracket is independently formed and finally attached to the mount 7. In this method, not only a dimensional error is generated in each bracket, but also an assembly error such as rotation, sagging, and displacement occurs in assembly. These errors appear as an imbalance of focus on the screen, residual distortion, and an increase in color shift.

Fig. 5 shows the correction angle of the concentration angle and MTF (Modulation Transfer).
Fanction) relationship is shown by a blue projection tube.
In the figure, the solid line C represents the MTF change on the right side of the screen as an average value, and the broken line D similarly represents the MTF change on the left side as an average value. As is clear from the figure, when the correction angle of the concentration angle becomes smaller than the design value, the MTF on the right side of the screen becomes extremely bad, and the image quality becomes worse as left and right imbalance more than the deterioration of the left and right average MTF. Even when the correction angle of the concentration angle is larger than the design value, the left and right are simply reversed, and the imbalance increases.

Further, an assembly error between the bracket 3 and the mounting base 7 mainly appears as a deviation of the image center on the screen 5. If this is done, an image (not shown) of the fluorescent surface of the projection tube 1 is electrically moved and corrected, but since the image is output at a place different from the position at the time of design, the fluorescent surface is When the image is aspherical, the image is distorted on the fluorescent surface, and in an extreme case, the correction circuit cannot correct the image, which causes residual distortion and color misregistration.

FIG. 6 is a schematic view of the assembly bracket of the projection tube and the lens made by the prior art as in FIG. In the figure, the same numbers as in FIG. 4 represent the same parts. 4 is different from FIG. 4 in that the mount 7 of FIG. 4 is provided with a portion corresponding to the focusing angle, and the mounting base gives the lens 2 a focusing angle and the side plates 10a and 10b. It consists of. In this method, the relative positions of the lenses 2 are assembled with relatively higher accuracy, but the brackets 8B, 8G, and 8R are still independent from each other, and thus basically have the same problem as in the example of FIG. .

As described above, in the method according to the prior art, since the brackets have complicated angles, if each of them is independent, in addition to the angle error peculiar to the bracket, an error at the time of assembly is a factor that deteriorates the image quality. On the other hand,
The method disclosed in Japanese Patent Laid-Open No. 61-95689 is a method in which a bracket, which is prone to error, does not have a concentration angle and a correction angle, and instead the lens group of the portion incorporated in the lens barrel is tilted. This method has the advantage that the angle error during assembly of the bracket is almost zero because no angle is given to the bracket where the error is easy to occur, but on the other hand, the lens closest to the projection tube (usually a concave lens) is Since it is parallel to the face panel of the projection tube, the MTF is a little inferior compared to the method in which the bracket has an angle.

[Problems to be solved by the invention]

In the projection television, according to the above-mentioned conventional technique, one image is obtained by three sets of projection tubes and lenses of three colors of red, green, and blue, so that the respective positional relationships should function as if they were one cathode ray tube. No consideration was given to the fact that the three lenses and the three projection tubes were integrated, and there was a problem that the component error and the assembly error of each component appeared on the screen as the deterioration of the image quality.

The object of the present invention is to eliminate the above-mentioned problems of the prior art,
It is an object of the present invention to provide an optical system for a projection television equipped with an assembly bracket in which three lenses and three projection tubes are integrated.

[Means for solving problems]

The above-mentioned purpose is to mount three lenses on an upper plate whose both ends are bent at an angle equal to the concentration angle with respect to the central part, and to attach three projection tubes to the central part at both ends for the concentration angle and its correction angle. It is achieved by attaching the lower plate bent by an angle equal to the sum of the above, and further combining the upper plate having the three lenses attached thereto and the lower plate having the three projection tubes attached thereto.

[Action]

The three lenses are attached to an upper plate whose both ends are bent at an angle equal to the concentration angle with respect to the central portion. Since they are fixed to one part, their mutual intervals, mounting angles, etc. can be assembled with extremely high precision.

Similarly, since the three projection tubes are also attached to the lower plate whose both ends are bent at an angle equal to the sum of the concentration angle and the correction angle with respect to the central portion, their mutual intervals and attachment angles are extremely high. Assembled with precision.

Regarding the assembling of the upper plate and the lower plate, the two parts are aligned, and the assembling can be performed with relatively high accuracy.

Therefore, according to the integrated assembly bracket of the present invention,
Since three lenses and three projection tubes can be assembled with extremely high accuracy, they can function as if they were one CRT, and a projection television with high image quality can be realized.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 (a) and 1 (b). FIG. 1 (a) is a partial sectional view of an integrated bracket according to the present invention, and FIG. 1 (b) is an exploded perspective view thereof.

In the figure, 2 is a lens, 11 is an upper plate for mounting the lens,
1B, 1G and 1R are blue, green and red projection tubes, respectively, and 12 is a lower plate to which three projection tubes 1B, 1G and 1R are attached. The lower plate 12 has a dish shape as shown in FIG. 1 (b), and even when combined with the upper plate 11, a constant space is maintained between the lens 2 and the projection tubes 1B, 1G, 1R. Composed to lean.

The gap between the lens 2 and the projection tubes 1B, 1G, 1R may be an air layer, but in order to improve the contrast normally, a silicon gel or ethylene glycol-based liquid is sealed as optical coupling.

Reference numeral 13 is a light-shielding plate provided so that the lights of the projection tubes do not leak to each other, and 14a and 14b are side plates.

Reference numeral 15 is a first lens that constitutes the lens 2. In this embodiment, a thin hemispherical lens forms a concave lens together with the liquid enclosed between the upper plate 11 and the lower plate 12.

According to the present invention, since the three lenses are fixed to one component, their mutual intervals and mounting angles can be assembled with extremely high precision. Further, since the three projection tubes are also fixed to one component, their mutual intervals and mounting angles can be assembled with extremely high accuracy.

Further, regarding the assembling of the upper plate 11 to which the three lenses are attached and the lower plate 12 to which the three projection tubes are attached, the two parts are aligned and can be assembled with high accuracy.

Therefore, according to the present invention, the three lenses and the three projection tubes can be assembled with extremely high precision, so that these can function as if they were one cathode ray tube.
It is possible to realize a projection television with high image quality.

A second embodiment of the present invention will be described with reference to FIGS. 7 (a), (b), FIG. 8, FIG. 9, FIG. 10, and FIG. Figure 7 (a)
Is a partial sectional view of an integrated bracket according to the invention,
(B) is an exploded perspective view thereof. FIG. 8 is a schematic diagram for explaining the flow of the refrigerant in the integrated bracket according to the present invention, FIG. 9 is a schematic diagram for explaining the flow of the refrigerant in the conventional bracket, and FIG. 10 is the integrated according to the present invention. 11 is a waist cross-sectional view for explaining the reflection of unnecessary light in the bracket
The figure is a cross-sectional view for explaining reflection of unnecessary light in a bracket according to the prior art.

In the above figures, the same numbers as in FIG. 1 represent the same parts.

The second embodiment according to the present invention shown in FIGS. 7 (a) and 7 (b) differs from the first embodiment shown in FIGS. 1 (a) and 1 (b) in that the second embodiment is different. Then, the light shielding plate 13 of the first embodiment
With respect to the optical axis extending from the projection tubes 1B, 1G, 1R to the lens 2, the optical axis is separated from the optical axis as the projection tube approaches the lens. In order to realize such a shading plate, one pair is required in the left-right direction for each combination of each projection tube and lens. The lower plate 12 has a similar shape in the vertical direction.

Specifically, the shading plate between the blue projection tube 1B and the green projection tube 1G and between the green projection tube 1G and the red projection tube 1R is a channel-shaped double shading plate 16a, and the outer ends of the projection tubes at both ends. The light shield plate of is a single light shield plate 16b. A gap is provided between the double shading plate 16a and the single shading plate 16b between the double shading plate 16a and the single shading plate 16b so that the refrigerant enclosed in the flat lower plate 12 can freely move. .

With the above configuration, the following two effects can be obtained.

It has been described above that the liquid is filled between the projection tube and the concave lens 15 as an optical coupling, but this liquid not only serves as an optical coupling, but also functions to cool the projection tube.

The flow of the refrigerant in the bracket according to the prior art will be described with reference to FIG. In the prior art, the width of the bracket 3 is the width of the projection tube 1
Is approximately equal to the width of the projection tube 1, and the refrigerant liquid is merely enclosed in the width of the panel surface P of the projection tube 1. The entire panel surface P of the projection tube 1 is a surface to be cooled (heating surface), and the heated refrigerant has a smaller specific gravity and moves upward. At this time, since there is no path through which the refrigerant circulates, the heated refrigerant accumulates in the upper part, resulting in a temperature difference between the upper and lower parts. Also, of course, there was a problem that the cooling performance was not good.

The flow of the refrigerant in the integrated bracket according to the present invention will be described with reference to FIG. In the present invention, the double shading plate 16
A return path of the refrigerant is formed between a and the single light shielding plate 16b and the lower plate 12. Therefore, as shown in FIG. 8, the refrigerant convects extremely smoothly. As a result, the temperature difference between the refrigerants is small and the refrigerant performance is improved.

The second effect of the integrated bracket according to the present invention is that there is little reduction in contrast due to unnecessary reflection.

The reflection of unnecessary light in the bracket according to the prior art will be described with reference to FIG. In the prior art, since the side portion of the bracket 3 is substantially parallel to the optical axis extending from the projection tube 1 to the lens 2, some unnecessary light other than the effective light beam that directly enters the concave lens 15 from the projection tube 1 is partially included in the side portion of the bracket 3. Reflected on concave lens 15
Incident on the light source, which was a cause of contrast deterioration.

FIG. 10 illustrates reflection of unnecessary light in the integrated bracket according to the present invention. In the present invention, the light shielding plate 16a is arranged so as to move away from the optical axis from the projection tube 1 toward the lens 2 as it approaches the lens 2 from the projection tube 1, so that the projection tube 1 is directly connected to the concave lens 15. Even when unnecessary light other than the incident effective light flux is reflected by the light shielding plate 16a, it rarely returns to the concave lens again, and therefore, the deterioration of contrast is also small.

〔The invention's effect〕

According to the present invention, the three lenses, the three projection tubes, and the mutual intervals and angles can be assembled with extremely high precision, so that they can function as if they were one cathode ray tube. It is possible to realize a projection television with high image quality.

Further, according to the second embodiment of the present invention, the cooling medium in the bracket can be made to flow smoothly, so that the cooling efficiency of the projection tube can be improved. Further, since the reflection of unnecessary light in the bracket can be reduced, the deterioration of contrast is small.

[Brief description of drawings]

FIG. 1 (a) is a partial sectional view of an integrated bracket as an essential part of one embodiment of the present invention, FIG. 1 (b) is an exploded perspective view thereof, and FIG. 2 is a vertical sectional view of a projection type television. 3 and 4 are explanatory views of the concentration angle, FIG. 4 is a mounting diagram of a bracket according to the prior art, FIG. 5 is a characteristic diagram showing the relationship between the correction angle of the concentration angle and MTF, and FIG. 6 is according to the prior art. FIG. 7 (a) is a partial cross-sectional view of a second embodiment of an integrated bracket according to the present invention, FIG. 7 (b) is an exploded perspective view thereof, and FIG. 8 and 9 are schematic diagrams for explaining the flow of the refrigerant, and FIGS. 10 and 11 are schematic diagrams for explaining the reflection of unnecessary light. Explanation of symbols 1B, 1G, 1R …… Blue, green, red projection tube 2 …… Lens, 11 …… Upper plate 12 …… Lower plate, 13 …… Shading plate 16a …… Double shading plate, 16b …… Single shading Board

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Muranaka, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Home Appliances Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-61-269590 (JP, A) Open 61-95689 (JP, A) Open 59-61677 (JP, U) Open 57-168374 (JP, U)

Claims (5)

[Claims] 1. A projection type television optical system comprising blue, green and red projection tubes and lenses provided in front of the respective projection tubes, wherein the three projections for blue, green and red are provided. With respect to the plane for fixing the projection tube located in the center, the planes for fixing the projection tubes located on both sides of the tube are located at an angle equal to the sum of the concentration angle and the correction angle of the optical system. While fixing to the first mounting component configured as described above, the respective planes for fixing the lenses located on both sides of the optical system are fixed to the planes for fixing the lenses located at the center of the three lenses. Is fixed to a second mounting part configured to be positioned at an angle equal to the concentration angle of, and a transparent liquid is filled between the first mounting part and the second mounting part. An optical system for a projection television. 2. The optical system for a projection television according to claim 1, wherein the second mounting component is the red, green,
An optical system for a projection television characterized in that at least one light-shielding plate is provided from the second mounting part to the first mounting part so as to be substantially orthogonal to the axis connecting the blue lenses. 3. An optical system for a projection television according to claim 1, wherein the first mounting component is the red component,
An optical system for a projection television, characterized in that at least one light-shielding plate is provided from the first mounting part to the first mounting part so as to be substantially orthogonal to the axis connecting the green and blue projection tubes. 4. The projection television optical system according to claim 2 or 3, wherein the shading plate is projected at a distance between an optical axis connecting the center of the projection tube and the lens center and the shading plate. An optical system for a projection television, characterized in that it is configured to be narrow on the tube side and wide on the lens side. 5. Claims 2, 3, or 4 in the claims.
In the optical system for a projection television according to the item, the light shielding plate is composed of at least two or more plates, and at least 2 is provided so that the transparent liquid can flow in a gap between the light shielding plates.
An optical system for a projection television, characterized by having openings at more than one place.