JPS6048735B2 - television projection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to more easily and accurately position a correction lens in a Schmidt optical system for television projection.

FIG. 1 shows the arrangement of the Schmidt optical system for television projection.

In the figure, 1 is a spherical reflecting mirror, 2 is a projection cathode ray tube (hereinafter referred to as projection CRT), 3 is a Schmitt correction lens,
4 is the center of curvature of the spherical reflecting mirror 1. As is clear from FIG. 1, in a general Schmidt optical system, the Schmidt correction lens 3 is installed at the center of curvature of the spherical reflecting mirror 1. In addition, the Schmitt optical system has a very high light utilization rate, and even in general systems, an F number of about OJ is obtained. Therefore, not only the positioning of the projection CRT 2 but also the installation error of the correction lens 3 from its original position have a very large effect on the projected image. The position of the projection CRT 2 is generally not adjusted because it is necessary to adjust the front and back position on the optical axis and the inclination of the front surface of the CRT depending on changes in magnification, the direction of projection with respect to the projection screen surface (not shown), etc. It has a position adjustment part that allows for optimal position adjustment in each case.

However, as for the Schmidt correction lens 3, if its center is initially set to be at the center of curvature of the spherical reflecting mirror 1, no adjustment is necessary thereafter. Because of this, a position adjustment section is usually not provided. As shown in FIG. 2, a general method for determining the position of the correction lens 3 is that a light beam that passes through the center of curvature of the spherical reflector 1 is reflected 7 by the spherical reflector 1, and then the rays enter the center of curvature of the spherical reflector 1. The property of light passing through the center is utilized. Specifically, a transparent scattering plate 5 with some kind of marking is inserted into the center of the correction lens 3, and the scattering plate 5 is irradiated from the outside with a light source 17.

Then, an image by the spherical reflecting mirror 1 is generated at a position symmetrical to the marking with respect to the center of curvature. Figure 3 shows this situation. In the figure, 6 is a marking on the scattering plate 5 located at the center of the correction lens 3, and 7 is a marking on the spherical reflecting mirror 1.
This is an image formed by being reflected by. Move the correction lens 3 back and forth to find the position where the image of 7 is best focused on the scattering surface, and then move the lens 3 to the left in the case of the third figure. Statue 6 is Statue 7
can be completely superimposed. This is spherical reflector 1
This is the point where the center of curvature of and the center of the correction lens 3 coincide. The general Schmitt optical system arrangement and the method of positioning the correction lens have been described above.

On the other hand, a Schmidt projector having a structure as shown in FIG. 4A has recently been devised. In the figure, 8 is a bulb, 9 is a cylindrical metal fitting, 9' is a target support metal fitting, 10 is a phosphor target, 11 is an electronic mirror, 12 is a front sealing glass, 13
is the correction plate support frame. Here, the phosphor target 10 has phosphor coated on a metal block, and has very good heat dissipation compared to a general CRT in which phosphor is coated on a glass plate, and maximizes the use of phosphor. There is a very effective method for obtaining high-brightness projected images. The positioning of the correction lens 3 is very important even in a projector with such a structure, and mounting errors will have a negative effect on the projected image. The same is true.

Therefore, the center of the correction lens 3 needs to be installed correctly at the center of curvature of the spherical reflector, but in this case, since the front sealing glass 12 is present, the lens can be installed using the method shown in Figure 2 as is. If the center and the center of curvature of the spherical reflector are made to coincide, an error will occur in the front-rear direction. The present invention aims to provide a method for easily and accurately aligning the center of the lens with the center of curvature of a spherical reflecting mirror using a simple method even in a projection CRT having the structure shown in FIG. It is.

First, the influence of the front sealing glass 12 is shown in FIG.
This will be explained below. In the figure, C indicates the center of curvature of the spherical reflecting mirror 1, but after being reflected by the spherical reflecting mirror 1, the ray of light emitted from this point C does not return to the C point but returns to the A point.

The value of AC is determined by the thickness and curvature of the front sealing glass 12, and by selecting a specific value, it is possible to freely select the value of AC. Further, there is a point C', which can be regarded as the center of curvature of the spherical reflecting mirror 1, around the middle of the point A6C. The value of this CC' is also A
Like C, it can be freely selected, and since the light emitted from point C' is reflected by the spherical reflector 1 and then passes through point C' again, it can be used as a standard. Therefore, the present invention has a correction lens 3 as shown in FIG.
The thickness of the correction lens 3 and the thickness and curvature of the front sealing glass 12 are selected so that the outside (projection screen surface side) intersects the optical axis at the position C'.

Then, some kind of marking is applied to the outer part of the correction lens 13, and a scattering surface is provided around it. Of course, the correction lens 3 in this case is designed assuming that the center of the lens 3 is located at the center of curvature of the spherical reflecting mirror 1 and that the front sealing glass 12 is present. In addition, correction lens 3
It is not necessary to provide a special scattering surface around the center marking, and only when aligning the lens 3, attach a transparent vinyl tape with appropriate light scattering properties to the lens 3 and adjust it. It may be removed later.

In the configuration shown in FIG. 6, there is a slight difference between the position of C' shown in FIG. 6 and the position of C' in FIG. 6 due to the inclusion of the correction lens 3. An aspherical curve is a slight change from a flat surface, and if a molded product such as acrylic is used, the refractive index will be around 1.4, and if the front glass is made of a material with a higher refractive index, it will be as shown in Figures 5 and 6.
The movement of the position of point C' between the figures can be made small enough to be insignificant compared to the value of CC'. The image by mirror 1 is slightly out of focus, and C
'It's not so much that it becomes difficult to find the points. Figure 7 shows the markings, the scattering surface, and the attached lens.

In the figure, 14 is a mark provided at the center of the lens, and 15 is a scattering surface. These can be molded at the same time as the aspherical surface at the time of molding the lens, and it is not particularly difficult to make a correction lens having the structure shown in FIG. 7. With this configuration, the correction lens can be easily and accurately set at the center of curvature in a projection Schmidt tube that includes a spherical reflector and a phosphor target inside, resulting in high-quality projection. You can get the image.

In addition, as another embodiment of the present invention, as shown in FIG. 8, the lens 3 has a shape in which the required thickness is achieved only in the vicinity of the center marking position (FIG. 8 shows the concave portion). It is also possible to reduce the thickness by forming a thin film, and it is clear that the same effects as in the above embodiment can be obtained in this embodiment as well.

In this case, when light passes through the circumferential surface extending in the optical axis direction, the direction of the circumferential surface is largely shifted from the originally desired direction, resulting in a projection error on the projection screen surface. Therefore, it is desirable to paint this part black. Also, by doing so, the amount of light will not be significantly reduced. Here, 16 indicates the black painted surface. In this case, a scattering surface may be provided around the marked portion, or a scattering tape may be attached for adjustment.

As described above, according to the present invention, a projection cathode ray tube in which a spherical reflector, a phosphor target, and an electron gun are sealed in a vacuum bulb by a front sealing glass is used, and the surface of the correction lens on the projection screen side and the optical axis are The thickness of the correction lens is set so that the light emitted from the intersection with the lens passes through the front sealing glass, is reflected on the spherical reflecting mirror, and then passes through the front sealing glass again and returns to the intersection. Therefore, when using the above-mentioned projection cathode ray tube, it is possible to easily accurately align the correction lens with respect to the spherical reflecting mirror.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional television projection device, Figures 2 and 3 are diagrams for explaining the method of determining the position of the correction lens in Figure 1, and Figure 4 A and Mouth are to which the present invention is applied. FIG. 5 is a diagram for explaining the present invention in detail, and FIGS. 6, 7, and 8 are diagrams showing a television projection apparatus according to an embodiment of the present invention. This is a diagram showing the configuration of the main parts of the device. 1... Spherical reflecting mirror, 3... Correction lens, 4... Center of curvature, 10... Fluorescent target, 14... Center mark, 1
5...Scattered surface.

Claims (1)

[Scope of Claims] 1. Using a projection cathode ray tube in which a spherical reflector, a phosphor target, and an electron gun are sealed in a vacuum by a front sealing glass, and sandwiching the phosphor target and front sealing glass, the spherical reflector is When a correction lens facing the mirror is provided and the center of the thickness of the correction lens is set to the center of curvature of the spherical reflecting mirror, light emitted from the intersection of the projection screen side surface of the correction lens and the optical axis. is transmitted through the front sealing glass, reflected on the spherical reflecting mirror, and then transmitted through the front sealing glass again to return to the intersection point. Device. 2. The television projection device according to claim 1, wherein the thickness of the correction lens is reduced only in the vicinity of the point where the correction lens intersects with the optical axis. 3. The television projection device according to claim 1 or 2, characterized in that a light-diffusing surface is provided near a point where the correction lens intersects with the optical axis.