JPH0520034B2 - - Google Patents

Description

Detailed Description of the Invention Field of the Invention The present invention relates to a video projector that projects image light formed on a CRT fluorescent surface onto a screen through an optical system having lenses and mirrors to obtain an enlarged image. It is.

BACKGROUND OF THE INVENTION In recent years, particularly in transmissive video projectors, attempts have been made to make the set more compact and to make the image light incident on the screen obliquely, mainly to reduce the depth. Moreover, the more compact the light is, the more it becomes necessary to make the light incident at an extreme angle. In this video projector, the image light projected diagonally is focused across the entire screen.
It has a so-called "tilt" function in which the CRT is placed diagonally to the lens optical axis.

FIG. 3 shows such a conventional video projector. In Figure 3, 1 is CRT,
2 is a lens, 3 is a mirror, and 4 is a screen.

The CRT and lens portion of the video projector configured as described above will be explained using FIGS. 4 and 5. FIG. 4 shows a case with the "tilt" function, and FIG. 5 shows a case without the "tilt" function. Here, 2 is a lens and 5 is a CRT full glass.

In FIG. 5, for example, consider a point O at the center of the CRT fluorescent surface. The positions O of the CRT fluorescent surface viewed from lens ends CD and EF appear to be points A and A'. However, point A and point A' are symmetrical with respect to the optical axis. This is because, as is well known, the refractive index n of the CRT front glass is greater than the refractive index no of air, so when viewed from an angle, it appears to be floating.
For this reason, the focus point shifts between the center and the periphery of the lens, causing aberrations. but,
In this way, if there is no "tilt", there is no problem in practical use.

Problems to be Solved by the Invention However, in video projectors that require light to be incident on the screen obliquely,
As mentioned above, a "tilt" function is required depending on the degree of obliqueness. As shown in FIG. 4, when the "tilt" function increases, the point O seen from the lens ends CD and EF appears to be points B and B' and becomes asymmetrical with respect to the optical axis. This further increases aberrations. As an example, even if we consider a case where there is only "tilt" in the x-y plane and no "tilt" in the y-z plane, the aberrations occurring in the x-y plane and the y-
Since the aberrations generated in the z-plane are different, differences in distance due to aberrations in both directions also occur. One way to improve these problems is to make the CRT front glass extremely thin. but
It is impossible to make the CRT extremely thin due to its strength, X-ray leakage, etc. Therefore, there was a problem in that the image on the screen deteriorated significantly, making it unusable.

The present invention has been made in view of the above-mentioned problems, and does not deteriorate the image even when there is "tilt". The purpose is to provide a video projector.

Means for Solving the Problems In order to solve the above problems, the video projector of the present invention has a configuration in which the space between the CRT and the lens is filled with a transparent medium.

Effects The present invention has the above configuration by filling the space between the CRT front glass and the lens with a medium n having almost the same refractive index as the CRT front glass n.
The light emitted from the CRT fluorescent surface can be made to travel straight without being refracted, allowing it to be seen through the lens.
It is designed to return the CRT fluorescent surface O to its original position without lifting it up. Therefore, the increase in aberration caused by increasing the "tilt" is eliminated, and the effect of preventing deterioration of the image on the screen is achieved.

Embodiment A video projector according to an embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show one embodiment of the present invention. In Figures 1 and 2, 1 is a CRT arranged obliquely to the optical axis of an optical system having a lens 2, 3 is a mirror, 4 is a screen, and 5 is a
The CRT front glass 6 is a transparent medium filled between the CRT front glass 5 and the lens 2, and prevents deterioration of optical performance caused by arranging the CRT 1 and the lens 2 obliquely to the optical axis.

According to this embodiment, in a video projector with a large "tilting" function, a transparent medium 6 having a refractive index very close to the refractive index (n≒1.5) of the CRT front glass 5, such as silicon, is placed between the CRT front glass 5 and the lens 2. By filling the gel (n≈1.4), it is possible to eliminate aberrations caused by having the "tilt" function and improve the deterioration of the image on the screen.

Effects of the Invention As described above, the present invention provides a video projector that has a so-called "tilt" function in which the CRT is arranged obliquely with respect to the optical axis of the optical system.
By filling the space between the front glass and the lens with a transparent medium having a refractive index almost equal to the refractive index of the CRT front glass, it is possible to improve the deterioration in optical performance that occurs as a result of the "tilting" function.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a video projector in an embodiment of the present invention, and FIG. 2 is an enlarged top view showing the configuration between a CRT and a lens in an embodiment of the present invention.
Figure 3 is a configuration diagram of a conventional video projector.
FIGS. 4 and 5 are enlarged top views showing the structure between a CRT and a lens in a conventional example. 1...CRT, 2...lens, 3...mirror,
4...Screen, 5...CRT front glass, 6
...transparent medium.

Claims (1)

[Scope of Claims] 1. A video projector that enlarges and projects a display image of a CRT disposed so as to have an optical axis in a direction different from the normal direction of the screen surface onto the screen via an optical system, comprising: In order to align the focus on the screen according to the incident angle of the image light incident on the CTR, the image display surface of the CTR and the lens surface of the optical system are diagonally opposed to each other, so that each optical axis is aligned with the CRT surface. with respect to the optical axis of the lens of the optical system.
The optical axis of the CRT is made to coincide with the optical axis of the lens of the optical system in a direction perpendicular to the screen, and the CRT is placed on the screen side in a plane perpendicular to the screen.
The optical axis of is relative to the optical axis of the lens of the optical system,
The space formed by the image display surface of the CRT and the lens surface, which are arranged at an angle smaller than 180 degrees, has a refractive index substantially the same as that of the front glass of the CRT. A video projector characterized by being filled with a transparent medium having