JPH04212141A - Video projector - Google Patents

Abstract

PURPOSE:To project a video image having high color purity and excellent contrast on a screen. CONSTITUTION:A lens part 4 is arranged in the front of a cathode ray tube (CRT)2 projecting the video image on a fluorescent screen 3, video image light 7 projected from the fluorescent screen 3 by light emission is made incident on a mirror 5, and reflected, and then, the video image is projected on the screen 6. Then, a dichroic mirror 11 having the a dichroic coating layer on a black glass plate absorbing visible light is provided. In other words, the light of an unnecessary component in the light component of the emitted light of the CRT2 and external light except the reflection zone of the dichroic mirror are absorbed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video projector device suitable for application to, for example, a rear projector device.

0002

[Prior Art] Conventionally, a video projector device has been proposed in which light from a cathode ray tube (CRT) is projected onto a mirror, and the reflected light is incident on the back of the screen, thereby projecting a video image onto the screen. (Refer to Utility Model Publication No. 62-33425). In order to obtain a color video image using the video projector device as described above, three cathode ray tubes (CRTs) are provided for red (R), green (G), and blue (B), and video image light R. G. All you have to do is project B onto the screen. However, in this case, the color purity is poor due to the emission characteristics of each CRT. That is, red (R
), the red R light has blue (B) and green (G) components in addition to that component, and the green (G)
In a commercial CRT, the green (G) light has blue (B) and red (R) components in addition to that component.
), the blue (B) light includes green (G) and red (R) components in addition to that component.

[0003] Conventionally, therefore, color filters have been inserted into optical systems. That is, dye materials have been mixed into the liquid in the liquid cooling tube of the CRT, or lenses made of glass or plastic have been colored. Furthermore, dichroic filters and dichroic mirrors are inserted into optical systems. That is, a dichroic coating layer has been formed on the lens surface of an optical system, or a dichroic coating layer has been formed on a glass plate.

0004

However, in the above-described method of inserting a color filter into an optical system, due to its absorption characteristics, it is not possible to completely separate light of a wavelength that is desired to be transmitted from light of a wavelength that is not desired to be transmitted. This has the disadvantage that no improvement in color purity can be expected. Further, as shown in FIG. 7, in the method of providing a dichroic coating layer 11b on the lens surface of the optical system, for example, C for green (G)
Taking RT (2g) and its optical system as an example, lens 11e
Of the incident light 14 on the surface, red (R) component r and blue (B) component b, which are unnecessary components, are reflected, and green (G) component g is transmitted. However, unnecessary red (R) component r and blue (B)
A portion of component b returns to the CRT phosphor screen, and a further portion becomes stray light, significantly deteriorating the contrast of the image on the screen. Further, as shown in FIG. 6, the glass plate 11
For example, if the dichroic coating part 11b is formed on the green (G) CRT, as shown in FIG.
As components of light from
) components are present.

Therefore, as shown in FIG. 6, when the incident light 14 from the CRT for green (G) is incident on the dichroic mirror 11, for example, among the light components of the incident light 14, the green (G) ) is reflected by the surface of the dichroic coating layer 11b of the dichroic mirror 11, and becomes reflected light 15g. Therefore, the light of only this green (G) component, ie, the reflected light 15g, may be reflected by a reflecting mirror and then incident on the back surface of the screen.

However, as shown by the dotted line in the figure, a part of the incident light 14, that is, the blue (B) and red (R) components of the incident light 14 are absorbed by the dichroic coating layer 1.
After being refracted by 1b, it enters the glass plate 11a and is repeatedly reflected within this glass plate 11a (this will be referred to as stray light). The blue (B) and red (R) component reflected light 15 passes through the layer 11b after being reflected.
b, 15R, the light enters the back surface of the screen via the reflecting mirror. The same applies to the light from the red (R) and blue (B) CRTs. by this,
On the screen, unnecessary blue (B) and red (R) component light also enter into a portion where green (G) component light should enter. Therefore, the method of dichroic coating the lens surface of an optical system has the disadvantage of degrading the contrast of the image on the screen, and the method of using a dichroic mirror does not sufficiently separate unnecessary light (unwanted components) as it is. The present invention has been made in view of the above points, and it absorbs unnecessary component light in the emitted light components from each cathode ray tube and external light outside the reflection band of the dichroic mirror, and has high color purity and contrast. The present invention attempts to propose a video projector device that can project good video images onto a screen.

[0007]

[Means for Solving the Problems] The video projector device of the present invention, as shown in FIGS. 1 to 4, for example, transmits light 15 from a plurality of primary color cathode ray tubes 2r, 2g, and 2b through dichroic mirrors 11 to a common source. Projected onto screen 6,
The base 11c of this dichroic mirror is made of light absorbing glass 11c.

[0008]

[Operation] According to the present invention, each cathode ray tube 2r, 2g
, 2b as unnecessary components in the emitted light component consisting of 15b, 1
5r and external light outside the reflection band of the dichroic mirror 11, a video image with high color purity and good contrast can be projected onto the screen 6.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the video projector device (rear projector) of the present invention will be described in detail below with reference to FIG. In FIG. 2, reference numeral 1 indicates the entire rear projector, and reference numeral 2 indicates a cathode ray tube (CRT) on which a video image is projected on a fluorescent screen 3. A lens section 4 is disposed in front of the CRT 2. The video image light 7 emitted from the fluorescent screen 3 of the CRT 2 is incident on the mirror 5.
After being reflected by the mirror 5, the light enters a screen 6, and a video image is projected onto the screen 6. In addition, the line shown with a dashed-dotted line in the figure shows the optical axis 8. FIG. 3 equivalently shows a more detailed configuration of this rear projector 1 and a mechanism for projecting video images.

In FIG. 3, 2b is the fluorescent screen 3.
In the blue (B) CRT 2b, a video image is projected on the blue (B) CRT 2b, and a lens section 4b is disposed in front of the blue (B) CRT 2b. 2g is a green (G) CRT on which a video image is projected on its phosphor screen 3g, and a lens section 4g is arranged in front of this green (G) CRT 2g. 2r is a CRT for red (R) on which a video image is projected on the fluorescent screen 3r;
) A lens portion 4r is disposed in front of the CRT 2r. R for each CRT2r, 2g, 2b. G. When the video signals of B are supplied, the respective fluorescent screens 3r, 3g, 3b are made to emit light, and the video image lights 7r, 7g, 7b are emitted from the fluorescent screens 3r, 3g, 3b.
The light is incident on the screen 6 via the mirror 5 through the lens portions 4r, 4g, and 4b arranged respectively, as shown in the figure. At this time, the positions and focal lengths of the respective CRTs 2r, 2g, 2b and the lenses of the lens sections 4r, 4g, 4b are set so that the optical axes 8r, 8g, 8b are focused on O on the screen 6. There is.

[0011] Thus, a color image is projected onto the screen 6. Now, these lens parts 4r, 4g, 4
b has a configuration as shown in FIG. In FIG. 4, the lens portion 4 disposed in front of the fluorescent screen 3 of the CRT 2 is shown as a whole. 9 is a concave lens for curvature of field, 10 is a main lens for projection, and 11 is an aspherical lens for correcting aberrations. 11 is a dichroic mirror, and this dichroic mirror 11 is configured as follows. That is,
A dichroic coating layer 11b is formed on a black glass plate 11c in which a pigment or the like that completely absorbs visible light is dissolved.

Now, when the dichroic mirror 11 formed in this way is arranged in the lens section 4, as shown in FIG. It is reflected by the dichroic coating layer 11b of No. 11, and becomes reflected light 16g. On the other hand, among the incident light 15 from the green (G) CRT 2g, the blue (B) and red (R) component lights enter the black glass plate 11c via the dichroic coating layer 11b, and the black glass plate 11c enters the black glass plate 11c. completely absorbed. In this example, the transparent glass plate 11a has been described as a black absorbing material, but as shown in FIG. 1B, substantially the same result can be obtained even if a black paint layer is formed on the transparent surface. Further, in this example, an example in which the video projector device of the present invention is applied to a rear projector device has been described, but it will be easily understood that the same effect can be obtained even if the video projector device of the present invention is applied to a front projector device. Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist thereof.

[0013]

[Effects of the Invention] According to the present invention, unnecessary component light of the emitted light component from each primary color cathode ray tube and external light outside the reflection band of the dichroic mirror are absorbed, resulting in high color purity and good contrast. A video image can be projected onto the screen.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a dichroic mirror used in a video projector device of the present invention.

FIG. 2 is a configuration diagram showing an example of a video projector device of the present invention.

FIG. 3 is a configuration diagram showing an example of a video projector device of the present invention.

FIG. 4 is a configuration diagram of a lens section.

FIG. 5 is a diagram showing unnecessary components in green component light.

FIG. 6 is a diagram showing the operation of light in a dichroic mirror.

FIG. 7 is an explanatory diagram of unnecessary components of incident light.

[Explanation of symbols]

2 CRT 6 Screen 11 Dichroic mirror 11a Transparent glass plate 11b Dichroic coating layer 11c Black glass plate 14 Reflected light

Claims (1)

[Claims] 1. A video projector device, wherein light from a plurality of primary color cathode ray tubes is projected onto a common screen through dichroic mirrors, and the base of the dichroic mirror is made of light-absorbing glass.