JP2528515Y2 - Lens unit structure of video projector - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is a video having a structure in which red, blue, and green projection lights are combined with a mirror to form one projection light and then projected on a screen by a lens. The present invention relates to the structure of a lens unit of a projector.

[Conventional technology]

FIG. 2 is a sectional view showing the structure of this type of conventional lens unit. In the figure, reference numeral 1 denotes a projection screen for converting projection light into an image, and 2 denotes a projection lens for forming projection light, which is a combination of three colors of red, blue, and green, on the screen 1.
Reference numerals 4 and 5 are disposed on the rear side portions and the rear portion of the projection lens, respectively, and CRTs each emitting a single color of red, blue, and green, and 6 refracts the projection light of the CRT 3 toward the lens 2, and A reflecting mirror 7 having a characteristic of transmitting the projection light of the cathode ray tube 4 directly to the lens 2, similarly having a characteristic of refracting the projection light of the cathode ray tube 5 toward the lens 2 and transmitting the projection light of the cathode ray tube 4 directly to the lens 2. Is a reflecting mirror having

In the lens unit structure as described above, the lens 2 is
Since the projection light of each of the cathode-ray tubes 3, 4, and 5 passes through, the distance from the lens 2 to the image plane of each of the cathode-ray tubes 3, 4, and 5 is optically required to form an image on the projection screen 1 correctly. Must be equal. That is, in FIG. 2, a + f = b + f = c + f in terms of optical distance. This means that the cathode-ray tubes 3 and 5 need to have image planes facing each other.

On the other hand, when viewed from the projection lens 2, when viewed from the projection lens 2, when viewed from the projection lens 2, when viewed from the projection lens 2, the shape and dimensions viewed from the structure of the cathode-ray tube are sufficiently longer in the so-called net portion having the electron gun than in the image surface m. Requires a dimension that is at least twice the width of the image plane of the Brass CRT, which is twice the length l of the CRT.

[Problems to be solved by the invention]

As described above, in the conventional lens unit, the cathode ray tubes must be arranged to face each other, and furthermore, the dimensions up to the image surface are added, so that the dimension in the width direction as viewed from the projection lens is large, and the lens unit structure is A large projection area is required, so that the video projector employing the lens unit cannot be made compact.

This invention has been made to solve the above-mentioned drawbacks, and aims to obtain the same function in a minimum space by changing the arrangement of the CRT.

[Means for solving the problem]

The lens unit structure of the video projector according to the present invention is such that a correcting lens and a reflecting mirror are provided between an orthogonal reflecting mirror that combines light beams into one and a projection tube arranged in parallel on the back side thereof, The image planes of the projection tubes having different dimensional relationships from the rear surface of the projection lens are corrected so as to be optically at the same distance.

[Action]

The lens unit structure of the video projector according to the present invention has three smaller projection tubes than the conventional one by arranging three projection tubes in parallel on the back side of the lens, making it easier to handle. Also, installation is simplified.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals 1 and 2 denote the same as those in FIG. 2, and reference numerals 3, 4, and 5 denote CRTs each emitting a single color of red, blue, and green, all of which are parallel to the rear surface of the projection lens 2. They are arranged side by side, and their rear ends are aligned at almost the same position. Reference numeral 6 denotes a reflecting mirror which refracts the projection light from the cathode ray tube 3 toward the lens 2 and transmits the projection light of the cathode ray tube 4 directly to the lens 2. Is a reflecting mirror that refracts the projection light of the cathode ray tube 3 toward the reflecting mirror 6, and 9 is a reflecting mirror that similarly refracts the projection light of the cathode ray tube 5 toward the reflecting mirror 7. It is.

Reference numeral 10 is disposed on the front surface of the CRT 3 and optically determines the difference between the distance (f) + (b) from the CRT 4 to the lens 2 and the distance (f) + (d) from the CRT 3 to the lens 2. A correction lens 11 for matching them is a correction lens on the side of the cathode ray tube 5 having the same function.

Here, for example, if there is no correction lens 10, the CRT 4
When the image of the CRT 3 is correctly projected on the screen 1, the image of the CRT 3 reaches the lens 2 via the reflecting mirrors 8 and 6 and is projected on the screen 1. In order to take an optical path of (f) + (d) longer than () + (b), the projection through the lens 2 results in an inconsistent focus. The same applies to the case of the other correction lens 11, and the image of the CRT 5 having the optical path (f) + (e) longer than (f) + (b) is a projection that does not focus on the screen 1 correctly. .

In this regard, if the correction lenses 10 and 11 are used, since the lens is a concave lens as shown in FIG. 1, for example,
The cross-sectional area of the image of the projection light (convergent light) emitted from the cathode ray tubes 3 and 5 becomes slightly larger. Therefore, the correction lenses 10 and 11
If there is no image light, the cross-sectional area of the image light projected from the cathode ray tubes 3 and 5 becomes narrower at the incident surfaces of the reflecting mirrors 6 and 7 which are orthogonal to each other by the longer optical path length. 11 corrects this, and as a result, the image cross-sectional area at the entrance surface of the reflecting mirrors 6 and 7 due to the projected light from the CRTs 3 and 5 having a long optical path, and the reflecting mirror due to the projected light from the CRT 4 having a short optical path. The image cross-sectional areas of the incident surfaces 6 and 7 are made equivalent. That is, optically (f) + (b) = (f) +
(D), (f) + (b) = (f) + (e). For this reason,
(F) + (b) = (f) + (a) =
The same optical relationship as (f) + (c) is obtained, and the images of red, blue, and green are projected on the projection screen 1 in a correctly focused state.

In the above embodiment, the correction lenses 10 and 11 were inserted in front of the cathode ray tubes 3 and 5, but the correction lenses 10 and 11 were inserted.
The same effect can be obtained by inserting a correction lens only in front of the cathode ray tube 4 without inserting the correction lens 11.

[Effect of the invention]

As described above, according to the present invention, all three projection tubes are arranged in parallel on the back side of the mutually orthogonal reflecting mirrors, and the rear ends of the projection tubes are arranged at substantially the same position. By inserting a correction lens on the front side to optically match the distance from the projection lens to the projection tube, the three projection tubes that make up the video projector can be arranged in the minimum space. The entire projector can be made compact. In addition, the degree of freedom in design is improved, installation and storage space can be reduced, and handling is facilitated. Further, the projection screen has an effect that the image is projected in a state where the image is correctly focused.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional lens unit. In the figure, 1 is a projection screen, 2 is a projection lens, 3, 4,
5 is a projection CRT, 6, 7, 8, and 9 are reflectors, 10,
11 is a correction lens. In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04N 9/31 H04N 9/31 C

Claims (1)

(57) [Scope of request for utility model registration] 1. A lens unit of a video projector in which light emitted from three projection tubes is projected onto one lens by a reflecting mirror orthogonal to each other and projected as one light beam. All are arranged in parallel on the back side of the mutually perpendicular reflecting mirrors, and the rear end of the projection tube is arranged at substantially the same position. The distance from the projection lens to the front of the projection tube as viewed from the projection lens A lens unit structure for a video projector, wherein a correction lens for optically matching the lens is inserted.