JPH079187Y2 - Video projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a video projector for projecting an image of a video projector unit through a projection lens.

[Conventional technology]

In recent years, a video projector unit that applies a liquid crystal light valve has been put to practical use, and it is possible to project an actual TV broadcast image on a screen together with a projection lens, or connect a video tape recorder to play a recorded image on the screen. Projectors are coming into the home.

In this case, a Japanese house is generally small, and arranging a screen on the wall and a projector directly in front of it causes the inconvenience that people cannot sit at the optimum viewing position.

Therefore, the video projector is often installed on the ceiling, or directly on the floor or on a table with a low height.

FIG. 7 shows an example in which the video projector 1 is installed on the ceiling. The video projector 1 takes in a video signal from a television antenna (not shown) or a video tape recorder to produce R (red), G (green), and B (blue) images, and synthesizes these images for projection. The video projector unit 2 and the projection lens 4 exposed to the side of the case 3 that houses the video projector 2 are provided.

Of these, the case 3 has a flange-shaped mounting portion 5, which is mounted on the ceiling 6. Further, a focusing mechanism 7 for focusing by driving the projection lens 4 by a motor and a tilt mechanism 8 for similarly adjusting the image distortion by shifting the optical axis by the motor are provided so that these can be operated remotely. It has become.

When the screen 9 is installed on the front wall of the video projector 1 and the video projector unit 2 is operated, a video image is projected on the screen 9. In this case, the image is distorted into a trapezoidal shape as shown in FIG. 8 as is clear from the geometrical relationship between the video projector 1 and the screen 9. A tilt mechanism 8 is provided to adjust this trapezoidal distortion.

On the other hand, as shown in FIG. 9, the above-mentioned video projector 1 is installed on the floor 5 via the low table 11, and if the video image is projected on the screen 9 provided on the front wall, it is installed on the ceiling 5. Contrary to the case, the image is distorted into an inverted trapezoidal shape as shown in FIG. The inverse trapezoidal distortion is also adjusted by the tilt function 8.

[Problems to be solved by the device]

In the above-described conventional video projector, the trapezoidal distortion when installed on the ceiling or the inverted trapezoidal distortion when installed on the floor is adjusted by the tilting mechanism.

However, if a liquid crystal is used as the video projector unit 2, the back focus of the projection lens 4 is long, and since a prism is inserted between the liquid crystal and the projection lens 4, the image angle (angle of view) becomes wide. .

Therefore, it is difficult to manufacture the projection lens 4, and the tilt mechanism 8
Even if is adjusted, it is difficult to suppress the difference between the width U of the upper portion and the width D of the lower portion to 10% or less in an image corresponding to 47 inches, for example.

The present invention has been made to solve the above problems, and is a video projector that can easily correct trapezoidal distortion or inverse trapezoidal distortion of a projection screen due to an optical axis being oblique to the screen. Aim to get.

[Means for Solving the Problems]

Therefore, the present invention has been made in view of the above-mentioned conventional drawbacks, and when an image is obliquely projected on a screen through a projection lens, trapezoidal distortion that occurs in the width direction of the projection screen obliquely projected on the screen is generated. In a video projector having an anamorphic lens device for correction, the anamorphic lens device is formed by forming a convex curved surface whose radius of curvature continuously changes from one end to the other end corresponding to the height direction of the projection screen. A combination of a convex cylindrical lens and a deformed concave cylindrical lens having a concave curved surface whose curvature radius continuously changes from one end to the other end corresponding to the convex curved surface in the height direction of the projection screen. Therefore, it has an inverse trapezoidal characteristic for correcting the trapezoidal distortion generated in the width direction of the projection screen. A video projector characterized by the above.

[Action]

The use of a semi-cylindrical lens for filming and projection of movies provides a screen with a high degree of landscape. This type of lens is called an anamorphic lens. By the way, instead of this semi-cylindrical lens, by holding a deformed convex cylindrical lens having a flat surface on one side and a curvature of the other surface gradually decreasing from infinity and a deformed concave cylindrical lens at a predetermined interval, , Inverse trapezoidal characteristics (or trapezoidal characteristics) satisfying the afocal condition can be provided. In the present invention, this lens assembly is called an anamorphic lens device, and this anamorphic lens device is provided in front of the projection lens to correct trapezoidal distortion (or inverse trapezoidal distortion) of the projection screen.

Therefore, it is possible to correct the trapezoidal distortion (or inverse trapezoidal distortion) of the projection screen, which cannot be sufficiently corrected by the tilting mechanism, and further, it is possible to use a projection lens having a simple structure which is not premised on the correction by the tilting mechanism. .

〔Example〕

FIG. 1 is a partial sectional view showing the construction of an embodiment of the video projector of the present invention. In the same figure, those denoted by the same reference numerals as those in FIG. 7 indicate the same elements, and the mounting portion 5 of the video projector 1 accommodating the video projector unit is mounted on the ceiling 6 and the side surface of this video projector is shown. The anamorphic lens device 20 is mounted in front of the projection lens 4 exposed to the outside.

In this anamorphic lens device 20, a deformed convex cylindrical lens 21 and a deformed concave cylindrical lens 22 are integrated at a predetermined interval, and a lens barrel 23 is fixed to a video projector 1 by a bracket 24.

FIG. 2 is a perspective view of a cylindrical lens that constitutes the anamorphic lens device 20. Here, the surface of the deformed convex cylindrical lens 21 on the projection lens 4 side is P ₄ , the surface of the modified concave cylindrical lens 22 is P _3, and the surface of the deformed concave cylindrical lens 22 on the projection lens 4 side is P ₂ and the screen side surface. To P ₁
, The surface P ₁ and the surface P ₄ are flat surfaces, and the surface P ₃ corresponds to the height direction of the projection screen with an infinite radius of curvature at one lower end of the drawing and a radius of curvature at the other upper end. Is 129.08 [mm], and a convex curved surface with a continuously changing radius of curvature is formed in the middle. On the contrary, the surface P ₂ has an infinite radius of curvature at one end on the lower side of the drawing, The radius of curvature of the end is 72.9 (mm)
Thus, a concave curved surface whose radius of curvature continuously changes is formed on the way.

Now, these deformed concavo-convex cylindrical lenses 21 and 22,
If the plane is cut at the virtual plane A closest to the uppermost end of the drawing and further cut at the virtual plane B closest to the lowermost end of the drawing,
The radius of curvature r, the distance d, the refractive index η _d , and the Abbe number ν _d of P ₁ , P ₂ , P ₃ , and P ₄ are as shown in Tables 1 and 2.

Incidentally, assuming that the deformed convex cylindrical lens 21 and the deformed concave cylindrical lens 22 are cut on the virtual plane A, the optical path diagram together with the projection lens 4 on the virtual plane A is as shown in FIG. The spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are as shown in FIGS. 4 (a) and 4 (b).

Further, assuming that the deformed convex cylindrical lens 21 and the deformed concave cylindrical lens 22 are cut on the virtual plane B, an optical path diagram together with the projection lens 4 on the virtual plane B is as shown in FIG. The spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are as shown in FIGS. 6 (a) to 6 (d).

Therefore, an anamorphic lens device 20 having an inverse trapezoidal characteristic formed by integrally combining these cylindrical lenses is used.
, The projection lens 4 of the video projector installed on the ceiling
If it is mounted in front of, the trapezoidal distortion of the projected image due to the optical axis being inclined with respect to the screen 9 is corrected and a rectangular projected image can be obtained.

On the other hand, as shown in FIG. 9, when it is installed on the floor 12 through the low table 11, the projected image is distorted into an inverted trapezoidal shape as shown in FIG. 10, but the top and bottom of the anamorphic lens device 20 is changed. On the contrary, if the trapezoidal characteristic is provided and it is installed in front of the projection lens 4, it is obvious that the inverse trapezoidal distortion of the projected image is corrected and a rectangular projected image is obtained. The inverse trapezoidal distortion in this case is obtained by simply reversing the above-mentioned trapezoidal distortion, and the inverse trapezoidal distortion is naturally equivalent to the trapezoidal distortion. Therefore, the present invention includes correction of the inverse trapezoidal distortion.

In addition, although the video projector to which the liquid crystal light valve is applied has been described in the above embodiment, the present invention is not limited to this, and the projection tubes of R, G, and B colors are used.
It is also applicable to a tube type video projector.

[Effect of device]

As is clear from the above description, according to the video projector of the present invention, by combining the convex curved surface of the deformed convex cylindrical lens and the concave curved surface of the deformed concave cylindrical lens forming the anamorphic lens device,
Since it has an inverse trapezoidal characteristic for correcting the trapezoidal distortion that occurs in the width direction of the projection screen that is obliquely projected, the anamorphic lens device can be simply configured, and moreover, it is completely corrected in the height direction of the projection screen. Since it is not necessary, the trapezoidal distortion that occurs in the width direction of the projection screen can be satisfactorily corrected without changing the height dimension of the projection screen.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of a video projector of the present invention, partially shown in section, and FIG. 2 is a perspective view showing the detailed structure of the main elements of the embodiment, FIGS. 3 and 5. FIG. 4 is an optical path diagram for this main element, FIGS. 4 (a) to (d) and FIGS. 6 (a) to (d) are characteristic diagrams showing aberrations of this main element, and FIG. 7 is a conventional video projector. 10 is a side view partially showing a cross section, FIG. 8 is an example of a projection screen of this video projector, FIG. 9 is a side view showing the installation position of this video projector, and FIG.
The figure is an example of the projection screen of this video projector. 1 ... video projector, 2 ... video projector unit, 4 ... projection lens, 9 ... screen, 20 ...
… Anamorphic lens device, 21 …… Deformed convex cylindrical lens, 22 …… Deformed concave cylindrical lens.

Claims (1)

[Scope of utility model registration request] 1. A video projector having an anamorphic lens device for correcting trapezoidal distortion generated in a width direction of a projection screen which is obliquely projected on a screen when the image is obliquely projected on the screen through a projection lens, The anamorphic lens device includes a deformed convex cylindrical lens having a convex curved surface whose radius of curvature continuously changes from one end to the other end corresponding to the height direction of the projection screen, and the convex curved surface facing the convex curved surface. By combining with a deformed concave cylindrical lens that forms a concave curved surface whose radius of curvature continuously changes from one end to the other end corresponding to the height direction of the projection screen, trapezoidal distortion that occurs in the width direction of the projection screen A video projector having an inverse trapezoidal characteristic for correction.