JPH05346559A - Projection system of projection television - Google Patents

Abstract

PURPOSE:To suppress the increase in calorific value and halo generation by offsetting the optical axis of a projection lens, which has an incident angle at right angles to a screen, from the center of a screen in the decreasing direction of the incident angle. CONSTITUTION:The projection system has the of incident angle phi at right angles to the screen S and a photographic lens 2G is offset in the direction where a half view angle A and a half view angle B become equal, namely, in the decreasing direction of the incident angle phi. In concrete, the optical axis of the photographic lens 2G is offset in the decreasing direction of the incident angle phi by positioning the lens so that four solid angles that the optical axis of the photographic lens 2G form in the diagonal directions of the screen S becomes nearly equal. Consequently, the vertical brightness balance on the screen S becomes excellent and the brightness at the upper end part (a) of the screen S becomes equal to that at the lower end part (b) of the screen S, so that the performance balance of the whole screen becomes excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection television projection system, and more particularly to a projection television projection system for realizing a projection television having improved performance balance such as luminance balance and color balance of the entire screen. ..

[0002]

2. Description of the Related Art For example, a red (R) projection tube, a green (G)
A three-tube color projection television, which forms an image on a screen using three projection tubes, a projection tube and a blue (B) projection tube, by using a projection lens, changes the projection size to a large size of 200 inches or more, for example. Since it can be easily adapted to the screen, it is becoming popular not only for business use but also for home use.

In this projection television, it is known that a projection system including a projection tube and a projection lens has an incident angle in the vertical direction with respect to the screen and one having an incident angle in the horizontal direction with respect to the screen. ing.

In a projection system having an incident angle in the direction perpendicular to the screen, the optical axis 10Gs of the projection lens 10G is conventionally directed to the center of the screen S, as shown in FIG. For example, as shown in FIG. 7, the optical axis 10Gs of the projection lens 10G is oriented in the direction in which the incident angle ψ with respect to the screen S increases. In particular, when there is a demand for smaller and thinner projection television cabinets in recent years, there is no problem in a system in which the projection lens is arranged on the normal line of the screen, but the projection lens is arranged on the normal line of the screen. For systems that have not been developed, it is urgent to cope with miniaturization and thinning of cabinets. In addition, in FIG. 6 and FIG.
0G is a CRT.

[0005]

However, it is known that in a system in which the projection lens is not arranged on the normal line of the screen, the brightness of the lens decreases in proportion to the half angle of view, which is proportional to the cosine fourth power. Therefore, in the conventional projection system shown in FIGS. 6 and 7, since the half field angle A> the half field angle B, the brightness on the upper side of the screen becomes smaller than the brightness on the lower side of the screen, and The brightness balance has a problem that the upper side of the screen is darker than the lower side.

It is generally known that the image forming performance of a lens deteriorates as the angle of view increases. Therefore,
Focusing on the lens, in the conventional projection system,
The focus performance on the upper side is deteriorated. Moreover,
As a lens, it is necessary to guarantee performance up to half angle of view A,
Even if the half angle of view A and the half angle of view B are unbalanced, there is a problem that a larger half angle of view must be guaranteed.

On the other hand, in the projection television,
When the screen distortion is electrically corrected by convergence, problems such as an increase in power consumption and an increase in heat generation occur with an increase in the correction amount.Therefore, a centering magnet for the external magnetic field is usually used to apply an external magnetic field to the electrodes of the projection tube. The image distortion is corrected by moving the image, but when the movement amount is large, a so-called halo, which is a phenomenon in which the image is blurred in the direction of moving the image, may occur. There is.

The present invention has been made in view of such circumstances, and an object of the present invention is to balance the brightness of the entire screen,
A projection television projection system that has an extremely good performance balance such as color balance and requires little electrical correction or external magnetic field correction, and has solved the problems of increased heat generation and halo generation. To provide.

[0009]

The structure of the present invention for achieving the above-mentioned object is a projection television projection system for forming an image on a screen through a projection lens on a screen. On the other hand, in the projection system of the projection television, the optical axis of the projection lens having an incident angle in the vertical direction is offset from the center of the screen in the direction in which the incident angle becomes smaller. At any position of 60% to 100% of the diagonal distance toward the corner of the screen, the four solid angles formed by the optical axis of the projection lens in the direction of the corner of the screen have an angular difference of 10% or less. The optical axis of the projection lens is offset with respect to the center of the screen so that they are substantially equal to each other. It is an E action television of the projection system.

[0010]

In the projection system of the projection television of the present invention, the optical axis of the projection lens forming the projection system having an incident angle in the direction perpendicular to the screen is set so that the incident angle ψ becomes smaller with respect to the center of the screen. It is offset. As a result, the half angle of view A and the half angle of view B can be equalized, and the vertical luminance balance of the screen can be improved. Therefore, it is possible to prevent the deterioration of the focus performance on one side (upper side or lower side) of the lens, which has been a problem in the conventional projection system, and the performance balance of the entire screen is improved.

Further, when the incident angle ψ becomes small, the screen distortion becomes small, so that the electric distortion correction can be reduced. As a result, the amount of heat generated is reduced, and the cost is reduced by reducing the amount of power consumption.

Moreover, 60% to 10% of the diagonal distance from the center of the screen to the corner of the screen.
By offsetting the optical axis of the projection lens with respect to the center of the screen so that the four solid angles formed by the optical axis of the projection lens in the direction of the corner portion of the screen become substantially equal at any position of 0%. Performance balance such as luminance balance and color balance can be evaluated for the entire screen.

Therefore, in the projection system of the projection television of the present invention, the performance balance such as the brightness balance and the color balance is remarkably improved.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a projection system of a green (G) projection tube 1G among projection systems of a so-called RGB three-tube projection television having a red (R) projection tube, a green (G) projection tube and a blue (B) projection tube. Shown on both sides of this green (G) projection tube 1G. A red (R) projection tube and a blue (B) projection tube are provided side by side.

As shown in FIG. 1, the projection system of this projection television has a projection tube 1G and a projection lens 2G. Moreover, in FIG. 1, the projection lens 2G is arranged above the normal line of the screen S, and
It is designed to project from above. The present invention has a problem when the optical axis of the projection lens does not coincide with the normal line of the screen. The same applies to the projection system of the projection lens arranged below the normal line of the screen. Here, a CRT is preferably used as the projection tube 1G, but a liquid crystal panel can also be used.

This projection system has an incident angle ψ in the direction perpendicular to the screen S, and the projection lens 2G has a direction in which the half angle of view A and the half angle of view B become equal, that is, the direction in which the incident angle ψ decreases. Is offset to. More specifically,
By aligning the optical axis of the projection lens 2G so that the four solid angles formed in the diagonal direction of the screen S are substantially equal to each other, the incident angle ψ is offset in the direction of decreasing.

As a result, the vertical luminance balance of the screen S in FIG. 1 becomes good, the luminance at the upper end portion a of the screen and the luminance at the lower end portion b of the screen match, and the performance balance of the entire screen is good. become. Further, since the angle of view of the projection lens is well balanced, the imaging performance of the projection lens is also improved in the balance between the upper end and the lower end of the lens. Further, since the angle of view for which the performance should be guaranteed becomes small, it is only necessary to improve the performance of the projection lens in a narrow range in design.

In this projection system, as shown in FIGS. 2 and ₃ , in the diagonal direction from the center of the screen S to the corners C ₁ , C ₂ , C ₃ , C ₄ of the screen S. At any position of 60% to 100% of the distance, the center of the projection lens 2G is located at the corners C ₁ , C.
The optical axis of the projection lens 2G is offset with respect to the center of the screen S so that the four solid angles formed in the directions of ₂ , C ₃ , and C ₄ are approximately equal. This is because the performance balance such as the brightness balance of the entire screen is further improved.

From the center of the screen S, the screen
Each corner C of S₁, C₂, C₃, C_FourHead to
Any position between 60% and 100% of the diagonal distance
Is indicated by a thick line on the diagonal line of the screen S in FIG.
Any point within the range. This point is the screen
Each corner portion C of the screen S from the center of S₁，
C ₂, C₃, C_Four60% of the diagonal distance toward
If it is located closer to the center than the display, the brightness balance of the entire screen, etc.
The improvement of the performance balance may not be sufficient. one
On the other hand, if it goes outside the 100% position, the correction is excessive.
And the brightness distribution may be reversed,
The brightness balance may not be maintained.

Further, the offset amount of the optical axis of the projection lens 2G with the center of the screen S as a reference point is such that when any one of the above four solid angles is used as a reference, the other three solid angles are used. It is determined within a range in which the angles are approximately equal within a difference of 10%.

On the other hand, the projection tube 1G for the projection lens 2G
As for the positional relationship of, the center 1Gs of the fluorescent surface of the projection tube 1G and the image center Ps on scanning are positioned so as to be substantially equal as shown in FIG. As a result, the amount of electrical screen distortion correction is reduced, and the amount of movement of the image due to the centering magnet of the external magnetic field is reduced, so that the occurrence of halo can be prevented.

In this embodiment, the combination of the green (G) projection tube 1G and the projection lens 2G has been described, but this relationship with the screen S is the combination of the red (R) projection tube 1R and the projection lens 2R, and the blue ( The same applies to the combination of the projection tube 1B and the projection lens 2G in B), and the same effects are achieved by arranging the projection tubes and the projection lenses in the same manner. That is, in a so-called RGB three-tube projection television, it is preferable that the projection tubes and projection lenses for each color are arranged as described above. However, with respect to the solid angle with respect to the entire screen, the red (R) projection system and the blue (B) projection system are displaced from the center of the screen, and thus are arranged offset by that amount. That is, the solid angle with respect to the entire screen is determined in consideration of the offset in the horizontal direction with respect to the screen (see Japanese Patent Laid-Open No. 2-116285).

The projection system having the above-mentioned configuration is so-called RGB3.
The present invention can be suitably applied not only to a tube type projection television, but also to a liquid crystal projection television including one lens or a projection television in which an arbitrary number of projection tubes are arbitrarily arranged. Not only a so-called front projection television that directly projects the transmitted light on the screen to form an image, but also the light that has passed through the projection lens 1G is reflected by the mirror 3 as shown in FIG. The present invention is also suitably applicable to a so-called rear projection television that projects an image on top and forms an image.

[0024]

As described above, according to the present invention, the performance balance such as the brightness balance and the color balance of the entire screen is excellent, and the electrical correction by the convergence and the external magnetic field using the centering magnet are performed. It is possible to provide a projection television projection system which has the advantages of being able to reduce the amount of heat generation, preventing halos from occurring, and being applicable to various types of projection televisions. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a projection system of a projection television of the present invention.

FIG. 2 is a conceptual explanatory diagram showing a relationship between object space nodes and a screen in the projection system of the projection television of the present invention.

FIG. 3 is an explanatory view showing a diagonal position range in which a diagonal solid angle of the screen is determined.

FIG. 4 is an explanatory diagram showing the relationship between the center of the fluorescent surface of the projection tube and the center of the image on scanning.

FIG. 5 is an explanatory diagram showing another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a conventional example of the projection system of the projection television.

FIG. 7 is an explanatory diagram showing another conventional example of the projection system of the projection television.

[Explanation of symbols]

 1G ... Projection tube 2G ... Projection lens S ... Screen ψ ... Incident angle

Claims (2)

[Claims] 1. In a projection system of a projection television for forming an image on a screen on a screen through a projection lens, an optical axis of the projection lens having an incident angle in a direction perpendicular to the screen is a center of the screen. The projection system of the projection television is characterized in that the projection angle is offset in a direction in which the incident angle becomes smaller. 2. 60% to 100 of the diagonal distance from the center of the screen to the corner of the screen
% At any position, the four solid angles formed in the direction of the corner of the screen of the optical axis of the projection lens are:
2. The projection system for a projection television according to claim 1, wherein the optical axis of the projection lens is offset with respect to the center of the screen so as to be substantially equal with an angular difference of 10% or less.