JPH05122712A - Projection type television receiver - Google Patents

Abstract

PURPOSE:To realize a television receiver with a thin profile by improving color slurring at left/right and diagonal corners of red and blue screen due to a concentrated angle in the projection type television receiver employing plural video sources. CONSTITUTION:A red (blue) color optical axis 4R is arranged to be made incident on a different position 11 from a screen center 6 into which a light along with a green optical axis 4G is made incident. As a result, since picture angles W1, W2 of the red (blue) ray made incident on the screen diagonal corners with respect to a projection lens 2 are made almost equal to each other, the projected video image is obtained without a color slurring in four screen corners or in all diagonal directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type television which enlarges and projects images of a plurality of display elements to easily obtain a full-color large screen image.

[0002]

2. Description of the Related Art In recent years, projection type televisions for optically enlarging and projecting an image source such as a small CRT to realize a large screen have become popular for home and business use. FIG. 9 is a block diagram of a conventional three-tube projection television. In the figure, 1 is a CRT which is an image source, 2 is a projection lens which projects each CRT,
3 is a screen.

The CRT 1 is a red, blue, green monochrome tube 1R,
It consists of 1B and 1G, and is arranged in the horizontal direction of the screen. Each CRT 1 has a projection lens 2R, 2
It is enlarged by B and 2G and synthesized on the screen 3 to obtain a full-color large screen image. At this time, each projection lens 2
With respect to the optical axis 4 of 4G, 4R and 4B form a converging angle 5 and intersect at the screen center 6.

[0004]

In the conventional projection television, as shown in FIG. 10, 4R and 4B have a converging angle 5 with respect to the optical axis 4G of the reference projection lens, and the central position of the screen. Since it is incident on 6, the illuminance distributions of the red screen and the blue screen are asymmetrical at the four corners of the screen where the angle of view of the projection lens is maximum, and as a result, the green on the screen is
Partial reddish or bluish color unevenness occurs in the red and blue composite image.

Hereinafter, this problem will be described in detail with reference to FIG. FIG. 11 is an optical path diagram as seen from the top, focusing on only the green and red optical systems of the projection optical system of FIG. 10, where 8 is the pupil of the projection lens and 9 is the image plane drawn on the CRT 1. Is. Further, 7a is the upper right corner of the screen and 7b is the upper left corner. L1 is the distance from the image plane 9 to the pupil 8, L2
Is the distance from the pupil 8 to the screen 3, and h is the distance from the center of the screen to the left and right diagonal corners.

Now, assuming that the angle of view formed by the light beam traveling toward the green optical axis 4G and the diagonal corner 7 of the screen is W0, 7a, 7b
The angles of view of the rays going toward are equal to W0. On the other hand, in the red optical system, the angles of view formed by the light rays traveling toward the optical axes 7a and 7b are W1 and W2, respectively. The distances from the feet 10a and 10b of the perpendiculars drawn from the optical axes 4R to the pupils 8R of the red projection lens are different from each other, and the lengths S of the perpendiculars are equal. Therefore, the angles of view W1 and W2 are obviously different, W1 is greater than W2.

However, in the projection lens, the amount of emitted light differs depending on the angle of view, and generally the amount of light decreases as the angle of view increases. The light amount ratio compared with the light amount at the angle of view of 0 degree has the characteristic shown in FIG. Since the angle of view W1 is larger than W2, the red projected image is darker at the screen right corner 7a than at the left corner 7b. On the contrary, the blue projection image (not shown) is darker in 7b, and as a result, the illuminance distribution on the screen diagonal becomes as shown in FIG. FIG. 12 shows the illuminance ratio when the illuminances at the screen centers of green, red, and blue are normalized to 1 on the diagonal from the center of the screen to the upper right corner 7a. The vertical axis represents the illuminance ratio, and the horizontal axis represents the distance from the screen center to the diagonal corner.

Further, the illuminance of the green projected image on the screen is uniformly distributed concentrically with the center of the screen as a symmetrical point. Therefore, by taking the relative illuminance ratio of red and blue illuminance to green with respect to the illuminance of green, it is possible to know the nonuniformity of the illuminance of red and blue at any screen position, that is, the degree of color unevenness.

FIG. 13 shows the relative illuminance ratio of the conventional projection optical system. The vertical axis represents the relative illuminance ratio, and the horizontal axis represents the diagonal distance from the center of the screen to the upper right corner 7a. Therefore, it can be seen that the conventional projection optical system causes large color unevenness particularly in the corners of the screen.

When the projection optical system is symmetrical with respect to the horizontal axis passing through the center of the screen, the same applies to the lower right corner and the lower left corner of the screen. For this reason, color unevenness occurs in which the left corner of the screen is reddish and the right corner is bluish.

The color unevenness due to the difference in the illuminance at the diagonal corners on the left and right can be reduced by electrically correcting the luminance of the peripheral portion of the CRT which is the image source, but it occurs at the corners of the screen. A large amount of current needs to be supplied to correct large color unevenness, which leads to expansion of the beam spot on the CRT phosphor screen, that is, deterioration of resolution.

In recent years, there has been a strong demand for downsizing of a projection television set, and a projection lens having a short projection distance has been required. However, with a short projection distance projection lens,
The concentration angle 5 must be increased in order to secure the arrangement margin of the CRT 1. Therefore, the difference in the amount of light caused by the difference between the view angles W1 and W2 becomes large. That is, this problem hinders the downsizing of the projection television.

The present invention has been made in order to solve the above-mentioned problems, and alleviates the asymmetry of the light amounts of red and blue images obliquely incident on the screen with a converging angle, and has a small size with less color unevenness. The purpose is to obtain a projection television.

[0014]

A projection television according to the present invention is a projection optical system which forms a converging angle 5 and is arranged in the horizontal direction passing through the center of the screen, and is directed to the right corner of the screen with respect to the optical axis. Let W1 be the angle formed by the light rays and W2 be the angle formed by the light rays traveling to the left corner of the screen. The optical axis of the green projection lens is the position where the optical axis of each projection lens is incident on the screen so that W1 and W2 are equal. It is provided at a position different from.

In the projection type television having the above optical arrangement, the red and blue CRTs are provided with the drive current generating circuit for correcting the remaining color unevenness.

Further, the optical axes of the red and blue projection lenses of the present invention are incident on the screen at different positions from the optical axes of the green projection lens, and the distance from the center of the screen to the diagonal corner is S1, the left and right sides of the screen. The distance to an arbitrary point x in the diagonal direction is S2, and x is on the right diagonal of each of the red and blue projection lenses.
a, where the angles formed with the optical axis of the light beam incident on the left diagonal xb are W11 and W22, respectively, so that W11 and W22 are equal to each other at least within the range of formula (1) below. The screen incident position of the optical axis is determined.

0.5 <S2 / S1 <0.9 (1)

Further, in a projection optical system which is arranged not only with a converging angle but also with an elevation angle, it is arranged so that the optical axis of each projection lens is incident on the screen at a position deviated from the horizontal axis passing through the center of the screen. It was done.

[0019]

In the projection television according to the present invention, the optical axis incident positions are determined so that the angles of view W1 and W2 of the light rays directed to the left and right corners of the screen of the projection optical system arranged at a converging angle are equal. There is no difference in the amount of light at the four corners of the screen, and color unevenness is reduced.

In the above-mentioned optical system, the unevenness of the illuminance slightly remaining outside the four corners of the screen is corrected by providing a driving current circuit for correction in the red and blue CRTs. Get reduced footage.

In the projection television according to the present invention, the angles of view W11 and W22 at the point satisfying the formula (1) on the diagonal left and right with respect to the center of the screen are equal, and therefore the color unevenness over the entire screen is reduced only by the optical arrangement.

In the above-mentioned optical system arranged with a converging angle, for the optical system arranged not only with a converging angle but also with an elevation angle, the screen incident position of each projection lens optical axis is set to the screen. By being provided at a position off the horizontal axis passing through the center, the same operation as described above is achieved and color unevenness on the screen is reduced.

[0023]

EXAMPLES Example 1. An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a view of the red and green projection optical systems of the present invention taken out and seen from the upper surface. In this projection optical system, since each projection lens is arranged in the horizontal direction that passes through the center of the screen, the same effect can be obtained at the lower left and right diagonal corners that are symmetrical with respect to the horizontal axis. Only explain.

The optical axis 4G of the green projection lens is the screen 3
The angles formed by the rays incident on the center 6 of the screen and entering the screen upper right corner 7a and the screen upper left corner 7b are equal to W0. On the other hand, in the red projection optical system, the optical axis 4R enters the incident position 11 different from the screen center 6. At this time, the incident position 11 is determined so that the angle W1 formed by the light ray traveling toward the upper right corner 7a of the screen and the angle W2 formed by the light ray traveling toward the upper left corner 7b of the screen are substantially equal.

Therefore, even though the red projection optical system is incident on the screen 3 at the converging angle 5, the angles of view of the light rays traveling to the diagonal corners of the screen are almost equal, so that the incident light amounts are almost equal and color unevenness occurs. Will be reduced.

FIG. 2 shows the illuminance distribution in the upper right direction on the diagonal of the screen at this time. The vertical axis of FIG. 2 shows the illuminance ratio when the illuminance at the screen center of each of green, red, and blue is normalized to 1,
The horizontal axis represents the screen diagonal distance. FIG. 4 shows a state of color unevenness in which the vertical illuminance ratio of red and blue is based on the diagonal illuminance of green. From FIG. 4, the color unevenness in the peripheral portion of the screen is significantly improved as compared with FIG.

Example 2. In the above embodiment, the optical arrangement is adopted so as to eliminate the color unevenness at the center and the corners of the screen. However, as shown in FIG. 4, color unevenness remains in other parts of the screen. This problem is solved by providing each display element with a drive current generation circuit for correcting color unevenness. This circuit generates a correction current having an opposite phase to the color unevenness as shown in FIG. 7 every 1H period of the horizontal scanning waveform shown in FIG. Since the amount of remaining color unevenness at this time is smaller than the amount of color unevenness shown in the related art shown in FIG. 13, there is almost no deterioration in resolution due to current application.

Example 3. In the above-mentioned two embodiments, the optical axis of the red projection optical system is arranged so as to eliminate the color unevenness at the diagonal corners of the screen, and the color unevenness of the entire screen is eliminated by adding electrical means. However, it is empirically known that the variation in the illuminance of red and the illuminance of blue is 7% or less with respect to the illuminance of green, and the color unevenness can be visually permissible.

Therefore, as shown in FIG. 10, the distance from the center of the screen to the diagonal corner is S1, the distance to an arbitrary point x on the left and right diagonals is S2, and the right diagonal xa of each of the red and blue projection lenses is xa. , The angle formed with the optical axis of the ray incident on the left diagonal xb is W
By setting the optical axes of the red and blue optical systems so as to satisfy the formula (1) when the values are 11 and W22, it is possible to reduce the color unevenness of the entire screen only by the optical arrangement. If the upper limit of the conditional expression (1) is exceeded, color unevenness more than the permissible value will occur in the vicinity of the center on the diagonal, and if the lower limit is exceeded, the color unevenness will exceed the allowable value.

The illuminance distribution at this time is shown in FIG. 3, and the appearance of red and blue color unevenness is shown in FIG. At this time, the concentration angle 5 allows the amounts of color unevenness generated inside and outside to be substantially equal, so that the relative illuminance ratio can be kept within 7%.

In the above-mentioned first to third embodiments, the screen incidence position of each projection lens is in the horizontal direction passing through the center of the screen. However, not only the concentration angle but also the projection optical system in which the elevation angle is added, the incident positions of the optical axis are provided at positions 12, 13, and 14 which are deviated from the horizontal direction as shown in FIG. By doing so, the same effect as the above is achieved,
Color unevenness on the screen can be reduced.

Embodiments 1 to 4 above and FIGS. 1 and 11
Then, only the red projection optical system has been described for description, but the present invention can be similarly applied to the blue projection optical system symmetrically arranged via the green optical system.

[0033]

As described above, according to the present invention, the optical axis of the optical system of a color having a converging angle and incident on the screen is arranged so as to be incident on a position deviated from the center of the screen. So
Color unevenness at the four corners of the screen can be easily improved.

By adding electrical correction,
Color unevenness is reduced on the entire screen without significantly degrading the resolution.

In addition, the angle of view W1 within the range satisfying the expression (1)
By determining the optical axis incident positions of red and blue such that 1 and W22 are equal to each other, the amount of color unevenness is kept within a visually permissible value, and the color unevenness of the entire screen can be reduced only by the optical arrangement.

Further, for an optical system having not only the angle of concentration but also the angle of elevation, the screen incident position of each projection lens optical axis is provided at a position deviated from the horizontal axis passing through the center of the screen. The effect of reduces the color unevenness of the composite image.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a projection optical system of the present invention.

FIG. 2 is an illuminance distribution chart of the first embodiment according to the present invention.

FIG. 3 is an illuminance distribution diagram of a third embodiment according to the present invention.

FIG. 4 is a diagram showing color unevenness according to the first embodiment of the present invention.

FIG. 5 is a diagram showing color unevenness according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a scanning waveform of a CRT.

FIG. 7 is a diagram of a color unevenness correction waveform of the present invention.

FIG. 8 is a diagram showing an optical axis incident position of an optical system having an elevation angle according to the present invention.

FIG. 9 is a block diagram of a conventional three-tube projection television.

FIG. 10 is a configuration diagram of a conventional projection optical system.

FIG. 11 is a configuration diagram of a conventional projection optical system.

FIG. 12 is an illuminance distribution diagram in a conventional projection optical system.

FIG. 13 is a diagram showing color unevenness in a conventional projection optical system.

FIG. 14 is an explanatory diagram of an amount of transmitted light of a projection lens.

[Explanation of symbols]

 1 CRT 2 Projection lens 3 Screen 4 Optical axis 5 Convergence angle 6 Screen center 7a Screen upper right corner 7b Screen upper left corner 11 Incident position

[Procedure amendment]

[Submission date] March 16, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] Figure 12

[Correction method] Change

[Correction content]

[Fig. 12]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 13

[Correction method] Change

[Correction content]

[Fig. 13]

Claims (4)

[Claims] 1. A plurality of display elements, a projection lens arranged in front of each display element, and a screen. A reference first lens of the projection lenses is provided at the center of the screen. The optical axes of the other projection lenses are arranged so as to be incident, and the optical axes of the other projection lenses form an angle with the optical axis of the first projection lens to make a screen.
In a projection television that obliquely enters the screen and magnifies and combines the images of a plurality of display elements on the screen, the optical axis of the other projection lens alleviates the unevenness of the illuminance at the four corners of the screen. The projection television is arranged so as to enter the screen at a position different from the optical axis of the reference first projection lens. 2. The projection type apparatus according to claim 1, wherein a correction drive current generating circuit is provided in each of the display elements in order to eliminate unevenness of illuminance outside the corners of the screen 4. TV set. 3. When the distance from the center of the screen to the diagonal corner is S1 and the distance to an arbitrary point x on the diagonal is S2,
At a point x that satisfies the following expression, the optical axis of the other projection lens may be incident on a position different from the reference first projection lens optical axis so as to eliminate the non-uniformity of the illuminance. A distinctive projection TV. 0.5 <s2 / s1 <0.9 (1) 4. In an optical system in which the reference first lens and other projection lenses are arranged not only at a converging angle but also at an elevation angle, each projection lens is placed at a position deviated from a horizontal axis passing through the center of the screen. The projection television according to claim 1, wherein the optical axis is incident.