JPH0678252A - Projection television receiver - Google Patents

Abstract

PURPOSE:To provide a compact projection television receiver with improved uniformity for realizing the wide screen of 9:16 relating to the projection television receiver for magnified projecting the video images of 9:16 using a projection lens by using a cathod-ray tube provided with the aspect ratio of 3:4. CONSTITUTION:The video images on the cathod-ray tube 1 are vertically shifted from the center axis of a lens 2 by utilizing the difference of sizes in a longitudinal direction of 3:4 and 9:16 so that the positions of the video images on a screen 4 are moved and a luminance correction circuit in a vertical direction for electrically correcting luminance gradation from a center to a periphery by the projection lens 2 is provided. Without changing the functions of the projection lens 2 and the cathod-ray tube 1, by optical axis shifting and electrical correction, the miniaturization and uniformity of the receiver are realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides an image of a cathode ray tube,
The present invention relates to a rear projection type television device for enlarging and projecting from the rear side of a transmissive screen by a projection lens, and more particularly to a projection type television device compatible with a 16: 9 wide screen.

[0002]

2. Description of the Related Art In recent years, a projection type television device has attracted attention, which optically synthesizes images of a cathode ray tube having red, green and blue monochromatic light emission and enlarges and projects them by a projection lens.

In a projection television device, for example (FIG. 8)
As shown in, red CRT 31 and green CRT 3
2. Projection lens 3 for each image of blue CRT 33
A method of enlarging and projecting with 4, 35, and 36 and combining three colors on the screen 37 is often used. 16: 9
Even in a projection type TV device compatible with the wide screen of, the center position of the screen is the same as the center position of the screen having a conventional aspect ratio of 3: 4 in order to display and magnify and project the image in the center of the cathode ray tube. It was a match.

[0004]

As described above, in the projection type television apparatus which enlarges and projects an image having an aspect ratio of 16: 9 with a lens by using a cathode ray tube having an aspect ratio of 3: 4, the position of the center of the screen is conventionally set. If the image is placed at the same position as the 3: 4 image, the height of the projection device and the angle of incidence on the screen will not change, and the image will be small, but the effect on the 16: 9 screen will not be sufficient.

[0005]

The projection television apparatus of the present invention uses a cathode ray tube having an aspect ratio of 3: 4.
An image with an aspect ratio of 6: 9 is magnified and projected by using a projection lens. At this time, the position of the image on the cathode ray tube is moved as much as possible in one direction above or below the center of the cathode ray tube and the center of the projection lens is moved. By displacing the axis and the center of the image, the image on the screen is moved from the central axis of the projection lens, thereby enabling downsizing and reduction of the incident angle projected on the screen.

Further, since the projection lens has a brightness gradient from the center to the periphery, if the center of the image does not coincide with the center of the projection lens, the image on the screen has a difference in brightness between the upper and lower sides. The projection television apparatus of the present invention solves this problem by providing a bias circuit for canceling this brightness difference in the vertical direction of the video signal in order to eliminate this brightness difference.

[0007]

According to the projection television apparatus of the present invention, which enlarges and projects an image having an aspect ratio of 16: 9 with a lens using a cathode ray tube having an aspect ratio of 3: 4, optical optical axis deviation and electrical luminance correction are performed. Due to the small size and good uniformity, 16:
It is possible to configure a projection type television device corresponding to 9 wide screens.

[0008]

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 shows a rear projection type television apparatus which is an embodiment of the present invention. An image of a cathode ray tube 1 is magnified by a projection lens 2, folded by a reflection mirror 3 and transmitted through a transmission screen. It is projected on screen 4. A, B, and C indicate the height of the projection television apparatus main body 5, and a, b, and
c indicates the height of the corresponding transmission screen.

FIG. 2 shows the relationship between the image on the cathode ray tube and the image projected on the screen through the projection lens. When the image position of the cathode ray tube is a'and the effective range of the cathode ray tube is fully used, a is displayed on the screen. The width of
At this time, the aspect ratio is 3: 4, and the height of the device is A. When the aspect ratio is set to 9:16, the center of the screen is conventionally aligned with the center of the lens, so in a CRT (Fig. 2).
There is an image at the position of b'of, and it becomes the height of b on the screen, and the height of the device at this time becomes B of (Fig. 1). In the device of the present invention, the position of the image on the cathode ray tube is shifted in one direction, and the image is projected at the position of c on the screen by setting it to b ′ in FIG. 2 and the projection television shown in FIG. The height of the device can be minimized as indicated by C.
At 40 inches, the difference between B and C is 60 mm, which is effective for downsizing. Also, the projection lens 2 and the cathode ray tube 1
Can be shared regardless of the aspect ratio.

FIG. 3 shows a front projection type television apparatus of another embodiment, and FIG. 4 shows the positions of the image on the cathode ray tube and the projected image on the screen at that time.
When the aspect ratio is 4: 3, the effective area of the cathode ray tube is used up to the height of d '(Fig. 4), and the projected image on the screen is (Fig. 3), d of Fig. 4). It will be high. At this time, the incident angle of the lens optical axis with respect to the screen becomes α in (FIG. 4). When the aspect ratio is 9:16,
In the past, the image was projected at the center of the cathode ray tube as shown in e'of (Fig. 4), and the projected image on the screen (Fig. 3)
The center position did not change, as indicated by e. At this time, the angle between the optical axis of the lens and the screen is set to α in FIG. 3 and actually set to about 14 degrees.

In the wide projection television apparatus of the present invention, the image on the cathode ray tube is shifted in one direction as indicated by f'in FIG. 4 so that the center position of the screen on the screen is not changed. The incident angle β of the lens optical axis can be about 11 degrees. When this angle becomes smaller,
It has a big effect on the focus on the top and bottom and the improvement of the trapezoidal distortion.

FIG. 5 shows an example of the illuminance distribution up to the diagonal ends with the center of the screen as 100. In the projection television apparatus according to the present invention, the screen is shifted because the optical axis is displaced.
The upper and lower ends are not equidistant from the optical axis (i.e., positions indicated by i and j in FIG. 5), which causes a difference in luminance between the upper and lower sides.

FIG. 6 shows the vertical illuminance distribution of the rear projection type television device of the present invention. As can be seen from this figure, in order to eliminate the difference between the upper and lower illuminances, linear correction may be applied so that a bias of 20% is applied to each of the upper and lower sides.

[0015]

According to the projection television apparatus of the present invention, by shifting the position of the image on the cathode-ray tube, a compact wide rear projection television apparatus and a wide front projection with a small incident angle to the screen are provided. Type television device can be realized. In addition, the electric bias circuit can easily solve the difference in brightness between the upper and lower sides when the present invention is carried out.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a wide-view rear projection television device according to an embodiment of the present invention.

FIG. 2 is a picture position of a cathode ray tube and a projection position on a screen according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a wide front projection type television device according to an embodiment of the present invention.

FIG. 4 is a picture position of a cathode ray tube and a projection position on a screen according to an embodiment of the present invention.

FIG. 5 is a peripheral light amount ratio in one embodiment of the present invention.

FIG. 6 is a vertical illuminance distribution of a wide-view rear projection type television device according to an embodiment of the present invention.

FIG. 7 is a bias correction amount according to one embodiment of the present invention.

FIG. 8 is a cross-sectional view of a projection television device of a conventional example.

[Explanation of symbols]

 1 Braun tube 2 Projection lens 3 Reflection mirror 4 Transmissive screen 5 Device body 6 Image on cathode ray tube 7 Projected image on screen 8 Projection lens 8'Projection lens 9 Screen 10 Floor 11 Image on cathode ray tube 12 Projected image on screen 31 Red CRT 32 Green CRT 33 Blue CRT 34 Projection lens 35 Projection lens 36 Projection lens 37 Screen

Claims (3)

[Claims] 1. An N having an outer aspect ratio of 3: 4.
Aspect ratio is 1 using the cathode ray tube for TSC
In a rear-projection wide video projector that magnifies and projects an image display close to 6: 9 from the back side of a transmissive screen by a projection lens, the image display section is shifted from the center of the fluorescent screen of the cathode ray tube, and the three screens of the image display section are displayed as fluorescent screens. And a projection lens provided on the central axis of the cathode ray tube so as to be close to the outer edge of the projection television, and the optical axis is shifted. 2. An N having an outer aspect ratio of 3: 4.
Aspect ratio is 1 using the cathode ray tube for TSC
In a front projection type wide video projector that magnifies and projects an image display close to 6: 9 on a reflection type screen by a projection lens, the image display unit is shifted from the center of the fluorescent screen of the cathode ray tube and the three faces of the image display unit are the outer edges of the fluorescent screen. The projection lens provided on the central axis of the cathode ray tube and the optical axis are shifted so that the inclination angle of the screen of the projection lens of the front projection type wide video projector device is made smaller. Projection TV device. 3. In the wide projection television device, the bias for correcting the vertical luminance is applied to the drive circuit of the cathode ray tube in order to eliminate the luminance imbalance generated on the upper and lower sides of the screen due to the optical axis shift. A projection television device characterized by.