JP2000180954A - Color projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce production cost and to omit conventional focusing operation by making the depth of focus of right and left projection lenses longer than that of a central projection lens so that a swing angle may be zero. SOLUTION: The projection lens Lr is arranged in front of an R color cathode ray tube CRT-r so that its optical axis may be orthogonal to the display screen of the CRT-r. The projection lenses Lg and Lb are similarly arranged. The lenses Lr, Lg and Lb are designed to be focused on the point O of a screen S, and designed so that the depth of focus of the lens Lr +fR11 to -fR2 and the depth of focus of the lens Lb +fB1 to -fB2 may be longer than the depth of focus of the lens Lg +fG1 to -fG2. When the swing angles of the CRT-r and the CRT-b are zero, a projected picture is inclined at the position of the screen S and projected, but the depth of focus of the lenses Lr and Lb is made longer, so that out-of-focus on the periphery parts of the R and B color projected pictures is inconspicuous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color projector which projects a color image by synthesizing images of three primary colors of red, blue and green on a screen. The present invention relates to a color projector capable of simplifying a coupling structure of an optical lens.

[0002]

2. Description of the Related Art A color projector using a red (R), blue (B), and green (G) high-intensity cathode ray tube as an image projection means is extremely difficult when viewing an image enlarged on a large screen. This is effective, and in that case, for home use, a rear projector that projects an image from behind a screen is widely used as a television receiver. Further, in a video theater or the like using a larger screen, a front projector that projects an image from the front of the screen has become widespread. FIG. 4 is a schematic diagram showing the principle of such a three-tube type color projector, where 11R, 11G, and 11B are high-brightness cathode ray tubes (CRTs) displaying projected images of red, green, and blue, respectively, 12R, 12G, and 12R. Reference numeral 12B denotes an optical unit constituted by a projection lens. Reference numeral 13 denotes a screen for displaying an image radiated through the optical means 12R, 12G, and 12B.
G is arranged so as to be parallel to the display surface of G, and the projection surface is inclined with respect to the left and right cathode ray tubes 13R and 13B.

[0003] Three picture tubes (cathode ray tubes) 11 (R, G,
B) is usually arranged so as to be coplanar in the horizontal direction, but may be arranged with an inclination angle with respect to the vertical direction of the screen 13. In the case of a small rear projector, one or two reflecting mirrors are arranged between the optical means 12 (R, G, B) and the screen 13 to reduce the size of the projector device. .

By the way, in the case of such a three-tube type color projector, a central cathode ray tube (CRT) 1 is usually used.
Since the left and right CRTs 11R and 11B are arranged at an angle to the screen with respect to 1G, the projected image on the screen for the CRT 31G can be a jas focus point on the screen, as shown in the figure. As described above, the projected images FR and FB from the left and right CRTs 11R and 11B cannot be completely focused on the entire surface of the screen, and are in a so-called out-of-focus state around the screen.

Therefore, usually, the right and left cathode ray tubes 11 (R,
The tilting mechanism provided at the joint between B) and the optical means 12 (R, B) is adjusted so that the projected images of the left and right CRTs can be just focused on the screen. That is, as shown in FIG. 5, with respect to the angle α between the projection lens 12R and the display surface D of the cathode ray tube 11R, the facing angle between the projection lens 12R and the screen is set to β,
By setting the tilt angle α so that tan β = mtan α when the projection magnification is m, the composite image of the three primary colors is focused on the screen.

FIG. 6 shows a cathode ray tube 11 (R, G,
B) shows an example of a mechanism for setting an arbitrary tilt angle when coupling the optical means 12 (R, G, B). In this figure, CRT is a high-intensity cathode ray tube, and 20 is this cathode ray tube. A pair of support legs 20a that are fitted and fixed to the front surface of the tube CRT and that project above and below the center.
Supports a two-axis mechanism including a horizontal frame 22 and a vertical frame 24. 21 is a CRT spacer 2
And a bellows connected between the vertical frame 24 for fixing the lens and the inside of the bellows 21.
A transparent liquid having substantially the same refractive index as the optical lens is injected so that the tube surface can be cooled.

The horizontal frame 22 is supported by the legs 70a of the CRT spacer 70 by the horizontal rotation shaft 23, and is inclined at an arbitrary angle in the horizontal direction about the Y axis by rotating the horizontal tilt angle adjustment screw B1. It has been made like that.

The vertical frame 24 is the horizontal frame 2
The left and right sides are supported by vertical rotation shafts 26, 26. By rotating the vertical tilt angle adjusting screw B2, the vertical tilt angle adjustment screw B2 can be fixed at an arbitrary angle in the vertical direction about the X axis. ing.

The vertical tilt angle adjusting screw B2 is screwed into an L-shaped projection 24b (cross-sectional view) provided at the upper end, and is arranged such that its tip abuts on the horizontal frame 22. I have. Reference numeral 24a denotes a screw hole for fixing an optical lens to the vertical frame 24, and reference numeral 25 denotes a concave lens element formed at the center of the vertical frame 24.

[0010]

As described above, in the case of a general three-tube type color projector, the cathode-ray tubes 11 (R,
B) requires a tilt angle mechanism which is connected to the optical member having the projection lens at least at a predetermined angle in the horizontal direction, and the tilt angle of the tilt angle mechanism after mounting the cathode ray tube is required. An operation of rotating and adjusting the angle adjusting screw B1 is required. The adjusting mechanism has a considerably complicated mechanism, and the adjusting operation is performed by the eyes of a skilled worker. Therefore, there is a problem that the convergence adjustment and the cost of the product are increased.

[0011]

In order to solve the above-mentioned problems, a color projector according to the present invention is provided with a cathode ray tube for displaying three primary colors arranged at the center, left and right sides thereof, and a display of each of the cathode ray tubes. An optical means for projecting a display screen onto a screen as a composite color image, the optical system being arranged opposite to the surface, wherein the depth of focus of the projection lenses constituting the left and right optical means is set to the optical position located at the center. By making the focal length longer than the depth of focus of the projection lens that constitutes the means, the tilt angle of the mechanism that couples the left and right image projecting means and the optical means is made zero.

Further, even when each of the three primary color cathode ray tubes is set to be at an elevation angle with respect to the screen, the depth of focus of the projection lens for projecting the image screen of each cathode ray tube is set to be deep. The vertical tilt angle can also be reduced to zero.

[0013] When the depth of focus is increased, the distance of the focal point generally becomes longer. Therefore, even in the case of a color projector not provided with a tilting mechanism, the R color,
By increasing the depth of focus of the optical means for B and B, it is possible to obtain a projection image that is not so dark in practical use.

[0014]

FIG. 1 shows an optical system of a color projector according to the present invention.
Tr indicates an R color cathode ray tube (CRT), CRT-g indicates a G color cathode ray tube, and CRT-b indicates a B color cathode ray tube. Lr
Denotes a projection lens of optical means, which is disposed on the front surface of an R color cathode ray tube CRT-r, disposed so that its optical axis is orthogonal to its display screen, and fixed by a coupler mechanism (not shown). Lg and Lb denote projection lenses disposed on the front surfaces of the cathode ray tubes CRT-g and CRT-b, respectively, and coupled by a coupler (not shown) so that their optical axes are orthogonal to the tube surface.

Each of the projection lenses Lr, Lg, Lb is designed to focus on the point O of the screen S. -FB2 is the projection lens L
It is designed to be longer than the depth of focus of g + fG1 to -fG2.

By the way, the depth of focus δ can be represented by δ = ± Fc where F is the f-number of the projection lens and c is the permissible circle of confusion of the focus in the case of lenses having the same focal length. To make an optical system like
The f-number of the projection lens Lr and the f-number of the projection lens Lb may be larger than the f-number of the projection lens Lg. Further, since the f number is inversely proportional to the brightness of light passing through the lens, in the above color projector apparatus, a suitable aperture for the projection lens Lr and the projection lens Lb, for example, such that the entrance pupil of the lens is reduced. This can be easily achieved by attaching a ring-shaped shielding member or using a lens having a small diameter.

Thus, the left and right cathode ray tubes CRT-r and C
When the tilt angle at RT-b is zero, the projected images projected by the left and right cathode ray tubes CRT (r, b) are projected at a position inclined to the screen S as indicated by a dotted line or a dashed line. Since the left and right projection lenses Lr and Lb are designed to have a long depth of focus, defocusing of the projected images of the R color and the B color due to the tilt image, particularly the peripheral image, becomes less noticeable.

In this case, the green image greatly affects the resolution of the projected image on the color image screen, and the images of R and B colors are considerably reduced in human eye sensitivity. CRT-r and CRT-b
Even if you increase the depth of focus of the projection lens that projects the image of
There is an advantage that blurring of focus is not conspicuous. However, since the brightness of the left and right projection lenses Lr and Lb is sacrificed, the signals supplied to the left and right cathode rays are the same as the video signal adjusted with a slightly stronger contrast than the contrast of the center video signal. Is preferred.

In the embodiment of the present invention, ideally, the focal depth of the R color and the focal depth of the B color are Er, which cause a focus error at the periphery of the projected image when the projection screen is tilted in FIG. Alternatively, it should be Eb, but need not necessarily be lengthened by this length. Also, the brightness of the projection images of the three primary colors can be made uniform by setting the depth of focus of the projection lens Lg at the center to be long.

In the above embodiment, each cathode ray tube CRT (r, g,
b) is described in a case where the cathode ray tubes CRT are laterally juxtaposed and there is no vertical elevation angle with respect to the screen. However, as shown in FIG. Even in the case of (1), by increasing the depth of focus of each picture tube, a mechanism having no vertical tilt angle can be adopted to simplify the coupling mechanism (coupler) between the projection lens and the CRT.

However, in any case, the left and right cathode ray tubes CRT (r, b) arranged horizontally with respect to the central cathode ray tube CRT-g make a predetermined concentration angle θ with respect to the screen S. Therefore, the video signal supplied to each cathode ray tube has a red raster R as shown in FIG.
It is necessary to correct the distortion so that the blue raster B and the blue raster B are trapezoidal at least in the horizontal direction so that image distortion and misconvergence do not occur.

[0022]

As described above, the color projector according to the present invention increases the depth of focus of the left and right projection lenses at least with respect to the central projection lens, thereby achieving various types of color projectors required in the conventional color projector. The tilting mechanism can be omitted, the production cost of the color projector can be reduced, and the operation time can be shortened by omitting the conventional focusing operation.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of a cathode ray tube and a projection lens according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for a vertical tilt angle.

FIG. 3 is an explanatory diagram of a raster image for correcting image distortion.

FIG. 4 is an explanatory diagram of a conventional color projector.

FIG. 5 is an explanatory diagram of a tilt angle when a three-tube color projector is configured.

FIG. 6 is a perspective view showing an example of a coupler that couples a cathode ray tube and a projection lens.

[Explanation of symbols]

 CRT-g, CRT-r, CRT-b Cathode ray tube Lg, Lr, Lb Projection lens S screen

Claims (6)

[Claims] 1. A cathode ray tube for displaying an image of three primary colors arranged at the center and left and right sides thereof, and arranged opposite to a display surface of the cathode ray tube, and projecting a display screen on a screen as a composite color image. In a color projector comprising an optical unit, the depth of focus of the projection lens forming the left and right optical units is made longer than the depth of focus of the projection lens forming the optical unit located at the center, so that the left and right A color projector, wherein a tilt angle of a mechanism for coupling a cathode ray tube and an optical means is set to zero. 2. A cathode ray tube for displaying an image of three primary colors arranged at the center and left and right sides thereof, and arranged opposite to a display surface of the cathode ray tube, and projecting a display screen as a composite color image on a screen. A color projector comprising: a projection lens constituting at least the left and right optical means, the focal length of which is longer than a focus error (Er, Eb) of an image projected on the screen. And a coupler for coupling the left and right cathode ray tubes and the optical means so that the tilt angle of the coupler is zero. 3. The color projector according to claim 1, wherein the central cathode ray tube is arranged to be green, and the left and right cathode ray tubes are arranged to be red and blue. 4. The color projector according to claim 3, wherein the depth of focus of the projection lenses constituting the left and right optical means is set to ± 100 mm or more. 5. The color projector according to claim 3, wherein a ring-shaped shielding plate is attached to the projection lenses of the left and right optical means so as to increase the depth of focus. 6. The projection lens of each of the optical means has a deep focal depth such that the vertical tilt angle of the cathode ray tube with respect to the screen becomes zero. 6. The color projector according to 5.