JPH02190817A - Optical system for projection image display devices - Google Patents

Abstract

PURPOSE:To contrive the decrease of a color unevenness in an image on a screen by providing a clapboard having a nonaxisymmetric clap shape with regard to its optical axis on a projection lens provided in front of a video source of one color. CONSTITUTION:On projection lenses 2R, 2B provided in front of a video source of at least one color in video sources, clapboards 4R, 4B having a nonaxisymmetric clap shape with regard to its optical axis are provided. Also, the clap shape is determined at every color so that when a white image is reflected on the whole surface of a screen, the ratio of illuminance of each color of red, green and blue of the incident surface of the screen becomes almost the same as the ratio of illuminance of each color in the vicinity of the center of the screen, in the vicinity of the left and the right ends of the screen, or in the vicinity of four corners of each upper and lower part of the left and the right. In such a manner, a color unevenness in the screen surface becomes a level which cannot be detected immediately by a viewer, and a very satisfactory image quality is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a projection optical device that enlarges an image displayed on an image source using a projection lens and displays it on a screen, and particularly relates to a projection optical device that enlarges an image displayed on an image source and displays it on a screen. The present invention relates to a projection optical device suitable for reducing color unevenness in projection.

[Conventional technology]

Small image sources such as projection type cathode ray tubes (projection type televisions enlarge the displayed image using a projection lens and project it onto a screen).In recent years, semiconductor large capacity memories have been developed, and digital control of the dynamic convergence of cathode ray tubes, etc. Thanks to the ease with which images can be performed, the image quality has significantly improved, and the large screen allows users to enjoy the powerful sense of reality, so they are becoming more and more popular for home and business use.

In projection televisions, when a projection cathode ray tube is used as an image source, the brightness of the screen on the screen must be sufficiently bright (T).
As described in Japanese Patent No. 95689, it is common practice to combine a cathode ray tube and a projection lens for each of the three primary colors red, green, and blue to synthesize an image of the three primary colors on a screen.

[Problem that the invention seeks to solve]

In the above conventional technology, the CRTs for the five primary colors of red, green, and blue are arranged parallel to each other in the left-right direction of the screen, but normally the green CRT is placed in the center, and the red and blue CRTs are arranged parallel to each other in the horizontal direction of the screen. They are placed on the left and right, and power is distributed so that the optical axes of each color intersect at a single point near the screen surface. For this reason,
Red, green, and blue color images are projected onto the screen in different directions, and the brightness distribution of each color tends to be different on the screen. When projected, color unevenness occurs, with localized reddish or bluish tints. This color unevenness will be quantitatively explained below.

FIG. 10 is a horizontal development view of the conventional projection optical system, where IR, IG, and 1B are red and green, respectively.

The blue projection type cathode ray tube, 2R, 2G, and 2B are projection lenses for the projection type cathode ray tubes IR, IC, and IB, respectively, 8 is the screen, and 8C is the center of the screen.

8R is the right edge of the screen, 8L is the left edge of the screen.

9R, 9G, 9B are red, green, and blue dosing light fluxes, S
R, 5G, and 3B are projection lenses 2R, respectively.

This is the optical axis of 2G and 2B.

FIG. 11 is a front view of the screen 8, with the center 8C of the screen as the origin and facing right in the horizontal direction.

A coordinate system is defined in which the vertically upward direction is the positive direction of the X-axis and the positive direction of the y-axis, respectively. Point P(x,y) is on screen 8
Let it be any point above.

In Figures 10 and 11, w, 4,
Wv is the width of the screen, daylight, D is the distance between the exit pupils (not shown) of the projection lenses 2R, 2G, and 2B and the screen center 8C, and θ is the optical axis concentration angle, 10R.

10G and 10B are cathode ray tubes I R-I G
This is the optical axis of the light flux from +1B to point P on the screen 3.

Now, in FIG. 10, when a white image is projected on the entire screen, the point p(x
, y), calculate the illuminance on the screen incident surface side at 8.

For simplicity, it is assumed that the cathode ray tubes IR, IG, and IB are completely diffuse surface light sources located at an infinite distance from the projection lenses 2R, 2Q, and 2B, respectively.
The light that reaches point P on the screen 8 from R, IG, and IB is
Both have projection lens 2R.

It is assumed that the light is incident on 2G and 2B as parallel light beams with -like brightness.

Also, from the cathode ray tube IR, IG, IB to the projection lens 2R
, 2G, and 2B are assumed to exit from the centers of the exit pupils of the projection lenses 2R, 2G, and 2B, respectively, without loss.

Here, from the cathode ray tubes IR, IG, and IB to the screen B
The angles that the optical axes 10R, 10G, and IOB leading to the upper point P make with the optical axes 5R, 3G, and 5B (hereinafter referred to as the angle of view of point P) are ωLRvωLG, ωLB, and the optical axes 10R, 10
G, the angle that 10B makes with the normal line of the screen 8 (hereinafter,
(denoted as screen incidence angle) are respectively nωsR1ωSG
+ωSB, the distance 1i between the output − of the projection lens 2 R+ 20 T 2 B and the point P! DR + DGI D respectively
B + Red, green, and blue illuminance at point P are ER+
EG +EB r At the center 8C of the screen,
Green and blue illuminance are ERO+ Eo□ and EB, respectively.
Let's say O.

In addition, in the calculation formula below, the subscript 1 ” Rw Ge
B represents red, green, and blue, respectively.

Now, under the above assumption, the illuminance Ei of each color at the point Pf is proportional to the area of the entrance pupils of the projection lenses 2R, 2G, and 2B. The area of this entrance pupil is such that the angle of view of point P is ωLi
When , it is proportional to cosωLi. In addition, when a projection lens is composed of multiple single lenses, ``vignetting'' of light often occurs due to the finite diameter of each lens (and the aperture efficiency at that time is Angle of view ωLi of point P
, the point P
The illuminance Ei at is 0, which is proportional to ■(ωLi).
The illuminance Ei at point P is determined by the inverse square law of distance,
Distance 4D between the exit pupils of the projection lenses 2R, 2G, and 2B and point P
It is inversely proportional to the square of i, and according to the law of cosines of the incident angle, when the screen incident angle is ωsi, it is proportional to CO3ωsi.

Therefore, the illuminance Ei at point P is (i=R,G,
B)...Represented by (1). however,
sl is.

Here, DR2 is Di2= (x-siDsinθ)2"y2"D"
(I Bi25in”θ)=x2-2siDxs
inθ+y2+D2-(5).

Before, C01i (IJI, i + C08G)81 is 0 according to the cosine theorem.Here, when i=G, that is, for green projection light, from formula (5) (4) (5), % Equation % Therefore, Equation (1) becomes Ec = Eao V (ωLG ) cos' ωI, G
Tonari, the illuminance at point P on the screen 8 is the angle of view ωL
It can be seen that it is proportional to the fourth power of the cosine of G.

This is nothing but the so-called cosine fourth law formula,
.

Now, in equation (1), a specific example of the illuminance at point P (hereinafter referred to as relative illuminance) when the illuminance at the screen center 8C is set to Ei□=1 will be shown below.

FIG. 12 shows the illuminance distribution on the horizontal incident plane at the center of the screen 8, where the horizontal axis is the horizontal coordinate and the vertical axis is t.
ζ is red at screen center 8C.

The relative illuminance is taken when the illuminance of green and blue are both 1, and the illuminance of red is shown by a broken line, the illuminance of green is shown by a dotted line, and the illuminance of blue is shown by a solid line. For calculation, assume that the size of screen 3 is approximately 40 inches diagonally, and W8H = 812 + x
l, WBV = 610 u, D = 9QQ*ac,
θ=8°. In addition, the aperture efficiency of the projection lens ■(ω
L1) was approximated as (ωLi) #cos8(1)Li.

From Figure 812, the green illuminance distribution is symmetrical with the center of the screen as the axis, whereas the red illuminance distribution is biased toward the left of the screen, and the blue illuminance distribution is biased toward the right of the screen. I know that there is. This deviation becomes alarming when the optical axis concentration angle θ is large.

As a result, from the top left corner to the bottom left corner of the screen,
The relative illuminance of red is high compared to that of green, and the relative illuminance of blue is low, so it appears reddish, which is the opposite; from the upper left corner to the lower right corner of this screen, the relative illuminance of green is l. The relative illuminance of red is low and the relative illuminance of blue is high, giving it a bluish appearance. This color unevenness is not only when a white image is projected on the entire screen, but also when a general television broadcast image is displayed - it is at a level that can be easily detected by the viewer. However, in projection image display devices, such as rear projection televisions for home use, which require the installation space to be as small as possible, mounting and rewiring problems have been a problem. In order to make the housing compact, it is necessary to shorten the projection distance from the projection lens force in the projection optical system to the screen, but in this case, the original axis concentration angle formed by the optical axis of each color projection lens is As the size increases, the unevenness of color increases, which poses a problem in making it more compact.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an optical system for a compact projection type image display device with a high surface quality and less color unevenness in an image on a screen.

[Means for solving problems]

In order to achieve the above object, in the optical system for a projection image display device of the present invention, a projection lens disposed in front of at least one color image source among the image sources has a non-axial symmetry with respect to its optical axis. Alternatively, each color projection lens may have a different clap shape for each color material, with the optical axis of each projection lens being provided with a different clap shape for each colorant, with the vertical and horizontal directions of the image source screen as a reference. The configuration includes a clap plate having a clap shape that is asymmetrical about the axis.

Alternatively, image sources of red, green, and JPR colors are arranged in a direction approximately parallel to the horizontal direction of the screen surface with the green image source at the center, and the red and blue projection lenses are placed on the screen of the image source. The construction includes clap plates each having a lug shape that is symmetrical with respect to the vertical and horizontal directions of the projection lens and having a clap shape that is axisymmetric with respect to the optical axis of each projection lens.

[Effect]

In the optical system for a projection image display device with the above configuration, when a white image is projected on the entire screen, the red, green, and green images on the screen incidence surface are For each color, create a clap shape with a relatively small ramp radius centered on the light @ in a specific direction so that the ratio of the illuminance of each color of blue is almost the same as the ratio of the illuminance of each color near the left and right sides of the screen. can be determined.

As a result, the color unevenness on the screen surface is at a level that is difficult for the viewer to immediately detect, and very good image quality can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is an exploded perspective view of an optical system for a projected image tick play device according to the present invention, showing IR, IG.

1B are red, green, and blue projection cathode ray tubes.

2R, 2G, and 2B are projection type cathode ray tubes IR and I, respectively.
This is a projection lens for G and IB. 21R~24R, 21
G~24G and 21B~24B are projection lenses 2R, respectively.
, 2G, and 2B, and among these, the third lens 25R, 25Q.

25B contributes to image enlargement as a power lens, and the other lenses mainly contribute to aberration correction.

3R, 5G, and 5B are projection lenses 2R, respectively.

The optical axes of 2G and 2B intersect at - point So.

The screen (not shown) has a normal line passing through the center of the screen that almost coincides with the optical axis 3G, and is at a point S. Clap plates 04R and 4B are arranged so that the screen is centered on the projection lenses 2R and 2B, respectively, and have a non-axially symmetrical clap shape with respect to the optical axes 5R and 5Bf, respectively. are doing.

FIG. 2 is a sectional view of the assembled state of the red projection type cathode ray tube 1R and the projection lens 2R, where 5R is a lens barrel and 6R is a coupler that connects the projection type cathode ray tube 1R and the projection lens 2R. . 7R is a transparent liquid refrigerant, which is sealed in a space surrounded by the projection cathode ray tube 1R, the second lens 22R, and the coupler 6R, and helps dissipate heat generated by the projection cathode ray tube 1R through convection. .

In FIG. 2, since the fifth lens 25R is a power lens, the entrance pupil of the projection lens 2R is approximately the second
It is located between the lens 22R and the sixth lens 23R, and what is the exit pupil? It is generally located between the 43rd lens 23R and the 4th lens 24R. Therefore, the gangway plate 4R is provided between the projection type cathode ray tube 1R and the entrance pupil of the projection lens 2R. At this time, the image projected on the screen is projected onto the projection type cathode ray tube 1R. For example, the light beam emitted from a pixel near the right end of the projection type cathode ray tube 1R when viewed from the screen passes through the right side of the hole in the clap plate 4R, near the center of the power lens 23R, and then ends up near the left end of the screen. focus on. Further, the light beam emitted from the pixel near the upper left corner of the projection type cathode ray tube 1R passes through the upper left corner of the hole in the clap plate 4R, near the center of the power lens 23R, and then converges near the lower right corner of the screen. Therefore, if the clap radius of the clap plate 4R when centered on the optical axis 3R8 is changed depending on the direction,
The luminous flux from the projection type cathode ray tube 1R to the screen and lean,
The ``vignetting'' caused by the clap plate 4R1 changes depending on the projection direction, and it is possible to change the illuminance distribution on the screen entrance surface near the left and right ends of the screen and near the upper and lower corners of the left and right sides.

Green and blue projection cathode ray tubes IG and IB and projection lens 2
G and 2B are also assembled in the same manner as in FIG. However, in this embodiment, the green projection lens is not provided with a clap plate. FIGS. 3(a) and 3(b) show the above-mentioned clap plate 4R, respectively.

Figure 3 is a plan view of 4B viewed from the screen side (
In the clap plate 4R shown in a), the clap radius is smaller on the right side when viewed from the screen side, and the red illuminance near the left end of the screen can be suppressed. Also,
In the clap plate 4B shown in FIG. 5(b), the clap radius is smaller on the left side when viewed from the screen side, and the blue illuminance near the right end of the screen can be suppressed.

In the optical system for a projection image display device shown in FIG. 1, changes in the illuminance distribution on the screen entrance surface depending on the presence or absence of the clap plates 4R, 4B will be further explained.

Figure 4 shows the horizontal illuminance distribution at the center of the screen. Relative illuminance is taken, and red illuminance is shown by a broken line, green illuminance by a dotted line, and blue illuminance by a solid line.

In the case where the clap plates 4R and 4B are not present in Fig. 1, the illuminance distribution is similar to that of the conventional example shown in Fig. 12, and as shown in Fig. 4, the illuminance of red is high near the left edge of the screen and the illuminance of blue is high. It gets lower. Conversely, near the right edge of the screen, the illuminance of red is low and the illuminance of blue is high.

On the other hand, the clamp plates 4R, 4B as shown in FIG.
When placed in the position shown in Figure 2, the red illuminance is suppressed near the left edge of the screen, as described above.
The evening illumination is suppressed near the right edge of the screen. Therefore, in FIG. 4, the illuminance of red near the left end of the screen decreases as indicated by the two-dot chain line, and the difference between the illuminance of green and blue decreases. Furthermore, the blue illuminance near the right edge of the screen decreases as indicated by the dashed line, and the difference between the red and green illuminances decreases. As a result, even if the projection distance between the projection lens and the screen is small, for example, about 700 to 800 mg, and the angle of concentration of the optical axis of each projection lens is large, about 7 to 10 degrees, color unevenness on the screen surface may occur. is reduced,
This has the effect of providing very good image quality.

In this embodiment, the shapes of the clap plates 4R and 4B are shown in FIGS. 3(a) and 3(b), but the shapes of the clap plates are not limited thereto.

Figures 5(a) and 5(b) show the clap plates 4R and 4, respectively.
FIG. 5(a) is a plan view showing an example of another shape of B;
Compared to (b), the clap radius is larger in the upper right and lower right directions for clap plate 4R, and in the upper left and lower left directions for clap plate 4B.

When these clap boards are used, compared to the case where the clap board shown in Figure 3 is used, the illuminance of red in the upper left and lower left of the screen surface is slightly larger, and the illuminance of blue in the upper right and lower right is slightly larger. 69 (a) (b) (c) are for line projection. Clap plates 4R and 4G when the lens is also provided with clap plates 4G8
.

It is a top view which shows the example of the shape of 4B. When the blue projection type cathode ray tube 1B has a remarkable brightness saturation, in which the amount of light emitted is not proportional to the energy of the electron beam incident on the fluorescent surface and is saturated, the blue illuminance near the left edge of the screen is as shown in Figure 4. This will further decrease. This is because in the optical system for the projected image display device shown in Fig. 1, the left end of the screen is farther from the projection lens 2B than the center of the screen, so the projection magnification is greater, and the left end of the screen is longer than the center of the screen. This is due to the fact that in order to project an image of the same size at the center, an image smaller than the center must be projected at the right end of the projection type cathode ray tube 1B. In this case, the clap plate 4R shown in FIGS. 6(a), (b), and (c)
, 4G, and 4B, the illuminance of red and green near the left edge of the screen is slightly lower, and the illuminance of blue near the right edge is slightly lower, reducing the difference in illuminance between each color, thereby reducing color unevenness on the screen surface. This has the effect of reducing the image quality and providing good single-image quality.

Next, other embodiments of the present invention will be explained with reference to FIGS. 7 to 9. FIG. 7 is a horizontally schematic expanded view of another embodiment of the optical system for a projection image display device according to the present invention. Yes, first
Components that are the same as those in FIG.

The difference between the optical system in Fig. 7 and the optical system in Fig. 1 is that in Fig. 1, the screen is centered at the intersection S0 of the optical axes 3R, 5G, and 5B, whereas , the screen is arranged closer to the projection lens than the intersection S0.

Also in the optical system of FIG. 7, as shown in FIG. 2, a clap plate 4R is provided in the projection lenses 2R and 2B.

4B is provided.

If the optical system shown in Fig. 7 does not have clap plates 4R and 4B,
Compared to the optical system shown in Fig. 1 without the clap plates 4R and 4B, the difference in illuminance between each color near the center of the screen is slightly larger, but the difference in illuminance between each color is smaller near both left and right ends, and In the horizontal direction ζ, overall color unevenness is reduced. However, at the four corners of the screen, the difference in illuminance between the colors becomes large, so clap plates 4R and 4B are provided inside the projection lenses 2R and 2B.

FIGS. 8(a) and 8(b) are plan views of the clap plates 4R and 4B used in this embodiment, viewed from the screen side. When viewed from the side, the clap radius is smaller at the top left and bottom left, making it possible to suppress red illuminance near the top right and bottom right of the screen. In addition, the clap plate 4 shown in FIG. 8(b)
In B, the clap radius is smaller at the upper right and lower right when viewed from the screen side, and the evening illuminance near the upper left and lower left of the screen can be suppressed.

Figure 9 shows the incident surface illuminance distribution in the diagonal direction of the screen, where the horizontal axis is the diagonal coordinate and the vertical axis is the relative illuminance when the red, green, and blue illuminances at the center of the screen are all 1. The illuminance is shown by a broken line for red, a dotted line for green, and a solid line for blue.

In the optical system shown in Figure IJ7, projection lens 2R.

If 2B does not have clap boards 4R and 4B, if you follow the screen from the center of the screen to the upper left or lower left, the illuminance of red will be high near the center and the illumination of blue will be low, but on the contrary, near the upper left corner and lower left corner, the illuminance of the evening will change. The illuminance is high and the red illuminance is low. Furthermore, there is an opposite tendency from the center of the screen to the upper right or lower right.

On the other hand, when the clamp plates 4R and 4B as shown in FIGS. 8(a) and 8(b) are installed in the positions shown in FIG. The illuminance is suppressed and the top right of the screen.

Red illuminance is suppressed near the bottom right. Therefore, in FIG. 9, the illuminance of blue near the upper left and lower left of the screen decreases as indicated by the dashed line, and the difference in illuminance between red and green decreases. Also on the top right of the screen.

The red illuminance near the lower right decreases as shown by the two-dot chain line, and the difference between the green and blue illuminances decreases. As a result, as in the case of the first embodiment, color unevenness on the screen surface is reduced,
This has the effect of providing good image quality.

In each of the above embodiments, as shown in FIG.
G, IB, and projection lenses 2R, 2G.

Although these clap plates are inserted between the entrance pupils of the projection lenses 2B and 2B, they may be inserted between the exit pupils of the projection lenses 2R, 2G, and 2B and the screen. However, in this case, as mentioned above, the image projected on the screen is an inverted image compared to the image projected on the projection cathode ray tube, so each clap plate is centered on the optical axis 3R, 5G, 5B. In this case, the ``vignetting'' of the light flux due to the clap shape is not limited to the periphery of the screen (it also affects pixels quite close to the center). As a result, the brightness of the entire screen is slightly sacrificed, but in terms of reducing color unevenness, the same effect as in each of the above embodiments is achieved.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the projection distance between the projection lens and the screen is, for example, 700 mm.
Even if the angle of concentration of the optical axis of each projection lens is as small as about 8,001 degrees and as large as about 7 to 10 degrees, color unevenness on the screen surface is reduced and very good image quality can be obtained. Furthermore, this allows the reflection f! !
By using this, it becomes possible to reduce the size of the device housing that houses the projection optical system without increasing color unevenness on the screen, which has the effect of narrowing the installation space for the image display device. .

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a first embodiment of the invention. Fig. 2 is a sectional view of the assembled projection type cathode ray tube and projection lens, Fig. 5 is a plan view of the clap plate of the first embodiment of the present invention, and Fig. 4 is a horizontal screen surface in the first embodiment of 41. FIG. 5 and FIG. 6 are plan views of other examples of ramp boards, and FIG. FIG. 3 is a plan view of the clap plate of the second embodiment. 9 is an illuminance distribution diagram of the incident surface in the diagonal direction of the screen surface in the second embodiment, FIG. 10 is a horizontal development view of the conventional projection optical system, FIG. 11 is a front view of the screen, and FIG. The figure is an illuminance distribution diagram of the incident surface in the horizontal direction of the screen surface in the conventional projection optical system shown in FIG. 10.
2B... Projection lens 4R, 4G, 4B... Clap plate (OL) Closed figure Fig. 4 f''5 Fig. (b) Q,) Fig. 8 Fig. 3 (b) Fig. 10 of the lower right child

Claims (1)

[Claims] 1. An image source of each color of red, green, and blue, a projection lens disposed in front of each image source, and an image source disposed on the opposite side of the image source with the projection lens in between. In the optical system for a projection image display device, the optical system includes a projection lens disposed in front of the image source of at least one color among the image sources, and a clap having a clap shape that is asymmetrical with respect to the optical axis of the projection lens. An optical system for a projection image display device, characterized in that it is provided with a plate. 2. Projection consisting of red, green, and blue video sources, a projection lens placed in front of each video source, and a screen placed on the opposite side of the video source with the projection lens in between. In the optical system for a shaped image display device, a clap plate provided on the projection lens and having a clap shape that is axisymmetric with respect to the optical axis adjusts the illuminance distribution of at least one color among the illuminance distributions of each color on the screen incidence surface. An optical system for a projection type image display device characterized by modulation. 3. The projection type image display device according to claim 1 or 2, wherein the clap plate has a different clap shape for each color of projection lens with reference to the vertical and horizontal directions of the screen of the image source. Optical system. 4. The image source is arranged such that red, red,
The clap plates are arranged in the order of green and blue, and
4. The optical system for a projection image display device according to claim 1, wherein the red and blue projection lenses each have a symmetrical clap shape with respect to the vertical and horizontal directions of the screen of the image source. . 5. When a white image is projected on the entire surface of the screen, the clamp plate adjusts the illuminance of each color of red, green, and blue on the screen incidence surface near the left and right edges of the screen, or near the four upper and lower corners of the left and right sides. Claim 1 or 2, characterized in that the clap has a clap shape in which the clap radius centered on the optical axis is relatively small in a specific direction so that the ratio is approximately the same as the ratio of illuminance of each color near the center of the screen. 4. The optical system for a projection image display device according to 4. 6. In a projection lens for a projection image display device comprising one or more lenses and a lens barrel for holding and fixing the lens, a clap plate having a non-axially symmetrical clap shape with respect to the optical axis is attached to the lens barrel. A projection lens for a projection type image display device, characterized in that the projection lens is incorporated into a projection type image display device. 7. The clap plate is arranged so that when a uniform monochromatic image is projected on the entire surface of the screen, depending on the relative position between the screen on which the image is projected by the projection lens and the projection lens, 7. The clap shape according to claim 6, characterized in that the clap shape has a clap radius centered on the optical axis that is relatively small in a specific direction so that the illuminance distribution becomes close to an axisymmetric distribution about the center of the screen. Projection lens for projection image display devices. 8. A projection type image display device using the optical system for a projection type image display device according to any one of claims 1 to 5.