JP2001356408A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the luminance distribution of a display image plane on a screen where the lowering of luminance or irregular luminance is found at a peripheral part in an enlarging projection type display device. SOLUTION: In this display device by which video light generated from an optical image forming part 11 is enlarged by an enlarging lens 12 and projected to the screen 13 as shown by (B) of Figure 8, the display uniform in the luminance on the screen can be realized by providing distribution in the enlargement ratio of the enlarging lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for equalizing the brightness of a screen in a display device of a system in which a magnifying lens projects an image on a screen.

[0002]

2. Description of the Related Art In a display device using an enlarged projection system, FIG.
As shown in (1), the image light generated from the optical image forming unit 11 is enlarged by the magnifying lens 14 and projected on the screen 13.

However, when the image light is magnified by the magnifying lens, the refraction angle becomes larger toward the periphery, the projection distance becomes longer, and the luminous flux diverges from the center. Therefore, the central part of the optical axis follows the cosine fourth law of the lens aperture efficiency. The light amount in the peripheral portion is lower than that in the peripheral portion. In addition, as shown in FIG. 4, a light beam such as the incident light 42 or 43 may be blocked by the peripheral portion of the magnifying lens 41, so that the screen does not have a uniform brightness.
A decrease in peripheral luminance occurs as in the display dark portion 31 shown in FIG.

[0004] As an example of making the luminance uniform, Japanese Patent Laid-Open No. 5-1 is disclosed.
As disclosed in Japanese Patent No. 42655, a technique for increasing the light amount at one screen edge by shifting the center of the liquid crystal panel in the optical image forming unit and the optical axis of the magnifying concave lens, or reducing the luminance at the center of the optical axis by using a light shielding plate There is a technique for making the peripheral luminance uniform.

[0005]

The conventional technique for making the luminance uniform is disclosed in Japanese Patent Application Laid-Open No. 5-142655, in which the light quantity at one screen edge increases, but the light quantity at the other screen edge decreases. There is a problem, and in the technique of lowering the luminance at the center of the optical axis by a light shielding plate, the luminance of the entire screen is reduced as shown in FIG.
To the luminance value of the display dark portion 31 of FIG.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is intended to suppress a decrease in peripheral luminance and to suppress luminance non-uniformity and luminance decrease peculiar to a light source tube in an optical image forming unit. The goal is to equalize.

[0007]

According to the present invention, in order to achieve the above object, a magnifying lens in a projection display device is changed in magnification for each part, and a light beam in a high luminance portion is moved to a low luminance portion. is there.

[0008] The projection display device according to claim 1 of the present invention comprises:
It is characterized in that the magnification is changed so that the luminous flux in the central part is collected in the peripheral part when the luminance is reduced in the peripheral part of the screen.

A projection display apparatus according to a second aspect of the present invention is characterized in that the luminance is made uniform even when the luminance is reduced except at the peripheral portion of the screen. It is characterized by changing the magnification so that the light beam is collected at the part where it is located. The magnification distribution of the magnifying lens does not necessarily have to be as small as the outside, and the magnification depends on the luminance distribution of the image of the optical image forming unit. The distribution is determined. Further, in the projection display device according to claim 3 of the present invention, the optical image forming unit includes a light valve 82 that forms an image according to a video signal as shown in FIG.
A light source tube 81 having an electron beam generating means and a light emitting portion made of a phosphor layer emitting light by electron beam excitation is provided.

A projection display apparatus according to a fourth aspect of the present invention is characterized in that the screen display screen luminance is made uniform.

Further, in the projection display device according to any one of the first to fourth aspects, if the video signal of the optical image forming section is displayed on the screen as it is, distortion occurs. Therefore, the projection display device according to the fifth aspect of the present invention. Is characterized in that the distortion is improved by using original image signal distortion correction by image processing. The distortion correction by this image processing is disclosed in
It is possible by the conventional technique described in 05061 and the like. FIG.
Is an example of improvement by the distortion correction technique by this image processing. Before the above-described correction technique is used, the image on the screen is distorted such that the image at the center of the screen is extended and the image at the periphery of the screen is reduced as shown in the upper right. Using the above-described correction technique, the distortion of the image of the optical image forming unit is corrected so that the image is concentrated at the center as shown in the lower left. Correction of distortion by image processing is performed by the correction circuit 84 shown in FIG.
Do for Thereby, the image on the screen becomes an image of a correct shape without distortion.

A projection display device according to a sixth aspect of the present invention is characterized in that a plurality of the display devices are combined to form one large screen display.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is an explanatory view showing one embodiment of a projection display apparatus according to the present invention. The image light generated from the optical image forming unit 11 is enlarged by using the concave lens 12 and the screen 1 is enlarged.
3 is a method of projecting. In this description, the optical image forming unit 11 includes a light valve 82 shown in FIG.
It is assumed that the image forming lens 83 is composed of a sidelight type backlight and the imaging lens 83 is composed of a convex lens. In the light source tube 81, the same effect is obtained by a discharge lamp such as a metal halide lamp or a xenon lamp, and in the imaging lens 83, the same effect is obtained by a Fresnel convex lens or the like.

In order to make the brightness on the screen screen uniform, the magnification is changed for each concave lens portion, and the light flux in the high brightness portion is moved to the low brightness portion. Find the lens formula at that time. FIG. 9 shows an example of a lens system of a general concave lens 12.
The following equation is given in the coordinate system of Z = C · Y ² / (1+ (1- (1 + K) · C ² · Y ² ) ^1/2 ) (1) where K is a constant and C is a curvature.

FIG. 8A shows a state in which the light beam is expanded by the conventional concave lens 14, and the expansion ratio distribution is constant. Since this lens is a rotator having the z axis as a rotation axis, it can be satisfied by expressing Y ² as X ² + Y ² . Also, K, C
Is a constant. The present invention uses one or both of these constants.
The tilt of the lens is changed for each location as a function of X and Y, and the magnification is changed for each part. Expressed by the lens formula, Z = (C (X, Y)) S ² / (1+ (1- (1 + K (X, Y)) ・ (C (X, Y)) ²・ S ² ) ^1/2 ) (2) where S ² = X ² + Y ² FIG. 8B shows how the light beam is enlarged by the concave lens 12 of the present invention. By using the lens system, concave lenses having different magnifications at the optical axis center portion and the peripheral portion can be formed.

Next, the curvature distribution of the lens is actually obtained.
First, it is calculated how the display dots of the image on the liquid crystal panel are enlarged and displayed on the screen by the concave lens.
Conventionally, as shown in FIG. 12, the coordinates on the liquid crystal panel are (x, y), the coordinates on the screen are (x ′, y ′), and the size of the liquid crystal panel is 2 · lx × 2 · ly. The size is 2 lx 'x 2 ly',
Let the magnification be k. Conventionally, k is constant because the enlargement ratio is constant. x '/ x = lx' / lx = k ... (3) y '/ y = ly' / ly = k ... (4)

On the other hand, when the enlargement ratio is changed for each part as in the present invention, a distribution of the enlargement ratio that makes the luminance on the screen uniform is obtained, and then the lens equation is obtained.

A case where the luminance distribution on the screen is represented by the cosine fourth law of the lens aperture ratio as shown in FIG. 15 will be described. If the brightness is I, the angle before the change is θ, the angle after the change is θ ', the x coordinate of the screen before the change is xs, and the x coordinate of the destination after further increasing the magnification is xs', I (θ) = A · cos ⁴ θ (A is a constant)… (5) When the average brightness H from 0 [rad] to θ ₀ [rad] is obtained, ∫A · cos ⁴ θ · dθ = A · [tanθ ₀ / _{^{{4 · (tan 2 θ 0}} + 1) 2} + 3 · tanθ 0 / {8 · (tan 2 θ 0 + 1) 2} + 3 · θ 0/8] ... (6) H = A · [tanθ ^{_{0 / {4 · (tan 2}} θ 0 + 1) 2} + 3 · tanθ 0 / {8 · (tan 2 θ 0 + 1) 2} + 3 · θ 0/8] / θ 0 ... (7) brightness一 様 A · cos ⁴ θ · dθ = H · θ '(8) From this, θ' = {2 · tan θ / (tan ² θ + 1) ² + 3 ・ tan θ / (tan ² θ + 1) ² + 3 ・ θ} / [{2 ・ tan θ ₀ / (tan ² θ ₀ + 1) ² + 3 ・ tan θ ₀ / (tan ² θ ₀ + 1) ² + 3 · θ ₀ } / θ ₀ ] (9) On the other hand, the enlargement factor k is k = xs '/ xs ≒ θ' / θ (10). Calculating this ^{k = - B · xs 2 +} C (B, C is a constant) can be approximated with ... (11), k can be assumed to be proportional to the square of xs'.

On the other hand, the enlargement ratio at the time of enlargement in the x direction is k
(x), the enlargement ratio at the time of enlargement in the y direction is k (y). First, assuming that the end portion has the same enlargement ratio k (x) = k (y) = k0 as in the past, lx ′ = k0 · lx (12) ly ′ = k0 · ly (13) The enlargement ratio at the center is set to k (x) = k (y) = k1, and k1 is the maximum enlargement ratio.

In the portion between them, the enlargement ratio increases squarely from the peripheral portion to the central portion as shown in equation (2) so that the distribution of luminance is eliminated.

Assuming that the position (x, y) of the image dot on the liquid crystal panel is projected to the position (x ', y') on the screen, k
(x), k (x), x ', y' are expressed by the following equations. k (x) = k1-(x / lx) ²・ (k1-k0)… (14) k (y) = k1-(y / ly) ²・ (k1-k0)… (15) x '= k (x) · x… (16) y '= k (y) · y… (17) From (14), (15), (16) and (17), x' = (k1-(x / lx) ² · (k1-k0)) · x (18) y ′ = (k1− (y / ly) ² · (k1-k0)) · y (19)

Next, the incident angle of the incident light on the screen
(Emission angle from concave lens) is obtained.

FIG. 13 shows a liquid crystal panel, a concave lens, and a screen, which are shown in an xz coordinate system. The same applies to the figures viewed on the yz plane.

Now, the display dots of the image on the liquid crystal panel section
When projected from (x, y) to a point (x ', y') on the screen,
The emission angle (θx, θy) from the concave lens is expressed as follows, where the distance between the concave lens and the screen is L (L >> x, y). θx = tan ^-1 ((x'-x) / L) ... (20) θy = tan ^-1 ((y'-y) / L) ... (21).

Next, the emission angles (θx, θy) from the concave lens
The lens curvature distribution at the time of emission is determined. FIG. 14 shows that a light ray is incident on the concave lens having the refractive index n of the lens from the surface A (δx,
δy), and exit at an exit angle (δ′x, δ′y). Then, light enters from the surface B at an incident angle (γx, γy), and is emitted (θx,
θy).

According to Snell's law on planes A and B, sinδx = n · sinδ′x (22) sinθx = n · sinγx (23) From the figure, δx = δ′x + γx (24) (22) ), (23), (24), δx = -tan ^-1 [sin θx / {1-n · cos · sin ^-1 (sin (θx) / n)}]… (25) δx is the curvature of the lens. Since it is the same as the x component, the lens is determined from this.

Similarly, the y component is calculated as follows: δy = −tan ⁻¹ [sin θy / {1−n · cos · sin ⁻¹ (sin (θy) / n)}] (26)

As shown in FIG. 10, when a concave lens having a curvature distribution of the above-mentioned formulas (25) and (26) having a long horizontal side is designed, the lateral magnification distribution is more than the vertical magnification distribution. Becomes gentle, so that the angle of the lens in the sectional view is δ ₁ <δ
_It becomes _{2 and} the enlargement ratio of the part b becomes larger than that of the part a. Also,
FIG. 8A is a cross-sectional view taken along the line OA 'in FIG. In the conventional concave lens, the lens surfaces 91a, 9
The light beams incident on 1b, 91c and 91d were emitted on the screen 13 at equal intervals of km. However, in this embodiment, the lens surfaces 91a, 91b, 91c, 9 are formed at equal intervals m as shown in FIG.
Light beams respectively incident on 1d exit on the screen 13 at intervals not equal to the intervals n ₁ , n ₂ , n ₃ (n ₁ > n ₂ > n ₃ ).

According to the present embodiment by the method described above,
The central luminous flux can be brought to the periphery, and the luminance distribution can be made uniform.

When a video image of the optical image forming unit is displayed using such a technique, distortion occurs. Therefore, the original video image is improved by using a distortion correction technique based on existing image processing. FIG. 5 is an example of improvement by a distortion correction technique by image processing. Before performing distortion correction by image processing, the display screen is distorted as shown in the upper right figure. Thus, distortion of the liquid crystal panel surface is corrected by image processing as shown in the lower left diagram, and a display screen without distortion can be realized on the screen as shown in the lower right diagram.

Assuming that the coordinates on the liquid crystal panel are (x, y) and the coordinates on the screen are (x ′, y ′), the above equations (16) and (17)
Is expressed as x '= k (x) x, y' = k (y) y so that the liquid crystal like x = f (x '), y = f (y') Since the coordinates on the panel surface and the coordinates on the screen can be converted one-to-one, distortion correction may be performed according to these equations.

In another embodiment, when it is known that there is a specific brightness distribution of the backlight portion in the optical image forming portion, the light flux in the low brightness portion is supplemented by compensating for the light flux in the low brightness portion. Can be done as follows.

For example, when the luminance distribution of the backlight unit in the optical image forming unit has a low luminance portion at the upper part of the screen as shown in FIG. The distribution of the magnification is such that the luminous flux gathers.

In terms of the lens formula, the x component is the same as before, and the enlargement ratio when expanding in the y direction is k (y), and only k (y) is calculated. Enlargement ratio k (y) = k
It is set to 0, the magnification at y = y1 above the center is set to k (y) = k1, and k1 is the maximum magnification. To linearly increase the enlargement ratio from the periphery to y = y1, if y1 <y <ly: k (y) = (k1ly-k0y1) / (ly-y1) + y ・ (k0-k1) / (ly-y1)… (27) When ly <y <y2: k (y) = (-k1 ・ ly-k0 ・ y1) / (ly-y1) + y ・(k0−k1) / (ly + y1) (28). Similarly, (17), (21), and (26) are similarly calculated to obtain a lens equation.

In the description of the previous embodiment, a concave lens is taken up as a magnifying lens. However, similar effects can be obtained with other magnifying lenses such as a Fresnel concave lens by using a lens type that determines the light emission angle in the same manner. be able to.

The same technique can be used for a multi-display device in which a plurality of display devices are arranged as shown in FIG. Conventionally, in a portion connecting display devices to each other, an unnatural display in which a lattice-like pattern is seen due to a decrease in peripheral luminance, but a multi-display with uniform luminance and no lattice-like pattern can be realized by using such a technique. . Although FIG. 6 is an explanatory diagram of a 2 × 2 multi-display device, the same effect can be achieved even if the number of devices is further increased.

[0037]

According to the present invention, since the luminance can be made uniform by changing the distribution of the magnification of the magnifying lens as described above, a high-quality display image can be displayed in a monochromatic display such as a single white color. Obtainable. Further, the present invention can also be used for a multi-display device in which a plurality of display devices are combined, and a high-quality large-screen device is obtained in which a lattice pattern disappears due to a decrease in luminance between the display devices. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an enlarged projection type display device according to the present invention.

FIG. 2 is an explanatory diagram of a conventional enlarged projection type display device.

FIG. 3 is an explanatory diagram of the screen display of FIG. 2;

FIG. 4 is an explanatory diagram of a decrease in peripheral luminance caused by a magnifying lens.

FIG. 5 is an explanatory diagram of a distortion correction technique by image processing.

FIG. 6 is an explanatory view showing an embodiment of a 2 × 2 multi-display device.

FIG. 7 is an explanatory view showing an embodiment of an optical image forming unit.

FIG. 8 is an explanatory view showing one embodiment of a display device of an enlarged projection system according to the present invention.

FIG. 9 is an explanatory diagram of a lens-based coordinate system.

FIG. 10 is an explanatory diagram of a lens surface curvature.

FIG. 11 is an explanatory view showing an embodiment of a display device of the enlarged projection system according to the present invention.

FIG. 12 shows x of a liquid crystal panel and a screen according to the present invention.
Explanatory diagram showing -y coordinate system

FIG. 13 shows x of a liquid crystal panel and a screen according to the present invention.
Explanatory drawing showing a -z coordinate system

FIG. 14 is an explanatory diagram showing incident light and outgoing light of a magnifying lens according to the present invention.

FIG. 15 is an explanatory diagram of the cosine fourth law of the aperture ratio.

[Explanation of symbols]

11 optical image forming unit, 12 magnifying lens according to the present invention,
Reference numeral 13: screen, 14: conventional magnifying lens, 15: magnifying lens according to the present invention, 31: display dark part, 41: magnifying lens, 42: light incident on the periphery of the magnifying lens, 43: light flux blocked by the lens end, 44 ... Enlarged light, 61 ... Upper left display screen of the multi display device, 62 ... Upper right display screen of the multi display device, 63 ... Lower left display screen of the multi display device, 64 ... Lower right display screen of the multi display device 81 light source tube 82 light valve 83 imaging lens 84
Distortion correction circuit 85 input video signal 91a-91e
Conventional concave lens surfaces, 92a to 92e: lens surfaces of the concave lens of the present invention.

Continued on the front page (72) Inventor Hironori Oikawa 810 Shimoimaizumi, Ebina-shi, Kanagawa F-term in PC Division Hitachi, Ltd. (Reference) 2H088 EA17 HA09 HA24 MA04 5C058 AA06 AB03 BA06 BA23 BA24 BA35 BB25 EA02 EA12 EA26

Claims (6)

[Claims] An optical image forming unit for forming and displaying an optical image in accordance with a video signal; an enlarging lens for enlarging and projecting the optical image; and a screen for projecting an image of the optical image forming unit. In the projection display device, an enlargement ratio is changed from a center of an optical axis of the magnifying lens toward a peripheral portion. 2. An optical image forming section for forming and displaying an optical image in accordance with a video signal, a magnifying lens for enlarging and projecting the optical image, and a screen for projecting an image of the optical image forming section. In the projection display device, the magnifying lens defines a magnification distribution according to a luminance distribution of an image of the optical image forming unit. 3. An optical image forming section, comprising: a light valve having a light valve for forming an image in accordance with a video signal, an electron beam generating means, and a light emitting section comprising a phosphor layer which emits light by electron beam excitation. The projection display device according to claim 1, further comprising: 4. The projection display device according to claim 3, wherein the screen display screen luminance is made uniform. 5. The projection type display device according to claim 4, wherein the projection type display device has a function of performing distortion correction by image processing on a video signal according to distortion of a display image. 6. A projection display device comprising a plurality of display devices according to claim 5 combined to form one large screen display.