JP2003057589A - Illuminating optical system and projection type picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve the problem that an outward coma occurs in an illuminated area on a picture display element and the quantity of light falls at four corners of the highest image height to reduce the brightness of a display picture in the case that a double convex condenser lens is used in an illuminating optical system for a projection type picture display device. SOLUTION: The illuminating optical system includes luminous flux dividing means 3 and 4 which divide an illuminating luminous flux from a light source 1 into a plurality of luminous flux parts and uniforming means 6, 7b, and 8G which irradiates a picture display element 9G with the illuminating luminous flux divided into a plurality of luminous flux parts by the luminous flux dividing means so as to obtain an approximately uniform light intensity distribution, and such shape is given to a positive lens 6 closest to the luminous flux dividing means out of lenses constituting the uniforming means that -2<=(R1+R2)/(R1-R2)<=-1 may be satisfied where R1 is the radius of curvature of the face on the luminous flux dividing means side of the positive lens and R2 is that of the face on the picture display element side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device for enlarging and projecting an image formed by light modulated by an image display element, and an illumination optical system used for the same.

[0002]

2. Description of the Related Art In the illumination optical system and the projection type image display device as described above, it is required to improve the brightness of an image projected and displayed and to make the device compact.

FIG. 6 shows the configuration of a conventional projection type image display device. In this figure, a light source unit 1 such as a halogen lamp, a metal halide lamp or an ultra-high pressure mercury lamp
Part of the white light flux emitted from 01 is directly reflected, and the rest is reflected by the reflector 102 to enter the fly-eye lenses 103 and 104, and is divided into a plurality of light flux portions. Then, the polarization direction of the illumination light flux divided into a plurality of light flux portions is aligned by the PS conversion element 105, and the light intensity distribution is made substantially uniform by the condenser lens 106 and the field lens 107, and then the image display element such as LCD. It is incident on 108.

The light incident on the image display element 108 is modulated by the image display element 108 on which an image is formed by the settling signal, and projected onto a screen (not shown) by the projection lens 109.

Here, the brightness of the image projected and displayed by the projection type image display device is determined by the incident angle of the illumination light incident on the image display element 108 and the Fno. Depends heavily on the balance of.

In the image display device shown in FIG. 6, the incident angle of the illumination light to the image display element 108 is determined by the condenser lens 1.
It is substantially determined by the diameter of 06 and the distance D between the condenser lens 106 and the image display element 108.

If the distance D is shortened in order to make the apparatus compact, the angle of incidence of the illumination light on the image display element 108 becomes large, and the number of light beams that cannot enter the pupil of the projection lens 109 increases. , The brightness of the projected image is reduced.

In order to solve this, for example, Japanese Unexamined Patent Application Publication No.
000-98488 and Japanese Patent Laid-Open No. 2000-2418.
As proposed in Japanese Patent Publication No. 82, there is a method of disposing a concave lens between the condenser lens 106 and the image display element 108. As a result, the interval between the condenser lens and the image display element can be reduced without increasing the angle of incidence of the illumination light on the image display element 108, a bright display image can be obtained, and the device can be made compact. You can

[0009]

However, as proposed in the above publications, when the condenser lens is a double-sided convex lens, the sine condition is not satisfied. Therefore, as shown in FIG. Outward coma tends to occur in the illumination area above.

In this case, the amount of light drops at the four corners of the highest image height, so the illumination area must be expanded in order to make the light intensity uniform on the image display element. Therefore, there is a problem that the light flux that is not actually projected on the screen increases and the brightness of the display image decreases.

[0011]

In order to solve the above problems, according to the present invention, a luminous flux splitting means for splitting an illumination luminous flux from a light source into a plurality of luminous flux parts and a plurality of luminous flux parts are divided by the luminous flux splitting means. An illumination optical system including a homogenizing means for irradiating the image display device with an illumination light flux so as to have a substantially uniform light intensity distribution, wherein the homogenizing means includes at least one positive lens and at least one negative lens. And the lens closest to the light beam splitting means among the lenses of the homogenizing means is a positive lens, and the radius of curvature of the surface of the positive lens on the light beam splitting means side is R1,
When the radius of curvature of the surface on the image display element side is R2, it has a shape satisfying the condition of −2 ≦ (R1 + R2) / (R1−R2) ≦ −1.

By satisfying the condition of the above equation (1),
It is possible to suppress the occurrence of outward coma aberration of the illumination light on the image display element and prevent the light amount drop at the four corners with the highest image height. In addition, it is possible to suppress the entire blur of the illumination area on the image display element and the occurrence of spherical aberration that causes a reduction in the brightness of the displayed image. Therefore, the illumination light intensity can be made substantially uniform without widening the illumination area on the image display element, and it is possible to realize a compact projection type image display device that can obtain a bright display image. .

The above equation (1) shows the shape of the positive lens (eg, condenser lens) arranged closest to the light beam splitting means for splitting the light beam emitted from the light source into a plurality of light beam portions. If the value exceeds the upper limit of the expression (1), outward coma aberration is likely to occur on the image display element, and the light amount drop at the four corners of the highest image height becomes remarkable. In order to make the light intensity uniform, the illumination area must be expanded. Therefore, the light flux that is not actually projected on the screen or the like increases, and the brightness of the display image decreases.

If the lower limit of the expression (1) is exceeded, it becomes difficult to correct spherical aberration, the illumination area is totally blurred, and the brightness of the image on the screen is lowered. become.

Further, in order to achieve the above object, in the present invention, a luminous flux splitting means for splitting an illumination luminous flux from a light source into a plurality of luminous flux portions and an illumination luminous flux divided into a plurality of luminous flux portions by the luminous flux splitting means. Is an illumination optical system including a uniformizing means for irradiating the image display element so as to have a substantially uniform light intensity distribution. The coma is generated.

With this structure, it is possible to prevent light intensity drop at the four corners with the highest image height. In addition, it is possible to suppress the entire blur of the illumination area on the image display element and the occurrence of spherical aberration that causes a reduction in the brightness of the displayed image. Therefore,
Even if the illumination area on the image display element is not widened, the illumination light intensity can be made substantially uniform, and it is possible to realize a compact projection type image display device that can obtain a bright display image.

[0017]

1 shows the configuration of a projection type image display apparatus according to an embodiment of the present invention, and FIG.
The dichroic mirrors DM1 and DM2 and the trimming filter TR used in the projection type image display device.
Shows the spectral transmittance of the. These spectral transmittances are design examples when an ultra-high pressure mercury lamp is used. However,
These numerical values are merely examples, and the dichroic mirror and trimming filter used in the image display device according to the present invention are not limited to these values. For example, various values can be set according to the type of light source.

In FIG. 1, a part of the white illumination light emitted from the light source unit 1 is directly reflected, and the rest is reflected by the reflector 2 to pass through the first fly-eye lens 3 to pass through the mirror M.
After being reflected by 1, the light passes through the second fly-eye lens 4, the polarization conversion element 5, and the condenser lens 6. Generally, as the light source unit 1, a halogen lamp, a metal halide lamp, an ultra-high pressure mercury lamp or the like is used.

Also, the first and second fly-eye lenses 4
The (light flux splitting means) splits the light flux of the white illumination light from the light source unit 1 into a plurality of light flux portions. The condenser lens (positive lens) 6 condenses the white illumination light divided into a plurality of light flux portions.

Of the white illumination light emitted from the condenser lens 6, the blue band light is reflected by the first dichroic mirror (color separation means) DM1 and the green to red band light is transmitted.

The blue band light reflected by the first dichroic mirror DM1 having the spectral transmittance shown in FIG. 2 (a) passes through the negative lens 7a, and its optical path is changed by the reflection mirror M2. The light enters the liquid crystal image display element 9B for blue through 8B.

At this time, due to the optical actions of the condenser lens 6, the negative lens 7a and the field lens 8B, the blue band light has a substantially uniform light intensity distribution.
A predetermined illumination area on B is illuminated.

The image display element 9B is driven in response to a drive signal from a drive circuit (not shown), forms a liquid crystal image, and modulates incident blue band light. The drive circuit is a personal computer (not shown), a video, a television, a DVD.
A drive signal corresponding to an image signal input from an image information supply device such as a player is input to the image display element 9B.

The modulated blue band light is incident on the dichroic prism 10 and the dichroic prism 1
The optical path is changed within 0 and the light enters the projection lens 11.

Here, the dichroic prism (color synthesizing means) 10 is formed by combining and integrating four prism type elements, and dichroic films having different spectral transmittance characteristics are formed between predetermined prism type elements. Has been done.

On the other hand, the green to red band light transmitted through the first dichroic mirror DM1 passes through the negative lens 7b and is incident on the second dichroic mirror (color separation means) DM2 having the spectral transmittance shown in FIG. 2 (b). To do. As shown in FIG. 2B, the second dichroic mirror DM2 has a characteristic of reflecting the green band light G, so that the green band light is reflected here, its optical path is changed, and the field lens (positive lens) 8G. The light enters the image display element 9G for green through.

At this time, due to the optical actions of the condenser lens 6, the negative lens 7b, and the field lens 8G, the green band light has a substantially uniform light intensity distribution.
A predetermined illumination area on G is illuminated.

The image display element 9G is driven in response to a drive signal from a drive circuit (not shown), forms a liquid crystal image, and modulates incident green band light. The drive circuit inputs a drive signal corresponding to the image signal input from the image information supply device described above to the image display element 9G.

The modulated green band light is incident on the dichroic prism 10 and the dichroic prism 1
The optical path is changed within 0 and the light enters the projection lens 11.

The red band light transmitted through the second dichroic mirror DM2 has a trimming filter TR having a spectral transmittance shown in FIG. 2C and concave mirrors M3, M4 and M.
The incident light enters the image display element 9R for red through the line 5.

The image display element 9R is driven in response to a drive signal from a drive circuit (not shown), forms a liquid crystal image, and modulates incident red band light. The drive circuit inputs a drive signal corresponding to the image signal input from the image information supply device described above to the image display element 9R.

At this time, the red band light is applied to a predetermined illumination area on the image display element 9R with a substantially uniform light intensity distribution by the optical actions of the condenser lens 6 and the mirrors M3 to M5.

The modulated red band light enters the dichroic prism 10, the optical path of which is changed by the dichroic prism 10 and enters the projection lens 11.

The light source unit 1 to the field lenses 8B and 8G in the optical paths of the blue and green band lights and the mirror M5 in the optical path of the red band light correspond to the illumination optical system in the claims and the condenser lens 6 When,
The negative lenses 7a and 7b and the field lenses 8B and 8G in the optical path of the blue / green band light and the mirrors M3 to M5 in the optical path of the red band light correspond to the homogenizing means in the claims.

In this way, the blue, green and red band lights incident on the dichroic prism 10 are changed in their optical paths in the dichroic prism 10 and are color-synthesized. It is enlarged and projected. By
A color image is displayed.

FIG. 3 is a development view from the condenser lens 6 closest to the fly-eye lenses 3 and 4 to the image display surface of the image display element 9G in the illumination optical path of the green band light that most affects the brightness of the displayed image. Is shown.

Further, in Numerical Example 1 shown below, the radius of curvature ri of the i-th surface from the entrance surface of the condenser lens 6 to the image display surface of the image display element 9G and the interval (air conversion value) di are shown. , The refractive index ni and the Abbe number νi of the material of each optical element are shown. Note that f is the focal length, fno
Indicates the F number, and ω indicates the half angle of view.

Numerical Example 1 f = 137.20 fno = 1: 2.5 2ω = 7.4 ° r1 = 49.748 d1 = 8.45 n1 = 1.713 ν1 = 53.87 r2 = 319.65 d2 = 51.4 r3 = −27.165 d3 = 1.30 n2 = 1.516 ν2 = 64.14 r4 = 226.60 d4 = 33.15 r5 = 36.474 d5 = 3.6 n3 = 1.516 ν3 = 64.14 r6 = ∞ d6 = 6 r7 = ∞ In the numerical example 1, the shape of the condenser lens 6 is R1 on the light source unit 1 side. And the surface R2 is the image display element 9
When the radius of curvature of the G side surface is used, (R1 + R2) / (R1-R2) = (49.748 + 319.65)
/(49.748-319.65) = -1.37, which satisfies the expression (1).

FIG. 4 shows spot distributions (light intensity distributions) at the four corners of the illumination area on the image display element 9G (image display surface) in Numerical Example 1. As can be seen from FIG. 4, the occurrence of outward coma at the four corners of the illumination area is suppressed. Here, inward coma may be generated at the four corners of the illumination area.

Therefore, it is possible to irradiate the illumination light (green band light) with a uniform intensity distribution without expanding the illumination area to the image display element 9G, and it is possible to prevent the brightness of the displayed image from decreasing.

Next, there is shown Numerical Embodiment 2 in which the lens arrangement is the same as Numerical Embodiment 1 but the focal length is different.

Numerical Example 2 f = 120.07 fno = 1: 2.2 2 ω = 8.4 ° r1 = 50.966 d1 = 8.45 n1 = 1.713 ν1 = 53.87 r2 = 263.51 d2 = 51.4 r3 = −38.020 d3 = 1.30 n2 = 1.516 ν2 = 64.14 r4 = ∞ d4 = 33.15 r5 = 37.86 d5 = 3.6 n3 = 1.516 ν3 = 64.14 r6 = ∞ d6 = 6 r7 = ∞ In the numerical example 2, the shape of the condenser lens 6 is R1 on the light source unit 1 side. And the surface R2 is the image display element 9
When the radius of curvature of the G side surface is used, (R1 + R2) / (R1-R2) = (50.966 + 263.51)
/(50.966-263.51)=-1.48, which satisfies the equation (1).

FIG. 5 shows spot distributions (light intensity distributions) at the four corners of the illumination area on the image display element 9G (image display surface) in Numerical Example 2. As can be seen from FIG. 5, the occurrence of outward coma is suppressed at the four corners of the illumination area. Here, the coma may be intentionally generated inward at the four corners of the illumination area.

Therefore, it is possible to irradiate the illumination light (green band light) with a uniform intensity distribution without expanding the illumination area to the image display element 9G, and it is possible to prevent a decrease in the brightness of the displayed image.

In the present embodiment, the case where three concave mirrors are used in the optical path of the red band light having the longest optical path length has been described, but the number and shape of the mirrors are not limited to this in the image display device according to the present invention. However, a system combining a convex mirror and a plane mirror may be used. Also, a system in which a lens and a mirror are combined may be used.

Furthermore, in the present embodiment, a so-called three-plate type image display device using three image display devices for three colors has been described, but the number of image display devices in the image display device of the present invention is not limited to this. Not something that, for example,
The present invention can be applied to a single-plate type image display device using only one image display element.

In this embodiment, the case where a so-called 4P prism is used as the dichroic prism has been described, but a 3P prism or a cross dichroic prism may be used.

[0048]

As described above, according to the present invention, by satisfying the condition of the above expression (1), it is possible to suppress the occurrence of outward coma aberration in the illumination light on the image display element. It is possible to prevent light falloff at the four highest corners of. Further, even if inward coma is generated in the illumination light on the image display element, it is possible to prevent the light amount from dropping at the four corners of the image display element.

Moreover, it is possible to suppress the occurrence of spherical aberration that causes the entire blur of the illumination area on the image display element and the accompanying reduction in the brightness of the displayed image.

Therefore, the illumination light intensity can be made substantially uniform without expanding the illumination area on the image display element, and it is possible to realize a projection type image display device which is compact and can obtain a bright display image. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an optical system of a projection type image display device which is an embodiment of the present invention.

FIG. 2 is a schematic diagram showing spectral transmittance characteristics of a dichroic mirror and a trimming filter used in the projection type image display device.

FIG. 3 is a development view from a condenser lens of an optical path of green band light to an image display surface of an image display element in the projection type image display device.

FIG. 4 is a spot distribution chart of four corners of an illumination area in Numerical Example 1 of the projection type image display device.

FIG. 5 is a spot distribution chart of four corners of an illumination area in Numerical Example 2 of the projection type image display device.

FIG. 6 is a development view of an optical path of a conventional projection type image display device.

FIG. 7 is a spot distribution chart of four corners of an illumination area in the case where a condenser lens having a double-sided convex is used in an illumination optical system of a conventional projection type image display device.

[Explanation of symbols]

1 light source 2 reflector 3 First fly-eye lens 4 second fly-eye lens 5 Polarization conversion element 6 condenser lens 7a, 7b negative lens 8R, 8G, 8B field lens 9R, 9G, 9B image display device 10 dichroic prism 11 Projection lens M1, M2 reflective mirror M3, M4, M5 concave mirror DM1, DM2 Dichroic mirror TR trimming filter 101 light source 102 reflector 103,104 Fly-eye lens 105 Polarization conversion element 106 condenser lens 107 field lens 108 image display device 109 Projection lens

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Claims (12)

[Claims] 1. A luminous flux splitting means for splitting an illuminating luminous flux from a light source into a plurality of luminous flux parts, and an illuminating luminous flux divided into a plurality of luminous flux parts by the luminous flux splitting means into a substantially uniform light intensity distribution on an image display element. An illumination optical system including a homogenizing unit that irradiates the light so that the homogenizing unit has at least one positive lens and at least one negative lens, and When the lens closest to the beam splitting means is a positive lens, the radius of curvature of the surface of the positive lens on the side of the beam splitting means is R1, and the radius of curvature of the surface on the image display element side is R2, An illumination optical system having a shape satisfying a condition of −2 ≦ (R1 + R2) / (R1−R2) ≦ −1. 2. The illumination optical system according to claim 1, wherein the uniformizing means has two positive lenses and one negative lens. 3. The illumination optical system according to claim 1, wherein the homogenizing means has a positive lens, a negative lens and a positive lens in this order from the side of the light beam splitting means. 4. The illumination optical system according to claim 1, wherein the homogenizing means causes inward coma aberration in the illumination light on the image display element. 5. A luminous flux splitting means for splitting an illuminating luminous flux from a light source into a plurality of luminous flux parts, and an illuminating luminous flux divided into a plurality of luminous flux parts by the luminous flux splitting means into a substantially uniform light intensity distribution on an image display element. An illumination optical system including a homogenizing means for irradiating the image display element, wherein illumination light emitted from the homogenizing means and illuminating the image display element causes inward coma aberration. system. 6. The homogenizing means includes at least one optical element having a positive refractive power and at least one optical element having a negative refractive power.
The illumination optical system described in. 7. The homogenizing means has two optical elements having positive refractive power and one optical element having negative refractive power, according to claim 5 or 6. Illumination optics. 8. The uniformizing means includes an optical element having a positive refracting power, an optical element having a negative refracting power, and an optical element having a positive refracting power in this order from the side of the light beam splitting means. The illumination optical system according to any one of claims 5 to 7. 9. A plurality of image display elements, each of which includes a color separation unit that separates an illumination light beam divided into a plurality of light beam portions by the light beam division unit into a plurality of color light beams, the color light beams being provided for each color. The illumination according to any one of claims 1 to 8, further comprising a color synthesizing unit that illuminates and synthesizes a plurality of color light fluxes modulated by these image display elements to project and display a color image. Optical system. The projection-type image display device according to claim 3, wherein 10. The color separation means is configured by using a dichroic mirror.
The illumination optical system described in. 11. The color synthesizing means is configured by using a dichroic prism configured by combining three or more prism type elements.
Or the illumination optical system according to item 10. 12. The illumination optical system according to claim 1, an image display element to which an illumination light beam is guided by the illumination optical system, and image light modulated by the image display element. A projection-type image display device, comprising: