JP2009175486A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device reducing color unevenness of a projection image by correcting optical characteristics of the whole optical element. <P>SOLUTION: Since a first dichroic mirror 31a has optical characteristics matching incident angles α, β, γ and δ of illumination light in A-A and B-B cross sectional directions, deviation of optical characteristics generated according to incident angle dependence of illumination light can be correctly or approximately corrected in the whole of the first dichroic mirror 31a. Accordingly, prescribed wavelength components can be suitably reflected or transmitted in respective regions AL, AC, AR, AU and AD of an element surface 3c of the first dichroic mirror 31a and color unevenness of the whole projection image can be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an image display device that illuminates a liquid crystal panel or the like with an illumination optical system and forms an image on the liquid crystal panel or the like.

In an image display device, an optical element such as a dichroic mirror has dependency on a light incident angle, and an optical characteristic (specifically, for example, a cutoff half-value wavelength) changes for each light incident angle.
For this reason, for example, there is a problem that the optical characteristics of the dichroic mirror disposed in an inclined manner with respect to the optical axis in the color separation optical system change in the plane, and the color characteristics of the image display device vary. Therefore, there is a technique in which the dichroic characteristics are changed in accordance with the incident angle by giving a characteristic inclination to the left and right (corresponding to the lateral direction of the surface length) of the multilayer film of the dichroic mirror, thereby canceling the angle dependence of the incident light ( For example, see Patent Document 1). In addition, there is one that prevents unevenness in optical characteristics by providing thickness unevenness or refractive index unevenness inclined in a specific direction according to the position of the dichroic mirror (see, for example, Patent Document 2). Here, the cut-off half-value wavelength means a wavelength at which the transmittance is 50%.
JP-A-3-291644 Japanese Patent Laid-Open No. 6-18834

However, like the dichroic mirror described above, the optical characteristics are, for example, left and right directions (
In the case of changing in the horizontal direction (longitudinal direction), the angle dependency of the light ray incident in the vertical direction (vertical direction) cannot be canceled. Therefore, the angle dependency of the incident light remains in the vertical direction, and there is a problem that the color unevenness of the entire projected image cannot be reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image display device that reduces color unevenness of a projected image by making it possible to correct the entire optical characteristics of an optical element.

In order to solve the above problem, an image display device according to the present invention includes a light source that emits light source light,
Illumination optical system for making light source light uniform, color separation optical system for separating illumination light emitted from the illumination optical system into each color light, and light beams of each color light separated by the color separation optical system, respectively The color separation optical system is disposed at a predetermined angle with respect to the system optical axis, reflects a predetermined wavelength component of the illumination light, and transmits other wavelength components. As a result, the illumination light is branched, and at least one of reflectance and transmittance corresponds to a tilt direction having a predetermined angle along the element surface and a predetermined angle with respect to the first direction along the element surface. A flat optical element having optical characteristics that change with respect to the second direction.

In the image display device, the optical element has optical characteristics corresponding to the incident angle of the illumination light in the first direction and the second direction, so that the optical characteristic shift caused by the incident angle dependency of the illumination light. Can be corrected accurately or approximately in the entire optical element. Thereby, the predetermined wavelength component can be appropriately reflected or transmitted at each position on the element surface of the optical element,
Color unevenness of the entire projected image can be suppressed.

Further, in a specific aspect or viewpoint of the present invention, the optical characteristics of the optical element are corrected by changing the half-value wavelength of the cutoff depending on the film thickness configuration of the multilayer film. In this case, by changing the half-value wavelength of the cutoff, it is possible to cope with a shift in optical characteristics depending on the incident angle at each position on the element surface of the optical element.

According to another aspect of the present invention, the first direction and the second direction are in a vertical relationship. In this case, for example, the optical characteristics of the entire optical element can be corrected by changing the optical characteristics in the horizontal and vertical directions of the optical element.

According to still another aspect of the present invention, the rate of change of the optical characteristics of the optical element monotonously increases or decreases monotonously in the first direction, and is one end of the element surface with respect to the system optical axis in the second direction. Monotonically increases on the side and monotonically decreases on the other side. In this case, the optical characteristics of the entire optical element can be corrected by changing the optical characteristics in the two directions corresponding to the incident angle of the illumination light at each position on the element surface of the optical element.

According to still another aspect of the present invention, the optical characteristics of the optical element change at a constant rate in the first direction, and change symmetrically with respect to the system optical axis in the second direction. In this case, the optical characteristics in two directions corresponding to the incident angle of the illumination light incident at a uniform angle change with respect to the second direction incident on the element surface of the optical element with a symmetrical angle change with respect to the first direction. By changing, the optical characteristics of the entire optical element can be corrected.

According to still another aspect of the present invention, the optical element is a dichroic mirror.
In this case, by correcting the optical characteristics of the dichroic mirror, it is possible to efficiently transmit or reflect a predetermined wavelength of the illumination light.

The structure and the like of an image display device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram for explaining the structure of an image display apparatus according to an embodiment. The image display device 100 is a light source 10, an illumination optical system 20, a color separation optical system 30, liquid crystal light valves 40a, 40b, and 40c that are light modulation devices, a cross dichroic prism 50, and a projection optical system. A projection lens 60.

In the image display device 100, the light source 10 is a light source device that generates substantially white light having a light quantity sufficient for image light formation, such as a high-pressure mercury lamp, and includes a light emitting tube 10a that generates light source light, and light emission. Reflector 10b having a concave mirror that reflects light source light from tube 10a forward
With.

The illumination optical system 20 includes a collimating lens 22 that is a light collimating unit that collimates the light from the light source, and first and second fly-eye lenses 23a that constitute an integrator optical system for equalizing the light by dividing and superimposing it. , 23b, a polarization conversion element 24 that aligns the polarization direction of light, and a superimposing lens 25 that superimposes the light that has passed through both fly-eye lenses 23a, 23b, and forms substantially white illumination light. In the illumination optical system 20, the collimating lens 22 converts the luminous flux direction of the illumination light emitted from the light source 10 to be substantially parallel. The first and second fly-eye lenses 23a and 23b are each composed of a plurality of element lenses arranged in a matrix, and the light that has passed through the collimating lens 22 is divided by the element lenses constituting the first fly-eye lens 23a. The first fly-eye lens 23 is collected by an element lens that individually collects light and constitutes the second fly-eye lens 23 b.
The split luminous flux from a is emitted with an appropriate divergence angle. The polarization conversion element 24 is formed of an array having a PBS, a mirror, a phase difference plate and the like as a set of elements, and the first fly-eye lens 23.
It has the role of aligning the polarization direction of each partial light beam divided by a with linearly polarized light in one direction. The superimposing lens 25 appropriately converges the illumination light that has passed through the polarization conversion element 24 as a whole, and enables superimposing illumination on the illuminated areas of the liquid crystal light valves 40a, 40b, and 40c, which are the light modulation devices of the subsequent stages.

The color separation optical system 30 includes first and second dichroic mirrors 31a and 31b, reflection mirrors 32a, 32b, and 32c, and three field lenses 33a, 33b, and 33c. Here, as shown in FIG. 1, the first and second dichroic mirrors 31a and 31b are
The optical system 20 is disposed with an inclination of 45 degrees with respect to the system optical axis OA extending from the illumination optical system 20. The color separation optical system 30 separates the illumination light uniformized by the illumination optical system 20 into three colors of blue (B), green (G), and red (R), and separates each color light into a subsequent liquid crystal light valve. 40a, 40b
, 40c. More specifically, first, the first dichroic mirror 31a is B
Of the three colors of GR, G light and R light are transmitted and B light is reflected. The second dichroic mirror 31b reflects G light and transmits R light out of the two colors of GR. Next, in the color separation optical system 30, the B light reflected by the first dichroic mirror 31 a is reflected by the reflection mirror 32.
It enters into the field lens 33a for adjusting an incident angle through a. Further, the G light transmitted through the first dichroic mirror 31a and reflected by the second dichroic mirror 31b is incident on the field lens 33b for adjusting the incident angle. Further, the R light transmitted through the second dichroic mirror 31b is transmitted to the relay lenses LL1 and LL2 and the reflection mirror 32.
The light enters the field lens 33c for adjusting the incident angle through b and 32c.

The liquid crystal light valves 40 a, 40 b, and 40 c are non-light-emitting light modulation devices that modulate the spatial intensity distribution of incident illumination light, and are illuminated corresponding to each color light emitted from the color separation optical system 30. The The B light reflected by the first dichroic mirror 31a enters the liquid crystal light valve 40a through the field lens 33a and the like. First dichroic mirror 3
The G light transmitted through 1a and reflected by the second dichroic mirror 31b enters the liquid crystal light valve 40b via the field lens 33b and the like. The R light transmitted through the first and second dichroic mirrors 31a and 31b is incident on the liquid crystal light valve 40c via the field lens 33c and the like. Each liquid crystal light valve 40a, 40b, 40c forms image light of each color corresponding to each.

The cross dichroic prism 50 combines the image lights of the respective colors from the liquid crystal light valves 40a, 40b, and 40c. More specifically, the cross dichroic prism 50
Has a substantially square shape in plan view in which four right-angle prisms are bonded together, and a pair of dielectric multilayer films 51a and 51b intersecting in an X shape are formed at the interface where the right-angle prisms are bonded together. One first dielectric multilayer film 51a reflects B light and the other second dielectric multilayer film 51b.
Reflects R light. The cross dichroic prism 50 reflects the B light from the liquid crystal light valve 40a by the dielectric multilayer film 51a and emits it to the right in the traveling direction, so that the liquid crystal light valve 4
The G light from 0b goes straight and is emitted through the dielectric multilayer films 51a and 51b, and the R light from the liquid crystal light valve 40c is reflected by the dielectric multilayer film 51b and emitted to the left in the traveling direction. In this manner, the B light, the G light, and the R light are combined by the cross dichroic prism 50 to form combined light that is image light corresponding to a color image.

The projection lens 60 is a projection optical system, and projects the color image on a screen (not shown) by enlarging the image light by the combined light formed through the cross dichroic prism 50 with a desired magnification.

Hereinafter, the first dichroic mirror 31 constituting the color separation optical system 30 will be described with reference to the drawings.
The structure and function of a will be described. FIG. 2 is a conceptual diagram of the first dichroic mirror 31a, FIG. 2 (A) is a front view of the first dichroic mirror 31a, and FIG. 2 (B) is a cross-sectional view taken along the line A-A in FIG. 2 (C) is a cross-sectional view taken along the line BB. FIG. 3 is a diagram showing the relationship between the position of the first dichroic mirror 31a and the film thickness of the dielectric multilayer film 3b. FIG. 3 (A) shows the film in the section AA in FIG. 2 (B). FIG. 3 (B) is a diagram showing thickness characteristics.
These are figures which show the film thickness characteristic in the BB cross section of FIG.2 (C).

The illumination light incident on the first dichroic mirror 31a is converged by the superimposing lens 25 and is not uniform. For this reason, as will be described in detail below, the first dichroic mirror 31a has optical characteristics that are secondarily distributed in the longitudinal lateral direction and the longitudinal direction perpendicular thereto. As shown in FIG. 1, the first dichroic mirror 31 a is disposed with an inclination of 45 degrees with respect to the system optical axis OA extending from the illumination optical system 20. As shown in FIG.
The dichroic mirror 31a has a configuration in which a dielectric multilayer film 3b is formed on one surface of a transparent flat glass 3a as a substrate. The dielectric multilayer film 3b is disposed facing the vapor deposition source while rotating the flat glass 3a, for example, rotating and revolving, etc., and is dielectrically applied to each position on the surface of the flat glass 3a with a mask or the like interposed between the dielectric glass 3a and the vapor deposition source. It is formed by adjusting the deposition amount of the body. The surface of the dielectric multilayer film 3b is the element surface 3c of the first dichroic mirror 31a.

As shown in FIG. 2, in the image display apparatus 100 described above, since the illumination light from the light source 10 is not a perfect parallel light beam, the incident angles α, β, and the incident light on the element surface 3c of the first dichroic mirror 31a. γ and δ differ depending on the position of the first dichroic mirror 31a. Therefore, illumination light having an incident angle shifted from 45 degrees according to the position on the element surface 3c is incident on the element surface 3c. For this reason, the dielectric multilayer film 3b of the first dichroic mirror 31a is set to have different thicknesses corresponding to the incident angles α, β, γ, and δ of the illumination light, and the optical characteristics, for example, the transmittance characteristics change. It is the composition to do. That is, the dielectric multilayer film 3b has a first direction, that is, a second direction that is perpendicular to the AA cross-sectional direction and the AA cross-sectional direction, that is, BB.
The transmittance characteristic varies along the element surface 3c in the cross-sectional direction. More specifically, in FIGS. 1 and 2, the incident angle β of the light beam a incident on the left side of the first dichroic mirror 31a is larger than the incident angle α of the light beam b incident on the center of the first dichroic mirror 31a. The thickness of the region AL of the dielectric multilayer film 3b is smaller than the thickness of the region AC. On the other hand, the incident angle γ of the light ray c incident on the right side of the first dichroic mirror 31a is smaller than the incident angle α, and the thickness of the region AR of the dielectric multilayer film 3b is larger than the thickness of the region AC. Further, the incident angle δ of the rays d1 and d2 incident on the upper and lower sides of the first dichroic mirror 31a is larger than the incident angle α, and the thicknesses of the areas AU and AD of the dielectric multilayer film 3b are the areas AC.
Thinner than the thickness. That is, as shown in FIG. 3, the thickness of the dielectric multilayer film 3b increases at a constant rate from the region AL to the region AR in the AA cross-sectional direction, and with respect to the system optical axis OA in the BB cross-sectional direction. In contrast, the thickness of the dielectric multilayer film 3b in the regions AU and AD decreases toward the outside. Here, the areas AL, AC, AR, AU, and AD are in continuous relation with the areas AL, AC, AR, AU, and AD on the element surface 3c.

FIG. 4 is a diagram showing the relationship between the wavelength of illumination light incident on the first dichroic mirror 31a and its transmittance. FIG. 5 shows the incident angle dependence of the transmittance characteristic in the region AC of the first dichroic mirror 31a. The transmittance characteristics e, f, and g shown in FIG.
This corresponds to the case where the incident angle to c is 45 degrees, and corresponds to the transmittance characteristics in the regions AL, AC, and AR in which the light rays a, b, and c in FIGS. 1 and 2 are incident, respectively. Further, the transmittance characteristics h, i, and j shown in FIG. 5 are transmittance characteristics when the incident angles α of the illumination light incident on the element surface 3c in the region AC are 30 degrees, 45 degrees, and 60 degrees, respectively.

As shown in FIG. 5, in the region AC, the half-value wavelength moves to the short wavelength side as the incident angle α increases, and the half-value wavelength moves to the long wavelength side as the incident angle α decreases. This is another area AL
The same applies to AR. That is, the half-value wavelength shifts to the short wavelength side as the incident angles β and γ increase, and the half-value wavelength moves to the long wavelength side as the incident angles β and γ decrease. Therefore, FIG.
By using this relationship, the transmittance characteristic e is apparently shifted to the transmittance characteristic f by thinning the film thickness so as to cancel the increase in the incident angle β in the region AL where the incident angle β is generally large. Thus, it can be apparently matched with the transmittance characteristic of the region AC. Further, by increasing the film thickness so as to cancel the increase in the incident angle γ in the area AR in which the incident angle γ is generally small, the transmittance characteristic g is apparently shifted to the transmittance characteristic f, and the area AC is increased. Apparently, it can be matched with the transmittance characteristic. As described above, the optical characteristics of the first dichroic mirror 31a in the AA cross-sectional direction correspond to the incident angles α, β, and γ of the illumination light. Therefore, the transmission at the incident position of the illumination light in the AA cross-sectional direction is performed. The rate is corrected and a predetermined wavelength can be transmitted or reflected.

The above is the same for the optical characteristics in the BB cross-sectional direction of the first dichroic mirror 31a, and the optical characteristics in the BB cross-sectional direction correspond to the incident angle δ of the illumination light.
The transmittance at the incident position of the illumination light in the BB cross-sectional direction is corrected, and a predetermined wavelength can be transmitted or reflected.

As is apparent from the above description, in the image display device 100 of the present embodiment, the first dichroic mirror 31a has transmittance characteristics corresponding to the incident angles α, β, γ, and δ of the illumination light. As shown in FIG. 4, the transmittance characteristic e generated according to the incident angle dependency of the illumination light
, G can be apparently shifted to the transmittance characteristic f. In this embodiment, A-
Since the half-value wavelength of the cut-off is changed in the A cross-sectional direction and the BB cross-sectional direction, it can be corrected in the entire first dichroic mirror 31a. Thereby, a predetermined wavelength component can be reflected or transmitted in each region AL, AC, AR, AU, AD of the element surface 3c of the first dichroic mirror 31a, and color unevenness of the entire projected image can be suppressed.

In addition, this invention is not restricted to said embodiment, In the range which does not deviate from the summary, it can implement in a various aspect, For example, the following deformation | transformation is also possible.

In the image display apparatus 100 described above, the film thickness characteristic of the first dichroic mirror 31a is not limited to the above-described film thickness characteristic, and can be an appropriate film thickness characteristic corresponding to the incident angle of illumination light.

In the above embodiment, the optical characteristics of the first dichroic mirror 31a are corrected.
The optical characteristics of the second dichroic mirror 31b may also be corrected. In this case, for example, correction is performed according to the transmittance characteristic deviation of the second dichroic mirror 31b.

Moreover, in the said embodiment, although the optical characteristic of the 1st dichroic mirror 31a when illumination light converges, when illumination light diverges, it can correct | amend according to the optical characteristic.

Moreover, in the said embodiment, although the 1st dichroic mirror 31a reflected B light, when it uses what reflects R light, it can correct | amend according to the optical characteristic.

Moreover, in the said embodiment, although the high pressure mercury lamp was used as a lamp used for the light source 10,
A metal halide lamp or the like may be used.

In the above embodiment, the first dichroic mirror 31a is disposed at 45 degrees with respect to the system optical axis OA of the illumination optical system 20. However, the first dichroic mirror 31a may be disposed at an arbitrary angle at which the optical characteristics are optimized by the optical element.

Moreover, in the said embodiment, although the 1st dichroic mirror 31a assumed that it had a film thickness characteristic as shown in FIG. 3, FIG. 3 is only an illustration and a film thickness characteristic is according to the structure of the dielectric multilayer film 3b. Therefore, the amount of inclination of the film thickness characteristic may be adjusted according to the incident angle of the light beam with respect to the first dichroic mirror 31a.

In the above embodiment, a pair of fly-eye lenses 23a and 23b is used to divide the light from the light source 10 into a plurality of partial light beams. However, the present invention uses such a fly-eye lens, that is, a lens array. The present invention can also be applied to an image display device that is not used. Further, the fly-eye lenses 23a and 23b can be replaced with rod integrators.

Moreover, in the said embodiment, the polarization conversion element 24 which makes the light from the light source 10 polarized light of a specific direction.
However, the present invention is also applicable to an image display apparatus that does not use such a polarization conversion element 24.

In the above embodiment, an example in which the present invention is applied to a transmissive image display device has been described. However, the present invention can also be applied to a reflective image display device. here,"
"Transmission type" means that the liquid crystal light valve including the liquid crystal panel is a type that transmits light, and "Reflective type" means that the liquid crystal light valve is a type that reflects light is doing. The light modulation device is not limited to a liquid crystal panel or the like, and may be a light modulation device using a micromirror, for example.

Further, as the image display device, there are a front image display device that performs image projection from the direction of observing the projection surface and a rear image display device that performs image projection from the opposite side to the direction of observing the projection surface. The configuration of the image display apparatus shown in 1 can be applied to any of them.

Moreover, in the said embodiment, although the example of the image display apparatus 100 using three liquid crystal light valves 40a-40c was given, this invention is an image display apparatus using only one liquid crystal panel,
The present invention can also be applied to an image display device using two liquid crystal panels or an image display device using four or more liquid crystal panels.

In the above embodiment, the color separation optical system 30 and the liquid crystal light valves 40a, 40b, 40
The light modulation of each color is performed using c or the like, but instead, for example, a color wheel that is illuminated by the light source 10 and the illumination optical system 20 and the light of the color wheel that is composed of pixels of the micromirror is irradiated. By using a combination with a device to be used, color light modulation and synthesis can be performed.

It is a figure explaining the image display apparatus which concerns on one Embodiment of this invention. (A)-(C) are the conceptual diagrams of the 1st dichroic mirror of FIG. (A), (B) is a figure which shows the film thickness characteristic of the 1st dichroic mirror of FIG. It is a figure which shows the transmittance | permeability characteristic of the 1st dichroic mirror of FIG. It is a figure which shows the incident angle dependence of the transmittance | permeability characteristic in area | region AC of a 1st dichroic mirror.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source, 20 ... Illumination optical system, 30 ... Color separation optical system, 31a, 31b ... Dichroic mirror, 40a, 40b, 40c ... Liquid crystal light valve, 50 ... Cross dichroic prism, 60 ... Projection lens, 100 ... Image display apparatus , OA ... System optical axis

Claims (6)

A light source that emits light source light;
An illumination optical system for making the light source light uniform;
A color separation optical system that separates the illumination light emitted from the illumination optical system into each color light;
A light modulation device for each color illuminated by a light beam of each color light separated by the color separation optical system,
The color separation optical system is disposed at a predetermined angle with respect to the system optical axis, reflects a predetermined wavelength component of the illumination light, and splits the illumination light by transmitting other wavelength components. In addition, at least one of reflectance and transmittance is a first direction corresponding to the inclination direction of the predetermined angle along the element surface and a second angle that forms a predetermined angle with respect to the first direction along the element surface. An image display device having a flat plate-like optical element having optical characteristics that change with respect to the direction of the image. The image display apparatus according to claim 1, wherein the optical characteristic of the optical element is corrected by changing a half-value wavelength of a cutoff depending on a film thickness configuration of the multilayer film. The image display apparatus according to claim 1, wherein the first direction and the second direction are in a vertical relationship. The change rate of the optical characteristic of the optical element monotonously increases or monotonously decreases in the first direction, and monotonically increases on one end side of the element surface with respect to the system optical axis in the second direction, and the other end side. The image display device according to claim 3, wherein the image display device monotonously decreases. The image display device according to claim 4, wherein the optical characteristics of the optical element change at a constant rate in the first direction and change symmetrically with respect to the system optical axis in the second direction. The image display device according to claim 1, wherein the optical element is a dichroic mirror.

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