JPH05181135A - Polarizing illuminating device and projection display device using it - Google Patents

Abstract

PURPOSE:To reduce the unevenness of brightness and the irregularity of color which are caused corresponding to the pitch of a polarizing beam splitter when the polarizing beam splitter is formed into an array in order to make a polarizing illuminating device compact. CONSTITUTION:In the polarizing illuminating device provided with a light source 1 and a polarizing beam splitter 20 which is formed into the array, the pitch P is set to 2Ltantheta>=P when it is assumed that the spread angle of a luminous flux made incident on the beam splitter 20 is + or -theta, a distance between a substance to be illuminated and the beam splitter 20 is L and the pitch of the beam splitter 20 is P. Thus, the irregularity of the color and the unevenness of the brightness of illuminating light on the substance to be illuminated are made inconspicuous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized illumination device and a projection display device having the polarized illumination device.

[0002]

2. Description of the Related Art In recent years, a polarized illumination device equipped with arrayed polarizing elements has been proposed in order to reduce the size and weight of the polarized illumination device. FIG. 16 is a main part configuration diagram showing a conventional example of a projection display device using such a polarized illumination device, which is described in JP-A-2-62475.

Reference numeral 1 is a light source, 2 is a reflection mirror, 20 is a polarizing element, 203a and 203b are polarization separating films, 7 is a liquid crystal light valve, and 22 is a λ / 4 optical phase plate. In FIG. 16, the two polarization separation action films 203a and 203b are in contact with each other at their ends at an angle of approximately 90 degrees, and the polarization element 20
Has a repeating structure with them as a unit as shown in the figure. Random light Ao from the light source 1 that has been converted into substantially parallel light by the reflecting mirror 2 is used as the polarization separation film 20 of the polarization element 20.
The P-polarized light Ap is transmitted and the S-polarized light As is reflected by 3a. The S-polarized light As is further reflected by the other polarization separation film 203b installed in the optical path, passes through the λ / 4 optical phase plate 22 whose optical axis is set in the desired direction, and becomes circularly polarized light Ar. , P-polarized light A by passing through the λ / 4 optical phase plate 22 again via the light source 1 and the reflecting mirror 2.
It becomes p ′, passes through the polarization splitting film, and enters the liquid crystal light valve 7. In this projection display device, both the P-polarized light Ap and the S-polarized light As separated by the polarization separation action film 203a or 203b are polarized lights Ap and Ap 'having the same polarization direction, and the liquid crystal light valve 7 is turned on. Since it can illuminate, the light utilization efficiency can be significantly improved compared to a projection display device that does not use a polarized light illumination device, and the arrayed structure achieves weight and size reduction compared to general polarized light illumination devices. it can.

[0004]

However, when the polarizing elements are arrayed, unevenness in brightness or unevenness in color with one unit width being the pitch P occurs, and a polarized illumination device using such a polarizing element. If the projection display device is configured with, the projected image becomes very difficult to see.

A state in which color unevenness occurs will be described using a conventional example. Since the light source has a finite diameter, the light directed to the object to be illuminated (the liquid crystal light valve in the conventional example) by the reflection mirror is not a perfect parallel light but a light with a certain divergence angle. FIG. 17 shows how such light passes through the polarization splitting film and enters the liquid crystal light valve.

As is well known, the polarization splitting action film which is a dielectric multilayer film has an angle dependence, and the polarization splitting characteristic is degraded unless the light is incident at a desired angle, or the light after passing through the polarization splitting action film. The wavelength component of changes. For example, it is assumed that when white light is incident on the polarization separating film at an angle larger than 45 degrees, the emitted light is reddish, and when the angle is smaller than 45 degrees, the emitted light is bluish. Then, as shown in FIG. 17, the illumination light that illuminates the liquid crystal light valve 7 is divided into a reddish region C, a bluish region B, and a mixed region A, resulting in color unevenness. ..

The brightness unevenness can be similarly explained. For example, if light is incident on the polarization splitting film at an angle larger than 45 degrees, the transmittance of P-polarized light becomes poor, and if the angle is smaller than 45 degrees, the transmittance of P-polarized light becomes good. A dark area occurs, that is, uneven brightness occurs.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin polarizing element in which brightness unevenness and color unevenness corresponding to the pitch of the array of polarizing elements are not noticeable. Due to the fact that the luminous flux from the illumination means is never a perfect parallel light due to its finiteness, the divergence angle ± θ of the luminous flux incident on the polarizing element and the distance L between the polarizing element and the illuminated body The optimum pitch P of the arrayed polarizing means is determined.

[0009]

FIG. 1 shows the configuration of a projection display apparatus using a polarizing element of the present invention, which is a light source 1 composed of a halogen lamp, a metal halide lamp or the like, and a part of a light beam emitted from the light source 1 is reflected. A reflecting mirror 2, a heat ray cut filter 3 that absorbs or reflects heat rays of a light flux incident from the light source 1 directly or through the reflecting mirror 2, a condenser lens 4 that converts the light flux from which the heat rays are removed into a parallel light flux, and an optical rotator. A λ / 4 optical phase plate 22, a polarizing element 20 for converting a parallel light beam into a linearly polarized light, and a condenser lens 2 for condensing the parallel light beam that has become the linearly polarized light into the pupil of the projection lens 10.
1. A liquid crystal light valve 7 that modulates linearly polarized light according to an image signal, a polarizing plate 8 that transmits only the component in the transmission axis direction of the modulated linearly polarized light, and a screen (not shown) that transmits the linearly polarized light. And a projection lens 10 for enlarging and projecting.

FIG. 2 is a perspective view of a part of the polarizing element of the present invention, and FIG. 3 is a sectional view of the same.

One unit is composed of a right-angle prism 201 having a surface on the incident light side, a right-angle prism 202 having a surface on the output light side, and a polarization splitting action film 203 provided at the joint portion of the right-angle prisms 201 and 202. Has been done. The polarizing element has a structure in which a plurality of the individual units are joined as shown in the drawing, and a total reflection mirror 204 is provided in the joined portion.

The operation of the polarizing element 20 of the present invention will be described with reference to FIG.

The polarization splitting action film 203 reflects the polarization component parallel to the plane of the polarization splitting action film (referred to as S-polarized light) with respect to the 45 ° incident light on the polarization splitting action film 203, and the S polarization light. A polarized light component perpendicular to (a P-polarized light) has a transmitting effect.

In FIG. 4, the light beam α which is indefinite polarized light is P-polarized light L of the light beam α in the polarization separation film 203.
_P is transmitted as it is and emitted from the polarization element 20.
On the other hand, the reflected S-polarized light L _S is vertically reflected by the total reflection mirror 204, reflected again by the polarization splitting film 203, and then emitted as L _S ′ in the direction opposite to L _P.
As is apparent from the figure, the back side of the total reflection mirror 204, that is, the side facing the right-angle prism 202 does not need to reflect the light flux, and thus may be a light absorbing surface to prevent irregular reflection.

The process after the S-polarized light L _S ′ will be described with reference to FIG. For simplicity, FIG. 5 shows a light source 1, a reflecting mirror 2, a condenser lens 4, a λ / 4 optical phase plate 22, and a polarizing element 2.
Only 0 is shown and the others are omitted.

As described with reference to FIG. 4, the S-polarized light L _S ′ separated by the polarization element 20 is subjected to the action of the λ / 4 optical phase plate 22 whose optical axis is set in the desired direction and is circularly polarized light. After reaching L _C , it goes through the condenser lens 4 to the light source 1 located at the focal position of the condenser lens 4 and at the position of the center of curvature of the reflecting mirror 2. A part of the circularly polarized light L _C incident on the light source 1 is transmitted while maintaining its polarization state as shown in the figure, and is reflected by the reflecting mirror 2. When the circularly polarized light L _C is reflected, The rotation direction is changed with respect to the traveling direction to become circularly polarized light L _C ′, which is directed to the light source 1. Here, for the sake of clarity, the optical paths before and after reflection are shifted. The circularly polarized light L _C ′ that has passed through the light source 1 again travels through the condenser lens 4 to the λ / 4 optical phase plate 22 and the polarizing element 20. The S-polarized light L _S ′ is thus converted into the condition L _S ′ → L _C → L _C ′ → L _P ′, and as a result, passes through the λ / 4 optical phase plate twice. Therefore, the λ / 4 optical phase plate 22 has the same function as that of the λ / 2 optical phase plate and can rotate the polarization direction of the S-polarized light L _S ′ by 90 degrees, so that the S-polarized light L _{S is obtained.} ′ Is P
The polarized light L _P ′ is transmitted through the polarizing element 20.

On the other hand, among the circularly polarized light L _C , the light diffused by the light source 1 and having a slightly changed polarization state behaves like light emitted from the light source and illuminates the polarizing element 20 via the condenser lens 4. .. Then, the same operation is repeated until P-polarized light L _P ′ is obtained.

In the present embodiment, as shown in FIG. 5, the pitch of the repeating structure is P, the divergence angle of the light beam incident on the polarizing element is θ, which is not shown, and the distance between the illuminated object and the polarizing element is L. Then, if 2Ltan θ ≧ P, the color unevenness and the brightness unevenness caused by the array structure of the polarizing element can be canceled well on the illuminated body. This state is shown in FIG. 6 by taking the luminance unevenness as an example. FIG. 6 shows an arrangement that satisfies the condition of 2L tan θ = P. Angle θ from the illumination means (not shown)
Of the light flux entering with the spread of
Since the light beam striking the light is reflected by the reflection surface 204 as shown by the arrow in the figure (absorption if the back surface of the reflection surface 204 is an absorption surface), the luminance decreases in the shaded area, , Uneven brightness should occur on the liquid crystal light valve that is the illuminated surface. However, due to the above conditions, the area where the brightness is reduced overlaps the adjacent area where the brightness is reduced, so that the uneven brightness is eliminated. When 2Ltan θ> P, the superimposing effect is further promoted.

In this embodiment, right angle prisms 201 and 202
Was used, but it does not have to be a right angle. For example, prism 20
When 1 is shifted slightly from the right angle, the optical axis of the circularly polarized light L _C returning to the light source shifts, and at least a part of the circularly polarized light L _C passes through the light source 1, so that the circularly polarized light L _C that directly strikes the light source 1 Will be less.

Normally, when light strikes a light source, in addition to being transmitted and diffused, loss of light due to absorption occurs. Since the amount of the lost light is by no means negligible, reducing the amount of circularly polarized light L _C that directly strikes the light source 1 leads to an increase in light utilization efficiency, as described above.

FIG. 7 shows another embodiment of the polarizing element.

FIG. 7 shows a prism 201 'and a prism 20.
2 ', a polarization beam splitter composed of a polarization splitting action film 203', a prism 201 ", a prism 202",
The polarization beam splitter composed of the polarization splitting film 203 ″ is laminated so that the polarization splitting films 203 ′ and 203 ″ are orthogonal to each other, and the total reflection mirror 204 is provided at the joint portion to form an array as shown in the figure. It is a thing. In this case, 204 is a total reflection surface on both the front and back surfaces, and since the S-polarized light reflected by the polarization splitting films 203 ′ and 203 ″ is reflected on both surfaces, the surface on which the total reflection mirror 204 is provided is halved. In addition, the prism 202′2
02 ″ can be manufactured as one prism.

Even in this embodiment, uneven brightness, uneven color, etc. should appear in accordance with the period of the polarizing element structure. However, as in the previous embodiment, the pitch P of one unit of the polarizing element, the polarizing element 2
If the divergence angle θ of the light flux incident on 0 and the distance L between the object to be illuminated and the polarizing element are matched with the conditions of the present invention, the above-mentioned brightness unevenness, color unevenness, etc. become inconspicuous due to the superimposing effect of the light flux divergence angle. ..

FIG. 8 shows another embodiment of the present invention.

FIG. 8 shows one surface of a plate-shaped member made of glass or the like, a surface perpendicular to the other surface of the plate-shaped member,
Similarly, inclined surfaces that form approximately 45 degrees with the other surface are alternately provided, and the total reflection mirror 204 is provided on the vertical surface.
A polarization splitting action film is provided on the surface forming the 45 degrees, and a member having the same shape as the plate-like member is attached to the film, and the action on the light flux from the illumination system is the same as in the first embodiment. However, this embodiment also has the effect of being very excellent in terms of strength.

FIG. 9 shows a main part of another embodiment of the polarized light illuminating device of the present invention, and only a part corresponding to the polarizing element 20 is shown.

The polarizing element 20 of this embodiment is composed of right-angle prisms 201 and 2 in the shape of a triangular prism whose cross section is a right-angled triangle.
No. 02, a polarization splitting film is provided on either one of the surfaces sandwiching a right angle, and the surfaces having the polarization splitting film are bonded together. The polarization separating film may be provided on only one of the right angle prisms 201 and 202.

The polarization splitting action film 203 reflects S-polarized light having a polarization direction parallel to the polarization splitting action film 203 with respect to light incident on the polarization splitting action film 203 at an incident angle of approximately 45 degrees, and P-polarized light having a polarization direction perpendicular to the polarized light has a function of transmitting. In the polarization splitting action film 203, the P polarized light L _P of the indefinitely polarized light flux (a) is transmitted through the polarization splitting action film 203 and emitted from the polarization element 20. On the other hand, the S-polarized light L _S of the indefinite polarized light beam (a) is reflected by the polarization separation film 203, and is further reflected by the total reflection mirror 20.
The light is reflected at 4 and is emitted from the polarizing element 20 as L _S ′.

The other indefinite polarized light beam (b) is reflected by the total reflection mirror 204 together with the P and S polarized light beams, and P of the indefinite polarized light beam (b) is reflected by the polarization separation film 203.
Only the polarized light L _P is directly transmitted. And P-polarized light
L _P is reflected by the total reflection mirror 204 ′ in the same traveling direction as the P-polarized light L _P, and is emitted from the polarization element 20.
On the other hand, the S-polarized light reflected by the polarization splitting action film 203 is
It is emitted from the polarizing element 20 as L _S.

The subsequent process of the S-polarized light L _S ′ and L _S ′ will be described with reference to FIG. FIG. 10 shows the light source 1 for simplicity.
Spherical reflecting mirror 2, λ / 4 optical phase plate 22, polarizing element 2
Only 0 is shown and the others are omitted.

As described with reference to FIG. 9, the S-polarized light L _S ′ separated by the polarization element 20 is subjected to the action of the λ / 4 optical phase plate 22 whose optical axis is set in the desired direction and is circularly polarized light. After reaching L _C , it goes through the condenser lens 21 to the light source 1 located at the focal position of the condenser lens 21 and at the position of the center of curvature of the spherical reflecting mirror 2. A part of the circularly polarized light L _C incident on the light source 1 is transmitted while maintaining its polarization state as shown in the figure, and is reflected by the spherical reflecting mirror 2. When the circularly polarized light L _C is reflected, The rotation direction with respect to the traveling direction is changed to become circularly polarized light L _C ′, which is directed to the light source 1.
Here, for the sake of clarity, the optical paths before and after reflection are shifted. Circularly polarized light L transmitted through the light source 1 again
_C ′ again goes to the λ / 4 optical phase plate 22 and the polarization element 20 via the condenser lens 21. S-polarized light L
_Since S'is thus converted into the order of L _S '→ L _C → L _C ′ → L _P ′, as a result, the λ / 4 optical phase plate becomes 2
Pass by. Therefore, the λ / 4 optical phase plate 22 has the same function as that of the λ / 2 optical phase plate and can rotate the polarization direction of the S-polarized light L _S ′ by 90 degrees, so that the S-polarized light L _{S is} L-polarized light. ′ Passes through the polarization element 20 as P-polarized light L _P ′.

On the other hand, of the circularly polarized light L _C , the light that has been diffused by the light source 1 and whose polarization state has changed slightly behaves like light emitted from the light source, and illuminates the polarizing element 20 via the condenser lens 21. .. Then, the same operation is repeated until P-polarized light L _P ′ is obtained.

[0033] is the same 'is also L _S for' and L _S.

Even in this embodiment, the uneven brightness, the uneven color, etc. should appear in accordance with the period P of the polarizing element structure as shown in the figure, but the light flux incident on the polarizing element 20 with the pitch P as in the previous embodiment. If the divergence angle .theta.

FIG. 11 shows a main part of another embodiment of the polarized light illuminating device of the present invention, and only a part corresponding to the polarizing element 20 is shown.

The polarizing element 20 of this embodiment is composed of right-angle prisms 201 and 2 in the shape of a triangular prism whose cross section is a right-angled triangle.
No. 02 is provided with a polarization splitting action film on both surfaces sandwiching a right angle, and the faces having the polarization splitting action film are bonded together. The polarization separating film is a right angle prism 2
It may be provided in only one of 01 and 202.

The polarization splitting action film 203 reflects S-polarized light having a polarization direction parallel to the polarization splitting action film 203 with respect to light incident on the polarization splitting action film 203 at an incident angle of approximately 45 degrees, and P-polarized light having a polarization direction perpendicular to the polarized light has a function of transmitting. In the polarization splitting action film 203, the P polarized light L _P of the indefinitely polarized light flux (a) is transmitted through the polarization splitting action film 203 and emitted from the polarization element 20. On the other hand, the S-polarized light L _S of the indefinite polarized light beam (a) is reflected by the polarization separation film 203, is further reflected by the adjacent polarization separation film 203, and is emitted from the polarization element 20 as L _S ′.

The other indefinite polarized light beam (b) is similarly split into P polarized light L _P and S polarized light L _S.

The subsequent behavior of the S-polarized light L _S ′ and L _S ′ is the same as that shown in FIG.

Even in the present embodiment, the uneven brightness, the uneven color, etc. should appear in accordance with the period P of the polarizing element structure as shown in the figure, but the pitch P and the luminous flux incident on the polarizing element 20 are the same as in the previous embodiment. If the divergence angle .theta.

FIG. 12 shows a main part of another embodiment of the polarized light illuminating device of the present invention, and only a part corresponding to the polarizing element 20 is shown.

The polarizing element of the present embodiment comprises a light beam splitting unit 301 that splits an incident light beam into a plurality of light beams, and a polarization conversion unit 302 that converts each of the multiple light beams into linearly polarized light. There is.

The light beam splitting unit 301 has a row of focusing surface 301a having a function of focusing the light beam on the incident side, and a row of diverging surface 301b having a function of diverging the light beam on the output side. In this embodiment, the focusing action surface 301a is a lenticular lens having a positive power, and the divergence action surface 3
Reference numeral 01b is a negative power lenticular lens having the same period as that of the focusing surface 301a and confocal with the pair of focusing surfaces, and the absolute value of the focal length of the negative power lens is defined as the positive power. By setting the focal length of the lens to ½, the incident parallel light flux is divided into substantially parallel light flux having a light flux width of ½ of the lenticular lens pitch. The diverging surface 301b is the focusing surface 301a.
Since it is not necessary to have the same width as the above, a part of the non-action surface 301c may be formed as long as it does not hinder the progress of the light flux. Further, by providing the absorbing film on the non-acting surface 301c, it is possible to reduce the adverse effects due to diffused reflection and the like in the light beam splitting portion.

The polarization converting section 302 corresponds to the light beam emitting section 301b of the light beam splitting section, and has a parallelogram glass section 206, and a glass member 205 having the same shape and arranged between the glass members 206 and the glass member 205. Members 206, 2
Of the surfaces in contact with 05, the polarization splitting film 203 formed on the surface corresponding to the optical path of the light beam emitting portion 301b, the reflecting surface 204 formed on the other surface, and the λ / 2 optical phase plate 11
Consists of.

The light beam (a) incident on the polarization conversion section 302 is transmitted through the polarization separation film 203 as P polarized light L _{P and} reflected as S polarized light L _S. The reflected S-polarized light L _S changes its direction by 90 ° on the reflecting surface 204, and then the λ / 2 optical phase plate 1
At 1, the plane of polarization is rotated by 90 ° to become P-polarized light L _P ′, which is emitted together with P-polarized light L _P as the same linearly polarized light.

Even in this embodiment, the uneven brightness, the uneven color, etc. should appear in accordance with the period P of the polarizing element structure as shown in the figure, but the pitch P and the divergence angle θ ′ of the light beam incident on the polarization conversion unit 302 are shown. If the distance L between the object to be illuminated and the polarizing element is adjusted to the conditions of the present invention, the uneven brightness, uneven color and the like become inconspicuous due to the superimposing effect of the spread angle of the light flux.

The present embodiment is different from the other embodiments in that the light beam splitting section 301 is used to compress the light beam corresponding to each unit to about half the width. With respect to each divergence θ, the divergence angle of the luminous flux emitted from the luminous flux splitting unit 301 changes to θ ′. Spread angle θ
And θ ′ are inversely proportional to the compression rate of the light flux, and in the case of the present embodiment, the width of the light flux becomes about 1/2, so that θ′≈2θ.

FIG. 13 shows the structure of a color projection display apparatus using the polarizing element of the present invention.

The parallel luminous flux collimated by the condenser lens 4 reflects a red color and transmits a green color and a blue color through a dichroic mirror 28, a green color reflects a blue color through a dichroic mirror 23 and a total reflection mirror 24 into a red / green color.・
It is decomposed into three colors of blue, converted into linearly polarized light by the polarizing elements 20R, 20G, 20B provided corresponding to each color, and is converted into liquid crystal light valves 7R, 7G, 7B via condenser lenses 21R, 21G, 21B. Incident. The light modulated by the liquid crystal light valves 7R, 7G and 7B is analyzed by the analyzers 8R and 8R.
Transmission and absorption are selected by G and 8B, and they are combined again by a dichroic mirror 26 that reflects green and transmits red, a dichroic mirror 27 that transmits red and green and reflects blue, and a total reflection mirror 25. The combined light is projected and displayed on the screen (not shown) by the projection lens 10.

In this embodiment, after being separated into three colors,
The polarizing elements 20R, 20G, and 20 having the configurations of the above-described embodiments
Providing B has the following effects.

Generally, it is difficult for the polarization splitting film to suppress the wavelength dependence to zero, and there is a limit in efficiency for the incident light flux of white light. Therefore, by constructing the polarizing element for each of the three colors as in the present embodiment, it is possible to improve efficiency and design better with respect to good color reproducibility.

As a constitution using the polarizing element of the present invention,
The present invention is not limited to this embodiment, a color separation system uses a cross dichroic mirror, a color synthesis system uses a cross dichroic mirror, a color synthesis system does not use a projection lens for each of the three colors, and the like. , Applicable to various configurations. Further, the arrangement position of the polarizing element is not limited to the one after the three-color separation, and it can be placed in the middle of the color separation system or before the color separation system, and the required number of the polarizing elements is different in each case. Will be different. Further, it goes without saying that it can also be used in a projection display device using a reflective liquid crystal light valve. In any case, when using a plurality of polarizing elements, it is necessary to arrange them at optically equivalent positions in order to suppress the occurrence of color unevenness. The term “optically equivalent position” as used herein means that the distribution of light flux (incident angle distribution to each polarization element, intensity distribution, etc.) is similar, except that it has the same positional relationship in the optical path. ..

In the above embodiments, the spherical reflecting mirror is used as the reflecting mirror provided on the back surface of the light source, but a parabolic reflecting mirror, an elliptic reflecting mirror or the like is also conceivable. Generally, when obtaining a parallel light flux, the parabolic reflector has a higher light utilization efficiency than the spherical reflector, but the polarization conversion efficiency is a spherical surface where the number of reflections of the light flux returning from the polarizing element by the reflector is an odd number. It is advantageous to use a reflector.

If the number of reflections by the reflector is even, as in the case of a parabolic reflector, the polarization conversion efficiency will deteriorate, but as an illumination means for compensating for this, the one shown in FIG. 14 can be considered.

In the illuminating means shown in FIG. 14, the λ / 4 optical phase plate 22a and the λ / 4 optical phase plate 22a are separated from each other with the optical axis from the light source as a boundary.
4 optical phase plate 22b and λ / 4 optical phase plates 22a and λ /, respectively, so that more outgoing light can be obtained as P polarized light L _{P with} respect to S polarized light L _S that is incident light. Four
The optical axis of the optical phase plate 22b is set. Normally, the polarization conversion efficiency is maximized when the λ / 4 optical phase plate 22a and the λ / 4 optical phase plate b are set so that their optical axes form approximately 90 degrees.

Next, the divergence angle of the luminous flux from the illumination means will be described with reference to FIG. In a combination of a light source 1 having a radius r, a reflecting mirror 2 having a radius R (a spherical mirror in this case), and a convex lens 4, assuming that the opening of the reflecting mirror is 2 m and the distance from the opening to the polarizing element is 1, tan θ ₁ = m / L tan θ ₂ = r / R The spread angle θ of the light beam incident on the polarizing element is tan θ ₁ ≦ tan θ ₂ that is m / l ≦ r / R θ = θ ₁ tan θ ₁ ≧ tan θ ₂ that is m / l ≧ r When / R θ = θ ₂

That is, when the distance 1 is sufficiently large, it depends on the apparent size of the aperture that is separated from the polarizing element 20 by the distance 1, and when the distance 1 is small, the light source 1 viewed from above the reflecting mirror 2 is shown.
Depends on the apparent size of. In the actual device, the latter is often the case.

When a parabolic mirror having a focal length f is used as the reflecting mirror 2, the above R becomes variable and the spread angle θ = θ ₂ becomes maximum when R has a minimum value f, that is, It corresponds to the light reflected at the bottom of the parabolic mirror. However, in general, considering the light distribution of the light source 1, since a small amount of light travels to the bottom of the parabolic mirror, and in fact there is a hole for attaching a support member for the light source in the bottom. There is almost no light as described above. Therefore, the minimum value of R is actually larger than f.

Numerical examples of the present invention will be shown below.

Usually, the emission diameter of a 150-w metal halide lamp is about 5 mm, and it is combined with a parabolic mirror having a focal length of 16 mm, and the distance from the lamp to the polarizing element is 15 mm.
When it is set to 0 mm, the divergence angle of the light beam incident on the polarizing element is about ± 8.9 ° at the maximum. As shown in FIG. 13, assuming that the polarizing elements corresponding to the respective liquid crystal light valves are installed 30 mm apart from the liquid crystal light valves, if the pitch of the polarizing elements is set to about 9.4 mm or less from the conditional expression, the uneven brightness will be caused. It is possible to obtain a projected image in which color unevenness is not noticeable.

Needless to say, the present invention is not limited to the above embodiments, and various configurations can be made without departing from the spirit of the invention.

For the prism used in the polarization conversion section, an optical glass having a large degree of freedom in selecting the refractive index is often used in order to keep the separation function of the polarization separation action film optimal, but a plastic material is also possible. .. Further, it is possible to use a combination of parallel plates without using a prism, but the transmittance of P-polarized light is inferior to that of a prism.

The polarization splitting action film 203 can be constituted by an ordinary optical multilayer film, but a similar effect can be obtained by using a grid polarizer instead of the polarization splitting action film 203. In this case, the polarization splitting function can be kept in an optimum state without sandwiching the grid polarizer by the prisms, so that a further effect of reducing the weight of the polarization illumination device can be expected.

The grid polarizer has a very fine lattice structure in which metals are arranged in parallel. When light having a wavelength of at least twice the lattice spacing is incident, the polarized component parallel to the lattice is reflected. , The polarization component perpendicular to the grating is transmitted.

The present invention can also be applied by using a cholesteric liquid crystal layer or the like instead of the polarization splitting film.

The λ / 4 optical phase plate 22 is a crystalline material such as mica or quartz, a stretched polymer film, a low-molecular liquid crystal having a certain thickness and oriented in a certain direction with its molecular axes aligned, or a side surface. A chain type polymer liquid crystal, a low molecular weight liquid crystal dispersed in a polymer, or the like can be used. An aluminum vapor deposition mirror or a thin-film multilayer film is often used as the total reflection mirror 204, but a total reflection mirror may be similarly provided on the back surface of the total reflection mirror 204.

[0067]

As described above, according to the present invention, the polarizing element provided in the optical path of the light flux having the predetermined divergence angle from the illuminating means causes the light flux to have the first polarized light and the second polarized light having different polarization planes. The first polarized light is directed to the first direction, the second polarized light is returned to the illuminating means by the polarizing element, and the polarization plane of the second polarized light is changed to the first by the illuminating means. The second light is converted into the same polarization plane as the polarized light and
In a polarized illumination device that directs polarized light in the first direction through the polarization element, a plurality of the polarization elements are repeatedly arranged along a predetermined direction so as to cross an optical path of a light beam from the illumination unit. 2Ltan θ ≧ P, where the divergence angle of the light beam incident on the polarizing element is ± θ, the distance between the object to be illuminated and the polarizing element is L, and the pitch of the repeating structure is P. Therefore, it is possible to obtain a polarized light illumination device in which uneven brightness and uneven color are not noticeable.

If the polarized illumination device of the present invention is used for a projection display device, it is possible to provide a lightweight, compact and inexpensive high-luminance projection display device without degrading the image quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a projection display device showing an embodiment of the present invention.

FIG. 2 is a perspective view of a polarizing element showing an embodiment of the present invention.

FIG. 3 is a sectional view of a polarizing element showing an embodiment of the present invention.

FIG. 4 is an explanatory view of the action of the polarizing element showing the embodiment of the present invention.

FIG. 5 is an operation explanatory view of the polarized illumination device showing the embodiment of the present invention.

FIG. 6 is an operation explanatory view showing the effect of the present invention.

FIG. 7 is another embodiment of the polarizing element of the present invention.

FIG. 8 is another embodiment of the polarizing element of the present invention.

FIG. 9 is a diagram illustrating another embodiment of the polarizing element of the present invention and its operation explanatory diagram.

FIG. 10 is an operation explanatory view of another embodiment of the polarized illumination device of the present invention.

FIG. 11 is a diagram illustrating another embodiment of the polarizing element of the present invention and its operation explanatory diagram.

FIG. 12 is a schematic view of another embodiment of the polarizing element of the present invention and its operation.

FIG. 13 is a schematic configuration diagram of a color projection display device showing an embodiment of the present invention.

FIG. 14 is an example of an illuminating means used in the polarized illumination device of the present invention.

FIG. 15 is an explanatory diagram of a divergence angle of the polarized illumination device.

FIG. 16 is a conventional example of a projection display device using a polarized illumination device.

FIG. 17 is an explanatory view of the operation of a conventional example of a polarizing element.

[Explanation of symbols]

 1 Light Source 2 Reflection Mirror 3 Heat Ray Cut Filter 4 Condenser Lens 5, 8 Polarizer 7 Liquid Crystal Light Valve (LCD) 10 Projection Lens 11 λ / 2 Optical Phase Plate 20 Polarizing Element 21 Condenser Lens 22 λ / 4 Optical Phase Plate 201, 202 Right angle prism 203 Polarization separating film 24, 25, 204 Reflective surface 23, 26, 27, 28 Dichroic mirror

Claims (7)

[Claims] 1. A polarizing element provided in an optical path of a light beam having a predetermined spread angle from an illuminating device separates the light beam into first polarized light and second polarized light having different polarization planes, and the first polarized light The light is directed to the first direction and the second polarized light is returned to the illuminating means by the polarizing element, and the illuminating means converts the polarization plane of the second polarized light into the same polarization plane as the first polarized light. At the same time, in the polarized illuminating device for directing the second polarized light in the first direction through the polarizing element, a plurality of the polarizing elements are set as one unit along a predetermined direction so as to cross the optical path of the light flux from the illuminating means. When the divergence angle of the light beam incident on the polarizing element is ± θ, the distance between the object to be illuminated and the polarizing element is L, and the pitch of the repeating structure is P, 2L tan θ ≧ P Polarizing illumination device according to claim. 2. The illuminating means comprises a light source, a reflecting mirror provided behind the light source, and a λ / 4 optical phase plate provided in front of the light source, wherein the polarizing element is arranged with respect to an optical axis of the illuminating means. 2. The polarized illumination device according to claim 1, wherein the polarized light separating film is inclined and the reflecting surface is substantially parallel to the optical axis. 3. The illuminating means comprises a light source, a reflecting mirror provided behind the light source, and a λ / 4 optical phase plate provided in front of the light source, and the polarizing element has a polarization separation film and one end thereof. A total reflection mirror, which is in contact with one end of the polarization splitting action film at an angle, is obliquely provided in the optical path from the illuminating means, and a second total reflection mirror is provided on the back surface of the total reflection mirror. The polarized illumination device according to claim 1. 4. The illuminating means comprises a light source, a reflecting mirror provided behind the light source, and a λ / 4 optical phase plate provided in front of the light source, and the polarization element has a polarization separation film and one end thereof. Second contact with one end of the polarization splitting film at an angle
The polarized light illuminating device according to claim 1, wherein the polarized light separating action film and the polarized light separating action film are obliquely provided in an optical path from the illuminating means, respectively. 5. A polarized illuminating device, an image forming unit that forms an image by modulating polarized light from the polarized illuminating device, and a projection unit that projects the image light formed by the image forming unit. In the projection display device, the polarized illumination device separates the light beam into first polarized light and second polarized light having different polarization planes by a polarizing element provided in an optical path of the light beam having a predetermined divergence angle. Then, the first polarized light is directed to the first direction and the second polarized light is returned to the illuminating means by the polarizing element, and the illuminating means changes the polarization plane of the second polarized light to the first polarized light. In a polarized illumination device that converts the same polarization plane and directs the second polarized light in the first direction through the polarization element, the polarization element is taken as a unit to cross an optical path of a light beam from the illumination means. Predetermined person A plurality of repeating structures are arrayed along the direction, the divergence angle of the light beam incident on the polarizing element is ± θ, the distance between the image forming unit and the polarizing element is L, and the pitch of the repeating structure. The projection display device is characterized in that 2Ltan θ ≧ P, where P is P. 6. The second polarized light is divided into a first polarized light and a second polarized light having different polarization planes in the optical path of the light flux having a predetermined divergence angle from the illuminating means, and the second polarized light. In a polarization illuminating device provided with a polarization element that converts the same to the same plane of polarization as the first polarized light and makes the traveling directions of the second polarized light and the first polarized light the same. As a unit, it has a repeating structure in which a plurality of light beams from the illuminating means are arranged along a predetermined direction so as to cross the optical path, and the divergence angle of the light beam incident on the polarizing element is ±.
Polarized illuminating device, wherein 2Ltan θ ′ ≧ P, where θ ′, the distance between the illuminated object and the polarizing element is L, and the pitch of the repeating structure is P. 7. A polarized illuminating device, an image forming unit that forms an image by modulating polarized light from the polarized illuminating device, and a projecting unit that projects the image light formed by the image forming unit. In the projection display device, the polarized illumination device separates the light beam into a first polarized light beam and a second polarized light beam having different polarization planes according to a traveling direction in an optical path of the light beam having a predetermined spread angle from the illumination means. , Converting the second polarized light to the same plane of polarization as the first polarized light and
In a polarized illuminating device provided with a polarizing element that makes the traveling directions of the polarized light and the first polarized light the same, the polarizing element is taken as a unit along a predetermined direction so as to cross the optical path of the light beam from the illuminating means. It has a repeating structure in which a plurality of light beams are incident on the polarizing element.
The projection display device is characterized in that 2Ltan θ ′ ≧ P, where θ ′, the distance between the image forming means and the polarizing element is L, and the pitch of the repeating structure is P.