JP3205693B2 - Optical element and projection type liquid crystal display device having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element which uses light from a light source with high efficiency and provides irradiation light with high illuminance uniformity, and a projection type liquid crystal display device using the optical element.

[0002]

2. Description of the Related Art A reflection type liquid crystal panel using a dispersion type liquid crystal is known as a liquid crystal panel of a projection type liquid crystal display device (hereinafter, referred to as a liquid crystal projector) for projecting and displaying an image formed by a liquid crystal panel on a screen or the like. ing. As an example of this, as shown in FIG. 1 of JP-A-4-194921, an aperture stop and a mirror are provided, and irradiation light from a light source is irradiated on a liquid crystal panel through a mirror, and reflected from the liquid crystal panel. There is a so-called Schlieren optical system in which light is projected on a screen by a projection lens via an aperture stop.

[0003] Such a liquid crystal projector does not require a polarizing plate as compared with a projector using a TN (twisted nematic) liquid crystal panel, so that a brighter image can be obtained on a screen. There is also an advantage that the optical system can be made smaller than a transmissive liquid crystal panel.

In a liquid crystal projector,
It is important to use the light from the light source with high efficiency and to reduce the illuminance unevenness on the screen.

As a means for improving the efficiency of use of light from a light source and for improving uneven illuminance on a screen, an integrator comprising two lens arrays is known.
Japanese Patent Application Publication No. 111806 discloses a configuration of a liquid crystal projector using the integrator optical system.

The integrator divides a light beam from a light source into a plurality of light beams by a first lens array,
These light beams are superimposed and formed on the display area of the liquid crystal panel while being enlarged by the lens array.

In this method, a light beam having a small illuminance non-uniformity after division is superimposed, so that irradiation light with high uniformity is obtained, and the illuminance non-uniformity on the screen is greatly improved. Also, the first
If each opening of the lens array has a rectangular shape similar to the display area of the liquid crystal panel, the luminous flux after division is radiated to the display area without leakage, so that the efficiency of irradiation light is improved, and the efficiency of light source light utilization is improved. it can.

[0008]

However, when the integrator is used, the second lens array apparently becomes a large light source, and the parallelism of the light beam is deteriorated.
Therefore, to project and use all light beams incident on the liquid crystal panel, a considerably large projection lens is required,
As a result, the size of the projector is increased, which leads to an increase in cost.

Further, in the projector constituting the above-mentioned schlieren optical system, when the parallelism of the light beam incident on the liquid crystal panel is deteriorated, the diameter of the aperture stop is made sufficiently large in order to use the light from the light source with high efficiency. , F value must be set small. However, when the F value is reduced, there arises a problem that the contrast required for practical use cannot be realized.

[0010] It is an object of the present invention to provide an optical element capable of efficiently using light from a light source without deteriorating the parallelism of a light beam and obtaining irradiation light with high uniformity of illuminance.

It is another object of the present invention to provide a liquid crystal projector having the above-mentioned optical element capable of obtaining a brighter and higher-quality projected image.

[0012]

The gist of the present invention to achieve the above object is as follows.

An optical element which receives an incident light beam from a light source and emits the light beam to a surface to be irradiated; a light beam dividing means for dividing a cross section of the light beam emitted from the light source into two; A light beam splitting means for splitting the light beam into two, a transmitted light beam and a reflected light beam; and a light beam synthesizing means for synthesizing and emitting the four light beams split and separated by the light beam splitting device and the light beam splitting device to an irradiation target. The cross-sectional shape of the combined light beam of two of the four separated light beams forms an outgoing light beam having substantially the same shape as the cross-sectional shape of the incident light beam, and the cross-sectional shape of the combined light beam of the other two light beams. The cross-sectional shape of the incident light beam is inverted in two directions, that is, the light beam is inverted up and down or left and right to form an output light beam having a combined shape, and the four light beams are combined on the irradiation target surface. In optical element characterized.

Further, the optical element includes a first total reflection surface and a second total reflection surface having the same shape, and a light beam separation surface for separating an incident light beam into reflected light and transmitted light. , Second
Are totally parallel to each other and the reflection surfaces of the first and second total reflection surfaces are arranged to face each other with the light beam separation surface interposed therebetween. The angle is set to 45 degrees with respect to the optical axis.
The total reflection surface and the light beam splitting surface are configured so that an incident light beam incident almost parallel does not become a shadow of another surface, and the incident light beam does not leak from between the surfaces.

Further, another optical element according to the present invention provides a first total reflection surface and a second total reflection surface (or first and second total reflection surfaces) having the same shape and provided on the same plane without any gap. May be constituted by a single total reflection surface), and a light beam separation surface having the same shape as the first and second total reflection surfaces for separating the incident light beam into reflected light and transmitted light. The second total reflection surface and the light beam splitting surface are parallel to each other, and are set at an angle of 45 degrees with respect to the optical axis of the incident light beam. , Half of the incident light beam incident almost parallel is directly incident on the light beam separation surface, the other half is incident on the first total reflection surface, and the incident light beam is not directly incident on the second total reflection surface. I have.

Further, in the projection type liquid crystal display device according to the present invention, the optical element is moved from a light source to a liquid crystal light valve (liquid crystal panel).
The light beam emitted from the light source is incident on the optical element, and the light beam emitted from the optical element is used as irradiation light to the liquid crystal ride valve.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, an optical element 1 according to the present invention comprises a light beam (11) incident on the optical element from a light source.
Is a first light beam (11) incident on the first total reflection surface (6).
a) and the second light beam (1) directly incident on the light beam separation surface (4).
1b).

The first light beam (11a) incident on the first total reflection surface (6) is reflected by the first total reflection surface (6), is incident on the light beam separation surface (4), and becomes the third light beam. (A reflected light beam 13a on the light beam separation surface) and a fourth light beam (a transmitted light beam 12a on the light beam separation surface). The third light beam is emitted from the optical element 1 as it is, but the fourth light beam is reflected by the second total reflection surface (7) and then emitted in the same direction as the third light beam.

On the other hand, the second light beam (11b) directly incident on the light beam separation surface (4) is separated by the light beam separation surface (4).
The fifth light beam (transmitted light beam 12b on the light beam separation surface) and the sixth light beam (reflected light beam 13b on the light beam separation surface) are separated from each other.
The fifth light beam exits in the same direction as the third light beam as it is,
After being reflected by the second total reflection surface (7), the sixth light beam exits in the same direction as the fourth light beam.

At this time, assuming that the cross section of the incident light beam (11) from the light source is circular, the first and second light beams are respectively line-symmetrical semicircles as shown in FIG.

On the other hand, the cross-sectional shape of the light beam separated into the transmitted light beam and the reflected light beam on the light beam separation surface (4) of the optical element is also semicircular. However, the combined light beam 1 passing through the optical element
The cross-sectional shape of No. 4 is a shape obtained by combining the third to sixth four semi-circles, that is, a circular portion having the same shape as the incident light beam contacting at the two semi-circular chords that are line-symmetric, It has a shape in which two semicircles arranged side by side at the center of two semicircular arcs overlap each other.

When the light emitted from the light source is irradiated as it is, the illuminance at the center of the illuminated light is higher than the illuminance at the periphery. However, by using the optical element of the present invention, the incident light is reduced to four lights. Since the light is divided, separated, and synthesized while shifting the illuminance peak, more uniform irradiation light can be obtained on the irradiation surface.

Further, since the present optical element does not use a lens, and divides, separates and combines the incident light beams by a total reflection surface and a light beam separation surface arranged in parallel with each other, the parallelism of the light beams does not deteriorate.

The liquid crystal projector constituted by using the present optical element and the schlieren optical system can form a bright and uniform image on a screen.

Hereinafter, more specific embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a schematic perspective view showing an embodiment of the optical element of the present invention.

This optical element 1 has a total reflection prisms 3 and 5 each having a triangular prism shape whose bottom surface is a right-angled isosceles triangle, and a side having a length equal to an equal side of a right-angled isosceles triangle on the bottom surface of the total reflection prisms 3 and 5. And a rectangular parallelepiped beam splitter prism 2 having a square bottom surface. Therefore, the shape of the optical element 1 is a quadrangular prism whose bottom surface is a parallelogram. The parallelogram on the bottom has inner angles of 45 degrees and 135 degrees and a side ratio of 2: √2.

The beam splitter prism 2
Are formed by joining inclined surfaces of two triangular prisms each having the same bottom shape having a right-angled isosceles triangle shape, and a light beam separating surface 4 is formed on the joining surface by an optical multilayer thin film.

By forming a polarizing film on the light beam separating surface 4, a polarizing beam splitter can be formed.

The surfaces of the total reflection prisms 3 and 5 facing the inside of the optical element 1 are total reflection mirror surfaces 6 and 7 and are in a positional relationship parallel to the light beam separation surface 4 of the beam splitter prism 2. .

In FIG. 1, the shapes of the total reflection mirror surfaces 6 and 7 and the light beam splitting surface 4 are the same, but the shapes can be changed according to the cross-sectional shape of the incident light beam.

As a glass material for forming the total reflection prisms 3 and 5 and the beam splitter prism 2, an optical glass BK-7, which is generally widely used, is used. If a polarizing beam splitter having an excellent extinction ratio performance with respect to incident white light is to be obtained, a glass material having a higher refractive index than BK-7 may be used.

In order to obtain a low-cost polarization beam splitter, an optical plastic such as PMMA (Poly Methyl Methacrylate) having a small retardation (birefringence phase difference) may be used. In this case, if the optical multilayer thin film is formed directly on the optical plastic, the number of layers cannot be increased so much because the film is easily peeled off by the film tension. Therefore, an optical multilayer thin film is formed on a thin glass plate in advance,
This is preferably sandwiched between optical plastics to produce a polarizing beam splitter.

When the optical element 1 is used as an optical system for a liquid crystal projector or the like, the surface shape does not need to have a high precision of the order of wavelength. Furthermore, the beam splitter prism 2 can be manufactured relatively inexpensively if it is not necessarily a polarizing beam splitter as described later.

Next, the operation of the optical element 1 of the present invention will be described with reference to FIGS. FIG. 2 is a schematic cross-sectional view of the optical element 1 as viewed from above, and FIG. 3 is a schematic perspective view of the optical element 1 with a light state added for explanation.

As shown in FIGS. 2A and 2B, the optical element 1
With respect to the optical axes of the incident light beams 11a and 11b incident in parallel to
They are arranged at an angle of 5 degrees, and are arranged such that the other surfaces do not cast a shadow on the incident light flux 11 and that the incident light does not pass between the surfaces. In this case, as shown in FIG. 2B, the distance between the surfaces is L / 2, where L is the length of each side of the total reflection mirror surfaces 6, 7 (or the light beam separation surface 4). Have been.

The optical element 1 is arranged such that half of the incident light beam 11a of the incident light beam 11 is directly incident on the total reflection mirror surface 6, and the other half of the incident light beam 11b is directly incident on the light beam separating surface 4. Therefore, the incident light beam 11 is
And the light beam 11b.

In the case where the cross section of the incident light beam is circular, assuming that the incident portion of the optical element 1 is a square circumscribing the cross section of the incident light beam 11 as shown in FIG.
As shown in (a), the light is reflected by the total reflection mirror surface 6 and is directed to the light beam separation surface 4, where the reflected light beam 13a is reflected by the light beam separation surface 4.
And the transmitted light flux 12a.

The reflected light beam 13a is directly incident light beam 11a.
The transmitted light flux 12a is once reflected by the total reflection mirror surface 7 and emitted in the same direction as the reflected light flux 13a.

On the other hand, the incident light beam 11b is split on the light beam separation surface 4 into a reflected light beam 13b and a transmitted light beam 12b as shown in FIG.

The transmitted light beam 12b is directly incident light beam 11b.
The reflected light flux 13b is once reflected by the total reflection mirror surface 7 and then emitted in the same direction as the transmitted light flux 12b.

At this time, the incident light beams 11a and 11b each have a semicircular cross-sectional shape, and these light beam
Transmitted light flux 1 which is separated into transmitted light and reflected light by
2a, 12b and the reflected light fluxes 13a, 13b also have semicircular cross-sectional shapes.

Accordingly, the sectional shape of the combined light beam 14 of the outgoing light beams is a combination of four semicircles. In other words, two semicircles in which the semicircular arcs are arranged side by side,
The shape is such that two semicircles that are back-to-back at the semicircular chord portion are overlapped.

FIG. 4 is a schematic diagram when light is applied to the display unit 21 of a liquid crystal panel having an aspect ratio (horizontal: vertical) of 4: 3. FIG. 4A shows irradiation light 22 irradiated by an illumination system composed of a light source and a parabolic mirror, and FIG. 4B shows irradiation by inserting the optical element 1 of this embodiment into the above-described illumination system. Show the case.

FIG. 4A shows a case where irradiation light having a circular cross section of a light beam is applied to the entire surface of the display unit 21 of the liquid crystal panel. Irradiation light having the same length of diameter is required. In this case, the area of the portion of the liquid crystal panel that is not irradiated with the display unit 21 is 39% of the cross-sectional area of the total irradiation light flux, and the light loss is large.

On the other hand, when the optical element 1 is used, the sectional shape of the combined light beam of the light emitted from the optical element 1 is closer to the shape of the display section of the liquid crystal panel than in the case of the circular illumination light. , Light loss is small.

Therefore, as shown in FIG. 4 (b), even if the diameter of the incident light beam incident on the optical element 1 is reduced to 4/5 of the case where the optical element 1 is not used, the display section 21 of the liquid crystal panel is not affected.
Can be applied to the entire surface of the liquid crystal panel, and the area of the portion that is not irradiated to the display unit 21 of the liquid crystal panel can be greatly improved to about 5% of the sectional area of the incident light beam.

FIG. 5 is an explanatory view of the uniformity of the illuminance distribution when the optical element 1 is used.
1) Illumination distribution above is shown.

The horizontal axis shows the diagonal position on the irradiation surface, and the vertical axis shows the illuminance. Illuminance distribution 23 when no optical element is used
And the illuminance distribution of each of the light fluxes 12a, 12b, 13a and 13b divided and separated in the optical element 1, and the illuminance distribution 24 of the combined light when the optical element is used.

When no optical element is used, the illuminance at the center of the irradiation light is higher than that at the end (peripheral portion), and the illuminance at the center is 100%.
The illuminance at the end portion (peripheral portion) (hereinafter, referred to as the peripheral illuminance ratio) in the case of% is a very small value at about 25%.

On the other hand, even if the incident light beam has an illuminance peak at the center, the peripheral illuminance ratio is greatly improved to 50% or more by using the optical element.

FIG. 6 is a graph showing an example of the relation between the ratio of the peripheral illuminance (%) to the ratio of the transmission and reflection at the light beam separating surface 4 of the optical element 1. It can be seen from FIG. 6 that the ratio between the transmission and reflection of the light beam separating surface 4 has an optimum value at which the peripheral illuminance ratio is maximized. In this case, transmission: reflection = 8.2: 1.8 has the maximum value.

Therefore, by optimizing the ratio of transmission and reflection on the light beam separation surface 4 according to the cross-sectional shape of the incident light beam of the optical element 1 and the illuminance distribution of the incident light, a higher peripheral illuminance ratio can be obtained. More uniform illumination can be performed.

In addition, since the present optical element 1 does not use a lens but performs only with a total reflection mirror surface and a light beam separating surface arranged in parallel with each other, there is no deterioration in the parallelism of the light beam.

[Embodiment 2] FIG. 7 shows another embodiment of the present invention.
This will be described with reference to FIG.

FIG. 7 is a schematic perspective view showing the structure of the optical element, and FIG. 8 is a schematic sectional view of the optical element of FIG. 7 as viewed from above.

The present optical element comprises a plate type beam splitter 32 and plate type total reflection mirrors 33 and 34.
The total reflection mirror surfaces 6 and 7 and the light beam splitting surface 4 of the optical element 1 shown in FIG. 1 are the plate type total reflection mirrors 33 and 34 and the plate type beam splitter 32 of the present embodiment. It corresponds to. That is, instead of using a prism-type total reflection surface or a light beam separation surface, only a plate-type mirror and a plate-type beam splitter are used, and their positional relationship and size are the same as those of the optical element of FIG. Match.

According to this embodiment, as in the case of the optical element 1 shown in FIG. 1, the light use efficiency and the peripheral illuminance ratio are improved without impairing the parallelism of the light beam, and uniform and brighter illumination is performed. It becomes possible.

The plate type has an advantage that both the mirror and the beam splitter can be reduced in cost as compared with the prism type.

[Embodiment 3] FIG. 9 shows another embodiment of the present invention.
This will be described with reference to FIG.

FIG. 9 is a schematic perspective view showing the structure of the optical element, and FIG. 10 is a schematic sectional view of the optical element as viewed from above.

The optical element 41 has the same shape as a quadrangular prism.
The total reflection prisms 43 and 45 are joined.
The shape of the bottom surface of this prism is a parallelogram, the interior angle is 45 degrees and 135 degrees, the ratio of the length of the sides is 1: √2, and the total reflection prisms 43 and 45 are joined. The optical element 41 has the same shape as the optical element 1 of FIG. 1 as a whole.

The square columnar total reflection prisms 43 and 45 are
It is made of the same material as the prism of the optical element 1 shown in FIG. 1, and a light beam splitting surface 44 is formed on the joining surface by an optical multilayer thin film. Further, a polarizing beam splitter can be formed by forming a polarizing film, which is an optical multilayer thin film, on the light beam splitting surface 44.

The surfaces 46 and 47 of the prism are the total reflection mirror surfaces 46 and 47, and have a positional relationship parallel to the light beam splitting surface 44.

The position and size of the total reflection mirror surfaces 6 and 7 and the light beam separation surface 4 of the optical device 1 of FIG. 1 are basically the same as those of the total reflection mirror surfaces 46 and 47 and the light beam separation surface 44. It corresponds to. That is, the present optical element 41 has the same configuration as the optical element 1 of FIG. 1 except that the number of prisms is as small as two, and similarly, the light utilization efficiency and the peripheral illuminance are maintained without impairing the parallelism of the light flux. The ratio can be improved, and uniform and brighter illumination can be performed.

Furthermore, the present optical element 41 has the advantage that the number of constituent prisms is as small as two and the number of joint surfaces is one, so that the manufacturing cost is reduced.

Embodiment 4 FIG. 11 is a schematic perspective view of another embodiment of the optical element of the present invention.

The optical element 51 has a triangular prism-shaped total reflection prism 3 or 5 having a right bottom isosceles triangle, and a bottom surface having a length equal to that of the right isosceles triangle of the bottom surface of the total reflection prism 3 or 5. A rectangular parallelepiped beam splitter prism 2 having a side of
As a whole, the bottom surface has a triangular prism shape having a right-angled isosceles triangle.

The beam splitter prism 2 is formed by joining the inclined surfaces of two triangular prisms having the same shape and the bottom surface of which is a right-angled isosceles triangle. The beam splitting surface 4 is formed on the joining surface by an optical multilayer thin film. I have.

The surfaces facing the insides of the total reflection prisms 3 and 5 are mirror surfaces 6 and 7 for total reflection, and these two surfaces are arranged on the same plane without any gap. Furthermore, the total reflection mirror surface 6,
Reference numeral 7 denotes a position parallel to the light beam splitting surface 4 of the beam splitter prism 2.

In this embodiment, each of the total reflection mirror surfaces 6 and 7 and the light beam splitting surface 4 have the same shape, but may be changed according to the cross-sectional shape of the incident light beam.

Optical glass BK-7 was used as a glass material for the total reflection prisms 3 and 5 and the beam splitter prism 2.

Next, the operation of the optical element 51 will be described with reference to FIGS. FIG. 12 is a schematic sectional view of the optical element 51 as viewed from above, and FIG. 13 is a schematic perspective view of the optical element 51 with a light state added for explanation.

As shown in FIG. 12, the total reflection mirror surfaces 6 and 7 and the light beam splitting surface 4 make an angle of 45 degrees with the optical axis of the incident light beam 11 which enters the optical element 51 in a substantially parallel state. The total reflection mirror surfaces 6 and 7 are in a positional relationship parallel to the light beam separation surface 4.

Further, as shown in FIG. 12 (a), half of the light beams 11 which are incident in parallel are directly incident on the total reflection mirror surface 7, and as shown in FIG. 12 (b), the other half are incident. The incident light beam 11 b is configured to be incident on the light beam separation surface 4, and the incident light beam 11 is not directly incident on the total reflection mirror surface 6.

As shown in FIG. 13, the opening of the optical element 51 has a square circumscribed when the cross section of the incident light beam (11a + 11b) is circular. Therefore, the incident light beam 11 is divided into two at the opening of the optical element 51 into incident light beams 11a and 11b having a semicircular cross-sectional shape.

The incident light beam 11a is reflected on the total reflection mirror surface 7 as shown in FIG. 12A, and is separated on the light beam separation surface 4 into a reflected light beam 13a and a transmitted light beam 12a.

The transmitted light beam 12a is emitted in a direction at an angle of 90 degrees with the optical axis of the incident light beam 11a, and the reflected light beam 13a is reflected by the total reflection mirror surface 6 and then emitted in the same direction as the transmitted light beam 12a.

On the other hand, the incident light beam 11b is separated on the light beam separation surface 4 into a reflected light beam 13b and a transmitted light beam 12b as shown in FIG.

The reflected light flux 13b is emitted in a direction at an angle of 90 degrees with the optical axis of the incident light flux 11b, and the transmitted light flux 12b is reflected by the total reflection mirror surface 6 and then emitted in the same direction as the reflected light flux 13b.

At this time, the emitted light fluxes 12a, 12a
Since b, 13a, and 13b merely divide the incident light beams 11a and 11b having a semicircular cross-sectional shape into transmitted light and reflected light by the light beam separating surface 4, their cross-sectional shapes are also semicircular. Therefore, the cross-sectional shape of the combined light beam 14 of the outgoing light beams is a combination of four semicircles.

However, as in the case of the light beam emitted from the optical element 1 shown in FIG. 1, two semicircles are arranged so that the semicircular arc portions meet each other, and two semicircles are arranged back to back with semicircular chord portions. It has a shape in which a semicircle is superimposed.

That is, the present optical element 51 obtains a combined light beam 14 similar to that of the optical element 1 in FIG. 1 except that the light emitting direction is at an angle of 90 degrees with the optical axis of the incident light. Therefore,
Like the optical element 1 of FIG. 1, it has a uniform illuminance distribution and does not degrade the parallelism of the light flux.

If the ratio of the transmission and reflection of the light beam separating surface 4 is optimized in the same manner as described above according to the conditions such as the cross-sectional shape of the light beam incident on the optical element 51 and the illuminance distribution of the incident light,
It is possible to perform more uniform illumination.

[Embodiment 5] FIG. 14 is a schematic perspective view of another embodiment of the optical element of the present invention, and FIG. 15 is a schematic sectional view of the optical element viewed from above.

This optical element is composed of a plate-type beam splitter 32 and a plate-type total reflection mirror 33 having a size twice as large as the beam splitter 32. The two optical elements 51 shown in FIG. The total reflection mirror surfaces 6 and 7 correspond to the total reflection mirror 33, and the light beam separation surface 4 corresponds to the beam splitter 32. That is,
Instead of a prism-type total reflection surface or a light beam separation surface, a plate-type total reflection mirror or a beam splitter was used.
Same as 1 corresponding site.

Therefore, as in the case of the optical element 51 shown in FIG. 11, it is possible to improve the light use efficiency and the peripheral illuminance ratio without impairing the parallelism of the incident light beam, and to perform uniform and bright illumination. .

The plate type has the advantage that the manufacturing cost can be further reduced.

[Embodiment 6] FIG. 16 is a schematic perspective view of another embodiment of the optical element of the present invention, and FIG. 17 is a schematic sectional view of the optical element as viewed from above.

The optical element 61 of this embodiment is a prism having a trapezoidal bottom surface in the shape of a trapezoid. Optical element 61
This prism is made of BK-7 in the same manner as in the first embodiment. The inner surface of the prism is a total reflection mirror surface 66, and the surface 64 is a light beam separating surface 64.

The shape of the total reflection mirror surface 66 is
4 have the same shape as two side by side, and are in a parallel positional relationship with the light beam dividing surface 64.

That is, the optical element 61 basically corresponds to FIG.
The total reflection mirror surfaces 6 and 7 of the optical element 51 shown in (1) correspond to the total reflection mirror surface 66 of the present element, and the light beam separation surface 4 also corresponds to the light beam separation surface 64.

The present optical element 61 is composed of a single prism, but the shape and positional relationship of the total reflection surface and the light beam separation surface correspond to the corresponding parts of the optical element 51 in FIG. , Without compromising the parallelism of the incident beam
It is possible to improve the light use efficiency and the peripheral illuminance ratio, and to perform uniform and brighter illumination.

The present optical element has the advantage that the cost is reduced because the number of prisms constituting the optical element is one and there is no joint surface.

Embodiment 7 FIG. 18 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention.

In this liquid crystal projector, the light sources are a metal halide lamp 71, a parabolic mirror 72, an optical element 1, a condenser lens 73, a projection lens 74, a dichroic prism 76, and reflection type liquid crystal panels 77 and 78 in which a dispersion type liquid crystal is sealed. , 79.

The projection lens 74 has a total reflection mirror 81 and an aperture stop 75 in addition to the lens group, and forms a Schlieren optical system.

Of the luminous flux of the metal halide lamp 71, the luminous flux reflected by the parabolic mirror 72 becomes a substantially parallel luminous flux and enters the optical element 1. The light beam that has entered the optical element 1 is split and separated into four light beams without deteriorating the parallelism, and emitted. At this time, the combined luminous flux of the outgoing luminous flux has a uniform illuminance distribution, and its cross-sectional shape is close to a rectangle having an aspect ratio of 4: 3, which is the shape of the display unit of the liquid crystal panel.

The light beam emitted from the optical element 1 is condensed near the total reflection mirror 81 by the condenser lens 73 and is reflected toward the dichroic prism 76. After the reflected light flux becomes almost parallel light flux again by the lens group,
The light enters the dichroic prism 76.

The dichroic prism 76 has two dichroic thin films having different reflectance characteristics with respect to wavelength, and separates incident light into three primary colors of red (R), green (G), and blue (B). Each of the separated color lights is supplied to the liquid crystal panel 7 respectively.
7, 78 and 79, and undergoes modulation according to the image signal. That is, incident light is specularly reflected when each pixel of the liquid crystal panel is in the reflection mode, and scattered when it is in the scattering mode.

The modulated light reflected by the liquid crystal panel is recombined by the dichroic prism 76 and collected by the lens group. At this time, the incident angle of light on the liquid crystal panel is 90
The light reflected by the liquid crystal panel is condensed near the aperture stop 75 at a position slightly deviated from the total reflection mirror 81 because the light is tilted by several degrees, not by degrees.

The light of the specularly reflected pixel among the pixels of the liquid crystal panel passes through the aperture stop 75, is enlarged by the lens group, and reaches the screen 82. On the other hand, since the light of the scattered pixel is almost blocked by the aperture stop 75 and cannot reach the screen 82, the pixel is displayed dark.

In general, a liquid crystal projector using a schlieren optical system using the above-described liquid crystal panel does not use a polarizing plate, and therefore has a brighter image on a screen than a liquid crystal projector using a TN (twisted nematic) type liquid crystal panel. Is obtained.

There is also an advantage that the optical system can be made more compact than when a transmissive liquid crystal panel is used.

In the liquid crystal projector of this embodiment, the cross-sectional shape of the light irradiated on the liquid crystal panel by the optical element 1 has a shape close to a rectangle having an aspect ratio of 4: 3, and has a uniform illuminance distribution. As a result, the ratio of light that was not incident on the liquid crystal panel and was lost can be reduced, so that the light use efficiency is improved, and a brighter image is obtained, and a high-quality full-color projected image having a uniform illuminance distribution is obtained. Can be

Further, since the present optical element does not impair the parallelism of the incident light beam unlike an optical integrator using a conventional lens array, irradiation light can be used with high efficiency even if the aperture stop is small. A sufficient contrast can be secured.

[Embodiment 8] FIG. 19 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention.

A metal halide lamp 71 as a light source, a parabolic mirror 72, an optical element 61, a filter 83, a condenser lens 73, a projection lens 74, a cross dichroic prism 84, a scattering type liquid crystal panel 77, 78, 7
9 is comprised.

In the projection lens 74, in addition to the lens group, a total reflection mirror 81 and an aperture stop 75 are arranged to form a Schlieren optical system.

Of the luminous flux of the metal halide lamp 71, the luminous flux reflected by the parabolic mirror 72 becomes almost parallel luminous flux. After being cut off the heat rays and ultraviolet rays by the filter 83, the luminous flux enters the optical element 61. The incident light beam incident on the optical element 61 is divided and separated into four light beams without deteriorating the parallelism, and emitted in a direction at an angle of 90 degrees with the optical axis of the incident light beam. At this time, the combined luminous flux of the emitted light has a uniform illuminance distribution, and its sectional shape is close to a rectangle having an aspect ratio of 4: 3, which is the shape of the display unit of the liquid crystal panel.

The light beam emitted from the optical element 61 is condensed on the total reflection mirror 81 by the condenser lens 73 and is reflected toward the cross dichroic prism 84. The reflected light beam is again converted into a substantially parallel light beam by the lens group, and then enters the cross dichroic prism 84. The cross dichroic prism 84 has two cross dichroic thin films having different reflectance characteristics with respect to wavelength,
The incident light is separated into three primary colors of red (R), green (G), and blue (B). The decomposed lights are the liquid crystal panels 77, 78, respectively.
At 79, the light is modulated according to the image signal. That is,
The incident light is specularly reflected when each pixel of the liquid crystal panel is in the reflection mode, and scattered when it is in the scattering mode.

The modulated light reflected by the liquid crystal panel is recombined by the cross dichroic prism 84 and collected by the lens group. At this time, since the angle of incidence of light on the liquid crystal panel is not 90 degrees but inclined by several degrees, the light reflected by the liquid crystal panel is condensed by the aperture stop 75 at a position slightly shifted from the total reflection mirror 72. Is done. At this time, of the light incident on the liquid crystal panel, the light of the pixel that has been specularly reflected passes through the aperture stop 75, is enlarged by the lens group, and reaches the screen, so that the pixel becomes bright. On the other hand, the light of the scattered pixels is almost blocked by the aperture stop 75 and cannot reach the screen, so that the pixels become dark.

The liquid crystal projector of the present embodiment has the optical element 6
According to 1, the cross-sectional shape of the irradiation light applied to the liquid crystal panel has a shape close to a rectangle having an aspect ratio of 4: 3, and has a more uniform illuminance distribution.
A bright, uniform and high-quality projected image can be obtained on the screen.

Incidentally, the optical element 61 used in this embodiment is
In particular, since the light traveling direction can be changed by 90 degrees,
This is advantageous for miniaturizing a liquid crystal projector.

[Embodiment 9] FIG. 20 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention, in which a transmission type liquid crystal panel is used.

Light source metal halide lamp 91, parabolic mirror 92, UV / IR cut filter 90, optical element 1, total reflection mirrors 93 and 94, blue light reflection dichroic mirror 95, green light reflection dichroic mirror 96,
97, a red light reflecting dichroic mirror 98, a liquid crystal panel 99 for red light, a liquid crystal panel 100 for green light, a liquid crystal panel 101 for blue light, and a projection lens 102.
Note that transmission liquid crystal panels were used as the liquid crystal panels for each of the above colors.

Of the luminous flux of the metal halide lamp 91, the luminous flux reflected by the parabolic mirror 92 becomes almost a parallel luminous flux. The incident light beam incident on the optical element 1 is divided and separated into four light beams without deteriorating the parallelism, and emitted in the same direction as the optical axis of the incident light beam.
At this time, the combined luminous flux of the emitted light has a uniform illuminance distribution, and its sectional shape is close to a rectangle having an aspect ratio of 4: 3, which is the shape of the display unit of the liquid crystal panel.

The light beam emitted from the optical element 1 reflects the blue light decomposed by the blue light reflecting dichroic mirror 95, and changes its angle by the total reflection mirror 93, and irradiates the liquid crystal panel 101 for blue light. Similarly, green light reflecting dichroic mirrors 96 and 97 and green light liquid crystal panel 100,
By combining the red light liquid crystal panel 99, the total reflection mirror 94, and the red light reflection dichroic mirror 98, the R, G, and B images formed by each liquid crystal panel are superimposed to form a full-color image. This is projected on a screen by the projection lens 102.

The liquid crystal projector of the present embodiment has the optical element 1
As a result, the cross-sectional shape of the irradiation light applied to the liquid crystal panel has a shape close to a rectangle having an aspect ratio of 4: 3, and has a more uniform illuminance distribution. A uniform and high-quality projected image can be obtained.

[0120]

As described above, by using the optical element of the present invention, the light use efficiency and the peripheral illuminance ratio can be improved without deteriorating the parallelism of the light beam, and uniform and brighter illumination can be performed. It becomes possible.

Further, the liquid crystal projector using the optical element of the present invention can provide a high-quality projected image having brighter and more uniform illuminance on the screen and provide a smaller liquid crystal projector. .

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing one embodiment of an optical element of the present invention.

FIG. 2 is a schematic sectional view of the optical element of FIG. 1 as viewed from above.

FIG. 3 is a schematic perspective view showing an example of the optical element of the present invention in which a light state is added.

FIG. 4 is a schematic diagram when light is applied to a display unit of a liquid crystal panel having an aspect ratio of 4: 3.

FIG. 5 is an explanatory diagram of an illuminance distribution of an optical element, and is a graph showing an illuminance distribution on an irradiation surface (a display unit of a liquid crystal panel).

FIG. 6 is a graph showing an example of a relationship between a peripheral illuminance ratio (%) and a ratio of transmission and reflection on a light beam separation surface of the optical element of the present invention.

FIG. 7 is a schematic perspective view showing one embodiment of the optical element of the present invention.

8 is a schematic sectional view of the optical element of FIG. 7 as viewed from above.

FIG. 9 is a schematic perspective view showing one embodiment of the optical element of the present invention.

FIG. 10 is a schematic sectional view of the optical element of FIG. 9 as viewed from above.

FIG. 11 is a schematic perspective view showing one embodiment of the optical element of the present invention.

12 is a schematic sectional view of the optical element of FIG. 11 as viewed from above.

FIG. 13 is a schematic perspective view showing an example of the optical element of the present invention in which a light state is added.

FIG. 14 is a schematic perspective view showing one embodiment of the optical element of the present invention.

FIG. 15 is a schematic sectional view of the optical element of FIG. 14 as viewed from above.

FIG. 16 is a schematic perspective view showing one embodiment of the optical element of the present invention.

FIG. 17 is a schematic sectional view of the optical element of FIG. 16 as viewed from above.

FIG. 18 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention.

FIG. 19 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention.

FIG. 20 is a schematic sectional view of a liquid crystal projector provided with the optical element of the present invention.

[Explanation of symbols]

1, 41, 51, 61: optical element, 2: beam splitter prism, 3, 5, 43, 45: total reflection prism, 4, 4
4, 66: light beam separating surface, 6, 7, 46, 47, 66: total reflection mirror surface, 11: incident light beam, 12: transmitted light beam, 13: reflected light beam, 14: combined light beam, 21: display section of liquid crystal panel ,
22: irradiation light, 23: illuminance distribution when no optical element is used, 24: illuminance distribution of combined light when an optical element is used,
32 ... Beam splitter, 33,34,81,93,94 ...
Total reflection mirror, 71, 91 ... Metal halide lamp, 7
2, 92: parabolic mirror, 73: condenser lens, 7
4, 102: projection lens, 75: aperture stop, 76: dichroic prism, 77, 78, 79: liquid crystal panel, 8
2 screen, 83 filter, 84 cross dichroic prism, 90 UV, IR cut filter,
95 ... Blue light reflecting dichroic mirror, 96,97 ...
Green light reflecting dichroic mirror, 98 ... Red light reflecting dichroic mirror, 99 ... Red light liquid crystal panel, 10
0: liquid crystal panel for green light, 101: liquid crystal panel for blue light.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Makoto Tsumura 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-5-241240 (JP, A) JP-A-7-72428 (JP, A) JP-A-5-241103 (JP, A) JP-A-7-225379 (JP, A) JP-A-4-194921 (JP, A) (58) Int.Cl. ⁷ , DB name) G02F 1/13 505 G02B 5/00 G02F 1/13357

Claims (2)

(57) [Claims] 1. An optical element for receiving an incident light beam from a light source and emitting the light beam to an irradiation target surface, wherein the first total reflection surface and the second total reflection surface having the same shape and provided on the same plane with no space therebetween. A reflection surface, and a light beam separation surface having the same shape as the first and second total reflection surfaces for separating the incident light beam into reflected light and transmitted light, wherein the first and second total reflection surfaces and the light beam separation surface are Parallel to each other,
Further, the angle is set to 45 degrees with respect to the optical axis of the incident light beam, and the first and second total reflection surfaces and the light beam separation surface are such that half of the incident light beam incident almost in parallel is directly the light beam separation surface. An optical element characterized in that the other half is incident on the first total reflection surface and the incident light beam is not directly incident on the second total reflection surface. 2. A projection type liquid crystal display device having a liquid crystal light valve, wherein an incident light beam from a light source is received between the liquid crystal light valve and a light source for projection, and the light beam is irradiated onto a surface to be irradiated by the liquid crystal light valve. includes an optical element that emits the said optical element has a first total reflection surface and the second total reflection surface of the gap without features the same shape on the same plane, the incident light beam and the reflected light transmitted light A first and second total reflection surface and a light separation surface having the same shape as those of the first and second total reflection surfaces;
Further, the angle is set to 45 degrees with respect to the optical axis of the incident light beam, and the first and second total reflection surfaces and the light beam separation surface are such that half of the incident light beam incident almost in parallel is directly the light beam separation surface. , the remaining half enters the first total reflection surface, the projection type liquid crystal display device in the second total reflection surface and wherein the Turkey is configured to incident light beam is not incident directly.