JPH0566503A - Projection type liquid crystal projection - Google Patents

Abstract

PURPOSE:To suppress deterioration in color characteristics by making the brightness of a liquid crystal projector image high. CONSTITUTION:This device is equipped with cholesteric liquid crystal cells 23, 24, and 25 which generate parallel luminous flux by a light source 20, a spherical mirror 21, and a condenser lens 22, and transmit the clockwise circular polarized light component of the parallel light on the optical axis of this parallel light and reflect the anticlockwise circular polarized light component, a l/4 wavelength plate 26 which converts the transmitted light of the cells into linear polarized light, and dichroic mirrors 27, 28, and 29 which separate the converted linear polarized light into an R(red), a G(green), and a B(blue) component, reflect them by 90 deg., and irradiate respective liquid crystal panels 13, 14, and 15. The reflected light (anticlockwise polarized light component) of the cholesteric liquid crystal cells 23, 24, and 25 is passed through the condenser lens 22 and converted by the spherical mirror 21 into the clockwise circular polarized light component, which is transmitted through the 1st-3rd cholesteric liquid crystal cells 23, 24, and 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal projection capable of displaying an image on a large screen, and more particularly to a projection type liquid crystal for improving the light utilization efficiency of a light source to increase the brightness of an image. It's about projection.

[0002]

2. Description of the Related Art In recent years, this type of projection-type liquid crystal projection has become smaller and smaller overall because the liquid crystal panel that forms the display image is smaller, making it more convenient to carry and popular for business and home use. It is possible to expand.

In the projection type liquid crystal projection, brightness is a problem, and the larger the screen such as the screen, the darker the display image, that is, the brightness of the screen decreases.

That is, of the polarizing plates provided on both side surfaces of the liquid crystal panel, the polarizing plate on the incident light side has approximately 50% of the incident light.
This is because% is cut.

Therefore, for example, as shown in FIG. 3, a projection type liquid crystal projection using a cholesteric liquid crystal instead of the polarizing plate has been considered.

In this case, right-handed circularly polarized light components of R (red), G (green) and B (blue) light are transmitted on the optical axis of parallel light obtained by condensing the light from the light source. However, a cholesteric liquid crystal cell 1 with a left-handed spiral pitch that reflects the left-handed circularly polarized light component 1,
The cholesteric liquid crystal cells 4, 5 and 6 are arranged at an angle of 45 degrees and have right-handed circular pitches for reflecting the right-handed circularly polarized light components of the R, G and B lights in the same direction. It is formed at right angles to the liquid crystal cells 1, 2, 3.

Further, the cholesteric liquid crystal cell 1,
Total reflection mirrors 7, 8 and 9 are arranged at 45 degrees with respect to 2 and 3, and these cholesteric liquid crystal cells 1, 2, and
The light of the right-handed circularly polarized light component reflected in 3 is reflected respectively,
The right-handed circularly polarized light component of the polarized light due to this reflection is returned to and transmitted through the cholesteric liquid crystal cells 1, 2, and 3, and the right-handed circularly polarized light component of the light from the light source is also the transmitted light of the respective cholesteric liquid crystal cells 1, 2, and 3. I am trying to contribute to.

Then, the cholesteric liquid crystal cell 1,
The transmitted light of 2 and 3 and the reflected light of the cholesteric liquid crystal cells 4, 5 and 6 having a right-handed spiral pitch are converted into linearly polarized light by the λ / 4 wave plates 10, 11 and 12, respectively, and converted into this linearly polarized light. The R, G, and B lights are respectively on the liquid crystal panel 1.
Irradiation to 3, 14, and 15.

As described above, by using the cholesteric liquid crystal having excellent selectivity of the reflection wavelength and having the action of separating right-handed and left-handed circularly polarized light, not only the right-handed circularly polarized component of the light of the light source but also the left-handed circular The polarized component can also be color-separated into R, G, and B, and the irradiation light of each liquid crystal panel 13, 14, 15 is not limited to one circularly polarized light component of the light of the light source, for example, a right-handed circularly polarized light component. The left-handed circularly polarized light component also contributes.

Referring to FIG. 4, for example, the color separation of R (red) will be described. Of the incident light (parallel light), R
The left-handed circularly polarized light component of the (red) light is at a right angle in the cholesteric liquid crystal cell 1 with a left-handed spiral pitch (upward in the drawing).
The light having the left-handed circularly polarized light component reflected by the total reflection mirror 7 is reflected and polarized. At this time, the light converted into the right-handed polarized light by the polarized light is again made incident on the cholesteric liquid crystal cell 1 having the left-handed spiral pitch.

As a result, the light of the right-handed circularly polarized light component by the total reflection mirror 7, that is, the light of the right-handed circularly polarized light component which is once reflected and converted is transmitted through the cholesteric liquid crystal cell 1 having the left-handed spiral pitch. It is incident on the λ / 4 wave plate 10.

On the other hand, of the incident light, the right-handed circularly polarized light component of the R light is transmitted through the cholesteric liquid crystal cell 1, but is transmitted in the right-angled direction (see the same drawing) by the right-handed spiral pitch choristeric liquid crystal plate 4. Λ / 4 wave plate 1
It is incident on 0.

Then, by the λ / 4 wave plate 10,
The incident circularly polarized light is converted into linearly polarized light, and this linearly polarized light is applied to the liquid crystal panel 13. Therefore, of the incident light, most of the R light is in the λ / 4 wave plate 10.
Since the light is converted into linearly polarized light by the above, not only the right-handed circularly polarized light component of the parallel light (R) but also its left-handed circularly polarized light component contributes to the irradiation light of the liquid crystal panel 13, and the light utilization efficiency of the light source It is possible to improve.

As for the G (green) and B (blue) lights, most of the parallel G and B lights (left-handed circularly polarized light component and right-handed circularly polarized light component) also contribute. It will be.

The liquid crystal panels 13, 14, 15
As, for example, twisted nematic liquid crystal (TN liquid crystal)
In the case of using, a predetermined voltage is applied to the twisted nematic liquid crystal so that each λ / 4 wave plate 10, 11,
The R, G, and B lights that have been linearly polarized by 12 are transmitted or blocked, and a predetermined image can be formed.

Further, as shown in FIG. 3, light transmitted through the liquid crystal panels 13, 14 and 15 is converted into circularly polarized light by the polarizer 16, and if the circularly polarized light is, for example, R light. The light is reflected at a right angle in the total reflection mirror 17 (to the right in the drawing), and the same G and B light is reflected by the dichroic mirrors 18 and 19 in the same direction as that of the total reflection mirror 17, respectively. To be done.

Although not shown, the above-mentioned liquid crystal panels 13, 14 and 15 are formed by a projection lens on the optical axis of the reflected light.
The image constituted by is displayed on a large screen such as a screen.

In this way, the light utilization efficiency of the light source is increased,
In addition, since it is not necessary to use a polarizing plate on the incident light side of each liquid crystal panel 13, 14, 15, it is possible to increase the displayable brightness of the large screen and realize a projection type liquid crystal projection of a bright screen. You can

[0019]

However, in the above-mentioned projection type liquid crystal projection, the light from the light source is changed to R,
Since two types of cholesteric liquid crystals that are color-separated into G and B light (right-handed spiral pitch and left-handed spiral pitch) are required, cholesteric liquid crystals of right circularly polarized light and left circularly polarized light having the same helical pitch are required. It is extremely difficult to combine the images, and if the spiral pitch is deviated, it does not contribute to the higher brightness of the image, that is, the brightness of the image does not become so high.

Further, if the spiral pitch of each of the above cholesteric liquid crystals is changed by temperature and the change tendency is opposite between the right circularly polarized cholesteric liquid crystal and the left circularly polarized cholesteric liquid crystal, the above synthesized cholesteric liquid crystal. The light transmission band (or the light reflection band) of is shifted in the opposite direction, and the color characteristics are extremely deteriorated.

The present invention has been made in view of the above problems, and its object is to separate each cholesteric liquid crystal into either right-handed circularly polarized light or left-handed circularly polarized light when color-separating the light from the light source. It is an object of the present invention to provide a projection type liquid crystal projection capable of improving utilization efficiency, suppressing the influence of temperature, and displaying an image with high brightness and good color characteristics.

[0022]

In order to achieve the above object, the present invention condenses light from a light source with a condenser lens into parallel light, and, behind the light source, uses a spherical mirror to reflect the light from the light source. The reflected light is reflected and condensed by the condenser lens to form parallel light, and the parallel light is separated into R, G, and B to irradiate each liquid crystal panel forming a predetermined image, and the parallel light passes through the liquid crystal panel. In a projection type liquid crystal projection for synthesizing a predetermined light and projecting a predetermined image on a screen or the like, on the optical axis of the condenser lens, the clockwise circularly polarized light component or the counterclockwise circularly polarized light component of the parallel light is transmitted, The first to third cholesteric liquid crystal cells of the same circular polarization that reflect the left-handed circularly polarized light component or the right-handed circularly polarized light component are provided, and the transmitted light of the first to third cholesteric liquid crystal cells is λ.
/ 4 wavelength plate converts to linearly polarized light, and the linearly polarized light is color-separated into R, G, and B.
When irradiating the liquid crystal panels forming a predetermined image with G and B lights, respectively, the light of the left-handed circularly polarized light component or the right-handed circularly polarized light component reflected by the first to third cholesteric liquid crystal cells is returned to the spherical mirror. The gist is that the light is converted into circularly polarized light that can be transmitted through the first to third cholesteric liquid crystal cells.

[0023]

With the above structure, the light from the light source is condensed by the condenser lens, reflected by the spherical mirror at the rear, and condensed by the condenser lens. One of the circularly polarized light components of the light made parallel by this light collection, for example, the clockwise circularly polarized light component is transmitted through the first to third cholesteric liquid crystal cells.

At this time, the left-handed circularly polarized light components of the parallel light are respectively reflected by the first to third cholesteric liquid crystal cells and returned to the light source and the spherical mirror side via the condenser lens, but are reflected by this spherical mirror. , Is polarized by this reflection.

The light (reflected light) of the right-handed circularly polarized light component due to the above-mentioned polarized light returns to the original optical path, enters the first to third cholesteric liquid crystal cells again, and is transmitted.

The transmitted light of each cholesteric liquid crystal cell is
Through the third dichroic mirror, the light is separated into R, G, and B colors, and the color-separated lights are applied to the respective liquid crystal panels arranged in the same direction.

Thus, no polarizing plate is used on the incident side of each liquid crystal panel, and not only the right-handed circularly polarized light component of the light from the light source,
Since the left-handed circularly polarized light component also contributes to the irradiation light of each liquid crystal panel, when an image composed of each liquid crystal panel is displayed on a screen or the like, the brightness of the displayed image can be increased, and Since the first to third cholesteric liquid crystal cells have the same circular polarization, the color characteristics of the image do not deteriorate.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the figure, the same parts as those in FIG.

In FIG. 1, this projection type liquid crystal projection has a first to a third liquid crystal panels 13, 14 and 15.
A light source 20 that emits light (white light) for irradiating the light source, and a spherical mirror 21 that has the light source 20 as a spherical center behind the light source 20.
And a condenser lens (optical system) 22 that condenses the direct light from the light source 20 and the reflected light from the spherical mirror 21 into parallel light, and the parallel light (R) on the optical axis of the condenser lens 22. , G, B) which transmits the right-handed circularly polarized light component and reflects the left-handed circularly polarized light component, the first to third cholesteric liquid crystal cells 23, 24, 2 having a left-handed spiral pitch.
5, and the light transmitted through the first to third cholesteric liquid crystal cells 23, 24 and 25 (right circularly polarized light component) on the same axis as the light source 20, the spherical mirror 21 and the condenser lens 22, R (red), Color separation into G (green) and B (blue),
The R, G, and B lights are reflected in the same direction (right angle direction), and the reflected lights are reflected by the first to third liquid crystal panels 1 to 3.
It is provided with first to third dichroic mirrors 27, 28, 29 for irradiating 3, 14, 15 respectively.

Here, as shown in FIG. 2, the first to third cholesteric liquid crystal cells 23, 24, 25 are integrated by laminating liquid crystals with a transparent glass plate as a boundary, for example. It is circularly polarized light, and transmits the right-handed circularly polarized light component of incident light and reflects the left-handed circularly polarized light component.

The light reflected by the first to third cholesteric liquid crystal cells 23, 24 and 25 (counterclockwise circularly polarized light component) passes through the condenser lens 22, that is, the original optical path, and the light source 20 and the spherical mirror 21. Returned to the side.

Moreover, the respective returned R, G, B lights (left-handed circularly polarized light components) are reflected by the spherical mirror 21, and the right-handed circularly polarized light components of the light polarized by this reflection are passed through the condenser lens 22. The light passes through the original optical path to enter the first to third cholesteric liquid crystal cells 23, 24, 25 and is transmitted therethrough.

That is, most of the lights of the parallel colors (R, G, B) condensed by the condenser lens 22 among the lights of the light source 20 are the first to third cholesteric liquid crystal cells 2.
It will be transmitted at 3, 24 and 25, respectively.

The transmitted light (right-handed circularly polarized light component) of each of the first to third cholesteric liquid crystal cells 23, 24 and 25 is converted into a linearly polarized light by the λ / 4 wavelength plate 26, and the converted linearly polarized light is converted. Is the first to third dichroic
Color separation into R, G and B is performed by the mirrors 27, 28 and 29.

Further, each dichroic mirror 27, 2
The R, G, and B lights that have been color-separated by 8 and 29 are reflected at right angles in the same direction, and are applied to the first to third liquid crystal panels 13, 14, and 15 that form a display image.

The image of each light (R, G, B) which has passed through each liquid crystal panel 13, 14, 15 is reflected by the total reflection mirror 17, the fourth dichroic mirror 18 and the fifth dichroic mirror 19, respectively. , Synthesized.

Then, like the conventional example, the total reflection mirror 17, the fourth and fifth dichroic mirrors 1 are provided.
The projection lens 30 on the same axis 8 and 19 displays the above-mentioned images of R, G, and B on a screen or the like.

As described above, the light from the light source 20 is incident on the first to third cholesteric liquid crystal cells 23, 24 and 25 of the left-handed spiral pitch in which the polarizing plate is replaced, and the light is rotated in the right-handed circularly polarized light. The first to the third cholesteric liquid crystal cells 26, 27 that transmit the component, reflect the left-handed circularly polarized light component of the light, and reflect the reflected light by the spherical mirror 21 to convert it into the right-handed circularly polarized light component. , 28 are made transmissive, and the transmitted light of each cholesteric liquid crystal cell is color-separated into each R, G, B to irradiate each liquid crystal panel 13, 14, 15 to obtain a display image. Not only the right-handed circularly polarized light component of the light, but its left-handed circularly polarized light component
By contributing to the irradiation light of 3, 14, and 15, the light utilization efficiency of the light source 20 can be improved, the brightness of the display image can be increased, and thus the projection type liquid crystal projection of the clear image. Can be realized.

Further, the first to third cholesteric liquid crystal cells 23, 24 and 25 have the same left-handed spiral pitch,
Since two types (right circularly polarized light and left circularly polarized light) are not necessary and the cholesteric liquid crystal cells 23, 24, 25 are laminated and integrated, the production thereof is easy.

Further, each cholesteric liquid crystal cell 23,
Since 24 and 25 can be done with one type,
The spiral pitch of these cholesteric liquid crystals changes due to temperature change, and does not affect the light transmission band (light reflection band) so much. In addition, the spiral pitch may shift in the same direction, and the color characteristics of the image It does not get worse.

Furthermore, it is possible to use only one λ / 4 wavelength plate 26 for converting circularly polarized light into linearly polarized light, and the cost can be reduced accordingly.

In the above embodiment, the first to third cholesteric liquid crystal cells 23, 24 and 25 are left-handed circularly polarized light. However, even if the right-handed circularly polarized cholesteric liquid crystal cells are used,
The same effect can be obtained.

[0043]

As described above, according to the projection type liquid crystal projection of the present invention, the light of the light source is condensed by the condenser lens to be parallel light, and the light of the light source is spherical mirror behind the light source. The parallel light is condensed by the same condenser lens, and the parallel light is reflected by R, G, and B.
In the projection type liquid crystal projection that irradiates each liquid crystal panel that separates the color into a predetermined image and synthesizes the light that has passed through the liquid crystal panel and projects the predetermined image on a screen, etc., on the optical axis of the condenser lens. The first to third cholesteric liquid crystal cells of the same circular polarization that transmit the right-handed circularly polarized light component or the left-handed circularly polarized light component of the parallel light and reflect the left-handed circularly polarized light component or the right-handed circularly polarized light component, respectively. The transmission light of the first to third cholesteric liquid crystal cells is converted into linearly polarized light by a λ / 4 wavelength plate, the linearly polarized light is color-separated into R, G, B, and the color-separated R is separated. , G, B are respectively applied to the liquid crystal panel forming a predetermined image, the light reflected by the first to third cholesteric liquid crystal cells (counterclockwise circularly polarized light component or rightward circularly polarized light component) The light is returned to the spherical mirror side through the condenser lens, and is converted into the right-handed circularly polarized light component or the left-handed circularly polarized light component by this spherical mirror, and the first to third cholesteric liquid crystal cells can be transmitted. Not only the circularly polarized light component of the above, but also the other circularly polarized light component contributes to the irradiation of each liquid crystal panel, the light utilization efficiency of the light source can be extremely increased, and the brightness of the display image by those liquid crystal panels can be increased. You can

The first to third cholesteric liquid crystal cells may be of the same circularly polarized light (left-handed helical pitch or right-handed helical pitch), that is, one type of cholesteric liquid crystal cell may be used and they may be laminated and integrated. Therefore, it is easy to create a cholesteric liquid crystal cell, and even if the helical pitch changes due to temperature change, there is little shift in the mutual transmission band (or reflection band). The influence of the change can be reduced, the deterioration of the color characteristics can be suppressed, and furthermore, only one λ / 4 wavelength plate for linearly polarizing the light irradiating each liquid crystal panel is required, so that the cost of the device can be reduced. There is an effect that it can be lowered.

[Brief description of drawings]

FIG. 1 is a schematic partial optical configuration diagram of a projection type liquid crystal projection showing an embodiment of the present invention.

FIG. 2 is a schematic partial optical configuration diagram of the projection type liquid crystal projection shown in FIG.

FIG. 3 is a schematic partial optical configuration diagram of a conventional projection type liquid crystal projection.

FIG. 4 is a schematic partial optical configuration diagram of the projection type liquid crystal projection shown in FIG.

[Explanation of symbols]

 13, 14, 15 Liquid crystal panel 16 Polarizer 17 Total reflection mirror 18 Fourth dichroic mirror 19 Fifth dichroic mirror 20 Light source 21 Spherical mirror 22 Condenser lens (optical system) 23 First cholesteric liquid crystal cell 24 Second Cholesteric liquid crystal cell 25 Third cholesteric liquid crystal cell 26 λ / 4 wavelength plate 27 First dichroic mirror 28 Second dichroic mirror 29 Third dichroic mirror

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H04N 9/31 C 9187-5C

Claims (2)

[Claims] 1. The light from a light source is condensed by an optical system into parallel light, and the light from the same light source is reflected by a mirror behind the same light source, and the reflected light is condensed by the same optical system and collimated. A projection type in which the parallel light is separated into R, G, and B to irradiate each liquid crystal panel forming a predetermined image, and the light passing through the liquid crystal panel is combined to project a predetermined image on a screen or the like. In the liquid crystal projection, on the optical axis of the optical system, the same circle that transmits the clockwise circularly polarized light component or the counterclockwise circularly polarized light component of the parallel light and reflects the counterclockwise circularly polarized light component or the clockwise circularly polarized light component, respectively. Polarized first to third cholesteric liquid crystal cells are provided, the transmitted light of the first to third cholesteric liquid crystal cells is converted into linearly polarized light by a λ / 4 wavelength plate, and the linearly polarized light is converted into R, G, In addition to color separation into B, this color separated R,
When irradiating the liquid crystal panels forming a predetermined image with G and B lights, the light of the left-handed circularly polarized light component or the right-handed circularly polarized light component reflected by the first to third cholesteric liquid crystal cells is returned to the mirror. The projection type liquid crystal projection is characterized in that the first to third cholesteric liquid crystal cells are converted into circularly polarized light that can be transmitted. 2. The projection type liquid crystal projection according to claim 1, wherein the first to third cholesteric liquid crystal cells are laminated and integrated.