JPS63168622A - Optical deflecting element - Google Patents

Abstract

PURPOSE:To improve the brightness on a screen by providing a means, which divides an incident light into a parallel component and a vertical component, and a polarization plane rotating means where twisted nematic liquid crystal is arranged to rotate the plane of polarization at 90 deg.. CONSTITUTION:A polarizing beam splitter 12 divides the light incident from a light source 11 into a P component (parallel component) and an S component (vertical component), and twisted nematic liquid crystal (TN liquid crystal) 13 rotates the plane of polarization at 90 deg.. That is, TN liquid crystal 13 is given to a pair of substrates so that axes of uniaxial orientation treatment cross at 90 deg., and molecular axes of nematic liquid crystal packed between this pair of substrates form a 90 deg. helical structure between one and the other substrates, and the incident polarized light is rotated along this helical structure. The polarized light made incident as the P component is rotated at 90 deg. and is emitted as the P component as the result. Thus, the light use efficiency is practically improved twice.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a light deflection element, and more particularly to a light deflection element for a light source used when displaying content on a liquid crystal display panel is displayed by a projector.

[Prior art] In general, liquid crystal element panels are, for example, M, 5 chadt
Written by W. He1frich “Applied
Physics Letters”Vo, 18.
No. 4 (1971, 2, 15), P, +27~12
8 “Voitage-Dependent 0pti
cal Activity of a Twisted
This type of liquid crystal uses the twisted nematic type liquid crystal shown in ``Nematic Liqvid Crystal'', and this type of liquid crystal has nematic liquid crystal molecules that have positive dielectric anisotropy in the absence of an electric field. °
When an electric field is applied, nematic liquid crystals with positive dielectric anisotropy are aligned in the direction of the electric field. However, the helical structure will disappear. By detecting these two states with a pair of crossed Nicol polarizers, high-value modulation or contrast can be identified.

This type of liquid crystal display panel uses two polarizers in a crossed nicol configuration, so the light utilization efficiency is less than 50%. Therefore, for example, in the case of display using a projector, it is necessary to use a light source with sufficiently high illuminance in order to form a display with sufficiently high luminance. For this reason, conventional light sources include high-voltage, high-current light sources and large-diameter lenses.

In order to solve these problems, for example, JP-A-Sho, SL
? -/270If, the entrance color light is divided into a vertical component and a parallel component by a polarizing beam splitter, and one of the components, the vertical component light (or parallel component light), is input into the /2 By converting the light into parallel component light (or perpendicular component light) using a plate and irradiating only the two parallel component lights (or perpendicular component light) to the liquid crystal element, it is possible to substantially double the light utilization efficiency. It's here.

However, the input/half plate used in the printer head disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-127019 is limited to a narrow range of applicable wavelength bands, so in the case of display using a projector, There was a problem in that the displayed content could not be projected onto the screen using white light.

Therefore, an object of the present invention is to provide a light deflection element that solves the above-mentioned problems, and in particular, a novel light deflection element that can illuminate a liquid crystal display panel with white light and twice the amount of light compared to conventional light deflection elements. An object of the present invention is to provide a light deflection element.

[Summary of the Invention] In short, the present invention provides means for dividing incident light into parallel components and perpendicular components, and means for converting parallel component light (or perpendicular component light) into combined perpendicular component light (or parallel component light). The first feature is an optical deflection element having a polarization plane rotation means arranged with a twisted nematic liquid crystal that rotates the polarization plane at an angle of 909 degrees, and the second feature is that the incident light is rotated in a wavelength range of 4 degrees.
The first divided into parallel and perpendicular components of 00 to 500 nIl.
The first beam splitter means and the twisted nematic liquid crystal which rotates the plane of polarization to an angle of 90@ are arranged.
polarization plane rotating means and the incident light in the wavelength range of 500 to 600.
a second beam splitter means that separates the incident light into a parallel component and a perpendicular component of nm, and a second polarization plane rotation means arranged with a twisted nematic liquid crystal that rotates the polarization plane at an angle of 90°, and a second beam splitter means that divides the incident light into a parallel component and a perpendicular component of 90°. A second feature is provided in the optical deflection element having a third beam splitter means for dividing the beam into a parallel component and a perpendicular component, and a third polarization plane rotation means disposed with a twisted nematic liquid crystal for rotating the polarization plane at an angle of 90'. have.

[Detailed Description of One Island of the Invention] FIG. 1 shows a cross-sectional view of a brochure device using the optical deflection element of the present invention. In the figure, 11 is a light source (preferably a light source that lights up white light), 12 is a polarizing beam splitter that divides the light beam (p+s) incident from the light source 11 into a P component (parallel component) and an S component (perpendicular component), and 13 is a polarizing beam splitter. A twisted nematic liquid crystal (TN liquid crystal) that rotates the plane of polarization at an angle of 90 degrees, 14 a transmission type liquid crystal display panel that forms display contents, 15 a projection lens, 16 a screen, 1
7 is a condenser lens. Furthermore, in the present invention, since the P component is not necessarily completely converted into the S component by the TN liquid crystal 13, another polarizing beam splitter 18 is placed behind the TN liquid crystal 13 to convert the S component into the S component. The other P component light (indicated by α in FIG. 1) is excluded. The S component reflected by the polarizing beam splitter 18 illuminates the liquid crystal display panel 14 in the same way as the S component reflected by the polarizing beam splitter 2.

The TN liquid crystal 13 used in the present invention has a pair of substrates (for example,
(glass, plastic), -axial orientation processing axes (e.g., Ravinck processing axis, oblique evaporation processing axis) are provided so as to intersect with each other at an angle of 90'', and the substrate is filled between the pair of substrates. The molecular axes of the nematic liquid crystal form a helical structure with an angle of 90' between one substrate and the other, and the incident polarized light will be rotated along this helical structure. As shown, the polarized light incident as a P component undergoes optical rotation at an angle of 90°, and the combined P component is output.

Further, as the liquid crystal display panel 14 used in the present invention, a transmissive liquid crystal display panel is preferably used. This transmissive liquid crystal panel uses, for example, a transparent substrate on which a pair of transparent electrodes are wired. In a preferred embodiment of the present invention, transparent electrodes wired on one substrate are used as a plurality of scanning electrodes, transparent electrodes wired on the other substrate are applied as a plurality of information electrodes, and scanning signals are sequentially applied to the scanning electrodes, It is preferable to apply a matrix drive method in which information is displayed by applying an information signal to the information electrodes in synchronization with this scanning signal.

The liquid crystal used is Twisted, Doomatic liquid crystal, U.S. Patent No. 4563059 and U.S. Patent No. 4367.
Chiral smectic liquid crystal disclosed in Japanese Patent No. 924 can be used. An analyzer 19 is disposed behind such a liquid crystal display panel 14, and optical switching is performed according to an information signal input to the liquid crystal display panel 14.

FIG. 2 is another preferred embodiment of the invention. In the figure,
24G is a liquid crystal display panel controlled by green image information,
24R is a liquid crystal display panel controlled by red image information, 2
4B is a liquid crystal display panel controlled by blue image information. The projector shown in FIG. 2 is illuminated by a light source 11 that emits white light. The white light from this light source 11 is focused by a condenser lens 17, and is sequentially focused by a polarizing beam splitter 21G for green and a polarizing beam splitter 21G for red. Green light (B1), red light (R1), and blue light (B, ) are reflected as S components by the polarizing beam splitter 21R and the blue polarizing beam splitter 21B, respectively. In addition, in the incident optical path, TN liquid crystals 221, 222 and 223, similar to the TN liquid crystal shown in FIG. is S
Polarizing beam splitters 23G, 23R, and 238 are arranged to reflect only the component polarized light.

S passing through liquid crystal display panels 24G, 24R and 2'4B
The component polarized light (G, R, and B□) is analyzed by analyzer 2812.
The light is irradiated onto the screen 16 through reflecting mirrors 261 and 262 and the dichroic mirror 27 through 82 and 283, and a color display is formed on the screen 16.

In addition, the light polarizing element of the present invention has a wavelength range of 500 to 600 nm in order from the incident light in order to reduce uneven brightness caused by the combination of the beam splitter and the dichroic mirror.
Green polarizing beam splitter 21G that reflects the incident light of
, a red polarizing beam splitter 21R that reflects incident light in a wavelength range of 600 to 700 nm, and a wavelength range of 400 to 5 nm.
A blue polarizing beam splitter 21B that reflects incident light of 00 nm may be provided.

[Effects of the Invention] As explained above, the light polarizing element of the present invention can increase the light utilization efficiency of a projector using a liquid crystal panel, and can improve the light on the screen without changing the power supply voltage, lens, etc. There is something that can be done to improve the brightness.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing embodiments of the optical deflection element of the present invention.

Claims (5)

[Claims] (1) Means for dividing incident light into parallel and perpendicular components, and means for converting parallel component light (or perpendicular component light) into perpendicular component light (or parallel component light), the plane of polarization being 90
1. A light deflection element comprising: a polarization plane rotating means in which a twisted nematic liquid crystal is arranged to rotate the crystal at an angle of .degree. (2) The optical deflection element according to claim 1, further comprising a beam splitter means for dividing the light beam passing through the polarization plane rotation means into a horizontal component and a perpendicular component. (3) A first beam splitter means that separates incident light into a parallel component and a perpendicular component in the wavelength range of 400 to 500 nm, and a first polarization plane rotation means that includes a twisted nematic liquid crystal that rotates the polarization plane to an angle of 90°. and a second beam splitter means for dividing the incident light into a parallel component and a perpendicular component in a wavelength range of 500 to 600 nm, and a second polarization plane rotation means disposed with a twisted nematic liquid crystal that rotates the polarization plane to an angle of 90°. , the wavelength range of the incident light is 600
Light characterized by having a third beam splitter means for dividing the beam into a parallel component of ~700 nm and a perpendicular component, and a third polarization plane rotation means in which a twisted nematic liquid crystal for rotating the polarization plane at an angle of 90° is arranged. Polarizing element. (4) The first beam splitter means, the second beam splitter means, and the third beam splitter means,
A second beam splitter means, a third beam splitter means, and a third beam splitter means are arranged in the optical path of the incident light in order.
4. The optical polarizing element according to claim 3, wherein the beam splitter means and the first beam splitter means are arranged. (5) Claim 3, wherein the first polarization plane rotation means, the second polarization plane rotation means, and the third polarization plane rotation means are arranged with beam splitter means for dividing the light beam into a parallel component and a perpendicular component. The optical deflection element described above.