JP2864014B2 - Light polarizing element and liquid crystal projector having the light polarizing element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light polarizing element and a liquid crystal projector having the light polarizing element, and more particularly to a liquid crystal projector using a liquid crystal display that transmits only one-way linearly polarized light. Things. <Conventional Technology> As a conventional liquid crystal display projector, a configuration as shown in FIG. 2 is known. That is, white light generated from the light source 1 is incident on the liquid crystal display 3 via the condenser lens 2, and the white light is modulated by the liquid crystal display 3 as a change in transmittance, and is projected on the screen 5 by the projection lens 4. . Then, the structure of the liquid crystal display 3 is composed of a polarizer 3a, a liquid crystal layer 3b and an analyzer 3c as shown in FIG. 3, and only vertical nodes of the white light incident by the polarizer 3a pass therethrough. The parallel component is absorbed or reflected, and when this vertical component is rotated by 90 degrees in the liquid crystal layer 3b, it passes through an analyzer 3c orthogonal to the polarizer 3a. <Problems to be Solved by the Invention> According to the above-described conventional example, about half of the white light is modulated on the liquid crystal display 3 and then projected on the screen 5, but the other half is blocked by the polarizer 3a. No, the light use efficiency cannot be made more than 50%. Therefore, the only way to increase the brightness (illuminance, brightness) of the screen is to increase the power supply voltage of the light source or to increase the effective aperture of the lens. This causes a problem that the apparatus itself becomes large and heavy, resulting in high cost. There was a point. The present invention solves the above-described problems of the conventional example, increases the amount of light passing through the liquid crystal display while using the same light source as the conventional one, and improves the light use efficiency without changing the power supply voltage, lens, etc. It is an object to provide a liquid crystal projector having an element and the light changing element. <Means for Solving the Problems> In order to achieve the above object, the light polarizing element of the present invention is a polarized light having a multilayer film that divides incident light into a vertical polarization component and a parallel polarization component between a pair of prisms. In an optical polarizing element having a beam splitter, a TN liquid crystal for rotating the polarization direction of incident light by 90 degrees is provided between one prism and the multilayer film. In addition, between a pair of prisms, incident light is converted into a vertical polarization component (hereinafter, referred to as “vertical component”) and a parallel polarization component (hereinafter, referred to as “vertical component”).
An optical polarizing element that has a polarizing beam splitter with a multilayer film that divides it into “parallel components” and a TN liquid crystal that rotates the polarization direction of incident light by 90 degrees between one of the prisms and the multilayer film The light from the light source is converted into a pair of vertical polarization components, and the pair of vertical components is irradiated on a liquid crystal display to form a liquid crystal projector. <Operation> The incident light from the light source is first split into a vertical component and a parallel component by a polarizing beam splitter, and the vertical component is reflected and incident on the liquid crystal display. The light passes through, is converted into a vertical component, is reflected by the next polarization beam splitter, and is incident on the liquid crystal display in the same manner as the above-described vertical component. As a result, the liquid crystal display is 100
% Of the light is incident, so that the light use efficiency can be increased and the entire device can be reduced in size. <Example> Hereinafter, an example of the present invention will be described with reference to FIG. In the figure, 13 is a liquid crystal display for a projector that transmits only one-way linearly polarized light that modulates white light, and 14 is a light polarizing element that converts white light from a light source into one-way linearly polarized light to display the liquid crystal display. 13 The light polarizing element 14 is a polarizing beam splitter 14
A multilayer film is provided on the prism interface between the a and 14b and the polarizing beam splitter 14a, and is formed of a 90-degree rotated TN liquid crystal 14c provided directly between the prism interface and the multilayer film. In the present embodiment having the above-described configuration, white light generated from a light source (not shown) is incident on the polarizing beam splitter 14a via a condenser lens (not shown), and the vertical component S of the white light is reflected at the prism boundary surface to form a liquid crystal display. It is incident on 13. On the other hand, although the parallel component P of the white light passes through the prism boundary surface, the polarization beam splitter
The light is vertically polarized by the TN liquid crystal 14c rotated by 90 degrees, which is a part of the multilayer film on the prism boundary surface 14a. The vertical component S thus converted is reflected by the next polarization beam splitter 14b, and the component α generated by a defect of the TN liquid crystal 14c or the like passes through as it is. The reflected vertical component S is incident on the liquid crystal display 13 in the same manner as the vertical component S reflected by the polarization beam splitter 14a, and nearly 100% of the light is incident, thereby increasing the light use efficiency. Therefore, the light, which was conventionally halved by the polarizer of the liquid crystal display, is almost completely incident on the liquid crystal display, and as a result, the transmittance of the liquid crystal display is increased, and the brightness on the screen is increased. (Brightness, illuminance) also doubles without increasing the power supply voltage. In addition, since the polarizer of the liquid crystal display becomes unnecessary and the component of light absorbed by the polarizer is eliminated, deterioration due to heat is reduced, and the life and color reproducibility of the liquid crystal display are improved. Furthermore, if TN liquid crystal is used to convert the parallel component of light into a vertical component, it can be used as a part of the multilayer film of the polarizing beam splitter, and it becomes compact, reducing illuminance unevenness due to light incident on the liquid crystal display. In addition, there is no wavelength dependency like a half-wave plate, and on-off control is not required. Note that when performing color display, three black-and-white liquid crystal displays are used, and a polarizing beam splitter 14 is used.
A dichroic prism that separates white light into red, green, and blue and a mirror that adjusts the optical path are placed between the liquid crystal display 13 and the light polarizing element composed of a, 14b and TN liquid crystal 14c.
The same function as described above can be achieved by using a polarizing beam splitter having wavelength characteristics corresponding to green and blue while separating white light into three colors. <Effects of the Invention> As described above, the present invention relates to an optical polarization element provided with a TN liquid crystal that rotates the polarization direction of incident light by 90 degrees between one of a pair of prisms of a polarizing beam splitter and a multilayer film. By using this light polarizing element in a liquid crystal display projector, the light use efficiency can be increased, and the brightness on the screen can be increased without changing the power supply voltage of the light source or the lens. The whole device can be made compact by using TN liquid crystal as a part of the polarizing beam splitter.
There is an effect that illuminance unevenness due to light incident on the liquid crystal display can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of a light polarizing element in a liquid crystal projector according to the present invention, FIG. 2 is a block diagram of a conventional liquid crystal display projector, and FIG. It is explanatory drawing of a part. 13 …… Liquid crystal display, 14 …… Light polarizing element, 14a, 14b
…… Polarizing beam splitter, 14c …… TN liquid crystal rotated 90 degrees.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-121821 (JP, A) JP-A-61-90584 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G09F 9/00 G02F 1/1335

Claims (1)

(57) [Claims] In a light polarizing element having a polarizing beam splitter including a multilayer film that divides incident light into a vertical polarization component and a parallel polarization component between a pair of prisms, the polarization direction of the incident light is set to 90 between one prism and the multilayer film. A light polarizing element comprising a TN liquid crystal rotated by degrees. 2. It has a polarizing beam splitter with a multilayer film that divides incident light into a vertical polarization component and a parallel polarization component between a pair of prisms, and rotates the polarization direction of the incident light by 90 degrees between one of the prisms and the multilayer film. A liquid crystal projector characterized in that light from a light source is converted into a pair of vertical polarization components by a light polarization element provided with a TN liquid crystal to be made, and the pair of vertical polarization components is irradiated on a liquid crystal display.