JPH0384537A - Projection type display device - Google Patents

Abstract

PURPOSE:To improve the utilization efficiency of light source light in the entire device by projecting an image, which is formed by a liquid crystal display element, chromatically without using any polarizing plate. CONSTITUTION:Polarized light separation characteristics that a dichroic film has are utilized to project modulated light from liquid crystal display elements 5R, 5G, and 5B without using any polarizing plate. Namely, the S-polarized component of red light is modulated by the liquid crystal display element 5R and the modulated polarized light component of the red light P reaches a projec tion lens 7. Further, the S-polarized component of green light is modulated by the liquid crystal display element 5G and only the S-polarized component of the green light which is modulated by the liquid crystal display element 5G reaches the projection lens 7. Further, the P-polarized component of blue light is modulated by the liquid crystal display element 5B and the modulated P-polarized light component of the green light P reaches the projection lens 7. Consequently, the utilization efficiency of the light source light in the whole device is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection type display device that projects images on a liquid crystal display element in color.

[Prior Art] As shown in FIG. 4, a liquid crystal display element has a liquid crystal sealed between a pair of opposing glass substrates 52 and a transparent electrode 53 attached to the inner surface of the pair of glass substrates 52. ,
Images formed by the optical rotation of the liquid crystal display element are usually obtained by disposing polarizing plates 51 on both sides thereof.

A projection display device that enlarges and projects a color image onto a screen or the like using a liquid crystal display element using such a polarizing plate uses, for example, a white light source to drive the liquid crystal display elements driven by red, green, and blue image information. The transmitted light from each liquid crystal display element was passed through red, green, and blue filters and projected onto a screen by a projection lens.

[Problems to be Solved by the Invention] However, in the conventional example described above, most of the incident light that enters the liquid crystal display element from the light source is absorbed by the polarizing plate, so the transmittance of the liquid crystal display element becomes low and the projection This method has disadvantages in that the utilization efficiency of the light source in the entire display device is low, and that the light absorbed by the polarizing plate is converted into heat, leading to a rise in temperature and deteriorating the characteristics of the liquid crystal display element.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a projection display device that can color project an image formed by a liquid crystal display element without using a polarizing plate.

[Means for Solving the Problems] One of the typical configurations for achieving the object of the present invention is as follows:
A plurality of guichroic films having color separation characteristics and polarization separation characteristics form an optical path that separates the light source light of the illumination means into each color component light, and a transmissive liquid crystal display element is arranged in these optical paths, and these A projection type display device that combines image light modulated by a transmissive liquid crystal display element emitted from an optical path and projects the combined image light using a projection lens, in which any one of these guichroic films emits the light source light of the illumination means. The projection type display device is characterized in that each optical path is arranged so as to guide the polarized light.

[Function] The projection display device configured as described above can emit modulated light from the liquid crystal display element without using a polarizing plate by utilizing the polarization separation characteristics of the guichroic film.

[Example] Example 1 FIG. 1 is a schematic configuration diagram showing Example 1 of a projection type display device according to the present invention.

1 is a light source such as a metal halide lamp, 2 is a lens that reflects the light emitted from the light source 1 or converts it into approximately parallel light such as the light reflected from the flexor 3, and 4 is a lens that causes temperature rise among the light source lights. A heat shielding filter that absorbs infrared light,
These constitute the illumination optical system of the projection display device. Reference numeral 7 denotes a projection lens, which is attached to the housing 10 of the main body of the apparatus as shown in the figure, so that its optical axis is orthogonal to the optical axis of the illumination optical system.

On the inner surface of the casing 10, a (1) total reflection mirror 11 and a second total reflection mirror 12 are provided, as well as a first light shielding surface 13 and a second light shielding surface 14.

Inside the casing of the device main body (not shown), there are
Dichroic mirrors 6a, 6b, 6c having spectral and polarized light transmittance characteristics shown in FIG.

Transmissive liquid crystal display devices 5R, 5 6d are arranged at an angle as shown in the figure, and are driven by red, green, and blue video signals.
G and 5B are arranged as shown in the figure, and transmissive liquid crystal display devices 5R and 5G.

As shown in FIG. 3, 5B is not provided with a polarizing plate.

In the projection display device configured as described above, the light emitted from the light source 1 is converted into substantially parallel light by the reflector 2 and the lens 3, and the infrared light (wavelength of about 700 nm or more) is absorbed by the heat shielding filter 4.

The light source light first reaches the dichroic mirror 68, but since this dichroic mirror 6a has the characteristics shown in FIG. is dichroic mirror 6
reaches 0. The dichroic mirror 60 is shown in FIG. 2(c).
Since the P polarized light component is transmitted through the dichroic mirror 60, the blue liquid crystal display element
B, the plane of polarization is rotated for each pixel, and the light is modulated into a P polarization component and an S polarization component, reflected by the second total reflection mirror 12, and incident on the dichroic mirror 6d. Since this dichroic mirror 6d has the characteristics shown in FIG. 2(d), only the P-polarized component of blue light (light with a wavelength of about 500 nm or less) passes through the dichroic mirror 6d and reaches the projection lens 7. Other components are dichroic mirror 6
d and is absorbed by the second light shielding surface 14.

On the other hand, among the light source lights, red light (wavelength of approximately 600nrQ or more)
The S-polarized light component of the light (light of 00 nm or less) is reflected by the dichroic mirror 6a and the first total reflection mirror 11 and enters the red liquid crystal display element 5R, and the plane of polarization rotates in each pixel to turn the red light into P-polarized light. component and red light S polarization component are modulated,
It reaches the dichroic mirror 6b. Since this dichroic mirror 6b has the characteristics shown in FIG.
b and reaches the dichroic mirror 6d, but the red S polarized light component is reflected by the dichroic mirror 6b and absorbed by the first light shielding surface 13. dichroic mirror 6
d transmits only P-polarized light having a wavelength of about 500 nm or less, so the P-polarized red light component is reflected by the dichroic mirror 6d and reaches the projection lens 7.

On the other hand, the light transmitted through the dichroic mirror 6a is the P-polarized component of the light source light described above and the S-polarized component with a wavelength of about 600 nm or less, and the dichroic mirror 60 has a wavelength of about 600 nm or less.
Since it has the characteristic of reflecting S-polarized light components of 0Or++n or less, this light of S-polarized light components of wavelengths of about 600 nm or less enters the green liquid crystal display element 5G, and the plane of polarization is rotated for each pixel, so that the light has a wavelength of about 600 nm. The light is modulated into the following S-polarized light component and the P-polarized light component with a wavelength of about 600 nm or less, and reaches the dichroic mirror 6b. Since the dichroic mirror 6b transmits the P polarized light component and the S polarized light component with a wavelength of about 500 nm or less, the S reflected by the dichroic mirror 6b
The polarized light component becomes green light having a wavelength of approximately 500 nm or more and 600 nm or less, and the S-polarized component of this green light reaches the dichroic mirror 6d. As described above, the dichroic mirror 6d has the characteristic of transmitting only the P polarized light component with a wavelength of about 500 nm or less, so the S polarized light component of the green light is reflected by the dichroic mirror 6d and reaches the projection lens 7. . Note that the P-polarized light component and the S-polarized light component having a wavelength of about 500 nm or less that have passed through the dichroic mirror 6b are absorbed by the first light shielding surface 13.

Therefore, the S-polarized component of the red light of the light source light is modulated by the liquid crystal display element 5R, the P-polarized component of the modulated red light reaches the projection lens 7, and the S-polarized component of the green light is modulated by the liquid crystal display element 5G. Of the light modulated by the liquid crystal display element 5G, only the S-polarized green light component reaches the projection lens 7.
Further, the P-polarized component of the blue light is modulated by the liquid crystal display element 5B, the modulated P-polarized component of the blue light reaches the projection lens 7, and a color image is enlarged and projected onto a screen (not shown).

Embodiment 2 FIG. 5 is a schematic configuration diagram showing Embodiment 2 of a projection type display device according to the present invention.

In the first embodiment described above, four dichroic mirrors 6a to 6d each having different characteristics were used, but in this embodiment, two dichroic mirrors 16a and 16b having the spectral and polarization transmittance characteristics shown in FIG. 6 were used. The dichroic mirrors 6a to 6d are arranged as shown in the figure, and a polarizing beam splitter 8 is provided between the illumination optical system and the dichroic mirror 6e. A third total reflection mirror 15 is provided which totally reflects the S-polarized light component.

That is, of the parallel light from the illumination optical system emitted by the light source 1, the S-polarized component is reflected by the polarizing beam splitter 8, reflected by the third total reflection mirror 15, and then reflected by the polarizing beam splitter 8 again. Then, returning to the illumination optical system, only the P-polarized light component reaches the lower half of the dichroic mirror 16a.

Since the dichroic mirror 16a has the characteristics shown in FIG.
1, the light enters the red liquid crystal display element 5R, and is modulated by the red liquid crystal display element 5R into a red light P polarization component and a red light S polarization component, and reaches the upper half of the dichroic mirror 16a. Since the dichroic mirror 16a has a transmission characteristic for the S polarized component of the red light, the dichroic mirror 16a transmits the red light S! which is modulated by the red liquid crystal display element 5R. The light component passes through the upper half of the dichroic mirror 16a and reaches the upper half of the dichroic mirror 16b, and the P-polarized red light component is reflected by the upper half of the dichroic mirror 16a and absorbed by the first light shielding surface 13.

Since this dichroic mirror 16b has the characteristics shown in FIG. 6(b), the S-polarized component of the red light is reflected by the upper half of the dichroic mirror 16b and
reach.

On the other hand, among the P-polarized light components that have passed through the polarizing beam splitter 8 and reached the lower half of the dichroic mirror 16a, the wavelength is approximately 6
Light of 00 nm or less passes through the lower half of the dichroic mirror 16a and reaches the lower half of the dichroic mirror 16b.

This dichroic mirror 16b has a wavelength of approximately 500 nm.
Since it has the property of transmitting the following P-polarized light component, the light of the P-polarized light component of the green light is transmitted to the dichroic mirror 16.
The light is reflected at the lower half of the dichroic mirror 16a, enters the green liquid crystal display element 5G, is modulated into a green light P polarization component and a green light S polarization component, and reaches the upper half of the dichroic mirror 16a.

The S-polarized component of the green light is reflected by the upper half of the dichroic mirror 16a, and the P-polarized component of the green light is transmitted through the upper half of the dichroic mirror 16a and absorbed by the first light-shielding surface 3.

The S-polarized green light component reflected by the upper half of the dichroic mirror 16a reaches the upper half of the dichroic mirror 16b, is reflected by the dichroic mirror 16b, and reaches the projection lens 7.

On the other hand, the wavelength of about 5 transmitted through the dichroic mirror 16b
The P-polarized light component of 00 nm or less, that is, the P-polarized blue light component, enters the blue liquid crystal display element 5B, and the blue light P
The light is modulated into a polarized light component and an S-polarized light component of the blue light, and is totally reflected by the second total reflection mirror 12, reaching the upper half of the dichroic mirror 16b.

Since the dichroic mirror 16b transmits P-polarized light having a wavelength of about 500 nm or less, the modulated blue light P-polarized light passes through the upper half of the dichroic mirror 16b, reaches the projection lens 7, and is modulated. Blue light S
The polarized light component is reflected by the upper half of the dichroic mirror 16b and absorbed by the second light shielding surface 14.

Therefore, of the light source light, the P-polarized red light component is modulated by the liquid crystal display element 5R for red, the S-polarized component of the modulated red light reaches the projection lens 7, and the P-polarized component of the green light reaches the P-polarized light component for green. The S polarized light component of the green light modulated by the liquid crystal display element 5G reaches the projection lens 7, and then the blue light P
The polarized light component is modulated by the blue liquid crystal display element 5B,
The modulated P-polarized blue light component reaches the projection lens 7 and is projected onto a screen (not shown).

[Effects of the Invention] As described above, according to the present invention, a polarizing plate is not required, the efficiency of using the light source light in the entire device is increased, and furthermore, characteristic deterioration due to temperature rise of the liquid crystal display element is suppressed.

According to the first invention, red, green, and blue optical paths can be formed using, for example, four dichroic mirrors each having different color separation and polarization separation characteristics.

Further, according to the second invention, for example, dichroic mirrors can be shared, and a color separation optical system and a color synthesis optical system can be configured with two dichroic mirrors, which improves the ease of assembly of the device and reduces costs. This has the effect of reducing the amount of water used.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a projection type display device according to the present invention, and FIGS. 2(a), (b), and (c). (d) is a diagram showing the spectral and polarized light transmittance characteristics of the dichroic mirror in Example 1, FIG. 3 is a cross-sectional view of the liquid crystal display element in Example 1, and FIG. 4 is a diagram showing the liquid crystal display element in a conventional display device. A sectional view showing the arrangement state of the polarizing plate and the polarizing plate, the fifth
The figure is a schematic diagram showing Example 2, Figures 6(a) and (b)
2 is a diagram showing the spectral and polarized light transmittance characteristics of the guichroic mirror in Example 1. FIG. 1: Light source 3: Lenses 5R, 5G, 5B 6a, 6b, 6c, 6d Near: Projection lens 8: Polarizing beam splitter 16a, 16b: Dichroic mirror 2: Reflector 4: Heat shielding filter: Transmissive liquid crystal display element Gikroic Miller and 4 others Figure 2 (α) Figure 6

Claims (1)

[Claims] 1. A plurality of dichroic films having color separation characteristics and polarization separation characteristics form an optical path that separates the light source light of the illumination means into each color component light, and a transmissive liquid crystal is installed in these optical paths. A projection type display device in which display elements are arranged, image light modulated by a transmission type liquid crystal display element emitted from these optical paths is combined and projected by a projection lens, and any one of these dichroic films is used. A projection type display device, characterized in that said light source light of said illumination means is arranged to polarize the light source light and guide the polarized light to said respective optical paths. 2. A plurality of dichroic films having color separation characteristics and polarization separation characteristics have an optical path that separates the light source light of the illumination means into each color component light, and a transmissive liquid crystal display element is disposed in these optical paths, and these A projection type display device that projects image light modulated by a transmissive liquid crystal display element emitted from an optical path by a projection lens, the light source light of the illumination means being polarized by a polarizing beam splitter and sent to each of the optical paths. A projection display device characterized by guiding polarized light.