JP2800909B2 - Liquid crystal projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector, and more particularly to a liquid crystal projector which increases brightness of an image, increases color purity, and reduces uneven brightness.

[0002]

2. Description of the Related Art A TN (twisted nematic) liquid crystal of a liquid crystal panel such as a liquid crystal projector device uses a polarizing plate.
The contrast is maximized when tilted 45 degrees. In order to support this liquid crystal panel, color separation and
When a polarization plane set at a 45-degree tilt is used as the dichroic mirror for color synthesis, the reflection characteristic of the dichroic mirror is s-polarized reflection as shown in the example of FIG. 3 (polarization transmittance characteristic of the dichroic mirror for green transmission). The reflection characteristic (Th) is an intermediate value between the characteristic (Ts) and the p-polarization reflection characteristic (Tp), and the shoulder characteristic (rise / fall slope) becomes gentle as shown in the figure. May be possible.

In a three-panel type liquid crystal projector, a light source light such as a metal halide lamp is separated into three color lights of red (R), green (G) and blue (B) by a dichroic mirror, and each color light is converted to a corresponding liquid crystal panel. Incoming and outgoing light are combined by a dichroic mirror and projected onto a screen. In order to increase the color purity of a projected image, it is necessary to minimize the overlap of each color light. However, when the shoulder characteristics of the dichroic mirror are gradual as described above, the overlap naturally increases, and the color purity deteriorates. When the transmission wavelength range of the filter is narrowed to avoid this overlap, the reflectivity of the dichroic mirror has the property of depending on the incident angle.
Since green is a color with high visibility, when the transmission wavelength range of the green filter is narrowed, uneven brightness occurs, and uneven brightness tends to occur in the projected image. In addition, the peak near 580 nm (nanometer), which is indispensable to metal halide lamps and is unique to mercury, is a highly visible color (orange) and has a large effect on color purity, so it is removed by a dichroic mirror. The components of 600 nm to 630 nm are considerably attenuated due to the above-mentioned gradual shoulder characteristics. However,
Since 600nm-650nm is the high visibility range of red light, this attenuation reduces the brightness of the red light, and the blue and green energies must be reduced to balance the image white, making the image darker Contributes.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a dichroic mirror having a gradual shoulder characteristic of a reflection characteristic, which results in a decrease in color purity, a decrease in luminance, or uneven brightness of a projected image of a liquid crystal projector. It is to provide what reduces the.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a liquid crystal projector using liquid crystal panels for a red image, a green image and a blue image. A group of dichroic mirrors for color separation made corresponding to the s-polarized light incident on the corresponding liquid crystal panel after being decomposed into light and blue light, and polarized light disposed on the incident light side of each liquid crystal panel with respect to the polarization plane of the s-polarized light The axis is, for example, an incident light side polarizing plate inclined 45 degrees counterclockwise, and the crystal axis is inclined 22.5 degrees counterclockwise with respect to the polarization plane of the s-polarized light mounted on the incident surface of the incident light side polarizing plate. A half-wave plate, an output light-side polarizing plate disposed on the output light side of each of the liquid crystal panels, and having a polarization axis inclined, for example, 45 degrees clockwise with respect to the polarization plane of the s-polarized light; The crystal axis is attached to the exit plane of the polarizing plate with respect to the plane of polarization of s-polarized light. Inclined 22.5 degrees in a clockwise direction 1 /
An object of the present invention is to provide a liquid crystal projector device provided with a two-wavelength plate and a color synthesizing dichroic mirror group having s-polarization characteristics for synthesizing each color light from each liquid crystal panel.

[0006]

With the above arrangement, in the liquid crystal projector according to the present invention, the s-polarized light component of each color from the light source reflected or transmitted by the color separation dichroic mirror is converted by the half-wave plate into the polarization plane. Is rotated by 45 degrees, transmits through the polarizing plate on the incident light side of the liquid crystal panel, undergoes polarization plane modulation by the liquid crystal, is given contrast by the polarizing plate on the outgoing light side, and is 45 ° shifted by the half-wave plate. The light is rotated by an angle, is incident on the dichroic mirror for color synthesis with the light of the polarization plane of the s-polarized light, is synthesized, and is projected on the screen via the projection lens.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid crystal projector according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a main part configuration diagram (side view) of an embodiment of a liquid crystal projector according to the present invention. In the figure, reference numeral 1 denotes a light source, which emits white light by a metal halide lamp or the like. 2 is UV
An IR cut filter cuts ultraviolet rays and infrared rays and transmits visible light. Reference numeral 3 denotes a green transmission dichroic mirror that transmits green light (G). A total reflection mirror 4 reflects the green light from the green transmission dichroic mirror 3. Reference numeral 5 denotes a condenser lens which collects green light from the total reflection mirror 4. Reference numeral 6 denotes a half-wave plate, which is formed by, for example, a polymer compound with a crystal axis inclined by 22.5 degrees, and is provided on the incident side of the incident light-side polarizing plate 7 with respect to the polarization plane of the s-polarized light.
Mount so that the crystal axis tilts 22.5 degrees counterclockwise. The incident light side polarizing plate 7 is disposed, for example, with the polarization axis inclined 45 degrees counterclockwise with respect to the polarization plane of the s-polarized light. Reference numeral 8 denotes a green liquid crystal unit which is driven by a green image signal and modulates the polarization plane of green light. Reference numeral 9 denotes an outgoing light-side polarizing plate, which is disposed, for example, with the polarization axis inclined 45 degrees clockwise with respect to the polarization plane of the s-polarized light. 10 is a half-wave plate, similar to the half-wave plate 6,
A crystal axis is formed with a polymer compound at an inclination of 22.5 degrees, and the crystal axis is attached to the exit side of the exit-side polarizing plate 9 with the crystal axis inclined, for example, 22.5 degrees clockwise with respect to the polarization plane of the s-polarized light. Reference numeral 11 denotes a green / blue light reflecting dichroic mirror that reflects the green image light and a blue image light, which will be described later, transmits the red image light, and is projected on a screen via a projection lens 12.

Reference numeral 13 denotes a blue light reflecting dichroic mirror,
The blue light reflected by the green light transmitting dichroic mirror 3 is reflected. Reference numeral 14 denotes a condenser lens which collects blue light from the blue light reflecting dichroic mirror 13. 15 is 1 /
A two-wave plate and an incident-light-side polarizing plate;
And the same configuration as that of the incident light side polarizing plate 7.
Reference numeral 16 denotes a blue liquid crystal unit which is driven by a blue image signal and modulates the plane of polarization of blue light. Reference numeral 17 denotes an outgoing light-side polarizing plate and a half-wave plate, which have the same configuration as that of the outgoing light-side polarizing plate 9 and the half-wave plate 10. Reference numeral 18 denotes a blue light reflecting dichroic mirror that reflects the blue image light and transmits the green image light.

Reference numeral 19 denotes a condenser lens which collects red light transmitted through the blue light reflecting dichroic mirror 13. Reference numeral 20 denotes a half-wave plate and an incident-light-side polarizing plate, which are configured similarly to the half-wave plate 6 and the incident-light-side polarizing plate 7. Reference numeral 21 denotes a red liquid crystal unit which is driven by a red image signal and modulates the plane of polarization of red light. Reference numeral 22 denotes an outgoing light-side polarizing plate and a half-wave plate.
The configuration is the same as that of the half-wave plate 10. A total reflection mirror 22 reflects the red image light.

Next, the operation of the liquid crystal projector according to the present invention will be described. FIG. 2 is a diagram illustrating rotation of the plane of polarization by the half-wave plate and the polarizing plate. White light from a metal halide lamp or the like of the light source 1 cuts unnecessary components such as infrared rays and ultraviolet rays by a UV / IR cut filter 2 and reflects blue light and red light by a green light transmitting dichroic mirror 3 and transmits green light. I do. The green light is reflected by the total reflection mirror 4, condensed by the condenser lens 5, and enters the incident light-side polarizing plate 7 having the half-wave plate 6 attached to the incident light side.

The half-wave plate 6 is, for example, a film formed by a polymer compound so that the crystal axis is inclined by 22.5 degrees. As shown in FIG. On the other hand, for example, it is mounted on the incident side of the incident light side polarizing plate 7 with the crystal axis tilted 22.5 degrees counterclockwise. As a result, the s-polarized green light incident from the condenser lens 5 rotates the polarization plane by 22.5 degrees × 2 = 45 degrees counterclockwise about the crystal axis of the half-wave plate 6. As shown in FIG. 2B, for example, the incident light side polarizing plate 7 has a polarization axis inclined at 45 degrees in a counterclockwise direction. Almost all of the light passes through the incident light side polarizing plate 7. This green light is incident on the green liquid crystal unit 8 driven by the green image signal, and undergoes polarization plane modulation as shown in FIG.

The green image light from the green liquid crystal unit 8 enters the outgoing light side polarizing plate 9. For example, as shown in FIG. 2D, the emission light side polarizing plate 9 has a polarization axis inclined 45 degrees clockwise with respect to the polarization plane of the s-polarized light. Only the light transmitted through the output light-side polarizing plate 9
/ 2 wavelength plate 10 is incident. The half-wave plate 10 is the half-wave plate
It is formed in the same manner as the wavelength plate 6, and as shown in FIG. 2 (e), for example, the crystal axis is inclined 22.5 degrees clockwise with respect to the polarization plane of the s-polarized light. Rotates the polarization plane 22.5 degrees.times.2 = 45 degrees counterclockwise with respect to the crystal axis, and emits light having the same polarization plane as the s-polarization plane. Then, the light passes through the blue light reflecting dichroic mirror 18 made corresponding to the s-polarized light, and is reflected by the green / blue light reflecting dichroic mirror 11 made corresponding to the s-polarized light.
The image is projected on a screen via the projection lens 12.

A green light transmitting dichroic mirror 3
The s-polarized light component of the blue light reflected by the light is reflected by a blue light dichroic mirror 13 made corresponding to the s-polarized light, condensed by a condenser lens 14, and is a half-wave plate and an incident light-side polarizing plate 15. The blue liquid crystal part 16, the output light side polarizing plate, and the half-wave plate 17 process the green light in the same manner as the green light to produce blue image light having a polarization plane of s-polarized light. Blue light reflecting dichroic mirror 18 and s
The light is reflected by a green / blue light reflecting dichroic mirror 11 made corresponding to the polarized light, and is projected on a screen via a projection lens 12.

The s-polarized light component of the red light reflected by the green light transmitting dichroic mirror 3 and transmitted through the blue light dichroic mirror 13 is condensed by a condenser lens 19, and is subjected to a 波長 wavelength plate and an incident light side polarizing plate 20. The red liquid crystal part 21, the outgoing light side polarizing plate, and the half-wave plate 22 process the green light in the same manner as the green light to become s-polarized red image light, reflected by the total reflection mirror 23, and The light passes through the blue light reflecting dichroic mirror 11 and is projected on the screen via the projection lens 12.

[0015]

As described above, according to the liquid crystal projector of the present invention, the light incident on the liquid crystal panel is incident, for example, at an angle of 45 degrees counterclockwise with respect to the polarization plane of the s-polarized light. Then, means for emitting the light emitted from the liquid crystal panel at an angle of 45 degrees clockwise with respect to the polarization plane of the s-polarized light is provided, so that the dichroic mirrors for color separation and color synthesis have characteristics of s-polarized light, respectively. Since they can be set together, the shoulder characteristics of the transmittance / reflectance of the dichroic mirror can be made steep, so that good transmission / reflection can be obtained in a narrow wavelength region. As a result, the overlap between the red and green filters can be made as close as possible, so that the brightness of the screen image can be improved and the orange color peak of the light source light can be easily removed, so the color purity of the red color in particular can be increased. In addition, since the green filter characteristics are improved, it is possible to reduce uneven brightness of an image due to the dependency of the reflectance of the dichroic mirror on the incident angle.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an embodiment of a liquid crystal projector according to the present invention.

FIG. 2 is a half of a liquid crystal projector according to the present invention.
FIG. 4 is a diagram illustrating rotation of a polarization plane by a wave plate and a polarizing plate.

FIG. 3 is an example of characteristics of a dichroic mirror.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 UV / IR cut filter 3 Dichroic mirror 4 Total reflection mirror 5 Condenser lens 6 1/2 wavelength plate 7 Polarizer 8 Liquid crystal part 9 Polarizer 10 1/2 wavelength plate 11 Dichroic mirror 12 Projection lens 13 Dichroic mirror 15 1 Half-wave plate and polarizer 17 Polarizer and half-wave plate 18 Dichroic mirror 23 Total reflection mirror

Claims (1)

(57) [Claims] In a liquid crystal projector using liquid crystal panels for red, green and blue images, light from a light source is decomposed into s-polarized red light, green light and blue light, and the light is separated into respective liquid crystal panels. a color separation dichroic mirrors made to correspond to the s-polarized light incident, is disposed on the incident light side of the liquid crystal panel, the incident light is inclined 45 degrees polarization axis with respect to the polarization plane of the s-polarized light in one direction and the side polarizing plate is attached to the incident surface of the incident light side polarizing plate, a half-wave plate is inclined 22.5 degrees crystal axis in one direction relative to the polarization plane of the s-polarized light, out of the respective liquid crystal panels disposed Shako side, the outgoing light side polarizing plate is inclined 45 degrees the polarization axis in the other direction relative to the polarization plane of the s-polarized light, is mounted on the exit surface of the exit light side polarizing plate, the polarization plane of the s-polarized light On the other hand, the crystal axis is inclined by 22.5 degrees in the other direction.
A liquid crystal projector device comprising a wave plate and a group of color synthesizing dichroic mirrors having s-polarization characteristics for synthesizing each color light from each grade panel.