JPH0822006A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To provide a liquid crystal projector which is specified in the beginning point position of perpendicular scanning of the RGB striped luminous fluxes of a liquid crystal panel, is nearly specified in intervals and has the high linearity of a moving speed for irradiation. CONSTITUTION:This liquid crystal projector has a light source 11, a reflector 12 for reflecting and condensing the light from this light source 11, a means for separating the condensed luminous fluxes to the luminous fluxes of three colors; red, green and blue, the liquid crystal panel 8, and a columnar body having a regular polygonal section having opposite parallel planes axisymmetrical with the axis of rotation. In addition, the projector has a rotary prism 6 which scans the surface of the liquid crystal panel with the stripes of three colors by receiving the luminous fluxes of the three colors on its side face and irradiates the surface of the liquid crystal panel with luminous fluxes to a stripe form these. One of the luminous fluxes of the three colors is used as a main optical axis and this main optical axis is intersected orthogonally with the axis A of rotation. The liquid crystal projector has a pair of incident means 14, 15 which incline the remaining two of the luminous fluxes of the three colors as auxiliary optical axes symetrically with the main optical axis and intersect these auxiliary optical axes with the intersected point of the main optical axis and the axis A of rotation and assembling means 21 to 23 which arrange the auxiliary optical axes parallel with the main optical axis.

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 which transmits a light beam to a liquid crystal panel and projects the transmitted light on a screen by a projection optical system.

[0002]

2. Description of the Related Art As a liquid crystal projector, three primary color images of red, green and blue are simultaneously formed on three corresponding liquid crystal panels, and the same parallel luminous flux is passed through these liquid crystal panels and corresponding filters to perform color mixing. However, there is known a three liquid crystal panel type that projects on a screen by a downstream projection optical system. In these three-color liquid crystal panels, dot-sequential red, green, and blue individual monochrome images are reproduced.

Further, as a liquid crystal projector, FIG.
It consists of a single liquid crystal panel and a prism with a square cross-section, as shown in, and R (red) and G are attached to the side of the rotating prism.
Light fluxes R, G, and B of three colors (green) and B (blue) are emitted in parallel, and the parallel refracted light is emitted in the shape of an elliptical spot on the liquid crystal panel. A liquid crystal projector of a single liquid crystal panel type has also been developed in which scanning is performed while moving on the liquid crystal panel, and at the same time, a video stripe sandwiched by a light-shielding band is synchronized with an oval spot to obtain a projected image (“A novel single light valve hight brightnes
s HD color projector ”P. Janssen, PP-249-252).

As shown in FIG. 1, such a single liquid crystal panel type liquid crystal projector includes a metal halide lamp 1 as a white light source, a hemispherical reflector 2 for collecting light into a downstream optical system as a thin light beam, and focused light. A dichroic prism 3 which is a light splitting means for splitting the RGB light flux, mirrors 4, 5 for making the split RB light flux parallel to the G light flux,
A rotary prism 6 having a square cross section, an anamorphic lens 7 for making RGB light flux into an elliptical spot shape, a liquid crystal panel 8 for displaying a monochromatic image partial stripe corresponding to the RGB oval spot, and a projection lens 9 are provided. There is. The rotation axis A of the prism 6 is orthogonal to the optical axis of the G light flux.
The reflector 2 receives the light from the lamp 1 on the downstream liquid crystal panel 8
Then, the anamorphic lens 7 in the middle changes the aspect ratio of the cross section of the light flux to form an oval spot on the liquid crystal panel 8. That is, in the single liquid crystal panel type liquid crystal projector, the anamorphic lens 7 is used to provide a horizontal spot in which the light from the linear light emitting region between the lamp discharge electrodes on the optical axis should become a circular spot. It is formed as an oval spot extending in the direction of the normal line of the drawing. The oval spot is irradiated so that the rectangular image stripe formed on the liquid crystal panel is inscribed in the oval spot, and thus the light amount is unavoidable. Furthermore, the periphery of the oval spot is prevented to prevent crosstalk. Must be shielded by the light strip of the image stripe.

In the system in which the RGB light flux is incident on the prism in parallel (hereinafter referred to as RGB parallel system),
White light is condensed on the dichroic prism 3, divided into RGB light beams, and the light beams are incident on the rotating prism 6 in parallel. By rotating the prism, the RGB oval spot light fluxes are moved in parallel from top to bottom of the liquid crystal panel, so that the 90 ° rotation of the prism is restored in one cycle. Each rotation of the prism 6 vertically scans each oval spot light four times from top to bottom.

Here, three-color stripe partial images corresponding to a part of the three primary color images are sequentially formed on the liquid crystal panel 8 in accordance with the RGB oval spot widths of the vertical scanning.
Vertical scanning RGB elliptical spot light passes through the liquid crystal panel and is projected onto the screen 10 by the projection optical system 9 to form a full-color image by vertical scanning of stripe image of three colors.

In addition, as shown in FIGS. 2A and 2B, the optical system of the RGB parallel type rotating prism has the G main optical axis, the RB two sub optical axes, and the RB sub optical axis being the G main optical axis. 2C, D from the case where the light beam is incident on the camera (paraxial)
As shown in (1), the optical path is taken into consideration when the distance is gradually increased (far axis). The left side of FIG. 2 shows changes in the irradiation position of the RGB oval spot S on the liquid crystal panel due to the rotation of the prism corresponding to each optical path.

That is, when the refractive index of the prism upon paraxial incidence is small (FIG. 2A) or large (FIG. 2B), since the light beams are incident closely, the elliptical spot width (minor diameter) on the panel is increased. It is difficult to brighten the screen. When the prism refractive index is large at paraxial incidence (FIG. 2B), the spacing between BRs of adjacent RGB pairs becomes wide, and since the RB incident position is different from the G incident position, it is above the elliptical spot after vertical scanning. Return position is R
There are different problems between B and G.

In the single liquid crystal panel system at the far-axis incidence shown in FIGS. 2C and 2D, in addition to the problem of the upward return position of the elliptical spot of the RB sub-optical axis, the luminous flux of the BR sub-optical axis is approximately 90 ° to the prism. Since the light is incident at a large angle up to 4 degrees, there is a problem that the color shift becomes large at the start or end of scanning on the panel due to dispersion, and there is no antireflection film that can cover a wide frequency range at an incident angle of 45 ° or more. Anti-reflection measures are not possible and there is a problem of light loss. Further, when the prism has a small refractive index due to the incidence on the far axis (FIG. 2C), the light flux of the sub optical axis cannot obtain the outgoing light path from the parallel surfaces facing each other of the prism (see the optical path f), and the elliptical spot Is not formed on the liquid crystal panel.

Even if the refractive index of the prism is large at the far-axis incidence (FIG. 2D), there is a problem that the elliptical spot of the RB sub-optical axis is not formed on the liquid crystal panel. That is, as shown in FIGS. 3 and 4, when the prism is rotated from a rotation angle of 0 degree, the RGB oval spot has a B light flux in the prism parallel to the optical axis (FIGS. 3A and 4A) and downstream of the prism. 3B and FIG.
Vertical scanning is performed in parallel as in B. When the incident point of the B light flux reaches the edge d on the upstream side of the prism, as shown in FIGS. 3C and 4C, the B light flux enters from the lower surface of the prism beyond the apex on the upstream side of the lower surface of the prism and is refracted due to the high refractive index. Did B
The light flux temporarily crosses the prism edge e, and is emitted parallel to the optical axis from the upper parallel surface facing the incident surface of the B light flux. However, when further rotated, as shown in FIGS. 3D and 4D, the prism edge e crosses the refracted B light flux, and B
The light flux does not emerge from the facing upper parallel surface, and is not parallel to the RG light flux and is reflected by the surface adjacent to the incident surface. The R light flux that is further rotated and refracted reaches the prism edge e shown in FIGS. 3E and 4E, and as shown in FIGS.
Like the B light flux of D, the R light flux is reflected by the surface adjacent to the incident surface. After that, the RB light flux does not reach the liquid crystal panel, and only the G light flux forms an elliptical spot on the panel. When the prism rotation angle reaches 45 degrees (FIGS. 3G and 4G), the G light flux is emitted parallel to the axis from the upper parallel surface facing the incident surface. In this way, even in the case of a far-incident high-refractive-index prism, an elliptical spot of the light flux of the RB sub-optical axis may not be formed on the liquid crystal panel. Note that, in FIG. 4, the height h from the main optical axis of the prism to the emission point of the RGB light flux is shown in a range up to a rotation angle of 90 degrees with reference to the time when the prism side surface is perpendicular to the main optical axis (0 degree). Show changes. FIG.
In the R, G, and B curves, the solid line portion is an elliptical spot formed on the panel corresponding to the emission height of the RGB luminous flux, and the broken line portions Rn and Bn are the elliptical spots not formed on the panel and the RB luminous flux is reflected. Indicates that Also, FIG.
Arrows A to G indicate the prism rotation angle positions shown in FIGS.

As described above, in any of the cases, the RGB parallel system single liquid crystal panel type projector has many problems in forming parallel RGB oval spots on the panel, and the refractive index and size of the rotating prism and the secondary light. There are many restrictions on the incident position of the axial light flux, and the degree of freedom in design is small, making it difficult to design.

[0012]

In such a single liquid crystal panel type liquid crystal projector, as shown in FIG. 1, a metal halide lamp 1 is placed with its longitudinal direction along the main optical axis, and has a parabolic rotational symmetry. The reflector 2 is used. In the conventional light source in which the longitudinal direction of the metal halide lamp 1 is aligned with the optical axis, it is necessary to reduce the space between the discharge electrodes and downsize the lantern-type lamp part in order to improve the light-collecting performance, but there is a limit to that. Electrode protection parts extending from the lantern-type lamp part on both sides in the optical axis direction block light and cause light scattering, which not only results in light-collecting performance but also in loss of light quantity.
It is desired in a liquid crystal projector to reduce the light amount loss of a light beam that passes through an optical component and secure the light amount.

Even if the incident position of the light beam of the sub optical axis on the rotating prism is set to a moderate incident position instead of the far axis or the paraxial direction, as shown in FIG. 5, the RB sub optical axis on the liquid crystal panel is shown. The vertical scanning start position of the elliptical spot of the
Unlike that of the optical axis, the elliptical spot of BR does not have the same irradiation movement speed as that of G in the curved portions shown by M and N in FIG. This variation in the irradiation moving speed of the elliptical spot causes unevenness of the brightness of the BR spot, which causes color unevenness of the projected image.

Therefore, in order to solve the above-mentioned problems, an object of the present invention is to provide a liquid crystal projector in which the intervals of RGB oval spots are kept uniform, the irradiation moving speed thereof is high in linearity, and the projection screen is bright and has no color unevenness. To provide.

[0015]

A liquid crystal projector of the present invention includes a light source, a reflector that reflects and collects light from the light source, and separates the collected light flux into three light fluxes of red, green, and blue. Light separating means, a liquid crystal panel, and a columnar body having a regular polygonal cross section having line-symmetrical opposing parallel surfaces with respect to a rotation axis, and the side surfaces thereof receive the light beams of the three colors, and these are striped on the liquid crystal panel. A rotating prism that irradiates the liquid crystal panel with three colors and scans the three-color stripes on the liquid crystal panel, and the main optical axis is orthogonal to the rotation axis with one of the light beams of the three colors as the main optical axis. A liquid crystal projector, comprising:
Incidenting means for inclining the sub-optical axis symmetrically with respect to the main optical axis with the remaining two color light fluxes as the sub-optical axes and entering the intersection at the main optical axis and the rotation axis, and the sub-optical axis. A liquid crystal projector comprising: a collecting unit that collects optical axes in parallel with the main optical axis.

[0016]

According to the present invention, it is possible to obtain a liquid crystal projector in which the starting points of vertical scanning of RGB stripe light beams on a liquid crystal panel are constant, their intervals are almost constant, and the irradiation moving speed is highly linear. That is, according to the present invention, vertical scanning can be performed at the same speed, stripe widths and intervals can be set wider than those in the RGB parallel system, and a liquid crystal projector with a bright projection screen and no color unevenness can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 shows an RGB intersecting type liquid crystal projector according to this embodiment. In FIG. 6, members indicated by the same reference numerals shown in FIG. 1 indicate the same members. The RGB crossing type single liquid crystal panel liquid crystal projector includes a metal halide lamp 11 as a white light source, and a bowl-shaped elliptical reflector 1 having different vertical and horizontal eccentricity for making a light beam from the light source into a thin light flux.
2 is provided with a light source optical system. Further, in this embodiment, the rotating prism 6 for scanning the light beam, the dichroic prism 3 which is a means for dividing the white light beam into the RGB light beams, and the RB sub-optical axis divided by this are directed to the rotating prism 6. It includes a pair of mirrors 14 and 15 which are symmetrically inclined with respect to the main optical axis of G and are incident so as to intersect with the rotation axis A, and an assembling means for aligning the sub optical axis of RB with the main optical axis of G. It is equipped with a rotating prism system. The collecting means is a second dichroic prism 2 on the main optical axis.
3 and the mirrors 14 and 15 with respect to the main optical axis and the rotation axis A, and the second dichroic prism 2
The second reflection mirrors 21 and 22 guide the sub optical axis of RB to 3 and make these coincide with the main optical axis of G. In addition, this embodiment includes an irradiation optical system including an anamorphic lens 7, a liquid crystal panel 8 and a projection lens 9 which are arranged on the sub optical axis of RB and the main optical axis of G which coincide with each other.

Here, both dichroic prisms 3 and 2
The reference numeral 3 divides the incident light into wavelength components that allow the incident light to pass in parallel as it is and two wavelength components that reflect the incident light in the opposite directions perpendicularly to each other (the wavelength components are further superimposed). As described above, the prism having the inclined multilayer thin film is used, but the present invention is not limited to this, and it is sufficient that the prism can be divided into three wavelength components.

The light source optical system, the rotating prism system including the collecting means, and the irradiation optical system will be described in detail below. (Light Source Optical System) First, the light source optical system has a configuration suitable for irradiating the liquid crystal panel in the form of a narrow linear stripe. As shown in FIG. 7, coordinates in which the Z axis is aligned with the main optical axis, the stripe extension direction perpendicular to the main optical axis on the liquid crystal panel is aligned with the X axis, and the vertical scanning direction of the stripe is aligned with the Y axis. In the system, the elliptical reflector 12 is a bowl-shaped reflecting mirror having a reflecting inner surface whose eccentricity in the vertical Y axis is smaller than that in the horizontal X axis. The elongated metal high-ride lamp 11 is placed horizontally at the focal point P inside the elliptical reflector 12 such that its longitudinal direction is parallel to the stripe to be formed. In the YZ plane including the stripe scanning direction,
The lantern-shaped light emitting portion 11a in the center of the lamp is attached to the elliptical reflector 12.
It is an optical system which is placed at the internal focal point P and basically guides the light emission pattern of the elongated lantern-type light emitting section 11a to the liquid crystal panel as it is. Therefore, the light collecting performance in the Y direction is improved. X
On the Z-plane, light is basically guided in the direction of the liquid crystal panel while maintaining a long emission shape. Therefore, at the external focus Q of the elliptical reflector 12, a long and narrow light collecting region in the Z direction can be obtained. As a result, the stripe width on the liquid crystal panel becomes denser, but further, in consideration of the effective diameter of the downstream optical system, an anamorphic optical system with a smaller refractive power than before is placed in front of the liquid crystal panel. Can be adjusted.

Further, in this embodiment, the maximum irradiation line width of the stripes on the liquid crystal panel is made as thin as the image display portion of the stripes on the liquid crystal panel by the collimator system described later, and the light quantity per unit area of the screen is reduced. Increase. Unlike the method of irradiating the liquid crystal panel on the surface, such as the three-panel method, in this embodiment, since the irradiation is performed in the line stripe, the energy per unit area of light and heat becomes high.

As shown in FIGS. 6 and 7, the light source optical system is provided with a collimator lens 17, and a concave internal reflection surface is provided between the collimator lens 17 and the elliptical reflector 12 for heat protection of the liquid crystal panel and optical parts. It has a circular mirror 16. The circular mirror 16 has a slit 16a extending in the X direction only in a portion of the external focus Q through which the light flux passes, and the center of the radius of curvature thereof is arranged so as to coincide with the internal focus P of the elliptical reflector. As a result, the light that reaches the circular mirror 16 directly from the lamp 11 is reflected to the focal point P and is reused as effective light. Collimator lens 17 has slit 1
The divergent light emitted from 6a is converted into a plate-like parallel light flux on the XZ plane.

As shown in FIGS. 6 and 8, the light source optical system further includes a polarization beam splitter (PB) which transmits only the P-polarized light of the parallel light flux emitted from the collimator lens 17.
S) 18 is also provided. The P-polarized light is used because the downstream liquid crystal panel modulates the transmission amount of one of the P-polarized light and the S-polarized light. Further, a cold mirror 19 for returning light to the light source is provided on the surface of the PBS where the S-polarized light is reflected inside the PBS 18 for effective use of the light quantity. This bundle of P-polarized parallel rays is guided to the dichroic prism 3.

In the above-described embodiment, the circular mirror 16 and the PBS 18 are provided to increase the light amount at the same time as the countermeasure against heat, but it is also possible to use the S-polarized light effectively as shown in FIG. Instead of removing the cold mirror of the PBS 18, the S-polarized light reflected inside the PBS is taken out from the previous PBS surface, the optical path of the S-polarized light is changed by the mirror 30, and the S-polarized light is changed to the P-polarized light by the λ / 2 wave plate 31. P polarization and PB
The P-polarized light in S18 is combined by the V-shaped columnar lens 32 and the collimator lens systems 33 and 34. Inside the V-shaped columnar lens 32, both P-polarized light become parallel and the lens 3
It is focused by 3 and becomes a bundle of parallel rays by the lens 34. Although the λ / 2 wavelength plate 31 is used here, in practice, instead of the λ / 2 wavelength plate, several layers of phase adjusting thin films are provided on the surface of the reflection mirror 30 to change the phase of reflected light by 90 °. However, this results in less assembly parts. (Rotating Prism System) As shown in FIG. 10, the rotating prism system has a G main optical axis 51 and RB sub optical axes 52 and 53. The dichroic prisms 3, 23 and the reflection mirrors 14, 15, 21, 22 define a main optical axis 51 and sub optical axes 52, 53. The mirrors 14 and 15 tilt the sub optical axis of RB perpendicular to the main optical axis 51 divided by the dichroic prism 3 toward the rotating prism 6 symmetrically with respect to the main optical axis 51 of G at an angle θ. And intersects the rotation axis A. Therefore, the deflection of the light beam incident along each of the main optical axis and the sub optical axis becomes equivalent with respect to the rotation angle of the rotating prism.

In the liquid crystal projector shown in FIG. 6,
The sub optical axes of RB are inclined symmetrically with respect to the main optical axis of G at an angle θ of 30 degrees. 11 (A) to 11 (E), FIG.
Rotation prism angle of 0 to 45
Some optical path conditions within a rotation angle range of up to degrees are shown.
It can be seen that in each case, RGB light beams are vertically scanned in parallel.

In FIG. 12, the RGB light fluxes from the prisms in the rotary prism system of FIG. 6 are projected from the main optical axis of the RGB light fluxes emitted from the prisms in a range up to a rotation angle of 90 degrees with the prism rotation angle of parallel incidence and emission of 0 degrees. The graph of the change of the position (height) of is shown. In the RGB curve of FIG. 12, R
It can be seen that stripes are formed on the panel corresponding to the emission height of the GB light flux, and are vertically scanned in parallel at substantially equal intervals. Further, (A) to (E) of FIG. 12 are shown in FIG.
The prism rotation positions of (A) to (E) are shown.

Further, as shown in FIG. 9, an antireflection film 6a is attached to the rotating prism. In the RGB crossing method of the embodiment, since the rotating prism, which is a columnar body having a square cross-section that is line-symmetric with respect to the rotating shaft having the facing parallel surface, is used, the incident angle of the light beam is 45 ° at the maximum, and reflection on the surface of the rotating prism is prevented. It is possible to attach the membrane 6a. In contrast, conventional R
In the GB parallel system, the light flux of the sub optical axis is incident at an incident angle of 45 ° or more, but there is no antireflection film that can cover a wide frequency region at an incident angle of 45 ° or more, and antireflection measures were impossible. The present invention enables antireflection measures.

FIG. 13 shows the non-linear degree of the irradiation moving speed. When G of RGB luminous flux is taken as an example, the stripe vertical scanning (0 to 90) with respect to the prism rotation angle is examined.
(Range of degrees) and the transition time is 1.3 for linear movement near the prism rotation angles of 30 ° and 60 °, respectively.
mm and 10 μs are the maximum. Therefore, these are not the displacement distances and transition times to be corrected which are particularly large in practice. If the influence is exerted, as shown in FIG. 10, the correction plate 50 made of a transparent resin material or glass is directly attached to the emission surface of the second dichroic prism 23 or is provided by being inserted on the emission side. For example, the movement of the luminous flux becomes perfectly linear. The profile of the vertical section of the correction plate 50 is formed based on the degree of non-linearity shown in FIG.

14A to 14D, the inclination angle θ of the sub optical axes 52 and 53 with respect to the main optical axis 51 shown in FIG.
The arrangement of each member of the rotating prism system when changed within an angle range of ≦ 45 degrees is shown. When the inclination angles θ≈0 degrees and θ≈45 degrees, the respective members are close to or far from each other, and therefore the mirror cannot be arranged. Therefore, the respective members are appropriately arranged in such a range. FIGS. 15A to 15D are graphs of changes in the emission height of the RGB light flux with respect to the rotation angle of the rotating prism corresponding to the arrangement of the members of the rotating prism system shown in FIGS. 14A to 14D. Indicates.

As shown in FIGS. 15A and 15D, FIG.
At the inclination angles θ = 45 degrees and θ = 0 degrees of the sub optical axes corresponding to (A) and (D), the RB light flux and the RGB light flux are not separated but become one stripe. As is clear from these, the tilt angle θ of the sub optical axis is about 45 degrees and the tilt angle θ is about
It can be seen that at 0 degrees, the RGB light fluxes are close to each other and overlap, which is not preferable.

As shown in FIG. 15B, when the sub-optical axis tilt angle 30 ° <θ <45 ° corresponding to FIG. 14B, the RB light beam is separated, but the RB light beam interval and the G light beam and The case where the R or B intervals are equal and the case where they are not equal appear alternately, which causes flickering of the screen. Figure 15 (B)
As can be seen from the graph, RG is not satisfied when the inclination angle is 30 <θ <45 degrees
It can be seen that the intervals of the B light flux are not uniform, which is not preferable.

On the other hand, as is apparent from FIG. 12, when the inclination angle θ = 30 degrees, even within the set of RGB light fluxes, the RG is equally spaced.
After the B feedback, scanning is performed at even intervals as the RB intervals. Further, as is clear from FIG. 15 (C), when 0 <θ <30 degrees, R
It can be seen that although the RB interval after the GB return is wide, scanning at equal intervals is performed within the set of RGB light fluxes. Therefore, the inclination angles of the sub optical axes 52 and 53 with respect to the main optical axis 51 can be selected within an angle range of 0 <θ ≦ 30 degrees in consideration of the contact and size of each member.

As another embodiment, as shown in FIG. 16, instead of the pair of expensive dichroic prisms 3 and 23 shown in FIG. 10, inexpensive dichroic mirrors 3a and 3b and 23a and 23b are used as main optical axes. 51, and the corresponding reflecting mirrors 14, 15, 21, 22
Can be displaced along the sub optical axes 52 and 53 so that the axes of the incident and outgoing luminous fluxes coincide with each other. The second dichroic prism 23 and the reflection mirrors 21 and 22 are arranged conjugate with the dichroic prism 3 and the reflection mirrors 14 and 15 with respect to the rotation axis A of the rotation prism 6 in the main optical axis 51, and each axis is equivalent. Therefore, the optical path length of each axis does not matter. Further, only one of the pair of dichroic prisms may be replaced with a dichroic mirror.

In the RGB crossing method shown in FIG. 10 of the above embodiment, a rotating prism, which is a columnar member having a square cross section, is used, but instead of this, a regular hexagonal or regular octagonal line symmetric with respect to the rotation axis having opposing parallel surfaces. It can be configured by using a rotating prism which is a columnar body having a regular polygonal cross section such as a prism. In the above embodiment,
With G of RGB light flux as the sub-optical axis and RB as the sub-optical axis, the sub-optical axis is tilted symmetrically with respect to the main optical axis and intersects the prism rotation axis so that the sub-optical axis coincides with the main optical axis. Therefore, in the case of a square-section prism, the maximum incident angle of the light beam is 45 degrees, vertical scanning of one cycle of the RGB light beam is obtained in the angle range of 0 <θ ≦ 90 degrees, and the sub-optical axis is symmetrical. R at equal intervals (cycles) when the tilt angle θ is 90 degrees / 3 = 30 degrees
Vertical scanning of GB light flux is obtained. Therefore, as an example using another regular polygonal section prism, as shown in FIG. 17, for example, a columnar body rotation prism 60 having a regular hexagonal section.
, The maximum incident angle of the light flux is 30 degrees, and
Vertical scanning of one cycle of RGB luminous flux is obtained in an angle range of <θ ≦ 60 degrees, and the symmetric tilt angle θ of the sub optical axis is 60 degrees / 3 = 2.
An evenly spaced vertical scan is obtained at 0 degrees. In FIG. 17, members designated by the same reference numerals shown in FIG. 6 are the same members. Also, when using a columnar rotating prism of regular octagonal cross section,
The maximum incident angle of the light flux is 22.5 degrees, and 0 <θ ≦ 45
One cycle of vertical scanning of the RGB light flux is obtained in the angular range of degrees, and the vertical scanning at equal intervals is obtained when the symmetric tilt angle θ of the sub optical axis is 45 degrees / 3 = 15 degrees.

When using a regular polygonal prism having a regular hexagonal shape or a regular octagonal shape exceeding a regular square shape, the non-linear degree of the moving speed of the stripe light flux on the liquid crystal panel is higher than that of the regular square shape prism. This is because the distance of the radius difference between the circumscribed circle and the inscribed circle of the corresponding regular polygon is further reduced, and the radial displacement of the incident light flux on the prism surface is reduced. Therefore, it is not necessary to provide a correction plate on the emission surface of the second dichroic prism. (Irradiation optical system) Although sheet-like RGB luminous fluxes are incident on the liquid crystal panel 8 of the liquid crystal projector shown in FIG. 6, when the stripe width is more clearly reflected on the liquid crystal panel 8, the anamorphic lens 7 has the same RGB color. Is located on the main optical axis of. Since this anamorphic lens is an optical system that produces images with different vertical and horizontal magnifications on the image plane, it is performed simultaneously with the design of the light source portion. The anamorphic lens is one of magnification adjusting means for changing the magnification of the projection optical system immediately before the liquid crystal panel.

Since the liquid crystal panel 8 has a large number of pixels,
Further, since it is necessary to increase the light transmittance so as to make it brighter, it is necessary to project the magnifying lens 7a as a further magnification adjusting means in order to keep optical components such as a relatively small rotating prism system small in size. It can also be provided between the lens 9 and the rotating prism 6. As a result, it is possible to make the liquid crystal panel larger and the rotating prism system smaller.

The liquid crystal panel 8 is a TFT (Thin Film Transistor) type liquid crystal panel having a response time of 2.5 milliseconds. For example, if the size is 60 mm (horizontal direction) × 34 mm (vertical direction), Stripe irradiation area is 60m
The size within m (horizontal direction) × 15 mm (vertical direction) is 60 mm (horizontal direction) × 5.7 mm (vertical direction) when the duty ratio of the partial image display part and the light shielding part is 1: 1. It is the size of the partial image display part and the light shield part. This is because the stripes are illuminated in a range that does not exceed the light shielding portions on the upper and lower sides of the image display portion of the liquid crystal panel so that crosstalk does not occur. According to the present embodiment, since the plate-shaped (sheet-shaped) RGB light flux is generated from the light source and the RGB light flux is incident on the rotation axis of the rotating prism, the duty of the partial image display portion and the light-shielding portion is reduced. The ratio can be set wider than in the case of the conventional RGB parallel system.

Further, as shown in FIG. 6, the liquid crystal panel 8 is provided with angle adjusting means 70 for varying the angle of the main surface with respect to the main optical axis. The liquid crystal panel 8 is pivotally supported by a journal on a rotation axis on its main optical axis,
The angle adjusting means 70 drives, for example, the lower end edge of the liquid crystal panel 8 along the main optical axis. As shown in FIG. 18, when the angle of the main surface of the liquid crystal panel 8 is changed with respect to the main optical axis, the normal line of the screen 10 is inclined with respect to the main optical axis because of the single liquid crystal panel system. However, it is possible to obtain an image without trapezoidal distortion. (Liquid crystal panel and prism drive system) As shown in FIG.
0, frame buffer memory 101R, 101G, 10
1B, stripe signal selection circuits 102R, 102G, 1
02B, controller 103, time compression circuit 104R,
It has 104G and 104B, a time division circuit 105, a liquid crystal panel drive circuit 106, and a prism drive means 107.

RGB conversion circuit 100 including A / D converter
However, for example, the NTSC signal video signal is divided into R, G, and B digital signals, and the signals are respectively written in the frame buffer memories 101R, 101G, and 101B.
Stripe signal selection circuits 102R, 102G, 102B
In accordance with a selection command from the controller 103, the luminance data of the upper partial raster of the R image, the central partial raster of the G image, and the lower partial raster of the B image are selectively extracted from the written frame data. Time compression circuit 104
The R, 104G, and 104B respectively compress these extracted data according to the compression command from the controller 103.
A time division circuit 105 including a selector, a delay circuit, a multiplexer, and a D / A converter sets all of the reduced partial raster data into one on the basis of a selection command from the controller 103, and drives the liquid crystal panel. Transfer to 106. The drive circuit 106 vertically scans and displays the stripe image formed by the partial raster data of the brightness of each RGB on the liquid crystal panel from top to bottom.

A prism driving means 107, which includes a spindle motor and a rotation detector, and drives the prism to rotate, is connected to the controller 103. Controller 103
Controls the prism driving means 107 to rotate the prism based on the rotation data from the rotation detector, and synchronizes with the vertical scanning of the RGB stripe image,
Vertically scan the stripe light flux of each RGB brightness from top to bottom. Then, it is possible to irradiate each of the RGB luminance information display portions of the liquid crystal panel with the RGB stripes to form a screen from top to bottom. In this way, three-color stripe partial images (partial rasters) corresponding to a part of the three primary color images are sequentially formed on a single liquid crystal panel, and a striped luminous flux corresponding to the stripe partial images is synchronized with the liquid crystal panel. Make it transparent to create full-color images.

In order to solve the problem that the color flicker (color flicker) is conspicuous in the highly saturated color portion in the visual sense, the decomposed three primary color video signals are time-compressed to 1/3,
The frame frequency is tripled to 180 Hz and the stripes are sequentially switched. Furthermore, it is possible to suppress a phenomenon called "color breakup" in which the contour portion of the image is colored. In this display method, if the image shift for each frame is large, 3
If the moving image is faster than the time required to synthesize the primary colors, the outline may look different from the actual color, but the frame frequency is 180 Hz using the time compression circuit.
By setting it to a level at which practically no problem occurs.

[0041]

As described above, according to the present invention, a light source,
It has a reflector for reflecting and condensing the light from the light source, a means for separating the condensed luminous flux into luminous fluxes of three colors of red, green and blue, a liquid crystal panel, and a parallel plane opposed to the rotation axis in line symmetry. And a rotating prism which is composed of a columnar body having a regular polygonal cross section, and whose side faces receive light beams of three colors and irradiate them in a stripe shape on the liquid crystal panel to scan the stripes of the three colors on the liquid crystal panel. In a liquid crystal projector in which one of the three color light beams is the main optical axis and the main optical axis is orthogonal to the rotation axis, the remaining two light beams of the three colors are the sub optical axes and the sub optical axis is the main light. Since the means for inclining symmetrically with respect to the axis and for entering the intersection of the main optical axis and the rotation axis and the means for collecting the sub optical axis in parallel with the main optical axis are provided, the RGB stripes in the liquid crystal panel are relaxed. Is formed reliably under the specified conditions, Linearity of the point position is irradiated moving speed almost constant constant and intervals can obtain high liquid crystal projector, it is possible to obtain a bright projected image.

[Brief description of drawings]

FIG. 1 is a structural diagram showing an outline of an RGB parallel type liquid crystal projector.

FIG. 2 is an explanatory diagram showing a state of a rotating prism of a liquid crystal projector of RGB parallel system and stripes vertically scanned.

FIG. 3 is a schematic cross-sectional view of a rotating prism of an RGB parallel type liquid crystal projector.

FIG. 4 is a graph showing a relationship between a rotation angle of a rotating prism of an RGB parallel system liquid crystal projector and a height of a light flux emitted from a main optical axis.

FIG. 5 is a graph showing the relationship between the rotation angle of the rotating prism of the RGB parallel system liquid crystal projector and the height of the light beam emitted from the main optical axis.

FIG. 6 is a structural diagram showing an outline of an RGB crossing type liquid crystal projector of an embodiment.

FIG. 7 is a perspective view showing a metal halide lamp and a reflector of a light source portion in the liquid crystal projector of the embodiment.

FIG. 8 is a schematic cross-sectional view of a light source portion in the liquid crystal projector of the embodiment.

FIG. 9 is a schematic cross-sectional view of a light source portion in a liquid crystal projector of another embodiment.

FIG. 10 is a schematic cross-sectional view of a rotating prism portion in the RGB crossing type liquid crystal projector of the embodiment.

FIG. 11 is a schematic cross-sectional view of a rotating prism in the RGB crossing type liquid crystal projector of the embodiment.

FIG. 12 is a graph showing the relationship between the rotation angle of the rotating prism and the height of the light beam emitted from the main optical axis in the RGB intersecting type liquid crystal projector of the embodiment.

FIG. 13 is a graph showing a non-linear degree of irradiation moving speed of stripes on a liquid crystal panel in an RGB crossing type liquid crystal projector of an example, and a graph showing a moving distance and a moving time of stripe vertical scanning with respect to a prism rotation angle.

FIG. 14 is a schematic cross-sectional view of a rotating prism portion in a liquid crystal projector of another embodiment.

FIG. 15 is a graph showing the relationship between the rotation angle of the rotating prism and the height of the light beam emitted from the main optical axis, which corresponds to the other example shown in FIG. It is a schematic sectional drawing of a light source part.

FIG. 16 is a schematic cross-sectional view of a rotating prism portion in an RGB intersecting type liquid crystal projector of another embodiment.

FIG. 17 is a schematic cross-sectional view of a rotating prism portion in an RGB intersecting type liquid crystal projector of another embodiment.

FIG. 18 is a schematic cross-sectional view of an irradiation optical system portion in the RGB crossing type liquid crystal projector of the embodiment.

[Explanation of symbols for main parts]

3,23 Dichroic prism 3a, 3b, 23a, 23b Dichroic mirror 6 Square-section prism 6a Antireflection film 7 Anamorphic lens 8 Liquid crystal panel 9 Projection lens 10 Screen 11 Metal halide lamp 12 Elliptical reflector 14, 15 Mirror 16 Circular mirror 16a Slit 17 Collimator Lens 18 Polarization Beam Splitter (PBS) 19 Cold Mirror 21,22,30 Reflecting Mirror 31 λ / 2 Wavelength Plate 32 V-Shaped Columnar Lens 33,34 Collimator Lens System 35 Phase Adjustment Thin Film 35 50 Correction Plate 51 Main Optical Axis 52, 53 Sub optical axis 60 Regular hexagonal section prism 70 Angle adjusting means 100 RGB conversion circuit 101R, 101G, 101B Frame buffer memory 102R, 102G, 102B Stripe signal Selection circuit 103 controller 104R, 104G, 104B time compression circuit 105 time-division circuit 106 liquid crystal panel drive circuit 107 prism drive means

Claims (8)

[Claims] 1. A light source, a reflector for reflecting and condensing light from the light source, a light separating means for separating the collected light into three light beams of red, green and blue, a liquid crystal panel, and a rotation. It is composed of a columnar body having a regular polygonal cross section which is line-symmetric with respect to the axis and has opposing parallel surfaces, and the side faces thereof receive the light fluxes of the three colors and irradiate them in stripes on the liquid crystal panel to form stripes of the three colors. A liquid crystal projector having a rotating prism for scanning on the liquid crystal panel, wherein one main light axis of the three colors is a main optical axis and the main optical axis is orthogonal to the rotation axis. Of the remaining two are used as sub-optical axes, the sub-optical axis is inclined symmetrically with respect to the main optical axis, and the sub-optical axis is provided with an incident means that is incident on an intersection of the main optical axis and the rotation axis. A liquid crystal comprising a collecting means for collecting in parallel with the main optical axis. projector. 2. The liquid crystal projector according to claim 1, wherein the rotating prism is a columnar body having a square cross section. 3. The liquid crystal projector according to claim 1, wherein each of the sub optical axes is tilted symmetrically with respect to the main optical axis within an angle range of 0 <θ ≦ 30 degrees. 4. The liquid crystal projector according to claim 3, wherein the sub optical axes are inclined symmetrically with respect to the main optical axis at an angle of 30 degrees. 5. The liquid crystal projector according to claim 1, wherein the reflector is a bowl-shaped elliptical reflector having different vertical and horizontal eccentricities. 6. A slit extending in the extension direction of the stripe is provided only in a portion of the external focus of the elliptical reflector through which a light beam passes, and the slit is arranged such that the center of its radius of curvature coincides with the internal focus of the elliptical reflector. 6. A circular mirror having a concave internal reflection surface, and a collimator lens for converting the light flux into parallel rays downstream of the circular mirror are provided between the light separating means and the elliptical reflector. LCD projector. 7. The liquid crystal projector according to claim 1, wherein the liquid crystal panel is provided with an angle adjusting means for varying a tilt angle of a main surface of the liquid crystal panel with respect to the main optical axis. 8. The liquid crystal projector according to claim 1, further comprising magnification adjusting means for changing a magnification of a projection optical system downstream between the rotary prism and the liquid crystal panel.