JPH10206813A - Liquid crystal projector and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a liquid crystal projector system in which resolution and luminance are satisfactory by moving incident positions of luminous fluxes of a liquid crystal panel by the amount equivalent to an integer multiple of the pitch of a pixel. SOLUTION: Positions of light beams passing through a lens array 7 on the light incident surface of a liquid crystal panel 9 are moved by the amount equivalent to the integer multiple of the pitch of the pixel. For this purpose, a moving mechanism 27 is connected to the lens array 7 and a control circuit 29 controlling the moving mechanism 27 is provided in order to control the liquid crystal panel 9. Then, the moving mechanism 27 moves the lens array 7 in parallel with the light incident surface of the panel 9 according to the position control signal generated from the control circuit 29 by the amount equivalent to the integer multiple of the pitch of the pixel of the panel 9. Since the lens array 7 is moved by the moving mechanism 27 by the amount equivalent to the integer multiple of the pitch of the pixel of the liquid crystal panel 9, a certain pixel becomes the pixel of a red color light (R), the pixel of a green color light (G) and the pixel of a blue color light (B) from time to time. Thus, three-primary colors can be expressed with one pixel just as in the case of a color sequential system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector (liquid crystal projector) using a liquid crystal cell as an optical modulator. The present invention particularly relates to a liquid crystal projector (single-panel liquid crystal projector) that performs color display using only one liquid crystal panel.

[0002]

2. Description of the Related Art A CRT system has been used for many years as an apparatus for projecting and enlarging an image on a television or the like. On the other hand, there is a method of displaying such an image using a liquid crystal projector (a liquid crystal projector method). The liquid crystal projector system has excellent characteristics such as a wide color reproduction range, easy downsizing and weight reduction, and no need for convergence adjustment or the like, as compared with the CRT system.

On the other hand, the liquid crystal projector system is C
In addition to the drawbacks in display characteristics such as lower luminance and inferior moving image display characteristics as compared with the RT method, there are commercial drawbacks such as higher cost. However, according to the liquid crystal projector system, it is undeniable that there are advantages in display characteristics, such as uniform brightness on the screen and less flicker on the screen. Among the two types of comparison, the most problematic one is the cost of the liquid crystal projector system. Cost issues are also associated with improving the brightness of liquid crystal projectors. In other words, since the liquid crystal element itself does not emit light, it is necessary to provide a separate light source. However, a high-luminance light source is correspondingly expensive and large, so that the advantages of the liquid crystal projector system cannot be utilized.

[0004] In addition, the cost of the liquid crystal element itself is also a problem. There is a method of using three liquid crystal panels when performing color display by a liquid crystal projector method (three-panel method). In this method, red light (R), green light (G), and blue light (B) are incident on each of three liquid crystal panels, and light modulated by these liquid crystal panels is optically superimposed on one liquid crystal panel. This is a method of obtaining an image. However, this method causes serious cost problems due to the use of three liquid crystal panels, and may sacrifice the small size and light weight, which is an inherent advantage of the liquid crystal projector method. .

Therefore, in recent years, a system (single-plate system) for performing color display using only one liquid crystal panel is becoming mainstream. As a typical single-panel type liquid crystal display device or liquid crystal projector, as disclosed in JP-A-59-230383, a liquid crystal having a so-called mosaic or stripe color filter pattern of three primary colors is used. The display panel is configured to emit white light by an optical system. However, according to this method, since all the light passes through the color filter, only about one third of the light emitted from the white light source is used. Therefore,
In order to obtain the same brightness as a single-panel type, it is necessary to use a light source three times or more brighter, but there is a problem that the apparatus becomes large, heavy, and expensive. For the liquid crystal projector system, such a decrease in light use efficiency is fatal not only in terms of luminance but also in terms of cost and the like.

Japanese Patent Laid-Open No. 4-605 discloses a single-panel type liquid crystal projector which solves the above-mentioned problem of luminance (light use efficiency).
No. 38 discloses this. In this method, the color filter was successfully removed, and the light absorption by the color filter was completely eliminated. According to this method, a plurality of dichroic mirrors arranged at slightly different angles with respect to the traveling direction of light are irradiated with white light, and R, G, B
And the R, G, and B light beams enter the light incident surface of the liquid crystal panel at different positions for each of the light beams via the microlens array (new single-panel system). The present invention is an improved invention based on a new single-panel liquid crystal projector.

The new single-panel liquid crystal projector will be described in detail with reference to FIG. White light is emitted from the light source 1 and is converted into substantially parallel light by the condenser lens 3. The white light is then reflected by the three dichroic mirrors 5 whose angles are slightly different from each other in the direction in which the liquid crystal panel 9 is located. The dichroic mirror 5 has a function of separating white light into R, G, and B colors, and reflecting the separated color lights in three directions having slightly different directions. For example, the dichroic mirror 5R related to _R is arranged at θ = 44.5 ° in the figure, the dichroic mirror 5G related to _G is arranged at θ = 45 °,
The dichroic mirror 5B related to _B is θ = 45.5 °
Are located in The light decomposed by these dichroic mirrors 5 passes through a lens array 7 to a liquid crystal panel 9.
At a slightly different angle (for example, -1 °, 0 °, 1 °) with respect to the normal to the light incident surface of

FIG. 4 is an enlarged view of the dotted line portion 20 in FIG. 3 to show the details. The white light, which is incident on the liquid crystal panel 9 and is divided into light beams of a plurality of colors, passes through a lens array 7 having irregularities with a pitch approximately three times the cell pitch of the liquid crystal panel. The focal point of the lens array 7 is adjusted to the light incident surface of the liquid crystal panel 9, and a plurality of light beams are focused on the light incident surface of the liquid crystal panel 9 to form stripes in the order of B, G, and R, respectively. When one pixel of the liquid crystal panel is formed corresponding to the position of the stripe, it is possible to perform color display with one liquid crystal panel by controlling the transmittance for each pixel.

Returning to FIG. 3, the light that has been modulated for each pixel in the liquid crystal panel 9 passes through the liquid crystal panel at a controlled transmittance, and is converged by the field lens 11 before being projected by the projection lens 13. And projected on the screen 15.

[0010] Such a new single-panel system is epoch-making in that high luminance can be realized by removing a color filter when performing color display. However, in order to form one color pixel by three pixels of the liquid crystal panel as in the single-panel type, there is a problem that the resolution of the liquid crystal panel itself must be tripled as compared with the three-panel type. For example, in the new single-panel system, a liquid crystal panel having 920,000 cells is required for VGA color display of 640 dots in width and 480 dots in height, but such a liquid crystal panel is extremely expensive and has a thin film transistor (TFT). ) And the proportion of wiring is high, so the aperture ratio is low,
The projection screen becomes dark. When trying to solve this problem,
Although the size of the panel is increased, the peripheral components of the lens and the mirror are increased in size.

In order to eliminate such disadvantages of the new single-panel system, a method of realizing color display with a single liquid crystal panel without increasing the resolution has been developed by using a recently developed ferroelectric liquid crystal or the like. A structure as shown in FIG. 5 using a liquid crystal panel using a responsive liquid crystal material can be considered. This method does not separate colors by using a plurality of dichroic mirrors, but separates colors by passing white light through a rotating color filter 17.
Is a method of sequentially using one pixel for each of R, G, and B colors (color sequential method). In this method, one color pixel is formed by one pixel of the liquid crystal panel by using an illusion caused by an afterimage of an eye, so that the resolution problem unlike the new single panel method does not occur. The other components described with reference to FIG. 3 have basically the same functions, and thus are assigned the same numbers.

Certainly, according to the color sequential system, the resolution is improved as compared with the new single-plate system, and there are few problems of an increase in size and cost of the apparatus. However, since a color filter is used for color separation, there is a problem that the luminance is low, which is a drawback of the old single plate system.

[0013]

As described above, each of the currently known liquid crystal projector systems has a problem in either resolution or luminance, and a system which satisfies all of them is not known. It is an object of the present invention to devise a liquid crystal projector system having good resolution and luminance by incorporating the advantages of the color sequential system while incorporating the new single-panel system as a base, and combining these two systems. More specifically, a first object of the present invention is to enable a plurality of colors to be sequentially expressed by one pixel in a new single-panel liquid crystal projector,
An object of the present invention is to provide a liquid crystal projector having a high resolution. A second object of the present invention is to provide a liquid crystal projector with high luminance by removing a color filter in a color sequential type liquid crystal projector. A third object of the present invention is to provide a liquid crystal projector which realizes high brightness and high resolution and does not impair the small size and light weight which are advantages of the liquid crystal projector system.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light source that emits white light, a separating / reflecting mechanism that separates white light into light beams of a plurality of colors, and reflects the light beams at different angles. A liquid crystal panel that applies optical modulation to the liquid crystal panel, a lens mechanism that focuses the light beam on each pixel of the liquid crystal panel, and a mechanism that enlarges and projects the light beam emitted from the liquid crystal panel. The problem can be solved by a liquid crystal projector having a moving mechanism that moves by an integral multiple of the pixel pitch.

At this time, a preferred example of the moving mechanism is connected to a lens mechanism, and has an action of moving the lens mechanism in a direction parallel to the light incident surface of the liquid crystal panel. Further, it is desirable that the movement mechanism controls the color appearing in each pixel so as to be temporally uniform to move the position where the light flux enters the liquid crystal panel. The position of the moving mechanism is defined by a position control signal issued from a control circuit connected to the moving mechanism, and the transmittance for each pixel of the liquid crystal panel is defined by a transmittance control signal issued from the control circuit. The control circuit creates a coherent image by synchronizing the position control signal and the transmittance control signal.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows one embodiment of the present invention. Of the components described in the related art, those having the same function in the embodiment of the present invention are given the same reference numerals. The basic structure of the present invention is the same as that of the new single plate system.

That is, the white light emitted from the light source 1 is converted into substantially parallel light by the condenser lens 3, and thereafter, the three dichroic mirrors 5 whose angles are slightly different from each other are obtained.
As a result, white light is separated into light beams of a plurality of colors, and each light beam is reflected in a different direction in the direction in which the liquid crystal panel 9 is located. The light separated by the dichroic mirror 5 enters the liquid crystal panel 9 via the lens array 7 at slightly different angles (for example, -1 °, 0 °, 1 °). The separated white light incident on the liquid crystal panel 9 passes through the lens array 7 having irregularities with a pitch approximately three times as large as the cell pitch of the liquid crystal panel.
Focus on the above and make stripes in the order of B, G, R respectively.
By forming one pixel of the liquid crystal panel corresponding to the position of the stripe and controlling the transmittance for each pixel, it is possible to perform color display with one liquid crystal panel. Light modulated by the liquid crystal panel 9 for each pixel passes through the liquid crystal panel at a controlled transmittance, and the field lens 1
After being converged by 1, it is enlarged by the projection lens 13 and projected on the screen 15. These points are based on the new veneer method.

However, the present invention is different in that the position of the light passing through the lens array 7 on the light incident surface of the liquid crystal panel 9 is moved by an integral multiple of the pixel pitch. In the embodiment of the present invention, a moving mechanism 27 is connected to the lens array 7 for this purpose, and a control circuit 29 is provided to control the moving mechanism 27 and the liquid crystal panel 9. The moving mechanism 27 has a function of moving the lens array 7 in parallel with the light incident surface of the liquid crystal panel 9 by an integral multiple of the pixel pitch of the liquid crystal panel 9 in accordance with a position control signal issued from the control circuit 29. As specific embodiments of the moving mechanism 27, for example, driving by a linear stepping motor, driving by a combination of a voice coil motor and a position sensor, and the like can be considered. Since the lens array 7 is moved by an integral multiple of the pitch of the pixels of the liquid crystal panel 9 by the moving mechanism 27, a certain pixel becomes an R pixel, a G pixel, or a B pixel depending on the time. Therefore, the three primary colors can be expressed by one pixel in the same manner as in the color sequential system, so that the resolution problem, which is a drawback of the new single-chip system, is solved, and this can be achieved without using a color filter at all. Since it is realized, luminance is not sacrificed unlike the color sequential method.
Similarly, the color of the pixel next to the pixel starts at the time when the pixel functions as a G pixel, and sequentially changes color tones such as a B pixel and an R pixel. Then, a transmittance control signal is supplied to the liquid crystal panel 9 from the control circuit 29 to change the transmittance of each pixel in synchronization with the change of the color tone of each pixel. Therefore, it is possible to display one coherent image as the whole liquid crystal projector.

FIG. 2 shows the operation of the embodiment of the present invention.
This will be described with reference to FIG. First, as shown in FIG. 2 (b), each of the three pixels 31, 32, and 33 B that light passing through the region 30 of the lens array 7 at a certain time t ₁ constitutes a stripe, G, R-state Suppose that Then, at time t
The case where the lens array 7 is moved one pixel to the left in ₂ shown in FIG. 2 (a). At this time, of the luminous fluxes that have passed through the area 30 of the lens array 7,
1 is illuminated, and those related to R illuminate the pixel 32. Also, of the luminous flux passing through the area 30 of the lens array 7, B
2 irradiates a pixel 35 adjacent to the pixel 31 which is not displayed in FIG. 2B. The pixel 33 is illuminated by a light flux passing through the area 40 on the right side of the area 30 of the lens array 7 relating to B. Therefore, if attention is paid to the pixels 31, 32, and 33,
These pixels have changed from the arrangement of the states of B, G, and R from the left of FIG. 2B to the arrangement of G, R, and B from the left of FIG. 2A.

Similarly, FIG. 2C shows a case where the lens array 7 is moved rightward by one pixel at time t ₃ . At this time, of the luminous fluxes that have passed through the area 30 of the lens array 7, those associated with B illuminate the pixel 32, and those associated with G illuminate the pixel 33. The area 3 of the lens array 7
Of the luminous fluxes that have passed through 0, those associated with R illuminate the pixels 36 adjacent to the pixels 33 that were not displayed in FIG. 2B. In addition, the pixel 31 is the lens array 7
Of the light beam passing through the region 50 on the left of the region 30 of the region 30 is irradiated with R. Therefore, the pixels 31, 3
Focusing on 2, 33, these pixels change from the arrangement of B, G, and R states from the left in FIG. 2B to the arrangement of R, B, and G states from the left in FIG. 2C. It will be done.

Assuming that the position of the lens array 7 shown in FIG. 2B is 0, the position of the lens array 7 shown in FIG. The position of the lens array 7 shown in FIG. Then, for example, 0 → -1 → 1 → 0 → -1 → 1.
.. by repeatedly moving the lens array 7,
The pixel 31 changes in the order of B → G → R → B → G → R. Similarly, the pixel 32 changes as G → R → B → G → R → B, and the pixel 33 changes as R → B → G → R → B → G.
Then, as such in each pixel in response to a change in color of each pixel at each time t ₁ ~t ₃ to impart a desired potential, 1 pixel by controlling the transmittance is 1 pixel color Color images can be reproduced. The point that color display is performed by sequentially changing the color appearing in one pixel has the same feature as the color sequential method.

As a method of moving the lens array 7, it is preferable that R, G, and B appear uniformly in each pixel when a time average is taken. As another movement pattern for causing R, G, and B to appear evenly, for example, the position of the lens array 7 is defined as described above, and 0 → 1 → 2 → 3
A pattern of → 4 → 5 → 5 → 4 → 3 → 2 → 1 → 0...

However, when importance is placed on the moving image display characteristics, it is not always necessary to stick to the appearance of R, G, and B evenly. For example, 0 → -1 → 0 → 1 → 0 → -1 →
It is also possible to move the lens array 7 repeatedly as 0 → 1. In this case, for example, the pixel 31 is B → G → B
→ R → B → G → B → R, and the time to display B is twice as long as the time to display R and G. Therefore, although the image quality is inferior, the moving distance of the lens array 7 for each drive becomes shorter, so that a more responsive moving image can be displayed.

In the above description, the incident position of the light beam on the liquid crystal panel is changed by moving the lens array. However, other methods can be used. For example,
How to move the LCD panel while keeping the lens array stationary,
A method of moving both the lens array and the liquid crystal panel simultaneously, a method of tilting the dichroic mirror as a whole and shifting the reflection direction, and a method of inserting a galvano mirror, a deformable prism, etc. between the dichroic mirror and the lens array to deflect the light beam, etc. Conceivable. In other words, as long as the means for moving the incident position of the light beam on the liquid crystal panel by an integral multiple of the pixel pitch, the purpose of the present invention can be achieved.

[0025]

As described above, according to the present invention, a liquid crystal projector excellent in resolution and brightness can be provided because the advantages of the color sequential system are adopted while the new single-panel system is basically used. is there.

More specifically, the present invention is based on a color-sequential type liquid crystal projector while removing a color filter and performing color separation by a dichroic mirror instead. It is possible to provide a liquid crystal projector in which the low brightness which is a drawback of the above is eliminated.

Further, the present invention is based on a new single-panel type liquid crystal projector and uses a lens array instead of using a rotary color filter so that three colors can be sequentially expressed by one pixel. It moves in a direction parallel to the surface of the liquid crystal panel. Therefore, it is possible to provide a liquid crystal projector that has solved the problem of low resolution, which is a disadvantage of the new single-panel liquid crystal projector.

Further, in the present invention, a high-brightness, high-resolution color display is realized by using a single liquid crystal panel. A color display device that does not impair the performance can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a lens array and pixels of a liquid crystal panel according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional liquid crystal projector according to a new single-panel system.

FIG. 4 is a diagram showing a positional relationship between a lens array of a liquid crystal projector and pixels of a liquid crystal panel according to a new single panel system.

FIG. 5 is a schematic diagram of a liquid crystal projector according to a conventional color sequential system.

[Explanation of symbols]

 Reference Signs List 1 light source 3 condenser lens 5 dichroic mirror 7 lens array 9 liquid crystal panel 11 field lens 13 projection lens 15 screen 27 lens array moving mechanism 29 control circuit 31, 32, 33 pixels on liquid crystal panel

Continued on the front page (72) Inventor Tetsuo Kanno 1031 Fujisawa, Fujisawa-shi, Kanagawa Prefecture Apty Inc.

Claims (5)

[Claims] A light source that emits white light; a separation / reflection mechanism that separates the white light into light beams of a plurality of colors and reflects the light beams at different angles; and a liquid crystal panel that optically modulates the light beams. A lens mechanism for converging and entering the light flux into each pixel of the liquid crystal panel; a mechanism for enlarging and projecting the light flux emitted from the liquid crystal panel; and an incident position of the light flux on the liquid crystal panel for the pixel. A liquid crystal projector comprising: a moving mechanism that moves by an integral multiple of the pitch; 2. The liquid crystal projector according to claim 1, wherein said moving mechanism is connected to said lens mechanism, and moves said lens mechanism in a direction parallel to a light incident surface of said liquid crystal panel. 3. The liquid crystal projector according to claim 1, wherein the moving mechanism moves the incident position by controlling the colors appearing in the pixels to be temporally uniform. 4. A light source that emits white light, a separating / reflecting mechanism that separates the white light into light beams of a plurality of colors and reflects the light beams at different angles, and a lens mechanism that converges the light beams.
A method of driving a liquid crystal projector, comprising: a liquid crystal panel for optically modulating a light beam converged by the lens mechanism; and a mechanism for enlarging and projecting the light beam emitted from the liquid crystal panel. A method of driving a liquid crystal projector, wherein the method moves in a direction parallel to a light incident surface of the liquid crystal panel so that the plurality of colors appear evenly and temporally in pixels of the liquid crystal panel. 5. The driving method for a liquid crystal projector according to claim 4, wherein the position of incidence of the light beam on the liquid crystal panel is moved by a single drive by a distance that is an integral multiple of a pitch of pixels related to the liquid crystal panel.