JP4552412B2 - Projector system and driving method thereof - Google Patents

Description

  The present invention relates to a projector system and a driving method thereof.

Conventionally, methods for expanding the dynamic range of a projector are known as disclosed in the following Patent Documents 1 and 2. In this method, dimming means such as a liquid crystal device or a light shielding plate is provided between the illumination light source and the light valve, and the amount of illumination light incident on the light valve is changed at the same time as the image brightness. The video signal is decompressed.
JP-A-9-116840 Japanese Patent Laid-Open No. 2001-1000068

However, even if the above-described method is adopted, black floating occurs when the projector is used in a bright room, and the dynamic range cannot be sufficiently expanded.
SUMMARY An advantage of some aspects of the invention is that it provides a projector system that can perform display with high contrast even in a bright room.

In order to achieve the above object, a projector system according to the present invention includes a projector that projects video light and a screen as a projection target of the video light, and controls the screen according to the brightness of the video. By doing so, the amount of reflected light of the image light can be adjusted.
The projector system of the present invention enables adaptive control that adjusts the brightness of a display image based on image information. In this system, for example, if the video scene is a bright scene, the brightness of the display video is increased, and if it is a dark scene, the display brightness is decreased to increase the power of the video. By expanding the video signal, the dynamic range can be expanded.

  In the present invention, the brightness of the display image is adjusted by directly controlling the reflectance of the screen instead of adjusting the light amount of the image light before being projected onto the screen as in the prior art. A reduction in contrast caused by reflection of illumination light (external light) on the screen can be made smaller than in the past. In other words, when displaying an image on a screen, two types of light, that is, reflected light of image light and reflected light of external light are observed on the observer side. Since the reflected light amount of outside light is always a constant value regardless of the light control amount, the entire screen becomes whitish in a dark scene. On the other hand, in the present invention, since dimming is performed on the screen, the reflected light amount of external light can be performed simultaneously with dimming of the image light. Therefore, in a dark scene, the amount of reflected external light can be reduced, and sufficient black display can be performed. In a bright scene, the amount of reflected external light increases due to an increase in the reflectance of the screen. However, since the entire image is bright, the improvement in the luminance of the black display portion does not significantly affect the contrast. Therefore, even when a projector is used in a bright room, it is possible to display an image with high contrast.

As a specific form of the screen, the screen includes a reflective liquid crystal panel on the incident surface of the image light, and the amount of reflected light of the image light can be adjusted by changing the orientation of the liquid crystal molecules of the liquid crystal panel. Can be exemplified.
According to this configuration, the reflectance of the screen can be adjusted at high speed and with high accuracy by changing the alignment state of the liquid crystal molecules by the voltage applied to the liquid crystal panel. Therefore, it is possible to finely control the brightness of the video based on the video signal of one frame. In this specification, “reflection” means that a part of incident light is returned to the viewer side by scattering between different materials having different refractive indexes, in addition to specular reflection and diffuse reflection by the metal reflection film surface. Is also included.

As a specific form of the reflective liquid crystal panel, the liquid crystal panel is composed of a polymer dispersed liquid crystal layer in which liquid crystal molecules and a polymer are phase-separated, and light transmitted through the liquid crystal layer. The thing provided with the light absorption layer which absorbs can be illustrated.
In this configuration, when the image light output from the projector is linearly polarized light, the liquid crystal molecules and the polymer of the liquid crystal panel are aligned in approximately one direction when no voltage is applied, and the liquid crystal It is preferable that the molecular orientation change be performed in a plane including the polarization direction of the image light and the propagation direction of the image light.

  In an ordinary polymer-dispersed liquid crystal panel, since the alignment state of the polymer is disordered, even when the effective refractive indexes of the liquid crystal molecule and the polymer are matched, a sufficient transparent state cannot be obtained. In addition, since the orientation of the liquid crystal molecules dispersed in the polymer becomes disordered, the difference between the average refractive index of the liquid crystal molecules and the refractive index of the polymer is reduced, and the orientation of the liquid crystal molecules and the polymer is different. However, a sufficient scattering state cannot be obtained. On the other hand, in this configuration, since the liquid crystal molecules and the polymer in a state where no voltage is applied are aligned substantially in one direction, the alignment of the liquid crystal molecules is larger than the conventional one in which the polymers are aligned randomly. To control both the transmittance of the liquid crystal panel when the refractive index of the liquid crystal molecules and the polymer are matched, and the scattering intensity of the liquid crystal panel when the refractive index of the liquid crystal molecules and the polymer are different. it can. In particular, in this configuration, the change in the orientation of the liquid crystal molecules occurs in a plane that includes the polarization direction of the incident light and the propagation direction of this incident light, so the refractive index change felt by the incident light is the largest, and the scattering characteristics of the panel are Further increase.

As another form of the reflective liquid crystal panel, the liquid crystal panel reflects a guest-host liquid crystal layer in which liquid crystal molecules and a dichroic dye are mixed, and reflects light transmitted through the liquid crystal layer. The thing provided with the layer can be illustrated.
In this configuration, when the image light output from the projector is linearly polarized light, the liquid crystal molecules and the dichroic dye of the liquid crystal panel are aligned in substantially one direction in a state where no voltage is applied, It is preferable that the orientation change between the liquid crystal molecules and the dichroic dye is performed in a plane including the polarization direction of the image light and the propagation direction of the image light.
In this configuration, since the orientation change of the liquid crystal molecules and the dichroic dye occurs in a plane including the polarization direction of the incident light and the propagation direction of the incident light, the light absorption characteristic by the dichroic dye becomes the largest. .

As described above, in the case where a dichroic dye is mixed in a liquid crystal, an absorptive polarization having a transmission axis substantially parallel to the polarization direction of the image light on the image light incident surface side of the liquid crystal panel. A layer is preferably provided.
In the above configuration, although the light absorption characteristics of the image light can be improved, polarized light perpendicular to the light is not absorbed. Therefore, the image light out of the external light which is disordered light (that is, light having two kinds of orthogonal polarization components). The polarized light component perpendicular to the polarization direction is not absorbed by the dichroic dye but reflected directly to the viewer. On the other hand, in this configuration, since the polarization component perpendicular to the polarization direction of the image light is absorbed by the polarization layer, it is possible to sufficiently suppress a decrease in contrast due to external light.

The projector system of the present invention described above further includes control signal determining means for determining a control signal for controlling the screen based on a video signal per unit time constituting the video, and the control signal determining means based on the control signal. It is preferable to include screen control means for controlling the screen and video signal expansion means for expanding the video signal based on the control signal.
According to this configuration, first, a control signal for controlling the screen is determined based on the video signal per unit time (for example, one frame) constituting the video in the control signal determining means, and the screen control means determines the control signal as Based on the control of the screen, video light whose brightness changes according to the video content is projected onto the screen, while the video signal expansion means expands the video signal based on the control signal. With this operation, the dynamic range of the projected image can be expanded, and a projector system excellent in image expression power and adaptability to the usage environment can be realized.

According to the projector system driving method of the present invention, a control signal for controlling the screen is determined based on a video signal per unit time constituting an image, and the screen is controlled by controlling the screen based on the control signal. The reflected light amount of incident light is adjusted, the video signal is expanded based on the control signal, and an image is generated by supplying the expanded video signal to the projector.
According to this configuration, the dynamic range of the projected video can be extended, and a video with high video expression power can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a liquid crystal projector system which is an example of the projector system of the present invention will be described with reference to FIGS.
The projector 30 of the present embodiment is a three-plate color liquid crystal projector provided with a transmissive liquid crystal light valve for each of different colors of R (red), G (green), and B (blue). FIG. 6 is a schematic configuration diagram showing the liquid crystal projector. In the figure, reference numeral 1 is an illumination device, 2 is a light source, 3 and 4 are fly-eye lenses (uniform illumination means), 13 and 14 are dichroic mirrors, Reference numerals 16 and 17 denote reflection mirrors; 22, 23 and 24, liquid crystal light valves (light modulation means); 25, a cross dichroic prism; and 26, a projection lens (projection means). Reference numeral 40 denotes a screen as a projection target of video light projected from the projector 30. The projector 30 and the screen 40 constitute a projector system of the present invention.

  The illuminating device 1 in this Embodiment is comprised from the light source 2 and the fly eye lenses 3 and 4. FIG. The light source 2 includes a lamp 7 such as a high-pressure mercury lamp and a reflector 8 that reflects light from the lamp 7. Further, as uniform illumination means for making the illuminance distribution of the light source light uniform in the liquid crystal light valves 22, 23, 24 that are the illuminated areas, the first fly-eye lens 3 and the second fly-eye lens from the light source 2 side. 4 are installed sequentially. Here, the first fly-eye lens 3 forms a plurality of secondary light source images, and the second fly-eye lens 4 functions as a superimposing lens that superimposes them at the light valve position. In some cases, a condenser lens for superimposing the secondary light source image may be arranged at the position of the second fly-eye lens 4 or at the subsequent stage.

The configuration of the latter stage of the lighting device 1 will be described below together with the operation of each component.
The dichroic mirror 13 of the blue light, green light reflection, transmits red light L _R of the light beam from the light source 2, is intended to reflect the blue light L _B and the green light L _G. The red light _{LR that} has passed through the dichroic mirror 13 is reflected by the reflection mirror 17 and enters the liquid crystal light valve 22 for red light. Meanwhile, among the color light reflected by the dichroic mirror 13, the green light L _G is reflected by the dichroic mirror 14 for reflecting green light, is incident on the green light liquid crystal light valve 23. On the other hand, the blue light L _B dichroic mirror 14 also passes through the relay lens 18, reflecting mirror 15, a relay lens 19, reflecting mirror 16, is incident on the liquid crystal light valve 24 for blue light through a relay system 21 comprising a relay lens 20 The

The three color lights (color image light) modulated by the liquid crystal light valves 22, 23, and 24 are incident on the cross dichroic prism 25. This prism has a structure in which four right-angle prisms are bonded together, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface thereof. By these dielectric multilayer films, three color lights are combined to form light (video light) representing a color image. The synthesized light is projected onto a screen 27 by a projection lens 26 which is a projection optical system, and an enlarged image is displayed.
In the case of the present embodiment, the screen 40 is composed of a reflective liquid crystal panel, and the amount of reflected light of the screen 40 can be variably adjusted in synchronization with information from the outside, for example, the brightness of an image at a certain moment. . The configuration of the screen 40 will be described later.

Next, a method for driving the projector system according to the present embodiment will be described.
FIG. 7 is a block diagram showing the configuration of the drive circuit of the projector system of the present embodiment. In the case of a projector system that does not have a dimming function, the image light projected from the projector is reflected with the same brightness by a screen with a fixed reflectance, but the dimming function is provided on the screen itself, and In the case of this embodiment for controlling the image signal based on the video signal, as a basic configuration, circuits such as DSP (1) to DSP (3) which are digital signal processing blocks are required as described below.

  In this embodiment, as shown in FIG. 7, the video signal input as an analog signal is input to the DSP (1) 32 (control signal determining means) which is the first digital signal processing circuit via the AD converter 31. The In the DSP (1) 32, the brightness control signal is determined from the video signal. The DSP (2) 33 (screen control means) controls the screen driver 34 based on the brightness control signal, and finally the screen driver 34 actually drives the screen 40.

  On the other hand, the brightness control signal determined by the DSP (1) 32 is also input to the DSP (3) 36 (video signal expansion means) together with the video signal. The DSP (3) 36 expands the video signal to an appropriate gradation range based on the brightness control signal. The video signal after the expansion processing is converted again to an analog signal by the DA converter 37 and then input to the panel driver 38. The liquid crystal light valve 22 for red light (R panel in FIG. 7) from the panel driver 38, for green light It is supplied to each of the liquid crystal light valve 23 (G panel) and the blue light liquid crystal light valve 24 (B panel).

Here, regarding the control method of the screen 40, in addition to [1] display video adaptive control, [2] control by projection magnification, [3] control from the outside, and the like are conceivable. Each method will be described below.
[1] Display video adaptive control First, consider the case of performing display video adaptive control, that is, brightness control adapted to a display video in which the amount of light increases in a bright scene and decreases in a dark scene. . In this case, as described above, the brightness control signal is determined based on the video signal by the DSP (1) 32. For example, the following three methods are conceivable.

(A) A method in which the brightness control signal is the number of gradations having the maximum brightness among the pixel data included in the frame of interest.
For example, a video signal including the number of gradations of 256 steps from 0 to 255 is assumed. When attention is paid to an arbitrary frame constituting a continuous video, it is assumed that the appearance number distribution (histogram) for each gradation number of pixel data included in the frame is as shown in FIG. In this case, since the brightest number of gradations included in the histogram is 190, this number of gradations 190 is used as the brightness control signal. This method is a method that can express the brightness most faithfully to the input video signal.

(B) From the appearance number distribution (histogram) for each number of gradations included in the frame of interest, the number of gradations that have a certain ratio (for example, 10%) with respect to the number of appearances from the maximum brightness. A method of using a control signal.
For example, when the appearance number distribution of the video signal is as shown in FIG. 9, a region of 10% is taken from the brighter side than the histogram. If the number of gradations corresponding to 10% is 230, the number of gradations 230 is used as the brightness control signal. As shown in the histogram of FIG. 9, when there is a sudden peak in the vicinity of the number of gradations 255, the number of gradations 255 becomes the brightness control signal if the method (a) is adopted. However, this sudden peak portion does not make much sense as information on the entire screen. On the other hand, the present method using the number of gradations 230 as the brightness control signal can be said to be a method of determining by a region having meaning as information in the entire screen. In addition, you may change said ratio in about 2 to 50% of range.

(C) A method in which the screen is divided into a plurality of blocks, an average value of the number of gradations of the included pixels is obtained for each block, and the maximum one is used as the brightness control signal.
For example, as shown in FIG. 10, the screen is divided into m × n blocks, and the average value of the brightness (number of gradations) for each block A ₁₁ ,..., A _mn is calculated. A thing is used as a brightness control signal. The number of screen divisions is preferably about 6 to 200. In this method, the brightness can be controlled without deteriorating the atmosphere of the entire screen.
Regarding the methods (a) to (c), in addition to determining the brightness control signal for the entire display region, the method may be applied only to a specific portion such as a central portion of the display region. it can. In this case, it is possible to perform a control method in which the brightness is determined from the portion that is viewed by the viewer.

  Next, in the DSP (2) 33, the screen driver 34 is controlled based on the brightness control signal determined by the above method. For example, the following three methods are conceivable.

(A) A method of controlling in real time according to the output brightness control signal.
In this case, since the brightness control signal output from the DSP (1) 32 may be supplied to the screen driver 34 as it is, signal processing in the DSP (2) 33 is not necessary. This method is ideal in that it perfectly follows the brightness of the video, but the brightness of the screen may change in a short cycle depending on the content of the video, causing problems such as feeling extra stress during viewing. There is a fear.

(B) A method in which an LPF (low pass filter) is applied to the output brightness control signal and control is performed using the output.
For example, the change of the brightness control signal of 1 to 30 seconds or less is cut by the LPF, and the output is controlled by the output. According to this method, since the minute change in time is cut, it is possible to avoid the change in brightness in the short cycle as described above.

(C) A method for detecting a switching edge of a brightness control signal.
The screen driver 34 is controlled only when the brightness control signal changes by a predetermined magnitude or more (for example, 60 gradations or more). According to this method, it is possible to perform control according to only scene switching.

  In this way, for example, when the number of gradations 190 is determined as the brightness control signal, a light amount of 190/255 = 75% can be obtained assuming that the reflected light amount of the maximum brightness (the number of gradations 255) is 100%. The screen 40 is driven as follows. In the case of the present embodiment, since the screen 40 is specifically a reflective liquid crystal panel, the alignment state of the liquid crystal molecules is changed so that the reflectance is 75% (transmittance is 25%). Similarly, when the number of gradations 230 is a brightness control signal, the screen 40 is driven so as to obtain a reflected light amount of 230/255 = 90%.

  On the other hand, the DSP (3) 36 expands the video signal to an appropriate gradation range based on the brightness control signal and the video signal determined by the DSP (1) 32. For example, when expanding to the maximum gradation range, the maximum number of gradations that can be displayed is 255 in the above example. Therefore, when the brightness control signal is the gradation number 190 in the example of FIG. Video signals from 0 to 190 are expanded to 0 to 255 gradations as shown in FIG. By controlling the amount of illumination light and expanding the video signal, smooth gradation expression can be realized while extending the dynamic range of the video.

[2] Control by Projection Magnification Control is performed according to zooming of the projection lens 26. Usually, since the amount of light projected from the projector 30 is constant, the screen tends to be dark on the enlargement side and bright on the reduction side. Therefore, in order to correct this, the screen 40 is controlled so that the amount of reflected light increases when changed to the enlargement side, and the amount of reflected light decreases when changed to the reduction side.

[3] External control The user can control the screen 40 according to his / her preference. For example, the screen 40 is controlled so that the amount of reflected light is small in a dark viewing environment and the amount of reflected light is increased in a bright viewing environment. In this case, a configuration in which the user adjusts by using a controller or directly operating the screen 40, or a configuration in which a brightness sensor or the like is provided and automatically controlled may be employed. However, in order to control these [2] and [3], circuits such as DSP (1) 32 to DSP (3) 36 in FIG. 7 are not necessary, but other circuit configurations are necessary. Become.

[Screen-1]
Next, the screen according to the first embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view illustrating a schematic configuration of a screen according to the present embodiment, FIG. 2 is a schematic perspective view illustrating an alignment state of liquid crystal provided in the screen, together with a polarization state of image light incident on the screen, and FIG. FIG. 4 is a diagram for explaining the operation of the screen.

  The screen 40 according to the present embodiment is composed of a polymer dispersion type liquid crystal panel having a light absorption layer 48 on the back side. By controlling the orientation of the liquid crystal molecules of the panel, the scattering state of the panel, that is, the amount of reflected light. Adjustments are made. That is, as shown in FIG. 1, the screen 40 of the present embodiment includes a pair of translucent substrates 41 and 44 made of a plastic film or the like, and liquid crystal molecules and polymers are interposed between these substrates. A polymer-dispersed liquid crystal layer 47 dispersed in a phase-separated state is sandwiched. Among these base materials, the light-absorbing layer 48 for absorbing the light transmitted through the liquid crystal layer 47 without being scattered by the base material 41 opposite to the liquid crystal layer 47 from the incident side of the image light. Is provided.

Electrodes 42 and 45 made of a light-transmitting conductive film such as ITO are provided on the inner surfaces (the liquid crystal layer 47 side) of the two substrates 41 and 44, respectively. Are stacked with alignment films 43 and 46, respectively.
In the liquid crystal layer 47, polymer dispersions that are chained together in a liquid crystal are mixed in the liquid crystal layer 47. These polymers 47b and liquid crystal molecules 47a are in an initial alignment state (voltage-free mark) as shown in FIG. In one state in a substantially aligned state. In addition, the liquid crystal molecules 47 a are adapted to change the alignment state in a plane including the polarization direction of the image light and the propagation direction of the image light by applying a voltage to the liquid crystal layer 47. In the present embodiment, the refractive index of the liquid crystal molecules 47a and the polymer 47b in the above direction is such that light in the polarization direction perpendicular to the incident video light is transmitted through the liquid crystal layer 47 as it is and absorbed by the light absorption layer 48. Are equally configured.

Such a liquid crystal layer 47 can be formed by the following method, for example.
First, a mixture is prepared by uniformly mixing the polymer precursor, which is the material of the polymer 47b, in the liquid crystal, and this mixture is formed between the base material 41 and the base material 44 on which the alignment films 43 and 46 are formed. To fill. At this time, as the polymer precursor, a material having liquid crystallinity, for example, a liquid crystal ultraviolet curable monomer or an oligomer thereof is used. Thereby, the liquid crystal molecules 47a and the polymer precursors arranged between the substrates are aligned in one direction in a state of being aligned with each other by the action of the alignment films 43 and 46. Next, the panel filled with the mixture is irradiated with ultraviolet rays or the like, and the polymer precursor is polymerized while maintaining the alignment state as described above. As a result, the polymer dispersed liquid crystal layer 47 in which the alignment of the liquid crystal molecules 47a and the polymer 47b is aligned is formed.

Specific examples of orientation of the liquid crystal layer 47 include the following (1) and (2).
(1) In the initial alignment state, the liquid crystal molecules 47a and the polymer 47b are aligned in one direction in a state of being substantially parallel to the substrates 41 and 44 and aligned with each other (homogeneous alignment). 47a stands substantially perpendicular to the substrates 41 and 44 (homeotropic orientation).
In this case, nematic liquid crystal having positive dielectric anisotropy is used as the liquid crystal molecules 47a, and the alignment films 43 and 46 are subjected to a horizontal alignment process such as rubbing. At this time, the alignment directions of the alignment films 43 and 46 are parallel to each other, and the alignment directions are substantially parallel to the polarization direction of the incident video light.

(2) In the initial alignment state, the liquid crystal molecules 47a and the polymer 47b stand substantially perpendicular to the substrates 41 and 44 (homeotropic alignment). In the voltage application state, the liquid crystal molecules 47a are applied to the substrates 41 and 44. Align in parallel and aligned in one direction (homogeneous alignment).
In this case, nematic liquid crystal having negative dielectric anisotropy is used as the liquid crystal molecules 47a, and the alignment films 43 and 46 are both vertical alignment films. The alignment films 43 and 46 are subjected to a pretilt angle providing process such as rubbing in order to define the alignment direction of the liquid crystal molecules 47a when a voltage is applied to one direction. At this time, the pretilt directions of the alignment films 43 and 46 are parallel to each other, and these pretilt directions are substantially parallel to the polarization direction of the incident video light.
In these alignment forms, the shape and alignment state of the polymer are fixed, and even if the alignment state of the liquid crystal molecules is changed by applying a voltage, the alignment state of the polymer is not affected.

  Thus, in this embodiment, since the screen 40 itself has a dimming function, for example, the screen scattering intensity is increased in a scene where the video scene is bright (see FIG. 3A), and the screen 40 is scattered in a dark scene. By reducing the intensity (see FIG. 3B), the brightness can be controlled according to the video as in the conventional case, which can contribute to the expansion of the dynamic range. However, in this embodiment, the brightness of the display image is adjusted by directly controlling the reflectance of the screen, rather than adjusting the amount of image light before being projected onto the screen as in the prior art. In addition, a decrease in contrast caused by reflection of indoor illumination light (external light) on the screen can be made smaller than in the past. In other words, when displaying an image on a screen, two types of light, that is, reflected light of image light and reflected light of external light are observed on the observer side. Since the reflected light amount of outside light is always a constant value regardless of the light control amount, the entire screen becomes whitish in a dark scene. On the other hand, in the present embodiment, since dimming is performed on the screen, the amount of reflected external light can be performed simultaneously with the dimming of image light. Therefore, in a dark scene, the amount of reflected external light can be reduced, and sufficient black display can be performed. In a bright scene, the amount of reflected external light increases due to an increase in the reflectance of the screen. However, since the entire image is bright, the improvement in the luminance of the black display portion does not significantly affect the contrast. Therefore, even when a projector is used in a bright room, it is possible to display an image with high contrast.

  In the present embodiment, since the screen 40 is configured as a liquid crystal panel, the light scattering state (that is, the reflectance of the image light) can be adjusted with high speed and high accuracy by the voltage applied to the panel. Therefore, it is possible to finely control the brightness of the video based on the video signal of one frame. At this time, in this embodiment, the liquid crystal molecules and the polymer in the liquid crystal layer 47 are aligned in approximately one direction in the state where no voltage is applied, and the orientation change of the liquid crystal molecules changes the polarization direction of the image light and the image light. Therefore, when the image light is output as linearly polarized light as in a projector using a liquid crystal light valve, the amount of adjustment of the light amount of the image light can be increased.

In other words, in a normal polymer-dispersed liquid crystal panel, the alignment state of the polymer is disordered, so that even when the effective refractive index of the liquid crystal molecule and the polymer are matched, a sufficient transparent state cannot be obtained. . In addition, since the orientation of the liquid crystal molecules dispersed in the polymer becomes disordered, the difference between the average refractive index of the liquid crystal molecules and the refractive index of the polymer is reduced, and the orientation of the liquid crystal molecules and the polymer is different. However, a sufficient scattering state cannot be obtained. On the other hand, in this embodiment, since the liquid crystal molecules and the polymer in a state where no voltage is applied are aligned in substantially one direction, the liquid crystal molecules are compared with the conventional one in which the polymers are aligned randomly. Increasing both the transmittance of the liquid crystal panel when the alignment is controlled and the refractive index of the liquid crystal molecule and the polymer are matched, and the scattering intensity of the liquid crystal panel when the refractive index of the liquid crystal molecule and the polymer is different. Can do. In particular, in this configuration, the change in the orientation of the liquid crystal molecules occurs in a plane that includes the polarization direction of the incident light and the propagation direction of this incident light, so the refractive index change felt by the incident light is the largest, and the scattering characteristics of the panel are Further increase. Further, in this configuration, since the polarized light perpendicular to the image light is not scattered by the change in the orientation of the liquid crystal molecules, it passes through the liquid crystal layer 47 as it is and is absorbed by the light absorption layer 48. For this reason, even if it does not depend on light control, half of the external light which consists of disordered light is cut, and a display with few black floating is obtained.
As described above, in this embodiment, since the scattering state (light reflectance) of the panel can be adjusted in a wide range, it is possible to display a higher quality image.

[Screen-2]
Next, a screen according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view illustrating a schematic configuration of the screen according to the present embodiment, and FIG. 5 is a schematic perspective view illustrating an alignment state of liquid crystal provided in the screen together with a polarization state of image light incident on the screen. In the present embodiment, the same reference numerals are given to the same members or parts as those in the first embodiment, and the description thereof is omitted.

  The screen 50 of the present embodiment is composed of a guest-host type liquid crystal panel provided with an absorption type polarizing layer 58 on the front surface. By controlling the orientation of liquid crystal molecules of this panel, the reflectance of the panel, that is, the adjustment of the amount of reflected light is adjusted. Is to be performed. That is, as shown in FIG. 4, the screen 50 of this embodiment includes a pair of translucent substrates 41 and 44 made of a plastic film or the like, and liquid crystal molecules and dichroic dyes are interposed between these substrates. And a guest-host type liquid crystal layer 57 in which is mixed. Among these base materials, the base material 41 on the incident side of the image light with respect to the liquid crystal layer 57 absorbs the light in the changing direction perpendicular to the image light, and is substantially parallel to the polarization direction of the image light. An absorptive polarizing layer 58 having a transparent transmission axis is provided.

  Electrodes 42 and 45 for applying a voltage to the liquid crystal layer 57 are provided on the inner surfaces (the liquid crystal layer 47 side) of the two base materials 41 and 44, and further on these electrodes 42 and 45. The alignment films 43 and 46 are respectively laminated. In the present embodiment, in order to reflect the light transmitted through the liquid crystal layer 57, a high reflective metal reflective film such as Al or Ag is provided on the electrode 42 on the opposite side to the incident side of the image light with respect to the liquid crystal layer 57. The reflective layer of the present invention is constituted by this metal reflective film. However, when a reflective film is separately provided on the substrate 41, both the electrodes 42 and 45 can be made of a light-transmitting conductive film such as ITO. In order to improve the viewing angle characteristics, it is preferable that the reflection film for reflecting the image light is a diffuse reflection film.

  As shown in FIG. 5, the liquid crystal molecules 57a and the dichroic dye 57b constituting the liquid crystal layer 57 are aligned in one direction in a substantially aligned state in the initial alignment state. The liquid crystal molecules 57a are changed in the alignment state in a plane including the polarization direction of the image light and the propagation direction of the image light by applying a voltage to the liquid crystal layer 57, and accordingly, the dichroic dye The molecular long axis 57b is also rotated in this plane. As the dichroic dye 57b, it is desirable to use a dichroic dye that absorbs in the entire visible light wavelength region (black dye).

Specific examples of the alignment mode of the liquid crystal layer 57 include the following (1) and (2).
(1) A state in which the liquid crystal molecules 57a and the dichroic dye 57b are parallel to the substrates 41 and 44 and aligned with each other (homogeneous orientation) when no voltage is applied. The dye 57b is oriented in one direction while being substantially perpendicular to the substrates 41 and 44 (homeotropic orientation).
In this case, nematic liquid crystal having positive dielectric anisotropy is used as the liquid crystal molecules 57a, and the alignment films 43 and 46 are subjected to a horizontal alignment process such as rubbing. At this time, the alignment directions of the alignment films 43 and 46 are parallel to each other, and the alignment directions are substantially parallel to the polarization direction of the incident video light.

(2) The liquid crystal molecules 57a and the dichroic dye 57b are aligned in one direction in a state of being substantially perpendicular to the substrate in the state where no voltage is applied (homeotropic alignment). And the dichroic dye 57b are both parallel to the substrates 41 and 44 and aligned with each other (homogeneous orientation).
In this case, nematic liquid crystal having negative dielectric anisotropy is used as the liquid crystal molecules 57a, and the alignment films 43 and 46 are both vertical alignment films. The alignment films 43 and 46 are subjected to a pretilt angle providing process such as rubbing in order to define the alignment direction of the liquid crystal molecules 57a when a voltage is applied to one direction. At this time, the pretilt directions of the alignment films 43 and 46 are parallel to each other, and these pretilt directions are substantially parallel to the polarization direction of the incident video light.

Therefore, a decrease in contrast due to external light can be suppressed also in this embodiment.
In the present embodiment, the orientation change of the liquid crystal molecules and the dichroic dye in the liquid crystal layer 57 is performed in a plane including the polarization direction of the image light and the propagation direction of the image light. The light absorption characteristic by is the highest. For this reason, in the case where the image light is output as linearly polarized light as in the present embodiment, it is possible to increase the light amount adjustment range of the image light, and it is possible to display a high-quality image with a wide dynamic range.
In this embodiment, the polarizing layer 58 provided on the front surface of the panel absorbs light having a polarization direction perpendicular to the image light, so that the influence of external light is not affected without deteriorating the brightness of the image. It can be further reduced.

In addition, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation in the range which does not deviate from the meaning of this invention.
For example, in the above embodiment, the screen is a reflective liquid crystal panel, but the present invention is not limited to this, and the screen can be configured by various panels such as an electrophoretic panel capable of adjusting light reflection.

1 is a cross-sectional view showing a schematic configuration of a screen according to a first embodiment of the present invention. The schematic perspective view which shows the orientation state of the liquid crystal with which a screen is provided with the polarization state of the image light which injects into this screen. The figure for demonstrating the effect | action of a screen. 1 is a cross-sectional view showing a schematic configuration of a screen according to a first embodiment of the present invention. The schematic perspective view which shows the orientation state of the liquid crystal with which a screen is provided with the polarization state of the image light which injects into this screen. 1 is a diagram showing a schematic configuration of a projector system according to a first embodiment of the present invention. It is a block diagram which shows the structure of the drive circuit of a projection type liquid crystal display device equally. FIG. 4 is a diagram for explaining a first method for determining a brightness control signal from a video signal in the projection type liquid crystal display device. It is a figure for demonstrating the 2nd method same as the above. It is a figure for demonstrating the 3rd method same as the above.

Explanation of symbols

30 ... color liquid crystal projector, 40, 50 ... screen, 47, 57 ... liquid crystal layer, 47a, 57a ... liquid crystal molecule, 47b ... polymer, 48 ... light absorption layer, 57b ... Dichroic dye, 58 ... Polarizing layer, 32 ... DSP (1) (control signal determining means), 33 ... DSP (2) (screen control means), 36 ... DSP ( 3) (Video signal decompression means)

Claims (8)

A projector for projecting image light; a screen as a projection target of the image light; control signal determining means for determining a control signal for controlling the screen based on a video signal; and the screen based on the control signal. Screen control means for controlling the video signal, and video signal decompression means for decompressing the video signal based on the control signal ,
Based on the video signal, the amount of reflected light of the video light incident on the screen is adjusted , the video signal is expanded based on the control signal, and the expanded video signal is supplied to the projector. A projector system, characterized by generating image light .   2. The screen according to claim 1, wherein a reflection type liquid crystal panel is provided on an incident surface of the image light, and a reflected light amount of the image light can be adjusted by a change in orientation of liquid crystal molecules of the liquid crystal panel. The projector system described.   The liquid crystal panel includes a polymer-dispersed liquid crystal layer in which liquid crystal molecules and a polymer are phase-separated, and a light absorption layer that absorbs light transmitted through the liquid crystal layer. The projector system according to claim 2. The image light output from the projector consists of linearly polarized light,
The liquid crystal molecules and the polymer of the liquid crystal panel are aligned in substantially one direction when no voltage is applied, and the alignment change of the liquid crystal molecules changes the polarization direction of the image light and the propagation direction of the image light. The projector system according to claim 3, wherein the projector system is performed within a plane including the projector system.   The liquid crystal panel comprises a guest-host type liquid crystal layer in which liquid crystal molecules and a dichroic dye are mixed, and a reflective layer that reflects light transmitted through the liquid crystal layer. The projector system described. The image light output from the projector consists of linearly polarized light,
The liquid crystal molecules and the dichroic dye of the liquid crystal panel are aligned in substantially one direction when no voltage is applied, and the change in the alignment of the liquid crystal molecules and the dichroic dye is caused by the polarization direction of the image light and this 6. The projector system according to claim 5, wherein the projector system is performed in a plane including a propagation direction of image light.   The projector system according to claim 6, wherein an absorption-type polarizing layer having a transmission axis substantially parallel to the polarization direction of the image light is provided on the image light incident surface side of the liquid crystal panel. A driving method of a projector system according to any one of claims 1 to 7 ,
A control signal for controlling the screen is determined based on a video signal per unit time constituting the video, and the amount of reflected light incident on the screen is adjusted by controlling the screen based on the control signal. A method for driving a projector system, comprising: expanding the video signal based on the control signal; and generating the video by supplying the expanded video signal to the projector.

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