JP4654573B2 - Screen, projector system, and image display method for projector system - Google Patents

Description

  The present invention relates to a screen, a projector system, and an image display method for the projector system.

  2. Description of the Related Art A front type (front projection type) projector system including a reflective screen that reflects and displays image light projected from a projector is known. The projector projects the three primary colors of image light by additive color mixing. The reflective screen reflects the projected image light and displays a color image.

Patent Document 1 and Patent Document 2 describe the invention of a reflective screen. This reflects only the three primary colors necessary for additive color mixing of image light on the reflection type screen and absorbs the other color lights. As a result, it is said that natural color images can be projected even in a bright room with excellent chromatic color contrast.
JP-A-5-216123 JP-A-6-289491

  However, the screens described in Patent Document 1 and Patent Document 2 perform image display by simultaneously reflecting the three primary colors necessary for additive color mixing of image light. In this case, the three primary color lights included in the external light are also reflected at the same time. Therefore, when the screen is used in a bright environment, the display image is affected by outside light, and there is a problem in that there is a limit in improving the contrast.

  SUMMARY An advantage of some aspects of the invention is that it provides a screen, a projector system, and an image display method for the projector system that can perform high-contrast image display even in a bright environment.

In order to achieve the above object, a screen of the present invention is laminated on the front side of a light absorption layer, and can reflect a plurality of cholesteric liquid crystal layers capable of reflecting different color lights constituting image light, and the color light in each of the cholesteric liquid crystal layers. It has switching means capable of switching between reflection and transmission, and a timing controller that drives each switching means in time sequence, and reflects different color lights constituting image light in time sequence .
According to this configuration, since different color lights are reflected sequentially in time, the reflected color light among the color lights included in the external light can be limited. Therefore, it becomes difficult to be influenced by external light, and high-contrast image display can be performed even in a bright environment.

In this case, different colored lights can be reflected in time sequence with a simple configuration. In addition, although the clockwise light polarized light, the counterclockwise circularly polarized light, etc. are mixed in the color light included in the external light, the cholesteric liquid crystal layer reflects only one of the circularly polarized light. Accordingly, it is possible to further limit the reflected color light among the color lights included in the external light, and high contrast image display can be performed even in a bright environment.

The switching means may have a pair of conductors for applying an electric field to the cholesteric liquid crystal layer.
In this case, the reflection and transmission of the color light incident on the cholesteric liquid crystal layer can be switched with a simple configuration.

Further, the switching means is disposed on the light incident side of the cholesteric liquid crystal layer, and an electro-optical material capable of switching the rotation direction of the circularly polarized light incident depending on whether or not an electric field is applied; It is good also as a structure which has these.
According to this configuration, incident light can be transmitted without applying an electric field, and incident light can be reflected with an electric field applied. Therefore, power consumption can be reduced.

On the other hand, the projector system of the present invention, the above-described screen, the projector that projects the different color lights constituting the image light in time sequence toward the screen, and the screen and the projector are driven in time sequence in synchronization. And a timing controller.
According to this configuration, different color lights constituting the image light can be displayed in time sequence, so that a color image can be displayed by additive color mixing. In addition, since the color light reflected by the screen among the color lights included in the external light is limited, an image display with high contrast can be performed even in a bright environment.

The projector includes a light source that sequentially emits different color lights and a light modulation unit that sequentially modulates each color light from the light source, and the timing controller includes the light source and the light modulation unit. It is desirable to drive in time sequence synchronously.
According to this configuration, since different color lights can be projected sequentially by one light modulation means, the manufacturing cost of the projector system can be reduced.

The projector preferably projects circularly polarized light.
According to this configuration, since the cholesteric liquid crystal layer that reflects circularly polarized light can be used for the screen, it is possible to further limit the color light reflected by the screen among the color lights included in the external light. Therefore, high-contrast image display can be performed even in a bright environment.

The projector preferably includes a solid light source.
Since the solid-state light source has a narrow emission wavelength width, the reflection wavelength width of the screen can be reduced. Thereby, the color light reflected by a screen among the color lights contained in external light can be restrict | limited more. Therefore, it becomes difficult to be influenced by external light, and high-contrast image display can be performed even in a bright environment.

On the other hand, the image display method of the projector system of the present invention projects different color lights constituting the image light from the projector in time sequence, and the different color lights projected from the projector in time sequence on the screen in synchronization with the projector. A color image is displayed on the screen by reflection.
According to this configuration, different color lights constituting the image light can be displayed in time sequence, so that a color image can be displayed by additive color mixing. In addition, since the color light reflected by the screen among the color lights included in the external light is limited, an image display with high contrast can be performed even in a bright environment.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size. In this specification, the incident side of image light in each member is referred to as the front, and the opposite side is referred to as the back. As for the liquid crystal panel, the liquid crystal layer side of the constituent members is referred to as the inside.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a projector system according to the first embodiment. The projector system 1 of FIG. 1 includes a projector 30 that projects image light of different color lights in time sequence and a screen 10 that reflects image light of each color light projected in time sequence, and displays a color image in a field sequential manner. To do. The screen 10 is configured by laminating a plurality of cholesteric liquid crystal panels 10B, 10G, and 10R capable of reflecting each color light on the surface of the light absorption layer 10a.

[screen]
FIG. 2 is a side sectional view of the cholesteric liquid crystal panel. In FIG. 2, a liquid crystal panel 10B capable of reflecting blue light will be described as an example. The cholesteric liquid crystal panel (hereinafter simply referred to as a liquid crystal panel) 10B is configured by sandwiching a liquid crystal layer 18B made of cholesteric liquid crystal between a front substrate 11 and a back substrate 12.

  The front substrate 11 is made of a light transmissive material such as glass or a plastic film. A transparent electrode 13 made of a conductive material having optical transparency such as ITO is formed on the inner surface of the front substrate 11. The transparent electrode 13 is formed on almost the entire inner surface of the front substrate 11. An alignment film 15 of cholesteric liquid crystal molecules is formed on the inner surface of the transparent electrode 13. As the alignment film 15, a surface of a thin film such as polyimide that has been rubbed can be employed. On the other hand, the transparent electrode 14 and the alignment film 16 are similarly formed on the inner surface of the back substrate 12.

  A liquid crystal layer 18 </ b> B made of cholesteric liquid crystal is sandwiched between the front substrate 11 and the back substrate 12. A cholesteric liquid crystal is a liquid crystal in which liquid crystal molecules are aligned in a spiral shape in the stacking direction. This cholesteric liquid crystal has a property of reflecting colored light having the same wavelength as the helical pitch. Therefore, by adopting cholesteric liquid crystal having a helical pitch of about 450 nm, it becomes possible to reflect blue light. A sealing material (not shown) is applied to the peripheral edge between the substrates 11 and 12, and a cholesteric liquid crystal layer 18B is sealed inside.

  In the liquid crystal panel 10B configured as described above, the cholesteric liquid crystal layer 18B maintains the helical alignment state when no electric field is applied to the cholesteric liquid crystal layer 18B (OFF state). Therefore, the blue light incident from the surface of the liquid crystal panel 10B is reflected by the cholesteric liquid crystal layer 18B. On the other hand, when an electric field is applied to the cholesteric liquid crystal layer 18B by the transparent electrodes 13 and 14 (ON state), the liquid crystal molecules are reorientated vertically along the electric field, and the helical alignment state is lost. Therefore, the blue light incident from the surface of the liquid crystal panel 10B passes through the cholesteric liquid crystal layer 18B. Thus, in the liquid crystal panel of the first embodiment, the reflection mode is set when no electric field is applied, and the transmission mode is set when an electric field is applied.

  In the screen 10 shown in FIG. 1, a liquid crystal panel 10G capable of reflecting green light and a liquid crystal panel 10R capable of reflecting red light are formed in the same manner as the liquid crystal panel 10B described above. The liquid crystal panel 10G employs cholesteric liquid crystal having a helical pitch of about 550 nm, and the liquid crystal panel 10R employs cholesteric liquid crystal having a helical pitch of about 600 nm. Then, the liquid crystal panels 10B, 10G, and 10R are laminated on the surface of the light absorption layer 10a to constitute the screen 10. The light absorption layer 10a absorbs the color light transmitted through all the liquid crystal panels. The light absorption layer 10a can be made of a black metal material having excellent light absorption.

  The liquid crystal panels 10B, 10G, and 10R are connected to a driving power source 56. The driving power source 56 applies an electric field to the cholesteric liquid crystal layer through the transparent electrode of each liquid crystal panel.

[Projector system]
On the other hand, in the projector system 1 shown in FIG. 1, the projector 30 is disposed so as to face the screen 10 described above. The projector 30 projects image light of different color lights in time sequence.

As the light source of the projector 30, LED light sources 32R, 32G, and 32B, which are solid light sources, are employed. An LED is a diode that emits light when a current flows through a pn junction, and is excellent in high-speed response. The LED emitting blue light and green light is formed by growing a GaInN-based compound semiconductor crystal on the surface of a substrate such as sapphire (Al ₂ O ₃ ). The LED emitting red light is formed by growing an AlGaInP-based compound semiconductor crystal on a substrate such as gallium arsenide (GaAs).
The LED light sources 32R, 32G, and 32B are connected to the drive power source 52. The drive power source 52 supplies current to each LED light source.

  Each of the LED light sources 32R, 32G, and 32B is disposed to face the three sides of the cross dichroic prism 34. In this prism 34, a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged on the bonding surface of four right-angle prisms. By these dielectric multilayer films, the light source light emitted from each LED light source can be emitted from the remaining one side of the prism 34. A condensing lens or the like may be disposed between each LED light source and the prism 34.

  A liquid crystal light valve 36, which is a light modulation means, is arranged facing the remaining one side of the prism 34. The liquid crystal light valve 36 modulates color light from each LED light source to produce image light. Therefore, the liquid crystal light valve 36 includes pixels arranged in a matrix and switching elements that drive the pixels. Further, the liquid crystal light valve 36 is connected to the drive circuit 54. The driving circuit 54 supplies a scanning signal and an image signal to each switching element of the liquid crystal light valve.

  A polarizing plate (not shown) is disposed on the exit surface of the liquid crystal light valve 36. Thereby, the image light emitted from the liquid crystal light valve 36 is constituted by linearly polarized light. By the way, the above-described cholesteric liquid crystal layer has a property of reflecting all of incident light when the incident light is predetermined circularly polarized light (either clockwise circularly polarized light or counterclockwise circularly polarized light). However, since the linearly polarized light includes half each of the clockwise component and the counterclockwise component, only half of the incident light of the linearly polarized light is reflected. Therefore, it is desirable to dispose the phase difference plate 39 on the emission surface side of the liquid crystal light valve 36. In particular, if a λ / 4 plate is used as the phase difference plate 39, linearly polarized light can be converted into predetermined circularly polarized light. Instead of arranging the phase difference plate 39 on the projector 30, a phase difference plate may be arranged on the surface of the screen 10.

  A projection lens 38 is disposed on the exit surface side of the liquid crystal light valve 36. As a result, the image light can be enlarged and projected toward the screen. The above-described members are housed inside the housing, and the projector 30 is configured.

  FIG. 3 is a block diagram of the projector system. In the projector system of the present embodiment, image light of different color lights is projected from the projector 30 in time sequence, and the projected color lights are reflected by the screen 10 in time sequence. Therefore, it is necessary to drive the projector 30 and the screen in synchronization. Therefore, a timing controller 50 is provided. The timing controller 50 is connected to an LED light source driving power source 52, a liquid crystal light valve driving circuit 54, and a screen driving power source 56. The timing controller 50 is configured to output a drive signal to each of these devices at a predetermined timing.

  On the other hand, a field memory 58 for outputting an image signal to the driving circuit 54 of the liquid crystal light valve is provided. A memory controller 59 is connected to the field memory 58, and an image signal output command is transmitted from the memory controller 59. The memory controller 59 is connected to the timing controller 50 described above. The timing controller 50 is configured to output a drive signal to the memory controller 59 at a predetermined timing.

[Image display method of projector system]
Next, the image display method of the projector system configured as described above will be described with reference to FIG. 1, FIG. 3, and FIG. First, as shown in FIG. 3, a synchronization signal is input to the timing controller 50. This synchronization signal is made up of a pulse signal or the like, and the pulse interval is an operation unit time of the projector system. For example, a 180 Hz pulse signal is input as the synchronization signal.

FIG. 4 is a timing chart of driving signal output in the timing controller. In the timing controller 50, three units are set to one frame in the operation unit time defined by the inputted synchronization signal.
During one frame, the timing controller 50 outputs the drive signals R1, G1, and B1 to the drive power source 52 of the LED light source in time sequence. The drive signal R1 is a power supply drive signal for the red LED light source 32R, and the drive signals G1 and B1 are the same. In accordance with this drive signal, a current is supplied from the drive power supply 52 to each LED light source, and each LED light source 32R, 32G, 32B emits light in time sequence.

Further, during one frame, the timing controller 50 outputs the drive signals R2, G2, and B2 to the liquid crystal light valve drive circuit 54 in time sequence. The drive signal R2 is a drive signal for the switching element for modulating red light, and the drive signals G2 and B2 are the same. In accordance with this drive signal, a scan signal is supplied from the drive circuit 54 to each switching element of the liquid crystal light valve 36.
During one frame, the timing controller 50 outputs the drive signals R3, G3, and B3 to the memory controller 59 in time sequence. The drive signal R3 is a drive signal for the output command of the red light image signal, and the drive signals G3 and B3 are the same. In accordance with this drive signal, an image signal output command is transmitted from the memory controller 59 to the field memory 58, and the image signal is output from the field memory 58.
This image signal is input to the drive circuit 54 of the liquid crystal light valve, and is supplied from the drive circuit 54 to each switching element of the liquid crystal light valve 36. As described above, each color light emitted from each LED light source is modulated in time sequence by the liquid crystal light valve 36.

  In this way, the timing controller 50 outputs drive signals simultaneously to the LED light source drive power supply 52, the liquid crystal light valve drive circuit 54, and the memory controller 59, so the LED light source and the liquid crystal light valve are driven in synchronization. Can be made. As a result, image light of different colors is emitted from the projector 30 in time sequence.

  Further, during one frame, the timing controller 50 outputs the drive signals R4, G4, and B4 to the drive power source 56 of the screen 10 in time sequence. The drive signal R4 is a drive signal for the power source of the liquid crystal panel 10R that can reflect red light, and the drive signals G4 and B4 are the same. The liquid crystal panel 10R is in a reflection mode when no electric field is applied to the cholesteric liquid crystal layer (OFF state), and is in a transmission mode when an electric field is applied (ON state). Therefore, the drive power supply 56 is set so as to always apply an electric field to the liquid crystal panel while stopping the application of the electric field when a drive signal is input. Instead of outputting the drive signals R4, G4, and B4 in time sequence from the timing controller 50, the drive signals G4 + B4, R4 + B4, and R4 + G4 may be output in time sequence. In this case, the drive power source 56 can apply an electric field to the liquid crystal panel according to the drive signal.

  FIG. 5 is an explanatory diagram of the reflection effect of red image light by the screen. When the drive signal R4 is output from the timing controller, the liquid crystal panel 10R enters the reflection mode, and the other liquid crystal panels 10G and 10B enter the transmission mode. Then, the red image light projected from the projector is transmitted through the liquid crystal panels 10G and 10B and reflected by the liquid crystal panel 10R. The reflected red image light is transmitted through the liquid crystal panels 10G and 10B again and emitted from the screen 10. Thereby, red image light is displayed on the surface of the screen 10. Similarly, each color light emitted from the projector in time sequence is reflected by the screen 10 in time sequence. Each color light is additively mixed for each frame, and a color image is displayed on the surface of the screen 10.

  By the way, when the projector system is used in a bright environment where there is external light such as room lighting, the external light may be reflected on the surface of the screen 10 to reduce the contrast of the display image. However, in the case of FIG. 5, the green light and the blue light included in the external light are transmitted through the liquid crystal panels 10G and 10B in the transmission mode, and further transmitted through the liquid crystal panel 10R that reflects only red light. Are absorbed by the light absorption layer 10a. In addition, since the cholesteric liquid crystal layer reflects only clockwise circularly polarized light (or counterclockwise circularly polarized light), light other than clockwise circularly polarized light (or counterclockwise circularly polarized light) out of red light included in the external light is liquid crystal panel. 10R is transmitted and absorbed by the light absorption layer 10a. The same applies when other liquid crystal panels are in the reflection mode. Thus, since the screen of this embodiment reflects each color image light sequentially in time, the color light reflected among the color lights contained in external light can be restrict | limited. Therefore, the influence of external light is reduced, and high-contrast image display can be performed even in a bright environment.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in that a plurality of liquid crystal panels constituting the screen are in a transmission mode when an electric field is not applied and are in a reflection mode when an electric field is applied. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

FIG. 6 is a side sectional view of the liquid crystal panel of the screen according to the second embodiment. In FIG. 6, the liquid crystal panel 110B capable of reflecting blue light will be described as an example. In the liquid crystal panel 110B, a cholesteric liquid crystal layer 118B is provided on the inner surface of the back substrate 112. The cholesteric liquid crystal layer 118B has a fixed helical alignment state. The helical pitch is set to about 450 nm.
The cholesteric liquid crystal layer 118B can be formed by using a liquid crystalline monomer that has photopolymerizability that initiates polymerization by ultraviolet irradiation or the like, and the polymer after polymerization exhibits liquid crystallinity. When this liquid crystalline monomer is uniformly applied to the inner surface of the back substrate 112 and then irradiated with a predetermined amount of ultraviolet light, a cholesteric liquid crystal layer 118B having a selective reflection wavelength of about 450 nm can be obtained. It is also possible to form a cholesteric liquid crystal layer capable of reflecting green light and red light by adjusting the amount of ultraviolet light.

  Further, a transparent electrode 114 is formed on the inner surface of the cholesteric liquid crystal layer 118B, and an alignment film 116 is formed on the inner surface of the transparent electrode 114. On the other hand, a transparent electrode 113 is also formed on the inner surface of the front substrate 111, and an alignment film 115 is formed on the inner surface of the transparent electrode 113. A pair of alignment films 115 and 116 sandwich a liquid crystal layer (phase modulation liquid crystal layer) 120 made of ECB (Electrically Controlled Birefringence) liquid crystal or the like.

  The operation when blue light composed of clockwise circularly polarized light is incident on the liquid crystal panel 110B configured as described above will be described. First, when an electric field is applied to the ECB liquid crystal layer 120 through the transparent electrodes 113 and 114 (ON state), the liquid crystal molecules of the ECB liquid crystal layer 120 are vertically aligned along the electric field. Thereby, the blue light incident from the surface of the liquid crystal panel 110B is transmitted through the ECB liquid crystal layer 120 while maintaining the clockwise circularly polarized light. Then, the light is reflected by the cholesteric liquid crystal layer 118B and emitted from the surface of the liquid crystal panel 110B. On the other hand, when no electric field is applied to the ECB liquid crystal layer 120 (OFF state), the liquid crystal molecules of the ECB liquid crystal layer 120 are aligned in parallel with the alignment films 115 and 116. Therefore, the blue light incident from the surface of the liquid crystal panel 110B is converted into counterclockwise circularly polarized light in the process of passing through the ECB liquid crystal layer 120. Then, the light passes through the cholesteric liquid crystal layer 118B and is emitted from the back surface of the liquid crystal panel 110B. Thus, in the liquid crystal panel of the second embodiment, the transmission mode is set when no electric field is applied, and the reflection mode is set when an electric field is applied.

When the liquid crystal panel of the second embodiment is employed, the timing controller 50 shown in FIG. 1 may output the drive signals R4, G4, and B4 to the screen drive power supply 56 in time sequence. The screen driving power source 56 may apply an electric field to the liquid crystal panel according to the driving signal. Thus, in the second embodiment, the screen control system can be simplified.
The liquid crystal panel according to the first embodiment is in the reflection mode when no electric field is applied, and is in the transmission mode when the electric field is applied. It is necessary to use the two liquid crystal panels in a state where an electric field is always applied. On the other hand, the liquid crystal panel of the second embodiment is in the transmission mode when no electric field is applied, and is in the reflection mode when an electric field is applied. In this case, it is possible to apply an electric field to only one liquid crystal panel that is in the reflection mode. Therefore, power consumption can be reduced, and the durability of the screen can be improved.

  The technical scope of the present invention is not limited to the above-described embodiments, and includes various modifications made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.

It is a schematic block diagram of the projector system of 1st Embodiment. It is side surface sectional drawing of a cholesteric liquid crystal panel. It is a block diagram of a projector system. It is a timing chart of the drive signal output in a timing controller. It is explanatory drawing of the reflection effect | action of the red image light by a screen. It is side surface sectional drawing of the liquid crystal panel of the screen which concerns on 2nd Embodiment.

Explanation of symbols

  1 projector system 10 screen 10a light absorption layer 10B, 10G, 10R cholesteric liquid crystal panel 30 projector 50 timing controller

Claims (8)

A plurality of cholesteric liquid crystal layers laminated on the front side of the light absorption layer and capable of reflecting different color lights constituting the image light,
Switching means capable of switching reflection and transmission of the colored light in each cholesteric liquid crystal layer;
A timing controller for sequentially driving each of the switching means;
And a different color light constituting the image light is reflected in time sequence . The screen according to claim 1 , wherein the switching unit includes a pair of conductors for applying an electric field to the cholesteric liquid crystal layer. The switching means is
An electro-optic material disposed on the light incident side of the cholesteric liquid crystal layer and capable of switching the rotation direction of the circularly polarized light incident upon the presence or absence of an electric field applied;
The screen according to claim 1 , further comprising: a pair of conductors that apply an electric field to the electro-optic material. A screen according to any one of claims 1 to 3 ,
A projector that sequentially projects the different color lights constituting the image light toward the screen,
A projector system comprising: a timing controller that drives the screen and the projector synchronously in time sequence. The projector has a light source that emits different color lights in time sequence, and a light modulation unit that modulates each color light from the light source in time sequence,
5. The projector system according to claim 4 , wherein the timing controller drives the light source and the light modulation unit synchronously in time sequence. The projector, a projector system according to claim 4 or claim 5, characterized in that projecting the circularly polarized light. The projector, a projector system according to any of claims 4 to 5, characterized in that it has a solid-state light sources. An image display method for a projector system for displaying an image on a screen according to any one of claims 1 to 3,
Project different color lights that make up the image light from the projector in time sequence,
In synchronization with the projector, by reflecting in sequentially the screen projected different color light time from the projector,
An image display method for a projector system, wherein a color image is displayed on the screen.

Images