WO2013140628A1

WO2013140628A1 - Display device, method for driving same, and display screen device

Info

Publication number: WO2013140628A1
Application number: PCT/JP2012/057611
Authority: WO
Inventors: 吉岡　俊博
Original assignee: パイオニア株式会社
Priority date: 2012-03-23
Filing date: 2012-03-23
Publication date: 2013-09-26
Also published as: JP5856285B2; JPWO2013140628A1

Abstract

The present invention reduces video-quality degradation caused by a plurality of control electrodes lined up in a screen onto which video light is projected, controlling the optical state of each segment of said screen. This display device (1) has the following: a screen (21) comprising a plurality of control electrodes (27) laid out with spaces therebetween on one surface of an optical layer (25), the optical properties of which are changed by the application of voltage; a projector (11) that shines video light onto the screen (21) so as to display video; and a synchronization control unit (31) that controls the application of voltage to the plurality of control electrodes (27) and the cessation thereof over the course of a video-light scanning cycle (T), using the application of voltage to switch the segment (22) corresponding to each control electrode (27) from a non-video state to a video state. Upon video-light exposure, the synchronization control unit (31) applies voltages of the same polarity to two adjacent control electrodes (27) to control the optical state of a region (28) between the corresponding two segments (22).

Description

Display device, driving method thereof, and display screen device

The present invention relates to a display device, a driving method thereof, and a display screen device.

Some display devices project image light onto a screen to display the image on the screen.
There exists a liquid crystal light control device which can control the transmittance | permeability in the light control device (patent document 1).

JP 2007-219419 A

By the way, it is conceivable to form a dimming screen using the technology of the liquid crystal dimming device and to use this dimming screen as a screen for projecting an image.

In such a display device, a plurality of control electrodes may be arranged side by side on one surface of the screen, and the optical state of the screen may be controlled for each divided region corresponding to each control electrode.
For example, the divided area where the image is projected on the screen is controlled to be in a scattering state, and the other divided areas are controlled to be in a transparent transmission state in which scattering of incident light is small.
In this case, the screen can be controlled to the see-through state during the projection period of the image light. On the screen, the projected image and the background on the other side of the screen can be displayed in an overlapping manner.

However, when a plurality of control electrodes are provided on the screen in this way and the optical state of the screen is controlled for each divided area, the image displayed on the screen may be deteriorated.
That is, the plurality of divided regions need to be controlled by individual voltages.
The plurality of divided regions need to be arranged apart from each other on one surface of the screen.
An interval is formed between two adjacent divided regions.
For this reason, even if a voltage is applied to each control electrode during the scanning period of the image light, the optical state of the gap region corresponding to the two divided regions is the same optical state as the central portion of the control electrode. Difficult to do.
As a result, the image is disturbed in the gap region.

Thus, in a display device, it is required to improve image quality deterioration of a projected image caused by arranging a plurality of control electrodes on a screen and controlling an optical state for each divided region.

The invention according to claim 1 includes an optical layer whose optical state changes by application of a voltage, and a plurality of control electrodes arranged along the optical layer and spaced apart from each other in order to apply a voltage to the optical layer. A screen, a projector that irradiates the screen with image light and displays an image, and controls the application and stop of voltage to a plurality of control electrodes during the image light projection period, and the division corresponding to each control electrode by voltage application And a control unit that switches a region from a video state that scatters video light to a predetermined non-video state that is an optical state different from the video state. And a control part applies the voltage of the same polarity to two control electrodes arrange | positioned adjacently at the timing with which image light is irradiated to these boundaries, and the optical of the area | region between two corresponding division areas It is a display device that controls the state.

The invention according to claim 8 is a method for driving a display device that displays an image of image light emitted from a projector on a screen having an optical layer whose optical state changes by application of a voltage, the optical state of the screen being changed. The control unit for controlling applies a voltage to the plurality of control electrodes arranged along the optical layer and spaced apart from each other, and images by the image light irradiated on the screen having the optical layer and the plurality of control electrodes And controlling voltage application and stop to the plurality of control electrodes during the projection period of the image light, and by applying the voltage, the divided regions corresponding to the control electrodes are separated from the image state in which the image light is scattered. Switching to a predetermined non-image state that is a different optical state, and applying a voltage of the same polarity to two adjacent control electrodes at the timing of image light irradiation, Controlling the optical state of the area between the two divided regions to respond, a method of driving a display device.

The invention according to claim 9 has an optical layer whose optical state changes when a voltage is applied, and a plurality of control electrodes arranged along the optical layer and spaced apart from each other in order to apply a voltage to the optical layer. And controlling the voltage application and stop to the plurality of control electrodes in the projection period of the image light, the screen displaying the image by the irradiated image light, the divided regions corresponding to each control electrode by the voltage application, A control unit that switches from a video state that scatters video light to a predetermined non-video state that is an optical state different from the video state, and the control unit is arranged adjacent to the timing at which the video light is irradiated This is a display screen device that applies a voltage of the same polarity to two control electrodes and controls the optical state of a region between two corresponding divided regions.

FIG. 1 is a schematic configuration diagram of a display device according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram of the synchronous control of screen scanning and driving. FIG. 3 is an explanatory diagram of a projector that continuously projects a plane image. FIG. 4 is an explanatory diagram of a projector that projects a plane image by time modulation. FIG. 5 is an explanatory diagram of a projector that scans the screen. FIG. 6 is a schematic cross-sectional view of the screen. FIG. 7 is a schematic front view of a screen showing the arrangement of a plurality of control electrodes. FIG. 8 is a schematic timing chart of screen scanning and driving. FIG. 9 is an explanatory diagram of a display state in which the image by the image light overlaps the screen background. FIG. 10 is an explanatory diagram of the electric field distribution that affects the optical state of the gap region between the two divided regions. FIG. 11 is a schematic timing chart showing the relationship between the optical state of the plurality of divided regions and the drive voltage waveform in the present embodiment. FIG. 12 is a schematic timing chart showing the relationship between the optical state of the plurality of divided regions and the drive voltage waveform in the first comparative example. FIG. 13 is an explanatory diagram of line inversion control of drive voltage waveforms applied to a plurality of control electrodes in the second embodiment. FIG. 14 is an explanatory diagram of the control of the pulse width and the cycle number of the drive voltage waveform applied to the plurality of control electrodes in the third embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a display device 1 according to the first embodiment.
The display device 1 in FIG. 1 includes a projector 11 that projects image light, a screen 21 that can control the optical state, and a synchronization control unit 31. The synchronization control unit 31 is connected to the projector 11 and the screen 21.
The display device 1 of the present embodiment is a transmissive projection device that scatters and transmits the image light of the projector 11 by a screen 21.
The synchronization control unit 31 controls the screen 21 on which the image is projected so as to scatter and transmit the projected image light, and when not projected, controls the screen 21 to a transparent transmission state in which the scattering of incident light is small. .
As for the optical state of the screen 21, a state where it is scattered and transmitted is an image state, and a transparent state where the scattering of incident light is smaller and the transmittance of parallel rays is higher than that is a non-image state.
The display device 1 can be used as, for example, a sign boat that displays advertisements and the like.

Next, the basic operation principle of the display device 1 of FIG. 1 will be described.
FIG. 2 is an explanatory diagram of synchronous control of scanning and driving of the screen 21.
The projector 11 vertically scans the screen 21 from the top to the bottom with image light modulated by the image information. The projector 11 scans the screen 21 vertically from top to bottom for each scanning repetition period (hereinafter referred to as a scanning cycle).
2A to 2E show the scanning state at each time point in one scanning cycle in the scanning order.
The screen 21 in FIG. 2 has five divided regions 22. The five divided regions 22 are arranged vertically along the scanning direction of the image light.
The synchronization control unit 31 controls the optical states of the five divided regions 22 individually in synchronization with the one-dimensional vertical scanning of the screen 21 by the projector 11. When the image light is not projected, each divided region 22 is controlled to a non-image state, that is, a transparent transmissive state with small scattering of incident light.

When the scanning of the image light is started, the scanning light of the projector 11 is first applied to the uppermost divided area 22 of the screen 21 as shown in FIG. Hereinafter, in this description, reference numeral 221 is used to distinguish the divided region 22 irradiated with the scanning light from other divided regions 22 that are not scanned. The synchronization control unit 31 specifies a period during which the uppermost divided area 221 is scanned in the scanning cycle based on the synchronization signal from the projector, and controls the uppermost divided area 221 to the video state. The image light that scans the uppermost divided area 221 is scattered by the divided area 221 in the scattering state and passes through the screen 21.
Next, the scanning of the image light moves to the second divided area 22 from the top of the screen 21 as shown in FIG. The synchronization control unit 31 specifies a period during which the second divided region 221 from the top in the scanning cycle is scanned, and controls the second divided region 221 from the top to the video state. The image light that scans the second divided region 221 from the top is scattered by the divided region 221 in the scattering state and passes through the screen 21. Further, the synchronization control unit 31 controls the second divided area 221 from the top to the video state, and then controls the uppermost divided area 22 to the non-video state.
Thereafter, as shown in FIGS. 2C to 2E, the synchronization control unit 31 controls the divided area 221 scanned by the scanning light to the video state, and sets the other divided areas 22 to the non-video state. Control.

Through the above-described synchronization control, the portion of the screen 21 irradiated with the scanning light is maintained in the video state. Thereby, the image light that scans the screen 21 is scattered by the screen 21 in the scattering state.
Further, the portion of the screen 21 that is not irradiated with the scanning light is controlled to a non-image state. Each divided region 22 is controlled to a transparent transmission state in which the scattering of incident light in a non-image state is small in most periods during which scanning with the scanning light is not performed. Therefore, the see-through characteristic of the screen 21 can be obtained while maintaining the visibility of the image during the projection period of the image light.

The projector 11 only needs to be able to project video light modulated by video information onto the screen 21.
Note that the video information is obtained from a video signal input to the projector 11. Video signals include, for example, NTSC (National Television Standards Committee), analog video signals such as PAL (Phase Alternation by Line), MPEG-TS (Moving Picture Experts Group-Transport Stream) format, HDV (High -There are video signals in digital format such as Definition Video) format. The projector 11 may receive not only a moving image video signal but also a still image video signal such as JPEG (Joint Photographic Experts Group). In this case, the projector 11 may scan the screen 21 repeatedly with the same video light for displaying a still image.

3 to 5 are explanatory diagrams of the projection method of the projector 11. FIG. 3 is an explanatory diagram of the projector 11 that continuously projects a plane image. FIG. 4 is an explanatory diagram of the projector 11 that projects a plane image by time modulation. FIG. 5 is an explanatory diagram of the projector 11 that scans the screen 21.

FIG. 3A is an explanatory diagram of a method in which the projector 11 regularly projects image light. In this case, as shown in FIG. 3B, image light is always projected onto the screen 21 in the scanning cycle. As shown in FIG. 3C, the screen 21 must always be in a scattering state. In this case, if the optical state of the screen 21 is controlled so as to increase the parallel light transmittance, the luminance of the image decreases.
Note that the horizontal axis of FIGS. 3B and 3C is the scanning cycle (time). The same applies to FIGS. 4B, 4C, 5B, and 5C.

FIG. 4A is an explanatory diagram of a method in which the projector 11 projects image light at an interval. In this case, as shown in FIG. 4B, image light is projected on the screen 21 in a short period of time during a part of the scanning cycle. As shown in FIG. 4C, the screen 21 may be in a scattering state during the partial period. When the optical state of the screen 21 is controlled so as to increase the parallel light transmittance of the screen 21 in a period other than the part, the see-through characteristic of the screen 21 is not caused in the scanning cycle without causing a decrease in the luminance of the image. Is obtained. Compared to the case of projecting image light regularly, to obtain the same brightness, the projection light needs to have an intensity that is approximately the reciprocal of the duty (duty: a) in the scattering state with respect to the scanning period. Become. Therefore, in order to obtain a high see-through characteristic, a powerful pulsed projection light output is required.

FIG. 5A is an explanatory diagram of a projection method in which the projector 11 scans the screen 21. In this case, video light is always projected onto the screen 21 during the scanning cycle. However, paying attention to each part of the screen 21, the image light is projected in a part of the scanning period as shown in FIG. For this reason, as shown in FIG. 5C, each part of the screen only needs to be in a scattering state in the partial scanning period TP in which each part is scanned. Further, if each part of the screen 21 is controlled so as to increase the parallel light transmittance in a period other than the partial scanning period TP, the see-through characteristic of the screen 21 can be achieved without causing a decrease in the luminance of the image in the scanning period. can get.

The projector 11 that projects the image light may be of any of the above projection methods.
However, in order to suppress the generation of image light that is not used for scattering, the method of FIG. 4 or FIG. 5 is desirable. Moreover, a response time is required for the change in the optical state of the screen 21. For this reason, the projection method of FIG. 5 in which the response time is easily secured is preferable to FIG. In the following description, a case where the projector 11 of the projection method shown in FIG. 5 is used will be described.

In the driving method of FIG. 5, a line-shaped image corresponding to a part of the screen 21 is sequentially projected onto the display surface of the screen 21 during the scanning period of the image light.
The projector 11 can be a transmissive or reflective liquid crystal light valve that sequentially shifts the black state (the state in which no projection light is emitted) on the screen 21 during the scanning cycle, but other elements can also be used. Good.
Alternatively, the projector 11 may perform raster scanning in a video scanning cycle and project video light on the display surface of the screen 21 dot-sequentially. As the projector 11, for example, a laser projector that reflects and shakes the irradiation direction of the image-modulated light beam with a movable mirror can be used. The projector 11 can be considered in the same manner as the image light irradiation position being sequentially scanned in one direction on the screen 21.

The screen 21 may be anything that can change the optical state by an electrical signal such as voltage or current.
For example, it may be a dimming screen that uses a liquid crystal material and changes a scattering state and a transparent transmission state in which the scattering of incident light is small. The light control screen uses, for example, a liquid crystal element such as a polymer-dispersed liquid crystal, or an element that controls a transparent transmission state with small scattering of incident light by moving white powder in a transparent cell. There is something that uses.
In the present embodiment, the screen 21 operating in the reverse mode will be described as an example.
In the screen 21 operating in the reverse mode, the screen 21 is in a transparent transmissive state in a normal state where no voltage is applied. When a voltage is applied, a scattering state of parallel light scattering rate (transmittance) according to the applied voltage is obtained.

In addition, the screen 21 can be switched between a transparent transmission state where the scattering of incident light is small and a scattering state when the plurality of divided regions 22 dividing the screen 21 are independent of each other. Good.
For example, the screen 21 only needs to have a plurality of divided regions divided into strips so as to correspond to the main scanning direction of the projector 11 (for example, the vertical direction in FIG. 2).
In addition, the screen 21 may be a screen in which regions divided into rectangles are arranged in a matrix so as to correspond to the main scanning direction and the sub-scanning direction (for example, the horizontal direction of the image) of the projector 11.

FIG. 6 is a schematic cross-sectional view of the screen 21 that can control the optical state for each divided region 22. FIG. 6 also shows the synchronization control unit 31.
FIG. 7 is a schematic front view of a screen showing the arrangement of a plurality of control electrodes on the screen 21 of FIG.
The screen 21 in the example of FIG. 6 has an optical layer 25 in which a composite material containing liquid crystal is sandwiched between a pair of

transparent glass plates

23 and 24.
A counter electrode 26 is formed on the entire surface of one glass plate 24 on the optical layer 25 side.
A plurality of control electrodes 27 are arranged side by side on the optical layer 25 side of the other glass plate 23.
An intermediate layer made of an insulator may be formed between the

electrodes

26 and 27 and the optical layer 25.
The counter electrode 26 and the control electrode 27 are formed as transparent electrodes by using, for example, ITO (indium tin oxide).
The optical layer 25 is disposed between the plurality of control electrodes 27 and the counter electrode 26.

The plurality of control electrodes 27 divide the area of the screen 21 irradiated with the image light into strips in one direction (for example, the scanning direction).
The plurality of control electrodes 27 are individually connected to the synchronization control unit 31 and applied with individual voltages.
Adjacent control electrodes 27 are arranged apart from each other.
A gap region 28 is formed in the optical layer 25 corresponding to a region where the control electrode 27 is not formed between the two adjacent control electrodes 27.
In FIG. 6, the counter electrode 26 is grounded.
A voltage is applied so as to generate a potential difference between the control electrode 27 and the counter electrode 26. Note that the voltage of the driving waveform described below indicates a potential difference between the control electrode 27 and the counter electrode 26.
The voltage applied to the control electrode 27 is applied to the optical layer 25 in a region corresponding to the control electrode 27. The alignment state of the liquid crystal in the optical layer 25 changes depending on the voltage applied to the control electrode 27. The optical layer 25 can be adjusted for each divided region 22 between a transparent transmission state where the scattering of incident light is small and a scattering state where the incident light is scattered.
The gap region 28 corresponding to the control electrode 27 is about 5 to 100 micrometers, and is desirably as narrow as possible. The thickness of the optical layer 25 is several to several tens of micrometers, and is determined in consideration of optical characteristics and drive voltage.

The synchronization control unit 31 is connected to the projector 11 and the screen 21.
The synchronization control unit 31 controls the optical state of the screen 21 in synchronization with the projection of the image light of the projector 11.
As the synchronization signal input from the projector 11 to the synchronization control unit 31, for example, a synchronization signal synchronized with the scanning cycle of the projector 11 can be used.

When the screen 21 is divided into strips in one direction like the screen 21 in FIG. 7, the projection light of the projector 11 is sequentially scanned in the division direction of the screen 21.
Based on the synchronization signal from the projector 11, the synchronization control unit 31 sets the plurality of divided regions 22 so that the portion irradiated with the projection light of the projector 11 is maintained in the video state (scattering state in the present embodiment). In the scanning order, the transparent transmission state is controlled to the scattering state.
By this synchronization control, each divided region 22 of the screen 21 is in a scattering state as a video state in a period Ton including a video period in which projection light is irradiated to the region. Further, in the non-image period Toff where the projection light is not irradiated, a transparent transmission state as a non-image state is obtained.
The screen 21 can scatter image light with the same brightness as when the screen 21 is always in a scattering state while having transparency that can recognize the object on the back surface. That is, it is possible to achieve both a see-through property capable of recognizing a background object and a high image visibility.

FIG. 8 is a schematic timing chart of scanning and driving of the screen 21. The horizontal axis is time. The vertical axis indicates the position in the vertical direction of the screen, and corresponds to a plurality of divided regions 22 on the screen 21.
Each divided region 22 of the screen 21 is controlled from a transparent transmission state to a scattering state before the timing at which the image light starts to scan each region. Further, the divided region 22 in the scattering state is controlled from the scattering state to the transparent transmission state after the scanning of the image light for the region is completed.
The plurality of divided regions 22 are controlled to be in a video state in synchronization with a partial scanning period TP timing in which video light is irradiated to each region by scanning, thereby sequentially shifting to a video state in the scanning order. Can be switched. The image light that scans the screen 21 is efficiently scattered by the portion maintained in the image state, and it is possible to obtain bright and high visibility.

Information on the switching timing for the synchronization control is sent from the projector 11 to the synchronization control unit 31 as a synchronization signal.
The synchronization control unit 31 preferably controls the voltage applied to each control electrode 27 so that the projection light is irradiated during a period in which the optical state of each divided region 22 is stable in a predetermined scattering state. The optical state of each divided region 22 is switched according to the signal waveform of the voltage applied to the control electrode 27.
In particular, the information on the switching timing output from the projector 11 to the synchronization control unit 31 may include information on timing at which the projector 11 starts scanning in each scanning cycle and scanning speed (scanning delay / shift). . As a result, even when the frequency of the scanning cycle changes, good see-through display can be realized without disturbing the image.
The projector 11 and the synchronization control unit 31 may be capable of wireless communication using electromagnetic waves such as microwaves and infrared rays, and information for obtaining these synchronizations may be exchanged by radio signals.

Through the above-described synchronization control, the synchronization control unit 31 of the present embodiment switches the optical state of the plurality of divided regions 22 in the scanning period T of the video light in synchronization with the scanning of the video light by the projector 11 and The optical state of the part where the image light is projected is defined as an image state.
Therefore, the screen 21 can display an image because the portion irradiated with the image light is maintained in the scattering state in the period Ton including the timing when the image light is irradiated.
Moreover, since the screen 21 is controlled to be in a transparent transmissive state at times other than the period Ton during the projection period of the image light, the screen 21 can be seen through. Since the light transmitted through the screen 21 appears to be averaged (integrated) to the human eye, a see-through characteristic without flicker is obtained in a sufficiently short scanning period.
Thereby, for example, in the installation environment of FIG. 1, the image of FIG. 9 can be visually recognized through the screen 21.
FIG. 9 is an explanatory diagram of a display state in which the image by the image light and the background of the screen 21 overlap.
In FIG. 9, an image of a person 41 by video light is shown on the right side of the screen 21, and a tree 42 as a background on the other side of the screen 21 can be seen on the left side.

In the present embodiment, the synchronization control unit 31 switches the voltage applied to the plurality of divided regions 22 in the scanning order in the scanning period of the image light, and the partial scanning period TP in which each divided region 22 is scanned. In the non-video state during the period when each is not scanned, that is, during the period other than the partial scanning period TP.

In the present embodiment, the synchronization control unit 31 sets the voltage applied to the control electrode 27 as a low-frequency AC voltage.
Therefore, the DC component of the voltage applied to the optical layer 25 in each scanning period T of the image light can be suppressed.

By the way, when a plurality of control electrodes 27 to which individual drive voltages are applied are formed on one surface of the reverse mode screen 21, as shown in FIG. 6 and FIG. A gap region 28 of the optical layer 25 corresponding to a region where the control electrode 27 is not formed is formed.
FIG. 10 is an explanatory diagram of the electric field distribution in the optical layer in the gap region 28.
10A and 10B are schematic cross-sectional views of the screen 21 in a state where a voltage is applied to the adjacent control electrode 27. FIG. The arrows in the figure indicate a rough electric field distribution.

As shown in FIG. 10A, even when an AC voltage having the same amplitude is applied to each control electrode 27, a positive voltage is applied to one control electrode 27 on the right side of the figure, and the other on the left side of the figure. When a negative voltage is applied to the control electrode 27 and 0 V is applied to the counter electrode 26, that is, when a reverse polarity voltage is applied to the adjacent control electrode 27, the gap region 28 corresponds to the control electrode 27. An electric field different from the portion corresponding to the divided region 22 is formed.
The alignment of the liquid crystal in the optical layer 25 is affected by this electric field. Therefore, the optical state of the gap region 28 is different from the optical state due to voltage application.
The difference in optical characteristics due to the difference in electric field and the difference in liquid crystal alignment from other parts is visually recognized as a gap-like luminance unevenness in the case where the image light is irradiated.
In the optical state screen 21 of FIG. 10A, the optical state is the same in both divided regions 22, but is different in the gap region 28. As a result, a singular part in the optical state is generated along the gap region 28, and luminance unevenness occurs in the video state.

Therefore, the synchronization control unit 31 of the present embodiment applies a voltage having the same polarity to the adjacent control electrode 27 as shown in FIG.
In the case of FIG. 10B, the direction of the electric field of the gap region 28 is the direction along the electric field of the divided region 22, and the optical state of the gap region 28 at the time of voltage application is controlled to a scattering state by voltage application. The optical state of the divided area 22 is substantially the same.
As a result, in the screen 21 of the counter electrode shown in FIG. 10B, the optical state of the gap region 28 is substantially the same as that of both the divided regions 22, so that the gap region when the gap region 22 is irradiated with video light. The luminance unevenness of the video at 28 is effectively suppressed, and uniform see-through performance and display are possible.
By making the adjacent control electrodes 27 have the same potential or the same polarity, the direction of the electric field in the gap region 28 is in the direction along that of the divided region 22, and the stripe-like unevenness caused by the orientation being different from other portions. Can be suppressed.

FIG. 11 is a schematic timing chart showing the relationship between the optical state of the plurality of divided regions 22 and the drive voltage waveform in the present embodiment.
11A to 11D show voltages applied to the four consecutive control electrodes 27. FIG. In the following description, a waveform in which a voltage is applied to the control electrode 27 is described, but it can be considered as a voltage waveform applied to a region including the optical layer 25 as a potential difference from the counter electrode 26. The horizontal axis is time, and the vertical axis is voltage. FIGS. 11E to 11H show optical characteristics of four continuous divided regions 22 corresponding to FIGS. 11A to 11D. The horizontal axis is time, and the vertical axis is parallel light transmittance. In the following description, changes in the optical state are described using changes in parallel light transmittance. In the screen of the present invention, the decrease in parallel light transmittance indicates an increase in scattering.
As shown in FIGS. 11A to 11D, in the non-video period Toff in which each of the four consecutive control electrodes 27 is not scanned, voltage application is stopped in order to control the transparent transmission state. The Then, voltage application is started before the partial scanning period TP in which each is scanned. The applied voltage is AC. By applying such a voltage waveform, as shown in FIGS. 11E to 11H, the four continuous divided regions 22 are controlled from the transmission state to the scattering state.
Further, as shown in FIGS. 11A to 11D, the application of voltage to the four consecutive control electrodes 27 is stopped after each scan is finished in order to control the transmission state. By applying such a voltage waveform, as shown in FIGS. 11E to 11H, the four continuous divided regions 22 are controlled from the scattering state to the transparent transmission state.
The reference timing information for the synchronization control is sent from the projector 11 to the synchronization control unit 31. The synchronization control unit 31 sequentially switches the voltage applied to the plurality of control electrodes 27 based on the reference timing so that the projection light is irradiated during a period when the scattering characteristics are constant and stable.

The scanning of the image light moves from the divided area 22 in FIG. 11A to the divided area 22 in FIG. 11B at a timing T1 in FIGS. At this timing T1, the image light is scanned so as to pass through the gap region 28 between the two divided regions 22.
At this timing T1, voltages having the same polarity and the same potential are applied to the control electrode 27 in FIG. 11A and the control electrode 27 in FIG.
Therefore, the optical state of the gap region 28 is controlled to the video state of FIG. The gap region 28 scatters and transmits image light in the same optical state as the divided region 22.
Similarly, at timing T2 in FIGS. 11A to 11D, the control electrode 27 in FIG. 11B and the control electrode 27 in FIG. Is applied.
Similarly, at timing T3 in FIGS. 11A to 11D, the control electrode 27 in FIG. 11C and the control electrode 27 in FIG. Is applied.
As a result, the image light is scattered and transmitted in the gap region 28 in substantially the same scattering state as that of the divided region 22.

As described above, in the present embodiment, the synchronization control unit 31 applies a voltage of the same polarity to the two control electrodes 27 arranged adjacent to each other at the timing when the image light scans the gap region between these electrodes. .
Thereby, the optical state of the gap region 28 of the optical layer corresponding to the region between the two corresponding divided regions 22 where the control electrode 27 is not formed can be controlled to a desired state.
In particular, the projector 11 scans the screen 21 with image light, and the screen 21 operates in a reverse mode in which parallel light transmittance is reduced by applying a voltage, and scatters the irradiated image light. Therefore, in the reverse mode screen 21, the optical state of the gap region 28 between the two corresponding divided regions 22 can be controlled to the video state.
Further, when the image light moves from one divided region 22 to another adjacent divided region 22, the synchronization control unit 31 applies a voltage having the same polarity and the same amplitude to the corresponding two control electrodes 27. Therefore, the optical state of the gap region 28 of the screen 21 in the reverse mode can be controlled to the same video state as that of the divided region 22.
Thereby, in the image formed by the scattering of the screen 21, the influence of luminance unevenness in the gap region 28 is suppressed. Unevenness is less likely to occur in the projected image over the entire screen 21.

[First comparative example]
The display device of the first comparative example is the same as that of the first embodiment. However, the synchronization control unit 31 applies a drive voltage not considering the control of the gap region 28 to the plurality of control electrodes 27.
FIG. 12 is a schematic timing chart showing the relationship between the optical state of the plurality of divided regions 22 and the drive voltage waveform in the first comparative example.
FIGS. 12A to 12H correspond to FIGS. 11A to 11H.
In the first comparative example, at the timings T11 to T13 in FIGS. 11A to 11D in which the scanning of the image light becomes the gap region 28, the control electrodes 27 on both sides of the gap region 28 have the opposite polarity and A voltage having the same amplitude is applied.
Therefore, the optical state of the gap region 28 is controlled to the video state of FIG. The gap region 28 scatters image light in an optical state different from that of the divided region 22.
As a result, the scattering in the gap region 28 has a different characteristic from the scattering in the divided region 22, and the projected image is uneven over the entire screen 21.

[Second Embodiment]
In the second embodiment, a modification of the display device 1 of the first embodiment will be described.
The time required for the image light projected from the projector 11 to the screen 21 to pass through one divided region 22 is substantially uniform among the plurality of divided regions 22. Hereinafter, this time is referred to as a scanning delay time Td.
For example, the scanning delay time Td is small when the projector 11 is separated from the screen 21 (the effective number of image area divisions is large), and is large when close to the reverse (the effective number of image area divisions is small). Become).
In addition, since the scanning of the projector 11 is unique to each projector 11, it is not constant. In particular, in the last divided region 22 in the scanning period, the difference between individual differences becomes large.

The synchronization control unit 31 of the second embodiment adjusts the drive voltage waveform so that the polarity of the voltage of the control electrodes 27 on both sides thereof is aligned at the timing when the gap region 28 is scanned with respect to the scanning delay time Td that is not constant. To do.
Specifically, for example, the synchronization control unit 31 determines, for each control electrode 27, based on both the scanning delay time Td obtained from the scanning period of the image light and the frequency of the AC voltage applied to the plurality of control electrodes 27. It is determined whether the drive voltage waveform needs to be inverted.
Then, the synchronization control unit 31 appropriately inverts the drive voltage waveform so that the polarities of the voltages of the control electrodes 27 on both sides thereof are aligned at the timing when the gap region 28 is scanned.
FIG. 13 is an explanatory diagram of line inversion control of drive voltage waveforms applied to the plurality of control electrodes 27 in the second embodiment.
The three sets of drive voltage waveforms in FIGS. 13A to 13C are drive voltage waveforms with a constant period. The horizontal axis is time, and the vertical axis is voltage.

As shown in FIG. 13A, when the scanning delay time Td is small, the timings T31 to T33 at which the scanning light scans the gap region 28 fall within the half cycle of the drive voltage waveform.
In this case, the synchronization control unit 31 determines that inversion is not necessary in determining inversion of each drive voltage waveform.
As a result, as shown in FIG. 13A, the four drive voltage waveforms are applied to the respective control electrodes 27 as voltages whose polarity changes in phase without being inverted.
Note that the synchronization control unit 31 calculates a value obtained by dividing the time for actually scanning the screen divided into a plurality of regions by the number of the control electrodes 27 in the scanning period of the image light notified from the projector 11. What is necessary is just to use for the scanning delay time Td.

As shown in FIG. 13B, when the scanning delay time Td becomes slightly longer, the timings T41 to T43 at which the scanning light scans the gap region 28 do not fit in the half cycle of the drive voltage waveform.
In this case, the synchronization control unit 31 determines that the inversion is necessary in the inversion determination of each drive voltage waveform.
As a result, as shown in FIG. 13B, the second drive voltage waveform from the top is inverted with respect to the first, the third drive voltage waveform from the top is further inverted with respect to the second, and from the top. The fourth drive voltage waveform is further inverted with respect to the third.

As shown in FIG. 13C, when the scanning delay time Td is further increased, the interval from the timing T51 to T53 when the scanning light scans the gap region 28 is further widened.
In this case, the synchronization control unit 31 determines that the inversion is necessary in the inversion determination of each drive voltage waveform.
However, in the case of FIG. 13C, the voltage is applied to each control electrode 27 as a voltage whose polarity changes in phase without being inverted.

As described above, the synchronization control unit 31 of this embodiment applies a common waveform AC voltage to the plurality of control electrodes 27.
In addition, the synchronization control unit 31 adjusts the waveform of the AC voltage applied to the plurality of control electrodes 27 based on the scanning period T of the image light and the frequency of the AC voltage applied to the plurality of control electrodes 27.
Specifically, the synchronization control unit 31 adjusts the polarities of the voltages applied to the control electrodes 27 corresponding to the divided regions 22 on both sides of the gap region 28 at the timing when the gap region 28 is scanned with video light. The AC voltage waveform applied to some control electrodes 27 is adjusted so as to be inverted with respect to the AC voltage waveform applied to other control electrodes 27.
That is, in the present embodiment, the divided regions 22 on both sides of the gap region 28 at the timing when the image light is scanned are set to the same potential according to the scanning delay determined by the projection region of the projector 11 and the drive voltage waveform (pulse width). Alternatively, line inversion / non-inversion is controlled so as to have the same polarity. When the drive voltage waveform includes a half cycle, it is inverted in units of scanning cycle.
Therefore, in the present embodiment, even if the scanning period T of the screen 11 by the projector 11 changes, the plurality of gap regions 28 of the screen 11 are controlled to be in a scattering state (video state) equivalent to the divided region 22 in synchronization with it. it can.

[Third Embodiment]
In the third embodiment, a modification of the display device 1 of the second embodiment will be described.
The synchronization control unit 31 of the third embodiment controls the pulse width and the number of cycles of the drive voltage waveform instead of controlling the line inversion of the drive voltage waveform.
FIG. 14 is an explanatory diagram of the control of the pulse width and the number of cycles of the drive voltage waveform applied to the plurality of control electrodes 27 in the third embodiment.
14A to 14C, the drive voltage waveforms are applied to the control electrodes 27 corresponding to the divided regions 22 on both sides of the gap region 28 at the timing when the gap region 28 is scanned by the image light. The pulse width and the number of cycles of the drive voltage waveform are controlled so that the voltages have the same polarity.
The horizontal axis is time, and the vertical axis is voltage.

As shown in FIG. 14A, when the scanning delay time Td is small, timings T61 to T63 at which the scanning light scans the gap region 28 fall within a half cycle of a standard driving voltage waveform.
In this case, the synchronization control unit 31 determines that adjustment is not necessary in determining whether the drive voltage waveform needs to be adjusted.
As a result, as shown in FIG. 14A, the four drive voltage waveforms are applied to the respective control electrodes 27 as voltages having the same phase and changing in polarity while maintaining the standard waveforms.

As shown in FIG. 14B, when the scanning delay time Td becomes slightly longer, the timings T71 to T73 at which the scanning light scans the gap region 28 do not fit within the half cycle of the standard driving voltage waveform.
In this case, the synchronization control unit 31 determines that adjustment is necessary in determining whether the drive voltage waveform needs to be adjusted.
As a result, as shown in FIG. 14B, the number of cycles of the drive voltage waveform is reduced to, for example, half. The four drive voltage waveforms are applied to the respective control electrodes 27 as voltages whose polarities change in the same phase according to waveforms adjusted so that the pulse width is widened.

As shown in FIG. 14C, when the scanning delay time Td is further increased, the interval from the timing T81 to T83 when the scanning light scans the gap region 28 is further increased.
In this case, the synchronization control unit 31 determines that adjustment is not necessary in determining whether the drive voltage waveform needs to be adjusted.
As a result, as shown in FIG. 14C, the four drive voltage waveforms are applied to the respective control electrodes 27 as voltages having the same phase and changing polarity while maintaining the standard waveforms.

As described above, the synchronization control unit 31 of this embodiment applies a common waveform AC voltage to the plurality of control electrodes 27.
In addition, the synchronization control unit 31 adjusts the waveform of the AC voltage applied to the plurality of control electrodes 27 based on the scanning period T of the image light and the frequency of the AC voltage applied to the plurality of control electrodes 27.
Specifically, the synchronization control unit 31 adjusts the polarities of the voltages applied to the control electrodes 27 corresponding to the divided regions 22 on both sides of the gap region 28 at the timing when the gap region 28 is scanned with video light. Adjust the pulse width and cycle number of the driving voltage waveform.
That is, in the present embodiment, the divided regions 22 on both sides of the gap region 28 at the timing when the image light is scanned are set to the same potential according to the scanning delay determined by the projection region of the projector 11 and the drive voltage waveform (pulse width). Alternatively, the pulse width or the number of cycles is controlled so as to have the same polarity. When the pulse includes a half cycle, the pulse may be reversed in units of scanning cycle.
Therefore, in the present embodiment, even if the scanning period T of the screen 11 by the projector 11 changes, the plurality of gap regions 28 of the screen 11 are controlled to be in a scattering state (video state) equivalent to the divided region 22 in synchronization with it. it can.

Each of the above embodiments is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications or changes can be made without departing from the scope of the invention. .

For example, the synchronization control unit 31 performs line inversion control in the second embodiment, and controls the pulse width in the third embodiment. In addition, for example, the synchronization control unit 31 may adjust each drive voltage waveform by combining line inversion and pulse width control in accordance with the scanning delay Td determined by the projection area of the projector 11.

In the above embodiment, the screen 21 is controlled to be in the scattering state in the image state, and is scattered while transmitting the image light. In addition, for example, the screen 21 may be controlled to be in a high scattering state in the video state, and may be scattered while reflecting the video light. In this case, the screen 21 functions as a reflective screen in which the viewer is positioned on the side where the image light from the projector 11 is projected.

In the above embodiment, the reverse mode screen 21 is used. In addition, for example, the screen 21 in the normal mode may be used.
The screen 21 in the normal mode increases the parallel light transmittance when a voltage is applied, but can be used when driven by applying a voltage to a scattering state that is an image state.
For example, when the image light irradiated with the screen 21 in the normal mode is scattered, the synchronization control unit 31 moves the two image lights when the scanned image light moves from one divided region 22 to another divided region 22. A voltage having the same polarity may be applied to the control electrode 27 corresponding to the divided area 22 to control the optical characteristics of the gap area 28 corresponding to the two divided areas 22 to the video state.

DESCRIPTION OF SYMBOLS 1 Display apparatus 11 Projector 21 Screen 22 Division | segmentation area | region 25 Optical layer 27 Control electrode 28 Gap area | region 31 Synchronization control part (control part)
T scanning period TP partial scanning period Ton period including video period Toff non-video period

Claims

An optical layer whose optical properties change by application of a voltage, and a screen having a plurality of control electrodes arranged along the optical layer and spaced apart from each other in order to apply a voltage to the optical layer;
A projector that displays image by irradiating image light on the screen;
The voltage application to the plurality of control electrodes is controlled and stopped during the projection period of the image light, and the divided regions corresponding to the control electrodes are different from the image state in which the image light is scattered by voltage application. A control unit for switching to a predetermined non-video state in an optical state;
Have
The controller is
At the timing when the image light is irradiated, a voltage having the same polarity is applied to two adjacent control electrodes, and the optical state of the region between the two corresponding divided regions is controlled.
Display device.
The projector scans the screen with image light,
The screen operates in a reverse mode in which a parallel light transmittance is lowered by applying a voltage, and scatters and transmits the irradiated image light.
The controller is
When the image light to be scanned moves from one divided region to another divided region, a voltage having the same polarity is applied to the control electrodes corresponding to the two divided regions, and the region between the two divided regions To the video state,
The display device according to claim 1.
The controller is
When the image light moves from one divided region to another divided region, a voltage having the same polarity and the same amplitude is applied to the control electrodes of the two divided regions, and the region between the two divided regions is imaged. Control to the state,
The display device according to claim 2.
The controller is
Applying a common waveform AC voltage to the plurality of control electrodes,
Applied to some of the control electrodes so that the polarities of the voltages applied to the control electrodes corresponding to the divided regions on both sides of the region are aligned at the timing when the region between the two divided regions is scanned by image light Adjusting the AC voltage waveform to reverse the polarity with respect to the AC voltage waveform applied to the other control electrode,
The display device according to claim 2 or 3.
The controller is
Applying a common waveform AC voltage to the plurality of control electrodes,
Applied to the plurality of control electrodes so that the polarities of the voltages applied to the control electrodes corresponding to the divided regions on both sides of the region are aligned at the timing when the region between the two divided regions is scanned by the image light Adjust the pulse width or number of cycles in the AC voltage waveform,
The display device according to claim 2 or 3.
The controller is
Adjusting the waveform of the AC voltage applied to the plurality of control electrodes based on at least one of the scanning period of the image light and the frequency of the AC voltage applied to the plurality of control electrodes;
The display device according to claim 4 or 5.
The projector scans the screen with image light,
The screen operates in a normal mode in which the parallel light transmittance is increased when a voltage is applied, and scatters and transmits the irradiated image light.
The controller is
When the image light to be scanned moves from one divided region to another divided region, a voltage having the same polarity is applied to the control electrodes corresponding to the two divided regions, and the region between the two divided regions To control the optical characteristics of the
The display device according to claim 1.
A display device driving method for displaying an image of image light emitted from a projector on a screen having an optical layer whose optical characteristics change by application of a voltage,
The control unit for controlling the optical state of the screen,
A voltage is applied to a plurality of control electrodes arranged along the optical layer and spaced apart from each other, and an image of the irradiated image light is displayed on a screen having the optical layer and the plurality of control electrodes. ,
The voltage application to the plurality of control electrodes is controlled and stopped during the projection period of the image light, and the divided regions corresponding to the control electrodes are different from the image state in which the image light is scattered by voltage application. Switch to a predetermined non-video state that is an optical state,
At the timing when the image light is irradiated, a voltage having the same polarity is applied to two adjacent control electrodes, and the optical state of the region between the two corresponding divided regions is controlled.
A driving method of a display device.
An optical layer having an optical layer whose optical characteristics change when a voltage is applied, and a plurality of control electrodes arranged along the optical layer and spaced apart from each other in order to apply a voltage to the optical layer. A screen for displaying images of light;
The voltage application to the plurality of control electrodes is controlled and stopped during the projection period of the image light, and the divided regions corresponding to the control electrodes are different from the image state in which the image light is scattered by voltage application. A control unit for switching to a predetermined non-video state in an optical state;
Have
The controller is
At the timing when the image light is irradiated, a voltage having the same polarity is applied to two adjacent control electrodes, and the optical state of the region between the two corresponding divided regions is controlled.
Screen device for display.