JP2004258125A - Information display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that an image projection device which makes display with definition higher than resolution characteristic of display elements by using a pixel shift technique can synchronize display elements, whose scanning directions are unilateral, only in one direction when shifting pixels in two dimensions although an image is scanned while pixel shifting is synchronized in the switching scanning direction of image frames of the display elements because of trouble such that images before and after being shifted appear to be continuous when displayed in a very short time wherein a pixel shifting element makes luminous flux shift in one direction. <P>SOLUTION: The image display device makes a display with definition higher than the resolution characteristic of display elements by using the pixel shift technique. The scanning of a 1st pixel shifting element is carried out almost in synchronism with information update scanning in pixel column units from the X-axial right side of display elements which can be scanned in both two-dimensional directions. Redisplay is carried out from a pixel column where pixel shifting is completed, and then scanning of a 2nd pixel shift element is performed nearly in synchronism with information update scanning in pixel column units from the Y-axial top this time, after a specified time when all pixels are displayed. The image is shifted orthogonally to the scanning direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a display device for displaying an image on a display element having a plurality of pixels arranged two-dimensionally. More specifically, the present invention relates to a technique for displaying a fine image using pixel shifting means.
[0002]
[Prior art]
A display device having a spatial light modulation element such as a liquid crystal light valve or LCoS (Liquid Crystal on Silicon), and a display element in which a plurality of pixels emitting different colors are arranged in a broad sense, specifically, a projector, a head mounted display , Etc., the number of pixels of the display element is increasing year by year.
FIG. 9 is a schematic diagram illustrating an example of a display element.
FIG. 10 is a diagram for explaining the concept of enlarged projection.
In both figures, reference numeral 1 denotes a display element, 2 denotes a projected image on a screen, and X, Y and Z denote coordinate axes.
[0003]
When the traveling direction of light is taken on the Z axis, the display element 1 has pixels arranged two-dimensionally in the XY directions. In correspondence with the drawings, the X-axis direction may be expressed as a horizontal direction and the Y-axis direction as a vertical direction for convenience. However, this does not necessarily mean the horizontal direction in actual use. The method of obtaining these coordinates is the same in all the following descriptions.
Examples of the display element include a transmission type, a reflection type, and a self-luminous type. An enlargement projection unit, a pixel shift unit, and the like are arranged between the display element and the screen. Also, lighting means are arranged near them as necessary.
Along with the increase in the number of pixels, the pixel size is reduced, and the driving mechanism of the pixels tends to be finer and more complicated, and there is a problem that the cost increases. Also, when the pixel size is reduced, the effective pixel area ratio is reduced, and the light use efficiency may be reduced.
[0004]
On the other hand, techniques for increasing the effective number of displayed pixels without increasing the number of pixels of the display element include a pixel shifting technique and a wobbling technique. In these techniques, an image in which the pixels of the display element are shifted by a distance smaller than the pixel size on the display surface and an image that is not shifted, or the shifted images are simultaneously superimposed, or superimposed in a time-division manner. To display. When the display is performed while changing the position of the pixel to be displayed in a time-division manner, an image is displayed at the second display position while the image at the first display position is being viewed by the afterimage effect, so that an apparent 2 It can appear as if there are two pixels (see, for example, Patent Document 1). Alternatively, there is a method in which a plurality of display elements are used to perform overlapping display so that the pixel positions are slightly shifted. There is an example where the distance for shifting the pixel is 1/2 or 1/4 of the pixel size.
[0005]
The step of performing pixel shifting includes the step of displaying an image of a pixel at a first position, the step of moving an image of a pixel to a second position, the step of displaying an image of a pixel at a second position, and the first position. And moving the image of the pixel. In this case, the number of pixels that are moved and displayed is two, and the number of image frames formed by the pixels is twice the normal number.
[0006]
As an application of the above display principle, it can be easily understood that the number of pixels to be displayed can be four by moving the pixels in two directions. In this case, the pixel shifting means is means for shifting the pixel in two directions in the vertical and horizontal directions. In this case, the number of image frames to be displayed is quadrupled, and the amount of displayed information is also quadrupled.
[0007]
To shift in two directions, assuming that the optical axis is Z, an element for shifting in the ± X direction and an element for shifting in the ± Y direction may be used together. At this time, if the vertical and horizontal arrangement directions of the display elements are also made to coincide with the XY directions, the pixels are shifted in two directions of ± X and ± Y.
[0008]
11 to 15 are diagrams for explaining an example of pixel shift.
FIG. 11 schematically shows the arrangement of pixels on the screen when the projection is performed with the number of pixels of the display element. Reference numeral 3 indicates one pixel.
FIG. 12 is a diagram showing a state of division when one pixel 3 is divided into four and displayed. Reference numeral 4 (4a to 4d) indicates a sub-pixel. If the sub-pixels 4 have image information corresponding to the respective positions, an image finer than the image displayed in FIG. 11 is displayed.
FIG. 13 is a diagram showing a state where all the pixels 3 are displayed by the sub-pixels 4. The sub-pixel 4 is configured to be half the pixel pitch of the pixel 3 in both the vertical and horizontal directions, but the ratio to the pixel pitch changes as the number of divisions changes.
[0009]
Originally, a display element having only the number of pixels shown in FIG. 11 is used to display four times the number of pixels, and therefore, only the time division method has to be used.
FIG. 14 is an example of a procedure for displaying an image four times in a time-division manner and synthesizing the image on a screen. In the first image display, only the sub-pixel 4a corresponding to each pixel 3 is discretely displayed on the screen as shown in FIG. After a predetermined time has elapsed in this state, only the sub-pixel 4b is discretely displayed as shown in FIG. Similarly, an image of only the sub-pixel 4c and an image of only the sub-pixel 4d are sequentially displayed. The switching of these four images is performed within the time period following the afterimage phenomenon of the human eye. Then, the result of combining the four discrete images can be recognized as one image having no gaps and no overlap as a whole.
[0010]
In the display element shown in FIG. 11, adjacent pixels are not particularly discretely formed, and therefore, some measures are taken to form sub-pixels.
FIG. 15 is a diagram in which a microlens array is provided on the front surface of the display element.
In the figure, reference numeral 5 denotes a display pixel, 5 'denotes a reduced image of the display pixel 5 by a microlens, and 6 denotes a microlens array.
The display pixels 5a to 5e provided at a slight distance from each other are reduced in size in the air by a microlens array 6 provided with lens elements corresponding thereto, and are reduced images 5a 'to 1/2 of the pixel pitch in the air. An image is formed as 5e ', which is projected as a discrete image on a screen by a projection means provided thereafter. However, simply projecting this will result in the same position being projected every time, no matter how many times the projection is made, so that the need for pixel shifting arises here.
[0011]
Among the pixel shifting means for shifting the display position of the pixel image, there is a means using liquid crystal. More specifically, the optical axis of the light passing through the liquid crystal is deflected (shifted in a narrow sense), and the image of the pixel on the display element is displayed on the projection surface. When the birefringence of the liquid crystal is used, the extraordinary ray component is subjected to a birefringence effect by tilting the orientation angle of the liquid crystal with the optical axis, that is, by arranging the liquid crystal molecules with the main axis and the optical axis inclined. Further, the orientation angle of the liquid crystal molecules can be switched by, for example, a voltage applied to the liquid crystal layer. Therefore, the switching operation of the optical axis shift of the light passing through the liquid crystal can be performed by the liquid crystal and the element having the voltage applying means to the liquid crystal. Pixel shifting means using the above principle is already known.
[0012]
FIGS. 16 to 20 are diagrams for explaining pixel shifting means using liquid crystal.
In the figure, reference numeral 7 denotes a pixel shifting element, 8 denotes a liquid crystal molecule, 9 denotes an optical path of an ordinary ray, 10 denotes an optical path of an extraordinary ray, and L denotes an incident ray.
When an electric field is applied from any direction to the XY plane of the pixel shift element 7 (hereinafter simply referred to as a liquid crystal plate for simplicity), the liquid crystal molecules 8 move in any direction of the cone bus shown schematically in FIG. It is located in an inclined state.
[0013]
Now, when an electric field of a certain magnitude is applied in the positive direction of X, the liquid crystal molecules 8 are aligned in a right-up state as shown in a cross section in FIG. At this time, the liquid crystal plate 7 becomes optically anisotropic and has birefringence. In this state, when a normal light beam L is incident from the left, the ordinary light beam for the liquid crystal plate 7 goes straight along the optical path 9 without receiving any action. On the other hand, the extraordinary ray is refracted by the liquid crystal plate 7, exits along the optical path 10a, and is shifted upward from the optical path 9 by a distance s, that is, shifted in the positive Y direction.
Here, when the polarity of the electric field is reversed and an electric field is applied in the negative direction of X, the arrangement of the liquid crystal molecules 8 is reversed as shown in FIG. As a result, the extraordinary ray of the incident light L is emitted along the optical path 10b, and is shifted downward from the optical path 9 by a distance s, that is, shifted in the negative Y direction.
[0014]
In this way, by applying an electric field of a certain magnitude in the X direction and reversing its polarity, it is possible to give a difference in the emission position to the extraordinary ray by a distance of 2 s in the Y direction. By adjusting the magnitude of the electric field and the characteristics of the liquid crystal so that the distance 2 s is just の of one side of the size of the pixel 3 and adjusting the incident light L so that only the extraordinary light is generated for the liquid crystal plate, FIG. Pixel shifts as shown in a) to (b) and (c) to (d) can be achieved. The electric field that produces such a result is hereinafter referred to as a predetermined electric field. The shift from (b) to (c) and from (d) to (a) in the same figure is performed by making the light flux transmitted through the liquid crystal plate incident on the second liquid crystal plate and applying a predetermined electric field in the Y direction to the second liquid crystal plate. The light beam may be shifted in the X direction. However, it is necessary to make the incident light extraordinary light for the second liquid crystal plate.
[0015]
FIG. 19 is a schematic diagram of a configuration of a liquid crystal plate for performing two-dimensional pixel shift as shown in FIG.
In the figure, reference numeral 11 denotes a first pixel shift element, 12 denotes a λ / 2 wavelength plate, 13 denotes a second pixel shift element, and A denotes a polarization direction of incident light.
A light beam composed of a discrete reduced image formed by the method shown in FIG. 15 is adjusted to linearly polarized light in the Y direction at any one of positions before and after the image form as shown by an arrow A. (Hereinafter simply referred to as the liquid crystal plate 11 and the same applies to the others). Here, the light beam is shifted in the Y direction because the polarization direction of the light beam corresponds to the extraordinary ray due to a predetermined electric field in the X direction applied to an electrode (not shown). The polarization direction of the light beam is rotated by 90 ° by the λ / 2 wavelength plate 12 provided immediately after this, and this light beam becomes an extraordinary ray for the second liquid crystal plate 13 to which a predetermined electric field is applied in the Y direction. Therefore, the light beam is shifted in the X direction, and is consequently projected onto any one of the positions where the pixel 3 is divided into four.
[0016]
FIG. 20 is a timing chart of the electric field applied to the two liquid crystal plates shown in FIG.
In FIG. ₀ Is a potential applied to an electrode for applying a predetermined electric field to the liquid crystal plate.
An electric field is applied to the first liquid crystal plate in the X direction, and the light flux is shifted in the Y direction. Here, the relationship is such that when a positive potential is applied, the shift is made in the positive Y direction. That is, the image is displaced up at a positive potential and down at a negative potential.
An electric field is applied to the second liquid crystal plate in the Y direction, and the light flux is shifted in the X direction. Here, the relationship is such that when a positive potential is applied, the X is shifted in the positive direction. That is, the image is displaced right at a positive potential and left at a negative potential. On the enlarged and projected screen, the upper, lower, left, and right sides are usually inverted, but the image on the screen is displayed in the same relationship as the image on the display element because it becomes complicated.
[0017]
In the case of pixel-shifted display, it is necessary to move the pixel while the afterimage effect of the image displayed at the first position is maintained, and display the image at the second position. Further, in the case of moving image reproduction display, it is general to set the display frequency of one screen frame to 60 Hz or more. Therefore, it is necessary to move the liquid crystal alignment at a relatively high speed. A liquid crystal having a quick response to an applied voltage includes a ferroelectric liquid crystal.
A vertical alignment type ferroelectric liquid crystal in which the main axis of the liquid crystal is aligned in the thickness direction of the liquid crystal layer is known as a suitable material for performing pixel shifting at high speed.
[0018]
In the case of pixel-shifted display, if the image of the moving pixel is still displayed, the pixels may be connected. For example, when the image information difference to be displayed is large, when the images of the adjacent pixels are not connected, the separation between the pixels is better and the display performance with high resolution can be obtained. Therefore, Patent Document 1 discloses an invention that prevents an image of a moving pixel from being displayed. Although the patent mainly addresses the problem particularly in liquid crystal panels having pixels arranged in a delta arrangement, the patent mentions the concept of preventing moving pixels from being displayed.
[0019]
Apart from this, the image displayed by the pixel of the display element is generally read and updated from the frame memory for each frame. In general, high speed is required to update all the pixels at the same time in updating the frame of the display element. Therefore, the update is often performed line-sequentially in units of a scanning line composed of pixel columns. In the case of pixel shifting, pixel shifting is performed a plurality of times in one frame. If a frame displayed by shifting pixels is referred to as a sub-frame, the speed required for updating the sub-frame is even faster than this, so that it is more difficult to perform simultaneous update over the entire surface, and there is a high possibility that line-sequential updating will be performed.
[0020]
What matters here is the relationship between the pixel shifting timing and the subframe image update timing.
FIG. 21 is a timing chart showing the operation of the pixel shift element using the liquid crystal as shown in FIGS.
From a state in which a potential is applied to the electrode in one direction and a shift of −s occurs, a time t ₁ When the potential is switched to the opposite polarity at the time, the shift amount changes to + s, but the change is completed at time t. ₂ And a small but Δt = t ₂ -T ₁ It takes time.
[0021]
FIGS. 22 to 24 are diagrams for explaining problems in the timing of image display and pixel shifting.
The symbol T in these figures represents time, the vertical axis represents the vertical position of the display element, and the horizontal axis represents time.
The diagrams T1 and T3 are lines indicating line-sequential image start timings from the time when the highest pixel row starts updating the image to the time when the lowest pixel row starts updating the image. In detail, since T1 and T3 are not straight lines but give a minute delay time for each pixel column, they should be indicated by step-shaped broken lines for each pixel column. Therefore, it is shown by a straight line for convenience.
[0022]
If the display element is modulated and controlled so that the display gradation is set to the zero level during the image update period, and the pixel shift is completed within the image update period, the image of the moving pixel is not displayed.
Diagrams T2 and T4 correspond to T1 and T3, and indicate timings at which the image update ends. No image is displayed in the regions included in the quadrilaterals T1, T3, T4, and T2. Although image display is partially performed from time T1 to T3, the time from time T3 to T2 is a time period in which no image is displayed on the screen.
The time T5 to T6 is a time zone during which the pixel is shifted, and the time width is equal to the above-mentioned Δt. Therefore, if the time width Δt = T6−T5 is shorter than the time width T2−T3, the pixels may be simultaneously shifted during the image update.
[0023]
Since the image is not displayed during the image update period, it is a wasteful time for the display function, so that it must be minimized.
FIG. 23 is a diagram showing a case where the image update time is minimized.
The time width T3-T2 cannot be shorter than the time width T6-T5 as long as the pixels are simultaneously shifted while the image is not displayed. That is, the pixel shift period must be performed between the start of updating the last scanning line and the end of updating the first scanning line. That is, the update time of the entire display element must be longer than the time required for pixel shifting.
[0024]
FIG. 24 is a diagram showing a case where the image update period and the time required for pixel shifting are substantially equal.
If the display element is composed of liquid crystal, the image should be able to be updated in approximately the same time as the pixel shift element.However, as is clear from the figure, the pixel shift is performed at any timing during the image update period. However, pixel shift occurs partially during image display.
These points are not mentioned in Patent Document 1.
[0025]
There is an example that mentions a method of shifting a pixel position so as to synchronize with vertical scanning of a scanning line (for example, see Patent Document 2). According to this method, only the scanning line area whose frame has been updated is subjected to the polarization action and the pixels are shifted and displayed, and the scanning line area in the state one frame before is not affected by the polarization action and the pixels do not shift. is there. However, the above-mentioned problem in the operation and operation during the frame update period is not mentioned. Further, it is difficult to shift pixels in two directions by using the technology disclosed in the patent.
[0026]
In the known configuration of the pixel shift unit using the vertical alignment type ferroelectric liquid crystal described above (for example, Japanese Patent Application No. 2002-261339), the pixel shift direction is the X-axis direction and the Y-axis direction with respect to the optical axis Z. Although pixel shifting in two directions is realized by using both means, in this configuration, pixel shifting can be performed while moving the pixel shifting area in only one of the two directions in accordance with the update scanning line moving direction. it can. In the remaining one direction, the update scanning line moving direction and the direction of moving the pixel shift area are orthogonal to each other, so that the update scanning and the pixel shift cannot be synchronized. As a result, in order to prevent a pixel shifted in that direction from being displayed, the update time must be lengthened or a standby time must be taken from the completion of the update to the display of the next frame.
[0027]
A display device capable of switching the scanning direction of a display element from a vertical direction to a horizontal direction or vice versa as necessary has been proposed (for example, see Patent Document 3). This switching is performed automatically or at the will of the user, depending on the installation direction of the display element and the use condition, and always aims to give an erect image to the user. Therefore, the application for switching the scanning direction for each subframe is not shown.
[0028]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-15548 (page 5, FIG. 2)
[Patent Document 2]
JP-A-6-324320 (Page 10, FIGS. 22, 23)
[Patent Document 3]
JP-A-10-268848 (page 3, FIG. 1)
[0029]
[Problems to be solved by the invention]
In order to solve the above problem, according to the present invention, the pixel shift timing in the pixel shift area is adjusted in accordance with the movement of the pixel column, that is, the scanning line in the display element, so as to match the update timing of the area to be shifted. I do. When the entire display area is viewed, the image update period of the display element is delayed line-sequentially, but the timing for shifting the pixels is similarly delayed. The above operation can be performed in any of the pixel shifting in two directions. By doing so, the time required for preventing the moving pixel from being displayed can be shortened, and the display time can be lengthened. As a result, the display can be brightened. At the same time, blurring of the image is reduced. It is an object of the present invention to realize such a display device.
[0030]
[Means for Solving the Problems]
According to the first aspect of the present invention, an information display element in which a plurality of pixels are arranged and two-dimensionally scan line-sequentially in two directions, a light flux from the information display element is transmitted, and a pixel shift change position can be scanned. A first pixel shifting element whose scanning direction matches one of the two scanning directions of the information display element, and a second pixel whose scanning direction matches the other scanning direction of the information display element A shift device and a control device for applying a predetermined electric field to each pixel shift device, wherein the information display device has a sub-pixel corresponding to a sub-pixel smaller than its own pixel pitch in any of two-dimensional directions. The image information of the frame is sequentially displayed, and the scanning direction is switched at the time of updating the information of each sub-frame. And performing pixel shift scanning element towards that.
[0031]
According to a second aspect of the present invention, in the information display device according to the first aspect, the first and second pixel shift elements are arranged such that a direction line for applying the predetermined electric field coincides with the scanning direction line, The light beam is shifted in a direction orthogonal to the scanning direction line.
According to a third aspect of the present invention, in the information display device according to the first or second aspect, the first and second pixel shift elements shift channels of light beams from a plurality of pixel columns of the information display element at the same time. , And scanning is performed in units of the channel.
[0032]
According to a fourth aspect of the present invention, in the information display device according to the third aspect, the number of the channels is an integer fraction of the number of pixel columns in each of the two-dimensional directions of the information display element. .
According to a fifth aspect of the present invention, in the information display device according to the third or fourth aspect, an operation start time between adjacent channels of the first and second pixel shift elements is the information display element corresponding to the channel. Are delayed by a time equal to the sum of the delay times of the plurality of pixel columns.
[0033]
According to a sixth aspect of the present invention, in the information display device according to the fifth aspect, the sum of the delay times is obtained by adding a basic clock for a pixel column of the display element to a number of pixel columns corresponding to one channel. It is characterized by.
According to a seventh aspect of the present invention, in the information display device according to any one of the third to sixth aspects, the number of pixel columns of the display element corresponding to the one channel is 2 with n being a positive integer. ⁿ And wherein the operation start time between adjacent channels of the first and second pixel shift elements is delayed by n clocks of the basic clock for the pixel row of the display element.
According to an eighth aspect of the present invention, in the information display device according to any one of the first to seventh aspects, each of the plurality of pixels is divided into two or more sub-pixels in any of the two scanning directions. It is characterized by having been done.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described according to embodiments.
FIG. 1 is a diagram showing an example of an image display device to which the present invention is applied.
In the figure, reference numeral 101 denotes an illumination light source, 102 denotes an infrared ray removing filter, 103 denotes an illuminance distribution uniformizing means (a fly-eye lens array, a rod integrator, etc.), 104 denotes a polarizing plate, 105 denotes a polarizing beam splitter, 106 denotes a dichroic prism, Reference numerals 107R, 107G, and 107B denote reflective image display elements of liquid crystal for each of three primary colors, 108 denotes a liquid crystal plate as a first pixel shift element, 109 denotes a λ / 2 wavelength plate, and 110 denotes a liquid crystal as a second pixel shift element. Reference numeral 111 denotes a magnifying projection unit, and 112 denotes a screen.
Both pixel shift elements are connected to a control device (not shown), and perform the operation described with reference to FIGS.
[0035]
The white luminous flux that has exited the illumination light source 101 and has been removed from the thermal battle by the infrared ray elimination filter is converted into a luminous flux having a substantially uniform intensity distribution by the illuminance equalizing unit 103, and is adjusted to linearly polarized light by the polarizing plate 104. When the polarized light beam enters the polarizing beam splitter 105, only the polarized light component is reflected by the reflecting surface and enters the dichroic prism 106. The red component of the white light flux is reflected upward and the blue component is reflected downward by the spectral mirror provided in the prism. The green component not reflected by either mirror goes straight on.
[0036]
Each of the split light beams is incident on a reflective image display device (hereinafter simply referred to as a display device) 107R, 107G, 107B of a corresponding color, and is reflected after being modulated by each color information. The direction of polarization of the reflected light is rotated by 90 ° with respect to the incident light.
The reflected light follows the optical path by the dichroic prism in the reverse direction, but when it reaches the polarization beam splitter, the polarization direction is now changed by 90 °, so it is transmitted without being reflected, and enters the first liquid crystal plate 108. . At this time, the polarization direction of the incident light is set to be an extraordinary ray for the first liquid crystal plate 108. As described above, since the setting is made such that only the extraordinary ray is always incident on the liquid crystal plate, the light flux composed of the extraordinary ray incident on the liquid crystal plate is hereinafter simply referred to as a light flux.
[0037]
The operations of the first liquid crystal plate 108, the λ / 2 wavelength plate 109, and the second liquid crystal plate 110 are as described with reference to FIGS. As a result, the images shown in FIGS. 14A to 14D are projected and displayed on the screen 112 while changing in time series.
[0038]
Next, a description will be given of the pixel shifting element disclosed in the above-mentioned Japanese Patent Application No. 2002-261339.
2 to 4 are diagrams for explaining an example of a liquid crystal plate as a pixel shift element used in the present invention. 2A is a schematic cross-sectional view, FIG. 2B is a plan view, FIG. 3 is an operation explanatory diagram, and FIG. 4 is a graph showing a potential gradient between electrodes.
In these figures, reference numeral 201 denotes a liquid crystal plate, 202 denotes an upper substrate, 203 denotes a lower substrate, 204 denotes an alignment film, 205 denotes a vertical alignment type ferroelectric liquid crystal, 206 denotes a spacer, 207 denotes a control device, and 208 denotes a liquid crystal plate. Wiring connecting the control devices, 209 is a series resistor, 210 is an electrode plate, and 211 to 223 are individual strip electrodes.
In FIG. 3, reference numeral TR denotes a switching element, V denotes a potential, and X, Y, and Z denote coordinate axes. In FIG. 4, the horizontal axis indicates the electrode position, and the vertical axis indicates the applied voltage.
[0039]
The liquid crystal plate 201 faces two transparent substrates 202 and 203 each having an electrode plate 210 and an alignment film 204 superposed on one surface via a spacer 206 such that the alignment films 204 are inside each other. The liquid crystal 205 is filled.
When the coordinate axes are set as shown in the figure and the Z-axis direction is the light transmission direction, the electrode plate 210 has a plurality of transparent strip electrodes (hereinafter simply referred to as electrodes) long in the Y-axis direction at equal intervals in the X-axis direction. Lined up. For convenience of explanation, the number of electrodes is shown smaller than actual. The electrodes provided on the transparent substrates 202 and 203 are shifted from the counterpart substrate by half of the above-mentioned equally spaced pitch. Therefore, in the plan view of FIG. 2B, when electrode numbers 211 to 223 are assigned from left to right in the X-axis direction, all the electrodes on the transparent substrate 202 side are odd-numbered, and All electrodes are even.
[0040]
Although the Z direction is exaggerated in FIG. 2A, the electrodes 211 and 212 are actually closer in the Z direction. Here, when a positive electric field is applied from the electrode 211 to the electrode 212, the electric field is substantially directed in the X direction in the liquid crystal 205. If the intensity of the electric field is at a level sufficient to change the orientation direction of the liquid crystal 205 (hereinafter referred to as a predetermined level), the liquid crystal 205 between the two electrodes is aligned in a specific direction. As a result, the transmitted light flux is shifted downward in the Y direction. The liquid crystal region between adjacent electrodes is called a shift region for convenience.
[0041]
FIG. 3 is a diagram showing a part of the control device 207 in detail. By directly controlling the potentials applied to all the electrodes, all the shift regions can be individually controlled. However, here, several shift regions are collectively treated as one control unit, and the whole is controlled by a plurality of control regions. A method of dividing into units will be described.
For example, the whole is divided into four control units. The three shift regions included between the electrodes 211 to 214 are referred to as a channel 1, the next three shift regions are referred to as a channel 2, and similarly, a channel 3 and a channel 4.
[0042]
A control potential is directly applied to the electrodes at both ends of each channel (hereinafter abbreviated as Ch) from the control device 207, and the middle electrode is applied to the middle electrode by a series resistor 209 built in the control device 207. The potential difference applied to the electrodes is divided and a potential is indirectly applied. If the resistance values sandwiched between the electrodes are equal, the electric field levels applied to the three shift regions are all equal.
When the potential difference between the potentials applied to the electrodes at both ends of the channel is reversed and the polarity of the electric field applied to the shift region is reversed, the three shift regions included in the middle do not operate individually and the shift directions are simultaneously reversed.
Note that the series resistor 209 can be provided on the liquid crystal plate 201 side. In that case, the wiring 208 connecting the control device 207 and the liquid crystal plate 201 can be simplified.
[0043]
In FIG. 3, the supply voltage V4 is equally divided into four stages of V3, V2 and V1 by dividing the voltage between the supply voltage V4 and the reference 0 level V0. The potential difference in each stage is set to a magnitude at which the electric field of the predetermined level is applied to the liquid crystal 205. The potential difference between the stages is referred to as a unit voltage Vu for convenience.
The switching circuits TR00 to TR04 determine the potential to be applied to the electrode 211 at any one of V0 to V4.
The switching circuits TR40 to TR44 determine the potential to be applied to the electrode 223 at any one of V0 to V4. The switching circuits TR10 and TR14 are configured to supply the potential applied to the electrode 214 to the highest potential V4 and the lowest potential V0, respectively, and are controlled so as to apply either one of the potentials or neither. . The switching circuit connected to each of the electrode 217 and the electrode 220 performs the same operation.
[0044]
As an example, assume that the highest potential V4 is applied to the electrode 214. At this time, the electrodes 217 and 220 have their switching circuits cut off, and no specific potential is applied. The potential of V3 is applied to the electrode 211 and the potential of V1 is applied to the electrode 223.
In the Ch1 shift region, the electric potential applied to the electrode 214 is higher than the electric potential applied to the electrode 211, and therefore, when viewed in the X-axis direction, an electric field is applied in the negative direction by the unit voltage Vu.
[0045]
In the shift regions Ch2 to Ch4, the potential of V4 is applied to the electrode 214 and the potential of V1 is applied to the electrode 223. That is, three times the unit voltage Vu is applied to the three Chs, and the potential V3 is applied to the electrode 217 and the potential V2 is applied to the electrode 220 due to the series resistance sandwiched between the two electrodes. Will be. Accordingly, when viewed in the X-axis direction, the electric field due to the unit voltage Vu is applied to all the shift regions of Ch2 to Ch4 in the X-axis direction.
By doing so, the electric field levels applied to the respective shift regions have the same absolute value.
[0046]
In this control state, when a light beam enters in the positive direction of the Z axis, the light beam is shifted in the positive direction of the Y axis in Ch1, and the light beam is shifted in the negative direction of the Y axis in Ch2 to Ch4. The potential of each electrode in this state is shown by the solid line graph in FIG. In the same graph, the white circle plot indicates that the potential was directly applied to the electrode. The black circle plot indicates that the potential was indirectly applied to the electrode by the partial pressure.
In the graph connecting the electrodes, a shift region rising to the right indicates that a negative electric field is applied, and a shift region falling to the right indicates that a positive electric field is applied.
[0047]
If the electrode 211 is set to the highest potential V4, the electrode 223 is set to the lowest potential V0, and no specific potential is applied to the intermediate electrode, the luminous flux transmitted through all the shift regions Ch1 to Ch4 becomes Shifted down. One of the intermediate electrodes 214, 217, and 220 is selected to apply the highest potential V4, and both ends of the electrodes 211 and 223 are opposite in polarity so that the unit voltage Vu is applied to each Ch. Is selected, the transmitted luminous flux is shifted upward on the left side and downward on the right side of the selected intermediate electrode.
If the electrode 223 is set to the highest potential V4, the electrode 211 is set to the lowest potential V0, and no specific potential is applied to the intermediate electrode, the luminous flux transmitted through all the shift regions Ch1 to Ch4 becomes Shifted up.
[0048]
In the above control method, if only the electrode that gives the maximum potential V4 is determined, the potentials given to the other electrodes are uniquely determined. Therefore, in the following description of the control, the control state is represented only by the electrode that gives the maximum potential V4. It shall be.
It is assumed that the electrode that gives the highest potential V4 is sequentially switched to the electrodes 211, 214, 217, 220, and 223. The position of the electrode thus selected is referred to as a pixel shift change position since the pixel shift direction is reversed before and after that. As an example, a case will be described in which the state where the electrode 214 is selected is switched to the state where the electrode 217 is selected as described above.
[0049]
This state is shown by the broken-line graph in FIG. In the same graph, a plot with a triangle indicates that the potential was directly applied to the electrode. The black circle plot indicates that the potential was indirectly applied to the electrode by the partial pressure.
In this state, the light flux is shifted upward in Ch1 and Ch2, and shifted downward in Ch3 and Ch4. That is, only Ch2 reverses the direction of the electric field, and changes from a downward shift to an upward shift.
As described above, as the selected position of the electrode providing the highest potential V4 moves to the right, the direction of the electric field of Ch located immediately to the left of the electrode is reversed, and the shift direction of the light beam is reversed from below to above. .
[0050]
On the other hand, when the selection position of the electrode that gives the lowest potential V0 is moved to the right, the direction of the electric field of Ch located immediately to the left of the electrode is reversed, and the light beam shifts from the upper to the lower direction. Turns around.
The movement of the selected position of the electrode is referred to as scanning, similar to scanning in updating image information of the display element. There are positive and negative polarities in the direction in which the electric field is applied, but when it is simply used in a meaning such as a horizontal direction without considering the polarity, it is called a direction line of the electric field. The same applies to the scanning direction, shift direction, and the like.
[0051]
It is assumed that the liquid crystal plates 108 and 110 in FIG. 1 use a pixel shift element having such a configuration.
The scanning direction of the display elements 107R, 107G, and 107B is set to be the same as the scanning direction of the first liquid crystal plate 108. That is, as shown in FIG. 2, the liquid crystal plate is arranged so that the longitudinal direction of the electrodes is the vertical direction, and the electrodes are scanned in the horizontal direction in Ch units. The directions of the horizontal scanning for one sub-frame by the three display elements are matched, and the scanning of the first liquid crystal plate 108 is performed substantially in synchronization with the scanning. However, the scanning of the liquid crystal plate is performed in Ch units, and one Ch corresponds to a plurality of scanning lines of the display element. With this configuration, an image shift as shown in FIGS. 14A and 14B is performed.
[0052]
FIG. 5 is a timing chart of signals applied to the liquid crystal plate. FIG. 2A is a chart showing a signal applied to the first liquid crystal plate 108, and FIG. 2B is a chart showing a signal applied to the second liquid crystal plate 110, respectively. However, here, it is shown that Ch is 4 or more.
In the figure, the vertical axis represents a voltage given in Ch units, and the above-mentioned unit voltage Vu is given to each Ch with its polarity reversed. The horizontal axis indicates time. The time Tu is equal to the period of the subframe. The time difference between each Ch, that is, the delay time δt, is set equal to the sum of the above-described delay times for the number of scanning lines (the number of pixel columns) of the display element corresponding to one Ch. This delay time δt corresponds to the delay time when the selection electrode is switched to the electrode 214 and then to the electrode 217 in FIG.
Since a drive circuit (not shown) of the display element is provided with a basic clock generating means for performing scanning in units of pixel columns, the basic clocks are summed up by the number of pixel columns corresponding to 1Ch to obtain a time δt. be able to.
[0053]
The problem here is the above-mentioned problem of the scanning direction mismatch between the second liquid crystal plate and the display element. Therefore, in the present invention, as the display elements 107R and 107B, display elements that can be scanned vertically and horizontally as shown in Patent Document 3 are used. The electrodes of the second liquid crystal plate are arranged in the horizontal direction, and scanning of the electrodes is performed in the vertical direction, in order to correspond to the information update of the sub-frame that shifts the image in the horizontal direction. In response to this, the display element also scans in the up-down direction with the scanning directions coincident. By doing so, the image shift as shown in FIGS. 14B to 14C can be performed in the shortest time.
[0054]
As shown in FIG. 5B, the timing at which the potential of Ch1 switches from positive to negative is delayed by the time Tu from the same switching timing of the first liquid crystal plate. Further, the switching timing of Ch2 is delayed by δt with respect to Ch1, as in the first liquid crystal plate.
[0055]
The relationship between Tu and δt is determined by the number of pixel columns and the display time of the display element corresponding to one Ch. For example, assuming that the number of pixel columns is 1024, eight columns correspond to 1Ch, and the time width from the end of information update to the start of the next information update is Td,
Tu = Td + δt (1024/8) = Td + 128δt
It becomes.
Thus, 1Ch is 2 ⁿ It is convenient to correspond to a column (n = 3 in the above example) because a scanning clock for a liquid crystal plate can be obtained simply by dividing the basic clock input to the display element by n stages.
[0056]
FIG. 6 is a diagram showing the relationship between image display and pixel shifting.
In the figure, reference numeral 25 denotes a sub-frame display time zone including the sub-pixels 4a, 26 denotes a Y-direction pixel shift time zone, 27 denotes a sub-frame display time zone including the sub-pixels 4b, 28 denotes an X-direction pixel shift time zone, Reference numeral 29 denotes a sub-frame display time zone including the sub-pixels 4c.
In the figure, the horizontal axis represents time, and the vertical axis represents the position of the pixel column of the display element. However, the vertical axis is in the X-axis direction before and after the time zone 26, and is switched to the Y-axis direction before and after the time zone 28.
[0057]
7 and 8 are diagrams showing the timing relationship of FIG. 6 by the relationship between the display element and the liquid crystal plate. Both figures show only elements related to the operation for ease of understanding, and other members are omitted.
Hereinafter, the relationship between scanning and pixel shift will be described with reference to FIGS.
The uppermost pixel row in the time zone 25 is the rightmost vertical pixel row on the display element. In order to avoid complication, the upper and lower parts of the pixel column are shown in abbreviated form. In updating the image information, horizontal scanning is sequentially performed to the left. That is, the scanning direction is opposite to the scanning direction shown in FIG.
Corresponding to this, the liquid crystal plate is also arranged to perform horizontal scanning. It is assumed that 1Ch of the liquid crystal plate corresponds to n rows of pixels of the display element and is composed of NCh in total. For convenience of explanation, it is assumed that the number of scanning lines of the display element and the number of scanning Ch of the liquid crystal plate are the same in the vertical and horizontal directions.
[0058]
At time T5, which is delayed by time δt from time T1 at which information update of display element 107 is started, horizontal scanning of liquid crystal plate 108 is started by reversing the polarity of the potential applied to Ch1 shown in FIG. This δt corresponds to the delay time of the n columns of the display elements. Thereafter, the next Ch is scanned every time δt elapses. Therefore, although the scanning of the liquid crystal plate has a delay time of δt with respect to the scanning of the display element, it can be said that the scanning is almost synchronized as a whole.
When the configuration of the liquid crystal panel is configured to have exactly the same number of scanning lines as the display element, a delay time of δt is not required, and the liquid crystal panel may be scanned completely in synchronization with the display element.
Such complete synchronization is also included in the above “substantially synchronization”.
[0059]
If the information update is completed by the time T2 after the pixel shift end time T6 of Ch1 and the image display is started, the displayed image does not move.
From the time T4 at which the leftmost pixel column, at which the information update is started at the time T3, ends the update, the NCh pixel shift is also ended, and the display is started, to the information update start time T1 'for the next subframe. In the interval, all images of the sub-frame are displayed.
[0060]
FIG. 7 is a diagram schematically showing a state in the middle of horizontal scanning. The large arrows shown in the elements indicate the direction of scanning. The small arrow indicates the shift direction of the light beam. The directions of both arrows are orthogonal.
The state where the kx-th Ch of the liquid crystal plate 108 is currently performing the pixel shifting operation in accordance with the information update position of the display element 107 is shown. The light beam that has been shifted upwards up to that point is shifted downwards when subjected to pixel shift scanning. Thus, the shift from FIG. 14A to FIG. 14B is performed.
However, as shown in FIG. 6, even if Chkx actually starts pixel shifting, the pixel shifting of Ch before that does not necessarily end, and FIGS. 7 and 8 merely show the concept. Things.
[0061]
The description will be made on the assumption that the vertical axis is switched in the Y-axis direction when the sub-frame by the sub-pixel 4b is displayed in the entire image in the time zone 27.
The top pixel column at the display end time T1 ′ in the time zone 27 is the top pixel column of the display element 107. In the following, in the time zone 28, vertical scanning is performed by the same operation as in the time zone 26, even though there is a difference between up and down and left and right, and the light beam is shifted rightward, as shown in FIG. From (c) to (c).
[0062]
FIG. 8 is a diagram schematically showing a state in the middle of vertical scanning. The large arrows shown in the elements indicate the direction of scanning. The small arrow indicates the shift direction of the light beam.
This shows a state in which the ky-th Ch of the liquid crystal panel 110 is currently performing a pixel shifting operation in accordance with the information update position of the display element 107. The luminous flux that has been shifted to the left until then undergoes pixel shift scanning, and is shifted to the right. Thus, the shift from FIG. 14B to FIG. 14C is performed.
[0063]
Although illustration is omitted, pixel shifting in the opposite direction to FIGS. 7 and 8 can be performed according to the same principle. This makes it possible to shift the image from FIG. 14 (c) to (d) and from FIG. 14 (d) to (a). That is, when the sub-pixel 4 is divided into four pixels 3, the vertical scanning and the horizontal scanning are performed alternately.
In the above description, the reflection type image display device is described as an example. However, even in the case of a transmission type image display device or a self-emission type image display device, two-dimensional Obviously, any display element that can scan in the direction can be used.
In addition, although an example in which a vertical alignment type ferroelectric liquid crystal is used as the pixel shifting element has been described, a pixel shifting element as disclosed in Patent Document 2 may be used.
[0064]
Until now, the shift position in the X-axis direction and the Y-axis direction has been described as two places each, and therefore, the case where there are four subframes has been described. However, the shift position in each axial direction is made three places or four or more places. However, the principle of the present invention can be applied in exactly the same manner. In other words, the number of subframes is not limited to four, but may be six, eight, nine, twelve, sixteen, or more in principle. However, as the number of subframes increases, high-speed image processing is required, and the maximum number of subframes is limited by the processing speed capability. Further, in this case, the pixel shift element also provides a plurality of voltage application levels for light beam shift, so that the shift amount in each axis direction is not simply ± s, but is, for example, ± s and ± 2s. , Multi-stages in each of the positive and negative directions.
[0065]
【The invention's effect】
According to the present invention, it is possible to obtain an image projection device that can take a sufficient image display time even when performing two-dimensional pixel shift.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image display device to which the present invention is applied.
FIG. 2 is a diagram illustrating an example of a liquid crystal plate as a pixel shifting element used in the present invention.
FIG. 3 is a diagram for explaining an example of a liquid crystal plate as a pixel shifting element used in the present invention.
FIG. 4 is a diagram for explaining an example of a liquid crystal plate as a pixel shifting element used in the present invention.
FIG. 5 is a timing chart of signals applied to a liquid crystal plate.
FIG. 6 is a diagram illustrating a relationship between image display and pixel shifting.
FIG. 7 is a diagram showing the timing relationship in FIG. 6 by the relationship between a display element and a liquid crystal plate.
FIG. 8 is a diagram showing a timing relationship in FIG. 6 by a relationship between a display element and a liquid crystal plate.
FIG. 9 is a schematic diagram illustrating an example of a display element.
FIG. 10 is a diagram for explaining the concept of enlarged projection.
FIG. 11 is a diagram illustrating an example of pixel shifting.
FIG. 12 is a diagram illustrating an example of pixel shifting.
FIG. 13 is a diagram illustrating an example of pixel shifting.
FIG. 14 is a diagram illustrating an example of pixel shifting.
FIG. 15 is a diagram illustrating an example of pixel shifting.
FIG. 16 is a diagram for explaining pixel shifting means using liquid crystal.
FIG. 17 is a diagram for explaining pixel shifting means using liquid crystal.
FIG. 18 is a diagram for explaining pixel shifting means using liquid crystal.
FIG. 19 is a diagram for explaining pixel shifting means using liquid crystal.
FIG. 20 is a diagram for explaining pixel shifting means using liquid crystal.
FIG. 21 is a timing chart showing the operation of the pixel shift element using the liquid crystal as shown in FIGS.
FIG. 22 is a diagram for describing a problem in timing of image display and pixel shifting.
FIG. 23 is a diagram for explaining a problem in image display and pixel shifting timing.
FIG. 24 is a diagram for describing a problem in image display and pixel shifting timing.
[Explanation of symbols]
3 pixels
4 sub-pixels
107 Reflective image display device
108 First Pixel Shifting Element
109 λ / 2 wave plate
110 Second pixel shifting element
201 Pixel shift element
205 liquid crystal
210 electrode plate

Claims (8)

An information display element in which a plurality of pixels are arranged and which can be scanned line-sequentially in two directions in two dimensions; and a light beam from the information display element is transmitted, and a pixel shift change position can be scanned. A first pixel shifting element whose scanning direction matches one of the scanning directions, a second pixel shifting element whose scanning direction matches the other scanning direction of the information display element, and each pixel A control device for applying a predetermined electric field to the shift element, wherein the information display element sequentially displays image information of subframes corresponding to subpixels smaller than the pixel pitch of the information display element in any of two-dimensional directions. When the information of each sub-frame is updated, the scanning direction is switched, and in response to the information updating accompanied by the switching of the scanning direction, there is no pixel corresponding to the scanning direction of the information display element. Information display apparatus and performs scanning of the element is. 2. The information display device according to claim 1, wherein the first and second pixel shift elements have a direction line in which the predetermined electric field is applied coincides with the scanning direction line, and the light flux is aligned with the scanning direction line. 3. An information display device characterized in that the information display device is shifted in an orthogonal direction. 3. The information display device according to claim 1, wherein the first and second pixel shift elements have a plurality of channels for simultaneously shifting pixels from light beams from a plurality of pixel columns of the information display element. 4. An information display device characterized by being scanned in units. 4. The information display device according to claim 3, wherein the number of the channels is an integer fraction of the number of pixel columns in each of the two-dimensional directions of the information display element. 5. The information display device according to claim 3, wherein an operation start time between adjacent channels of the first and second pixel shift elements is a delay of a plurality of pixel columns of the information display element corresponding to the channel. An information display device characterized by being delayed by a time equal to the sum of the times. 6. The information display device according to claim 5, wherein the sum of the delay times is obtained by adding a basic clock for a pixel column of the display element to a number of pixel columns corresponding to one channel. . 7. The information display device according to claim 3, wherein the number of pixel columns of the display element corresponding to the one channel is 2 ⁿ columns, where n is a positive integer. An information display device, wherein an operation start time between adjacent channels of two pixel shift elements is delayed by a clock obtained by dividing a basic clock for a pixel column of the display element by n stages. The information display device according to any one of claims 1 to 7, wherein each of the plurality of pixels is divided into two or more sub-pixels in any of the two scanning directions. Information display device.

Images