JP2008203626A - Display device, projection type display device, control circuit of optical path shift element and optical path shift element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively render a gap between pixels inconspicuous. <P>SOLUTION: Liquid crystal light valves 100R, 100G and 100B modulate polarization states of incident light according to respective data signals Rv, Gv and Bv. Light transmitted by these liquid crystal light valves is synthesized by a dichroic prism 212 and magnified and projected on a screen 300 by a projecting lens system 214 via an optical path shift element 10. The optical path shift element 10 is constituted of a liquid crystal functional element where an average tilt angle of liquid crystal molecules in a liquid crystal interposed between light transmissive substrates is changed by application of an electric field and changes the average tilt angle during the period of time that a same or continuous frame is displayed by the liquid crystal light valves 100R, 100G and 100B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for making a gap between pixels of a displayed image inconspicuous.

In recent years, a projection display device (projector) that forms a reduced image using a spatial light modulator such as a liquid crystal element and enlarges and projects the reduced image using an optical system is becoming widespread. However, in general display devices including this type of projector, a problem has been pointed out that gaps between pixels (so-called black matrix) are easily noticeable.
Therefore, on the emission side of the modulated light by the spatial light modulator, an optical rotation control liquid crystal panel for controlling non-optical rotation and 90-degree optical rotation, and a birefringent optical element for branching an unpolarized incident light beam into an ordinary ray and an extraordinary ray. A technique has been proposed in which the black matrix is made inconspicuous by disposing the display pixels due to the extraordinary rays vertically, horizontally, or obliquely with respect to the display pixels due to the ordinary rays by sequentially arranging them (see Patent Document 1). .
Japanese Patent Laid-Open No. 11-167163

However, it has been pointed out that the above technique has a fixed pixel shift amount. It has also been pointed out that birefringent optical elements applied to the above technique are generally expensive and it is difficult to reduce the cost of the entire apparatus.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a display device, a projection display device, and these devices that can realize the gap between pixels inconspicuously at low cost. It is an object of the present invention to provide a control circuit for an optical path shift element or an optical path shift element applied in the above.

In order to achieve the above object, in the display device according to the present invention, a spatial light modulator that modulates light according to an image input signal, and an optical path shift that shifts an optical path of modulated light by the spatial light modulator A display device that displays an image based on the modulated light shifted by the optical path shift element, wherein the optical path shift element includes a liquid crystal sandwiched between translucent substrates by an applied electric field. It is composed of a liquid crystal functional element in which an average tilt angle of liquid crystal molecules changes, and the applied electric field is changed within a period of displaying the same or continuous frames in the spatial modulator. According to the present invention, it is not necessary to use an expensive element such as a birefringent optical element, so that the gap between pixels can be made inconspicuous at a low cost.
The term “frame” used herein refers to a complete image displayed by the spatial light modulator. For example, if a method of sequentially displaying three fields (field sequential), the number of frames is three. An image obtained by combining the primary color images of R (red), G (green), and B (blue) according to the field. If the interlace method is used, the scanned image of the odd-numbered row and the scanned image of the even-numbered row are combined. If the non-interlace method is used, it means an image displayed by vertical scanning.

In the present invention, it may be configured to have an adjusting means for adjusting the amount of shift. According to this configuration, it is possible to appropriately adjust the inconspicuousness of the gap between pixels.
Further, the present invention may be configured to include means for switching the shift amount in accordance with the image input signal. According to this configuration, the difficulty of conspicuous gaps between pixels can be appropriately switched depending on the image to be displayed.
In the present invention, the spatial light modulator includes a plurality of pixels each having a shape having at least one side, and the optical path shift element is configured such that a displayed image is in one side direction of the pixel or in a direction perpendicular to the one side direction. The optical path of the modulated light may be shifted so as to be deviated. The spatial light modulator includes a plurality of pixels having at least one side, and the optical path shift element includes pixels to be displayed. The optical path of the modulated light may be shifted so as to be displaced obliquely with respect to the one side direction of the pixel.

  In the present invention, the spatial light modulator includes a plurality of pixels each having a shape having at least one side, and the optical path shift element has two or more directions in which displayed pixels are different from one side direction of the pixel. The optical path of the modulated light may be shifted so as to deviate. In such a configuration, an aspect having an optical path shift device in which two optical path shift elements having different optical path shift directions are arranged in series on the optical path is preferable. Thereby, the gap between the pixels can be made inconspicuous with a simple configuration.

In the present invention, the optical path shifting element includes a pair of translucent substrates, a liquid crystal composed of a chiral smectic C phase having a homeotropic orientation filled between the pair of translucent substrates, and an electric field applied to the liquid crystal. It is good also as a structure provided with an electric field application means. In this configuration, it is preferable that the electric field applying means can change the strength of the electric field applied to the liquid crystal.
In the present invention, the spatial light modulator is preferably a transmissive liquid crystal display element.
On the other hand, in the present invention, the image processing apparatus further comprises resolution conversion means for converting the number of pixels of the image defined by the image input signal into the number of pixels of the display image of the spatial light modulator, and the spatial light modulator comprises the resolution conversion means It is good also as a structure which displays the image in which the number of pixels was converted by this.
Further, the display device, a light source that emits visible light, an illumination optical system that irradiates the spatial light modulator with light emitted from the light source, and an image based on the modulated light shifted by the optical path shift element. Projection means for enlarging and projecting.
Further, the present invention is a display device that includes an optical path shift element that shifts an optical path of modulated light by the spatial light modulator, and displays an image based on the modulated light shifted by the optical path shift element. The optical path shift element is characterized in that the shift amount is changed within a period in which the spatial modulator displays the same or continuous frames. Even with this configuration, it is not necessary to use an expensive element such as a birefringent optical element, so that the gap between the pixels can be made inconspicuous at a low cost. The “shift” here includes not only the shift of the optical path using polarized light but also the shift of the optical path using reflection or refraction.
The present invention can be conceptualized not only as a display device or a projection display device, but also as a control circuit for an optical path shift element and an optical path shift element.

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

<First Embodiment>
First, a projector (projection display device) according to a first embodiment of the invention will be described. This projector enlarges and projects an image displayed on a liquid crystal light valve, and FIG. 1 is a plan view showing the optical configuration thereof.
As shown in this figure, a lamp unit 202 made of a white light source such as a halogen lamp is provided inside the projector 1. The white light (visible light) emitted from the lamp unit 202 is converted into three primary colors of R (red), G (green), and B (blue) by three mirrors 206 and dichroic mirrors 208a and 208b arranged inside. And are led to the liquid crystal light valves 100R, 100G and 100B corresponding to the respective primary colors.
More specifically, the dichroic mirror 208a transmits light in the R wavelength region of white light, reflects light in the G and B wavelength regions, and the dichroic mirror 208b reflects the G and B reflected by the dichroic mirror 208a. The light in the B wavelength region is transmitted and the light in the G wavelength region is reflected. Since the optical path length of B is longer than the other optical path lengths of R and G, a relay lens 223 is disposed in the middle of the optical path of B in order to correct the optical path length.

Here, the liquid crystal light valves 100R, 100G, and 100B are each used as a spatial light modulator in the present embodiment. The liquid crystal light valves 100R, 100G, and 100B are transmissive liquid crystal display elements corresponding to the primary colors of R, G, and B, respectively. In the present embodiment, the liquid crystal light valves 100R, 100G, and 100B have pixels arranged in a matrix of 1080 rows × 1920 columns. In each pixel, the polarization state of outgoing (transmitted) light with respect to incident light is controlled according to the gradation.
Although not described in detail, the liquid crystal light valves 100R, 100G, and 100B have 1080 rows of scanning lines and 1920 columns of data lines, and have a substantially square shape corresponding to the intersection of these scanning lines and data lines. For example, a TN type liquid crystal is sandwiched between the pixel electrode having a shape and a common counter electrode facing each of the pixel electrodes. In such a configuration, when a certain scanning line is selected, the voltage of the data line corresponding to the pixel electrode is applied to the pixel electrode located on the selected scanning line, and the selection is canceled. The applied voltage is held by the capacitance.
Here, in the configuration, if the voltage held by the pixel electrode and the counter electrode is zero (or in the vicinity), the incident light is polarized by the liquid crystal layer, and thus the emitted (transmitted) light is polarized by the incident light. Most of the light is polarized light components that are shifted by 90 degrees from the light components. On the other hand, as the holding voltage is gradually increased, the alignment angle of the liquid crystal molecules changes. As a result, the light emitted from the polarized light component deviated by approximately 90 degrees from the polarized light component of the incident light gradually decreases. The light of the polarization component in the same direction as the polarization component of is gradually included.
For this reason, when polarizing plates (not shown) whose transmission axes are shifted by 90 degrees from each other are arranged on the incident side and the outgoing side of the liquid crystal light valves 100R, 100G, and 100B, the polarization voltage increases as the voltage held in the liquid crystal layer increases. Less light passes through the plate (normally white mode).

The lights modulated by the liquid crystal light valves 100R, 100G, and 100B are incident on the dichroic prism 212 from three directions. In this dichroic prism 212, R and B light is refracted at 90 degrees, while G light travels straight, so that images of primary colors of R and B are synthesized.
On the exit side of the dichroic prism 212, the optical path shift element 10 and the projection lens system 214 are sequentially arranged. Here, the optical path shift element 10 shifts outgoing light in a predetermined direction with respect to incident light, as will be described in detail later, and the projection lens system 214 generates a composite image via the optical path shift element 10. The projection is enlarged and projected onto the screen 300.
Since light corresponding to the primary colors of R, G, and B corresponding to the liquid crystal light valves 100R, 100G, and 100B is incident by the dichroic mirrors 208a and 208b, it is not necessary to provide a color filter.
Further, the transmission images of the liquid crystal light valves 100R and 100B are projected after being reflected by the dichroic prism 212, whereas the transmission image of the liquid crystal light valve 100G is projected straight through the dichroic prism 212, so that the liquid crystal light An image formed by the valves 100R and 100B and an image formed by the liquid crystal light valve 100G are in a horizontally reversed relationship.

Next, the electrical configuration of the projector 1 will be described with reference to FIG.
In this figure, the control circuit 50 controls the data signal writing operation to the liquid crystal light valves 100R, 100G and 100B, the optical path shift operation in the optical path shift element 10, and the supply of the data signal in the image signal processing circuit 60. To do.
Here, for the liquid crystal light valves 100R, 100G, and 100B, the control circuit 50 sequentially selects the scanning lines from the first row to the last 1080 rows one by one, and the selected scanning lines. Control is performed so that the data signals Rv, Gv, and Bv are written in the liquid crystal layers of the pixels in the first column to the 1920th column that are positioned at.
Further, the control circuit 50 supplies the following drive signal As to the optical path shift element 10. That is, in the present embodiment, as shown in FIG. 6, the control circuit 50 uses the pulse signal that alternately takes one of the voltages + Va and −Va every half cycle Ts / 2 as the drive signal As, as an optical path shift element. 10 is supplied.
In this embodiment, the half cycle Ts / 2 is set shorter than the frame cycle Tf (16.7 milliseconds) in the liquid crystal light valves 100, 100G, and 100B. For this reason, in the present embodiment, the voltage of the drive signal As is always switched during the period in which an image for one frame is displayed.
The image signal processing circuit 60 separates an image signal Vid supplied from an external device (not shown) into primary color components of R (red), G (green), and B (blue), and liquid crystal light valves 100R and 100G, respectively. And data signals Rv, Gv, and Bv suitable for driving 100 and 100 are supplied. In the present embodiment, since the normally white mode is used as described above, it is converted into a data signal having a voltage that increases the voltage applied to the liquid crystal layer as the gray level becomes darker.

Next, details of the optical path shift element 10 will be described. FIG. 3 is a diagram illustrating a configuration of the optical path shift element 10.
As shown in this figure, the optical path shifting element 10 has a configuration in which a pair of transparent substrates 12a and 12b are arranged opposite to each other while maintaining a certain gap, and the liquid crystal 16 is filled in the gap. Specifically, the optical path shift element 10 has an alignment film 14 formed on at least one of the substrates 12a and 12b, in this example, on the surface of the substrate 12a that faces the substrate 12b. The liquid crystal 16 which consists of a chiral smectic C phase which makes homeotropic alignment between 12b, and has a positive spontaneous polarization is filled.
In the optical path shift element 10, a pair of electrodes 18a and 18b corresponding to the target light deflection direction are further arranged. Of these, the drive signal As is supplied to the electrode 18a, while the electrode 18b is grounded to a potential Gnd of zero voltage.
The electrodes 18 a and 18 b function as an electric field applying unit that applies an electric field in a direction perpendicular to the rotation axis of the liquid crystal 16. FIG. 3 shows a configuration in which the electrodes 18a and 18b are integrated with the substrates 12a and 12b, but they may be provided separately from the substrates 12a and 12b. Furthermore, the electrodes 18a and 18b may also be used as spacers for defining the cell gap of the substrates 12a and 12b.

Here, the principle of the optical path shift by the optical path shift element 10 will be described.
For convenience, in FIG. 3, the direction of electric field applied by the electrodes 18a and 18b is the X axis (the direction of the electrodes 18a → 18b is positive), the vertical direction of the paper is the Y axis (the front side from the back side of the paper is positive), the substrate 12a, An orthogonal coordinate system with the substrate surface normal direction of 12b as the Z axis (substrate 12a → 12b is positive) is defined.
In the orthogonal coordinate system thus defined, the light path shift element 10 is arranged so that the light emitted from the dichroic prism 212 is incident along the Z-axis direction. The optical path shift element 10 is arranged so that the Y axis orthogonal to the electric field application direction coincides with the transmission axis of the polarizing plate provided on the emission side of the liquid crystal light valves 100R, 100G, and 100B.

FIGS. 4A and 4B respectively show end surfaces of a configuration in which the optical path shift element 10 shown in FIG. 3 is rotated 90 degrees clockwise as viewed from the positive Z-axis direction (that is, the emission side). For this reason, in FIG. 4A and FIG. 4B, the electrode 18a is located on the back side of the drawing, and the electrode 18b is located on the front side of the drawing.
The drive signal As is supplied to the electrode 18a as described above, and the applied voltage is either the voltage + Va or -Va in this embodiment. Here, when the voltage of the drive signal As is + Va, the electric field application direction is the positive direction of the X axis, that is, the forward direction from the back of the page in FIG. 4A, so that the spontaneous polarization is positive in the liquid crystal 16. The director (macroscopic molecule) 16c is distributed in the first orientation state as shown in FIG. On the other hand, when the voltage of the drive signal As is −Va, the electric field application direction is the X-axis negative direction, that is, the front side to the back side in FIG. 4B, and the director 16c is shown in FIG. Distributed in the second orientation state. That is, in any case, the director 16c is inclined along the YZ plane.

When the director 16c is in the first or second orientation state, incident light along the Z-axis direction is shifted in the direction along the Y-axis due to birefringence when passing through the director 16c.
The tilt angle of the director 16c is θ, the refractive index in the major axis direction of the director 16c is ne, and the refractive index in the minor axis direction is no with respect to the Z axis that is the light incident / exit direction in the optical path shift element 10. To do.
Since the light incident on the optical path shift element 10 is transmitted through the polarizing plate provided on the emission side of the liquid crystal light valves 100R, 100G, and 100B, the polarization direction is the Y-axis direction in FIG. Here, when the linearly polarized light in the Y-axis direction is incident on the optical path shift element 10, the refractive index in the incident direction is that of light passing through the center of the ellipsoid in a refractive index ellipsoid having refractive indexes no and ne as principal axes. From the relationship, it is obtained from the inclination angle θ of the director 16c and the refractive indexes no and ne, but the details are omitted. However, the incident light is deflected according to its refractive index, and in the first orientation state, the incident light is in the Y-axis positive direction as shown in FIG. 4A, and in the second orientation state, FIG. As shown in (b), the shift amount Sa is shifted in the Y-axis negative direction with respect to the straight traveling direction of the incident light, which is the normal direction of the substrate.
Here, when the cell gap (the thickness of the liquid crystal layer) between the substrate 12a (alignment film 14) and the substrate 12b is d, the shift amount Sa is expressed by the following equation.
Sa = {(1 / no) ² − (1 / ne) ² } ² cos 2θ · d
÷ [2 {(1 / ne) ² 2sin 2θ + (1 / no) ² 2cos 2θ · d}] (1)

  As described above, in the optical path shift element 10, by switching the voltage of the drive signal As applied to the electrode 18 a from one of + Va or −Va to the other, the optical path of the emitted light is shifted by 2Sa with respect to the straight traveling direction of the incident light. It will be.

Next, a description will be given of how the image projected on the screen 300 is changed by the optical path shift of the optical path shift element 10. FIG. 5 is a diagram illustrating a state in which the projection image is displaced (shifted) due to the optical path shift. In this figure, the solid line indicates the optical path when the liquid crystal is in the first alignment state in the optical path shift element 10, and the broken line indicates the optical path when the liquid crystal is in the second alignment state in the optical path shift element 10. Show. When the light emitted from the liquid crystal light valve 100R (100G, 100B) is shifted by the shift amount 2Sa by the optical path shift element 10, the shift is enlarged in the projected image on the screen 300 and appears as a displacement of 2Sb. .
In practice, as shown in FIG. 1, three color images resulting from transmission through the liquid crystal light valves 100R, 100G, and 100B are combined by the dichroic prism 212, and the combined light is optically shifted by the optical path shift element 10. Although the liquid crystal light valves 100R, 100G, and 100B have the same positional relationship with each other when viewed from the optical path shift element 10, only the liquid crystal light valve 100R is shown in FIG. . Further, the projection lens system 214 is shown in a simplified manner as compared with FIG.

FIG. 6 is a diagram showing the relationship between the image update by the liquid crystal light valve and the drive signal As to the optical path shift element 10.
As described above, in the liquid crystal light valves 100R, 100G, and 100B, the scanning lines from the first line to the 1080th line are selected in order, and the data signal is supplied to the pixels located on the selected scanning line. . Here, in FIG. 6, symbol ■ indicates selection for one scanning line, and this indicates a state in which selection is performed in order from the first line to the 1080th line over the frame period Tf. Here, the region located on the right side of the symbol ■ indicates the period held at the gradation corresponding to the voltage of the data signal written by the selection of the symbol ■. Therefore, FIG. 6 shows a state in which the image of the frame is sequentially updated every frame period Tf (16.7 milliseconds).
Here, in the present embodiment, since the half cycle Ts / 2 is set shorter than the frame cycle Tf (16.7 milliseconds), the drive signal is displayed during the period in which the image of the same frame is displayed. There are two states, a state where the voltage of As is + Va and a state where it is −Va.
For this reason, in the present embodiment, the image of the same frame includes the period projected when the drive signal As is the voltage + Va and the liquid crystal of the optical path shift element 10 is in the first alignment state, and the drive signal As is the voltage. It is divided into the period projected when -Va and the liquid crystal of the optical path shift element 10 is in the second alignment state.
Note that the optical response speed of the liquid crystal 16 used in the optical path shift element 10 is less than 1 millisecond, which is sufficiently higher than the optical response speed of the liquid crystal light valves 100R, 100G, and 100B. For this reason, it is possible to set Ts / 2 <Tf.

FIG. 7B is a partially enlarged view of a projected image on the screen 300. As shown in this figure, in this embodiment, the image projected by the optical path when in the second orientation state is the image projected by the optical path when in the first orientation state. In the diagonal direction with respect to the pixel array, it is deviated by the distance 2Sb.
In the optical path shift element 10, the linear polarization direction of incident light and the electric field application direction are orthogonal to each other (see FIG. 4), and the linear polarization direction of the polarizing plate disposed on the output side of the liquid crystal light valves 100R, 100G, and 100B. It coincides with the transmission axis. For this reason, the transmission axes of the output side polarizing plates of the liquid crystal light valves 100R, 100G, and 100G may be set to be oblique with respect to the pixel arrangement, and the Y axis of the optical path shift element may be set to coincide with the oblique direction. In addition, the polarizing plates on the incident side of the liquid crystal light valves 100R, 100G, and 100B may be aligned with the direction orthogonal to the transmission axis on the outgoing side (the liquid crystal alignment directions in the liquid crystal light valves 100R, 100G, and 100B are also those It goes without saying that it is aligned with the transmission axis direction).

Now, as shown in FIG. 7B, the shape of the pixel is a substantially square, and the gap between the squares is a black matrix.
Here, if there is no optical path shift element, pixel displacement does not occur in the projected image, so the portion corresponding to the black matrix is always in a dark state (hatched in the drawing) as shown in FIG. (A white part not marked with), and the lattice pattern becomes conspicuous. On the other hand, according to the present embodiment, as shown in FIG. 7B, the image projected by the optical path shift is deviated. As a result, the portion corresponding to the black matrix is also deviated. The pixels displayed when the liquid crystal is in the second alignment state are overlaid on the black matrix displayed when the liquid crystal is in the first alignment state. For this reason, in this embodiment, it becomes difficult to visually recognize a lattice pattern.

In this example, the optical path shift direction by the optical path shift element 10 is an oblique direction with respect to the pixel array, but it may be one direction of the pixel array, that is, the vertical direction of the pixel shape as shown in FIG. As described above, when the vertical shift is performed, the black matrix formed in the vertical stripe shape can be effectively inconspicuous. In order to shift in this way, the Y-axis direction of the optical path shift element may be matched with the vertical direction of the pixel array.
In this example, the pixel has a substantially square shape, but may be a parallelogram, a trapezoid, a pentagon, a hexagon, an octagon, or the like.
The optical path shift direction may be the other direction of the pixel arrangement, that is, the left-right direction of the pixel shape. Although not shown in particular in the case of shifting in the left-right direction, the black matrix formed in a stripe shape in the left-right direction can be effectively made inconspicuous. In order to shift in this way, the Y-axis direction of the optical path shift element may be matched with the left-right direction of the pixel array.

In the present embodiment, the optical path shift element 10 uses the birefringence of the liquid crystal 16 to shift the optical path of the light emitted from the light valve, so that the optical path shift element 10 is low in comparison with a method using a nonlinear optical crystal having birefringence. Cost can be reduced.
Further, in this embodiment, compared to the second and third embodiments described later, only one optical path shift element is used, and a half-wave plate is not required, so that the configuration can be simplified. Can do.
In the present embodiment, the optical path shift element 10 has been described on the assumption that the emitted light in the first and second alignment states is symmetric with respect to the straight direction of the incident light. However, the effect of making the black matrix inconspicuous is as follows. If the shift amount is not zero, it is good. For this reason, the average tilt angle of the liquid crystal only needs to be different depending on the applied voltage.
Here, the tilt angle of the liquid crystal molecules described in the present invention is an angle θ between the optical axis of the liquid crystal (the long axis of the liquid crystal molecules) and the normal direction of the substrate, and the refractive indexes no and ne of the liquid crystal are measured in advance. By doing so, it can be easily obtained through observation of a conoscopic image. In addition, the “average” of the average tilt angle is due to the fact that there are a plurality of liquid crystal molecules, but the change in the position of the cross line in the conoscopic image is due to the change in the average tilt angle of the plurality of liquid crystal molecules. Don't be.

  In this example, the control circuit 50 that supplies the drive signal As to the optical path shift element 10 is handled as a separate body. However, the optical path shift element can be integrated by incorporating the control circuit 50 in the optical path shift element 10 or by integrating it. It is also possible to conceptualize including the control circuit. For this reason, in order to control the operation of the optical path shift, the control circuit 50 for controlling the applied electric field of the optical path shift element to change within the frame period in the liquid crystal light valves 100, 100G and 100B is provided in the optical path shift element 10. May be included.

Further, in the optical path shift element 10, the shift amount can be adjusted according to the voltage applied to the electrodes 18a and 18b. For this reason, as shown in FIG. 9, an operation element 52 such as a volume is provided, and the control circuit 50 controls the voltages + Va and -Va as shown in FIG. By adjusting the amplitude of, the user can set the most appropriate shift amount (the black matrix is least noticeable) while viewing the projected image. In this configuration, the control circuit 50 and the operator 52 function as adjusting means for adjusting the shift amount.
In the adjustment described here, the amplitude value of the drive voltage As may be set to zero. When the amplitude value is set to zero, the optical path shift does not occur in the optical path shift element 10, but the intention can be reflected when the user does not want the optical path shift.

On the other hand, the appropriate shift amount may differ depending on the type of image to be displayed, for example, the type of video source such as cinema, OA, game, and television as well as the distinction between moving images and still images. Therefore, the voltage amplitude of the drive signal As is preset according to these types, the user specifies the type of the input image signal Vid, and the drive signal according to the type of the specified image signal Vid. The control circuit 50 may set the voltage amplitude of As to set an appropriate shift amount according to the input image signal Vid.
Alternatively, as shown in FIG. 11, the determination circuit 54 may determine the type of the input image signal Vid, and the control circuit 50 may set the voltage amplitude of the drive signal As corresponding to the determination result. In this configuration, the control circuit 50 and the discrimination circuit 54 function as means for switching the shift amount in accordance with the input image signal.

<Modification of First Embodiment: Part 1>
Next, a modified example (part 1) in which the relationship between the half cycle Ts / 2 of the drive signal As and the frame cycle Tf is changed in the first embodiment will be described.
In the first embodiment, the half cycle Ts / 2 of the drive signal As is set shorter than the frame cycle Tf to satisfy Ts / 2 <Tf. However, in this modification, as shown in FIG. 12, Ts / 2 = Tf.
As shown in the figure, if the switching timing of the voltages + Va and -Va does not coincide with the frame, an optical path shift occurs during the period in which the same frame is displayed.
Note that, in a period of a frame, when a period in which the drive signal As is the voltage + Va is Tfa and a period in which the drive signal As is the voltage −Va is Tfb, the periods Tfa and Tfb are set according to the position of the scanning line. The ratios are different. That is, the ratio of the period Tfa displayed at the position shifted corresponding to the first alignment state and the period Tfb displayed at the position shifted corresponding to the second alignment state is the position of the scanning line. Depending on. However, there is no change in that the black matrix can be made inconspicuous. Thus, when Ts / 2 = Tf is set, there is an advantage that the driving period of the optical path shift element can be suppressed to be lower than that in FIG.

<Modification of First Embodiment: Part 2>
Next, a modified example (part 2) in which the relationship between the half cycle Ts / 2 of the drive signal As and the frame cycle Tf in the first embodiment is changed will be described.
In this modification, as shown in FIG. 13, the frame period Tf is shorter than 16.7 milliseconds, and Ts / 2> Tf.
For this reason, after the image by the liquid crystal light valve is updated a plurality of times, the optical path shift by the optical path shift element 10 occurs. That is, an optical path shift occurs during a period in which two or more consecutive frames are displayed.
In this way, the reason for setting Ts / 2> Tf is that there is no need to switch the shift position within one frame when displaying a still image or a moving image that moves relatively slowly. However, in order to prevent flicker caused by the optical path shift by the optical path shift element from being recognized, the time for which the projected pixel is kept at a position corresponding to the first or second orientation state with the drive frequency of the optical path shift element being 30 Hz or more, It is desirable to make it 16.7 milliseconds or less. Further, the liquid crystal light valves 100R, 100G, and 100B to be applied preferably have high-speed response.

<Modification of First Embodiment: Others>
As described above, in the optical path shift element 10, the shift amount is adjusted according to the voltage applied to the electrodes 18 a and 18 b, so that the drive signal As is not a pulse signal that is either the voltage + Va or −Va, It may be an analog signal such as a sine wave or a triangular wave with the voltages + Va and -Va as peak values.
As described above, when the drive signal As is an analog signal having the voltages + Va and −Va as the peak values, the pixels of the projected image are second from the position corresponding to the first orientation state in FIG. The black matrix can be made less noticeable and projected by staying in one of the two locations of the pixel arrangement because it moves continuously to the position corresponding to the orientation state or in the opposite direction. It is also possible to correct the adverse effect of locally brightening pixels.

Second Embodiment
Next, a projector according to a second embodiment of the invention will be described. FIG. 14 is a plan view showing the optical configuration.
As shown in this figure, the projector 2 according to the second embodiment uses an optical path shift device 30 instead of the optical path shift element 10 in the first embodiment (see FIG. 1).

FIG. 16 is a perspective view showing the configuration of the optical path shift device 30. As shown in this figure, the optical path shift device 30 includes an optical path shift element 10 similar to that of the first embodiment, an optical path shift element 20 having the same configuration as the optical path shift element 10, and the optical path shift elements 10 and 20. And a half-wave plate 15 inserted between the two. Here, the optical path shift element 20 is on the emission side of the optical path shift element 10 and has a positional relationship in which the optical path shift element 10 is rotated 90 degrees clockwise when viewed from the positive Z-axis direction. That is, two optical path shift elements 10 and 20 are arranged in series in the path of the emitted light by the liquid crystal light valves 100R, 100G, and 100B so that the shift directions of the optical paths are orthogonal to each other.
When the electrodes 18a and 18b in the optical path shift element 10 are located on the X axis negative side and the X axis positive side, respectively, the electrodes 28a and 28b in the optical path shift element 20 are located on the Y axis negative side and the Y axis positive side, respectively. It will be.
Further, the drive signal Bs is supplied to the electrode 28a in the optical path shift element 20, and the electrode 28b is grounded to the potential Gnd.

Since the polarization direction of the outgoing light of the optical path shift element 10 is in the Y-axis direction, when this outgoing light passes through the half-wave plate 15, the polarization direction is converted into the X-axis direction, and the optical path shift element 20 is incident. For this reason, the optical path shift direction of the optical path shift element 20 in a positional relationship rotated 90 degrees along the substrate surface of the optical path shift element 10 is the X-axis direction orthogonal to the optical path shift direction by the optical path shift element 10.
In the second embodiment, the Y-axis direction that is the optical path shift direction by the optical path shift element 10 is not the oblique direction of the pixel arrangement of the liquid crystal light valves 100R, 100G, and 100B, but is aligned in the vertical direction as in FIG. Is set to Therefore, the X-axis direction that is the optical path shift direction by the optical path shift element 20 is the left-right direction of the pixel arrangement of the liquid crystal light valves 100R, 100G, and 100B.

FIG. 15 is a block diagram showing an electrical configuration of the projector 2. The configuration shown in this figure is different from the first embodiment (see FIG. 2) in that the control circuit 50 supplies the drive signal As to the optical path shift element 10 and also supplies the drive signal Bs to the optical path shift element 20. There is in point to do.
In the second embodiment, the drive signals As and Bs supplied by the control circuit 50 are as shown in FIG. That is, in the second embodiment, the drive signals As and Bs are both pulse signals of the same frequency that alternately take one of the voltages + Va and −Va every half cycle Ts / 2, but with respect to the drive signal As. Thus, the phase of the drive signal Bs is delayed by 90 degrees.
In this embodiment, the cycle Ts of the drive signals As and Bs is set to be the same as the cycle Tf of the frame, and the timing at which the drive signal Bs switches from the voltage + Va to the voltage −Va and the start of the frame (one row). Is set to coincide with the timing at which the eye scanning line is selected.
For this reason, in the second embodiment, the frame period can be classified into the following four states according to the voltages in the drive signals As and Bs. That is, for the frame period, the A state where the voltages of the drive signals As, Bs are (−Va, −Va), the B state where (+ Va, −Va) is reached, the C state where (+ Va, + Va) is reached, And it can classify | categorize into D state used as (-Va, + Va) in time series, respectively.

FIG. 18 is a partially enlarged view of an image projected on the screen 300 by the projector 2 according to the second embodiment. In a display period of one frame, the A state, the B state, the C state, and the D state proceed in this order. Among these, in the B state, the voltage of the drive signal As is switched to + Va as compared with the immediately preceding A state. Therefore, the projected image is shifted upward by 2Sb. Next, in the C state, the voltage of the drive signal Bs is switched to + Va as compared with the immediately preceding B state, so that the projected image is deviated by 2Sb in the left direction. Further, in the D state, the voltage of the drive signal As is switched to -Va as compared with the immediately preceding C state, and thus the projected image is shifted downward by 2Sb. In addition, when it transfers to the next frame, it will be in A state again. In the A state, the voltage of the drive signal Bs is switched to -Va as compared with the immediately preceding D state, so that the projected image is shifted rightward by 2Sb and returned to the original position.
For this reason, according to the present embodiment, the pixels are sequentially projected at positions corresponding to the four states displaced vertically and horizontally, so that the black matrix is further inconspicuous compared to the first embodiment. Is possible.
Also in the second embodiment, the drive signal As (Bs) can be adjusted in terms of changing the relationship between the half cycle Ts / 2 and the frame cycle Tf and the voltage amplitude, as in the first embodiment. In addition, it is possible to apply an analog signal or the like.

<Third Embodiment>
Next, a projector according to a third embodiment of the invention will be described.
In the third embodiment, the liquid crystal light valves 100R, 100G, and 100B that perform display with a resolution of vertical 1080 rows × horizontal 1920 columns are used to change the size of the projected image substantially without changing the size of the projected image. An image reduced to a resolution of 1280 columns is displayed.
Here, reducing the resolution of vertical 1080 rows × horizontal 1920 columns to the resolution of vertical 720 rows × horizontal 1280 columns means reducing the resolution of vertical 1080 rows × horizontal 1920 columns to 2/3. A display corresponding to vertical 2 rows × horizontal 2 columns may be performed by a pixel arrangement of vertical 3 rows × horizontal 3 columns.
However, since the pixel arrangement of vertical 1080 rows × horizontal 1920 columns in the liquid crystal light valve is physically fixed, fractional pixels are generated and cannot be reduced to 2/3 resolution without interpolation processing or the like.
Therefore, in the third embodiment, as shown in FIG. 19, a certain frame is divided into first to fourth subfields, each of the subfields is displayed later, and the first to fourth subfields are displayed. Are sequentially assigned to the A, B, C, and D states of the optical path shift device 30, respectively.

The configuration of the projector according to the third embodiment is substantially the same as that of the second embodiment (FIGS. 14 and 15) using the optical path shift device 30. However, in the third embodiment, since one frame is divided into first to fourth subfields, the control circuit 50 forms an image corresponding to each subfeed on the liquid crystal light valves 100R, 100G, and 100B. And the image signal processing circuit 60 is controlled to output data signals Rv, Gv, and Bv corresponding to the images corresponding to the subfields.
Here, the image signal processing circuit 60 displays data corresponding to each subfield for each of the liquid crystal light valves 100R, 100G, and 100B with respect to pixels of vertical 1080 rows × horizontal 1920 columns as will be described later. Signals Rv, Gv, Bv are supplied.

Next, images displayed in the first to fourth subfields will be described with reference to FIGS. 20 and 21. FIG.
In the third embodiment, a vertical 1080 row × horizontal 1920 column pixel array in a liquid crystal light valve is grouped into an array of vertical 3 rows × horizontal 3 columns, and the vertical 3 rows × horizontal 3 columns of pixels are substantially divided. Thus, display of 2 vertical rows × 2 horizontal columns is performed.
Note that the nine pixels of 3 vertical rows by 3 horizontal columns exist in correspondence with the liquid crystal light valves 100R, 100G, and 100B, and may be referred to as actual pixels. On the other hand, the four pixels in the resolution of 2 rows × 2 columns, which are converted in resolution, do not correspond to the pixel arrays of the liquid crystal light valves 100R, 100G, and 100B, and may be called imaginary pixels.
For the convenience of explanation, the actual pixels of 3 vertical rows × 3 horizontal columns belonging to one group are divided into 3 rows of p rows, (p + 1) rows, (p + 2) rows, q columns, and (q + 1) columns. , (Q + 2) columns, and the intersection of three columns, and these nine real pixels reduce the resolution i row j column, i row (j + 1) column, (i + 1) row j column, ( It is assumed that display corresponding to four imaginary pixels in i + 1) rows (j + 1) columns is performed.

  The display with nine real pixels is shown in FIGS. 20 and 21, respectively. Specifically, FIG. 20 (1) shows the display of the A state, FIG. 20 (2) shows the C state, FIG. 21 (3) shows the C state, and FIG. 21 (4) shows the D state. As shown in these drawings, among the actual pixels of 3 rows × 3 columns, p rows q columns, p rows (q + 2) columns, (p + 2) rows q columns, (p + 2) rows corresponding to the four corners ( The pixels in the (q + 2) column are imaginary in the i-th row-j column, the i-th row-j column, the (i + 1) -row j-column, and the (i + 1) -th row (j + 1) column when the resolution is lowered over the first to fourth subfields. The display content (gradation) is the same as that of the pixel.

On the other hand, among the five real pixels other than the four corners, the real pixel in the (p + 1) row (q + 1) column located at the center has the same gradation as the real pixel located on the displacement direction side. In addition, if the actual pixels in the upper and lower p rows (q + 1) and (p + 2) rows (q + 1) are displaced in the lower right or upper right direction, the same gradation as the actual pixels adjacent in the right direction is obtained. On the other hand, if it is shifted to the lower left or upper left direction, the same gradation as the actual pixel adjacent in the left direction is obtained, and the actual pixels in the (p + 1) rows and q columns (p + 1) rows and (p + 1) rows (q + 2) columns at the left and right ends. If it is shifted in the lower right or lower left direction, the gradation is the same as that of the actual pixel adjacent in the lower direction, while if it is shifted in the upper right or upper left direction, it is the same level as the actual pixel adjacent in the upper direction. Tones.
That is, among the four states, when projected onto the screen 300, in the A state where the position is displaced in the lower left direction when viewed from the projector, as shown in FIG.
The real pixel in p row (q + 1) column becomes the gradation of the imaginary pixel in i row (j + 1) column,
The real pixel in (p + 1) rows and q columns is the gray level of the imaginary pixel in (i + 1) rows and j columns,
The real pixel in the (p + 1) row (q + 1) column becomes the gray level of the imaginary pixel in the (i + 1) row (j + 1) column,
The real pixel in the (p + 1) row (q + 2) column becomes the gradation of the imaginary pixel in the (i + 1) row (j + 1) column,
The real pixel in the (p + 2) row (q + 1) column has the gradation of the imaginary pixel in the (i + 1) row (j + 1) column.

Moreover, in the B state which is a position displaced to the upper left side in the projection image among the four states, as shown in FIG.
The real pixel in p row (q + 1) column becomes the gradation of the imaginary pixel in i row (j + 1) column,
The real pixel in (p + 1) rows and q columns is the gray level of the imaginary pixel in i rows and j columns,
The real pixel in the (p + 1) row (q + 1) column becomes the gradation of the imaginary pixel in the i row (j + 1) column,
The real pixel in the (p + 1) row (q + 2) column becomes the gradation of the imaginary pixel in the i row (j + 1) column,
The real pixel in the (p + 2) row (q + 1) column has the gradation of the imaginary pixel in the (i + 1) row (j + 1) column.

Moreover, in C state which becomes a position shifted to the upper right side in the projection image among the four states, as shown in FIG. 21 (3),
The real pixel of p row (q + 1) column becomes the gradation of the imaginary pixel of i row j column,
The real pixel in (p + 1) rows and q columns is the gray level of the imaginary pixel in i rows and j columns,
The real pixel in (p + 1) row (q + 1) column is the gray level of the imaginary pixel in i row j column,
The real pixel in the (p + 1) row (q + 2) column becomes the gradation of the imaginary pixel in the i row (j + 1) column,
The real pixel in the (p + 2) row (q + 1) column is the gray level of the imaginary pixel in the (i + 1) row j column.

And in D state which becomes a position shifted to the lower right side in a projection image among four states, as shown in Drawing 21 (4),
The real pixel of p row (q + 1) column becomes the gradation of the imaginary pixel of i row j column,
The real pixel in (p + 1) rows and q columns is the gray level of the imaginary pixel in (i + 1) rows and j columns,
The real pixel in (p + 1) row (q + 1) column is the gray level of the imaginary pixel in (i + 1) row j column,
The real pixel in the (p + 1) row (q + 2) column becomes the gradation of the imaginary pixel in the (i + 1) row (j + 1) column,
The real pixel in the (p + 2) row (q + 1) column is the gray level of the imaginary pixel in the (i + 1) row j column.

In the third embodiment, during a certain frame period, the A state of the first subfield, the B state of the second subfield, the C state of the third subfield, and the D state of the fourth subfield proceed in this order. Therefore, in the B state, it is deviated by 2Sb upward from the A state, in the C state, it is deviated by 2Sb in the left direction from the B state, and in the D state, it is deviated by 2Sb downward from the C state. When the frame shifts to the A state again, the state shifts to the right by 2Sb from the D state and returns to the original position.
For this reason, an image projected when viewed through one frame is as shown in FIG. 22, and is substantially vertical 2 rows × horizontal 2 columns by 9 real pixels of vertical 3 rows × horizontal 3 columns. These four imaginary pixels are displayed after making the black matrix inconspicuous.
Here, in the liquid crystal light valve, in the vertical 1080 row × horizontal 1920 column pixel arrangement, there can be 360 × 640 group arrangements of vertical 3 rows × horizontal 3 columns. Since the arrangement of these groups performs display of 2 vertical rows × 2 horizontal columns corresponding to imaginary pixels, it is possible to substantially reduce the display to a resolution of 720 vertical rows × 1280 horizontal columns.

<Application and modification>
In the first to third embodiments described above, the optical path shift element 10 (20) is configured to shift the optical path using the birefringence of the liquid crystal, but it is also possible to shift the optical path simply by refraction or reflection. .
As shown in FIG. 23, a substrate 35 such as glass having transparency and a predetermined refractive index is rotated by an actuator (not shown) or the like about an axis perpendicular to the optical axis. Therefore, it is possible to shift the optical path. In this configuration, the shift amount can be adjusted by adjusting the inclination of the substrate 35. For example, in order to obtain 7 μm as the shift amount 2Sa, if the thickness of the substrate 35 is 2 mm and the refractive index is 1.52, the inclination of the substrate 35 with respect to the rotation axis may be switched by ± 0.29 degrees. .

In addition, as shown in FIG. 24, it is possible to shift the optical path by changing the reflection angle of the reflection plate 37 with an actuator (not shown) or the like. In this configuration, the shift amount can be adjusted by adjusting the reflection angle of the reflection plate 37. For example, in order to obtain 7 μm as the shift amount 2Sa, if the distance between the liquid crystal light valve 100R and the reflection plate 37 is 15 mm, the angle of the reflection plate 37 with respect to the rotation axis may be switched at ± 0.0067 degrees.
When the optical path shift direction is an oblique direction with respect to the pixel array (see FIG. 7B), as shown in FIG. 25, the rotation axis 37a of the reflection plate 37 is oblique with respect to the projection lens system 214. What should I do?

  The first to third embodiments described above have been described as projectors that project images onto the screen 300 using the projection lens system 214. However, the projectors can be applied to so-called rear projection televisions that combine reflection. The present invention can be applied to a so-called direct-view display device instead of the enlarged projection.

1 is a plan view showing an optical configuration of a projector according to a first embodiment of the invention. FIG. 2 is a block diagram showing an electrical configuration of the projector. It is a figure which shows the structure of the optical path shift element in the projector. It is a figure which shows the operation | movement of the optical path shift in the same optical path shift element. It is a figure which shows the optical path change by an optical path shift. It is a figure which shows the drive signal of the same optical path shift element in relation to a formation image. It is the elements on larger scale of the projection image by an optical path shift. It is the elements on larger scale of the projection image by an optical path shift. It is a figure which shows the structure in the case of enabling adjustment of the optical path shift amount. It is a figure which shows the waveform of the drive signal in the case of enabling adjustment of the optical path shift amount. It is a figure which shows the structure in the case of setting optical path shift amount according to the classification of an image signal. It is a figure which shows another example (the 1) of the drive signal of the same optical path shift element. It is a figure which shows another example (the 2) of the drive signal of the same optical path shift element. It is a top view which shows the optical structure of the projector which concerns on 2nd Embodiment of this invention. FIG. 2 is a block diagram showing an electrical configuration of the projector. It is a figure which shows the structure of the optical path shift device in the projector. It is a figure which shows the drive signal of the same optical path shift device in relation to a formation image. It is the elements on larger scale of the projection image by an optical path shift. It is a figure which shows the drive signal of the optical path shift device in 3rd Embodiment. It is the elements on larger scale of the projection image in the projector. It is the elements on larger scale of the projection image in the projector. It is the elements on larger scale of the projection image in the projector. It is a figure which shows the example at the time of using refraction as an optical path shift element. It is a figure which shows the example at the time of using reflection as an optical path shift element. It is a figure which shows the rotating shaft of a reflecting plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 (2) ... Projector, 10 (20) ... Optical path shift element, 16 ... Liquid crystal, 18a, 18b (28a, 28b) ... Electrode, 30 ... Optical path shift device, 50 ... Control circuit, 52 ... Operator, 54 ... Discrimination Circuit, 100R, 100G, 100B ... Liquid crystal light bulb, 202 ... Lamp unit, 214 ... Projection lens system, 300 ... Screen

Claims (15)

A spatial light modulator that modulates light according to an image input signal;
An optical path shift element for shifting the optical path of the modulated light by the spatial light modulator;
A display device for displaying an image based on the modulated light shifted by the optical path shift element,
The optical path shift element is
The liquid crystal sandwiched between the translucent substrates is composed of liquid crystal functional elements in which the average inclination angle of the liquid crystal molecules changes according to the applied electric field, and the applied electric field is applied within a period in which the spatial modulator displays the same or continuous frames. A display device characterized by being changed. The display device according to claim 1,
A display device comprising adjusting means for adjusting the shift amount. The display device according to claim 1 or 2,
A display device comprising: means for switching the shift amount according to the image input signal. The display device according to any one of claims 1 to 3,
The spatial light modulator has a plurality of pixels having a shape having at least one side,
The display device, wherein the optical path shift element shifts the optical path of the modulated light so that a displayed image is deviated in a direction of one side of the pixel or in a direction perpendicular to the one side direction. The display device according to any one of claims 1 to 3,
The spatial light modulator has a plurality of pixels having a shape having at least one side,
The display device characterized in that the optical path shift element shifts the optical path of the modulated light so that a pixel to be displayed is displaced obliquely with respect to one side direction of the pixel. The display device according to any one of claims 1 to 3,
The spatial light modulator has a plurality of pixels having a shape having at least one side,
The display device characterized in that the optical path shift element shifts the optical path of the modulated light so that a pixel to be displayed is displaced in two or more directions different from one side direction of the pixel. The display device according to claim 6,
A display device comprising: an optical path shift device in which two optical path shift elements having different optical path shift directions are arranged in series on an optical path. The display device according to claim 1, wherein the optical path shift element is
A pair of translucent substrates;
A liquid crystal composed of a chiral smectic C phase having a homeotropic orientation filled between the pair of translucent substrates;
Electric field applying means for applying an electric field to the liquid crystal;
A display device comprising: The display device according to claim 8, wherein
The display device characterized in that the electric field applying means makes variable the strength of the electric field applied to the liquid crystal. The display device according to any one of claims 1 to 9,
The display device, wherein the spatial light modulator is a transmissive liquid crystal display element. The display device according to any one of claims 1 to 9,
Resolution conversion means for converting the number of pixels of the image defined by the image input signal into the number of pixels of the display image of the spatial light modulator;
The spatial light modulator displays an image in which the number of pixels is converted by the resolution conversion means. A display device according to any one of claims 1 to 11,
A light source that emits visible light;
An illumination optical system for irradiating the spatial light modulator with light emitted from the light source;
Projection means for enlarging and projecting an image based on the modulated light shifted by the optical path shift element;
A projection type display device comprising: A spatial light modulator that modulates light according to an image input signal;
An optical path shift element for shifting the optical path of the modulated light by the spatial light modulator;
A display device for displaying an image based on the modulated light shifted by the optical path shift element,
The optical path shift element is
The display device characterized in that the amount of shift is changed within a period in which the spatial modulator displays the same or continuous frames. A spatial light modulator that modulates light according to an image input signal;
A liquid crystal sandwiched between the translucent substrates is composed of a liquid crystal functional element in which an average inclination angle of the liquid crystal molecules changes by an applied electric field, and an optical path shift element that shifts an optical path of modulated light by the spatial light modulator;
A display device that displays an image based on the modulated light shifted by the optical path shift element, and a control circuit that controls the shift by the optical path shift element,
A control circuit for an optical path shift element, wherein the applied electric field is changed within a period of the same or consecutive frames in the spatial modulator. A spatial light modulator that modulates light according to an image input signal;
An optical path shift element used in a display device having an optical path shift element that shifts an optical path of modulated light by the spatial light modulator,
The optical path shift element is composed of a liquid crystal functional element in which the liquid crystal sandwiched between the translucent substrates changes the average tilt angle of the liquid crystal molecules by an applied electric field, and the same or continuous frame period in the spatial light modulator. An optical path shift element characterized by having control means for controlling the applied electric field to change.

Images