JP2006003654A - Image display device and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device, with which lowering of the utilization factor of the light caused by light shielding, also lowering of the contrast caused by correction panel insertion, difficulty in manufacture, and the tendency for enlargement of the device are solved, and an image display method. <P>SOLUTION: The image display device is equipped with first and second lighting optical systems 21, 22 taking on mutually different polarization states, and a means 20 for switching lighting switching the light from them, based on time and illuminating an image display element 1. Directions of laser beams emitted by first and second light sources 23, 24 of the first and second lighting optical systems 21, 22 are set so as to take on polarization directions shown in optical paths in the figure. A lighting light beam, from the first lighting optical system 21, passes through a polarization beam splitter 27 and that from the second lighting optical system 22 is reflected by the polarization beam splitter 27, and consequently, either of the lighting light beams arrives at the image display element 1. The means 20 for switching lighting controls on and off of the first and second light sources 23, 24 by switching them, in synchronization with an image rewrite timing of the image display element 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display apparatus and an image display method using an image display element made of a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

  Image display elements using ferroelectric liquid crystals or antiferroelectric liquid crystals are widely researched and developed because they can be driven at higher speeds than image display elements using nematic liquid crystals. It has become. On the other hand, an image display device using ferroelectric liquid crystal or anti-ferroelectric liquid crystal is good because an ionic substance is generated if a direct current (DC) component remains in the applied voltage when the liquid crystal is driven by an electric field. Is known to hinder proper driving. Therefore, the conventional image display device using the ferroelectric liquid crystal or the anti-ferroelectric liquid crystal divides one frame as a time unit of image display into two subframes and responds to the image display signal in half time. The emitted light from the image display element is emitted so that the observer can visually recognize the applied voltage (+ V), and the remaining half of the time is shielded while applying a voltage (-V) having a polarity opposite to the applied voltage. (For example, refer nonpatent literature 1).

In another conventional image display device, a display panel as an image display element and a correction panel are provided in this order between a first polarizing plate and a second polarizing plate, and a polarization plane of image light emitted from the display panel is provided. Switching is performed by a correction panel (see, for example, Patent Document 1).
Hirokazu Furuta, Jun Xu, Shunsuke Kobayashi, `` Electro-optic properties of an intrinsic half-V-mode FLCD and its application to field-sequential full color LCDs using a poly-Si TFT matrix array, Journal of the SID '' V. 11 , No. 3, 2003, P. 433 JP 2003-121872 A

  However, among the conventional image display devices described above, the former image display device has an advantage that a high-contrast image can be obtained with a relatively simple structure, but light use efficiency is substantially halved by light shielding. There was a problem such as. Further, in the latter image display device, it is difficult to manufacture a correction panel that can switch the polarization plane with high accuracy over the entire visible light range, and not only it tends to cause a decrease in contrast, but also the correction panel. Is inserted between the image display element and the projection lens, there is a problem that the back focus length of the projection lens becomes long and the projection lens becomes large.

  The present invention has been made in order to solve the conventional problems, and prevents a decrease in light utilization efficiency due to light shielding, as well as a decrease in contrast due to insertion of a correction panel, difficulty in manufacturing, and large size of the apparatus. An object of the present invention is to provide an image display device and an image display method that can eliminate the problem.

  The image display device of the present invention according to claim 1 includes a pair of substrates at least one of which is transparent, and a ferroelectric liquid crystal or anti-strength which is provided between the substrates and whose orientation direction is switched in a plane parallel to the substrate. An image display element having a liquid crystal layer made of a dielectric liquid crystal and an image electrode element provided on the liquid crystal layer side of a transparent substrate and switching the arrangement direction of the ferroelectric liquid crystal or the antiferroelectric liquid crystal according to an image display signal In the image display device that displays the image by illuminating the image display element with illumination light that changes the polarization state from the light source of the illumination optical system, the emission image before and after the polarity reversal of the image display element in the illumination optical system It has a configuration provided with a polarization state switching means for temporally switching the polarization state of incident light incident on the image display element so that the polarization state of the light becomes the same.

  According to a second aspect of the present invention, in the image display device according to the first aspect, the polarization state switching means temporally switches between the plurality of illumination optical systems having different polarization states and the illumination light of the illumination optical system. And an illumination switching means for illuminating the image display element.

  According to a third aspect of the present invention, in the image display device according to the second aspect, the light sources of the plurality of illumination optical systems having different polarization states are solid-state lasers.

  According to a fourth aspect of the present invention, in the image display device according to the first aspect, the polarization state switching means switches the orientation direction in a plane parallel to the transparent substrate provided between the pair of transparent substrates and the transparent substrate. The optical element includes a liquid crystal layer made of ferroelectric liquid crystal or anti-ferroelectric liquid crystal, and an electrode provided on the inner surface side of the transparent substrate to switch the orientation direction of the liquid crystal layer according to a frame signal.

  According to a fifth aspect of the present invention, in the image display device according to the first aspect, the polarization state switching means includes a plurality of polarizing filter surfaces having different polarization directions which are the incident surface and the exit surface of the illumination light, and are rotated. Arranged between the light source and the image display element with the center facing the direction orthogonal to the optical axis of the illumination light, rotated at a rotational speed synchronized with the frame frequency, and the incident surface and the exit surface of the illumination light beam It has a configuration including a polygonal polarizing filter that switches the polarization state by changing the combination.

  According to a sixth aspect of the present invention, in the image display device according to the fifth aspect of the present invention, the polygonal polarizing filter has a configuration in which there are four polarizing filter surfaces.

  According to a seventh aspect of the present invention, in the image display device according to the fifth or sixth aspect, the timing at which the polarization state of the light incident on the pixels on the image display element is switched by the polygonal polarization filter and the image display signal are used. It has a configuration in which the pixel rewriting timing coincides.

  According to an eighth aspect of the present invention, in the image display device according to any one of the first to seventh aspects, the position of the emitted light from the image display element is displaced for each of a plurality of subframes constituting one image frame. The optical path deflecting means for displaying the image display element by increasing the number of apparent pixels is provided.

  The image display element of the invention according to claim 9 is the image display element used in the image display device according to any one of claims 1 to 8, wherein the pair of substrates are both transparent substrates. It has a configuration provided with a condensing element that is provided on the incident light side upper part of each pixel of the element and condenses illumination light at the center of the pixel.

  The image display method of the present invention according to claim 10 includes a pair of substrates at least one of which is transparent, and a ferroelectric liquid crystal or anti-strength which is provided between the substrates and whose orientation direction is switched in a plane parallel to the substrate. An image display element having a liquid crystal layer made of a dielectric liquid crystal and a pixel electrode provided on the liquid crystal layer side of a transparent substrate and switching the arrangement direction of the ferroelectric liquid crystal or the antiferroelectric liquid crystal according to an image display signal In an image display method for displaying an image by illuminating the image display element with illumination light that changes the polarization state from the light source of the illumination optical system, the polarization state of incident light incident on the image display element is switched over time Accordingly, the polarization state of the emitted image light before and after the polarity inversion of the image display element is made to be the same.

  According to an eleventh aspect of the present invention, in the image display method according to the tenth aspect, the illumination light irradiated from a plurality of illumination optical systems having different polarization states is temporally switched to enter the image display element. The polarization state of incident light to be switched is switched.

  According to a twelfth aspect of the present invention, in the image display method according to the eleventh aspect, the light sources of the plurality of illumination optical systems having different polarization states are solid-state lasers.

  According to a thirteenth aspect of the present invention, in the image display method according to the tenth aspect, the switching of the polarization state of incident light incident on the image display element is provided between the pair of transparent substrates and the transparent substrate. A liquid crystal layer made of a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal whose orientation direction is switched in a plane parallel to the surface, and an electrode provided on the inner surface side of the transparent substrate to switch the orientation direction of the liquid crystal layer according to a frame signal It has the structure performed by the optical element which has these.

  According to a fourteenth aspect of the present invention, in the image display method according to the tenth aspect, the polarization state of the incident light incident on the image display element is changed to a plurality of different polarized lights that become the incident surface and the exit surface of the illumination light. Is formed between the light source and the image display element in a state where the center of rotation faces the direction orthogonal to the optical axis of the illumination light, and is rotated at a rotation speed synchronized with the frame frequency. It has a configuration that is performed by a polygonal polarizing filter that switches the polarization state by changing the combination of the incident surface and the exit surface of the illumination light beam.

  A fifteenth aspect of the present invention is the image display method according to the fourteenth aspect, wherein the polyhedral polarizing filter has four polarizing filter surfaces.

  According to a sixteenth aspect of the present invention, in the image display method according to the fourteenth or fifteenth aspect, the timing at which the polarization state of light incident on the pixel on the previous image display element is switched by the polygonal polarization filter, and the image display signal The configuration is such that the pixel rewriting timing according to is consistent with the pixel rewriting timing.

  According to a seventeenth aspect of the present invention, in the image display method according to any one of the tenth to sixteenth aspects, the position of the emitted light from the image display element is displaced for each of a plurality of sub-frames constituting one image frame. The image display element has a configuration in which the number of apparent pixels is increased for display.

  The invention according to claim 18 is the image display method using the image display element according to any one of claims 10 to 17, wherein the pair of substrates are both transparent substrates. It has a configuration including a condensing element that is provided on the incident light side of the pixel and condenses the illumination light at the center of the pixel.

  According to the image display device of the first aspect of the present invention, it is possible to prevent the light use efficiency from being lowered due to light shielding, and to reduce the contrast, difficulty in manufacturing, and enlargement of the projection lens due to the insertion of the correction panel. Can be eliminated.

  According to the second aspect of the present invention, a good polarization state can be obtained over the entire visible light region.

  According to the third aspect of the invention, since the solid-state laser is linearly polarized in the emission state, an illumination optical system can be constructed without any polarization conversion loss. In addition, a wide color reproduction range can be obtained by a fixed laser, and an image display device having excellent color rendering properties compared to the case of using a lamp light source can be configured.

  According to the invention of claim 4, the liquid crystal alignment direction in the optical element is set in accordance with the vibration direction or rotation direction of the polarized light incident on the optical element and is switched over time, so that the polarization state is temporally changed. Illumination light for switching between the two can be formed. In this case, an illumination optical system having substantially the same size as that of a conventional image display device using a lamp can be obtained.

  According to the fifth aspect of the present invention, when the image display element is driven line-sequentially, the rewriting timing of the image can be matched with the switching timing of the polarization state of the illumination, and the contrast can be further improved. Can do.

  According to the sixth aspect of the present invention, the polarization state switching means can be made compact with the smallest number of polarization planes, and as a result, the entire apparatus can be miniaturized. Moreover, since the shape is a rectangular parallelepiped shape, processing is easy and cost can be reduced.

  According to the seventh aspect of the present invention, it is possible to make the image rewriting timing coincide with the switching timing of the polarization state of the illumination, and the contrast can be further improved.

  According to the eighth aspect of the present invention, by using an image element that can be switched at high speed, the contrast of the image can be improved and the light utilization efficiency can be increased. In particular, when a transmissive image display element is used, it is not necessary to insert a polarizing beam splitter or the like between the optical path deflecting means and the image display element, and the enlargement of the optical path deflecting means can be suppressed.

  According to the invention of claim 9, the illumination range of each pixel liquid crystal part of the image display element can be smaller than the pixel range, and the illumination light can be transmitted without being blocked by the non-transparent part such as a liquid crystal driving transistor. The light utilization efficiency can be improved, the contrast can be improved by the high-speed driving characteristics, and the overlap between the pixels when the apparent number of pixels is increased can be easily avoided.

  According to the image display method of the present invention as set forth in claim 10, while preventing a decrease in light utilization efficiency due to light shielding, a decrease in contrast due to insertion of a correction panel, difficulty in production, and a large projection lens Can be eliminated.

  According to the eleventh aspect of the present invention, a good polarization state can be obtained over the entire visible light range.

  According to the invention described in claim 12, since the solid-state laser is linearly polarized in the emission state, an illumination optical system can be constructed without any polarization conversion loss. In addition, a wide color reproduction range can be obtained by a fixed laser, and an image display method having excellent color rendering properties compared to the case of using a lamp light source can be configured.

  According to the invention of claim 13, the liquid crystal alignment direction in the optical element is set in accordance with the vibration direction or the rotation direction of the polarized light incident on the optical element and is switched over time, so that the polarization state is temporally changed. Illumination light for switching between the two can be formed. In this case, an illumination optical system having substantially the same size as that of a conventional image display device using a lamp can be obtained.

  According to the fourteenth aspect of the present invention, when the image display element is line-sequentially driven, the image rewriting timing and the illumination polarization state switching timing can be matched, thereby further improving the contrast. Can do.

  According to the fifteenth aspect of the present invention, the polygonal polarizing filter can be made compact with the smallest number of polarization planes, and as a result, the entire apparatus can be miniaturized. Moreover, since the shape is a rectangular parallelepiped shape, processing is easy and cost can be reduced.

  According to the sixteenth aspect of the present invention, the image rewriting timing and the illumination polarization state switching timing can be matched, and the contrast can be further improved.

  According to the seventeenth aspect of the present invention, it is possible to improve the contrast of an image and increase the light utilization efficiency by using an image element that can be switched at high speed. In particular, when a transmissive image display element is used, it is not necessary to insert a polarizing beam splitter or the like between the optical path deflecting means and the image display element, and the enlargement of the optical path deflecting means can be suppressed.

  According to the invention described in claim 18, since the illumination range of each pixel liquid crystal portion of the image display element can be made smaller than the pixel range, and the illumination light can be transmitted without being blocked by a non-transparent portion such as a liquid crystal driving transistor. The light utilization efficiency can be improved, the contrast can be improved by the high-speed driving characteristics, and the overlap between the pixels when the apparent number of pixels is increased can be easily avoided.

  Hereinafter, an image display device and an image display method according to embodiments of the present invention will be described with reference to the drawings. In the following embodiments, substantially the same parts are denoted by the same reference numerals, and description thereof is omitted.

  First, the configuration of a pixel display element used in an image display device will be described with reference to FIG. 1A is a plan view of the image display element 1, and FIG. 1B is a side sectional view of the image display element 1. FIG. As shown in the figure, the image display element 1 has a plurality of pixels 1a arranged two-dimensionally, and a pixel electrode 3 capable of independently applying a voltage to the liquid crystal layer 5 is provided for each pixel 1a. Yes.

  The liquid crystal layer 5 is made of a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal, and is sandwiched between a pair of transparent substrates 2a and 2b. Of the pair of substrates 2a and 2b, on the surface of the substrate 2a on the incident light side on the liquid crystal layer 5 side, the pixel electrode 3 made of a transparent conductive material is provided over the entire image display region of the pixel display element 1. The counter electrode 4 made of a transparent conductive material is provided on the entire surface of the image display area of the pixel display element 1 on the surface of the substrate 2b on the outgoing light side on the liquid crystal layer 5 side. Depending on the image display device, an alignment film for aligning the liquid crystal in a predetermined direction and a spacer for keeping the thickness of the liquid crystal layer uniform may be used, but these are omitted in FIG.

  As the incident light, linearly polarized light, circularly polarized light or the like is used, and the light is emitted through the liquid crystal layer 5 whose polarization state is changed by an applied voltage. A polarization filter is provided on the outgoing light side of the image display element 1, and the change in the polarization state is replaced with the change in the light amount and projected onto the screen.

  Here, the image display device of the present invention may be any device as long as it can illuminate the image display element 1 and use the emitted light as image light, regardless of the viewer's visual form. That is, in the case of a front type that visually recognizes an image from the same side as the projection optical system with respect to the screen, and in the case of a rear type that visually recognizes an image from the opposite side of the projection optical system relative to the screen However, in the image display apparatus of the present invention, either projection type is applicable. Further, the present invention is applicable even to a non-projection type in which an observer visually recognizes an aerial image without projecting on a screen.

  FIG. 2 is an enlarged view of one pixel 1a of the image display element 1 and shows an alignment state of liquid crystal in the pixel 1a. As the image display element 1, it is also possible to use either a smectic C liquid crystal classified as a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal.

  A smectic liquid crystal is a liquid crystal molecule in which the major axis direction of the liquid crystal molecules is arranged in a layered manner, and the normal direction (layer normal direction) of this layer coincides with the major axis direction of the liquid crystal molecule. Is called a smectic A phase, and a liquid crystal in which the normal direction of the layer does not coincide with the major axis direction of the liquid crystal molecule is called a chiral smectic C phase. The chiral smectic C-phase ferroelectric liquid crystal generally has a so-called spiral structure in which the direction of the liquid crystal director rotates spirally for each layer in the state where no external electric field is applied. In the chiral smectic C reciprocal ferroelectric liquid crystal, the liquid crystal directors face each other in the respective layers. Such a spiral pitch of the spiral structure is called a smectic layer pitch.

  Here, if the thickness of the liquid crystal layer of the chiral smectic C phase is set so thin that the liquid crystal molecules cannot take a helical structure, the liquid crystal molecules in the liquid crystal layer are regulated by the molecular major axis direction at the interface of the liquid crystal layer. It will take the same direction. These liquid crystal molecules have asymmetric carbon in the molecular structure, and as a result of spontaneous polarization by the asymmetric carbon, the liquid crystal molecules are rearranged in a direction determined from the spontaneous polarization Ps and the external electric field E. Therefore, the optical characteristics can be controlled.

  The structure of the chiral smectic C-phase ferroelectric liquid crystal is composed of a main chain, a spacer, a skeleton, a bonding part, a chiral part, and the like. As the main chain structure, polyacrylate, polymethacrylate, polysiloxane, polyoxyethylene and the like can be used. The spacer binds a skeleton, a bonding part, and a chiral part that are responsible for molecular rotation to the main chain, and a methylene chain having an appropriate length is selected. In addition, a —COO— bond or the like is selected as a bond portion that connects the chiral portion and a rigid skeleton such as a biphenyl structure.

  FIG. 2 shows a change in the orientation direction of the liquid crystal molecules 5a when the direction of the electric field is changed in the vertical direction with respect to the paper surface. Here, it is assumed that the liquid crystal has a negative spontaneous polarization Ps. Although the liquid crystal shows a so-called bistable direction here, even a liquid crystal in a monostable direction can be used without any problem. In the figure, the inversion center 8 is a direction perpendicular to the layer surface of the smectic layer in which the liquid crystal molecules 5a are arranged between the one-dot chain line 6 and the one-dot chain line 7, and the same angle ("cone" The liquid crystal molecules 5a are stabilized in a state in which the angle is referred to as “left and right”.

  Here, when the cone angle θ is set to 22.5 degrees and there is a relationship of Δn · d = λ / 2 between the refractive index difference Δn of the liquid crystal at a certain wavelength λ and the liquid crystal layer thickness d, the incident light How the polarization state changes will be described.

  The traveling direction of the illumination light and the polarization direction before incidence are set as shown in FIG. That is, the polarized light is linearly polarized light and is in the longitudinal direction parallel to the major axis direction of the liquid crystal molecules 5a. In this case, the linearly polarized light is emitted while maintaining the polarization state in the vertical direction without feeling the refractive index anisotropy of the liquid crystal molecules 5a. On the other hand, in the case of the figure (b) in which the major axis direction of the liquid crystal molecules 5a and the linearly polarized light have an inclination of 45 degrees, the phase shift is caused by a component perpendicular to the major axis of the liquid crystal molecules 5a and a component perpendicular to the major axis of the liquid crystal molecules 5a. Occurs, and a phase shift of λ / 2 occurs while passing through the liquid crystal layer. In other words, rotation of the polarization plane occurs, and as a result, the incident light is emitted in a state inclined at a right angle from the polarization plane. In this case, if a polarizer having a transmission axis parallel to the polarization direction of the incident light is provided on the outgoing light side, bright display is obtained in the state of FIG. 5A and dark display is obtained in the state of FIG. Will be.

  Next, polarity inversion of the ferroelectric liquid crystal and the antiferroelectric liquid crystal will be described. Polarity reversal is a driving method performed to eliminate a problem caused by the DC component remaining in the voltage during driving of the ferroelectric liquid crystal or the anti-ferroelectric liquid crystal. Here, in order to understand the polarity inversion method, the polarity inversion that has been conventionally used will be described with reference to the two methods shown in FIGS. 3 and 4, and then each of the present invention will be compared with these. The features will be described for each embodiment.

  FIG. 3 is a time chart for explaining a method using light shielding for displaying an image while reversing the polarity.

  That is, in this polarity reversal, as shown in the figure, the illumination light is set so that the illumination period and the light shielding period have the same time length during one frame Tf as a time unit of image display. In the illumination period, the period T1 of the liquid crystal drive signal on is a “bright” display period, and the period T2 of the liquid crystal drive signal off is a “dark” display period. Note that the length of the period T1 of the liquid crystal drive signal on is determined by the gradation information of the display image.

  On the other hand, the light-shielding period is a period provided for reversing the polarity of the liquid crystal because the illumination light is shielded so that the liquid crystal drive signal off period T1 ′ and the liquid crystal drive signal on period T2 are provided. 'Is set to have the same length as the periods T1 and T2, respectively. As a result, the voltages of the period T1 and the period T1 ′ and the period T2 and the period T2 ′ are neutralized on average, and the DC component is eliminated. As described above, in the polarity inversion, the DC component is canceled by applying the reverse polarity voltage for the same time as the voltage for displaying the image.

  FIG. 4 is different from FIG. 3 in that polarity inversion is possible without using light shielding, and an example using a correction panel is shown. In the figure, the illumination light is directed from left to right, and the image display element 1 and the correction panel 13 are arranged in this order with respect to the light traveling direction between the first polarizing plate 11 and the second polarizing plate 12. . If the orientation direction of the correction panel 13 is changed while synchronizing the polarity of the image display element 1, an image can be displayed without reducing the light use efficiency as in the case of using the light shielding in FIG. 3. It becomes possible.

  Hereinafter, image display devices according to embodiments of the present invention will be described with reference to the drawings.

[Example 1]
FIG. 5 shows the configuration of the image display apparatus according to the first embodiment of the present invention.

  The image display device switches the light of the first illumination optical system 21 and the second illumination optical system 22 having different polarization states, and the light of the first and second illumination optical systems 21 and 22 in time to change the image display element 1. And illumination switching means 20 for illuminating. Here, different polarization states refer to polarization states in which the alignment state can be changed by switching the liquid crystal alignment direction of the image display element 1, such as the vibration direction of linearly polarized light and the rotational direction of circularly polarized light. The first and second illumination optical systems 21 and 22 and the illumination switching unit 20 constitute the polarization state switching unit of the present invention.

  The first and second illumination optical systems 21 and 22 have a first light source 23 and a second light source 24 for emitting lasers, respectively, so that their orientations are taken in advance so as to take the polarization directions shown in the optical path in the drawing. Is set. The light emitted from the first light source 23 and the second light source 24 is a collimator lens 25, an integrator (not shown) for obtaining a uniform light amount distribution, a diffusion plate (not shown) for suppressing speckle patterns, and the like. Thus, it is generated as illumination light having a uniform light amount distribution within a predetermined range.

  The polarized illumination light from the first light source 23 is incident on the polarization beam splitter (PBS) 27 disposed behind the first light source 23 as p-polarized light and passes through the PBS 27. On the other hand, the polarized light from the second light source 24 is incident as s-polarized light on the PBS 27 disposed behind the second light source 24 and reflected by the PBS 27. Thus, the illumination light from the first illumination optical system 21 passes through the PBS 27 and the illumination light from the second illumination optical system 22 is reflected by the PBS 27, so that any illumination light reaches the image display element 1. .

  The illumination switching unit 20 switches on and off the first light source 23 and the second light source 24 in synchronization with the image rewriting timing of the image display element 1. For example, as shown in FIG. 6, three primary colors (red R, green G, and blue B) are arranged in the first light source 23 and the second light source 24, respectively, and are driven in a field sequential manner. That is, when performing such field sequential driving while inverting the polarity, in order to reduce the color break, the order is not 1R → 2R → 1G → 2G → 1B → 2B →... 1R as shown in FIG. It is preferable to drive in the order of 1G → 1B → 2R → 2G → 2B →.

  Even if the polarity of the liquid crystal drive signal is reversed and the liquid crystal alignment direction is reversed as described above, bright display can be performed for the same time (for example, T1 and T1 ′ in FIG. 6) before and after the polarity reversal. This will be described with reference to FIGS.

  In FIG. 2, the incident polarized light is set in the vertical direction, but in the case of FIG. 2A, since the emitted light is also vertically polarized light, this light is brightened by the polarizer provided behind the image display element. It was mentioned above that it becomes a display. This corresponds to the case where the on (+ V) voltage of the liquid crystal drive signal in FIG. 6 generates an electric field in the same direction as the electric field direction shown in FIG. 2A, and the liquid crystal is in this state during the period T1. Display.

  On the other hand, in the case of FIG. 2B, since the emitted light is laterally polarized, this light is darkly displayed by the polarizer provided behind the image display element. This corresponds to the state of the liquid crystal in the period T2 in FIG. 6, and dark display is performed in the period T2. Here, it is assumed that the first illumination optical system 21 in FIG. 5 illuminates the image display element 1, and the polarization direction thereof is the vertical direction in FIG. In the state of the period T1 ′, the liquid crystal state is the same as that in FIG. 2B, but the direction of the incident polarized light becomes the horizontal direction by the second illumination optical system 22 in FIG. The vertical direction. In other words, the polarization state of the emitted light during this period is equal to the polarization state during the period T1, resulting in bright display. Similarly, in the period T2 ′, the liquid crystal state is the same as in FIG. 2A, but since the direction of incident polarized light is the horizontal direction, the emitted polarized light remains in the horizontal direction, The polarization state of the emitted light is equal to the polarization state in period T2.

As described above, in the image display apparatus according to the first embodiment, it is possible to output a desired amount of light set by T1 and T1 ′ (where T1 ′ = T1) while performing polarity inversion. Therefore, the light utilization efficiency can be improved compared to the case shown in FIG.
[Example 2]
FIG. 7 shows the configuration of the image display apparatus of Example 2 according to the present invention.

  In this embodiment, the light source 30 is the same as the first light source 23 in FIG. A polarization state switching optical element 32 is disposed between the collimating lens 31 behind the light source 30 and the image display element 1 behind the light source 30. This polarization state switching optical element 32 constitutes the polarization state switching means of the present invention, and is provided between a pair of transparent substrates and these transparent substrates in parallel with the substrate, as shown in FIG. A liquid crystal layer composed of a ferroelectric liquid crystal or an antiferroelectric liquid crystal whose orientation direction can be switched in the plane, and an electrode provided on the inner surface side of the transparent substrate for switching the alignment direction of the liquid crystal layer according to a frame signal. Yes.

  The arrangement of the liquid crystals in the polarization state switching optical element 32 is the same as that shown in FIG. The function is to make the polarization direction of the illumination light incident on the polarization state switching optical element 32 coincide with the timing of polarity inversion and rotate it by 90 degrees. Except for switching all over the entire surface, the liquid crystal in the pixel in FIG. Since this operation is the same as that in FIG.

  When the image display element 1 is line-sequentially driven, an extremely good image can be obtained by matching the image rewriting timing with the polarization state switching timing, and the electrodes shown in FIG. It may be divided into several strip electrodes parallel to the sub-scanning direction so that the voltage inversion timing of the strip electrodes matches the image rewriting timing.

  FIG. 8 shows a time chart of the illumination light from the light source 30, the liquid crystal drive signal of the polarization state switching optical element 32, and the liquid crystal drive signal of the image display element 1.

  When both the liquid crystal drive signal of the polarization state switching optical element 32 and the liquid crystal drive signal of the image display element 1 are on, the linearly polarized light from the light source 30 proceeds without rotating and provides a bright display. When the liquid crystal drive signal of the polarization state switching optical element 32 is off and the liquid crystal drive signal of the image display element 1 is on, the polarized light emitted from the polarization state switching optical element 32 is rotated by 90 degrees, and the image display element 1 Then, since the polarized light is transmitted while maintaining this polarization state, a dark display is obtained. When the liquid crystal drive signal of the polarization state switching optical element 32 is on and the liquid crystal drive signal of the image display element 1 is off, the polarized light emitted from the polarization state switching optical element 32 is transmitted without rotating, and the image Since the display element 1 is rotated 90 degrees, dark display is performed. When both the liquid crystal drive signal of the polarization state switching optical element 32 and the liquid crystal drive signal of the image display element 1 are off, the polarized light emitted from the polarization state switching optical element 32 is rotated by 90 degrees, and the image display element Since 1 is further rotated 90 degrees, a bright display is obtained.

  7 and 8, three color lasers are used for the light source 30, but field sequential color generation by a rotating color wheel or the like may be performed using a lamp light source.

As described above, the image display apparatus according to the second embodiment can output a desired light amount set by T1 and T1 ′ (T1 ′ = T1) while performing polarity inversion. Since light shielding is not required as compared with the above example, light utilization efficiency can be improved. Further, since there is no correction panel between the image display element 1 and the projection lens 28 (not shown in FIG. 4) located at the end in the light traveling direction, the contrast is reduced as compared with the configuration of FIG. Can be suppressed.
[Example 3]
FIG. 9 shows the configuration of the image display apparatus according to the third embodiment.

  In the image display apparatus according to the third embodiment, a light source that emits non-polarized light, such as a high-pressure mercury lamp, is applied as the light source 40 of the illumination optical system. The light emitted from the light source 40 is time-divisionally divided into three or more colors by the rotating color wheel 41 and the like, and after the illumination angle is adjusted by the collimating lens 42, the light is incident on the polygonal polarizing filter 43. The polygonal polarizing filter 43 is a polygonal columnar rotating body in which polarizing filters in different directions are periodically provided. The polygonal polarizing filter 43 is provided in a state in which the rotation faces a direction orthogonal to the optical axis of the illumination light, and the frame frequency and The illumination light is rotated at a synchronized rotational speed, and illumination light also has a function of switching the polarization state by a combination of the entrance surface and the exit surface of the polygonal polarizing filter 43 through which light enters and exits. Therefore, the polygonal polarizing filter 43 constitutes the polarization state switching means of the present invention. A fly-eye lens or the like for improving the uniformity of illumination light may be provided before and after the polygonal polarizing filter 43. The light emitted from the polygonal polarizing filter 43 is incident on the image display element 1 through the condenser lens 44, exits from here, and passes through the projection lens 28.

  10 and 11 show examples of the surface structure of the polygonal polarizing filter 43. FIG. When the linearly polarized light is incident, the polygonal polarizing filter 43 needs to set the transmission axes of the entrance surface and the exit surface in parallel, and thus the number of surfaces is set to be a multiple of four. For example, the polygonal polarizing filter 43 in FIG. 10 is formed in a quadrangular prism shape such that the polarizing filter surfaces 43a, 43b,... Are four, and the polygonal polarizing filter 45 in FIG. 45a, 45b, 45c,... Are formed in an octagonal column shape such that there are eight sides. Comparing these, the latter is more advantageous than the former when switching the polarizing filter surface particularly at high speed, and this tendency becomes stronger as the number of surfaces increases. On the other hand, the former has the advantage that it is possible to reduce the size while using the polarization plane of the same area, and to save the space of the apparatus. In general, since an image display device is driven at a driving frequency of several tens of Hz, there is no problem even with four polarization planes in terms of speed. Therefore, a four-sided polygonal polarization filter is usually used. Is preferred.

  FIG. 12 is a diagram conceptually illustrating the function of the polygonal polarizing filter 43. The polygonal polarization filter 43 is positioned in the illumination optical path, and is rotated as shown in FIGS. The polarizing filter shown in FIG. 10 is provided on the surface of the polygonal polarizing filter 43. In the state of FIG. 12A, the polarizing filter located on the incident surface and the exit surface of the illumination light and the optical axis are perpendicular, and all the illumination light is incident from one surface (incident surface 50a). The light exits from (exit surface 50b). By providing a polarizing filter having a transmission axis in the vertical direction on the incident surface 50a and the output surface 50b, only polarized light in the vertical direction is emitted. Similarly, in the state of (c) in the same figure, only the component in the horizontal direction is shot. In the state shown in FIG. 5B, both the incident surfaces 51a and 52a and the emission surfaces 51b and 52b extend over two surfaces. Since the polarizing filter has a longitudinal transmission axis at the first incident surface 51a, only the longitudinal component is transmitted. However, this light is refracted according to the refractive index of the transparent material inside the polyhedral polarizing filter 43 and is transmitted through the first exit surface. 51b. Since the first exit surface 51b transmits longitudinally polarized light in the same manner as the first entrance surface 51a, the exit light has only the longitudinally polarized light component. Since the polarizing filter has a horizontal transmission axis at the second incident surface 52a, only the component in the horizontal direction is transmitted. Similarly to the above, this light is refracted according to the refractive index of the polygonal polarizing filter 43, and the second output surface. 52b. Similarly to the second incident surface 52a, the second emission surface 52b transmits laterally polarized light, and thus the emitted light has only a laterally polarized component.

  As shown in FIG. 9, by appropriately setting the power of the condenser lens 44 arranged behind the polygonal polarizing filter 43, the polarization direction of the illumination light reaching the image display element 1 changes sequentially from top to bottom. It will be.

  As shown in FIG. 12D, when the image display element 1 is line-sequentially driven, an extremely good image is obtained by matching the polarization state switching timing with the image rewriting timing. be able to.

  Here, the non-polarized illumination light is made incident on the polygonal polarizing filter 43. However, even if it is linearly polarized incident light, the polygonal polarizing filter 43 can be used. An example is shown.

  In the figure, a quarter wavelength filter is provided as a polygonal polarizing filter 43 on a surface located on the first incident surface 51a and the first exit surface 51b, and on a surface located on the second entrance surface 52a and the second exit surface 52b. Is provided with an isotropic medium equivalent to the transmittance of the ¼ wavelength filter. As a result, the illumination light incident from the first incident surface 51a becomes circularly polarized light in the polygonal polarizing filter 43, and after passing through the first output surface 51b, the polarization surface becomes linearly polarized light that is 90 degrees different from the incident light. The illumination light incident from the second incident surface 52a exits from the second exit surface 52b without changing its polarization state.

  In addition, as a method for converting non-polarized illumination light such as a lamp light source into linearly polarized light, it has been conventionally proposed to use a polarization conversion element, which can also be used in the present image display apparatus.

  Next, an image display apparatus according to another embodiment of the present invention will be described with reference to the drawings. In this image display device, a reflective image display element 10 is used, and its configuration is shown in FIG.

  In this image display apparatus, the illumination optical system changes the power of the condenser lens 44 for illuminating the image display element 1 in the illumination optical system of FIG. 9 and adjusts the back focus length of the projection lens 28. It is possible to configure. Thus, it is also possible to obtain an image display device using the reflective image display element 10.

As shown in FIG. 15, the image apparatus of the present embodiment separates light illumination from the light source 40 into three colors by dichroic mirrors 49a4, 9b, and 49c, and then changes the polarization state by polygonal polarizing filters 43a, 43b, and 43c. After switching and transmitting through the condenser lenses 44a, 44b, and 44c, the direction is changed by the dichroic mirrors 50a, 50b, and 50c, and the projection lens 28 is transmitted. Further, a condenser lens 45a and a condenser lens 45b are disposed between the dichroic mirrors 49a and 49b and between the dichroic mirrors 49b and 49c, respectively. By configuring in this way, it is possible to increase the light use efficiency as compared with the image display device using the rotating color wheel of FIG. Here, the polygonal polarization filters 43a, 43b and 43c constitute the polarization state switching means of the present invention. Although not shown here, the image display element is disposed between the dichroic mirror 50 c and the projection lens 28.
[Example 4]
The image display apparatus according to the fourth embodiment shown in FIG. 16 has an optical path deflecting element 47 disposed between the image display element 1 and the projection lens 28 in the illumination optical system shown in FIG. It is the same as that of 9. In the image display device using this illumination optical system, one image frame is constituted by a plurality of sub-frames, and the position of the emitted light from the image display element 1 is displaced for each sub-frame by the optical path deflecting element 47. It is possible to display by increasing the number of pixels that are apparently one. Here, as the optical path deflecting element 47 and its driving method, for example, those described in JP-A-2002-328402 are used. In this case as well, a polygonal polarizing filter 43 as a polarization state switching unit is used.
[Example 5]
As shown in FIG. 17, the image display element of the fifth embodiment is a transmissive image display element 15 mounted on a projection type image display device, and the illumination range of each pixel liquid crystal unit is smaller than the pixel range. In addition, a plurality of lenses 48 as light condensing elements are arranged on the incident-side substrate 2a so as to correspond to each pixel. Other configurations are the same as those in FIG.

  Conventionally, there are transmissive pixel display elements using nematic liquid crystal, but the response speed is several ms to several tens of ms, and the response speed is not sufficient for mounting in the projection type image display apparatus of FIG. It was. The pixel display element made of the ferroelectric liquid crystal or the antiferroelectric liquid crystal targeted at this time has a quick response of several tens μs to several hundreds μs, and is extremely effective in improving contrast. By providing the lens 48 as a condensing element, the illumination light can be transmitted without being blocked by the non-transparent portion such as the liquid crystal driving transistor, so that the light use efficiency can be increased, and the apparent deflection is achieved by the light deflection. It is possible to avoid overlap between pixels when the number of pixels is improved.

  As described above, the image display device and the image display method according to the present invention have effects of preventing a decrease in light utilization efficiency and suppressing a decrease in contrast, difficulty in manufacturing, and an increase in size of the device. It is useful as an apparatus and method for image display and image formation using liquid crystals.

It is the top view and side sectional view of an image display element concerning an embodiment of the invention. FIG. 2 is a diagram for explaining a change in the alignment direction of liquid crystal molecules in accordance with an electric field direction in a pixel of the image display element in FIG. 1. It is a time chart of the liquid crystal drive current for obtaining polarity inversion utilized conventionally. It is explanatory drawing of what is a method of obtaining another polarity reversal utilized conventionally, and uses a correction panel. It is a figure which shows the structure of the image display apparatus of Example 1 which concerns on this invention. 3 is a time chart of a liquid crystal drive signal used in the image display apparatus of Example 1. It is a figure which shows the structure of the image display apparatus of Example 2 which concerns on this invention. 6 is a time chart of a liquid crystal drive signal used in the image display device of Example 2. It is a figure which shows the structure of the image display apparatus of Example 3 which concerns on this invention. It is a perspective view of the polyhedral polarizing filter which has four polarizing filter surfaces used with the image display apparatus of Example 3. FIG. FIG. 10 is a perspective view of a polygonal polarizing filter having eight polarizing filter surfaces used in the image display device of Example 3. It is a figure explaining the relationship between the rotation position of a polygonal polarizing filter, incident light, and outgoing light. It is a figure explaining the relationship between the square body polarizing filter at the time of using non-polarized incident light, incident light, and outgoing light. It is a figure which shows the structure of the reflection type image display apparatus which is another embodiment of this invention. It is a figure which shows the image display apparatus which applied the dichroic mirror which isolate | separates illumination light into three colors to the reflection type image display apparatus of FIG. It is a figure which shows the structure of the image display apparatus of Example 4 which concerns on this invention. It is side surface sectional drawing of the image display element which attached the condensing element of Example 5 which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10, 15 Image display element 1a Pixel 2a, 2b Substrate 3 Pixel electrode 5 Liquid crystal layer 5a Liquid crystal molecule 20 Illumination switching means 21 First illumination optical system 22 Second illumination optical system 23, 24, 30, 40 Light source 27 Polarized beam Splitter 28 Projection lens 32 Polarization state switching optical element 43, 45 Polyhedral polarization filter 43a, 43b, 45a, 45b, 45c Polarization filter surface 48 Lens (light condensing element)
50a, 51a, 52a entrance surface 50b, 51b, 52b exit surface

Claims (18)

A pair of substrates at least one of which is transparent, a liquid crystal layer made of a ferroelectric liquid crystal or an antiferroelectric liquid crystal provided between the substrates and capable of switching the orientation direction in a plane parallel to the substrate, and the transparent An image display element provided on a liquid crystal layer side of a substrate and having a pixel electrode that switches an arrangement direction of the ferroelectric liquid crystal or the antiferroelectric liquid crystal according to an image display signal, and the image display element is optically illuminated In an image display device that displays an image by illuminating with illumination light that changes a polarization state from a light source of the system,
Polarization state switching that temporally switches the polarization state of incident light incident on the image display element so that the polarization state of the output image light before and after the polarity inversion of the image display element is the same in the illumination optical system. An image display device comprising means. The image display device according to claim 1,
The polarization state switching means includes a plurality of illumination optical systems having different polarization states, and illumination switching means for illuminating the image display element by temporally switching the illumination light of the illumination optical system. An image display device. The image display device according to claim 2,
An image display device, wherein the light sources of the plurality of illumination optical systems having different polarization states are solid-state lasers. The image display device according to claim 1,
The polarization state switching means includes a pair of transparent substrates, and a liquid crystal layer made of a ferroelectric liquid crystal or an antiferroelectric liquid crystal that is provided between the transparent substrates and whose orientation direction is switched in a plane parallel to the transparent substrate; An image display device comprising: an electrode provided on an inner surface side of the transparent substrate and having an electrode for switching an orientation direction of the liquid crystal layer according to a frame signal. The image display device according to claim 1,
The light source in a state in which the polarization state switching unit has a plurality of polarization filter surfaces with different polarization directions to be an entrance surface and an exit surface of the illumination light, and the rotation center faces a direction orthogonal to the optical axis of the illumination light. The polygonal polarization is arranged between the image display element and rotated at a rotational speed synchronized with a frame frequency, and switches the polarization state by changing the combination of the incident surface and the exit surface of the illumination light beam. An image display device having a filter. The image display device according to claim 5,
An image display device, wherein the polygonal polarizing filter has four polarizing filter surfaces. The image display device according to claim 5 or 6,
An image display characterized in that a timing at which a polarization state of light incident on a pixel on the image display element is switched by the polygonal polarization filter coincides with a timing at which the pixel is rewritten by the image display signal. apparatus. The image display device according to claim 1,
Optical path deflecting means is provided for displacing the position of the emitted light from the image display element for each of a plurality of sub-frames constituting one image frame and increasing the number of pixels apparently displayed on the image display element. A characteristic image display device. 9. The image display element used in the image display device according to claim 1, wherein both of the pair of substrates are made of a transparent substrate, and provided on the incident light side upper part of each pixel of the image display element. And an image display element having a condensing element for condensing illumination light at the center of the pixel. A pair of substrates at least one of which is transparent, a liquid crystal layer made of a ferroelectric liquid crystal or an antiferroelectric liquid crystal provided between the substrates and capable of switching the orientation direction in a plane parallel to the substrate, and the transparent An image display element provided on the liquid crystal layer side of the substrate and having an image element that switches the arrangement direction of the ferroelectric liquid crystal or the antiferroelectric liquid crystal according to an image display signal is used to illuminate the image display element In an image display method of displaying an image by illuminating with illumination light that changes a polarization state from a light source of an optical system,
An image display characterized in that the polarization state of the output image light before and after the polarity inversion of the image display element is made to be the same by temporally switching the polarization state of the incident light incident on the image display element. apparatus. The image display method according to claim 10.
An image display method characterized in that the polarization state of incident light incident on the image display element is switched by temporally switching illumination light emitted from a plurality of illumination optical systems having different polarization states. The image display method according to claim 11,
The image display method characterized in that the light sources of the plurality of illumination optical systems having different polarization states are solid-state lasers. The image display method according to claim 10.
The polarization state of incident light incident on the image display element is switched between the pair of transparent substrates and a ferroelectric liquid crystal provided between the transparent substrates and whose orientation direction is switched in a plane parallel to the transparent substrate. An image display comprising: a liquid crystal layer composed of an antiferroelectric liquid crystal; and an electrode provided on an inner surface side of the transparent substrate and switching an orientation direction of the liquid crystal layer according to a frame signal. Method. The image display method according to claim 10.
Switching the polarization state of incident light incident on the image display element is formed with a plurality of polarizing filter surfaces with different polarization directions, which are the incident surface and the exit surface of the illumination light, and the center of rotation is the optical axis of the illumination light. Arranged between the light source and the image display element in a state of being orthogonal to each other, rotated at a rotational speed synchronized with a frame frequency, and the combination of the incident surface and the exit surface of the illumination light beam is different. An image display method comprising: a polygonal polarizing filter that switches a polarization state by performing The image display method according to claim 14,
The image display method according to claim 1, wherein the polygonal polarizing filter has four polarizing filter surfaces. The image display method according to claim 14 or 15,
An image display characterized in that a timing at which a polarization state of light incident on a pixel on the image display element is switched by the polygonal polarization filter coincides with a timing at which the pixel is rewritten by the image display signal. Method. The image display method according to any one of claims 10 to 16,
An image display method characterized by displacing the position of emitted light from the image display element for each of a plurality of sub-frames constituting one image frame and increasing the number of apparent pixels on the image display element. . The image display method using an image display element according to any one of claims 10 to 17, wherein the pair of substrates are both transparent substrates.
An image display method, wherein the image display element includes a condensing element that is provided on an incident light side upper portion of each pixel and collects illumination light at a center of the pixel.

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