JP4485773B2 - Optical deflection device and image display device - Google Patents

Description

  The present invention relates to an optical deflecting device using liquid crystal and an image display device including the optical deflecting device.

  Various proposals have heretofore been made for optical elements that are light deflection elements using liquid crystal materials (see Patent Documents 1 to 3).

  Various proposals have been made regarding pixel shift elements (see Patent Documents 4 to 7).

Japanese Patent Laid-Open No. 6-18940 JP-A-9-133904 JP-A-10-221703 Japanese Patent No. 2939826 JP-A-5-313116 JP-A-6-324320 JP-A-10-133135 JP 2002-328402 A

  Regarding the technology relating to the optical deflection element, first, in Patent Document 1, a light beam shifter made of an artificial birefringent plate is proposed for the purpose of reducing the light loss of the optical space switch. In detail, a light beam shifter in which two wedge-shaped transparent substrates are arranged in opposite directions, a liquid crystal layer is sandwiched between the transparent substrates, and the light beam shifter is connected to the rear surface of a matrix type deflection control element. A beam shifter has been proposed. At the same time, two wedge-shaped transparent substrates are arranged in opposite directions, matrix drive is possible between the transparent substrates, and a light beam shifter sandwiching a liquid crystal layer that shifts the incident light beam by a half cell is provided. There has been proposed a light beam shifter in which multiple stages are shifted by half a cell.

  Patent Document 2 proposes an optical deflection switch that can obtain a large deflection, has high deflection efficiency, and can arbitrarily set a deflection angle and a deflection distance. Specifically, two transparent substrates are arranged opposite to each other at a predetermined interval, a vertical alignment process is performed on the opposed surfaces, and a smectic A phase ferroelectric liquid crystal is sealed between the transparent substrates. The liquid crystal element includes a driving device that is vertically aligned with respect to the electrode pair, the electrode pair is arranged so that an AC electric field can be applied in parallel with the smectic layer, and the AC electric field is applied to the electrode pair. In other words, the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by the birefringence due to the inclination of the liquid crystal molecules by using the electroclinic effect of the smectic A phase ferroelectric liquid crystal.

  In the technique of Patent Document 1, since nematic liquid crystal is used as the liquid crystal material, it is difficult to increase the response speed to sub-milliseconds, and it cannot be used for applications that require high-speed switching. Further, in the technique of Patent Document 2, switching by an electroclinic effect using a smectic A-phase ferroelectric liquid crystal is proposed, but the electroclinic effect is highly temperature dependent and a stable shift cannot be expected.

  Therefore, in Patent Document 3, a first window having an optically transparent common electrode, a second window having a large number of transparent conductive electrodes in an electrically bundled parallel stripe shape, a first window, and a second window. An optical element comprising a liquid crystal molecular layer provided in the middle of the window, wherein the optical device is positioned such that the optical beam is incident on the first window and reflected or transmitted by the second window, and further includes a control signal Is applied to the outer electrode of each cell individually to generate a voltage gradient of linear information along the junction electrode and through the cell region, thereby making the linear or non-linear of the electro-optical characteristics of the LC An apparatus for wavefront modulating an optical beam is proposed, which is configured to cause a local change in the refractive index in the liquid crystal layer depending on the portion. Also, according to claim 4, by addressing the active area with a voltage from within the linear portion of the LC electro-optical properties of the CL layer at a predetermined tilt angle between 0 and 3 degrees, the transmission area is reflected from the transmitted or reflected optical wavefront. A device is proposed which is used to deflect an optical beam by generating a phase characteristic with a blaze effect.

  According to the technique of Patent Document 3, nematic liquid crystal is also used as the liquid crystal, and therefore, as in Patent Document 1, it is not suitable for applications that require high-speed response. Further, in Patent Document 3, a transparent conductive electrode having a parallel stripe shape is described. However, in this structure, there is a possibility that a local variation of the electric field described as the subject of the present invention occurs. It is difficult to obtain a uniform amount of light deflection.

  Next, regarding the technology related to the pixel shift element, first, in Patent Document 4, in a projection display device that enlarges and projects an image displayed on a display element onto a screen by a projection optical system, an optical path from the display element to the screen is disclosed. Means for shifting a projected image having at least one optical element capable of rotating the polarization direction of transmitted light and at least one transparent element having a birefringence effect, and an aperture ratio of the display element And a means for discretely projecting the projection area of each pixel of the display element on the screen is disclosed.

In Patent Document 4, at least one optical element (referred to as an optical rotatory element) capable of rotating the polarization direction and at least one transparent element (referred to as a birefringent element) having a birefringence effect are included. The pixel shift is performed by the projection image shift means (pixel shift means). However, as a problem, since the optical rotation element and the birefringence element are used in combination, the light amount loss is large, and the pixel shift amount depends on the wavelength of light. Fluctuation and resolution is likely to decrease, optical noise such as ghost due to leaked light is likely to occur at positions outside the pixel shift where images are not originally formed due to mismatch of optical characteristics between the optical rotation element and birefringence element, It is mentioned that the cost for this is large. In particular, the first-order electro-optic effect (Pockels effect) such as KH ₂ PO ₄ (KDP), NH ₄ H ₂ PO ₄ (ADP), LiNbO ₃ , LiTaO ₃ , GaAs, and CdTe as described above for the birefringent element. This is remarkable when a large material is used.

  In the projector disclosed in Patent Document 5, the image to be originally displayed stored in the image storage circuit is sampled in a checkered pattern in the pixel selection circuit by the control circuit and sequentially displayed on the spatial light modulator. Further, the control circuit controls the panel rocking mechanism in response to this display to move the adjacent pixel pitch distance of the spatial light modulator by an integer, thereby allowing the image to be originally displayed to be displayed in time. It is reproduced by a typical synthesis. As a result, an image can be displayed with a resolution that is an integral multiple of the pixels of the spatial light modulator, and a projector can be constructed at low cost by using a spatial light modulator with coarse pixels and a simple optical system.

  However, Patent Document 5 describes a pixel shift method in which the image display element itself is swung at a high speed by a distance smaller than the pixel pitch. In this method, the optical system is fixed, and various aberrations are thus eliminated. Although the occurrence is small, since the image display element itself needs to be translated accurately and at high speed, the accuracy and durability of the movable part is required, and vibration and sound become a problem.

  Furthermore, according to the technique disclosed in Patent Document 6, the display image is arranged in the vertical direction and the horizontal direction in order to improve the resolution of the display image apparently without increasing the number of pixels of the image display device such as an LCD. Each of the plurality of pixels emits light according to the display pixel pattern, and an optical member that changes the optical path for each field is disposed between the image display device on which the image is displayed and the observer or the screen. In addition, for each field, a display pixel pattern whose display position is shifted in accordance with the change of the optical path is displayed on the image display device. Here, the optical path is changed by causing the portions having different refractive indexes to appear alternately in the optical path between the image display device and the observer or the screen for each field of the image information. It is.

  In the technique of Patent Document 6, a combination mechanism of an electro-optic element and a birefringent material, a lens shift mechanism, a vari-angle prism, a rotating mirror, a rotating glass, and the like are described as means for changing the optical path. In addition to the method of combining birefringent elements, a method of switching optical paths by displacing (translating, tilting) optical elements such as lenses, reflectors, and birefringent plates by means of voice coils, piezoelectric elements, etc. has been proposed. In this method, the configuration is complicated to drive the optical element, and the cost is increased.

  Further, according to the technique of Patent Document 7, a light beam deflecting device that can eliminate the need for a rotating machine element, can achieve a reduction in overall size, high accuracy and high resolution, and is hardly affected by external vibration is proposed. Has been. Specifically, a translucent piezoelectric element disposed on the traveling path of the light beam, a transparent electrode provided on the surface of the piezoelectric element, a light beam incident surface A and a light beam emitting surface B of the piezoelectric element. Voltage applying means for applying a voltage to the piezoelectric element through the electrode in order to change the optical path length between and the electrode to deflect the optical axis of the light beam.

  In this technique, a method has been proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes and the thickness is changed by applying a voltage to shift the optical path, but a relatively large transparent piezoelectric element is required, There are the same problems as in the case of Patent Document 6 described above, such as an increase in apparatus cost.

When the above-mentioned problems of the prior art are arranged, the problem with the conventional pixel shift element is that
1. 1. High cost due to the complicated structure, optical equipment size increase, light loss, ghost and other optical noise or resolution reduction 2. Problems with positional accuracy, durability, vibration and sound, especially in the case of a configuration having moving parts. Response speed in nematic liquid crystal.

  Therefore, in Patent Document 8, the present inventors have disclosed a pair of transparent substrates, a liquid crystal composed of a chiral smectic C phase having a homeotropic orientation filled between the substrates, and at least one set that causes an electric field to act on the liquid crystals. And an electric field applying means.

  According to this optical deflecting element, liquid crystal composed of a chiral smectic C phase is used. Therefore, compared with the conventional optical deflecting element, the manufacturing cost is increased due to the complicated structure, the size of the apparatus is increased, and the amount of light is increased. Problems such as loss and optical noise can be improved, and dullness of response in conventional smectic A liquid crystals and nematic liquid crystals can be improved, and high-speed response is possible.

  In the optical deflecting element of Patent Document 8, it is considered that when an electric field is applied in a direction perpendicular to the helical axis of the chiral smectic C phase, that is, in the horizontal direction of the smectic layer, liquid crystal molecules rotate in a conical virtual plane within the smectic layer. It is done. At this time, the ratio of the liquid crystal molecules aligned in the same direction changes according to the characteristics such as the helical pitch and spontaneous polarization of the liquid crystal layer, and the inclination direction of the optical axis of the liquid crystal layer corresponding to the average alignment direction of the liquid crystal molecules is Change. When a sufficiently large electric field is applied, the alignment directions of the liquid crystal molecules in each smectic layer are aligned and the spiral is unwound. When the electric field direction is reversed, the tilt direction of the optical axis of the liquid crystal layer is also reversed, so that it functions as a dynamic birefringent plate and can be applied to an optical deflection element or the like.

  An object of the present invention is to improve contrast and improve light utilization efficiency when a light deflection element is used for image display.

In the present invention, a liquid crystal layer including a liquid crystal composed of a chiral smectic C phase and having homeotropic alignment is provided between a pair of transparent substrates, and an electrode for applying an electric field in the plate surface direction of the substrate to the liquid crystal layer is formed. And an optical deflecting element that deflects an optical path of light transmitted through the liquid crystal layer, an AC voltage is applied to the electrode to generate the electric field, and the liquid crystal is driven. The voltage to be applied by at least a part of the optical deflection direction switching time that is the time during which the deflection direction is switched and the optical deflection state holding time that is the time during which the deflection direction after the switching is maintained A liquid crystal driving device in which the absolute value of the former is greater than that of the latter, and the optical deflection element has a positive dielectric anisotropy in a frequency region in which the liquid crystal has a dielectric dispersion relaxation frequency or higher, LCD drive device Superimposing said high AC voltage frequency than the AC voltage voltage applied when the light deflection direction switching time, the liquid crystal driving device, the voltage to be the application time of the light deflection direction switching time, the AC an optical deflecting device for superimposing an AC voltage of more than the dielectric dispersion relaxation frequency to a higher AC voltage frequency than the voltage.

  According to the present invention, since the liquid crystal can be operated at high speed by increasing the absolute value of the applied voltage during the optical deflection direction switching time, the pixel shift image resolution is improved by applying the optical deflection element to the image display device. In such a case, it is possible to reduce the transient scattering of the light deflection direction switching time and to improve the deflection direction switching speed, so that the contrast of the image display can be improved and the light utilization efficiency can be improved. . When applied to an optical switch, the average communication speed can be improved by improving the switching speed.

[Definition]
Hereinafter, main terms used in the present specification will be described.

(1) Optical deflection element An "optical deflection element" is a device that deflects the optical path of light by an external electric signal, that is, shifts outgoing light parallel to incident light or rotates it with a certain angle. Alternatively, it means an optical element capable of switching the optical path by combining both. In this description, the magnitude of the shift is referred to as “shift amount” with respect to the light deflection due to the parallel shift, and the rotation amount is referred to as “rotation angle” with respect to the light deflection due to rotation. The “light deflection device” means a device that includes such a light deflection element and deflects the optical path of light.

(2) Light deflection direction switching time The light deflection direction switching time is the time required for switching the optical path and is the time corresponding to the liquid crystal switching time.

(3) Subfield Normally, in an image display device such as a liquid crystal projector, images are sequentially rewritten and displayed at a certain cycle. The image per sheet is called a field. In the present invention, as described above, the optical path shift is performed in a time division manner so that the pixels are doubled and displayed. An image that is time division and displayed is called a subfield. Therefore, for example, when the number of divisions is 2, that is, when the optical path shift is switched at two positions, an image of one field is formed by two subfields.

  At the time of subfield switching, it is the time for shifting the optical path, and at the time of displaying the subfield, it is the time for completing the optical path shift and displaying one subfield.

(4) Pixel Shift Element “Pixel shift element” means an image display element in which a plurality of pixels that can control light according to image information is two-dimensionally arranged, a light source that illuminates the image display element, and an image display element An optical member for observing the image pattern displayed on the optical field, and an optical deflecting means for deflecting an optical path between the image display element and the optical member for each of a plurality of subfields obtained by temporally dividing the image field. Light in an image display device that displays an image pattern in which the display position is shifted in accordance with the deflection of the optical path for each subfield by the deflecting unit, thereby multiplying the apparent number of pixels of the image display element. Means deflection means. Therefore, basically, it can be said that the optical deflection element and the optical deflection device defined above can be applied as the optical deflection means.

[Best Mode for Carrying Out the Invention]
The best mode for carrying out the present invention will be described.

  Fig.1 (a) is explanatory drawing of the optical deflection | deviation apparatus 10 which is this Embodiment. The optical deflecting device 10 includes the optical deflecting element 1 and a liquid crystal driving device 7.

  The light deflection element 1 is provided with a pair of transparent substrates 2 and 3 facing each other. An alignment film 4 is formed on at least one of the inner surfaces of the substrate 2 here, and between the alignment film 4 and the other substrate 3, a ferroelectric film composed of a chiral smectic C phase forming a homeotropic alignment. A liquid crystal layer 5 of liquid crystal is filled.

  The light deflection element 1 composed of the pair of substrates 2 and 3 and the liquid crystal layer 5 is provided with a pair of electrodes 6a and 6b for applying an electric field to the liquid crystal in correspondence with a target light deflection direction. The liquid crystal driving device 7 is connected. The electrodes 6 a and 6 b are installed so that the electric field vector is oriented in a direction substantially perpendicular to the liquid crystal rotation axis of the optical deflection element 1 in order to apply an electric field in the plate surface direction of the substrates 2 and 3 to the liquid crystal layer 5. . This may be provided integrally with the substrates 2 and 3, or may be provided separately. In addition, a spacer for defining the film thickness of the liquid crystal layer 5 can also be used as an electrode.

  FIG. 1B is an explanatory diagram of another configuration example of the light deflection element 1. In FIG. 1B, the difference from the configuration of FIG. 1A is the electrode structure. In this example, the electrodes are a plurality of lines for applying an electric field in the plate surface direction of the substrates 2 and 3 to the liquid crystal layer 5. It consists of the transparent electrode group 6c comprised from the electrode 6d. Each line electrode 6d is provided outside the optical path of the optical deflection element 1 and is connected to each resistance end of a plurality of resistors 7a arranged in series. A potential gradient is generated between adjacent line electrodes 6d, and an electric field is applied. It is configured to be.

  Here, the liquid crystal constituting the liquid crystal layer 5 will be described. A “smectic liquid crystal” is a liquid crystal molecule formed by arranging the major axis directions of liquid crystal molecules in layers. With regard to such a liquid crystal, a liquid crystal in which the normal direction of the layer (layer normal direction) and the major axis direction of the liquid crystal molecules coincide with each other is referred to as “smectic A phase”, and a liquid crystal that does not coincide with the normal direction is referred to as “ It is called “chiral smectic C phase”. The ferroelectric liquid crystal layer 5 composed of a chiral smectic C phase generally has a so-called helical structure in which the liquid crystal molecular direction is helically rotated for each layer in the state where an external electric field does not work, and the chiral smectic C phase antiferroelectric liquid crystal. Indicates the direction in which the liquid crystal molecules face each other. Since the liquid crystal composed of these chiral smectic C phases has an asymmetric carbon in the molecular structure and is spontaneously polarized by this, the liquid crystal molecules are rearranged in a direction determined by the spontaneous polarization Ps and the external electric field E. Optical properties are controlled. In this example, the light deflection element 1 will be described by taking a ferroelectric liquid crystal as an example of the liquid crystal used in the liquid crystal layer 5, but the same can be used for an antiferroelectric liquid crystal.

  The structure of a ferroelectric liquid crystal composed of a chiral smectic C phase 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 is for linking a skeleton, a bonding part, and a chiral part 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 bonds the chiral portion and a rigid skeleton such as a biphenyl structure.

  In the optical deflection element 1 of the present embodiment, the ferroelectric liquid crystal layer 5 made of a chiral smectic C phase has a molecular helical rotation axis oriented perpendicularly to the planes of the substrates 2 and 3 by the alignment film 4, so-called homeotropic. Make an orientation. As an alignment method for such homeotropic alignment, a well-known method can be applied. That is: Shear stress method, 2. 2. magnetic field orientation method; 3. Temperature gradient method 4. SiO oblique deposition method, (For example, see page 235 of “Structure and Physical Properties of Ferroelectric Liquid Crystal” written by Takezo and Fukuda, published by Corona).

  One of the features of the present optical deflection element 1 is that the chiral smectic C phase has an extremely fast response as compared with the nematic liquid crystal, and switching at sub ms is possible. In addition, the liquid crystal molecule direction is uniquely determined with respect to the electric field direction, and the director direction is fixed above a certain electric field strength. Therefore, the smectic A phase utilizing the electroclinic effect that takes the director angle proportional to the electric field strength is used. Compared to the liquid crystal, the director direction is easily controlled and easy to handle.

  In addition, the liquid crystal layer 5 made of a chiral smectic C phase having homeotopic orientation is more effective in the operation of the liquid crystal molecules than in the case of taking the homogeneous orientation (the state in which the liquid crystal molecules are oriented parallel to the substrate surface). , 3 is less susceptible to the regulation force, the light deflection direction can be easily controlled by adjusting the direction of the external electric field, and the required electric field is low. Further, when the liquid crystal molecules are homogeneously aligned, the liquid crystal molecules strongly depend not only on the direction of the electric field but also on the substrate surface, so that more positional accuracy is required for the installation of the optical deflection element. Conversely, in the case of homeotopic orientation as in the present embodiment, the setting margin of the optical deflection element 1 increases with respect to optical deflection. In making use of these features, it is not necessary that the spiral axis be strictly oriented perpendicular to the substrate surface, and it may be tilted to some extent. For example, even if a part of the side surface forming the spiral structure is perpendicular to the substrates 2 and 3 and the spiral axis itself is tilted from the normal direction of the substrate, the liquid crystal molecules exert a regulating force from the substrates 2 and 3. What is necessary is just to be able to face two directions without receiving.

  Next, the operation principle of the present optical deflection element 1 will be described with reference to FIGS. FIG. 2 is an explanatory diagram schematically showing liquid crystal alignment in the configuration shown in FIG. However, in FIG. 1, the electric field is drawn so as to be applied in the vertical direction, but in FIG. 2, it is drawn so as to be applied in the front and back direction of the paper for convenience, and the electric field is generated in the front and back of the paper. The direction of the electric field is switched by the liquid crystal driving device 7 in accordance with the target light deflection direction. The electrodes 6a and 6b in FIG. 2 may be integrated with or separated from the substrates 2 and 3 as described above.

  In addition, the incident light with respect to the light deflection element 1 is linearly polarized light, and the polarization direction thereof is the vertical direction as shown by the up and down arrows in FIG. 2 (the incident light of the light deflection element 1 is deflected by the white arrows. The electrodes 6a and 6b are arranged to face each other so that the electric field direction is orthogonal to the polarization direction. In addition, a spacer for defining the film thickness of the liquid crystal layer 5 can also be used as an electrode. In any case, it is desirable to provide an electromagnetic shield so that the leakage electric field from the electrodes 6a and 6b does not adversely affect the devices around the optical deflection element 1. The liquid crystal molecules 8 schematically shown can take an orientation direction spirally as described above depending on the applied electric field direction, and FIG. 2 shows the possible orientation states in a cone shape. .

  FIG. 3 shows an XZ cross section in the liquid crystal layer 5 when the XYZ orthogonal coordinate system is taken as shown in FIG. As shown in FIG. 3, if the liquid crystal molecule 8 has a sufficiently large electric field, it takes either the first alignment state or the second alignment state (see FIG. 3B) depending on the electric field direction. Distributed. θ is the tilt angle of the liquid crystal molecules 8 from the liquid crystal rotation axis, and is simply referred to as “tilt angle” hereinafter. Assuming that the spontaneous polarization Ps of the liquid crystal layer 5 is positive and an electric field E is applied in the positive direction of the Y axis (upward on the paper surface), the liquid crystal molecules 8 have a liquid crystal rotation axis substantially in the direction perpendicular to the substrate. It coincides with the first orientation direction shown in b).

  Here, when the refractive index in the major axis direction of the liquid crystal layer 5 is ne and the refractive index in the minor axis direction is no, linearly polarized light having a polarization direction in the Y axis direction is selected as incident light, and incident in the positive X axis direction. When light travels, the light travels straight in the direction of arrow a in FIG. 3A upon receiving the refractive index no as ordinary light in the liquid crystal layer 5. That is, no light deflection is received.

  On the other hand, when linearly polarized light whose polarization direction is the Z-axis direction is incident, the refractive index in the incident direction is obtained from both the direction of the liquid crystal molecules 8 and the refractive indexes no and ne. More specifically, it is obtained from the relationship with the direction of light passing through the center of the ellipsoid in a refractive index ellipsoid having refractive indexes no and ne as principal axes, but details are omitted here. The light is deflected corresponding to the refractive indexes no and ne and the direction of the liquid crystal molecules 8 (tilt angle θ), and shifted in the direction shown by the arrow b (in the first alignment state) in FIG.

  Now, assuming that the thickness (gap) of the liquid crystal layer 5 is d, the shift amount S is expressed by the following equation (for example, “Crystal optics” (Applied Physics Society, edited by Optical Society), 198 Page).

S = [(1 / no) ^2- (1 / ne) ² ] sin (2θ · d) / [2 ((1 / ne) ² sin ² θ
+ (1 / no) ² cos ² θ)]… (1)
Further, when the electric field direction is reversed, the liquid crystal molecules 8 take a line-symmetrical arrangement (second alignment state) about the X axis in FIG. 3 and the traveling direction of linearly polarized light whose polarization direction is the Z axis direction. Is as shown by the arrow b ′ in FIG.

  Therefore, by controlling the direction of the electric field applied to the liquid crystal layer 5 with respect to this linearly polarized light, two positions of the arrow b and the arrow b ′, that is, light deflection for 2S can be performed.

Here, the result of calculating the light deflection amount S with respect to the light deflection amount obtained with respect to the representative physical property values (no = 1.6, ne = 1.8) of the material of the liquid crystal layer 5 is shown in FIG. In FIG. 4, the amount of light deflection is the largest in the vicinity of θ = 45 °. If the tilt angle θ of the liquid crystal molecules 8 is 22.5 °, in order to obtain a deflection amount of “2S = 5 (μm)”, the thickness of the liquid crystal may be set to 32 μm as shown here. . In addition, in homeotropic alignment ferroelectric liquid crystal, a response speed of 0.1 ms is reported for an electric field of about 700 V / cm (Ozaki et al., JJAppl. Physics, Vol. 30, No. 9B, pages 2366-2368. (See (1991)), a sufficiently high response speed on the order of sub ms is obtained.
Further, in a liquid crystal composed of a chiral smectic C phase, the tilt angle θ changes with temperature T, and there is a relationship of “θ− (T−Tc) β” where the phase transition point is Tc. β varies depending on the material, but takes a value of about 0.5. It is also possible to control the amount of light deflection by temperature control utilizing this characteristic.

  For example, if the above-mentioned 22.5 ° is set as the tilt angle θ and the corresponding temperature is “Tθ = 22.5 °”, “θ <22” when “T> Tθ = 22.5 °”. .5 ° ”and“ θ <22.5 ° ”when“ T <Tθ = 22.5 ° ”, the tilt angle θ can be controlled by the temperature, and thereby the amount of light deflection can be controlled. As for position control, fine adjustment by an electric field can be performed in the same manner, and appropriate light deflection can be achieved by temperature, electric field, or a combination of both.

  The above describes the case where the electric field strength is Es or higher and the spiral structure is dissolved and the tilt angle θ is equal to the tilt angle of the optical axis. However, when the electric field strength is equal to or lower than Es, θ is averaged in the liquid crystal molecular direction. It can be handled as the tilt angle of the optical axis.

  FIG. 5 is a graph showing an example of changes in the applied voltage for generating an electric field applied by the liquid crystal driving device 7 and the change in the amount of light deflection accompanying the applied light deflecting element 1 having the structure shown in FIG. The applied voltage is a rectangular-wave AC voltage, and the time during which the deflection direction is switched (light deflection direction switching time) is also the time during which the deflection direction is maintained after the deflection direction is switched (holding the light deflection direction). The same voltage value is applied for (time). 1A and 1B, an electric field in a predetermined direction is generated in the liquid crystal layer by applying this voltage. Immediately after the voltage is switched, the liquid crystal molecules rotate, and the light deflection amount becomes constant after the light deflection direction switching time determined by the liquid crystal properties and the generated electric field. This deflection direction does not change during the optical deflection direction holding time.

  In contrast to the applied voltage shown in FIG. 5, in the present embodiment, a voltage as described below is applied to the optical deflection element 1 to drive the liquid crystal. Next, the characteristics of the applied voltage and the configuration of the device that generates the applied voltage will be described.

  FIG. 6 is a graph showing an example of the waveform of the voltage applied to the optical deflection element 1.

  In FIG. 6, the waveform of (a) is the same as that of FIG. 5, whereas (b) to (h) are driving applied to the optical deflecting element 1 by the liquid crystal driving device 7 in the present embodiment. Various examples of voltage waveforms are shown. Each example of (b) to (h) is an AC voltage, and the voltage value is set to a different value between the light deflection direction switching time and the light deflection state holding time. In (b), the voltage absolute value V1 of the light deflection direction switching time is set larger than the voltage absolute value V2 of the light deflection state holding time, and the liquid crystal can be operated at a higher speed than in the case of (a). It becomes.

  The voltage value set here may be set to the same voltage value within the entire optical deflection direction switching time as shown in (b), but the optical deflection direction switching as shown in (c). The voltage value V1 may be applied only during a very short period of time, and the voltage V2 of the light deflection state holding time may be applied during the remaining light deflection direction switching time. In this case, by applying a strong electric field at the moment when the liquid crystal molecules start to move, and once starting to move, the voltage value is returned to normal, thereby preventing a problem that the liquid crystal changes the orientation direction in a domain shape. In order to enhance this effect, as shown in (d), the voltage value may be once lowered to a voltage V3 lower than the voltage V2 of the light deflection state holding time just before the end of switching of the light deflection direction. .

  FIG. 7 shows a configuration example of the liquid crystal driving device 7 for controlling the voltage applied to the electrodes 6a and 6b for setting the voltage absolute value of the light deflection direction switching time to be larger than the voltage absolute value of the light deflection state holding time. Show. The liquid crystal driving device 7 includes two sets of different voltage generators 7a and 7b and a signal generator 7c for controlling the output timing of the voltages of these voltage generators 7a and 7b. The signal generator 7c may be further configured to be externally controlled (image display control circuit 20 described later) as necessary. The voltage generator 7a generates a voltage (voltage V2 in FIG. 6B) to be applied during the optical deflection direction state holding time, and the voltage generator 7b is a voltage of the difference between the voltages V1 and V2 in FIG. 6B. And the voltage generator 7b is output to the output voltage of the voltage generator 7a only during the entire optical deflection direction switching time (in the case of FIG. 6B) or only in a part of the time (in the case of FIG. 6C). The signal generator 7c controls the voltage generators 7a and 7b so that the output voltage is superimposed and applied to the optical deflection element 1. In the case of FIG. 6C, the voltage generator may be further increased by one to generate three types of voltages, and these may be superimposed at a predetermined timing.

  6 (e) to 6 (g) show an alternating current having a frequency higher than that of the rectangular wave alternating voltage in FIG. 6 (a) at least one of the applied voltage value in the light deflection direction switching time or the applied voltage value in the light deflection state holding time. The waveform of the drive voltage of the optical deflection element 1 with superimposed voltage is shown, and the transient scattering phenomenon that occurs during switching of the optical path deflection can be reduced by superimposing the AC voltage.

The effect of superimposing an alternating voltage on the liquid crystal is due to the dielectric anisotropy of the liquid crystal molecules. In the optical deflecting element 1, a liquid crystal composed of a chiral smectic C phase is used. The dielectric constant of this liquid crystal is biaxial, and generally, the dielectric constant ε _{3 in} the molecular major axis direction is perpendicular to the molecular major axis. It is represented by a dielectric constant ε _{2 in} a direction parallel to the chiral smectic layer and a dielectric constant ε ₃ in a direction perpendicular to them. However, it is often simply expressed by the dielectric constant ε _{|| in the} direction of the helical axis and the dielectric constant ε _の in the direction perpendicular thereto. Here, the latter will also be considered.

The dielectric constant of liquid crystal molecules strongly depends on the liquid crystal layer thickness, electric field strength, and frequency. For chiral smectic C liquid crystal, typically a dielectric anisotropy in the low frequency region with respect to frequency, i.e. "ε _|| -ε _⊥" is negative, toward a direction perpendicular to the previously described electric field direction. However, as the frequency increases, the dielectric anisotropy approaches zero, and some materials, such as DOBAMBC and DOBACPC, which are typical chiral smectic C liquid crystals, are positive (Takezoe and Fukuda, “Structure of ferroelectric liquid crystals”. And physical properties "(first edition), published by Corona, page 310). In other words, by superimposing a high-frequency AC voltage, it is possible to relatively increase the dielectric constant in the vertical direction, that is, in the direction of the helical axis, and control fluctuations associated with movement of the liquid crystal molecules around the helical axis. The rotation can be stabilized. Therefore, for example, by superimposing the high-frequency voltage on the voltage of the light deflection direction switching time, it becomes possible to reduce alignment defects and transient scattering. This effect is more remarkable in the chiral smectic C liquid crystal having positive dielectric anisotropy in a frequency region equal to or higher than the dielectric dispersion relaxation frequency.

  The drive waveform at this time is shown in FIG. The high frequency to be superimposed when switching the light deflection direction of the light deflection element 1 is desirably equal to or higher than the relaxation frequency. For example, in the above-described DOBAMBC and DOBACPC, the frequency is 20 kHz or higher. The amplitude should be appropriately determined according to the thickness of the liquid crystal layer 5, the frequency applied to the liquid crystal layer 5 and the like. For example, an intensity of 0.1 to 10 V / mm is selected.

  In order to control the responsiveness of the liquid crystal molecules to the electric field, it is also effective to superimpose the high frequency superposition during the optical deflection direction holding time. In this case, the amplitude is changed as shown in FIG. As shown in FIG. 6 (g), by changing the voltage waveform before superposition between the light deflection direction switching time and the light deflection direction holding time, the effect of improving the liquid crystal alignment can be obtained without impairing the high-speed response described above. It is done.

  FIG. 8 shows a configuration example of the liquid crystal drive device 71 that generates the drive voltage shown in FIG. The liquid crystal driving device 71 that controls the voltage applied to the electrodes 6a and 6b has two sets of voltage generators 71a and 71b that generate different voltages and a signal that controls the timing of the voltage output of these voltage generators 71a and 71b. It consists of a signal generator 71c to be generated. The signal generator may be further controlled from the outside (an image display control circuit described later) as necessary. The voltage generator 71a generates a voltage (rectangular wave AC voltage shown in FIG. 6A) to be applied during the optical deflection direction holding time, and the voltage generator 71b applies the rectangular wave superimposed on the rectangular wave AC voltage. A high-frequency AC voltage is generated from the AC voltage, and the latter voltage is controlled so as to be output for a certain period within the light deflection direction switching time and to be superimposed on the former voltage. In order to generate the voltage in FIG. 6F, a voltage generator that generates a high-frequency voltage superimposed on the optical deflection direction holding time may be prepared. The waveform of FIG. 6 (g) shows an example in which a high frequency voltage is superimposed on the optical deflection direction switching time in the waveform of FIG. 6 (b), and the waveform of FIG. 6 (h) is the waveform of FIG. 6 (b). The example in which a high frequency voltage is superimposed on both the light deflection direction switching time and the light deflection direction holding time is shown.

  FIG. 9 includes a light detection device 80 that captures and detects a part of the light emitted from the light deflection element 1 in order to detect the light deflection direction switching time, and performs light deflection based on the detection signal of the light detection device 80. It is explanatory drawing which shows an example of the optical deflection | deviation apparatus 10 which has the liquid crystal drive device 7 which controls to adjust direction switching time.

  In FIG. 9, the light deflecting device 10 is provided with a spectroscopic element 81 made of a half mirror or the like for incorporating a part of the light emitted from the light deflecting element 1 into another optical path. Arrows b and b ′ indicate two optical paths when the optical path is switched by the optical deflection element 1. The light detection device 80 includes a light receiving element such as a photodiode, a photomultiplier, and a CCD having two openings for independently receiving light of the two switched optical paths. Then, the liquid crystal driving device 7 counts the time from when the light reception is completed by one of the two light receiving elements until the light reception is started by the other light receiving elements by a predetermined counter, and measures the light deflection direction switching time (measurement). means). Then, the liquid crystal driving device 7 controls the circuits exemplified in FIGS. 7 and 8 based on the measured light deflection direction switching time (specifically, the output of the voltage generated by the voltage generators 71b and 71b). (Controlling the timing) (control means), the waveform of the drive voltage applied to the optical deflection element 1 is adjusted so that the optical deflection direction switching time in the waveforms of FIGS. .

  FIG. 10 is a conceptual diagram illustrating another device configuration example of the light deflecting device 10. In FIG. 10, reference numeral 11 denotes a light source for illumination, and any type or type of light source can be used as long as it can quickly turn on or off white or light of any color. . For example, an LED lamp, a laser light source, a white lamp light source, or the like arranged in a two-dimensional array and combined with a shutter that operates at high speed with respect to the light source can be used as a light source for illumination.

  Reference numeral 12 denotes an illumination device for uniformly irradiating the image display element 13 with light emitted from the light source, and includes a diffusion plate 12a, a condenser lens 12b, and the like.

  Reference numeral 13 designates uniform illumination light incident from the illuminating device 12 and spatially modulates it based on image information for each of a plurality of image subfields obtained by further subdividing the image field in time, and emits the image light as image light. This is an image display element. As the image display element 13, a transmissive liquid crystal light valve, a reflective liquid crystal light valve, a DMD element, or the like can be used.

  Reference numeral 14 denotes an optical deflecting element that deflects the optical path of the image light emitted from the image display element 13 for each image subfield and emits the deflected image light. The light deflection element 14 can display an image pattern in which the image display position projected on the screen 16 is shifted in accordance with the deflection amount of the optical path for each image subfield. The actual number of pixels can be displayed as the number of pixels that is apparently multiplied.

  Reference numeral 15 denotes an optical member for observing an image pattern displayed on the image display element 13, reference numeral 5 denotes a projection lens, and reference numeral 6 denotes a screen. Further, reference numeral 17 denotes a light source driving means for driving the light source 11, reference numeral 18 denotes a display driving circuit for driving the image display element 13, and reference numeral 19 denotes an optical deflection for driving the optical deflection element 1. It is a drive circuit. Reference numeral 20 denotes an image display control circuit for controlling the entire image display apparatus including the light source drive circuit 17, the display drive circuit 18, the light deflection drive circuit 19, and the like. The liquid crystal driving device 7 described above is provided in the light deflection driving circuit 19.

  Next, the basic operation of the image display apparatus shown in FIG. 10 will be described. The light emitted from the light source 11 under the control of the light source driving circuit 17 becomes illumination light made uniform by the diffusion plate 12a, and is controlled by the display driving circuit 18 operating in synchronization with the light source driving circuit 17 by the condenser lens 12b. The image display element 13 is illuminated critically. Here, as an example of the image display element 13, a transmissive liquid crystal panel, that is, a transmissive liquid crystal light valve is used. Illumination light spatially modulated by the image display element 13 composed of a transmissive liquid crystal light valve is incident on the light deflection element 1 as image light, and the emitted light emitted from the light deflection element 1 is projected as deflection image light. After being magnified by the lens 15, it is projected onto the screen 16. That is, image light is arranged in accordance with a drive signal from the light deflection drive circuit 19 by the light deflection element 1 arranged on the image light output side of the image display element 13 formed of a transmissive liquid crystal light valve. The light is emitted as deflected image light shifted (deflected) by an arbitrary distance in the direction, and is projected onto the screen 16 through the projection lens 15.

  In FIG. 10, the light deflection element 1 is disposed immediately after the image display element 13 formed of a transmissive liquid crystal light valve. However, the position of the light deflection element 1 is not limited to this case. It may be arranged immediately before the screen 16 or the like. However, when it is arranged near the screen 16, the size of the light deflection element forming the light deflection element 1, the arrangement pitch of the transparent electrodes forming the light deflection element, and the like are determined at the position where the light deflection element 1 is arranged. It is necessary to set according to the screen size and pixel size.

  However, it is desirable that the amount of shift (deflection) of the optical path of the deflected image light is 1 / integer of the pixel pitch, regardless of the arrangement position of the light deflection element 14. That is, when the pixel multiplication is performed twice in the pixel arrangement direction, the shift amount of the optical path of the deflected image light is ½ of the pixel pitch, and the pixel multiplication is three times in the arrangement direction. When performing, it is desirable to set to 1/3 of the pixel pitch. Further, when the shift amount of the optical path of the deflected image light is larger than the pixel pitch due to the configuration of the light deflection element 4, the shift amount of the optical path is set to a distance of (integer multiple + 1 / integer) of the pixel pitch. May be.

  By using this optical deflecting element 1 in two dimensions vertically and horizontally in the pixel arrangement direction, for example, by using two optical deflecting elements that perform double image multiplication, an apparent fourfold effect can be obtained and used. High-definition images exceeding the resolution of the transmissive liquid crystal light valve can be displayed. Further, when the shift amount becomes large depending on the configuration of the optical deflection element 1, the shift amount may be set to a distance of (integer multiple + 1 / integer) of the pixel pitch. In either case, the image display element 13 which is a transmissive liquid crystal light valve is driven by an image signal in a subfield corresponding to the pixel shift position.

  In FIG. 10, a single-color image display device using a single-plate transmissive liquid crystal light bulb and a single-color LED lamp is shown, but the three primary color light sources 11, the illumination device 12, and the three image display elements 13 are shown. And a full color image can be displayed by mixing three primary color images. A full-color image can also be displayed by a field sequential method in which the single-panel image display element 13 is illuminated with the three primary colors in time sequence. In this case, the light paths from the three color light sources 11 may be mixed and illuminated by a cross prism, or time-sequential three primary color lights may be generated by a combination of the white lamp light source 11 and a rotating color filter.

  FIG. 11 is a schematic diagram showing the relationship among the field, subfield, drive signal of the optical path deflection element 1 (light deflection element drive signal), drive signal of the image display element 13 (light valve image signal), and the like of this image display device. is there. The image display control circuit 20 generates a field pulse (FP) and a subfield pulse (SFP) based on the reference clock. In this example, the case where there are two subfields is shown. Prior to the subfield display time (first SF, second SF), the subfield switching time is set, and the rewrite signal of the image display element 13 is updated at this subfield switching time, and the display of the image display element 13 is rewritten. It is desirable that the light deflection switching in the light deflecting element 1 is executed in accordance with the subfield switching time in terms of light utilization efficiency and image contrast. As described above, in this example, the light deflection element drive signal generated by the liquid crystal drive device 7 and applied to the light deflection element 1 is a binary control in which a predetermined voltage is applied while switching the polarity (FIG. 6A). ), The optical path deflection unit drive signal is used as the drive signal shown in FIGS. 6B to 6H, so that a higher-definition image can be obtained.

  Examples of the present invention will be described.

[Example 1]
An embodiment will be described regarding the fabrication of the optical deflection element 1 and the application of an electric field thereof. 100 line electrodes 6d made of indium tin oxide (ITO) with a pitch of 0.1 mm and a width of 0.01 mm are formed on the surface of the central region of a glass substrate having a size of 30 mm × 40 mm and a thickness of 3 mm by sputtering to form an electrode 6c. did. This surface was covered with a 100 μm thick transparent dielectric layer, and this surface was further treated with a silane coupling agent to form a vertical alignment film. This was used as the liquid crystal substrates 2 and 3, and the two liquid crystal substrates 2 and 3 manufactured under the same conditions were overlapped with ITO being shifted by a half pitch to form empty cells. A spacer for adjusting the gap between the substrates 2 and 3 was disposed at the end of the substrate, and this portion was fixed with an adhesive. In a state where the substrates 2 and 3 are heated to about 90 degrees, a ferroelectric liquid crystal (CS1029 and DOBAMBC manufactured by Chisso Corporation) is injected between the two substrates 2 and 3 by a capillary method to form a liquid crystal layer 5. . After cooling and sealing the liquid crystal, each line electrode 6d was connected to an electrode formed in a flexible substrate (FPC) shape through an anisotropic conductive film.

  The FPC electrode was connected to the resistor 7a as shown in FIG. Each resistance value was set to 100 kΩ. Both ends of the resistor circuit composed of the resistor 7a were connected to a high voltage power source. A potential gradient is generated at the line electrodes 6 d of the upper and lower substrates 2 and 3, and an electric field in one direction is applied to the liquid crystal layer 5.

  A mask pattern having a line / space width of 24.5 μm was provided on the incident surface side of the light deflection element 1 created in this way, and illumination was performed with the linearly polarized light collimated from the mask pattern side. The direction of linearly polarized light was set to be the same as the longitudinal direction of the line electrode 6d. In the state where the temperature of the light deflection element 1 is 25 ° C., the light transmitted through the mask pattern was observed through the light deflection element 1 with a microscope. A high speed CCD camera with a sampling rate of 25 μs was used for this observation. When a rectangular voltage with a period of 16.7 ms was applied by a high voltage power source as a voltage generator so that the voltage between each line electrode 6d was ± 10 V, the mask pattern was shifted by about 8 μm in parallel at the center of the element 1. Observed. Since the mask pattern, the light deflection element 1, and the microscope are mechanically stationary, it has been confirmed that the optical path shifts electro-optically. As the light deflection direction switching time, the time required for 10% to 90% change before and after the shift was taken. This light deflection direction switching time was 1.2 ms. In addition, a scattering phenomenon in which the mask pattern image was blurred during the shift was confirmed. The shape of this voltage corresponds to that in FIG.

  Subsequently, a high voltage was applied so as to be ± 15 V in a period of 0.6 ms within the light deflection direction switching time in the same cycle. In order to apply this voltage, two voltage generators were prepared and the configuration of the liquid crystal driving device 7 shown in FIG. 7 was adopted. The two voltage generators can be controlled by a TTL level trigger voltage, and an arbitrary waveform generator is used as a signal generator for controlling the voltage generation timing.

  Due to this voltage action, the optical path shift of the optical deflection element 1 was also generated by about 8 μm, and the optical deflection direction switching time was shortened to 0.9 ms. This is a waveform shape corresponding to FIG.

  As a comparative example of Example 1, when ± 15 V was applied in a rectangular voltage waveform shape as shown in FIG. 6A, liquid crystal alignment failure occurred, and good light deflection characteristics could not be obtained. .

[Example 2]
As another example, a high frequency was applied for 0.6 ms during the optical deflection direction switching time using the optical deflection element 1 of Example 1. One of the power sources shown in Example 1 was replaced with a voltage generator capable of applying a 20 kHz alternating current. When a frequency of 20 kHz and an amplitude of 0.5 V were applied, the optical deflection switching time was the same, but the phenomenon that the mask pattern image was blurred during the optical path shift, that is, transient scattering was reduced. This voltage waveform corresponds to that shown in FIG.

[Example 3]
Using the optical deflection element 1 of Example 1, the voltage was increased and a high frequency was applied for 0.6 ms during the optical deflection direction switching time. As a voltage generator, one of the power sources shown in Example 1 was replaced with one capable of applying an alternating current of 20 kHz, and a bias voltage of 5 V was generated by a bias voltage adding function of the alternating current power source. When 20 kHz and an amplitude of 0.5 V were applied, the optical deflection switching time was reduced to 0.8 ms, and the phenomenon that the mask pattern image was blurred during the optical path shift, that is, transient scattering was reduced. This voltage waveform corresponds to that shown in FIG.

[Example 4]
Optical deflection having a light detection device 80 that captures a part of the light emitted from the light deflection element 1 shown in FIG. 9 and detects the light deflection direction switching time, and a liquid crystal drive device 7 that controls the voltage application time by this detection signal. Apparatus 10 was configured. A half mirror was used as the spectroscopic element 81 in order to incorporate a part of the emitted light into another optical path. As the light detection device 80, a photodiode having an opening for receiving the switched light independently is used. With the trigger signal shown in the first embodiment for optical deflection switching as a reference, the amount of light detected by the photodiode is increased by the optical deflection, but when the amount of change becomes 1% or less by sampling every 50 μs, the optical deflection is performed. Considered finished. It was confirmed that the detection by the photodiode was correlated with the measurement by the CCD camera described above, and the timing of the voltage control can be obtained by detecting the light deflection direction switching time.

[Example 5]
Image evaluation was performed using the light deflection element 1 of Example 1. An image display element 13 shown in FIG. 10 was used for image display. The frame frequency was 60 Hz. At this time, the subfield time corresponds to 8.3 ms. When ± 10 V is applied by applying a rectangular voltage as shown in FIG. 6A, the effect of high-definition image due to pixel shift has been confirmed, but this is particularly associated with image switching at the pixel shift time in an image having a high spatial frequency. A decrease in contrast was observed. Moreover, when the drive voltage shown in Example 3 was applied, it was confirmed that the contrast reduction was improved and a good image could be displayed.

It is explanatory drawing of the optical deflection apparatus which is the best form for implementing this invention. It is explanatory drawing which showed typically the liquid crystal orientation in the structure shown in FIG. FIG. 3 is an explanatory diagram of an XZ cross section in a liquid crystal layer when an XYZ orthogonal coordinate system is taken as illustrated in FIG. 2. It is explanatory drawing of the result calculated about the optical deflection amount obtained with respect to the typical physical property value of the material of a liquid-crystal layer. It is a graph which compares and shows an example of the change of the applied voltage for electric field generation applied with a liquid crystal drive device, and the amount of optical deflection accompanying it. It is a graph which shows the example of the waveform of the applied voltage of an optical deflection | deviation element. It is explanatory drawing which shows the structural example of a liquid crystal drive device. It is explanatory drawing which shows the other structural example of a liquid crystal drive device. It is explanatory drawing which shows the structure of an optical deflection apparatus. It is explanatory drawing which shows the whole structure of an image display apparatus. It is explanatory drawing explaining operation | movement of an image display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical deflecting element 2,3 Substrate 5 Liquid crystal layer 6a, 6b, 6c Electrode 7,71 Liquid crystal drive device 7a. 7b, 71a, 71b Voltage generator 7c, 71c Signal generator 10 Optical deflection device 13 Image display element 80 Light receiving element

Claims (2)

A liquid crystal layer including a liquid crystal composed of a chiral smectic C phase and having a homeotropic alignment is provided between a pair of transparent substrates, and an electrode for applying an electric field in the plate surface direction of the substrate to the liquid crystal layer is formed. An optical deflection element for deflecting an optical path of light transmitted through the liquid crystal layer;
An AC voltage is applied to the electrode to generate the electric field to drive the liquid crystal, and at least a part of a light deflection direction switching time which is a time during which the deflection direction is switched by a change in the direction of the electric field; A liquid crystal driving device in which the absolute value of the voltage to be applied is larger than the latter in the optical deflection state holding time, which is the time during which the direction of the deflection after the switching is maintained,
The light deflection element has a positive dielectric anisotropy in a frequency region where the liquid crystal is at least a dielectric dispersion relaxation frequency,
The liquid crystal driving device, by superimposing an alternating current high voltage frequency than the AC voltage voltage to the applied time of the light deflection direction switching time,
The liquid crystal driving device, the voltage to be the application time of the light deflection direction switching time, the optical deflecting device for superimposing an AC voltage of more than the dielectric dispersion relaxation frequency to a higher AC voltage frequency than the AC voltage. An image display element that spatially modulates illumination light based on image information and emits it as image light for each of a plurality of image subfields obtained by further subdividing the image field in time;
An apparent pixel of the image display element by deflecting the optical path of the image light incident from each pixel of the image display element driven for each image subfield by the deflection of the optical path in synchronization with the image display element The optical deflecting device according to claim 1, wherein the optical deflecting device displays the number multiplied.
An image display device comprising:

Images