KR102022529B1 - System for displaying a hologram - Google Patents

Abstract

In a first embodiment of the present invention, in a system for displaying a hologram using an interference fringe, a display panel for forming a hologram in a space, a sensing camera for detecting a position of a viewer, and a viewer detected by forming a prism pattern A holographic display system includes a light path conversion cell that refracts light according to a position, and a driving part that applies a driving voltage for determining a slope value of the prism pattern to the light path conversion cell.

Description

System for displaying a hologram

The present invention relates to a display system that solves the viewing angle problem when viewing a hologram.

Recently, researches on three-dimensional (3D) image and image reproduction technology have been actively conducted. 3D image related media is expected to lead the next generation of image devices as a new concept of realistic image media that raises the level of visual information. Conventional 2D imaging systems provide planar images, but 3D imaging systems are the ultimate image rendering technology in view of showing the actual image information of objects to the viewer.

As a method for reproducing a 3D stereoscopic image, it is classified into a binocular parallax and an autostereoscopic method. The binocular parallax method uses a parallax image of the left and right eyes having a large stereoscopic effect, and a stereoscopic image display apparatus of a spectacle method that realizes a binocular parallax image using glasses has recently been commercialized. The glasses method displays polarized glasses and left and right parallax images by time-dividing the polarized glasses and left and right parallax images on the direct-view display device or the projector, and realizes stereoscopic images using polarized glasses. It is divided into shutter glasses type to implement. However, the glasses method is inconvenient to watch stereoscopic images only when the viewer wears the glasses. In order to solve this problem, a glasses-free method for viewing stereoscopic images without wearing glasses has been developed. In particular, the volumetric display method, which is one of auto glasses-free methods, can provide continuous parallax and color information, thereby providing an advantage that an observer can move the viewpoint relatively freely.

The hologram method, which is a volume expression display method, uses a principle of recording and reproducing an interference signal obtained by overlapping light reflected on an object (object wave) and coherent light (reference wave). An interference fringe formed by colliding an object wave scattered by an object with a reference wave incident in another direction using a highly coherent laser light is recorded on a photographic film. When the object wave and the reference wave meet, an interference fringe is formed by the interference, and the amplitude and phase information of the object are recorded together with the interference fringe. By irradiating the reference light to the recorded interference fringes, the interference information recorded on the hologram is restored to give a three-dimensional impression. A series of processes for creating three-dimensional images using these recording and reconstruction principles are called holograms.

A computer generated hologram (CGH) has been developed as a method for generating a hologram by a computer for storing, transmitting and image processing. The computer-generated holograms have been developed in various ways so far. Recently, due to the development of the digital industry, a system for displaying computer-generated holograms of moving images is developed without remaining in the computer-generated holograms of still images.

Computer-generated holograms create interference fringes that are stored directly on the hologram using a computer. Computation of the interference fringe image generated by a computer, and then transmitted to a spatial light modulator such as a liquid crystal-spatial light modulator (LC-SLM), which irradiates a reference light to restore the stereoscopic image. Play it. 1 is a diagram showing the configuration of a digital holographic image reproducing apparatus implementing the computer-generated hologram method according to the prior art.

Referring to FIG. 1, an interference fringe image corresponding to a stereoscopic image to be implemented in the computer 100 is generated. The generated interference fringe is transmitted to the SLM 200. The SLM 200 may be formed of a transmissive liquid crystal display panel to display an interference fringe. On one side of the SLM 200 is a laser light source 300 to be used as reference light. In order to evenly project the reference light 900 irradiated from the laser light source 300 onto the front surface of the SLM 200, the expander 400 and the lens 500 are sequentially disposed. The reference light 900 emitted from the laser light source 300 is irradiated to one side of the SLM 200 via the expander 400 and the lens 500. Accordingly, the 3D stereoscopic image 800 is displayed on the other side of the SLM 200 by the interference fringe of the hologram implemented in the SLM 200.

However, in the case of reproducing the hologram based on the LCD, the pixel pitch of one pixel is so large that the diffraction angle is too small. For this reason, there is a problem that the viewing angle for viewing the hologram is very small, and the viewer can only watch the hologram in a very narrow range.

The present invention has been devised in such a background, and allows a viewer to watch the hologram regardless of the viewing position despite the narrow viewing angle.

In a first embodiment of the present invention, in a system for displaying a hologram using an interference fringe, a display panel for forming a hologram in a space, a sensing camera for detecting a position of a viewer, and a viewer detected by forming a prism pattern A holographic display system includes a light path conversion cell that refracts light according to a position, and a driving part that applies a driving voltage for determining a slope value of the prism pattern to the light path conversion cell.

The optical path conversion cell includes a liquid crystal cell sandwiched between a first substrate and a second substrate, and a first electrode and a second electrode generating an electric field for controlling an arrangement of liquid crystal molecules constituting the liquid crystal cell. The liquid crystal molecules constituting the liquid crystal cell are arranged in a form gradually changing according to the electric field to form the prism pattern.

The liquid crystal cell is an ECB mode liquid crystal cell, and the first electrode is formed to form a stripe arrangement in a direction parallel to the initial arrangement of the ECB mode liquid crystal molecules on a first substrate in a direction in which light is incident. It is formed in the whole to the 2nd board | substrate of the output direction.

The display panel linearly polarizes light in a direction parallel to the first electrode and supplies the light to the optical path conversion cell.

The prism pattern includes n first electrodes (n = natural numbers), and the driving unit includes driving voltages having voltages linearly decreasing from the maximum to the minimum directions of the n first electrodes. Is applied to form the first prism pattern, and the second prism pattern is formed by applying a driving voltage consisting of voltages whose voltage increases linearly from the minimum to the maximum direction.

In a second embodiment of the present invention, the optical path conversion cell includes a first optical path conversion cell for refracting light in an up / down direction, and a second optical path conversion cell for refracting light in a left / right direction. The first optical path conversion cell is disposed to be close to the display panel.

Each of the first light path conversion cell and the second light path conversion cell includes a liquid crystal cell sandwiched between the first substrate and the second substrate, and a first field for controlling an arrangement of liquid crystal molecules constituting the liquid crystal cell. Comprising an electrode and a second electrode, the liquid crystal molecules constituting the liquid crystal cell are arranged in a form gradually changing in accordance with the electric field to form the prism pattern.

The liquid crystal cell is composed of an ECB mode liquid crystal cell, and the liquid crystal molecules forming the liquid crystal cell are initially arranged in parallel with the first electrode.

The first electrode constituting the first optical path conversion cell and the second optical path conversion cell are formed to form a stripe arrangement on a first substrate in a direction in which light is incident, and the second electrode is a direction in which light is output. The second substrate is formed as a whole.

The first electrode of the first light path conversion cell is arranged in a horizontal direction, and the second electrode of the second light path conversion cell is arranged in a vertical direction.

And a phase delay plate for retarding light by 90 degrees between the first light path conversion cell and the second light path conversion cell.

According to the first embodiment of the present invention, the optical path conversion cell is disposed in front of the display panel, and the optical path conversion cell is controlled by differently forming a prism pattern in accordance with the left / right position change of the viewer. . As a result, one embodiment of the present invention can move the position of generating the hologram according to the position of the viewer, it is possible to watch the hologram even in a position where the viewer could not see the hologram due to the narrow viewing angle.

According to the second exemplary embodiment of the present invention, two light path conversion cells are arranged in front of the display panel, and different prism patterns are formed in the light path conversion cells in accordance with the up / down, left / right position change of the viewer to provide light. Control light path conversion. As a result, one embodiment of the present invention can move the position of generating the hologram according to the viewer's up, down, left, right position, it is possible to watch the hologram even in the position where the viewer could not watch the hologram due to the narrow viewing angle .

In addition, in the second embodiment of the present invention, the crosstalk problem caused by the diffraction of light when passing through the optical path conversion cell is solved through the distance between the first optical path conversion cell and the second optical path conversion cell. .

1 is a diagram illustrating a system for displaying a conventional hologram.
2 is a view showing a schematic configuration of a hologram system according to a first embodiment of the present invention.
3 is a cross-sectional view of a light path conversion cell by cutting along line III-III of FIG. 2.
4 and 5 are diagrams for explaining the principle that the light is refracted according to the prism pattern formed in the optical path conversion cell.
FIG. 6 is a view for explaining a driving method of the hologram display system of the first embodiment.
7 is a view showing a schematic configuration of a hologram system according to a second embodiment of the present invention.
8 and 9 are diagrams illustrating a principle of refraction of light according to a prism pattern formed in a first optical path conversion cell.
10 is a view for explaining a driving method of the hologram display system according to the second embodiment.
11 is a view illustrating a viewing distance at which a hologram can be viewed without a crosstalk problem when viewing the hologram through the hologram system of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout. In the following description, when it is determined that a detailed description of known functions or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Component names used in the following description may be selected in consideration of ease of specification, and may be different from actual product part names.

2 shows a schematic configuration of a hologram system according to a first embodiment of the present invention. As illustrated in FIG. 2, the hologram display panel 10, the optical path conversion cell 30, the display panel driver 50, the optical path conversion cell driver 60, the controller 80, and the sensing camera 90 Include.

In this first embodiment, the hologram display panel 10 has the same configuration as described above with reference to FIG. That is, the hologram display panel 10 is composed of a transmissive LCD. The hologram display panel 10 receives an interference fringe pattern and displays the hologram display panel 10. Accordingly, the hologram may be displayed on the other side of the display panel 10 while light emitted from the laser light source passes through the hologram display panel 10. have.

The light path conversion cell 30 is disposed in front of the display panel 10 based on a direction in which light travels (the + z axis direction of the drawing). The optical path conversion cell 30 passes light incident from the display panel 10 as it is or forms a prism pattern in the left direction (-θ) or the right direction (+ θ) (based on the x-axis direction of the drawing). Refraction Therefore, the generated position of the hologram generated by the predetermined distance away from the display panel 10 is adjusted in the horizontal axis (x-axis) direction, that is, the left / right direction by the optical path conversion cell 30.

The display panel driver 50 includes a gate driver and a data driver. The data driver receives the hologram data DATA from the controller 80 and uses the positive / negative gamma compensation voltage supplied from the gamma voltage generation circuit (not shown) to convert the hologram data DATA to the positive / negative polarity. Convert to analog data voltage. The data driver supplies a positive / negative analog data voltage to the data lines of the display panel 10. The gate driver sequentially supplies a gate pulse (or scan pulse) synchronized with the data voltage to the gate lines of the display panel 10 under the control of the controller 80.

The optical path conversion cell driver 60 supplies a driving voltage for driving the optical path conversion cell 30 to the optical path conversion cell 30. This driving voltage adjusts the inclination value of the prism pattern formed in the optical path conversion cell so that the hologram can be displayed according to the position of the viewer. The driving voltage may be composed of sets of voltages that decrease or increase linearly to linearly adjust the arrangement direction of the liquid crystal molecules constituting the liquid crystal cell.

The controller 80 controls the display panel driver 50 to drive the display panel 10. The controller 80 supplies the gate driver control signal GCS to the gate driver, and supplies the hologram data DATA and the data driver control signal DCS to the data driver. The gate driver control signal GCS may include a gate start pulse, a gate shift clock, a gate output enable signal, and the like. The data driver control signal DCS may include a source start pulse, a source sampling clock, a source output enable signal, a polarity control signal, and the like.

The sensing camera 90 captures an image of the viewer and transmits the captured image to the controller 80. The controller 80 analyzes the captured image to calculate coordinates at which the viewer is located. The controller 80 compares the calculated position coordinates of the viewer with the reference point to determine where the viewer is located relative to the reference point. The controller 80 controls the light path conversion cell driver 60 according to the viewer position information to form a prism pattern having a predetermined inclination value in the light path conversion cell 30. When the viewer moves in the horizontal axis relative to the reference point, the optical path conversion cell driver 60 forms a prism pattern in the optical path conversion cell 30 to refracted incident light in the horizontal axis (x-axis) direction. Control 30. In particular, the optical path conversion cell 30 controls the direction in which incident light is refracted differently depending on whether the horizontal axis (x-axis) value of the viewer's position coordinate is positive or negative. For example, the light path conversion cell 30 forms a first prism pattern when the horizontal axis (x-axis) value of the viewer's position coordinates is positive, thereby refracting incident light in the + θ direction, and the horizontal axis of the viewer's position coordinates. If the (x-axis) value is negative, the second prism pattern is formed to refrac the incident light in the -θ direction. In addition, when the difference between the abscissa (x-axis) value of the viewer's position coordinates and the abscissa (x-axis) value of the reference point is smaller than a predetermined threshold value, the viewer may be determined to be located at the reference point. Passes the incident light as it is without forming a prism pattern.

Meanwhile, the optical path conversion cell driver 60 refracts the first driving voltage for allowing the light path conversion cell 30 to pass the incident light therein, the second driving voltage for refracting the + θ direction, and the -θ direction. It may include a look-up table that stores a third driving voltage for. In this case, the optical path conversion cell driver 60 selects and outputs any one of the first to third driving voltages from the look-up table in response to the control signal of the controller 80. Here, the look-up table may store a plurality of second driving voltages and a plurality of third driving voltages so that the prism patterns have different inclination values in order to correspond to various positions of the viewer.

Hereinafter, the configuration of the optical path conversion cell 30 will be described in detail with reference to FIG. 3. 3 is a cross-sectional view taken along line III-III of FIG. 2.

In FIG. 3, the optical path conversion cell 30 forms a structure in which the liquid crystal cell LC is sandwiched between the first substrate 31 and the second substrate 32.

The first substrate 31 is composed of a plastic substrate or a glass substrate and faces the display panel 10. That is, the first substrate 31 is disposed in the direction in which light is incident on the optical path conversion cell 30. The first electrode 33 is formed on the first substrate 31. The first electrode 33 may be formed on the first substrate 31 by using a transparent conductive material, for example, a transparent conductive oxide such as ITO or IZO through a photolithography process. The first electrode 113 extends long in one direction, is spaced apart from the neighboring by a predetermined distance, and is disposed side by side to form a lattice. In FIG. 3, the first electrodes 33 are arranged parallel to each other in a direction penetrating the drawing (y-axis direction relative to the drawing), and are linearly polarized in the vertical direction to be parallel to light supplied from the display panel 10. Is arranged. The first electrode 33 is covered with a transparent protective layer 35 and protected. The transparent protective layer 35 is made of an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx).

The second substrate 32 is composed of a glass substrate or a plastic substrate, similarly to the first substrate 31, and is disposed in a direction in which light passes through the optical path conversion cell 30.

The second electrode 34 is formed on the second substrate 32. Unlike the first electrode 33, the second electrode 32 is formed in common throughout the second substrate 32. The second electrode 34 may be formed of a transparent material such as transparent conductive oxide such as ITO or IZO to allow light to pass therethrough. The second electrode 34 is covered with a transparent protective layer 36 and protected. The transparent protective layer 36 is made of an inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx).

The liquid crystal cell LC sandwiched between the first substrate 31 and the second substrate 32 is arranged in an electrically controlled irefringence (ECB) mode.

As is known, the liquid crystal molecules in the ECB mode have the same rubbing direction of the alignment layers (not shown) formed inside the first and second substrates. The liquid crystals present therebetween are initially oriented in a direction in which the major axis is parallel to the first electrode (the y axis direction in the drawing). Accordingly, in this ECB mode, all the liquid crystal molecules in the liquid crystal cell are arranged with the long axis parallel to the first electrode 33 before the voltage is applied, and when the voltage is applied, the liquid crystal molecules are arranged in the same direction as the electric field. Rotate to achieve That is, in the ECB mode, the liquid crystal molecules rotate 90 degrees between the horizontal direction and the vertical direction.

4 and 5 are diagrams illustrating a prism pattern of the optical path conversion cell. 4 shows a prism pattern that refracts light in the + θ direction, and FIG. 5 shows a prism pattern that refracts light in the -θ direction.

As shown, in the ECB mode, the prism patterns 1PP and 2PP are implemented by adjusting the alignment direction of the liquid crystal. That is, in the ECB mode, the liquid crystal forms an arrangement state between the state parallel to the first electrode (y-axis direction in the drawing) and the state perpendicular to the first electrode (z-axis direction in the drawing). In the ECB mode, the liquid crystal molecules have a minimum refractive index no when in a direction perpendicular to the first electrode, and a maximum refractive index ne when in a direction parallel to the first electrode. Accordingly, since the light transmitted from the display panel 10 is linearly polarized light in the vertical direction (y-axis direction of the drawing), the refractive index varies according to the arrangement direction of the liquid crystal molecules. That is, the liquid crystal molecules arranged in the horizontal direction (the z-axis direction of the drawing) with respect to the linearly polarized light in the vertical direction (the y-axis direction of the drawing) are the minimum refractive index (no), while the liquid crystal molecules arranged in the vertical direction have the maximum refractive index ( ne).

Therefore, when the alignment direction of the liquid crystal is adjusted along the + x axis so that the alignment direction of the liquid crystal included in one pitch 1P of the prism patterns 1PP and 2PP is gradually vertical in the horizontal state, the tilt is tan. A prism pattern of (+ θ) can be formed (see Fig. 4), and if the alignment direction of the liquid crystal is adjusted along the -x axis, a prism pattern of tan (-θ) can be formed (see Fig. 5). ).

First, as shown in FIG. 4, in the case of forming a prism pattern having a tan (+ θ) slope, a second driving voltage consisting of voltages gradually decreasing along the + x axis direction is applied to the first electrode 33. . For example, five first electrodes 33 are disposed in one pitch 1P of the first prism pattern 1PP, and the first electrodes 33 are arranged along the + x-axis direction. It is called electrode, multi-electrode, Ra-electrode, and Ma-electrode, V1 voltage is applied to provisional electrode, V2 voltage is applied to bare electrode, V3 voltage is applied to multielectrode, V4 voltage is applied to Ra-electrode, and Assuming that the voltage V5 is applied to the electrode, the magnitude of the voltage satisfies the relationship of "V1> V2> V3> V4> V5".

In addition, as shown in FIG. 5, in the case of forming a prism pattern having a tan (−θ), a third driving voltage including progressively increasing voltages along the + x axis direction is applied to the first electrode 33. . Under the same assumption as above, the voltages forming the third driving voltage satisfy a relationship of V1 <V2 <V3 <V4 <V5.

On the other hand, in the ECB mode, the liquid crystal cell is in a state in which all liquid crystal molecules are arranged in a vertical direction (y-axis direction in the drawing) without an electric field applied. As such, since all of the liquid crystal molecules of the liquid crystal cell LC maintain the vertically aligned state, there is no change in the refractive index of the liquid crystal molecules depending on the position. Accordingly, the light linearly polarized in the vertical direction passes through the optical path conversion cell 30 as it is.

6 is a flowchart illustrating a method of driving a hologram system according to the first embodiment described above.

In FIG. 6, in step S101, the display panel 10 receives hologram data and displays holograms in a space.

In operation S102, the sensing camera 90 captures an image of the viewer and transmits the captured image to the controller 80. The controller 80 analyzes the captured image to calculate coordinates at which the viewer is located. The controller 80 compares the calculated position coordinates of the viewer with the reference point to determine where the viewer is located relative to the reference point. When the viewer moves in a direction of + θ relative to the reference point, the controller 80 inputs the second driving voltage according to the viewer's position to the first electrode 31 of the optical path conversion cell 30, respectively. As a result, the light path conversion cell 30 forms a prism pattern to refract the light incident from the display panel 10 to the place where the viewer is located.

In particular, the light path conversion cell 30 controls the light to be refracted in different directions depending on whether the viewer's position has moved by + θ or -θ. The optical path conversion cell 30 forms a prism pattern as shown in FIG. 4 when the viewer's position is shifted by + θ so that light is refracted by + θ, and the viewer is moved by -θ. By forming a prism pattern as shown in FIG. 5 so that light is refracted by -θ, a 3D image is displayed at the viewer's position (S103 to S106).

 In addition, when the position change of the viewer is smaller than the predetermined threshold value, since there is no movement of the position of the viewer, the light path conversion cell 30 is controlled to transmit light as it is without forming a prism pattern (S107).

As described above, in the first exemplary embodiment of the present invention, the optical path conversion cell 30 is disposed in front of the display panel 10, and the prism is formed in the optical path conversion cell 30 in accordance with the left / right position change of the viewer. Different patterns are formed to control light path transitions. As a result, according to an embodiment of the present invention, since the position of generating the hologram may be moved according to the position of the viewer, the hologram may be viewed even at a position where the viewer could not watch the hologram due to the narrow viewing angle.

Hereinafter, a hologram system according to a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that the position of the viewer is adjusted by adjusting the position of the viewer in the up and down directions (y-axis direction of the drawing).

7 shows a schematic configuration of a hologram system according to a second embodiment of the present invention. As illustrated in FIG. 7, the hologram display system of this second embodiment includes a hologram display panel 10, first and second optical path conversion cells 30a and 30b, and a phase retardation plate 30c positioned therebetween. And a light path conversion cell 30, a display panel driver 50, a light path conversion cell driver 60, a controller 80, and a sensing camera 90.

In this second embodiment, the hologram display panel 10 is the same as that of the first embodiment described above, and thus its detailed description is omitted.

The first light path conversion cell 30a is disposed in front of the display panel 10 with respect to the direction in which light travels (the + z axis direction of the drawing). The first light path converting cell 30a passes light incident from the display panel 10 as it is, or forms a prism pattern in a horizontal direction (x-axis direction in the drawing) so that the light is directed upward or downward. Refraction Therefore, the generated position of the hologram can be adjusted in the up / down direction by the first light path conversion cell 30a.

The second light path conversion cell 30b is further positioned in front of the first light path conversion cell 30a. The second optical path conversion cell 30b passes the light supplied from the first optical path conversion cell 30a as it is, or forms a prism pattern in a vertical direction (y-axis direction in the drawing) to the left direction (-θ). ) Or the light is refracted in the right direction (+ θ) (based on the x-axis direction in the drawing). Therefore, the generated position of the hologram can be adjusted in the horizontal axis (x-axis) direction, that is, the left / right direction by the second optical path conversion cell 30b.

The display panel driver 50 includes a gate driver and a data driver. The data driver receives the hologram data DATA from the controller 80 and uses the positive / negative gamma compensation voltage supplied from the gamma voltage generation circuit (not shown) to convert the hologram data DATA to the positive / negative polarity. Convert to analog data voltage. The data driver supplies a positive / negative analog data voltage to the data lines of the display panel 10. The gate driver sequentially supplies a gate pulse (or scan pulse) synchronized with the data voltage to the gate lines of the display panel 10 under the control of the controller 80.

The light path conversion cell driver 60 supplies driving voltages for driving the light path conversion cell 30 to the first light path conversion cell 30a and the second light path conversion cell 30b, respectively. The driving voltage adjusts the inclination value of the prism pattern formed in the optical path conversion cell so that the hologram can be displayed according to the position of the user. The driving voltage may be composed of sets of voltages that decrease or increase linearly to linearly adjust the arrangement direction of the liquid crystal molecules constituting the liquid crystal cell.

The optical path conversion cell driver 60 may include a first driving voltage for passing light supplied to the first optical path conversion cell 30a as it is, a second driving voltage for refracting upward, and a direction for refracting downward. The third driving voltage, the fourth driving voltage for passing the light supplied to the second light path conversion cell 30b as it is, the fifth driving voltage for refracting in the left direction, and the sixth driving voltage for refracting in the right direction It may include a stored look-up table. In this case, the optical path conversion cell driver 60 selectively reads and outputs the first to sixth driving voltages recorded in the look-up table in response to the control signal of the controller 80. Here, the look-up table may store a plurality of driving voltages for the prism pattern to have different inclination values in order to correspond to various positions of the user.

The controller 80 controls the display panel driver 50 to drive the display panel 10. The controller 80 supplies the gate driver control signal GCS to the gate driver, and supplies the hologram data DATA and the data driver control signal DCS to the data driver. The gate driver control signal GCS may include a gate start pulse, a gate shift clock, a gate output enable signal, and the like. The data driver control signal DCS may include a source start pulse, a source sampling clock, a source output enable signal, a polarity control signal, and the like.

The detection camera 90 captures an image of a user and transmits the captured image to the controller 80. The controller 80 analyzes the captured image to calculate the coordinates where the user is located. The controller 80 compares the calculated position coordinates of the user with the reference point to determine how much the user has moved in the left / right and up / down directions with respect to the reference point. The controller 80 controls the light path conversion cell driver 60 based on the positional information to have a prism pattern having predetermined inclination values in the first light path conversion cell 30a and the second light path conversion cell 30b, respectively. Supply a driving voltage to be formed in the.

Hereinafter, the optical path conversion cell 30 will be described. The configuration of the optical path conversion cell 30 is the same as that of the optical path conversion cell 30 of the first embodiment described above. However, since the first optical path conversion cell 30a forms a prism pattern in a horizontal direction (x-axis direction in the drawing), the first electrode 33 is in the x-axis direction in the drawing, that is, the same horizontal direction as the prism pattern. It is formed side by side with its neighbors. In addition, since the second optical path conversion cell 30b forms a prism pattern in a vertical direction (y-axis direction in the drawing), the first electrode 33 is perpendicular to the y-axis direction of the drawing, that is, the prism pattern. It is formed side by side with neighbors in the direction. This second light path conversion cell 30b is configured in the same manner as the light path conversion cell of the first embodiment described above, and its function is also the same.

8 and 9 are diagrams illustrating a prism pattern of the first optical path conversion cell 30a added in the second embodiment. 8 shows a prism pattern that refracts light in the + θ direction (upward direction), and FIG. 9 shows a prism pattern that refracts light in the -θ direction (downward direction).

As shown, in the ECB mode, the prism patterns 1PP and 2PP are implemented by adjusting the alignment direction of the liquid crystal. That is, in the ECB mode, the liquid crystal rotates 90 degrees between the state parallel to the first electrode 33 (the x-axis direction in the drawing) and the state perpendicular to the first electrode (the z-axis direction in the drawing).

 In ECB mode, the liquid crystal has a refractive index of minimum when the liquid crystal is perpendicular to the first electrode 33 (z-axis direction in the drawing) and a refractive index when the liquid crystal is in parallel with the first electrode (x-axis direction in the drawing). ne) is the maximum. Accordingly, since the light supplied from the display panel 10 is linearly polarized light in the horizontal direction (x-axis direction of the drawing), the refractive index varies according to the arrangement direction of the liquid crystal molecules. That is, the liquid crystal molecules arranged in the direction perpendicular to the linearly polarized light in the horizontal direction (the z-axis direction of the drawing) are the minimum refractive index no, while the liquid crystal molecules arranged in the horizontal direction (the x-axis direction of the drawing) are maximum. The refractive index ne is obtained.

Therefore, + y so that the alignment direction of the liquid crystals contained in one pitch 1P of the prism patterns 1PP and 2PP becomes a gradually horizontal state (the x-axis direction in the drawing) in the vertical state (the z-axis direction in the drawing). By adjusting the alignment direction of the liquid crystal along the axis (up to down), it is possible to form a prism pattern with a tan (+ θ) inclination (see FIG. 8), and along the -x axis (down to up). By adjusting the arrangement direction, it is possible to form a prism pattern having a tan (−θ) inclination (see FIG. 9).

First, as shown in FIG. 8, in the case of forming a prism pattern having a tan (+ θ) slope, a second driving voltage consisting of voltages gradually decreasing along the -y axis direction is applied to the first electrode 33. . For example, five first electrodes 33 are disposed in one pitch 1P of the first prism pattern 1PP, and the first electrodes 33 are arranged along the −y axis direction. It is called electrode, multi-electrode, Ra-electrode, and Ma-electrode, V1 voltage is applied to provisional electrode, V2 voltage is applied to bare electrode, V3 voltage is applied to multielectrode, V4 voltage is applied to Ra-electrode, and Assuming that the voltage V5 is applied to the electrode, the magnitude of the voltage satisfies the relationship of "V1> V2> V3> V4> V5".

In addition, as shown in FIG. 9, in the case of forming a prism pattern having a tan (−θ), a third driving voltage including progressively increasing voltages along the −y axis direction is applied to the first electrode 33. . Under the same assumption as above, the voltages forming the third driving voltage satisfy a relationship of V1 <V2 <V3 <V4 <V5.

On the other hand, in the ECB mode, since the liquid crystal cell is in a state in which all liquid crystal molecules are arranged in a direction parallel to the first electrode in the state where no electric field is applied, there is no change in the refractive index of the liquid crystal molecules depending on the position. Accordingly, light linearly polarized in the vertical direction passes through the first optical path conversion cell 30a as it is.

On the other hand, since the first electrode 33 to which the driving voltage is applied in the first optical path conversion cell 30a is arranged in the horizontal direction, the liquid crystal cells of the ECB mode rotate 90 degrees in the initial arrangement in the horizontal direction. . Therefore, in order to form the prism pattern, light linearly polarized in the horizontal direction (x-axis direction in the drawing) is required.

However, in the second optical path conversion cell 30b, the first electrodes 33 are arranged in the vertical direction. Accordingly, the liquid crystal molecules constituting the liquid crystal cell in the second optical path conversion cell 30b rotate 90 degrees while being aligned in the initial vertical direction (x-axis direction in the drawing) in parallel with the first electrode 33. Therefore, when light linearly paralleled in the horizontal direction is supplied to the second optical path conversion cell 30b, the refractive index anisotropy according to the direction of the liquid crystal does not appear, and the prism pattern is not made.

Therefore, in this second embodiment, the phase delay plate 30c is further included between the first light path conversion cell 30a and the second light path conversion cell 30b. The phase retardation plate 30c may convert the polarization direction of the provided light by 90 degrees. Therefore, the light in the horizontal direction transmitted through the first light path conversion cell 30a is linearly polarized by the light in the vertical direction while passing through the phase retardation plate 30c.

Meanwhile, since the light is refracted in the left / right direction in the second light path conversion cell 30b is the same as described with reference to FIGS. 4 and 5, the description thereof will be omitted.

10 is a flowchart illustrating a method of driving a hologram system according to the second embodiment.

In FIG. 10, in operation S11, the display panel 10 receives hologram data and displays holograms in a space.

In operation S12, the sensing camera 90 captures an image of the user and transmits the captured image to the controller 80. The controller 80 analyzes the captured image to calculate the coordinates where the user is located. Here, the coordinates are (x, y) coordinates corresponding to the left / right and (a, b) coordinates corresponding to the up / down. The control unit 80 compares the calculated position coordinates of the user with the reference point and the user moves up / down from the reference point. Determine how much you moved left / right.

According to the determination result, the controller 80 selects the first driving voltage and the second driving voltage according to the position of the user. Here, the first driving voltage is supplied to the first optical path conversion cell 30a at a voltage selected based on the (a, b) coordinates to form a prism pattern, and the second driving voltage is based on the (x, y) coordinates. Is supplied to the second optical path conversion cell 30b at a voltage selected to form a prism pattern.

On the other hand, if the change in the user's position is less than the predetermined threshold value because the user does not move the position, the light path conversion cell 30 is controlled to transmit the light as it is without forming a prism pattern (S13).

11 is a diagram illustrating a viewing distance where no crosstalk occurs. Hereinafter, with reference to FIG. 11, the viewing distance D which can watch a hologram without causing a crosstalk problem in the hologram display system mentioned above is demonstrated.

When light passes through the above-described optical path conversion cell due to diffraction, light is divided into light of different orders. However, when the hologram displays the left eye image and the right eye image for each frame in a binocular parallax manner, when light of different orders is visible from the same eye, a crosstalk problem occurs. For example, when displaying the left eye image in the first frame and the right eye image in the second frame, the left eye image of the first frame may look like the right eye image due to diffraction phenomenon in the second frame.

In order to watch the hologram without this cross talk problem, the viewer must be at least a distance that satisfies the following conditions.

Equation 1 below shows the relationship between the diffraction angle α and the prism pattern described above. According to Equation 1, it can be seen that the diffraction angle α increases as the width P of the prism pattern decreases.

[Equation 1]

Sin (α) = λ / P (λ: wavelength of light)

Further, assuming that the light of each diffraction order having a diffraction angle ((α) according to the prism pattern is 6.5 mm, the minimum D value at which crosstalk does not occur is defined as in Equation 2 below. .

[Equation 2]

tan (α / 2) = (L / 2) / D, (L: distance between both eyes, D: distance from the light path conversion cell to both eyes)

However, since the distance L between both eyes and the diffraction angle α are given values, when the viewer views the hologram at a distance greater than or equal to the D value obtained through Equation 2, the light of different orders is the same due to the diffraction phenomenon. It is possible to watch holograms without any visible crosstalk problems.

As described above, those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (15)

In a system for displaying a hologram using an interference fringe,
A display panel forming a hologram in the space;
A detection camera that detects the viewer's position,
A first optical path conversion cell for refracting the light in the up / down direction, and a second optical path conversion cell for refracting the light in the left / right direction, thereby forming a prism pattern to provide light to the detected viewer's position. An optical path conversion cell for refracting;
A driving unit configured to apply a driving voltage to the optical path conversion cell to determine a slope value of the prism pattern,
The first light path conversion cell is disposed closer to the display panel among the first light path conversion cell and the second light path conversion cell;
And the left and right directions are spaced apart directions of both viewers.
delete delete delete delete delete delete The method of claim 1,
Each of the first light path conversion cell and the second light path conversion cell,
A liquid crystal cell sandwiched between the first substrate and the second substrate,
It comprises a first electrode and a second electrode for generating an electric field for controlling the arrangement of the liquid crystal molecules constituting the liquid crystal cell,
The liquid crystal molecules forming the liquid crystal cell are arranged in a form gradually changing according to the electric field to form the prism pattern.
The method of claim 8,
The liquid crystal cell comprises an ECB mode liquid crystal cell, wherein the liquid crystal molecules forming the liquid crystal cell are initially arranged in parallel with the first electrode.
The method of claim 9,
The first electrode constituting the first optical path conversion cell and the second optical path conversion cell are formed to form a stripe arrangement on a first substrate in a direction in which light is incident, and the second electrode is a direction in which light is output. A hologram display system formed entirely on a second substrate of the substrate.
The method of claim 10,
The first electrode of the first optical path conversion cell is arranged in a horizontal direction, the second electrode of the second optical path conversion cell is arranged in a vertical direction.
The method of claim 11,
And a phase retardation plate disposed between the first light path conversion cell and the second light path conversion cell to convert the polarization direction of the provided light by 90 degrees.
The method of claim 10,
The display panel,
And a polarized light in a direction parallel to the first electrode to supply the light to the first optical path conversion cell.
The method of claim 10,
And n (n = natural numbers) first electrodes arranged on the prism pattern.
The method of claim 14,
The driving unit,
The first prism pattern is formed by applying a driving voltage consisting of voltages of which voltages are linearly decreased from maximum to minimum directions to the n first electrodes, and voltages of which voltages increase linearly from minimum to maximum directions. A hologram display system for applying a driving voltage consisting of a second prism pattern.

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