KR102612039B1 - Holographic Display - Google Patents

Abstract

The present invention relates to a holographic display in which the view window is enlarged by changing the structure, and includes a light source unit that emits straight light to an exit surface, and a space including subpixels arranged in a matrix on the light source unit. It may include a light modulator, a field lens on the spatial light modulator that collects the optical path diffracted through the spatial light modulator, and a viewing window control unit disposed close to the viewer's viewing surface.

Description

Holographic Display {Holographic Display}

The present invention relates to a three-dimensional display device, and particularly to a holographic display in which the view window is adjusted by changing the structure.

Stereoscopic display devices can be divided into glasses type and glasses-free type depending on the presence or absence of glasses.

A typical example of the glasses method is to spatially separate left and right images and display them, or to divide and display left and right images using a time division method. This glasses type has the inconvenience of requiring viewers to wear glasses when watching 3D (3-dimension) images, so a glasses-free stereoscopic image display device is considered an alternative.

The glasses-free method generally implements 3D images by installing optical elements such as a parallax barrier in front or behind the display screen to separate the optical axes of the left-eye image and the right-eye image.

Meanwhile, holographic displays have recently been proposed as part of a glasses-free method. The holographic display utilizes the coherence characteristics caused by diffraction of light, and the diffraction power is determined by the pixel size of the spatial light modulator (SLM), and the viewing window through which the viewer can view is determined by the diffraction power. . In other words, the smaller the pixel size of the spatial light modulator, the greater the diffraction power, and the better the diffraction power, the larger the viewing window. However, the pixel size is related to resolution, and because there is a limit in the process, the pixel size of the spatial light modulator cannot be reduced indefinitely. Additionally, as the pixel size increases, the resolution increases, and the amount of data transmission increases accordingly. As the resolution increases, there are also problems when driving data.

The present invention was devised to solve the above-mentioned problems, and its purpose is to provide a holographic display that can enlarge the view window by changing the structure.

The holographic display of the present invention for achieving the above object includes a light source unit that emits straight light to an exit surface, a spatial light modulator including subpixels arranged in a matrix on the light source unit, and the spatial light. On the modulator, it may include a field lens that collects the optical path diffracted through the spatial light modulator and a viewing window control unit that is disposed close to the viewer's viewing surface and expands the viewing window.

In this case, the light source unit may be a laser light source unit, each of the subpixels has a first pitch in the horizontal direction, and the viewing window control unit may include a unit lens with a second pitch corresponding to twice the first pitch. can be consecutive in the horizontal direction.

In addition, images of a hologram pattern for the left eye and a hologram pattern for the right eye may be displayed in two subpixels corresponding to the second pitch of the lenticular lens array, respectively. In this case, the light emitted through the spatial light modulator is separated for both eyes at the exit surface of each unit lens of the lenticular lens, and can transmit images of a hologram pattern for the left eye and a hologram pattern for the right eye to both eyes of the viewer.

Additionally, in response to the second pitch, a hologram pattern for the left eye and a hologram pattern for the right eye may be supplied to the spatial light modulator in a vertical direction.

For example, the spatial light modulator may be a liquid crystal panel.

Additionally, the field lens may be a film.

The field lens and the viewing window control unit may be in contact with each other.

Meanwhile, the viewing window control unit may have a curved surface in the period of the second pitch on the glass surface, or may be patterned in the period of the second pitch on the upper surface of the film.

Alternatively, the viewing window control unit may include first and second substrates facing each other, a plurality of first electrodes provided for each unit lens on the first substrate and spaced apart from each other, and a second electrode provided on the second substrate. It may include an electrode, a liquid crystal layer filled between the first and second substrates, and a voltage application unit that controls a change in the refractive index of each unit lens. In this case, the voltage application unit can change the size of the viewing window by adjusting the range between the lowest refractive index and the maximum refractive index, and when the range between the lowest refractive index and the maximum refractive index increases, the size of the viewing window can increase.

The holographic display of the present invention has the following effects.

By placing the viewing window control unit above the spatial light modulator close to the viewing surface, the diffraction power is not determined only by the resolution of the spatial light modulator, and the viewing angle limitations of the holographic display can be overcome by diffusing the light path on the surface of the lenticular lens. . In particular, even when using a liquid crystal panel with a pixel pitch determined above a certain level, from a few ㎛ to tens of ㎛ (2 to 99 ㎛), as a spatial light modulator, the viewing window can be increased according to the curvature of the viewing window control unit. In this case, the viewing window for the same viewer can be increased, or it can be increased to correspond to multiple viewers.

In addition, since there is no need to reduce the pixel size of the spatial light modulator, there is no need to increase the amount of data transmission, so there can be no limitations during driving.

In addition, the pixel in which a significant holographic pattern enters the left eye and the pixel in which a significant holographic pattern enters the right eye are set as one set, and through matching between the unit lenses of the lenticular lens, a significant image in the left and right eyes enters each eye, creating a stereoscopic hologram for both eyes. Perception is possible.

In addition, the viewing window control unit can be formed in the form of a lenticular lens array or a liquid crystal panel. When it has the form of a liquid crystal panel, the size of the viewing window can be adjusted through changes in the refractive index of each unit lens, so the viewer has a fixed view window. When high brightness is required, the size of the viewing window can be reduced, and when targeting multiple viewers or moving viewers, the size of the viewing window can be adjusted to increase, thereby meeting the various needs of the holographic display.

Meanwhile, the holographic display of the present invention delivers holographic images using a spatial division method rather than a time division method, and can improve the frame rate compared to the existing time division method.

1 is a schematic layout diagram showing a holographic display of the present invention.
Figure 2 is a diagram showing the correspondence between the spatial light modulator and the viewing window control unit of the holographic display of the present invention.
Figure 3 is a diagram showing the relationship between pixels of a spatial light modulator and diffraction angles on a viewing plane at a certain viewing distance.
4A and 4B are diagrams showing the viewing window relationship according to subpixel pitch according to the lens function of the viewing window control unit.
FIGS. 5A and 5B are diagrams showing image points and viewing areas corresponding to hologram patterns according to the lens function of the viewing window control unit.
Figure 6 is a diagram showing optical paths corresponding to both eyes of a holographic display according to the first embodiment of the present invention.
FIG. 7 is a diagram showing the correspondence between the spatial light modulator and the viewing window control unit of FIG. 6.
Figure 8 is a diagram showing expansion of the viewing area in the holographic display according to the first embodiment of the present invention.
Figure 9 is a diagram showing optical paths corresponding to both eyes of a viewer according to the first embodiment of the present invention.
FIG. 10 is a diagram illustrating an optical path for a plurality of viewers by adding holographic pattern information to a spatial light modulator corresponding to a single viewing window control unit in a holographic display according to the first embodiment of the present invention.
Figure 11 is a cross-sectional view showing a viewing window control unit of a holographic display according to a second embodiment of the present invention.
Figures 12a and 12b are plan views showing the first and second substrates of the viewing window control unit of Figure 11;
13A and 13B are diagrams showing viewing window adjustment of a holographic display according to a second embodiment of the present invention.

Hereinafter, the holographic display of the present invention will be described in detail with reference to the attached drawings.

1 is a schematic layout diagram showing a holographic display of the present invention.

As shown in FIG. 1, the holographic display of the present invention includes a light source unit 110 that emits straight light to an emission surface, a spatial light modulator 120 including subpixels arranged in a matrix on the light source unit, and On the spatial light modulator, it may include a field lens 130 that collects the optical path diffracted through the spatial light modulator and a viewing window control unit 1400 disposed close to the viewer's viewing surface. .

The light source unit 110 is a laser light source capable of outputting straight light toward the emission surface, and is adjacent to the spatial light modulator 120, and each image displayed from a pixel of the spatial light modulator 120 is converted into a pixel. It is transmitted in a straight line to the field lens 130 and the viewing window control unit 1400 corresponding to the position. In order to improve straightness, it is recommended to reduce the spatial separation between the spatial light modulator 120, the field lens 130, and the viewing window control unit 1400.

Meanwhile, by displaying a hologram pattern on the spatial light modulator 120, the hologram pattern displayed on each sub-pixel can be varied under the control of the SLM control unit (not shown), and the hologram pattern can be changed according to the control signal of the SLM control unit. In that it can be changed according to the present invention, the hologram display of the present invention can be called a digital hologram display.

As shown in the field lens 130 and the viewing window control unit 1400, the side adjacent to the spatial light modulator 120 may be the field lens 130 or the viewing window control unit 1400.

In addition, the field lens 130 and the viewing window control unit 1400 may each be in the form of a lens whose surface has a physical curvature, or may be a liquid crystal panel with an optical function having a flat film shape or modulation of the refractive index. .

Figure 2 is a diagram showing the correspondence between the spatial light modulator and the viewing window control unit of the holographic display of the present invention.

As shown in FIG. 2, the subpixels of the spatial light modulator (SLM) 110 of the present invention each have a first pitch (P1) in the horizontal direction, and the viewing window control unit 1400 has the first pitch (P1). ) may have unit lenses (L) of a second pitch (P2=2P1) corresponding to twice the pitch continuously in the horizontal direction. Here, the unit lens may be a lens of a physical shape, or may be a liquid crystal electric field lens that has a lens effect as a kind of optical effect. A liquid crystal electric field lens is a type of liquid crystal panel and has a change in refractive index with the cycle of a unit lens (L).

In the arrangement shown in FIG. 2, images of a hologram pattern (LH) for the left eye and a hologram pattern (RH) for the right eye may be displayed in two subpixels corresponding to the second pitch of the viewing window control unit 1400, respectively. In this case, the light emitted through the spatial light modulator 120 is separated for both eyes at the unit lens of the viewing window control unit 1400, and can transmit images of a hologram pattern for the left eye and a hologram pattern for the right eye to both eyes of the viewer, This allows viewing of two spatially separated holographic images. In this case, the viewing window control unit 1400 can separate the images of the left and right eyes and enlarge the viewing window according to the lens effect of the unit lens (L).

In the holographic display of the present invention, the reason for having the viewing window control unit 1400 is as follows.

Figure 3 is a diagram showing the relationship between diffraction angles between pixels of a spatial light modulator and a viewing plane at a certain viewing distance.

When the viewing distance is fixed, according to Bragg's law of diffraction, the relationship between the center of each pitch (p) and the angle Θ at the time of maximum diffraction is sin Θ ∝λ/2p (where λ is the wavelength of light) ) is in a relationship.

In other words, as the pitch size increases, the diffraction angle Θ decreases. Here, the diffraction angle Θ is proportional to the size of the view window, and thus the diffraction angle corresponds to the diffraction power. Looking at the above equation, it can be derived the relationship that the diffraction power (sin Θ) decreases as the unit pitch size of the spatial light modulator increases.

For example, in a holographic display without a viewing window control unit, assuming a viewing distance of 1 m, a spatial light modulator whose pixels have a unit pitch of about 1㎛ creates a viewing window of approximately 24 cm. You can get it. Additionally, at the same viewing distance, in the case of a spatial light modulator whose pixels have a unit pitch of about 2㎛, the diffraction power is inversely proportional to the pitch size, so a view window of approximately 12cm can be obtained.

However, the spatial light modulator that reproduces the hologram pattern is made of an optical medium whose phase and amplitude can be adjusted by voltage application conditions, such as a liquid crystal panel, and the unit pitch of the liquid crystal panel is at the level of 1㎛. It is difficult to adjust it accurately, and a 1㎛ unit pitch has 100 times the resolution of a panel with a unit pitch of 10㎛. However, as the resolution increases, the amount of data transmission increases, causing driving problems. Therefore, considering only the diffraction power, the pitch of the spatial light modulator cannot be infinitely reduced.

In addition, the liquid crystal panel forming the spatial light modulator 120, in its basic form, includes a first SLM substrate, a second SLM substrate facing each other, and a plurality of patterned pixels or sub-pixels on the first SLM substrate. It includes pixel electrodes, a counter electrode located on the second SLM substrate, and a liquid crystal layer filled between the first and second SLM substrates. Here, a pixel has two or more subpixels, and if the unit pitch of the liquid crystal panel is 1㎛ or less, the horizontal and vertical lengths of the pixel electrode of each unit subpixel are 1 due to limitations in exposure and patterning equipment. The size is less than ㎛, and such fine patterns may be difficult to form due to the process, making it physically impossible to refine the pattern of the spatial light modulator. Therefore, in addition to the spatial light modulator of the present invention, a holographic display is proposed that further includes a viewing window control unit that can separately adjust the viewing window.

Here, the inside of the liquid crystal panel forming the spatial light modulator 120 may additionally include a color filter to display a color image. In some cases, excluding the color filter, the light source unit 110 is provided with red, green, and blue laser light sources, and the driving of the spatial light modulator 120 and the driving of the light source unit 110 are time-divided to create a hologram. Color images can also be expressed.

That is, the holographic display of the present invention proposes to enlarge the viewing window by the optical configuration of the viewing window control unit 1400 in contact with the field lens even without reducing the pitch of the spatial light modulator.

The viewing window control unit 1400 of the present invention includes a field lens 130 and a field lens 130 so that the holographic image coming from the optical unit 110 through the spatial light modulator 120 and the field lens 130 can be input while maintaining straightness. It can be placed in a contiguous form.

The holographic display of the present invention has a light source with strong linearity such as a laser light source below the spatial light modulator 120, and has a viewing window control unit 1400 above the spatial light modulator 120 close to the viewing surface, so as to provide a field of view. By utilizing the light collection and diffusion characteristics of the surface of the window control unit 1400, an effect in which light is dispersed at a wide angle, similar to the effect of diffraction, is implemented.

The principle of implementing a holographic image is to create an image using the diffraction and interference of various lights emitted from a spatial light modulator, diffract it, and display a holographic image in a view window. Here, since the range where the image is diffracted refers to the view window, a certain degree of diffraction occurs in each pixel of the spatial light modulator 120, but due to the characteristic that light with strong straight propagation is dispersed, only simple diffraction power is used. When equipped with the viewing window control unit 1400 of the present invention, it is possible to view holographic images in a wider area than before.

Meanwhile, the viewing window control unit 1400 is arranged in a long semi-cylindrical shape in a direction perpendicular to the viewing surface viewed by the viewer, and has a shape in which semicircular lenses are repeated at a second pitch (P2) in the horizontal direction.

In addition, for each unit lens of the viewing window control unit 1400 arranged in a direction perpendicular to the viewing plane, two pixel columns of the spatial light modulator 120 are disposed, and the two pixel columns correspond to the left eye and the right eye, respectively. A hologram pattern is displayed.

Figures 4a and 4b are diagrams showing the viewing window relationship according to the subpixel pitch depending on the presence or absence of a lens function of the viewing window control unit.

FIGS. 4A and 4B respectively show viewing windows VW1 and VW2 corresponding to unit pixels, and are divided into cases without and with the viewing window control unit 1400.

Even in the case of having unit pixels of the same pitch, as shown in FIG. 4A, the size of the viewing window (VW1) is inevitably limited due to diffraction of the pixel 20a itself, and as shown in FIG. 4B, straight light from the pixel 120a is The optical path emitted from the final viewing window control unit 1400 is refracted at the surface of the exit surface of the viewing window control unit 1400 and is thus spread, making it possible to expand the viewing window VW2. This viewing window diffusion effect has a viewing window size for a single eye, which is the viewing window of FIG. 4A, and has a viewing window for multiple eyes when the viewing window control unit 1400 is provided, so that the viewing window has the same viewing distance. This means that 3D stereoscopic display is possible without distortion even if multiple viewers are placed or viewers are moving within a certain range.

Meanwhile, in Figure 4b, the viewing window control unit 1400 is expressed as a lens shape to show that it has a functional lens refraction effect, and is not limited to this physical shape, and is optically attached to the upper surface of the film having a lens function. It can also be changed to the form of a film patterned with the cycle of the second pitch or a liquid crystal electric field lens.

That is, the holographic display of the present invention utilizes the coherent interference characteristics due to diffraction of light. To this end, a holographic pattern is reproduced in the subpixels provided in the spatial light modulator 120, and the holographic pattern is generated by the spatial light modulator ( When the light is diffracted and emitted through 120), the field lens 130 collects the light path and focuses it at a specific location, and then spreads it again to focus on both eyes of the viewer.

Figures 5a and 5b are diagrams showing image points and viewing areas corresponding to hologram patterns depending on the presence or absence of the lens function of the viewing window control unit.

FIGS. 5A and 5B each show a hologram pattern applied to a vertical pixel column of the spatial light modulator 120 to display an image of a 'dot' at a specific location in space. As shown in FIG. 5A, when there is no viewing window control unit or the viewing window control unit does not function to expand the viewing window, a single point is located only at a specific location in space, but as shown in FIG. 5B, after the viewing window control unit 1400 is applied, In response to the same hologram pattern, the light passing through the field lens 130 is refracted and diffracted on the lens surface of the viewing window control unit 1400 to generate 'dot' images of the same image at multiple locations, thereby generating a plurality of viewing positions. You can watch the video of 'Dot'.

In addition, in the holographic display of the present invention, the holographic image supplied to the spatial light modulator (SLM) 120 is in a vertical direction (VPO: Vertical Parallax Only), and the viewing window control unit 1400 with a lens effect The length direction of each lens also follows the vertical direction, which is the direction in which the hologram image is supplied. The holographic image shown here is based on a column of single subpixels, but in reality, the pitch of the unit lens (see L in FIG. 2) of the viewing window control unit 1400 and the subpixel pitch of the spatial light modulator 120 Since there is a 2:1 relationship, a left eye hologram image and a right eye hologram image are supplied to the light modulator 120 in two subpixel columns, respectively, corresponding to one unit lens. In addition, when the left eye holographic image and the right eye holographic image are supplied, in the column of the corresponding subpixel, the shape of the individual slit / pattern of the supplied image for coherent interference is horizontal, and the actual left and right eye holographic images are transmitted to the viewing window control unit ( 1400) is disposed along the length direction of the lens. This is to prevent distortion due to phase information.

Hereinafter, operations will be described for each embodiment divided according to the type of the viewing window control unit.

*First Embodiment*

Figure 6 is a diagram showing the optical path corresponding to both eyes of the holographic display according to the first embodiment of the present invention, and Figure 7 is a diagram showing the correspondence between the spatial light modulator and the focal length control unit of Figure 6. FIG. 8 is a diagram showing the expansion of the viewing area in the holographic display according to the first embodiment of the present invention, and FIG. 9 is a diagram showing the optical path corresponding to both eyes of the viewer according to the first embodiment of the present invention.

6 to 9, the holographic display according to the first embodiment of the present invention is equipped with a viewing window control unit 1400 in the form of a lenticular lens array 140.

Here, the lenticular lens array 140 in FIGS. 6 to 9 is shown to have a curved surface on the glass surface with a period of a second pitch that is twice the first pitch of the subpixel of the spatial light modulator. . In some cases, it may be a film that is patterned identically for each unit lens to have an optical lens effect, or it may be a film that has an optical effect by controlling the internal medium. In the case of film, the unit lens will have a period twice the first pitch of the subpixel of the spatial light modulator 120.

Figure 8 shows a hologram pattern applied to a vertical pixel row of a spatial light modulator to display an image of a 'point' at a specific location in space. After the viewing window control unit in the form of a lenticular lens array 140 is applied, In response to the same holographic pattern, the surface of each unit lens of the lenticular lens array generates a 'dot' image of the same image at multiple locations through refraction and diffraction, and thus, the 'dot' image can be viewed from multiple viewing positions. will be.

Figure 9 shows that the image of the left eye hologram pattern and the image of the right eye hologram pattern are supplied to both left and right eyes of the viewer, and the spatial light modulator 120, field lens 130, and lenticular lens array 140 on the light source unit. ) The arrangement is as shown in Figure 1.

Figure 9 shows that a left-eye hologram pattern (red) and a right-eye hologram pattern (green) are supplied to two adjacent pixels of the spatial light modulator 120, respectively, and these left-eye and right-eye hologram patterns are supplied simultaneously in the same frame. , the spatial light modulator 120 receives separate control from a control unit (not shown).

In addition, the viewer adds up all the optical paths coming from different areas of the lenticular lens array 140, and a viewing window is generated in a common overlapping area. When both eyes are located in the viewing window where the optical paths commonly overlap, the corresponding holographic image You can watch . The lenticular lens array 140 of the present invention increases the width of the viewing window, allowing spatially divided images to be supplied to both eyes through a wide viewing window, making it possible to view three-dimensional holographic images with a high degree of freedom in the viewing area. In particular, compared to the method in which the diffraction power depends on the pixel pitch size of the spatial light modulator (SLM), it is not greatly influenced by the pixel pitch within the spatial light modulator, and increases the curvature of the lenticular lens array 140 to enlarge the left and right size of the viewing window. Diffraction power can be adjusted. Accordingly, the viewing window can be enlarged even in the case of having an SLM (spatial light modulator) with a pixel pitch of 2 μm or more without being greatly dependent on the diffraction power of the SLM. At this time, the viewing area for one viewer becomes large, making it possible to view a three-dimensional holographic image not only from a fixed position but also when the viewer moves slightly to the left or right (when moving).

Additionally, since the left and right eye hologram patterns are supplied together in the same frame, the frame rate can be doubled compared to the time division method of existing stereoscopic displays.

FIG. 10 is a diagram illustrating an optical path for a plurality of viewers by adding holographic pattern information to a spatial light modulator corresponding to a single viewing window control unit in a holographic display according to the first embodiment of the present invention.

Figure 10 shows that, due to the extended viewing window, a plurality of viewers can be accommodated within the viewing window, making it possible for multiple viewers to watch. Since the viewing window of the hologram with parallax is generated in multiple parts at the same viewing distance, the viewer can actually view the three-dimensional hologram from positions that do not overlap.

*Second Embodiment*

FIG. 11 is a cross-sectional view showing the viewing window control unit of the holographic display according to the second embodiment of the present invention, and FIGS. 12A and 12B are plan views showing the first and second substrates of the viewing window control unit of FIG. 11.

The viewing window control unit according to the second embodiment of the present invention is implemented in the form of a liquid crystal electric field lens 240.

As shown in FIGS. 11 to 12B, this liquid crystal electric field lens includes first and second substrates 241 and 242 facing each other, and a plurality of first electrodes provided for each unit lens on the first substrate and spaced apart from each other ( 243), a second electrode 244 provided on the second substrate, a liquid crystal layer 245 filled between the first and second substrates, and a voltage application unit that controls the change in the refractive index of each unit lens ( 250).

Here, the first electrode 243 is formed to be long in the longitudinal direction for each unit lens area, and adjacent unit lens areas are spaced apart from each other, so that they can be driven independently of each other.

In addition, the second electrode 244 is formed to cover all areas that function as a lens, excluding the edge pad area.

Meanwhile, the illustrated example of the liquid crystal electric field lens is limited to one example, and in some cases, a plurality of first electrodes may be provided for each unit lens area on the first substrate 241, and the first electrode provided in each unit lens area By applying a voltage that gradually increases or decreases from the center to the edge to the electrodes, it may be possible to implement a lens with a finer curvature.

The holographic display according to the second embodiment of the present invention can change the focus of light emitted from the liquid crystal electric field lens 240, allowing adjustment of the viewing window. That is, in the case of the first embodiment described above, since the lenticular lens array 140 has a single curved shape, the expanded viewing window cannot be adjusted after being provided in the holographic display device, but a liquid crystal electric field lens capable of controlling the electric field In the case of (240), the width of the viewing window can be varied.

Figures 13a and 13b are diagrams showing viewing window adjustment of a holographic display according to a second embodiment of the present invention.

13A and 13B, by adjusting the value of the voltage difference applied to the first electrode 243 and the second electrode 244, the maximum refractive index (Rmax) and minimum refractive index (Rmin1, Rmin2) of each unit lens ) can be changed. For example, as shown in Figure 13a, when the voltage difference applied to the first electrode 243 and the second electrode 244 is increased and the maximum refractive index (Rmax) and minimum refractive index (Rmin1) are increased, the liquid crystal electric field The focus f1 of the lens 240 is between the liquid crystal electric field lens 240 and the viewing surface, so it is focused closer to the liquid crystal electric field lens 240, which means that the curvature of each optically implemented unit lens is large. This means that, as a result, the width of the incident light diffracted from the focus to the viewing window is increased, resulting in the effect of expanding the viewing window.

And, as shown in Figure 13b, the voltage difference applied to the second electrode 243 and the second electrode 244 is reduced or close to 0, so that the difference between the maximum refractive index (Rmax) and the minimum refractive index (Rmin2) is almost reduced. In one case, the liquid crystal electric field lens 240 has almost no lens effect, and similar to a structure without a viewing window control unit, the focus f2 of the liquid crystal electric field lens 240 is the same as that of the liquid crystal electric field lens 240. Between the viewing planes, the focus is closer to the viewing plane side. As a result, the curvature of the unit lens at this time becomes small, and as a result, the width through which the incident light is diffracted at the focus is small, resulting in the effect of narrowing the viewing window compared to FIG. 13a.

That is, in the holographic display according to the second embodiment of the present invention, the voltage applied by the voltage application unit 250 to the first and second electrodes 243 and 244, respectively, has the lowest refractive index and maximum for each unit lens. The size of the viewing window can be changed by adjusting the range between the refractive indices, as shown in Figure 13a, when the range between the lowest and maximum refractive indices increases, the size of the viewing window increases, and as shown in Figure 13b, the minimum and maximum refractive indices When the value between the maximum refractive indices is close to 0, the viewing window size becomes small.

The holographic display according to the second embodiment of the present invention can adjust the refractive index displacement (Rv: Rmax-Rmin) by adjusting the voltage difference applied to the first and second electrodes 243 and 244, thereby The size of the viewing window can be controlled.

As shown in Figure 13a, expanding the viewing window size has the advantage of increasing the degree of freedom in the viewer's position and expanding the viewing area. In addition, as shown in Figure 13b, the focal length is moved closer to the viewing plane, thereby reducing the size of the viewing window, but there is an advantage in that the amount of light is concentrated in the viewing window in a narrow area, thereby increasing luminance.

This liquid crystal electric field lens 240 can secure a viewing window compensated for the required luminance by selectively adjusting the refractive index displacement according to the viewer's needs. In addition, various refractive index changes can be achieved according to changes in the voltage value applied to the first and second electrodes, so the possible range of the viewing window can be variable according to the viewer's choice or environment.

13A and 13B show only the unit lens area to illustrate the relationship between the change in refractive index of each lens and the viewing window. In the unit lens area, the first and second substrates facing the liquid crystal electric field lens 240 each have a first lens area. It indicates that the electrode and the second electrode are formed without dividing the area. 11 to 12B, the first electrodes 243 between adjacent unit lens areas are spaced apart from each other, and the second electrode 244 is formed as a pattern 244 integrated with the lens area through which light passes. do.

Meanwhile, the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention. It will be clear to a person with ordinary knowledge.

110: light source unit 120: spatial light modulator
130: field lens 140: lenticular lens array
240: liquid crystal electric field lens 1400: viewing window control unit

Claims (14)

A light source unit that emits straight light to the emission surface;
On the light source unit, a spatial light modulator including subpixels arranged in a matrix;
On the spatial light modulator, a field lens that collects the optical path diffracted through the spatial light modulator; and
A viewing window control unit disposed closer to the viewer's viewing surface than the field lens and expanding the viewing window,
Each of the subpixels has a first pitch in the horizontal direction,
The viewing window control unit has unit lenses of a second pitch corresponding to twice the first pitch continuously in the horizontal direction,
The viewing window control unit,
First and second substrates facing each other;
a plurality of first electrodes provided for each unit lens on the first substrate and spaced apart from each other;
a second electrode provided on the second substrate;
a liquid crystal layer filled between the first and second substrates; and
It includes a voltage application unit that controls the change in refractive index of each unit lens,
A holographic display in which the voltage application unit changes the size of the viewing window by adjusting the range between the lowest refractive index and the maximum refractive index. According to clause 1,
A hologram display in which the light source unit is a laser light source unit. delete According to clause 1,
A holographic display in which images of a hologram pattern for the left eye and a hologram pattern for the right eye are displayed on two subpixels corresponding to the second pitch of the viewing window control unit. According to clause 4,
The light emitted through the spatial light modulator is separated for both eyes at the exit surface of each unit lens of the viewing window control unit, and transmits images of a holographic pattern for the left eye and a holographic pattern for the right eye to both eyes of the viewer. According to clause 1,
A holographic display in which a left-eye hologram pattern and a right-eye hologram pattern are supplied to the spatial light modulator in a vertical direction in response to the second pitch. According to clause 1,
A holographic display in which the spatial light modulator is a liquid crystal panel. According to clause 1,
A holographic display in which the field lens is a film. According to clause 8,
A holographic display in which the field lens and the viewing window control unit are in contact with each other. delete delete delete delete According to clause 1,
A holographic display in which the size of the viewing window increases as the range between the lowest and highest refractive indices increases.