Patent Description:
Glass-required three-dimensional (3D) technology and glasses-free 3D technology are widely used to present a 3D image. Examples of the glass-required three-dimensional (3D) technology include polarized glasses-type methods and shutter glasses-type methods. Examples of the glasses-free 3D technology include lenticular methods and parallax barrier methods. These methods use binocular parallax and increasing the number of viewpoints is limited. In addition, these methods may make the viewers feel tired due to the difference between the depth perceived by the brain and the focus of the eyes.

Recently, holographic display methods have been suggested to have the brain feel consistency between the perceived depth and the focus of the eyes. According to a holographic display technique, when reference light is emitted onto a hologram pattern having recorded thereon an interference pattern obtained by interference between object light reflected from an original object and the reference light, the reference light is diffracted and an image of the original object is reproduced. When a currently commercialized holographic display technique is used, a computer-original object to light, is provided as an electric signal to a spatial light modulator. Then, the spatial light modulator forms a hologram pattern and diffracts reference light according to the input CGH signal, thereby generating a 3D image.

Document <CIT> discloses a color transflective liquid crystal display that is capable of display in both a reflective mode and a transmissive mode.

The invention is directed to a spatial light modulator as recited in appended independent claim <NUM> and to a holographic display apparatus as recited in appended dependent claim <NUM>. Other aspects of the invention are recited in the other appended dependent claims.

Embodiments may thus provide an extendable viewing angle holographic 3D image display device. Put another way, embodiments may provide a larger/wider viewing angle within which a viewer can observe a hologram image. A 3D image display device according to an embodiment may therefore be used for a personal mobile display device, a monitor, a TV, and the like.

It is proposed to split a pixel by adding black masks to the pixel structure. If a pixel pitch decreases, a size of viewing window increases. Split pixels merely split by the additional black mask, and split pixels corresponding to existing pixels have the same physical property by an address signal. That is, in the case of splitting one pixel into four portions for example, the split pixels are merely blocked by the black mask of the existing pixel, and it changes identically by an electric address signal. However, as stated above, the viewing window increases (e.g. gets larger) since the pixel pitch decreased.

There is proposed a method of expanding the viewing window by adding a black mask to split an existing pixel structure, for example either inside the spatial light modulator (SLM) or outside the SLM. A manufacturing process of adding a black mask to an existing SLM is very easy since it is performed by an operation identical to the existing SLM manufacturing process.

Embodiments therefore propose a concept for expanding a viewing window (i.e. range of viewing angles) by splitting pixels using an additional black mask to an SLM.

The above and/or other aspects will be more apparent by describing certain exemplary embodiments, with reference to the accompanying drawings, in which:.

Exemplary embodiments are described in greater detail below with reference to the accompanying drawings.

The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. However, it is apparent that the exemplary embodiments can be practiced without those specifically defined matters.

In a layer structure described below, an expression "above" or "on" may include not only "immediately on in a contact manner" but also "on in a non-contact manner".

<FIG> is a diagram schematically showing a structure of a holographic display apparatus <NUM> according to an exemplary embodiment.

Referring to <FIG>, the holographic display apparatus <NUM> according to an exemplary embodiment may include a light source <NUM> providing light and a spatial light modulator <NUM> forming a hologram pattern to modulate incident light. The holographic display apparatus <NUM> may further include a Fourier lens <NUM> that allows the light modulated by the spatial light modulator <NUM> to be focused in a predetermined space. The modulated light may be focused on the predetermined space by the Fourier lens <NUM>, and thus a hologram image may be reproduced in space. The light may be converged by the Fourier lens <NUM>, and thus a viewing angle of the reproduced hologram image may increase. However, if the light source <NUM> provides collimated convergence light, the Fourier lens <NUM> may be omitted. The light source <NUM> may be a laser source that provides light having a high spatial coherence to the spatial light modulator <NUM>. However, if the light provided by the light source <NUM> has a certain degree of spatial coherence, since the light may be sufficiently diffracted and modulated by the spatial light modulator <NUM>, a light-emitting diode (LED) may be used as the light source <NUM>. For example, the light source <NUM> may include an array of a plurality of lasers or LEDs. In addition to the laser source or the LED, any other light sources may be used as the light source <NUM> as long as light having spatial coherence is emitted.

Meanwhile, if the holographic display apparatus <NUM> employs a binocular hologram method of providing a right eye hologram image and a left eye hologram image respectively having viewpoints corresponding to both eyes of an observer, i.e. a right eye viewpoint and a left eye viewpoint, the light source <NUM> may include a right eye light source 110a and a left eye light source 110b. For example, the right eye light source 110a may provide a right eye viewing zone of the observer with light, and the left eye light source 110b may provide a left eye viewing zone of the observer with light. Therefore, if the light emitted by the right eye light source 110a is modulated by the spatial light modulator <NUM>, the right eye hologram image may be formed in the right eye viewing zone of the observer. If the light emitted by the left eye light source 110b is modulated by the spatial light modulator <NUM>, the left eye hologram image may be formed in the left eye viewing zone of the observer. Each of the eye light source 110a and the left eye light source 110b may include the array of the plurality of lasers or LEDs. Although the eye light source 110a and the left eye light source 110b are separately illustrated in <FIG> for convenience of description, one backlight panel including the array of LEDs may be used to provide the right eye viewing zone and the left eye viewing zone with light.

The spatial light modulator <NUM> may form a hologram pattern for diffracting and modulating the incidence light, according to a hologram data signal provided by a processor. The light spatial modulator <NUM> may use a phase modulator that performs phase modulation or an amplitude modulator that performs amplitude modulation. Although the spatial light modulator <NUM> of <FIG> is a transmissive spatial light modulator, a reflective spatial light modulator may also be used. The transmissive light spatial modulator may use, for example, a light modulator using a liquid crystal device (LCD) or a semiconductor light modulator based on a compound semiconductor such as GaAs. The reflective spatial light modulator may use, for example, a digital micromirror device (DMD), a liquid crystal on silicon (LCoS), or a semiconductor light modulator.

The spatial light modulator <NUM> according to the present exemplary embodiment may provide the same effect as reducing a pixel pitch without increasing resolution. For example, <FIG> is a cross-sectional view schematically showing a structure of a pixel of the spatial light modulator <NUM> according to an exemplary embodiment.

Hereinafter, although the structure of the pixel of the spatial light modulator <NUM> is described for the case when the spatial light modulator <NUM> includes an LCD according to an exemplary embodiment, the same principle may apply when the spatial light modulator <NUM> includes other light modulation device.

Referring to <FIG>, the spatial light modulator <NUM> may include, for example, a first transparent substrate <NUM> and a second transparent substrate <NUM> that are disposed to face each other, a liquid crystal cell <NUM> disposed between the first transparent substrate <NUM> and the second transparent substrate <NUM>, a driving circuit <NUM> disposed on the first transparent substrate <NUM> and driving the liquid crystal cell <NUM>, an opaque black matrix <NUM> disposed on the second transparent substrate <NUM> and blocking light such that the driving circuit <NUM> may not be seen, and a mask member <NUM> disposed on the second transparent substrate <NUM> and splitting the liquid crystal cell <NUM>. The spatial light modulator <NUM> may further include a first polarizing plate <NUM> disposed on an external surface of the first transparent substrate <NUM> and a second polarizing plate <NUM> disposed on an external surface of the second transparent substrate <NUM>.

Although only one pixel of the spatial light modulator <NUM> is illustrated in <FIG> for convenience of description, the spatial light modulator <NUM> may include a two-dimensional (2D) array of a plurality of pixels. The black matrix <NUM> may be disposed between a plurality of pixels of the spatial light modulator <NUM>. The mask member <NUM> may be disposed on the same layer as the black matrix <NUM> on the second transparent substrate <NUM>. A light transmittance layer <NUM> may be placed in an area facing the liquid crystal cell <NUM> on the second transparent substrate <NUM> such that light modulated by the liquid crystal cell <NUM> may pass through the light transmittance layer <NUM>. The light transmittance layer <NUM> may be replaced with a color filter which selectively transmits light of different wavelengths. The mask member <NUM> may be disposed in the area facing the liquid crystal cell <NUM> and may split the light transmittance layer <NUM>.

As shown in <FIG>, the mask member <NUM> is disposed on the same layer as the black matrix <NUM>, and thus the mask member <NUM> and the black matrix <NUM> may be simultaneously formed during a same process when the spatial light modulator <NUM> is manufactured. However, the mask member <NUM> and the black matrix <NUM> may not be necessarily disposed on the same layer. For example, the mask member <NUM> may be disposed in the liquid crystal cell <NUM> or may be disposed on the same layer as the driving circuit <NUM> on the first transparent substrate <NUM>. That is, the mask member <NUM> may be disposed on any layers inside the spatial light modulator <NUM>.

As will be described later, the black matrix <NUM> may act as a pixel lattice that diffracts incidence light and forms unnecessary lattice spots. The lattice spots formed by the black matrix <NUM> may function as noise and deteriorate quality of a hologram image. According to an exemplary embodiment, spaces between the lattice spots may be increased in order to reduce an influence of the lattice spots on the reproduced hologram image. The higher the resolution of the spatial light modulator <NUM>, the smaller the pitch of the pixel. The smaller the spaces between the black matrixes <NUM>, the larger the spaces between the lattice spots. However, there is a technical limitation to an increase in the resolution of the spatial light modulator <NUM>. The mask member <NUM>, along with the black matrix <NUM>, may function as the pixel lattice to increase spaces between the lattice spots without reducing the pixel pitch of the pixel (i.e. while not increasing the resolution of the spatial light modulator <NUM>).

<FIG> is a plan view schematically showing a relative location relationship between the black matrixes <NUM> and the mask members <NUM> of the spatial light modulator <NUM> according to an exemplary embodiment. The spatial light modulator <NUM> may include a two-dimensional (2D) array of a plurality of pixels. A inter-pixel gap exists between the plurality of pixels. A black matrix <NUM> surrounds the boundaries of each of the plurality of pixels to fill in the inter-pixel gap. A mask member <NUM> may divide an area of each of the plurality of pixels into, for example, four sub-areas. As a result, it is possible to have the same effect as reducing a pixel pitch of the plurality of pixels by half without actually reducing the pixel pitch of the plurality of pixels. The pixel pitch may refer to a center-to-center spacing between two adjacent pixels among the plurality of pixels. The Inter-pixel gap may refer to an edge-to-edge spacing between two adjacent pixels among the plurality of pixels.

Referring to <FIG>, the black matrixes <NUM> may have periodic lattice type patterns. The mask members <NUM> may also have the periodic lattice type patterns, like the black matrixes <NUM>, and may be disposed to shift with respect to the black matrixes <NUM> to split each pixel. Thus, periodic patterns of the mask members <NUM> may be disposed between patterns of the black matrixes <NUM> and may extend in a direction in parallel to the patterns of the black matrixes <NUM>.

<FIG> illustrates that the periodic patterns of the mask members <NUM> may be the same as the patterns of the black matrixes <NUM> but the exemplary embodiments are not limited thereto. Pitches of the periodic patterns of the mask members <NUM> may be the same as or different from pitches of the patterns of the black matrixes <NUM>. For example, although <FIG> illustrates that each pixel is split into four portions by the periodic patterns of the mask members <NUM>, the periodic patterns of the mask members <NUM> may split each pixel into two portions or more than six portions. In this regard, splitting may be understood not as physical splitting of a pixel but as virtual splitting of an image display area of the pixel into several sections by the mask members <NUM>. As shown in <FIG>, although the pitches of the mask member <NUM> and the black matrix <NUM> are P2, since the mask member <NUM> and the black matrix <NUM> co-act as pixel lattices, the same effect as reducing pitches of the pixel lattices to P1 is achieved, and thus spaces between lattices spots may increase.

The operation of the above-described holographic display apparatus <NUM> will now be described below. A processor may generate and provide a hologram data signal to the spatial light modulator <NUM>. The hologram data signal may be a computer-generated hologram (CGH) signal that is computed to reproduce a target hologram image on a space. The processor may generate the hologram data signal according to the hologram image that is to be reproduced. The spatial light modulator <NUM> may form a hologram pattern on a surface of the spatial light modulator <NUM> according to the hologram data signal provided from the processor. A principle that the spatial light modulator <NUM> forms the hologram pattern may be the same as a principle that, for example, a display panel displays an image. For example, the hologram pattern may be displayed on the spatial light modulator <NUM> as an interference pattern including information regarding the hologram image that is to be reproduced.

Simultaneously, the light source <NUM> may provide light to the spatial light modulator <NUM>. Incidence light may be diffracted and interfered by the hologram pattern formed by the spatial light modulator <NUM>, and thus a three-dimensional hologram image may be reproduced on a predetermined space in front of the spatial light modulator <NUM>. A distance between the space in which the reproduced hologram image is located and the spatial light modulator <NUM> may be referred to as a depth. In general, a shape and the depth of the reproduced hologram image may be determined according to the hologram pattern formed by the spatial light modulator <NUM>. When the hologram image is reproduced, an observer may appreciate the hologram image located away from the spatial light modulator <NUM> by distance d. In this regard, a virtual plane including observer's pupils at a viewing position in which the hologram image may be appreciated may be referred to as a pupil plane.

However, the spatial light modulator <NUM> is configured as an array of a plurality of pixels, and thus the array of the plurality of pixels function as a lattice. Thus, the incidence light may be diffracted and interfered by the hologram pattern formed by the spatial light modulator <NUM> and also by a pixel lattice configured as the array of the pixels of the spatial light modulator <NUM>. Also, a part of the incidence light may pass through the spatial light modulator <NUM> without being diffracted by the hologram pattern. As a result, a plurality of lattice spots may appear on the pupil plane on which the hologram image is collected as a spot. The plurality of lattice spots may function as image noise that deteriorates quality of the hologram image and may make it inconvenient to appreciate the hologram image.

The plurality of lattice spots may be generated due to an internal structure of the spatial light modulator <NUM> and is unrelated to the hologram pattern, and thus the plurality of lattice spots are positioned at a fixed location. However, a location of the hologram image on the pupil plane may vary according to the hologram pattern, and thus the hologram pattern may be formed such that the hologram image may be reproduced at a location where the plurality of lattice spots is not present. According to this principle, to prevent the plurality of lattice spots from being seen by the observer at the viewing position, the hologram image may be reproduced in order to prevent an area (hereinafter referred to as an image window) on which the hologram image is focused on the pupil plane from overlapping the plurality of lattice spots. Such a reproduction technique is usually referred to an off-axis technique.

However, when the hologram image is reproduced via the off-axis technique, if a general spatial light modulator is used, since an area (hereinafter referred to as a viewing window) including no lattice spot surrounded by the plurality of lattice spots is small due to a limited resolution of the general spatial light modulator, it is difficult to completely avoid an influence of the lattice spots. For example, a width w of the viewing window may be proportional to a distance d between the general spatial light modulator and the viewing position and a wavelength λ of light and may be inversely proportional to a pixel pitch p of the general spatial light modulator. That is, a relationship w=λ• d/p may be established. Thus, although increasing a size of the viewing window by sufficiently reducing the pixel pitch p of the general spatial light modulator may be considered, reduction of the pixel pitch p of the general spatial light modulator is technically limited. Moreover, when the lattice spots are diffused due to aberration of the Fourier lens <NUM>, even though the image window is located so that the lattice spots are avoided, noise may occur in the hologram image due to light diffused from the lattice spots.

The spatial light modulator <NUM> according to the present exemplary embodiment may provide the same effect as reducing the pixel pitch p using the mask member <NUM> without increasing resolution, as described above, thereby providing a viewing window having a sufficiently expanded size. For example, <FIG> schematically illustrates a relationship between the viewing window VW and the image window IW that are formed by the mask members <NUM> of <FIG> according to an exemplary embodiment. Referring to <FIG>, a plurality of lattice spots LS may be generated by diffraction and interference of incident light caused by the mask member <NUM> and the black matrix <NUM> at uniform intervals from each other. As indicated with a broken line box of <FIG>, an area surrounded by the plurality of lattice spots LS is the viewing window VW. The image window IW that is an area in which a hologram image is focused on a pupil plane may be located in the viewing window VW. When a pupil location of an observer is identical to a location of the image window IW, the observer may appreciate a perfect hologram image.

The mask member <NUM> may provide the same effect as reducing a pitch of a pixel lattice, and thus the width w of the viewing window VW is greater than that of the image window IW. Since pixels of the spatial light modulator <NUM> are not reduced, the size of the image window IW does not change. For example, when the mask member <NUM> splits each pixel into four portions, a size of the viewing window VW may be approximately four times greater than a size of the image window IW. Although <FIG> illustrates that the image window IW is located at one corner of the viewing window VW, a location of the image window IW may be adjusted according to a hologram patterns formed by the spatial light modulator <NUM>. As described above, the holographic display apparatus <NUM> may reproduce a hologram image inside the expanded viewing window VW, thereby inhibiting quality of the hologram image from deteriorating due to the lattice spots LS. Thus, the holographic display apparatus <NUM> may provide the hologram image having an improved quality.

<FIG> illustrates the viewing window VW with respect to a case where periodic patterns of the mask members <NUM> have the same shapes as those of the black matrixes <NUM>. However, as described above, shapes of the periodic patterns of the mask members <NUM> may be selected in various ways. For example, the shapes of the periodic patterns of the mask member <NUM> may be selected according to a desired size of the viewing window VW.

For example, <FIG> is a plan view schematically showing a relative location relationship between the black matrixes <NUM> and the mask members <NUM> of the spatial light modulator <NUM> according to another exemplary embodiment. Referring to <FIG>, periodic patterns of the mask members <NUM> may be formed so that each pixel is split into two portions in a vertical direction. That is, the mask members <NUM> may include a plurality of periodic patterns extending in a horizontal direction. <FIG> schematically illustrates a relationship between the viewing window VW and the image window IW that are formed by the mask members <NUM> of <FIG> according to an exemplary embodiment. As shown in <FIG>, a pitch of a pixel lattice that is commonly formed by the black matrixes <NUM> and the mask members <NUM> is reduced to <NUM>/<NUM> in a vertical direction, and thus a size of the viewing window VW may increase two times in the vertical direction only.

<FIG> is a plan view schematically showing a relative location relationship between the black matrixes <NUM> and the mask members <NUM> of the spatial light modulator <NUM> according to another exemplary embodiment. Referring to <FIG>, periodic patterns of the mask members <NUM> may be formed so that each pixel is split into two portions in a horizontal direction. That is, the mask members <NUM> may include a plurality of periodic patterns extending in a vertical direction. <FIG> schematically illustrates a relationship between the viewing window VW and the image window IW that are formed by the mask members <NUM> of <FIG> according to an exemplary embodiment. As shown in <FIG>, a pitch of a pixel lattice that is commonly formed by the black matrixes <NUM> and the mask members <NUM> is reduced to <NUM>/<NUM> in a horizontal direction, and thus a size of the viewing window VW may increase two times in the horizontal direction only.

As described above, a pattern pitch of the periodic patterns of the mask members <NUM> may be selected to be the same as or different from a pixel pitch of pixels of the spatial light modulator <NUM>. In order for the mask member <NUM> to equally split each pixel into two or more portions, the pattern pitch of the periodic patterns of the mask members <NUM> may be the same as <NUM>/integer of the pixel pitch of the pixels of the spatial light modulator <NUM>. In greater detail, the patterns of the mask members <NUM> may have a first pattern pitch in a horizontal direction and a second pattern pitch in a vertical direction, and a ratio of the first pattern pitch and a pixel pitch of the pixels in the horizontal direction may be different from or may be the same as a ratio of the second pattern pitch and a pixel pitch of the pixels in the vertical direction. For example, the first pattern pitch may be the same as <NUM>/integer of the pixel pitch of the pixels in the horizontal direction, and the second pattern pitch may be the same as <NUM>/integer of the pixel pitch of the pixels in the vertical direction. The patterns of the mask members <NUM> may have an arbitrary pattern pitch irrespective of the pixel pitch of the pixels.

A case where the hologram image is formed by convergence light is described above. However, if the spatial light modulator <NUM> for itself provides a sufficient viewing angle, the convergence light may not be necessarily used. That is, the Fourier lens <NUM> may be omitted, and the light source <NUM> may not necessarily provide the convergence light. For example, mere parallel light or divergent light may be used to reproduce a hologram image. When the parallel light or the divergent light is used other than the convergence light, a problem of deterioration of the image quality due to the above-described lattice spots may be reduced. However, if the hologram image is reproduced using a spatial light modulator that does not include the mask member <NUM>, a crosstalk may occur between a plurality of hologram images.

For example, <FIG> exemplarily illustrates a crosstalk that occurs between hologram images I1, I2, and I3 when a holographic display apparatus that does not use convergence light reproduces the hologram images I1, I2, and I3 using a spatial light modulator <NUM>' that does not include the mask member <NUM>. The hologram images I1, I2, and I3 may be referred to as a 0th order hologram image, a +1st order hologram image, and a -1st order hologram image, respectively. As shown in <FIG>, when parallel light is incident into the spatial light modulator <NUM>', the <NUM>th order hologram image I1 may be formed on a light axis OX of the spatial light modulator <NUM>' on a pupil plane. The ±1st order hologram images I2 and I3 may be additionally formed in a direction perpendicular to the light axis OX on the pupil plane. Although <FIG> illustrates that the ±1st order hologram images I2 and I3 are formed up and down, a 1st order hologram image may be further formed in a lateral direction. However, if the spatial light modulator <NUM>' does not modulate incident light to have a sufficiently large diffraction angle, the crosstalk between the <NUM>th order hologram image I1 and the ±1st order hologram images I2 and I3 may occur on the pupil plane. As a result, quality of the <NUM>th order hologram image I1 and the ±1st order hologram images I2 and I3 may deteriorate.

<FIG> is an exemplary diagram for describing a case where a holographic display apparatus that does not use convergence light prevents a crosstalk using the spatial light modulator <NUM> that includes the mask member <NUM> according to the present exemplary embodiment. Referring to <FIG>, since a diffraction angle becomes large due to the spatial light modulator <NUM> that includes the mask member <NUM>, the ±1st order hologram images I2 and I3 may be moved by a sufficient distance in a direction perpendicular to the light axis OX. Thus, crosstalk between the <NUM>th order hologram image I1 and the ±<NUM> st order hologram images I2 and I3 may be prevented. Meanwhile, the mask member <NUM> is disposed inside the spatial light modulator <NUM> of <FIG> but a location of the mask member <NUM> is not necessarily limited thereto.

For example, <FIG> is a cross-sectional view schematically showing a structure of a pixel of the spatial light modulator <NUM> according to another exemplary embodiment. Referring to <FIG>, the mask member <NUM> is not disposed inside the spatial light modulator <NUM>. Instead, the mask member <NUM> may be disposed on an external surface of the spatial light modulator <NUM>. Although <FIG> illustrates that the mask member <NUM> is disposed adjacent to the second transparent substrate <NUM>, the mask member <NUM> may be disposed adjacent to the first transparent substrate <NUM>. For example, the mask member <NUM> may be disposed on an outer surface of the first polarizing plate <NUM> or inside the first transparent substrate <NUM>.

Periodic patterns of the mask members <NUM> may be directly printed on the external surface of the spatial light modulator <NUM>. Instead, the mask member <NUM> may be provided separately from the spatial light modulator <NUM> so that the mask members <NUM> may be attached onto the external surface of the spatial light modulator <NUM>. For example, the mask member <NUM> may be in the form of a transparent film <NUM> on which the periodic patterns are printed. When the mask member <NUM> is manufactured in the form of the transparent film <NUM>, the mask member <NUM> may be attached to an already manufactured existing spatial light modulator.

A case where the mask member <NUM> is an opaque black mask of which periodic patterns do not allow transmission of light has been described above. However, instead of the black mask that completely blocks light, a phase mask that delays a phase of transmittance light may be used. For example, <FIG> is a cross-sectional view schematically showing a structure of a mask member <NUM> of the spatial light modulator <NUM> according to an exemplary embodiment. Referring to <FIG>, the mask member <NUM> according to the present exemplary embodiment may include periodic patterns having a different refractive index from that of a transparent film <NUM>. For example, an area of the transparent film <NUM> may have a first refractive index, and an area forming periodic patterns of the mask member <NUM> may have a second refractive index different from the first refractive index.

A phase of transmittance light may be delayed by adjusting a thickness instead of a refractive index. For example, <FIG> is a cross-sectional view schematically showing a structure of a mask member <NUM> of the spatial light modulator <NUM> according to another exemplary embodiment. Referring to <FIG>, the mask member <NUM> may include periodic patterns having a different thickness from that of the transparent film <NUM>. In other words, the mask member <NUM> includes protrusions. For example, an area of the transparent film <NUM> may have a first thickness, and an area forming the periodic patterns of the mask member <NUM> may have a second thickness different from the first thickness. <FIG> illustrates that the second thickness of the mask member <NUM> is greater than the first thickness of the transparent film <NUM> but this is merely an example, and the first thickness may be greater than the second thickness.

Although the mask member <NUM> and <NUM> including the phase mask are provided in the form of the transparent film <NUM> in <FIG>, the mask member <NUM> and <NUM> may be disposed inside the spatial light modulator <NUM>, like the mask member <NUM> including the black mask. For example, the mask member <NUM> and <NUM> may be disposed on the same layer as the black matrix <NUM> inside the spatial light modulator <NUM>. In this case, periodic patterns of the mask member <NUM> may have a different refractive index from that of the light transmittance layer <NUM>. Alternatively, the periodic patterns of the mask member <NUM> may have a different thickness from that of the light transmittance layer <NUM>.

A combination of the mask member <NUM> including the black mask and the mask members <NUM> and <NUM> including the phase mask may be possible. For example, <FIG> is a cross-sectional view schematically showing a structure of a pixel of the spatial light modulator <NUM> according to another exemplary embodiment. As shown in <FIG>, the mask member <NUM> including the black mask may be disposed on the same layer as the black matrix <NUM>, and the mask member <NUM> including the phase mask may be disposed on an external surface of the spatial light modulator <NUM>. However, this is merely an example of various combinations of the mask members <NUM>, <NUM>, and <NUM>. For example, the mask member <NUM> including the phase mask may be disposed on the same layer as the black matrix <NUM>, and the mask member <NUM> including the black mask may be disposed on the external surface of the spatial light modulator <NUM>. Alternatively, the mask member <NUM> of a heterogeneous thickness structure may be disposed, instead of the mask member <NUM> of a heterogeneous refractive index structure. Alternatively, the mask member <NUM> of the heterogeneous thickness structure may be disposed, instead of the mask member <NUM> including the black mask.

<FIG> illustrates that the two mask members <NUM> and <NUM> may have a same lattice structure. That is, a periodic opaque pattern of the black mask of the mask member <NUM> and a periodic phase delay pattern of the phase mask of the mask member <NUM> may have a same shape. However, the present exemplary embodiment is not limited thereto. The periodic opaque pattern of the black mask of the mask member <NUM> and the periodic phase delay pattern of the phase mask of the mask member <NUM> may have a different pattern pitch or shape. Alternatively, the periodic opaque pattern of the black mask of the mask member <NUM> and the periodic phase delay pattern of the phase mask of the mask member <NUM> may be shifted with each other while having the same shape. In this case, the periodic opaque pattern of the black mask of the mask member <NUM> and the periodic phase delay pattern of the phase mask of the mask member <NUM> may be disposed in different locations with respect to each pixel of the spatial light modulator <NUM>.

Various simulations are performed in order to determine an expansion effect of a viewing window by the above-described mask members <NUM>, <NUM>, and <NUM>.

First, <FIG> is a graph showing a simulation result of lattice spots formed by a spatial light modulator according to a comparative example that does not include a mask member. In this regard, it is assumed that a pattern width of the black matrix <NUM> is <NUM>, and a pixel width between the black matrixes <NUM> is <NUM>. In the graph of <FIG>, a light intensity of a lattice spot caused by a <NUM>th order diffraction is normalized as <NUM>. Referring to <FIG>, a lattice spot caused by the <NUM>th order diffraction appears at <NUM> degree, that is, in a center part, and lattice spots appear due to a higher order diffraction than ±<NUM>st order appear at an interval of about <NUM> degree. <FIG> are graphs showing a simulation result of lattice spots formed by the spatial light modulator <NUM> of <FIG>. That is, a simulation is performed on the assumption that the mask member <NUM> including a black mask is disposed on the same layer as the black matrix <NUM>. In <FIG>, it is assumed that a width of periodic patterns of the mask member <NUM> is <NUM> that is the same as the pattern width of the black matrix <NUM>, and a space between the mask member <NUM> and the black matrix <NUM> is <NUM>. In <FIG>, it is assumed that the width of periodic patterns of the mask member <NUM> is <NUM> that is different from the pattern width of the black matrix <NUM>, and the space between the mask member <NUM> and the black matrix <NUM> is <NUM>.

Referring to the graph of <FIG>, a light intensity of a lattice spot caused by a <NUM>th order diffraction is reduced to <NUM>, and lattice spots caused by a higher order diffraction than ±<NUM>st order appear at an interval of about <NUM> degree. Thus, a width of a viewing window may be expanded by <NUM> times. Referring to the graph of <FIG>, the light intensity of the lattice spot caused by the <NUM>th order diffraction is reduced to <NUM>, and the lattice spots caused by the higher order diffraction than ±<NUM>st order appear at an interval of about <NUM> degree. Thus, the width of the viewing window may be expanded by <NUM> times. However, two diffraction patterns having a very weak light intensity may remain in the viewing window in <FIG>.

<FIG> are graphs showing a simulation result of lattice spots formed by the spatial light modulator <NUM> of <FIG>. That is, a simulation is performed on the assumption that the mask member <NUM> including a black mask is disposed on an external surface of the spatial light modulator <NUM>. In <FIG>, it is assumed that a width of periodic patterns of the mask member <NUM> is <NUM> that is the same as the pattern width of the black matrix <NUM>, and a space between the mask member <NUM> and the black matrix <NUM> is <NUM>, and a space between the mask member <NUM> and the black matrix <NUM> in a vertical direction that is a thickness direction of the spatial light modulator <NUM> is <NUM> in consideration of a thickness of a substrate. In <FIG>, it is assumed that the width of periodic patterns of the mask member <NUM> is <NUM> that is different from the pattern width of the black matrix <NUM>, and the space between the mask member <NUM> and the black matrix <NUM> is <NUM>, and the space between the mask member <NUM> and the black matrix <NUM> in the vertical direction is <NUM>.

Referring to the graph of <FIG>, the same like in <FIG>, a light intensity of a lattice spot caused by a <NUM>th order diffraction is reduced to about <NUM>, and lattice spots caused by a higher order diffraction than ±<NUM>st appear order at an interval of about ±<NUM> degree. Thus, a width of a viewing window may be expanded by <NUM> times. Referring to the graph of <FIG>, the light intensity of the lattice spot caused by the <NUM>th order diffraction is further reduced to about <NUM>, and the lattice spots caused by the higher order diffraction than ±<NUM>st order appear at an interval of about ±<NUM> degree. Thus, the width of the viewing window may be expanded by <NUM> times. However, one diffraction pattern having a very weak light intensity may remain in the viewing window in <FIG>.

<FIG> is a cross-sectional view schematically showing a relative location relationship between the black matrixes <NUM> and the mask members <NUM> according to another exemplary embodiment. The mask members <NUM> may be disposed on an external surface of the spatial light modulator <NUM> as shown in <FIG>. The mask members <NUM> of <FIG> may include first patterns 128a having a pattern width as that of the black matrixes <NUM> and second patterns 128b having a different pattern width from that of the black matrixes <NUM>. The first patterns 128a may be aligned with the patterns of the black matrixes <NUM> in a longitudinal direction. When viewed from the top, the second patterns 128b may appear as being formed between the first patterns 128a in the longitudinal direction.

<FIG> is a graph showing a simulation result of lattice spots formed by the black matrixes <NUM> and the mask members <NUM> of <FIG>. In <FIG>, it is assumed that a pattern width of the black matrixes <NUM> and the first patterns 128a is <NUM>, and a pattern width of the second patterns 128b is <NUM>. It is also assumed that a space between the black matrixes <NUM> and the mask members <NUM> in a vertical direction is <NUM>. Referring to the graph of <FIG>, a light intensity of a lattice spot caused by a <NUM>th order diffraction is reduced to about <NUM>, and lattice spots caused by a ±<NUM>st order diffraction appear at about ±<NUM> degree. Thus, in this case, a width of a viewing window may also be expanded <NUM> times. No diffraction pattern may be present in the viewing window.

<FIG> is a cross-sectional view schematically showing a relative location relationship between the black matrixes <NUM>, the mask members <NUM> including black masks, and the mask members <NUM> including phase mask according to another exemplary embodiment. The mask members <NUM> including the black mask may be disposed on the same layer as the black matrixes <NUM> inside the spatial light modulator <NUM>. The mask members <NUM> including the phase mask may be disposed on an external surface of the spatial light modulator <NUM>. A pattern width of the mask members <NUM> may be the same as that of the black matrixes <NUM>. The mask members <NUM> may include first refractive index area 132a having a phase delay of <NUM> and second refractive index areas 132b having a phase delay of π. A width of the first refractive index area 132a may be the same as the pattern width of the black matrixes <NUM>. When seen from a vertical direction, the first refractive index area 132a may appear as being formed t locations identical to those of periodic patterns of the black matrixes <NUM> and the mask members <NUM>.

<FIG> is a graph showing a simulation result of lattice spots formed by the black matrixes <NUM> and the mask members <NUM> and <NUM> of <FIG>. It is assumed that a pattern width of the black matrixes <NUM>, a pattern width of the mask members <NUM>, and a width of the first refractive index area 132a of the mask members <NUM> are <NUM>, and a space between the black matrixes <NUM> and the mask members <NUM> in a vertical direction is <NUM>. Referring to the graph of <FIG>, no <NUM>th order diffraction light is present, and lattice spots caused by a ±<NUM>st order diffraction appear at about ±<NUM> degree. Thus, in this case, a width of a viewing window may also be expanded by <NUM> times. No diffraction pattern may be present in the viewing window.

Claim 1:
A spatial light modulator (<NUM>) comprising:
a two-dimensional, 2D, array of a plurality of pixels, each of the plurality of pixels including a single liquid crystal cell and a driving circuit configured to drive the liquid crystal cell;
a black matrix (<NUM>)arranged between the plurality of pixels, the black matrix being disposed to block light such that the driving circuit is not seen; and
a mask member (<NUM>) having a periodic pattern that is arranged to split an area of the liquid crystal cell of each of the plurality of pixels into at least two portions, wherein the periodic pattern comprises an opaque black mask that blocks transmission of light and wherein a pattern width of the mask member is substantially equal to a pattern width of the black matrix.