Patent Description:
Known near-eye light field projectors comprise a light source typically comprising an array of point-light sources that are collimated into collimated beams. The collimated beams illuminate a spatial light modulator (SLM) or diffraction grating under a different set of angles of incidence. Each reflected (or transmitted) beam will carry out a certain image information, produced by the modulation of the SLM or diffraction grating. Intermediate optics re-images the point-light sources into viewpoints. The viewpoints form a light field eye box, allowing a user to see an authentic 3D rendering of a digital scene.

The SLM or diffraction grating typically comprises a two-dimensional array of pixels. The illumination of a two-dimensional array of pixels is equivalent to the illumination of a two-dimensional grating. The collimated illumination of a two-dimensional grating may produce a two-dimensional diffraction interference pattern when viewed at infinity. The pattern consists of multiple diffraction orders with varying intensity. The diffraction interference pattern can be observed in the Fourier plane of the SLM or diffraction grating. In the diffraction interference pattern, the maximum intensity of the center of the diffraction envelope may not match the center of the diffraction pattern. The maximum diffraction may not correspond with the zero order, and multiple diffraction orders with relatively high intensities can be observed instead of a single bright image. Thus, this is detrimental to the light-field image since the information a viewer sees comprises multiple images of various intensities (ghost images) coming from various directions.

Document <CIT> discloses an optical system that includes a micro-mirror array optical modulator of the digital light processing (DLP) type. An optical element has an optimized limiting aperture for defining portions of a modulated light beam that are blocked and remaining portions that are transmitted. The optical element allows for optimizing light collection and contrast in a projection device.

<CIT> discloses a near-to-eye display device comprising a light source, a spatial light modulator, and a spatial filter.

The present disclosure concerns a near-eye light field projector comprising a light source comprising a plurality of point-light sources arranged in a light source plane, wherein at least two point-light sources have different wavelengths, and each point-light source is configured to emit an incident light beam. The projector further comprises a modulation device configured to diffract the incident light beams and generate diffracted modulated light beams. The projector further comprises projection optics configured to project the diffracted modulated light beams and form images in an image plane, the images forming a two-dimensional diffraction interference pattern comprising a plurality of diffraction orders, and relay optics configured to receive the images and to form viewpoints in a viewpoint plane destined to be in a user's eye box. The point-light sources are arranged in the light source plane such that the modulated light beams comprise combined modulated light beams forming combined images, each combined image corresponding to an image of the point-light sources of different wavelength, and diffracted modulated light beams forming diffracted images. The light field projector further comprises a spatial filter configured to block the diffracted modulated light beams forming the diffracted images, such that the relay optics projects only viewpoints from the combined images.

Said at least two point-light sources are arranged in the light source plane such that the diffracted images are distant from a combined image by the image separation distance large enough to avoid the diffracted images overlapping the combined image. A viewpoint separation distance between two adjacent combined viewpoints is such that at least two combined viewpoints simultaneously enter a viewpoint plane opening of between <NUM> and <NUM> in the viewpoint plane.

The present disclosure further concerns a wearable device comprising the near-eye light field projector, such as augmented/mixed reality or smart glasses.

The near-eye light field projector allows avoiding unwanted diffraction orders of a diffraction interference pattern produced by the modulation device to overlap with the projected image to the eyes of a user. The near-eye light field projector further allows point-light sources having different wavelengths to overlap in a single combined image.

<FIG> represents a sequential near-eye light field projector <NUM> comprises a light source <NUM> comprising a plurality of point-light sources <NUM>, <NUM>, <NUM>, wherein at least two point-light sources have different wavelengths. Each point-light source <NUM>, <NUM>, <NUM> is configured to emit an incident light beam <NUM>. The point-light sources <NUM>, <NUM>, <NUM> can be arranged in a light source plane <NUM>. The point-light sources <NUM>, <NUM>, <NUM> can comprise LEDs, µLEDs, lasers, or any other point-light-sources capable of emitting an incident light beam <NUM>.

Each point-light source <NUM>, <NUM>, <NUM> can be configured to emit an incident light beam <NUM> of which a wavelength spectrum is a narrow band. Then, the point-light sources <NUM>, <NUM>, <NUM> can comprise point-light sources capable of emitting a narrow-band incident light beam <NUM> of which a wavelength spectrum is a narrow band.

The point-light sources <NUM>, <NUM>, <NUM> are configured to illuminate a modulation device <NUM> configured to modulate the incident light beams <NUM> and generate modulated light beams <NUM> and a point-light image <NUM>, <NUM>, <NUM> of each point-light source, for each incident light beam <NUM>. The modulation device <NUM> can comprise a spatial light modulator (SLM) that behaves like a diffraction grating. The spatial light modulator <NUM> can comprise a two-dimensional array of pixels. The illumination of a two-dimensional array of pixels is equivalent to the illumination of a two-dimensional grating. In one aspect, the SLM <NUM> can comprise an electrically addressed spatial light modulator ferroelectric liquid crystals (FLCoS) or a digital light processing (DLP). Here, a pixel can be a single mirror of a DLP-type SLM or a pixel in an FLCOS device, etc..

The light field projector <NUM> further comprises projection optics <NUM>, <NUM> configured to project the incident light beams <NUM> and form the point-light images <NUM>, <NUM>, <NUM> in an image plane <NUM>. In the example of <FIG>, the projection optics comprise a first projection optics <NUM> configured to form a first focal plane <NUM>, and a second projection optics <NUM> configured to project the point-light image <NUM>, <NUM>, <NUM> of the modulated light beams <NUM> in the image plane <NUM>. In some embodiments, the first projection optics <NUM> can be configured to collimate the incident light beams <NUM> (see <FIG>), such that the incident light beams <NUM> are collimated.

In one aspect, the modulation device <NUM> can be arranged in the first focal plane <NUM>. More generally, the modulation device <NUM> can be arranged so that the modulator is completely illuminated by the incident light beams <NUM>.

The light field projector <NUM> can further comprise relay optics. For example, the relay optics can comprise a first relay optical element <NUM> configured to project the modulated light beams <NUM> and form intermediate images (not shown) in an intermediate image plane <NUM> and a second relay optical element <NUM> configured to project the modulated beam light <NUM> to form viewpoints <NUM>, <NUM>, <NUM> in a viewpoint plane <NUM>. The viewpoint plane <NUM> can correspond to an eye box of a user. In the absence of diffraction by modulation device <NUM>, the viewpoints <NUM>, <NUM>, <NUM> appear to be coming from a single point in space with a specific direction.

In one aspect, the plurality of optical elements <NUM>, <NUM> and relay optics <NUM>, <NUM> can comprise lenses or metalenses.

The near-eye light field projector <NUM> is configured for sequentially generating the virtual viewpoints <NUM>, <NUM>, <NUM> that form the light-field.

<FIG> shows a simplified representation , not according to the claimed invention, of the light field projector <NUM> without the relay optics <NUM>, <NUM>.

Depending on the type of modulation device <NUM>, the latter can diffract the incident light beams <NUM> and produces a two-dimensional diffraction interference pattern when viewed at infinity. For example, <FIG> shows a simplified representation of the light field projector <NUM> without the relay optics <NUM>, <NUM>, where the modulation device <NUM> illuminated by the incident light beams <NUM> diffracts the incident light beams <NUM>. The modulation device <NUM> projects modulated light beams <NUM> comprising diffracted beams <NUM>, <NUM> forming diffracted images <NUM>, <NUM> (diffraction orders forming a diffraction interference pattern). In <FIG>, only one point-light source <NUM> is represented and is diffracted by the modulation device <NUM> into a plurality of diffracted beams <NUM>, <NUM> (two are shown) which form a plurality of diffracted images <NUM>, <NUM> (two are shown). In the absence of diffraction interference, the modulated light beams <NUM> (shown by the dashed lines) would form the point-light image <NUM>.

The degradation of the information viewed at the viewpoints <NUM>, <NUM>, <NUM> due to diffraction interference may not be significant when a user is looking at an image in the focal plane of the modulation device <NUM> (for example at infinity). However, when a user's eye focuses on a different plane than the plane where the modulation device <NUM> is arranged (such as the first focal plane <NUM>), for example a focus plane indicated by numeral <NUM> in <FIG>, the information at the viewpoints <NUM>, <NUM>, <NUM> appears as coming from multiple directions, for instance, as many directions as there are diffraction orders.

More particularly, the diffracted images <NUM>, <NUM> create a two-dimensional diffraction interference pattern overlapping the point-light images <NUM> (in the absence of diffraction) in the image plane <NUM>. The two-dimensional diffraction interference pattern may comprise multiple diffraction orders with varying intensity. Since the diffraction orders appear in the image plane <NUM>, which may or may not coincide with the Fourier plane of the second projection optics <NUM>, the diffraction pattern forms a grid of diffraction orders which appear in the image plane <NUM>.

Therefore, the user sees two identical diffracted images <NUM>, <NUM> at the same time, the modulated beams <NUM>, <NUM> being displaced in the focus plane <NUM>. This is detrimental to the light-field image as it creates multiple images of various intensities (ghost images) coming from the wrong directions, adding noise. Moreover, the diffraction interference pattern can vary for each wavelength of the incident light beams <NUM>. This results in red, green, and blue modulated beams <NUM>, <NUM> for a single viewpoint that seem to come from different directions as well.

An example of modulation device <NUM> generating a diffraction interference pattern can comprise DLP-type SLM. For instance, the DLP® digital micromirror device (DMD) from Texas Instrument comprises tilting mirrors. The illumination of an array of tilted mirrors is equivalent to the illumination of a blazed grating. Blazed gratings produce diffraction orders where the maximum intensity of the diffracted light does not coincide with the direction of specular reflection. In other words, the center of the diffraction envelope does not match the center of the diffraction interference pattern. Here, the diffraction envelope corresponds to the diffraction pattern of a single pixel of the modulation device <NUM>.

This results in an illumination pattern at infinity where the maximum of diffraction does not correspond with the zero order. Consequently, multiple diffraction orders with relatively high intensities can be observed instead of a single bright spot.

<FIG> shows a simplified representation , not according to the claimed invention, of the light field projector <NUM> without the relay optics <NUM>, <NUM>, wherein the light source <NUM> comprises point-light sources <NUM>, <NUM>, <NUM> of different wavelengths. The point-light sources <NUM>, <NUM>, <NUM> are spatially separated in the light source plane <NUM>. In one aspect, the point-light sources <NUM>, <NUM>, <NUM> can be arranged in the light source plane <NUM> such that part of the diffracted modulated light beams <NUM>, <NUM> are combined (in combined modulated light beams <NUM>) to form combined images <NUM>. Each combined image <NUM> corresponds to an image of the multiple point-light sources <NUM>, <NUM>, <NUM> of different wavelengths.

The point-light sources <NUM>, <NUM>, <NUM> can be arranged in the light source plane <NUM> by placing the different point-light sources <NUM>, <NUM>, <NUM> at defined positions along the orthogonal axis x, y in the light source plane <NUM>.

Other diffracted modulated light beams <NUM>, <NUM> form diffracted images <NUM>, <NUM> in the image plane <NUM>. In the example of <FIG>, the light source <NUM> is shown comprising three point-light sources <NUM>, <NUM>, <NUM>, each having a different wavelength.

The point-light sources <NUM>, <NUM>, <NUM> can be further arranged in the light source plane <NUM> such that the diffracted images <NUM>, <NUM> are distant from a combined image <NUM> by an image separation distance di that is large enough such that the diffracted images <NUM>, <NUM> do not overlap the combined image <NUM>. Since the image separation distance di only depends on the wavelength and the grating pitch. Thus, the image separation distance di depends on the distance set by the shortest wavelength (see <FIG>).

<FIG> shows the light field projector <NUM> of <FIG> further comprising the relay optics <NUM>, <NUM> and a spatial filter <NUM>. The spatial filter <NUM> is configured to filter unwanted diffraction orders, i.e., to block the propagation of the diffracted modulated light beam <NUM>, <NUM> that form the diffracted images <NUM>, <NUM>. The diffracted modulated light beam <NUM>, <NUM> thus cannot form diffracted viewpoints in the viewpoint plane <NUM>. Consequently, only the combined modulated light beams <NUM> are allowed to propagate and pass through the relay optics <NUM>, <NUM>, forming combined viewpoints <NUM> in the viewpoint plane <NUM>.

Although <FIG> shows only one combined viewpoint <NUM>, the light field projector <NUM> is configured to from at least two combined viewpoint <NUM>, where each combined viewpoint <NUM> corresponds to a projected image in the viewpoint plane <NUM>, that appears to be always in focus and appears to be coming from a single point in space with a specific direction.

The spatial filter <NUM> can comprise an array of pinholes <NUM> (see <FIG>). Here, the point-light sources <NUM>, <NUM>, <NUM> should be arranged in the light source plane <NUM> such that the positions of the combined images <NUM> correspond to the positions of the pinholes <NUM>. The array can be a regular array or any irregular or random array of pinholes <NUM>. The unwanted diffraction orders (diffracted images <NUM>, <NUM>) do not pass through the pinholes <NUM> and are blocked by the spatial filter <NUM>. Moreover, the point-light sources <NUM>, <NUM>, <NUM> should be arranged in the light source plane <NUM> such that the unwanted diffraction orders corresponding to a given combined viewpoint <NUM> do not overlap another combined viewpoint. The pinholes <NUM> can have a lateral size that is equal or smaller than the image separation distance di.

Alternatively, the spatial filter <NUM> can comprise a wavelength filter. In the case the light source <NUM> comprises point-light sources <NUM>, <NUM>, <NUM> that emit light in a narrow band, each point-light source <NUM>, <NUM>, <NUM> can be individually filtered by the wavelength filter <NUM>.

Alternatively, the spatial filter <NUM> can comprise an active shutter array. The use of an active shutter array also allows for relaxing the requirement that the point-light sources <NUM>, <NUM>, <NUM> should be arranged in the light source plane <NUM> such that the unwanted diffraction orders corresponding to a given combined viewpoint <NUM> do not overlap another combined viewpoint. On the other hand, an active shutter array requires a fast shutter speed, matching the high speed of the modulation device <NUM>, and more especially of the SLM. In one aspect, the spatial filter <NUM> can comprise an electro-optical shutter used as a tunable filter.

The spatial filter <NUM> can be arranged in the image plane <NUM>. Alternatively, the spatial filter <NUM> can be arranged in the vicinity of the image plane <NUM>, where the distance between the spatial filter <NUM> and the image plane <NUM> should be small enough such that the spatial filter <NUM> allows the selective passage of the combined modulated light beams <NUM> while blocking the diffracted beams <NUM>, <NUM>.

The light field projector <NUM> of <FIG> allows for a user to see a light field image with correct depth of focus cues when combined viewpoints <NUM> reach the user's eye pupil.

<FIG> shows the light field projector <NUM> of <FIG> showing the light source <NUM> comprising point-light sources <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of different wavelengths. The point-light sources <NUM>-<NUM> are spatially separated in the light source plane <NUM>. When illuminating the modulation device <NUM>, the point-light sources <NUM>, <NUM>, <NUM> generate modulated light beams comprising diffracted beams <NUM>, <NUM>, <NUM>, the point-light sources <NUM>, <NUM>, <NUM> generate modulated light beams comprising diffracted beams <NUM>, <NUM>, <NUM>, and the point-light sources <NUM>, <NUM>, <NUM> generate modulated light beams comprising diffracted beams <NUM>, <NUM>, <NUM>. The diffracted beams <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> form, respectively, diffracted images <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (diffraction orders forming a diffraction interference pattern).

The point-light sources <NUM>-<NUM> are arranged in the light source plane <NUM> such that at least a portion of the diffracted modulated light beams <NUM>-<NUM> are combined in a combined modulated light beams <NUM> to form a combined image <NUM>. Similarly, point-light sources <NUM>-<NUM> and <NUM>-<NUM> are arranged in the light source plane <NUM> such that at least a portion of the diffracted modulated light beams <NUM>-<NUM> and <NUM>-<NUM> are combined in a combined modulated light beams <NUM> and <NUM>, respectively, to form a combined image <NUM> and <NUM>.

The spatial filter <NUM> is configured to filter unwanted diffraction orders from the diffracted modulated light beams <NUM>-<NUM>. In other words, the spatial filter <NUM> is configured to allow only the combined modulated light beams <NUM>, <NUM>, <NUM> and the combined images <NUM>, <NUM>, <NUM> to propagate towards the viewpoint plane <NUM> while preventing the diffracted modulated light beams <NUM>-<NUM> and diffracted images <NUM>-<NUM> to pass through the spatial filter <NUM>. Thus, only the combined images <NUM>, <NUM>, <NUM> propagate through the relay optical elements <NUM>, <NUM>, and form combined viewpoints <NUM>, <NUM>, <NUM> in the viewpoint plane <NUM>.

In an embodiment, the combined viewpoints <NUM>, <NUM>, <NUM> are configured to be formed in the viewpoint plane <NUM> (and reach the user's eye) simultaneously. This requires that a viewpoint separation distance dv between two adjacent combined viewpoints <NUM>, <NUM>, <NUM> is such that at least two but preferably more than three combined viewpoints <NUM>, <NUM>, <NUM> enter simultaneously a viewpoint plane opening <NUM> (see <FIG>) in the viewpoint plane <NUM>. The viewpoint plane opening <NUM> can typically correspond to an eye pupil.

The plurality of combined viewpoints <NUM>, <NUM>, <NUM> simultaneously entering the viewpoint plane opening <NUM> (for example pupil) allows the formation of a light field image with correct depth cues. More particularly, the viewpoint separation distance dv between two adjacent combined viewpoints <NUM>, <NUM>, <NUM> is such that at least two but preferably more than three combined viewpoints <NUM>, <NUM>, <NUM> simultaneously enter the viewpoint plane opening <NUM> having a lateral size of between <NUM> and <NUM>. In a particular embodiment, the viewpoint separation distance dv is such that more than ten combined viewpoints <NUM>, <NUM>, <NUM> simultaneously enter the viewpoint plane opening <NUM> having a lateral size of between <NUM> and <NUM>.

Increasing the number of combined viewpoints <NUM>, <NUM>, <NUM> entering the viewpoint plane opening <NUM> requires increasing the proximity of the diffraction orders (diffracted images <NUM>-<NUM>) relative to the combined images <NUM>, <NUM>, <NUM> and thus, decreasing the image separation distance di.

In an embodiment, the spatial filter <NUM> comprises an array of pinholes <NUM> and the point light sources <NUM>-<NUM> are arranged in the light source plane <NUM> such that the unwanted diffraction orders corresponding to a given combined image <NUM>, <NUM>, <NUM> do not pass through any one of the pinholes <NUM>.

Although only three combined images <NUM>-<NUM> and combined viewpoints <NUM>-<NUM> are represented in <FIG>, the light field projector <NUM> can comprise a greater number of the combined images and combined viewpoints, wherein the plurality of combined viewpoints <NUM>-<NUM> are formed simultaneously in the viewpoint plane <NUM> to improve the light field image viewed by the user. The spatial filter <NUM> should be configured to let pass only the combined images <NUM>-<NUM> towards the viewpoint plane <NUM> and block all diffracted images <NUM>-<NUM>.

<FIG> illustrates a method for obtaining an optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM>, in order to avoid unwanted diffraction orders of a diffraction interference pattern produced by the modulation device do not overlap with the projected image to the eyes of a user, thus minimizing ghost images and noise. The method comprises the steps of:.

The diffraction interference pattern produced by the wavelength of each point-light source <NUM>-<NUM> can be calculated using the grating equation (<NUM>), which provides the diffraction angle in the plane along the plane of the modulation device <NUM>, i.e., along orthogonal axis x, y of the modulation device <NUM>: <MAT> where m is the diffraction order, λ is the wavelength, d is the period of the grating, θi the incident angle of an incident light beam <NUM> on the modulation device <NUM>, and θm the output angle of a modulated light beam <NUM>-<NUM>, <NUM>-<NUM>. The diffraction interference pattern forms a grid of diffraction orders which appear in the image plane <NUM>.

A combined image <NUM>-<NUM> can be formed by the superposition of three point-light sources <NUM>-<NUM>, each having a different wavelength. Knowing the diffraction interference patterns for each wavelength, it is possible to calculate the sum of all diffraction interference patterns, as shown in <FIG>. This pattern corresponds to the diffraction interference pattern created by a two-dimensional grating, combined with the diffraction of a pixel of the modulation device <NUM>.

In the example of <FIG>, the diffraction interference pattern is generated from a red, green and blue point-light sources <NUM>-<NUM> that are spatially shifted in the light source plane <NUM> such as to overlap their brightest diffraction orders and forming a white spot, the white spot corresponding to the combined image <NUM>-<NUM>. <FIG> only represents a limited number of diffraction orders.

The theoretical amplitude of a diffraction order is proportional to equation (<NUM>) (see reference: Using Lasers with DLP DMD technology, DLPA037, Texas Instruments, Sept <NUM>, https://www. com/lit/pdf/dlpa037): <MAT> where θ and ϕ are the angles of diffraction in the two axis x, y of the modulation device <NUM>, a is the lateral size of a pixel of the modulation device <NUM>, mx and my are the diffraction orders in the different orthogonal axis x, y of the modulation device <NUM>, λ is the wavelength, and i denotes the angle of the center of the diffraction envelope (specular reflection). The calculated diffraction interference pattern takes into account multiple orders of diffraction for each axis x, y of the modulation device <NUM>.

The optimized lattice of combined and diffracted images <NUM>-<NUM>, <NUM>-<NUM> is then calculated by maximizing the distance between the positions of the combined and diffracted images <NUM>-<NUM> and the secondary diffraction orders in the image plane <NUM>, such that the diffracted images <NUM>-<NUM> are distant from a combined image <NUM>-<NUM> by the image separation distance di.

Calculating an optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM> thus depends on the number of combined viewpoints <NUM>-<NUM> entering the viewpoint plane opening <NUM>. The image separation distance di and the viewpoint separation distance dv decrease with increasing the number of combined viewpoints <NUM>-<NUM> entering the viewpoint plane opening <NUM>. The optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM> can be calculated such that the viewpoint separation distance dv between two adjacent combined viewpoints <NUM>, <NUM>, <NUM> is such that at least two but preferably more than three combined viewpoints <NUM>, <NUM>, <NUM> enter simultaneously a viewpoint plane opening <NUM> of between <NUM> and <NUM> in the viewpoint plane <NUM>.

In one aspect, when the combined and diffracted images <NUM>-<NUM>, <NUM>-<NUM> are imaged at an eye pupil (at the viewpoint plane <NUM>), diffracted viewpoints (not shown) from the diffracted modulated light beams <NUM>-<NUM> can be separated from each combined viewpoint <NUM>-<NUM> from the combined images <NUM>-<NUM>, by a viewpoint separation distance dv corresponding to a diameter of at least <NUM> around the combined viewpoint <NUM>-<NUM>. This condition corresponds to the image separation distance di multiplied by a magnification factor of the relay optics <NUM>, <NUM>. If the latter condition is fulfilled, the combined viewpoints <NUM>-<NUM> are free of unwanted diffraction orders in a circle of at least <NUM> diameter. Unwanted diffraction orders cannot be seen when the combined modulated light beams <NUM> are projected at the pupil of a user.

An example of an optimized lattice of combined and diffracted images <NUM>-<NUM>, <NUM>-<NUM> is represented in <FIG>. In this example, the optimized lattice is obtained with the diffraction interference pattern of the diffracted images <NUM>-<NUM> is generated by red, green, and blue point-light sources <NUM>-<NUM> and the optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM>. Only a limited number of diffraction orders are represented in <FIG>.

Calculating an optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM> can be performed by ray tracing using a complete optical model of the near-eye light field projector <NUM>, i.e., a numerical model including the optical components between the light source plane <NUM> and the image plane <NUM>, allowing to simulate accurately the propagation of light in the near-eye light field projector <NUM>. This step can comprise calculating positions for the different point-light sources <NUM>-<NUM> along the orthogonal axis x, y in the light source plane <NUM>.

In one aspect, the output intensity of the combined images <NUM>-<NUM> can be maximized by selecting the brightest diffraction order that matches a desired combined or diffracted image <NUM>-<NUM>, <NUM>-<NUM>. In other words, a refraction angle with which the combined modulated light beam <NUM>-<NUM> outputs the modulation device <NUM> is selected. The refraction angle corresponds to a position in the orthogonal axis x, y of the image plane <NUM>.

In certain instances, the brightest diffraction order matching a desired combined or diffracted image <NUM>-<NUM>, <NUM>-<NUM> may not be the absolute brightest diffraction order. In that case, the step of calculating an optimized lattice of point-light sources <NUM>-<NUM> in the light source plane <NUM> can be repeated for each combined or diffracted image <NUM>-<NUM>, <NUM>-<NUM> and each wavelength λ. An example of a resulting optimized lattice of point-light sources <NUM>-<NUM> producing combined and diffracted images <NUM>-<NUM>, <NUM>-<NUM> is shown in <FIG>, where the point-light sources <NUM>-<NUM> belonging to a single combined image <NUM>-<NUM> are tagged with the same number.

In the case the spatial filter <NUM> comprises an active shutter array (such as an electro-optical shutter) used as a tunable filter, the optimized arrangement of the point-light sources <NUM>-<NUM> in the light source plane <NUM> can be calculated individually per diffracted image <NUM>-<NUM>, without taking into account possible overlap between different combined images <NUM>-<NUM> and diffracted images <NUM>-<NUM>.

Claim 1:
A near-eye light field projector (<NUM>) comprising:
a light source (<NUM>) comprising a plurality of point light sources (<NUM>-<NUM>) arranged in a light source plane (<NUM>), wherein at least two point-light sources (<NUM>-<NUM>) have different wavelengths and each point light source (<NUM>-<NUM>) is configured to emit an incident light beam (<NUM>);
a modulation device (<NUM>) configured to diffract the incident light beams (<NUM>) and generate modulated light beams (<NUM>, <NUM>-<NUM>);
projection optics (<NUM>, <NUM>) configured to project the modulated light beams (<NUM>, <NUM>-<NUM>) and form images (<NUM>-<NUM>, <NUM>-<NUM>) in an image plane (<NUM>), the images (<NUM>, <NUM>-<NUM>) forming a two-dimensional diffraction interference pattern comprising a plurality of diffraction orders; and
relay optics (<NUM>, <NUM>) configured to receive the images (<NUM>, <NUM>-<NUM>) and to form viewpoints (<NUM>-<NUM>) in a viewpoint plane (<NUM>) destined to be in a user's eye box;
wherein the point light sources (<NUM>-<NUM>) are arranged in the light source plane (<NUM>) such that the modulated light beams comprise combined modulated light beams (<NUM>, <NUM>-<NUM>) forming combined images (<NUM>-<NUM>), each combined image (<NUM>-<NUM>) corresponding to an image of the point-light sources (<NUM>-<NUM>) of different wavelength, and diffracted modulated light beams (<NUM>-<NUM>) forming diffracted images (<NUM>-<NUM>);
wherein the light field projector (<NUM>) further comprises a spatial filter (<NUM>) configured to block the diffracted modulated light beams (<NUM>-<NUM>), such that the relay optics (<NUM>, <NUM>) projects only viewpoints (<NUM>-<NUM>) from the combined images (<NUM>-<NUM>);
wherein said at least two point-light sources (<NUM>-<NUM>) are arranged in the light source plane (<NUM>) such that the diffracted images (<NUM>-<NUM>) are distant from a combined image (<NUM>-<NUM>) by the image separation distance (di) large enough to avoid the diffracted images (<NUM>-<NUM>) overlapping the combined image (<NUM>-<NUM>); and
wherein a viewpoint separation distance (dv) between two adjacent combined viewpoints (<NUM>, <NUM>, <NUM>) is such that at least two combined viewpoints (<NUM>, <NUM>, <NUM>) simultaneously enter a viewpoint plane opening (<NUM>) of between <NUM> and <NUM> in the viewpoint plane (<NUM>).