A light-field image projection system that generates a time-sequential virtual image using a single narrowband light source for each color.

Abstract

To make a light field image projection device using multiple light sources more compact. The light source (10) comprises a single narrowband point source (10) for each color emitting narrowband light (200); a splitting device (20, 30, 70, 80) for sequentially generating an incident light beam (220) and forming a virtual light source (50); a spatial light modulator (40) for generating a modulated beam of light (240) and a virtual image for each incident light beam (220); a combiner (100) for projecting virtual images at virtual viewpoints (60) within an eyebox region (121) and transmitting natural light from the real world (80) toward the eyebox (121), each virtual viewpoint (60) including an image of a virtual scene as seen from that viewpoint (60); A light field image projection system comprising: a splitter for directing an incident light beam (220) to a spatial light modulator (40) such that the incident light beam (220) is incident at different angles of incidence (θ) on a surface of the spatial light modulator (40); a ratio of the illuminance of the single virtual light source (50) to the illuminance of the narrow band light (200) is at least 1%.

Description

[Technical Field]

[0001] This disclosure relates to near-eye, light field image projection systems, and more particularly to light field image projection systems with small form factors. This disclosure relates to wearable devices that include light field image projection systems. [Background technology]

[0002] Known light field image projection devices typically include a light source consisting of an array of point sources collimated into parallel light rays. The collimated light rays illuminate a spatial light modulator (SLM) at different angles of incidence. Each reflected (or transmitted) light ray carries specific image information generated by the modulation of the SLM. Intermediate optics (which may include a combiner optic) reproject the point sources onto viewpoints. The multiple viewpoints form a light field eyebox, allowing a user to view a realistic 3D rendering of a digital scene. The point source array typically uses LED light sources to sequentially generate the viewpoints that form the light field. Summary of the Invention [Problem to be solved by the invention]

[0003] A large number of spatially separated light sources makes it impossible to build a compact and cost-effective light field image projection device. [Means for solving the problem]

[0004] The present disclosure provides: a light source including a single narrowband point light source for each color, the point light source configured to emit narrowband light having a narrow wavelength spectrum; a splitting device configured to sequentially generate a plurality of incident light beams to form a plurality of virtual light sources at different locations within the first image plane; or beam steering device and, a spatial light modulator (SLM) configured to generate a modulated beam of light and a virtual image for each incident light beam; a combiner configured to project virtual images of virtual viewpoints within an eyebox region and transmit natural light from the real world toward the eyebox, each (virtual) viewpoint containing an image of a virtual scene (a virtual scene or view) as seen from that viewpoint; The present invention relates to a light field image projection system comprising: splitting device or beam steering device is further configured to direct the (plurality of) incident light beams onto the SLM so that the incident light beams are incident on the surface of the SLM at different angles of incidence and to sequentially select at least one of the virtual viewpoints visible within the eyebox.

[0005] In one embodiment, Projection system teeth, a diffractive element configured to generate a plurality of incident light beams at different angles of incidence from a narrowband light source; an optical lens configured to form a plurality of virtual light sources; an active shutter array configured to sequentially select at least one of the virtual viewpoints visible within the eyebox; and Equipped with Equipped with a dividing device .

[0006] In another embodiment, the splitting device comprises a lens array comprising a plurality of lenslets (lenslets), each lenslet generating an incident light beam at an angle of incidence different from the angles of incidence of incident light beams generated by other lenses, the lenslets generating focused or defocused beams.

[0007] In yet another embodiment, Projection system teeth, a beam steering device and a lens array comprising a plurality of lenslets; Equipped with The beam steering device steers narrowband light towards one of the lenslets to produce an incident light beam at an angle of incidence.

[0008] The point light sources may comprise laser light sources, and in particular may comprise a red laser point light source configured to generate red light, a green laser point light source configured to generate green light, and a blue laser point light source configured to generate blue light.

[0009] The combiner may comprise a reflective holographic combiner.

[0010] The present disclosure is further directed to wearable devices comprising a light field image projection system, such as augmented or mixed reality glasses or smart glasses.

[0011] The light field image projection system disclosed herein is compact. When used with a holographic reflection holographic combiner, the light field image projection system can be made more compact and has a high degree of freedom in shape. The light field image projection system has excellent perspective performance.

[0012] A light field image projection system does not require an array of point light sources, but may use only a single point light source or a small number of point light sources, in either case the number of point light sources required by the light field image projection system is less than the total number of viewpoints.

[0013] Representative embodiments of the present invention are disclosed in the description and illustrated by the drawings herein. [Brief explanation of the drawings]

[0014] [Figure 1a] FIG. 1a illustrates a schematic diagram of a light field image projection system according to one embodiment. [Figure 1b] FIG. 1b shows a light field image projection system according to an alternative configuration. [Figure 2a] FIG. 2a illustrates a light field image projection system according to one embodiment. [Figure 2b]FIG. 2b shows an alternative configuration of the light field image projection system of FIG. 2a. [Figure 2c] FIG. 2c shows another alternative configuration of the light field image projection system of FIG. 2a. [Figure 3] FIG. 3 illustrates a light field image projection system according to yet another embodiment. [Figure 4] FIG. 4 illustrates a light field image projection system including projection optics and a combiner according to one embodiment. [Figure 5a] Figures 5a to 5c show different embodiments of the light source comprising three narrowband point sources (Figure 5a). [Figure 5b] Figures 5a to 5c show different embodiments of the light source comprising three narrowband point sources (Figure 5a). [Figure 5c] Figures 5a to 5c show different embodiments of the light source comprising three narrowband point sources (Figure 5a). [Figure 6a] FIG. 6a reports the temporal sequence of switching states of a ferroelectric liquid crystal on silicon (FLCoS) based spatial light modulator in a light field image projection system according to one embodiment. [Figure 6b] FIG. 6b reports the temporal sequence of the switching states of a FLCoS-based spatial light modulator of a light field image projection system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] 1a shows a schematic diagram of a near-eye light field image projection system according to one embodiment, comprising a light source 10. The light source 10 comprises a single narrowband point light source for each color, the point light sources configured to emit narrowband light 200 having a narrow wavelength spectrum.

[0016] The light field image projection system includes splitters 20, 30, 70 configured to sequentially generate a plurality of incident light beams 220 and form a plurality of virtual light sources 50 at different positions in a first image plane 31. or beam steering device It also has 80.

[0017] The light field image projection system further comprises an SLM 40 configured to generate a modulated beam of light 240 and a virtual image for each incident light beam 220 .

[0018] The light field image projection system includes a combiner 100 (see FIG. 4). The combiner 100 is configured to project virtual images at virtual viewpoints 60a-60c within an eyebox region 121, and transmits natural light from the real world 180 toward the eyebox 121. Each virtual image generated by the spatial light modulator 40 corresponds to a viewpoint as seen at the location of the virtual viewpoint, from which a light field image can be formed. Thus, each virtual viewpoint 60a-60c includes a virtual image of a virtual scene (a virtual scene or view) as seen from that virtual viewpoint 60a-60c.

[0019] In the configuration of Figure 1a, the splitting device comprises a diffractive element 20 configured to generate a plurality of incident light beams 220 that are incident on the surface of the SLM 40 at different angles of incidence θ.

[0020] The diffractive element 20 may comprise a diffractive optical element (DOE), a holographic optical element (HOE), a liquid crystal polarization grating (LCPG), a semi-reflective surface, a Fresnel lens array, a mirror, or a metasurface (a two-dimensional arrangement of structures significantly smaller than the wavelength of light that have properties not found in nature, such as negative refractive index). The splitting device further comprises a first optical lens 70 configured to form multiple virtual light sources 50a-50c. The first optical lens 70 focuses the incident light beam 220, which forms the incident light beam 220, onto the first image plane 31 to form the array of virtual light sources 50a-50c. In FIG. 1a, three incident light beams 220 are shown, forming three virtual light sources 50a-50c at different positions on the first image plane 31. The diffractive element 20 and the first optical lens 70 may be configured to generate any number of incident light beams 220 and virtual light sources 50a-50c. Virtual light sources 50a to 50c can further be formed in any two-dimensional arrangement at first image plane 31.

[0021] 1a, the first optical lens 70 is a single lens. Each incident light beam 220 passes through a portion of the first optical lens 70 depending on the angle of incidence θ of the incident light beam 220. The portion of the first optical lens 70 focuses the incident light beam 220 passing therethrough to form the light sources 50a-50c at the first image plane 31.

[0022] In one aspect, the splitting device further comprises a pixelated active shutter array 30 configured to sequentially select at least one of the virtual viewpoints 60a-60c visible within the eyebox 121. The active shutter array 30 allows each incident light beam 220 to be transmitted or not transmitted to the remainder of the optical system. The active shutters 30 may comprise transparent or reflective ferroelectric liquid crystal devices. Alternatively, the active shutter 30 may comprise a liquid crystal array or an active micromirror array. The choice of type of active shutter 30 may depend on the required shutter speed. The active shutter array may be configured to function in transmission or reflection.

[0023] Each virtual viewpoint 60a-60c can be projected in time sequence. For example, pixelated shutter array 30 can allow virtual light source 50a to reach virtual viewpoint 60a while blocking virtual light sources 50b and 50c, thereby blocking virtual viewpoints 60b and 60c. At this moment, only virtual viewpoint 60a is seen and transmitted or reflected through the optical system. At a later moment, only virtual light source 50b is transmitted by active shutter 30, and virtual viewpoint 60b is seen. Similarly, for virtual light source 50c.

[0024] The SLM 40 generates images corresponding to each virtual viewpoint 60a-60c. For example, when the shutter array 30 allows the virtual light source 50a to reach the virtual viewpoint 60a, the SLM 40 generates a 2D image of the virtual scene corresponding to the viewpoint seen at the virtual viewpoint location 60a. The same process is repeated in temporal order for the other virtual viewpoint locations 60b and 60c. Each time, a 2D image of the virtual scene corresponds to the viewpoint seen from the virtual viewpoint location 60b or 60c. A light field image is then formed. Note that because any number of virtual light sources 50a-50c can be generated, the light field image projection system can project any number of virtual viewpoints 60a-60c in temporal order.

[0025] The refresh rate of the sequence that generates the virtual viewpoints 60a to 60c may be fast enough to occur within the eye's integration time, which is typically between 20 Hz and 1000 Hz.

[0026] The light field image projection system enables the generation of temporally continuous virtual viewpoints by using at least a single narrowband point light source per color, based on the passive light dividing device 20 and active shutter array 30 sequentially selecting visible virtual viewpoints 60a to 60c. Light field image projection systems also enable the projection of 3D images with monocular depth of field, allowing virtual content to be placed at any depth plane.

[0027] The light field image projection system includes splitters 20, 30, and 70. or beam steering device The light field image projection system may further include a first projection optical system 27 disposed between the SLM 40 and the eyebox 121. The first projection optical system 27 is configured to collimate and project the incident light beam 220 to form an intermediate image at an intermediate image plane 127 that coincides with the position of the SLM 30. The light field image projection system may further include a second projection optical system 90 disposed between the SLM 40 and the eyebox 121. The projection system is also configured to project the modulated beam of light 240 to form the virtual viewpoints 60a-60c.

[0028] The incident light beam 220 has an illuminance (light output weighted by the wavelengths emitted by the incident light beam 220). This illuminance is essentially equivalent to the luminous intensity of the narrowband light 200 divided by the number of virtual light sources 50. If we assume that the intensity profile (intensity distribution) of the narrowband light 200 is a Gaussian distribution, then the intensity profile of the envelope of each virtual light source 50 will also be a Gaussian distribution, and the intensities of each of the separated virtual light sources 50 will not be equal but will follow the Gaussian envelope.

[0029] For the light field image projection system shown in Figure 1a, the numerical numerical aperture NA of the system can be defined by NA = D / 2f, where f is the focal length of the first optical lens 70 and D is the size of the incident light beam 220.

[0030] Assuming a 10 mm incident light beam 220 and 25 virtual light sources 50 (e.g., a 5x5 array of virtual light sources 50), the ratio of the illuminance of a single virtual light source 50 to the illuminance of the narrowband light 200 is 4%. In this configuration, the numerical numerical aperture NA of the virtual light sources 50 corresponds to 0.2 (f=5 mm and D=2 mm).

[0031] 1b shows an alternative configuration of the light field image projection system, in which the first optical lens 70 is a lens array comprising a plurality of lenslets 71 (lenslets 71). In this configuration, each incident light beam 220 passes through one of the lenslets 71 depending on the angle of incidence θ. Each lenslet 71 focuses the incident light beam 220 passing through it to form light sources 50a-50c at the first image plane 31. Optionally, the light field image projection system may further comprise a second optical element 25. The second optical element 25 enables the main rays (or first-class rays) of each incident light beam 220 to be aligned parallel to one another before reaching the first optical lens 70. Without the second optical element 25, the main rays of the incident light beams 220 would diverge from one another, requiring not only a larger first optical lens 70, but also a larger active shutter 30 and first projection optics 27, resulting in a larger projection system.

[0032] As shown in FIG. 1b, the size of the narrowband light 200 can be made to substantially match the size of the lenslets 71.

[0033] 2a illustrates a light field image projection system according to another embodiment. The splitting device includes a lens array 70 including a plurality of lenslets 71. The lens array 70 is configured to focus at least a portion of the narrowband light 200 to generate incident light beams 220 and form an array of virtual light sources 50a-50c at the first image plane 31. In particular, each lenslet 71 generates an incident light beam 220 and forms a corresponding virtual light source 50a-50c. The generated incident light beams 220 are incident on the surface of the SLM 40 at different angles of incidence θ. The lenslets 71 may comprise converging or diverging lenses.

[0034] The splitting device may further comprise the active shutter array 30 described above.

[0035] The active shutter array 30 may be located at different positions in the optical path of the incident light beam 220 or the modulated beam of light 240 .

[0036] 1a and 2a, the active shutter array 30 is located substantially at a first image plane 31 and is positioned such that at least one of the virtual light sources 50a to 50c is transmitted or reflected at some point.

[0037] In the configuration of FIG. 1 b , the active shutter array 30 is located near the focal point of the lenslets 71 , specifically between the lens array 70 and the first image plane 31 .

[0038] Figure 2b shows an alternative configuration of the light field image projection system of Figure 2a, in which an active shutter array 30 is provided between the light source 10 and the splitting device 20.

[0039] Figure 2c shows an alternative configuration of the light field image projection system of Figure 2a, in which an active shutter array 30 is located between the SLM 40 and the eyebox 121. For example, the active shutter array 30 may be located near the virtual viewpoints 60a to 60c.

[0040] As shown in FIGS. 2a-2c, the size of the narrowband light 200 may correspond substantially to the size of the lens array 70.

[0041] The active shutter array 30 arrangement shown in Figures 2a to 2c can be implemented in the light field image projection system configuration shown in Figures 1a and 1b.

[0042] This position can also be used in configurations with splitter 20. Note that one or more light sources 10 can be passed simultaneously. This can be used to create a brighter image, a peripheral image, or to fill in the color of an object.

[0043] For the light field image projection system shown in Figures 1b, 2a-2c, the numerical numerical aperture NA of virtual light source 50 can be defined as NA = D / 2f, where f is the focal length of first optical lens 70 and D is the diameter size of lenslet 71 when the beam (ray) fills the lenslet aperture. As mentioned above, assuming a 10 mm incident light beam 220 and 25 virtual light sources 50 (e.g., a 5x5 array of virtual light sources 50), the ratio of the illuminance of a single virtual light source 50 to the illuminance of narrowband light 200 is 4%. The size of lenslet 71 gives the numerical numerical aperture NA (NA = 0.2 for a 2 mm lenslet diameter).

[0044] More generally, for the light field image projection systems shown in Figures 1a, 1b, 2a-2c, the ratio of the illuminance of the narrowband light 200 to the illuminance of a single virtual light source 50 depends on the number of virtual light sources 50. In one embodiment, the ratio of the illuminance of the single virtual light source 50 to the illuminance of the narrowband light 200 is at least 1%. Alternatively, the ratio of the illuminance of the single virtual light source 50 to the illuminance of the narrowband light 200 may be at least 5%, 10%, or 20%.

[0045] A light field image projection system is shown in Figure 3 according to yet another embodiment. In this configuration: Light Field Image Projection System comprises a beam steering device 80 and a lens array 70 comprising a plurality of lenslets 71. The beam steering device 80 is steerable to direct narrowband light 200 towards one of the lenslets 71 to generate an incident light beam 220 at a predetermined angle of incidence θ.

[0046] Beam steering device 80 may include a tilting mirror that can be tilted to direct narrowband light 200 towards one of lenslets 71 .

[0047] Beam steering device 80 may be configured to be steered in a first position and stop its movement in the first position while light source 10 is on, so that incident light beam 220 is directed toward one of lenslets 71. Beam steering device 80 may be further configured to be steered in a second position and stop its movement in the second position while light source 10 is on, so that incident light beam 220 is directed toward another lenslet 71. While beam steering device 80 is steering, light source 10 is turned off. Beam steering device 80 may be configured to be steered to any number of positions corresponding to the number of lenslets 71 in lens array 70, and to stop its movement so that incident light beam 220 is directed toward one of the lenslets 71. Each time light source 10 is turned on and incident light beam 220 is directed toward one of the lenslets 71, virtual viewpoints 60a-60c are generated.

[0048] In one aspect, the incident light beams 220 can pass through the second optical element 25 before reaching the lenslets 71 of the lens array 70. As discussed in conjunction with FIG. 1b, the second optical element 25 allows the chief rays of each incident light beam 220 to be aligned parallel to one another before reaching the first optical lens 70.

[0049] 3, the size of narrowband light 200 may substantially match the size of lenslet 71. In this configuration, a majority of narrowband light 200, and possibly the entire narrowband light 200, is used to generate incident light beam 220 and form virtual light source 50, and thus virtual viewpoints 60a-60c. In contrast, in the light field image projection system configurations shown in Figures 1a, 1b, and 2a-2c, when narrowband light 200 is split, only a portion of narrowband light 200 is used to generate incident light beam 220 to form virtual viewpoints 60a-60c, while the remaining portion of narrowband light 200 is blocked by active shutter 30. Thus, only a small portion of the initial narrowband light 200 is used to create the virtual viewpoints 60a-60c. Thus, the incident light beam 220 has an illuminance that substantially matches the illuminance of the narrowband light 200.

[0050] In one optional configuration, narrowband light 200 can be collimated (parallelized) by collimating optic 101 .

[0051] The light field image projection system in the configurations of FIGS. 1b to 3 includes splitters 20, 30, 70, or beam steering device 80 and the SLM 40, and the first projection optical system 27 is configured to collimate and project the incident light beam 220.

[0052] FIG. 4 shows a schematic diagram of a light field image projection system including a second projection optical system 90 disposed between the SLM 40 and a combiner 100. The second projection optical system 90 is configured to form intermediate virtual viewpoints 60a-60c at an intermediate image plane 110 between the second projection optical system 90 and the combiner 100. The second projection optical system 90 may include multiple refractive, reflective, diffractive, or freeform surfaces. The combiner 100 is transparent or translucent and projects virtual images at the virtual viewpoints 60a-60c within an eyebox region 121, transmitting natural light from the real world 180 toward the eyebox 121. The combiner 100 may include a reflective holographic, a transmissive holographic, a refractive, reflective, or a diffractive combiner.

[0053] In one preferred embodiment, combiner 100 comprises a holographic reflective combiner that selectively reflects the projector's RGB three color components while transmitting the remainder of the visible spectrum. Holographic reflective combiner 100 has a broadband acceptance angle of incident light between 15° and 80°.

[0054] In one embodiment, light source 10 comprises a laser point light source. In one possible configuration, light source 10 may comprise a red laser point light source configured to generate red light, a green laser point light source configured to generate green light, and a blue laser point light source configured to generate blue light. In another possible configuration, light source 10 may comprise a single narrowband point light source configured to emit white light composed of red, green, and blue light.

[0055] In contrast to LED light sources, laser light sources have sufficient optical power density to be split into multiple virtual light sources. Therefore, a split single laser point source may be advantageously used in combination with a holographic combiner. Alternatively, an array of compact VCSEL (Vertical Cavity Surface Emitting) lasers may be provided, with each VCSEL laser being a single point source. When using a VCSEL laser array, no splitting device is needed to generate multiple incident light beams 220. In fact, each incident light beam 220 is generated by a VCSEL laser in the array. However, VCSEL laser arrays are currently only available that emit red light. Edge-emitting lasers, on the other hand, are technically challenging and too large and expensive to integrate into an array.

[0056] "Also, in contrast to LED light sources, laser light sources are essentially monochromatic, significantly reducing chromatic dispersion in projection systems, especially combiners. Using multiple laser light sources to replace current LEDs presents challenges in terms of device size, packaging, and power consumption. Therefore, light field image projection systems using a single narrowband light source for each color are advantageous."

[0057] Figures 5a to 5c show different embodiments of the light source 10. In particular, Figure 5a shows that the light source 10 comprises three narrowband point light sources 10a to 10c, for example, one narrowband point light source for each color. The light source 10 comprises a first narrowband point light source 10a that emits red narrowband light 200, a second narrowband point light source 10c that emits green narrowband light 200, and a third narrowband point light source 10c that emits blue narrowband light 200.

[0058] In one aspect, the first point light source 10a can be collimated by the collimating optical element 101 and then reflected by the mirror 102. Similarly, the second point light source 10b and the third point light source 10c can be collimated by the collimating optical element 101 and then reflected by the dichroic plate 103. The dichroic plate 103 reflects certain colors and transmits other colors. For example, the first point light source 10a transmits through the dichroic plate 102, and the second point light source 10b is reflected by the dichroic plate 102, effectively combining the first point light source 10a and the second point light source 10b. At the exit of the light source 10, the first point light source 10a, the second point light source 10b, and the third point light source 10c are combined into a single narrowband light 200. An aperture lens 105 can be added to expand the numerical aperture of the light source 10.

[0059] In the configuration of FIG. 5b, the light source 10 does not include a lens 105 and the narrowband light 200 remains collimated or has a small numerical aperture.

[0060] In the configuration of Figure 5c, point light sources 10a to 10c are combined using a single collimating optical element 106. Point light sources 10a, 10b, and 10c may be arranged along a line (as shown in Figure 5c), stacked on top of each other, in a triangular or square configuration. When the single collimating optical element 106 is positioned at a distance close to the focal length f of point light sources 10a to 10c from the single collimating optical element 106, the latter overlap at the focal plane 107 of the collimating optical element 106 at the distance f, on the side of the collimating optical element 106 opposite light sources 10a to 10c.

[0061] 3, the SLM 40 may comprise a ferroelectric liquid crystal on silicon (FLCoS). The light field image projection system may further comprise a controller 300 configured to control the switching state of the SLM 40 in synchronization with the beam steering device 80 and the light source 10.

[0062] Figure 6a reports the switching states of the FLCoS-based SLM 40 as a function of time t. The FLCoS can display image information corresponding to the illumination of the light source as a display, which in Figure 6a is shown in colors such as red (R), green (G), and blue (B), corresponding to narrowband point light sources 10a to 10c emitting red, green, and blue narrowband light 200, respectively. In Figure 6a, the numbers 0, 1, and 2 correspond to the positions of the virtual light sources 50a to 50c, respectively.

[0063] As shown in FIG. 6a, for one piece of image information R1, e.g., red image information, the FLCoS takes a certain time (or positive setup time t11) to switch to the correct state. The positive setup time t11 corresponds to the positive data of the FLCoS R channel of virtual light sources 50a to 50c. The FLCoS maintains the correct state during the positive illumination time t111, which corresponds to the time when the light source 10 is actually turned on to project an image. Illuminating the FLCoS before or after the window of illumination time t111 will reduce the contrast of the image.

[0064] After the positive illumination time t111, negative image information is sent to the FLCoS at approximately the same time as the positive image information to balance the charge level on the FLCoS (indicated by the negative setup time T11 and the dashed -R1 step during the negative illumination time T111). Without this charge balance, the SLM on the FLCoS could be damaged. During the negative setup time T11 and the negative illumination time T111, there is no light source illumination. In other words, the controller 300 turns on the light source 10 during the positive illumination times t111, t121, and t131 when the beam steering device 80 is not moving, shining narrowband light 200 toward one of the lenslets 71, and turns the light source 10 off at other times.

[0065] The same lighting sequence described above can be performed as follows: green (G1) with a positive setup time t12 and a negative setup time T12 and a positive illumination time t121 and a negative illumination time T121; Blue (B1) with a positive setup time t13 and a negative setup time T13 and a positive illumination time t131 and a negative illumination time T131; This also applies to other colors, including

[0066] Looking at the global RGB sequence illumination of a given virtual light source position 50a-50c (e.g., R1 / G1 / B1), the beam steering device 80 (e.g., tilt mirror) must be in a stable position for at least stabilization time t3, which includes three RGB illumination times t111, t121, and t131. Thereafter, the beam steering device 80 needs a certain amount of time, switching time t4, to switch to the next position corresponding to the next virtual light source 50a-50c in the virtual point source array 50, before another image information R2, e.g., red image information, is turned on during t211. Switching time t4 is shown here as the sum of times T13, T131, and t21, which are essentially related to the overall projection data flow of the high-level system architecture. As such, the switching time t4 can be very short, in the range of 50 ps to 500 ps. Therefore, the beam steering device 80 needs to switch at least as fast as the switching time t4, which can be a very severe physical constraint.

[0067] 6b reports an alternative time sequence of the switching states of the FLCoS-based SLM 40. The timing of the positive setup time t11 and positive illumination time t111, and the negative illumination time T11 and negative illumination time T111, are reversed compared to the timing of FIG. 6a. In other words, at least one positive setup time t11, t12, t13 and positive illumination time t111, t112, t113 of a color has a corresponding negative setup time T11, T12, T13 and negative illumination time T111, T112, T113.

[0068] The beam steering device moves from one position to another between the negative setup times T11, T12, T13 of the previous illumination step, the negative illumination times T111, T121, T131, and the positive setup times of the next illumination step. Thus, the beam steering device 80 has a longer time to move from one position to another between the negative setup times and negative illumination times of the previous illumination step, and the negative setup times, negative illumination times, and positive setup times of the next illumination step.

[0069] By reversing the timing, the switching time t4 can be increased by at least 30% (increased switching time t41) depending on the values ​​of the illumination times t121 and t131. Compared with the timing of Fig. 6a, the reversed timing of Fig. 6b will cause irreversible damage to the FLCoS-based SLM 40, since sequential positive and negative image data of the same color and virtual light source position transmitted to the FLCoS-based SLM 40 will be preserved.

[0070] Optionally, For green, a positive setup time t12 and a positive exposure time t121, and a negative setup time T12 and a negative exposure time T121; For blue, a positive setup time t13 and a positive exposure time t131, and a negative setup time T13 and a negative exposure time T131. The timing of may also be inverted compared to that of FIG. 6a.

[0071] It is understood that the present invention is not limited to the exemplary embodiments described above, and that other implementations are possible within the scope of the claims. For example, the light source 10 may be two or more narrowband point light sources 10a to 10c; two or more virtual light sources 50a to 50c; The present invention may include both or one of the following: The present application provides the following aspects, for example: [Point 1] a light source (10) configured to emit narrowband light (200) having a narrow wavelength spectrum, the light source having a single narrowband point light source for each color; a splitting device (20, 30, 70, 80) configured to sequentially generate a plurality of incident light beams (220) to form a plurality of virtual light sources (50) at different locations within a first image plane (31); a spatial light modulator (40) configured to generate a modulated beam of light (240) and a virtual image for each incident light beam (220); a combiner (100) configured to project the virtual image at virtual viewpoints (60) within an eyebox region (121) and transmit natural light from the real world (80) toward the eyebox (121), each viewpoint (60) including an image of the virtual scene as seen from that viewpoint (60); In a light field image projection system comprising: the splitting device (20, 30, 70, 80) is further configured to direct the incident light beam (220) to the spatial light modulator (40) so that the incident light beam (220) is incident on a surface of the spatial light modulator (40) at different angles of incidence (θ) and to sequentially select at least one of the virtual viewpoints (60) visible within the eyebox (121); The ratio of the illuminance of the single virtual light source 50 to the illuminance of the narrow band light (200) is at least 1%; Light field image projection system. [Point 2] The projection system of aspect 1, wherein the incident light beam (220) has an illuminance substantially equivalent to the illuminance of the narrowband light (200) divided by the number of the virtual light sources (50). [Point 3] The dividing device a diffractive element (20) configured to generate the plurality of incident light beams (220) at the different angles of incidence (θ) from the narrowband light (200); an optical lens (70) configured to form the plurality of virtual light sources (50); an active shutter array (30) configured to sequentially select at least one of the virtual viewpoints (60) visible within the eyebox (121); 3. The projection system according to aspect 1 or 2, comprising: [Point 4] A projection system as described in aspect 3, wherein the optical lens is a single lens (70) and each incident light beam (220) passes through a portion of the lens (70) depending on the incident angle (θ) of the incident light beam (220). [Point 5] A projection system as described in aspect 3, wherein the optical lens (70) is a lens array comprising a plurality of lenslets (71), and each incident light beam (220) passes through one of the lenslets (71) depending on the angle of incidence (θ). [Point 6] The diffraction element (20) may be a diffractive optical element (DOE), a holographic optical element (HOE), 6. The projection system of any one of aspects 3 to 5, comprising a liquid crystal polarization grating (LCPG), a semi-reflective surface, a mirror, or a metasurface. [Point 7] A projection system as described in aspect 1 or 2, wherein the splitting device comprises a lens array (70) comprising a plurality of lenslets (71), each lenslet (71) generating the incident light beam (220) at an angle of incidence (θ) different from the angle of incidence (θ) of the incident light beam (220) generated by another lens (71). [Point 8] Aspects 8. The projection system according to any one of aspects 5 to 7, wherein the size of the narrowband light (200) substantially matches the size of the lens array (70). [Point 9] the splitting device comprises a beam steering device (80) and a lens array (70) comprising a plurality of lenslets (71); The projection system of aspect 1, wherein the beam steering device (80) is steerable to direct the narrowband light (200) toward one of the lenslets (71) and to generate the incident light beam (220) at the incident angle (θ). [Point 10] A projection system as described in aspect 9, wherein the size of the narrowband light (200) substantially matches the size of the lenslet (71), and the incident light beam (220) has an illuminance that is substantially 100% of the illuminance of the narrowband light (200). [Point 11] 11. The projection system of any one of aspects 1 to 10, wherein the active shutter array (30) comprises a transparent or reflective ferroelectric liquid crystal device, or an active micromirror array. [Point 12] 11. A projection system according to any one of aspects 1 to 10, wherein the active shutter array (30) is arranged substantially within the first image plane (31) and is configured to transmit at least one of the virtual light sources (50) at a given time. [Point 13] 11. The projection system according to any one of aspects 1 to 10, wherein the active shutter array (30) is provided between the light source (10) and the splitting device (70). [Point 14] 11. The projection system according to any one of aspects 1 to 10, wherein the active shutter array (30) is provided between the spatial light modulator (40) and the eyebox (121). [Point 15] 15. The projection system according to any one of aspects 1 to 14, wherein the light source (10) comprises a laser light source. [Point 16] 16. The projection system of any one of aspects 1 to 15, wherein the light source (10) comprises a red laser point source configured to generate red light, a green laser point source configured to generate green light, and a blue laser point source configured to generate blue light. [Point 17] 16. The projection system of any one of aspects 1 to 15, wherein the light source (10) comprises a single narrowband point light source configured to emit white light comprising red, green and blue light. [Point 18] 17. The projection system of any one of aspects 1 to 16, wherein the combiner (100) comprises a reflective holographic combiner. [Point 19] the spatial light modulator (SLM) (40) comprises a ferroelectric liquid crystal on silicon; 19. The projection system of any one of aspects 9 to 18, wherein the light field image projection system comprises a control device (300) configured to control the switching state of the SLM (40) in synchronization with the beam steering device (80) and the light source (10). [Point of View 20] The control device (300) configured to switch the color state of the SLM (40) during positive setup times (t11, t12, t13) and negative setup times (T11, T12, T13), and to place the SLM (40) in a switched color state during positive illumination times (t111, t121, t131) and negative illumination times (T111, T121, T131); The control device (300) further configured to turn on the light source (10) during positive illumination times (t111, t121, t131) while the beam steering device (80) is not moving and to direct the narrowband light (200) toward one of the lenslets (71), and to turn off the light source (10) at other times; the beam steering device moving from one position to another between the negative setup times (T11, T12, T13) and negative illumination times (T111, T121, T131) of a previous illumination step and the positive setup times of a subsequent illumination step; at least one positive setup time (t11, t12, t113) and positive illumination time (t111, t112, t113) per color is inverted with respect to a corresponding negative setup time (T11, T12, T13) and negative illumination time (T111, T112, T113) so that the beam steering device (80) has a longer time to move from one position to another during the negative setup time and negative illumination time of the previous illumination step plus the negative setup time and negative illumination time of the next illumination step plus the positive setup time of the next illumination step; A projection system according to aspect 19. [Point of View 21] A wearable device comprising a light field image projection system according to any one of aspects 1 to 20. [Point of View 22] A wearable device according to aspect 21, comprising an augmented reality or mixed reality device or smart glasses. [Explanation of symbols]

[0072] 10 light source 10a First narrowband point light source 10b Second narrowband point source 10c Third narrowband point source 20 Beam splitter, splitting device 25 Second optical element 30 Active Shutter 31 1st image plane 40 Spatial Light Modulator 50, 50a, 50b, 50c Virtual Light Source 60, 60a, 60b, 60c Virtual Viewpoint 70 First optical lens, lens array 71 Lenses (lenslets, small lenses) 80 Beam steering device 90 Second projection optical system 100 Combiner 101 Collimating optical element 102 Mirror 103 Dichroic plate 105 Lens 106 Collimating Optical Element 107 Focal plane 110 Intermediate image plane 180 Natural Light from the Real World 200 narrowband light 220 incident light beam 240 Modulated Beam Light 300 Controller θ angle of incidence t11 Red R1 positive setup time t111 Red R1 positive illumination time T11 Negative setup time for red R1 T111 Negative illumination time of red R1 t12 Green G1 positive setup time t121 Green G1 positive illumination time T12 Green G1 negative setup time T121 Green G1 Negative Illumination Time T13 Blue B1 positive setup time t131 Blue B1 positive illumination time T13 Blue B1 negative setup time T131 Blue B1 Negative Illumination Time t3 stabilization time t4 Switching time

Claims

1. a light source configured to emit narrowband light having a narrow wavelength spectrum, the light source including a single narrowband point light source for each color; a splitting or beam steering device configured to sequentially generate a plurality of incident light beams to form a plurality of virtual light sources at different locations within the first image plane; a spatial light modulator configured to generate a modulated beam of light and a virtual image for each incident light beam; a combiner configured to project the virtual image at virtual viewpoints within the eyebox region and transmit natural light from the real world toward the eyebox, each viewpoint including an image of the virtual scene as seen from that viewpoint; In a light field image projection system comprising: the splitting device or the beam steering device is further configured to direct the incident light beam to the spatial light modulator such that the incident light beam is incident on a surface of the spatial light modulator at different angles of incidence and in a manner that sequentially selects at least one of the virtual viewpoints viewable within the eyebox; The ratio of the illuminance of the single virtual light source to the illuminance of the narrow-band light is at least 1%; Light field image projection system.

2. 2. The projection system of claim 1, wherein the incident light beam has an illuminance substantially equal to an illuminance of the narrowband light divided by the number of the virtual light sources.

3. A diffractive element configured to generate the plurality of incident light beams at the different angles of incidence from the narrowband light; an optical lens configured to form the plurality of virtual light sources; an active shutter array configured to sequentially select at least one of the virtual viewpoints visible within the eyebox; 10. The projection system of claim 1, comprising a splitting device comprising:

4. 4. The projection system of claim 3, wherein the optical lens is a single lens, and each incident light beam passes through a portion of the single lens depending on the angle of incidence of the incident light beam.

5. 4. The projection system of claim 3, wherein the optical lens is a lens array comprising a plurality of lenslets, each incident light beam passing through one of the lenslets depending on the angle of incidence.

6. The diffractive element may be a diffractive optical element (DOE), a holographic optical element (HOE), 4. The projection system of claim 3, comprising a liquid crystal polarization grating (LCPG), a semi-reflective surface, a mirror, or a metasurface.

7. A lens array comprising a plurality of lenslets, each lenslet generating an incident light beam at an angle of incidence different from the angle of incidence of the incident light beam generated by another lens; an active shutter array configured to sequentially select at least one of the virtual viewpoints visible to the eyebox; and 10. The projection system of claim 1, comprising a splitting device comprising:

8. The projection system of claim 5 , wherein the size of the narrow band light substantially matches the size of the lens array.

9. the projection system further comprising a beam steering device and a lens array comprising a plurality of lenslets; 2. The projection system of claim 1, wherein the beam steering device is steerable to direct the narrowband light toward one of the lenslets and to generate the incident light beam at the angle of incidence.

10. 10. The projection system of claim 9, wherein a size of the narrowband light substantially matches a size of the lenslet, and the incident light beam has an illuminance that is substantially 100% of an illuminance of the narrowband light.

11. 4. The projection system of claim 3, wherein the active shutter array comprises a transparent or reflective ferroelectric liquid crystal device or an active micromirror array.

12. 4. The projection system of claim 3, wherein the active shutter array is disposed substantially in the first image plane and configured to transmit at least one of the virtual light sources at a given time.

13. 4. The projection system of claim 3, wherein the active shutter array is disposed between the light source and the splitting device.

14. 4. The projection system of claim 3, wherein the active shutter array is disposed between the spatial light modulator and the eyebox.

15. The projection system of claim 1 , wherein the light source comprises a laser light source.

16. 10. The projection system of claim 1, wherein the light sources comprise a red laser point source configured to generate red light, a green laser point source configured to generate green light, and a blue laser point source configured to generate blue light.

17. 10. The projection system of claim 1, wherein the light source comprises a single narrowband point source configured to emit white light comprising red, green, and blue light.

18. 10. The projection system of claim 1, wherein the combiner comprises a reflective holographic combiner.

19. the spatial light modulator comprises a ferroelectric liquid crystal on silicon; 10. The projection system of claim 9, wherein the light field image projection system comprises a controller configured to control the switching state of the spatial light modulator in synchronization with the beam steering device and the light source.

20. The control device configured to switch a color state of the spatial light modulator during positive and negative setup times, and to place the spatial light modulator in a switched color state during positive and negative illumination times; The control device further configured to turn on the light source during a positive illumination time while the beam steering device is not moving and directing the narrowband light toward one of the lenslets, and to turn off the light source at other times; the beam steering device moving from one position to another between a negative setup time and a negative illumination time of a previous illumination step and a positive setup time of a subsequent illumination step; at least one positive setup time and positive illumination time per color is reversed with respect to a corresponding negative setup time and negative illumination time, so that the beam steering device has a longer time to move from one position to another during the negative setup time and negative illumination time of a previous illumination step plus the negative setup time and negative illumination time of a next illumination step plus the positive setup time of the next illumination step; 20. The projection system of claim 19.

21. A wearable device comprising the light field image projection system of claim 1.

22. 22. The wearable device of claim 21, comprising an augmented or mixed reality device or smart glasses.

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