Direct retinal holographic projector with speckle reduction including multiple spatial light modulators

Abstract

A direct retinal holographic projection system includes first and second spatial light modulators (SLMs) and a control module. The first SLM receives a light beam and dithers the light beam at a predetermined frequency to provide multiple instances of the light beam. The second SLM receives an instance of the light beam, displays a coded phase hologram of a graphic image to be projected, and diffracts the instance of the light beam to provide an instance of the coded phase hologram having the same graphic image but multiplied by the dithered wavefront. The control module: iteratively adjusts the parameters of the first SLM to generate instances of the light beam; and based on the instances of the light beam, controls the operation of the second SLM to display multiple instances of the graphic image on the retina of the viewer's eye.

Description

[0001] introduction

[0002] The information provided in this section is for the purpose of generally presenting the background of the present disclosure. To the extent described in this section, the work of the presently named inventors, and aspects that may otherwise not qualify as prior art at the time of filing, are neither explicitly nor implicitly admitted to be prior art against the present disclosure. Technical Field

[0003] The present disclosure relates to direct retinal projection holographic display systems and heads-up display systems for vehicles. Background Art

[0004] Display devices are used in a wide variety of applications. Some example display devices are flat panel displays, projection displays, and heads-up displays. Display devices can be transmissive or reflective.

[0005] Traditionally, the driver of a vehicle observes the surroundings of the vehicle through the windows, windshield, and other glass of the vehicle. The driver can control the acceleration, deceleration, and steering of the vehicle based on the driver's visual observation of the surroundings of the vehicle. The vehicle may include one or more displays that display various information to the driver. For example, some vehicles include an infotainment system that includes a display that displays various infotainment and other vehicle information. The vehicle may also include a head-up display (HUD) that displays information by forming a virtual image at a certain distance using the reflection of the windshield. For example, the HUD can display vehicle speed and other vehicle information (e.g., warnings, such as lane departure warnings and collision avoidance warnings). Summary of the invention

[0006] A direct retinal holographic projection system is provided, and includes a first spatial light modulator, a second spatial light modulator, and a control module. The first spatial light modulator is configured to receive a light beam from a light source and to jitter the light beam at a predetermined frequency to provide multiple instances of the light beam. The second spatial light modulator is configured to receive an instance of the light beam from the first spatial light modulator, display a coded phase hologram of a graphic image to be projected, and diffract an instance of the light beam to provide an instance of a coded phase hologram having the same graphic information as the graphic image but multiplied by a jittered wavefront. The control module is configured to: iteratively adjust the parameters of the first spatial light module to generate an instance of the light beam; and control the operation of the second spatial light modulator to display multiple instances of the graphic image on the retina of the viewer's eye based on the instance of the light beam by directing an instance of the coded phase hologram of the graphic image to a reflector or the viewer's eye.

[0007] In other features, the second spatial light modulator directs an instance of the coded phase hologram directly to the eye of a viewer without forming a real image on a diffuser and without reflecting the image with a mirror.

[0008] In other features, the second spatial light modulator directs an instance of the coded phase hologram directly onto a reflector to be seen by an eye of a viewer without forming a real image on a diffuser. The reflector is a windshield of a vehicle.

[0009] In other features, the control module is configured to dither the light beam via the first spatial light modulator at a frequency greater than or equal to 60 Hz.

[0010] In other features, the control module is configured to dither the light beam between the first angle and the second angle at a predetermined frequency.

[0011] In other features, the difference between the first angle and the second angle is less than or equal to 5°.

[0012] In other features, the difference between the first angle and the second angle is less than or equal to 1°.

[0013] In other features, the first spatial light modulator includes a digital light processing micro-electromechanical system mirror.

[0014] In other features, the first spatial light modulator comprises a piston mode spatial light modulator.

[0015] In other features, the first spatial light modulator comprises a ferroelectric liquid crystal spatial light modulator.

[0016] In other features, the direct retinal holographic projection system further includes a device driver. The control module is configured to control the device driver to generate one or more driving voltages. The first spatial light modulator changes the dithering angle based on the driving voltage.

[0017] In other features, a method of operating a direct retinal holographic projection system is provided. The method includes: receiving a light beam from a light source at a first spatial light modulator; dithering the light beam at a predetermined frequency to provide multiple instances of the light beam, wherein the dithering includes iteratively adjusting parameters of the first spatial light module to generate instances of the light beam; receiving the instances of the light beam at a second spatial light modulator; converting the instances of the light beam into multiple instances of a coded phase hologram; and controlling the operation of the second spatial light modulator to display multiple instances of an image on a retina of an eye of a viewer based on the instances of the light beam by directing the instances of the coded phase hologram to a reflector or an eye of the viewer.

[0018] In other features, the method further includes directing an instance of the coded phase hologram directly from the second spatial light modulator to a reflector or an eye of a viewer.

[0019] In other features, the light beam is dithered via the first spatial light modulator at a frequency greater than or equal to 60 Hz.

[0020] In other features, the light beam is dithered at a predetermined frequency between a first angle and a second angle via a first spatial light modulator.

[0021] In other features, the difference between the first angle and the second angle is less than or equal to 5°.

[0022] In other features, the difference between the first angle and the second angle is less than or equal to 5°.

[0023] In other features, the dithering of the light beam comprises varying a drive voltage of a digital light processing micro-electromechanical system mirror of the first spatial light modulator.

[0024] In other features, the dithering of the light beam includes varying a drive voltage of a piston-mode spatial light modulator.

[0025] In other features, the dithering of the light beam includes varying a drive voltage of a ferroelectric liquid crystal spatial light modulator.

[0026] The present invention provides the following technical solutions:

[0027] 1. A direct retinal holographic projection system, comprising:

[0028] a first spatial light modulator configured to receive a light beam from a light source and to dither the light beam at a predetermined frequency to provide a plurality of instances of the light beam;

[0029] a second spatial light modulator configured to receive multiple instances of the light beam from the first spatial light modulator, display a coded phase hologram of a graphic image to be projected, and diffract the multiple instances of the light beam to provide multiple instances of the coded phase hologram having the same graphic information as the graphic image but multiplied by a plurality of dithered wavefronts; and

[0030] A control module configured to

[0031] Iteratively adjust parameters of the first spatial light module to generate multiple instances of the light beam, and control the operation of the second spatial light modulator to display multiple instances of the graphic image on the retina of the viewer's eyes based on the multiple instances of the light beam by directing the multiple instances of the encoded phase hologram of the graphic image toward a reflector or the viewer's eyes.

[0032] 2. A direct retinal holographic projection system according to technical solution 1, wherein the second spatial light modulator guides multiple instances of the encoded phase hologram directly to the eyes of the viewer without forming a real image on a diffuser and without reflecting the image with a mirror.

[0033] 3. The direct retinal holographic projection system according to technical solution 1, wherein:

[0034] the second spatial light modulator directs the plurality of instances of the coded phase hologram directly to the reflector to be seen by an eye of a viewer without forming a real image on a diffuser; and

[0035] The reflector is the windshield of the vehicle.

[0036] 4. The direct retinal holographic projection system according to technical solution 1, wherein the control module is configured to dither the light beam via the first spatial light modulator at a frequency greater than or equal to 60 Hz.

[0037] 5. The direct retinal holographic projection system according to technical solution 1, wherein the control module is configured to dither the light beam between the first angle and the second angle at a predetermined frequency.

[0038] 6. A direct retinal holographic projection system according to technical solution 5, wherein the difference between the first angle and the second angle is less than or equal to 5°.

[0039] 7. A direct retinal holographic projection system according to technical solution 5, wherein the difference between the first angle and the second angle is less than or equal to 1°.

[0040] 8. According to the direct retinal holographic projection system of technical solution 1, the first spatial light modulator comprises: a digital light processing micro-electromechanical system reflector.

[0041] 9. A direct retinal holographic projection system according to technical solution 1, wherein the first spatial light modulator comprises a piston mode spatial light modulator.

[0042] 10. A direct retinal holographic projection system according to technical solution 1, wherein the first spatial light modulator comprises a ferroelectric liquid crystal spatial light modulator.

[0043] 11. The direct retinal holographic projection system according to technical solution 1 further comprises a device driver, wherein:

[0044] The control module is configured to control the device driver to generate one or more driving voltages; and

[0045] The first spatial light modulator changes a dithering angle based on the driving voltage.

[0046] 12. A method of operating a direct retinal holographic projection system, the method comprising:

[0047] receiving a light beam from a light source at a first spatial light modulator;

[0048] dithering the light beam at a predetermined frequency to provide a plurality of instances of the light beam, wherein the dithering comprises iteratively adjusting a parameter of the first spatial light module to generate the plurality of instances of the light beam;

[0049] receiving a plurality of instances of the light beam at a second spatial light modulator;

[0050] converting the plurality of instances of the light beam into a plurality of instances of a coded phase hologram; and

[0051] The operation of the second spatial light modulator is controlled to display multiple instances of an image on a retina of a viewer's eye based on the multiple instances of the light beam by directing the multiple instances of the coded phase hologram toward a reflector or the viewer's eye.

[0052] 13. The method according to technical solution 12 further includes: directing multiple instances of the encoded phase hologram directly from the second spatial light modulator to a reflector or the eyes of a viewer.

[0053] 14. A method according to technical solution 12, wherein the light beam is jittered at a frequency greater than or equal to 60 Hz via the first spatial light modulator.

[0054] 15. The method according to technical solution 12, wherein the light beam is jittered at a predetermined frequency between a first angle and a second angle via a first spatial light modulator.

[0055] 16. A method according to technical solution 15, wherein the difference between the first angle and the second angle is less than or equal to 5°.

[0056] 17. A method according to technical solution 15, wherein the difference between the first angle and the second angle is less than or equal to 5°.

[0057] 18. A method according to technical solution 12, wherein the jittering of the light beam comprises: changing the driving voltage of a digital light processing micro-electromechanical system reflector of the first spatial light modulator.

[0058] 19. The method according to technical solution 12, wherein the jittering of the light beam includes: changing the driving voltage of the piston mode spatial light modulator.

[0059] 20. The method according to technical solution 12, wherein the jittering of the light beam includes: changing the driving voltage of the ferroelectric liquid crystal spatial light modulator.

[0060] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the accompanying drawings.The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0062] Figure 1 is a functional block diagram of an example of a direct retinal holographic projection system according to the present disclosure;

[0063] Figure 2 is a perspective view of an example interior of a vehicle including a HUD;

[0064] Figure 3 yes Figure 1 Functional block diagram of an example implementation of a direct retinal holographic projection system;

[0065] Figure 4 An exemplary direct retinal holographic projection method according to the present disclosure is illustrated;

[0066] Figure 5 is a diagram including example resolved, semi-resolved, and unresolved plots;

[0067] Figure 6 is a cross-sectional view of an example of a liquid crystal on silicon (LCoS) spatial light modulator (SLM) according to the present disclosure;

[0068] Figure 7 is a functional block diagram of an example of a portion of an LCoS SLM and a control module according to the present disclosure; and

[0069] Figure 8 is a functional block diagram of an exemplary switching SLM and corresponding device drivers and control modules according to the present disclosure.

[0070] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0071] A vehicle may include a holographic HUD that includes an SLM and a coherent or partially coherent light source. A phase hologram is encoded on the SLM. Light from the coherent or partially coherent light source illuminates the SLM encoded with the phase hologram, and the light is diffracted in a manner dictated by the hologram. The diffracted light is reflected by the vehicle's windshield and forms a real image on the driver's retina.

[0072] Display systems typically employ a coherent light source, such as a laser, in combination with other display components. Coherent light may refer to light that is in phase in space and time. When coherent light is reflected from a diffuse surface, a large amount of "speckle" is produced. When coherent light is reflected from a diffuse surface, each point on the surface emits a light wave. Typically, the reflected light waves have the same frequency, but the phase of the light reflected from different points on the surface may vary, resulting in granular, non-uniform intensity due to quasi-random interference. The reflected light interferes constructively and destructively to produce random light patterns and dark spots or bands. The entire non-uniform pattern is referred to as "speckle". When an image is formed from the reflected light, the speckle adds noise to the image.

[0073] Some holographic projection systems reduce speckle by vibrating one or more diffusers, or by including and operating an active diffuser (such as a vibrating projection screen). These types of holographic projection systems do not project a phase hologram directly onto the retina of a person viewing the generated image without first reflecting the light from the diffuser.

[0074] In a direct retinal projection holographic display system, a projected phase hologram is directed to the viewer's eye without being reflected by a diffuser. Although removing the diffuser reduces the amount of speckle in the holographic display system, some speckle may still occur due to light reflecting from, for example, one or more other surfaces. Examples described herein include: a direct retinal projection holographic display system that does not include a diffuser and is configured to reduce and / or eliminate the amount of speckle. The direct retinal projection holographic display system includes: a plurality of spatial light modulators (SLMs) that include a fast switching SLM for dithering and a second SLM for hologram generation. The second SLM may be a liquid crystal on silicon (LCoS). The fast switching SLM is implemented as an optical dithering SLM that dithers a light beam between predetermined angles and at a high frequency (e.g., greater than or equal to 60 Hertz (Hz)). This dithering is provided before the LCoS SLM generates the encoded hologram, which reduces speckle and / or blurring of the image seen by the viewer.

[0075] Figure 1 An example of a direct retinal holographic projection system 110 is shown, which includes one or more light sources (or laser sources) 112 (one laser 112 is shown), a beam expander 114, a switching (or first) SLM 16, an LCoS (or second) SLM 118, and a control module 120. The laser 112 generates a laser beam 122, which is received at the beam expander 114. The beam expander 114 expands the width of the laser beam 122 to provide an expanded beam 124.

[0076] The switching SLM 116 receives the expanded beam 124 and iteratively changes the incident angle of the expanded beam 124 reflected at the LCoS SLM 118 to provide a dithered expanded beam 128. Although primarily referred to herein is an LCoS SLM, the second SLM 118 may be replaced with a different type of SLM. The dithered expanded beam 128 includes multiple instances of the expanded beam 124. The control module 120 switches the angular state and / or the mirror height of the switching SLM 116 to change the incident angle of the expanded beam 124 at a high frequency (e.g., greater than or equal to 60 Hz). The expanded beam 124 is dithered to provide multiple beams at corresponding incident angles, referred to as dithered expanded beams 128. The dithered expanded beam 128 can be viewed as multiple light sources illuminating the LCoS SLM 118 at slightly different incident angles.

[0077] Example incident vectors showing three different events of the same beam (or three beams) occurring at three different times to illustrate the change in the incident angle of the expanded beam 124. Vector The angle of is at an acute predetermined angle (eg, 45°) relative to, for example, the front surface 129 of the switching SLM 116. The vector Relative to vector The angles α1 and α2 are represented as α1 and α2, respectively. Angle α2 can be equal and the opposite of angle α1. For example, α2 can be -1° and α1 can be 1°. As another example, the expanded beam 124 can be jittered by ±2.5° or more from a reference angle (e.g., 45°), with a total scanning range less than or equal to 5°. Angles α1 and α2 and the difference between angles α1 and α2 can be referred to as jitter angles, and / or angles that define the change in the projection direction of the expanded beam 124 from the switched SLM 116 to the LCoSSLM 118. Although three vectors are shown, the expanded beam 124 can be jittered in any predetermined and / or selected pattern and between any number of angles.

[0078] The switching SLM 116 can be implemented as an array of fast switching spatial light modulators, each having a response time of less than 1 millisecond (ms). As a first example, the fast switching spatial light modulator array can include a digital light processing (DLP) micro-electromechanical system (MEMS) mirror. One of the device drivers 140 controls the tilt angles of the DLP MEMS mirrors. These angles are based on an input drive voltage provided by one of the device drivers 140 and change the angle of incidence of the light beam provided to the LCoS SLM 118.

[0079] As a second example, the switching SLM 116 can be implemented as one or more piston-mode SLMs, where the height of the mirror of the piston-mode SLM is adjusted by a corresponding input drive voltage. The switching SLM 116 can include an array of piston-mode SLMs, and one of the device drivers 140 of the control module 120 can provide the corresponding input drive voltage. Changing the height of the mirror changes the synthetic incident angle of the light beam provided to the LCoS SLM 118.

[0080] As yet another example, the switchable SLM 116 may be implemented as one or more ferroelectric liquid crystal SLMs that are controlled by one of the device drivers 140. The molecular orientation (effective refractive index) of the ferroelectric liquid crystal SLM is controlled based on an input drive voltage provided by one of the device drivers 140 to change the incident angle of the light beam provided to the LCoS SLM 118.

[0081] The dithered expanded beam 128 is incident on the LCoS SLM 118. The LCoS SLM 118 receives a control signal from a control module 120, which provides a phase hologram of the pattern to be projected. The diffracted phase hologram beam 130 from the LCoS SLM 118 is the product of the tilted wavefront and the phase hologram of the pattern to be projected in the frequency domain. The output of the switched SLM 116 is diffracted by the LCoS SLM 118 and forms an image on the retina of the viewer. In each case, the image formed on the retina is slightly shifted due to the slightly different angles of incidence of the expanded beam 128 on the LCoS SLM 118. The shift in the image occurs at a dithered rate. The dithering rate can be a frequency greater than 60 Hz so that (i) the human eye is unable to detect flicker and (2) the slightly shifted image and corresponding speckle are averaged by the viewer's retina.

[0082] The coded phase hologram beam 130 also has multiple different occurrences at different corresponding reflection angles. An example reflection wave vector is shown For three different occurrences and three different reflection angles. These three different events correspond directly to the dithering performed by the switched SLM 116.

[0083] The control module 120 may include one or more display drivers 140. One or more display drivers 140 may adjust the angular state and / or the reflector height of the switching SLM 116. Another one or more display drivers 140 may be used to control the state of the LCoS SLM 118. The display drivers 140 may be implemented at the control module 120 and / or at the switching SLM 116 and / or the LCoS SLM 118.

[0084] The LCoS SLM 118 may include a limiting aperture 150 to mitigate stray light. The limiting aperture 150 may be implemented as a frame that holds the LCoS SLM 118.

[0085] The coded phase hologram of the LCoS SLM 118 can be represented as P(fx, fy), where fx and fy are coordinates in the frequency domain. The coded phase hologram beam 130 is output from the LCoS SLM 118 at different angles and is received at the eye of the viewer (one eye 160 is shown). The corneal lens (one corneal lens 162 is shown) performs an inverse Fourier transform and converts the coded phase hologram beam 130 (represented as ) is converted into a real image p(x, y) seen via the viewer's retina (one retina 164 is shown).

[0086] The in-phase dithered expanded beam 128 can be represented as where i is an imaginary number (or the square root of -1), is the angle of incidence vector, and is the optical path length of the wave propagating from the switching SLM 116 to the LCoS SLM 118.

[0087] The inverse Fourier transform performed by the eye 160 may be represented by Equation 1:

[0088]

[0089] As an example, Equation 1 may be modified to represent the inverse Fourier transform of each of the three different coded phase hologram beams 130 from the LCoS SLM 118 for three different times t1, t2, t3. Equations 2-4 provide exemplary representations of these beams.

[0090]

[0091] Equation 3-4 provides an equivalent representation of t1, which shows (or the angle of incidence vector Equations 5-6 represent the transition from t2 and t3 to t1, which includes the wave vectors at different times.

[0092]

[0093] Based on the shift theorem of Fourier transform described in Equation 7 and Equation 8, the tilt of the wave vector k in the frequency domain results in a shift in the projected pattern.

[0094] g(x,y)=F -1 {G(fx,fy)} (7)

[0095]

[0096] The above-described tilt provided by the switched SLM 116 tilts the wavefront, which causes a shift p(x,y) in the real image formed on the retina. The retina averages the received images, which reduces and / or eliminates speckle and / or blur and provides a single image without speckle and / or blur regions.

[0097] Figure 2 An exemplary perspective view from a driver's seat of a vehicle 200 is shown. The vehicle 200 includes a windshield 204 located at a front opening of the vehicle 200. Passengers in a passenger cabin 208 of the vehicle 200 can see the front of the vehicle 200 through the windshield 204. Although an example of a land-based vehicle is described, the present application is also applicable to air-based vehicles (e.g., airplanes, helicopters, etc.) and water-based vehicles (e.g., boats, etc.). Moreover, although some examples of vehicle implementations are disclosed herein, these examples are applicable to non-vehicle implementations.

[0098] like Figure 2 As shown, windshield 204 is visually located above dashboard 206 of vehicle 200. Vehicle 200 may include steering wheel 210. Vehicle 200 may be an autonomous vehicle, a semi-autonomous vehicle, or a non-autonomous vehicle.

[0099] HUD system 300 (such as Figure 3 As shown) Figure 2 The hologram 212 is shown projected onto a portion of the windshield 204 through an aperture 216 in the instrument panel 204. The hologram 212 includes various vehicle information, such as the current speed of the vehicle 200, the current gear of the transmission of the vehicle 200, the engine speed, the directional heading of the vehicle 200, the current infotainment system settings, and / or other vehicle information. The hologram 212 presents data to the driver of the vehicle without the driver having to look away from the object in front of the vehicle. As discussed further below, the hologram 212 includes a replica of a hologram provided by the dithering disclosed herein.

[0100] Figure 3 A HUD system 300 is shown, which includes a reflector 302 of a vehicle and Figure 1A direct retinal holographic projection system 100 is provided with a modified version of a control module 120 (identified as control module 120'). In the example shown, the reflector is implemented as a windshield, but it can be a different reflector. The control module 120 can perform the above operations and additional operations, such as determining vehicle information displayed via the reflector (or windshield 302). The direct retinal holographic projection system 100 includes one or more light sources (one laser 112 is shown), a beam expander 114, a switching SLM 116, an LCoS SLM 118, and a control module 120'. The laser 112 generates a laser beam 122, which is received at the beam expander 114. The beam expander 114 expands the width of the laser beam 122 to provide an expanded beam 124.

[0101] The switching SLM 116 receives the expanded light beam 124 and iteratively changes the incident angle of the expanded light beam 124 reflected at the LCoS SLM 118 to provide a dithered expanded light beam 128 including multiple instances of the expanded light beam 124. The control module 120' switches the angular state and / or the mirror height of the switching SLM 116 to change the incident angle of the expanded light beam 124 at a high frequency (e.g., greater than or equal to 60 Hz). The dithered expanded light beam 128 is dithered to provide multiple light beams at corresponding incident angles.

[0102] Example incident vectors showing three different occurrences of the same beam (or three beams) occurring at three different times to illustrate the change in the angle of incidence of the expanded beam 124. The switched SLM 116 may be configured and controlled as described above.

[0103] The LCoS SLM 118 receives the dithered expanded beam 128 and encodes and transforms the dithered expanded beam 128 based on a control signal from the control module 120' to provide a coded phase hologram beam 130. The coded phase hologram beam 130 also has multiple different occurrences (or instances) at different corresponding reflection angles. An exemplary reflection vector is shown. For three different occurrences and three different reflection angles. The three different occurrences directly correspond to the dithering performed by the switched SLM 116.

[0104] The control module 120' may include one or more display drivers 140. One or more display drivers 140 may adjust the angular state and / or the reflector height of the switching SLM 116. Another one or more display drivers 140 may be used to control the state of the LCoS SLM 118. The display driver 140 may be implemented at the control module 120' and / or at the switching SLM 116 and / or the LCoS SLM 118.

[0105] The LCoS SLM 118 may include a limiting aperture 150 to mitigate stray light. The limiting aperture 150 may be implemented as a frame that holds the LCoS SLM 118.

[0106] Figure 4 A direct retinal holographic projection method is shown, which can be Figure 3 The direct retinal holographic projection system 100 and the control module 120' are implemented. Although the following operations are mainly about Figure 3 The above is described in detail with reference to the implementation of the present disclosure, but the operations can be easily modified to be applied to other implementations of the present disclosure. These operations can be performed iteratively.

[0107] The method may begin at 400. At 402, the control module 120' determines a dither angle and a switching (or dithering) frequency for switching between angles. This may include determining an order of switching patterns and / or dither angles, determining a mirror tilt angle, and / or determining the height of one or more piston mode spatial light modulators. The dither angle and / or other corresponding information may be determined based on (i) a predetermined distance between the switching SLM 116 and the LCoS SLM 118, (ii) a predetermined distance between the LCoS SLM 118 and the reflector 302, and / or (iii) a predetermined estimate of the distance between the reflector 302 and the viewer's eyes. Other corresponding information may be directly related to the dither angle and include a tilt angle of the light beam output from the switching SLM 116, a mirror tilt angle, a height of the piston mode spatial light modulator, etc. The dither angle is determined to prevent a viewer from discerning shifted instances of the projected image. When instances of the projected image are discerned, the viewer sees speckle and / or a blurred image.

[0108] Figure 5 A diagram including an exemplary resolved plot 500, an exemplary semi-resolved plot 502, and an exemplary unresolved plot 504 is shown. A Rayleigh criterion value σ is shown and is directly related to the selected shake angle of the switching SLM 116. The Rayleigh criterion value σ is the distance between the peaks of the plotted intensity signal. The intensity signal may refer to different instances of the same image. The larger the shake angle, the larger the Rayleigh criterion value σ, and the higher the resolution of the image appears to the viewer. The smaller the shake angle, the smaller the Rayleigh criterion value σ, and the more difficult it is for the viewer to resolve the image. The control module 120' determines that the shake angle and / or other relevant information is within an appropriate range so that the instance of the image is not resolved. For example, the control module 120' may select the tilt and / or shake angle of the switching SLM 116 to be less than a predetermined angle. As the tilt and / or shake angle increases above the predetermined angle, the instance of the image becomes semi-resolved.

[0109] refer to Figure 4 At 404 , the control module 120 ′ activates the laser 112 to generate a laser beam 122 . The laser beam 122 is directed to the beam expander 114 , which expands the laser beam 122 to provide an expanded laser beam 124 , which is provided to the switched SLM 116 .

[0110] At 406, the control module 120' controls the dithering of the switching SLM 116. Dithering is achieved by rapidly switching the switching SLM 116 to direct the expanded laser beam 124 to slightly different angles of incidence on the SLM 118. This may include generating drive voltages based on the determined dithering angle and the selected switching (or dithering) frequency via one or more device drivers 140 to change the tilt angle of the switching SLM 116, the tilt angle of the mirrors of the switching SLM 116, the height of the (one or more) piston mode spatial light modulators, etc. The dithering and switching (or scanning) angles are set so that the dithering of the spot formed on the retina of the viewer is indistinguishable. The switching SLM 116 can dither light from a collimated light source (such as a laser 112 and a beam expander 114) and cause multiple illumination angles of incidence on the LCoS SLM 118 during the display of each image frame.

[0111] At 408, the control module 120' controls the operation of the LCoS SLM 118 to display a phase hologram of the pattern to be projected. The LCoS SLM 118 with the pattern phase hologram is illuminated with the dithered expanded laser beam 124, and a coded phase hologram beam 130 is generated. The coded phase hologram beam 130 includes instances of the same phase hologram at different angles, such as Figure 3 This may include controlling one or more device drivers 140 to generate drive voltages to control the state of the LCoS SLM 118.

[0112] At 410, an instance of the coded phase hologram can be directed toward the eye of a viewer via reflector 302. The reflected hologram at a slightly different angle of incidence forms a slightly shifted image. The speckle of the image is slightly shifted and averaged by the viewer's retina, so that the viewer sees a reduced amount of speckle or no speckle.

[0113] The phase hologram can be generated based on a signal from a vehicle control module. The control module 120' can be implemented as a vehicle control module, or can communicate with a vehicle control module. The control module 120' generates a phase hologram based on vehicle data. The control module 120' can obtain vehicle data, for example, from a communication bus of the vehicle. For example, the vehicle data may include the current speed of the vehicle, the current gear of the vehicle transmission, the current engine speed, the current direction heading of the vehicle, the current infotainment system settings, and / or other vehicle information. The method can end at 412.

[0114] Figure 6 Shows Figure 1 and Figure 3 6. An example of an LCoS SLM 118 of FIG. 6. The LCoS SLM 118 may be used in any of the embodiments disclosed herein. The LCoS SLM 118 may include a silicon backplane layer 602; an LCoS SLM (or phase modulator) layer including a circuit (or pixelated electrode) layer 604, a first alignment layer 608, a liquid crystal layer 610, a second alignment layer 612, and a transparent electrode layer 614; and a glass substrate layer 616.

[0115] The circuit layer 604 includes control circuits and / or pixel drivers for controlling the liquid crystal layer 610. The circuit layer 604 may include transistors for each pixel. Each pixel independently modulates the phase of the light emitted from the LCoS SLM. For example, if the voltages supplied to the pixels are different, the phases of the light rays emitted from the corresponding parts of the LCoS SLM have different phases. Each pixel may have an associated voltage setting. The voltage range supplied to each pixel may change the phase of the corresponding part of the phase hologram beam 130, for example, between 0-2π, to advance or delay the corresponding part of the light wave from the LCoS SLM 118.

[0116] Circuit layer 604 controls the amount and phase of light emitted from liquid crystal layer 610. The orientation of the molecules in liquid crystal layer 610 and associated with the pixels of LCoS SLM 118 varies with voltage. The voltage-dependent orientation of the molecules induces a spatially varying phase distribution on LCoS SLM 118. Depending on the physical properties of the liquid crystal, the relationship between the amount of phase modulated and the applied voltage can be positive or negative. The LCoS SLM layer will be about Figure 7 Further described. The LCoS SLM 118 may include a reflective film layer when implemented as a reflective holographic projector.

[0117] Figure 7 A portion 700 of the LCoS SLM layer and a control module 120' are shown, which may be Figure 1 and Figure 3is implemented in an embodiment. The LCoS SLM layer may include pixels 704 arranged in an array and connected to drive circuits 706, 708. The LCoS SLM layer may also include: an SLM control module 710, which can control the driver circuits 706 and 708. The driver circuits 706, 708 can receive power from the SLM control module 710 or the control module 120' via switches 707, 709. The SLM control module 710 can receive signals directly from the wavefront sensor and / or receive control signals from the control module 120'. The control module 120' can receive a phase detection signal and control the operation of the SLM control module 710 to adjust the voltage provided to the pixel 704. In another embodiment, the SLM control module 710 directly receives the phase detection signal and controls the drive circuits 706, 708 to generate an appropriate voltage applied at the pixel 704.

[0118] Figure 8 A control module 120', one of the device drivers 140, and the switching SLM 116 are shown. As described above, the switching SLM 116 may include a DLP MEMS mirror array 800, a piston mode spatial light modulator array 802, and / or one or more ferroelectric liquid crystal spatial light modulators 804. The device driver 140 may be implemented as part of the control module 120', or as part of the switching SLM 116.

[0119] The foregoing description is merely illustrative in nature and is by no means intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because after studying the drawings, the specification and the appended claims, other modifications will become apparent. It should be understood that one or more steps in the method can be performed in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described in any embodiment of the present disclosure can be implemented in any other embodiment, and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with each other is still within the scope of the present disclosure.

[0120] Spatial and functional relationships between elements (e.g., relationships between modules, circuit elements, layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "immediately adjacent," "on," "above," "below," and "arranged." Unless explicitly described as "direct," when describing a relationship between a first and a second element in the above disclosure, the relationship may be a direct relationship in which no other intervening elements exist between the first and second elements, but may also be an indirect relationship in which one or more intervening elements (spatially or functionally) exist between the first and second elements. As used herein, the phrase "at least one of A, B, and C" should be interpreted as using a non-exclusive logical "OR" to represent a logical "A or (OR) B (OR) C," and should not be interpreted as "at least one of A, at least one of B, and at least one of C."

[0121] In the various figures, the direction of the arrows (as indicated by the arrows) generally indicates the flow of information (such as data or instructions) of interest to the illustration. For example, when element A and element B exchange various information, but the information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This one-way arrow does not mean that no other information is transmitted from element A to element B. In addition, for information sent from element A to element B, element B may send a request or a receipt confirmation of the information to element A.

[0122] In this application, including the following definitions, the term "module" or the term "controller" may be replaced with the term "circuit". The term "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the functionality; or a combination of some or all of the above, such as in a system on a chip.

Claims

1. A direct retinal holographic projection system, comprising: a first spatial light modulator configured to receive a light beam from a light source and to dither the light beam at a predetermined frequency to provide a plurality of instances of the light beam; a second spatial light modulator configured to receive a plurality of instances of the light beam from the first spatial light modulator, displaying a coded phase hologram of a graphic image to be projected, and to diffract the plurality of instances of the light beam to provide a plurality of instances of the coded phase hologram having the same graphic information as the graphic image but multiplied by a plurality of dithered wavefronts; as well as A control module configured to iteratively adjusting parameters of the first spatial light modulator to generate multiple instances of the light beam, and controlling operation of the second spatial light modulator to display multiple instances of the graphic image on a retina of a viewer's eye by directing the multiple instances of the coded phase hologram of the graphic image toward a reflector or toward the viewer's eye based on the multiple instances of the light beam, The control module is configured to dither the light beam between a first angle and a second angle at a predetermined frequency, The difference between the first angle and the second angle is less than or equal to 5°. The direct retinal holographic projection system further comprises a device driver, wherein: The control module is configured to control the device driver to generate one or more driving voltages; and The first spatial light modulator changes a dithering angle based on the driving voltage.

2. The direct retinal holographic projection system according to claim 1, wherein: The second spatial light modulator directs multiple instances of the coded phase hologram directly to the eyes of a viewer without forming a real image on a diffuser and without reflecting the image with a mirror.

3. The direct retinal holographic projection system according to claim 1, wherein: the second spatial light modulator directs the plurality of instances of the coded phase hologram directly to the reflector to be seen by an eye of a viewer without forming a real image on a diffuser; as well as The reflector is the windshield of the vehicle.

4. The direct retinal holographic projection system according to claim 1, wherein: The control module is configured to dither the light beam via the first spatial light modulator at a frequency greater than or equal to 60 Hz.

5. The direct retinal holographic projection system according to claim 1, wherein: A difference between the first angle and the second angle is less than or equal to 1°.

6. The direct retinal holographic projection system according to claim 1, wherein: The first spatial light modulator comprises a digital light processing micro-electromechanical system reflector.

7. The direct retinal holographic projection system according to claim 1, wherein: The first spatial light modulator comprises a piston mode spatial light modulator.

8. The direct retinal holographic projection system according to claim 1, wherein: The first spatial light modulator comprises a ferroelectric liquid crystal spatial light modulator.

9. A method of operating a direct retinal holographic projection system according to any one of claims 1 to 8, the method comprising: receiving a light beam from a light source at a first spatial light modulator; dithering the light beam at a predetermined frequency to provide a plurality of instances of the light beam, wherein the dithering comprises iteratively adjusting a parameter of the first spatial light modulator to generate the plurality of instances of the light beam; receiving a plurality of instances of the light beam at a second spatial light modulator; converting the plurality of instances of the light beam into a plurality of instances of a coded phase hologram; and The operation of the second spatial light modulator is controlled to display multiple instances of an image on a retina of a viewer's eye based on the multiple instances of the light beam by directing the multiple instances of the coded phase hologram toward a reflector or the viewer's eye.

10. The method according to claim 9, further comprising: Multiple instances of the coded phase hologram are directed directly from the second spatial light modulator to a reflector or a viewer's eye.

11. The method according to claim 9, wherein: The light beam is dithered at a frequency greater than or equal to 60 Hz via the first spatial light modulator.

12. The method according to claim 9, wherein: A difference between the first angle and the second angle is less than or equal to 1°.

13. The method according to claim 9, wherein: The dithering of the light beam includes changing the driving voltage of the digital light processing micro-electromechanical system reflector of the first spatial light modulator.

14. The method according to claim 9, wherein: The first spatial light modulator comprises a piston mode spatial light modulator, and the dithering of the light beam comprises: changing a driving voltage of the piston mode spatial light modulator.

15. The method according to claim 9, wherein: The first spatial light modulator includes a ferroelectric liquid crystal spatial light modulator, and the dithering of the light beam includes: changing a driving voltage of the ferroelectric liquid crystal spatial light modulator.

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