Apparatus for projecting an image to a user - Patent application

Abstract

To provide a device that enables achieving a fuller color gamut.SOLUTION: A device of the present invention comprises an exit pupil expander, and the exit pupil expander includes: display means that is provided with an outcoupling element configured so as to outcouple light in a forward direction toward users, or in a backward direction away from the user; and a dynamically controllable reflector that is configured to provide selective reflection with respect to the light outcoupled from the exit pupil expander, in which selectivity of the reflection of the light is dynamically controllable, and in which the selective reflection of the light is in a direction back to the user.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to devices such as light guide displays that can be used to project images towards a user. [Background technology]

[0002] Light guide displays can be used to project images to a user. They are attractive because they can have a large exit pupil and therefore do not require precise positioning of the viewing user. However, light guide displays such as exit pupil expanders are often optimized for use with a narrow wavelength band.

[0003] Multiple light guides, each with a relatively narrow color gamut, can be used together to provide a more complete color gamut, however this increases cost.

[0004] Exit pupil expanders use diffraction to project light that forms an image towards the user, which in at least some cases projects visible light forward towards the user, but also backwards away from the user.

[0005] In some implementations, the rear-projected light is recycled back in direction by reflection off a reflective surface, in some implementations, only the rear-projected light is reflected back towards the user, while the amount of original forward-projected light is minimized or directed away from the user.

[0006] In some implementations, refractive and / or reflective optics can be used to control the projection of light.

[0007] The path of visible light from the projector through the light-guiding display system to the user has multiple stages. Different stages and different paths can result in uniformity problems where certain light along certain paths is attenuated more effectively than other light. Summary of the Invention

[0008] According to various, but not necessarily all, examples, an apparatus is provided, the apparatus comprising an exit pupil expander, the exit pupil expander comprising a display means comprising an outcoupling element configured to outcouple light in a forward direction towards a user and in a rearward direction away from the user, and a dynamically controllable reflector configured to provide selective reflection of light outcoupled from the exit pupil expander, the selectivity of the reflection of light being dynamically controllable, the selective reflection of light being in a direction back towards the user.

[0009] In some, but not necessarily all, examples, the dynamically controllable reflector is configured to adjust the ratio of intensities of different colors present in the light entering the dynamically controllable reflector from the exit pupil expander to provide selectively reflected light towards a user.

[0010] In some, but not necessarily all, examples, the device is configured to adjust the color temperature or white point of the light provided to a user by a dynamically controllable reflector.

[0011] In some, but not necessarily all, examples, the selectivity of the dynamically controllable reflector depends on the output from one or more sensors of ambient illumination.

[0012] In some, but not necessarily all, examples, the dynamically controllable reflector is a color-controllable reflector configured to differentially reflect light of different colors outcoupled in reverse directions from the exit pupil expander towards the user, the color-controllable reflector configured to reflect more light of a first color than light of a second color.

[0013] In some, but not necessarily all, examples, the dynamically controllable reflector comprises a reflective surface and a color filter.

[0014] In some, but not necessarily all, examples, the color filters are tunable wavelength-selective color filters.

[0015] In some, but not necessarily all, examples, the color filters are configured to sequentially adjust the duty cycle for each color.

[0016] In some, but not necessarily all, examples, the color filters are configured to be spatially non-uniform.

[0017] In some, but not necessarily all, examples, the exit pupil expander includes an in-coupler diffractive element, an expander element, and an out-coupler diffractive element, and the dynamically controllable reflector is disposed adjacent to the out-coupler diffractive element.

[0018] In some, but not necessarily all, examples, the device is configured as an Exit Pupil Expander (EPE) head-up display, and optionally as a vehicular head-up display.

[0019] According to various, but not necessarily all, examples, a computer program is provided that includes computer program instructions that, when loaded into at least one processor, dynamically control selectivity of reflection by a reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting the light towards a user.

[0020] In some, but not necessarily all, examples, the computer program is configured to adjust the ratio of intensities of different colors present in the light entering the dynamically controllable reflector from the exit pupil expander to provide selectively reflected light towards a user.

[0021] According to various, but not necessarily all, examples, a method is provided that dynamically controls selectivity of reflection by a reflector to selectively reflect light outcoupled from an exit pupil expander, the reflection reflecting the light towards a user.

[0022] In some, but not necessarily all, examples, the method includes adjusting a ratio of intensities of different colors present in light incident on a dynamically controllable reflector from an exit pupil expander to provide selectively reflected light towards a user.

[0023] Various, but not necessarily all, examples are provided which are claimed in the appended claims.

[0024] Color accuracy and balance can be optimized for the best user experience.

[0025] The following portions of this "Summary of the Invention" section describe various features that may be features of any of the examples described in the preceding portions of the "Summary of the Invention" section. A description of a function should also be considered to disclose any means suitable for performing that function.

[0026] Although the above examples and optional features of the present disclosure are described separately, it is to be understood that the provision of them in all possible combinations and permutations is included within the present disclosure. It is to be understood that various examples of the present disclosure can include any or all of the features described with respect to other examples of the present disclosure, and vice versa. It is also to be understood that any one or more or all of the features can be implemented by, can be executable ...

[0027] Some examples will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] 1 shows an example of the subject matter described herein. [Diagram 2] 1 illustrates another example of the subject matter described herein. [Figure 3A] 1 illustrates another example of the subject matter described herein. [Figure 3B] 1 illustrates another example of the subject matter described herein. [Figure 4] 1 illustrates another example of the subject matter described herein. [Diagram 5] 1 illustrates another example of the subject matter described herein. [Figure 6] 1 illustrates another example of the subject matter described herein. [Figure 7] 1 illustrates another example of the subject matter described herein. [Figure 8] 1 illustrates another example of the subject matter described herein. [Figure 9] 1 illustrates another example of the subject matter described herein. [Figure 10] 1 illustrates another example of the subject matter described herein. [Figure 11] 1 illustrates another example of the subject matter described herein. [Figure 12] 1 illustrates another example of the subject matter described herein. [Figure 13] 1 illustrates another example of the subject matter described herein.

[0029] The drawings are not necessarily to scale. Certain features and views of the drawings may be shown diagrammatically or exaggerated in scale for clarity and conciseness. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to aid in clarity. Like reference numbers are used in the drawings to denote like features. For clarity, not all reference numbers are necessarily shown in every figure.

[0030] In the following description, a class (or set) may be referred to using a reference number without a subscript index (e.g., 10), a specific instance of a class (a member of a set) may be referred to using a reference number with a numeric type subscript index (e.g., 10_1), and a non-specific instance of a class (a member of a set) is referred to using a reference number with a variable type subscript index (e.g., 10_i). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The following figure shows an example of an apparatus 10 for projecting visible light 14 forming an image towards a user 50.

[0032] With reference to FIGS. 1 and 2, the device 10 comprises a display means 62 and a dynamically controllable reflector 72 .

[0033] The display means 62 comprises an exit pupil expander 92 comprising an outcoupling element 96C configured to outcouple the visible light 14 in a forward direction 12_F towards the user 50 and also in a rearward direction 12_B away from the user 50.

[0034] The dynamically controllable reflector 72 is configured to provide selective reflection to the visible light 14 outcoupled from the exit pupil expander 92 .

[0035] Visible light is reflected from a rear 12_B away from the user to a front 12_F towards the user 50.

[0036] The selectivity of the visible light reflection is dynamically controllable, meaning that it is controllable during use, but is not fixed at the time of manufacture.

[0037] Thus, the device 10 allows for selective recycling of the visible light 14. The recycled visible light 14 is indicated using dashed lines in Figures 1 and 2.

[0038] In these examples, PGU 80 acts as a projector and projects an image using light 14 into light guide 90. The image is viewed by user 50 (FIG. 2, not shown in FIG. 1).

[0039] The dynamically controllable reflector 72 is configured to condition the light 14 entering the dynamically controllable reflector 72 from the exit pupil expander 92 to provide selectively reflected light 14 towards the user 50.

[0040] For example, in at least some examples, the dynamically controllable reflector 72 is a color-controllable reflector configured to differentially reflect light of different colors coupled from the exit pupil expander 92 to the rear end 12_B toward the user 50. The color-controllable reflector may be configured, for example, to reflect more light of a first color than light of a second color.

[0041] For example, in at least some instances, the dynamically controllable reflector 72 is configured to adjust the ratio of intensities of different colors present in the light 14 incident on the dynamically controllable reflector 72. The white point (color temperature) of the reflected light 14 may be controlled to have a different white point (color temperature) than the incident light 14.

[0042] For example, in at least some examples, the dynamically controllable reflector 72 is configured to be selective for each primary color (red, green, blue). For example, in at least some examples, the dynamically controllable reflector 72 is configured to independently attenuate incident red light to generate reflected red light, and / or to independently attenuate incident green light to generate reflected green light, and / or to independently attenuate incident blue light to generate reflected blue light.

[0043] 1 and 2, in at least some examples, the dynamically controllable reflector 72 comprises a reflective surface 76 and a color filter 78. In at least some examples, the color filter 78 is a tunable wavelength-selective color filter 78.

[0044] Examples of tunable wavelength-selective color filters 78 include, but are not limited to, electrically tunable filters, birefringent tunable filters, liquid crystal tunable filters, and electro-optical tunable filters.

[0045] Electronically tunable filters (TF) are optical filters that are electronically controlled to transmit selectable wavelengths of light and reject others (not necessarily all others). They can be made, for example, by using dynamically controlled optical elements, such as liquid crystals or electro-optical cells, or by mechanically adjusting static optical elements, such as rotating wave (phase) plates.

[0046] Birefringent tunable filters (BTFs) are electronically tunable filters that use electronically controlled birefringent elements to transmit selectable wavelengths of light and reject others (not necessarily all others). These can be made, for example, by using dynamically controlled variable birefringence optical elements, such as liquid crystals or electro-optic cells.

[0047] A liquid crystal tunable filter (LCTF) is a birefringent electronically tunable filter that uses electronically controlled liquid crystal (LC) elements to transmit selectable wavelengths of light and reject others (not necessarily all others). In some, but not necessarily all, instances, a liquid crystal tunable filter (LCTF) is a birefringent tunable filter (BTF).

[0048] An example of how birefringence can be used to create an electronically tunable filter is described below.

[0049] Orthogonal linearly polarized components of light have different refractive indices and different phase velocities when passing through a waveplate (birefringent plate). Thus, the polarization state of the light can be modified, which can be converted into attenuation in the subsequent polarizer. For a particular wavelength, the optical path length difference for the different polarizations is an integer multiple of the wavelength, and the attenuation is small. Thus, the filter selectively attenuates certain frequencies.

[0050] The undampened frequencies can be controlled electronically by changing the phase relationship between the waveplates, which can be accomplished by physically rotating one waveplate relative to another, or by varying the birefringent properties of the waveplates.

[0051] Electrically adjustable birefringent elements can be used as waveplates to control birefringence. Examples include nematic liquid crystals or electro-optical cells. Some or all of the waveplates can be electrically adjustable birefringent elements. Some or all of the waveplates can be fixed birefringent elements, such as λ / 4 waveplates.

[0052] If a single waveplate is used, it determines the bandwidth and free spectral range. If waveplates are used in series, the first (thickest) waveplate determines the bandwidth and the last (thinnest) waveplate determines the free spectral range (the frequency gap between two successive light intensity maxima).

[0053] Electro-optic tunable filters (EOTFs) use the electro-optic effect, which is a change in the optical properties of a material in response to an applied electric field (which varies slowly compared to the frequency of light). The effect can be, for example, a change in absorption and / or a change in refractive index / transmittance / birefringence. The electro-optic effect can be achieved using non-crystalline solid electro-optic materials, such as, for example, organic / plastic / polymeric electro-optic materials. At least some examples include non-linear optical chromophores in polymer lattices.

[0054] Figure 2 shows a side view of an example of the device 10. Figure 10 shows a perspective view of the device 10.

[0055] In this example, but not necessarily in all examples, the device 10 comprises, in a stacked configuration, a display means 62 and a dynamically controllable reflector 72. The display means 62 is positioned on the side closer to the user 50.

[0056] Light 14 emitted from the display means 62 travels through the light guide 90 of the light guide display 62 and is directed forward 12_F towards the user 50 and backward 12_B away from the user 50. The backward directed light 14 is selectively reflected by the controllable reflector 72 into recycled light 14 that is now directed forward 12_F.

[0057] Forward 12_F is the direction of the forward light path to the user. Rear 12_B is the direction of the rear light path to the controllable reflector 72 where it is reflected and recycled onto the forward light path to the user. The terms forward and rear should be interpreted accordingly. The forward light 14 (solid lines in FIG. 2) and the recycled light 14 (dashed lines in FIG. 2) reflect off a light director such as a windshield 82 (optional) and are directed towards the eyes 54_1, 54_2 of the user 50.

[0058] In some examples, the reflective surface 76 is not parallel to the light guide 90, and only the recycled light 14 is directed towards the eyes 54_1, 54_2 of the user 50. The forward light 14 reflects off the light guide in another direction and is not directed towards the eyes 54_1, 54_2 of the user 50.

[0059] The distorting effects of a curved windshield can be compensated for by fitting a light grating, or by fitting it onto the light guide, or by using a separate optical component stacked with the light guide, or by using a curved reflective surface 76, or a combination of the above.

[0060] In at least some examples, the display means 62 is configured to sequentially display different colors, for example red (R), green (G), and blue (B), depending on the display duty.

[0061] 3 illustrates an example of a display duty cycle 101 of visible light 14. Visible light 14 is projected forward 12_F towards a user 50. Visible light 14 projected backward 12_B from the user 50 towards a selective reflector 72 can be assumed to have a similar duty cycle.

[0062] The light 14 is frequency or time multiplexed into separate time division periods. These are sequential displays of different colors: red (R), green (G), and blue (B). The display means 62 can, for example, include a number of different light emitting diodes (LEDs) for each color.

[0063] Display duty cycle 101 shows a constant intensity duty cycle, which allows the LED to be operated at a constant voltage. The duration of activation is used to affect the perceived color intensity.

[0064] The data cycle 103 is synchronized with the display duty cycle 101. The data cycle controls which pixels are activated and which pixels are not activated, and for how long.

[0065] Figure 3A shows an example of a display duty cycle 105 of visible light 14 projected forward 12_F towards a user 50. Visible light 14 projected backward 12_B away from the user 50 towards the selective reflector 72 can be assumed to have a similar duty cycle 113 (Figure 4).

[0066] In some examples, the visible light 14 can also include infrared light, which is invisible to the human eye but visible to common types of imaging / light sensors. A sequential display of different colors can include, for example, red (R), green (G), blue (B), and infrared (IR).

[0067] Figure 4 shows the effect of non-selective reflection. Figure 4 shows the duty cycle 113 of the light 14 after it has been reflected. This duty cycle 113 is combined with the duty cycle 105 of the light projected towards the user 50. The duty cycle 115 is the composite duty cycle as perceived by the user 50. The combined duty cycle 115 combines (adds) the duty cycle 105 of the light 14 projected forward 12_F towards the user 50 and the duty cycle 113 of the light selectively reflected towards the user 50. In this example, there is no selective attenuation 111.

[0068] Figures 5 and 6 show different examples of selective reflection, each of which shows the effect of selective attenuation 111 provided by a filter 78 on the reflected light 14. The selective attenuation can be controlled to different attenuation levels for the different colors R, G, B.

[0069] The diagram shows the duty cycle 113 of the light 14 after it has been selectively reflected, which is combined with the duty cycle 105 of the light projected towards the user 50. The effect of the selective attenuation 111 can be seen by comparing the duty cycle 105 of the light 14 projected forward 12_F towards the user 50 and the duty cycle 113 of the light selectively reflected towards the user 50.

[0070] Duty cycle 115 is a composite duty cycle that combines (adds) the duty cycle 105 of the light 14 projected forward 12_F towards the user 50 and the duty cycle 113 of the light selectively reflected towards the user 50.

[0071] At high refresh rates, the user 50 does not notice individual peaks, but rather notices an average brightness level, which is not shown.

[0072] In this example, the color space and white point can be adjusted by adjusting the light recycling selectivity.

[0073] Filter 78 has various states of duty cycle adjustment; (i) Passing a controlled proportion of certain wavelengths of incident light over a period of time (see Figure 5); (ii) passing specific wavelengths of incident light for a controlled period of time (see Figure 6); (ii) Performing (i) and (ii) includes passing a controlled percentage of particular wavelengths of incident light for a controlled period of time.

[0074] 5, the reflected light 113 has the same duration as the equivalent non-reflected light 105. The filter 78 partially attenuates the reflected light 113 in the same manner over that duration.

[0075] 6, the reflected light 113 has a duration that is different from the duration of the equivalent unreflected light 105. The filter 78 completely attenuates the reflected light 113 for only a portion of the duration of the unreflected light.

[0076] In some examples, the reflected light 113 has a controlled profile over a controlled duration. The filter 78 variably attenuates the reflected light 113 for the duration of the equivalent non-reflected light.

[0077] In at least some examples, the filter 78 is a tunable color filter. In this embodiment, the filter 78 characteristics can be adjusted based on the characteristics of the EPE, the ambient lighting conditions, and / or situational awareness. This can be achieved using a calibration to compensate for possible non-uniformity of the EPE, for example, each EPE is characterized (optical properties are measured) as part of the manufacturing process, and the relevant data is used as a baseline for the calibration of the tunable filter 78. The ambient lighting conditions can be measured using an ambient lighting sensor or a camera, and the filter transmittance per wavelength can be adjusted according to the results. In situations where some important information is presented to the user 50 or there is a risk that the user 50 will not pay much attention to important information displayed on the HUD, select wavelengths can be emphasized by adjusting the filter transmittance. This feature can be based on the user 50 monitoring and sensing the vehicle's external environment.

[0078] The control can be sequential, as presented in all provided examples, and / or spatial, with different regions of the filter 78 controlling the light passage in different ways. Thus, the filter 78 can be configured to sequentially adjust the duty cycle for each color. Additionally or alternatively, the filter 78 can be configured to adjust for spatial non-uniformity.

[0079] In at least some examples, PGU 80 is a projector with continuous RGB color channels and is synchronized with adjustable filter 78 so that the combined effect can be used for white point adjustment.

[0080] The PGU illumination duty cycle 101 uses sequential color fields with controllable variable length color fields. The field / frame rate can be set very high so that no motion or color artifacts are observed.

[0081] The PGU Data Cycle 103 controls what data for each of the color fields is rendered separately on the display. The Sync signal is used to keep the display data aligned with the illumination source duty cycle 101.

[0082] In some, but not necessarily all, examples, the device 10 includes one or more sensors 30, such as those shown in FIGS. 1 and 2, for example.

[0083] For example, the device 10 may be equipped with one or more sensors for detecting ambient lighting levels and ambient color temperature, and the selectivity of the dynamically controllable reflector 72 may then depend on (based on) the output from the one or more sensors 30 of ambient lighting.

[0084] For example, the characteristics of filter 78 may be adjusted in response to output from one or more sensors 30 of ambient illumination. The color temperature of the environment may change, and device 10 may control dynamically controllable reflector 72 to prevent eye strain in changing conditions, for example, by adjusting the white point of the displayed image. Changes in color temperature may occur, for example, gradually during the day, or suddenly, for example, when entering a tunnel where artificial lighting may have a different spectrum than sunlight.

[0085] 7 shows an example of a light guide display comprising a light guide 90. The light guide 90 in this example, but not necessarily in all examples, comprises incoupling diffraction means 93 for receiving input light defining image 20_3, and outcoupling diffraction means 94 configured to outcouple light defining image 10_3.

[0086] In some embodiments, diffractive element 96A is used to provide in-coupling diffractive means 93 and diffractive element 96C is used to provide out-coupling diffractive means 94 .

[0087] The light guide 90 may be configured as an exit pupil expander 92 that increases the number of acceptable viewing positions for the user 50 .

[0088] An example of a two-dimensional exit pupil expander is shown in Figure 8 (and Figure 9). Figure 8 is a perspective view. Figure 9 includes three separate views: (i) a top plan view, (ii) a first side view defining a first dimension, and (iii) a second side view defining a second dimension.

[0089] The exit pupil expander 92 comprises an in-coupling diffraction means 93 configured to in-couple one or more input light beams into the light guide 90, an expanding means 96B configured to expand the one or more input light beams, and an out-coupling diffraction means 94 configured to out-couple the one or more expanded light beams from the light guide 90. A diffractive element 96A provides the in-coupling diffraction means 93, and a diffractive element 96C provides the out-coupling diffraction means 94. The expanding means 96B may be a diffractive element, at least in some examples.

[0090] Examples of diffractive elements include, but are not limited to, diffraction gratings and other periodic structures.

[0091] The pupil is a virtual aperture. The input pupil is dilated (multiplied, multiplied) to form a larger exit pupil. In the example shown, the exit pupil is expanded to two different dimensions.

[0092] Typically, 2D exit pupil expanders use diffractive optics. However, 1D exit pupil expanders can use refractive optics with angled mirror surfaces (or prisms) inside the light guide 90. 2D expansion with refractive optics is possible, but more difficult.

[0093] The light guide 90 may include a stack of multiple light guides, or overlapping light guides 90, or adjacent light guides 90. The term "light guide" should be interpreted accordingly. In some examples, the light guide 90 is a single light guide configured to operate at a narrow band of wavelengths.

[0094] The glare or stray light in the examples may be caused by reflections on different surfaces, unwanted diffraction (e.g., higher orders) on a diffraction grating, or some other equivalent cause. Measures to reduce such effects may be used. Examples include, but are not limited to, anti-reflective coatings on different surfaces, and special diffraction grating solutions.

[0095] Apparatus 10 may include additional optical elements not described, such as, for example, a Fresnel lens for distorting the image from light guide 90, additional lenses for compensating for distortion resulting from reflections at windshield combiner 10, etc.

[0096] In the above example, an Exit Pupil Expander (EPE) Head Up Display (HUD) can be constructed from a standard EPE solution based on a PGU projector 80 and a diffractive light guide 90 with in-coupler 96A, expander 96B, and out-coupler 96C gratings. Other types of EPE layouts are possible as well.

[0097] The displayed virtual image 20_3 (see FIG. 10) can be focused at infinity (using a flat light guide 90), or at a finite distance (e.g., using a spherical light guide 90 or a flat light guide 90 with additional lenses), or can have multiple focal planes (e.g., using a stack of spherical light guides 90).

[0098] Only one EPE plate 90 is shown in all embodiments and may be sufficient to achieve full color, off-center exit pupil / eyebox size, and eye relief / viewing distance from an EPE HUD system. Nevertheless, the device 10 may also use multiple EPE elements to multiplex color, focal length, FOV, exit pupil, or some other feature.

[0099] Adjustments to the exit pupil position may be required to compensate for the size or position of the user. The adjustments may be of a mechanical type (e.g., tilt) or some other type, automatic or manual, and may be synchronized with the vehicle's seat, HUD, steering wheel, or any other adjustments available in the vehicle.

[0100] The device 10 described above can be used as a head mounted display (HMD) or a head up display (HUD). The device can be an exit pupil expander (EPE) head up display, optionally a vehicular head up display. The white point of the EPE HUD can be adjusted and the HUD can be calibrated for color accuracy.

[0101] The apparatus 10 described above may be included in a module, a device, a vehicle or in the cab of a vehicle.

[0102] The above-mentioned solution can be used in augmented reality (AR) headsets as well as avionics and automotive head-up display (HUD) systems. Automotive EPE HUDs require large light guides, perhaps 400 mm wide or wider. Manufacturing such large light guides is costly, and it is highly desirable to include only one light guide to generate the full RGB color gamut, instead of two or more light guides in a typical stacked EPE structure. However, the problem with having only one light guide is related to design optimization. It becomes very difficult to achieve high efficiency and uniformity for a wide wavelength band. Typically, grating optimization can only be done for certain wavelengths, not for the full RGB spectrum. The described solution allows the use of fewer light guides (e.g., only one EPE) to generate the full color gamut.

[0103] FIG. 11 illustrates an example of a method 500 for projecting image-forming light 14 towards a user 50.

[0104] The method includes, at block 504, dynamically controlling a selectivity of reflection by the reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting the light towards a user.

[0105] In some, but not necessarily all, examples, this may depend on the detection of ambient lighting in block 502.

[0106] As shown in FIG. 12, the controller 400 may be implemented using instructions enabling hardware functionality, for example, by using executable instructions of a computer program 406 in a general-purpose or special-purpose processor 402, which may be stored on a computer-readable storage medium (disk, memory, etc.) for execution by such processor 402.

[0107] 12 illustrates an example of a controller 400 suitable for use in the device 10. The implementation of the controller 400 may be as a controller circuit. The controller 400 may be implemented solely in hardware, may have certain aspects in software including solely in firmware, or may be a combination of hardware and software (including firmware).

[0108] The processor 402 is configured to read from and write to the memory 404. The processor 402 may also include an output interface through which data and / or commands are output by the processor 402, and an input interface through which data and / or commands are input to the processor 402.

[0109] The memory 404 stores a computer program 406 that includes computer program instructions (computer program code) that, when loaded into the processor 402, control the operation of the apparatus 10. The computer program instructions of the computer program 406 provide logic and routines that enable the apparatus to perform the methods illustrated in the accompanying drawings. The processor 402 can load and execute the computer program 406 by reading the memory 404.

[0110] The apparatus 10 includes at least one processor 402, at least one memory 404 including computer program code, and computer program code configured to, using the at least one memory 404 and the at least one processor 402, cause the apparatus 10 to at least perform the following: dynamically control selectivity of reflection by a reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting the light towards a user.

[0111] The apparatus 10 includes at least one processor 402 and at least one memory 404 containing computer program code, the at least one memory storing instructions which, when executed by the at least one processor 402, dynamically control the selectivity of reflection by the reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting the light towards a user.

[0112] As shown in Fig. 13, the computer program 406 can arrive at the device 10 via any suitable delivery mechanism 408. The delivery mechanism 408 can be, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a recording medium such as a compact disc read-only memory (CD-ROM) or a digital versatile disc (DVD), or a solid-state memory, an article of manufacture that includes or tangibly embodies the computer program 406. The delivery mechanism can also be a signal configured to reliably transfer the computer program 406. The device 10 can propagate or transmit the computer program 406 as a computer data signal.

[0113] Computer program instructions for causing the apparatus to at least perform, or computer program instructions for causing at least the following to perform, dynamically control the selectivity of reflection by the reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting light towards a user.

[0114] The computer program instructions may be included in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium, etc. In some, but not necessarily all, examples, the computer program instructions may be distributed across multiple computer programs.

[0115] Although memory 404 is shown as a single component / circuit, it may be implemented as one or more separate components / circuits, some or all of which may be integrated / removable and / or provide permanent / semi-permanent / dynamic / cached storage.

[0116] Although the processor 402 is shown as a single component / circuit, it may be implemented as one or more separate components / circuits, some or all of which may be integrated / removable. The processor 402 may be a single-core or multi-core processor.

[0117] References to a "computer-readable storage medium," "computer program product," "tangibly embodied computer program," etc., or to a "controller," "computer," "processor," etc., should be understood to encompass computers having different architectures, such as single / multi-processor architectures and sequential (Von Neumann) / parallel architectures, as well as special purpose circuitry, such as field programmable gate arrays (FPGAs), application specific circuits (ASICs), signal processing devices, and other processing circuitry. References to computer programs, instructions, code, etc., should be understood to encompass software or firmware for a programmable processor, such as the programmable contents of a hardware device, whether for example, instructions for a processor, or configuration settings for a fixed function device, gate array, or programmable logic device, etc.

[0118] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) Hardware-only circuit implementation (e.g., implementation in analog and / or digital circuits only) (b) A combination of hardware circuitry and software, where applicable. (i) Any combination of analog and / or digital hardware circuitry and software / firmware. (ii) Any portion of software (including digital signal processors), software, and hardware processors with memory, which operate together to cause a device, such as a mobile phone or server, to perform various functions. (c) Hardware circuitry and / or processors, such as a microprocessor or portions of a microprocessor, that require software (e.g., firmware) for operation, but the software may not be present when not needed for operation.

[0119] This definition of circuitry applies to all uses of the term in this application, including any claims. As a further example, the term circuitry, as used in this application, also encompasses merely hardware circuits or processors and their (or their) accompanying software and / or firmware implementations. The term circuitry also encompasses, for example, baseband integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices, if applicable to certain claim elements.

[0120] The blocks illustrated in the accompanying figures may represent steps in a method and / or sections of code in the computer program 406. The illustration of a particular order to the blocks does not necessarily imply a required or preferred order to the blocks, and the order and arrangement of the blocks may be modified. Additionally, some blocks may be omitted.

[0121] Where a structural feature is described, it may be replaced by a means for performing one or more of the functions of the structural feature, whether that function or those functions are explicitly or implicitly described.

[0122] As used herein, "module" refers to a unit or device that excludes certain parts / components to be added by the end manufacturer or user. The device 10 may be a module or a system.

[0123] The above examples find use as enabling components in automotive systems; communication systems; electronic systems, including consumer electronic products; distributed computing systems; media systems for generating or rendering media content, including audio content, visual content, and audiovisual content, as well as mixed reality, mediated reality, virtual reality, and / or augmented reality, and personal systems, including personal health systems or personal fitness systems; navigation systems; user interfaces, also known as human-machine interfaces; networks, including cellular, non-cellular, and optical networks; ad-hoc networks; the Internet; the Internet of Things; virtual networks; and related software and services.

[0124] The apparatus may be provided in an electronic device, such as a mobile terminal, according to examples of the present disclosure. However, it should be understood that the mobile terminal is merely an example of an electronic device that would benefit from examples of implementations of the present disclosure, and thus should not be construed as limiting the scope of the present disclosure thereto. In some implementations, the apparatus may be provided in a mobile terminal, as well as other types of electronic devices, including but not limited to mobile communication devices, hand-portable electronic devices, wearable computing devices, personal digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices, and other types of electronic systems, that can readily use examples of the present disclosure. Furthermore, the device may readily use examples of the present disclosure, regardless of whether it is intended to provide mobility.

[0125] The term "comprise" is used herein in an inclusive rather than exclusive sense, i.e. any reference to X containing Y indicates that X may contain only one Y or may contain multiple Y. If it is intended to use "comprise" in the exclusive sense, this will be made clear in the context by reference to "comprising only one..." or by using "consisting".

[0126] In this description, the terms "connects," "couple," and "communication," along with their derivatives, mean to be operatively connected / coupled / communicating. It is to be understood that any number or combination of intervening components (including no intervening components) may be present, i.e., providing direct or indirect connections / couplings / communications. Any such intervening components may include hardware and / or software components.

[0127] As used herein, the term "determine / determining" (and grammatical variations thereof) can include, among others, calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (e.g., searching a table, database or another data structure), ascertaining, and the like. Also, "determining" can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), obtaining, and the like. Also, "determining / determining" can include resolving, selecting, choosing, establishing, and the like.

[0128] In this description, various examples are referenced. The description of features or functions with respect to an example indicates that those features or functions are present in that example. Use of the terms "example" or "for example" or "can" or "may" in the text, whether or not explicitly stated, indicates that such features or functions are present in at least the example described, whether or not described as an example, and that they may, but not necessarily, be present in some or all other examples. Thus, "example," "for example," "can" or "may" refers to a particular instance in a class of examples. A property of an instance may be a property of only that instance, or a property of the class, or a property of a subclass of the class that includes some but not all of the instances in the class. Thus, a feature described with respect to one example but not with respect to another example is implicitly disclosed to be usable as part of a working combination in other examples, where possible, but not necessarily in the other examples.

[0129] Although embodiments have been described in the preceding paragraphs with reference to various embodiments, it should be understood that modifications can be made to the given embodiments without departing from the scope of the claims.

[0130] Features set forth in the foregoing description may be used in combinations other than those explicitly set forth above.

[0131] Although functions are described with reference to particular features, these functions may be performed by other features, whether or not described.

[0132] Although features have been described with reference to particular examples, these features may be present in other examples, whether or not described.

[0133] The terms "a", "an" or "The" are used herein in an inclusive rather than exclusive sense. That is, any reference to X containing a / an / Y indicates that X may contain only one Y or may contain more than one Y, unless the context clearly indicates the contrary. If it is intended to use "a", "an" or "the" in an exclusive sense, it will be clear in the context. In some situations, the use of "at least one" or "one or more" may be used to emphasize an inclusive sense, but the absence of these terms should not be construed to infer any exclusive sense.

[0134] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) per se, and to features that achieve substantially the same technical effect (equivalent features). Equivalent features include, for example, features that are modifications and achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0135] In this description, reference is made to various examples that use adjectives or adjective phrases to describe features of the examples. Such description of a property with respect to the examples indicates that the property is present in some examples exactly as described and in other examples substantially as described.

[0136] While the above description describes several examples of the present disclosure, those skilled in the art will know of possible alternative structures and method features that provide equivalent functionality to the specific examples of such structures and features described herein above, and that have been omitted from the above description for brevity and clarity. Nonetheless, the above description should be read as implicitly including references to such alternative structures and method features that provide equivalent functionality, unless such alternative structures or method features are expressly excluded in the above description of examples of the present disclosure.

[0137] While the foregoing specification has attempted to draw attention to those features which are believed to be important, it should be understood that applicants may seek protection through the claims for any patentable feature or combination of features referred to hereinabove and / or shown in the drawings, whether emphasized or not.

Claims

1. a display means comprising an exit pupil expander, the exit pupil expander comprising an outcoupling element configured to outcouple light in a forward direction towards a user and in a rearward direction away from the user; a dynamically controllable reflector configured to provide selective reflection of light outcoupled from the exit pupil expander, a selectivity of the reflection of light being dynamically controllable, the selective reflection of light being in a direction back to the user; Equipped with the dynamically controllable reflector is configured to adjust a ratio of intensities of different colors present in light incident on the dynamically controllable reflector from the exit pupil expander to provide the selectively reflected light towards the user.

2. A display means comprising an exit pupil expander, the exit pupil expander comprising an outcoupling element configured to outcouple light in a forward direction towards a user and in a rearward direction away from the user; a dynamically controllable reflector configured to provide selective reflection of light outcoupled from the exit pupil expander, a selectivity of the reflection of light being dynamically controllable, the selective reflection of light being in a direction back to the user; Equipped with 13. An apparatus configured to adjust a color temperature or white point of light provided to the user by the dynamically controllable reflector.

3. 3. The apparatus of claim 1 or 2, wherein the selectivity of the dynamically controllable reflector depends on the output from one or more sensors that detect ambient illumination.

4. 3. The apparatus of claim 1 or 2, wherein the dynamically controllable reflector is a color-controllable reflector configured to differentially reflect light of different colors outcoupled in a rear direction from the exit pupil expander towards the user, the color-controllable reflector configured to reflect more light of a first color than light of a second color.

5. 3. An apparatus according to claim 1 or 2, wherein the dynamically controllable reflector comprises a reflective surface and a colour filter.

6. 6. The apparatus of claim 5, wherein the color filter is a tunable selective color filter.

7. 7. The apparatus of claim 6, wherein the color filters are configured to sequentially adjust the duty cycle for each color.

8. 6. The apparatus of claim 5, wherein the color filters are configured to be spatially inhomogeneous.

9. the exit pupil expander includes an in-coupler diffractive element, an expander element, and an out-coupler diffractive element; 3. The apparatus of claim 1, wherein the dynamically controllable reflector is disposed adjacent to the extra-coupler diffractive element.

10. 3. The device according to claim 1 or 2, characterized in that it is configured as an Exit Pupil Expander (EPE) head-up display, optionally a vehicle head-up display.

11. A computer program comprising computer program instructions which, when loaded into at least one processor, outcoupling the light to an outcoupling element of the exit pupil expander in a forward direction towards a user and a rearward direction away from said user; dynamically controlling a selectivity of reflection by the reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting light towards a user; and a computer program configured to adjust a ratio of intensities of different colors present in light incident on a dynamically controllable reflector from the exit pupil expander and provide the selectively reflected light to the user.

12. An exit pupil expander comprising an outcoupling element for outcoupling light in a forward direction towards a user and a rearward direction away from the user; dynamically controlling a selectivity of reflection by a reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting light towards a user; adjusting a ratio of intensities of different colors present in light incident on a dynamically controllable reflector from the exit pupil expander, and providing the selectively reflected light to the user.

13. A computer program comprising computer program instructions which, when loaded into at least one processor, outcoupling the light to an outcoupling element of the exit pupil expander in a forward direction towards a user and a rearward direction away from said user; dynamically controlling a selectivity of reflection by a reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting light towards a user; A computer program product for adjusting a color temperature or white point of light provided to the user by the dynamically controllable reflector.

14. An exit pupil expander having an outcoupling element for outcoupling light in a forward direction towards a user and in a rearward direction away from the user; dynamically controlling a selectivity of reflection by a reflector to selectively reflect light outcoupled from the exit pupil expander, the reflection reflecting light towards a user; adjusting a color temperature or white point of light provided to the user by the dynamically controllable reflector.

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