Micro LED and micro lens assembly

Abstract

A light source includes micro-LEDs of two or more colors together with a shared micro-lens arranged to compensate for chromatic aberration of the micro-lens by placing the micro-LEDs at different distances from the micro-lens. The micro-LED that emits shorter wavelength light is placed closer to the micro-lens than the micro-LED that emits longer wavelength light. A display includes an array of microlenses and a plurality of pixels, where each pixel is paired with one of the microlenses, and micro LEDs within the pixel are arranged to compensate for chromatic aberration of the lenses of the pixel. The inventors have recognized that the focal length of the microlens for blue light may differ from the focal length of the microlens for red light by approximately the same order of magnitude as the thickness of the micro-LED epitaxial structure. Accordingly, when manufacturing the micro LED array, it is possible to easily achieve a distance change required for achieving compensation for the chromatic aberration of the micro lens.

Description

[0001] Cross - Reference to Related Applications This application claims the benefit of the priority of U.S. Provisional Patent Application 63 / 432,778, filed on Dec. 15, 2022, which is hereby incorporated by reference in its entirety. Technical Field

[0002] The present invention generally relates to micro - LEDs, microlenses, displays including micro - LED arrays associated with microlens arrays, and visualization systems including such displays. Background Art

[0003] Semiconductor light - emitting diodes and laser diodes (collectively referred to herein as “LEDs”) are one of the most efficient light sources currently available. The emission spectrum of an LED typically exhibits a single narrow peak at a wavelength determined by the structure of the device and the composition of the semiconductor material of which it is made. By appropriately selecting the device structure and material system, an LED can be designed to operate at ultraviolet, visible, or infrared wavelengths.

[0004] An LED can be combined with one or more wavelength - converting materials (generally referred to herein as “phosphors”) that absorb the light emitted by the LED and in response emit light of a longer wavelength. For such phosphor - converted LEDs (“pcLEDs”), the fraction of the light emitted by the LED that is absorbed by the phosphor depends on the amount of phosphor material in the optical path of the light emitted by the LED, e.g., on the concentration of the phosphor material in a phosphor layer disposed on or around the LED and the thickness of the layer. A pcLED can be designed such that all of the light emitted by the LED is absorbed by one or more phosphors, in which case the emission from the pcLED comes entirely from the phosphors. In such a case, for example, the phosphor can be selected to emit light in a narrow spectral region that is not directly and efficiently generated by the LED. Alternatively, a pcLED can be designed such that only a portion of the light emitted by the LED is absorbed by the phosphor, in which case the emission from the pcLED is a mixture of the light emitted by the LED and the light emitted by the phosphor. By appropriately selecting the LED, phosphor, and phosphor composition, such a pcLED can be designed to emit, for example, white light with a desired color temperature and desired color - rendering properties.

[0005] Inorganic LEDs and pcLEDs have been widely used in manufacturing different types of displays, such as augmented reality (AR) displays, virtual reality (VR) displays, mixed reality (MR) displays (AR, VR, and MR systems are referred to as visualization systems in this document), smart glasses, and displays for mobile phones, smart watches, monitors, and televisions. Depending on the display size and its pixel-per-inch requirements, individual LEDs or pcLEDs in these architectures can have an area ranging from a few square millimeters down to a few square micrometers (e.g., microLEDs). SUMMARY OF THE INVENTION

[0006] This specification discloses a light source including microLEDs of two or more colors together with a shared microlens, which is arranged to compensate for the chromatic aberration of the microlens. A microlens is a small lens typically less than one millimeter in diameter. Chromatic aberration is the inability of a lens to focus light of all colors in a collimated beam to the same point, i.e., the focal length of the lens varies with the wavelength of light. Conversely, chromatic aberration is the inability of a lens to collimate equivalently light of different wavelengths emitted from the same point. Instead, the beams of different colors formed by the lens from light emitted from the same point will have different divergences. The chromatic aberration of a lens is caused by the dispersion (wavelength dependence) of the refractive index of the material from which the lens is made. For visible light and near-infrared light, the refractive index of the lens material is greater at shorter wavelengths (e.g., blue light) than at longer wavelengths (e.g., red light).

[0007] The light source disclosed in this specification compensates for the chromatic aberration of the shared microlens by placing the microLEDs at different distances from the microlens, where the microLEDs emitting shorter-wavelength light are placed closer to the microlens than the microLEDs emitting longer-wavelength light. For example, for the wavelength of light emitted by each microLED, the microLED can be placed at a distance equal to or approximately equal to the focal length of the microlens. This results in light emitted by different-color microLEDs being collimated equivalently into a beam. If a diverging beam rather than a collimated beam is desired, the microLEDs can be placed slightly closer than the wavelength-dependent focal length.

[0008] The inventors have recognized that the focal length of a microlens for blue light can differ from the focal length of a microlens for red light by approximately the same order of magnitude as the thickness of the microLED epitaxial structure. Therefore, when manufacturing a microLED array, it is easy to achieve the distance variations required to compensate for the chromatic aberration of the microlens.

[0009] A display device including microLED pixels (e.g., R, G, B pixels) together with a microlens (where the chromatic aberration is compensated as just described) will produce a better (e.g., sharper) image than a conventional display.

[0010] In one variant, a light source includes a microlens, a first micro-LED, a second micro-LED, and a third micro-LED. The first micro-LED includes a light-emitting surface and is configured to emit light having a first peak wavelength toward the microlens through its light-emitting surface. The first micro-LED is arranged such that its light-emitting surface is at a first distance from the microlens, and for the first distance, the microlens collimates or partially collimates the light emitted by the first micro-LED through its light-emitting surface at the first peak wavelength.

[0011] The second micro-LED includes a light-emitting surface and is configured to emit light having a second peak wavelength toward the microlens through its light-emitting surface. The second micro-LED is arranged such that its light-emitting surface is at a second distance from the microlens, and for the second distance, the microlens collimates or partially collimates the light emitted by the second micro-LED through its light-emitting surface at the second peak wavelength.

[0012] The third micro-LED includes a light-emitting surface and is configured to emit light having a third peak wavelength toward the microlens through its light-emitting surface. The third micro-LED is arranged such that its light-emitting surface is at a third distance from the microlens, and for the third distance, the microlens collimates or partially collimates the light emitted by the third micro-LED through its light-emitting surface at the third peak wavelength.

[0013] The second peak wavelength is longer than the first peak wavelength, and the second distance is longer than the first distance. The third peak wavelength is longer than the second peak wavelength, and the third distance is longer than the second distance.

[0014] The length differences between the first distance, the second distance, and the third distance can at least partially compensate for the chromatic aberration presented by the microlens.

[0015] The first peak wavelength, the second peak wavelength, and the third peak wavelength can all be visible light wavelengths, for example. For example, the first peak wavelength can be a blue light wavelength, and the third peak wavelength can be a red light wavelength.

[0016] The length difference between the first distance and the third distance can be, for example, from about 3 micrometers to about 7 micrometers, such as about 5 micrometers.

[0017] The light-emitting surfaces of the first micro-LED, the second micro-LED, and the third micro-LED can be shifted from each other perpendicular to the optical axis of the microlens.

[0018] The second micro-LED can be stacked on the third micro-LED, and the first micro-LED can be stacked on the second micro-LED.

[0019] The micro-LEDs can be direct-emission micro-LEDs or wavelength-converting micro-LEDs. The light source can include one or more direct-emission micro-LEDs and one or more wavelength-converting micro-LEDs.

[0020] The microlens may have a diameter perpendicular to its optical axis, for example, from about 4 micrometers to about 200 micrometers. The microlens may have a focal length of, for example, from about 1 millimeter (mm) to about 20 mm.

[0021] In another variant, a display includes a substrate, a microlens array including a plurality of microlenses, and a plurality of pixels disposed on the substrate. Each pixel is paired with a different microlens among the microlenses. Each pixel includes a first micro-LED, a second micro-LED, and a third micro-LED.

[0022] The first micro-LED includes a light-emitting surface and is configured to emit light having a first peak wavelength toward the microlens of the pixel through its light-emitting surface. The first micro-LED is arranged such that its light-emitting surface is at a first distance from the microlens of the pixel, and for the first distance, the microlens collimates or partially collimates the light emitted by the first micro-LED through its light-emitting surface at the first peak wavelength.

[0023] The second micro-LED includes a light-emitting surface and is configured to emit light having a second peak wavelength toward the microlens of the pixel through its light-emitting surface. The second micro-LED is arranged such that its light-emitting surface is at a second distance from the microlens of the pixel, and for the second distance, the microlens collimates or partially collimates the light emitted by the second micro-LED through its light-emitting surface at the second peak wavelength. The second peak wavelength is longer than the first peak wavelength, and the second distance is longer than the first distance.

[0024] The third micro-LED includes a light-emitting surface and is configured to emit light having a third peak wavelength toward the microlens of the pixel through its light-emitting surface. The third micro-LED is arranged such that its light-emitting surface is at a third distance from the microlens of the pixel, and for the third distance, the microlens collimates or partially collimates the light emitted by the third micro-LED through its light-emitting surface at the third peak wavelength. The third peak wavelength is longer than the second peak wavelength, and the third distance is longer than the second distance.

[0025] For each pixel, the length differences among the first distance, the second distance, and the third distance may at least partially compensate for the chromatic aberration presented by the microlens of the pixel.

[0026] For each pixel, the first peak wavelength, the second peak wavelength, and the third peak wavelength may all be, for example, visible light wavelengths. For example, the first peak wavelength may be a blue light wavelength, and the third peak wavelength may be a red light wavelength.

[0027] For each pixel, the length difference between the first distance and the third distance may be, for example, from about 3 micrometers to about 7 micrometers, for example, about 5 micrometers.

[0028] The pixels may be disposed on the substrate, where the center-to-center pitch of adjacent pixels is, for example, from about 4 micrometers to about 200 micrometers.

[0029] These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when the following more detailed description of the present invention is considered in conjunction with the accompanying drawings, which are briefly described first. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic cross-sectional view of an exemplary pcLED is shown.

[0031] Figure 2A and Figure 2B Schematic cross-sectional and top views of a pcLED array are shown, respectively. Figure 2C A schematic top view of an LED wafer is shown, from which an LED array such as Figure 2A and Figure 2B the LED arrays shown in

[0032] Figure 3 An exemplary display system is schematically shown.

[0033] Figure 4 A block diagram of an exemplary visualization system is shown.

[0034] Figure 5A 、 Figure 5B and Figure 5C Schematic cross-sectional views of an exemplary light source are shown, the exemplary light source including microLEDs of different colors together with a shared microlens, which are arranged to compensate for chromatic aberration of the microlens.

[0035] Figure 6A and Figure 6B Schematic cross-sectional and top views of a display including a microlens array and a plurality of pixels are shown, respectively, wherein each pixel is paired with one of the microlenses, and the microLEDs within the pixel are arranged to compensate for chromatic aberration of the lens of the pixel.

[0036] Figure 7 A schematic cross-sectional view of a device including a single lens and a plurality of pixels is shown, wherein the microLEDs within each pixel are arranged to compensate for chromatic aberration of the lens of the pixel. DETAILED DESCRIPTION

[0037] The following detailed description should be read with reference to the drawings, in which like reference numerals refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict alternative embodiments and are not intended to limit the scope of the present invention. The detailed description illustrates the principles of the present invention by way of example, not by way of limitation.

[0038] Figure 1An example of a single pcLED 100 is shown, which includes a light-emitting semiconductor diode (LED) structure 102 disposed on a substrate 104, and a phosphor layer 106 (which may also be referred to herein as a wavelength conversion structure) disposed on the LED. The light-emitting semiconductor diode structure 102 generally includes an active region disposed between an n-type layer and a p-type layer. Applying a suitable forward bias across the diode structure causes light to be emitted from the active region. The wavelength of the emitted light is determined by the composition and structure of the active region.

[0039] For example, the LED can be a Group III nitride LED that emits ultraviolet, blue, green, or red light. LEDs formed from any other suitable material system and emitting light of any other suitable wavelength can also be used. Other suitable material systems can include, for example, Group III phosphide materials, Group III arsenide materials, and II-IV group materials.

[0040] Any suitable phosphor material can be used, depending on the desired optical output and color specifications from the pcLED. The phosphor layer can, for example, include phosphor particles dispersed in a binder material or bonded to each other with a binder material, or can be or include a sintered ceramic phosphor plate.

[0041] Figure 2A - Figure 2B A cross-sectional view and a top view of an array 200 of pcLEDs 100 including a phosphor layer 106 disposed on a substrate 202 are shown, respectively. Such an array can include any suitable number of pcLEDs arranged in any suitable manner. An array of LEDs or pcLEDs can be formed monolithically on a shared substrate, but alternatively, an array of LEDs or pcLEDs can be formed from individually mechanically separated LEDs or pcLEDs. The substrate 202 can optionally include CMOS circuitry for driving the LEDs and can be formed from any suitable material.

[0042] Although Figure 2A - Figure 2BA three-by-three array of nine pcLEDs is shown, but such arrays can include, for example, dozens, hundreds, or thousands of LEDs or pcLEDs. The width (e.g., side length) of each LED or pcLED in the plane of the array can be, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, or less than or equal to 10 micrometers. The LEDs in such an array can be spaced apart from each other by streets or lanes that have a width in the plane of the array of, for example, hundreds of micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. Although the example shown depicts rectangular LEDs or pcLEDs arranged in a symmetric matrix, the LEDs or pcLEDs and the array can have any suitable shape or arrangement and do not all need to have the same shape or size. For example, the LEDs or pcLEDs located in the central portion of the array may be larger than the LEDs or pcLEDs located in the peripheral portion of the array. Alternatively, the LEDs or pcLEDs located in the central portion of the array can be smaller than the LEDs or pcLEDs located in the peripheral portion of the array.

[0043] Figure 2C A schematic top view of a portion of an LED wafer 210 is shown from which an LED array such as Figure 2A and Figure 2B the LED arrays shown in can be formed. Figure 2C An enlarged 3×3 portion of the wafer is also shown. In the example wafer, each LED or pcLED 111 having a side length (e.g., width) of W1 is arranged in a square matrix with a center-to-center distance D1 between adjacent LEDs or pcLEDs and separated by a lane 113 having a width of W2. W1 can be, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, or less than or equal to 10 micrometers. W2 can be, for example, hundreds of micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. D1 = W1 + W2.

[0044] For example, an array can be formed by cutting the wafer 210 into individual LEDs or pcLEDs and arranging the die on a substrate. Alternatively, the array can be formed from the entire wafer 210 or by dividing the wafer 210 into smaller LED or pcLED arrays.

[0045] LEDs or pcLEDs having dimensions (e.g., side length) in the plane of the array that are less than or equal to about 50 micrometers are generally referred to as microLEDs, and an array of such microLEDs can be referred to as a microLED array.

[0046] In a pcLED array, all pcLEDs can be configured to emit light of substantially the same spectrum. Alternatively, the pcLED array can be a multicolor array, where different pcLEDs in the array can be configured to emit light of different spectra (colors) by employing different phosphor compositions. Similarly, in an array of direct-emitting LEDs (i.e., without wavelength conversion by a phosphor), all LEDs in the array can be configured to emit light of substantially the same spectrum, or the array can be a multicolor array that includes LEDs configured to emit light of different colors.

[0047] Each LED or pcLED in the array can be individually operable (addressable) and / or can be operable as part of a group or subset of LEDs or pcLEDs in the array (e.g., adjacent).

[0048] An array of LEDs or pcLEDs, or portions of such an array, can be formed as a segmented monolithic structure, where each LED or pcLED is electrically isolated or partially electrically isolated from one another by trenches and / or insulating materials, but the electrically isolated or partially electrically isolated segments remain physically connected to one another through other portions of the semiconductor structure. For example, in such a monolithic structure, an active region and a first semiconductor layer of a first conductivity type (n or p) on one side of the active region can be segmented, and a second unsegmented semiconductor layer of the opposite conductivity type (p or n) is located on the side of the active region opposite the first semiconductor layer. The second semiconductor layer can then physically and electrically connect the segmented structures to one another on one side of the active region, where the segmented structures are otherwise electrically isolated from one another and can thus be operated individually as separate LEDs.

[0049] Thus, an LED or pcLED array can be or include a monolithic multicolor matrix of individually operable LED or pcLED light emitters. The LEDs or pcLEDs in the monolithic array can be, for example, microLEDs as described above.

[0050] A single individually operable LED or pcLED or a group of adjacent such LEDs or pcLEDs can correspond to a single pixel (picture element) in a display. For example, a group of three individually operable adjacent LEDs or pcLEDs including a red emitter, a blue emitter, and a green emitter can correspond to a single color-tunable pixel in a display. In some variations, a group of six individually operable adjacent LEDs or pcLEDs including two red emitters, two blue emitters, and two green emitters corresponds to a single color-tunable pixel in a display, where the additional red, blue, and green emitters provide redundancy in the event that another emitter of the same color fails.

[0051] Figure 3FIG. 0 schematically shows an example display system 300, which includes an array 310 of individually operable or group-operable LEDs or pcLEDs, a display 320, a light-emitting array controller 330, a sensor system 340, and a system controller 350. As described above, the array 310 can be a monolithic array, or include one or more monolithic arrays. The array can be monochromatic. Alternatively, the array can be a multi-color array, where different LEDs or pcLEDs in the array are configured to emit different colors of light, as described above. Thus, the array can be or include a monolithic multi-color matrix of individually operable LED or pcLED light emitters, which can be, for example, micro-LEDs as described above. An individual, separately operable LED or pcLED in the array, or a group of adjacent such LEDs or pcLEDs, can correspond to a single pixel (picture element) in the display. For example, a group of three separately operable adjacent LEDs or pcLEDs including a red emitter, a blue emitter, and a green emitter can correspond to a single color-tunable pixel in the display. Similarly, to provide redundancy in the case of a defective LED or pcLED, a group of six separately operable adjacent LEDs or pcLEDs including two red emitters, two blue emitters, and two green emitters can correspond to a single color-tunable pixel in the display. The array 310 can be used to project light in a graphic pattern or an object pattern, which can support, for example, an AR / VR / MR system.

[0052] Sensor inputs are provided to the sensor system 340, while power and user data inputs are provided to the system controller 350. In some embodiments, the modules included in the system 300 can be compactly arranged in a single structure, or one or more elements can be separately mounted and connected via wireless or wired communication. For example, the array 310, the display 320, and the sensor system 340 can be mounted on a headset or glasses, where the light-emitting array controller and / or the system controller 350 are separately mounted.

[0053] The system 300 can incorporate a variety of optical devices (not shown) to couple the light emitted by the array 310 into the display 320. Such optical devices can include, for example, a microlens array as disclosed herein and used in combination with an LED or pcLED array. Any suitable optical device can be used for this purpose.

[0054] The sensor system 340 may include, for example: external sensors that monitor the environment, such as cameras, depth sensors, or audio sensors; and internal sensors that monitor the position of the AR / VR / MR headset, such as accelerometers or two-axis or three-axis gyroscopes. Other sensors may include, but are not limited to, barometric pressure, stress sensors, temperature sensors, or any other suitable sensors required for local or remote environmental monitoring. In some embodiments, control inputs through the sensor system may include detected touches or taps, gesture inputs, or controls based on the position of the headset or display.

[0055] In response to data from the sensor system 340, the system controller 350 may send images or instructions to the light emitting array controller 330. Changes or modifications to the images or instructions may also be made through user data input or automatic data input as needed. User data input may include, but is not limited to, data input provided by audio instructions, tactile feedback, eye or pupil positioning, or a connected keyboard, mouse, or game controller.

[0056] As described above, AR, VR, and MR systems may be more generally referred to as examples of visualization systems. In a virtual reality system, the display may present a view of a scene (such as a three-dimensional scene) to the user. The user may move within the scene, such as by repositioning the user's head or by walking. The virtual reality system may detect the user's movement and change the view of the scene to account for the movement. For example, when the user rotates the user's head, the system may present a view of the scene that changes in the direction of the view to match the user's gaze. In this way, the virtual reality system may simulate the user's presence in a three-dimensional scene. Additionally, the virtual reality system may receive tactile sensory input, such as from a wearable position sensor, and may optionally provide tactile feedback to the user.

[0057] In an augmented reality system, the display may incorporate elements from the user's surrounding environment into the view of the scene. For example, an augmented reality system may add text captions and / or visual elements to the view of the user's surrounding environment. For example, a retailer may use an augmented reality system to show a user what a piece of furniture would look like in a room in the user's home by combining a visualization of the piece of furniture over a captured image of the user's surrounding environment. As the user walks around in the user's room, the visualization interprets the user's movement and changes the visualization of the furniture in a manner consistent with the movement. For example, an augmented reality system may place a virtual chair in the room. The user may stand in front of the virtual chair position in the room to view the front side of the chair. The user may move to an area behind the virtual chair position in the room to view the back side of the chair. In this way, the augmented reality system may add elements to a dynamic view of the user's surrounding environment.

[0058] Figure 4 A general block diagram of an example visualization system 410 is shown. The visualization system 410 may include a wearable housing 412, such as a headset or goggles. The housing 412 may mechanically support and house the elements detailed below. In some examples, one or more of the elements detailed below may be included in one or more additional housings that may be separate from the wearable housing 412 and coupled to the wearable housing 412 wirelessly and / or via a wired connection. For example, a separate housing may reduce the weight of the wearable goggles, such as by including a battery, radio, and other elements. The housing 412 may include one or more batteries 414 that may power any or all of the elements detailed below. The housing 412 may include circuitry that may be electrically coupled to an external power source, such as a wall outlet, to charge the battery 414. The housing 412 may include one or more radios 416 to communicate wirelessly with a server or network via a suitable protocol, such as WiFi.

[0059] The visualization system 410 may include one or more sensors 418, such as optical sensors, audio sensors, tactile sensors, thermal sensors, gyroscopic sensors, time-of-flight sensors, triangulation-based sensors, and so on. In some examples, one or more sensors may sense a user's location, position, and / or orientation. In some examples, one or more sensors 418 may generate a sensor signal in response to the sensed location, position, and / or orientation. The sensor signal may include sensor data corresponding to the sensed location, position, and / or orientation. For example, the sensor data may include a depth map of the surrounding environment. In some examples, such as for an augmented reality system, one or more sensors 418 may capture real-time video images of the surrounding environment near the user.

[0060] The visualization system 410 may include one or more video generation processors 420. The one or more video generation processors 420 may receive scene data representing a three-dimensional scene, such as a set of position coordinates of objects in the scene or a depth map of the scene, from a server and / or a storage medium. The one or more video generation processors 420 may receive one or more sensor signals from one or more sensors 418. In response to the scene data representing the surrounding environment and at least one sensor signal representing the location and / or orientation of the user relative to the surrounding environment, the one or more video generation processors 420 may generate at least one video signal corresponding to a view of the scene. In some examples, the one or more video generation processors 420 may generate two video signals, one for each eye of the user, the two video signals respectively representing views of the scene seen from the left and right eyes of the user. In some examples, the one or more video generation processors 420 may generate more than two video signals and combine these video signals to provide one video signal for both eyes, two video signals for both eyes, or other combinations.

[0061] The visualization system 410 may include one or more light sources 422 that may provide light for a display of the visualization system 410. Suitable light sources 422 may include any of the LEDs, pcLEDs, LED arrays, and pcLED arrays discussed above, such as those discussed above with respect to the display system 300.

[0062] The visualization system 410 may include one or more modulators 424. The modulator 424 may be implemented in one of at least two configurations.

[0063] In a first configuration, the modulator 424 may include circuitry that may directly modulate the light source 422. For example, the light source 422 may include an array of light-emitting diodes, and the modulator 424 may directly modulate the electrical power, voltage, and / or current directed to each light-emitting diode in the array to form modulated light. The modulation may be performed in an analog manner and / or a digital manner. In some examples, the light source 422 may include an array of red light-emitting diodes, an array of green light-emitting diodes, and an array of blue light-emitting diodes, and the modulator 424 may directly modulate the red light-emitting diodes, green light-emitting diodes, and blue light-emitting diodes to form modulated light to produce a particular image.

[0064] In a second configuration, the modulator 424 can include a modulation panel, such as a liquid crystal panel. The light source 422 can generate uniform illumination or near-uniform illumination to illuminate the modulation panel. The modulation panel can include pixels. Each pixel can selectively attenuate a corresponding portion of the modulation panel area in response to an electrical modulation signal to form modulated light. In some examples, the modulator 424 can include multiple modulation panels that can modulate light of different colors. For example, the modulator 424 can include a red modulation panel that can attenuate red light from a red light source, such as a red light-emitting diode, a green modulation panel that can attenuate green light from a green light source, such as a green light-emitting diode, and a blue modulation panel that can attenuate blue light from a blue light source, such as a blue light-emitting diode.

[0065] In some examples of the second configuration, the modulator 424 can receive uniform white light or near-uniform white light from a white light source, such as a white light-emitting diode. The modulation panel can include wavelength-selective filters on each pixel of the modulation panel. The panel pixels can be arranged in groups (such as three or four groups), where each group can form a pixel of a color image. For example, each group can include panel pixels with a red filter, panel pixels with a green filter, and panel pixels with a blue filter. Other suitable configurations can also be used.

[0066] The visualization system 410 can include one or more modulation processors 426 that can receive video signals (such as from one or more video generation processors 420) and, in response, can generate electrical modulation signals. For configurations in which the modulator 424 directly modulates the light source 422, the electrical modulation signal can drive the light source 422. For configurations in which the modulator 424 includes a modulation panel, the electrical modulation signal can drive the modulation panel.

[0067] The visualization system 410 can include one or more beam combiners 428 (also referred to as beam splitters 428) that can combine beams of different colors to form a single multi-color beam. For configurations in which the light source 422 can include multiple light-emitting diodes of different colors, the visualization system 410 can include one or more wavelength-sensitive (e.g., dichroic) beam splitters 428 that can combine light of different colors to form a single multi-color beam.

[0068] The visualization system 410 can direct modulated light towards the observer's eyes in at least one of two configurations. In a first configuration, the visualization system 410 can function as a projector and can include suitable projection optics 430 that can project the modulated light onto one or more screens 432. The screen 432 can be positioned at a suitable distance from the user's eyes. The visualization system 410 can optionally include one or more lenses 434 that can position a virtual image of the screen 432 at a suitable distance from the eyes, such as a close-focus distance, such as 500 mm, 750 mm, or another suitable distance. In some examples, the visualization system 410 can include a single screen 432 such that the modulated light can be directed towards the user's binocular eyes. In some examples, the visualization system 410 can include two screens 432 such that the modulated light from each screen 432 can be directed towards the user's respective eyes. In some examples, the visualization system 410 can include more than two screens 432. In a second configuration, the visualization system 410 can direct the modulated light directly into one or both of the observer's eyes. For example, the projection optics 430 can form an image on the retina of one of the user's eyes, or on the retina of each of the user's eyes.

[0069] For some configurations of the augmented reality system, the visualization system 410 can include at least a partially transparent display such that the user can view the user's surrounding environment through the display. For such a configuration, the augmented reality system can generate enhanced modulated light corresponding to the surrounding environment rather than the surrounding environment itself. For example, in the example of a retailer displaying a chair, the augmented reality system can direct the modulated light corresponding to the chair rather than the rest of the room towards the screen or towards the user's eyes.

[0070] As described above, an optical lens has chromatic aberration, which is caused by the inherent dispersion of the refractive index of the lens material. As a result, the focal lengths of different colors are different: the focal length in the blue range is shorter, and the focal length in the red range is longer. As an example, commercially available flint glass (relatively large dispersion) Schott SF-11 has, for example, a refractive index of 1.82 for blue light and a refractive index of 1.78 for red light. The focal length f of a plano-convex lens is given by where n is the refractive index and R is the radius of curvature of the lens. For a lens formed of SF-11, the focal length difference between blue and red is calculated to be 1.05R. If R is 100 µm, the focal length difference is approximately 5 µm.

[0071] This means that when the blue and red microLEDs are located at their respective focal lengths (difference of about 5 µm, with the blue microLED being closer) on the optical axis of the SF-11 lens element, a collimated beam of blue and red light is obtained in the image space. The green microLED should be placed at a distance between the blue and red microLEDs. Additional microLEDs emitting at intermediate wavelengths between blue and red can be appropriately distributed in the focal length scheme, depending on the wavelength of light and the corresponding refractive index of the lens. If a wider (divergent) beam is desired in the image space instead of a collimated beam, the position of the microLEDs is adjusted accordingly (e.g., closer to the lens than the focal length).

[0072] If the micro-LEDs of different colors are not all on the optical axis, but are instead displaced perpendicularly to each other, the idea here still holds true: micro-LEDs with shorter wavelengths should be placed closer to the micro-lenses than micro-LEDs with longer wavelengths.

[0073] The inventors have realized that the difference in focal length of such microlenses for blue and red light (about 5 microns) is comparable to the thickness of the epitaxial structure of the microLED. Therefore, when manufacturing the microLED array, the distance variation required to achieve compensation for the chromatic aberration of the microlenses can be easily achieved.

[0074] As described above, the present specification discloses a light source including microLEDs of two or more colors together with a shared microlens, which is arranged to compensate for chromatic aberration of the microlens by placing the microLEDs at different distances from the microlens. MicroLEDs that emit shorter wavelength light are placed closer to the microlens than microLEDs that emit longer wavelength light. A microLED display can similarly compensate for chromatic aberration, where the display includes a microlens array and a plurality of pixels, where each pixel is paired with one of the microlenses, and the microLEDs within the pixel are arranged to compensate for chromatic aberration of the lens of the pixel.

[0075] Figure 5A , Figure 5B and Figure 5C Schematic cross-sectional views of example light sources are shown, each including micro-LEDs 515, 510, and 515 of different colors, which are grouped into pixels 520, together with a shared micro-lens 530. The micro-LEDs are arranged to compensate for the chromatic aberration of the micro-lens 530. The wavelength of light emitted by micro-LED 505 is shorter than the wavelength of light emitted by micro-LED 510. The wavelength of light emitted by micro-LED 510 is shorter than the wavelength of light emitted by micro-LED 515. Micro-LED 505 is positioned so that the distance between its front emitting surface and micro-lens 530 is less than the distance between the front emitting surface of micro-LED 510 and micro-lens 530. Micro-LED 510 is positioned so that the distance between its front emitting surface and micro-lens 530 is less than the distance between the front emitting surface of micro-LED 515 and micro-lens 530.

[0076] For the light of the peak wavelength emitted by each micro-LED, the micro-LED can be placed at or near the focal point of, for example, the microlens 530.

[0077] Each micro-LED can each emit light with a peak wavelength within the visible spectrum. For example, in one variant, the micro-LED 505 emits blue light, the micro-LED 510 emits cyan, green, or yellow light, and the micro-LED 515 emits red light. Alternatively, one or more of the micro-LEDs can emit light with a peak wavelength within the infrared portion of the spectrum.

[0078] The difference in distance between different micro-LEDs and the microlens can be on the order of micrometers. If the microlens has a focal length of approximately 100 micrometers (ignoring chromatic aberration), the distance from the front light-emitting surface of the micro-LED 505 to the microlens 530 and the distance from the front light-emitting surface of the micro-LED 515 to the microlens 530 can differ by, for example, approximately 3 micrometers to approximately 7 micrometers, for example, if the micro-LED 505 emits blue light and the micro-LED 515 emits red light, the difference is approximately 5 micrometers.

[0079] The focal length of the microlens can be, for example, approximately 1 mm to approximately 20 mm, and the diameter of the microlens can be, for example, approximately 4 micrometers to approximately 200 micrometers.

[0080] The micro-LED can have a light-emitting surface with a size (e.g., side length) perpendicular to the optical axis of the microlens that is, for example, approximately 2 micrometers to approximately 195 micrometers.

[0081] The ratio of the diameter of the microlens to the size of the light-emitting surface of the micro-LED perpendicular to the optical axis of the microlens can be, for example, greater than or equal to 10.

[0082] In Figure 5A 's example, the micro-LEDs 515, 510, and 515 are stacked on top of each other along the optical axis of the microlens 530. This requires the micro-LED 505 to transmit the light emitted by the micro-LED 510 and the micro-LED 515, and also requires the micro-LED 510 to transmit the light emitted by the micro-LED 515.

[0083] In Figure 5B 's example, the micro-LED 510 is on the optical axis of the microlens 530, and the micro-LEDs 515 and 515 are each vertically displaced from the optical axis of the microlens 530. This arrangement does not require any micro-LED to transmit the light emitted by any of the other micro-LEDs.

[0084] In Figure 5CIn the example, the micro-LEDs 515, 510, and 515 are stacked on top of each other, but their (unobstructed) light-emitting surfaces are shifted relative to each other in a plane perpendicular to the optical axis of the microlens 530. This arrangement does not require any micro-LED to transmit the light emitted by any of the other micro-LEDs.

[0085] Figure 6A and Figure 6B respectively show a cross-sectional view and a top view of an example display that includes a microlens array 610 of microlenses 530 disposed on a substrate 615 and a micro-LED array 620 that includes a plurality of pixels 520 disposed on a substrate 625. Optionally, the substrate 625 can be transparent to visible light. Each pixel 520 is paired with one of the microlenses 530, and the micro-LEDs within the pixel are arranged to compensate for the chromatic aberration of the lens of the pixel, as described above. Such a display can be used, for example, in micro-LED direct-view and head-mounted applications, or in other applications (such as those described in the Background section above).

[0086] The pixels 520 can be spaced apart from each other on the substrate 620 by a distance D of, for example, about 2 micrometers to about 10 micrometers. This can correspond to a center-to-center spacing between adjacent pixels of, for example, about 4 micrometers to about 200 micrometers. Although shown as adjacent to each other in the Figure 6A - Figure 6B example, the microlenses 530 in the microlens array 610 can be spaced apart from each other on the substrate 615, or otherwise arranged separately, to match the center-to-center spacing of the pixels.

[0087] Although the examples described with respect to Figure 5A - Figure 5C and Figure 6A - Figure 6B employ microlenses, the same approach can be used to compensate for the chromatic aberration of conventional-sized lenses that are larger in diameter than the microlenses (i.e., having a diameter greater than about 1 mm). The focal length of such a lens can be, for example, about 1 mm to about 20 mm, as described above for the examples employing microlenses. The conventional-sized lens can be used in combination with two or more pixels, for example, where the micro-LEDs within the pixel are arranged to compensate for the chromatic aberration of the lens.

[0088] Figure 7 shows a cross-sectional view of an example device that includes the micro-LED array 620 as described above together with a lens 710 that is arranged to collimate or partially collimate the light emitted from a plurality of pixels 520 in the micro-LED array. The lens 710 is of a conventional size, i.e., larger than the microlenses. Figure 7 The arrangement shown in Figure 6A is similar to the arrangement shown inFigure 7 The arrangement shown may be a display.

[0089] This disclosure is illustrative and not restrictive. Given this disclosure, further modifications will be apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Claims

1. A light source, comprising: a microlens; a first micro-LED, which includes a light-emitting surface and is configured to emit light having a first peak wavelength toward the microlens through its light-emitting surface, the first micro-LED being arranged such that its light-emitting surface is at a first distance from the microlens, and for the first distance, the microlens collimates or partially collimates the light emitted by the first micro-LED through its light-emitting surface at the first peak wavelength; a second micro-LED, which includes a light-emitting surface and is configured to emit light having a second peak wavelength toward the microlens through its light-emitting surface, the second micro-LED being arranged such that its light-emitting surface is at a second distance from the microlens, and for the second distance, the microlens collimates or partially collimates the light emitted by the second micro-LED through its light-emitting surface at the second peak wavelength, the second peak wavelength being longer than the first peak wavelength, and the second distance being longer than the first distance; and a third micro-LED, which includes a light-emitting surface and is configured to emit light having a third peak wavelength toward the microlens through its light-emitting surface, the third micro-LED being arranged such that its light-emitting surface is at a third distance from the microlens, and for the third distance, the microlens collimates or partially collimates the light emitted by the third micro-LED through its light-emitting surface at the third peak wavelength, the third peak wavelength being longer than the second peak wavelength, and the third distance being longer than the second distance.

2. The light source according to claim 1, wherein a length difference between the first distance, the second distance, and the third distance at least partially compensates for chromatic aberration presented by the microlens.

3. The light source according to claim 1, wherein the first peak wavelength, the second peak wavelength, and the third peak wavelength are visible light wavelengths.

4. The light source according to claim 3, wherein the first peak wavelength is a blue light wavelength, and the third peak wavelength is a red light wavelength.

5. The light source according to claim 4, wherein a length difference between the first distance and the third distance is from about 3 micrometers to about 7 micrometers.

6. The light source according to claim 5, wherein a length difference between the first distance and the third distance is about 5 micrometers.

7. The light source according to claim 1, wherein the light-emitting surfaces of the first micro-LED, the second micro-LED, and the third micro-LED are displaced from each other perpendicular to the optical axis of the microlens.

8. The light source according to claim 1, wherein the second micro-LED is stacked on the third micro-LED, and the first micro-LED is stacked on the second micro-LED.

9. The light source according to claim 8, wherein the light-emitting surfaces of the first micro-LED, the second micro-LED, and the third micro-LED are displaced from each other perpendicular to the optical axis of the microlens.

10. The light source according to claim 1, wherein one or more of the micro-LEDs are direct emission micro-LEDs.

11. The light source according to claim 1, wherein one or more of the micro-LEDs are wavelength conversion micro-LEDs.

12. The light source according to claim 1, wherein the microlens has a diameter perpendicular to its optical axis of from about 4 microns to about 200 microns.

13. The light source according to claim 1, wherein the microlens has a focal length of from about 1 mm to about 20 mm.

14. A display, comprising: a substrate; a microlens array including a plurality of microlenses; and a plurality of pixels disposed on the substrate, each pixel being paired with a different microlens of the microlenses, each pixel comprising: a first micro-LED including a light-emitting surface and configured to emit light having a first peak wavelength toward the microlens of the pixel through its light-emitting surface, the first micro-LED being arranged such that its light-emitting surface is at a first distance from the microlens of the pixel, for which the microlens collimates or partially collimates the light emitted by the first micro-LED through its light-emitting surface at the first peak wavelength, a second micro-LED including a light-emitting surface and configured to emit light having a second peak wavelength toward the microlens of the pixel through its light-emitting surface, the second micro-LED being arranged such that its light-emitting surface is at a second distance from the microlens of the pixel, for which the microlens collimates or partially collimates the light emitted by the second micro-LED through its light-emitting surface at the second peak wavelength, the second peak wavelength being longer than the first peak wavelength, and the second distance being longer than the first distance, and a third micro-LED including a light-emitting surface and configured to emit light having a third peak wavelength toward the microlens of the pixel through its light-emitting surface, the third micro-LED being arranged such that its light-emitting surface is at a third distance from the microlens of the pixel, for which the microlens collimates or partially collimates the light emitted by the third micro-LED through its light-emitting surface at the third peak wavelength, the third peak wavelength being longer than the second peak wavelength, and the third distance being longer than the second distance.

15. The display according to claim 14, wherein for each pixel, the length differences between the first distance, the second distance, and the third distance at least partially compensate for the chromatic aberration presented by the microlens of the pixel.

16. The display according to claim 14, wherein for each pixel, the first peak wavelength, the second peak wavelength, and the third peak wavelength are visible light wavelengths.

17. The display according to claim 16, wherein for each pixel, the first peak wavelength is a blue light wavelength and the third peak wavelength is a red light wavelength.

18. The display according to claim 17, wherein for each pixel, the length difference between the first distance and the third distance is from about 3 microns to about 7 microns.

19. The display according to claim 18, wherein for each pixel, the length difference between the first distance and the third distance is about 5 microns.

20. The display according to claim 18, wherein the pixels are arranged on the substrate, and the center-to-center pitch of adjacent pixels is from about 4 microns to about 200 microns.

21. A device, comprising: a substrate; a lens; and a plurality of pixels disposed on the substrate, each pixel comprising: A first micro-LED, which includes a light-emitting surface and is configured to emit light having a first peak wavelength toward a lens through its light-emitting surface, the first micro-LED being arranged such that its light-emitting surface is at a first distance from the lens, for which distance the lens collimates or partially collimates the light emitted by the first micro-LED through its light-emitting surface at the first peak wavelength, A second micro-LED, which includes a light-emitting surface and is configured to emit light having a second peak wavelength toward a lens through its light-emitting surface, the second micro-LED being arranged such that its light-emitting surface is at a second distance from the lens, for which distance the lens collimates or partially collimates the light emitted by the second micro-LED through its light-emitting surface at the second peak wavelength, the second peak wavelength being longer than the first peak wavelength, and the second distance being longer than the first distance, and A third micro-LED, which includes a light-emitting surface and is configured to emit light having a third peak wavelength toward a lens through its light-emitting surface, the third micro-LED being arranged such that its light-emitting surface is at a third distance from the lens, for which distance the lens collimates or partially collimates the light emitted by the third micro-LED through its light-emitting surface at the third peak wavelength, the third peak wavelength being longer than the second peak wavelength, and the third distance being longer than the second distance.

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