Patent Publication Number: US-2021191005-A1

Title: Light-emitting apparatus including a reflective cavity

Description:
TECHNICAL FIELD 
     The present disclosure relates to a light-emitting apparatus configured to diffuse infrared light. Some embodiments provide a near-uniform intensity after a diffuser. 
     BACKGROUND 
     In some applications, such as sensors for autonomous driving vehicles, illumination is provided at one or more infrared wavelengths. Under certain circumstances, such as at night, a human eye can perceive the infrared illumination as being red light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures show various views of an apparatus, including a lens that can shape light emerging from one or more light emitting diodes (LEDs), in accordance with some embodiments. In the views presented herein, it is assumed that light emerges from a front of the lens, such that the LED or LEDs can be positioned towards a rear of the lens. The terms “front,” “rear,” “top,” “side,” and other directional terms are used merely for convenience in describing the lens and other elements and should not be construed as limiting in any way. 
         FIG. 1  shows a side view of an example of a light-emitting apparatus, in accordance with some examples. 
         FIG. 2  shows a rear-view cross-section of the light-emitting apparatus of  FIG. 1 , in accordance with some examples. 
         FIG. 3  shows a top-view cross-section of the light-emitting apparatus, in accordance with some examples. 
         FIG. 4  shows an exploded view diagram of the light-emitting apparatus, in accordance with some examples. 
         FIG. 5  shows a cross-section diagram of a diffuser, in accordance with some examples. 
         FIG. 6  shows plots of a radiance profile of an infrared light-emitting apparatus without a reflective cavity and a diffuser, in accordance with some examples. 
         FIG. 7  shows plots of a radiance profile of the light-emitting apparatus of a light-emitting apparatus that includes the reflective cavity and the diffuser, in accordance with some examples. 
         FIG. 8  shows a flow chart of an example of a method for forming a light-emitting apparatus, in accordance with some examples. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Elements in the drawings are not necessarily drawn to scale. The configurations shown in the drawings are merely examples and should not be construed as limiting the scope of the disclosed subject matter in any manner. 
     DETAILED DESCRIPTION 
     There are government regulations (e.g., Society of Automotive Engineers (SAE) J578, a standard defined and promulgated by SAE International) regarding the color of lights positioned on an exterior of a vehicle. In general, for typical passenger vehicles, the government regulations require that lights on a front of a vehicle only emit white light, lights on a left and right sides of a vehicle only emit amber light, and lights on a rear of a vehicle only emit red light. In other countries of the world that do not adhere to the SAE J578 standard, other visible colors of light may be acceptable in various locations on a vehicle. 
     Modern safety systems on a vehicle can produce images of a vehicle&#39;s surroundings, or retrieve data regarding the vehicle&#39;s surroundings, for use in accident prevention and object avoidance. In addition, autonomous driving or assisted-driving applications can also retrieve data regarding the vehicle&#39;s surroundings. Because the government regulations place requirements on light emitted from the vehicle for wavelengths up to 780 nm and are silent regarding infrared light emitted at wavelengths longer than 780 nm, using such infrared light to illuminate the vehicle&#39;s surroundings can benefit the safety systems on the vehicle. 
     For example, illuminating the surroundings, rather than relying on reflections of ambient light, can be beneficial because illumination can allow the safety system to operate at night. Using infrared light for illumination, rather than illuminating with visible light, can be beneficial because infrared light is largely invisible to the human eye and does not create issues for other vehicle drivers. Further, using a specific, and relatively narrow, wavelength range for illumination and detection can be beneficial, because the illumination and detection can occur at a brightness level that can be significantly larger than what is present in ambient sunlight. For example, if illumination and detection occur in a relatively narrow infrared wavelength range centered about 940 nm (or another suitable infrared wavelength), it can be straightforward to illuminate with enough power to drown out any illumination effects caused by ambient sunlight or by other light-emitting elements in the surroundings. The power used for such narrowband illumination and detection can be small enough to avoid damaging eye tissue or other living tissue in the surroundings. 
     However, illuminating the surroundings with infrared light can cause an unexpected problem. As an artifact of human vision, emissions from an infrared light source can spuriously be perceived by the human eye as being red. Specifically, while the infrared light reflected from the surroundings can be at an intensity low enough to be invisible to the human eye, a viewer looking directly into the infrared light source may view the relatively high intensity of the light source as spuriously glowing red. As the emitting wavelengths increase (and, therefore, move farther away from the long-wavelength end of the visible spectrum, which is typically considered to be around 700 nm), the spurious effect decreases, but is still present. The human eye sensitivity to near-IR light is very small but it is not zero (photopic sensitivity values are about 1@λ=555 nm, about 1.2×10 −4 @λ=750 nm, ˜7×10 −7 @λ=850 nm, ˜10 −9 @λ=950 nm). The near IR LEDs visually appear with a very bright red glow specifically in the dark ambient. Using a low pass filter which cuts off the lower tail of the emitted spectrum below 800 nm is not always effective to remove the red glow of the near-IR light since the human eye sensitivity is not zero even beyond 940 nm. 
     For illumination applications that are aimed to be visually invisible, the near-IR spectral region is preferable since all silicon-based camera sensors have their maximum sensitivity in the visible and near-IR spectral region. High power near-IR LEDs are used in several applications such as object avoidance and detection, driver monitoring, scene illumination, or the like. 
     As a result, simply placing an infrared source on the front or sides of the vehicle can be problematic, because to the human eye, such a source would be perceived as a red light, which is prohibited by the government regulations. To overcome the problem of the infrared light source positioned on a front or sides of a vehicle exterior being perceived as a red light, a diffuser can be positioned to receive and diffuse the light from the infrared light source. The light from the infrared light source can be imperceptible or nearly imperceptible to the human eye. 
     The foregoing discussion regards infrared light external to a vehicle, which is but one example application of the technology described. Other applications of the technology described include infrared light internal to the vehicle, such as for driver monitoring or gesture control. Another application of the technology includes virtual reality or augmented reality games or programs. Further, the technology can be used in a mobile three-dimensional 3D sensor, on a drone for obstacle avoidance, as part of a time of flight sensor, or as part of a surveillance system. Many other applications are possible for the technology discussed herein. 
     The apparatus discussed herein can be suitable for providing a diffused infrared light discussed above. The apparatus can include a lens that can shape a beam output from one or more infrared light-emitting diodes, for example, to provide infrared illumination at a specified brightness over a specified angular range. The apparatus can further diffuse the infrared illumination to address the spurious viewing issues discussed above. 
     As used herein, the phrase “generally planar” is intended to mean planar to within typical manufacturing tolerance and/or typical alignment tolerances. For the purposes of this document, a vertical-cavity surface-emitting laser can be considered to be a light-emitting diode. For the purposes of this document, the use of the term “visible light” can be generalized to light having a first wavelength, and the use of the term “infrared light” can be generalized to light having a second wavelength different from the first wavelength, where the first wavelength and/or the second wavelength can be in an ultraviolet portion of the electromagnetic spectrum, a visible portion of the portion of the electromagnetic spectrum, or an infrared portion of the electromagnetic spectrum. 
       FIG. 1  shows a side view of an example of a light-emitting apparatus  100 , in accordance with some examples. The light-emitting apparatus  100  as illustrated includes a light emitting element  102 , a light reflecting element  104 , offsets  106 , and a diffuser  108 . The light-emitting element  102  is electrically and mechanically connected to a substrate  110 . 
     The light-emitting element  102  can include one or more solid-state light emitters. Examples of solid-state light emitters include light emitting diodes (LEDs), laser diodes, and organic LEDs (OLEDs). In an embodiment in which the solid state light emitter is an LEDs, the LEDs may be top-fire LEDs or side-fire LEDs, and may be broad spectrum LEDs (e.g., white light emitters) or LEDs that emit light of a desired color or spectrum (e.g., red light, green light, blue light, or ultraviolet light), or a mixture of broad-spectrum LEDs and LEDs that emit narrow-band light of a desired color. In one embodiment, the solid-state light emitters emit light with operably-effective intensity at wavelengths greater than 700 nanometers (nm) (i.e., the solid-state light emitters emit light at wavelengths that are predominantly greater than 700 nm). For a near-IR light-emitting element  102 , the wavelength of light emitted therefrom can be between about 700 nm and about 2500 nm. For an IR light-emitting element  102 , the wavelength of light emitted therefrom can be between about 700 nm and about 1 mm. 
     The light emitting element  102  can be mechanically and electrically coupled to the substrate  110 . In example embodiments, the substrate  110  can be electrically and mechanically connected to a printed circuit board (PCB) (see  FIG. 4 ). 
     In example embodiments, the light emitting element  102  protrudes through an opening in the reflecting element  104  (see  FIG. 4 ). In example embodiments, a surface  112  of the reflecting element  104  rests on a surface  114  of the substrate  110 . The surface  112  is opposite a surface  116  of the reflecting element  104  to which the offsets  106  are attached. A radiating surface of the light emitting element  102  can be surrounded by the reflecting element  104 . The radiating surface of the light emitting element  102  is the surface through which light is emitted. Not all surfaces of the light emitting element are radiating surfaces. In the example of  FIG. 1 , the radiating surface is above the dashed line  118 . 
     The reflecting element  104  includes a reflective surface (see  FIG. 3 ) facing the light emitting element  102 . Light rays  120  incident on the reflective surface of the reflecting element  104  are reflected towards the diffusing element  108 . Light rays  122  not incident on the reflective surface of the reflecting element  104  are already incident on the diffusing elements  108 . The reflective surface can include a coating, a foil, a paint, or the like. The reflective material of the reflecting element  104  can reflect greater than 90%, 95%, 99%, or a greater or lesser amount of some amount therebetween, of light at wavelengths above (and including) 700 nm. The reflective surface forms a reflective cavity that reflects the IR light from the light-emitting element  102 . The reflecting material of the reflective surface  104  can include aluminum, gold, silver, a combination thereof, or the like. 
     In example embodiments, the reflective element  104  includes a shape for guiding light incident on the reflecting surface (internal to the reflecting element  104 ) to the diffuser  108 . In example embodiments, the reflective element  104  includes a contoured outer surface formed of angled sidewalls  126 ,  128 . The angled sidewalls  126 ,  128  form different angles relative to the surface  114 . The sidewall  128  is closer to perpendicular to the surface  114  than the sidewall  126 . The different angles of the sidewalls  126 ,  128  help reflect light to the diffuser  108 . A light ray incident on the sidewall  126  at an angle, θ (relative to the surface  114 ), will have a smaller angle of reflection than a light ray incident on the sidewall  128  at the same angle, θ (relative to the surface  114 ). 
     The reflecting element  104  includes a parabolic connector shape  130  between legs thereof. A leg includes the sidewalls  126 ,  128  up to the surface  116 . A better view of three (of four total) legs is provided in  FIG. 2 . The leg can extend to about a top of a housing  132 . The leg can provide mechanical support to the diffuser  108  after the diffuser  108  is attached to the housing  132 . The connector shape  130 , in the example of  FIG. 1 , is parabolic with an opening in the parabola facing the diffuser  108  (away from the light emitting element  102 ). 
     Offsets  106  of the reflecting element  104  as illustrated in  FIG. 1  continue the surface  116 . The offsets can connect to the diffuser  108 . In example embodiments, the offsets  106  include a taper. In the example of  FIG. 1 , the taper of the offsets  106  is wider at the surface  116  (closer to the light emitting element  102 ) and narrower at the diffusing element  108 . The offsets  106  provide physical separation between the light emitting element  102  and the diffuser  106 . The offsets  106 , in the example of  FIG. 1 , include a surface that conforms with the parabolic connector  130 , such as to continue the parabolic shape of the connector shape  330  towards the diffuser  108 . The offsets  106  can include an internal reflective surface. 
     The diffuser  108  is a refractive diffuser. Light incident on the diffuser  108  refracts to a specified profile. In embodiments, the profile can include a uniform distribution, such as to uniformly intensity. For example, a single light ray striking the diffuser  108  can refract based on a specified pattern. 
     The diffuser  108  can include a microlens array. Each microlens acts as a “scattering center”. The individual design of each microlens allows for the arbitrary control of the size, shape, and profile of an optical distribution of the light emitted from the diffuser  108 . 
     The reflective surface can be substantially smooth, so as not to substantially scatter light that strikes the concave portion (at least compared with a roughened surface). In particular, it is intended that light striking the concave portion (relative to the diffuser  108 ) can refract at the surface of the concave portion, rather than scatter. For example, a single light ray striking the smooth surface of the concave portion can refract at the surface and exit the surface along a single direction, in accordance with the application of Snell&#39;s Law at the surface. In practice, and as previously discussed, contaminants and surface defects can cause a small amount of unintentional scattering, typically amounting to less than 1% of the optical power incident on the smooth surface. Such unintentional scattering can be neglected for the purposes of this detailed description, and any surface that supports specular (e.g., non-diffuse) reflection or refraction can be considered to be substantially smooth. 
     The light emitting element  102 , substrate  110 , reflective element  104 , and offsets  106  can be situated in a housing  132 . The housing  132  can help protect the lighting apparatus  100  from debris, external light, or other contamination. The housing  132  can be opaque, transparent, or translucent. A top of the housing  132  can be open. The top of the housing  132  is opposite a bottom surface  114  of the housing  132 . The housing  132  can have four sidewalls extending between the bottom surface  114  and the top. The diffuser  108  can be attached to the top of the housing  132 . A perimeter of the diffuser  108  can be about a same shape as a shape of a perimeter of the housing  132 . 
       FIG. 2  illustrates, by way of example, a rear-view diagram of the light emitting apparatus  100  of  FIG. 1  from the perspective indicated by arrows labelled “2” in  FIG. 1 . The light emitting element  102  is illustrated in dashed lines as it may not be in view depending on materials of an external surface  220  of the reflective element  104 . The external surface  220  is opposite an internal surface of the reflective element  104 . The external surface  220  is generally not struck by light emitted by the light emitting element  102 . 
       FIG. 3  illustrates, by way of example, a top view diagram of the light emitting apparatus  100  of  FIG. 1  from the perspective indicated by arrows labelled “3” in  FIG. 1 . The diffuser  108  is illustrated over the offsets  106  in dashed lines as the diffuser may be the only item in view in this perspective. The diffuser  108  includes a surface facing a reflective surface  330  of the reflective element  104 . The reflective surface  330  is opposite the external surface  220 . 
     With reference to both  FIG. 3  and  FIG. 4 , in example embodiments, the light emitting element  102  is inserted through an opening  444  in a collar  332  of the reflective element  132  (see  FIG. 4 ). In some such example embodiments, the substrate  110  is situated in a cutout  446  in the housing  132  (see  FIG. 4 ). A perimeter of the opening  444  can be within (completely within) a perimeter of the cutout  446 . In Examples, the light emitting element  102  can be friction fit into the opening  444  of the collar  332 . In other examples, the light emitting element  102  is secured to the substrate  110  and the substrate  110  is secured to the housing  132 , such as by a friction fit, adhesive, or the like. 
       FIG. 4  illustrates, by way of example, an exploded view diagram of a system  400  that include the light emitting apparatus  100  and a circuit board  440 . To form the light emitting apparatus  100 , the light emitting element  102  is pushed into the opening  444 , the substrate  110  is situated in the cutout in the housing  132 , and the diffuser  108  is attached (e.g., by an adhesive or clamp or the like) to the top  448  of the housing  132  (opposite the bottom  134 ). The light emitting element  102  can then be powered, such as through a power device (e.g., a battery, electrical outlet, or the like) electrically coupled to or on the circuit board  440 . The substrate  110  can be electrically coupled to the power device and provide power to the light emitting element  102 . The light emitting element  102  can then produce light that is (a) reflected from the reflective surface  330  to the diffuser  108  and (b) directly incident on the diffuser. The diffuser  108  receives the reflected light from the reflective element  104  and the directly incident light from the light emitting element  102 . The diffuser  108  shapes the light incident thereon about evenly. The combination of the reflective element  104  and the diffuser  108  essentially expands an active emitting area in all the viewing angles of the light emitting element  102  (from the perspective outside the diffuser looking towards the light emitting element  102 ). The luminance of the light emitting element  102  is thus uniformly reduced so that the red glow of the infrared light (e.g., near IR light) is angle invariant. 
       FIG. 5  illustrates, by way of example, a cross-section diagram of the diffuser  108  from the perspective indicated by arrows labelled “5” in  FIG. 4 . The diffuser  108 , in example embodiments, includes arcuate structures  550  configured to shape light incident thereon. The arcuate structures  550  can act as lenses, individually, but when overlapped (indicated by arrow  552 ) the arcuate structures  550  shape light. The arcuate structures  550  can be concave relative to the light emitting element  102 . The light reflected from the reflective element  104  and directly from the light emitting element  102  can be spread out by the arcuate structures  550 . Directly adjacent arcuate structures  550  can overlap each other by about one-third, one-fourth, half, more or less completely overlap, or some overlap therebetween (relative to an overall length of the arcuate structure  550  (indicated by arrow  554 )). 
       FIG. 6  illustrates, by way of example, plots of a radiance profile of the light emitting element  102  without the reflective element  104  and the diffuser  108  at different viewing angles.  FIG. 7  illustrates, by way of example, plots of a radiance profile of the light emitting element  102  with the reflective element  104  and the diffuser  108  at different viewing angles. As can be seen in  FIG. 7 , the radiated power of the light emitting element  102  from  FIG. 6  is spread significantly by the reflective element and the diffuser  108 . In examples, the radiated power is spread about uniformly, so as to make the reduction in radiated power angle invariant. Such a reduction in power allows an infrared light emitting element  102  to be present external to a vehicle without being perceived by the human eye. 
       FIG. 8  shows a flow chart of an example of a method  800  for forming a light-emitting apparatus, in accordance with some examples. The method  800  can be used to form any of the apparatuses of  FIGS. 1-7 , among other apparatuses. The method  800  is but one method for forming a light-emitting apparatus; other suitable methods can also be used. 
     At operation  802 , a diffuser is attached to a top of a housing that contains a reflective element therein. 
     At operation  804 , an infrared light-emitting diode is translated into a reflective cavity of the reflective element through an opening in a bottom surface of the housing, the bottom surface opposite the top of the housing. 
     At operation  806 , the infrared light-emitting diode is mounted on a circuit board. 
     The housing can include a cutout complementary to a perimeter of a substrate of the light-emitting diode. The reflective element can include an opening through which the infrared light-emitting diode is situated into the reflective cavity, the opening including a perimeter inside a perimeter of the cutout. 
     The method  800  can further include attaching an offset to the reflective element between the reflective element and the diffuser to provide distance between the reflective element and the diffuser. The reflective element can include first and second legs extending toward the diffuser. The reflective element can include a parabolic shape between the first and second legs. 
     The offset can include a first offset and the light-emitting apparatus further includes a second offset. The first and second offsets can include a perimeter that continues the parabolic shape. The reflective element and the diffuser combine to expand an emitting area of the infrared light-emitting diode to mitigate red glow perception of the infrared light in an angle-invariant manner. 
     To further illustrate the apparatus and related method disclosed herein, a non-limiting list of examples is provided below. Each of the following non-limiting examples can stand on its own or can be combined in any permutation or combination with any one or more of the other examples. 
     In Example 1, a light-emitting apparatus includes an infrared light-emitting diode extending into a reflective cavity and configured to emit infrared light into the reflective cavity, a reflective element including the reflective cavity configured to reflect the infrared light incident thereon away from the infrared light-emitting diode, and a diffuser to receive infrared light directly from the infrared light-emitting diode and from the reflective element, the diffuser configured to shape the received infrared light. 
     In Example 2, Example 1 further includes a housing around the infrared light-emitting diode and the reflective element, and wherein, the diffuser is attached to a top opening in the housing. 
     In Example 3, Example 2 further includes a circuit board having the infrared light-emitting diode and the housing mounted thereon. 
     In Example 4, at least one of Examples 2-3 further includes, wherein the housing includes a cutout complementary to a perimeter of a substrate of the infrared light-emitting diode. 
     In Example 5, Example 4 further includes, wherein the reflective element includes an opening through which the infrared light-emitting diode is situated into the reflective cavity, the opening including an opening perimeter inside a cutout perimeter of the cutout. 
     In Example 6, at least one of Examples 1-5 further includes an offset attached to the reflective element between the reflective element and the diffuser and providing distance between the reflective element and the diffuser. 
     In Example 7, Example 6 further includes, wherein the reflective element includes first and second legs extending toward the diffuser, and the reflective element includes a parabolic shape between the first and second legs. 
     In Example 8, Example 7 further includes, wherein the offset is a first offset and the light-emitting apparatus further includes a second offset, the first and second offsets including a perimeter that continues the parabolic shape. 
     In Example 9, Example 8 further includes, wherein the reflective element and the diffuser combine to expand an emitting area of the infrared light-emitting diode to mitigate red glow perception of the infrared light in an angle-invariant manner. 
     Example 10 includes a method for forming a light-emitting apparatus, the method comprising attaching a diffuser to a top of a housing that contains a reflective element therein, translating an infrared light-emitting diode into a reflective cavity of the reflective element through an opening in a bottom surface of the housing, the bottom surface opposite the top of the housing, and mounting the infrared light-emitting diode on a circuit board. 
     In Example 11, Example 10 further includes, wherein the housing includes a cutout complementary to a perimeter of a substrate of the light-emitting diode. 
     In Example 12, Example 11 further includes, wherein the reflective element includes an opening through which the infrared light-emitting diode is situated into the reflective cavity, the opening including a perimeter inside a perimeter of the cutout. 
     In Example 13, at least one of Examples 10-12 further includes attaching an offset to the reflective element between the reflective element and the diffuser to provide distance between the reflective element and the diffuser. 
     In Example 14, Example 13 further includes, wherein the reflective element includes first and second legs extending toward the diffuser, and the reflective element includes a parabolic shape between the first and second legs. 
     In Example 15, Example 14 further includes, wherein the offset is a first offset and the light-emitting apparatus further includes a second offset, the first and second offsets including a perimeter that continues the parabolic shape. 
     In Example 16, Example 15 further includes, wherein the reflective element and the diffuser combine to expand an emitting area of the infrared light-emitting diode to mitigate red glow perception of the infrared light in an angle-invariant manner. 
     Example 17 includes a light-emitting apparatus includes a reflective element including a reflective cavity configured to reflect infrared light incident thereon, the reflective element including first, second, third, and fourth legs extending toward a diffuser, and a parabolic shape between directly adjacent legs of the first, second, third, and fourth legs, an infrared light-emitting diode extending into the reflective cavity and configured to emit the infrared light into the reflective cavity, a housing around the infrared light-emitting diode and the reflective element, a diffuser attached to a top opening in the housing to receive infrared light directly from the infrared light-emitting diode and from the reflective element, the diffuser configured to shape the received infrared light, and first, second, third, and fourth offsets, in the housing, attached to the first, second, third, and fourth legs, respectively, the first, second, third, and fourth offsets situated between the reflective element and the diffuser to provide distance between the reflective element and the diffuser, the first, second, third, and fourth offsets including a perimeter that continues the parabolic shape. 
     In Example 18, Example 17 further includes a circuit board having the infrared light-emitting diode and the housing mounted thereon. 
     In Example 19, at least one of Examples 17-18 further includes, wherein the housing includes a cutout complementary to a perimeter of a substrate of the infrared light-emitting diode. 
     In Example 20, Example 19 further includes, wherein the reflective element includes an opening through which the infrared light-emitting diode is situated into the reflective cavity, the opening including a perimeter inside a perimeter of the cutout. 
     While example embodiments of the present disclosed subject matter have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art, upon reading and understanding the material provided herein, without departing from the disclosed subject matter. It should be understood that various alternatives to the embodiments of the disclosed subject matter described herein may be employed in practicing the various embodiments of the subject matter. It is intended that the following claims define the scope of the disclosed subject matter and that methods and structures within the scope of these claims and their equivalents be covered thereby.