Micro-lens arrays are arrays of small lenses that can be used in conjunction with light emitters, such as semiconductor-based light emitters, to form compact imaging devices. Compact imaging devices are used in vehicles, e.g., autonomous vehicles, and in mobile computing devices, such as mobile phones.
In an aspect, a system includes a first light source; an optical element disposed on a face of a transparent substrate. The optical element is positioned to receive light from the first light source. The transparent substrate has edges that are beveled relative to the first face of the transparent substrate. The system includes a second light source positioned to illuminate the face of the transparent substrate at a position aligned with a first one of the beveled edges of the transparent substrate. The system includes a light detector positioned to receive light reflected from a second one of the beveled edges of the transparent substrate.
Embodiments can include one or more of the following features.
An angle of the beveled edges is sufficient to enable total internal reflection within the transparent substrate of at least some of the light from the second light source.
An angle of the beveled edges is between about 30° and about 60° relative to the face of the transparent substrate.
The system includes a controller configured to control operation of the first light source. The controller is configured to control operation of the first light source based on an intensity of the light received by the light detector. The controller is configured to prevent operation of the first light source when the intensity of the received light exceeds a threshold intensity. The intensity of the received light exceeds the threshold intensity when the optical element is damaged or absent. The controller is configured to enable operation of the first light source when the intensity of the received light is below a threshold intensity. The intensity of the received light is below the threshold intensity when the optical element is intact.
The first face of the transparent substrate faces the first light source, the second light source, and the light detector.
The first light source, the second light source, and the light detector are disposed on a common substrate. The first light source, the second light source, and the light detector are disposed on a printed circuit board (PCB) substrate.
The first light source includes an array of first light sources. The optical element includes a micro-lens array (MLA).
The first light source includes a VCSEL.
The transparent substrate includes a glass substrate.
The system includes a shield layer disposed on a second face of the transparent substrate.
The system includes a filter configured to transmit light of a wavelength emitted by the first light source and to prevent transmission of light of a wavelength emitted by the second light source.
In an aspect, a vehicle includes a system having any one or more of the foregoing features.
In an aspect, a mobile computing device includes a system having any one or more of the foregoing features.
In an aspect, a method includes illuminating a position on a face of a transparent substrate with light from a second light source, the illuminated position being aligned with a first beveled edge of the transparent substrate, in which an optical element is disposed on the face of the transparent substrate; by a light detector, detecting light reflected from a second beveled edge of the transparent substrate; and controlling operation of a first light source based on an intensity of the detected light, the first light source being positioned to illuminate the optical element disposed on the face of the transparent substrate.
Embodiments can include one or more of the following features.
A condition of the optical element disposed on the first face of the transparent substrate affects the intensity of the detected light. When the optical element is damaged, the intensity of the detected light exceeds a threshold intensity. When the optical element is intact, the intensity of the detected light is below a threshold intensity.
Detecting light reflected from the second beveled edge of the transparent substrate includes detecting light from the second light source that is subject to total internal reflection within the transparent substrate.
Controlling operation of the first light source includes preventing operation of the first light source when the intensity of the detected light exceeds a threshold intensity.
Controlling operation of the first light source includes controlling the first light source to illuminate the optical element when the intensity of the detected light is below a threshold intensity.
In an aspect, a system includes a first light source; an optical element disposed on a face of a transparent substrate. The optical element is positioned to receive light from the first light source. The optical element includes a transmissive grating with a groove pitch sufficient to enable total internal reflection within the transparent substrate. The system includes a second light source positioned to illuminate a first side of the optical element on the transparent substrate; and a light detector positioned to receive light from a second side of the optical element.
In an embodiment, a pitch of the transmissive grating is sufficient to enable total internal reflection within the transparent substrate of at least some of the light from the second light source.
The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.
We describe here safety features for a light source system. A first light source of the light source system emits light that is incident on an optical element, such as a microlens array. The light emitted by the first light source can be light of a wavelength or intensity that is potentially dangerous, e.g., to human eyesight. Damage to or absence of the optical element can sometimes all light from the first light source to be emitted to an exterior of the light source system, e.g., reaching the eye of a user. To mitigate the risk of light reaching an exterior of the light source system, the light source system includes a second light source and a photodetector that are arranged such that the intensity of light received by the photodetector is indicative of whether the optical element is intact. When the intensity of light received by the photodetector indicates that the optical element is not intact, e.g., damaged or absent, the operation of the first light source can be halted to reduce the risk of light escaping to an exterior of the light source system.
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An optical element 104 is disposed on a first face 106 of a transparent substrate 108, such as a glass substrate, and positioned to receive light 140 from the first light source 102. The transparent substrate 108 is sufficiently transparent such that at least some light of the wavelength emitted by the light source 102 is transmitted through the transparent substrate. The transparent substrate 108 forms one wall of the housing 101, with the first face 106 of the transparent substrate 108 facing an interior 103 of the housing 101. The optical element 104 is an element that can diffract, diffuse, or otherwise affect the light emitted by the light source 102, such that the light is coupled out of the housing 101. For instance, the optical element 104 can be one or more lenses, such as a microlens array (MLA).
The edges 110a, 110b of the transparent substrate 108 are beveled relative to the first face 106 of the transparent substrate 108. For instance, the edges 110a, 110b can be disposed at an angle of between about 30° and about 60°, e.g., about 30°, about 35°,about 40°, about 45°, about 50°, about 55°, or about 60°, relative to the plane of the first face 106. The angle of the beveled edges 110a, 110b is sufficient to enable total internal reflection into the transparent substrate 108 of at least some light incident on the beveled edges. In some examples, the transparent substrate 108 can have only a single edge, e.g., when the transparent substrate 108 is round or oval-shaped, and different regions of the single edge are referred to as the edges 110a, 110b.
A second light source 112 is disposed in the interior 103 of the housing 101 such that the second light source 112 faces the first face 106 of the transparent substrate 108. The second light source 112 can be, e.g., a VCSEL, a laser, a laser diode, a light emitting diode, or another suitable light source. The second light source 112 is positioned to emit light 152 that is incident on the first face 106 of the transparent substrate at a position 114 aligned with the beveled edge 110a. In the example of
A light detector 116, such as one or more photodiodes, such as an array of photodiodes, is disposed in the interior 103 of the housing 101 and facing the first face 106 of the transparent substrate 108. The light detector 116 is positioned to receive light 154, if any, that is reflected downwards by the beveled edge 110b of the transparent substrate 108. In the example of
Signals indicative of light detected by the light detector 116 are sent to a controller 118. The controller 118 can control operation of the first light source 102 based at least in part on the signals from the light detector 116.
A shield layer 120 is disposed on portions of a second face 122 of the transparent substrate 108, such as on portions that are not aligned with the optical element 104 or on portions that are aligned with the second light source 112. The shield layer 120 is formed of a material that is not transparent to light of the wavelength emitted by the second light source 112. A filter (not shown) can be disposed outside of the housing and facing the second face 122 of the transparent substrate 108. The filter can be, e.g., a notch filter, a band pass filter, or another type of filter that is configured to transmit light of the wavelength emitted by the first light source 102 and to prevent transmission of light of the wavelength emitted by the second light source 112. In some examples, the light source system 100 includes only one of the shield layer 120 and the filter. For instance, when the first and second light sources 102, 112 emit light of the same wavelength, the light source system 100 may not include a filter. In some examples, the light source system 100 includes both the shield layer 120 and the filter.
The light emitted by the first light source 102 can be light of a wavelength or intensity that that is potentially dangerous, e.g., to human eyesight. Damage to or absence of the optical element 104 can sometimes allow light from the light source 102 to be emitted to an exterior of the light source system 100, e.g., reaching the eye of a user. The second light source 112 and the light detector 116 provide safety functionality to the light source system 100. When a signal from the light detector 116 indicates that the optical element 104 may not be intact, e.g., may be damaged or absent, the operation of the first light source 102 can be halted, thereby mitigating the risk of emission of light from the light source 102 to the exterior of the light source system.
More particularly, when the optical element 104 is intact (e.g., present and undamaged), light from the second light source 112 is coupled out of the housing by the optical element 104, and little to no light reaches the light detector 116. When the optical element 104 is not intact (e.g., absent or damaged), at least some of the light from the second light source 112 reaches the light detector 116. Detection of light by the light detector 116 can thus be a proxy for the state of the optical element 104. For instance, an intensity of light detected by the light detector 116 exceeding a threshold can be an indication that the optical element 104 is not intact, and the controller 118 can stop operation of the first light source 102 to prevent or mitigate potential damage that could arise due to a not intact optical element 104.
When the light in the interior of the transparent substrate 108 reaches the opposite beveled edge 110b of the transparent substrate 108, the beveled edge 110b reflects light 154 downward, e.g., back into the interior of the housing 101. The light reflected back into the interior of the housing by the beveled edge 110b is sometimes referred to as returned light 154. The returned light 154 is incident on the light detector 116.
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A signal indicative of the intensity of the light detected by the light detector 116 can be provided to the controller. When the intensity of the detected light exceeds a threshold, the controller can stop operation of the first light source 102 or can prevent the first light source 102 from initiating operation. The threshold can be high enough to account for noise, e.g., for stray light reflected within the interior of the housing 101 but low enough to recognize that any light beyond a background level of noise has arrived at the light detector 116 because of an optical element 104 that is not intact. The threshold can be set to provide a margin of safety, e.g., such that any intensity of light detected beyond a background level of noise exceeds the threshold.
Simulations of the distribution of light intensity in the light source system 100 were performed for various configurations of the optical element 104, such as various configurations of damage to the optical element 104.
In simulations of the distribution of the light intensity for each of the example configurations of
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Light reflected from a second beveled edge of the transparent substrate is detected by a light detector (902). When the optical element is intact, little to no light reaches the light detector, because light from the second light source is coupled out of the housing of the light source system by the optical element. However, when the optical element is not intact, light propagates through the interior of the transparent substrate and is reflected by the second beveled edge of the transparent substrate onto the light detector.
Operation of a first light source is controlled based on an intensity of the detected light (904). The first light source is positioned to illuminate the optical element disposed on the first face of the transparent substrate. When the intensity of the detected light exceeds a threshold, e.g., a threshold indicative that the optical element is not intact, operation of the first light source can be stopped, or prevented from initiating. This control of the operation of the first light source helps to mitigate the risk of potentially dangerous light escaping the light source system, e.g., because of an optical element that is not intact.
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Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.
Number | Date | Country | Kind |
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2108327.4 | Jun 2021 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/SG2021/050336 | 6/11/2021 | WO |