Patent Publication Number: US-2022236381-A1

Title: Light emitting module combining enhanced safety features and thermal management

Description:
TECHNICAL FIELD OF THE DISCLOSURE 
     This disclosure relates to a compact optical module or light emitting package that combines efficient electrical connection routing and thermal management. 
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure relates to an optical module, which may form part of an electronic device such as a mobile phone. 
     An example of a known optical module  100  is illustrated in  FIG. 1 . The known optical module  100  may be referred to as a known light emitter package. The known optical module  100  comprises a printed circuit board  120  on which is mounted an emitter  130 , and a detector  150 . The emitter  130  is configured to emit electromagnetic radiation. A driver  140  that is separate to and located outside of the known optical module  100  is configured to control the emitter  130 . The driver  140  is connected to the emitter  130  by wiring  134 . The detector  150  is configured to detect electromagnetic radiation reflected from an optical assembly  160 , which includes a transmissive carrier  170  for an optical element  180 . Spacers  190  serve as lateral outer sidewalls of the known optical module  100  and define a separation distance between the printed circuit board  120  and the optical assembly  160 . 
     If the structure of the known optical module  100  becomes compromised (e.g., the transmissive carrier  170  cracks) then a user&#39;s eyes and skin may be at risk of being damaged by the electromagnetic radiation emitted by the emitter  130 . Another problem with the known optical module  100  is that inefficient electrical routing exists between different components (e.g. the driver  140  and the emitter  130 ). A further problem is that the known optical module  100  is not compact and may not be suitable for uses that require a more compact optical module (e.g. in a mobile electronic device, such as a mobile phone). The driver  140  is located outside the known optical module  100  at least partly to ease management of thermal energy produced by the components of the known optical module  100  during use. Overheating of components negatively affects a performance of the known optical module  100 . 
     It is therefore an aim of the present disclosure to provide an optical module that address one or more of the problems above, or at least provides a useful alternative. 
     SUMMARY 
     According to one aspect of the present disclosure, there is provided an optical module comprising an emitter configured to emit electromagnetic radiation, a first substrate configured to support the emitter, a driver configured to control the emitter, and a second substrate configured to support the driver. The first substrate has a greater thermal conductivity than the second substrate. 
     The first substrate may be configured to provide thermal management (e.g. thermal transport and/or dissipation) for the emitter. 
     The material(s) and/or the structure(s) of the first substrate may be selected to improve an ability of the first substrate to conduct thermal energy away from the emitter during use of the optical module. 
     The second substrate may be configured to house electrical connections to the driver. The second substrate and the electrical connections may be considered to be separate entities. The thermal conductivity of the second substrate may be different to and separate from the thermal conductivity of the electrical connections. That is, the thermal conductivity of the second substrate may not include the thermal conductivity of the electrical connections. 
     The material(s) and/or structure(s) of the second substrate may be selected to improve an ability of the second substrate to house electrical connections for the driver. 
     The second substrate may house a greater number of electrical connections than the first substrate. 
     The first substrate may have a greater surface area than the second substrate. 
     Providing different substrates for mounting different components of the optical module advantageously allows each substrate to be optimized for different requirements. The first and second substrates may be tailored for different functions that allow thermal management and electrical routing functions to be decoupled from one another. This enables improved management of each function compared to known optical modules. The optical module according to the invention houses the driver and the emitter in a compact arrangement without compromising thermal energy management or electrical routing. 
     The components of the optical module are contained within a single light emitter package. That is, the driver is integrated into the light emitter package along with the emitter and the first and second substrates. In other words, the optical module enclosure that houses the emitter also houses the driver, the first substrate and the second substrate. This is in contrast to some known optical modules that involve disposing the driver outside of the light emitting package. By locating the driver inside of the light emitting package, the optical module is advantageously more compact than known optical modules. 
     The emitter may comprise a plurality of emitting elements. The plurality of emitting elements may be arranged in an array. 
     The emitter may comprise a vertical cavity surface emitting laser (VCSEL). The VCSEL may be a high power VCSEL, e.g. having a continuous wave optical power output of about 3 W or more. 
     The emitter may comprise a light emitting diode (LED). 
     The emitter may be configured to emit infrared light. The infrared light may have a wavelength of about 850 nm or more. The infrared light may have a wavelength of about 1400 nm or less. 
     The emitter may be configured to emit visible light. 
     The driver may comprise an integrated circuit. 
     The driver may comprise an integrated circuit chip. 
     The driver may be configured to convert a power supply to a level appropriate for the emitter. For example, the driver may receive a power supply from an external power source, convert the power supply into a pulsed current and provide the pulsed current to the emitter. The driver may provide the emitter with a power of about 2 W or more. The driver may provide the emitter with a power of about 8 W or less. 
     The driver may be electrically coupled to the emitter by wiring that passes through the second substrate. The wiring may travel along the first substrate to the emitter. 
     The first substrate may comprise a ceramic. The ceramic may comprise AlN. The ceramic may comprise AlO2 
     The first substrate may comprise a metallic frame. The metallic frame may be referred to as a lead frame. The metallic frame may comprise an alloy. The alloy may comprise iron and nickel. The alloy may comprise about 42% nickel. The metallic frame may comprise copper. 
     The second substrate may comprise an electrically insulating material configured to house a plurality of electrical connections. The electrically insulating material may comprise FR4. 
     The first and second substrates may be arranged in a stacked arrangement. 
     The stacked arrangement advantageously reduces an overall size of a footprint of the optical module, thereby making the optical module more compact than known optical modules. That is, the optical module has a smaller area and/or volume than known optical modules. The stacked arrangement advantageously utilizes vertical space within the optical module that otherwise goes to waste in known optical modules. 
     The first and second substrates may have parallel and vertically offset axes in the stacked arrangement. The first and second substrates may be located in two parallel planes in the stacked arrangement. 
     The stacked arrangement provides at least some overlap between the first and second substrates. The first and second substrates may overlap each other along an optical axis of the optical module. That is, the first substrate may occupy a first plane that is orthogonal to the optical axis of the optical module, and the second substrate may occupy a different plane that is orthogonal to the optical axis of the optical module. The stacked arrangement may provide complete overlap between the first and second substrates. 
     The second substrate may comprise an opening to accommodate the emitter. 
     The optical module may comprise an optical assembly configured to modify an optical characteristic of the electromagnetic radiation. 
     The optical assembly may comprise a transmissive (e.g., glass) carrier for supporting an optical element. 
     The optical element may comprise an optical structure operable to modify the optical characteristic of the light emitted by the light emitter. 
     The optical element may comprise a micro-lens array (MLA). The optical element may comprise an optical diffuser. The optical element may comprise a lens. The optical element may comprise a refractive or diffractive optical element. The optical element may comprise a diffuser. The optical element may comprise a spectral filter. The optical element may comprise a polarizing filter 
     The optical assembly may comprise an electrically conductive structure electrically coupled to the driver. The driver may be configured to monitor an electrical characteristic of the electrically conductive structure. 
     The electrical characteristic may be a resistance of the electrically conductive structure. 
     The electrical characteristic may be a capacitance of the electrically conductive structure. 
     In the event such monitoring indicates the integrity of the optical module is (or may be) compromised, the driver can turn off or otherwise regulate the output of the emitter to ensure eye and skin safety of a user of the optical module. 
     The driver may be electrically coupled to the electrically conductive structure by wiring. 
     The driver may be configured to regulate an optical output of the emitter if the electrical characteristic of the electrically conductive structure changes by more than a pre-determined amount. 
     If the monitored characteristic is resistance, then the pre-determined amount may be an open circuit resistance. That is, the circuit may be broken when the optical module is structurally compromised, thereby creating an open circuit with an effectively infinite resistance. 
     If the monitored characteristic is capacitance, then the pre-determined amount may be a change of about ±50% of an operating capacitance of the electrically conductive structure. 
     The driver may be configured to stop the optical output of the emitter if the electrical characteristic of the electrically conductive structure changes by more than the pre-determined amount. 
     The electrically conductive structure and the emitter may be arranged such that the electromagnetic radiation is at least partially incident on the electrically conductive structure. The electrically conductive structure may be substantially transparent to the electromagnetic radiation. Substantially transparent may be defined as about 90% transmission or more. 
     The electrically conductive structure may comprise Indium Tin Oxide. 
     The optical path of the electromagnetic radiation may be referred to as an optical footprint. The electrically conductive structure may be located at least partially inside the optical path of the light emitted by the emitter. 
     The electrically conductive structure and the emitter may be arranged such that the electromagnetic radiation is not incident on the electrically conductive structure. The electrically conductive structure may be substantially opaque to the electromagnetic radiation. Substantially transparent may be defined as about 5% transmission or less. 
     The electrically conductive structure may be located outside of an optical path of the electromagnetic radiation. 
     The electrically conductive structure may comprise chrome. 
     The optical module may comprise a spacer configured to define a separation distance between the second substrate and the optical assembly. The spacer may comprise a plastic. The spacer may comprise a liquid crystal polymer plastic. 
     The optical module may comprise a detector. The second substrate may be configured to support the detector. 
     The detector may comprise a photodiode. 
     The detector may be configured to detect electromagnetic radiation that is reflected by the optical assembly. 
     The detector may be configured to detect electromagnetic radiation that has been emitted by the emitter, travelled out of the optical module, reflected from an object and travelled back into the optical module and onto the detector. The emitter and the detector may form part of a time-of-flight sensor. The optical module may comprise the time-of-flight sensor. 
     According to another aspect of the present disclosure, there is provided an electronic device comprising the optical module of any preceding aspect. 
     The electronic device may be portable. The electronic device may be a mobile phone. 
     It is particularly advantageous to utilize the optical module in a mobile device because mobile devices tend to be more compact than comparable non-mobile devices. As such, incorporating a compact optical module having improved electrical routing and improved thermal management provides a particularly advantageous solution for mobile devices. 
     The electronic device may be a telecommunications system. The electronic device may be a computing device such as a mobile phone or a tablet computer. The electronic device may be a medical device such as a diagnostics device. 
     According to another aspect of the present disclosure, there is provided a method of manufacturing an optical module comprising providing a first substrate, attaching an emitter to the first substrate, providing a second substrate having a thermal conductivity that is less than a thermal conductivity of the first substrate, and attaching a driver to the second substrate, the driver being configured to control the emitter. 
     The first substrate may comprise a ceramic. 
     The first substrate may comprise a metallic frame. 
     The second substrate may comprise an electrically insulating material configured to house a plurality of electrical connections. 
     The method may comprise arranging the first and second substrates in a stacked arrangement. 
     The method may comprise providing an opening in the second substrate and accommodating the emitter within the opening. 
     The method may comprise providing an optical assembly configured to modify an optical characteristic of electromagnetic radiation emitted by the emitter. 
     The method may comprise providing the optical assembly with an electrically conductive structure and electrically coupling the electrically conductive structure to the driver. 
    
    
     
       BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       Some embodiments of the disclosure will now be described by way of example only and with reference to the accompanying drawings, in which: 
         FIG. 1  schematically depicts a cross-sectional view of a known optical module; 
         FIG. 2  schematically depicts a cross-sectional view of an optical module according to an aspect of the present disclosure; 
         FIG. 3  schematically depicts an electronic device comprising the optical module of  FIG. 2 ; 
         FIG. 4  shows a flow chart of a method of manufacturing an optical module according to an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     New features are being added to smart phones, tablets and other portable computing devices that include technologies to record three dimensional images, sense motion and/or gestures. Digital recording methods use various types of miniature illuminators, which interact with cameras to record dynamical events in three-dimensional regions. These illuminators can be of various forms and deliver different types of functions. Some illuminate a wide area with very short pulses for Light Detection and Ranging (LIDAR) type measurements recording time of flight information and hence deriving three-dimensional scene information. Other illuminators are pulsed or continuous wave (CW), and project structured light patterns onto a scene. The digital camera records an image of the structured light pattern, and software algorithms are used to determine three-dimensional scene information from modifications in the patterned image. 
     One light emitting technology that is suitable for miniature illuminators is high power vertical cavity surface emitting laser (VCSEL) devices and array devices. These devices can be pulsed with very fast rise times suitable for time-of-flight applications. They are small, but produce high power laser beams with efficient electro-optic conversion. Various optical components (e.g., an optical diffuser) can be placed in the beam path to modify the beam properties for specific applications. 
     The optical output power of a bare VCSEL typically can, in some cases, be so high that it may cause damage to a user&#39;s eye or skin in the event the quality of the optical component is compromised. Thus, it is important to ensure that the high power laser illuminators meet laser safety regulations, particularly when operated in the portable computing devices. For example, the illuminator may be part of an assembly that, under normal operating conditions, maintains eye-safe operation by preventing a user from getting too close to the illuminator. However, in some cases, damage (e.g., cracks) to the optical structure that modifies the output beam for safe operation, and/or the presence of moisture or chemical contamination on the optical structure, may result in safety hazards. Likewise, if the optical structure were to fall off or be removed, a user&#39;s safety could be compromised. 
     To facilitate detecting mechanical defects (e.g., a crack) or the presence of moisture in an optical package, an electrically conductive structure (e.g., an electrically conductive trace) can be provided on a surface of a transmissive cover (e.g., a glass substrate) disposed over the emitter. In some cases, the electrically conductive structure is composed of a material (e.g., indium tin oxide (ITO)) that is substantially transparent to the wavelength of light produced by the emitter (e.g., infra-red). Such electrically conductive structures thus can at least partially overlap a footprint of an optical beam emitted by the emitter. On the other hand, in some instances, the electrically conductive structure is composed of a material (e.g., chrome) that is substantially opaque to the wavelength of light produced by the emitter. In such cases, the electrically conductive structure preferably does not overlap a footprint of an optical beam emitted by the emitter. 
     The electrically conductive structure can be coupled electrically to a controller (e.g., a driver for the emitter) that is operable to monitor an electrical characteristic (e.g., resistance or capacitance) of the electrically conductive structure such that if the monitored characteristic changes by more than a predetermined amount, the controller regulates an optical output produced by the emitter. In some implementations, the controller is operable to monitor the electrical characteristic of the electrically conductive structure such that if the monitored characteristic changes by more than a respective predetermined amount, the controller causes the optical output produced by the emitter to be stopped. For example, the driver can turn off the VCSEL so that it no longer emits light. 
     If the driver is disposed outside the light emitter package (as is the case with the known optical module  100  of  FIG. 1 ), then the package can be tailored for thermal management and electrical contacts of the VCSEL or other emitter. However, for some applications, it is desirable to integrate the driver into the package. In such cases, a greater number of functions and more electrical routing must be managed within the package. 
     The present disclosure describes an approach for providing on-board eye-safety features, making the package more compact and improving electrical routing while maintaining thermal management of the VCSEL or other emitter. Thus, the present disclosure describes techniques for helping optimize thermal transport and dissipation, as well as electrical routing. 
     The present disclosure describes an optical module, illuminator or other light emitting package that includes a plurality of substrates, each of which can be optimized for different requirements. The plurality of substrates may be arranged in a stacked arrangement to reduce a width and/or length of the optical module. In particular, a first substrate in the stack can be optimized to provide good thermal management for the VCSEL or other emitter (e.g. a light emitting diode (LED)). A second substrate in the stack may be configured to house a high density routing of electrical connections (e.g. to provide electrical connections between the driver and the emitter and/or an electrically conductive structure). In this manner, the electrical routing and thermal management functions can be decoupled from one another. Further, by stacking the substrates one over the other, a relatively small overall footprint for the package (e.g. an area of the optical module) can be obtained. 
     As shown in  FIG. 2 , an optical module  200  includes a first substrate  212  (e.g., a lead frame (i.e. a metallic frame) or ceramic substrate) on which is mounted an emitter  214  (e.g., a VCSEL or LED). A second substrate  216  (e.g., an electrically insulating material, such as FR4) is stacked over the first substrate  212 . The second substrate  216  comprises an opening  218  to accommodate the emitter  214  in a stacked arrangement thereby advantageously reducing a size of the optical module  200 . 
     A driver  220  and a detector  222  (e.g., photodiode) are mounted on the second substrate  216 . The second substrate  216  may house a plurality of electrical connections  238 , 236 . The plurality of electrical connections may comprise multiple embedded layers of Copper routing (not shown). 
     The driver  220  may be referred to as a processor. The driver  220 , which can be implemented for example, as an integrated circuit (IC) chip, is configured to convert an external power supply (not shown) to a level appropriate for the VCSEL or other emitter  214 . For example, the driver  220  may be configured to receive an input voltage and convert the input voltage to a laser pulse train for controlling the VCSEL or other emitter  214 . 
     The detector  222  may be used, for example, to detect back reflectance from an optical assembly  224 . The optical assembly  224  may include a transmissive (e.g., glass) carrier  226  for supporting an optical element  228 . The optical element  228  may comprise, for example, a micro-lens array (MLA), an optical diffuser, a lens, a refractive or diffractive optical element, a diffuser, a spectral filter, a polarizing filter, and/or some other optical structure operable to modify the optical characteristics of the light emitted by the emitter  214  (e.g. a VCSEL output beam). 
     In the example of  FIG. 2 , the glass carrier  226  supports an electrically conductive structure  230  on the surface facing the VCSEL  214 . In some embodiments, there may be an electrically conductive structure on the outward-facing surface of the glass carrier  226  in addition to, or instead of, the electrically conductive structure  230 . The electrically conductive structure  230  may comprise, for example, an Indium Tin Oxide (ITO) trace. 
     In the example of  FIG. 2 , spacers  232  serve as lateral outer sidewalls of the optical module  210 . The spacers  232  may define a separation distance between the second substrate  216  and the optical assembly  224 . The separation distance may be selected in at least partial dependence on a divergence of the electromagnetic radiation emitted by the emitter  214  and/or a desired illumination (e.g. substantially uniform illumination) of the optical element  228 . The separation distance may be about 0.5 mm or more. The separation distance may be about 1.0 mm or less. The spacers  232  may comprise, for example, a liquid crystal polymer (LCP) plastic  232 . 
     The electrically conductive structure  230  is electrically coupled (e.g. by wiring  234 ) to the driver  220 . The driver  220  is electrically coupled (e.g. by vias  236  (i.e. a metallic connection) and circuitry (not shown) in the printed circuit board  212 ) to the emitter  214 . The driver  220  thus is operable to monitor a characteristic (e.g., a resistance and/or a capacitance) of the electrically conductive structure  230 . In the event such monitoring indicates the integrity of the optical assembly  224  is (or may be) compromised (e.g., because of a crack in the transmissive carrier  226 ), the driver  220  can turn off or otherwise regulate an optical output of the emitter  214 . This feature advantageously provides greater safety for a user because if the optical module  200  becomes compromised, the driver  220  can prevent the emitter  214  from emitting stray electromagnetic radiation that may otherwise damage a user&#39;s eyes and/or skin. 
     The specific material and structure of the first substrate  212 , on which is mounted the light emitting  214 , can be selected for thermal management (e.g., thermal transport and dissipation). On the other hand, the specific material and structure of the second substrate  216  can be selected for routing electrical connections for the driver  220 , the detector  222 , and/or other components (not shown) that may be mounted on the second substrate  216 . 
     As explained above, providing different substrates  212 ,  216  for mounting the various components of the optical module  200  allows each substrate  212 ,  216  to be optimized for different requirements. Stacking the substrates  212 ,  216  one over the other can help reduce the overall footprint (e.g. area) of the optical module  200 , thereby allowing the optical module  200  to be incorporated into smaller devices (e.g. a mobile phone). 
     The emitter  214  generates thermal energy when in use. The emitter  214  may become damaged, less efficient or non-operational if the emitter  214  becomes too hot. For example, a conversion efficiency of the emitter  214  (i.e. the energy supplied to the emitter  214  compared to the energy of electromagnetic radiation emitted by the emitter  214 ) may decrease as the temperature of the emitter  214  increases. The first substrate  212  is configured to conduct the thermal energy away from the emitter  214 . That is, the first substrate  212  acts as a heat sink for the thermal energy generated by the emitter  214 . The first substrate  212  thereby assists in preventing the emitter  214  from becoming too hot, which in turn improves an efficiency of the emitter  214  and reduces the risk of the emitter  214  becoming damaged. 
     The driver  220  is located inside the optical module  200  and is electrically connected to a plurality of components, including the emitter  214  and the electrically conductive structure  230 . The driver  220  may require a plurality of logic connections and/or multiple embedded layers of electrical routing (e.g., Copper routing) to communicate with other components of the optical module  200  and/or components of an electronic device (not shown) into which the optical module  200  is incorporated. The driver  220  includes a relatively large number (or high density) of ingoing and outgoing electrical connections (e.g. wiring  234  and/or vias  236 ). The second substrate  216  is configured to house the high density of electrical connections associated with the driver  220 . In addition, the second substrate  216  may support other components (such as the detector  222 ) which includes further electrical connections to other components (e.g., an external power supply (not shown) and/or an external processor (not shown)). The detector  222  may be electrically connected to the driver  220  through electrical connections (e.g. via  238 ) that run through the second substrate  216   
     The first substrate  212  and the second substrate  216  differ from each other in order to perform their separate functions of thermal management and high-density electrical routing. The first substrate  212  has a greater thermal conductivity than the second substrate  216 . For example, the first substrate  212  may comprise a ceramic, such as AlN or AlO2, whereas the second substrate  216  may comprise an electrically insulating material, such as FR4, having a lower thermal conductivity than the ceramic. The first substrate  212  may comprise a metallic frame, which may be referred to as a lead frame. The metallic frame may comprise an alloy comprising iron and nickel. The alloy may comprise about 42% nickel. 
     The second substrate  216  may house a plurality of electronic connections (e.g. power supplies, vias, logic connections, multiple embedded layers of Copper routing, etc.) that are used to operate the driver  220 . The second substrate  216  is better suited to housing high densities of electrical connections compared to the first substrate  212 . For example, the second substrate  216  may be configured to house a plurality of layers of electrical routing (e.g. between two and twelve embedded Copper layers). The first substrate  212  may be configured to support a single electrically conductive path on a surface of the ceramic to electrically connect the emitter  214  to the driver  220 . For example, the electrically conductive path may connect to a via  236  of the driver  220  that travels through the second substrate  216 . 
     The driver  220  generates thermal energy when in use. The driver  220  may become damaged, less efficient or non-operational if the driver  220  becomes too hot. The second substrate  216  may house a thermally conductive path  240  (e.g., a metallic connection, such as a via) that travels from the driver  220  to the first substrate  212 . Heat energy generated by the driver  220  is transported away from the driver  220  and towards the first substrate  212  by the thermally conductive path  240 . The thermally conductive path  240  and the first substrate  212  may therefore act as a heat sink for the driver  220 . The thermally conductive path  240  and the first substrate  212  thereby assist in preventing the driver  220  from becoming too hot, which in turn improves an efficiency of the driver  220  and reduces the risk of the driver  220  becoming damaged. 
     Stacked arrangements are avoided in known optical modules (e.g. the known optical module  100  of  FIG. 1 ) because stacked arrangements effectively form layers of thermal insulation that contribute to components of the optical module (e.g. the emitter) overheating. However, referring again to  FIG. 2 , separating the functions of the first and second substrates  212 ,  216  allows the substrates  212 ,  216  to be arranged in a stacked arrangement without causing overheating of the components of the optical module  200 . This advantageously reduces an area or footprint of the optical module  200  compared to known optical modules, thereby allowing the optical module  200  to be incorporated into smaller devices (e.g. mobile phones) compared to known optical modules. The second substrate  216  may be attached to the first substrate  212  by bonding and/or soldering pads  245 . The first substrate  212  may be attached to another substrate or structure (not shown) by bonding and/or soldering pads  247 . For example, the first substrate  212  may be attached to a printed circuit board of a mobile phone (not shown). 
     The optical module  200  may have a length of about 3.0 mm or more. The optical module  200  may have a length of about 6.0 mm or less. The optical module  200  may have a width of about 2.0 mm or more. The optical module  200  may have a width of about 4.5 mm or less. The optical module  200  may have a height of about 1.0 mm or more. The optical module  200  may have a height of about 4.0 mm or less. 
       FIG. 3  schematically depicts an electronic device  300  comprising the optical module  200  of  FIG. 2 . In the example of  FIG. 3 , the electronic  300  device is a mobile phone. The optical module  200  may be configured to act as a miniature illuminator for the mobile phone  300 . The optical module  200  may be configured to, for example, illuminate a wide area with very short pulses for Light Detection and Ranging (LIDAR) type measurements recording time of flight information. Alternatively, the optical module  200  may be configured to project a structured light pattern onto a scene, and a digital camera  310  of the electronic device  300  may be configured to record an image of the structured light pattern. Software algorithms stored in the electronic device  300  may then be used to determine three-dimensional scene information from modifications in the patterned image, e.g. three dimensional images, sense motion and/or gestures. 
     The optical module  200  may be incorporated into other kinds of electronic devices. For example, the optical module  200  may be incorporated into a telecommunications system, a tablet computer, a medical device such as a diagnostics device, etc. 
       FIG. 4  shows a flow chart of a method of manufacturing an optical module. A first step  410  of the method comprises providing a first substrate. The first substrate may comprise a ceramic or a metallic frame. 
     A second step  420  comprises attaching an emitter to the first substrate. The second step  420  may comprise soldering the emitter to the first substrate. 
     A third step  430  comprises providing a second substrate having a thermal conductivity that is less than a thermal conductivity of the first substrate. The second substrate may comprise an electrically insulating material, such as FR4, configured to house a plurality of electrical connections (e.g. multiple embedded layers of Copper). 
     A fourth step  440  comprises attaching a driver to the second substrate. The driver is configured to control the emitter. The fourth step  440  may comprise soldering the driver to the second substrate. 
     An optional fifth step  450  comprises attaching a detector to the second substrate. The detector may be configured to detect back reflectance within the optical module. The optional fifth step  450  may comprise soldering the detector to the second substrate. 
     An optional sixth step  460  comprises attaching the second substrate to the first substrate. The optional sixth step  460  may comprise forming an electrical connection and/or a thermal connection between the first substrate and the second substrate. The optional sixth step  460  may comprise gluing the second substrate to the first substrate. The glue may comprise electrically conductive glue. The optional sixth step  460  may comprise soldering the second substrate to the first substrate. 
     An optional seventh step  470  comprises attaching a spacer to the second substrate. The spacer may comprise wiring. The optional seventh step  470  may comprise forming an electrical connection between the driver and the wiring on the spacer. The optional seventh step  470  may comprise gluing the spacer to the second substrate. The glue may comprise electrically conductive glue. The optional seventh step  470  may comprise soldering the wiring of the spacer to the driver. 
     An optional eighth step  480  comprises attaching an optical assembly to the spacer. The optical assembly may comprise an electrically conductive structure. The optional eighth step  480  may comprise forming an electrical connection between the electrically conductive structure of the optical assembly and the wiring on the spacer. The optional eight step may form an electrically conductive path between the electrically conductive structure and the driver. The optional eighth step  480  may comprise gluing the optical assembly to the spacer. The glue may comprise electrically conductive glue. The optional eighth step  480  may comprise soldering the electrically conductive structure of the optical assembly to the wiring of the spacer. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               100  known optical module 
               120  printed circuit board 
               130  emitter 
               134  wiring 
               140  driver 
               150  detector 
               160  optical assembly 
               170  transmissive carrier 
               180  optical element 
               190  spacers 
               200  optical module 
               212  first substrate 
               214  emitter 
               216  second substrate 
               218  opening 
               220  driver 
               222  detector 
               224  optical assembly 
               226  transmissive carrier 
               228  optical element 
               230  electrically conductive structure 
               232  spacers 
               234  wiring 
               236  driver via 
               238  detector via 
               240  thermally conductive path 
               245  second substrate soldering pads 
               247  first substrate soldering pads 
               300  electronic device 
               310  camera 
               410  first step 
               420  second step 
               430  third step 
               440  fourth step 
               450  optional fifth step 
               460  optional sixth step 
               470  optional seventh step 
               480  optional eighth step 
           
         
       
    
     The skilled person will understand that in the preceding description and appended claims, positional terms such as ‘above’, ‘along’, ‘side’, etc. are made with reference to conceptual illustrations, such as those shown in the appended drawings. These terms are used for ease of reference but are not intended to be of limiting nature. These terms are therefore to be understood as referring to an object when in an orientation as shown in the accompanying drawings. 
     Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure that are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in any embodiments, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.