This disclosure relates to compact optoelectronic modules.
Various consumer electronic products and other devices include a packaged light emitter or detector modules designed for precision light projection or detection applications. The spatial dimensions of such modules are generally extremely small, thereby enabling their incorporation into portable devices. One technology that is suitable for miniature illuminators is high power vertical cavity surface emitting laser (VCSEL) devices and array devices.
The optical output power of a bare VCSEL typically can, in some cases, be so high that it may cause damage to a person'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 when in operation. For example, the illuminator may be part of an assembly that, under normal operating conditions, maintains eye-safe operation by preventing a person 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, 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, safety could be compromised.
It is therefore an aim of the present disclosure to provide an optoelectronic module that addresses one or more of the problems described above or at least provides a useful alternative.
The above problems is sought to be overcome by enabling detection of damage or the presence of moisture or chemical contamination on the optical structure. The arrangement does so without compromising the optical performance of the module and enabling straightforward manufacture.
According to an embodiment there is provided an optical assembly, the optical assembly comprising an interdigital capacitor, one or more electrical contacts in electrical connection with the interdigital capacitor and an insulating layer covering at least a portion of the interdigital capacitor. The one or more electrical contacts and a portion of the insulating layer are configured to receive conductive adhesive. The optical assembly further comprises a metallic layer positioned between the interdigital capacitor and the portion of the insulating layer configured to receive the conductive adhesive.
In one embodiment the optical assembly further comprises circuitry configured to detect a change in capacitance of the interdigital capacitor.
In one embodiment the interdigital capacitor comprises indium titanium oxide.
In one embodiment the metallic layer is transparent.
In one embodiment the metallic layer comprises indium titanium oxide.
In one embodiment the metallic layer is embedded in the insulating layer.
In one embodiment the metallic layer is electrically floating, i.e. no specific potential is applied to the metallic layer by circuitry and instead the potential of the metallic layer is allowed to fluctuate or ‘float’ under the influence of the electric fields the metallic layer is exposed to.
In one embodiment the metallic layer is adjacent to one or more edges of the optical assembly.
In one embodiment the conductive adhesive comprises a layer of conductive adhesive with a first dimension in a plane parallel to the first surface of the optical assembly ranging from 100 μm to 600 μm.
According to another embodiment there is provided an optical module comprising an optical assembly, the optical assembly comprising a interdigital capacitor, one or more electrical contacts in electrical connection with the interdigital capacitor, an insulating layer covering at least a portion of the interdigital capacitor, circuitry operable to detect a change in capacitance of the interdigital capacitor and conductive adhesive disposed on at least a portion of the one or more electrical contacts and a portion of the insulating layer and configured to maintain the circuitry and one or more electrical contacts in electrical connection. The optical assembly further comprises a metallic layer positioned between the interdigital capacitor and the portion of the insulating layer on which the conductive adhesive is disposed.
In one embodiment the optical module further comprises circuitry configured to detect a change in capacitance of the interdigital capacitor.
Finally, the present optical assembly disclosed herein utilises a novel approach in that a metal shielding layer is provided to shield a conductive trace for detecting changes in the optical assembly from the effect of conductive adhesive on its capacitance.
Some embodiments of the disclosure will now be described by way of example only and with reference to the accompanying drawings, in which:
Generally speaking, the disclosure provides an optoelectronic module solution which provides high sensitivity to damage to the optical component without compromising optical performance.
Some examples of the solution are given in the accompanying figures.
An optoelectronic module 101 comprising a light emitting element and eye-safety capability according to an embodiment is shown in
The VCSEL 107 is electrically connected to leadframe 109 via which power is supplied to the VSCEL 107. In an embodiment, power to the VCSEL 107 may be controlled by a current driver controller or other electronic control unit (ECU) (not shown). The controller can reside, for example, in a host device (e.g., smartphone) into which the module 101 is integrated.
In the discussion below it is assumed that the optical component 105 is a micro lens array (MLA). However, other optical assemblies such as 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 output beam of the light source, which is incident on the optical assembly may be employed in place of the MLA according to embodiments.
The glass 103 is held in position above the VCSEL 107 by a spacer 111 according to an embodiment. The spacer has a cavity 113 in which the VCSEL 107 is mounted. The spacer 111 can be composed, for example, of an electrically insulating material, such as a molded epoxy (e.g., a liquid crystal polymer-based material). In the embodiment of
In this embodiment, the MLA 105 is positioned on the inner surface 117 of the glass 103, facing the VCSEL 107. In other embodiments, the MLA 105 may be positioned on the outer surface of the glass 103.
An electrically conductive trace 119 is disposed on the surface of the glass 103, including over the portion of the glass comprising the MLA 105. This is shown more clearly in
The trace 117 is electrically connected to electrical contacts 201 on the surface 117 of the glass 103. The electrical contacts may comprise conductive pads composed of gold or silver or another suitable conducting material. In some instances, the trace 117 is covered with an insulating layer 301. In an embodiment the insulating layer may comprise SiO2 or another suitable insulating material. If an insulating layer is employed, openings in the insulating material are provided for the electrical contacts 201.
The module 101 comprises electrically conductive leads 121 which extend from the socket 115 of the spacer 111 and down to the leadframe 109. In other embodiments, leads may be integrated into the walls of the spacer 111 or otherwise arranged to provide an electrical connection from the portion of the spacer on which the glass 103 is mounted to the leadframe 109. In an embodiment, the trace 119 is electrically connected to the leads 121 via contacts 201 with conductive adhesive 123. In an embodiment, the conductive adhesive 123 is silver epoxy. In other embodiments, another suitable conductive adhesive may be employed. Thus, the trace 119 is connected to the leadframe 109 via contacts 201, conductive adhesive 123 and leads 121.
In an embodiment, the conductive adhesive is deposited on top of the insulating layer of the glass 103 as a strip running down the side of the MLA glass and interfacing with electrical contacts 201. This is shown in
This mechanical adhesion via the conductive adhesive 123 may be provided instead of, or in addition to use of another adhesive with only mechanical properties within the package. In other embodiments, the conductive adhesive may take other suitable forms, such as a dot or partial strip. The form and position of the conductive adhesive 123 may be selected according to the design of the spacer or positioning of the leads 121 and/or electrical contacts 201 according to embodiments.
In an embodiment, the strip of conductive glue on one side of the glass 3 is connected to one of the capacitor terminals 401 and assigned 1V potential via the leads 121. The second strip of conductive glue 407 on the opposite side of the glass is connected to the other terminal 405 in the trace 119 and connected to ground as shown in
In the embodiment of
In an embodiment, the electrically conductive trace 119 forms part of an electrical circuit that is coupled to a current driver controller or other electronic control unit (ECU) which controls power to the VCSEL 107, as discussed above. In this embodiment, the controller is operable to monitor an electrical characteristic (e.g., electrical continuity; or capacitance, as appropriate) of the trace 119 such that if the monitored characteristic changes by more than a predetermined amount, the controller regulates the optical output of the VCSEL or other light source according to embodiments. In an embodiment, the controller is operable to monitor the electrical characteristic of the trace such that if the monitored characteristic changes by more than a respective predetermined amount, the controller causes the optical output produced by the light source to be stopped. For example, the driver can turn off the VCSEL 107 so that it no longer emits light.
In order to enable changes in the capacitance of the trace to be detected and therefore eye safety of the module to be ensured, it is important that the nominal capacitance of the trace is well understood. However, the quantity of conductive adhesive present on the MLA glass will affect the capacitance of the trace 119. This is shown in
This change is quantified in
Thus, dispensing of conductive adhesive in the vicinity of a capacitive ITO trace leads to a significant increase in the system capacitance. The latter is due to the interaction between the ITO and glue potentials which create additional, unwanted parallel capacitors. Because it is difficult to control the width of the application of the conductive adhesive on such small scales, it is therefore difficult to quantify accurately the effect on the capacitance of the glue layer. As a result the overall system capacitance may largely vary from one sample to another. Because the eye safety system described above relies on monitoring changes in the capacitance of the trace on the MLA glass, it is important that the capacitance of the trace is well understood for effective functioning of the eye-safety features according to an embodiment.
In an embodiment, a shielding layer of metal 125 is provided on the MLA glass between at least a portion of the electrically conductive trace 119 and the conductive adhesive 123 in order to mitigate the above described problem. Such an arrangement is shown in
In the arrangement of
In one embodiment the structure shown in
Because the metal layer embedded in the insulating layer of SiO2, or other layer of other insulating material according to embodiments, the metal sheet is floating, i.e. it is not electrically connected to any other components in the module. In other embodiments, the metal sheet may be grounded.
The shielding layer of metal, provided in addition to the metallic trace 119, is provided in order to disrupt the electric field lines emanating from the adhesive, such that they do not interact with the sensing ITO trace 119. This effect is shown in
The table in
The shielding effect of the metal layer on the electric field is further demonstrated in
As shown above, the double layer ITO arrangement according to embodiments enables eye safety of an illuminator or other module to be ensured, with little to no impact on the optical performance of the module.
Embodiments of the present disclosure can be employed in many different applications including providing illumination for facial recognition sensors, for example, in smartphones and other technologies or time of flight sensors that find use in the automotive industry, amongst others.
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 which 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.
Filing Document | Filing Date | Country | Kind |
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PCT/SG2020/050763 | 12/18/2020 | WO |
Number | Date | Country | |
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62950485 | Dec 2019 | US |