Illumination device, optical camera and method for monitoring an optical output power of a light source

An illumination device is provided. The illumination device includes a light source and a current path configured to transport a supply current to the light source. Further, the illumination device includes a sensor configured to contactlessly measure a current strength of the supply current in the current path and to output a measurement signal indicative of the measured current strength. The illumination device additionally includes processing circuitry coupled to the sensor and configured to determine the optical output power of the light source based on the measured current strength indicated by the measurement signal.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No. 21214520 filed on Dec. 14, 2021, the content of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to monitoring an optical output power of a light source. In particular, examples of the present disclosure relate to an illumination device, an optical camera and a method for monitoring an optical output power of a light source.

BACKGROUND

Cameras included in consumer products (e.g., a smartphone) need to fulfill eye-safety regulations such as class 1 of the international laser safety standard (EN 60825). The used active illumination elements such as laser diodes are capable of providing several Watts of optical power. Special sensing and circuitry are used to monitor the emitted optical power, ensuring that while having peak power levels in the order of several watts for short laser pulses, all measures required for eye-safe and skin-safe operation on pulse-, pulse-train- and average optical power levels are fulfilled.

Conventionally, so-called monitor photodiodes are used. The monitor photodiodes are integrated inside the illumination module to directly sense a small fraction of the optical output power and convert it into current or voltage. A monitor photodiode allows to directly measure the optical power without significant additional power loss in the camera module. However, it is disadvantageous that a monitor diode needs to be installed in the illumination unit (e.g., a laser diode package) and that an additional readout circuitry is required.

In other conventional examples, a shunt resistor is used in the laser diode driving wire to sense the laser diode forward current flow. The current through a laser diode is proportional to the emitted optical power to a high degree. As a big drawback, the shunt-based approach comes with considerable energy/power loss. This method always leads to a voltage drop and power loss in the illumination circuit, so that the overall power consumption of such a module is increased. This is a very critical with respect to battery life in any mobile application. In addition, the power dissipation on the shunt resistor (e.g., up to 0.5 W) additionally heats up the module—which of course is not wanted.

Hence, there may be a demand for improved monitoring of a light source's optical output power.

SUMMARY

The demand may be satisfied by the subject-matter of the appended claims.

An example relates to an illumination device. The illumination device includes a light source and a current path configured to transport a supply current to the light source. Further, the illumination device includes a sensor configured to contactlessly measure a current strength of the supply current in the current path and to output a measurement signal indicative of the measured current strength. The illumination device additionally includes processing circuitry coupled to the sensor and configured to determine the optical output power of the light source based on the measured current strength indicated by the measurement signal.

Another example relates to an optical camera. The optical camera includes an illumination device as described herein and an image sensor. The image sensor is configured to generate measurement data based on received reflections of light output by the light source.

A further example relates to a method for monitoring an optical output power of a light source. The method includes contactlessly measuring a current strength of a supply current for the light source flowing through a current path using a sensor. Additionally, the method includes determining the optical output power of the light source based on the measured current strength.

DETAILED DESCRIPTION

FIG.1illustrates an example illumination device100. The illumination device100comprises at least one light source110. The light source110may be any kind of optical emitter. In particular, the light source110may be configured to controllably emit light of one or more predetermined wavelength. The light source110may comprise a single light-emitting device or a plurality of light-emitting devices such as an array of light-emitting devices. For example, the light source110may comprise one or more Light-Emitting Diode (LED) or one or more laser diode such as one or more Vertical-Cavity Surface-Emitting Laser (VCSEL). The light source110may, e.g., comprise a VCSEL array. In the example ofFIG.1, exactly one light source110is illustrated. However, it is to be noted that according to examples, the illumination device100may comprise more than one light source, e.g., a plurality of light sources.

The illumination device100further comprises a current path120configured to transport (conduct) a supply current IILLUto the at least one light source110. The current path120may be any structure capable of transporting (conducting) current. For example, the current path120may be an electrically conductive wire, trace or path. For example, the current path120may couple the at least one light source110to a power supply (not illustrated inFIG.1) providing the supply current IILLU.

Additionally, the illumination device100comprises a sensor130configured to contactlessly measure a current strength of the supply current IILLUin the current path120. The sensor130is further configured to output a measurement signal131indicative of the measured current strength. The sensor130is placed in proximity to the current path120. For example, the sensor130may be arranged sideways of the current path120as illustrated inFIG.1. However, the present disclosure is not limited thereto. In other examples, the sensor130may, e.g., be arranged on top of the current path120. No conductive path is formed between the sensor130and the current path120. In other words, the sensor120is galvanically isolated from the current path120. However, the sensor130may physically contact the current path120. For example, the sensor120and/or the current path may comprise a respective electrically isolating housing (casing) that allows to galvanically isolate the electrically conductive elements of the sensor130from the electrically conductive elements of the current path120. In other examples, one or more intermediate elements may be arranged between the sensor130and the current path120. For example, an isolating element (device) or an air gap may be arranged between the sensor130and the current path120. The sensor130may, e.g., be spaced apart from the current path by a few millimeters (e.g., less than 5 mm or 10 mm) up to a few centimeters (e.g., less 2 cm, 3 cm, 4 cm or 5 cm).

The sensor130uses a contactless measurement principle for measuring the current strength of the supply current IILLUin the current path120. The sensor130may, e.g., be configured to couple to the current path electrically or magnetically. For example, the sensor130may be a magnetic field sensor. The magnetic field sensor130may, e.g., be a Hall effect based sensor configured to measure the current strength of the supply current IILLUusing the Hall effect. In other examples, the magnetic field sensor130may, e.g., be a magnetoresistive sensor. In other words, the sensor130may comprise material (e.g., ferromagnetic material) or material structure that changes the value of its electrical resistance based on an externally-applied magnetic field, which is caused by the supply current IILLUin the current path120. Accordingly, the sensor130is sensitive to the current strength of the supply current IILLUin the current path120. The magnetoresistive sensor130may, e.g., be configured to measure the current strength of the supply current IILLUusing one or more of the Anisotropic MagnetoResistance (AMR) effect, the Giant MagnetoResistance (GMR) effect and the Tunnel MagnetoResistance (TMR) effect. In some examples, the magnetic field sensor130may use both the Hall effect and one or more magnetroresistive effect for measuring the current strength of the supply current IILLU. In other examples, the sensor130may be a magnetooptical sensor. In other words, the sensor130may be based on a measurement principle in in which an electromagnetic wave propagates through a medium that is altered based on an externally-applied magnetic field, which is caused by the supply current IILLUin the current path120. For example, the magnetooptical sensor130may be configured to measure the current strength of the supply current IILLUusing the Faraday effect. In still other examples, the sensor130may, e.g., be a magnetically coupled sensor using an inductive coil for measuring the current strength of the supply current IILLU. For example, the magnetically coupled sensor130may be configured to measure a voltage across the inductive coil induced by a magnetic field caused by the supply current IILLU. However, it is to be noted that the present disclosure is not limited to the above contactless measurement principles for measuring the current strength of the supply current IILLUin the current path120. In general, any contactless measurement principle for measuring the current strength of a current flowing through an electrically conductive element may be used.

Processing circuitry140of the illumination device100is coupled to the sensor130. For example, the processing circuitry140may be a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which or all of which may be shared, a digital signal processor (DSP) hardware, an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The processing circuitry140may optionally be coupled to, e.g., read only memory (ROM) for storing software, random access memory (RAM) and/or non-volatile memory. The processing circuitry140is configured to receive the measurement signal131and to determine the optical output power of the light source110based on the measured current strength indicated by the measurement signal131. The optical output power of the light source110is the energy of light output (emitted) by the light source110per unit time. For example, the processing circuitry140may determine the optical output power of the light source110using a predefined or learned (trained) correlation between the optical output power of the light source110and the measured current strength of the supply current IILLUin the current path120. For example, the processing circuitry140may determine the optical output power of the light source110based on the assumption that the optical output power of the light source110scales substantially linear with the current strength of the supply current IILLUin the current path120(e.g., over a certain current range).

The illumination device100may allow to indirectly determine (estimate) the optical output power of the light source110using non-contacting current sensing. Compared to conventional approaches using shunt resistors and/or monitor photodiodes, the illumination device100may allow to sense the supply current IILLUin the current path120with minimum power consumption and reduced heat dissipation. Due to the sensor130, no shunt resistor is needed to measure the optical output power of the light source110. Neither a voltage drop nor significant heat dissipation appears from the current sensing. The sensor130may consume substantially less power (e.g., up to one or two orders of magnitude) than conventional shunt resistor-based measurement approaches. The illumination device100may, hence, allow to reduce an overall power consumption of the system compared to conventional approaches. Similarly, there might be no need for separate monitor photodiodes and corresponding readout circuitry. Accordingly, the illumination device100may be less complex and more efficient in terms of area consumption and costs than conventional monitor photodiode-based measurement approaches.

The information about the determined optical output power of the light source110may be used for controlling the light source110. For example, the light source110may be controlled such that eye-safety and/or skin-safety regulations are met. According to some examples, the processing circuitry140may be used for controlling the light source110. For example, the processing circuitry140may be further configured to control the current strength of the supply current IILLUthrough the current path120based on the determined optical output power of the light source110. The processing circuitry140may, e.g., control a power supply supplying the supply current IILLUto the current path120to adjust the current strength of the supply current IILLU(e.g., to a specific value or to decrease or increase the current strength of the supply current IILLU). For example, the processing circuitry140may transmit one or more corresponding control signal to the power supply. In other examples, the processing circuitry140may transmit information (data) about the determined optical output power of the light source110to the power supply (e.g., via one or more signal) or dedicated circuitry for controlling the power supply such that the power supply or the dedicated circuitry for controlling the power supply is able to adjust or control the power supply to adjust the current strength of the supply current IILLUbased on the information (data) about the determined optical output power of the light source110.

As the sensor130is galvanically isolated from the current path120, also the processing circuitry140is galvanically isolated from the current path120. Accordingly, damaging of the sensor130and the processing circuitry140due to, e.g., overvoltage caused by the current path120may be avoided. Galvanically isolating the sensor130and the processing circuitry140from the current path120may, hence, allow to increase a safety of the illumination device100.

According to some examples, the illumination device100additionally comprises a carrier substrate (e.g., a Printed Circuit Board, PCB; not illustrated inFIG.1) holding (carrying) the various other elements of the illumination device100. For example, the carrier substrate may hold one or more of the light sources110, the current path120, the sensor130and the processing circuitry140.

The measurement settings of the sensor130may be fixedly predefined (preconfigured) or be adjustable. For example, a sensitivity of the sensor130or any other parameter of the sensor130may be adjustable. In other examples, the sensitivity of the sensor130or any other parameter of the sensor130may be fixedly predefined without separate communication or pre-assembly programming steps. The sensitivity of a sensor indicates how much a sensor's output changes when the input quantity being measured changes. Either in advance or during operation, the sensor130may be configured (adjusted) such that the sensor output is proportional to the sensed current strength of the supply current IILLUthrough the current path120. The sensor130may, e.g., be controlled by the processing circuitry140. According to examples, the processing circuitry140may be further be configured to transmit control data to the sensor130. Accordingly, the sensor130may be configured to adjust a sensor sensitivity based on the received control data. For example, the processing circuitry140and the sensor130may be coupled via an Inter-Integrated Circuit (I2C) bus.

In some examples, the illumination device100may further comprise switching circuitry (not illustrated inFIG.1) for selectively switching the light source110on and off. For example, the switching circuitry may comprise a plurality of coupled transistors acting as switches for selectively switching the light source110on and off. Accordingly, the current path120may be part of the switching circuitry (e.g., a conductive trace or path connecting two of the plurality of coupled transistors) and further the sensor130may be integrated into the switching circuitry. Accordingly, a switching circuit with integrated current measurement capability of optical output power determination may be provided.

Further details of the proposed illumination device are described below with reference toFIGS.2to9.

FIG.2andFIG.3illustrate a first example arrangement of the sensor130with respect to the current path120.FIG.2illustrates a top view of the example arrangement, whereasFIG.3illustrates a cross-sectional view of the example arrangement. As illustrated inFIG.2, the supply current IILLUflows through the current path120at a supply voltage VILLUto the light source.

In the example ofFIG.2andFIG.3, the sensor130is arranged above the current path120. As can be seen fromFIG.3, a carrier substrate150(e.g., a PCB) holds the current path120and the sensor130such that the current path120is arranged between the carrier substrate150and the sensor130. The current path120may, e.g., be a conductive trace or path on the carrier substrate150. Further illustrated inFIG.3are two contact (connection) pads151and152contacting input and/or output nodes (terminals) of the sensor130for coupling the sensor130to the processing circuitry (not illustrated inFIG.3).

The sensor130may, e.g., be a Hall effect based sensor providing a Hall voltage proportional to current strength of the supply current IILLUflowing through the current path120. The Hall voltage of the sensor130is indicative of the measured current strength and, hence, allows the coupled processing circuitry to determine the optical output power of the light source. However, it is to be noted that any other sensor using a non-contacting measurement principle for measuring the current strength of a current may be used as well. For example, the sensor130may alternatively be a magnetoresistive sensor using resistance changes induced by the magnetic field coupled from the supply current IILLUfor generating an output signal indicative of the measured current strength. The magnetoresistive sensor may, e.g., comprise a bridge circuit with magnetoresistive elements to measure resistance changes proportional to magnetic field changes within the sensor130.

FIG.4andFIG.5illustrate a second example arrangement of the sensor130with respect to the current path120.FIG.4illustrates a top view of the example arrangement, whereasFIG.5illustrates a cross-sectional view of the example arrangement. As illustrated inFIG.4, the supply current IILLUflows through the current path120at a supply voltage VILLUto the light source.

As can be seen fromFIG.4, the carrier substrate150(e.g., a PCB) again holds the current path120and the sensor130such that the current path120is arranged between the carrier substrate150and the sensor130.

In the example ofFIG.4andFIG.5, the sensor130is a magnetically coupled sensor and comprises an inductive coil135for measuring the current strength of the supply current IILLUflowing through the current path120. In order to maximize the surface (or volume) of the current path120covered and, hence, sensed by the coil135of the sensor, the current path120exhibits a meandering shape. However, it is to be noted that the present disclosure is not limited thereto. The current path120may exhibit any other shape as well.

The sensor130is configured to measure the voltage Ucoilacross the inductive coil135, which is induced by a magnetic field caused by the supply current supply current IILLUflowing through the current path120. The voltage Ucoilacross the inductive coil135is indicative of the measured current strength and, hence, allows the coupled processing circuitry to determine the optical output power of the light source.

Further illustrated inFIG.5is a contact (connection) pad151contacting input and/or output nodes (terminals) of the sensor130for coupling the sensor130to the processing circuitry (not illustrated inFIG.5). In the example ofFIG.4andFIG.5, a spacer155is arranged between the sensor130and the current path120. The spacer155is made of an electrically non-conductive material and acts as isolating element (device) to ensure galvanic isolation between the sensor130and the current path120.

FIG.6illustrates another illumination device600. The illumination device600is substantially identical to the illumination device100described above. In the example ofFIG.6, the sensor130is a magnetic field sensor such as a Hall effect based sensor or a magnetoresistive sensor. The magnetic field sensor130may provide a bandwidth of up to few MHz, which might be sufficient for short time averaged current monitoring as required to be conform with relevant eye safety standards. The magnetic field sensor130sensor may provide a typical low pass characteristic from DC up to the given bandwidth.

The magnetic field sensor130is susceptible to outside (external) magnetic fields. Therefore, in comparison to the illumination device100, the illumination device600additionally comprises another magnetic field sensor160spaced apart from the magnetic field sensor130. The magnetic field sensor160is configured to measure a magnetic field strength of a magnetic field in an environment of the illumination device600and to output a measurement signal161indicative of the measured magnetic field strength. The magnetic field sensor160is placed at a short distance from the magnetic field sensor130(e.g., a few millimeters to a few centimeters, less than 1 cm, less than 2 cm or less than 5 cm). Accordingly, the reading of the magnetic field sensor160may be used to compensate for the effects of the external magnetic field in the environment of the illumination device600on the measurement signal131of the magnetic field sensor130.

In the example ofFIG.6, the processing circuitry140is coupled to the magnetic field sensor160and configured to further determine the optical output power of the light source110based on the measured current strength indicated by the measurement signal131and further based on the measured magnetic field strength indicated by the measurement signal161. In particular, the processing circuitry140is configured to compensate for the effects of the external magnetic field in the environment of the illumination device600on the measurement signal131using the measurement signal161.

In other words,FIG.6illustrates a differential sensing approach using two sensors130and160, wherein the magnetic field sensor160measures the static magnetic field outside the vicinity of the conducting current path120.

In alternative examples, the above described compensation functionalities may be provided within the magnetic field sensor130such that the measurement signal131is compensated for the effects of the external magnetic field in the environment of the illumination device600.

FIG.7illustrates a further illumination device700. The illumination device700is substantially identical to the illumination device100described above. In comparison to the illumination device100, the illumination device700additionally comprises an optical sensor170. For example, the optical sensor170may be (comprise) one or more photodiode. The optical sensor170is configured to measure (at least a fraction, e.g., a defined fraction of) an optical power output by the light source110and to output a measurement signal171indicative of the measured optical power.

In the example ofFIG.7, the processing circuitry140is coupled to the optical sensor170and configured to determine the optical output power of the light source110based on the measured current strength indicated by the measurement signal131and further based on based on the measured optical power indicated by the measurement signal171.

In other words,FIG.7illustrates a redundant sensing approach using the measurement signals131and171of two different sensor types as input for the determination of the optical output power of the light source110. This may allow to increase the functional safety aspects of the illumination device700compared to the illumination device100. For example, the illumination device700may be beneficial to achieve a higher Automotive Safety Integrity Level (ASIL) on camera system level than with the illumination device100alone. Further, the reliability for monitoring of the illumination device700eye safety and/or skin safety may be increased compared to the illumination device100.

A still further illumination device800using a redundant sensing approach is illustrated inFIG.8. The illumination device800is substantially identical to the illumination device100described above. In comparison to the illumination device100, the illumination device800additionally comprises a shunt resistor180coupled in series between two (directly) succeeding sections121and122of the current path120.

In the example ofFIG.8, the processing circuitry140is coupled to the connection nodes (terminals) of the shunt resistor180to measure the voltage drop over the shunt resistor180. The processing circuitry140is configured to determine the optical output power of the light source110based on the measured current strength indicated by the measurement signal131and further based on voltage drop over the shunt resistor180.

Like in the example ofFIG.7, the illumination device800provides a redundant sensing approach using the measurement signals131and181of two different sensor types as input for the determination of the optical output power of the light source110. This may allow to increase the functional safety capabilities of the illumination device800compared to the illumination device100.

FIG.9illustrates another illumination device900. The illumination device900comprises a light source910(e.g., a VCSEL) and a current path920coupling the light source910between a power supply (not illustrated) providing an electrical supply power and ground (GND).

Further illustrated is a transistor switch905for selectively switching the light source910on and off. The transistor switch905is coupled between the light source910and GND. As illustrated inFIG.9, a supply current IILLUflows through the current path920when the transistor switch905is closed (e.g., in a conducting state).

The transistor switch905is controlled by processing circuitry940of the illumination device900. In particular, the processing circuitry comprises sub-circuitry942implemented as an ASIC for controlling the transistor switch905. The sub-circuitry942supplies a control signal943to a control node (terminal) of the transistor switch905(e.g., a gate node/terminal of the transistor switch905) for opening and closing the transistor switch905(e.g., for driving the transistor switch905either in the conducting state or the non-conducting state).

The illumination device900further comprises a sensor930configured to contactlessly measure a current strength of the supply current IILLUflowing through the current path920. The sensor930may, e.g., be a magnetic field sensor such as a Hall effect based sensor outputting a measurement voltage VMEASproportional to the current strength of the supply current IILLU.

The sensor930is coupled to the processing circuitry940. In particular, the sensor930is coupled to sub-circuitry941of the processing circuitry940. The sub-circuitry941is configured to determine the optical output power of the light source920based on the measurement voltage VMEAS, e.g., based on the measured current strength indicated by the measurement signal of the sensor930.

Similar what is described above, the illumination device900may allow indirect optical output power determination based on current sensing. The illumination device900may exhibit significantly reduced power consumption and heat dissipation compared to conventional optical output power measurement approaches using shunt resistors in the current path or photodiodes.

In alternative examples, one or more of the sensor930, the transistor switch905and the sub-circuitry941may be integrated into the same semiconductor device or package. For example, the sensor930and the transistor switch905may be integrated into a single semiconductor device or package. Optionally, the sub-circuitry941may be integrated together with the sensor930and the transistor switch905into a single semiconductor device or package. This may allow to reduce circuitry complexity and, hence, size and costs.

An illumination device as proposed herein may be used for various applications. For example, an illumination device as proposed herein may be used for automotive illumination systems (solutions) or laser illumination systems (solutions). Further, an illumination device as proposed herein may be used for any kind of optical camera. For example, an illumination device as proposed herein may be used in a Time-of-Flight (ToF) system such as a single-point, 1D, 2D or 3D LIght Detection And Ranging (LIDAR) system or any other 3D imaging system.

An example optical camera1000is illustrated inFIG.10. The optical camera1000comprises an illumination device1010as described herein. Only the light source1011of the illumination device1010is illustrated inFIG.10for reasons of simplicity. The light source1011outputs (emits) light1002to a scene. For example, the light source1011may selectively emit the light1002toward the scene based on one or more illumination (control) signal. The light1002may, e.g., be modulated light (e.g., one or more sequence of light pulses) or single light pulses. The illumination device1010and or the optical camera1000may comprise one or more additional light source for illuminating the scene.

An object1001is located in the scene and reflects the emitted modulated light1002. The object1001may be any kind of physical object. The reflected light1003travels at least partially (for diffuse reflections) back to the optical camera1000.

The optical camera1000further comprises an image sensor (optical sensor)1020configured to receive (capture) at least part of the reflected light1003. The image sensor1020may comprise various components such as e.g., optics (e.g., one or more lens) and electronic circuitry. In particular, the electronic circuitry comprises at least one photo-sensitive sensor element or pixel1021(e.g., comprising a Photonic Mixer Device, PMD, a (potentially gated) photodiode, an Avalanche Photo Diode, APD, a Single Photon Avalanche Diode, SPAD, a Silicon Photo Multiplier, SIPM, or a Charge-Coupled Device, CCD). For example, the image sensor1020may comprise a plurality of photo-sensitive sensor elements or pixels (e.g., N≥2 photo-sensitive sensor elements or pixels). The at least one photo-sensitive sensor element or pixel may be driven based on one or more drive (reference) signal. The image sensor1020is configured to generate and output measurement data1022based on the reflected light1003received by the image sensor1020. The measurement data1022may indicate one or more quantities of the reflected light1003and/or one or more quantities related to the reflected light1003such as, e.g., a light intensity, a change in light intensity, a ToF, a brightness, a change in brightness, a color of light, etc.

In general, the image sensor1020may be any type of sensor that is able to measure a physical quantity of the light (such as the reflected light1003) and then translate it into a form that is readable by further electronic circuitry. In particular, the image sensor1020may be any type of sensor that is able to convert light or a change in light into an electronic signal. For example, the image sensor1020may be a frame based image sensor comprising photo-sensitive sensor elements or pixels that operate uniformly and synchronously to detect light framewise. Alternatively, the image sensor1020may, e.g., be a LIDAR sensor or a ToF sensor measuring a ToF of the emitted light1002using the reflected light1003received at the image sensor1020. Further alternatively, the image sensor1020may, e.g., be an event based vision sensor such as a dynamic vision sensor (also known as event camera, neuromorphic camera or silicon retina) that responds to local changes in brightness. An event based vision sensor does not capture an images/frames using a shutter like a conventional image sensor does. Instead, the photo-sensitive sensor element or pixels of an event based vision sensor operate independently and asynchronously, detecting changes in brightness as they occur, and staying silent otherwise.

The optical camera1000may allow indirect optical output power determination for the light source1011based on current sensing. The optical camera1000may consume significantly less power and reduce heat dissipation compared to conventional optical output power measurement approaches. Further, the optical camera1000may enable increased eye and/or skin safety.

The above described elements of the optical camera1000may be arranged on one or more carrier substrate. For example, the above described elements of the optical camera1000may be arranged (encapsulated) in a common camera module.

The optical camera1000may be used for various applications. For example, the optical camera1000may be used in a mobile device, e.g., battery driven device, such as a mobile phone, a smartphone, a tablet-computer, augmented reality goggles or virtual reality goggles. However, it is to be noted that the present disclosure is not limited thereto.

FIG.11further illustrates a flowchart of an example of a method1100for monitoring an optical output power of a light source. The method1100comprises contactlessly measuring1102a current strength of a supply current for the light source flowing through a current path using a sensor. Additionally, the method1100comprises determining1104the optical output power of the light source based on the measured current strength.

Similar what is described above, the method1100may allow indirect optical output power determination based on current sensing. The method1100may consume significantly less power and reduce heat dissipation compared to conventional optical output power measurement approaches.

More details and aspects of the method1100are explained in connection with the proposed technique or one or more example described above. The method1100may comprise one or more additional optional features corresponding to one or more aspects of the proposed technique or one or more example described above.

Aspects of the present disclosure may allow non-contacting current sensing for 3DI or ToF eye safety. In particular, use of a non-contacting sensor for illumination current monitoring within a 3DI camera, instead of a shunt resistor in the current path is enabled.

ASPECTS

The aspects as described herein may be summarized as follows:

Aspect 1 is an illumination device. The illumination device comprises a light source and a current path configured to transport a supply current to the light source. Further, the illumination device comprises a sensor configured to contactlessly measure a current strength of the supply current in the current path and to output a measurement signal indicative of the measured current strength. The illumination device additionally comprises processing circuitry coupled to the sensor and configured to determine the optical output power of the light source based on the measured current strength indicated by the measurement signal.

Aspect 2 is the illumination device of aspect 1, wherein the sensor is configured to couple to the current path electrically or magnetically.

Aspect 3 is the illumination device of aspect 1 or aspect 2, wherein the sensor is a magnetic field sensor.

Aspect 4 is the illumination device of aspect 3, wherein the magnetic field sensor is configured to measure the current strength of the supply current using one or more of the Hall effect and a magnetoresistive effect.

Aspect 5 is the illumination device of aspect 4, wherein the magnetoresistive effect is one or more of the anisotropic magnetoresistance effect, the giant magnetoresistance effect and the tunnel magnetoresistance effect.

Aspect 6 is the illumination device of any one of aspects 3 to 5, further comprising another magnetic field sensor spaced apart from the magnetic field sensor, wherein the other magnetic field sensor is configured to measure a magnetic field strength of a magnetic field in an environment of the illumination device and to output a second measurement signal indicative of the measured magnetic field strength, and wherein the processing circuitry is coupled to the magnetic field sensor and configured to further determine the optical output power of the light source based on the measured magnetic field strength indicated by the second measurement signal.

Aspect 7 is the illumination device of aspect 1 or aspect 2, wherein the sensor is a magnetooptical sensor.

Aspect 8 is the illumination device of aspect 7, wherein the magnetooptical sensor is configured to measure the current strength of the supply current using the Faraday effect.

Aspect 9 is the illumination device of aspect 1 or aspect 2, wherein the sensor is a magnetically coupled sensor using an inductive coil for measuring the current strength of the supply current.

Aspect 10 is the illumination device of aspect 9, wherein the magnetically coupled sensor is configured to measure a voltage across the inductive coil induced by a magnetic field caused by the supply current.

Aspect 11 is the illumination device of any one of aspects 1 to 10, further comprising a carrier substrate holding the current path and the sensor, wherein the current path is arranged between the carrier substrate and the sensor.

Aspect 12 is the illumination device of any one of aspects 1 to 11, wherein the sensor and the processing circuitry are galvanically isolated from the current path.

Aspect 13 is the illumination device of any one of aspects 1 to 12, further comprising: an optical sensor configured to measure an optical power output by the light source and to output a third measurement signal indicative of the measured optical power; and/or a shunt resistor coupled in series between two sections of the current path, wherein the processing circuitry is configured to further determine the optical output power of the light source based on the measured optical power indicated by the third measurement signal and/or a voltage drop over the shunt resistor.

Aspect 14 is the illumination device of any one of aspects 1 to 13, further comprising switching circuitry comprising a plurality of coupled transistors for selectively switching the light source on and off, wherein the current path is part of the switching circuitry, and wherein the sensor is integrated into the switching circuitry.

Aspect 15 is the illumination device of any one of aspect 1 to 14, wherein the processing circuitry is further configured to control the current strength of the supply current through the current path based on the determined optical output power of the light source.

Aspect 16 is the illumination device of any one of aspect 1 to 15, wherein the processing circuitry is further configured to transmit control data to the sensor, and wherein the sensor is configured to adjust a sensor sensitivity based on the control data.

Aspect 17 is an optical camera. The optical camera comprises an illumination device according to any one of aspects 1 to 16. Further, the optical camera comprises an image sensor configured to generate measurement data based on received reflections of light output by the light source.

Aspect 18 is a method for monitoring an optical output power of a light source. The method comprises contactlessly measuring a current strength of a supply current for the light source flowing through a current path using a sensor. Additionally, the method comprises determining the optical output power of the light source based on the measured current strength.

The aspects and features described in relation to a particular one of the previous aspects may also be combined with one or more of the further aspects to replace an identical or similar feature of that further aspect or to additionally introduce the features into the further aspect.