Light source system

Abstract

The invention relates to a light source system. The invention relates to a light source system suitable for a time-of-flight camera. The light source system includes a light source, such as a laser, and a driver arranged to provide a drive current to the light source to open the light source to emit light. The driver includes two transistors coupled in series to the light source such that when both transistors are turned on, the driver circuit completes, the current flows and the light source is turned on. By switching one transistor to an on state to complete the driving circuit and turning off the other transistor in a short time to disconnect the driving circuit, very short light-emitting pulses can be effectively realized. In this way, light pulses of a magnitude of less than 1 nanosecond or less than 500 picoseconds can be achieved.

Description

[0001] This application is a divisional application of the invention patent application with application date of February 3, 2021, application number 202110148948.1, and invention name “Light Source System”.

[0002] Claiming priority

[0003] This application is a continuation-in-part of U.S. patent application serial number 16 / 780,761 filed on February 3, 2020 (attorney docket number 3867.722US1), and a continuation-in-part of U.S. patent application serial number 16 / 780,735 filed on February 3, 2020 (attorney docket number 3867.723US1), claiming the benefit of priority of each case and incorporated herein by reference in their entirety. Technical Field

[0004] The present disclosure relates to a light source system, which may be used, for example, as a light source in a time-of-flight camera system. Background Art

[0005] A time-of-flight (ToF) camera system is a range imaging system that can resolve the distance between the camera and an object by measuring the round-trip time of a light signal emitted by the ToF camera system. The system typically includes a light source (e.g., a laser or LED), a light source driver that controls light from the light source, an image sensor for imaging light reflected from an object, an image sensor driver for controlling the operation of the image sensor, optics for shaping the light emitted from the light source and focusing the light reflected from the object onto the image sensor, and a computing unit configured to determine the distance to an object by determining the time between light emitted from the light source and a corresponding reflection from the object.

[0006] The distances that a ToF camera system can measure range from a few centimeters to 100 to 1000 or 1000 meters. Given the high speed of light, the time difference between the emission of light and the reception of the reflected light is only 16.66ns, corresponding to a 2.5m object from the camera system. Therefore, a ToF camera system requires a high level of time precision and control to accurately measure distances. Summary of the invention

[0007] The present invention relates to a light source system suitable for a time-of-flight camera. The light source system includes a light source, such as a laser, and a driver arranged to provide a drive current to the light source to turn on the light source to emit light. The driver includes two transistors coupled in series to the light source, so that when both transistors are turned on, the drive circuit is completed, the current flows and the light source is turned on. By switching one transistor to an on state to complete the drive circuit, and turning off the other transistor for a short time to disconnect the drive circuit, very short light emission pulses can be effectively achieved. In this way, light pulses of the order of less than 1 nanosecond or less than 500 picoseconds can be achieved. Due to the turn-on characteristics of the light source, for example due to the threshold level of a VCSEL, the duration of the light emission may be shorter than the duration of the current.

[0008] The present disclosure also includes a light source system, which includes a light source such as a laser, and a driver, which is arranged to supply a driving current to the light source so that the light source is turned on to emit light. The driver includes a capacitor to store energy and then discharges to generate a driving current, and the driver is integrated into a semiconductor chip on which the light source is mounted. Therefore, the driver contains an energy source for the driving current, and the light source and the driver are very close, which means that the light source can be turned on and off very quickly with a relatively large driving current to output high optical power, short duration light pulses.

[0009] In a first aspect of the present disclosure, a laser light source system is provided, comprising: a laser light source; a first transistor device coupled to the laser light source; a second transistor device coupled to the laser light source, wherein the first transistor device and the second transistor device are arranged so that when the first transistor device and the second transistor device are both in an on state, a laser driving circuit is completed and a laser driving current flows through the laser light source; and a controller arranged to control a state of a first switch and a state of a second switch, wherein the controller is configured to control a pulse emission of light from the laser light source in the following manner: a) turning on the first transistor device when the second transistor device is in an off state; b) after turning on the first transistor device, turning on the laser light source by turning on the second transistor device so that the first transistor device and the second transistor device are both in an on state; and c) after turning on the second transistor device, turning off the laser light source by turning off the first transistor device.

[0010] The controller may be configured to turn off the laser light source by turning off the first transistor device while the second transistor device is still in the on state.

[0011] The laser light source system may be further configured to: d) after turning off the first transistor device, reset the laser light source system by turning off the second transistor device so that both the first transistor device and the second transistor device are in an off state.

[0012] Turning on the first transistor may include: pre-charging the first transistor by applying a turn-on voltage to a control terminal of the first transistor to charge a capacitance associated with the control terminal of the first transistor; and removing the turn-on voltage applied to the control terminal of the first transistor so that the first transistor is maintained in an on state through the capacitance associated with the control terminal of the first transistor.

[0013] The capacitance associated with the control terminal of the first transistor may be a parasitic capacitance of the first transistor.

[0014] The laser light source system may further include a pre-charge transistor for controlling application of an on-voltage to a control terminal of the first transistor, and the controller may be configured to apply and remove the on-voltage by controlling a state of the pre-charge transistor.

[0015] Turning off the first transistor may include discharging a capacitance associated with a control terminal of the first transistor.

[0016] The laser light source system may further include a cutoff transistor for controlling discharge of capacitance associated with the control terminal of the first transistor, wherein the controller may be configured to discharge capacitance associated with the control terminal of the first transistor by controlling a state of the cutoff transistor using a cutoff control signal.

[0017] The laser light source system may further include a cascode transistor in the capacitor discharge path.

[0018] The magnitude of the turn-on voltage may be greater than the magnitude of the laser driving voltage for providing the laser driving current.

[0019] The laser light source system may also include: a bootstrap capacitor, wherein a first plate of the bootstrap capacitor is coupled to a control terminal of the first transistor, and a second plate of the bootstrap capacitor is coupled to the controller; and wherein the controller is also configured to apply a bootstrap voltage to the second plate of the bootstrap capacitor before turning on the second transistor device to increase the voltage amplitude at the control terminal of the first transistor to an amplitude greater than the turn-on voltage.

[0020] The controller may be configured to: generate a first control signal for controlling the state of the first transistor; and generate a second control signal to control the state of the second transistor, wherein the controller is configured to control the duration of the pulse emission of light from the laser light source by setting a time difference between a change in the second control signal that turns on the second transistor and a change in the first control signal that turns off the first transistor.

[0021] The controller may be configured to control the laser light source to emit laser pulses having a duration of less than 1 nanosecond, or less than 800 picoseconds, or less than 500 picoseconds, or less than 200 picoseconds.

[0022] The laser light source system may also include a discharge transistor coupled to the laser light source and arranged to create a discharge path approximately when the first transistor device is turned off (for example, at the same time as the first transistor is turned off, or at some time shortly after the first transistor device is turned off) to discharge parasitic charges associated with the laser light source.

[0023] In a second aspect of the present disclosure, there is provided a laser light source controller for coupling to a laser driving circuit including a first transistor, a second transistor and a laser light source, wherein the laser light source controller is configured to: output a first control signal for controlling the first transistor; and output a second control signal to the second transistor coupled to the laser light source, wherein the first transistor, the second transistor and the laser light source are arranged in series so that when the first transistor and the second transistor are both turned on, the laser light source is turned on, wherein the laser light source controller is configured to control the pulse emission of light from the laser light source in the following manner: a) when the second transistor device is in a non-conducting state, setting the first transistor to a conducting state using a first control signal; b) after setting the first transistor to a conducting state, turning on the laser light source by setting the second transistor to a conducting state using a second control signal so that both the first transistor device and the second transistor device are turned on; and c) after setting the second transistor to a conducting state, turning off the laser light source by setting the first transistor to a non-conducting state.

[0024] The first control signal can be used to switch the first transistor from a non-conducting state to a conducting state, and wherein the laser light source controller can be further configured to output a third control signal for switching the first transistor from a conducting state to a non-conducting state, wherein the laser light source controller is configured to set the first transistor to a non-conducting state using the third control signal.

[0025] The laser light source controller may be further configured to control a time difference between setting the second transistor to a conductive state and setting the first transistor to a non-conductive state based on a target light emission duration.

[0026] In a third aspect of the present disclosure, there is provided a method for controlling the pulse emission of light from a laser light source, comprising: setting a first transistor coupled in series with the laser light source to a conducting state, while a second transistor coupled in series with the laser light source is in a non-conducting state; turning on the laser light source by setting the second transistor to a conducting state so that both the first transistor and the second transistor are turned on; and turning off the laser light source by setting the first transistor to a non-conducting state.

[0027] The method may further include: after setting the first transistor to a non-conducting state, setting the second transistor to a non-conducting state, so that both the first transistor and the second transistor are in a non-conducting state.

[0028] The duration of the pulse emission of light from the laser light source can be set by the time difference between setting the second transistor to the conducting state and setting the first transistor to the non-conducting state. Due to the turn-on characteristics of the light source and due to parasitic effects that require charging to reach the emission condition of the light, the duration of the light pulse can be shorter than the duration of the conduction time through the light source.

[0029] The duration of the pulse emission of light from the laser light source may be less than 500 picoseconds or less than 200 picoseconds.

[0030] In a fourth aspect of the present disclosure, a light source system is provided, comprising: a light source; a semiconductor chip on which the light source is mounted; a first driver coupled to the light source and configured to control the supply of a first drive current to the light source to control the operation of the light source, wherein the first driver comprises a first capacitor for storing electrical energy for generating the first driver current, wherein the first driver comprises a first switch integrated in the semiconductor chip for controlling the supply of the first drive current to the light source. .

[0031] The first driver can be configured to operate in a charging state, in which the first capacitor stores charge received from a power source, and in an emission state, in which the first capacitor discharges to generate a first drive current, which is provided to the light source to turn on the light source.

[0032] The first capacitor may be set to any suitable size (ie, capacitance) depending on the desired magnitude of the first drive current and / or the desired duration of the first drive current and / or the duty cycle between the charging state and the emission state.

[0033] At least 95% of the first driving current may be obtained from the electrical energy stored in the first capacitor.

[0034] The first driver may also include a first switch, which is configured to: during an emission state, close a first drive current circuit including a first capacitor and a light source to transmit a first drive current between the light source and the first driver; and in a charging state, open the first drive current circuit in the charging state to stop providing the first drive current to the light source.

[0035] The first switch may be coupled between a cathode terminal of the light source and a reference voltage of the first driver, and wherein the first capacitor is coupled between an anode terminal of the light source and the reference voltage of the first driver.

[0036] The light source system may further include a controller configured to control the first switch to control switching of the first driver between a charging state and an emission state.

[0037] The first switch may include a first transistor, the controller being configured to control operation of the first switch by controlling a first transistor driver signal at a gate / base terminal of the first transistor.

[0038] The light source system may further include a turned-on pre-driver, wherein the controller is configured to turn on the first transistor by applying a turn-on signal to a gate / base of the first transistor using the turned-on pre-driver to switch the first transistor from a charging state to an emitting state.

[0039] The light source system may further include a voltage regulator coupled to the first capacitor and the turn-on pre-driver, wherein the voltage regulator is configured to: receive energy from the first capacitor; and provide a regulated voltage to the turn-on pre-driver at least during a transition of the first driver from a charging state to an emitting state.

[0040] The light source system may further include a turned-on pre-driver, wherein the controller is configured to turn off the first transistor by applying a turn-off signal to a gate / base of the first transistor using the turned-off pre-driver to change the first driver from an emission state to a charging state.

[0041] To switch the first driver from the emission state to the charging state, the controller may be configured to apply both the on signal and the off signal to the gate / base terminal of the first transistor during a first time period, and then apply only the off signal to the gate / base of the first transistor during a second time period.

[0042] The light source system may further comprise a photodetector arranged to detect light emitted from the light source, wherein the light source system is further configured to charge the first capacitor only if the photodetector detects light emitted from the light source during a previous emission state.

[0043] The light source may include a laser, such as a vertical cavity surface emitting laser or a stacked edge emitting laser.

[0044] The light source may include at least one terminal of a first polarity on a first surface of the light source and at least one terminal of a second polarity on a second surface of the light source, wherein a first driver is coupled to at least one terminal of the first polarity and at least one terminal of the second polarity so that a first drive current can flow through the light source to turn on the light source.

[0045] The second surface of the light source may be secured to the first surface of the semiconductor chip, and wherein the first driver is coupled to at least one terminal of the first plurality through a first plurality of bond wires.

[0046] The light source may include a first terminal of a first polarity, a second terminal of the first polarity, and at least one third terminal of a second polarity, and wherein a first driver is coupled to the first terminal and the third terminal such that a first drive current can flow between the first terminal and the third terminal to turn on the light source, and wherein the semiconductor chip also includes an integrated second driver coupled to the second terminal and the third terminal, wherein the second driver is configured to control the supply of a second drive current to the light source such that the second drive current can flow between the second terminal and the third terminal to turn on the light source, wherein the second driver includes a second capacitor for storing electrical energy for generating the second drive current.

[0047] At least 95% of the second driving current may be obtained from the electrical energy stored in the second capacitor.

[0048] The first terminal and the second terminal may be arranged on the light source such that they are substantially symmetrical about a symmetry plane, wherein the first driver and the second driver are arranged within the chip such that they are substantially symmetrical about the symmetry plane.

[0049] In a fifth aspect of the present disclosure, a time-of-flight camera system is provided, comprising: a light source system, comprising: a light source for emitting light to an object to be imaged; and a semiconductor chip on which the light source is mounted; a first driver, coupled to the light source and configured to control the supply of a first drive current to the light source to control the operation of the light source, wherein the first driver comprises a first capacitor for storing electrical energy for generating electrical energy; a first drive current; and a photodetector for receiving light reflected from the object for imaging.

[0050] In a sixth aspect of the present disclosure, a driver is provided for coupling to a light source to drive the light source, the driver comprising: at least one capacitor for storing charge; a controllable switch for switching the driver between a charging state and an emission state; a turn-on pre-driver connected to the controllable switch, wherein the turn-on pre-driver is configured to control the controllable switch when transitioning from a charging state to an emission state; and a voltage regulator coupled to the at least one capacitor and the turn-on pre-driver and configured to provide a regulated voltage to the turn-on pre-driver, wherein the driver is configured such that in the charging state, the at least one capacitor stores charge, and in the emission state, the at least one capacitor discharger provides a driving current to the light source to turn on the light source.

[0051] The driver may be configured to be coupled to a power source such that during a charging state, the at least one capacitor stores charge received from the power source.

[0052] In the seventh aspect of the present disclosure, a light source system is provided, comprising: a light source; and a semiconductor chip including an integrated first driver, wherein the light source is mounted on the semiconductor chip, and the first driver is coupled to the light source and is configured to control the supply of a first drive current to the light source to control the operation of the light source, wherein the first driver includes a first capacitor for storing electrical energy to generate the first drive current. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Various aspects of the present disclosure are described, by way of example only, with reference to the following drawings, in which:

[0054] Figure 1 An example representation of a light source system according to one aspect of the present disclosure is shown;

[0055] Figure 2A Shown is the installation Figure 1 A view of an arrangement of VCSELs 110 on a semiconductor chip 120 of a light source system;

[0056] Figure 2B Shown is the installation Figure 1 Another view of an arrangement of VCSELs 110 on a semiconductor chip 120 of a light source system;

[0057] Figure 3 Shown Figure 1 An example diagram of a VCSEL driving current and the optical power of light output from the VCSEL of a light source system.

[0058] Figure 4 Shows Figure 1 Schematic diagram of details of an example implementation of a light source system.

[0059] Figure 5 Shown by Figure 4 An example representation of a first drive current generated by a first driver is shown.

[0060] Figure 6 Shows Figure 1 Schematic diagram of details of another example embodiment of a light source system.

[0061] Figure 7 Shows Figure 1 Schematic diagram of details of another example embodiment of a light source system.

[0062] Fig. 8A shows a simplified representation of another light source system according to one aspect of the present disclosure;

[0063] Figure 8B Shows Fig. 8A An example representation of control timing of a light source system;

[0064] Fig. 9 shows an example representation of another light source system according to one aspect of the present disclosure;

[0065] Fig.10 shows the control from Fig. 9 Example processing steps for pulse emission of light from a light source system;

[0066] Fig.11 Shows Fig. 9 An example representation of the control timing of a light source system.

[0067] Fig. 12A and 12B Shows Fig. 9 A representation of an exemplary embodiment of a system and control timing;

[0068] Fig.13a and 13b Shows Fig. 9 Another example embodiment of a system for representing and controlling timing;

[0069] Fig.14a and 14b Shows Fig. 9 Another example embodiment of a system for representing and controlling timing;

[0070] Fig.15a and 15b Shows Fig. 9 Another example embodiment of a system for representing and controlling timing;

[0071] Fig.16a and 16b Shows Fig. 9Another example embodiment of a system for representing and controlling timing;

[0072] Fig.17a and 17b Shows Fig. 9 Another example embodiment of a system for representing and controlling timing;

[0073] Fig.18 Shows Fig. 9 A representation of another example implementation of a system of

[0074] Fig.19 Shows Fig. 9 Representation of another example implementation of a system. DETAILED DESCRIPTION

[0075] Many factors can affect the accuracy with which a ToF camera system measures the distance to an object. One of these factors is the nature of the light emitted from the light source. The accuracy with which the system knows the moment the light was emitted can affect the accuracy with which the system determines the distance to an object. For example, if the time difference between the moment the system believes it emitted light and the moment it receives the reflected light is 20ns, then an object distance of approximately 3m will be determined. However, if the light emission actually occurred 0.4ns after the system believed it occurred, then the true time difference between the light emission and the light reflection is actually about 19.6ns, which equates to an object distance of 2.94m. Errors of this size can be significant for many safety-critical applications.

[0076] The inventors have recognized that the accuracy of a ToF camera system can be improved if the light source is controlled to emit very short pulses of light (on the order of 100ps or less). Longer light pulses can make it unclear whether the reflected light corresponds to a photon emitted at the very beginning, middle, or end of the light pulse. To address this issue, more samples can be collected to help deconvolve the shape of the laser, but this slows down the system and consumes more power. However, if the light pulses are very short (e.g., less than 100ps), this represents a maximum uncertainty of 0.1ns, which is acceptable for most applications. Therefore, the time between the emission of light and the corresponding reflection of the light can be measured with greater certainty.

[0077] In order to achieve very rapid turning on of the light source, the inventors have determined that a high current light source drive signal may be beneficial. Driving the light source with a relatively high, short duration current pulse should shorten the duration of the output light pulse and increase the peak optical power output. The inventors have recognized that this higher peak optical power may provide further benefits in improving the accuracy of the ToF camera system. In particular, many safety regulations limit the average optical power emitted from a ToF camera system, while there is no limit on the peak optical power output. By reducing the light emission duration, the system can emit higher optical power while staying within safety regulations. Emitting light with a higher peak optical power may help improve the range and accuracy of the ToF camera system.

[0078] However, there are many challenges in driving a light source to emit very short, high optical power light pulses. Very short, high current drive signals may be required to drive the light source, which may place considerable demands on the power supply / source providing the drive current and may impact other electrical components that are also using that power. For example, if a ToF camera system is integrated into a mobile phone, then consuming relatively high current for very short periods of time without impacting any other components or functions of the phone may require the use of a very high quality, expensive power supply system within the phone. Furthermore, if the ToF camera system operates with relatively high current pulses, then the relatively high current may pose a safety risk to the ToF camera system and / or nearby devices / components and / or an operator of the ToF camera system in the event of a system malfunction / failure.

[0079] Among other things, in order to achieve such short pulses of light emission, the laser source should be turned on and off quickly and precisely. The inherent resistance and inductance in the source driver circuit not only causes electrical losses (thereby increasing the amount of current required to obtain a specific optical power from the source), but also slows down the circuit conversion between current levels, thereby slowing down the speed of turning on and off. In addition, fast switching of control components (such as transistors) can be very challenging and can result in a lot of additional power consumption.

[0080] Taking all these challenges into consideration, the inventors have designed a light source system suitable for a ToF camera system. In the light source system, at least a portion of a light source driver (e.g., a switch for controlling current to drive a light source) is integrated into a semiconductor chip, and a capacitor (which may be integrated into or mounted on the semiconductor chip) is included as a capacitor for generating current to drive an energy source for the light source. The driver is designed so that the capacitor can be gradually charged using a relatively low current power supply / source, and then rapidly discharged to provide most, if not all, of the energy required to drive the light source with current (e.g., at least 95% (e.g., 96% or 98% or 100%) of the current to drive the light source may come from the discharged capacitor. As a result, a relatively high light source driving current can be generated without significantly affecting the low current power supply / source. In addition, the light source is mounted on or stacked on a semiconductor chip so that the physical distance between the driver and the light source is minimized. By minimizing the distance between the driver and the light source, the physical length of the current path between the driver and the light source can be reduced, thereby reducing resistance and inductance. In addition, by using a capacitor to provide most, if not all (e.g., at least 95%) of the energy required for the driver current, the physical size of the circuit loop carrying the driver current can be reduced compared to using a separate / external power supply unit, even further reducing resistance and inductance. Another benefit of using a capacitor in this manner is that in the event of a system fault / failure, only a limited amount of energy is available to generate a high current, which will improve the safety of the entire device.

[0081] In addition, the inventors have developed a circuit for controlling the turning on and off of a light source using two primary transistors in the current path of a drive current. The circuit is arranged so that if either transistor is turned off (not conducting), the current path of the drive current is disconnected. In this way, in order to control a very short duration light pulse from a light source, the circuit can be controlled to turn on the first main transistor and then turn on the second main transistor at a later time, when the current path will be completed and the light source will be turned off. After a short time corresponding to the target duration of the light pulse, the first transistor is turned off, thereby disconnecting the current path and turning off the light source. By turning on one transistor to initiate the start of a light pulse and ending the light pulse by turning off another transistor shortly thereafter, there is no need to turn on and then turn off the same current path transistor very quickly. This reduces the power consumption associated with quickly turning on and then turning off the transistor, thereby reducing the total power consumption associated with emitting a light pulse. Due to the turn-on characteristics of the light source and due to parasitic effects that require charging to reach the light emission condition of the light, the duration of the light pulse may be shorter than the duration of the conduction time through the light source.

[0082] Figure 1An example representation of a light source system 100 suitable for a ToF system according to one aspect of the present disclosure is shown. The light source system 100 includes a light source 110, which in this example is a vertical cavity surface emitting laser (VCSEL), and a semiconductor chip 120, such as a CMOS silicon chip, a GaN chip, or a GaAs chip, etc. Throughout the present disclosure, the light source 110 will generally be referred to as a VCSEL, although it should be understood that any other suitable type of light source may be used instead, such as other types of lasers (e.g., stacked edge emitting lasers) or any suitable type of LED.

[0083] The VCSEL includes a first surface 112 from which light is emitted and a second surface 114 opposite the first surface 112. The first surface 112 includes a first terminal 116 and a second terminal 118 of a first polarity, which in this example is the anode of the VCSEL diode. The second surface 114 includes one or more third terminals of a second polarity, which in this example is the cathode of the VCSEL diode. The VCSEL 110 is mounted on or stacked on a semiconductor chip 120. The second surface 114 of the VCSEL 110 is mounted on a first surface 122 of the semiconductor chip 120 and is bonded to an electrical connection of the first surface 122 of the semiconductor chip 120 using a bonding material 150 and an electrical interconnect so that an electrical connection is formed between the one or more third terminals of the VCSEL 110 and the first and second drivers 130 and 140. Any suitable bonding material 150 and bonding technique may be used for this purpose, such as epoxy or eutectic bonding.

[0084] The light source system 100 includes a first driver 130 and a second driver 140. In this example, the first driver 130 and the second driver 140 are integrated in the semiconductor chip 130. The first driver 130 is configured to control the supply of a first drive current 136 to the VCSEL 110 to control the operation of the VCSEL 110 (i.e., for controlling the emission of light from the VCSEL 110). The second driver 140 is configured to control the supply of a second drive current 146 to the VCSEL 110 to control the operation of the VCSEL 110 (i.e., for controlling the emission of light from the VCSEL 110). The first driver 130 includes a first switch 134, which is a first FET in this example, for controlling the flow of the first drive current 136, and the second driver 140 includes a second switch 146, which is a second FET in this example, for controlling the flow of the second drive current 146. The first driver 130 is electrically coupled to the first terminal 116 of the VCSEL 110 via one or more first bond wires 152 (although alternatively, any other suitable form of electrical coupling may be used, e.g., depending on the design of the VCSEL 110). The second driver 140 is electrically coupled to the second terminal 118 of the VCSEL 110 via one or more second bond wires 154 (although alternatively, any other suitable form of electrical coupling may be used, e.g., depending on the design of the VCSEL 110). When a sufficiently large first drive current 136 and / or second drive current 146 flows through the VCSEL 110, the VCSEL 110 will turn on and be excited to emit laser light and thus emit light. When no drive current, or insufficient drive current, flows through the VCSEL 110, no light should be emitted and the VCSEL is effectively turned off. More details of the operation of the first driver 130 and the second driver 140 will be given later in this disclosure.

[0085] Figure 2A and 2B Different views of an arrangement of a VCSEL 110 mounted on a semiconductor chip 120 are shown. It can be seen that in this example, there are eight first bond wires 152 and eight second bond wires 154, although any number of first bond wires 152 and second bond wires 154 (e.g., one, two, three, etc.) may be used. For a given size of first terminal 116 and second terminal 118, it may be preferable to use as many first bond wires 152 and second bond wires 154 as possible. By doing so, the resistance of the first drive current 136 and the second drive current 146 can be minimized, thereby improving the power efficiency of the light source system 110 and maximizing the amount of drive current delivered to the VCSEL 110.

[0086] Figure 3A graph is shown representing the drive current (labeled VCSEL Current) and the optical power of the light output from the VCSEL 110. It can be seen that in this example, the drivers 130, 140 can generate a drive current pulse duration of approximately 290 ps, ​​which can stimulate the emission of light pulses from the VCSEL 110 with an effective duration of approximately 30 ps. It will be appreciated that the drive current pulse duration is longer than the light pulse duration due to laser delay in the VCSEL 110. It will also be understood that this is merely one non-limiting example of drive current and light pulse duration, and that the light source system 100 can be configured to operate with different durations.

[0087] Mounting VCSEL 110 on semiconductor chip 120 may be counterintuitive, especially when the drive current is intended to be relatively high (e.g., >1A or >3A or >5A or >8A or >10A) due to heat dissipation difficulties. When the drive current flows, VCSEL 110 and drivers 130 and 140 may generate a large amount of heat, which should ideally be dissipated quickly and efficiently to avoid device damage and degradation. It can be expected that stacking VCSEL 110 on top of semiconductor chip 120 may make heat dissipation more difficult.

[0088] However, the inventors have recognized that by mounting the VCSEL 110 on the semiconductor chip 120, the physical distance between the VCSEL 110 and the drivers 130, 140 can be minimized. Therefore, the first drive current circuit formed by the VCSEL 110, the first capacitor 132, and the first switch 134 to carry the first drive current 136 can be significantly smaller than other arrangements (e.g., an arrangement in which the VCSEL 110 and the first driver 130 are mounted side by side on a PCB substrate via bonding wires that carry current to and from the VCSEL 110 side by side). Similarly, the size of the second drive current circuit formed by the VCSEL 110, the second capacitor 142, and the second switch 144 is also the same. This reduction in the size of the circuit carrying a relatively high drive current can reduce the resistance and inductance of the circuit, which can reduce circuit losses and increase the drive current and the speed at which the VCSEL 110 can be turned on and off. This enables the drive current to be generated as a very short duration pulse, resulting in a very short duration pulse from the VCSEL 110. Due to the turn-on characteristics of the light source and due to parasitic effects that require charging to reach the light emission condition, the duration of the light pulse may be shorter than the duration of the transmission time through the light source. Figure 1 , 2A2B, the VCSEL 110 can output a higher optical power pulse with a shorter duration (e.g., <200ps or <150ps or <100ps or <80ps or <50ps). As previously explained, in order to achieve a relatively short duration of light output from the VCSEL 110, a slightly longer duration of drive current pulses may be required. For example, to obtain a 30ps light pulse, a first drive current 136 with a duration of 300ps may be required.

[0089] Not only can this improve the accuracy of a ToF system using the light source system 100, but it is unexpectedly recognized that due to the short current duration achieved by this arrangement, heat dissipation may not actually be as severe as initially believed. A ToF system can operate by emitting light for a period of time and then turning it off for a period of time. For example, a typical light emission duration for a SPAD direct ToF system can be a pulse duration of approximately 1-3ns per 0.2μs, representing a duty cycle of light emission: no light emission of approximately 1:100. A typical light emission duration for a continuous wave (CW) indirect ToF system can be approximately 100-200ns per 2ms, representing a duty cycle of approximately 1:20 to 1:10. However, in the present disclosure, because such short, high optical power light pulses have been achieved, a duty cycle of at least 1:1,000, such as 1:5,000 or 1:10,000 can be achieved. For example, Figure 3 The approximately 30 ps light pulses represented in correspond to a duty cycle of approximately 1:30,000. Thus, there are relatively long periods of time during which the light source system 100 does not generate heat, during which the heat generated during the emission portion of the cycle may gradually dissipate into the surrounding environment and the body of the chip (and any other materials coupled to the chip).

[0090] exist Figure 1 , 2A In the example shown in 2B, the VCSEL 110 has two terminals 116 and 118 of the same polarity, which are arranged to be substantially symmetrical about the symmetry plane. In this example, the symmetry plane extends substantially perpendicular to the first surface 112 and the second surface 114 of the VCSEL 110 and substantially passes through the middle of the first surface 112 and the second surface 114, so that the first terminal 116 is on one side of the symmetry plane and the second terminal 118 is its mirror image on the other side of the symmetry plane. The inventors have recognized that the components of the first driver 130 and the second driver 140 can be arranged in such a way that they are substantially or approximately symmetrical about the symmetry plane (such as Figure 1). Thus, the direction of the path / loop of the first drive current 136 is substantially opposite to the direction / loop of the second drive current 146 (e.g., the path of the first drive current 136 may be in a clockwise direction and the path of the second drive current 146 may be in a counterclockwise direction). As a result, the EM radiation generated by one of the current paths / loops may be substantially or at least partially offset by the EM radiation generated by the other current path / loop, particularly in the far field. Thus, even when the drive current is relatively high, RF emissions from the light source system 100 (caused by the light source system 100 generating light pulses at radio frequency frequencies) may be reduced and maintained acceptably low. This means that the light source system 100 should not negatively impact other nearby electrical devices / components, nor should it violate RF emission regulations. It should be understood that while such a symmetrical arrangement may have benefits, such an arrangement is not essential, and the first driver 130 and the second driver 140 may be arranged relative to each other in any other suitable manner.

[0091] Figure 4 A schematic representation of example details of the light source system 110 is shown. The representation provides further details of an example implementation of the first driver 130 to help illustrate the operation of the first driver 130 to control the supply of the first drive current 136 to the VCSEL 110. In this example, the first driver 130 further includes a voltage regulator 410 (which can be implemented in any suitable manner known to those skilled in the art), a pre-driver 420, a pre-driver 422, and a FET 440 used as a first switch 134. The light source system 110 also includes a controller 430 configured to control the switching of the first driver 130 between the charging state and the emission state. The controller 430 can be implemented in any suitable manner, for example, as logic integrated in the semiconductor chip 420 or elsewhere, or using a microcontroller configured to operate as described below, or any other form of a processor configured to operate as described below. Likewise, the pre-driver 420 and the pre-driver 422 can be implemented in any suitable manner known to those skilled in the art, for example, as a buffer and / or a digital buffer and / or an amplifier.

[0092] The first driver 130 is coupled to a power supply / source PVDD and PVSS, which can be a relatively low current power supply (e.g., the first driver circuit 130 can draw less than 50 mA or less than 30 mA from the power supply, such as a typical average current of less than 20 mA). When the first driver 130 is in a charging state, the FET 440 is turned off (i.e., the first switch 134 is disconnected) so that the current flowing through the VCSEL 110 is 0 A or substantially 0 A (i.e., low enough that the VCSEL 110 does not emit any light). The power supply can be any suitable power supply to which the first driver 130 can be coupled. For example, if the light source system 100 is included as part of a larger device / system (such as a mobile device), the power supply can be a power supply of the larger device system (such as a battery of the mobile device). During the charging state, the first capacitor 130 is gradually charged by the power supply.

[0093] When light pulse emission is desired, the first driver 130 may transition from the charging state to the emission state. To control the transition, the controller 430 may control the operation of the FET 440 using control lines 434 and / or 436. For example, the controller 430 may receive an instruction via its input line 432 (which may take any suitable form, for example, it may be an LVDS differential signal) to start emitting light pulses from the VCSEL 110. The controller 430 may then drive the control line 434 so that the pre-driver 420, which is turned on, applies a turn-on signal to the gate of the FET 440 so as to turn on the FET 440 (i.e., close the first switch 134). In this example, the turn-on signal is a voltage signal that exceeds the turn-on threshold voltage of the FET 440. The turn-on pre-driver 420 is used in this example because the first drive current 136 that will flow through the FET 440 when turned on should be relatively large (e.g., between about 5A and 12A, such as >8A or >10A), and therefore the FET 440 should be a relatively high power FET 440. Most controllers may not be able to provide a large enough drive signal to FET 440 to turn on FET 440, or at least not be able to provide a large enough drive signal to turn FET 440 on quickly enough to achieve a fast transition from off to on. Therefore, the on pre-driver 420 effectively acts to increase the signal set by the controller 430 on the control line 434 to a level sufficient to drive FET 440 on quickly.

[0094] In this arrangement, the power consumed by the turned-on pre-driver 420 and the turned-off pre-driver 422 is provided by the voltage regulator 410, which in turn draws most, if not all, of the power from the discharge of the capacitor 132. By arranging in this manner, most, if not all, of the current required to switch the first driver 130 between the charging state and the transmitting state is maintained within the first driver 130 and is not drawn from elsewhere, such as the power supplies PVDD and PVSS. Some of the benefits of drawing most, if not all, of the required energy from the capacitor 132 rather than from an external source were explained earlier with reference to the first drive current 136. In addition, if the voltage regulator 410 and the pre-driver are also integrated into the chip 120, they can all be relatively close to each other and relatively close to the capacitor 132, thereby further improving switching speed and reducing losses.

[0095] When the FET 440 is turned on (ie, the first switch 134 is closed), the first driver 130 is in an emission state, the first drive current circuit is closed, and thus the first drive current 136 flows between the VCSELs 110 .

[0096] It can be seen that in this example arrangement of the first driver 130, the first capacitor 132 is coupled between the anode terminal of the VCSEL 110 and a reference voltage (ground in this example, but the reference voltage may be any other suitable voltage level) of the first driver 130 (i.e., one terminal of the capacitor 132 is coupled to the VCSEL 110, and the other terminal of the capacitor 132 is coupled to the reference voltage). Although this particular configuration is not essential, it has the benefit that the VCSEL 110 can be driven by a positive voltage within the first driver 130, so that driving the VCSEL 110 does not require the generation of a negative voltage within the first driver 130. This has the advantage of simplifying the operation of the first adapter 130 and enables the components of the first adapter 130 to be integrated in the semiconductor chip 120 using, for example, junction isolation, and without the need for dielectric isolation.

[0097] Figure 5An example representation of a first drive current 136 flowing through a first drive current circuit is shown. During the transmit state, the first capacitor 132 is discharged to generate the first drive current 136. Therefore, most (if not all) of the energy required for the first drive current 136 is provided by the first capacitor 132 during the drive time, such as if it is not effectively zero, and the draw on the power supplies PVDD and PVSS is very low (e.g., <5%, or <1% of the first drive current 136 can be drawn from the power supply). For example, the discharged first capacitor 132 can provide at least 95%, such as at least 97% or at least 99% of the first drive current 136. In this way, most (if not all) of the first drive current 136 is maintained within the first driver 130 in a relatively small first drive current circuit (i.e., not drawing current from current elsewhere or not drawing a large amount of current from other sources). In an alternative embodiment, when the first shunt 130 is in the transmit state, an additional switch can be used to isolate the first driver 130 from the power supply, although this is not necessary in most implementations because the first capacitor 130 provides so much energy during the transmit state that the drain on the power supply is negligible.

[0098] By utilizing the first capacitor 132 in this manner, the first capacitor 132 can be gradually and slowly charged by the power supply during the charging state, which should not affect the power supply in any noticeable way. The first capacitor 132 can then be discharged to generate the first drive current 136, so that the power supply can be effectively or completely unaffected by the relatively high first drive current 136. Therefore, the power supply can be of standard specifications, thereby minimizing costs, and can be used by other components / systems without being affected by the light source system 100. In addition, because the first drive current 136 is generated effectively entirely through the first capacitor 132 as a power source, the first current driver circuit remains relatively small (compared to the case where the first drive current 136 is drawn from an external power source), which reduces the delay in the start of the first drive current 136 and increases the speed of operation.

[0099] During the emission state, the first driver 130 can be configured such that the first capacitor 132 can be fully or only partially discharged in the process of generating the first drive current 136. In some embodiments, generating the first drive current 136 can only cause a partial discharge of the charge stored on the first capacitor 132, thereby causing the voltage across the first capacitor 132 to decrease (e.g., by a few volts), but at the end of the emission state, a non-zero voltage still exists across the first capacitor 132. In this case, the voltage across the capacitor 132 can be monitored before, during, and / or after the emission state, so that the amount of the first drive current 136 provided to the VCSEL 110 during the emission state can be determined. The size of the first capacitor 132 can be set to any suitable value based on the required voltage margin (i.e., the desired voltage across the capacitor at the end of the emission state) and / or the voltage of the power supplies PVSS and PVDD and / or the required first drive current level and / or the duration of the first drive current and / or the duty cycle of the emission state to the charging state. As a non-limiting example, if a first drive current 136 of approximately 10A is desired, for a first drive current duration of approximately 300ps, and it is desired to reduce the voltage across first capacitor 132 during the transmit state of approximately 3V, first capacitor 132 may have a capacitance of approximately 3nF.

[0100] Furthermore, because the capacitor 132 can only store a limited amount of energy, if there is a fault or failure in the system, the relatively high first drive current 136 can only be maintained for a limited, relatively short period of time. Therefore, the light source system 100 can have improved safety compared to other devices that draw drive current from less limited power sources.

[0101] To transition the first driver 130 from the emission state to the charging state, the FET 440 is turned off (i.e., the switch 134 is opened), thereby opening the first drive current circuit and preventing the first drive current 136 from flowing through the VCSEL 110. To control this transition, the controller 430 may control the operation of the FET 440 using the control lines 434 and / or 436. For example, the controller 430 may receive an instruction via its input line 432 to stop emitting light pulses from the VCSEL 110. The controller 430 may then set the control line 434 to a level that will turn off the FET 440, for example, to a voltage below the turn-on threshold voltage of the FET 440. The controller 430 may also apply a shutdown signal to the gate of the FET 440 using a shutdown pre-driver 422, which may be designed to have very high drive strength and speed in one direction (i.e., to pull down the gate of the FET 440). For example, because in this embodiment, the shutdown pre-driver 422 is an inverting type pre-driver, the controller 430 can set the voltage at the control line 436 to a "high" voltage (e.g., 3.3V or 5V), causing the output of the shutdown pre-driver 422 to go "low" (e.g., to 0V). Using the shutdown pre-driver 422 in this manner can increase the speed at which the relatively high current FET 440 can be turned off. The inventors have recognized that although control of turning on the pre-driver 420 and turning off the pre-driver 422 can be performed simultaneously, and a relatively fast turn-off speed can be achieved for the FET 440, a faster turn-off speed can be achieved by first applying the turn-off signal to the gate of the FET 440 (such that both the turn-on signal and the turn-off signal are applied to the gate of the FET 440 for a first time period), and then subsequently removing the turn-on signal so that only the turn-off signal is applied to the gate terminal of the FET 440 for a second time period. This effect can be particularly achieved when the off pre-driver 422 is designed to have a relatively high drive strength compared to the drive strength of the on pre-driver 420, which causes the off pre-driver 422 to overdrive the on pre-driver 420. Therefore, the superior drive strength of the off pre-driver 422 can thus result in pulling down the gate of the FET 440 faster than otherwise achieved. It may not be intuitive to drive the gate of the FET 440 with an on and off signal in order to turn off the FET 440 within a first time period, but the inventors still recognize that such driving can increase the turn-off speed of the FET 440.

[0102] It will be appreciated that each of the turn-on pre-driver 420 and the turn-off pre-driver 422 may be of the inverting or non-inverting type, and that the signals applied by the controller 430 to the control lines 434 and 436 are set accordingly. Furthermore, it will be appreciated that the turn-off pre-driver 422 is optional, and alternatively, it may be omitted entirely, wherein the FET 440 is turned off simply by varying the voltage applied to its gate to be below the turn-on threshold of the FET 440.

[0103] Figure 6 An exemplary alternative embodiment of the first driver 130 is shown. Figure 4 and Figure 5 The illustrated embodiment is similar, but includes an additional turn-on pre-driver driver 610, an additional control line 612 from the controller 430, and an additional FET 620. FET 620 is a relatively low current FET (e.g., rated at approximately 400 mA, while FET 440 is approximately 10 A) that acts as a pre-bias voltage for the VCSEL to cause a relatively low sub-laser threshold current to flow through the VCSEL 110 before FET 440 fully turns on the VCSEL 110. Thus, before turn-on of the VCSEL 110 is desired, the controller 612 can use the additional turn-on pre-driver 620 to apply a turn-on voltage to the gate of the additional FET 620 (i.e., a voltage that exceeds the turn-on threshold voltage of the additional FET 620). Once the additional FET 620 is turned on, a relatively low current can flow through the additional FET 620 (e.g., approximately 400 mA). Because the current is relatively low and below the lasing threshold of the VCSEL 110, the VCSEL 110 will not yet begin to emit light. However, ideally, the current level will be just below the lasing threshold. When VCSEL 110 is to be turned on, FET 440 may be turned on, as described above, so that the higher first drive current 136 may flow through the first drive current circuit and turn on VCSEL 110. Then, for example, once FET 440 is fully turned on, controller 430 may turn off additional FET 620 by reducing the gate voltage at additional FET 620. It will be appreciated that using additional FET 620 in this manner may speed up the time between when controller 430 begins turning on FET 440 and light is emitted from VCSEL 110, because when FET 440 begins to turn on, VCSEL 110 will already be close to lasing.

[0104] Figure 7 1 shows an example of another alternative implementation of aspects of the light source system 110. This embodiment shows a simplified implementation of the first driver 130 including only the first capacitor 132, the on pre-driver 420 and the FET 440. However, it will be understood that the first driver 130 may alternatively be Figure 4 , 5 Or it can be realized by the method shown in 6.

[0105] In this embodiment, the photodetector 710 is configured to receive light emitted from the VCSEL 110. For example, the photodetector 710 may be a photodetector for ToF imaging and may receive some stray light emitted from the VCSEL 110 and reflected directly back to the photodiode by the device optical package so that it can detect light emitted from the VCSEL 110 (rather than just detecting light reflected from the imaged object). Alternatively, it may be arranged in a manner to directly receive light emitted from the VCSEL 110. The photodetector 710 is coupled to a detector 720, which is configured to output a signal 722 indicating whether the photodetector 710 has received light output from the VCSEL 110. The controller 430 may then be configured to control the operation of the charge pump 740 based on the received signal 722. In particular, if the controller 430 transitions the first driver 130 to an emission state and subsequently receives a signal from the detector 720 indicating that the photodetector 710 has received light output from the VCSEL 110, the controller 430 may then enable the charge pump 740 using the control line 732. In this case, it can be assumed that the light source system is operating normally, and when the first driver 130 is next in the charging state, the charge pump 740 will then be operable to charge the first capacitor 132. However, if the detector 720 does not output the signal 722 indicating that the photodetector 710 has received light output from the VCSEL 110, the controller 430 can disable the charge pump 740 using the control line 732. Then, when the first driver 130 is next in the charging state, the charge pump 740 may not charge the first capacitor 132, so that the first capacitor 132 will no longer store more energy for attempting to drive the VCSEL 110. Therefore, the photodetector 710 may not have received any light emitted from the VCSEL 110 because there may be some error or failure in the light source system that prevents the VCSEL 110 from properly emitting light. Because the light source system may be used in a safety-critical ToF application, or the type of failure may pose an electrical hazard to the light source system and / or nearby systems and / or operators, preventing further charging of the capacitor and attempted emission from the VCSEL 110 may improve the overall safety of the light source system. Alternatively, controller 430 may be configured to output a fault warning to any other suitable system / entity.

[0106] Although a charge pump 740 is used in this particular example, any other suitable circuit / component may be used to control the connection / disconnection of the first driver 130 to the power source based on the detection of light emitted from the VCSEL 110. For example, the charge pump 740 may be replaced with a switch (e.g., a transistor) controlled by the controller 430 to connect or disconnect the first driver 130 to the power source PVDD. In another alternative, instead of using a charge pump 740, the power source may be a controllable power source, such as a switch mode power supply, which may be controlled by the controller 430 to provide or not provide power to the first driver 130.

[0107] although Figures 4 to 7 And the above description only refers to the first driver 130, but it should be understood that the second driver 140 can be implemented in exactly the same manner. The light source system 100 can have a single controller 430 that is configured to control the operation of the first driver 130 and the second driver 140 so that they each generate the first drive current 136 and the second drive current 146 at the same time, or each of the first driver 130 and the second driver 140 can have its own controller that operates as described above. Similarly, each of the first driver 130 and the second driver 140 can have its own voltage regulator, or a single voltage regulator can be used to power the pre-drivers in both the first driver 130 and the second driver 140.

[0108] although Figures 4 to 7 The arrangement shown is effective for rapidly switching VCSEL 110 on and off to achieve very short, high current pulses, but the inventors have discovered some potential disadvantages of the switch control. In particular, it is difficult to rapidly turn FET 440 on and then rapidly turn it off again for only a short period of time. This is a result of FET 440 being a relatively large FET 440 (needed to handle the relatively large drive current that will flow through it), which results in relatively large parasitic effects (particularly large gate-drain parasitic effects), which make it difficult to drive the gate of FET 440 with a short, controlled gate signal. For example, due to the parasitic effects, Figure 7 The on-off pulses on control line 434 in an arrangement of may have less controlled, longer gate voltage pulses on FET 440. This in turn may result in longer, less well controlled pulses of the drive current through VCSEL 110.

[0109] like Figures 4 to 6As shown, using two separate signals 434 and 436 to control the on and off switching of FET 440 can help improve this situation and enable faster and more controlled transitions in the gate voltage of FET 440, thereby driving current through VCSEL 110. However, this arrangement may result in additional power consumption due to the two signals competing with each other during the transition from the emission state to the charging state (e.g., when turning off VCSEL 110 at the end of a light pulse).

[0110] Fig. 8A and 8B Some additional details are shown to help explain this. Fig. 8A The circuit is based on Figure 4 , but includes an additional PMOS and an additional NMOS, which may form part of pre-drivers 420 and 422 for driving the gate of FET 440. Figure 8B The graph shows how the timing of the on pulse 434 and the off pulse is a relatively fast switching of the FET 440 from off to on and back to off again, resulting in a relatively short and well controlled drive current I laser However, during shutdown, the PMOS and NMOS represented may be turned on for a period of time, thus competing with each other. This causes a large current shoot-through current from the regulator to flow through both the PMOS and NMOS at the same time, resulting in a large amount of additional power dissipation. This Figure 8B It is expressed as "excessive current from the regulator".

[0111] To solve this problem, the inventors have developed a configuration of a driver circuit that includes two primary transistors in a driving current circuit in order to control the turning on and off of the VCSEL 110 .

[0112] Fig. 9 An example representation of a system 900 according to this aspect of the disclosure is shown. The system 900 includes a first FET 910, a second FET 920, and a controller 930 configured to control the operation of the FETs. The controller 931 is configured to output a first control signal 931 for controlling the state of the first FET 910 and to output a second control signal 932 for controlling the state of the second FET 920. The system 900 is adapted to be coupled to the VCSEL 110 in such a manner that when both FETs are in the on state (conducting), the laser drive circuit is complete and the drive current I laser132 may flow through VCSEL 110 to turn it on. If either FET is off, the laser drive circuit will be disconnected and the drive current will stop flowing, causing VCSEL 110 to turn off. In this example, the laser drive voltage is PVDD, and capacitor 132 provides most of the drive current, as described below. However, system 900 can be used with other power supplies, for example, capacitor 132 can be omitted and the drive current can be supplied from some other external power supply (e.g., a power supply that provides PVDD).

[0113] Fig.10 An example process for controlling the pulse emission of light from the VCSEL 110 is shown. In step S910, the controller 930 sets the first FET 910 to a conducting state (i.e., an on state) using a first control signal 931, and sets the second FET 920 to a non-conducting state (i.e., an off state) using a second control signal 932. In this example, the first FET 910 is an NMOS, so the first FET 910 can be turned on by converting the voltage of the signal 931 from a low signal to a high signal (i.e., increasing the signal voltage from below the threshold turn-on voltage of the first FET 910 to above the threshold turn-on voltage). The second FET 920 can be kept in a non-conducting state by simply keeping the signal 932 below the threshold turn-on voltage of the second FET 920.

[0114] In step S920, the controller 930 turns on the VCSEL 110 using the second control signal 932. In this example, because the second FET 920 is an NMOS, the controller 930 can do this by increasing the voltage of the signal 932 above the turn-on threshold of the second FET 920. Both FETs are now turned on, so that the laser drive circuit is complete, and the laser drive current begins to flow through the VCSEL 110, thereby initiating the laser pulse.

[0115] In step S930, the controller 930 turns off the VCSEL 110 using the first control signal 931 to set the first FET 910 to a non-conductive state. In this example, the controller 930 may do this by reducing the voltage of the signal 931 below the turn-on threshold of the first FET 910. This will destroy the laser drive circuit so that the laser drive current stops flowing through the VCSEL 110 and the laser pulse ends.

[0116] In step S940, the controller 930 may reset the system 900 by setting the second FET 920 to a non-conducting state using the second control signal 932. In this example, the controller 930 may do this by reducing the voltage of the signal 932 below the turn-on threshold of the second FET 920. The process may then return to step S910 when additional light pulses are needed.

[0117] In this process, the VCSEL 110 is turned on by changing the state of the second FET 920 (from off to on), and then turned off by changing the state of the first FET 910 (from on to off). As a result, it is not necessary to switch the state of a single transistor very quickly from off to on and then off again to achieve a relatively short light pulse from the VCSEL 110. The time period between turning on the first FET 910 in step S910 and turning on the second FET 920 in step S920 can be relatively long to allow the first transistor 910 to be fully turned on before the VCSEL 110 is turned on. As a result, the first FET 910 can be turned off directly in step S930 shortly after the second FET 920 is turned on in step S920. Thus, the time between turning on the second FET 920 and turning off the first FET 910 can be relatively short (e.g., approximately 100 picoseconds or less, such as less than 1 nanosecond, or less than 800 picoseconds, or less than 500 picoseconds, or less than 200 picoseconds, or less than 100 picoseconds) without suffering from the high power consumption associated with rapidly switching a single FET 440.

[0118] Fig.11 An example representation of the timing of the first signal 931 and the second signal 932 is shown. The controller 930 can set the time period between steps S920 and S930 based on the target light pulse emission duration because the time difference between the transition of step S920 and the transition of step S930 affects the time when the drive current flows through the VCSEL 110, and thus affects the time when the VCSEL 110 is turned on and emits light.

[0119] Fig. 9 The representation assumes that the controller 930 can set and control a sufficiently large and strong signal to quickly change the state of the FETs, particularly a fast and controlled turn-on of the second FET 920 and a fast and controlled turn-off of the first FET 910. However, this assumption may not always be reasonable, particularly where the FETs are relatively strong / large in order to handle relatively large drive currents (e.g., >1A or >3A or >5A or >8A or >10A). Various further detailed configurations designed to achieve such control of the FETs will now be described.

[0120] FIG. 12a shows an exemplary laser light source system 1200 according to another aspect of the present disclosure. FIG. 12b shows an example representation of the timing of control signals output by the controller 930 to perform reference Fig.10 Description of the process.

[0121] The system 1200 is similar to the previously described system 900, but includes some additional components for controlling the operation of the primary FETs 910 and 920. The controller 930 outputs a first control signal 1211 for controlling the state of the pre-charge transistor 1210. In step S910, the first control signal 1211 can be used to turn on the first FET 910 by turning on the pre-charge transistor 1210. In this example, the pre-charge transistor 1210 is a PMOS, so the controller 930 turns on the transistor 1210 by reducing the voltage of the first control signal 1211 below the turn-on threshold of the transistor 1210. Turning on the transistor 1210 will cause a turn-on voltage to be applied to the gate of the first FET 910, in this case, the laser drive voltage PVDD is applied to the gate of the first FET 910. This will pre-charge the first FET 910 by charging a capacitance associated with the control terminal (gate) of the FET 910 (e.g., the parasitic gate-source capacitance of the FET 910, although it may alternatively be a capacitor coupled between the control terminal and the channel terminal (e.g., between the gate and source terminals of the FET 910)). After a period of time, the controller 930 can use the first control signal 1211 to turn off the pre-charge transistor 1210 (e.g., increase the voltage to approximately PVDD), and the first FET 910 will be maintained in the on state by the charging capacitance associated with the control terminal of the first FET 910. This can be seen in the control signal timing diagram of the first control signal 1211 and the gate of the first FET 910 in FIG. 12b. By pre-charging the first FET 910 in this manner to turn on the first FET 910, the controller 930 does not need to output any particularly large or strong signals to control the operation of the relatively large / strong first FET 910. In addition, by turning off the precharge transistor 1210 once the precharge is completed, and then subsequently turning on the transistor 1240 at step S930 (described later), there is no time for both the precharge transistor 1210 and the transistor 1240 to be turned on. As a result, there should be no shoot-through current through the transistors 1210 and 1240, which can significantly reduce the power consumption associated with the fast switching of the VCSEL 110. In addition, the gate voltage of the first FET 910 can be increased to the laser supply voltage through the relatively weak transistor 1210. In order to precharge the gate of the FET 910, a relatively long time may be required (as shown in FIG. 12 b), but this is acceptable because the turn-on speed of the first FET 910 is not important in the arrangement of the laser drive circuit. Alternatively, the first control signal 1211 can be passed through a pre-driver powered by the laser drive voltage PVDD, similar to the pre-shunt 420 or 422 described previously.

[0122] Throughout this specification, reference will be made to relatively "weak" / "small" and "strong" / "large" transistors. The relative terms "weak" and "strong" refer to the relative drive strength of a transistor (i.e., how much current a transistor can deliver for a given gate drive voltage). A "weak" transistor provides a relatively lower channel current for a given gate drive voltage than a "strong" transistor. The relative strength of a transistor can be controlled by the design of the transistor, for example by its W / L ratio, which affects the drain-source current equation (saturation is approximated by I ds =W / L*G m *(V gs -V t ) 2 ). In order to quickly turn on or off the relatively strong / large FETs 910 and 920, the gates of the FETs 910 and 920 may need to be driven by a relatively large gate current, which may generally require a relatively strong driving transistor. However, the inventors have recognized that, where possible, it is preferred to design the drive circuit to control the switching of the FETs 910 and 920 using relatively weak transistors, and to try to minimize the number of relatively strong transistors used to switch the FETs 910 and 920. According to the present disclosure, in order to drive a relatively strong transistor, a gate signal with a current of at least 0.5A (e.g., 1A or 2A) may be required. The channel current may be in the range of 1A to 100A. According to the present disclosure, in order to drive a relatively weak transistor, a gate current of less than 100mA may be required, such as 50mA or 25mA. The channel current of a relatively weak transistor may be as high as about 300mA, such as 100mA or 200mA. Thus, it can be seen that it may be desirable to use weak transistors wherever possible to control the switching of the first and second FETs 910 and 920 in order to minimize current requirements and potentially enable direct gate control via control signals (if the controller 930 can output a signal with sufficient current to drive the weak transistors).

[0123] After turning on the first FET 910, in step S920, the controller 930 uses the second control signal 932 to turn on the second FET 920, thereby turning on the VCSEL 110. This is similar to the previous reference Fig. 912a . The arrangement of FIG. 12a is very similar to that described, but some other switching circuits are used in order to quickly turn on the relatively large / strong second FET 920. In particular, the push / pull transistors 1220 and 1230 are configured so that when the second FET 920 is to be turned on, the PMOS 1220 is turned on by the second signal 932 and the NMOS 1230 is turned off by the second signal. Turning on the PMOS 1220 and turning off the NMOS 1230 causes the regulated supply voltage output from the voltage regulator 410 (described previously) to be applied to the gate of the second FET 920 to quickly turn on the second FET 920. The PMOS 1220 can be relatively large / strong in order to control a sufficiently large and strong signal on the gate of the second FET 920. To help control the relatively large / strong FET, the second control signal 932 can be passed through a pre-driver (which can be powered by the regulated supply voltage output from the regulator 410, although this is not shown in FIG. 12a for simplicity). In Figure 12a, the pre-driver is shown as an inventive type, but it can be non-inverting if the nature of the signal level transition of the second control signal 932 is suitable. In addition, depending on the nature of the transistor 1220 and the nature of the control signal output from the controller 930, the use of the pre-driver is optional.

[0124] It will be understood that in this arrangement and in all arrangements described below, push / pull transistors 1220 and 1230 are optional. For example, the second control signal 932 (or the output of a driver through which the second control signal 932 passes) may be strong enough to drive the second FET 920.

[0125] In step S930, the controller 930 uses the third control signal 1214 to turn off the first FET 910. The third control signal controls the turn-off transistor 1240. The controller 930 sets the third control signal to turn on the transistor 1240, which causes the capacitance associated with the control terminal of the first transistor 910 to be discharged, thereby turning off the first FET 910. In order to achieve a relatively fast turn-off of the first FET 910, the turn-off transistor 1240 can be relatively large / strong so that it can quickly change state and quickly discharge the capacitance of the first FET 910. Therefore, the third control signal 1214 can optionally pass through a pre-driver (which can be inverting or non-inverting depending on the nature of the third control signal transition). Where a pre-driver is used, the pre-driver can be powered in any suitable manner, such as powered by the regulated supply voltage output by the voltage regulator 410.

[0126] In step S940, the controller 930 uses the second control signal 932 to turn off the second FET 920 by turning off the transistor 1220 and turning on the transistor 1230. This reduces the gate voltage of the second FET 920 below its turn-on threshold voltage, thereby turning off the second FET 920. The transistor 1230 can be a relatively small / weak transistor because fast turn-off of the second FET 920 is not important, so a slow turn-off of the FET 920 is acceptable (as can be seen from the control signal timing of FIG. 12b).

[0127] Fig.13a An exemplary laser source system 1300 is shown according to another aspect of the present disclosure. Fig.13b An exemplary representation of the timing of control signals output by the controller 930 is shown in order to perform the reference Fig.10 Describe the process.

[0128] In this arrangement, the first FET 910 is a PMOS. The system 1300 also includes a pre-charge voltage regulator 1310, which is arranged to set a pre-charge voltage to be applied to the gate of the first FET 910 to turn it on during step S910. The pre-charge supply voltage output by the regulator 1310 is lower than the laser supply voltage PVDD by an amount that exceeds the turn-on threshold voltage of the first FET 910. To pre-charge the first FET 910, the controller 930 increases the high level of the voltage signal 1211 to turn on the transistor 1310 and maintains the third control signal 1214 at a level that keeps the transistor 1340 off. When the transistor 1310 is turned on, as the capacitance associated with the first FET 910 is charged, the voltage at the gate of the first FET 910 is as shown in FIG. Fig.13b Once the first FET 910 is pre-charged, the controller 930 can then change the first control signal 1211 again so that the transistor 1310 is turned off and the first FET 910 remains turned on. In this arrangement, the transistor 1310 can be relatively small / weak because the turn-on speed of the first FET 910 is not important.

[0129] As previously described, steps S920 and S940 may be performed. Step S930 may be performed by the controller 930 by setting the third control signal 1214 to turn on the transistor 1340 and turn off the first FET 910. The transistor 1340 may be relatively large / strong in order to achieve a fast turn-off of the first FET 910. Depending on the transition of the third control signal 1214 and on the signal drive requirements of the gate of the transistor 1340, the gate of the transistor 1340 may be optionally driven by an inverting or non-inverting driver.

[0130] Fig.14aAn exemplary laser source system 1400 is shown according to another aspect of the present disclosure. Fig.14b An exemplary representation of the timing of control signals output by the controller 930 is shown in order to perform a reference Fig.10 Describe the process.

[0131] In this arrangement, both the first and second FETs 910 and 920 are PMOS FETs. The power supply voltage –PVDD is a negative power supply voltage. In step S910, the controller 930 precharges the first FET 910 to turn it on by turning on the precharge transistor 1410 using the first control signal 1211. Once the capacitance associated with the first transistor 910 is charged, the first control signal 1211 can turn off the precharge transistor 1410, and the first FET 910 will remain on. Since the turn-on speed of the first FET 910 is not important, the precharge transistor 1410 can be relatively small / weak.

[0132] In step S920, the controller 930 may turn on the second FET 920 by controlling the second control signal 932 to turn off the transistor 1240 and turn on the transistor 1430, thereby reducing the gate voltage of the second FET 920 and turning it on. The transistor 1430 may be relatively large / strong so as to apply a relatively strong gate voltage signal to the second FET 920, thereby turning on the second FET 920 quickly.

[0133] In step S930, the controller may turn off the first FET 910 by controlling the third control signal 1214 to turn on the transistor 1440, so that the pre-charge capacitor associated with the gate of the first FET 910 is discharged and the gate voltage of the first FET 910 increases to turn off the first FET 910. The transistor 1440 may be relatively large / strong so as to control the strong gate voltage of the first FET 910, thereby turning it off quickly.

[0134] Finally, in step S940, the controller 930 may turn off the second FET 920 by controlling the second control signal 932 to turn on the transistor 1420 and turn off the transistor 1430, thereby increasing the gate voltage of the second FET 920 to turn off the second FET 920. Since the turn-off speed of the second FET 920 is not important, the transistor 1420 may be relatively small / weak.

[0135] Fig.15a An exemplary laser source system 1500 is shown according to another aspect of the present disclosure. Fig.15b An example representation of the timing of control signals output by the controller 930 is shown in order to perform the reference Fig.10 Describe the process.

[0136] The system 1500 is very similar to the system 1200 described with reference to Figures 12a and 12b, but the pre-charge transistor 1210 is not coupled to the laser voltage supply PVDD, but is coupled to a separate pre-charge supply. The size of the pre-charge supply can be larger than the size of the laser voltage supply, which can help to turn on the first FET 910 more strongly. In more detail, in the system 1200 described earlier, when the pre-charge transistor 1210 is turned on, the gate of the first FET 910 can be pulled up to about PVDD, and the gate-source voltage of the first FET 910 will be about the threshold voltage of the first FET 910. The anode of the VCSEL 110 is coupled to the source of the first FET 910, and therefore will be at a level of about PVDD minus the threshold voltage of the first FET 910. However, in the system 1500, when the pre-charge transistor 1210 is turned on, the gate voltage of the first FET 910 is approximately the pre-charge supply. If the magnitude of the pre-charge power supply is greater than PVDD by an amount approximately equal to or greater than the turn-on threshold of the first FET 910, then when the first FET 910 is turned on, its source voltage may be approximately PVDD (in practice, it may be slightly less than PVDD due to the channel resistance of the first FET 910), which is higher than the channel resistance implemented in the system 1200. In addition, by further increasing the gate-source voltage of the first FET 910 above its threshold voltage, the channel resistance of the first FET 910 may be further reduced. The pre-charge power supply may be from any suitable power source.

[0137] Another difference is that when the first FET 910 is turned off, the discharge path includes the cascode transistor 1510. In step S930, including one or more cascode transistors 1510 in the discharge path of the first FET 910 can make it easier to discharge the charge stored on the gate of the first FET 910, which can make the transistor 1240 that controls the discharge a relatively faster and smaller low voltage transistor. The cascode transistor 1510 is an optional feature in the system 1500 and can be optionally included in the discharge path of the first FET 910 of any system described with reference to Figures 12-14 and Figures 16 and 17.

[0138] Fig.16a An exemplary laser source system 1600 is shown according to another aspect of the present disclosure. Fig.16b An exemplary representation of the timing of control signals output by the controller 930 is shown in order to perform the reference Fig.10 Describe the process.

[0139] The system 1600 is very similar to the system 1200 described with reference to Figures 12a and 12b, but the controller 930 is configured to output a fourth control signal 1610. The fourth control signal 1610 is configured to apply a voltage to the first plate of the bootstrap capacitor, wherein the second plate of the bootstrap capacitor is coupled to the control terminal of the first transistor 910. Applying this voltage increases the gate voltage of the first FET 910 so that it can be raised above the laser voltage source. The controller 930 can be configured to apply the voltage using the fourth control signal 1610 at any time after the first FET 910 is turned on in step S910 and before the second FET 920 is turned on in step S920. The voltage can be removed at any suitable time simultaneously with or after the first FET 910 is turned off in step S930 (which means that the transitions of the third control signal 1214 and the fourth control signal 1610 do not have to be aligned). In this way, the gate voltage of the first FET 910 can be taken above the laser voltage source without the need for a separate power supply. If controller 930 is powered, for example, by a regulator supply output by voltage regulator 410, the voltage applied to the bootstrap capacitor may be the regulator supply. The bootstrap arrangement of system 1600 may optionally be included in any of the systems described with reference to FIGS.

[0140] Fig.17a An exemplary laser source system 1700 is shown according to another aspect of the present disclosure. Fig.17b An exemplary representation of the timing of control signals output by the controller 930 is shown in order to perform the reference Fig.10 Describe the process.

[0141] The controller 930 can control the state of the first FET 910 directly (optionally via a pre-driver) using the first control signal 1641. Therefore, steps S910 and S930 can be implemented by appropriate transitions of the first control signal 1641 to set the gate voltage of the first FET above or below the turn-on threshold of the first FET 910 as required, such as Fig.17b In 17b it is assumed that the first control signal 1641 drives the gate voltage via a driver which is powered by a regulator power supply.

[0142] For step S920, the controller 930 may use the second control signal 1625 to turn off the transistor 1620 and turn on the transistor 1630. levelshiftThe gate voltage of the second FET 920 can be reduced below PVDD by an amount exceeding the turn-on threshold of the second FET 920, thereby turning on the second FET 920. The transistor 1630 can be a relatively strong transistor in order to control a strong signal at the gate of the second FET 920, thereby turning it on quickly. The transistor 1620 can be relatively weak because a strong signal does not need to be controlled when switching.

[0143] For step S940, the controller 930 may switch the second control signal 1625 back so that the transistor 1620 is turned on and the transistor 1630 is turned off. This will cause the gate voltage of the second FET 920 to be pulled back to a high level by the level shift capacitor, so that the gate voltage of the second FET 920 is raised back to PVDD and the second FET 920 is turned off. The transistor 1620 may be relatively weak, because it is not important for the second FET 920 to be turned off quickly in step S940.

[0144] Finally, the controller 930 may optionally output a third control signal 1611 to the gate of the transistor 1610. At some time before the switching of step S920, the controller 930 may set the level of the signal 1611 to high (e.g., at or near PVDD), which turns off the transistor 1610 and allows the gate of the second FET 920 to float and be controlled using the second control signal 1625 (as described above). At some time after step S940, the controller 930 may set the level of the signal 1611 to low (i.e., below the turn-on voltage of the transistor 1610), which turns on the transistor 1610 and holds the gate of the second FET 920 high. This may help prevent the gate voltage of the second FET 920 from drifting between light pulses (e.g., due to leakage or parasitic coupling), which may cause switching difficulties in steps S920 and S940. Alternatively, however, the transistor 1610 and the third control signal 1611 may be omitted, and the gate of the second transistor 920 is coupled only to the level shift capacitor. When transistor 1610 is used, it may be relatively weak because the timing of the transition in third control signal 1611 relative to the transition in second control signal 1625 may be arranged so that fast switching of transistor 1610 is not required.

[0145] Fig.18 An exemplary laser source system 1800 is shown according to another aspect of the present disclosure. Fig.18The system 1800 is very similar to the system 1200 described above, but includes an additional discharge transistor 1810 coupled in parallel to the VCSEL 110 and configured to conduct and create a discharge path (step S930) when the first FET 910 is turned off to release parasitic charges associated with the laser light source. The VCSEL may have a parasitic capacitance C p1 and / or C p2 One or all of these may result in residual energy that slows down the turn-off of VCSEL 110. The arrangement of discharge transistor 1810 may help discharge parasitic charges associated with VCSEL 110, thereby even further increasing the speed at which VCSEL 110 turns off. Discharge transistor 1810 may be used in conjunction with the above reference Figure 9 to Figure 1 7 can be used in combination with any of the configurations described in 7.

[0146] Fig.19 An exemplary laser source system 1900 is shown according to another aspect of the present disclosure. Fig.19 The system 1900 is very similar to the previously described system 1200, but includes an additional discharge transistor 1910 coupled to the VCSEL 110 to help discharge parasitic charges associated with the VCSEL 110. The discharge transistor 1910 is arranged to turn on and create a discharge path at approximately the time when the first FET 910 is turned off. This can help to increase the turn-off speed of the VCSEL 110 even further. Fig.19 19 includes an optional additional driver coupled to the gate of transistor 1910, which is included to increase the delay of driving transistor 1910, thereby reducing the chance of a shoot-through of current flowing through first FET 910 and discharge transistor 1910. Thus, the transistor can be arranged to be turned on at about the same time that VCSEL 110 is turned off (e.g., at the same time or shortly after the first FET 910 is turned off). Although discharge transistor 1910 is shown as being coupled to the cathode of VCSEL 110, it may alternatively be coupled to the anode.

[0147] From all Figures 9 to 17b It will be appreciated that the controller 930 may use a variety of different circuits to control the states of the first FET 910 and the second FET 920 in a variety of different ways in order to perform Fig.10The second FETs 910 and 920 may be n-type or p-type and may be coupled to the anode or cathode of the VCSEL 110. Furthermore, although in each of the systems described above, one of the FETs 910 and 920 is coupled to the anode of the VCSEL 110 and the other is coupled to the cathode of the VCSEL 110, in an alternative, the first and second FETs 910 and 920 may be coupled in series with each other, with both FETs being on the cathode side or the anode side of the VCSEL 110.

[0148] Typically, the second FET 920 can set the current flowing through the VCSEL 110, because the first FET 910 will usually be fully turned on at the beginning of step S920 without affecting the laser drive current. Figures 9 to 17b Another advantage of the arrangement is that the magnitude of the laser drive current can be controlled / set by means of the transistor selected for the second FET 920 and the manner in which its gate voltage is controlled to turn it on (e.g., how quickly the gate voltage can turn on the second FET 920).

[0149] A skilled person will readily appreciate that various changes or modifications may be made to the above-described aspects of the present disclosure without departing from the scope of the present disclosure.

[0150] For example, although the first driver 130 of the above example includes one or more pre-drivers 420, 422, etc., in an alternative, the pre-driver may be omitted entirely, and the FET 440 (and optionally the additional FET 620) may be driven directly by the controller 430. Alternatively, the voltage regulator 410 may be omitted entirely. Furthermore, even when the first driver 130 includes one or more pre-drivers, while it may be beneficial to use the voltage regulator 410 to power the pre-drivers, at least one of the one or more pre-drivers may alternatively be powered in any other suitable manner, and the voltage regulator omitted from the first driver 130.

[0151] Although FETs (e.g., FET 440 and additional FET 620) are used in the above examples, any other suitable type of controllable switch may be used, such as any other type of transistor, such as a BJT, etc. Therefore, whenever a gate of a FET is mentioned, it should be understood as the control terminal or gate / base of the transistor. In addition, whenever a source of a FET is mentioned, it should be understood as the channel terminal or source / emitter of the transistor, and whenever a drain of a FET is mentioned, it should be understood as the channel terminal or drain / collector of the transistor.

[0152] In some aspects disclosed above, two drivers (a first driver 130 and a second driver 140) are described. Figure 1 ,2A The use of two drivers may be particularly beneficial for the VCSEL 110 design shown in FIG. 2B , where there are two anode terminals on the surface of the VCSEL 110, so the two drivers can be symmetrically arranged within the chip 120. However, alternatively, only a single driver (e.g., only the first driver 130) may be implemented to provide all the drive current required to drive the VCSEL 110. For example, the VCSEL 110 may be a design with only one anode terminal. Alternatively, the VCSEL 110 may have a design with two or more anode terminals, in which case a single driver may be coupled to any one or more of the anode terminals. Alternatively, reference may be made to FIG. Figures 1 to 7 Each driver circuit described may include two transistors for controlling the pulse emission of the VCSEL 110, as shown in FIG. Figures 9 to 17b Arrange as described.

[0153] In another alternative, the system 100 may include more than two drivers arranged to drive the VCSEL 110. For example, it may include four drivers, each having the same design as the first driver 130 described above. These multiple drivers may be arranged in or on the chip 110 in any suitable manner, for example, the first and second drivers may be symmetrical to each other with respect to a first symmetry plane, and the third and fourth drivers may be symmetrical to each other with respect to a second symmetry plane perpendicular to the first symmetry plane.

[0154] Although the light source system 110 described above is described with particular reference to use with a ToF camera system, the light source system 110 is not limited to such use and may be used for any other purpose.

[0155] The terms “coupled” and “connected” are used throughout this disclosure to encompass both a direct electrical connection between two components / devices and an indirect electrical coupling between two components / devices where there are one or more intermediate components / devices in the electrical coupling path between the two components / devices.

[0156] Although the first driver 130 is described as having a switch 134 for controlling the transition or switching between the charging state and the emission state, it should be understood that the first driver 130 can be configured in any other suitable manner, using any other suitable components to switch or convert the first driver 130 between the charging state, in which the first capacitor 132 gradually stores the charge received from the power supply and the VCSEL 110 is turned off, and the emission state, in which the first capacitor 132 is discharged to generate the first drive current 136 to turn on the VCSEL 110. Likewise, it is not necessary for the controller 430 to control the switching or transition of the first driver 130 between the charging state and the emission state. Alternatively, any other suitable arrangement or circuit can be used for this purpose, such as a timer circuit configured to switch the first driver 130 at regular intervals, or a circuit configured to switch the first driver 130 based on the amount of charge stored on the first capacitor 132 (e.g., switching to the emission state when the charge stored on the first capacitor 132 reaches a predetermined level), etc.

[0157] The capacitors 132 and 142 described above may be either integrated with the semiconductor chip 120, or they may be lateral silicon design capacitors that may be bump bonded to the semiconductor surface due to 120 in order to couple them to the driver IC circuitry. Figure 1 In the description and the accompanying description, capacitors 132 and 142 are integrated within semiconductor chip 120, so that switches 134 and 144 and capacitors 132 and 142 are integrated devices. As a result, in this example, first driver 130 and second driver 140 are integrated drivers. However, in alternative embodiments, capacitors 132 and 142 may not be integrated capacitors, but may be capacitors mounted on the semiconductor chip, such as capacitors mounted on first surface 122. One terminal of each capacitor may be, for example, connected using a Figure 1 The bonding wires 152 and 154 shown couple the first capacitor 110 to the light source 110, and the other end of each capacitor is coupled to the corresponding integrated switches 134 and 144 by any suitable electrical coupling means. It will be appreciated by those skilled in the art that, for example, bump bonding, epoxy bonding or eutectic bonding. The first and second capacitors can be of any suitable type, such as, by way of non-limiting example, a lateral capacitor (e.g., a lateral silicon capacitor) or a vertical capacitor (e.g., a vertical silicon capacitor).

Claims

1. A laser light source system, comprising: Laser light source; a first transistor device coupled to the laser light source; a second transistor device coupled to the first transistor device; as well as A controller is arranged to control the state of the first switch and the state of the second switch, wherein the controller is configured to control the pulse emission of light from the laser light source by: a) turning on the first transistor device when the second transistor device is in an off state; b) after turning on the first transistor device, turning on the laser light source by turning on the second transistor device so that both the first transistor device and the second transistor device are in a conducting state; and c) after turning on the second transistor device, turning off the laser light source by turning off the first transistor device. 2 . The laser light source system according to claim 1 , wherein the controller is configured to shut down the laser light source by shutting down the first transistor device while the second transistor device is still in an on state.

3. The laser light source system according to claim 2, further configured as: d) after turning off the first transistor device, resetting the laser light source system by turning off the second transistor device so that both the first transistor device and the second transistor device are in an off state.

4. The laser light source system according to claim 1, wherein the controller is configured to: generating a first control signal for controlling a state of the first transistor; and generating a second control signal for controlling the state of the second transistor, wherein The controller is configured to control the duration of the pulsed emission of light from the laser light source by setting a time difference between a change in a second control signal that turns the second transistor on and a change in a first control signal that turns the first transistor device off. 5 . The laser light source system according to claim 1 , wherein the controller is configured to control the laser light source to emit a laser pulse having a duration less than 1 nanosecond.

6. The laser light source system according to claim 1, further comprising: A discharge transistor is coupled to the laser light source and is arranged to create a discharge path approximately when the first transistor device is turned off to discharge parasitic charges associated with the laser light source.

7. The laser light source system according to claim 1, further comprising: The first drive includes: an input terminal coupled to the controller for receiving a first control signal of the first transistor; and The output terminal is coupled to the control terminal of the first transistor and is used to output the buffered first control signal to the control terminal of the first transistor.

8. The laser light source system of claim 7, wherein turning on the first transistor comprises setting the first control signal to a voltage that causes the buffered first control signal to turn on the first transistor, and Turning off the first transistor includes setting the first control signal to a voltage that causes the buffered first control signal to turn off the first transistor.

9. The laser light source system according to claim 1, further comprising: Second drive, including an input terminal coupled to the controller for receiving a second control signal of the second transistor; as well as An output terminal is coupled to the control terminal of the second transistor for outputting a buffered second control signal to the control terminal of the second transistor.

10. The laser light source system of claim 9, wherein turning on the second transistor comprises setting the second control signal to a voltage that causes the buffered second control signal to turn on the second transistor.

11. The laser light source system according to claim 1, wherein turning on the first transistor comprises: precharging the first transistor by applying a turn-on voltage to a control terminal of the first transistor, and The turn-on voltage applied to the control terminal of the first transistor is removed so that the first transistor is maintained in an on state by a capacitance associated with the control terminal of the first transistor.

12. The laser source system of claim 11, wherein the capacitance associated with the control terminal of the first transistor is a parasitic capacitance of the first transistor.

13. A laser light source controller for coupling to a laser driving circuit, the laser driving circuit comprising at least a first transistor, a second transistor and a laser light source, wherein: The laser light source controller is configured as follows: outputting a first control signal for controlling the first transistor; and outputting a second control signal for controlling a second transistor, wherein the first transistor, the second transistor and the laser light source are arranged in series, The laser light source controller is configured to control the pulse emission of light from the laser light source in the following manner: a) when the second transistor device is in a non-conducting state, setting the first transistor to a conducting state using a first control signal; b) after setting the first transistor to an on state, turning on the laser light source by setting the second transistor to an on state using a second control signal so that both the first transistor and the second transistor are turned on; and c) after setting the second transistor to a conducting state, turning off the laser light source by setting the first transistor to a non-conducting state.

14. The laser light source controller according to claim 13, wherein the first control signal is used to switch the first transistor from a non-conductive state to a conductive state, and wherein the laser light source controller is further configured to: outputting a third control signal for switching the first transistor from a conducting state to a non-conducting state, wherein: The laser light source controller is configured to set the first transistor to a non-conductive state using the third control signal. 15 . The laser light source controller according to claim 13 , wherein the first control signal is used to switch the first transistor from a non-conducting state to a conducting state, and is used to switch the first transistor from a conducting state to a non-conducting state. 16 . The laser light source controller according to claim 13 , further configured to control a time difference between setting the second transistor to a conducting state and setting the first transistor to a non-conducting state based on a target light emission duration.

17. A laser light source controller configured to control pulses of light from a laser light source, wherein: The laser light source controller is configured as follows: When the second transistor coupled in series with the laser light source is in a non-conducting state, setting the first transistor coupled in series with the laser light source to a conducting state; turning on the laser light source by setting the second transistor to an on state so that both the first transistor and the second transistor are turned on; and The laser light source is turned off by setting the first transistor to a non-conductive state.

18. The laser light source controller according to claim 17, further configured as: After the first transistor is set to a non-conducting state, the second transistor is set to a non-conducting state, so that both the first transistor and the second transistor are in a non-conducting state.

19. The laser light source controller of claim 17, wherein the duration of the pulse of light from the laser light source is set by a time difference between setting the second transistor to a conducting state and setting the first transistor to a non-conducting state.

20. The laser light source controller of claim 17, wherein the laser light source controller is configured to output at least a first control signal for controlling a state of the first transistor, and to output at least a second control signal for controlling a state of the second transistor.

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