Laser emission module and depth camera

Abstract

The utility model relates to the technical field of depth cameras, and discloses a laser emission module and a depth camera, the laser emission module comprises a laser light source and a light source driving circuit, and the light source driving circuit comprises a voltage conversion circuit, a current sampling feedback circuit and a current switching circuit; the voltage conversion circuit is connected with a power supply and the current sampling feedback circuit, the current switching circuit is connected with the current sampling feedback circuit, and the current switching circuit is configured to be switched on or off based on a control signal of the control circuit so as to switch driving current output by the current sampling feedback circuit; the current sampling feedback circuit is configured to obtain real-time driving current of the laser light source and output feedback voltage to the feedback end based on the real-time driving current, and the voltage conversion circuit is configured to adjust the output current when the feedback voltage changes, so that the driving current is maintained at a target current value. The depth camera switches the driving current of the laser light source according to the working scene, and has a good recognition effect on objects with different reflectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of depth cameras, and in particular relates to a laser emission module and a depth camera. Background Art

[0002] With the rapid development of science and technology, robots are becoming more and more intelligent. Industrial mobile robots, commercial cleaning robots, delivery robots and other robots usually need to be equipped with sensors to avoid obstacles. Different sensor technologies are used according to different application scenarios. Sensor technologies generally include ultrasonic, LIDAR (Light Detection And Ranging), 3D sensors (structured light, ToF (Time of flight) or binocular). The advantage of the 3D structured light sensor solution is that it can generate overall spatial information, has strong scene applicability, and has a variety of uses. It is increasingly widely used in robot obstacle avoidance.

[0003] The robot's working scenes are relatively complex. In some scenes, there will be objects with low reflectivity and high reflectivity. Conventional 3D structured light sensors can only recognize objects with ordinary reflectivity, and have poor recognition effect on objects with low reflectivity and high reflectivity. Utility Model Content

[0004] In view of this, an embodiment of the present application provides a laser emission module and a depth camera, which aim to solve the problem that 3D structured light sensors have poor recognition effect on low-reflectivity objects and high-reflectivity objects.

[0005] In the first aspect, an embodiment of the present application provides a laser emission module, which is connected to a control circuit. The laser emission module includes a laser light source and a light source driving circuit. The light source driving circuit includes a voltage conversion circuit, a current sampling feedback circuit and a current switching circuit; the input end of the voltage conversion circuit is connected to a power supply, and the output end and the feedback end are connected to the current sampling feedback circuit, and the output end of the current sampling feedback circuit is connected to the laser light source; the input end of the current switching circuit is connected to the current sampling feedback circuit, the controlled end is connected to the control circuit, and the output end is grounded; the current switching circuit is configured to be turned on or off based on a control signal of the control circuit, so that the driving current output by the current sampling feedback circuit switches between multiple target current values; the current sampling feedback circuit is configured to obtain the real-time driving current of the laser light source and output a feedback voltage to the feedback end based on the real-time driving current, and the voltage conversion circuit is configured to adjust the output current when the feedback voltage changes, so that the driving current is maintained at the target current value.

[0006] In one embodiment, the current switching circuit includes a first switch element and a first resistor connected in series; the input end of the first switch element and the first resistor connected in series is connected to the current sampling feedback circuit, and the output end is grounded; the controlled end of the first switch element is connected to the control circuit, and the first switch element is configured to be turned on or off based on the control signal of the control circuit, so that the first resistor is connected to or not connected to the current sampling feedback circuit. In one embodiment, the current sampling feedback circuit includes an operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a MOS tube; the first end of the second resistor and the first end of the third resistor are commonly connected to the output end of the voltage conversion circuit, the second end of the second resistor and the first end of the fourth resistor are commonly connected to the laser light source, the second end of the third resistor is connected to the first input end of the operational amplifier, the second end of the fourth resistor is connected to the second input end of the operational amplifier, and the first end of the fifth resistor is connected to the output end of the voltage comparison amplifier; the drain of the MOS tube is connected to the second end of the third resistor, the gate of the MOS tube is connected to the second end of the fifth resistor, the source of the MOS tube is connected to the first end of the sixth resistor and the current switching circuit, and the second end of the sixth resistor is grounded.

[0007] In one embodiment, the voltage conversion circuit includes a DC-DC power chip, a seventh resistor, a first capacitor, a first inductor and a second capacitor; the enable pin of the DC-DC power chip is connected to the control circuit, the output pin of the DC-DC power chip is connected to the input end of the first inductor, and the feedback pin of the DC-DC power chip is connected to the current switching circuit and the current sampling feedback circuit; the seventh resistor and the first capacitor are connected in series between the bootstrap pin and the output pin of the DC-DC power chip, the output end of the first inductor is connected to the input end of the second capacitor and the input end of the current sampling feedback circuit, and the output end of the second capacitor is grounded.

[0008] In one embodiment, the light source driving circuit further includes a current limiting protection circuit, which is connected between the power supply and the voltage conversion circuit and is configured to shut down the output when the subsequent circuit is short-circuited or the driving current of the laser light source is greater than the current threshold. In one embodiment, the current limiting protection circuit includes a current limiting protection chip, a pull-up resistor and a current limiting resistor; the input pin of the current limiting protection chip is connected to the power supply, the output pin is connected to the voltage conversion circuit, the enable pin is connected to the control circuit, and the fault pin is connected to the output end of the pull-up resistor and the control circuit to output an overcurrent signal to the control circuit; the current setting pin is grounded through the current limiting resistor to configure the current threshold; the fault pin is connected to the pull-up power supply through the pull-up resistor.

[0009] In one of the embodiments, the light source driving circuit further includes a pulse width and voltage detection circuit, which is connected between the current sampling feedback circuit and the laser light source, and is configured to divide the working voltage of the laser light source, and output a voltage division signal to the control circuit to obtain the working pulse width and working voltage of the laser light source. In one of the embodiments, the pulse width and voltage detection circuit includes a first voltage division resistor and a second voltage division resistor, wherein the first end of the first voltage division resistor is connected to the output end of the current sampling feedback circuit and the input end of the laser light source, the second end of the first voltage division resistor is connected to the first end of the second voltage division resistor and the control circuit to output the voltage division signal to the control circuit, and the second end of the second voltage division resistor is grounded.

[0010] In one embodiment, the laser emission module also includes a temperature detection circuit, which is connected to the control circuit and is configured to sense the temperature of the laser light source and output a temperature signal to the control circuit to shut off the power supply when the temperature of the laser light source is greater than a temperature threshold.

[0011] In a second aspect, an embodiment of the present application provides a depth camera, comprising a laser emission module, a collection module and a control circuit as described in any embodiment of the first aspect above. The laser emission module is used to emit a laser beam to a target, the collection module is used to collect the laser beam reflected back by the target, and the control circuit is used to calculate a depth image based on the data collected by the collection module.

[0012] Compared with the related art, the embodiments of the present application have the following beneficial effects: the light source driving circuit in the laser emission module switches the output driving current value based on the control signal output by the control circuit by setting a current switching circuit, so that the laser light source can have a variety of driving currents, so that the depth camera can switch the driving current according to the working scene. For example, a large driving current can be switched for low-reflective objects, and a small driving current can be switched for objects with ordinary reflectivity, so that the depth camera can have a better recognition effect for objects with different reflectivities, and the depth camera is more compatible with the working scene; at the same time, the driving current of the laser light source can be kept constant at the corresponding target current value through the voltage conversion circuit and the current sampling circuit, thereby ensuring the stability of the depth camera and avoiding unnecessary power loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0014] Figure 1 A schematic diagram of the structure of a depth camera provided in one embodiment of the present application;

[0015] Figure 2 A schematic diagram of the structure of a laser emission module provided in one embodiment of the present application;

[0016] Figure 3 A schematic diagram of the structure of a laser emission module provided in one embodiment of the present application;

[0017] Figure 4 A schematic diagram of the structure of a laser emission module provided in one embodiment of the present application;

[0018] Figure 5 for Figure 4 An example circuit schematic of the laser emission module is shown. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] The robot's working scenes are relatively complex. In some scenes, there will be objects with low reflectivity and high reflectivity. Conventional depth cameras can only recognize objects with ordinary reflectivity, and have poor recognition effect on objects with low reflectivity and high reflectivity.

[0021] See also Figure 1 , shows a schematic diagram of the structure of a depth camera provided by an embodiment of the present application. For the sake of convenience, only the parts related to the present embodiment are shown, which are described in detail as follows:

[0022] The depth camera 100 includes a laser emission module 10, a collection module 30 and a control circuit 20. The laser emission module 10 is used to emit a laser beam 101 to a target 102, the collection module 30 is used to collect a laser beam 103 reflected by the target 102, and the control circuit 20 is used to calculate a depth image based on the data collected by the collection module 30.

[0023] The control circuit 20 is electrically connected to the laser emitting module 10 and the collection module 30 , and is used to control the laser emitting module 10 and the collection module 30 , so as to synchronously control the collection module 30 to collect the reflected laser beam 103 when the laser emitting module 10 emits the laser beam 101 .

[0024] The depth camera 100 may be a monocular / binocular structured light depth camera, a time-of-flight depth camera, etc., which are not listed here one by one. The embodiment of the present application takes the depth camera 100 as a structured light depth camera as an example for description, and other types of depth cameras are similar.

[0025] The laser emission module 10 includes a laser light source 11, a collimating element 17 and a diffractive optical element 18 which are arranged in sequence. The laser light source 11 is used to generate a laser beam, the collimating element 17 is used to collimate the laser beam, and the diffractive optical element 18 is used to replicate the collimated laser beam and output it to project it to the target 102. The laser light source 11 can be a vertical cavity surface emitting laser (VCSEL), an edge emitting laser (EEL), a light emitting diode (LED) or other types of lasers.

[0026] The acquisition module 30 includes a receiving lens 33, a filter element 32 and an image sensor 31 which are sequentially arranged along the incident direction of the laser beam 103. The receiving lens 33 is used to converge the beam reflected by the target, the filter element 32 is used to filter out interfering beams, such as ambient light, and the image sensor 31 is used to receive the filtered beam to generate a structured light image.

[0027] The control circuit 20 can receive the structured light image and calculate the depth image based on the structured light image. When the depth camera is a monocular structured light depth camera, the control circuit 20 can obtain the depth image after performing depth matching on the structured light image and the reference structured light image; when the depth camera is a binocular structured light depth camera, the number of acquisition modules 30 can be two, and the control circuit 20 can obtain the depth image after performing depth matching on the structured light images acquired by the two acquisition modules 30.

[0028] See also Figure 2 , a schematic diagram of the structure of a laser emission module provided in an embodiment of the present application, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0029] The laser emission module 10 is connected to the control circuit 20. The laser emission module 10 also includes a light source driving circuit 12 connected to the laser light source 11. The light source driving circuit 12 is used to drive the laser light source. The light source driving circuit 12 includes a voltage conversion circuit 121, a current sampling feedback circuit 122 and a current switching circuit 123.

[0030] The input end of the voltage conversion circuit 121 is connected to the power supply VCC_LD, the output end and the feedback end of the voltage conversion circuit 121 are connected to the current sampling feedback circuit 122, and the output end of the current sampling feedback circuit 122 is connected to the laser light source 11; the input end of the current switching circuit 123 is connected to the current sampling feedback circuit 122, the controlled end of the current switching circuit 123 is connected to the control circuit 20, and the output end of the current switching circuit 123 is grounded; the current switching circuit 123 is configured to be turned on or off based on the control signal of the control circuit 20, so that the driving current output by the current sampling feedback circuit 122 switches between multiple target current values. The current sampling feedback circuit 122 is configured to obtain the real-time driving current of the laser light source 11 and output a feedback voltage to the feedback end of the voltage conversion circuit 121 based on the real-time driving current. The voltage conversion circuit 121 is configured to adjust the output current when the feedback voltage changes, so that the driving current output by the current sampling feedback circuit 122 is maintained at the target current value.

[0031] In the laser emission module 10 and the depth camera of the embodiment of the present application, the light source driving circuit 12 sets a current switching circuit 123 to switch the output driving current value based on the control signal output by the control circuit 20, so that the laser light source 11 can have a variety of driving currents, so that the depth camera can switch the driving current according to the working scene. For example, a large driving current can be switched for low-reflective objects, and a small driving current can be switched for objects with ordinary reflectivity, so that the depth camera can have a better recognition effect for objects with different reflectivities, and the depth camera is more compatible with the working scene; at the same time, the driving current of the laser light source 11 can be kept constant at the corresponding target current value through the voltage conversion circuit 121 and the current sampling feedback circuit 122, so as to ensure the stability of the depth camera and avoid unnecessary power loss.

[0032] See also Figure 3 , a schematic diagram of the structure of a laser emission module provided in an embodiment of the present application, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0033] In one embodiment, the current switching circuit 123 includes at least one first switching element 1231 and at least one first resistor R10, the input end of a first switching element 1231 connected in series with a first resistor R10 is connected to the current sampling feedback circuit 122, the output end of the first resistor R10 connected in series with the first switching element 1231 is grounded, the controlled end of the first switching element 1231 is connected to the control circuit 20, and the first switching element 1231 is configured to be turned on or off based on a control signal of the control circuit 20 so that the first resistor R10 is connected to or not connected to the current sampling feedback circuit 122.

[0034] In one example, the controlled end of the first switch element 1231 is turned on when receiving the first trigger signal in the control signal transmitted by the control circuit 20, and the first resistor R10 is turned on and connected to the current sampling feedback circuit 122, and is connected in parallel with the resistor in the current sampling feedback circuit 122, so that the equivalent resistance of the current sampling feedback circuit 122 is reduced, and the output current of the current sampling feedback circuit 122 increases to the first target current value, so that the laser light source 11 can have a high energy level current, and the depth camera can be suitable for the detection of low-reflection scenes. The controlled end of the first switch element 1231 is cut off when receiving the second trigger signal in the control signal transmitted by the control circuit 20, so that the first resistor R10 is not connected to the current sampling feedback circuit 122, the equivalent resistance of the current sampling feedback circuit 122 increases, and the driving current output by the current sampling feedback circuit 122 is reduced to the second target current value. At this time, the depth camera is suitable for the detection of ordinary scenes. Among them, the first trigger signal can be a high-level signal, and the second trigger signal can be a low-level signal.

[0035] exist Figure 2 In the illustrated embodiment, there is one first switch element 1231 and one first resistor R10. In other embodiments, there are multiple first switch elements 1231 and multiple first resistors R10, wherein one first switch element 1231 is connected in series with one first resistor R10, and the first resistor R10 may include a chip resistor or a programmable digital resistor.

[0036] The laser emission module 10 of the embodiment of the present application may have two, three, four, five or more target current values. The present application only takes two as an example for illustration. Three, four, five or more are similar. For example, a plurality of current switching circuits 123 may be provided or the current switching circuit 123 may be provided with a plurality of first switching elements 1231 and a first resistor R10 to achieve three or more target current values ​​to realize the application of more scenarios (such as high reflection scenarios).

[0037] See also Figure 4 , a schematic diagram of the structure of a laser emission module provided in an embodiment of the present application, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0038] In one embodiment, the light source driving circuit 12 further includes a current limiting protection circuit 124, which is connected between the power supply and the voltage conversion circuit 121. The current limiting protection circuit 124 is configured to shut down the output when the subsequent circuit is short-circuited or the driving current of the laser light source 11 is greater than the current threshold, so as to protect the laser light source 11. The subsequent circuit includes any circuit through which the current flowing out of the current limiting protection circuit 124 passes, such as the voltage conversion circuit 121 and the current sampling feedback circuit 122.

[0039] In one embodiment, the light source driving circuit 12 also includes a pulse width and voltage detection circuit 125, which is connected between the current sampling feedback circuit 122 and the laser light source 11. The pulse width and voltage detection circuit 125 is configured to divide the working voltage of the laser light source 11 and output a divided voltage signal to the control circuit 20 to obtain the working pulse width and working voltage of the laser light source 11.

[0040] When the driving current of the laser light source 11 is fixed, the voltage across the laser light source 11 is also basically fixed. The control circuit 20 can set the upper limit of the working pulse width. When the working pulse width of the laser light source 11 exceeds the set upper limit of the pulse width, it is determined that the working pulse width is overtime, and the power supply of the laser light source 11 is disconnected. In addition, the pulse width and voltage detection circuit 125 is also used to detect the working voltage of the laser light source 11. The control circuit 20 sets a voltage upper limit. When the working voltage of the laser light source 11 exceeds the set voltage upper limit, it is determined that the laser light source 11 is overvoltage, and the power supply of the laser light source 11 is disconnected. In this way, laser safety protection of the laser emission module 10 can be achieved.

[0041] In one embodiment, the laser emission module 10 further includes a temperature detection circuit 13, which is connected to the control circuit 20. The temperature detection circuit 13 is configured to sense the temperature of the laser light source 11 and output a temperature signal to the control circuit 20, so as to shut off the power supply when the temperature of the laser light source 11 is greater than a temperature threshold, so as to perform over-temperature protection on the laser light source 11. The temperature detection circuit 13 may include a thermistor.

[0042] See also Figure 5 , a circuit diagram of a laser emission module provided in an embodiment of the present application, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0043] In one embodiment, the control circuit 20 is, for example, a SOC (System on Chip) or a dedicated integrated chip, regardless of whether the SOC has corresponding port resource functions.

[0044] In one embodiment, the voltage conversion circuit 121 includes a DC-DC power chip U2, a seventh resistor R3, a first capacitor C3, a first inductor L1 and a second capacitor C4. The VIN pin of the DC-DC power chip U2 is connected to the power supply, the enable pin EN of the DC-DC power chip U2 is connected to the control circuit 20, the output pin SW of the DC-DC power chip U2 is connected to the input end of the first inductor L1, and the feedback pin FB of the DC-DC power chip U2 is connected to the current switching circuit 123 and the current sampling feedback circuit 122; the seventh resistor R3 and the first capacitor C3 are connected in series between the bootstrap pin BST and the output pin SW of the DC-DC power chip U2 to form a DC-DC chip bootstrap circuit, the output end of the first inductor L1 is connected to the input end of the second capacitor C4 and the input end of the current sampling feedback circuit 122, and the output end of the second capacitor C4 is grounded. Among them, the feedback pin FB of the DC-DC power chip U2 is the feedback end of the voltage conversion circuit 121.

[0045] The DC-DC power supply chip U2 can select any chip in the prior art that can realize DC-DC boost, buck or buck-boost function. The power supply signal provided by the power supply VCC_LD is powered through the input pin IN of the DC-DC power supply chip U2. The enable pin EN is used to receive the PWM signal sent by the control pin 2 of the control circuit 20. The DC-DC power supply chip U2 can be switched on and off according to the PWM signal, so that the laser light source 11 works in pulse mode.

[0046] The feedback pin FB of the DC-DC power chip U2 is used to receive the feedback voltage output by the current sampling feedback circuit 122, and the feedback pin FB can be connected to the reverse input terminal of the error amplifier inside the DC-DC chip U2. The DC-DC power chip U2 can adjust the output current of the SW pin according to the change of the feedback voltage to make the output current constant. The output end of the first inductor L1 serves as the output end of the voltage conversion circuit 121 to output the driving current. The first inductor L1 is used for energy storage and continuous current, and the second capacitor C4 is used for filtering, so that the subsequent circuit obtains a stable driving current.

[0047] In one embodiment, the current sampling feedback circuit 122 includes an operational amplifier U3, a second resistor R4, a third resistor R5, a fourth resistor R6, a fifth resistor R9, a sixth resistor R11 and a MOS transistor Q1. The first end of the second resistor R4 and the first end of the third resistor R5 are commonly connected to the output end of the voltage conversion circuit, the second end of the second resistor R4 and the first end of the fourth resistor R6 are commonly connected to the laser light source, the second end of the third resistor R5 is connected to the first input end of the operational amplifier U3, the second end of the fourth resistor R6 is connected to the second input end of the operational amplifier U3, and the first end of the fifth resistor R9 is connected to the output end of the operational amplifier U3; the drain of the MOS transistor Q1 is connected to the second end of the third resistor R5, the gate of the MOS transistor Q1 is connected to the second end of the fifth resistor R9, the source of the MOS transistor Q1 is connected to the first end of the sixth resistor R11 and the current switching circuit, and the second end of the sixth resistor R11 is grounded.

[0048] The second resistor R4 is used to convert the driving current output by the voltage conversion circuit 121 into a voltage difference across the second resistor R4, which is received by the first input terminal and the second input terminal of the operational amplifier U3, amplified and output to the gate of the MOS tube Q1, and the voltage output by the source of the MOS tube Q1 is fed back to the feedback terminal of the voltage conversion circuit.

[0049] The second resistor R4 is connected in series with the laser light source 11, and the current flowing through the second resistor R4 is the driving current of the laser light source 11. The laser light source 11 is a constant current drive, and the target current value of the laser light source 11 can be set. By calculating and selecting device parameters, the current flowing through the laser light source 11 when the circuit is working normally is the required driving current.

[0050] The current sampling feedback circuit 122 can form a constant current source circuit with the voltage conversion circuit 121. The non-inverting input terminal of the error amplifier inside the DC-DC power supply chip U2 is a fixed reference voltage, such as the commonly used 0.6V, and the inverting input terminal is connected to the FB pin. According to the "virtual short and virtual break" characteristics of the op amp's non-inverting and inverting input terminals, after the circuit works stably, the FB pin is also 0.6V. Assuming that at a certain moment, due to external environment (such as temperature) or power supply fluctuation, the driving current of the laser light source 11 increases, the voltage across the second resistor R4 increases, the output voltage of the operational amplifier U3 will increase, the conduction degree of the MOS tube Q1 increases, the current flowing through the sixth resistor R11 increases, the terminal voltage of the sixth resistor R11 increases, and the voltage of the feedback pin FB will be greater than the reference voltage, resulting in a voltage difference between the inverting input terminal and the non-inverting input terminal of the internal error amplifier of the DC-DC power supply chip U2 increases, the internal error amplifier of the DC-DC power supply chip U2 will control the internal circuit to reduce the switching frequency, the output voltage of the voltage conversion circuit 121 will decrease, and the current flowing through the second resistor R4 and the laser light source 11 will eventually decrease. The adjustment process stops until the current of the laser light source 11 returns to the target current value, at which time the voltage of the feedback pin FB falls back to the reference voltage. Similarly, due to external environment (such as temperature) or power supply fluctuation, the driving current of the laser light source 11 decreases, and through the feedback adjustment path, the driving current of the laser light source 11 eventually increases to the target current value. In this way, the driving current of the laser light source 11 will always be maintained at the target current value, ensuring that the laser light source 11 is driven by a constant current source.

[0051] In one embodiment, the first switch element 1231 includes a MOS transistor Q2. The current switching circuit also includes a current limiting resistor R12 and a bias resistor R13. The current limiting resistor R12 is connected in series to the gate of the MOS transistor Q2 to protect the gate of the MOS transistor Q2. The bias resistor R13 is connected between the gate and the source of the MOS transistor Q2 to provide a bias voltage to the gate of the MOS transistor Q2 to make the control reliable. The sixth resistor R11 determines the driving current of the laser light source 11 together with the second resistor R4 and the third resistor R5 in the current sampling feedback circuit 122. Changing the resistance value of the sixth resistor R11 will change the driving current of the laser light source 11. By connecting or not connecting the first resistor R10 to the circuit sampling feedback circuit 122, the first resistor R10 and the sixth resistor R11 are connected in parallel or not in parallel, and the equivalent resistance of the sixth resistor R11 can be changed to achieve switching of the driving current.

[0052] Exemplarily, the MOS tube Q2 is an NMOS tube. The output pin 6 of the control circuit 20 outputs a high level, and the MOS tube Q2 is turned on. At this time, the first resistor R10 is connected in parallel with the sixth resistor R11, the equivalent resistance of the current sampling feedback circuit 122 is reduced, and the driving current of the laser light source 11 is increased. At this time, the laser emission module 10 is suitable for low-reflection scenarios. The output pin 6 of the control circuit 20 outputs a low level, the first resistor R10 is not connected, the equivalent resistance of the current sampling feedback circuit 122 is increased, and the driving current of the laser light source 11 is reduced. At this time, the laser emission module 10 is suitable for ordinary scenarios.

[0053] In one embodiment, the current limiting protection circuit 124 includes a current limiting protection chip U1, a pull-up resistor R1, and a current limiting resistor R2. The input pin IN of the current limiting protection chip U1 is connected to the power supply VCC_LD, and the output pin OUT of the current limiting protection chip U1 is connected to the voltage conversion circuit 121 for outputting the power supply current to the voltage conversion circuit 121. The enable pin EN of the current limiting protection chip U1 is connected to the control circuit 20, and the control circuit 20 controls the switch of the current limiting protection chip U1 through the enable pin EN. The fault pin FAULT of the current limiting protection chip U1 is connected to the output end of the pull-up resistor R1 and the control circuit 20, so as to output an overcurrent signal to the control circuit 20 when the output current exceeds the current threshold, so that the control circuit 20 stops outputting the enable signal PWR_EN, and then the current limiting protection chip U1 shuts off the output current; the input end of the pull-up resistor R1 is connected to the pull-up power supply VCC_IO, and the fault pin FAULT of the current limiting protection chip U1 is the open-drain output of the current limiting protection chip U1, and the pull-up resistor R1 is connected to the pull-up power supply VCC_IO, so that when there is no overcurrent, the fault pin FAULT outputs a high level to the control circuit 20 to indicate that the power supply current is normal at this time. The current setting pin I_SET of the current limiting protection chip U1 is grounded through the current limiting resistor R2, and the current threshold can be configured by changing the blocking of the current limiting resistor R2; optionally, the input pin IN is also connected to the ground filtering capacitor C1.

[0054] During normal operation, the power supply current flowing through the current limiting protection chip U1 will not exceed the set current threshold, and the fault pin FAULT is pulled high by the pull-up resistor R1. When the subsequent circuit is short-circuited or the driving current becomes abnormally large, the power supply current flowing through the current limiting protection chip U1 will exceed the current threshold. At this time, on the one hand, the internal circuit of the current limiting protection chip U1 will promptly shut down the output of the power supply current, and on the other hand, the fault pin FAULT will output a low level. The control circuit 20 reads the fault pin FAULT level state to determine whether the subsequent circuit of the current limiting protection chip U1 has an overcurrent. The enable pin EN of the current limiting protection chip U1 is generally enabled at a high level. The enable pin EN is connected to the output pin 1 of the control circuit 20. In the software initialization program of the control circuit 20, the enable pin EN can be pulled high to turn on the power supply of the laser light source 11. When it is necessary to actively turn off the power supply, the enable pin EN can be pulled low. For example, when overcurrent, pulse width timeout, overvoltage of the laser light source 11, and overtemperature of the laser light source 11 are detected, the enable pin EN can be pulled low to turn off the power supply.

[0055] When the driving current of the laser light source 11 is fixed, the terminal voltages at both ends thereof are also basically fixed. In one embodiment, the IO power supply domain of the control circuit 20 is generally 1.8V, while the terminal voltage of the laser light source 11 is generally above 2V. The control circuit 20 cannot directly detect the terminal voltage of the laser light source 11. For this purpose, a pulse width and voltage detection circuit 125 is provided to detect the terminal voltage of the laser light source 11.

[0056] In one embodiment, the pulse width and voltage detection circuit 125 includes a first voltage-dividing resistor R7 and a second voltage-dividing resistor R8, wherein the first end of the first voltage-dividing resistor R7 is connected to the output end of the current sampling feedback circuit 122 and the input end of the laser light source 11, the second end of the first voltage-dividing resistor R7 is connected to the first end of the second voltage-dividing resistor R8 and the control circuit 20 to output a voltage-dividing signal to the control circuit 20, and the second end of the second voltage-dividing resistor R8 is grounded.

[0057] The first voltage-dividing resistor R7 and the second voltage-dividing resistor R8 divide the working voltage of the laser light source 11. The voltage components after the voltage division are respectively connected to the GPI pin 4 and the ADC pin 5 of the control circuit 20 to set the upper limit of the pulse width. The GPI pin 4 of the control circuit 20 is used to detect the laser working pulse width according to the received voltage. When the working pulse width of the laser light source 11 exceeds the set upper limit of the pulse width, it is determined that the working pulse width is overtime, and the control circuit 20 disconnects the power supply of the laser light source 11. The ADC pin 5 is also used to detect the working voltage of the laser light source 11. When the working voltage of the laser light source 11 exceeds the set voltage upper limit, it is determined that it is overvoltage, and the control circuit 20 disconnects the power supply of the laser light source 11. In this way, more effective laser safety protection can be achieved to ensure the safe use of the depth camera.

[0058] In one embodiment, the temperature detection circuit 13 includes a thermistor RT1 and an eighth resistor R14, and the thermistor RT1 and the eighth resistor R14 are connected in series between the power supply VCC_ADC and the ground. The series node inputs the output voltage component as a temperature detection signal to the ACD pin 7 of the control circuit 20. The control circuit 20 can infer the temperature of the laser light source 11 according to the voltage classification received by the ACD pin 7, so as to shut off the power supply of the laser light source 11 when the temperature is too high.

[0059] The thermistor RT1 is arranged close to the laser light source 11, and the device temperature of the laser light source 11 when it is working normally will be close to the temperature of the thermistor RT1. The thermistor RT1 will have a corresponding resistance value at a certain temperature. Through the voltage divider circuit design, the control circuit 20 can collect the voltage signal according to the ADC pin 7, and can infer the resistance value of the thermistor RT1, and further infer the current temperature of the thermistor RT1 by looking up the table, that is, the temperature of the laser light source 11. When the driving current flowing through the laser light source 11 is too large or fails, the temperature of the laser light source 11 will rise. When the control circuit 20 detects that the temperature is greater than the alarm upper limit temperature, the power supply of the laser light source 11 can be disconnected in time to ensure the safety of the laser light source 11.

[0060] The laser emission module 10 and the depth camera 100 provided in the embodiments of the present application have the following advantages:

[0061] (1) It has multiple driving currents and can switch the driving current according to the scene requirements. For example, in ordinary scenes, a small driving current is used to reduce product energy consumption; in low-reflection scenes and high-speed robot applications, a large driving current is used to improve the recognition of low-reflection objects and increase the detection distance.

[0062] (2) A constant current source drive is formed by the voltage conversion circuit 121 and the current sampling feedback circuit 122. In actual application, a DC-DC chip with a high output current can be selected according to the large driving current required by the laser light source 11, and a large current constant current source drive circuit is easy to build.

[0063] (3) The light source driving circuit is streamlined and non-redundant, without excessive internal power consumption. The driving circuit has high conversion efficiency, which can directly reduce the power consumption of the entire module. The reduction in the power consumption of the entire module makes the depth camera more suitable for power supply from a standard USB port, reducing the difficulty of client power supply design.

[0064] (4) It has four laser safety protection measures: overcurrent protection, pulse width timeout detection, overvoltage detection, and temperature detection. As long as one of the protection measures is effective, the power supply of the laser light source can be shut down in time, ensuring the safety and stability of the laser light source.

[0065] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A laser emission module, characterized in that: Connected to the control circuit, the laser emission module includes a laser light source and a light source driving circuit, and the light source driving circuit includes a voltage conversion circuit, a current sampling feedback circuit and a current switching circuit; The input end of the voltage conversion circuit is connected to a power supply, the output end and the feedback end are connected to the current sampling feedback circuit, and the output end of the current sampling feedback circuit is connected to the laser light source; The input end of the current switching circuit is connected to the current sampling feedback circuit, the controlled end is connected to the control circuit, and the output end is grounded; The current switching circuit is configured to be turned on or off based on the control signal of the control circuit, so that the driving current output by the current sampling feedback circuit is switched between a plurality of target current values; The current sampling feedback circuit is configured to obtain the real-time driving current of the laser light source and output a feedback voltage to the feedback terminal based on the real-time driving current. The voltage conversion circuit is configured to adjust the output current when the feedback voltage changes so that the driving current is maintained at the target current value.

2. The laser emission module according to claim 1, characterized in that: The current switching circuit includes a first switch element and a first resistor connected in series; the input end of the first switch element and the first resistor connected in series is connected to the current sampling feedback circuit, and the output end is grounded; the controlled end of the first switch element is connected to the control circuit, and the first switch element is configured to be turned on or off based on a control signal of the control circuit, so that the first resistor is connected to or not connected to the current sampling feedback circuit.

3. The laser emission module according to claim 1, characterized in that: The current sampling feedback circuit includes an operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a MOS tube; The first end of the second resistor and the first end of the third resistor are commonly connected to the output end of the voltage conversion circuit, the second end of the second resistor and the first end of the fourth resistor are commonly connected to the laser light source, the second end of the third resistor is connected to the first input end of the operational amplifier, the second end of the fourth resistor is connected to the second input end of the operational amplifier, and the first end of the fifth resistor is connected to the output end of the voltage comparison amplifier; The drain of the MOS tube is connected to the second end of the third resistor, the gate of the MOS tube is connected to the second end of the fifth resistor, the source of the MOS tube is connected to the first end of the sixth resistor and the current switching circuit, and the second end of the sixth resistor is grounded.

4. The laser emission module according to claim 1, characterized in that: The voltage conversion circuit includes a DC-DC power chip, a seventh resistor, a first capacitor, a first inductor and a second capacitor; The enable pin of the DC-DC power chip is connected to the control circuit, the output pin of the DC-DC power chip is connected to the input end of the first inductor, and the feedback pin of the DC-DC power chip is connected to the current switching circuit and the current sampling feedback circuit; The seventh resistor and the first capacitor are connected in series between the bootstrap pin and the output pin of the DC-DC power supply chip, the output end of the first inductor is connected to the input end of the second capacitor and the input end of the current sampling feedback circuit, and the output end of the second capacitor is grounded.

5. The laser emission module according to any one of claims 1 to 4, characterized in that: The light source driving circuit also includes a current limiting protection circuit, which is connected between the power supply and the voltage conversion circuit and is configured to shut down the output when the subsequent circuit is short-circuited or the driving current of the laser light source is greater than a current threshold.

6. The laser emission module according to claim 5, characterized in that: The current limiting protection circuit includes a current limiting protection chip, a pull-up resistor and a current limiting resistor; The input pin of the current limiting protection chip is connected to the power supply, the output pin is connected to the voltage conversion circuit, the enable pin is connected to the control circuit, and the fault pin is connected to the output end of the pull-up resistor and the control circuit to output an overcurrent signal to the control circuit; The current setting pin is connected to ground through the current limiting resistor to configure the current threshold.

7. The laser emission module according to any one of claims 1 to 4, characterized in that: The light source driving circuit also includes a pulse width and voltage detection circuit, which is connected between the current sampling feedback circuit and the laser light source, and is configured to divide the working voltage of the laser light source and output a divided voltage signal to the control circuit to obtain the working pulse width and working voltage of the laser light source.

8. The laser emission module according to claim 7, characterized in that: The pulse width and voltage detection circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor, wherein the first end of the first voltage-dividing resistor is connected to the output end of the current sampling feedback circuit and the input end of the laser light source, the second end of the first voltage-dividing resistor is connected to the first end of the second voltage-dividing resistor and the control circuit to output the voltage-dividing signal to the control circuit, and the second end of the second voltage-dividing resistor is grounded.

9. The laser emission module according to any one of claims 1 to 4, characterized in that: The laser emission module also includes a temperature detection circuit, which is connected to the control circuit and is configured to sense the temperature of the laser light source and output a temperature signal to the control circuit to shut down the power supply when the temperature of the laser light source is greater than a temperature threshold.

10. A depth camera, characterized in that: include: The laser emission module according to any one of claims 1 to 9, used to emit a laser beam to a target; A collection module is used to collect the laser beam reflected back by the target; as well as The control circuit is used to calculate the depth image based on the data collected by the collection module.

Images