JP5222117B2 - Laser light generation circuit, laser radar device, and transportation equipment - Google Patents

Description

  The present invention relates to a laser light generation circuit that generates pulsed laser light, a laser radar device including the laser light generation circuit, and a transportation device including the laser radar device.

  Conventionally, various laser radar devices for vehicles have been proposed in order to measure the distance from the vehicle to the object. In the laser radar device, pulsed laser light is emitted from the light transmitting unit to the object, and reflected light from the object is received by the light receiving unit. The distance to the object is calculated by measuring the time required from the emission of the laser beam by the light transmitting unit to the reception of the reflected light by the light receiving unit.

In the light transmitter, in order to generate pulsed laser light, a pulsed current is supplied from the power source to the laser diode through the switching element. In this case, the switching element is pulse-driven. Further, in the conventional light transmission unit, a DC-DC converter (DC-DC converter) or a switching power supply including a switching regulator that generates a constant DC voltage is used in order to stably control the light emission power of the laser beam. (Patent Documents 1 and 2).
JP-A-6-334247 JP 2006-284369 A

  When detecting an object at a long distance using the laser radar apparatus as described above or detecting an object with a low reflectance, it is necessary to emit a laser beam having a high emission power.

  On the other hand, when the distance from the laser radar device to the object is short, the emitted laser light and reflected light are separated if the pulse width of the laser light is not shorter than the round trip time corresponding to the minimum detection distance. I can't. In addition, when detecting a plurality of objects adjacent to each other at a short distance, reflection from the objects should be performed unless the pulse width of the laser light is shorter than the round trip time corresponding to the distance between the objects adjacent to each other. The light cannot be separated from each other. Therefore, when detecting an object at a short distance or when detecting a plurality of objects adjacent to each other at a short distance, it is necessary to shorten the pulse width of the laser light.

  In order to emit laser light having a short pulse width, it is necessary to shorten the pulse width of the current supplied to the laser diode. On the other hand, in order to emit laser light with high emission power, it is necessary to pass a large current through the laser diode. For that purpose, it is necessary to use a high-breakdown-voltage switching element capable of flowing a large current.

  However, when a large current is passed through the high breakdown voltage switching element, the switching element is turned on instantaneously when the drive signal is turned on, but it is difficult to turn off instantaneously even when the drive signal is turned off. Therefore, it is difficult to allow a large current to flow through the laser diode only for a short time using a high breakdown voltage switching element.

  Therefore, in the drive circuit described in Patent Document 1, the capacitor is precharged by a DC-DC converter that generates a constant voltage, and the switching element is turned on to start supplying current from the capacitor to the laser diode. The supply of current to the laser diode is terminated by completely discharging the charge accumulated in the capacitor. Thereafter, the switching element is turned off, and the capacitor is charged again by the DC-DC converter. In this way, a short pulse current can be passed through the laser diode.

  In this case, the DC-DC converter that constantly generates a constant voltage continues to charge the capacitor. As a result, the pulse width of the current flowing through the laser diode is widened. Therefore, it is necessary to provide a current limiting resistor between the DC-DC converter and the capacitor in order to suppress the supply of current from the DC-DC converter when the switching element is on.

  However, the current supplied from the DC-DC converter flows through the current limiting resistor, so that power is consumed and converted into heat. Similarly, in the pulse radar device of Patent Document 2, it is necessary to provide a current limiting resistor in the switching power supply in order to emit laser light having a large light emission power. Also in this case, power is consumed by the current limiting resistor and converted into heat. Therefore, large parts are required for heat dissipation measures. Therefore, it is difficult to reduce the power consumption and size of the laser radar device.

  An object of the present invention is to provide a laser light generation circuit capable of generating laser light having a large light emission power and a short pulse width and capable of reducing power consumption and miniaturization, a laser radar device including the same, and a laser radar device including the same Is to provide transport equipment.

  (1) A laser beam generation circuit according to a first aspect of the present invention includes a power supply that generates a DC voltage, an inductor that stores magnetic energy generated by the power supply, a capacitor that is charged by the magnetic energy stored in the inductor, Laser diode for generating laser light by discharge current of capacitor, first switching element provided in series with laser diode, first control circuit for controlling on / off of first switching element, power supply, inductor And a switching circuit that switches a current path in the capacitor. The switching circuit forms a first current path that supplies current from the power source to the inductor, and then charges the capacitor with the magnetic energy accumulated in the inductor. A current path is formed and the capacitor is charged to a predetermined voltage value. Been blocked inductor from the power state, the first control circuit is for turning on the first switching element after the inductor is cut off from the power supply by the switching circuit.

  In the laser light generation circuit, first, a first current path is formed by the switching circuit. Thereby, current is supplied from the power source to the inductor, and magnetic energy is stored in the inductor. Thereafter, a second current path is formed by the switching circuit. Thereby, the capacitor is charged by the magnetic energy stored in the inductor. The inductor is cut off from the power source by the switching circuit while the capacitor is charged to a predetermined voltage value. After the inductor is disconnected from the power source, the first switching element is turned on by the first control circuit. Thereby, the electric charge accumulated in the capacitor is discharged through the first switching element, and a current flows through the laser diode. When the charge accumulated in the capacitor is completely discharged, the current flowing through the laser diode becomes zero. As a result, a pulsed current flows through the laser diode, and a pulsed laser beam is emitted from the laser diode.

  In this case, since the pulsed current is supplied to the laser diode by discharging the charge accumulated in the capacitor, the pulse width of the laser light emitted from the laser diode is shortened by adjusting the capacitance value of the capacitor. can do. Further, by adjusting the voltage value of the capacitor, the light emission power of the laser light emitted from the laser diode can be increased.

  Further, when the electric charge accumulated in the capacitor is discharged, no current is supplied from the power source to the inductor, and no magnetic energy is accumulated in the inductor. Therefore, the discharging capacitor is not charged by the magnetic energy stored in the inductor. Thereby, it is not necessary to provide a current limiting resistor in the current path for supplying current to the capacitor, and power consumption and heat generation by the current limiting resistor do not occur. Therefore, large parts for heat dissipation measures are not required.

  As a result, it is possible to generate laser light having a large light emission power and a short pulse width, and it is possible to reduce the power consumption and size of the laser light generation circuit.

  (2) The laser light generation circuit operates in response to a light emission trigger having a fixed period, and the switching circuit includes a second switching element connected between one electrode of the power supply and one end of the inductor, an inductor A third switching element connected between the other end of the first electrode and the ground potential, a voltage limiting circuit for limiting the voltage of the capacitor to a predetermined voltage value or less, and a first timing of each cycle of the light emission trigger The second switching element is turned on and the third switching element is turned on. When the current supplied from the power source to the inductor reaches a predetermined value, the third switching element is turned off, and the capacitor is predetermined. The second switching element is turned off in a state where the voltage is charged to a predetermined voltage value and the voltage of the capacitor is held at a predetermined voltage value by the voltage limiting circuit. The first current path is a path through which a current flows from the power source to the ground potential via the second switching element, the inductor, and the third switching element. The second current path is A path through which current flows from the inductor to the capacitor may be used.

  In this case, the second switching element and the third switching element are turned on by the second control circuit at the first timing of each cycle of the light emission trigger. Thereby, a first current path is formed in which a current flows from the power source to the ground potential via the second switching element, the inductor, and the third switching element. As a result, magnetic energy is accumulated in the inductor.

  Thereafter, when the current supplied from the power source to the inductor reaches a predetermined value, the third switching element is turned off by the second control circuit. This forms a second current path through which current flows from the inductor to the capacitor. As a result, the capacitor is charged by the magnetic energy stored in the inductor.

  The second switching element is turned off by the second control circuit while the capacitor is charged to a predetermined voltage value and the voltage of the capacitor is held at the predetermined voltage value by the voltage limiting circuit. Thereby, the inductor is disconnected from the power source.

  In this way, the voltage of the capacitor is reliably held at a predetermined voltage value before the first switching element is turned on. Thereby, laser light having stable light emission power and pulse width is emitted from the laser diode.

  Further, a current is supplied to the laser diode by discharging the charge accumulated in the capacitor after the second and third switching elements are turned on and off. This reliably prevents the switching noise of the third switching element from being generated when the laser diode emits pulsed laser light. Therefore, it is possible to reliably prevent the influence of noise on the operation of surrounding equipment when the laser beam is emitted.

  (3) The voltage limiting circuit includes a constant voltage diode that holds the voltage of the capacitor at a predetermined voltage value when the capacitor is charged to a predetermined voltage value, and the second control circuit includes a light emission trigger. A current detection circuit that turns on the third switching element at the first timing and turns off the third switching element when the current supplied from the power source to the inductor reaches a predetermined value; A voltage detection circuit that turns on the second switching element at the timing and turns off the second switching element in a state where the voltage of the capacitor is held at a predetermined voltage value by the constant voltage diode may be included.

  In this case, when the current supplied from the power source to the inductor reaches a predetermined value, the third switching element is reliably turned off by the current detection circuit. Further, when the capacitor is charged to a predetermined voltage value, the voltage of the capacitor is held at the predetermined voltage value by the constant voltage diode. In this case, when the voltage of the capacitor exceeds a predetermined voltage value, the constant voltage diode is turned on, and a current due to excess magnetic energy of the inductor flows through the constant voltage diode. Thereby, extra magnetic energy is consumed by the constant voltage diode. As a result, charging of the capacitor is prevented, and the voltage of the capacitor is reliably held at a predetermined voltage value. Further, the second switching element is reliably turned off by the voltage detection circuit while the voltage of the capacitor is held at a predetermined voltage value by the constant voltage diode.

  In this way, the voltage of the capacitor is reliably held at a predetermined voltage value before the first switching element is turned on by the operation of the constant voltage diode. In this case, the extra energy consumed by the constant voltage diode is much smaller than the energy consumed by the current limiting resistor, and thus hardly affects the power consumption efficiency.

  (4) The first control circuit may generate a drive pulse for turning on the first switching element at the second timing of each cycle of the light emission trigger.

  In this case, the first switching element is turned on in response to the drive pulse generated at the second timing of each cycle of the light emission trigger by the first control circuit. Thereby, discharge of the electric charge accumulated in the capacitor is started, and current is supplied to the laser diode.

  (5) The third switching element is in the on state for the first period from the first timing of each cycle of the light emission trigger and is in the off state for the remaining second period. The third period may be turned on for a third period longer than the first period from the first timing of the cycle, the remaining fourth period may be turned off, and the second timing may be set within the fourth period.

  In this case, within each period of the light emission trigger, the second current path is formed after the first current path is formed, and the capacitor is connected to the laser diode during the period in which the second and third switching elements are turned off. Is supplied with a pulsed current. This reliably prevents the occurrence of switching noise of the third switching element when the laser diode is emitted. Therefore, it is possible to reliably prevent the influence of noise on the operation of surrounding equipment when the laser beam is emitted.

  (6) The capacitance value of the capacitor may be set so that the half-value width of the current flowing through the laser diode is 5 ns or less.

  In this case, it is possible to accurately detect a detection object at a short distance and a plurality of detection objects adjacent at a short distance.

  (7) A laser radar device according to a second aspect of the invention is a light transmitting device that emits pulsed laser light to a detection target, a light receiving device that receives reflected light from the detection target, and a light receiving device that receives the light. And a light transmitting device including the laser light generation circuit according to the first aspect of the present invention.

  In the laser radar device, laser light is emitted by a light transmitting device, and reflected light from a detection target is received by a light receiving device. And the information regarding a detection target is calculated by the calculation part based on the reflected light received by the light-receiving device.

  The laser light generation circuit of the light transmitting device can generate laser light having a large light emission power and a short pulse width. Further, the laser light generation circuit can reduce power consumption and size.

  Therefore, according to the laser radar device, it is possible to detect a detection object at a long distance and a detection object with a low reflectance with high accuracy, and a plurality of adjacent detection objects at a short distance and a plurality of adjacent detection objects. Can be detected with high accuracy. In addition, it is possible to reduce the power consumption and size of the laser radar device.

  (8) A transport device according to a third aspect of the present invention provides a main body, a drive unit that moves the main body, the laser radar device according to the second invention provided in the main body, and information obtained by the laser radar device. And an informing unit for informing the passenger.

  In the transportation equipment, a laser radar device is provided in a main body that is moved by a drive unit. Information obtained by the laser radar device is notified to the occupant by the notification unit.

  Here, the laser radar apparatus can detect a detection object at a long distance and a detection object with a low reflectance with high accuracy, and a plurality of detection objects adjacent to each other at a short distance and a detection object at a short distance. The object can be detected with high accuracy. In addition, the laser radar device can reduce power consumption and size. Accordingly, it is possible to accurately notify the occupant of information related to various detection objects with a small-sized and low power consumption laser radar device.

  According to the present invention, it is possible to generate laser light having a large light emission power and a short pulse width, and it is possible to reduce the power consumption and the size of the laser light generation circuit.

(1) Signal Processing System of Laser Radar Device FIG. 1 is a block diagram showing a configuration of a signal processing system of a laser radar device according to an embodiment of the present invention. This laser radar device is mounted on, for example, transportation equipment.

  The laser radar device 1 in FIG. 1 is used to detect the distance to the detection target 10 and the orientation of the detection target 10. Here, the azimuth of the detection target 10 is represented by an angle from the reference direction. The reference direction is determined in a direction perpendicular to the traveling direction, for example. The reference direction is not limited to this, and may be a direction parallel to the traveling direction, or can be determined in an arbitrary direction.

  The light transmitter 70 emits pulsed laser light. Hereinafter, the pulsed laser beam emitted from the light transmission device 70 is referred to as emission light EL. The motor 30 rotates a reflecting mirror, which will be described later, in order to rotate the direction of the emitted light EL from the light transmitting device 70 within a predetermined plane (hereinafter referred to as a scanning plane) by 360 degrees. The encoder 40 outputs an encoder pulse EP corresponding to the rotation angle of the motor 30 and outputs an origin pulse OP for each rotation of the motor 30. The motor rotation speed control unit 20 controls the rotation speed of the motor 30 to be constant based on the encoder pulse EP output from the encoder 40.

  The light emission interval pulse generator 50 generates the light emission interval pulse EI by multiplying the encoder pulse EP output from the encoder 40. The light emission trigger generation unit 60 generates the light emission trigger ET in synchronization with the light emission interval pulse EI generated by the light emission interval pulse generation unit 50. The light transmission device 70 emits the emission light EL in synchronization with the light emission trigger ET generated by the light emission interval pulse generation unit 50.

  The light receiving device 80 receives the reflected light RL from the detection target 10, receives the emitted light EL from the light transmitting device 70, and outputs a light reception signal RE.

  The signal processing unit 90 outputs a binarized signal BS based on the light emission trigger ET generated by the light emission trigger generation unit 60 and the light reception signal RE output from the light receiving device 80.

  The distance generation unit 100 generates a distance signal DS indicating a distance based on the light emission trigger ET generated by the light emission trigger generation unit 60 and the binarized signal BS output from the signal processing unit 90, and generates a distance. The distance generation signal DG shown is output.

  On the other hand, the angle generation unit 110 indicates an angle based on the origin pulse OP output from the encoder 40, the light emission trigger ET generated by the light emission trigger generation unit 60, and the distance generation signal DG generated by the distance generation unit 100. A signal AS is generated.

  The radar image generation unit 120 displays an image indicating the distance and azimuth of the detection target 10 on the display screen based on the distance signal DS generated by the distance generation unit 100 and the angle signal AS generated by the angle generation unit 110. To do. The detection target recognition unit 140 recognizes the distance and orientation of the detection target 10 based on the distance signal DS generated by the distance generation unit 100 and the angle signal AS generated by the angle generation unit 110. The danger determination unit 150 presents information indicating whether or not the detection target object 10 is dangerous based on the distance and orientation of the detection target object 10 recognized by the detection target recognition unit 140 to an occupant using an image or a sound. .

  The light emission interval pulse generation unit 50, the light emission trigger generation unit 60, the signal processing unit 90, the distance generation unit 100, the angle generation unit 110, the radar image generation unit 120, the detection target recognition unit 140, and the danger determination unit 150 are CPU (central It is realized by hardware such as an arithmetic processing unit) and memory, and software such as a program.

  In addition, a part of the light emission interval pulse generation unit 50, the light emission trigger generation unit 60, the signal processing unit 90, the distance generation unit 100, the angle generation unit 110, the radar image generation unit 120, the detection target recognition unit 140, and the risk determination unit 150 All may be realized by hardware such as a logic circuit.

(2) Optical System of Laser Radar Device FIG. 2 (a) is a schematic diagram showing the configuration of the optical system of the laser radar device 1 of FIG. 1, and FIG. 2 (b) shows the configuration of the reflecting mirror 250 of the laser radar device 1. It is a perspective view.

  In FIG. 2A, the light transmitting device 70 is attached to the center of the bottom of the cylindrical holder 200. The light transmission device 70 includes a laser light generation circuit 700 and a holding member 72. The laser light generation circuit 700 includes a laser diode (hereinafter referred to as LD) 71. The LD 71 is held by a holding member 72 so as to emit laser light in a direction perpendicular to the scanning plane. In the present embodiment, for example, a near infrared pulse laser having a wavelength of 870 nm is used as the LD 71.

  Inside the holding body 200, a reflecting mirror 210 having an opening at the center is attached so as to be inclined at an angle of 45 degrees with respect to the scanning plane. A light receiving device 80 is provided on the side wall of the holding body 200. The light receiving device 80 includes an avalanche photodiode (hereinafter referred to as APD) 81, a holding member 81a, and a receiving circuit (not shown). The APD 81 is held by the holding member 81a so that the optical axis faces a direction parallel to the scanning plane.

  A light projecting / receiving lens 220 is attached above the reflecting mirror 210 inside the holder 200. The central axis of the light projecting / receiving lens 220 faces a direction perpendicular to the scanning plane.

  A holding member 240 is attached to the inner peripheral surface of the upper end portion of the holding body 200 via a plurality of bearings 230 so as to be rotatable around an axis in a direction perpendicular to the scanning plane. As shown in FIG. 2B, the reflecting mirror 250 is fixed to the holding member 240 so as to be inclined at an angle of 45 degrees with respect to the scanning plane.

  In FIG. 2A, the motor holding portion 201 is integrally formed so as to protrude from the outer peripheral surface of the upper end portion of the holding body 200 in a direction parallel to the scanning plane. The motor 30 is held by the motor holding unit 201 so that the rotation axis is oriented in a direction perpendicular to the scanning plane. A pulley 31 is attached to the rotating shaft of the motor 30. The pulley 31 and the holding member 240 are connected by a belt 32. As the motor 30 rotates, the holding member 240 rotates. Thereby, the reflecting mirror 250 rotates around an axis in a direction perpendicular to the scanning plane while being inclined by 45 degrees with respect to the scanning plane.

  Laser light (emitted light EL) emitted from the LD 71 of the light transmitting device 70 in a direction perpendicular to the scanning plane passes through the opening of the reflecting mirror 210 and the light projecting / receiving lens 220, is reflected by the reflecting mirror 250, and is scanned. Progress in a direction parallel to When the reflecting mirror 250 is rotated by the motor 30, the traveling direction of the emitted light EL is rotated 360 degrees about an axis perpendicular to the scanning plane.

  The reflected light RL from the detection target 10 is reflected downward by the reflecting mirror 250 and condensed by the light projecting / receiving lens 220. The condensed reflected light RL is reflected by the reflecting mirror 210 and enters the APD 81 of the light receiving device 80. In this case, part of the emitted light EL from the LD 71 is irregularly reflected on the surface of the light projecting / receiving lens 220 and enters the APD 81.

(3) Operation of Laser Radar Device FIG. 3 is a timing chart for explaining the operation of the laser radar device 1 of FIG. The operation of the laser radar device 1 of FIG. 1 will be described below with reference to FIG.

  The horizontal axis in FIG. 3 is time. The origin pulse OP and encoder pulse EP are shown in the first and second stages. In the third to fifth stages, the light emission interval pulse EI, the light emission trigger ET, and the emitted light EL are shown. The light emission interval pulse EI, the light emission trigger ET, and the emitted light EL are enlarged on the time axis compared to the encoder pulse EP. Further, the light reception signal RE and the binarized signal BS are shown in the sixth and seventh stages, respectively. The light reception signal RE and the binarization signal BS are further expanded on the time axis compared to the emission light EL.

  Each time the motor 30 in FIG. 1 rotates by a predetermined angle, the encoder 40 outputs an encoder pulse EP. In the present embodiment, the encoder pulse EP is generated every time the motor 30 rotates 6 °. Therefore, when the motor 30 makes one revolution, the encoder 40 generates 60 encoder pulses EP. Further, every time the motor 30 makes one rotation, the encoder 40 outputs an origin pulse OP. Therefore, the cycle T1 of the origin pulse OP corresponds to a cycle of one rotation of the motor 30. In the present embodiment, the encoder 40 generates the origin pulse OP every time 60 encoder pulses EP are generated.

  The motor rotation speed control unit 20 controls the rotation speed of the motor 30 to be constant in response to the encoder pulse EP. In this case, the motor rotation speed control unit 20 controls the motor 30 so that the cycle T1 of the origin pulse OP is constant.

  The light emission interval pulse generator 50 generates the light emission interval pulse EI by multiplying the encoder pulse EP. In the present embodiment, the cycle T2 of the light emission interval pulse EI is 1/20 of the cycle of the encoder pulse EP. Here, an angle at which the motor 30 rotates during the period T2 of the light emission interval pulse EI (hereinafter referred to as a unit angle) is denoted by Δθ. In the present embodiment, the unit angle Δθ is 0.3 °. In this case, the light emission interval pulse EI is generated every time the motor 30 rotates 0.3 °.

  The light emission trigger generation unit 60 generates a light emission trigger ET that falls in synchronization with the rise of the light emission interval pulse EI.

  The light transmission device 70 emits a pulsed laser beam as emission light EL in synchronization with the fall of the light emission trigger ET. Thereby, the emitted light EL is emitted every time the motor 30 rotates by the unit angle Δθ.

  The emitted light EL from the LD 71 of the light transmitting device 70 is irradiated to the detection target 10. A part of the emitted light EL is incident on the APD 81 of the light receiving device 80. Therefore, after the emitted light EL from the light transmitting device 70 is received by the light receiving device 80, the reflected light RL from the detection target 10 is received by the light receiving device 80. In this case, the time from when the light receiving device 80 receives the emitted light EL to when the reflected light RL is received is proportional to the distance from the laser radar device 1 to the detection target 10.

  As described above, the emitted light EL from the light transmitting device 70 and the reflected light RL from the detection target 10 are incident on the APD 81 of the light receiving device 80. Therefore, the received light signal RE output from the light receiving device 80 includes a pulse component of the emitted light EL (hereinafter referred to as the emitted light pulse Pe) and a pulse component of the reflected light RL (hereinafter referred to as the reflected light pulse Pr). It is.

  The signal processing unit 90 generates the binarized signal BS by comparing the level of the light reception signal RE with a predetermined threshold value Th. The binarized signal BS has a logical value “1” when the level of the light reception signal RE is higher than the threshold value Th, and has a logical value “0” when the level of the light reception signal RE is equal to or lower than the threshold value. . Thereby, the binarized signal BS includes a pulse PE corresponding to the emitted light pulse Pe and a pulse PR corresponding to the reflected light pulse Pr.

  The distance generation unit 100 calculates the distance from the laser radar device 1 to the detection target 10 based on the time interval between the pulses PE and PR of the binarized signal BS in response to the light emission trigger ET, and the calculated distance Is generated.

  The angle generation unit 110 calculates an angle θ [°] based on the origin pulse OP, the light emission trigger ET, and the distance generation signal DG, and generates an angle signal AS representing the angle θ.

  Specifically, the angle generation unit 110 resets the angle θ to 0 ° in response to the origin pulse OP, and adds the unit angle Δθ to the angle θ for each light emission trigger ET. When the distance generation signal DG is given by the distance generation unit 100, the angle generation unit 110 outputs an angle signal AS indicating the angle θ.

(4) Configuration of Laser Light Generation Circuit 700 FIG. 4 is a circuit diagram showing the configuration of the laser light generation circuit 700 included in the light transmitting device 70.

  The laser beam generation circuit 700 in FIG. 4 includes switching elements S1 to S5. Switching elements S1, S3, and S5 are N-channel field effect transistors, and switching elements S2 and S4 are P-channel field effect transistors.

  In the laser light generation circuit 700, the positive electrode of the DC power supply PS is connected to the node N1, and the negative electrode is connected to a ground terminal that is held at the ground potential. A bypass capacitor C1 is connected between the node N1 and the ground terminal. As the DC power supply PS, for example, a battery can be used.

  A switching element S4 is connected between the node N1 and the node N2. The gate of the switching element S4 is connected to the node N3. A resistor R1 is connected between the node N1 and the node N3, and a resistor R2 is connected between the node N3 and the node N4.

  A switching element S5 is connected between the node N4 and the ground terminal. A light emission trigger ET is given to the input terminal of the inverter INV by the light emission trigger generator 60 shown in FIG. The output terminal of the inverter INV is connected to the gate of the switching element S5. The potential of the node N4 becomes the charge determination signal CH.

  The switching element S2 is connected between the node N1 and the node N5. The gate of the switching element S2 is connected to the node N2, and a resistor R3 is connected between the node N2 and the ground terminal. The potential of the node N2 becomes the charging timing signal CT.

  The flywheel diode D1 has a cathode connected to the node N5 and an anode connected to the ground terminal. A discharge circuit 73 including a diode D2 and a resistor R4 is connected between the node N5 and the node N6.

  The current control circuit 74 includes a current integration circuit that includes a resistor R5, a capacitor C2, and a comparator CP1. The resistor R5 is connected between the node N5 and the node N6, and the capacitor C2 is connected between the node N6 and the ground terminal. The inverting input terminal of the comparator CP1 is connected to the node N6, and the non-inverting input terminal is connected to a reference voltage terminal that receives the reference voltage Vref. The output terminal of the comparator CP1 is connected to the node N7.

  A resistor R6 is connected between the node N5 and the node N7. An inductor L1 is connected between the node N5 and the node N8, and a switching element S3 is connected between the node N8 and the ground terminal. The gate of the switching element S3 is connected to the node N7. The potential of the node N7 becomes the switching signal SW.

  A constant voltage diode D3 and a rectifier diode D4 are directly connected between the node N8 and the node N4. A rectifier diode D5 is connected between the node N8 and the node N9. The inverting input terminal of the comparator CP2 is connected to the node N10, and the non-inverting input terminal is connected to a reference voltage terminal that receives the reference voltage Vref. The output terminal of the comparator CP2 is connected to the node N4. A resistor R7 is connected between the node N9 and the node N10, and a resistor R8 is connected between the node N10 and the ground terminal.

  A discharge capacitor C3 is connected between the node N9 and the ground terminal. Further, parasitic inductances L2, LD71, and a switching element S1 are connected in series between the node N9 and the ground terminal. The potential of the node N9 becomes the output voltage OT.

  The gate drive circuit 75 outputs a gate drive signal GD based on the light emission trigger ET. The gate drive signal GD is given to the gate of the switching element S1.

(5) Operation of Laser Light Generation Circuit 700 Hereinafter, the operation of the laser light generation circuit 700 of FIG. 4 will be described with reference to FIG. FIG. 5 is a signal waveform diagram showing the operation of the laser light generation circuit 700 of FIG. The horizontal axis in FIG. 5 is time.

  Before the time point t1 of each cycle T2, the switching elements S4 and S5 are turned on, and the switching elements S1, S2, and S3 are turned off.

  At time t1, the output signal of the inverter INV falls to a low level in synchronization with the fall of the light emission trigger ET. Thereby, the switching element S5 is turned off. On the other hand, the output voltage OT of the node N9 is 0V, which is lower than the reference voltage Vref. Therefore, the charge determination signal CH (potential of the node N4) output from the comparator CP2 rises to a high level, and the switching element S4 is turned off. Thereby, the charging timing signal CT (the potential of the node N2) falls to the low level, and the switching element S2 is turned on. As a result, current starts to flow through the inductor L1.

  Further, the switching signal SW (the potential of the node N7) becomes a high level. Thereby, the switching element S3 is turned on. Therefore, the inductor current IL flows through the switching element S3.

  In this way, a first current path is formed in which a current flows from the DC power source PS to the ground potential via the switching element S2, the inductor L1, and the switching element S3. Magnetic energy is stored in the inductor L1 by the first current path.

  In this case, a current also flows through the resistor R5 of the current control circuit 74, and the capacitor C2 is charged. As a result, the voltage at node N6 (current integrated voltage) increases.

  Here, the time constant of the current control circuit 74 is set so that the current integration voltage becomes equal to the reference voltage Vref when the inductor current IL reaches a predetermined target value. The current control circuit 74 functions as a current detection circuit.

  When the inductor current IL reaches the target value at time t2, the switching signal SW (potential of the node N7) output from the comparator CP1 falls to the low level, and the switching element S3 is turned off. Thereby, the potential of the node N8 rises and the rectifier diode D5 is turned on. As a result, the inductor current IL flows to the discharge capacitor C3 through the rectifier diode D5.

  In this way, a second current path is formed through which current flows from the inductor L1 to the discharge capacitor C3 via the diode D5. The discharge capacitor C3 is charged by the second current path, and the output voltage OT (the potential of the node N9) starts to rise.

  When the potential of the node N10 reaches the reference voltage Vref at time t3, the charge determination signal CH (potential of the node N4) output from the comparator CP2 falls to a low level. Thereby, the constant voltage diode D3 and the rectifier diode D4 are turned on.

Here, the inductor current IL flows so as to be slightly higher than the target value. Excess inductor current exceeding the target value flows through the constant voltage diode D3 and the rectifier diode D4. Accordingly, surplus energy is consumed by the constant voltage diode D3, and the output voltage OT is held at a predetermined voltage value VR. Here, when the resistance value of the resistor R7 and the resistor R8 to respectively and R ₇ and R _8, the voltage value VR is expressed by the following equation.

VR = (R ₇ + R ₈ ) · Vref / R ₈
In this case, the surplus energy consumed by the constant voltage diode D3 is much smaller than the energy consumed by the current limiting resistor, and therefore hardly affects the power consumption efficiency.

  At this time, the switching element S4 is turned on, and the charging timing signal CT rises to a high level. Thereby, the switching element S2 is turned off. As a result, the inductor L1 is disconnected from the DC power source PS. Further, the electric charge of the capacitor C2 of the current control circuit 74 is discharged.

  In this state, when the light emission trigger ET falls to the low level at the time t4, the gate drive circuit 75 raises the gate drive signal GD to the high level, and falls to the low level at the time t5. Accordingly, the switching element S1 is turned on after being turned on for a certain time. In this case, the electric charge accumulated in the discharge capacitor C3 is discharged through the LD 71 and the switching element S1. When the electric charge of the discharge capacitor C3 is completely discharged, the current flowing through the LD 71 becomes 0 and the potential of the node N10 becomes 0V. As a result, a pulsed current flows through the LD 71, and the emitted light EL is emitted from the LD 71.

  The time required until the discharge capacitor C3 is completely discharged is determined by the value of the parasitic inductance L2 and the capacitance value of the discharge capacitor C3. The value of the parasitic inductance L2 is a value unique to the wiring pattern of the LD 71, the switching element S1, and the printed circuit board on which these components are mounted.

  In the present embodiment, the capacitance value of the discharge capacitor C3 is set so that the half width of the emitted light EL is, for example, 5 ns or less. Further, the capacitance value of the discharge capacitor C3 and the reference voltage Vref are set so that the emission power of the emitted light EL emitted from the LD 71 is 20 W, for example.

  At this time, the charge determination signal CH (the potential of the node N4) output from the comparator CP2 is maintained at a low level. Therefore, the switching element S4 maintains the on state, and the switching element S2 maintains the off state.

  Thus, the half-value width of the current flowing through the LD 71 is determined by the time required for the discharge capacitor C3 to be completely discharged. Therefore, the half width of the emitted light EL emitted from the LD 71 can be made shorter than the on period of the switching element S1.

(6) Effects of the Embodiment In the laser light generation circuit 700 according to the present embodiment, since the charge accumulated in the discharge capacitor C3 is discharged, a pulsed current is supplied to the LD 71, so that the discharge capacitor By adjusting the capacitance value of C3, the pulse width of the emitted light EL emitted from the LD 71 can be shortened. Further, the emission power of the emitted light EL emitted from the LD 71 can be increased by adjusting the capacitance value of the discharge capacitor C3 and the reference voltage Vref.

  FIG. 6 is a diagram showing an example of the emitted light EL and the received light signal RE in the laser radar device 1 of FIG.

  FIG. 6A shows a case where a detection target object at a short distance is detected, and FIG. 6B shows a case where two detection target objects adjacent to each other at a short distance are detected.

  As shown in FIG. 6A, when the detection target is at a short distance, the reflection of the light reception signal RE based on the emission light pulse Pe of the light reception signal RE based on the emission light EL and the reflection light from the detection target. The time interval Da with the optical pulse Pr is short. According to the laser light generation circuit 700 according to the present embodiment, the half width of the emitted light EL can be made smaller than 10 ns, so that the emitted light pulse Pe and the reflected light pulse Pr in the received light signal RE are separated. Can do. In addition, the emission power of the emitted light EL can be increased. Therefore, it is possible to accurately measure the distance to the detection object with a small reflectance at a short distance.

  As shown in FIG. 6B, when two detection objects are adjacent to each other at a short distance, the time between the reflected light pulse Pr1 and the reflected light pulse Pr2 in the light reception signal RE based on the two detection objects. The interval Db is short. According to the laser light generation circuit 700 according to the present embodiment, the half width of the emitted light EL can be reduced to 5 ns or less, so that the reflected light pulse Pr1 and the reflected light pulse Pr2 in the light reception signal RE can be separated. it can. In addition, the emission power of the emitted light EL can be increased. Therefore, it is possible to accurately measure the distance to the detection objects with small reflectance adjacent to each other at a short distance or the distance to a plurality of detection objects adjacent to each other at a short distance and at a long distance.

  Further, when the electric charge accumulated in the discharge capacitor C3 is discharged, no current is supplied from the DC power source PS to the inductor L1, and no magnetic energy is accumulated in the inductor L1. Therefore, the discharging capacitor C3 being discharged is not charged by the magnetic energy accumulated in the inductor L1. Thereby, it is not necessary to provide a current limiting resistor in the current path for supplying current to the discharge capacitor C3, and power consumption and heat generation by the current limiting resistor do not occur. Therefore, large parts for heat dissipation measures are not required.

  As a result, it is possible to generate the emitted light EL having a large light emission power and a short pulse width, and it is possible to reduce the power consumption and the size of the laser light generation circuit 700.

  Furthermore, as shown in FIG. 5, the switching noise of the switching element S3 is generated in a period (noise generation period Tn) from time t2 to time t3 of each cycle T2. On the other hand, the switching element S1 is turned on in a period (measurement period Tm) from time t4 of each cycle T2 to time t1 of the next cycle T2. In this way, in the measurement period Tm that is completely separated from the noise generation period Tn within each period T2, a pulsed current is supplied to the LD 71 by discharging the charge accumulated in the discharge capacitor C3. Thereby, the switching noise of the switching element S3 does not affect the operation of the light receiving device 80 in the period Tm. Further, the extra magnetic energy due to the extra inductor current exceeding the target value is consumed by the constant voltage diode D3, so that the charging of the capacitor C3 is stopped and the voltage of the capacitor C3 is held at a predetermined voltage value VR. The Therefore, the emitted light EL having a stable light emission power and pulse width is emitted from the LD 71. As a result, the distance to the detection target can be measured with high accuracy.

(7) Transportation equipment provided with laser radar device Next, a motorcycle will be described as an example of transportation equipment provided with the laser radar device 1 according to the above embodiment.

  FIG. 7 is a schematic diagram showing a motorcycle equipped with the laser radar device 1.

  In the motorcycle 300 of FIG. 7, a front wheel 320 is provided below the front part of the vehicle body 310, and a rear wheel 330 is provided below the rear part. An ECU (electronic control unit) 340 is provided at the center of the vehicle body 310. The laser radar device 1 according to the above embodiment is attached to the front end portion and the rear end portion of the vehicle body 310, respectively.

  In addition, a display 350 is provided at a lower rear portion of the handle 360 in the vehicle body 310.

  The laser radar device 1 at the front end mainly measures the distance and azimuth of an object in front and side of the motorcycle 300. The laser radar device 1 at the rear end mainly measures the distance and direction of an object behind and on the side of the motorcycle 300. The distance and direction measured by the laser radar device 1 at the front end and the rear end are given to the ECU 340.

  The ECU 340 causes the display 350 to display the distance and direction measured by the laser radar device 1 at the front end and the rear end as radar images. Further, the occupant can recognize whether or not the detection target 10 is dangerous based on the information presented by the danger determination unit 150.

  The laser radar device 1 can detect a detection target at a long distance and a detection target with a low reflectance with high accuracy, and a detection target at a short distance and a plurality of detection targets adjacent at a short distance. Can be detected with high accuracy. Further, the laser radar device 1 can reduce power consumption and size. Therefore, it is possible to accurately notify the occupant of information related to various detection objects with the small-sized and low power consumption laser radar device 1.

(8) Correspondence between each constituent element of claim and each element of the embodiment Hereinafter, an example of correspondence between each constituent element of the claim and each element of the embodiment will be described. It is not limited to.

  In the present embodiment, the DC power source PS is an example of a power source, the inductor L1 is an example of an inductor, the LD 71 is an example of a laser diode, the switching element S1 is an example of a first switching element, and gate drive The circuit 75 is an example of the first control circuit, the switching elements S2 to S5, the resistors R1 to R8, the diodes D1 to D5, the comparators CP1 and CP2, and the inverter INV are examples of the switching circuit, and the voltage value VR is predetermined. It is an example of the obtained voltage value.

  The light emission trigger ET is an example of the light emission trigger, the positive electrode of the DC power supply PS is an example of one electrode of the power supply, the switching element S2 is an example of the second switching element, and the switching element S3 is the third one. An example of a switching element, switching elements S4 and S5, resistors R1 to R8, diodes D1 to D5, comparators CP1 and CP2, and an inverter INV are examples of a second control circuit.

  Further, the discharge circuit 73, the current control circuit 74, and the resistor R6 are examples of current detection circuits, and the inverter INV, the switching elements S4 and S5, the resistors R1 to R3, R7, R8, and the comparator CP2 are examples of voltage detection circuits. The diodes D3 to D5 are examples of voltage control circuits.

  In addition, the time point t1 of each cycle T2 is an example of the first timing, the time point t4 of each cycle T2 is an example of the second timing, the gate drive signal GD is an example of a drive pulse, and each cycle T2 The period from time t1 to time t2 is an example of the first period, the period from time t2 of each cycle T2 to time t1 of the next cycle T2 is an example of the second period, and the time of each cycle T2 The period from t1 to time t3 is an example of the third period, and the period from time t3 of each cycle T2 to time t1 of the next cycle T2 is an example of the fourth period.

  Further, the light transmitting device 70 is an example of a light transmitting device, the light receiving device 80 is an example of a light receiving device, the signal processing unit 90, the distance generating unit 100, and the angle generating unit 110 are examples of a calculating unit, and the vehicle body 301 Is an example of the main body, the rear wheel 330 is an example of the drive unit, and the display 350 is an example of the notification unit.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

(9) Other Embodiments The LD 71 of the light transmitting device 70 is not limited to the near-infrared pulse laser, and laser elements having various wavelengths can be used.

  The switching elements S1 to S5 are not limited to field effect transistors, and various switching elements such as bipolar transistors or thyristors can be used.

  Furthermore, instead of the current control circuit 74 formed of a current integration circuit, it may be detected that the inductor current IL has reached the target value using a Hall element.

  The laser radar device 1 described above can be used not only for motorcycles but also for various transportation equipment such as four-wheeled vehicles, three-wheeled vehicles, electric bicycles, planing boats, water bikes, electric wheelchairs, ships, and helicopters. .

  The present invention can be used to measure information such as a distance to a detection target using a laser beam.

It is a block diagram which shows the structure of the signal processing system of the laser radar apparatus which concerns on one embodiment of this invention. (A) is a schematic diagram which shows the structure of the optical system of the laser radar apparatus of FIG. 1, (b) is a perspective view which shows the structure of the reflective mirror of a laser radar apparatus. FIG. 2 is a timing diagram for explaining the operation of the laser radar device of FIG. 1. It is a circuit diagram which shows the structure of the laser beam generation circuit contained in a light transmission apparatus. FIG. 5 is a signal waveform diagram illustrating an operation of the laser light generation circuit of FIG. 4. It is a figure which shows an example of the emitted light and light reception signal in the laser radar apparatus of FIG. It is a mimetic diagram showing a motorcycle provided with a laser radar device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser radar apparatus 10 Target object 20 Motor rotation speed control part 30 Motor 31 Pulley 32 Belt 40 Encoder 50 Light emission interval pulse production | generation part 60 Light emission trigger production | generation part 70 Light transmission apparatus 71 LD
72, 81a Holding member 73 Discharge circuit 74 Current integration circuit 75 Gate drive circuit 80 Light receiving device 81 APD
DESCRIPTION OF SYMBOLS 90 Signal processing part 100 Distance generation part 110 Angle generation part 120 Radar image generation part 140 Detection target object recognition part 150 Risk determination part 200 Holder 201 Motor holding part 210,250 Reflector 220 Light projecting / receiving lens 230 Bearing 240 Holding member 300 Automatic Two-wheeled vehicle 310 Car body 320 Front wheel 330 Rear wheel 340 ECU
350 Display 700 Laser light generation circuit AS Angle signal BS Binary signal C1 Bypass capacitor C2 Capacitor C3 Discharge capacitor CH Charge determination signal CP1, CP2 Comparator CT Charge timing signal D1 Flywheel diode D2 Diode D3 Constant voltage diode D4, D5 Rectification Diode Db Time interval DG Distance generation signal DS Distance signal EI Emission interval pulse EL Emission light EP Encoder pulse ET Emission trigger GD Gate drive signal INV Inverter IL Inductor current L1 Inductor L2 Parasitic inductance N1 to N10 Node Pe Emission light pulse PE, PR pulse Pr, Pr1, Pr2 Reflected light pulse PS DC power supply R1 to R8, Resistor RE Light receiving signal RL Reflected light OP Origin pulse OT Output voltage S1 5 the switching element SW switching signal t1~t5 time T2 emission interval Vref reference voltage

Claims (8)

A power source that generates a DC voltage;
An inductor for storing magnetic energy generated by the power source;
A capacitor charged by the magnetic energy stored in the inductor;
A laser diode that generates laser light by the discharge current of the capacitor;
A first switching element provided in series with the laser diode;
A first control circuit for controlling on and off of the first switching element;
A switching circuit for switching a current path in the power source, the inductor and the capacitor,
The switching circuit forms a first current path for supplying current from the power source to the inductor, and then forms a second current path for charging the capacitor by magnetic energy accumulated in the inductor, and the capacitor Is disconnected from the power source in a state where is charged to a predetermined voltage value,
The first control circuit is a laser light generation circuit that turns on the first switching element after the inductor is disconnected from the power source by the switching circuit. The laser light generation circuit operates in response to a light emission trigger having a certain period,
The switching circuit is
A second switching element connected between one electrode of the power source and one end of the inductor;
A third switching element connected between the other end of the inductor and a ground potential;
A voltage limiting circuit for limiting the voltage of the capacitor to the predetermined voltage value or less;
At the first timing of each cycle of the light emission trigger, the second switching element is turned on and the third switching element is turned on, and the current supplied from the power source to the inductor reaches a predetermined value. The third switching element is turned off, the capacitor is charged to the predetermined voltage value, and the voltage of the capacitor is held at the predetermined voltage value by the voltage limiting circuit. And a second control circuit for turning off the second switching element,
The first current path is a path through which a current flows from the power source to a ground potential via the second switching element, the inductor, and the third switching element.
The laser light generation circuit according to claim 1, wherein the second current path is a path through which a current flows from the inductor to the capacitor. The voltage limiting circuit is:
A constant voltage diode that holds the voltage of the capacitor at the predetermined voltage value when the capacitor is charged to the predetermined voltage value;
The second control circuit includes:
The third switching element is turned on at the first timing of the light emission trigger, and the third switching element is turned off when a current supplied from the power source to the inductor reaches a predetermined value. A current detection circuit;
Voltage that turns on the second switching element at the first timing and turns off the second switching element in a state where the voltage of the capacitor is held at the predetermined voltage value by the constant voltage diode. The laser light generation circuit according to claim 2, further comprising a detection circuit. 4. The laser light generation circuit according to claim 2, wherein the first control circuit generates a drive pulse for turning on the first switching element at a second timing of each cycle of the light emission trigger. 5. The third switching element is turned on for a first period from the first timing of each cycle of the light emission trigger, and is turned off for the remaining second period,
The second switching element is turned on for a third period longer than the first period from the first timing of each cycle of the light emission trigger, and is turned off for the remaining fourth period,
The laser light generating circuit according to claim 2, wherein the second timing is set within the fourth period. 6. The laser light generation circuit according to claim 1, wherein the capacitance value of the capacitor is set such that a half-value width of a current flowing through the laser diode is less than 5 ns. A light transmission device that emits a pulsed laser beam to a detection object;
A light receiving device that receives reflected light from the detection object;
A calculation unit that calculates information on the detection object based on reflected light received by the light receiving device;
The said light transmission apparatus is a laser radar apparatus containing the laser beam generation circuit in any one of Claims 1-6. The main body,
A drive unit for moving the main body unit;
The laser radar device according to claim 7 provided in the main body,
A transportation device comprising: an informing unit for informing an occupant of information obtained by the laser radar device.

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