JP6149506B2 - Radar equipment - Google Patents

Description

  The present invention includes a light emitting unit that emits a transmission wave and a light receiving unit that receives a reflected wave coming from the light emitting direction of the transmission wave, and reflects the transmission wave based on an input signal from the light receiving unit. The present invention relates to a radar apparatus for measuring a relative value indicating a relative relationship with a target.

  Conventionally, using this type of radar apparatus, for example, the time from when a transmission wave is emitted until the reflected wave of the transmission wave is received (that is, the round-trip time of the transmission wave) is measured, and the transmission wave There is known a distance measuring device that measures a distance from a target reflected from the surface.

  This type of distance measuring device is mounted on a vehicle, for example, and measures the distance to other vehicles, pedestrians, obstacles, etc. as targets, thereby preventing collisions with these targets and suppressing collision damage. Used for safety control (for example, a pre-crash safety system) or for traveling control (for example, cruise control system) for traveling following other vehicles.

  By the way, for example, in a vehicle, there is a demand for downsizing of a radar device due to the limitation of installation space. In order to meet such demands, the radar device employs a configuration in which the light emitting unit and the light receiving unit are arranged in positions close to each other or optically coaxial. Has been.

  In the radar apparatus having such a configuration, the transmission wave (for example, laser light) emitted from the light emitting unit is reflected on the inside of the apparatus, for example, by a component such as a scanning mirror or a deflecting plate for the above arrangement reasons. However, there is a problem that it is unavoidable to be received by the light receiving unit as an internal reflected wave.

  In other words, if such an internal reflected wave is regarded as a reflected wave from a target, the above-described safety control or traveling control is performed by measuring the distance in a situation where there is no other vehicle, pedestrian, obstacle, etc. May affect vehicle control. Further, if the internal reflected wave is superimposed on the reflected wave from the target, for example, it is impossible to measure the exact distance from the target existing at a short distance from the own vehicle (in some cases, the target cannot be detected). In particular, this may affect the safety control performed before the collision with the target.

For this reason, for example, in a distance measuring device, it is desired to reduce a distance measuring error due to an internally reflected wave particularly when a downsized radar device is used.
On the other hand, in the distance measuring device, the sampling data when the light receiving unit receives only the internal reflected wave is stored in advance, and thereafter, when the input signal from the light receiving unit is A / D converted, the sampling data is stored. It has been proposed to subtract the sampling value corresponding to the internal reflected wave using the synthesizer or to correct the calculated distance based on the sampling data when measuring the distance (see, for example, Patent Documents 1 to 3). .

JP 2003-185747 A JP 2008-145237 A JP 2000-314835 A

  However, in the distance measuring apparatus, in the configuration in which the distance measurement error due to the internal reflected wave is reduced digitally as in the above-mentioned proposal, for example, in order to secure real-time characteristics related to distance measurement, a conventional method generally used Concerns that the need to install a high-speed A / D converter, high-speed DSP, etc. capable of processing at higher speeds than conventional A / D converters and microcomputers will lead to increased product costs was there.

  The present invention has been made in view of the above-mentioned concerns and the like, and an object thereof is to provide a radar apparatus capable of suppressing the product cost by reducing the influence of an internal reflected wave in an analog manner.

  In order to achieve the above object, the present invention provides a light emitting unit that emits a transmission wave having a waveform corresponding to a waveform of a current flowing in a light emitting circuit, and a reflection of the transmission wave coming from the light emitting direction of the transmission wave by the light emitting unit. A radar device that measures a relative value indicating a relative relationship with a target that reflects a transmission wave based on an input signal from the light receiving unit.

  Here, in the present invention, the light receiving unit includes a first light receiving unit, a second light receiving unit, and a cancel circuit. Specifically, in the present invention, the first light receiving unit has a light receiving element for receiving a reflected wave, and a light receiving signal indicating a voltage waveform corresponding to the waveform of the reflected wave received by the light receiving element. Generate. On the other hand, the second light receiving unit has a simulation circuit that simulates the light emitting circuit, and at a known time from when the transmission wave is emitted by the light emitting unit until the internally reflected wave of the transmission wave is received by the light receiving element. Based on the timing, a simulation signal indicating a voltage waveform corresponding to the waveform of the current flowing through the simulation circuit is generated. Then, the cancel circuit removes the voltage waveform corresponding to the waveform of the internal reflection wave from the voltage waveform indicated by the light reception signal generated by the first light receiving unit, using the simulation signal generated by the second light receiving unit. It was set as the structure to do.

  In such a configuration, when a current flows through the light emitting circuit and a transmission wave is emitted by the light emitting unit, a current flows through a simulated circuit that simulates the light emitting circuit in accordance with the timing at which the internal reflected wave is received by the light receiving element. A voltage waveform (simulated voltage waveform) corresponding to the waveform of the current flowing through the simulated circuit is generated. Here, since the simulated circuit is a circuit that simulates a light emitting circuit, the simulated voltage waveform is similar to the waveform of the current flowing through the light emitting circuit (light emitting current waveform), and the waveform of the internally reflected wave is similar to the light emitting current waveform. Therefore, in the simulation circuit, a voltage waveform similar to the waveform of the internal reflection wave is generated as the simulation voltage waveform.

  And, since the voltage waveform of the internal reflected wave can be known in advance by experiments, simulations, etc., so that the simulated voltage waveform generated by the simulation circuit is the same size as the voltage waveform of the internal reflected wave (clutter voltage waveform) A voltage waveform corresponding to the clutter voltage waveform can be generated as the simulated voltage waveform by adjusting the value of the current flowing through the simulated circuit in advance or adopting a configuration that amplifies the simulated voltage waveform.

  For this reason, when a simulated signal is input to the cancel circuit in synchronization with the timing at which the internal reflected wave is received by the light receiving element, the cancel circuit generates a simulated signal (simulated voltage waveform) with a simple configuration such as an operational amplifier. It is possible to remove the voltage waveform (clutter voltage waveform) corresponding to the waveform of the internal reflection wave from the voltage waveform indicated by the light reception signal generated by the first light receiving unit.

  Therefore, according to the present invention, it is possible to reduce the influence of the internal reflection wave in an analog manner without mounting a high-speed A / D converter, a high-speed DSP, and the like, thereby suppressing the product cost.

  In the present invention, the internal reflected wave refers to a reflected wave that is reflected by the light receiving element and reflected by the light receiving element among the reflected waves received by the light receiving element. In addition, the relative value indicating the relative relationship with the target refers to a value indicating, for example, the distance to the target, the relative speed, the direction in which the target is located, and the like.

Furthermore, the present invention can be limited by the following configurations.
For example, in the present invention, the light emitting circuit includes a light emitting element that emits a transmission wave and a first switching element for energizing the light emitting circuit, and the simulation circuit simulates the light emitting element of the light emitting circuit. And the second switching element for energizing the simulation circuit, the current flowing through the diode of the simulation circuit (simulation current) can be made smaller than the current flowing through the light-emitting element of the light-emitting circuit. is there.

  In such a configuration, it is desirable that the second switching element has a structure in which the simulation circuit is energized at a response speed at which the simulation current has the same rate of change with time as the light emission current. Specifically, for example, in the present invention, when the second switching element is configured by a MOSFET, the on-resistance value can be adjusted to be small by increasing the gate area (channel). When the switching element is formed of a bipolar transistor, the on-resistance value can be adjusted to be small by increasing the device size.

  In other words, if the amount of current flowing through the light emitting circuit is large, a linear region of voltage-current characteristics is used in the light emitting element (for example, a laser diode). When the amount of flowing current is small, a non-linear region of voltage-current characteristics is used in the diode, so that the time change rate of the simulated current is reduced by increasing the resistance component of the diode. On the other hand, by adopting the structure of the second switching element as described above, the time change rate of the simulated current can be made the same as the light emission current.

Therefore, according to such a configuration, it is possible to suitably generate a simulated voltage waveform that is the same as the waveform of the internally reflected wave (clutter voltage waveform) while reducing the amount of current flowing through the simulated circuit.
Further, for example, in the present invention, the first light receiving unit includes an amplifier circuit that amplifies the received light signal and a first filter circuit that removes a high frequency component of the received light signal, and the second light receiving unit includes the simulated signal. In the configuration having the second filter circuit that removes a high frequency component equal to or higher than a preset frequency threshold value, the frequency threshold value is set to a value that makes the simulated voltage waveform have the same time change rate waveform as the clutter voltage waveform. It is desirable.

  That is, when the received light signal passes through the amplifier circuit and the first filter circuit, high frequency components are removed by these circuits (even by being amplified not only by the first filter circuit but also by the amplifier circuit). The voltage waveform (light reception voltage waveform) indicated by the light reception signal that has passed through the circuit is a waveform (dull waveform) with a low rate of time change. On the other hand, by setting the frequency threshold in the second filter circuit to a value that has the same time change rate waveform as the clutter voltage waveform as the received light voltage waveform of the component of the internal reflection wave, the second filter The voltage waveform (simulated voltage waveform) indicated by the simulated signal that has passed through the circuit can be made dull as much as the received light voltage waveform (clutter voltage waveform).

  Therefore, according to such a configuration, it is possible to amplify the received light signal and remove the high frequency component. For example, the waveform of the internally reflected wave (clutter voltage) is less affected by external noise other than the internally reflected wave. Since the same simulated voltage waveform as the waveform) can be generated, the influence of the internal reflected wave can be suitably suppressed.

  Further, for example, in the present invention, when the second light receiving unit inputs a light emission trigger signal used when causing the light emitting unit to emit a transmission wave, the second switching element for energizing the simulation circuit and the first light emission trigger signal A configuration having a delay circuit that delays input to the two switching elements by a time corresponding to the internal reflection time may be employed.

  In such a configuration, for example, when a light emission trigger signal is input from a microcomputer or the like, a current flows through the light emitting circuit, a transmission wave is emitted by the light emitting unit, and a transmission wave is emitted. After a time corresponding to a known time (internal reflection time) until the light is received by the light receiving element, a light emission trigger signal is input through the delay circuit, and a current flows through the simulation circuit.

  Therefore, according to such a configuration, for example, a microcomputer or the like does not need to individually output trigger signals for flowing current to the light emitting circuit and the simulation circuit at different timings, so that the processing load of the microcomputer is reduced. The influence of the internal reflected wave can be suitably reduced in analog processing.

It is the schematic which illustrates the whole structure of a radar apparatus. It is the schematic for demonstrating the internal reflected wave in a radar apparatus. It is a circuit diagram which illustrates the composition of the principal part of a radar apparatus. It is a timing chart which illustrates operation of a radar device. It is explanatory drawing which illustrates the voltage-current characteristic of a light emitting element and a diode. It is explanatory drawing which illustrates the frequency characteristic of an amplifier circuit and a 1st filter circuit. It is explanatory drawing which illustrates the signal waveform which passed the amplifier circuit and the 1st filter circuit.

  A radar apparatus as an embodiment of the present invention will be described below with reference to the drawings. The radar apparatus according to the present embodiment is installed in the front portion of the vehicle, and distances and relative speeds with other vehicles, pedestrians, obstacles, and other targets located in front of the vehicle, and the direction in which the target is located. It is used to measure a relative value indicating a relative relationship with a target. Further, these measured values can be used for a pre-crash safety system, a cruise control system, etc. mounted on a vehicle.

<Overall configuration>
As shown in FIG. 1, the radar apparatus 1 of the present embodiment includes a light emitting unit 10 including a collimator lens 3, an aperture 4, a polarization beam splitter 5, a λ / 4 wavelength plate 6, an optical scanning unit 7, A light receiving unit 20 including a light receiving lens 8, a light emitting unit 10, an optical scanning unit 7, and a control unit 30 (see FIG. 3) for controlling the light receiving unit 20, and a housing (not shown) for housing these components. It has.

  The light emitting unit 10 has a light emitting element 2 (see FIG. 3) such as a semiconductor laser diode, which will be described in detail later. For example, the light emitting unit 10 receives a light emission trigger signal from the control unit 30 (see FIG. 3). When input, a linearly polarized pulsed laser beam is emitted as a transmission wave.

The collimating lens 3 converts the pulsed laser light emitted from the light emitting element 2 into parallel light and irradiates the aperture 4 toward the aperture 4.
The aperture 4 is a plate-like member partially having an opening 4 a and is disposed between the collimating lens 3 and the polarization beam splitter 5. Thereby, the aperture 4 reflects the pulse laser light incident on the region other than the opening 4a on the incident surface on which the pulse laser light is incident, and allows the pulse laser light incident on the region inside the opening 4a to pass therethrough. That is, the pulsed laser light incident on the aperture 4 from the collimator lens 3 is shaped into the shape of the opening 4 a and is irradiated toward the polarization beam splitter 5.

  The polarization beam splitter 5 transmits a component having a predetermined polarization direction among the pulsed laser light incident on the polarization beam splitter 5 from the aperture 4 and reflects a component having a polarization direction other than the predetermined polarization direction. Have

  The polarization beam splitter 5 is arranged so that the predetermined polarization direction matches the polarization direction of the pulsed laser light emitted from the light emitting element 2. Further, the polarization beam splitter 5 is a cube type formed by sticking right-angle prisms into a cube shape, and the direction perpendicular to the bonding surface is inclined with respect to the incident direction of the pulse laser beam (for example, (Tilt angle of 45 °).

The λ / 4 wavelength plate 6 has a function of converting linearly polarized light into circularly polarized light and converting circularly polarized light into linearly polarized light, and is disposed between the polarizing beam splitter 5 and the optical scanning unit 7.
In accordance with a control command from the control unit 30 (see FIG. 3), the optical scanning unit 7 oscillates the mirror 7a that reflects the pulsed laser light around the rotation axis provided in the mirror 7a, thereby λ / 4. Scanning of the pulsed laser light incident from the wave plate 6 is performed within a preset scanning angle range.

  As will be described in detail later, the light receiving unit 20 includes a light receiving element 9 (see FIG. 3) such as a photodiode. The light receiving unit 20 detects the pulse laser beam incident from the light receiving lens 8 and the detection result thereof. Is output to the control unit 30 (see FIG. 3).

The light receiving lens 8 guides the pulsed laser light incident from the optical scanning unit 7 side and reflected by the polarization beam splitter 5 to the light receiving element 9.
Next, a method for detecting an object (target) reflecting pulsed radar light in the radar apparatus 1 configured as described above will be described.

  First, the pulsed laser light emitted from the light emitting element 2 is converted into parallel light by the collimating lens 3, and the diameter of the light is further reduced by the aperture 4 to reach the polarization beam splitter 5.

  Then, the pulse laser beam that has reached the polarizing beam splitter 5 passes through the polarizing beam splitter 5 and further passes through the λ / 4 wavelength plate 6. As a result, the pulsed laser light is converted from linearly polarized light into circularly polarized light and reaches the optical scanning unit 7.

Then, the laser light that has reached the optical scanning unit 7 is reflected by the mirror 7a, and is irradiated as a radar wave in a direction corresponding to the scanning angle of the mirror 7a.
Thereafter, when the pulse laser beam (reflected wave) reflected by the target reaches the optical scanning unit 7, it is reflected by the mirror 7 a and passes through the λ / 4 wavelength plate 6 again. As a result, pulsed laser light reflected by the target (hereinafter referred to as “reflected laser light”) is converted from circularly polarized light to linearly polarized light and reaches the polarizing beam splitter 5.

  The polarization direction of the reflected laser light converted into linearly polarized light by the λ / 4 wavelength plate 6 is shifted by 90 ° with respect to the polarization direction of the pulsed laser light before being irradiated from the light emitting element 2 and converted into circularly polarized light. . For this reason, the reflected laser light that has reached the polarizing beam splitter 5 is reflected by the polarizing beam splitter 5 and irradiated toward the light receiving lens 8. Thereby, the reflected laser beam reaches the light receiving unit 20, and the object that reflects the pulse laser beam can be detected.

  For example, the control unit 30 determines the distance to the target that reflects the pulsed laser light based on the difference between the time when the light emitting unit 10 emits the pulsed laser light and the time when the reflected light is detected by the light receiving unit 20. It can be measured. Note that such distance measurement processing is not necessarily performed by the control unit 30 of the radar apparatus 1, and may be performed by another ECU or the like connected to the radar apparatus 1.

  By the way, in the radar apparatus 1 configured as described above, since the light emitting unit 10 and the light receiving unit 20 are disposed at optically coaxial positions, the pulses emitted by the light emitting unit 10 as shown in FIG. The laser light is reflected by, for example, the λ / 4 wavelength plate 6 and the mirror 7a inside the housing, and further reflected by the polarization beam splitter 5, thereby reaching the light receiving unit 20 as an internal reflected wave (hereinafter referred to as “clutter”). To do. For this reason, if the light receiving unit 20 superimposes the clutter on the reflected laser light or erroneously detects the clutter as the reflected laser light, the accuracy of the distance measurement processing is lowered.

  On the other hand, as described below, in the radar apparatus 1 of the present embodiment, the light receiving unit 20 has a circuit configuration for reducing the influence of clutter in an analog manner. In the following description, the clutter as the internal reflected wave after the pulsed laser light is emitted from the light emitting element 2 of the light emitting unit 10 by the measurement or simulation when the target is at infinity is the light receiving element of the light receiving unit 20 9 is assumed to be calculated in advance as a known time (hereinafter referred to as “internal reflection time”).

  The control unit 30 is configured around a known microcomputer having, for example, a CPU, a ROM, a RAM, and the like. The CPU uses the RAM as a work space based on a program stored in the ROM, and the light emitting unit 10. A trigger signal (hereinafter referred to as “light emission trigger signal”) for emitting pulsed laser light is output at predetermined intervals, or a control command for causing the optical scanning unit 7 to scan within the scanning angle range is output. Or In addition, the control unit 30 is configured to be able to perform distance measurement processing and the like as described above by inputting a light receiving signal described later from the light receiving unit 20.

<Configuration of light emitting unit>
As shown in FIG. 3, the light emitting unit 10 includes a light emitting circuit 11a having a light emitting element 2 for emitting pulsed laser light as a transmission wave, and a power source circuit 12 connected to the DC power source VC and the light emitting circuit 11a. In addition, it is configured.

  The light emitting circuit 11a is configured around a known RLC circuit in which a resistor 13, an inductor 14, and a capacitor 15 are connected in series, and includes a first switching element 16 for energizing the RLC circuit, The light emitting element 2 connected in series to the resistor 13 emits pulsed laser light having a waveform corresponding to the waveform of the current flowing through the RLC circuit.

  The power supply circuit 12 has one end connected to the DC power supply VC and the other end connected to the capacitor 15 and the inductor 14. The voltage supplied from the DC power supply VC is a voltage necessary for the RLC circuit (light emitting circuit 11 a) to operate. It has a resistance component to be converted into

  The first switching element 16 is configured by a well-known MOSFET, bipolar transistor, or the like, and is turned on while the light emission trigger signal is input from the control unit 30 as shown in FIG. The (light emitting circuit 11a) is energized, and the light emitting trigger signal is not input from the control unit 30, and the RLC circuit (light emitting circuit 11a) is deenergized while being turned off.

  For example, when the first switching element 16 is configured by a MOSFET, the light emitting element 2 is connected to the source side, the ground (ground) is connected to the drain side, and the control unit 30 is connected to the gate side. In the case of being constituted by a transistor, for example, a mode in which the light emitting element 2 is connected to the emitter side, the ground (ground) is connected to the collector side, and the control unit 30 is connected to the base side can be adopted.

  For example, one end of the capacitor 15 is connected to the ground (ground), and the other end is connected to the power supply circuit 12 and the inductor 14. As shown in FIG. 4B, the first switching element 16 is in an OFF state (RLC). The circuit (while the light emitting circuit 11a is not energized), the voltage (charge) supplied from the DC power supply VC via the power supply circuit 12 is stored, and the first switching element 16 is switched from the OFF state to the ON state, It is configured to discharge.

  In the light emitting unit 10, as shown in FIG. 4C, when the capacitor 15 is discharged, current flows from the capacitor 15 to the light emitting circuit 11 a including the inductor 14, the resistor 13, the light emitting element 2, and the first switching element 16. At this time, a pulsed laser beam having a waveform corresponding to the waveform of the current (hereinafter referred to as “light emission current”) flowing through the light emitting circuit 11 a is emitted from the light emitting element 2.

  In the light emitting unit 10, as shown in FIG. 5A, assuming that the light emission current flowing through the light emitting element 2 is I and the voltage across the light emitting element 2 at this time is V, the light emitting element 2 in FIG. The linear region of the VI characteristic shown in FIG. For this reason, the power supply circuit 12 is configured to supply a relatively large voltage to the capacitor 15, and the capacitor 15 is configured to include a capacitor having a size capable of storing this voltage.

  Thus, in the light emitting unit 10, when the light emission trigger signal is input from the control unit 30, the first switching element 16 is turned on, whereby a light emitting current flows through the light emitting circuit 11 a, and the waveform of the light emitting current is generated. A pulsed laser beam having a waveform corresponding to is emitted.

<Configuration of light receiving unit>
On the other hand, the light receiving unit 20 includes a first light receiving unit 20a having a light receiving element 9 for receiving reflected laser light as a reflected wave of pulsed laser light, and a second light receiving unit having a simulation circuit 11b simulating the light emitting circuit 11a. Cancel a voltage waveform (hereinafter referred to as “simulated voltage waveform”) corresponding to the above-described clutter waveform from the voltage waveform indicated by the light receiving signal (described later) generated by the unit 20b and the first light receiving unit 20a. And a circuit 20c. It is assumed that the simulated voltage waveform is calculated in advance as a waveform having a known shape and size by measurement or simulation when the target is at infinity.

<Configuration of first light receiving unit>
As shown in FIG. 4D, when a current is output according to the waveform of the reflected laser beam received by the light receiving element 9, as shown in FIG. A resistor 21 (see FIG. 3) for converting the current (light receiving current) output from the light receiving element 9 into a voltage at that time, and an amplifier circuit 22 and a first filter circuit 23 described later are configured. The

  For example, one end of the resistor 21 is connected to the ground (ground) and the other end is connected to the light receiving element 9 and the amplifier circuit 22, and a signal indicating a waveform of a voltage obtained by converting the current during light reception by the resistor 21 (hereinafter referred to as “light receiving signal”). Is supplied to the amplifying circuit 22. The light reception signal is a signal generated by simply converting a current corresponding to the waveform of the reflected laser light (current during light reception) into a voltage, and thus shows a voltage waveform corresponding to the waveform of the reflected laser light. .

  The amplifier circuit 22 is a circuit that amplifies the light reception signal supplied via the resistor 21. As shown in FIG. 4F, the light reception signal amplified by the amplifier circuit 22 is configured such that its voltage waveform is inverted and output to the first filter circuit 23. Further, when amplifying the received light signal, the amplifier circuit 22 attenuates the input voltage Vin having a frequency exceeding the first cut-off frequency fh1, as shown in FIG. 6A.

  The first filter circuit 23 is a circuit that removes a high-frequency component of the received light signal amplified by the amplifier circuit 22. As shown in FIG. 4G, the light reception signal that has passed through the first filter circuit 23 is configured to be output to the cancel circuit 20c as a waveform with a dull voltage waveform. Further, when removing the high frequency component of the light reception signal, the first filter circuit 23, as shown in FIG. 6B, sets a second value that is set in advance as a value smaller than the first cutoff frequency fh1. The input voltage Vin having a frequency exceeding the cut-off frequency fh2 is attenuated. Further, the first filter circuit 23 is configured as a band-pass filter that attenuates the input voltage Vin having a frequency lower than the third cutoff frequency fh3 set in advance as a value smaller than the second cutoff frequency fh2. be able to.

  That is, the amplification circuit 22 and the first filter circuit 23 are defined by at least the cutoff frequencies fh1 and fh2, as shown in FIG. 6C, when the received light signal is amplified and the high frequency components are removed. It is configured to attenuate high frequency components.

  For this reason, as shown in FIG. 7, the voltage waveform (input voltage Vin) indicated by the light reception signal containing a large amount of high-frequency components has a sharp rise, whereas the amplifier circuit 22 and the first filter circuit. The voltage waveform (output voltage Vout) indicated by the received light signal that has passed through 23 is reduced in sharpness by removing high-frequency components, and becomes a waveform having a low time change rate (dull waveform).

  As described above, when the light receiving element 9 receives the reflected laser beam, the first light receiving unit 20a generates a signal (light receiving signal) indicating a voltage waveform corresponding to the waveform of the reflected laser beam, and the generated light receiving signal. Is amplified by the amplifier circuit 22, and the high frequency component is removed by the first filter circuit 23, and the light reception signal that has passed through the amplifier circuit 22 and the first filter circuit 23 is output to the cancel circuit 20c. It is configured.

  Therefore, in the first light receiving unit 20a, when the light receiving element 9 receives clutter as an internal reflected wave in the reflected laser light, a light receiving signal including a voltage waveform (clutter voltage waveform) corresponding to the waveform of the clutter is cancelled. It is output to 20c. As the clutter voltage waveform, a voltage waveform before passing through the amplifier circuit 22 and the first filter circuit 23 and a voltage waveform after passing through the amplifier circuit 22 and the first filter circuit 23 are tested. And the waveform shape and size are calculated in advance by a simulation or the like.

<Configuration of second light receiving unit>
As shown in FIG. 4 (h), when the light emission trigger signal is input from the control unit 30, the second light receiving unit 20b delays by a time corresponding to the above-described internal reflection time, and then the simulation circuit at the subsequent stage. 11b includes a delay circuit 24 that outputs the light emission trigger signal, a simulation circuit 11b, and a second filter circuit 25. Here, the time corresponding to the internal reflection time is from the second light receiving unit 20b in synchronization with the timing when the clutter voltage waveform (light reception signal) is output from the first light receiving unit 20a to the cancel circuit 20c. This is a time set in advance to output a simulated voltage waveform (simulated signal) to be described later to the cancel circuit 20c.

  As shown in FIG. 3, the second light receiving unit 20b includes a delay circuit 24, a simulation circuit 11b, and a second filter circuit 25, as well as a power supply circuit 26 connected to the DC power supply VC and the simulation circuit 11b. It has.

  The simulation circuit 11b is a known RLC circuit in which a resistor 33 that simulates the resistor 13 of the light emitting circuit 11a, an inductor 34 that simulates the inductor 14 of the light emitting circuit 11a, and a capacitor 35 that simulates the capacitor 15 of the light emitting circuit 11a are connected in series. And a diode having the same VI characteristics as the light emitting element 2, which is a simulation of the second switching element 36 for energizing the RLC circuit and the light emitting element 2 of the light emitting circuit 11 a. 32.

  For example, one end of the power supply circuit 26 is connected to the DC power supply VC and the other end is connected to the capacitor 35 and the diode 32. The voltage supplied from the DC power supply VC is necessary for the RLC circuit (simulation circuit 11b) to operate. It has a resistance component that converts it into a voltage. However, the resistance component of the power supply circuit 26 is set larger than the resistance component of the power supply circuit 12 in the light emitting unit 10. For this reason, the current flowing through the simulation circuit 11b (hereinafter referred to as “simulation current”) has a smaller current value than the light emission current flowing through the light emitting circuit 11a. Therefore, in the first light receiving unit 20a, as shown in FIG. 5A, when the simulated current flowing in the diode 32 is I and the voltage across the diode 32 at this time is V, in the diode 32, FIG. The nonlinear region of the VI characteristic shown in FIG.

  The second switching element 36 is configured by a known MOSFET, bipolar transistor, or the like, and is turned on while a light emission trigger signal is input from the control unit 30 via the delay circuit 24 as shown in FIG. The RLC circuit (simulation circuit 11b) is energized, and the RLC circuit (simulation circuit 11b) is de-energized while the light emission trigger signal is not input from the control unit 30 via the delay circuit 24. It is configured to make it.

  For example, when the second switching element 36 is configured by a MOSFET, the diode 32 on the source side, ground (ground) on the drain side, and the delay circuit 24 (control unit 30 side) on the gate side are examples. For example, when a bipolar transistor is used, a diode 32 is connected to the emitter side, a ground (ground) is connected to the collector side, and a delay circuit 24 (control unit 30 side) is connected to the base side. can do.

  Further, when the second switching element 36 is configured by, for example, a MOSFET, the on-resistance value is adjusted to be small by increasing the gate area (channel). For example, when configured by a bipolar transistor, The on-resistance value is adjusted to be small by increasing the device size.

  As a result, the response speed of the second switching element 36 can be made larger than that of the first switching element 16, so that the nonlinear region of the VI characteristic shown in FIG. 5B is used in the diode 32. As a result, as shown in FIG. 5C, the resistance component of the diode 32 increases exponentially, so that even if the time change rate of the simulated current is lower than the emission current, The decrease in the rate of change of the simulated current with time can be offset.

  That is, in the second switching element 36, the on-resistance value is structurally adjusted so that the simulation circuit 11b is energized at a response speed at which the simulation current has the same rate of change with time as the light emission current. Since the time change rate of the light emission current is known, the on-resistance value (that is, the gate area and the device size) of the second switching element 36 that satisfies the above time change rate condition is adjusted in advance by experiment, simulation, or the like. Can be kept.

  For example, one end of the capacitor 35 is connected to the inductor 14 and the other end is connected to the power supply circuit 26 and the diode 32. As shown in FIG. 4I, the second switching element 36 is in an OFF state (RLC circuit ( While the simulation circuit 11b) is not energized), the voltage (charge) supplied from the DC power supply VC via the power supply circuit 26 is stored, and the second switching element 36 is discharged when it changes from the OFF state to the ON state. It is configured.

  Then, in the second light receiving unit 20b, as shown in FIG. 4 (j), when the capacitor 35 is discharged, the capacitor 35 is changed to the simulation circuit 11b including the inductor 34, the resistor 33, the diode 32, and the second switching element 36. Current flows. Note that the waveform of the current (simulated current) flowing through the simulation circuit 11b at this time is a waveform of the light emission current (light emission current waveform) flowing through the light emitting circuit 11a because the simulation circuit 11b is a circuit simulating the light emitting circuit 11a. Similar waveform.

  In the second light receiving unit 20b, the power supply circuit 12 is configured to supply a relatively small voltage to the capacitor 35, and the capacitor 35 has a capacitor having a size capable of storing this voltage. In the simulation circuit 11b, the resistor 33 has, for example, one end connected to the ground (ground) and the other end connected to the inductor 34 and the second filter circuit 25, and converts the simulation current flowing through the simulation circuit 11b into a voltage. Then, a signal (simulated signal) indicating the waveform of the voltage converted from the simulated current is supplied to the second filter circuit 25. Incidentally, since the simulation signal is a signal generated by simply converting the simulation current into a voltage, it shows a voltage waveform similar to the light emission current waveform. In this embodiment, as shown in FIG. 4 (k), the resistance value of the resistor 33 and the inductance of the inductor 34 are set in advance so that a simulated voltage waveform described later has the same magnitude as the clutter voltage waveform. .

  The second filter circuit 25 is provided between the simulation circuit 11b and the cancellation circuit 20c, and removes (attenuates) a high-frequency component equal to or higher than a preset frequency threshold value from the simulation signal supplied via the resistor 33. ) Circuit.

  As described above, in the first light receiving unit 20a, the amplification circuit 22 and the first filter circuit 23 are defined by the cutoff frequencies fh2 and fh3 when the received light signal is amplified and the high frequency components are removed. High frequency components are attenuated. Thus, the voltage waveform (light reception voltage waveform) indicated by the light reception signal that has passed through the amplifier circuit 22 and the first filter circuit 23 is reduced in steepness and becomes a waveform with a low time change rate (dull waveform).

  On the other hand, in the second filter circuit 25, as shown in FIG. 4L, the voltage waveform (hereinafter referred to as “simulated voltage waveform”) indicated by the simulated signal that has passed through the second filter circuit 25 is the clutter. A frequency threshold is set in advance to a value that becomes a waveform having the same time change rate as the clutter voltage waveform that is the received light voltage waveform. The frequency threshold is a value defined by the cutoff frequencies fh1 and fh2. The second filter circuit 25 can also be configured as a bandpass filter that attenuates the input voltage Vin having a frequency lower than the third cutoff frequency fh3.

  As described above, in the second light receiving unit 20b, when the light emission trigger signal is input from the control unit 30 via the delay circuit 24, the second switching element 36 is switched to the ON state, thereby causing the simulation circuit 11b to A simulated current flows, and a waveform signal (simulated signal) corresponding to the waveform of the simulated current is generated. In the second light receiving unit 20b, the high-frequency component of the generated simulation signal is removed by the second filter circuit 25, and the simulation signal that has passed through the second filter circuit 25 is output to the cancel circuit 20c. It has become.

  Further, in the second light receiving unit 20b, after the pulse laser beam is emitted by the light emitting unit 10, the reflected laser beam is received by the first light receiving unit 20a, and the clutter voltage is applied from the first light receiving unit 20a to the cancel circuit 20c. The simulated voltage waveform (simulated signal) is output to the cancel circuit 20c at the timing when the waveform (light reception signal) is output.

  The cancel circuit 20c uses a light reception signal from the first light receiving unit 20a as a non-inverted input (+) and a simulated signal from the second light receiving unit 20b as an inverted input (-), depending on the potential difference between the two inputs. A voltage indicated by a light receiving signal input from the first light receiving unit 20a using a simulated voltage waveform (simulated signal) input from the second light receiving unit 20b, which is configured by an operating differential amplifier circuit (for example, an operational amplifier). The clutter voltage waveform is removed from the waveform (see FIG. 4 (m)). The light reception signal from which the clutter voltage waveform is removed is output to the control unit 30.

<Effect>
As described above, in the radar apparatus 1 of the present embodiment, the first light receiving unit 20a generates a light reception signal indicating a voltage waveform corresponding to the waveform of the reflected wave received by the light receiving element 9, and the second light receiving unit 20a generates the light reception signal. The light receiving unit 20b generates a voltage waveform corresponding to the waveform of the current flowing through the simulation circuit 11b at a timing based on a known time from when the pulse laser beam is emitted by the light emitting unit 10 until the clutter is received by the light receiving element 9. A simulated signal is generated. Then, the cancel circuit 20c uses the simulation signal generated by the second light receiving unit 20b to generate a voltage waveform corresponding to the clutter waveform from the voltage waveform indicated by the light receiving signal generated by the first light receiving unit 20a. Remove.

  For this reason, when a current flows through the light emitting circuit 11a and a pulse laser beam is emitted by the light emitting unit 10, a current is supplied to the simulation circuit 11b that simulates the light emitting circuit 11a in accordance with the timing when the clutter is received by the light receiving element 9. A voltage waveform (simulated voltage waveform) corresponding to the waveform of the current flowing through the simulated circuit 11b is generated. Here, since the simulation circuit 11b is a circuit that simulates the light emitting circuit 11a, the simulated voltage waveform is similar to the waveform of the current flowing through the light emitting circuit 11a (light emission current waveform), and the waveform of the clutter becomes the light emission current waveform. Because of the similarity, the simulation circuit 11b generates a voltage waveform similar to the clutter waveform as the simulation voltage waveform.

  Then, since the voltage waveform of the clutter can be known in advance by experiments, simulations, etc., the simulation circuit 11b so that the simulation voltage waveform generated by the simulation circuit 11b has the same magnitude as the voltage waveform of the clutter (clutter voltage waveform). By adjusting in advance the value of the current flowing through, it is possible to generate the same voltage waveform as the clutter voltage waveform as the simulated voltage waveform.

  Therefore, when a simulation signal is input to the cancel circuit 20c in accordance with the timing at which the clutter is received by the light receiving element 9, the cancel circuit 20c generates a simulation signal (simulated voltage waveform) with a simple configuration such as an operational amplifier. It is possible to remove the clutter voltage waveform from the voltage waveform indicated by the light reception signal generated by the first light receiving unit 20a.

  Therefore, according to the radar apparatus 1, the influence of clutter can be reduced in analog processing without mounting a high-speed A / D converter, a high-speed DSP, etc., and the product cost can be suppressed.

In the radar apparatus 1, the second switching element 36 has a structure in which the simulation circuit 11 b is energized at a response speed at which the simulation current has the same time change rate as the light emission current.
In other words, when the amount of current flowing through the light emitting circuit 11a is large, the light emitting element 2 uses the linear region of the VI characteristic, and thus the temporal change rate of the light emitting current increases, whereas the current flowing through the simulation circuit 11b. If the amount is small, the diode 32 uses a non-linear region of the VI characteristic, so that the resistance component of the diode 32 increases, and the time change rate of the simulated current becomes low. On the other hand, by adopting the structure of the second switching element 36 as described above, the time change rate of the simulated current can be made the same as the light emission current.

Therefore, according to the radar apparatus 1, it is possible to suitably generate a simulated voltage waveform that is the same as the clutter voltage waveform while reducing the amount of current flowing through the simulated circuit 11b.
In the radar apparatus 1, the first light receiving unit 10 a includes the amplification circuit 22 that amplifies the light reception signal and the first filter circuit 23 that removes the high frequency component of the light reception signal, and the second light reception unit 20 b. However, in the configuration having the second filter circuit 25 that removes a high frequency component equal to or higher than a preset frequency threshold value from the simulated signal, the frequency threshold value becomes a waveform with the same time change rate as the clutter voltage waveform in the simulated voltage waveform. Is set to a value.

  That is, when the light reception signal passes through the amplifier circuit 22 and the first filter circuit 23, the high frequency component is removed. Therefore, the voltage waveform (light reception voltage waveform) indicated by the light reception signal that has passed through these circuits has a time change rate. The waveform is low (blunt waveform). On the other hand, by setting the frequency threshold value in the second filter circuit 25 to a value that has the same time change rate waveform as the clutter voltage waveform as the light reception voltage waveform of the clutter component, the second filter circuit 25 The voltage waveform (simulated voltage waveform) indicated by the simulated signal that has passed 25 can be made dull as much as the received light voltage waveform (clutter voltage waveform).

  Therefore, according to the radar apparatus 1, the received light signal can be amplified to remove the high-frequency component. For example, the simulated voltage waveform that is the same as the clutter voltage waveform is generated while being hardly affected by external noise other than the clutter. Therefore, the influence of clutter can be suitably suppressed.

  In the radar apparatus 1, when the second light receiving unit 20 b inputs a light emission trigger signal used when causing the light emitting unit 10 to emit pulsed laser light, the second switching element 36 that energizes the simulation circuit 11 b; The delay circuit 24 delays the input of the light emission trigger signal to the second switching element 36 by a time corresponding to the internal reflection time.

  Therefore, when a light emission trigger signal is input from the control unit 30, a current flows through the light emitting circuit 11 a, a pulse laser beam is emitted by the light emitting unit 10, and a clutter is generated by the light receiving element 9 after the pulse laser beam is emitted. After a time corresponding to a known time (internal reflection time) until the light is received, a light emission trigger signal is input via the delay circuit 24, and a current flows through the simulation circuit 11b.

  Therefore, according to the radar apparatus 1, it is not necessary for the control unit 30 to output trigger signals for causing current to flow through the light emitting circuit 11 a and the simulation circuit 11 b individually at different timings, thereby reducing the processing burden on the control unit 30. In addition, the influence of clutter can be suitably reduced in analog processing.

<Other embodiments>
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the radar apparatus 1 of the above embodiment, the voltage waveform having the same magnitude as the clutter voltage waveform as the simulated voltage waveform is obtained by adjusting in advance the value of the current flowing through the simulation circuit 11b in the second light receiving unit 20b. However, the present invention is not limited to this, and a voltage waveform having the same magnitude as the clutter voltage waveform may be generated as a simulated voltage waveform by providing an amplification circuit that amplifies the simulated voltage waveform.

  The circuit configurations of the light emitting circuit 11a and the simulation circuit 11b shown in the above embodiment are merely examples, and the simulation circuit 11b can have various circuit configurations as long as the circuit simulates the light emission circuit 11a.

  Further, in the radar device 1 of the above embodiment, the second light receiving unit 20b includes the delay circuit 24, thereby adjusting the timing at which the simulated voltage waveform is output from the second light receiving unit 20b to the cancel circuit 20c. However, the present invention is not limited to this, and the control unit 30 may output trigger signals for causing current to flow through the light emitting circuit 11a and the simulation circuit 11b individually at different timings.

  In the radar apparatus 1 of the above embodiment, the cancel circuit 20c such as a differential amplifier circuit is used. However, the present invention is not limited to this, and the light reception signal output from the first light receiving unit 20a, By adopting a configuration in which the sign of either one of the simulation signal output from the second light receiving unit 20 is inverted in advance before output (for example, an inverting circuit for inverting the sign of the input signal is provided) The output sides of the first light receiving unit 20a and the second light receiving unit 20 may be connected so that the cancel circuit 20c is unnecessary.

  DESCRIPTION OF SYMBOLS 1 ... Radar device, 2 ... Light emitting element, 3 ... Collimating lens, 4 ... Aperture, 4a ... Aperture, 5 ... Polarizing beam splitter, 6 ... λ / 4 wavelength plate, 7 ... Optical scanning part, 7a ... Mirror, 8 ... Light receiving lens, 9 ... light receiving element, 10 ... light emitting unit, 10a ... first light receiving unit, 11a ... light emitting circuit, 11b ... simulated circuit, 12 ... power supply circuit, 13 ... resistor, 14 ... inductor, 15 ... capacitor, 16 ... 1st switching element, 20 ... light receiving part, 20a ... 1st light receiving part, 20b ... 2nd light receiving part, 20c ... cancellation circuit, 21 ... resistance, 22 ... amplification circuit, 23 ... 1st filter circuit, 24 DESCRIPTION OF SYMBOLS ... Delay circuit, 25 ... 2nd filter circuit, 26 ... Power supply circuit, 30 ... Control part, 32 ... Diode, 33 ... Resistor, 34 ... Inductor, 35 ... Capacitor, 36 ... 2nd switching element, VC ... DC power .

Claims (3)

A light emitting section (10) for emitting a transmission wave having a waveform corresponding to the waveform of the current flowing through the light emitting circuit (11a);
A light receiving unit (20) for receiving a reflected wave of the transmission wave coming from the light emitting direction of the transmission wave by the light emitting unit;
With
A radar device (1) for measuring a relative value indicating a relative relationship with a target reflecting the transmission wave based on an input signal from the light receiving unit,
The light receiving unit is
A first light receiving unit (20a) having a light receiving element (9) for receiving the reflected wave, and generating a received light signal indicating a voltage waveform corresponding to the waveform of the reflected wave received by the light receiving element;
Of the reflected waves received by the light receiving element, the transmission wave is reflected inside the radar device and received by the light receiving element as an internal reflected wave.
Based on a known time from when the transmission wave is emitted by the light emitting unit to when the internal reflection wave of the transmission wave is received by the light receiving element. A second light receiving unit (20b) that generates a simulation signal indicating a voltage waveform corresponding to a waveform of a current flowing through the simulation circuit at a timing;
Cancel using the simulated signal generated by the second light receiving unit to remove the voltage waveform corresponding to the waveform of the internal reflected wave from the voltage waveform indicated by the light received signal generated by the first light receiving unit A circuit (20c);
Equipped with,
The light emitting circuit includes a light emitting element (2) for emitting the transmission wave, and a first switching element (16) for energizing the light emitting circuit,
The simulation circuit includes a diode (32) simulating the light emitting element and a second switching element (36) for energizing the simulation circuit,
The current flowing through the diode of the simulation circuit is a simulation current, the current flowing through the light emitting element of the light emitting circuit is a light emission current,
The simulated current is smaller than the light emission current,
The radar apparatus according to claim 2, wherein the second switching element has a structure in which the simulation circuit is energized at a response speed at which the simulation current has the same rate of time change as the light emission current. A light emitting section (10) for emitting a transmission wave having a waveform corresponding to the waveform of the current flowing through the light emitting circuit (11a);
A light receiving unit (20) for receiving a reflected wave of the transmission wave coming from the light emitting direction of the transmission wave by the light emitting unit;
With
A radar device (1) for measuring a relative value indicating a relative relationship with a target reflecting the transmission wave based on an input signal from the light receiving unit,
The light receiving unit is
A first light receiving unit (20a) having a light receiving element (9) for receiving the reflected wave, and generating a received light signal indicating a voltage waveform corresponding to the waveform of the reflected wave received by the light receiving element;
Of the reflected waves received by the light receiving element, the transmission wave is reflected inside the radar device and received by the light receiving element as an internal reflected wave.
Based on a known time from when the transmission wave is emitted by the light emitting unit to when the internal reflection wave of the transmission wave is received by the light receiving element. A second light receiving unit (20b) that generates a simulation signal indicating a voltage waveform corresponding to a waveform of a current flowing through the simulation circuit at a timing;
Cancel using the simulated signal generated by the second light receiving unit to remove the voltage waveform corresponding to the waveform of the internal reflected wave from the voltage waveform indicated by the light received signal generated by the first light receiving unit A circuit (20c);
Equipped with,
The first light receiving unit includes an amplification circuit (22) for amplifying the light reception signal, and a first filter circuit (23) for removing a high frequency component of the light reception signal,
The second light receiving unit includes a second filter circuit (25) that removes a high frequency component equal to or higher than a preset frequency threshold value from the simulation signal,
A voltage waveform indicated by the component of the internally reflected wave in the received light signal that has passed through the amplifier circuit and the first filter circuit is a clutter voltage waveform, and a voltage waveform that is indicated by the simulated signal that has passed through the second filter circuit. Simulated voltage waveform
The radar apparatus according to claim 1, wherein the frequency threshold is set to a value at which the simulated voltage waveform becomes a waveform having the same time change rate as the clutter voltage waveform. The internal reflection time is a known time from when the transmission wave is emitted by the light emitting unit until the internal reflection wave of the transmission wave is received by the light receiving element,
The second light receiving unit is
When a light emission trigger signal used for causing the light emitting unit to emit the transmission wave is input, a second switching element (36) for energizing the simulation circuit;
A delay circuit (24) for delaying an input of the light emission trigger signal to the second switching element by a time corresponding to the internal reflection time;
The radar apparatus according to claim 1 or claim 2, characterized in that it has a.

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