JP2019109193A - Distance measuring device, mobile device and distance measuring - Google Patents

Abstract

To provide a distance measuring device capable of outputting a proper measurement result without reference to an electric signal output from an optical detection system while suppressing a rise in cost.SOLUTION: A distance measuring device comprises: a projection system which includes a light source emitting light based upon a light emission signal; an optical detection system which receives the light emitted from the projection system and reflected by a body, and outputs an electric signal corresponding to the light reception quantity thereof; and a computation system which includes a time measurement part and a measurement control part for finding the distance to the body based upon the light emission signal and the electric signal (light reception signal) output from the optical detection system. It is determined whether the light reception signal is normal based upon the gradient of a straight line passing a point that the voltage of the light reception signal crosses a threshold voltage Vth1 first and a point that the voltage of the light reception signal crosses a threshold voltage Vth2 first when the voltage of the light reception signal crosses the threshold voltages Vth1 and Vth2, and the time from when the voltage of the light reception signal crosses a smaller threshold voltage between Vth1 and Vth2 first until when the voltage crosses it next.SELECTED DRAWING: Figure 27

Description

  The present invention relates to a distance measuring device, a mobile device and a distance measuring method.

  Conventionally, a light projection system including a light source that emits light based on a light emission signal, and a light detection system that receives light reflected from the light projection system and reflected by an object and outputs an electrical signal according to the light reception amount An apparatus is known which has a signal processing system for processing an output signal of the light detection system, and measures a distance to an object based on a light emission signal and an output signal of the signal processing system (for example, Patent Document 1) reference).

  However, in the device disclosed in Patent Document 1, there is a room for improvement with respect to enabling output of an appropriate measurement result regardless of the electrical signal output from the light detection system while suppressing cost increase. was there.

  The present invention is a light projection system including a light source that emits light based on a light emission signal, and a light detection unit that receives light reflected from an object by the light projection system and reflected by an object and outputs an electrical signal according to the light reception amount. A system, and an operation system for obtaining a distance to the object based on the light emission signal and the electric signal output from the light detection system, and the voltage of the electric signal crosses the threshold voltages Vth1 and Vth2. A slope of a straight line passing the point at which the voltage first crosses the threshold voltage Vth1 and the point at which the voltage first crosses the threshold voltage Vth2, and the voltage first crosses the smaller one of the threshold voltages Vth1 and Vth2. It is a distance measuring device characterized by judging whether said electric signal is normal based on time to next crossing.

  According to the present invention, it is possible to output an appropriate measurement result regardless of the electrical signal output from the light detection system while suppressing the cost increase.

It is a figure showing a schematic structure of an object detection device concerning one embodiment. FIG. 2 (A) is a diagram for explaining a light projecting optical system and a synchronization system, FIG. 2 (B) is a diagram for explaining a light receiving optical system, and FIG. 2 (C) is an LD 11 It is a figure which shows roughly the optical path of the light from to a reflective mirror, and the optical path of the light from a reflective mirror to PD for time measurement. FIG. 5 is a timing chart showing a synchronization signal and an LD drive signal. FIG. 4A is a timing chart showing an emission light pulse and a reflection light pulse, and FIG. 4B is a timing chart showing an emission light pulse and a reflection light pulse after binarization. It is a figure for demonstrating Tr ranging and Tm ranging. It is a figure for demonstrating saturation / desaturation of the light received signal in the experiment using a blackout. It is a figure which shows Tr ranging value in experiment using the black curtain in the distance of 3 m and 6 m. It is a figure which shows the aspect of the experiment using two blackouts, and the ideal ranging result with respect to two blackouts. It is a figure for demonstrating the comet phenomenon when the light reception signal is saturated. It is a figure for demonstrating the time P0 and voltage (P0 crossing voltage) of the point which the extension line of the standup of a light reception signal cross | intersects when light is irradiated to each of a plurality of objects with different reflectances in the same distance. It is a figure for demonstrating how to obtain | require the inclination of the standup of a light reception signal, and the output of a binarization circuit. It is a figure for demonstrating the correction formula of the ranging error in 30 m-70 m. It is a figure for demonstrating Tr ranging in case a light reception signal crosses only threshold value Vth1. It is a figure for demonstrating Tm ranging when a light reception signal is not saturated. It is a figure which shows the relationship between the inclination of a standup of a normal light reception signal, and a pulse width. It is a figure which shows the example 1 of the waveform of 2 peak comets. It is a figure for demonstrating the correction method (the 1) of ranging data of 2 peak comets. It is a figure which shows the 1st range for detecting 2 peak comets. It is a figure which shows the 2nd range for detecting 2 peak comets. It is a figure which shows the 3rd range for detecting 2 peak comets. It is a figure which shows the 4th range for detecting 2 peak comets. It is a figure which shows the 5th range for detecting 2 peak comets. It is a figure which shows the relationship between the 1st range as a detection range, and the coordinate by which 2 peak comets were actually observed. It is a figure which shows the relationship of the range which consists of the 1st and 4th range as a detection range, and the coordinate by which 2 peak comet was actually observed. It is a figure which shows the relationship between the range which consists of the 1st-5th range as a detection range, and the coordinate by which 2 peak comet was actually observed. It is a figure for demonstrating a sensing apparatus. It is a figure for demonstrating ranging processing 1. FIG. It is a figure for demonstrating ranging processing 2. FIG. It is a figure for demonstrating ranging processing 3. FIG. It is a figure for demonstrating ranging processing 4. FIG. FIG. 10 is a flowchart for describing distance measurement data acquisition processing 1; FIG. FIG. 10 is a flowchart for describing distance measurement data acquisition processing 2; FIG. FIG. 10 is a flowchart for describing distance measurement data acquisition processing 3; FIG. FIG. 16 is a flowchart for describing distance measurement data acquisition processing 4; FIG. FIG. 10 is a flowchart for describing distance measurement data acquisition processing 5; FIG. FIG. 16 is a flowchart for describing distance measurement data acquisition processing 6; FIG. It is a flowchart for demonstrating ranging process 5 (first half). It is a flowchart for demonstrating ranging process 5 (second half). FIG. 10 is a flowchart for describing distance measurement processing 6; FIG. It is a flowchart for demonstrating ranging process 7 (first half). It is a flowchart for demonstrating the ranging process 7 (second half). It is a figure for demonstrating ranging processing 8. FIG. It is a figure which shows the calibration curve showing the correspondence of P0 ranging value and the real distance in the case of 2nd saturation. It is a figure which shows the example 2 of the waveform of 2 peak comet. It is a figure which shows the example 3 of the waveform of 2 peak comet. It is a figure which shows the example 1 of the waveform of 3 peak comet. It is a figure which shows the example 2 of the waveform of 3 peak comet. It is a figure which shows the example 3 of the waveform of 3 peak comet. It is a figure for demonstrating the correction method (the 2) of ranging data of 2 peak comets.

  Hereinafter, an object detection apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings.

  A schematic configuration of the object detection apparatus 100 is shown in a block diagram in FIG.

The object detection apparatus 100 is, for example, mounted on a vehicle as a moving body, emits light, and receives light reflected (scattered) by an object (for example, a preceding vehicle, a stopped vehicle, an obstacle, a pedestrian, etc.) It is a scanning laser radar that detects information (hereinafter also referred to as “object information”) related to an object such as the presence or absence of the object and the distance to the object. The object detection apparatus 100 receives power supply from, for example, a battery (storage battery) of a vehicle.
That is, the object detection device 100 functions as an object presence / absence determination device, a distance measurement device (distance measurement device), or an object recognition device.

  As shown in FIG. 1, the object detection apparatus 100 includes a light projection system 10, a light detection system 40, a signal processing system 41, a signal determination circuit 49 (determination system), a time measurement unit 45 (part of an arithmetic system), The measurement control unit 46 (part of the calculation system), the synchronization system 50, the object recognition unit 47, and the like are provided.

  The light projecting system 10 includes an LD 11 (laser diode) as a light source, an LD driving unit 12, and a light projecting optical system 20.

  The LD 11 is also called an edge emitting laser, and is driven by the LD driving unit 12 to emit a laser beam. The LD drive unit 12 lights (emits light) the LD 11 using the LD drive signal (rectangular pulse signal) output from the measurement control unit 46. The LD driver 12 includes, as an example, a capacitor connected so as to supply current to the LD 11, a transistor for switching between conduction / non-conduction between the capacitor and the LD 11, charging means capable of charging the capacitor, and the like. . The measurement control unit 46 receives a measurement control signal (a measurement start signal or a measurement stop signal) from an ECU (Electronic Control Unit) of the automobile and performs measurement start or measurement stop.

  In addition, although LD11 is used as said light source, it is not restricted to this. For example, another light emitting element such as a VCSEL (surface emitting laser), an organic EL element, an LED (light emitting diode), an LD or a laser other than the VCSEL may be used.

  In FIG. 2A, the projection optical system 20 and the synchronization system 50 are schematically shown. The light receiving optical system 30 is schematically shown in FIG. 2 (B). In the following, description will be made using an XYZ three-dimensional orthogonal coordinate system in which the Z-axis direction shown in FIG. 2A or the like is the vertical direction, as appropriate.

  As shown in FIG. 2A, the projection optical system 20 is disposed on the optical path of the light from the LD 11 and on the optical path of the light passing through the coupling lens 22. And a rotating mirror 26 as a deflector disposed on the optical path of the light reflected by the reflecting mirror 24. Here, in order to miniaturize the apparatus, a reflection mirror 24 is provided on the optical path between the coupling lens 22 and the rotating mirror 26 as a deflector to fold the optical path.

  Therefore, the light emitted from the LD 11 is shaped into light of a predetermined beam profile by the coupling lens 22, then reflected by the reflection mirror 24, and deflected around the Z axis by the rotation mirror 26.

  The light deflected to a predetermined deflection range around the Z axis by the rotating mirror 26 is the light projected from the light projection optical system 20, that is, the light emitted from the object detection apparatus 100.

  The rotating mirror 26 has a plurality of reflecting surfaces around the rotation axis (Z axis), and reflects (deflects) the light from the reflecting mirror 24 while rotating it around the rotation axis, thereby corresponding to the above deflection range by the light The effective scanning area is scanned one-dimensionally in the horizontal one-axis direction (here, the Y-axis direction). Here, the deflection range and the effective scanning area are on the + X side of the object detection apparatus 100. Hereinafter, the rotation direction of the rotation mirror 26 is also referred to as “mirror rotation direction”.

  As can be seen from FIG. 2A, the rotating mirror 26 has two reflective surfaces (two opposing surfaces), but the present invention is not limited to this, and one or three or more reflective surfaces may be used. It is also possible to provide at least two reflecting surfaces and incline them at different angles with respect to the rotation axis of the rotating mirror, and switch the scanning / detecting area in the Z-axis direction.

  As the deflector, in place of the rotating mirror, for example, another mirror such as a polygon mirror (rotating polygon mirror), a galvano mirror, a MEMS mirror, etc. may be used.

  As shown in FIG. 2 (B) and FIG. 1, the light detection system 40 is a light receiving optical system 30 into which light projected from the light projecting optical system 20 and reflected by an object within the effective scanning area is incident; A PD for time measurement 42 for receiving light through the light receiving optical system 30, and an IV converter 43 (current / voltage converter) for converting an output current (photocurrent) of the PD for time measurement 42 into a voltage signal (light reception signal) And. Note that "PD" is an abbreviation for a photodiode.

  The light receiving optical system 30, as shown in FIG. 2B, includes a rotating mirror 26 for reflecting light projected from the light emitting optical system 20 and reflected by an object within the effective scanning area, and the rotating mirror 26. And an imaging optical system disposed on the optical path of the light from the reflection mirror 24 and focusing the light on a time measurement PD 42 described later.

  Here, the light projecting optical system 20 and the light receiving optical system 30 are installed in the same housing. This housing has an opening on the optical path of light emitted from the light projecting optical system 20 and the optical path of incident light on the light receiving optical system 30, and the opening is closed by a window (light transmission window member) It is done. The window can be made of, for example, glass or resin.

  FIG. 2C shows an optical path from the LD 11 to the reflection mirror 24 and an optical path from the reflection mirror 24 to the time measurement PD 42.

  As can be seen from FIG. 2C, the light projecting optical system 20 and the light receiving optical system 30 are disposed so as to overlap in the Z-axis direction, and the rotating mirror 26 and the reflecting mirror 24 receive the light projecting optical system 20 and the light receiving The optical system 30 is common. As a result, the relative positional deviation between the irradiation range of the LD 11 and the light receivable range of the time measurement PD 42 on the object can be reduced, and stable object detection can be realized.

  Therefore, light projected from the light projecting optical system 20 and reflected by the object is guided to the imaging optical system through the rotating mirror 26 and the reflecting mirror 24, and is condensed on the time measurement PD 42 by the imaging optical system ( See FIG. 2 (B)). In FIG. 2B, in order to miniaturize the apparatus, a reflection mirror 24 is provided between the rotating mirror 26 and the imaging optical system to fold the optical path. Here, the imaging optical system is composed of two lenses (imaging lenses), but it may be a single lens, three or more lenses, or a mirror optical system. good.

The signal processing system 41 binarizes the voltage signal amplified by the operational amplifier 48 on the basis of a threshold (threshold voltage) based on an operational amplifier 48 as a signal amplifier for amplifying the voltage signal (light reception signal) from the IV converter 43 And a binarization circuit 44 including a comparator that outputs a high level signal as a detection signal to the time measurement unit 45 while the voltage signal exceeds the threshold.
The operational amplifier 48 is not essential in the signal processing system 41.

  As shown in FIGS. 2A and 1, the synchronization system 50 is light emitted from the LD 11 and reflected by the reflection mirror 24 via the coupling lens 22, and is deflected by the rotation mirror 26 and reflected by the reflection mirror 24. The synchronous lens 52 is disposed on the optical path of the light reflected again, the synchronous detection PD 54 disposed on the optical path of the light through the synchronous lens 52, and the output current of the PD 54 for synchronous detection (photocurrent ), An operational amplifier 55 as a signal amplifier for amplifying the voltage signal from the IV converter 53, and the voltage signal from the operational amplifier 55 as a threshold. And a binarization circuit 56 including a comparator that outputs a high level signal as a synchronization signal to the measurement control unit 46 while the voltage signal exceeds the threshold.

  More specifically, the reflection mirror 24 is disposed on the upstream side in the rotation direction of the rotating mirror 26 with respect to the deflection range, and the light deflected to the upstream side of the deflection range by the rotation mirror 26 is incident. Then, the light deflected by the rotation mirror 26 and reflected by the reflection mirror 24 is incident on the synchronization detection PD 54 through the synchronization lens 52.

  The reflection mirror 24 may be disposed on the downstream side in the rotation direction of the rotary mirror 26 with respect to the deflection range. Then, the synchronization system 50 may be disposed on the optical path of the light deflected by the rotating mirror 26 and reflected by the reflecting mirror 24.

  Each time the light reflected by the reflecting surface of the rotating mirror 26 is received by the synchronization detection PD 54, a photocurrent is output from the synchronization detection PD 54. As a result, the binarization circuit 56 periodically outputs a synchronization signal (see FIG. 3).

  By performing synchronous lighting for irradiating the light from the rotation mirror 26 to the synchronization detection PD 54 in this manner, it is possible to obtain the rotation timing of the rotation mirror 26 from the light reception timing of the synchronization detection PD 54.

  Therefore, the effective scanning area can be optically scanned by pulsing the LD 11 after a predetermined time has elapsed since the LD 11 is synchronously turned on. That is, the effective scanning area can be optically scanned by pulse-lighting the LD 11 in a period before and after the timing when the synchronization detection PD 54 is irradiated with light.

  The synchronization system may not have a synchronization lens, or may have another optical element (for example, a light collecting mirror).

  Here, as a light receiving element used for time measurement and synchronization detection, in addition to PD (Photo Diode) described above, APD (Avalanche Photo Diode), Geiger mode APD SPAD (Single Photo Avalanche Diode), etc. can be used. It is. Since APD and SPAD have high sensitivity to PD, they are advantageous in terms of detection accuracy and detection distance.

  The measurement control unit 46 generates an LD drive signal based on the synchronization signal from the binarization circuit 56, and outputs the LD drive signal to the LD drive unit 12 and the time measurement unit 45.

That is, the LD drive signal is a light emission signal (pulse signal for causing the LD to emit light) delayed with respect to the synchronization signal (see FIG. 3).
When the LD drive signal is input to the LD drive unit 12, a drive current is applied from the LD drive unit 12 to the LD 11, and pulse light is output from the LD 11. Since the duty of light emission of the LD 11 is limited from the viewpoint of the safety of the LD 11 and the durability of the LD 11, the pulse light output from the LD 11 preferably has a narrow pulse width, and the pulse width is generally 10 ns to a number It is set to about 10 ns. Also, the pulse interval is generally on the order of tens of microseconds.

  The signal determination circuit 49 determines whether the light reception signal is normal or not based on the output signal of the binarization circuit 44, and outputs the determination result to the time measurement unit 45. Details of the determination method performed by the signal determination circuit 49 will be described later.

  The time measurement unit 45 does not depend on the determination result of the signal determination circuit 49 or when the determination result is positive, the rise timing of the LD drive signal (light emission timing of the LD 11) and the output signal of the binarization circuit 44 Based on the (high level signal), the time for light to reciprocate between the object detection apparatus 100 and the object (object to be measured) is measured, and the time is output to the measurement control unit 46 as a time measurement result.

When the time measurement result from the time measurement unit 45 is input, the measurement control unit 46 multiplies the time measurement result by the speed of light to convert it into a distance, and converts 1/2 of the converted value to the object detection device 100 and the object And output to the object recognition unit 47 as distance data representing the distance between
The measurement control unit 46 has a storage unit. Here, the storage unit is realized by, for example, a memory, but may be realized by a hard disk.

  The object recognition unit 47 recognizes where an object is present based on a plurality of distance data acquired by one scan or a plurality of scans from the measurement control unit 46, and outputs the result of the object recognition to the measurement control unit 46. . The measurement control unit 46 transfers the object recognition result to the ECU.

  The time measurement unit 45, the measurement control unit 46, and the object recognition unit 47 can be realized by, for example, a central processing unit (CPU) or an integrated circuit (IC).

  The ECU performs, for example, a steering control (for example, auto steering) of an automobile, a speed control (for example, an auto brake, an auto accelerator, etc.) and so on to the driver.

  Here, when the effective scanning region is scanned by the rotating mirror 26, the LD driving unit 12 drives (emits light) the LD 11 to emit pulsed light as shown in FIG. Light pulse)). Then, the pulse light (hereinafter also referred to as "reflected light pulse") emitted from the LD 11 and reflected (scattered) by the object is used for time measurement PD 42 (in FIG. 4A) using APD instead of PD as a light receiving element. Received).

  The distance to the object can be calculated by measuring the time t from when the LD 11 emits the emitted light pulse to when the reflected light pulse is received by the APD. With regard to time measurement, for example, as shown in FIG. 4B, an emitted light pulse is received by a light receiving element such as PD, photoelectrically converted, current-voltage converted (and further signal amplified as necessary). The resulting voltage signal is binarized into a rectangular pulse, and the reflected light pulse is received by the APD, photoelectrically converted, and current / voltage converted (and further signal amplified as necessary). The signal (light reception signal) may be binarized to form a rectangular pulse, and the time t between the rising timings of both rectangular pulses may be measured by the time measuring unit, or the waveforms of the emitted light pulse and the reflected light pulse are A / D converted. Then, it is also possible to measure time t by converting it into digital data and correlating the digital data of both waveforms.

An A / D converter is a circuit that performs A / D conversion (analog / digital conversion) of a light reception signal (analog signal). The peak position (peak time) of the light reception signal can be determined by using this A / D converter in a differentiation circuit that differentiates the light reception signal (analog signal), and accurate distance measurement by using the peak position Can.
However, if the magnitude of the peak of the light reception signal exceeds the range that the differential circuit can output, the signal output from the differential circuit is saturated, so the peak position can not be determined and accurate distance measurement can not be performed. .

The intensity of reflected light from an object with high reflectance at a short distance (hereinafter also referred to as “short distance highly reflective object”) is strong (the signal level is high) and an object with low reflectance at a long distance (hereinafter The intensity of light reflected from a long distance low reflection object is weak (the signal level is low). In order to avoid saturation of the signal output from the circuit in the signal processing system (for example, the op amp 48 as the signal amplifier is applicable), the near-field high-reflecting object with high signal level is possible It is common to adjust to the signal level of the reflected light from. In this case, the distance measuring device is a device in which the distance measuring range is matched to the short distance highly reflecting object.
However, such a distance measuring device is not suitable for distance measurement at least for a long distance low reflection object.
Furthermore, the A / D converter is very expensive, which increases the cost of the device.

  Therefore, the present inventors are capable of highly accurate ranging from a short distance highly reflecting object to a long distance low reflecting object, and an inexpensive distance measuring device (distance measuring device without using an expensive element such as an A / D converter) We have developed equipment to realize the Then, in the device development, it has been necessary to solve a phenomenon that causes an error in distance measurement due to a difference in reflectance of an object, which will be described in detail below, and inaccurate distance measurement results including the occurrence of ghosts.

Here, before describing the solution, the distance measurement method implemented by the object detection apparatus 100, the saturation / desaturation of the voltage of the signal in the circuit elements constituting the light detection system 40 and the signal processing system 41, etc. I will explain.
In the object detection apparatus 100, the light reception timing of the reflected light pulse emitted from the LD 11 and reflected by the object and returned is set based on the timing when the light reception signal based on the reflected light pulse crosses the predetermined threshold value Vth. From the time from the timing to the light reception timing, the distance to the object is obtained.

Therefore, first, Tr ranging and Tm ranging in which settings of light reception timing are different will be described with reference to FIG.
In Tr ranging, the time Tr from the light emission timing to the timing when the rising edge of the light reception signal exceeds (crosses) the threshold value Vth (light reception timing) is converted into a distance.
In Tm ranging, a time Tm from the light emission timing to the timing (light reception timing) between the timing when the rising edge of the light receiving signal exceeds (crosses) the threshold Vth and the falling timing of the light receiving signal falls below (crossing) the threshold Vth. Convert to distance.

Next, saturation / non-saturation of voltage of signals in circuit elements constituting the light detection system 40 and the signal processing system 41 will be described.
First, in the distance measurement data obtained in the experiment shown in FIG. 6, the oscilloscope signal observed through the coaxial cable has a black screen as a target (object to be measured) installed at a short distance (for example, 10 to 40 m) Sometimes the voltage saturates near 1.2 V, resulting in a saturated waveform where no peak can be confirmed. This is a phenomenon that occurs because an operational amplifier as a circuit element can not output a higher voltage.
On the other hand, when a black screen as a target is installed at a long distance (for example, 40 to 70 m), the light quantity of the reflected light from the black screen decreases, so that it has a non-saturated waveform where the peak of the signal can be confirmed.
The black screen used in this experiment has a size of 0.7 m × 1.5 m and a reflectance of about 10% for a wavelength of 870 nm (namely, product name: Cosmo black, manufacturer: Nakahiro Corporation). As the saturation of the voltage of the signal becomes stronger, the pulse width of the signal becomes wider, so if the A / D converter is not mounted to provide an inexpensive device, it is basically necessary to perform Tr distance measurement. The reason will be described later.
In the above experiment, distance measurement is performed using a black screen as a target as an example, but distance measurement may be performed using a target (for example, a white screen) of another color having higher reflectance.

  As shown in FIG. 6, as a cause of saturation of the light reception signal, an object located at a long distance from the IV converter 43 which is a circuit element of the light detection system 40 or an operational amplifier 48 which is a circuit element of the signal processing system 41 has a low reflectance. By setting the range in which even an object can be measured, it is possible that the voltage is saturated in the circuit element due to the reception of strong reflected light from an object at a short distance or an object having a high reflectance.

  When the device is not equipped with an A / D converter and the distance to the object is measured using circuit elements set so that voltage saturation occurs, a large number of ghosts appear behind the edge of the object. It can occur, and it looks like a comet's tail. Therefore, such a phenomenon is referred to as “comet phenomenon” in the present specification for the sake of convenience. When the comet phenomenon occurs, it is very distracting on the distance image (image in which the distance information for each pixel is integrated), and the distinction between the entity and the ghost can not be made, so that misidentification occurs when performing object recognition from a moving object There is a fear.

The comet phenomenon is roughly classified into the following two types.
(1) Comet phenomenon when the voltage of the light reception signal is saturated in the light detection system 40 or the signal processing system 41 (hereinafter, also referred to as "saturation comet")
(2) Comet phenomenon when the voltage of the light reception signal is non-saturated in the light detection system 40 and the signal processing system 41 (hereinafter also referred to as "non-saturated comet")

Below, the cause of each comet phenomenon is clarified, and the solution is presented.
These comet phenomena are problems caused by the same principle even for ranging errors that occur when ranging with respect to a plurality of objects having different reflectances at the same distance, so the solution is also the same.

First, the saturated comet will be described using experimental data shown in FIGS. 7 and 8 and the like. The experimental data in FIG. 7 shows that the black screen as a target (object to be measured) is horizontally shifted one by one at a distance of 3 m and 6 m (see the upper diagram in FIG. 8), and both black screens are scanned in the horizontal direction. It is the result of ranging. The horizontal axis in FIG. 7 is an angle of horizontal angle of view by 0.1 °, and the vertical axis is a distance measurement value obtained by Tr distance measurement.
As can be seen from FIG. 7, the distance measurement value does not immediately transition from 3 m to 6 m between the black curtains at a distance of 3 m and 6 m (near the angle 0 °), and the distance measurement value between 3 m and 6 m gradually appears And a comet phenomenon (saturated comet) which is a ghost occurs. Although the reflectance of the black screen is as low as 10%, the signal is saturated as shown in FIG. 6 in the measurement at a too short distance as in this experiment.

The comet phenomenon that occurs between two targets adjacent in the scanning direction in this way makes the signal with the reflected light from the two targets a signal with two peaks combined (see FIG. 16). Therefore, in the following, the comet phenomenon which causes the generation of such a signal having two peaks is also referred to as "two-peak comet". This two-peak comet is notably observed when the voltage of the light reception signal is saturated.
The points that should be noted in the light reception waveform (hereinafter also referred to as “comet waveform” or “two peak comet waveform”), which is the waveform of the light reception signal in which the two peak comets are observed, are the point at which Vth1 is first crossed and Vth2 The slope of the straight line passing through the point that first crosses is smaller than that of a normal light reception waveform (light reception waveform having one peak) having the same pulse width (see FIGS. 9 and 16).
Hereinafter, the slope of the straight line passing through the point at which the light reception signal first crosses Vth1 and the point at which the light reception signal first crosses Vth2 is also referred to as "straight line slope" or "slope".
Also, the time from when the voltage of the light reception signal first crosses the threshold voltage Vth1 to the next may be referred to as "pulse width". The timing at which the voltage of the light reception signal crosses the threshold voltage can be expressed by the time from the light emission timing of the light source, and can also be expressed by the distance (m) obtained by multiplying the time by the speed of light. Even when referred to as a pulse width, the unit of the pulse width is expressed by time or distance (m). In the present specification, description will be made using time and distance (m) as appropriate.

  On the other hand, assuming ideal distance measurement in which no saturated comet occurs, the distance measurement value immediately transitions from 3 m to 6 m between blackouts at a distance of 3 m and 6 m (near an angle of 0 °) (see lower figure in FIG. 8) ).

Next, a phenomenon that makes the problem of the saturation comet more complicated will be described using the waveform observed by the oscilloscope shown in FIG.
In FIG. 9, a black screen at a distance of 6 m from the black screen at a distance of 3 m on the left (field angle at the center of the scanning range of 0 ° and a field angle of −0.4 °) is shown in FIG. Saturation for each angle of view (here: -0.4 °, 0 °, + 0.4 °) when distance measurement is performed by moving to + 0.4 ° angle of view as 0 ° (see the upper figure in Fig. 8) The portion including the rising portion of the received light waveform is shown.
At this time, the slope of the rising portion of the saturated light reception waveform gradually decreases from the size when the black screen at a distance of 3 m is measured and then becomes minimum and then gradually increases to measure the black screen at a distance of 6 m. It will be the size of the distance.

That is, it is possible to confirm a rising portion which is a ghost in the middle of the rising portions of the saturated light reception waveform when the black screen at a distance of 3 m and 6 m is measured respectively.
The rising edge of the light reception waveform is not a straight line but a curved line because the rising edge of the light emission waveform (emission pulse) is blunted under the influence of the differential resistance of the LD 11 and the parasitic capacitance of the LD 11 and the LD driver 12. It is possible to approximate with a substantially straight line. Therefore, in the present specification, when the light receiving waveform is a normal waveform (waveform having one peak), the slope of the straight line of two points on the rising portion of the light receiving waveform (the rising of the light receiving signal) Also referred to as the "slope of the rising portion of" or "the slope of the rising of the light reception signal". Further, also in some figures, rising and falling of the light reception waveform are represented by straight lines.

  At this time, in the case of calculating the distance by Tr distance measurement with the threshold value Vth, the light reception waveform saturated when the black screen at a distance of 3 m is distance also the light reception waveform saturated when the black screen at a distance of 6 m Also, the distance measurement value gradually changes, and it can be seen that a ghost (comet) is clearly generated also in the middle part of the light reception waveforms.

Such comet phenomenon (2-peak comet) is, as shown in FIG. 9, as the spot position of the illumination beam moves from the black screen at a distance of 3 m to the black screen at a distance of 6 m, The slope of the rising portion of the light reception waveform saturated by the reflection from the black screen at a distance of 3 m gradually weakens at the end of the black screen gradually decreases and then becomes minimum, and then from the black screen at a distance of 6 m As a result of the reflected wave of the light intensity gradually becoming stronger at the end of the black screen, the rise of the light reception waveform saturated is gradually increased.
As described above, the reflected wave from the black screen gradually weakens or strengthens at the end of the black screen when the spot position of the irradiation beam moves near the end of the black screen. The size of the spot of the illumination beam changes.

  In addition, such a comet phenomenon (two-peak comet) is also a cause of a difference in distance measurement value (distance measurement error) between a plurality of targets having different reflectances at the same distance. The causes of the distance measurement error and the comet phenomenon are also the same, so the difference in the inclination of the rising portion of the light reception waveform and the method of correcting the distance measurement value will be uniformly discussed below.

As shown in FIG. 10, when performing the distance measurement using only one threshold value Vth, the value of Tr differs among a plurality of targets having the same distance but different reflectances, and an error occurs in the distance measurement value.
Therefore, when distance measurement is performed on a plurality of targets having different reflectances at the same distance, the slopes of the rising portions of the light reception waveform are different between the targets, and the targets with high reflectance have large slopes and low reflection. We focused on the fact that the rate target has a small slope.

Furthermore, as shown in FIG. 10, when extending the rising portions of the light reception waveforms of a plurality of targets having the same distance as shown in FIG. 10 to the negative voltage side, the extension line is based on the rising timing of the light emission signal It was found that it crosses a negative predetermined voltage at a certain time P0, which is time 0). Therefore, in the following, this predetermined voltage is also referred to as "P0 crossing voltage". Also, in the following, the time from the rise timing of the light emission signal to time P0 is also referred to as "P0".
That is, even if the reflectivities of a plurality of targets at the same distance are different, the same point can be obtained between the targets by obtaining the time of the origin of the rising portion of the light reception waveform of a plurality of targets, that is, P0 shown in FIG. It is possible to obtain a distance measurement value of
Specifically, a calibration curve representing the relationship between the distance obtained from an arbitrary time P0 (1/2 of the value obtained by converting the arbitrary time P0 into a distance) and the distance to an actual target (actual distance) is obtained in advance If P0 is determined at the time of measurement, accurate distance measurement without errors among a plurality of targets having different reflectances at the same distance becomes possible.

Next, distance measurement using P0 as described above (hereinafter also referred to as “P0 distance measurement”) will be described in detail.
The upper diagram of FIG. 11 shows elements for determining the slope of the rising portion of the light reception waveform.
Here, using the two thresholds Vth1 and Vth2 and the timings P1 and P2 at which the rising portion crosses the thresholds Vth1 and Vth2, respectively, in order to obtain the slope of the rising portion of the light reception waveform, The slope of the rising portion can be determined.
Slope of rising portion = (Vth2-Vth1) / (P2-P1) (1)
Note that Vth1 is set to a value (for example, about 0.3 V) which slightly exceeds the peak of shot noise generated at the time of light reception in the light detection system 40. Vth2 is set to a value (for example, about 0.9 V) slightly smaller than the saturation voltage (for example, 1.2 V) in the operational amplifier 48.

Here, as shown in the upper drawing of FIG. 11, the rising portion of a certain light reception waveform is extended to the negative voltage side, and a light emission signal (for example, LD drive signal) at a point intersecting with a certain set P0 crossing voltage. The time P0 based on the rising timing can be obtained by the following equation (2).
P0 = P2 + (P0 crossing voltage−Vth2) / slope (2)

In order to obtain this P0, targets with various reflectances are set at various distances (actual distances), and distance measurement is performed by setting the P0 crossover voltage to a certain value.
Then, in order to secure the reliability of P0, an error between an actual distance and a distance measurement value obtained from P0 (hereinafter also referred to as "P0 distance measurement value") among a plurality of targets having the same distance but different reflectances. Finely adjust the P0 crossing voltage so that the standard deviation of V.sub.x is minimized, and determine the P0 crossing voltage.

After the P0 crossover voltage is determined, the reflectance and P0 are obtained again for each distance, and a calibration curve (see FIG. 43) representing the correspondence between the distance measurement value obtained from any P0 and the actual distance is obtained. It is possible to realize a distance measurement device in which the distance measurement value is not affected by the reflectance of
Furthermore, the comet phenomenon (saturation comet) caused by the intensity of the reflected wave becoming gradually weaker or stronger at the target end can be solved simultaneously by P0 ranging.
Thus, P0 ranging does not change ranging values between targets even if the reflectances of a plurality of targets at the same distance are different, and it is accurate for each distance to the target regardless of the reflectivity of the targets Although a distance measurement value can be obtained, it is somewhat complicated.

Therefore, as a simpler distance measurement method in which the distance measurement result is not affected by the reflectance of the target, the distance measurement value obtained by Tr distance measurement using the slope of the rising portion of the light reception waveform (hereinafter referred to as “Tr distance measurement A distance measuring method for correcting a value (also referred to as “value”) is also conceivable.
Although this ranging method slightly lowers the ranging accuracy compared with the ranging method using P0, it has sufficient practicability, and similarly the solution of the comet phenomenon and the elimination of the ranging error due to the difference in reflectance Is possible.

The distance measurement method for correcting the Tr distance measurement value using the inclination of the rising portion of the light reception waveform will be specifically described below.
In FIG. 12, the rising slope of the light reception signal for each distance measurement, the reflectance, the Tr for each distance, and the distance for each distance measured when targets of various reflectances are placed at various distances within a range of 30 to 70 m. The relationship between the distance measurement value and the difference between the actual distance (actual distance) (distance measurement error) is shown.

  As shown in FIG. 12, even if targets of various reflectances are installed at various distances and ranging, it is found that the point determined by the rising inclination of the received light signal and the ranging error is on the almost same curve ing.

  This means that the Tr distance measurement value can be corrected by one correction equation regardless of the distance at which the target having any reflectance is. The approximate expression of the curve in FIG. 12 is a logarithmic correction expression as shown in FIG. In this correction formula, when the value of the rising slope of the light reception signal is input to x, the value (y) of the distance measurement error of the light reception signal is output, and the value (y) is corrected by subtracting it from the Tr distance measurement value. Accurate distance can be obtained.

  According to the two distance measuring methods described above, accurate distance measurement can be performed even if voltage saturation of a signal occurs in the light detection system 40 and the signal processing system 41 by an inexpensive device configuration that does not use an A / D converter.

In the above, the case where the light reception signal is saturated has been described as an example. However, even when the light reception signal is not saturated, the slope of the rising portion of the light reception waveform has similar characteristics.
That is, regardless of the saturation / non-saturation of the light reception signal, when the light reception signal crosses the two threshold values Vth1 and Vth2, the slope of the rising edge of the light reception signal can be determined, and the reflectance of the target is used using the slope. It is possible to perform accurate ranging (P0 ranging or a ranging method in which the Tr ranging value is corrected by the inclination) in which the ranging result is not affected.

Next, the above unsaturated comet will be described.
In the non-saturated comet, there are two cases: when the peak of the light reception signal exceeds the upper threshold Vth2 (non-saturated comet A) and when the peak of the light reception signal exceeds only the lower threshold Vth1 (non-saturated comet B) is there.

  In the non-saturated comet A, since the inclination of the rising edge of the light reception signal can be obtained, accurate distance measurement can be performed by P0 distance measurement and Tr distance measurement as in the case of the saturated comet.

In the non-saturated comet B, the slope of the rising edge of the light reception signal can not be determined (see FIG. 13). Therefore, when performing Tr distance measurement using only Vth1, the reflectance differs among a plurality of targets at the same distance with different reflectances A distance measurement value can be obtained (see FIG. 13).
The unsaturated comet B is also similar to the saturated comet, and for example, the reflected wave gradually weakens or intensifies at the end of the target, whereby the Tr distance measurement value is gradually increased between Tr1 and Tr2 in FIG. Occurs due to getting smaller or bigger.
In addition, the non-saturated comets A and B also cause a difference in distance measurement values (distance measurement error) between a plurality of targets having different reflectances at the same distance.
As described above, when the light reception signal crosses only the threshold value Vth1, it is not possible to obtain an accurate distance measurement value even if performing the distance measurement of Tr.

  Therefore, using the fact that the distance measurement value (also referred to as “Tm distance measurement value” below) obtained by Tm distance measurement is the same even if the magnitude of the peak of the light reception signal changes (see FIG. 14), non-saturation In Comet B, a calibration curve representing the correspondence between the actual distance of the target and the Tm distance measurement value is created, and accurate distance measurement is possible by using a correction equation obtained from the calibration curve.

  In the Tm distance measurement, when the light reception signal is not saturated and the peak of the light reception signal can be confirmed, an accurate distance measurement value can be obtained. Therefore, the Tm distance measurement may be performed even with the unsaturated comet A. That is, in the non-saturated comet A, accurate distance measurement values can be obtained regardless of whichever of P0 distance measurement, Tr distance measurement, and Tm distance measurement is performed.

  In the non-saturated comets A and B, the Tm range value itself is used without using the above calibration curve, that is, 1/2 of the value obtained by converting the time Tm into the distance is output as the distance to the target. good.

As can be understood from the above description, in order to obtain an accurate distance measurement value, whether saturation / desaturation of the light reception signal or the peak of the light reception signal exceeds the threshold value Vth2 (determinable by the output of the binarization circuit) It is preferable to select either P0 ranging or Tr ranging, or Tm ranging as the ranging method.
More specifically, if the light reception signal is saturated, it is preferable to select P0 distance measurement or Tr distance measurement, and if the light reception signal is not saturated and the peak of the light reception signal exceeds Vth2, P0 distance measurement, Tr distance measurement, Either of the Tm ranging may be selected, and it is preferable to select the Tm ranging when the peak of the light reception signal exceeds Vth1 and does not exceed Vth2.

Here, since the light reception signal is considered to be saturated when the slope of the rising edge exceeds a predetermined value, it is possible to determine saturation / desaturation of the light reception signal by comparing the predetermined value with the calculated value of the inclination. .
Hereinafter, an experiment for obtaining the predetermined value will be described.
In this experiment, the laser beam emitted from the LD is irradiated to a retroreflecting plate as a target through a variable ND filter, and the light reception waveform of the reflected light is measured by an oscilloscope.
Here, as the variable ND filter, one having 36 steps of light transmittance is used. Thereby, the reflected light from the retroreflector can be observed at 36 levels of intensity. This is equivalent to observing the case where the reflectance of the target changes in 36 steps. For example, it is possible to observe the light reception waveform of the reflected light from the targets having different reflectances at each distance (here, 30 m, 40 m, 50 m, 60 m, 70 m) in the distance range of 30 to 70 m, for example, with an oscilloscope.

FIG. 15 shows the relationship between the slope of the rising portion of the normal light reception waveform observed by the oscilloscope and the pulse width for each distance. From the waveform shape in FIG. 15, it can be seen that the light reception signal makes a rapid transition between the non-saturation state and the saturation state in the operational amplifier at a predetermined value near the pulse width 6 m (inclination 1.0E + 08 [V / s]).
Therefore, it is possible to determine saturation / desaturation using this predetermined value as a threshold. In FIG. 15 etc., a value obtained by converting the time from the first time the light reception signal first crosses to the threshold to the next time is converted into a distance is described as a pulse width, but as described above, the time itself is described as a pulse width. You may.

Furthermore, from the waveform shape of FIG. 15, there is another predetermined value (slope) in which the pulse width is rapidly increased from the vicinity of a pulse width of 8 m (slope of 2.5 E + 08 [V / s]). This is because the voltage after converting the output current is saturated in the IV converter that converts the output current of the PD to the current voltage. This saturation is saturation at a slope that greatly exceeds the slope at which the op amp saturates, and is also referred to as "supersaturation."
Therefore, it is possible to determine oversaturation / saturation with this other predetermined value as a threshold.

  Thus, multiple stages of saturation may occur due to the circuit elements that make up the device. Therefore, an inclination threshold value for determining saturation / non-saturation (or supersaturation / saturation) of each step in the device is determined, and the threshold value is compared with the calculated inclination value to obtain an appropriate measurement according to the calculated value. Accurate distance measurement can be performed by selecting the distance method and the correction formula.

  In addition, a plurality of inclination regions (for example, 1.0E + 08 to 2.5E + 08 [V / s]) divided by a plurality of inclination threshold values (for example, 1.0E + 08 [V / s], 2.5E + 08 [V / s]) For the correction formula applied to the area and the area of 2.5E + 08 to 4.5E + 08 [V / s], distance measurement with higher accuracy can be performed by setting the P0 crossover voltage for each inclination area Can. Even if the slopes of the rising edges of the plurality of light reception signals when projecting light onto a plurality of objects having different reflectances at the same distance are different, P0 needs to be at the same position for the rising edges of the plurality of light reception signals Although it exists, P0 crossing voltage exists in a different value by the difference in the saturation state.

  Furthermore, as can be seen from FIG. 15, the relationship between the pulse width of the normal received light signal and the slope of the rising edge agrees at each distance within the distance range of 30 to 70 m. That is, here, the distance measurement method and the correction formula are selected using the threshold of the rising slope of the light reception signal, but similar control is possible by using the threshold of the pulse width instead of the slope. .

By the way, even when two peaks comets are observed in the light reception waveform, that is, even when the light reception signal is a signal having two peaks, as described above, the light reception signal using the A / D converter in the differentiation circuit that differentiates the light reception signal. The distance to each target can be calculated by obtaining each peak position of
However, as described above, there is a concern that the A / D converter is expensive and that the peak position can not be determined depending on the magnitude of the peak of the light reception signal.

  Therefore, the inventors have determined the distance to each target for each pixel (for each scanning position, for each scanning angle) even when a two-peak comet is observed in the light reception waveform by an inexpensive device configuration not equipped with an A / D converter. The following considerations were made in order to realize high-precision output.

Even if P0 distance measurement, Tr distance measurement or Tm distance measurement is performed based on the comet waveform generated near 0 ° shown in FIG. 9, an accurate distance measurement value can not be obtained for each pixel.
For example, for the comet waveform shown in FIG. 16 (two-peak comet waveform), a straight line passing a point that first crosses the threshold Vth1 and a point that first crosses the threshold Vth2 has only the first peak that constitutes the comet waveform. This is because it does not have any rising portion of a small first waveform having a small waveform and a large second waveform having only a second peak, and neither the first nor second peaks are located at the center of the comet waveform. .

  Therefore, the inventors have determined that the light reception signal for each pixel is either a normal light reception signal having one peak or an abnormal light reception signal having two peaks (a light reception signal in which a two peak comet is generated). By determining the distance measurement data of the pixel whose light reception signal is determined to be abnormal with the distance measurement data of the pixel whose light reception signal is determined to be normal, it is possible to determine the substantially accurate distance to each target We proposed that we can output every time. The details will be described below.

First, the inventors focused on the relationship between the slope of the straight line and the pulse width in order to accurately determine the light reception signal (see FIG. 15).
Here, although only one threshold value is sufficient to obtain the pulse width of the light reception signal, two threshold values are required to obtain the slope of the straight line.
That is, in order to acquire the relationship of FIG. 15, two threshold values are required.
In addition, it is impossible to measure distance accurately using only one threshold. The reason is that it is not possible to determine whether the shape of the light reception signal is normal only by the pulse width of the light reception signal.

  The relationship between the slope of the rising edge of the normal received light signal (the slope of the straight line) and the pulse width does not change, regardless of the reflectance or distance of the target, as can be seen first in FIG. (Also referred to as “pulse width curve”). That is, it is understood that, for an object having any reflectance at any distance, there is a correlation between the rising slope of the normal received light signal and the pulse width as shown in the slope-pulse width curve of FIG.

Further, when observing FIG. 15, it can be seen that the light reception signal having a pulse width of 5 m or less becomes smaller in peak so that the inclination can not be calculated. That is, it can be seen that the peak of the light reception signal having a pulse width of 5 m or less is Vth2 or less.
In other words, if a pulse width of, for example, 10 m is observed in the light reception signal whose peak is equal to or less than Vth2, it can be determined that the signal is abnormal.

  Similarly, for a light receiving signal whose peak exceeds Vth2, for example, if the slope of the straight line is 2.0E + 08 and the pulse width is 15 m, the plot (point) determined by the slope and the pulse width is slope-pulse width curve In such a case, it can be determined that the signal is abnormal. It has become apparent from the analysis of the subsequent signals that the signal that can be determined to be such an abnormality is basically a two-peak comet.

  As described above, accurate distance measurement is impossible even if P0 distance measurement, Tr distance measurement, or Tm distance measurement is performed using two thresholds with respect to the 2 peak comet. In order to measure the distance accurately with respect to the two-peak comet, more threshold values are required, but in that case it is necessary to add a comparator, resulting in an increase in cost.

  Therefore, the inventors can determine that a signal whose plot determined by the slope of the straight line and the pulse width is clearly deviated from the slope-pulse width curve in FIG. 15 is an abnormal signal of two peak comets, and the signal is It focused on the fact that the distance measurement data based on this can also be determined as abnormal data.

Specifically, it is judged whether the light reception signal is normal or not by the position of the plot determined by the inclination of the straight line and the pulse width with respect to the inclination-pulse width curve in FIG. By adding a flag to the distance measurement data based on the signal or the distance measurement data based on the light reception signal judged to be not normal, it is possible to distinguish between normal distance measurement data and abnormal distance measurement data on the memory.
Alternatively, by adding a flag to the light reception signal determined to be normal or the light reception signal determined to be not normal, the normal light reception signal and the normal light reception signal can be determined in the arrangement on the memory.

  Then, the inventors measured the distance based on the light reception signal of the other adjacent pixel from which the normal light reception signal was obtained as the measurement result of the pixel in which the two peak comets that can not be accurately measured are observed. It has been found that if data is to be output, almost accurate distance measurement data can be output for each pixel without increasing the cost.

Here, the “flag” is set at least 1 bit on the memory so as to be in one-to-one correspondence with the distance measurement data for each pixel and the light reception signal, and each of the distance measurement data and the light reception signal is recorded. It temporarily saves the state of the pixel.
For example, to set the flag to the distance measurement data and the light reception signal, which is “0” in the initial state, is to write “1” specifically.
Therefore, the flag is not set when it is determined that the distance measurement data and the light reception signal are normal, and "0" is kept, and "1" is set when it is determined that the distance measurement data and the light reception signal are abnormal. The flag may not be set if it is determined that the distance measurement data or the light reception signal is abnormal, and the flag may remain "0". If it is determined that the distance measurement data or the light reception signal is normal, "1" You may set it. Further, a more complex bit signal may be used to provide an additional flag function.

Hereinafter, as a method of correcting distance measurement data, a method of replacing abnormal distance measurement data with normal distance measurement data will be described with reference to the tables of FIG. 17 and FIG. As described above, when distance measurement is performed on targets at a distance of 3 m and 6 m, 2 peak comets occur in the area between the targets (within the thick frames in FIGS. 17 and 49).
As described above, if it is known that two peak comets are generated within a certain angle of view, the numerical value of the distance measurement data in the bold frame in the fifth line from the top of FIGS. It can be judged that it is distance data, and “1” is set as a flag indicating that it is 2 peak comets, for example, within the thick frame on the fourth line from the top of FIGS. be able to.

At this time, a pixel row consisting of a series of pixels (scan angles) in which a flag within the angle of view determined to be a two-peak comet is set is equally divided into right and left (however, the number of pixels in the pixel row is odd) In this case, the central pixel is not divided into either right or left), and the distance measurement data (abnormal distance measurement data) of the right pixel for which the flag is set is adjacent to the right of the pixel row. Replace with the distance measurement data (normal distance measurement data) of the pixel for which the flag is not set, and place the distance measurement data (abnormal distance measurement data) of the left pixel for which the flag is set on the left side of the pixel row. Replace with the distance measurement data (normal distance measurement data) of the pixel for which the flag is not set.
If the number of pixels in the pixel column is an odd number, abnormal distance measurement data (hereinafter also referred to as "central pixel data") of the central pixel of the pixel column is adjacent to the right and left sides of the pixel column. Among the normal distance measurement data of the pixels to be selected, one having a smaller difference from the central pixel data from the viewpoint of distance measurement accuracy as shown in the bold line in the sixth line from the top of FIG. You may replace it with). Alternatively, the ranging data of a part of the pixels of the pixel column may be replaced with the smaller one of the normal ranging data of the pixels adjacent to the right and left sides of the pixel column.

The above will be described using the integer m and the integer n.
In the pixel array obtained by scanning the angle of view, it is determined that the m-th pixel is normal distance measurement data or light reception data from one end side to the other end side in the angle of view, and the angle of view A flag determined to be a 2-peak comet is set from the m + 1st pixel to the m + 2nth pixel from the one end side to the other end side of the inside, and the m + 2n + 1th pixel is normal distance measurement data or light reception data (Ie, the number of pixels for which the flag determined to be 2 peak comets is set is an even number), the distance measurement data (abnormal distance measurement data) from the (m + 1) th pixel to the (m + n) th pixel is Replace the distance measurement data (normal distance measurement data) of the pixel with the distance measurement data (abnormal distance measurement data) from the m + n + 1st pixel to the m + 2nth pixel, and the distance measurement data (normal Ranging Replace the over data).
Further, it is determined that the m-th pixel is normal distance measurement data and light reception data from one end side to the other end side in the angle of view, and from the one end side to the other end side in the angle of view A flag determined to be 2 peak comets is set from the m + 1 th pixel to the m + 2 n + 1 th pixel, and it is determined that the m + 2 n + 2 th pixel is normal distance measurement data or light reception data (ie, 2 peak comet The number of pixels for which the flag is set is an odd number, and distance measurement data (abnormal distance measurement data) from the m + 1st pixel to the m + nth pixel to distance measurement data of the mth pixel (normal distance measurement data From the ranging data of the m + n + 2 th pixel to the ranging data (abnormal ranging data) of the m + 2 n + 1 th pixel to the ranging data (normal ranging data) to the m + 2 n + 2 th pixel It can replace. The ranging data (center pixel data, abnormal ranging data) up to the m + 2n + 1th pixel is the ranging data (normal ranging data) of the mth pixel or the ranging data up to the m + 2n + 2th pixel ( Of the normal distance measurement data), the difference with the distance measurement data (center pixel data, abnormal distance measurement data) of the (m + 2n + 1) th pixels may be replaced with a smaller one. Alternatively, it may be replaced by the closer one of ranging data (normal ranging data) of the mth pixel or ranging data (normal ranging data) to the m + 2n + 2th pixel.

  Further, for example, as shown in the thick frame of the sixth line from the top of FIG. 49, the distance measurement data of all the pixels of the pixel row among the normal distance measurement data of the pixels adjacent to the right and left sides of the pixel row It may be replaced by the smaller value.

  As a result, in the correction method of FIG. 17, the actual distance (actual distance) and the numerical value of the distance measurement data after correction of the two peak comets will be approximately the same theoretically (the third line from the top of FIG. 17) And the bold line in line 6)).

  In FIG. 17 and FIG. 49, although the number of a series of pixels (scan angles) in which 2 peak comets are generated is five as an example, 2 peak comets are generated in at least one pixel. In some cases, ranging data can be replaced in a similar manner. At this time, when two peak comets are generated at least at one end pixel of the effective scan area, the distance measurement data of the pixel at one end is a pixel at which the two peak comets are not generated at the other end side of the effective scan area. It is preferable to replace with the distance measurement data of the nearest pixel among them. The same applies to the case where two peak comets occur in at least one pixel continuous to the pixel at one end.

Next, a method of detecting the two-peak comet will be described. Here, in the coordinate system of FIG. 15, at least one predetermined range out of the slope-pulse width curve is set as a detection range for detecting two-peak comets, and the slope of the straight line of the light reception signal and the pulse width When the determined plot is within the predetermined range, it is determined that two peak comets are generated in the light reception signal.
Although it may be determined strictly whether the plot determined by the slope of the straight line and the pulse width is on the slope-pulse width curve (one-to-one correspondence between the slope and the pulse width), a normal light reception signal However, the plot may be slightly deviated from the slope-pulse width curve due to the slope of the straight line or the calculation error of the pulse width, etc., so as described above, it is within a range somewhat distant from the slope-pulse width curve. It is preferable to determine whether the plot is present.
Further, by thickening the line width of the slope-pulse width curve within the range that does not impair the sameness, it is possible to suppress that the point determined by the slope of the straight line of the normal light reception signal and the pulse width deviates from the slope-pulse width curve .

Here, the first to fifth ranges were set as specific examples 1 to 5 of the predetermined range as described below, and experiments were performed. The first to fifth ranges are set to ranges in which the pulse width is too large for the magnitude of the slope where it is assumed that two peak comets occur.

The first range is a range in which the slope is 1.0E + 08 or less and the pulse width is 6 m or more (see FIG. 18).
The second range is a range in which the slope is 2.0 E + 08 or less and the pulse width is 8 m or more (see FIG. 19).
The third range is a range where the slope is 3.0 E + 08 or less and the pulse width is 10 m or more (see FIG. 20).
The fourth range is a range where the slope is 3.5 E + 08 or less and the pulse width is 15 m or more (see FIG. 21).
The fifth range is a range where the slope is 4.0 E + 08 or less and the pulse width is 20 m or more (see FIG. 22).
As described above, it is understood that the first to fifth ranges partially overlap with each other.

In FIG. 23, for example, when a first range is set as a detection range in the coordinate system of FIG. 15, data of two-peak comets actually observed are indicated by x marks.
It can be seen from FIG. 23 that when the detection range is only the first range, many two-peak comets are missed, and detection leaks occur (see crosses in ovals outside the detection range in FIG. 23). ).

  Therefore, as shown in FIG. 24, for example, a range consisting of the first and fourth ranges is set as a detection range in the coordinate system of FIG. It can be seen that x) within the detection range can be detected. Note that, in FIG. 24, in the detection range, tone differences (differences in light and shade) are given to portions where the ranges overlap and parts that do not overlap.

However, since some detection omissions still occur (refer to the cross in the ellipse outside the detection range in FIG. 24), for example, as shown in FIG. 25, the first to fifth ranges in the coordinate system of FIG. It can be seen that the detection omission can be suppressed by setting the range consisting of as the detection range and maximizing the detection range. In FIG. 25, in the detection range, tone differences are given stepwise from the portion where the ranges do not overlap to the portion where the number of overlaps is the largest among the portions where the ranges overlap.
As described above, by setting the range including the first to fifth ranges as the detection range, the two-peak comet can be reliably detected.
However, since a step-like gap is still found between the slope-pulse width curve and the detection range consisting of the first to fifth ranges, the detection range is further extended to fill at least a part of this gap. More reliable two-peak comet detection is possible.

  As a case where a two-peak comet is detected in the step-like gap, for example, as shown in FIG. 44, in the case of a two-peak comet in which a peak above Vth2 precedes and a peak below Vth2 follows. There are cases where the difference between the rising slope of the waveform on the front side (left side in FIG. 44) and the rising slope of a normal light reception signal having the same pulse width as that of the two-peak comet is relatively small.

  In addition, since the data of 2 peak comets do not appear on the lower side of the slope-pulse width curve due to the generation principle of 2 peak comets, the condition setting to the lower side is unnecessary.

  The first to fifth ranges described above are merely examples, and the number of the ranges, and the position, shape, and size of the ranges can be changed as appropriate.

Further, for example, as shown in FIG. 45, when the larger peak (maximum peak) of the two-peak comet falls below the threshold value Vth2, the slope can not be calculated and the above determination can not be performed. .
Therefore, if the pulse width (a value obtained by converting P4-P1 into a distance) of a normal light reception signal whose peak matches Vth2 (the amplitude matches Vth2-Vth1) is acquired in advance, a certain peak corresponds to threshold Vth2. It can be determined that the received light signal which is smaller than the above and whose pulse width is clearly larger than the previously acquired pulse width is an abnormal signal having a two-peak comet.

In the distance measurement method shown in FIG. 17, since the distance measurement value (distance measurement data) is corrected after one scan (after one scan), the display of the distance measurement value is delayed by that time, and real time property There is also a concern that
Therefore, more simply, calculation is not performed using a light reception signal in which the flag is set as the 2 peak comet, or distance measurement data in which the flag is set as the 2 peak comet is not output as a measurement result (not displayed or information ) Is also effective. According to this method, it is possible to erase the ghost in real time while measuring the distance without waiting for the end of one scan, so that it is possible to output normal ranging data without a flag set without delay. Become.
However, in such a method, since the ghost appearing at the end of the object is erased, this method is not suitable when it is desired to perform distance measurement such that the shape or size of the object is strictly determined. It is important to use properly according to the purpose.

  Further, although the above description has described the two-peak comet in which the light reception signal has two peaks, it is also assumed that a multi-peak comet in which the light reception signal has three or more peaks is generated. Also in the case of the multi-peak comet, the determination can be made with high accuracy by the same determination method as in the case of the two-peak comet described above.

46 to 48 show specific examples of three-peak comets in which the light reception signal has three peaks. As can be seen from FIGS. 46 to 48, the multi-peak comet is easier to detect than the two-peak comet because the pulse width tends to be larger with respect to the slope or | Vth2-Vth1 | as the number of peaks increases. It is believed that there is.
FIG. 46 shows a three-peak comet waveform in which only the last one peak exceeds the threshold value Vth2.
FIG. 47 shows a three-peak comet waveform in which only one middle peak exceeds the threshold value Vth2.
FIG. 48 shows a three-peak comet waveform in which three peaks are below the threshold value Vth2.

  Furthermore, although the above description has mainly described the non-saturated two-peak comets and the three-peak comets, the slope and the pulse width can be obtained even with the saturated two-peak comets or multi-peak comets. Thus, it is possible to determine whether the light reception signal is normal or abnormal.

  The determination as to whether or not the light reception signal described above is normal is performed by the signal determination circuit 49 of the object detection apparatus 100.

  The sensing device 1000 provided with the object detection device 100 is shown in FIG. The sensing device 1000 is mounted on a moving body, and in addition to the object detection device 100, includes a monitoring control device 300 electrically connected to the object detection device 100. The object detection device 100 is attached near a bumper of a vehicle or near a rearview mirror. The monitoring control device 300 performs processing such as estimation of the shape and size of the object, calculation of position information of the object, calculation of movement information, recognition of the type of the object, and the like based on the detection result of the object detection device 100. , Determine the presence or absence of danger. Then, when it is judged that there is a danger, an alarm such as an alarm is issued to alert the operator of the mobile body, or the steering control unit of the mobile body is instructed to turn off the steering wheel to avoid danger, or braking Issue a command to apply to the mobile ECU. Sensing device 1000 receives supply of power, for example, from a battery of the vehicle.

  The monitoring control device 300 may be provided integrally with the object detection device 100 or may be provided separately from the object detection device 100. Moreover, the monitoring control apparatus 300 may perform at least one part of the control which ECU performs.

  In the following, specific examples (ranging processes 1 to 8) of ranging processes performed by the object detection apparatus 100, ranging data acquisition processes Q performed in ranging processes 1 to 4, and ranging processes 5 to 8 The distance measurement data acquisition processing U to be executed will be described.

Here, in order to carry out each distance measurement process, the binarization circuit 44 of the object detection apparatus 100 binarizes the input signal based on the comparator 1 which binarizes the input signal based on the threshold value Vth1 and the threshold value Vth2. Is configured to include a comparator 2.
The comparators 1 and 2 are connected in parallel to each other, and light reception signals from the operational amplifier 48 are simultaneously input.
The comparator 1 outputs the high level signal 1 that rises at timing P1 at which the rising edge of the received light signal exceeds (crosses) the threshold Vth1 and falls at timing P4 at which the falling edge of the light received signal falls (crosses) below the threshold Vth1. (See Figure 11 below).
Further, the comparator 2 rises at a timing P2 at which the rising edge of the received light signal exceeds (crosses) the threshold Vth2 and the high level signal 2 falls at a timing P3 at which the falling edge of the light receiving signal falls (crosses) below the threshold Vth2. Output (refer to the lower figure in Fig. 11).

Further, the signal determination circuit 49 of the object detection apparatus 100 detects a plot determined by the inclination of the light reception signal and the pulse width with the range including the first to fifth ranges as a detection range in order to execute each distance measurement process. It is determined whether the light reception signal is normal if it is not within the detection range, and it is judged that the light reception signal is not normal (abnormal) if it is within the detection range. Do.
The signal determination circuit 49 outputs the determination result for each light reception signal to the time measurement unit 45.

<Distance measurement process 1>
The ranging process 1 will be described with reference to FIG. The flowchart of FIG. 27 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. Ranging process 1 is started when power is supplied to the object detection apparatus 100.

  In the first step S1, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S2, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S2 is affirmed, the process proceeds to step S3, and if the determination is denied, the same determination is performed again.

  In the next step S3, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S3 is affirmed, the process proceeds to step S4. If the determination in step S3 is negative, the process proceeds to step S5.

  In step S4, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S4 is performed, it will transfer to step S5.

  In step S5, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S6, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S7, it is determined whether the distance measurement data acquired in step S6 is normal. Specifically, the distance measurement data acquired based on the light reception signal determined to be normal by the signal determination circuit 49 is determined to be normal, and based on the light reception signal determined by the signal determination circuit 49 to be not normal. It is determined that the obtained distance measurement data is not normal. If the determination in step S7 is affirmed, the process proceeds to step S8. If the determination in step S7 is negative, the process proceeds to step S10.

  In step S8, the distance measurement data acquired in step S6 is output as a measurement result.

  In the next step S9, it is determined whether or not the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S9 is affirmed, the flow is ended, and if denied, the process returns to step S2 to perform measurement based on the next light reception signal.

  In step S10, a flag is added to the distance measurement data acquired in step S6. That is, in the memory, a flag is added to the distance measurement data determined to be not normal in step S7.

  In the next step S11, it is determined whether there is distance measurement data (normal distance measurement data) to which the flag acquired earlier (in the same scan) is not added in the same frame. If the determination here is affirmed, the process proceeds to step S12. If the determination is denied, the process returns to step S2.

  In step S12, as a measurement result at the scanning position (pixel) where the flag is added to the distance measurement data, the smallest one of the distance measurement data (distance measurement value) to which the flag already obtained in the same frame is not added Output distance measurement data (distance measurement value). If step S12 is performed, it will transfer to step S9.

  In the distance measurement process 1 described above, when abnormal distance measurement data is acquired at a certain scanning position (pixel), normal distance measurement data already acquired in the same frame as a measurement result of the scanning position. Among them, since the smallest distance measurement data is quickly output, the object detection device 100 can function as a distance measurement device that places importance on safety that can output measurement results for each pixel at high speed.

<Distance measurement process 2>
The distance measurement process 2 will be described with reference to FIG. The flowchart of FIG. 28 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The ranging process 2 is started when the object detection apparatus 100 is supplied with power.

  In the first step S21, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S22, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S22 is affirmed, the process proceeds to step S23, and if denied, the same determination is performed again.

  In the next step S23, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S23 is affirmed, the process proceeds to step S24. If the determination in step S23 is negative, the process proceeds to step S25.

  In step S24, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S24 is performed, it will transfer to step S25.

  In step S25, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S26, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S27, it is determined whether the distance measurement data acquired in step S26 is normal. Specifically, the distance measurement data acquired based on the light reception signal determined to be normal by the signal determination circuit 49 is determined to be normal, and based on the light reception signal determined by the signal determination circuit 49 to be not normal. It is determined that the obtained distance measurement data is not normal. If the determination in step S27 is affirmed, the process proceeds to step S28. If the determination in step S27 is negative, the process proceeds to step S30.

  In step S28, the distance measurement data acquired in step S26 is output as a measurement result.

  In the next step S29, it is determined whether or not the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S29 is affirmed, the flow is ended, and if denied, the process returns to step S22 to perform measurement based on the next light reception signal.

  In step S30, a flag is added to the distance measurement data acquired in step S26. That is, in the memory, a flag is added to the distance measurement data determined to be not normal in step S27.

  In the next step S31, it is determined whether or not there is ranging data (normal ranging data) to which the flag acquired earlier is not added in the same frame. If the determination here is affirmed, the process proceeds to step S32, and if denied, the process returns to step S22.

  In step S32, as the measurement result at the scanning position where the flag is added to the distance measurement data, the latest distance measurement data among the distance measurement data to which the flag is not added (more specifically, the normal data already acquired in the same frame) The distance measurement data of the nearest scanning position among the distance measurement data is output. If step S32 is performed, it will transfer to step S29.

  In the distance measurement processing 2 described above, when abnormal distance measurement data is acquired at a certain scanning position (pixel), normal distance measurement data already acquired in the same frame as a measurement result of the scanning position. Among them, the distance measurement data of the nearest scanning position is quickly output, so that the object detection device 100 can be functioned as a distance measurement device capable of outputting the measurement result for each pixel at high speed and with high accuracy.

<Ranging process 3>
Ranging process 3 will be described with reference to FIG. The flowchart of FIG. 29 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. Ranging process 3 is started when the object detection apparatus 100 is supplied with power.

  In the first step S41, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S42, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S42 is affirmed, the process proceeds to step S43, and if the determination is denied, the same determination is performed again.

  In step S43, the pulse width of the light reception signal is calculated. Specifically, the time from when the light reception signal first crosses Vth1 to the next (P4-P1), that is, the pulse width of high level signal 1 multiplied by the speed of light is the pulse width of the light reception signal Output as

  In the next step S44, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S44 is affirmed, the process proceeds to step S45. If the determination in step S44 is negative, the process proceeds to step S51.

  In step S45, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1).

  In the next step S46, it is determined whether the light reception signal is normal. Specifically, the light reception signal judged to be normal by the signal judgment circuit 49 is judged to be normal, and the light reception signal judged to be not normal by the signal judgment circuit 49 is judged to be not normal. If the determination in step S46 is affirmed, the process proceeds to step S47. If the determination in step S46 is negative, the process proceeds to step S55.

  In the next step S47, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S48, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S49, the distance measurement data acquired in step S48 is output as a measurement result. If step S49 is performed, it will transfer to step S50.

  In step S50, it is determined whether the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S50 is affirmed, the flow is ended, and if denied, the process returns to step S42 to perform measurement based on the next light reception signal.

  In step S51, it is determined whether the light reception signal is normal. The determination here is affirmed when the pulse width of the light reception signal calculated in step S43 is equal to the pulse width of the normal light reception signal whose amplitude is | Vth2-Vth1 |, and exceeds the pulse width. Denied. If the determination in step S51 is affirmed, the process proceeds to step S52. If the determination in step S51 is negative, the process proceeds to step S55.

  In step S52, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S53, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S54, the distance measurement data acquired in step S53 is output as a measurement result. If step S54 is performed, it will transfer to step S50.

  In step S55, a flag is added to the light reception signal, and the flag is temporarily stored in the memory in association with the corresponding scanning position. That is, in the memory, a flag is added to the light reception signal determined to be not normal in step S46.

  In the next step S56, it is determined whether or not there is a light reception signal to which the previously acquired flag is not added in the same frame. If the determination here is affirmed, the process proceeds to step S57, and if denied, the process returns to step S42.

  In step S57, as the measurement result at the scanning position where the flag is added to the light reception signal, the smallest distance measurement data among the distance measurement data acquired based on the light reception signal to which the flag is not added is output. The smallest distance measurement data out of the distance measurement data based on the normal light reception signal already acquired inside is output). If step S57 is performed, it will transfer to step S50.

  In the distance measurement process 3 described above, when distance measurement data based on an abnormal light reception signal is acquired at a certain scanning position (pixel), a normal measurement already acquired in the same frame as a measurement result of the scanning position. Since the minimum distance measurement data among the distance measurement data based on the light reception signal is rapidly output, the object detection device 100 can function as a distance measurement device that places importance on safety that can output measurement results for each pixel at high speed. .

<Distance measurement process 4>
The distance measurement process 4 will be described with reference to FIG. The flowchart of FIG. 30 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The ranging process 4 is started when the object detection apparatus 100 is supplied with power.

  In the first step S61, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S62, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S62 is affirmative, the process proceeds to step S63, and if the determination is negative, the same determination is again made.

  In step S63, the pulse width of the light reception signal is calculated. Specifically, the time from when the light reception signal first crosses Vth1 to the next (P4-P1), that is, the pulse width of high level signal 1 multiplied by the speed of light is the pulse width of the light reception signal Output as

  In the next step S64, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S64 is affirmed, the process proceeds to step S65. If the determination in step S64 is negative, the process proceeds to step S71.

  In step S65, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1).

  In the next step S66, it is determined whether the light reception signal is normal. Specifically, the light reception signal judged to be normal by the signal judgment circuit 49 is judged to be normal, and the light reception signal judged to be not normal by the signal judgment circuit 49 is judged to be not normal. If the determination in step S66 is affirmed, the process proceeds to step S67. If the determination in step S66 is negative, the process proceeds to step S75.

  In the next step S67, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S68, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S69, the distance measurement data acquired in step S68 is output as a measurement result. If step S69 is performed, it will transfer to step S70.

  In step S70, it is determined whether the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S70 is affirmed, the flow is ended, and if denied, the process returns to step S62 to perform measurement based on the next light reception signal.

  In step S71, it is determined whether the light reception signal is normal. The determination here is affirmed when the pulse width of the light reception signal calculated in step S43 is equal to the pulse width of the normal light reception signal whose amplitude is | Vth2-Vth1 |, and exceeds the pulse width. Denied. If the determination in step S71 is affirmed, the process proceeds to step S72. If the determination in step S71 is negative, the process proceeds to step S75.

  In step S72, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S73, distance measurement data acquisition processing Q is performed. Details of the distance measurement data acquisition processing Q will be described later.

  In the next step S74, the distance measurement data acquired in step S73 is output as a measurement result. If step S74 is performed, it will transfer to step S70.

  In step S75, a flag is added to the light reception signal, and the flag is temporarily stored in the memory in association with the corresponding scanning position. That is, in the memory, a flag is added to the light reception signal determined to be not normal in step S66.

  In the next step S76, it is determined whether or not there is a light reception signal to which the previously acquired flag is not added in the same frame. If the determination here is affirmed, the process proceeds to step S77. If the determination is denied, the process returns to step S62.

  In step S77, as the measurement result at the scanning position where the flag is added to the light reception signal, the latest distance measurement data among the distance measurement data acquired based on the light reception signal to which the flag is not added is output. Among the normal light reception signals already acquired inside, the distance measurement data based on the light reception signal of the nearest scanning position is output). If step S77 is performed, it will transfer to step S70.

  In the distance measurement process 4 described above, when distance measurement data based on an abnormal light reception signal is acquired at a certain scanning position (pixel), a normal measurement already acquired in the same frame as a measurement result of the scanning position. Since the distance measurement data of the nearest scanning position among the distance measurement data based on the light reception signal is promptly output, the object detection device 100 can be functioned as a distance measurement device capable of outputting the measurement result for each pixel with high accuracy and high speed. it can.

  Hereinafter, ranging data acquisition processes 1 to 6 which are specific examples of the ranging data acquisition process Q will be described.

<Distance Measurement Data Acquisition Process 1>
First, ranging data acquisition processing 1 will be described with reference to the flowchart in FIG.

  In the first step T1, it is determined whether the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. If the determination here is affirmed, the process proceeds to step T2, and if the determination is denied, the process proceeds to step T7.

  In the next step T2, it is determined whether the calculated inclination is 1.0E + 08 [V / s] or more. Here, 1.0E + 08 [V / s] is a value (slope) serving as a reference for determining the presence or absence of saturation (hereinafter also referred to as “first saturation”) of the light reception signal in the operational amplifier 48 (see FIG. 15). ). That is, it can be determined that the first saturation occurs when the calculated inclination is 1.0E + 08 [V / s] or more. If the determination in step T2 is affirmed, the process proceeds to step T3. If the determination in step T2 is negative, the process proceeds to step T7.

  In step T3, it is determined whether the calculated inclination is equal to or greater than 2.5E + 08 [V / s]. Here, 2.5E + 08 [V / s] is a value (slope) serving as a reference for determining the presence or absence of saturation (hereinafter also referred to as “second saturation”) of the light reception signal in the IV converter 43 (see FIG. 15). That is, it can be determined that the second saturation occurs when the calculated inclination is 2.5E + 08 [V / s] or more. If the determination in step T3 is affirmed, the process proceeds to step T4. If the determination in step T3 is negative, the process proceeds to step T9.

  In step T4, time P0 is calculated from the calculated inclination and P0 crossover voltage A. Specifically, the time P0 is calculated using the equation (2). Here, the P0 crossover voltage A is a crossover voltage set for 2.5E + 08 [V / s] (in the case of the second saturation).

  In the next step T5, a P0 distance measurement value is calculated. Specifically, the time from the light emission timing of the LD 11 to the time P0 calculated in step T4 is converted into a distance, and 1/2 of the converted value is output as a P0 distance measurement value.

In the next step T6, the distance to the object is acquired from the P0 distance measurement value calculated in step T5 and the calibration curve A, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve A is a calibration curve that represents the correspondence between the P0 distance measurement value and the actual distance in the case of the second saturation, which is acquired in advance using the P0 crossover voltage A (see FIG. 43), The approximate line (correction equation) is also calculated automatically. When step T6 is performed, the flow ends.
Here, an example of the calibration curve A and the correction formula thereof is shown in FIG. 43, but other calibration curves described below and the correction formula thereof are straight lines and formulas representing the same proportional relationship as in FIG. Illustration is omitted.

  In step T7, the Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T8, the distance to the object is acquired from the Tm distance measurement value calculated in step T7 and the calibration curve C, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve C is a calibration curve that represents the correspondence between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T7 is acquired as the distance to the object. When step T8 is performed, the flow ends.

  In step T9, time P0 is calculated from the calculated inclination and P0 crossover voltage B. Specifically, the time P0 can be calculated using the equation (2). Here, the P0 crossover voltage B is a crossover voltage set for 1.0E + 08 [V / s] (in the case of the first saturation).

  In the next step T10, a P0 distance measurement value is calculated. Specifically, the time from the light emission timing of the LD 11 to the time P0 calculated in step T9 is converted into a distance, and 1/2 of the converted value is output as a P0 distance measurement value.

  In the next step T11, the distance to the object is obtained from the calculated P0 distance measurement value and the calibration curve B, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve B is a calibration curve representing the relationship between the P0 distance measurement value in the case of the first saturation and the actual distance, which is acquired in advance using the P0 crossover voltage B. After step T11 is performed, the flow ends.

  In the distance measurement data acquisition processing 1 described above, since P0 distance measurement is performed using the cross voltage corresponding to each of the first and second saturations, high accuracy is obtained regardless of whether the first or second saturation occurs. Ranging is possible.

<Distance measurement data acquisition processing 2>
Next, ranging data acquisition processing 2 will be described with reference to the flowchart of FIG.

  In the first step T21, it is determined whether the inclination of a straight line passing through a point at which the light reception signal first crosses the threshold Vth1 and a point at which the light reception signal first crosses the threshold Vth2 is calculated. If the determination here is affirmed, the process proceeds to step T22. If the determination is denied, the process proceeds to step T26.

  In the next step T22, it is determined whether or not the calculated inclination is 1.0E + 08 [V / s] or more. Here, 1.0E + 08 [V / s] is a value (slope) serving as a reference for determining the presence or absence of saturation (first saturation) of the light reception signal in the operational amplifier 48 (see FIG. 15). That is, it can be determined that the first saturation occurs when the calculated inclination is 1.0E + 08 [V / s] or more. If the determination in step T22 is affirmed, the process proceeds to step T23. If the determination in step T22 is negative, the process proceeds to step T26.

  In step T23, time P0 is calculated from the calculated inclination and P0 crossover voltage B. Specifically, the time P0 is calculated using the equation (2). Here, the P0 crossover voltage B is a crossover voltage set for 1.0E + 08 [V / s] (in the case of the first saturation).

  In the next step T24, a P0 distance measurement value is calculated. Specifically, the time from the light emission timing of the LD 11 to the time P0 calculated in step T23 is converted into a distance, and 1/2 of the converted value is output as a P0 distance measurement value.

  In the next step T25, the distance to the object is acquired from the P0 distance measurement value calculated in step T24 and the calibration curve B, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve B is a calibration curve representing the relationship between the P0 distance measurement value in the case of the first saturation and the actual distance, which is acquired in advance using the P0 crossover voltage B. After step T25 is performed, the flow ends.

  At step T26, a Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T27, the distance to the object is acquired from the Tm distance measurement value calculated in step T26 and the calibration curve C, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve C is a calibration curve that represents the relationship between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T26 is acquired as the distance to the object. After step T27 is performed, the flow ends.

  As can be understood from the above description, in the distance measurement data acquisition processing 2, P0 is uniformly calculated using the cross voltage B when the first saturation occurs, but the first saturation to the second saturation ( There is no error in the value of P0 unless transitioning to oversaturation). Therefore, distance measurement data acquisition processing 2 simplifies the control when second saturation (supersaturation) is difficult to occur in IV converter 43 of light detection system 40 (for example, when the saturation voltage in IV converter 43 is high) It is effective in that it can be

<Distance measurement data acquisition processing 3>
Next, ranging data acquisition processing 3 will be described with reference to the flowchart of FIG.

  In the first step T31, it is determined whether the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. If the determination here is affirmed, the process proceeds to step T32, and if the determination is denied, the process proceeds to step T35.

  In step T32, time P0 is calculated from the calculated inclination and P0 crossover voltage B. Specifically, the time P0 is calculated using the equation (2). Here, the P0 crossover voltage B is a crossover voltage set for 1.0E + 08 [V / s] (in the case of the first saturation).

  In the next step T33, a P0 distance measurement value is calculated. Specifically, the time from the light emission timing of the LD 11 to the time P0 calculated in step T32 is converted into a distance, and 1/2 of the converted value is output as a P0 distance measurement value.

  In the next step T34, the distance to the object is acquired from the P0 distance measurement value calculated in step T33 and the calibration curve B, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve B is a calibration curve which represents the relationship between the P0 distance measurement value in the case of the first saturation and the actual distance, which is acquired in advance using the crossover voltage B. After step T34 is executed, the flow ends.

  At step T35, a Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T36, the distance to the object is obtained from the Tm distance measurement value calculated in step T35 and the calibration curve C, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve C is a calibration curve that represents the relationship between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T35 is acquired as the distance to the object. After step T36 is performed, the flow ends.

  As can be understood from the above description, in the distance measurement data acquisition processing 3, the time P0 is calculated using the cross voltage B uniformly when the light reception signal crosses the threshold value Vth2, but P0 distance measurement using the time P0 As a result, accurate distance measurement is possible regardless of the presence or absence of saturation (first saturation) of the light reception signal. Further, even in the distance measurement data acquisition processing 3, an error does not occur in the value of P0 unless transition from the first saturation to the second saturation (supersaturation) occurs. Therefore, distance measurement data acquisition processing 3 can further simplify control when second saturation is unlikely to occur in IV converter 43 of light detection system 40 (for example, when the saturation voltage in IV converter 43 is high) It is effective at the point.

<Distance measurement data acquisition processing 4>
Next, ranging data acquisition processing 4 will be described with reference to the flowchart in FIG.

  In the first step T41, it is determined whether the inclination of a straight line passing through a point at which the light reception signal first crosses the threshold Vth1 and a point at which the light reception signal first crosses the threshold Vth2 is calculated. If the determination here is affirmed, the process proceeds to step T42. If the determination is denied, the process proceeds to step T45.

  In step T42, it is determined whether the calculated inclination is 1.0E + 08 [V / s] or more. Here, 1.0E + 08 [V / s] is a value (slope) serving as a reference for determining the presence or absence of saturation (first saturation) of the light reception signal in the operational amplifier 48 (see FIG. 15). That is, it can be determined that the first saturation occurs when the calculated inclination is 1.0E + 08 [V / s] or more. If the determination in step T42 is affirmed, the process proceeds to step T43. If the determination in step T42 is negative, the process proceeds to step T45.

  At step T43, a Tr distance measurement value is calculated. Specifically, the time from the light emission timing to the rise timing P1 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1/2 of the converted value is output as the Tr distance measurement value.

  In the next step T44, the distance to the object is obtained from the calculated inclination and the Tr distance measurement value calculated in step T43 and the calibration curve D, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Save to Here, the calibration curve D is a calibration curve representing the relationship between the value obtained by subtracting the actual distance from the Tr distance measurement value (distance measurement error) and the slope of the rising edge of the light reception signal (see FIG. 12). Therefore, the distance measurement error corresponding to the calculated inclination is obtained from the calibration curve D, and the distance to the object can be obtained by subtracting the distance measurement error from the Tr distance measurement value calculated in step T43. . After step T44 is executed, the flow ends.

  At step T45, a Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T46, the distance to the object is acquired from the Tm distance measurement value calculated in step T45 and the calibration curve C, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve C is a calibration curve that represents the relationship between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T45 is acquired as the distance to the object. After step T46 is performed, the flow ends.

  As can be understood from the above description, in the distance measurement data acquisition processing 4, the Tr distance measurement value is uniformly corrected using the rising slope of the light reception signal when the first saturation occurs, but the first saturation As long as it does not shift to the second saturation (super saturation), it is possible to obtain an almost accurate distance measurement value. Therefore, distance measurement data acquisition processing 4 can simplify control when second saturation is unlikely to occur in IV converter 43 of light detection system 40 (for example, when the saturation voltage in IV converter 43 is high). Is effective.

<Distance measurement data acquisition processing 5>
Next, ranging data acquisition processing 5 will be described with reference to the flowchart of FIG.

  In the first step T51, it is determined whether the slope of a straight line passing through a point at which the light reception signal first crosses the threshold Vth1 and a point at which the light reception signal first crosses the threshold Vth2 is calculated. If the determination here is affirmed, the process proceeds to step T52, and if the determination is denied, the process proceeds to step T54.

  At step T52, a Tr distance measurement value is calculated. Specifically, the time from the light emission timing to the rise timing P1 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1/2 of the converted value is output as the Tr distance measurement value.

  In the next step T53, the distance to the object is obtained from the calculated inclination and the Tr distance measurement value calculated in step T52 and the calibration curve D, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Save to Here, the calibration curve D is a calibration curve representing the relationship between the value obtained by subtracting the actual distance from the Tr distance measurement value (distance measurement error) and the slope of the rising edge of the light reception signal (see FIG. 12). Therefore, the distance measurement error corresponding to the calculated inclination is obtained from the calibration curve D, and the distance to the object can be obtained by subtracting the distance measurement error from the Tr distance measurement value calculated in step T52. . After step T53 is executed, the flow ends.

  At step T54, a Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T55, the distance to the object is acquired from the Tm distance measurement value calculated in step T54 and the calibration curve C. Here, the calibration curve C is a calibration curve that represents the relationship between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T54 is acquired as the distance to the object. After step T55 is executed, the flow ends.

  As can be understood from the above description, in the distance measurement data acquisition processing 5, when the light reception signal crosses the threshold value Vth2, the Tr distance measurement value is uniformly corrected using the rising slope of the light reception signal. Accurate ranging is possible regardless of the presence or absence of (first saturation). Further, even in the distance measurement data acquisition process 5, substantially accurate distance measurement values can be obtained as long as the transition from the first saturation to the second saturation (supersaturation) is not made. Therefore, the distance measurement data acquisition processing 5 can simplify the control more when the second saturation is hard to occur in the IV converter 43 of the light detection system 40 (for example, when the saturation voltage in the IV converter 43 is high) It is effective at the point.

<Distance measurement data acquisition processing 6>
Next, distance measurement data acquisition processing 6 will be described with reference to the flowchart in FIG.

  In the first step T61, it is determined whether the calculated pulse width is 6 [m] or more. Here, 6 [m] is a value (pulse width) serving as a reference for determining the presence or absence of saturation (first saturation) of the light reception signal in the operational amplifier 48 (see FIG. 15). That is, it can be determined that the first saturation occurs when the calculated pulse width is 6 [m] or more. If the determination in step T61 is affirmed, the process proceeds to step T62. If the determination in step T61 is negative, the process proceeds to step T64.

  At step T62, a Tr distance measurement value is calculated. Specifically, the time from the light emission timing of the LD 11 to the rising timing P1 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1/2 of the converted value is output as a Tr distance measurement value. .

  In the next step T63, the distance to the object is obtained from the calculated pulse width, the Tr distance measurement value calculated in step T62, and the calibration curve E, and is temporarily stored in the memory as distance measurement data in association with the corresponding scanning position. Save. Here, the calibration curve E is a calibration curve representing the relationship between the value obtained by subtracting the actual distance from the Tr distance measurement value (distance measurement error) and the pulse width of the light reception signal. This calibration curve can be created based on FIG. 12 and FIG. Therefore, the distance measurement error corresponding to the calculated pulse width is obtained from the calibration curve E, and the distance measurement error is obtained from the Tr distance measurement value calculated in step T62 to obtain the distance to the object. it can. After step T63 is executed, the flow ends.

  At step T64, a Tm distance measurement value is calculated. Specifically, the time Tm from the light emission timing of the LD 11 to the intermediate timing between the rising timing P1 and the falling timing P4 of the high level signal 1 from the binarization circuit 44 is converted into a distance, and 1 / 2 is output as the Tm range value.

  In the next step T65, the distance to the object is acquired from the Tm distance measurement value calculated in step T64 and the calibration curve C, and stored in the memory as distance measurement data in association with the corresponding scanning position. Here, the calibration curve C is a calibration curve that represents the relationship between the Tm distance measurement value and the actual distance, which is acquired in advance. Therefore, from the calibration curve C, the actual distance corresponding to the Tm distance measurement value calculated in step T64 is acquired as the distance to the object. After step T65 is executed, the flow ends.

  As can be understood from the above description, in the distance measurement data acquisition processing 6, the Tr distance measurement value is uniformly corrected using the pulse width of the light reception signal when the first saturation occurs, but from the first saturation Nearly accurate ranging values can be obtained as long as the transition to the second saturation (supersaturation) is not made. Therefore, distance measurement data acquisition processing 6 can simplify control when second saturation is unlikely to occur in IV converter 43 of light detection system 40 (for example, when the saturation voltage in IV converter 43 is high). Is effective.

<Distance measurement process 5>
The ranging process 5 will be described with reference to FIGS. 37 and 38. FIG. The flowcharts of FIG. 37 and FIG. 38 are based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The ranging process 5 is started when the object detection apparatus 100 is supplied with power.

  In the first step S81, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S82, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S82 is affirmative, the process proceeds to step S83, and if the determination is negative, the same determination is made again.

  In the next step S83, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S83 is affirmed, the process proceeds to step S84. If the determination in step S83 is negative, the process proceeds to step S85.

  In step S84, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S84 is performed, it will transfer to step S85.

  In step S85, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S86, it is determined whether one scan is completed. Specifically, it is determined that one scan is completed when a predetermined time (time in which the rotating mirror 26 rotates by an angle corresponding to the effective scanning area) has elapsed since the generation of the LD drive signal. If the determination in step S86 is affirmed, the process proceeds to step S87, and if denied, the process returns to step S82.

  In step S87, distance measurement data acquisition processing U is performed. The distance measurement data acquisition process U collectively performs the above-described distance measurement data acquisition process Q (any of the distance measurement data acquisition processes 1 to 6) for all light reception signals obtained for each scanning position from the start to the end of each scan. Processing. When the distance measurement data acquisition process U is performed, a plurality of distance measurement data are arranged in the memory in a state associated with the corresponding scanning position.

  In the next step S88, it is determined whether or not there is abnormal distance measurement data in the distance measurement data acquired in step S87. The determination here is affirmed if there is distance measurement data acquired based on the light reception signal determined to be not normal by the signal determination circuit 49, and it is denied if the distance measurement data does not exist. If the determination in step S88 is affirmed, the process proceeds to step S91. If the determination in step S88 is negative, the process proceeds to step S89.

  In step S89, distance measurement data of the scanning position is output as a measurement result of each scanning position in the scanning range. If step S89 is performed, it will transfer to step S90.

  In step S90, it is determined whether the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S90 is affirmed, the flow is ended, and if denied, the process returns to step S82 to perform measurement by the next scan.

  In step S91, a flag is added to N (N ≧ 1) abnormal distance measurement data. That is, in the memory, a flag is added to all the abnormal distance measurement data determined in step S88.

  In the next step S92, n is set to 1.

  In the next step S93, it is determined whether there is a scan position where no flag is added to the distance measurement data on both sides of the scan position Rn at which the nth distance measurement data to which the flag is added is obtained. If the determination here is affirmed, the process proceeds to step S94. If the determination is denied, the process proceeds to step S97.

  In step S94, the distance measurement data of the scanning position Rn is obtained by adding the flag to the distance measurement data of the scanning position Rn closest to the scanning position Rn on one side (one side) of the scanning position Rn. The distance measurement data of the scanning position closest to the scanning position Rn is replaced with the distance measurement data having a smaller difference with the distance measuring data of the scanning position Rn (one closer to the distance measuring data of the scanning position Rn) See Figure 17).

  In the next step S95, it is determined whether n <N. If the determination here is affirmed, the process proceeds to step S96. If the determination is denied, the process proceeds to step S95.5.

  In step S95.5, the distance measurement data replaced as the measurement result of the scanning position Rn is output, and the distance measurement data of the scanning position is output as the measurement result of the scanning position other than the scanning position Rn. After step S95.5 is executed, the process proceeds to step S90.

  In step S96, n is incremented. After step S96 is executed, the process returns to step S93.

  In step S97, the distance measurement data of the scan position Rn is replaced with the distance measurement data of the scan position closest to the scan position Rn on one side of the scan position Rn, to which no flag is added. When step S97 is executed, the process proceeds to step S95.

  In the distance measurement processing 5 described above, when abnormal distance measurement data is acquired at a certain scan position Rn, normal distance measurement data at a scan position near the scan position Rn is output as a measurement result of the scan position. The object detection apparatus 100 can function as a distance measuring apparatus capable of outputting the measurement result of each pixel with higher accuracy.

<Distance measurement processing 6>
The distance measurement process 6 will be described with reference to FIG. The flowchart of FIG. 39 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The distance measurement process 6 is started when power is supplied to the object detection apparatus 100.

  In the first step S101, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S102, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S102 is affirmed, the process proceeds to step S103, and if the determination is denied, the same determination is performed again.

  In the next step S103, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S103 is affirmed, the process proceeds to step S104. If the determination in step S103 is negative, the process proceeds to step S105.

  In step S104, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S104 is performed, it will transfer to step S105.

  In step S105, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S106, it is determined whether one scan is completed. Specifically, it is determined that one scan is completed when a predetermined time (time in which the rotating mirror 26 rotates by an angle corresponding to the effective scanning area) has elapsed since the generation of the LD drive signal. If the determination in step S106 is affirmed, the process proceeds to step S107. If the determination in step S106 is negative, the process returns to step S102.

  In step S107, distance measurement data acquisition processing U is performed. The distance measurement data acquisition process U collectively performs the above-described distance measurement data acquisition process Q (any of the distance measurement data acquisition processes 1 to 6) for all light reception signals obtained for each scanning position from the start to the end of each scan. Processing. When the distance measurement data acquisition process U is performed, a plurality of distance measurement data are arranged in the memory in a state associated with the corresponding scanning position.

  In the next step S108, it is determined whether or not there is abnormal distance measurement data in the distance measurement data acquired in step S107. The determination here is affirmed if there is distance measurement data acquired based on the light reception signal determined to be not normal by the signal determination circuit 49, and it is denied if the distance measurement data does not exist. If the determination in step S108 is affirmed, the process proceeds to step S111. If the determination in step S108 is negative, the process proceeds to step S109.

  In step S109, distance measurement data of the scanning position is output as a measurement result of each scanning position of the scanning range. If step S109 is performed, it will transfer to step S110.

  In the next step S110, it is determined whether or not the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S110 is affirmed, the flow ends, and if denied, the process returns to step S102 to perform measurement by the next scan.

  In step S111, a flag is added to the abnormal distance measurement data. That is, in the memory, a flag is added to the distance measurement data determined to be not normal in step S108.

  In the next step S112, the distance measurement data of the scanning position in which the flag is added to the distance measurement data is replaced with the minimum distance measurement data in which the flag is not added (see FIG. 49).

  In the next step S113, the distance measurement data of the scanning position is output as the measurement result of the scanning position where the flag is not added to the distance measurement data, and replaced as the measurement result of the scanning position where the flag is added to the distance measurement data. Output the distance measurement data. If step S113 is performed, it will transfer to step S110.

  In the distance measurement process 6 described above, when abnormal distance measurement data is acquired at a certain scanning position (pixel), as a measurement result of the scanning position, among all the normal distance measurement data acquired in the same frame Since the minimum distance measurement data is output, the object detection device 100 can be functioned as a distance measurement device in which the safety for outputting the measurement result for each pixel can be further emphasized.

<Distance measurement process 7>
The ranging process 7 will be described with reference to FIGS. 40 and 41. FIG. The flowcharts of FIGS. 40 and 41 are based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The ranging process 7 is started when the object detection apparatus 100 is supplied with power.

  In the first step S121, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S122, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S122 is affirmed, the process proceeds to step S123, and if the determination is denied, the same determination is performed again.

  In the next step S123, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S123 is affirmed, the process proceeds to step S124. If the determination in step S123 is negative, the process proceeds to step S125.

  In step S124, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S124 is performed, it will transfer to step S125.

  In the next step S125, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S125.5, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S126, it is determined whether one scan is completed. Specifically, it is determined that one scan is completed when a predetermined time (time in which the rotating mirror 26 rotates by an angle corresponding to the effective scanning area) has elapsed since the generation of the LD drive signal. If the determination in step S126 is affirmed, the process proceeds to step S127, and if denied, the process returns to step S122.

  In the next step S127, it is determined whether or not there is an abnormal light reception signal among the light reception signals acquired in one scan. The judgment here is affirmed if there is a light reception signal which is judged to be not normal by the signal judgment circuit 49, and it is negated if there is no such light reception signal. If the determination in step S127 is affirmed, the process proceeds to step S131. If the determination in step S127 is negative, the process proceeds to step S128.

  In step S128, distance measurement data acquisition processing U is performed. The distance measurement data acquisition process U collectively performs the above-described distance measurement data acquisition process Q (any of the distance measurement data acquisition processes 1 to 6) for all light reception signals obtained for each scanning position from the start to the end of each scan. Processing. When the distance measurement data acquisition process U is performed, a plurality of distance measurement data are arranged in the memory in a state associated with the corresponding scanning position.

  In the next step S129, distance measurement data of the scanning position is output as a measurement result of each scanning position of the scanning range. If step S129 is performed, it will transfer to step S130.

  In step S130, it is determined whether the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S130 is affirmed, the flow is ended, and if denied, the process returns to step S122 to perform measurement by the next scan.

  In step S131, a flag is added to N (N ≧ 1) abnormal light reception signals. That is, in the memory, a flag is added to the abnormal light reception signal determined in step S127.

  In the next step S132, distance measurement data of the scanning position where the flag is not added to the light reception signal is acquired. Specifically, the distance measurement data acquisition process Q (one of the distance measurement data acquisition processes 1 to 6) is performed on all the light reception signals stored in the memory and to which no flag is added.

  In the next step S133, 1 is set to n.

  In the next step S134, it is determined whether there is a scanning position where the flag is not added to the light reception signal on both sides of the scanning position Rn at which the nth light reception signal to which the flag is added is obtained. When the determination here is affirmed, the process proceeds to step S135, and when the determination is denied, the process proceeds to step S138.

  In step S135, the measurement result of the scanning position Rn is obtained by adding the flag to the distance measurement data based on the light receiving signal of the scanning position closest to the scanning position Rn on one side of the scanning position Rn and the other side of the scanning position Rn. Of the distance measurement data based on the light reception signal at the scanning position closest to the scanning position Rn, the distance measurement data based on the light reception signal approximated by the nth light reception signal is determined. Here, a plot determined by the slope and the pulse width is used as an index for determining the degree of approximation of the light reception signal, and light reception signals closer to each other in the plot are approximated.

  In the next step S136, it is determined whether n <N. If the determination here is affirmed, the process proceeds to step S137, and if the determination is denied, the process proceeds to step S136.5.

  In step S136.5, the distance measurement data determined as the measurement result of the scanning position Rn is output, and the distance measurement data of the scanning position is output as the measurement result of the scanning position other than the scanning position Rn. If step S136.5 is performed, it will transfer to step S130.

  In step S137, n is incremented. After step S137 is executed, the process returns to step S134.

  In step S138, the measurement result of the scan position Rn is determined as distance measurement data based on the light reception signal of the scan position closest to the scan position Rn on one side (one side) of the scan position Rn. If step S138 is performed, it will transfer to step S136.

  In the distance measurement process 7 described above, when an abnormal light reception signal is acquired at a certain scanning position Rn, distance measurement data based on a normal light reception signal at a scanning position near the scanning position Rn as a measurement result of the scanning position Rn. Thus, the object detection apparatus 100 can function as a distance measuring apparatus capable of outputting the measurement result of each pixel with high accuracy.

<Distance measurement processing 8>
The distance measurement process 8 will be described with reference to FIG. The flowchart of FIG. 42 is based on a processing algorithm executed by an operation system including the time measurement unit 45 and the measurement control unit 46. The ranging process 8 is started when the object detection apparatus 100 is supplied with power.

  In the first step S141, the effective scanning area is optically scanned. Specifically, an LD drive signal generated based on the synchronization signal is output to the LD drive unit 12 to apply a drive current to the LD 11, causing the LD 11 to emit a pulse, and the pulse light is deflected by the rotating mirror 26 that rotates. Do.

  In the next step S142, it is determined whether the light reception signal crosses the threshold value Vth1. That is, it is determined whether a light reception signal is detected. The determination here is affirmed when the high level signal 1 is output from the binarization circuit 44, and is denied when it is not output. If the determination in step S142 is affirmed, the process proceeds to step S143, and if the determination is denied, the same determination is performed again.

  In the next step S143, it is determined whether the light reception signal crosses the threshold value Vth2. The determination here is affirmed when the high level signal 2 is output from the binarization circuit 44, and negated when it is not output. If the determination in step S143 is affirmed, the process proceeds to step S144. If the determination in step S143 is negative, the process proceeds to step S145.

  In step S144, the slope of a straight line passing through the point at which the light reception signal first crosses the threshold Vth1 and the point at which the light reception signal first crosses the threshold Vth2 is calculated. Specifically, the inclination is calculated using the rising timing P1 of the high level signal 1 from the binarization circuit 44, the rising timing P2 of the high level signal 2, Vth1 and Vth2, and the above equation (1). If step S144 is performed, it will transfer to step S145.

  In step S145, the pulse width of the light reception signal is calculated. Specifically, the distance obtained by multiplying the speed of light by the time (P4-P1) from when the light reception signal firstly crosses to Vth1 next time is output as a pulse width.

  In the next step S145.5, the light reception signal is associated with the corresponding scanning position and temporarily stored in the memory.

  In the next step S146, it is determined whether one scan is completed. Specifically, it is determined that one scan is completed when a predetermined time (time in which the rotating mirror 26 rotates by an angle corresponding to the effective scanning area) has elapsed since the generation of the LD drive signal. If the determination in step S146 is affirmed, the process proceeds to step S147. If the determination in step S146 is negative, the process returns to step S142.

  In the next step S147, it is determined whether or not there is an abnormal light reception signal among the light reception signals acquired in one scan. The judgment here is affirmed if there is a light reception signal which is judged to be not normal by the signal judgment circuit 49, and it is negated if there is no such light reception signal. If the determination in step S147 is affirmed, the process proceeds to step S151. If the determination in step S147 is negative, the process proceeds to step S148.

  In step S148, distance measurement data acquisition processing U is performed. The distance measurement data acquisition process U collectively performs the above-described distance measurement data acquisition process Q (any of the distance measurement data acquisition processes 1 to 6) for all light reception signals obtained for each scanning position from the start to the end of each scan. Processing. When the distance measurement data acquisition process U is performed, a plurality of distance measurement data are arranged in the memory in a state associated with the corresponding scanning position.

  In the next step S149, distance measurement data of the scanning position is output as a measurement result of each scanning position in the scanning range. If step S149 is performed, it will transfer to step S150.

  In the next step S150, it is determined whether the measurement is completed. Specifically, the determination here is affirmed when the supply of power to the object detection apparatus 100 is stopped, and is denied when the supply is not stopped. If the determination in step S150 is affirmed, the flow is ended, and if denied, the process returns to step S142 to perform measurement by the next scan.

  In step S151, a flag is added to the abnormal light reception signal. That is, in the memory, a flag is added to all the light reception signals determined to be not normal in step S147.

  In the next step S152, distance measurement data of all scanning positions where a flag is not added to the light reception signal is acquired.

  In the next step S153, as the measurement result of the scanning position where the flag is added to the light reception signal, the smallest distance measurement data among the distance measurement data based on the light reception signal not added with the flag is output. Distance measurement data of the scanning position is output as a measurement result of the scanning position not added. If step S153 is performed, it will transfer to step S150.

  In the distance measurement processing 8 described above, when an abnormal light reception signal is acquired at a certain scanning position (pixel), distance measurement based on all normal light reception signals acquired in the same frame as a measurement result of the scanning position. Since the minimum distance measurement data among the data is output, the object detection apparatus 100 can be functioned as a distance measurement device in which the safety for outputting the measurement result for each pixel can be emphasized.

  The object detection apparatus 100 according to the present embodiment described above receives the light projected from the light projection system 10 and reflected by the object from the light projection system 10 including the LD 11 (light source) that emits light based on the light emission signal. A light detection system 40 outputting an electric signal according to the amount of light received, and a process of binarizing a light reception signal which is an electric signal output from the light detection system 40 based on threshold voltages Vth1 and Vth2 And a signal determination circuit 49 (determination system) that determines whether the light reception signal is normal or not based on the output signal of the signal processing system 41; And an operation system including a time measurement unit 45 and a measurement control unit 46 capable of calculating the distance to the object based on the output signal of the signal processing system 41. The signal determination circuit 49 Voltage Vth1 and Vth2 When crossing, the slope of a straight line passing the point where the voltage of the light receiving signal first crosses the threshold voltage Vth1 and the point where the voltage of the light receiving signal first crosses the threshold voltage Vth2, and the voltage of the light receiving signal is smaller than the threshold voltages Vth1 and Vth2. It is a distance measuring device characterized by judging whether a light reception signal is normal based on the time (P4-P1) from first crossing to the next (P4-P1).

  In this case, it can be determined with high accuracy whether the light reception signal is normal or not, and the measurement result can be output according to the highly accurate determination result.

  As a result, while suppressing the cost increase (for example, without using an expensive circuit such as an A / D converter), it is appropriate (regardless of whether the light reception signal is normal or not) regardless of the light reception signal. In particular, it is possible to output measurement results that are appropriate for the intended use of the device.

  Further, according to the object detection apparatus 100, even when the light reception signal is saturated (when the amplitude of the light reception signal can not be obtained), the tilt and the time (P4-P1) can be obtained, so the light reception signal is normal. It can be determined with high accuracy whether or not.

On the other hand, for example, in Japanese Patent Application Laid-Open No. 2004-184333, the pulse width of the light reception signal is measured using two threshold values, and the pulse width at the lower threshold is small even though the light reception signal of the reflected wave does not reach the upper threshold. There is disclosed a technique for judging that two signals are not combined when it is longer than the reference time width and not performing ranging.
However, this technique can not distinguish abnormal signals that satisfy the upper threshold. Further, since normality / abnormality of the light reception signal is determined and only distance measurement is not performed when it is determined that the light reception signal is abnormal, there is no expansibility as signal processing.

  Further, the signal determination circuit 49 determines that the light reception signal is not normal when the inclination is not in a predetermined relationship with the pulse width (time (P4-P1) or a value obtained by converting the time (P4-P1) into distance). Is preferred.

  Further, in the two-dimensional orthogonal coordinate system in which the signal determination circuit 49 has an axis for distance and an axis for voltage / time as two axes orthogonal to each other, the point determined by the pulse width and the slope has an inclination-pulse width curve (a predetermined relationship It is preferable to determine that the light reception signal is not normal when it is in a predetermined range which is deviated from the above).

  Further, it is preferable that there are a plurality of predetermined ranges, and the signal determination circuit 49 determines that the light reception signal is not normal when the point determined by the pulse width and the inclination is in any of the plurality of predetermined ranges.

In addition, it is preferable that at least two of the plurality of predetermined ranges overlap with each other.
In this case, as compared with the case where the ranges do not overlap (when the ranges are adjacent), it is possible to suppress the detection leak of the abnormal light reception signal.
In addition, the plurality of predetermined ranges do not have to overlap with each other.

Further, the predetermined range may be a square or a rectangle in which two sides perpendicular to each other are parallel to the two axes. That is, the predetermined range may have an axial lower limit (e.g., 0.0E + 00 (V / s)) related to voltage / time and an axial upper limit (e.g., 30 m) related to the distance. )
The predetermined range may be, for example, another shape such as a circle, an ellipse, a triangle, a square, a square other than a square, and a polygon having five or more sides.

  Further, when the voltage of the light reception signal crosses only the smaller one of the threshold voltages Vth1 and Vth2 based on the time (P4-P1), the signal judgment circuit 49 judges whether the light reception signal is normal or not. Is preferred.

  In addition, the light projection system 10 projects a plurality of light beams having different optical paths, and the light detection system 40 includes at least two lights corresponding to at least two lights reflected and received by an object among the plurality of light beams projected. A signal is output, and the calculation system is a first electric signal that is an electric signal determined to be normal in the determination system to the at least two electric signals and an electric signal that is determined not to be normal in the determination system When two electric signals are included, calculation of the distance based on at least the first electric signal is performed, and calculation of the distance based on the first electric signal as a measurement result by projection of light corresponding to the second electric signal It is preferable to output the result.

  Further, it is preferable that the plurality of lights are at least three lights in which the light paths are arranged, and among the at least three lights, the light paths of two lights corresponding to the first and second electrical signals are adjacent to each other.

  Further, the plurality of lights are at least three lights in which optical paths are arranged, and the arithmetic system is a light in which at least one light not including the light at both ends of the at least three lights corresponds to the second electric signal. And, when the light adjacent to one side of the at least one light and the light adjacent to the other side of the at least one light are light corresponding to a first electrical signal, the projection of the at least one light Among the calculation results of the distance based on the first electric signal corresponding to the light adjacent to one side and the calculation results of the distance based on the first electric signal corresponding to light adjacent to the other side as the measurement result by It is preferable to output the smaller difference from the calculation result of the distance based on the second electrical signal corresponding to at least one light.

  Further, the plurality of lights are at least three lights in which optical paths are arranged, and the arithmetic system is a light in which at least one light not including the light at both ends of the at least three lights corresponds to the second electric signal. And, when the light adjacent to one side of the at least one light and the light adjacent to the other side of the at least one light are light corresponding to a first electrical signal, the projection of the at least one light The smaller of the calculation result of the distance based on the first electrical signal corresponding to the light adjacent to one side and the calculation result of the distance based on the first electrical signal corresponding to light adjacent to the other side as the measurement result by It is preferable to output

  In addition, the plurality of lights are at least four lights in which the optical paths are arranged, and the computing system is configured to calculate that the at least two consecutive (series of) lights not including the light at both ends of the at least four lights are the second electric signal. And at least two of the light adjacent to one side of the at least two light and the light adjacent to the other side of the at least two light correspond to a first electrical signal, As a measurement result by the light projection closer to the other side of the light than the light adjacent to the one side among the two lights, the calculation result of the distance based on the first electric signal corresponding to the light adjacent to the other side is output A distance based on a first electrical signal corresponding to the light adjacent to one side as a measurement result by the light projection closer to the light adjacent to the one side than the light adjacent to the other side among the at least two lights It is preferable to output the calculation result of

  In addition, when the number of the at least two lights is an odd number, the calculation system is adjacent to the one side as a measurement result by projecting light between the light adjacent to one side and the light adjacent to the other side. The second electric signal corresponding to the intermediate light among the calculation result of the distance based on the first electric signal corresponding to the light and the calculation result of the distance based on the first electric signal corresponding to the light adjacent to the other side It is preferable to output the smaller difference from the distance calculation result based on.

  In addition, the calculation system may perform both calculation of the distance based on the first electrical signal and calculation of the distance based on the second electrical signal.

  In addition, the calculation system may only calculate the distance based on the first electrical signal. That is, it is not necessary to calculate the distance based on the second electrical signal.

  Further, according to a vehicle device (mobile device device) including the object detection device 100 (distance measurement device) and a vehicle (mobile object) on which the object detection device 100 is mounted, the object detection device 100 is provided for each pixel. Since the measurement result can be output stably and almost accurately, the vehicle can be safely controlled using the measurement result.

  Further, from the first viewpoint, in the distance measuring method of the present embodiment, a light emitting process of emitting light, light receiving in the light emitting process and reflected by the object are received and photoelectrically converted to an electric signal. And a signal processing step of performing at least one processing including a photoelectric conversion step of outputting, and a light receiving signal which is an electric signal output in the photoelectric conversion step, binarizing the threshold voltages Vth1 and Vth2 as a reference. A determination step of determining whether the light reception signal is normal based on an output signal of the signal processing step, a distance to an object based on a light projection timing in the light projection step and an output signal of the signal processing step In the determination step, when the voltage of the light reception signal crosses the threshold voltages Vth1 and Vth2 in the determination step, the voltage of the light reception signal first crosses the threshold voltage Vth1 and the voltage of the light reception signal is a threshold. Voltage V Whether the light reception signal is normal based on the slope of the straight line passing the point that first crosses h2 and the time from when the voltage of the light reception signal first crosses the smaller one of threshold voltages Vth1 and Vth2 to the next It is a distance measurement method characterized by performing determination of no.

  Further, from the second point of view, the distance measuring method of the present embodiment receives a light projecting step of light projection and light reflected and reflected by the object in the light projecting step and outputs an electric signal by receiving and photoelectrically converting the light. A signal processing step of performing at least one process including a photoelectric conversion process, a light reception signal which is an electric signal output in the photoelectric conversion process, and a process of binarizing the threshold voltages Vth1 and Vth2 as a reference; A determination step of determining whether the light reception signal is normal or not based on the output signal of the processing step, and the light emission timing and signal in the light projection step if the determination result in the determination step is affirmative And, in the determination step, the voltage of the light reception signal is the threshold voltage when the voltage of the light reception signal crosses the threshold voltages Vth1 and Vth2 in the determination step. Vth1 The slope of a straight line passing through the point at which the light reception signal crosses the threshold voltage Vth2 and the time from when the voltage of the light reception signal first crosses the smaller one of the threshold voltages Vth1 and Vth2 ( It is preferable to determine whether the light reception signal is normal or not based on P4-P1).

  In the distance measurement method of the present embodiment, it can be determined with high accuracy whether the light reception signal is normal or not, and the measurement result can be output according to the high accuracy determination result.

  As a result, while suppressing the cost increase (for example, without using an expensive circuit such as an A / D converter), it is possible to output an appropriate measurement result regardless of the light reception signal.

  Further, according to the distance measurement method of the present embodiment, the inclination and time (P4-P1) can be obtained even when the light reception signal is saturated (when the amplitude of the light reception signal can not be obtained). It is possible to determine with high accuracy whether or not it is normal.

  In the determination step, if the pulse width (time (P4-P1) or a converted value obtained by converting the time (P4-P1) into a distance) and the slope do not have a predetermined relationship, it is determined that the light reception signal is not normal. Is preferred.

  Further, in the determination step, in a two-dimensional orthogonal coordinate system in which an axis relating to distance and an axis relating to voltage / time are orthogonal to each other, a point determined by pulse width and slope has a slope-pulse width curve It is preferable to determine that the light reception signal is not normal when it is in a predetermined range out of the curve).

  Further, there are a plurality of predetermined ranges, and in the determination step, it is preferable to determine that the light reception signal is not normal when the point determined by the pulse width and the inclination is in any of the plurality of predetermined ranges.

  Further, it is preferable that at least two of the plurality of predetermined ranges overlap with each other.

  Further, the predetermined range may be a square or a rectangle in which two sides perpendicular to each other are parallel to the two axes.

  In the determination step, it is preferable to determine whether the light reception signal is normal or not based on the time (P4-P1) when the voltage of the light reception signal crosses only the smaller one of the threshold voltages Vth1 and Vth2.

  In the light projection process, a plurality of light beams having different optical paths are projected, and in the photoelectric conversion process, at least two electric signals corresponding to at least two lights reflected and received by the object among the plurality of light beams projected In the distance calculation step, the at least two electric signals are a first electric signal that is an electric signal determined to be normal in the determination step, and a second electric signal that is determined to be not normal in the determination step Calculation of the distance based on at least the first electric signal, and the calculation result of the distance based on the first electric signal as the measurement result by light projection corresponding to the second electric signal It is preferable to output

  Further, it is preferable that the plurality of lights are at least three lights in which the light paths are arranged, and among the at least three lights, the light paths of the lights corresponding to the first and second electric signals are adjacent to each other.

  Further, the plurality of lights are at least three lights arranged in an optical path, and in the distance calculation step, at least one light not including the light at both ends of the at least three lights is a light corresponding to the second electric signal. The at least one light if the light adjacent to one side of the at least one light and the light adjacent to the other side of the at least one light correspond to a first electrical signal; Among the measurement results by the light, among the calculation result of the distance based on the first electric signal corresponding to the light adjacent to one side and the calculation result of the distance based on the first electric signal corresponding to the light adjacent to the other side, It is preferable to output the smaller difference from the calculation result of the distance based on the second electrical signal corresponding to the at least one light.

  Further, the plurality of lights are at least three lights arranged in an optical path, and in the distance calculation step, at least one light not including the light at both ends of the at least three lights is a light corresponding to the second electric signal. And projecting the at least one light if the light adjacent to one side of the at least one light and the light adjacent to the other side of the at least one light correspond to a first electrical signal. The smaller of the calculation result of the distance based on the first electrical signal corresponding to the light adjacent to one side and the calculation result of the distance based on the first electrical signal corresponding to light adjacent to the other side as the measurement result by It is preferable to output

  Further, the plurality of lights are at least four lights in which the optical paths are arranged, and in the distance calculation step, the continuous (series of) at least two lights not including the light at both ends among the at least four lights are the second electricity. In the case where the light corresponding to the signal and the light adjacent to one side of the at least two lights and the light adjacent to the other side of the at least two lights correspond to a first electrical signal, Calculation result of the distance based on the first electrical signal corresponding to the light adjacent to the other side as the measurement result by the light projection closer to the light adjacent to the other side than the light adjacent to one side among the at least two lights And, as a result of measurement by light projection closer to the light on one side than the light on the other side among the at least two lights, a first electric signal corresponding to the light adjacent to the one side. It is preferable to output the calculation result of the distance based on Arbitrariness.

  Further, in the distance calculation step, when the number of the at least two lights is an odd number, it is adjacent to the one side as a measurement result by projection of light between the light adjacent to one side and the light adjacent to the other side. Of the calculation result of the distance based on the first electrical signal corresponding to the light and the calculation result of the distance based on the first electrical signal corresponding to the other side, the second electricity corresponding to the intermediate light It is preferable to output one having a smaller difference from the calculation result of the distance based on the signal.

  Further, the larger threshold value Vth2 of the two threshold values is set to a value (for example, 0.9 V) smaller by 10 to 30% of the saturation voltage (for example, 1.2 V) at which the voltage signal is saturated in the operational amplifier 48. It is preferable to set. If the threshold value Vth2 is too far from the saturation voltage, the accuracy of the gradient calculated by the threshold values Vth2 and Vth1 becomes low, and if the threshold value Vth2 is too close to the saturation voltage, the relatively unstable high voltage region (region near the peak) of the voltage signal This crosses the threshold value Vth2, which may reduce the measurement accuracy.

  The difference between the threshold values Vth1 and Vth2 is preferably 40 to 90% (e.g., 0.6 V) of the saturation voltage (e.g., 1.2 V). If the difference between the threshold values Vth1 and Vth2 is too small, the accuracy of the inclination becomes low, and if the threshold voltage Vth1 is lowered to make the difference large, it becomes easy to detect noise.

  In addition, an object detection apparatus 100 and a monitoring control apparatus 300 for obtaining object information (at least one of presence / absence of an object, position of an object, moving direction of an object, and moving speed of an object) based on an output of the object detection apparatus 100. And the object information can be stably acquired.

  In addition, the sensing device 1000 is mounted on a moving object, and the monitoring control device 300 determines the presence or absence of a danger based on at least one of position information and movement information of an object. Can provide useful information for risk avoidance.

In addition, a mobile device provided with the sensing device 1000 and a mobile body on which the sensing device 1000 is mounted is excellent in collision safety.
The configuration of the object detection device 100 according to the above embodiment can be changed as appropriate.

The values of the rising slope and pulse width of the light reception signal described in the above embodiment, the threshold values Vth1 and Vth2, and the saturation voltage of the operational amplifier 48 are merely examples, and can be changed as appropriate according to the application and specification of the apparatus.
For example, three or more threshold values may be used as a reference for binarizing the light reception signal set in the binarization circuit 44. For example, in addition to the threshold values Vth1 and Vth2, at least one threshold value including the threshold value Vth3 is set between Vth1 and Vth2, and when the light reception signal crosses at least Vth1 and Vth3, at least two straight lines crossing Vth1 and Vth3 respectively. The inclination may be used to calculate the distance to the object or to determine whether the light reception signal is normal or abnormal.
However, it is not a good idea to increase the number of thresholds. This is because it is necessary to add comparators by the increased number, which leads to an increase in cost.

  In the above embodiment, when performing Tm distance measurement, a timing intermediate between the timing when the rising edge of the light reception signal crosses the threshold Vth1 and the timing when the falling edge of the light reception signal crosses the threshold Vth1 is used. Alternatively, an intermediate timing may be used between the timing when the rise of the light reception signal crosses the threshold Vth2 and the timing when the fall of the light reception signal crosses the threshold Vth2.

  Also, in the signal processing system, as a processing circuit, a filter such as a low pass filter or a high pass filter may be incorporated instead of or in addition to the operational amplifier. Such a filter is preferably connected between the operational amplifier and the binarization circuit when the operational amplifier is incorporated, and is connected between the IV converter and the binarization circuit when the operational amplifier is not incorporated. Is preferred.

  The light projection system 10 is a scanning type using a deflector, but may be a non-scanning type not using a deflector. That is, the light projection system only needs to have at least a light source, and a lens for adjusting the light projection range may be provided at a later stage of the light source.

Moreover, in the said embodiment, although single LD11 (end-face light emission laser) is used as a light source, it is not restricted to this.
For example, an LD 11 array in which a plurality of LDs 11 are arrayed in one or two dimensions, a VCSEL (surface emitting laser), a VCSEL array in which VCSELs are arrayed in one or two dimensions, lasers other than semiconductor lasers, light sources other than lasers, etc. May be used. Examples of the LD 11 array in which a plurality of LDs 11 are one-dimensionally arranged include a stacked LD 11 array in which a plurality of LDs 11 are stacked, and an LD 11 array in which a plurality of LDs 11 are arranged in a row. For example, by replacing the LD 11 with a VCSEL as a semiconductor laser, the number of light emitting points in the array can be set larger.

  In addition, the light projecting optical system may not have the coupling lens, or may have other lenses.

  Further, the light projecting optical system and the light receiving optical system may not have the reflection mirror. That is, the light from the LD 11 may be made incident on the rotating mirror without turning back the light path.

  The light receiving optical system may not have the light receiving lens, or may have another optical element (for example, a light collecting mirror).

  Also, as the deflector, in place of the rotating mirror, for example, another mirror such as a polygon mirror (rotating polygon mirror), a galvano mirror, a MEMS mirror, etc. may be used.

  The synchronization system may not have a synchronization lens, or may have another optical element (for example, a focusing mirror).

  Moreover, in the said embodiment, although the vehicle was demonstrated to the example as a mobile body by which an object detection apparatus is mounted, this mobile body may be an aircraft, a ship, a robot etc., for example.

  Further, it is needless to say that the specific numerical values, shapes and the like used in the above description are merely examples and can be suitably changed without departing from the scope of the present invention.

  As is apparent from the above description, the object detection apparatus 100, the sensing apparatus 1000, the mobile apparatus, the distance measurement method, the distance measurement processes 1 to 8, and the distance measurement data acquisition processes 1 to 6 of the above embodiment This technology uses the so-called Time of Flight (TOF) method to measure distance, and can be widely used in industrial fields such as motion capture technology, range finder, and three-dimensional shape measurement technology as well as sensing in moving objects . That is, the object detection apparatus of the present invention may not necessarily be mounted on a mobile body.

Below, the thought process in which inventors came to draft the said embodiment is demonstrated.
Conventionally, a light projecting unit, a light detecting unit, and a signal processing unit are included, and the light beam from the light projecting unit is irradiated to the object to be measured, and the reflected light from the object to be measured is received by the light detecting unit. The time from the light projection timing of the light section to the light reception timing of the light detection section, the phase delay is detected by processing the signal from the light detection section by the signal processing section to measure the round-trip distance to the measurement object A distance measuring apparatus using a Time of Flight (TOF) method is widely used in sensing of vehicles and the like, motion capture technology, and industrial fields such as distance measuring.

  One example is laser radar widely used in aircraft, railways, vehicles, and so on. Various types of laser radars are known, but as disclosed in, for example, Japanese Patent Laid-Open No. 2004-184333, laser light emitted from a light source is scanned by a rotating mirror, and light reflected by an object is reflected. Is detected again by the light detection unit via the rotating mirror, and the signal processing unit (signal reception signal) from the light detection unit is processed by the signal processing unit to detect the presence or absence of an object in a desired range and the distance to the object There is a scanning laser radar that can

  In distance measurement with a laser radar, for example, in the case of performing Tr distance measurement or Tm distance measurement by detecting timing at which a signal from a light detection unit that receives reflected light from an object irradiated with laser light crosses a threshold value, For example, if distance measurement (distance calculation) is performed based on an abnormal light reception signal generated by two peak comets, a distance measurement error occurs.

  Therefore, in Patent Document 1, in order to avoid the occurrence of such a ranging error, the A / D converter is incorporated in the signal processing unit, and the peak position of the signal (light reception signal) from the light detection unit is calculated by differential calculation processing. The distance is calculated using the peak position. However, a circuit using an A / D converter is expensive and is not suitable for being incorporated into a distance measuring device of a mobile object such as a vehicle for which mass production is required.

  That is, in Patent Document 1, there is room for improvement with regard to enabling output of an appropriate measurement result regardless of the electrical signal output from the light detection unit while suppressing increase in cost.

  Therefore, the inventors proposed the above-described embodiment so as to be able to output an appropriate measurement result regardless of the electrical signal output from the light detection system while suppressing the cost increase.

  DESCRIPTION OF SYMBOLS 10 ... Projection system, 11 ... LD (light source), 26 ... Rotation mirror (a part of projection system) 40 ... Photodetection system, 41 ... Signal processing system, 42 ... PD for time measurement 43) IV converter (part of light detection system) 44: binarization circuit (part of signal processing system) 45: time measurement part (part of operation system) 46: measurement control part (Part of calculation system) 49: Signal determination circuit (determination system) 100: Object detection device.

Patent No. 5804467

Claims (16)

A light projection system including a light source that emits light based on a light emission signal;
A light detection system that receives light emitted from the light projection system and reflected by an object, and outputs an electrical signal according to the amount of light received;
An arithmetic system for determining a distance to the object based on the light emission signal and the electrical signal output from the light detection system;
When the voltage of the electrical signal crosses the threshold voltages Vth1 and Vth2, the slope of a straight line passing the point at which the voltage first crosses the threshold voltage Vth1 and the point at which the voltage first crosses the threshold voltage Vth2 and the voltage It is determined whether or not the electric signal is normal based on the time from the first crossing of the smaller one of the threshold voltages Vth1 and Vth2 to the next crossing.   A point plotted based on the time or the converted value of the voltage of the electric signal and the inclination in a two-dimensional orthogonal coordinate system represented by the inclination or the conversion value obtained by converting the time or the time to another unit and the inclination If the curve is plotted in a predetermined range out of the curve representing the predetermined relationship represented by the time or the point determined by the conversion value and the slope, the curve The distance measuring device according to claim 1, wherein the electric signal is determined not to be normal when in a predetermined range.   The distance measuring apparatus according to claim 2, wherein a plurality of the predetermined ranges are set based on a relationship between the time or the magnitude of the conversion value and the magnitude of the inclination.   The distance measuring device according to claim 3, wherein at least two of the plurality of predetermined ranges overlap with each other.   When the voltage of the electrical signal crosses only the smaller one of the threshold voltages Vth1 and Vth2, it is determined whether the electrical signal is normal or not based on the time or the magnitude of the conversion value. The distance measuring device according to any one of claims 1 to 4.   The distance measurement according to any one of claims 1 to 5, wherein the distance determined based on the electric signal is not the distance to the object for the electric signal determined not to be normal. apparatus. The light projection system projects the first light and the second light at least where the light projection position is adjacent, and the light detection system is configured such that the first light is reflected by the object. And the second reflected light reflected by the object, and the first reflected light and the first electric signal corresponding to the second reflected light, respectively. Output a second electrical signal,
When it is determined that the first electrical signal is normal and the second electrical signal is not normal, the computing system determines a first distance based on the first electrical signal, The distance measuring device according to any one of claims 1 to 6, wherein the first distance is output as a measurement result by the projection of the second light. The light projection system projects a plurality of lights whose light projection positions are adjacent from one end to the other end,
The light detection system receives a plurality of reflected lights in which each of the plurality of projected lights is reflected by the object, and outputs a plurality of electrical signals corresponding to the plurality of reflected lights,
The computing system determines a plurality of distances corresponding to each of the plurality of electrical signals;
The distance based on the mth electrical signal corresponding to the mth (where m is an integer) light from one end to the other among the plurality of projected lights is defined as the mth distance From the mth light to the other end, where the nth (where n is an integer) light is defined as the m + nth light, and a distance based on the m + nth electrical signal corresponding to the m + nth light If we define m as the n + th distance,
When it is determined that the mth electrical signal and the m + 2n + 1st electrical signal are normal, and the m + 1st electrical signal to the m + 2nth electrical signal are determined not to be normal,
Outputting the m-th distance as a measurement result of the m-th light projection;
Outputting an m + 2n + 1st distance based on the m + 2n + 1th electrical signal as a measurement result by the projection of the m + 2n + 1st light,
outputting the m-th distance as a measurement result of light projection from the m + 1st light to the m + nth light,
The distance measuring apparatus according to any one of claims 1 to 6, wherein the m + 2n + 1st distance is output as a measurement result of light projection from the m + n + 1st light to the m + 2nth light. The light projection system projects a plurality of lights whose light projection positions are adjacent from one end to the other end,
The light detection system receives a plurality of reflected lights in which each of the plurality of projected lights is reflected by the object, and outputs a plurality of electrical signals corresponding to the plurality of reflected lights,
The computing system determines a plurality of distances corresponding to each of the plurality of electrical signals;
The distance based on the mth electrical signal corresponding to the mth (where m is an integer) light from one end to the other among the plurality of projected lights is defined as the mth distance From the mth light to the other end, where the nth (where n is an integer) light is defined as the m + nth light, and a distance based on the m + nth electrical signal corresponding to the m + nth light If we define m as the n + th distance,
When it is determined that the mth electrical signal and the m + 2n + 2th electrical signal are normal and the m + 1st electrical signal to the m + 2n + 1st electrical signal are not normal,
Outputting the m-th distance as a measurement result of the m-th light projection;
Outputting an m + 2n + 2th distance based on the m + 2n + 2th electrical signal as a measurement result by projecting the m + 2n + 2th light,
outputting the m-th distance as a measurement result of light projection from the m + 1st light to the m + nth light,
The m + 2n + 2th distance is output as a measurement result by projecting light from the m + n + 2th light to the m + 2n + 1st light,
As a measurement result by light projection to the m + n + 1st light, it is characterized by outputting one of the mth distance and the m + 2n + 2th distance, which has a smaller difference between the m + n + 1th distance based on the m + n + 1th electrical signal. The distance measuring device according to any one of claims 1 to 6, wherein The light projection system projects a plurality of lights whose light projection positions are adjacent from one end to the other end,
The light detection system receives a plurality of reflected lights in which each of the plurality of projected lights is reflected by the object, and outputs a plurality of electrical signals corresponding to the plurality of reflected lights,
The computing system determines a plurality of distances corresponding to each of the plurality of electrical signals;
The distance based on the mth electrical signal corresponding to the mth (where m is an integer) light from one end to the other among the plurality of projected lights is defined as the mth distance From the mth light to the other end, where the nth (where n is an integer) light is defined as the m + nth light, and a distance based on the m + nth electrical signal corresponding to the m + nth light If we define m as the n + th distance,
When it is determined that the mth electrical signal and the m + 2n + 2th electrical signal are normal and the m + 1st electrical signal to the m + 2n + 1st electrical signal are not normal,
Outputting the m-th distance as a measurement result of the m-th light projection;
Outputting an m + 2n + 2th distance based on the m + 2n + 2th electrical signal as a measurement result by projecting the m + 2n + 2th light,
outputting the m-th distance as a measurement result of light projection from the m + 1st light to the m + nth light,
The m + 2n + 2th distance is output as a measurement result by projecting light from the m + n + 2th light to the m + 2n + 1st light,
The smaller distance of the mth distance and the m + 2n + 2th distance is output as a measurement result of light projection to the m + n + 1st light. Distance measuring device as described. The distance measuring device according to any one of claims 1 to 10,
A mobile unit on which the distance measurement device is mounted. A floodlighting process to floodlight,
A photoelectric conversion step of receiving and photoelectrically converting the light projected in the light projection step and reflected by the object to output an electric signal;
A distance calculation step of calculating the distance to the object based on the light projection timing in the light projection step and the electric signal output in the photoelectric conversion step;
When the voltage of the electrical signal crosses the threshold voltages Vth1 and Vth2, the slope of a straight line passing the point at which the voltage first crosses the threshold voltage Vth1 and the point at which the voltage first crosses the threshold voltage Vth2 and the voltage Determining whether the electric signal is normal based on the time from the first crossing of the smaller one of the threshold voltages Vth1 and Vth2 to the next crossing. A floodlighting process to floodlight,
A photoelectric conversion step of receiving and photoelectrically converting the light projected in the light projection step and reflected by the object to output an electric signal;
When the voltage of the electrical signal crosses the threshold voltages Vth1 and Vth2, the slope of a straight line passing the point at which the voltage first crosses the threshold voltage Vth1 and the point at which the voltage first crosses the threshold voltage Vth2 and the voltage Determining whether the electrical signal is normal based on the time between the first crossing of the smaller one of the threshold voltages Vth1 and Vth2 and the next crossing;
A distance calculation for calculating the distance to the object based on the light emission timing in the light emission process and the electric signal output in the photoelectric conversion process when the determination result in the determination process is affirmative. A distance measurement method comprising the steps of:   In the determination step, the time or the converted value of the voltage of the electric signal and the inclination are represented in the two-dimensional orthogonal coordinate system represented by the inclination or the conversion value obtained by converting the time or the time into another unit. When the points plotted on the basis are plotted in a predetermined range out of the curve representing the predetermined relationship represented by the point determined by the time or the conversion value and the slope, the relationship is represented. The distance measuring method according to claim 12 or 13, wherein the electric signal is determined not to be normal when in a predetermined range out of the curve. There are a plurality of the predetermined ranges based on the relationship between the time or the magnitude of the conversion value and the magnitude of the inclination,
In the determination step, when the point plotted based on the time or the conversion value of the voltage of the electric signal and the inclination is in any of the plurality of predetermined ranges, it is determined that the electric signal is not normal The distance measuring method according to claim 14, characterized in that:   The determination according to any one of claims 12 to 15, wherein, in the determination step, the determination is performed based on the time when the voltage crosses only the smaller one of the threshold voltages Vth1 and Vth2. How to measure distance.