JP3365814B2 - Distance speed measurement device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance / velocity measuring apparatus, and more particularly to an apparatus for detecting an obstacle suitable for an automobile collision prediction apparatus .
The present invention relates to a distance / velocity measuring device, and more particularly to a means for avoiding interference between a distance / velocity measuring device mounted on its own collision prediction device and that of another vehicle or a means for discriminating between a signal and a noise. . 2. Description of the Related Art In a vehicle equipped with an active collision prediction sensor for projecting a light beam and detecting reflected light from an obstacle, there is a problem of interference in which a light beam transmitted from another vehicle is erroneously detected. There is. As a method to avoid erroneous measurement due to interference,
Conventionally, a method using polarized light as disclosed in Japanese Patent Application Laid-Open No. 4-79552 and a method as disclosed in Japanese Patent Application Laid-Open No. 61-149879, in which intervals between light emitting pulses are made random, are known. The former is to avoid the erroneous detection of sensing light from an oncoming vehicle by providing a light projecting / receiving unit having a polarization direction that forms an acute angle in the horizontal direction.
Shown in If the polarization direction of one of the light receiving portions of the two opposing vehicles is represented by AB, the polarization direction of the other vehicle having the light receiving portion of the same principle becomes CD, and the two vehicles cross each other. Interference is reduced. FIG. 7 shows the latter case. The intervals T _i (i = 1, 2, 3,...) Of the light transmission pulses are driven so as to be random, and the beam of the light receiving section is opened in synchronization with the interval T _i to transmit light transmission pulses from other vehicles. Avoids erroneous measurement. Specifically, assuming that the width of the light transmission pulse is t ₀ , a gate signal having a pulse width longer by t _{1 than the} light transmission pulse width is applied to the light receiving unit gate in synchronization with the light transmission pulse. t ₁
Is chosen to be a sufficient time interval for the light to travel back and forth to the obstacle. The interval T _{i of} light transmission pulses (i = 1, 2, 3,...)
..) Are random, so that the possibility of erroneously detecting sensing light from an oncoming vehicle can be reduced. Although it is important to determine whether a signal or noise occurs when the S / N ratio of a signal is poor, as in the case of interference,
As a conventional method for determining this, it is performed that the sum of signals from a plurality of light receiving units is compared with a predetermined threshold, and when the sum exceeds this threshold, the signal is determined. [0006] However, the method of using polarized light as a method of reducing interference generally uses AB and C in FIG. 6 except that the polarization direction is at 45 degrees with the horizontal.
D is not orthogonal. In the scattering by an obstacle, the polarization direction is not preserved. For these reasons, there is no guarantee that the scattered light from the opponent's car or obstacle will be completely eliminated, and there is a problem in terms of the signal S / N ratio because the amount of received light is small. Further, the interval T _{i of the} light transmission pulse shown in FIG.
(I = 1,2,3 ......) method to randomly, in order to ensure the spacing is random, it is necessary to increase the interval T _i as compared to the light-sending the pulse width t ₀ But,
On the other hand, when viewed from the point of monitoring the obstacle, it is not allowed to so much increase the interval T _i. Therefore, the light transmission pulse width t ₀ is selected to be considerably short, which requires a high-speed signal processing circuit, and thus has a disadvantage of being expensive. Further, the method of comparing the total amount of received light with a threshold value as a method of determining whether the signal is noise or noise is affected by the reflectance of an obstacle, and it is difficult to make a determination based on a fixed threshold value. There is a disadvantage that there is. The present invention solves the above-mentioned disadvantages of the prior art, makes it possible to predict the distance and speed in an extremely short time, and furthermore, eliminates the possibility of interference or erroneous detection.
It is an object to provide a speed prediction device. The principle of the present invention will be described with reference to FIG. The sensors 1 and 2 each include a light projecting unit 9 and a light receiving unit 10, and a light projecting unit 11 and a light receiving unit 12, respectively. The light projecting units 9 and 11 project a plurality of light beams 5, 6 and 7, 8 respectively. The light receiving units 10 and 12 detect scattered light generated by the intersection of the light beam and the obstacle 4, respectively. These two
It is assumed that two sensors are installed on the vehicle 3 with an interval of the base line length, and an obstacle 4 such as another vehicle is heading toward the vehicle 3 at a relative speed indicated by an arrow V. Light beams 5,6
Lights 7 and 8 are alternately emitted in time series in numerical order. Specifically, after the light beam 5 is emitted in a pulsed manner, the light beam 6 is emitted, the light beams 7 and 8 are sequentially emitted, and the light beam 5 is emitted again. It is. The point at which the obstacle 4 first cuts the light beam 5 is defined as P
_1, then the point of cutting the light beam 6 in the first and P _2. Point P
_The light scattered by ₁ is simultaneously detected by the light receiving units (position detecting devices) 10 and 12 provided in the sensors 1 and 2, and the time and the distance from the base line are obtained by the principle of triangulation. Similarly also measured the distance from the detection time and the baseline at point P _2, from the distance and time information at these two points, the vertical component is required to baseline velocity V, for example obstacle 4. It is assumed that the obstacle 4 also has the sensing device represented by the sensors 1 and 2 and emits a plurality of light beams in time series. At this time, the light receiving units 10 and 12 of the vehicle 3 may erroneously detect the light beam. However, since the light beams are emitted alternately in time series, the light beams are simultaneously transmitted to the light receiving units 10 and 12. It will not be detected. On the other hand, the light scattered by the obstacle 4 is simultaneously detected by the light receiving units 10 and 12. Therefore, it is possible to discriminate between the scattered light of the own light beam and the light beam of another vehicle by utilizing this synchronism, and it is possible to prevent so-called interference. In addition, the determination as to whether the signal is a noise is made by the logic of the output of the circuit element for determining the synchronism described above and the output of the comparator for comparing the output voltage corresponding to the total amount of received light with a predetermined threshold. By taking the product, it is possible to determine with higher accuracy than to determine whether the signal is a signal only from the sum of the light amounts. According to the present invention, a plurality of light projecting units and a light receiving unit are arranged at a distance of a base line length, and a light beam for obstacle detection is projected from the light projecting unit alternately in time series. When light scattered by obstacles is detected by multiple light-receiving units simultaneously, the light scattering position (distance from the base line length) is detected by the principle of triangulation,
Find the time at that time. A moving time and a moving distance are obtained from two or more detected positions and times, and a relative speed perpendicular to the base line is detected. At the time of position detection, data obtained when scattered light is simultaneously detected by a plurality of light receiving units is made valid, so that erroneous detection of a light beam of another vehicle as a signal is prevented. FIG. 2 shows an embodiment of the present invention. FIG. 2 shows an example of a signal processing circuit of the light receiving unit.
Corresponds to a circuit connected to the lens 20 and the PSD 21 and a circuit connected to the lens 40 and the PSD 41, respectively. Since both are the same circuit, only one will be described. The signal processing circuit includes preamplifiers 22, 23,
2-channel AGC 24, divider 25, output terminal 26,
It comprises an adder 27 and a comparator 28. The output from the comparator 28 together with the output signal from the comparator 31 which is the output signal from the sensor 2 and the logic element 29
, And are logically ANDed to form an output signal 30. As the preamplifiers 22 and 23, logarithmic amplifiers can be used in addition to linear amplifiers. Further, a narrow-band filter corresponding to the modulation frequency of the light-emitting unit whose luminance has been modulated can be arranged at the next stage. Next, the operation will be described. An optical pulse having a period t and a duration T shown in FIG. 3 is emitted from a light emitting unit (not shown) in a time series alternately with this as one unit, intersects with an obstacle (not shown), and is scattered. Then, the light spot images 50 and 51 are simultaneously formed on the PSDs 21 and 41 by the lenses 20 and 40. Photocurrents I ₁ and I ₂ are generated corresponding to the positions of the light spot image 50 on the PSD 21, and current / voltage conversion is performed by the preamplifiers 22 and 23, respectively, and the two-channel AGC is performed.
After being amplified at 24, the signal is supplied to a divider 25, which outputs an output signal 26 corresponding to the position of the light spot image 50 on the PSD 21.
Is obtained. The two-channel AGC 24 amplifies the output voltages from the preamplifiers 22 and 23 with the same amplification corresponding to the light intensity of the light spot image 50. In other words,
When the light intensity is weak, it has a high gain, and when it is strong, it has a low gain and outputs a constant voltage. The output signal of the two-channel AGC 24 is supplied to a divider 25 and also to an adder 27. Upper and lower limiters are provided at the output end of the two-channel AGC 24.
It is desirable to cut the input signal beyond the proper operating range of the channel AGC 24. The output signal of the adder 27 corresponding to the total amount of incident light is
, Is compared with a predetermined threshold value, is converted into a binary signal, and is supplied to the logic circuit 29. Logic circuit 29
Represents the binary signal from the comparator 28 and the light spot image 5
The logical product of the binary signal and the binary signal corresponding to 1 is obtained, and the output signal 30 is output only when the binary signal changes simultaneously. More specifically, even when the light intensity of the light spot images 50 and 51 is low and the S / N is reduced, the comparator 2
As shown in FIGS. 4 (a) and 4 (b), the outputs 8 and 31 are pulse trains with partial omission, and the binary signal output signal 30 shown in FIG. 4 (c) is obtained. Light spot image is P
The output signal 30 when not supplied to the SDs 21 and 41 is 0.
In view of the above, there is a clear difference. Therefore, erroneous detection can be prevented by monitoring the output signal 30. In other words, the output signal 30 makes use of a gate circuit (not shown) provided in the middle of the signal processing circuit, or outputs the output signal 30 to a CPU (not shown).
And send it as software. Specifically, FIG.
When the number of binary signal pulses shown in (1) is counted and the number of times exceeds a predetermined number, it is determined that the accuracy as a signal is high and the hardware circuit is driven, or it is determined whether the signal is a software signal. Next, the features of this embodiment will be described. Since the two-channel AGC 24 is inserted, even if there is a change in the intensity of the input signal of about 30 dB, the output signal is substantially constant. Light spot image 5
Since input signals having substantially the same value are supplied to the comparators 28 and 31 corresponding to 0 and 51,
Almost correct output values can be obtained even if the threshold values of 8 and 31 are the same, and the output signal of the logic circuit 29 enables correct determination of synchronization. Therefore, it is possible to provide effective means for reducing interference or discriminating between noise and a signal. This embodiment can be modified in various ways. It goes without saying that the two-channel AGC 24 can use two independent AGCs in parallel. Also, free amplifier 2
If a logarithmic amplifier is used as 2, 23, divider 2
Instead of 5, a subtractor can be used. Logic circuit 2
5, as shown in FIG. 5, by simultaneously considering the logical product of the driving pulses 60 for driving the light projectors 9 and 11 in FIG. 1, an output signal 30 that enables a more accurate determination can be obtained. . In the case of FIG. 5, it is desirable to slightly increase or slightly delay the pulse width of the light emitting section drive signal in consideration of the signal detection delay. As described above, according to the present invention, interference with a distance / velocity measuring device of another vehicle equipped with a distance / velocity measuring device having the same shape as the collision prediction device of the own vehicle is provided. Can be avoided, and it is possible to accurately determine whether the signal is a noise or noise. Therefore, it is possible to obtain a highly accurate distance and its speed signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the principle of the present invention. FIG. 2 is a diagram showing an embodiment of the present invention. FIG. 3 is a diagram showing an optical pulse train having a period t and a duration T. FIG. 4 is a diagram illustrating a binary signal extraction circuit. FIG. 5 is a diagram showing a binary signal extracting circuit in which a driving pulse is also considered. FIG. 6 is a diagram illustrating a polarization method. FIG. 7 is a diagram for explaining a method of randomizing intervals of light projection pulses. [Description of Signs] 4 Obstacles 5, 6, 7, 8 ... Light Beams 9, 11 ... Light Projecting Units 10, 12 ... Light Receiving Units 20, 40 ... Lenses 21, 41 ... PSD 22, 23 ... Preamplifiers 24 ... 2 Channel AGC 25 ... Divider 26 ... Output terminal 27 ... Adders 28 and 31 ... Comparator 29 ... Logic element 30 ... Output signal

Continuation of front page (56) References JP-A-48-74985 (JP, A) JP-A-2-291913 (JP, A) JP-A-3-24410 (JP, A) JP-A-4-164280 (JP) JP-A-5-52957 (JP, A) JP-A-5-107055 (JP, A) JP-A-5-240639 (JP, A) JP-A-6-3143 (JP, A) 6-242240 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/00 G01P 3/00 G01D 21/00 G01S 17/00

Claims (1)

(57) [Claims] [Claim 1] A compound that alternates in time series with respect to an obstacle
A light projecting unit for projecting several light beams for obstacle search is arranged at a base line distance from each other, and the obstacle search is performed.
Scattering point position direction where the inspection light beam is scattered by the obstacle
A distance / velocity measuring apparatus , comprising: a plurality of light receiving units for detecting the distance;