JPH0643176A - Spatial filter type speedometer and vehicle control system incorporating the same - Google Patents

Abstract

PURPOSE:To obtain a spatial filter type speedometer which outputs a speed detection signal when speed is properly measured and outputs a malfunction signal when the amount of reception light does not allow the speed to be measured. CONSTITUTION:When reflection light strength from an object to be measured is detected according to the signal received by a comb-type light reception element and it is judged that the reflection light intensity is not within a measurement range prescribed by a saturation level 6 and a non-detectable level 7 which are preset, it is Judged that the speed cannot be measured and a malfunction signal is outputted. Therefore, the speed measurement result when no malfunction signal is output is extremely reliable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial filter type speed measuring device for detecting the ground speed of an automobile or the like in a non-contact manner and a vehicle control system equipped with the speed measuring device.

[0002]

2. Description of the Related Art Conventionally, a spatial filter type velocity measuring device is mounted on an automobile or the like and is widely used as a vehicle speedometer. For example, as shown in FIG. 5, this vehicle speedometer irradiates a road surface 52 with light from a lamp 51, and the reflected light from the road surface 52 is received by a comb-shaped light receiving element 54 via a lens 53. A differential output signal is obtained from the received signal in the differential circuit 55, and this signal is output to the speed detection circuit 5
To enter. In the speed detection circuit 5, this signal is shaped into a waveform through the self-tracking bandpass filter 56, the center frequency is estimated by the center frequency estimation circuit 57, and this frequency is converted into a voltage by the frequency / voltage conversion circuit (F / V) 58. Convert to and output the speed of the car. The speed output is 0-5
It is an analog output of V.

[0003]

However, in such a conventional spatial filter type velocity measuring device, when there is a decrease in illuminance due to deterioration of the light source or dirt adhering to the device, the reflectance of newly installed asphalt or the like is reduced. When the road surface is low, the speed output may be 0 V due to a decrease in the light intensity received as a signal even if the vehicle is moving, and the vehicle speed may be measured as 0 km / h. In addition, in a situation where there is a high reflectance such as snow on the road surface and ambient light such as sunlight is present, the saturation of the photodetector (comb-shaped light receiving element 54 in FIG. 5) or the amplifier causes The speed output may be 0V.

Further, in recent years, a vehicle control system has been studied in which the output of the speed measuring device is compared with the rotation speed of the wheel of the automobile to control acceleration, deceleration and stability of the vehicle. The filter-type speed measuring device has a problem in that the reliability of the speed output is low due to the above-mentioned problems and is not suitable for vehicle control.

The present invention solves the above-mentioned problems. In addition to the velocity output of the spatial filter type velocity measuring device, the intensity of reflected light from the object to be measured is detected, and the amount of received light for which velocity measurement is impossible is performed. It is an object of the present invention to provide a spatial filter type velocity measuring device in which the reliability of velocity output is improved by detecting a malfunction and outputting a malfunction signal. Also,
An object of the present invention is to provide a vehicle control system having a safety function by mounting the spatial filter type speed measuring device to improve the reliability of speed output.

[0006]

In order to achieve the above object, the invention of claim 1 comprises a light projecting means for irradiating a measuring object with light and a light receiving element for receiving the reflected light from the measuring object. In a spatial filter type velocity measuring device for measuring velocity by detecting a spatial filter frequency from a light receiving signal of the light receiving element, a detection for detecting a reflected light intensity from the measurement object from a light receiving signal of the light receiving element Means and output means for outputting a malfunction signal based on the reflected light intensity detected by the detection means. The invention of claim 2 comprises a comparing means for comparing a preset saturation level and undetectable level with the reflected light intensity, and by this comparing means, the reflected light intensity is defined by the saturated level and undetectable level. When it is detected that it is not within the range, the output means outputs a malfunction signal. According to the invention of claim 3, the light projecting means is pulse-driven. According to a fourth aspect of the present invention, an aperture stop is provided at a focal position of a light receiving lens that receives reflected light from the measurement target, and the aperture stop is a slit having a narrow width with respect to a relative moving direction of the measurement target. It is what According to a fifth aspect of the present invention, there is provided a vehicle control system equipped with the spatial filter type speed measuring device, wherein when the output means outputs a malfunction signal, a vehicle control by the spatial filter type speed measuring device is changed to another device. The control is switched to the vehicle control by.

[0007]

According to the structure of claim 1, the detecting means detects the intensity of the reflected light from the object to be measured from the light receiving signal of the light receiving element, and based on the intensity of the reflected light, the reflection whose velocity cannot be measured. When the light intensity is obtained, the malfunction signal is output by the output means. Therefore, the speed measurement result when this malfunction signal is not output is highly reliable. According to the configuration of claim 2, when the comparison unit detects that the reflected light intensity is not within the range defined by the preset saturation level and undetectable level, the output unit outputs the malfunction signal. . Therefore, it becomes possible to deal with the case where strong light is incident on the light receiving element or the illuminance is reduced due to deterioration of the light projecting device assuming an unexpected situation, and speed measurement is performed when a malfunction signal is not output. The result is reliable. According to the structure of claim 3, the SN ratio of the detectable signal can be increased by pulse-driving the light projecting means. According to the configuration of claim 4, since the aperture stop is a slit having a narrow width with respect to the relative movement direction of the measurement object, only the reflected light component parallel to the optical axis is received by the light receiving element, and The depth of focus becomes deeper as a system. According to the configuration of claim 5, when the output unit outputs the malfunction signal, the vehicle control by the spatial filter type speed measuring device is switched to the vehicle control by another device, so that the vehicle control system has a safety function. You can

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a signal output of a spatial filter type velocity measuring device. In this embodiment, the comb-shaped light receiving element 1 having a spatial filter function is used as a photodetector for receiving the reflected light emitted from the light projecting means (not shown) and reflected by the target object. In the comb-shaped light receiving element 1, each light receiving element is alternately connected to obtain a differential output of the spatial filter, and each alternately connected light receiving element is connected to each of the amplifiers 2 and 3. A differential circuit 4 is connected to the output sides of the amplifiers 2 and 3, and a speed detection circuit 5 is connected to the output side of the differential circuit 4. The differential outputs of the amplifiers 2 and 3 are obtained in the differential circuit 4, and based on the spatial filter signal as this differential output,
The speed detection circuit 5 calculates and outputs the speed.
The output voltage in this case is 0 to 5V. It should be noted that the illustration of the light projecting means is omitted in FIG.

On the other hand, saturation level 6 and undetectable level 7
Is set in advance, and the saturation level 6 or the undetectable level 7 is detected in the comparison circuits 8, 9, 10, and 11 for detecting whether or not the intensity of the reflected light reflected by the target object is within a predetermined range. And the output (reflected light intensity) of each amplifier 2 and 3 are compared. The comparison circuits 8 and 9 compare the outputs of the amplifiers 2 and 3 with the saturation level 6, respectively, and the comparison circuits 10 and 11 compare the outputs of the amplifiers 2 and 3 with the undetectable level 7, respectively. The output ends of the comparison circuits 8 and 9 are connected to the input end of the OR circuit 12, the output ends of the comparison circuits 10 and 11 are connected to the input end of the OR circuit 13, and the OR
The output terminals of the circuits 12 and 13 are connected to the input terminal of the OR circuit 14. In this way, by taking the logical sum of the output signals from the comparison circuits 8, 9, 10, and 11, the comparison circuits 8, 9, 1
This is detected when the reflected light intensity of any one of 0 and 11 is not within the range defined by the saturation level 6 and the undetectable level 7. If it is determined from this detection result that the malfunction is not within the above range, the OR circuit 1
A malfunction signal is output from 4.

The amplification degrees of the amplifiers 2 and 3 are set so as not to be saturated at the light receiving level of an assumed road surface condition (for example, snow and sunlight), but strong light is incident on a part of the light receiving element. Saturation level 6 is set assuming an unpredictable situation such as Further, the undetectable level 7 makes it possible to detect an erroneous operation due to deterioration of the light source that illuminates the measurement object or a decrease in the amount of received light due to dirt adhering to the speed measuring device during traveling. As described above, while the speed analog signal detected by the speed detection circuit 5 is output, when the malfunction is determined, the malfunction signal is output from the OR circuit 14, so that the speed output of this speed measuring device can be detected. It is possible to guarantee that it is within the range by a malfunction signal. Furthermore, in a vehicle control system equipped with this speed measuring device, when a malfunction signal is output, the vehicle control by the spatial filter type speed measuring device is switched to the vehicle control by another device. The property is improved.

FIG. 2 shows a circuit configuration of signal processing of the speed analog output and the malfunction signal output. A switching thyristor (for example, a silicon bidirectional switch) 17 is connected to the speed analog output circuit 15, and the malfunction signal output circuit 1
6 includes a NOT circuit 18 and a switching thyristor 19
And are connected. The output terminal of the NOT circuit 18 is connected to the gate of the switching thyristor 17,
Depending on the ON / OFF output of the T circuit 18, whether or not the switching thyristor 17 is conducted is determined. Further, one end of the switching thyristor 19 is grounded.

When the malfunction signal is not output from the malfunction signal output circuit 16, the output of the NOT circuit 18 is turned on, the switching thyristor 17 is turned on, and the output voltage from the speed analog output circuit 15 is directly output. . The output voltage in this case is 1 to 5V. on the other hand,
When a malfunction signal is output from the malfunction signal output circuit 16, the output of the NOT circuit 18 is turned off and the switching thyristor 17 is not conducted, so that the output from the speed analog output circuit 15 is cut off. At this time, since the switching thyristor 19 whose one end is grounded is rendered conductive, the output voltage becomes 0V. That is, the speed output is 1 to 5 V within the measurement range, and is 0 V only when a malfunction signal is output. Therefore, the reliability of the speed measurement result when the malfunction signal is not output is increased, and The reliability of the speed measuring device is improved. Further, even when the illuminance is reduced due to the life of the light source and the performance of the speed measuring device is deteriorated, a malfunction signal is output, so that such a situation can be detected. It will be possible to inform the maintenance time.

Next, the spatial filter type velocity measuring device according to the second embodiment will be explained with reference to FIG. In this embodiment, a pulse-modulated infrared LED 2 is used as a light source (projecting means).
1 is used, the spatial filter is composed of a prism array 22, and two pin PDs (pin photo diodes) 23 and 24 are used as light receiving elements. This p
The signals received by the inPDs 23 and 24 are amplifiers 25 and 26.
Is amplified at and outputs a pulse signal. This embodiment is different from the first embodiment in that the peak level detection circuit 2
7 and 28, the peak level of the pulse signal is detected and the differential circuit 4 compares the peak level to output a signal, and the envelope detection 29 receives this signal and receives this signal. The point is that the signal is rectified, the envelope is reproduced through a low-pass filter (not shown), and the signal is transmitted to the speed detection circuit 5. In addition, since the infrared LED 21 is driven by the pulse output from the oscillator 20,
Thus, the light emission of the infrared LED 21 can be pulse-driven and controlled.
By adopting the configuration in which the light emission is pulse-driven and the peak level is detected as described above, the influence of ambient light can be prevented and the SN ratio can be improved.

Next, a spatial filter type velocity measuring device according to a third embodiment will be described with reference to FIG. In this embodiment, a pulse-modulated infrared LED is used as a light source (projecting means).
21 is used, the spatial filter is composed of a prism array 22, and two pin PDs 23 and 24 are used as light receiving elements.
Is used. An aperture stop 32 is provided at the focal position of the light receiving lens 31 that receives the reflected light from the measurement object 30, and an infrared ray L is provided downstream of the aperture stop 32 in the light traveling direction.
An optical filter 33, which is a wavelength selection filter that transmits only light having a wavelength equal to the wavelength of the ED 21 or a polarization filter in the polarization utilizing method, is provided. This aperture stop 3
Since 2 is a slit having a narrow width with respect to the relative movement direction of the measuring object 30, only the reflected light component parallel to the optical axis is received by the pin PDs 23 and 24 which are light receiving elements, and as a result, an image is formed. Magnification is the object to be measured 30 and pinPD
Not only is it almost unrelated to the distance between 23 and 24,
It has a deep depth of focus as an optical system. The present invention is not limited to the above embodiment, and various modifications can be made. For example, what is compared with the reflected light intensity in the comparison circuit is not limited to the saturation level and the undetectable level.

[0015]

As described above, according to the invention of claim 1,
Based on the reflected light intensity detected by the detection means, it is determined whether or not the amount of received light is such that speed measurement is possible, and if it is determined that speed measurement is impossible, a malfunction signal is output. By outputting the malfunction signal in this way, the reliability of the speed measurement result when the malfunction signal is not output is increased, and thus the reliability of the speed measuring device is improved. Further, it becomes possible to detect the performance deterioration due to the decrease of the illuminance due to the life of the light projecting means and the like, and to notify the maintenance and inspection time of the speed measuring device. Furthermore, since it is possible to detect a decrease in the amount of received light due to dirt on the speed measuring device at the same time, it is possible to remove dirt by operating the cleaning mechanism in synchronization with the malfunction signal. According to the second aspect of the present invention, the malfunction signal is output when it is detected that the reflected light intensity is not within the range defined by the preset saturation level and undetectable level. By doing so, it becomes possible to output a malfunction signal even when unexpectedly strong light is incident on the light receiving element or when the illuminance decreases due to deterioration of the light projecting means, and the malfunction signal is not output. In this case, the reliability of the speed measurement result increases, which in turn improves the reliability of the speed measurement device. According to the third aspect of the invention, the light emission of the light projecting means can be accurately controlled by pulse-driving the light projecting means. According to the configuration of claim 4, since the aperture stop is a slit having a narrow width with respect to the relative movement direction of the measurement object, only the reflected light component parallel to the optical axis is received by the light receiving element, and The depth of focus becomes deeper as a system.
According to the invention of claim 5, a vehicle such as an automobile is mounted by mounting the spatial filter type velocity measuring device as described above and switching from vehicle control by the spatial filter type velocity measuring device to vehicle control by another device. The control system can have a safety function.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a spatial filter type velocity measuring device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram for outputting a speed and malfunction signal according to the present embodiment.

FIG. 3 is a block circuit diagram of a spatial filter type velocity measuring device according to a second embodiment.

FIG. 4 is a configuration diagram of a spatial filter type velocity measuring device according to a third embodiment.

FIG. 5 is a block diagram of a conventional spatial filter type velocity measuring device.

[Explanation of symbols]

 1 Comb type light receiving element 5 Speed detection circuit 6 Saturation level 7 Undetectable level 8, 9, 10, 11 Comparison circuit 12, 13, 14 OR circuit 20 Oscillator 21 Infrared LED 22 Prism array 23, 24 pinPD 32 Aperture stop

Claims (5)

[Claims] 1. A velocity measuring device comprising: a light projecting means for irradiating a measuring object with light; and a light receiving element for receiving the reflected light from the measuring object, wherein the spatial filter frequency is detected from the light receiving signal of the light receiving element. In the spatial filter type velocity measuring device that performs measurement, from the light receiving signal of the light receiving element, a detection unit that detects the reflected light intensity from the measurement object,
An output means for outputting a malfunction signal based on the reflected light intensity detected by the detection means, and a spatial filter type velocity measuring device. 2. A comparison means for comparing a preset saturation level and undetectable level with the reflected light intensity,
The output means outputs a malfunction signal when the comparing means detects that the reflected light intensity is not within the range defined by the saturation level and the undetectable level. Spatial filter type velocity measuring device. 3. The spatial filter type velocity measuring device according to claim 1, wherein the light projecting means is pulse-driven. 4. An aperture stop is provided at a focal position of a light receiving lens that receives reflected light from the measurement target, and the aperture stop is a slit having a narrow width with respect to a relative moving direction of the measurement target. The spatial filter type velocity measuring device according to claim 1, 2, or 3. 5. A vehicle control system equipped with the spatial filter type speed measuring device according to claim 1, 2, 3 or 4, wherein the spatial filter type speed measuring device outputs a malfunction signal. A vehicle control system characterized by switching from vehicle control by a device to vehicle control by another device.