JP3146838B2 - Distance sensor head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring sensor head for a vehicle.

[0002]

2. Description of the Related Art As an example of conventional inter-vehicle distance measurement using a conventional vehicle ranging sensor head, there is a method shown in FIG. In this system, a distance measuring sensor head 61 for transmitting LED light toward the rear of the preceding vehicle 65 in FIG.
The LED light reflected at 6 is received by the distance measuring sensor head 61 (FIG. 6A), the time from light transmission to light reception is measured, and the distance to the preceding vehicle is calculated from the known speed of the LED light as R =
It is calculated as C × ΔT / 2 (FIG. 6B). here,
C is the speed (light speed) of the LED light, and ΔT is the round trip time of the LED light.

As a structure of the above-described distance measuring sensor head, for example, there is one shown in FIG.

[0004] The CPU 71 controls the LD drive circuit 72,
The laser diodes LD1, LD2, and LD3 are sequentially switched and driven to emit LED light.

The LED light is condensed by the light transmitting lens 73, passes through the transparent cover 74 on the front of the distance measuring sensor head 70, and reaches the reflector of the preceding vehicle. The LED light reflected by the reflector of the preceding vehicle is transmitted to the ranging sensor head 7.
0, the light passes through the front transparent cover 74 again, and is received by the light receiving lens 75 at the photodiode PD1 as a light receiving element.
The light enters the PD 2 and is output as a reflected light signal. The reflected light signal is amplified by the amplifier 76 and sent to the CPU 71, where
In U71, L which is known based on the time from light transmission to light reception
The distance to the preceding vehicle is calculated from the speed of the ED light using the above formula for calculating the following distance.

A transparent cover 74 through which LED light passes.
The distance measuring sensor head 70 is provided with a light emitting element LED (light emitting diode) and a light receiving element photodiode PD having a weak output in addition to a light transmitting / receiving element for measuring a distance in order to detect contamination of the light emitting element. Send the light from the LED,
Transparent cover 7 received by photodiode PD
The light reflected by 4 is converted into a reflected light signal, amplified by an amplifier 76, and transmitted to the CPU 71. The CPU 71 determines the presence of the dirt 16 on the transparent cover 74 from the input reflected light signal, and changes the amplification degree of the amplifier 76 according to the determination result.

[0007]

In the conventional distance measuring sensor head as described above, the light emitting elements PD1, PD2, P2 for distance measurement are used to detect dirt on the transparent cover 74.
When only D3 is used, the output is high. Therefore, regarding the reception of reflected light from the surface of the transparent cover 74 at a very short distance, the received light intensity is high both when the surface of the transparent cover 74 is dirty and when it is not dirty. Since the difference between the light receiving levels is very large and the transparent cover surface 74 is dirty, it cannot be determined whether or not the transparent cover surface 74 is dirty.

[0008] Therefore, an LED having light emitting elements PD1, PD2 and PD3 of high output in order to enable long distance measurement.
In order to detect dirt on the transparent cover 74 through which LED light is transmitted separately from the light transmitting unit, a light transmitting unit having a light emitting element LED with a weak output at a wavelength different from the wavelength emitted by the light emitting element for distance measurement is used. A light receiving unit that receives the weak LED light reflected by the dirt on the cover 74 is provided.

For this reason, there has been a problem that the volume of the distance measuring sensor head is increased and the number of parts is large.

The present invention has been made in view of such a conventional problem. In addition to a light transmitting unit and a light receiving unit provided for measuring a distance between vehicles, a light transmitting unit for detecting dirt on a transparent cover is provided. It is another object of the present invention to provide a distance measuring sensor head which does not need to be provided with a light receiving section.

[0011]

In order to achieve the above object, a distance measuring sensor head according to the first aspect of the present invention comprises:
As shown in FIG. 1, a light emitting unit A having a plurality of light emitting elements A1 to An for emitting light forward of a vehicle, and a plurality of light emitting units A
At least one of the light emitting elements A1 to An
A driving means E that emits light at predetermined timings, and a transmitting unit that transmits light emitted from the light emitting unit A to the outside in front of the vehicle and transmits incoming light from the outside in front of the vehicle based on the emitted light to the rear of the vehicle. B, a light-receiving element C for receiving the reflected light and the arriving light at the transmission section B due to the light emitted from at least one of the plurality of light-emitting elements A1 to An of the light-emitting section A; A light-emitting elements A1 to A
A distance for calculating the distance between the host vehicle and the preceding moving body in front of the host vehicle based on the round trip time from when An emits one outgoing light to when the light receiving element receives the incoming light. Calculation means D
And the light emitting element of the light emitting unit A emits the one outgoing light
And a dirt determining means F for determining dirt on the transmissive part B based on a light receiving level of the light reflected by the transmissive part B received by the light receiving element. In order to achieve the above object, the invention described in claim 2 is
2. The distance measuring sensor head according to claim 1, wherein the distance calculating means D compares an analog signal received by the light receiving element C with a predetermined reference level for each sampling pulse of a predetermined frequency, and Sampling means for converting the digital signal into a digital signal corresponding to "1" when the reference level is exceeded and "0" when the analog signal is equal to or less than the predetermined reference level; Adding means for calculating an added value obtained by adding a predetermined number of times of transmission for each sampling pulse, and the preceding moving object is regarded as a reflection signal from the preceding moving object with the sampling pulse indicating the maximum value as the added value. Is calculated .

[0012]

In the distance measuring sensor head according to the first aspect of the present invention , the plurality of light emitting elements of the light emitting section A are driven by the driving means E.
At least one of the light-emitting elements A1 to An
In order to emit light every time the light receiving element C receives the light coming from outside in front of the vehicle based on the light emitted from the light emitting element through the transmitting portion B, the light receiving element C obtains the light once.
The distance calculating means D can calculate the distance between the host vehicle and the preceding moving body ahead of the host vehicle based on the round trip time from when the emitted light is emitted to when the reflected light is received. In addition, the light emitting element of the light emitting section A emitted this one outgoing light.
At this time, the stain on the transmitting portion B can be determined by the stain determining means F based on the light receiving level of the reflected light received by the light receiving element C. According to the distance measuring sensor head according to the second aspect of the invention, the analog signal received by the light receiving element C is converted into a digital signal for each sampling pulse of a predetermined frequency, and this digital signal is added a predetermined number of times of transmission for each sampling pulse. However, by judging that the position where the added value becomes the maximum is the reflected signal from the preceding moving body, it is possible to separate the received light signal into the reflected light signal and the noise .

[0013]

FIG. 2 is a block diagram showing the configuration of an embodiment of a distance measuring sensor head according to the present invention.
(Control / arithmetic unit) 2 is a light transmitting drive circuit, 3 is a light emitting unit composed of a plurality of light emitting elements (for example, LEDs), 4 is a light transmitting lens, 5 is a transparent cover as a transmitting unit of a distance measuring sensor head, 6 Is a reflected wave from a preceding vehicle, 7 is reflected light due to dirt on a glass surface, 8 is a distance data output unit, 9 is a light receiving filter, 10 is a light receiving lens, 11 is a light receiving unit including a light receiving element (photodiode), and 12 is an amplifier. , 13 is a signal processing unit, 14 is a sampling circuit, 15 is an addition circuit, 16 is dirt attached to a glass surface, and 100 is a distance measuring sensor head for a vehicle.

In FIG. 2, the front glass 5 is used as a transmission part.
Is used, but may be any cover material made of a transparent material that transmits electromagnetic waves such as LED light without being limited to glass.

FIG. 3 is a flowchart showing the basic operation of the distance measuring sensor head according to the present invention.

[0016] In step S1, CPU 1 is (hereinafter referred to as LED) are sequentially driven so due to a low output level LED all of the plurality of light emitting elements 3 controls the light-sending driving circuit 2 emitting light
Then , the LED light is condensed by the light transmitting lens 4 to form a beam and transmitted through the front glass 5 of the distance measuring sensor head to be transmitted outside the head.

In step 2, both the reflected light from the glass surface of the front glass 5 and the reflected light from the target vehicle enter the light receiving element 11 and are converted into a reflected light signal (analog signal). CPU after amplification by amplifier 12
Given to one.

In step S3, the CPU 1 discriminates the reflected light from the glass surface and the reflected light from the target vehicle by comparing the light receiving level at each output timing of the LED light. The process proceeds to step S5 in the case of reflected light from the target vehicle.

Here, FIG. 4 is a waveform diagram of the light transmitting LED light and the light receiving signal, FIG. 4 (a) shows the waveform of the light transmitting LED output, and FIG. 4 (b) shows the case where the glass is clean. FIG. 4C shows the waveform of the light receiving signal when the glass is dirty. 4 (b) and 4 (c).
The section is a reflected light signal peak due to the reflected light from the glass surface, and the B section is a light receiving signal section in which the reflected light signal from the target vehicle and the noise are mixed.

The weak LED light transmitted for distance measurement is transmitted at a constant period as shown in FIG. 4A, and is received by the light receiving element 11 to become a reflected light signal. FIG.
As shown in section A of (b) and (c), there is a peak 41 of the reflected light signal due to the reflected light from the glass surface, followed by a received light signal due to the reflected light from the target vehicle. As described above, by detecting the peak from the output timing of the LED light, it is possible to determine the reflected light from the glass surface and the reflected light from the target vehicle.

In step 4, the CPU 1 determines whether or not the glass surface is dirty. If the dirt exceeds the reference value, the process proceeds to step S6. If the dirt is not dirty or the dirt is within the reference value, the process proceeds to step S6. Move to S5.

In the determination of the dirt on the glass surface, the transmitted LED light has a low output level, and as shown in FIG. 4, the intensity of the peak of the reflected light signal due to the reflected light from the very short glass surface is reduced. In this case, the intensity of the reflected light signal due to the reflected light from the target vehicle at a long distance (whether dirty or not) is larger. Thus, the CPU 1 can detect and determine whether or not the level of the analog signal converted by the amplifier 12 exceeds the reference value of the stain on the glass surface (for details, see (<1. Determination of stain>)). .

In step S5, the CPU 1 determines the reflected light signal based on the reflected light signal reference value based on the received light signal (reflected light signal + noise) reflected by the reflector at the rear part of the preceding vehicle and calculates the following distance. (See below for details (<
3. Calculation of distance between vehicles>))). Note that the reflected light signal reference value level can be obtained in advance as a median value from the fluctuation width of the analog signal in the case of only noise.

In step S6, since the dirt on the front glass 5 exceeds the limit (standard value of dirt),
As if the dirt is badly distance calculated out possible light intensity can not be ensured, for example, "the dirt glass distance measurement impossible" performed unmeasurable display, such as, the user needs to clean the front glass A notification can be made (for the reference value of dirt, see <2. Determination of dirt limit> below).

<1. Detection of dirt> The LED light exiting from the light emitting element 3 and passing through the light transmitting lens 4 reaches the front glass 5 of the sensor head.

At this time, if the dirt 16 does not adhere to the glass surface, the LED light is transmitted through the front glass 5 and transmitted to the outside of the sensor head.

On the other hand, when dirt 16 such as mud is attached to the front glass 5, the LED light is reflected on the glass surface of the portion of the front glass 5 where the dirt is attached. And the reflection LE
The D light enters a photodiode as the light receiving element 11 and is detected by the amplifier 12 as a reflected light signal.

Since the amount of reflected light varies depending on the area of the dirty portion of the front glass 5, the light receiving intensity entering the photodiode as the light receiving element 11 varies depending on the area of the dirty portion. The degree can be detected.

When there is no dirt on the surface of the front glass 5, most of the LED light passes through the front glass 5, so that the intensity of the reflected light from the glass surface is weak, and the light receiving element (photodiode) 11 The level of the analog signal converted by the amplifier 12 via the amplifier 12 is equal to or less than a reference value for determining dirt as shown in a section A (dirt reflected signal portion) of FIG.

On the other hand, when the surface of the glass is contaminated, the analog signal level converted by the amplifier 12 through the light receiving element 11 by the reflection of the contaminated portion from the glass surface is shown in FIG. As shown in section A, the value exceeds the reference value for dirt determination.

<2. Here the determination of the contamination limit>, as the basis for practical limit dirt on the front glass 5, LED light transmitted from the light-emitting element 3 is transmitted through the dirt glass portion adhered to the front glass 5 measuring object before intensity of the reflected light reflected back to the reflector of the preceding vehicle as it becomes the distance can be calculated by CPU1 can identify the signal and the noise in the signal processing unit 13, detected by the intensity of the lowest level of light The degree of dirt on the face glass 5, in other words, the intensity of the reflected light input to the photodiode (light receiving element 11) can be used. By using such a criterion, the dirt on the front glass 5 can be extremely disturbed.
It is possible to detect a case where the available light receiving intensity cannot be secured.

<3. Inter-vehicle distance measurement> As described above, the inter-vehicle distance is determined by transmitting the LED light from the light emitting element 3 to the light receiving element 1
The inter-vehicle distance is determined by measuring the time until 1 receives the reflected light of the reflector of the preceding vehicle, that is, the round trip time of the LED light to the reflecting object.

Here, the analog signal in the section B in FIG. 4 in which the reflected light signal and the noise are mixed is converted by the amplifier 12 as described above, and further the signal processing unit 13 samples the signal.
And packaging processing and addition processing, CPU 1 from the result of the addition process
Determines the reflected light signal and noise, and calculates the distance to the object based on the determined reflected light signal.

Since the transmitted LED light is weak, the reflected light from the target vehicle received by the light receiving element 11 is also weak, and it is difficult to determine the noise as it is. The mixed analog signal is amplified by the amplifier 12 and input to the signal processing unit 13 to distinguish between the reflected light signal and noise.

FIG. 5 is an explanatory diagram of the process of discriminating between the reflected light signal and the noise. The signal processing unit 13 converts the analog signal (reflected light signal + noise) shown in FIG. An analog signal level with respect to a reference level is compared for each sampling pulse of a predetermined frequency, and when the analog signal level exceeds the reference level, it corresponds to “1”, and when the analog signal level is less than the reference level, it corresponds to “0”. It is represented by a bit value as shown in FIG.

Next, as shown in FIG. 5C, the bit value for each sampling pulse obtained each time the light is transmitted and received is added by the adder 15 continuously for a predetermined number of times for each corresponding bit.

[0037] FIG. 5 (c) first bit value of each sampling pulse obtained by transmission and reception light, a second bit value of each sampling pulse obtained by transmitting and receiving light, ..., obtained in 5000 the beam transmitting and receiving FIG. 2 (d) is a graph showing the addition value of the bit value for each sampling pulse, and the addition value of the bit in which the reflected light signal from the object exists is the largest value. Becomes

Therefore, the noise and the reflected light signal can be distinguished by checking the added value for each bit. For this purpose, the CPU 1 obtains the number of the bit having the largest added value in the sampling pulse and the time required from the light transmission to the light reception based on the sampling period, and obtains the reflection object from the known speed of the LED light. Calculate the distance to.

The resolution of the time calculation depends on the size of the sampling frequency, and corresponds to the resolution of the distance calculation. The resolution of the distance calculation can be improved by reducing the sampling period.

As described above, in the distance measuring sensor head for a vehicle according to the present invention, the distance measuring function and the dirt detecting function can be shared by one light transmitting unit and one light receiving unit. It is not necessary to separately provide a light receiving unit.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made.

[0042]

As described above, according to the distance measuring sensor head of the present invention, a small number of the plurality of light emitting elements of the light emitting section are used.
At least one light-emitting element emits light at predetermined timings. <br/> Emits light forward through the transmitting portion, and emits one emitted light to receive incoming light based on the emitted light. based on round trip times, to be able to measure the distance between the vehicle and the vehicle ahead of the preceding mobile simultaneously, the 1
Since the dirt on the transmission part is determined using the emitted light of the first time, it is not necessary to provide a light emitting element and a light receiving element dedicated to dirt detection.
In addition, when an element such as an LED having a weak output is used as a light emitting element, it is possible to extract a reflected light signal from the received signal by sampling the received signal and performing an adding process, thereby achieving accurate distance measurement. It can be carried out.

As described above, the distance measuring sensor head according to the present invention can be configured with a simple structure having a small number of parts and can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a block diagram showing a configuration of an embodiment of a distance measuring sensor head according to the present invention.

FIG. 3 is a flowchart showing a basic operation of the distance measuring sensor head of the present invention.

FIG. 4 is a waveform diagram of a light transmitting LED light and a light receiving signal.

FIG. 5 is an explanatory diagram of a process of identifying a reflected signal and noise.

FIG. 6 is an example of the inter-vehicle distance measurement using a conventional vehicle ranging sensor head.

FIG. 7 is an example of the structure of a conventional ranging sensor head for a vehicle.

[Explanation of symbols]

Reference Signs List A light emitting section A _{1 to An} light emitting element B transmitting section C light receiving element D distance calculating means E driving means F dirt determining means 1 CPU (light emitting element driving means, dirt determining means, distance calculating means) 2 light transmitting drive circuit (light emitting Element driving means) 3 Light emitting element (light transmitting section) 5 Front glass (cover) of sensor head 11 Light receiving element (light receiving section) 13 Signal processing section (distance calculating means) 16 Dirt attached to glass surface 100 Distance measuring sensor head

Claims (2)

(57) [Claims] 1. A light emitting section having a plurality of light emitting elements for emitting light forward of a vehicle, and at least one of the plurality of light emitting elements of the light emitting section.
A driving unit for emitting an optical element at predetermined timings, and a transmitting unit for transmitting light emitted from the light emitting unit to the outside in front of the vehicle, and transmitting incoming light from outside in front of the vehicle based on the emitted light to the rear of the vehicle. And a light-receiving element that receives the reflected light and the incoming light at the transmission section due to emission light of at least one of the light-emitting elements of the plurality of light-emitting elements of the light-emitting section ; a distance calculation means for calculating the distance between the light emitted from the emission to the prior movement of the vehicle and the vehicle ahead based on the round-trip time to the light receiving element for receiving the incoming light, light emission of the light emitting portion When the element emits the light once
The distance measuring sensor head characterized by having a a dirt determining means for determining contamination of the transmissive portion based on the reflected light to the light receiving level of light received by the light receiving element in the transmissive portion. 2. The distance calculation means compares an analog signal received by the light receiving element with a predetermined reference level for each sampling pulse of a predetermined frequency, and sets “1” when the analog signal exceeds the predetermined reference level; Sampling means for converting a time when the analog signal is equal to or less than the predetermined reference level into a digital signal in correspondence with "0"; and adding the digital signal converted by the sampling means a predetermined number of times of transmission for each sampling pulse. Adding means for calculating an added value, wherein a distance from the preceding moving object is calculated by regarding the sampling pulse having the maximum value as a reflection signal from the preceding moving object. The distance measuring sensor head according to claim 1 .