JPH10319121A - Distance-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To self-diagnose the failure in an optical and electrical element with the minimum detection means by utilizing a measurement value by electromagnetically shielding a light-transmitting means with a leading means for leading scattered light toward the outside of a driving means and a scattered light detection means for detecting luminous flux from the leading means. SOLUTION: A light-transmitting part 100 consists of a light source 101, a lens 102 for transmitting light, and a light source drive circuit 130 and is accommodated in an electromagnetically shielded case. One portion of the quantity of light of light transmission pulses is guided to a light reception element 111 of a light reception part 150 through a Fresnel lens 110 via a scattered light condensation device 106 for acquiring scattered light from a light transmission optical system consisting of a light transmission pulse acquisition device 108, a window member 103, and a lens 102 for transmitting light. Then, the level of output from the light reception part 150 is evaluated by a reception signal output evaluation circuit 113 and the failure in a light source and the presence or absence of the contamination and dew formation of the light transmission part are judged by a measurement value check circuit 118 based on the evaluation result and the measurement result of a distance signal acquisition circuit 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly, to a method of transmitting a pulsed light beam to detect reflected light from a target, measuring the time required for the light beam to reciprocate, and obstructing the obstacle. The present invention relates to a distance measuring device for measuring a distance to an object.

[0002]

2. Description of the Related Art In a distance measuring device of a type in which a pulsed light beam is transmitted to detect reflected light from a target obstacle, reflected light from an obstacle is not detected or only a weak received signal is obtained. If there is no obstacle, there may be a case where there is no obstacle or whether any abnormality such as dirt or dew condensation or a failure of the light source has occurred in the distance measuring device. Or in a distance measuring device that has been used for many years, the received signal may decline, leading to a decrease in the reliability of the measurement result.
It is necessary to inform the user of the distance measuring device of this.

JP-A-8-292260 discloses an example of a distance measuring device having a self-diagnosis function. FIG. 12 is an explanatory diagram of the operation. In FIG. 12A, the vertical axis represents the light receiving level, and the horizontal axis represents time. Lb represents a stable light receiving level sufficient for the signal processing means to detect the object, and Ld represents a minimum light receiving level at which the signal processing means can detect the object, in other words, a stable light level obtained when the light receiving element is shielded from light. Indicates the light blocking level. La is called an operation level, and represents a transient level intermediate between a stable light receiving level and a stable light shielding level. If the distance measurement device is normal, the level changes from a level exceeding the stable light receiving level Lb to a level equal to or lower than the stable light blocking level Ld, or vice versa, and the period of staying at the transient level is instantaneous. In such a case, the probability of erroneous detection is extremely low, and a highly accurate distance signal is provided. Conversely, if the user stays at the transient level for a long time, the probability of erroneous detection increases, indicating that some trouble has occurred. FIG.
The self-diagnosis signal in (b) indicates this, and if the self-diagnosis signal is seen, it indicates that some trouble may have occurred.

Japanese Patent Laid-Open No. Hei 6-289134 discloses an example of another distance measuring device having a self-diagnosis function. FIG. 13 shows a schematic configuration thereof. The light transmitting unit 1301 includes a pulse driving circuit 1302, a light source 1303, and a light transmitting lens 1304.
The light pulse transmitted from the light source 1303 driven by the pulse driving circuit 1302 is
The divergence angle is controlled by the light emitting element 04, and the light is emitted toward the target object 1306 via the light transmitting window 1305. The scattered light from the object 1306 is taken into the light receiving unit 1310 through the light receiving window 1307 and passes through the light receiving lens 1308.
The light is detected by the light receiving element 1309. The light receiving element 130
The output of No. 9 is input to the distance measuring means 1312 in the processing circuit 1311 together with the reference pulse from the pulse drive circuit.
On the other hand, it is also supplied to an object detection means 1313 for judging the detection or non-detection of an object based on the output level of the light receiving element 1309. The distance to the object 1306 is measured by the distance measuring means 1312, and the object detecting means 131 is used for each measurement.
3, the detection and non-detection of the object are determined, and the number of distance measurements and the frequency of non-detection of the object are compared with the criterion obtained from experience. When the number becomes 8 or more, the light transmission path is determined to be dirty.

Japanese Patent Application Laid-Open No. 7-248374 discloses a distance measuring device capable of detecting dirt adhering to a transmission / reception optical system without increasing the number of components. FIG. 14 shows a schematic configuration thereof. A reference object 1410 is provided in an overlapping portion of the light transmitting / receiving path in front of the transmission / reception optical systems 1402 and 1403, and a light pulse from the light source 1401
And a reference signal is output by the light receiving means 1404. The magnitude of the reference signal is measured by measuring means 1417, and based on the magnitude, the transmission / reception optical system 1402,
Dirty on the front surface of 403 is detected. The output time of the reference signal is measured by the timer 1413. Distance calculation means 1416
Subtracts the output time of the reference signal from the round trip time to the target, thereby canceling out the influence of the delay time change of the electric circuit due to environmental temperature fluctuation and the like.

Japanese Patent Application Laid-Open No. 5-256947 discloses a distance measuring device in which a dirt detecting device is incorporated in a light transmitting unit to improve the dirt detecting sensitivity. The schematic configuration is shown in FIG.
Shown in Laser diode 1 in light transmitting unit 1501
The light pulse transmitted from 502 is converged by the convex lens 1503 and passes through the cover 1514. If there is a dirt 1541 there, a part thereof is scattered backward. Condensing lens 15 adjacent and integrated with convex lens 1503
31 collects the scattered light on the photodiode 1509 in the light transmitting unit 1501. Thereby, the front glass 1
Dirt 1541 on 514 is detected.

[0007]

When a self-diagnosis of an abnormality of an optical / electrical element related to a light transmitting unit, a light receiving unit, and a distance around the light transmitting unit, a light receiving unit, a method of making a judgment using measured values is a comprehensive judgment. This has the advantage of being easy to perform and having no extra hardware, which leads to an improvement in reliability. Conversely, it is not possible to eliminate a problem that occurs when a certain criterion is not satisfied. For example, in Japanese Patent Application Laid-Open No. 8-292260, a self-diagnosis signal is generated when a received signal level stays at a transient level, and when the received signal level is equal to or lower than a stable light shielding level, it is determined that the signal is normal. However, there is a failure in the light receiving element or the light transmitting unit, for example, when the light source does not emit light, the light receiving element does not work, or because the dirt and dew condensation are severe, the scattered light from the target is not received as a result. It is not possible to exclude a case where a received signal having a level equal to or lower than the stable light shielding level is obtained. Also, JP-A-6-2891
In 34, the determination is made according to the number of distance measurements and the frequency of undetected objects, which is based on an empirical frequency,
If the driving environment changes drastically, for example, in an environment such as a desert or a wilderness, it cannot be ruled out that the assumption that the ratio of the object non-detection period to the number of distance measurements is 0.8 or more does not apply. . JP-A-7-2483
74 denotes a case where the reference object 1410 is the transmission / reception optical system 1402, 1
It is provided in an overlapping portion of the light transmitting / receiving path before 403, and this portion is usually located outside the cover glass of the distance measuring device. This is a great constraint on mounting on a vehicle or the like, which is not preferable.

Japanese Patent Application Laid-Open No. 5-256947 discloses an example in which detection means is provided to cope with one cause of the problem of dirt. However, a dirt detection photodiode is required to detect dirt on the front glass. No mention is made of measures to be taken when a failure occurs in the photodiode or a signal processing system following the photodiode. In addition, electromagnetic induction noise generated when a dirt detection device is built in the light transmission unit is generated by, for example, a power supply system (including ground) in an amplification system of a light receiving unit in which the intensity of a scattered reception light signal from a target changes by several orders of magnitude. Via could have serious consequences.

The present invention pays attention to these points, and judges the abnormality of the optical / electrical element relating to the distance measurement of the light transmitting unit or the light receiving unit and its surroundings by using the measured values without having extra hardware. Another object of the present invention is to provide a distance measuring device with a self-diagnosis function which is realized by a minimum detecting means irrelevant to electromagnetic induction noise.

[0010]

According to the present invention, there is provided a light transmitting means for transmitting a light pulse toward a target, and a light receiving means for receiving scattered light of the light pulse transmitted from the light transmitting means from the target. In a distance measuring device having a means and measuring a distance to a target by detecting a time when a light pulse reciprocates, a deriving means for leading scattered light in the light transmitting means to outside the light transmitting means, And a scattered light detecting means for detecting a light beam from the deriving means, wherein the light transmitting means and the scattered light detecting means are electromagnetically shielded from each other. In the distance measuring device, the light receiving element included in the light receiving means and the light receiving element included in the scattered light detecting means are the same light receiving element.

[0011]

FIG. 1 shows the configuration of a distance measuring apparatus according to a first embodiment of the present invention. The light transmitting unit 100 includes a light source 101, a light transmitting lens 102, and a light source driving circuit 130.
And is housed in an electromagnetically shielded case. Also, a part of the light amount of the light transmission pulse is acquired and the light
A light transmitting pulse acquisition device 108 having a processed end 107 leading to the light receiving element 111 within 0 and a light receiving unit that acquires scattered light from a light transmitting unit optical system including the window member 103 and the light transmitting lens 102. It includes a scattered light collector 106 with a processed end 105 leading to a light receiving element 111 within 150. The light receiving unit 150 includes the Fresnel lens 110 and the light receiving element 11.
Consists of one. The Fresnel lens 110 is formed integrally with or separately from the window 103 and focuses a scattered light component from a target on the light receiving element 111.

The signal processing unit 140 is provided for the reception output evaluation circuit 11
3. It comprises a distance signal acquisition circuit 112 and a measurement value check circuit 118. The reception output evaluation circuit 113 includes the light receiving element 1
11 is divided into two outputs, one output is supplied, and
The divided signals are supplied to first and second comparators 114 and 115, and the first and second adders 116 and 117 add the binary outputs of the comparators a predetermined number of times. Output terminals of the adder 2 are output terminals 1
23 and 124.

The distance signal obtaining circuit 112 includes a circuit element illustrated in FIG. 11A including a logarithmic amplifier 1103 for amplifying the output of the light receiving element, as will be described later. The peak value of the logarithmic amplifier output and the logarithm A distance measurement value obtained from a start pulse and a stop pulse obtained by binarizing the amplifier output, and a start pulse flag indicating generation of the start pulse are output to output terminals 120 and 121, respectively.
122. The measurement value check circuit 118 receives the output from the distance signal acquisition circuit 112 and the reception output evaluation device 113 every time the distance is measured, and
The self-diagnosis result of the distance measurement device is displayed on a display (not shown) according to the logical operation exemplified in (1), and a trigger pulse supporting the next distance measurement is sent to the light source drive circuit 130.

Next, the operation of each section will be described. The light pulse output from the light source 101 driven by the light source driving circuit 130 is transmitted to a target obstacle with the divergence angle controlled by the lens 102. The window member 103 is transparent to the transmitted light pulse and mainly plays a role of dust prevention.

FIG. 6A and FIG. 6B show an example of the light transmission pulse acquisition device 108. In FIG. 6A, the optical fiber 61 is used.
By cutting and obliquely cutting the front end of the light transmitting portion as indicated by reference numeral 64 and inserting and fixing it in the optical path of the light transmitting portion, the propagation component indicated by the arrow of reference numeral 63 can be obtained. The other end of the optical fiber 61 is inserted and fixed in the light collecting path from the Fresnel lens 110 of the light receiving element 111 of FIG. FIG.
In (b), by inserting and fixing the mirror 67 in the light path of the light transmitting unit, a light pulse component heading toward the opening 66 provided on the side surface of the light transmitting unit 100 can be obtained. From the opening 66 to the light receiving element 111 via an optical fiber or through the opening 66
Is directed to the light receiving element 111 directly.

FIG. 8 shows another example of the light transmission pulse acquisition unit 108. In FIG. 8, reference numeral 86 denotes a mirror surface provided on the case of the light transmitting unit 100 and fixed to the support unit 87, and uses a glossy surface such as a metal or plastic surface. The reflected light of the light transmission pulse on the mirror surface 86 is supplied to the light receiving element 111 via the optical fiber 85 inserted and fixed in the opening 84 provided in the case 100 of the light transmission unit 100. In addition, a part of the scattered light 82 on the mirror surface 86 illuminates the light receiving optical system of FIG. 1, in other words, the window member 103 and the Fresnel lens 110, through an opening 83 provided on the side surface of the case of the light transmitting unit 100. By illuminating in this manner, if there is dirt or dew on the light receiving optical system, scattered light due to the dirt or dew enters the light receiving element 111. The case 100 is made of an electromagnetic shielding material such as iron or aluminum.
01 has the function of electromagnetically shielding the lighting noise of 01 so as not to leak outside.

The scattered light collecting device 106 mainly includes the window member 103.
7A, 7B, and 7C, which are obtained by processing the tip 72 of an optical fiber 71 as illustrated in FIG. 7A, FIG. 7B, and FIG. 7C. The optical fiber 71 is installed outside the optical path of the light transmitting unit, and the other end of the optical fiber 71 is inserted and fixed in the optical path of light collected from the Fresnel lens 110 of the light receiving element 111 of the light receiving unit 150.

FIG. 7A illustrates the optical path of scattered light due to dirt or condensation 70 attached to the inner or outer surface of the window member 103 by dotted lines. The distal end of the optical fiber 71 is cut obliquely as indicated by reference numeral 72, and the distal end is installed so as to avoid the light transmitting unit optical path. Part of the scattered light at the window member 103 is reflected at the end 72, becomes a propagation component of the optical fiber 71, and is guided to the light receiving element 111.

FIG. 7B is a side view of a configuration in which a flat light collector 73 is attached to the tip of the fiber 71. The light collector 73 is, as shown in FIG. An opening 74 is provided to avoid an optical path. The condensing plate 73 has scattering particles dispersed inside the plate, so that dirt or condensation 7
The optical fiber 71 has a function of scattering the light scattered by zero inside the plate and condensing a part of the scattered light as an axial propagation component of the optical fiber 71.

The reception output evaluation circuit 113 includes a light receiving element 111
Are evaluated by the first and second comparators 114 and 115 having different first and second thresholds, respectively. The waveform of the light pulse in FIG. 3 corresponds to the light pulse obtained from the light receiving element 111 when the normal operation is performed, and the threshold 1 of the first comparator 114 is higher than the peak value of this light pulse. Is set.

If there is dirt or dew on the light transmitting unit optical system or the light receiving unit, the scattered light due to the dirt or dew is generated by the scattered light collecting device 1.
Illumination light 8 to the light-receiving optical system through the light receiving optical system 06 or another example of the light transmission pulse acquisition device 108 shown in FIG.
The second scattered light is supplied to the light receiving element 111, exceeds the first threshold, and the first comparator 114 is turned on. In other words, the first comparator 1 of FIG.
When 14 works, it indicates that a problem such as dirt or dew condensation occurs in the light transmitting unit or the light receiving unit, which causes an increase in the scattered light component.

The threshold value 2 of the second comparator is for judging the life. If the light source is normal, the amount of light supplied from the light transmitting pulse acquisition device 108 is sufficient to exceed the threshold value 2, The second comparator 115 turns ON.
When the light source deteriorates due to its life, the peak of the waveform of the light pulse obtained by the light receiving element 111 becomes lower as shown by reference numeral 400 in FIG. 4, and the second comparator 115 does not operate. The level is set to, for example, half the peak value of a normal pulse waveform. The reason is that the amount of received light is inversely proportional to the square of the distance to the target (or the fourth power depending on conditions). When the amount of light from the light source is halved, the amount of received light is halved, and the reaching distance to the target is 70%. This is to determine this as one life.

The first and second adders 116 and 117 accumulate the number of times that the first and second comparators 114 and 115 are turned on each time each distance is measured.
The first adder 116 has a predetermined number of measurements N
After the measurement exceeds, the integrated value n is set to the set value n0
Is exceeded, it is determined to be abnormal. In other words, it indicates that there is a risk of dirt or condensation. Similarly, the second adder 1
Reference numeral 17 indicates that if the integrated value m is smaller than the set value m0 after the measurement exceeds the predetermined number of measurements N, it is determined that there is an abnormality. In other words, the life of the light source is concerned.

FIG. 11A shows an example of a circuit block of the distance signal acquisition circuit 112. In FIG. 11A, the terminal 1
Reference numeral 101 denotes a rectangular signal generated from a trigger pulse (not shown) for driving the light source, which has a waveform shown in FIG. 11B. The horizontal axis represents time. Terminal 1102
Receives an analog signal received by the light receiving element 111, is amplified by a logarithmic amplifier 1103, is divided into three, is delayed by a delay element 1104, and is then summed with an undelayed branch signal. The value is obtained by an adder 1105. The peak value of the output of the adder 1105 is taken by a peak value detector 1107, multiplied by a coefficient by a coefficient multiplying circuit 1108, which will be described later, and used as a threshold value of the comparator 1106.

FIG. 5 shows the concept of the above operation. In FIG. 5, a waveform 500 represents one half of the output of the logarithmic amplifier 1103, and a waveform 501 represents the output of the delay element 1104 with a delay represented by an arrow in the figure. The sum of the two waveforms is obtained by an adder 1105, and the adder 110
5 is taken by the peak value detector 1107, this peak value is obtained at the intersection Q of the two waveforms 500 and 501.
Is almost twice as large as By multiplying this by, for example, a coefficient of 1/2 by a resistance divider as a coefficient multiplying circuit 1108, the value of the intersection Q is approximately given. If this is set as the threshold value of the comparator 1106, the delayed signal waveform 5
01 is processed using the value of the intersection Q as the threshold value, and the rectangular pulse 503 in FIG. 5 is obtained as the output.

The received signal supplied to the terminal 1102 shown in FIG. 11A is obtained from the light transmitting pulse acquisition device 108 and scattered light from the target. As output
(B) Two rectangular pulses shown in 2 are obtained. AND
The role of the circuit 1109 is to take the logical product of 1 and 2 in FIG. 11B, and to output the rectangular pulse 3 in FIG. 11B. This gives the start pulse of the time in the distance measurement. Therefore, a start pulse for time measurement is output to the terminal 1114 in FIG.

The state of the flip-flop 1111 is inverted when a start pulse is generated, and the flip-flop 1111 outputs a start pulse flag to the output terminal 1113. The output of the comparator 1106 is divided into two parts, and the AND circuit 110
After the delay by the delay element 1110 by an amount equivalent to the delay time of No. 9, the exclusive OR with the output of the AND circuit 1109 is obtained by the EOR circuit 1112. This is shown in FIG.
This corresponds to the exclusive OR of 2 and 3 in (b), and a stop pulse for the measurement time in the distance measurement indicated by 4 in FIG. 11B is given.
It is output to the terminal 1115 in FIG.

The distance measurement circuit 1120 measures the distance by the start pulse and the stop pulse obtained from the terminals 1114 and 1115, respectively, and outputs the measured distance to the terminal 1121. An output from a peak value detector 1117 is output to a terminal 1116, which outputs the peak value of the received analog signal. By outputting to the terminal 1116 the output of the coefficient multiplication circuit 1108 via an appropriate buffer, the peak value of the analog signal to be received can be output approximately.

The outputs of the reception output evaluation circuit 113 and the distance signal acquisition circuit 112 shown in FIG. These outputs are the peak value of the received signal, the distance measurement value, the start pulse flag, the first adder output, and the second adder output, and the following logic operation is executed in the measurement value check circuit 118. You. An example is shown in FIG. When the start pulse flag is ON, it is confirmed that both the light source and the light receiving element are operating. When the start pulse flag is OFF, it is estimated that there is an abnormality in at least either the light source or the light receiving unit. If the integrated value n does not exceed the set value n0 after the measurement in which the output of the first adder has exceeded the predetermined number of measurements N, it indicates that the possibility of dirt or dew is small. Exceeding indicates that the possibility of dirt and condensation is large. Similarly, after the measurement of the output of the second adder 117 exceeding the predetermined number of measurements N, if the integrated value m exceeds the set value m0, the life of the light source is OK. It is judged that there is a high possibility that the life has expired.

FIG. 9 illustrates a frequency distribution of the relationship between the measured distance value and the peak value of the received signal. FIG. 9 shows the logarithm of the received signal peak value on the vertical axis and the distance to the target on the horizontal axis. The peak value of the received signal is 2 of the distance to the target (obstacle).
It is known that it is inversely proportional to the power or the fourth power, and is proportional to the reflectance of the target object, the light intensity of the light source, and the transmittance of the distance measuring device (each element of the light transmitting unit and the light receiving unit). Therefore,
When the logarithm of the received signal peak value is plotted on the vertical axis, the received signal peak value is expressed by a straight line 90 with respect to the distance (measured value). Will be shifted to.

Assuming that the light intensity of the light source and the transmittance of the distance measuring device take a predetermined standard value, the straight line 90 shifts up and down depending on the magnitude of the reflectance of the target object. Is a straight line 91 or a straight line 92, respectively. These are empirically obtained from the specifications of the distance measuring device. Therefore, the logarithmic value of the received signal peak value corresponding to the measured distance falls in the standard region II between the straight line 91 and the straight line 92. If an abnormality occurs in the light intensity of the light source and the transmittance of the distance measuring device, the frequency at which the logarithmic value of the received signal peak value deviates from this region increases.

In FIG. 9, the region above the straight line 91 is I, the region below the straight line 92 is III, and the mark of the received signal with respect to the measured value of each distance measurement is indicated by a triangle. If the frequency of the measured value that deviates from the standard region II and enters the region III, such as the measured value indicated by the reference numeral 93, increases, the light intensity of the light source or the transmittance of the distance measuring device is indirectly abnormal. Is suggested. In other words, it indicates whether the optical system of the light transmitting unit and the optical system of the light receiving unit are stained or dewed, or whether the life of the light source has expired.

Therefore, the peak value of the received signal and the measured distance value in each measurement are taken into the measurement check circuit 118, and the relationship shown in FIG. 9 is evaluated. If the value pm obtained by integrating the measured values deviating from the standard region II and entering the region III falls below the set value p0, the distance measuring device can be used continuously. Inspection is required. Note that the logarithm of the received signal peak value is obtained by using a logarithmic amplifier in the amplification system of the distance signal acquisition circuit 112 in FIG.

The flow of the determination performed by the measured value check circuit 118 shown in FIG. 10 will be described along the flow. The input terminals 1 to 4 respectively have a start pulse flag, an output of the first adder, an output of the second adder, and an integrated value of the number of times that the measured value of the peak value of the received signal falls in the region III (this integrated value is (Integrated by an integrating circuit (not shown) in the check circuit)
Is input and multiplied by the aforementioned criteria. For example, in the system following input terminal 1, the start pulse flag is ON or O
It is determined whether it is FF, and if ON, 1 is output, and if OFF, 0 is output. Similarly, for the input terminals 2 to 4, 1 is output if the respective inequalities are satisfied, and 0 otherwise. If these output results are all 1 (111
In the case of 1), an output 1004 is output, and “operation of sensor /
The display of "OK for both lifespan" is made to the user. Similarly, if all are 0 (0000), an output 1001 is issued, and the display of "NO in both the operation and the life of the sensor" is given to the user.
There are 16 such output types possible with four inputs, but each is not an independent factor but has redundancy and may not give a clear conclusion. FIG. 10 exemplifies 1001 to 4 as comparatively clear output examples, and Table 1 shows determination examples in all cases. A mark indicates a case where there is ambiguity.

[0035]

[Table 1]

The apparatus according to the present embodiment has a function of performing self-diagnosis with a combination of a minimum of hardware and software processing for light receiving and light emitting elements, one light receiving unit and one light source.

Various modifications can be made to the present embodiment. In FIG. 1, the peak value of the received signal is obtained from this output by providing a peak value detector 1117 in the distance signal obtaining circuit 112, but this can be transferred to the light receiving section output evaluation circuit 113 and obtained therefrom. is there. Further, the end portion 107 of the light transmission pulse acquisition device 108 may be formed with a lens portion having a spherical or aspheric surface shape other than the illustrated one. Further, the tip 105 of the scattered light collecting device 106
Can of course be combined with any other suitable focusing optics.

Next, a distance measuring apparatus according to a second embodiment of the present invention will be described with reference to FIG. The parts that do not overlap with FIG. 1 will be mainly described. In the light receiving section 150, a reference light receiving element 201 is added in addition to the light receiving element 111, and the light pulse from the light transmission pulse acquisition device 108 is supplied to the reference light receiving element 201. The light pulse from the scattered light collecting device 106 is also guided to the reference light receiving element 201.

The signal processing section 140 comprises a reference signal / reception output evaluation circuit 210, a distance signal acquisition circuit 220, and a measurement value check circuit 118. In the reference signal / received output evaluation circuit 210, a new comparator 202 and a flip-flop 203 are added. This is because the role of the start pulse flag output terminal 122 in FIG. 1 has been transferred to the reference signal / reception output evaluation circuit 210, and the start pulse is output to the output terminal 205 and supplied to the distance signal acquisition circuit 220. At the same time, a start pulse flag is output to the output terminal 204 via the flip-flop 203.

The functional difference from the first embodiment is that the signal supplied to the reference light receiving element 201 is different from that of the first embodiment.
In other words, it is limited to information on the operating state of the light source 101, the life, and the measurement results on dirt and dew on the light transmitting unit optical system.
Because it is separated from the measurement result due to the defect of
It is easy to identify the cause of the failure. Specifically, when the start pulse flag is not output to the output terminal 204, the device according to the first embodiment may have a problem with the light source 101 and / or the light receiving unit. In the device of the embodiment, the malfunction of the light source is first estimated.

The device of the present embodiment performs self-diagnosis in a system having two light receiving units and one light transmitting unit and one more light receiving unit in terms of hardware. Can be separated.

Various modifications can be made to the present embodiment.
The light transmission pulse acquisition device 108 can have the form shown in FIG. 8, illuminates the light receiving unit optical system with the scattered light 82 supplied from the opening 83, and receives the scattered light due to contamination of the light receiving unit optical system and condensation. The light can be received by the element 111. At this time, by providing the distance signal acquisition circuit 220 with the same function as the output evaluation function of the reference signal / reception output evaluation circuit 210, it is possible to obtain information on dirt and condensation on the light receiving unit optical system.

The present invention is not limited to the above embodiment. All implementations performed without departing from the gist of the present invention are included in the present invention. This specification includes the inventions described in the following items.

1. A light transmitting unit that transmits an optical pulse toward a target, a light receiving unit that receives scattered light from the target due to the light pulse, a signal processing unit that processes an output of the light receiving unit, and a light transmitting unit that is installed in the light transmitting unit. A light transmitting pulse obtaining unit for optically obtaining a part of the light amount of the light transmitting pulse and guiding the light to a light receiving unit, and optically obtaining scattered light from a light transmitting unit optical system in the light transmitting unit, and A scattered light condensing unit that guides the light, a reception output evaluation unit that is provided in the signal processing unit, and evaluates the magnitude of the output of the light receiving unit with respect to the light transmission pulse, and obtains a distance from the output of the light receiving unit to a target. A distance measuring device comprising: a distance measuring unit; and a measured value checking unit that determines reliability of a measured value from an output of the distance measuring unit and an output of the reception output evaluating unit.

(Corresponding Embodiment of the Invention) In the embodiment relating to the present invention, the first and second embodiments are the same as those shown in FIG.
11 (a), 11 (b) and 2) correspond. Here, "optically" means that a signal is obtained as it is without converting it into an electric signal.

(Effects) The light receiving section for receiving the scattered light from the target receives the light pulse from the light transmitting pulse acquiring means for acquiring a part of the light amount of the light transmitting pulse, and the scattered light from the light transmitting section optical system. The light pulse from the scattered light condensing means for simultaneously obtaining the above is input, and the magnitude of the output of the light receiving unit is evaluated by the reception output evaluation means. Based on the evaluation result and the measurement result of the distance measuring means, the measured value checking means determines whether there is an abnormality in the light source and whether the light transmitting portion is dirty or dewed.

2. 2. The distance measuring device according to claim 1, wherein the light receiving unit receives a first light receiving element that receives scattered light from the target, and an amount of light from the light transmission pulse acquisition unit and the scattered light collection unit. A second light receiving element, wherein the signal processing unit determines an operation of the light transmitting unit based on an output of the second light receiving element, and determines the target based on an output of the first light receiving element. A distance measuring device for measuring an operation of the light receiving unit.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the second embodiment (FIG. 2). (Operation and Effect) By providing the second light receiving element, it is possible to determine the abnormality of the light transmitting unit and the light receiving unit separately. Can be distinguished.

3. 3. The distance measuring apparatus according to claim 1 or 2, wherein the light transmission pulse acquiring unit illuminates the light receiving unit optical system with a part of the acquired light pulse, and the light receiving unit optical system illuminated by the illumination light. A distance measuring device for inputting scattered light from a light source to a light receiving unit.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention is the first embodiment (FIG. 6A,
(B)) corresponds.

(Function and Effect) An extra light source for detecting an abnormality such as dirt or dew on the light receiving unit optical system is not required.

4. 4. The distance measuring device according to any one of items 1 to 3, wherein the light transmitting pulse acquiring unit inserts and fixes an optical fiber having a processed end into a light transmitting optical path, and connects the other end to a light receiving unit receiving optical path. A distance measuring device, wherein the distance measuring device is inserted and fixed in a device.

(Corresponding Embodiment of the Invention) The embodiment of the present invention corresponds to the embodiment of FIG. (Function and Effect) Since the light pulse is guided to the light receiving portion by using the optical fiber, it is possible to obtain information about the abnormality of the light source without being affected by the electromagnetic noise of the light source driving system.

5. 4. The distance measuring device according to any one of items 1 to 3, wherein the light transmitting pulse acquiring unit is provided in a case of the light transmitting unit, and transmits a projecting portion having a mirror-finished tip. A distance measuring device provided in an optical optical path, wherein the reflected light at the tip is introduced into an optical path of a light receiving section through an opening or an optical fiber provided in a case of the light transmitting section.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention is the first embodiment (FIG. 6B).
Corresponds.

(Function and Effect) This is a modification of the device of the fourth item, and the operation and effect are the same as those of the device of the fourth item. 6. 6. The distance measuring device according to any one of items 1 to 5, wherein the reception output evaluation unit sets a value larger than a peak value of a reception signal at the light receiving unit when the light transmitting unit has no abnormality. A first comparison circuit having the obtained first threshold value, a first adder for integrating the comparison result of the first comparison circuit, and a second threshold value set to a value lower than the peak value. A distance measuring device, comprising: a second comparison circuit having the same; and a second adder for integrating the comparison result of the second comparison circuit.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the first embodiment (FIGS. 1 and 3). (Effect) When there is an input exceeding the first threshold,
It is conceivable that the amount of light guided to the light receiving element by the scattered light collecting means increases. This indicates the possibility of contamination and dew condensation on the light transmitting unit optical system. If there is an input below the second threshold, there is a concern about the life of the light source.

7. 7. The distance measuring device according to claim 6, wherein the distance measuring means includes a logarithmic amplifier for amplifying the output of the light receiving unit, and a peak value of the logarithmic amplifier output and a start obtained by binarizing the logarithmic amplifier output. A distance measuring device that outputs a distance measurement value obtained from a pulse and a stop pulse and a start pulse flag indicating generation of the start pulse.

(Corresponding Embodiment of the Invention) An embodiment according to the present invention is a first embodiment (FIGS. 1, 4).
5, 11 (a), (b)).

(Function / Effect) By employing the logarithmic amplifier, it is possible to make the relationship between the distance measurement value and the received light pulse peak value linear. The start pulse flag gives information on whether or not a start pulse has been generated, and indirectly notifies whether or not a light source abnormality or a light receiving element abnormality has occurred. The start pulse and the stop pulse give distance information.

8. 8. The distance measuring device according to claim 7, wherein the measured value checking means determines whether or not the start pulse flag calculated by the distance measuring means is present or not, and
And whether the output of the second adder has exceeded a predetermined threshold value and whether the integrated value has exceeded a predetermined threshold value is determined by a logical operation of four criteria for determining whether the light source / light receiving unit is normal or abnormal.
A distance measuring device for determining dirt / condensation of a light transmitting / receiving system and life of a light source.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the first embodiment (FIG. 10). (Effects) The duplicated information is sorted out, and the operation abnormality and the life of the distance measuring device or the sensor are comprehensively determined.

9. 9. The distance measuring device according to claim 8, wherein the measured value checking means is a peak value lower limit value obtained by linearly converting the distance measured value measured by the distance measuring means and a peak value calculated by the distance measuring means. A distance measuring device that accumulates the number of times the latter is less than the former and generates a warning signal when the integrated value exceeds a predetermined value after a predetermined number of distance measurements.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the first embodiment (FIG. 9). (Operation and Effect) The relationship between the distance measurement value and the received light pulse peak value is statistically considered to give indirectly information on the life of the light source and the contamination / condensation of the distance measurement device.

[0065]

According to the present invention, the abnormality of the optical / electrical element relating to the distance measurement of the light transmitting unit or the light receiving unit and its surroundings is determined by using the measured value without extra hardware, and A distance measuring device with a self-diagnosis function realized by a minimum detecting means irrespective of electromagnetic induction noise is provided.

[Brief description of the drawings]

FIG. 1 schematically shows a configuration of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 schematically shows a configuration of a distance measuring device according to a second embodiment of the present invention.

FIG. 3 shows a waveform of an optical pulse obtained from a light receiving element.

FIG. 4 shows waveforms of light pulses obtained for a normal light source and a light source that has already reached the end of its life.

FIG. 5 shows an output waveform of a logarithmic amplifier and an output waveform passed through a delay circuit.

FIG. 6 schematically shows a specific configuration of a light transmission pulse acquisition device.

FIG. 7 schematically shows a specific configuration of the scattered light collecting device.

FIG. 8 schematically shows another specific configuration of the light transmission pulse acquisition device.

FIG. 9 shows a frequency distribution of a relationship between a distance measurement value and a received signal peak value.

FIG. 10 shows a logical operation performed by the measured value check circuit based on outputs from the distance signal acquisition circuit and the reception output evaluation device.

FIG. 11 shows a specific block example of a distance signal acquisition circuit,
The timing chart is shown.

FIG. 12 is a diagram illustrating the operation of a conventional example of a distance measuring device having a self-diagnosis function.

FIG. 13 shows a schematic configuration of another conventional distance measuring device having a self-diagnosis function.

FIG. 14 shows a schematic configuration of a conventional example of a distance measuring device capable of detecting contamination attached to a transmission / reception optical system without increasing the number of components.

FIG. 15 shows a schematic configuration of a conventional example of a distance measuring device in which a dirt detecting device is incorporated in a light transmitting unit and sensitivity of dirt detection is improved.

[Explanation of symbols]

 Reference Signs List 100 light transmitting unit 106 scattered light condensing device 111 light receiving element 140 signal processing unit 150 light receiving unit

Claims (3)

[Claims] 1. A light transmitting means for transmitting an optical pulse toward a target, and a light receiving means for receiving scattered light from the target of the optical pulse transmitted from the light transmitting means, wherein the optical pulse is In a distance measuring device that measures a distance to a target by detecting a reciprocating time, a deriving unit that derives scattered light in the light transmitting unit to outside the light transmitting unit, and detects a light flux from the deriving unit. And a scattered light detecting unit, wherein the light transmitting unit and the scattered light detecting unit are electromagnetically shielded from each other. 2. The distance measuring device according to claim 1, wherein a light receiving element included in said light receiving means and a light receiving element included in said scattered light detecting means are the same light receiving element. apparatus. 3. The distance measuring device according to claim 1, further comprising: a light transmitting acquisition unit that acquires a part of the light transmitting pulse in the light transmitting unit and illuminates the light receiving unit with the part of the acquired light pulse. A distance measuring device, further comprising: