JP2008275379A - Laser range finder and laser range finding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly-accurate laser range finder and a laser range finding method. <P>SOLUTION: This laser range finder is equipped with a transmission part 1 for transmitting laser beam toward a measuring object, a reception part 2 for receiving a reception signal reflected by the measuring object and returned, a time measuring part 30 and an intensity measuring part 40 connected to an output terminal of the reception part 2, and a constant fraction discriminator. In the device, the laser light is transmitted toward the measuring object, and the reception signal 20 reflected by the measuring object and returned is received, and the distance to the measuring object is converted from a time difference between a transmission signal 10 transmitted by the laser light and the reception signal 20 by means of a relational expression with the velocity of light. The device is also equipped with distance determination parts 25, 26 for selecting the most probable time Δt from among a plurality of measurement results measured by the time measuring part 30 based on the intensity P of the reception signal 20 measured by the intensity measuring part 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Patent Document 1 below describes a radar apparatus that prevents deterioration in detection accuracy of an object due to the intensity of reflected waves being too high. In this radar apparatus, the laser radar sensor has a laser diode that emits laser light, and a polygon mirror that reflects the laser light emitted from the laser diode and scans a predetermined measurement area. This polygon mirror has reflecting surfaces with different laser beam reflectivities. Based on the traveling speed of the vehicle, the distance to the reflecting object, the received light intensity of the reflected wave from the reflecting object, etc. Switch the surface to change the intensity of the output laser beam. As a result, when detecting an object at a long distance or an object with a low reflectance of laser light, the intensity of the laser light is increased to detect an object at a short distance or an object with a high reflectance of laser light. Since the intensity can be changed so as to reduce the intensity of the laser beam, the object detection accuracy can be improved.

  Patent Document 2 below describes a laser distance measuring device that prevents fluctuations in measurement distance due to changes in the amount of received light in laser distance measurement. The laser distance measuring device includes a light receiving circuit that converts received laser light into an analog electric signal and outputs the signal, a digitizing circuit that converts the analog electric signal output from the light receiving circuit into a rectangular wave, and outputs the signal. A time measuring device that measures and records time by inputting a rectangular wave output from the digital circuit, and the digitizing circuit is a saturation countermeasure means that suppresses the output of the rectangular wave when an analog electric signal of a predetermined voltage or more is input. A saturation level detection circuit that outputs a control signal when an output of an amplification circuit that amplifies an analog electric signal exceeds an upper threshold, and a comparison circuit that suppresses conversion of the analog electric signal to a rectangular wave when the control signal is input. It is to have.

  Patent Document 3 listed below discloses a vehicle object recognition that can detect the adhesion of dirt on the surface of a laser radar sensor when laser light propagates inside or is scattered. An apparatus is described. In the vehicle object recognition device, when the laser light propagates inside the dirt or is scattered, a part of the laser light is received by the light receiving element of the laser radar sensor. Therefore, among the multiple irradiated laser beams, there is a laser beam whose intensity is so strong that the measurement time from irradiation until the reflected light is received is shorter than the predetermined measurement time and the received pulse of the reflected light exceeds the upper threshold. It is determined that dirt is attached on the condition that the number is not less than the first predetermined number. If the time from irradiation to light reception is shorter than the predetermined measurement time, it is reflected light due to the above-mentioned dirt, and if the intensity is so strong that the received light pulse exceeds the upper threshold, the amount of dirt attached is estimated to be large. it can. Therefore, when the number of such received light pulses exceeds the first predetermined number, it can be determined that the above-mentioned dirt has adhered.

  Further, Patent Document 3 also discloses the following technique. That is, the time width corresponding to the received light intensity and the correction time have a predetermined correspondence. Specifically, the correction time tends to monotonically increase as the time width corresponding to the received light intensity increases. Therefore, by obtaining the correspondence relationship by an experiment or the like in advance, the correction time can be obtained and corrected from the time width corresponding to the received light intensity. When the time when the received light signal reaches the maximum voltage is calculated, the distance to the reflecting object is measured based on the time difference from the light emission time of the laser diode to the time when it reaches the maximum voltage.

  Thereby, the measurement error due to the difference in the received light intensity of the reflected wave is corrected by the correction time, and the distance to the object is measured as the time difference up to the same time. The relationship between the time width corresponding to the received light intensity and the correction time is stored in a ROM or the like as a map (hereinafter also referred to as “correction table”).

  Further, in Patent Document 4 below, since an image of an object with a large amount of reflected light that exists at a short distance spreads and is recognized laterally, a technique that solves the problem that an object that exists at a long distance is hidden behind and cannot be recognized. Is disclosed. Specifically, the delay time measurement unit measures the delay time from the light emission signal to the light reception signal. The distance calculation unit calculates the distance to the object based on the delay time. The light reception level detection unit extracts a signal of the light reception level designated by the light reception level designation switching unit and sends it to the delay time measurement unit. Then, since the light reception level of the light reception signal designated by the light reception level designation switching unit is switched at a constant cycle, a different light reception signal is extracted as a signal for delay time measurement at every constant cycle.

JP 2005-77379 A JP 2003-294840 A Japanese Patent Laying-Open No. 2005-10094 JP-A-10-253759

  However, in the techniques described in Patent Documents 1 to 4, there is a problem that there is still room for improvement from the viewpoint of increasing the distance measurement accuracy. The present invention has been made in view of the above-described circumstances, and is most probable when measuring a time difference between a transmission signal transmitted toward a measurement target and a reception signal reflected back from the measurement target. An object of the present invention is to provide a laser distance measuring device that eliminates measurement errors by selecting a received signal that originally represents time.

  In order to achieve the object, the laser distance measuring apparatus according to the first invention employs the following first means. A transmitter that transmits laser light toward a measurement target, a receiver that receives a reception signal reflected back from the measurement target, and a time measurement unit and an intensity measurement unit connected to the output terminal of the reception unit And a constant fraction discriminator capable of extracting timing information independent of the wave height of the received signal, transmitting a laser beam toward the measurement target, and returning the received signal reflected by the measurement target In the laser distance measuring apparatus that converts the distance from the time difference between the transmission signal that has received and transmitted the laser beam and the received signal to the measurement target by the relational expression of the speed of light, the intensity of the received signal measured by the intensity measurement unit Based on this, a distance determination unit that selects the most probable time among a plurality of measurement results measured by the time measurement unit is employed.

According to the laser range finder according to the first aspect of the invention, the laser beam is transmitted from the transmission unit to the measurement target, and the reception signal reflected and returned from the measurement target is received by the reception unit. The output of the receiving unit is branched and input to the time measuring unit and the intensity measuring unit.
When the received signal in the laser distance measuring device is selected from the noise component and the original received signal by a single fixed simple threshold or gate signal, time measurement error (jitter) due to fluctuation of the received signal's wave height, etc. A measurement error occurs due to the distance.

  As described above, the constant fraction discriminator (CFD) is always operated in order to suppress the time measurement error included in the measurement time output by the time measurement unit. However, when a time measurement error exceeding the suppression limit in the CFD occurs, the distance determination unit operates to select highly accurate time information. That is, based on the intensity of the received signal measured by the intensity measuring unit, the most probable time is selected from a plurality of measurement results measured by the time measuring unit. By doing so, it is possible to provide a laser distance measuring device that eliminates measurement errors by selecting a reception signal that represents the most likely original time.

  Further, in the laser distance measuring device according to the second invention, in addition to the first means, the distance determining unit has a condition for selecting the most probable time that the intensity is maximum from the received signal. The second means is employed. In this way, the fact that the intensity is maximum is highly likely to be the most likely original received signal theoretically and from experience. Therefore, the corresponding signal is selected and used by a threshold value or logical operation. Thus, it is possible to obtain a highly accurate measurement result.

  In addition to the first means, the laser distance measuring apparatus according to the third invention employs the following third means. That is, a distance-intensity table in which distance determination criteria for selecting the most probable time or distance with respect to the intensity measured by the intensity measurement unit is stored in the distance determination unit and stored in a freely accessible manner, and the distance-intensity table. The third means is adopted in which the membership value is the maximum value as a condition for selecting the most probable time. The fact that this membership value is the maximum is likely to be the most likely original received signal based on the rule of thumb. Therefore, by selecting and using the corresponding signal, a highly accurate measurement result can be obtained. It is possible to obtain

The laser ranging method according to the fourth invention employs the following fourth means.
That is, a laser beam is transmitted toward a measurement target, a reception signal reflected and returned from the measurement target is received, and a relational expression of the speed of light from a time difference between the transmission signal that transmits the laser beam and the reception signal In the laser distance measuring method for converting the distance to the measurement object, the distance to the measurement object is converted using the time information indicated by the signal having the maximum signal intensity from the plurality of results obtained by measuring the time difference.

  According to the laser distance measuring method according to the fourth aspect of the invention, the same effects as those of the laser distance measuring apparatus according to the second aspect of the invention can be achieved.

The laser ranging method according to the fifth invention employs the following fifth means.
That is, a laser beam is transmitted toward a measurement target, a reception signal reflected and returned from the measurement target is received, and a relational expression of the speed of light from a time difference between the transmission signal that transmits the laser beam and the reception signal In the laser distance measuring method for converting the distance to the measurement object by referring to the distance-intensity table in which the distance determination standard for selecting the most probable time or distance for the measured intensity is selected and stored in a freely accessible manner, The distance to the measurement target is converted using the time information determined to be the most probable based on the membership value indicating the most probable degree from the plurality of results obtained by measuring the time difference.

  According to the laser distance measuring method according to the fifth aspect of the invention, the same effects as the laser distance measuring apparatus according to the third aspect of the invention can be achieved.

  According to the present invention, it is possible to provide a laser distance measuring device and a laser distance measuring method with improved measurement accuracy. In particular, when measuring the time difference between the transmitted signal transmitted to the measurement target and the received signal reflected back from the measurement target, more accurate time information is selected by selecting the most probable original signal. Therefore, measurement error can be eliminated.

  Hereinafter, with reference to the drawings, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described by appropriately interweaving the configuration and operation. In each figure, the same function is denoted by the same reference numeral, and description thereof is omitted.

  FIG. 1 is a block diagram showing a schematic configuration of a laser distance measuring device E according to the present embodiment. As shown in FIG. 1, the laser distance measuring device E includes a transmission unit 1 that transmits laser light toward the measurement target 12, a reception unit 2 that receives the reception signal 20 that is reflected back from the measurement target 12, and transmission and reception It is configured to include a scanner 3 interposed in the path, a signal processing unit 4 for branching and inputting the output of the receiving unit 2, a time measuring unit 30, and a control unit 5. In addition, the intensity | strength measurement part 40 mentioned later along FIG. 6 is arrange | positioned so that the time measurement part 30 may be paralleled.

  As shown in FIG. 1, the laser distance measuring device E transmits a transmission signal 10 by laser light from the transmission unit 1 to the measurement target 12 and receives a reception signal 20 that is reflected by the measurement target 12 and returns. A scanner 3 composed of a polygon mirror or the like for scanning the measurement area is interposed. That is, the transmission signal 10 transmitted from the transmission unit 1 is first projected onto the scanner 3, reflected so as to scan in an appropriate direction, and projected onto the measurement object 12.

The reception signal 20 reflected and returned from the measurement object 12 is also projected onto the scanner 3 and appropriately reflected toward the reception unit 2. The received signal 20 received by the receiving unit 2 is sent from the signal processing unit 4 to the time measuring unit 30 to the control unit 5. The control unit 5 selects the measurement time Δt ₁ obtained from the time measurement unit 30 or the measurement time Δt ₃ (FIG. 6) selected from only the more likely original received signal 21 (FIGS. 2 and 3). Used to control the scanner 3.

  FIG. 2 is a timing chart showing a method of invalidating short-distance data based on the gate signal 6 in the laser distance measuring device E according to the present embodiment. (A) Transmission pulse 10p, (b) Reception signal 20 (C) gate signal 6 and (d) received pulse 21p. As shown in FIG. 2, in the laser distance measuring device E, it is possible to invalidate the shot noise 22 and the stray light 23 which are short distance data based on the gate signal 6.

  That is, shot noise 22 and stray light 23 are applied to short-distance data input by the receiver 2 during a period until the gate signal 6 generated with a predetermined time delay from the transmission pulse 10p output from the transmitter 1 rises. It is invalidated as if it is. Then, since only the original signal (hereinafter also referred to as “reception signal”) 21 is extracted from the reception signal 20, it is possible to obtain an accurate reception pulse 21 p based on the original signal 21.

  FIG. 3 is a timing chart showing a method of removing a noise component based on the threshold value 7 in the laser distance measuring device E according to the present embodiment. (A) Transmission pulse 10p, (b) Threshold value 7, (c) Reception Signal 20, (d) received pulse 21p. As shown in FIG. 3, in the laser distance measuring device E, it is possible to remove noise components due to shot noise 22 and stray light 23 that are short-distance data based on the threshold value 7.

  That is, the received signal 20 is sorted by the threshold value 7, and if it is equal to or less than the threshold value 7, it is a noise component, and if it is equal to or greater than the threshold value 7, it is regarded as the original signal 21, thereby extracting only the original signal 21 from the received signal 20. Therefore, an accurate reception pulse 21p can be obtained based on the original signal 21.

  FIG. 4 is a timing chart showing a case where the original signal 21x returning from a short distance cannot be detected when the gate signal 6 is used in the laser distance measuring device E according to the present embodiment. (A) Transmission pulse 10p, (b) Received signal 20, (c) gate signal 6, (d) received pulse 21p. As shown in FIG. 4, in the laser distance measuring device E, shot noise 22 or stray light is used for the period from the transmission pulse 10 p until the gate signal 6 rises, that is, for the short distance data input by the receiver 2. Regardless of whether the signal is 23 or the original signal 21x, it is regarded as noise and is uniformly invalidated. At this time, if the original signal 21x is included in the short distance data, it is naturally invalidated, so that the original signal 21x returning from the short distance cannot be detected.

  FIG. 5 is a timing chart showing a case where the original signal 21y returning from a long distance cannot be detected when the threshold value 7 is increased in the laser distance measuring device E according to the present embodiment. (A) Transmission pulse 10p, (b) Threshold value 7, (c) received signal 20, (d) received pulse 21p. As shown in FIG. 5, according to the selection method that considers a noise component if the threshold value is 7 or less, and considers it as the original signal 21 if the threshold value is 7 or more, it is shot noise 22 or stray light 23 for long-distance data. Regardless of whether it is the original signal 21y or not, if it is equal to or less than the threshold value 7, it is regarded as noise and is uniformly invalidated. At this time, if the original signal 21x is at a low level like the long-distance data, it is naturally invalidated, so that the original signal 21y returning from the long distance cannot be detected.

  FIG. 6 is an explanatory diagram of a method for selecting a more probable time in the laser distance measuring device E according to the present embodiment. (A) A method for selecting the highest intensity, (b) From a distance-intensity map It is a way to select the most probable one. As shown in FIG. 6, the laser distance measuring device E includes a time measuring unit 30 and an intensity measuring unit 40 that branch and input the received signal 20 received by the receiving unit 2. A distance determination unit 25 is connected to the subsequent stage, and a distance determination unit 26 is connected to the subsequent stage of the intensity measurement unit 40.

More specifically, the received signal 20 received by the receiving unit 2 branches finely, and the first time measuring unit 31, the Nth time measuring unit 3N, the first intensity measuring unit 41, and the Nth intensity measuring unit 4N. , And Δt ₁ , P ₁ , Δt _n , P _n are output as measurement results. Here, the N value from the first intensity measurement unit 41 to the Nth intensity measurement unit 4N and the N value from the first time measurement unit 31 to the Nth time measurement unit 3N are counted up in conjunction with each other. However, the measurement unit sequentially shifts from 1 to N (see FIGS. 9 and 10A).

Next, the distance determination method will be described by dividing it into two types shown in FIGS. 6 (a) and 6 (b).
On the other hand, the distance determination unit 25 shown in FIG. 6A selects and outputs the one having the highest intensity. Specifically, as will be described later with reference to FIG. 9, the N values from the first intensity measurement unit 41 to the Nth intensity measurement unit 4N are counted up to 1 to N, and the measurement values of each measurement unit are counted. (Hereinafter also referred to as “pulse width” or “signal intensity”) P ₁ , P ₂ , P ₁ , P ₃ ,... _Pn are sequentially compared in order of magnitude, for example, P ₁ > P ₂ , P _{If 1} <P ₃ ,..., P _n <P ₃ , Δt ₃ is selected and output.

  On the other hand, the distance determination unit 26 shown in FIG. 6B selects and outputs the most probable one from the distance-intensity map. In other words, the distance determination unit 26 stores “distance-intensity map (hereinafter also referred to as“ correction table ”)”, which is back data obtained by collecting the relationship between distance and signal intensity based on empirical rules, and making it readable. is doing. This “distance-intensity map” can output the most probable measurement time based on the concept of “membership value” in the manner described later with reference to FIG.

FIG. 7 is a block diagram showing the time measuring unit 30 in the laser distance measuring device E according to the present embodiment. As shown in FIG. 7, the time measurement unit 30 distributes and inputs the time information via the constant fraction discriminator (hereinafter abbreviated as “CFD”) and the comparator 50 to each unit and performs a logical operation to measure time Δ t ₁ , Δt ₂ , Δt ₃ ,... Δt _n are output. In addition, AND circuits 61 and 62 are inserted at appropriate places for the convenience of logical operation. It should be noted that the CFD operating principle that utilizes the fact that the temporal position of the intersection of the delay signal and the attenuation signal is always constant without depending on the signal intensity is well known and will not be described.

Further, as shown in FIG. 6, the time measuring unit 30 is an aggregate of the first time measuring unit 31, the second time measuring unit 32, and the third time measuring unit 33 to the Nth time measuring unit 3N. It is. Each time measuring unit uses the received signal 20 and the threshold 7 and inputs the time information output from the D-type flip-flops 71 to 73 for inputting the time information processed through the CFD and the comparator 50 and the Q terminal. It comprises counters 81 to 83 that output measurement times Δt ₁ , Δt ₂ , Δt ₃ ,... Δt _n .

  As shown in FIG. 7, the transmission signal 10 is input only to the counter 81 and used as a reference time for time measurement. On the other hand, the received signal 20 is input to the CFD and the comparator 50, respectively, and used to measure the time elapsed from the reference time. The threshold 7 is input to the comparator 50 together with the received signal 20, and the received signal 20 exceeding the threshold 7 is regarded as the original signal 21 (FIG. 3) and input to the R terminal of the D-type flip-flop 71.

  The output of the Q terminal of the D flip-flop 71 and the original signal 21 are input to the AND circuits 61 and 62, and the AND output is input to the R terminals of the D flip-flops 72 and 73. Although omitted from FIG. 7, if there is an Nth time measuring unit 3N (FIG. 6), the AND output is also input to the R terminal of a D-type flip-flop 7N (not shown).

  The CFD output signal is input to each CLK terminal of the D-type flip-flops 71 to 73. The output signal of the CFD can be expected to be highly reliable time information without depending on the signal strength. On the other hand, the received signal 21 (original signal) obtained from the output terminal of the comparator 50 is input to the R terminal of each D-type flip-flop, and timing information independent of the wave height of the received signal 21 is input to the Q-type of each D-type flip-flop. Extract from terminal.

The Q terminals of the D-type flip-flops 71 to 73 are connected to the counters 81 to 83, and the counters 81 to 83 are reset at the light projection timing of the transmission signal 10 output from the transmission unit 1 of the laser distance measuring device E. The time Δt ₁ , Δt ₂ , Δt ₃ ,... Δt _{n of} the signal having a plurality of timings is measured and held with respect to the later time. Thus, the time measuring unit 30 functions as a highly accurate time measuring counter by selecting a plurality of measurement results. However, regarding the individual time measurement counters 81 to 83, those already made into one chip have been put into practical use, and thus further detailed description thereof will be omitted.

In this way, the CFD is always operating in order to suppress the time measurement error included in the measurement time Δt ₁ output by the time measurement unit 30. However, for a time measurement error exceeding a general suppression limit in CFD, the distance determination unit 25 shown in FIG. 6A is operated to output the most probable measurement time. Alternatively, the distance determination unit 26 shown in FIG. When the distance determination unit 26 operates, a CPU (not shown) performs correction with reference to a distance-intensity map read from the ROM.

FIG. 8 is a block diagram showing an intensity measurement unit (hereinafter also referred to as “pulse width measurement unit”) 40 in the laser distance measuring device E according to the present embodiment. As shown in FIG. 8, the intensity measuring unit 40 includes a first intensity measuring unit 41, a second intensity measuring unit 42, and a third intensity measuring unit 43 to an Nth intensity measuring unit 4N as shown in FIG. Is a collection of In addition to the transmission signal 10, each intensity measurement unit compares the received signal 20 and the threshold 7 with the comparators 51 to 54 and inputs them to the CLK terminal, and the D-type flip-flops 74 to 77. It comprises counters 84 and 85 for outputting signals of pulse widths (signal strength) P ₁ , P ₂ ,... P _n output from the Q terminal or D terminal.

  As shown in FIG. 8, the transmission signal 10 is input to the R terminal of only the D-type flip-flop 74 and used as a reference time for time measurement. On the other hand, the threshold 7 is input to the comparators 51 to 54 together with the received signal 20 and used to measure the time elapsed from the reference time. That is, the received signal 20 exceeding the threshold value 7 is regarded as the original signal 21 (FIG. 3) and input to the R terminals of the D-type flip-flops 74 to 77.

  Among these, the outputs of the Q terminals of the D-type flip-flops 74 and 76 are connected to the counters 84 and 85, and the counter is at the projection timing of the transmission signal 10 output from the transmission unit 1 of the laser distance measuring device E. By measuring the time after the reset, the intensity measuring unit 40 recognizes the pulse width and measures the signal intensity. That is, the principle that the wider the base is, the higher the peak is, and the fact that the signal intensity is larger as the signal has a wider pulse width. Using the signal intensity information thus obtained, it is possible to obtain highly accurate outputs from the distance determination units 25 and 26 as shown in FIG.

FIG. 9 is a flowchart showing a method for achieving both long distance and short distance measurement based on the maximum signal in the laser distance measuring device E according to the present embodiment. The processing stage after the end of time measurement (step S1) will be described below. As shown in [P = P ₁ , Δt = Δt ₁ ], signal strength verification (step S2) is performed to verify the time with the highest signal strength. Next, as shown in [ifN = 1], the N value from the first intensity measurement unit 41 to the Nth intensity measurement unit 4N and the N value from the first time measurement unit 31 to the Nth time measurement unit 3N. Whether the value is single? N value single / multiple confirmation (step S3) is executed.

When the N value single confirmation (step S3) is No and the N value is not N = 1, as shown in [if (P ₁ > P)], a P value size comparison (step S4) is executed. _{Then, [△ t = △ t 1} ] as shown in the time measurement value △ _n by the time measuring unit of the N corresponding one-to-one by the N value of the larger results of the comparison, determines that more probable The maximum intensity selection (step S5) for selecting Δt = Δt ₁ according to the maximum signal intensity to be executed is executed. These [P value magnitude comparison (step S4) to maximum intensity selection (step S5)] are sequentially executed from the first to the Nth as shown in [for (i = 1, N)].

By the maximum intensity selection (step S5), the time output (step S6) for outputting the time information determined to be the most probable is reached. Next, a distance conversion step (not shown) for calculating the distance from the measured time difference Δt to the measurement object 12 is executed. In this way, it is possible to achieve both long-distance measurement and short-distance measurement by selecting the time with the highest signal intensity.
On the other hand, if the N value single confirmation (step S3) is Yes and the N value is N = 1, the time measurement unit 30 adopts a single measurement result without hesitation, thereby outputting the time output (step S6). ).

FIG. 10 is a flowchart showing a method for achieving both long distance and short distance measurement based on the membership value in the laser distance measuring apparatus according to the present embodiment, and FIG. 10B is a diagram showing an example of the membership value. It is. The processing steps after the end of time measurement (step S1) will be described below with reference to FIG. As shown in [Δt = Δt ₁ , F = F ₁ ], membership value verification (step S12) is performed to verify the membership value F indicating the most probable degree. As can be seen from the example of membership values shown in FIG. 10B, the strength is inversely proportional to time (Δt). This time and altitude membership function represents a membership value assigned by a number from 0 to 1.

Next, as shown in [if (F ₁ > F)], an F value magnitude comparison (step S13) for comparing the magnitudes of the F values is executed. _{Then, [△ t = △ t 1} ] as shown in the time measurement value △ _n by the time measuring unit of the N corresponding one-to-one by the N value of the larger results of the comparison, determines that more probable The maximum F value selection (step S14) is selected as Δt = Δt ₁ depending on the maximum signal strength to be performed. These [F value magnitude comparison (step S13) to maximum F value selection (step S14)] are sequentially executed from the first to the Nth as shown in [for (i = 1, N)].

  By the maximum intensity selection (step S14), the time output (step S15) for outputting the time information determined to be the most probable is reached. Next, a distance conversion step (not shown) for calculating the distance from the measured time difference Δt to the measurement object 12 is executed. In this way, it is possible to achieve both long-distance measurement and short-distance measurement by selecting the time with the highest signal intensity.

  The various shapes and combinations of the constituent members shown in the above-described embodiments are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention. For example, regardless of the designation of “correction table” or “distance-intensity map” according to the present invention, as shown in FIG. Any of them may be used as long as they are predetermined and stored in a ROM or the like. Further, the storage medium is not limited to the ROM and is free.

  In short, the laser distance measuring device is provided with distance determining units 25 and 26 for selecting the original signals 21x and 21y from the received signal 20 including the time measurement error exceeding the suppression limit in the CFD so as to improve the distance measuring accuracy. All techniques related to E are included in the present invention.

  In the above embodiment, a laser radar sensor using laser light is employed, but electromagnetic waves, light (millimeter waves, X-rays, etc.) and ultrasonic waves may be used.

1 is a block diagram showing a schematic configuration of a laser distance measuring device according to an embodiment (this embodiment) of the present invention. FIG. 5 is a timing chart showing a method for invalidating short-range data based on a gate signal in the laser distance measuring device according to the present embodiment, wherein (a) a transmission pulse, (b) a reception signal, (c) a gate signal, (D) A received pulse. 4 is a timing chart showing a method of removing a noise component based on a threshold in the laser distance measuring device according to the present embodiment, wherein (a) a transmission pulse, (b) a threshold, (c) a reception signal, and (d) a reception pulse. . is there. 4 is a timing chart showing a case where an original signal returning from a short distance cannot be detected when a gate signal is used in the laser distance measuring device according to the present embodiment, and (a) a transmission pulse, (b) a reception signal, and (c) a gate. Signal, (d) received pulse. In the laser distance measuring device according to the present embodiment, it is a timing chart showing a case where an original signal returning from a long distance cannot be detected when a threshold value is raised, and (a) a transmission pulse, (b) a threshold value, (c) a received signal, (D) A received pulse. is there. In the laser ranging apparatus concerning this embodiment, it is explanatory drawing of the method of selecting more probable time, (a) The method of selecting the thing with the largest intensity | strength, (b) The most probable thing from a distance-intensity map It is a method of selecting. It is a block diagram which shows the time measurement part in the laser distance measuring device which concerns on this embodiment. It is a block diagram which shows the intensity | strength measurement part (pulse width measurement part) in the laser ranging apparatus which concerns on this embodiment. It is a flowchart which shows the method of making the long distance and short distance measurement compatible based on the maximum signal in the laser distance measuring device which concerns on this embodiment. In the laser distance measuring device according to the present embodiment, (a) a flowchart showing a method for achieving both long distance and short distance measurement based on a membership value, and (b) is a diagram showing an example of a membership value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmission part, 2 ... Reception part, 3 ... Scanner, 4 ... Signal processing part, 5 ... Control part,
6 ... Gate signal 7 ... Threshold value 10 ... Transmission signal 10p ... Transmission pulse
12 ... measurement object, 20 ... received signal, 21 ... (original) signal,
22 ... shot noise, 23 ... stray light, 21p ... received pulse,
21x ... (return from a short distance) original signal (received signal),
21y ... (return from a long distance) original signal (received signal),
30 ... Time measuring unit, 31 ... First time measuring unit, 3N ... Nth time measuring unit,
40: Strength measuring unit, 41: First strength measuring unit, 4N: Nth strength measuring unit,
50 to 54: comparator, 61, 62: AND circuit,
71-77 ... D-type flip-flop, 81-84 ... counter,
CFD: Constant fraction discriminator,
E: Laser distance measuring device, Δt ₁ , Δt ₂ , Δt ₃ , .about.Δt _n ... measurement time,
P ₁ , P ₂ , P ₁ , P ₃ ,..., P _n ..., Measured value (pulse width, signal intensity)

Claims (5)

A transmitter for transmitting laser light toward the measurement target;
A receiving unit for receiving a reception signal reflected back from the measurement object;
A time measuring unit and an intensity measuring unit connected to the output end of the receiving unit;
A constant fraction discriminator capable of extracting timing information independent of the wave height of the received signal,
A laser beam is transmitted toward the measurement object, a reception signal reflected and returned from the measurement object is received, and a measurement is performed according to a relational expression of the speed of light from a time difference between the transmission signal that transmits the laser beam and the reception signal. In the laser distance measuring device that converts the distance to the target,
A laser distance measuring device comprising a distance determining unit that selects the most probable time from a plurality of measurement results measured by the time measuring unit based on the intensity of the received signal measured by the intensity measuring unit. .   2. The laser distance measuring device according to claim 1, wherein the distance determination unit sets a maximum intensity among received signals as a condition for selecting a most probable time. A distance-intensity table in which a distance determination standard for selecting the most probable time or distance for the intensity measured by the intensity measurement unit is stored in the distance determination unit in a freely-referenced manner,
2. The laser distance measuring apparatus according to claim 1, wherein a membership value is a maximum value with reference to the distance-intensity table as a condition for selecting a most probable time. Send laser light to the measurement object,
Receive the received signal reflected back from the measurement object,
In the laser distance measuring method for converting the distance to the measurement object by the relational expression of the speed of light from the time difference between the transmission signal and the reception signal that transmitted the laser light,
A laser ranging method, wherein a distance to a measurement target is converted using time information indicated by a signal having a maximum signal intensity from a plurality of results obtained by measuring the time difference. Send laser light to the measurement object,
Receive the received signal reflected back from the measurement object,
In the laser distance measuring method for converting the distance to the measurement object by the relational expression of the speed of light from the time difference between the transmission signal and the reception signal that transmitted the laser light,
Refer to a distance-intensity table that predetermines a distance criterion for selecting the most probable time or distance for the measured intensity and stores it for reference.
The laser measurement according to claim 1, wherein the distance to the measurement target is converted using time information determined to be most probable based on a membership value indicating the most probable degree from a plurality of results obtained by measuring the time difference. Distance method.

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