JP4771796B2 - Pulse height detection circuit for pulse signals - Google Patents

Description

The present invention relates to a peak value detection circuit for a pulse signal applied to detection of a peak value of a received light pulse of an optical distance measuring device that measures a distance to an object to be measured using an optical pulse , and in particular, to detect a peak value of a received light pulse. The present invention relates to a pulse signal peak value detection circuit with improved accuracy.

  For example, a light pulse is projected onto an object to be measured, the reflected scattered light is received, the time from when the light pulse is projected until the reflected pulse is received is measured, and this measurement time is used. In the optical distance measuring device that measures the distance to the distance measuring object, the detection accuracy of the light reception time of the reflected pulse greatly affects the distance measurement accuracy. As one method for detecting the light reception time, there is a method for detecting a rising edge of a pulse signal (hereinafter referred to as a rising edge detection method). The rising edge detection method detects a time point (hereinafter referred to as an edge point) at which the level of a received light pulse generated by receiving a reflected pulse reaches a preset threshold value as a received light time.

  However, in the case of the rising edge detection method, the edge point changes according to the peak value of the received light pulse, and therefore, the peak value of the received light pulse differs due to the influence of the reflectance or the like even when the distance measurement object is at the same distance. As a result, there is a problem in that the detected light reception time is deviated, resulting in a ranging error. For this reason, in the optical distance measuring device of the rising edge detection method, the distance correction according to the peak value level of the received light pulse increases the measurement accuracy.

Conventionally, in this type of optical distance measuring device, the peak value of the intensity of the received light pulse signal is obtained and held using an integration peak hold circuit, and this peak value corresponds to the peak value of the received light pulse. There is one that calculates a correction value for distance correction based on the value (see, for example, Patent Document 1).
JP-A-8-240657

  However, Patent Document 1 has a configuration in which a received light pulse is directly input to a peak hold circuit, integrated, and held, and does not consider the offset (DC component) of the received light pulse. For this reason, the offset value is included in the integral value, and there is a problem that the peak value of the held integral value and the peak value of the received light pulse do not necessarily correspond accurately.

The present invention has been made paying attention to the above problems, and by calculating the integrated peak value by removing the offset of the received light pulse of the optical distance measuring device, the peak value of the received light pulse of the optical distance measuring device can be accurately obtained. It is an object of the present invention to provide a peak value detection circuit for a pulse signal that can be detected easily.

For this reason, the invention of claim 1 is directed to a light pulse projecting means for projecting a light pulse to a distance measuring object, and a reflected pulse from the distance measuring object based on the light projection pulse to receive a light receiving pulse. Light pulse receiving means for generating, peak value detecting means for detecting a peak value of the received light pulse, detecting the received light pulse using a threshold value, and projecting the optical pulse until detecting the received light pulse A distance measuring means for correcting the measured time according to the peak value of the received light pulse detected by the peak value detecting means, and calculating the distance to the distance measuring object using the corrected measurement time; A peak value detection circuit applied to the peak value detection means of an optical distance measuring device comprising: a differentiation circuit for differentiating the received light pulse ; an integration circuit for integrating a differential signal output from the differentiation circuit; Integration output from the integration circuit And a peak value detecting means for detecting a peak value of the item, characterized in that the detected peak value of the peak value detecting means is configured to detect as the peak value.

In such a configuration, the offset (DC component) of the input pulse signal is removed by differentiating the received pulse of the optical distance measuring device with a differentiating circuit. The differential signal is integrated by an integration circuit, and the integrated peak value is detected by the peak value detecting means, whereby the peak value of the received light pulse from which the offset is removed can be obtained as the integrated peak value.

  As in claim 2, the peak value detection means comprises a differentiation circuit for differentiating the integration signal and a sampling circuit for sampling the integration signal level at the zero cross point of the differentiation signal output from the differentiation circuit. Good.

According to a third aspect of the present invention, the time constant of the differentiating circuit is set so that there is only one zero cross point of the differential signal.
In such a configuration, the integral output does not increase from the initial peak value.
According to a third aspect of the present invention, as in the fourth aspect, the peak value detecting means is configured by a peak hold circuit that holds a peak value of the integrated signal.
In such a configuration, the integrated output does not increase from the peak point, so if the peak value is maintained during the sampling period by the peak hold circuit, the input pulse signal is a high-speed pulse signal that makes it difficult to accurately detect the integrated peak position. Even if it exists, it becomes possible to easily sample the integrated peak value.

According to a fifth aspect of the present invention, the distance measuring means of the optical distance measuring device regards the time when the level of the received light pulse input from the optical pulse light receiving means reaches a predetermined threshold as the light reception time of the reflected pulse, and a stop timing signal. The rising edge detector that outputs the light and the start timing signal indicating the light projection time of the light pulse projected from the light pulse light projecting means is input to measure the time from when the stop timing signal is input. A timing unit that calculates the distance to the distance object, and this timing unit includes a timing correction unit that corrects the measurement time in accordance with the peak value of the received light pulse detected by the peak value detection means. The distance to the distance measuring object is calculated using the corrected measurement time corrected by the unit .

  According to a sixth aspect of the present invention, the optical distance measuring device detects a zero cross point of a signal after filtering the received light pulse separately from the distance measuring means, and detects the zero cross point after projecting the optical pulse. A distance measuring means for measuring a time until the measurement is performed, and calculating a distance to the distance measuring object based on the measurement time, and calculating a distance value of both distance measuring means from the wave detected by the peak value detecting means. It is the structure which selects according to a high value and makes it a ranging output.

According to the pulse signal peak value detection circuit of the present invention, since the input pulse signal is differentiated by the differentiation circuit and then integrated, the offset of the input pulse signal can be removed from the integration peak value. It is possible to detect the peak value of the corresponding input pulse signal with high accuracy.
Also, if the time constant of the differentiation circuit is set so that there is only one zero-cross point of the differentiation signal, the integrated output does not increase from the first peak value, and the integrated peak value is maintained by the peak hold circuit. If sampling is performed in the meantime, the peak value of the pulse signal can be detected easily and accurately even if the input pulse signal is a high-speed pulse.

Further, by applying the pulse signal peak value detection circuit of the present invention to the detection of the peak value of the received light pulse of the optical distance measuring device employing the rising edge detection method, this kind of optical measurement is possible. The ranging accuracy of the distance device can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of a pulse signal peak value detection circuit according to the present invention, which is applied to detection of a peak value of a received light pulse of an optical distance measuring device to be described later .
In FIG. 1, a peak value detection circuit 1 of the present embodiment includes a differentiation circuit 2 that differentiates an input pulse signal, an integration circuit 3 that integrates a differentiation signal output from the differentiation circuit 2, and an integration circuit 3. And a peak hold circuit 4 as a peak value detecting means for detecting the peak value of the output integral signal. Then, by setting the time constant of the differentiation circuit 2 so that there is only one zero-cross point of the differentiation signal, the integration signal waveform of the integration circuit 3 becomes a waveform in which the peak value does not increase from the first peak point. It is trying to become.

Next, the operation of the peak value detection circuit 1 will be described with reference to FIG. 2 showing the output waveform of each circuit.
When a pulse signal having a waveform including an offset (DC component) as shown in FIG. 2 is input to the differentiating circuit 2, the differentiating circuit 2 differentiates the input pulse signal and outputs a differential signal having a waveform as shown in the figure. By the differentiation process by the differentiating circuit 2, the offset of the input pulse signal can be removed. Thereafter, the integration signal is integrated by the integration circuit 3 to output an integration signal having a waveform as shown in the figure. The peak value of the integrated signal corresponds to the area (shaded portion) of the differential signal waveform, and corresponds to the peak value of the input pulse signal from which the offset is removed. This peak value is held by the peak hold circuit 4 and maintained during a predetermined sampling period as shown in the figure, and output as the peak value of the input pulse signal. The peak hold output may be sampled by a sampling circuit (not shown) during the sampling period.

  According to the peak value detection circuit of this embodiment having such a configuration, the peak value is obtained by the integration circuit 3 after the differential circuit 2 removes the offset of the input pulse signal, so that the integration peak value of the integration circuit 3 is obtained. Does not include the offset of the input pulse signal, and the peak value of the input pulse signal can be detected with high accuracy. In addition, the time constant of the differentiation circuit 2 is set so that there is only one zero-cross point of the differentiation signal, and the peak value of the integrated signal waveform does not increase from the first peak point so that the peak hold circuit 4 can increase the first peak. Since the value is maintained for a certain time (sampling period), it is only necessary to sample the output of the peak hold circuit 4 during the sampling period to obtain the peak value. High-speed pulse signals that can easily and accurately sample integrated signal peak values even with high-speed pulse signals (pulse signals with a narrow pulse width (eg, several ns order) and steep rises) that are difficult to sample accurately. It is effective for detecting the peak value of

When the input pulse signal is not a high-speed pulse signal, it can be configured as in the second embodiment shown in FIG. That is, instead of the peak hold circuit 4, the peak value detection means is constituted by a differentiation circuit 5 and a sampling circuit 6.
In the configuration of FIG. 3, the differentiating circuit 5 differentiates the integrated signal of the integrating circuit 3 and detects its peak position, and outputs a falling signal at the peak position of the integrated signal. The sampling circuit 6 samples the peak value of the integration signal, samples the integration value when the falling signal is input from the differentiation circuit 5, and outputs the sampling value as the peak value of the input pulse signal.

Next, an example of an optical distance measuring apparatus to which the pulse signal peak value detection circuit according to the present invention is applied will be described with reference to FIG.
In FIG. 4, the optical distance measuring device includes an optical pulse projecting unit 12 including, for example, a laser light source, which is an optical pulse projecting unit that emits an optical pulse to a target 11 that is an object to be measured, and the target 11. A light pulse receiving unit 13 which is a light pulse receiving unit that receives a part of the reflected scattered light from the light as a reflected pulse and generates a light receiving pulse, and a part of the light projecting pulse of the light pulse projecting unit 12 are input. A projection timing detector 14 for detecting the projection timing (projection time) of the projection pulse and outputting a timing start timing signal; and a zero cross of the signal after filtering the received pulse input from the optical pulse receiver 13 Using the point as the light reception timing (light reception time) of the reflected pulse, the time from the light pulse projection time to the light reception time is measured, and the target 11 is reached based on the measurement time. The first distance measuring unit 15 which is a distance measuring means for calculating the distance and the time when the level of the received light pulse input from the light pulse light receiving unit 13 reaches a predetermined threshold is used as the light reception timing (light reception time) of the reflected pulse. A second distance measuring unit 16 that is a distance measuring unit that measures a time from a light projecting time to a light receiving time and calculates a distance to the target 11 based on the measured time, and inputs from the light pulse light receiving unit 3. As the peak value detecting means for detecting the peak value of the received light pulse, the peak value detecting unit 17 configured by the peak value detecting circuit 1 shown in FIG. 1 and the detected peak value output from the peak value detecting unit 17 during the sampling period described above. The A / D converter 18 that performs sampling and A / D conversion, and the detected peak value sampled by the A / D converter 18 and a preset reference peak value are compared, and the detected peak value is the reference peak value. If it is below the reference peak value, a ranging output selection command from the first ranging unit 15 is output. If it is higher than the reference peak value, a ranging output selection command from the second ranging unit 16 is output. And the distance measurement output of the first distance measurement unit 15 and the distance measurement output of the second distance measurement unit 16 are switched and selected based on the selection command, and the distance measurement of the optical distance measurement device is performed. And a ranging value selection unit 20 that outputs the value as a value.

  The first distance measuring unit 15 extracts, for example, a fundamental frequency component as a specific frequency component included in the received light pulse input from the optical pulse light receiving unit 3 using a resonance circuit, and detects a zero cross point of the extracted fundamental frequency signal. The zero cross point is regarded as the light reception time of the reflected pulse, and the stop timing signal of the zero cross detecting unit 21 is output after the start timing signal from the light projection timing detecting unit 14 is input. A first time measuring unit 22 that measures the time until input and calculates the distance to the target 11 based on the measured time is provided. By extracting the fundamental frequency component as the specific frequency component, the noise superimposed on the received light pulse can be effectively removed, so that the influence of noise on the detection of the zero cross point can be suppressed. The zero cross detector 21 may be configured to detect a zero cross point by extracting a harmonic component as a specific frequency component included in the received light pulse using a high-pass filter.

  The second distance measuring unit 16 detects a time point when the level of the received light pulse input from the light pulse light receiving unit 13 reaches a predetermined threshold value, regards this detected time point as a light receiving time of the reflected pulse, and stops the timing. The rising edge detector 31 that outputs a signal and the time from when the start timing signal is input from the light projection timing detector 14 until the stop timing signal of the rising edge detector 31 is input are measured, and based on the measurement time And a second timer 32 that calculates the distance to the target 11. The second timer 32 includes a timer corrector 32 </ b> A that corrects the measurement time in accordance with the peak value detected by the peak value detector 17.

  The peak value detection unit 17 has the same configuration as the peak value detection circuit 1 shown in FIG. 1 and includes a differentiating circuit 2, an integrating circuit 3, and a peak hold circuit 4, and has a projected pulse waveform and a received pulse waveform. Assuming similarities (same pulse width, rise time, and fall time), the light intensity peak value of the received light pulse corresponds to the peak value, so the light intensity peak value is detected and output as the peak value of the received light pulse. .

Next, the operation of the optical distance measuring device will be briefly described.
A light pulse having a narrow pulse width of, for example, about several ns is emitted from the light pulse projecting unit 12 toward the target 11, and a part of the reflected scattered light from the target 11 is received by the light pulse light receiving unit 13. Further, when a light pulse is emitted from the light pulse projector 12, the light projection timing detector 14 receives a part of the light pulse, detects the light projection timing (light projection time) of the light pulse, and the first A start timing signal for timekeeping is transmitted to the first timekeeping section 22 of the distance measuring section 15 and the second timekeeping section 32 of the second distance measuring section 16, respectively. When receiving the reflected pulse light, the light pulse light receiving unit 13 generates a light receiving pulse, which is input to the first and second distance measuring units 15 and 16 and the peak value detecting unit 17.

  When the received light pulse is input to the zero cross detecting unit 21, the first distance measuring unit 15 extracts a fundamental frequency component included in the received light pulse using a resonance circuit, detects a zero cross point of the vibration waveform, and determines the detection time point. A stop timing signal for time counting is transmitted to the first time counting unit 22 by regarding the time when the reflected pulse is received. The first timer 22 measures the time from the input timing of the start timing signal from the light projection timing detector 14 to the input timing of the stop timing signal, and the light propagation speed (stored in advance) in this measurement time. Multiply and convert to distance. Furthermore, since the measured time corresponds to the time required to reciprocate between the optical distance measuring device and the target 11, the distance to the target 11 is calculated by multiplying the converted distance value by ½.

  When the light receiving pulse is input to the rising edge detecting unit 31, the second distance measuring unit 16 detects a time point when the level of the light receiving pulse reaches a predetermined threshold value, and sends a stop timing signal to the second time measuring unit 32. Send. The second timer 32 measures the time from the input timing of the start timing signal to the input timing of the stop timing signal. Furthermore, in the rising edge detection method of the second distance measuring unit 32, when the threshold Eth is constant, the edge point changes according to the peak value level of the received light pulse, and the timed stop timing changes. For this reason, according to the peak value of the received light pulse obtained from the output of the A / D converter 18 by the time correction unit 32A of the second timer unit 32, the correction value of the measurement time increases as the peak value decreases. After that, the correction measurement time is converted into a distance in the same manner as in the first time measuring unit 22, and the distance to the target 1 is calculated by multiplying the converted distance value by 1/2.

The peak value of the received light pulse output from the A / D converter 18 is also output to the peak value determination unit 19. The peak value discriminating unit 19 compares the input detected peak value with a preset reference peak value, and when the input peak value is equal to or less than the reference peak value, the first ranging unit 15 selects a ranging output selection command. When the input peak value is larger than the reference peak value, the distance measurement output selection command of the second distance measuring unit 16 is output to the distance value selecting unit 20. The reference peak value is determined by the dynamic range (upper limit) of the receiving amplifier of the zero-cross detector 21.
The distance measurement value selection unit 20 switches and selects the distance measurement value of the first distance measurement unit 15 and the distance measurement value of the second distance measurement unit 16 based on the selection command of the peak value determination unit 19 to select the optical distance measurement device. Is output as a ranging value output.

  According to such an optical distance measuring device, when the peak value level of the received light pulse is low, the distance value of the first distance measuring unit 15 calculated from the received light time information acquired by the zero cross detection method is adopted, and the peak value level of the received light pulse is adopted. When the distance is high, the distance value of the second distance measuring unit 16 calculated from the light reception time information acquired by the rising edge detection method is adopted, and the distance value of the second distance measuring unit 16 is corrected by the peak value of the received light pulse. Therefore, the distance measurement accuracy is greatly improved without being affected by the peak value level of the received light pulse.

Further, since the peak value of the received light pulse is detected as the peak value using the peak value detection circuit 1 of FIG. 1, in the case of the optical distance measuring device using the high-speed pulse as described above for the light pulse to be projected. But, Ru can peak value detected with high accuracy.

The block diagram which shows 1st Embodiment of the peak value detection circuit of the pulse signal which concerns on this invention Output waveform diagram of each circuit for explaining the operation of the first embodiment Configuration diagram showing a second embodiment of a peak value detection circuit of a pulse signal The block diagram which shows an example of the optical ranging apparatus to which the peak value detection circuit of the pulse signal which concerns on this invention is applied

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Peak value detection circuit 2 Differentiation circuit 3 Integration circuit 4 Peak hold circuit 5 Differentiation circuit 6 Sampling circuit 11 Target 12 Optical pulse light projection part 13 Optical pulse light reception part 14 Light projection timing detection part 15 1st ranging part 16 2nd measurement Distance unit 17 Peak value detector 19 Peak value discriminator 20 Distance value selector 32A Time correction unit

Claims (6)

A light pulse light projecting means for projecting a light pulse onto a distance measuring object; a light pulse light receiving means for receiving a reflected pulse from the distance measuring object based on the light projection pulse to generate a light receiving pulse; A peak value detecting means for detecting a peak value of the pulse, and detecting the received light pulse using a threshold value, measuring a time from projecting the light pulse to detecting the received light pulse, and calculating the measurement time The wave height value of the optical distance measuring device comprising: distance measuring means that corrects the wave height value of the received light pulse detected by the wave height value detecting means and calculates the distance to the distance measuring object using the corrected measurement time. A peak value detection circuit applied to the detection means ,
A differentiating circuit for differentiating the received light pulse ;
An integrating circuit for integrating the differential signal output from the differentiating circuit;
A peak value detecting means for detecting a peak value of an integrated signal output from the integrating circuit;
With
A pulse signal peak value detection circuit characterized in that the detection peak value of the peak value detection means is detected as the peak value of the received light pulse .   2. The pulse according to claim 1, wherein the peak value detecting means includes a differentiating circuit for differentiating the integrated signal and a sampling circuit for sampling the integrated signal level at a zero-cross point of the differential signal output from the differentiating circuit. Signal peak value detection circuit.   2. The pulse signal peak value detection circuit according to claim 1, wherein the time constant of the differential circuit is set so that there is only one zero-cross point of the differential signal.   4. The pulse signal peak value detection circuit according to claim 3, wherein the peak value detection means is a peak hold circuit that holds a peak value of the integrated signal. The distance measuring means of the optical distance measuring device regards the time when the level of the received light pulse input from the light pulse light receiving means reaches a predetermined threshold as the light reception time of the reflected pulse and outputs a stop timing signal The detection unit and the time until the stop timing signal is input after the start timing signal indicating the light projection time of the light pulse projected from the light pulse projecting means is input to the distance measuring object A timing unit that calculates a distance, and this timing unit includes a timing correction unit that corrects the measurement time according to the peak value of the received light pulse detected by the peak value detection means, and the correction corrected by the timing correction unit The pulse signal peak value detection circuit according to any one of claims 1 to 4, wherein the distance to the object to be measured is calculated using the measurement time. In addition to the distance measuring means, the optical distance measuring device detects a zero-cross point of the signal after filtering the received light pulse, and calculates a time from when the light pulse is projected until the zero-cross point is detected. A distance measuring unit that measures and calculates the distance to the distance measuring object based on the measurement time is provided, and the calculated distance value of both distance measuring units is selected according to the peak value detected by the peak value detecting unit The pulse signal peak value detection circuit according to claim 1, wherein the pulse signal output is a ranging output.

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