JP3755216B2 - Shape measuring apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shape measuring apparatus and method for measuring an object shape from a remote location without contact.
[0002]
[Prior art]
In order to recognize the shape and distance of a three-dimensional object from a remote location, for example, a “three-dimensional shape and distance recognition method” (Japanese Patent Laid-Open No. 5-18720) has been proposed. This method is a television camera in which a directivity direction is variably provided in a horizontal direction and a vertical direction, an object having a three-dimensional shape is imaged from a predetermined position, and the captured video signal is image-processed by an image processing apparatus. The coordinate value of the two-dimensional outer shape and the center of gravity position as viewed from the predetermined position of the object is set by the arithmetic unit, and the distance measuring device irradiates the target part from the predetermined position based on the coordinate value. Then, based on the reflected light, the arithmetic unit or the central processing unit recognizes the three-dimensional shape of the object viewed from the predetermined position and the distance from the predetermined position.
[0003]
As a similar device, a laser radar device is known. As schematically shown in FIG. 6, this apparatus includes a laser device 1, a telescope 2, a light detection device 3, a data processing device 4, and the like. The laser device 1 applies an object (for example, a scatterer 6). The laser beam 5 is emitted (transmitted), the Mie scattered light 7 from the object is received by the telescope 2, and the distance to the scatterer 6, its density, thickness, and speed are detected by the light detection device 3 and the data processing device 4. Etc. are to be detected. In this figure, 3a is a polarization beam splitter, 4a, 4b and 4c are an amplifier, a recorder and a computer, respectively.
[0004]
[Problems to be solved by the invention]
There is a demand for measuring the shape of an object located at a relatively short distance by applying the above-described conventional measurement and measurement means. For example, by measuring the stacking height (surface position) of coal, iron ore, etc. stacked in a shipboard using a laser beam, the object (for example, coal or iron ore) is compared with conventional visual judgment. Can be accurately measured in a non-contact manner.
[0005]
However, when the object is located at a relatively short distance of about 10 to 50 m, (1) if dust or water vapor exists between the objects to be measured, the light does not reach the object to be measured. In some cases, dust and water vapor are judged as objects to be measured. That is, there is a problem in that it is difficult to distinguish between reflected light from a window of a distance measuring device, dust and the like and reflected light from an object (coal / iron ore), which may cause a large measurement error. (2) In the conventional signal detection method for detecting a transmission signal and a reception signal using a threshold value, when the output level of the reception signal is reduced due to attenuation or the like, the number of pulses of the oscillator being used is more than For example, at 100 MHz, since one pulse corresponds to about 1 nsec, there is a problem that an error several times the distance (about 15 cm) corresponding to 1 nsec occurs.
[0006]
The present invention has been made to solve such problems. That is, the object of the present invention is a shape that is not affected by dust or water vapor, and can reliably discriminate between reflected light from a distance measuring device window, dust, and the like, and reflected light from an object (coal / iron ore). It is to provide a measuring device. Another object of the present invention is to provide a shape measuring device capable of measuring the distance to an object with high accuracy comparable to a single pulse of an oscillator to be used, even when the output level of a received signal decreases due to attenuation or the like. It is to provide a method.
[0007]
[Means for Solving the Problems]
According to the present invention, a sensing device that transmits pulsed laser light toward an object and receives reflected laser light from the object, and a signal processing device that calculates a distance from the transmission signal and the received signal to the object. The signal processing device includes a pulse laser beam transmission trigger signal output and a time measurement counter that outputs a round trip time of the laser beam when a transmission signal and a plurality of reception signals are input. Detects and starts time measurement, opens the gate only for a predetermined time according to the object, stores the detection time and maximum signal value of the received signal during that time, and if this received signal is one, the received signal detection from the time the signal maximum value, of if the received signal is more from the detection time and the signal maximum of the slowest received signal of which, to the central position of the received signal from the central position of the transmission signal During and calculates the is provided a shape measurement device, characterized in that.
[0008]
In addition, according to the present invention, a pulse laser beam transmission signal is detected and time measurement is started, the gate is opened only for a predetermined time according to the object, and the reception signal detection time and signal maximum value during that time are stored. If there is only one reception signal, the transmission signal is detected from the detection time and maximum signal value of the reception signal. If there are a plurality of reception signals, the transmission signal is calculated from the detection time and maximum signal value of the latest reception signal. A shape measuring method is provided which calculates a time from the center position of the received signal to the center position of the received signal.
[0009]
According to a preferred embodiment of the present invention, a round trip time is calculated by detecting a transmission signal and a reception signal with a predetermined threshold voltage and approximating the reception signal with a parabola or the like.
[0010]
According to the apparatus and method of the present invention, the time measurement counter opens the gate only for a predetermined time according to the object, stores the detection time of the received signal and the maximum signal value during that time, and one received signal is stored. If there are multiple received signals, the round trip time of the laser beam, that is, the outgoing laser pulse is reflected by the object and returned from the latest received signal. It is possible to measure without being affected by the reflected light from the window of the distance measuring device located in front of the object to be measured, dust, etc., so that the low reflectance object buried in the dust / water vapor Distance measurement up to is possible.
[0011]
Further, according to the apparatus and method of the present invention, the time from the center position of the transmission signal to the center position of the reception signal is calculated from the detection time of the reception signal and the signal maximum value, so that the waveform of the reception signal can be predicted ( For example, if the threshold voltage is kept constant, the time difference until it reaches the peak exceeding the threshold voltage can be accurately corrected, and even when the output level of the received signal decreases due to attenuation or the like, The distance to the object can be measured with high accuracy comparable to the single pulse of the oscillator used.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and used for the common part in each figure.
FIG. 1 is an overall configuration diagram of a shape measuring apparatus according to the present invention. In this figure, the stacking height (surface position) of objects such as coal and steel stone piled in the ship 8 is measured using the pulse laser beam 5. The shape measuring device of the present invention includes a sensing device 10 that transmits pulsed laser light 5 toward an object 9 and receives reflected laser light from the object 9, and a distance from the transmission signal and the received signal to the object 9. And a signal processing device 20 for calculating
[0013]
FIG. 2 is a block diagram of a shape measuring apparatus according to the present invention. As shown in the figure, the sensing device 10 includes a light projecting optical system 11, light receiving optical systems 12a and 12b, mirrors 13a and 13b, scanner motors 14a and 14b, a separation mirror 15, and the like. The pulse laser beam 5 is emitted (projected) toward the object 9 (coal, steel stone, etc.) in the boat 8 through the mirror 15, the mirrors 13a and 13b, and the transparent window 16. The mirrors 13a and 13b are driven by scanner motors 14a and 14b, respectively, to control the direction of the pulse laser beam 5 about the X axis and the Y axis. With this configuration, the pulsed laser beam 5 is emitted to the entire surface of the object 9 by projecting the pulsed laser beam 5 along the surface of the object 9 in the boat 8 in the X-axis direction and the Y-axis direction (projection). )can do.
[0014]
Further, the pulsed laser light 5 reflected by the object 9 enters the light receiving optical systems 12a and 12b through the transparent window 16, the mirrors 13a and 13b, and the separation mirror 15. Therefore, by detecting the time lag (time difference) from the transmission signal of the laser beam to the reception signal, the position of the object 9 in the boat 8 from the sensing device 10, that is, the shape of the object 9 is measured three-dimensionally. be able to.
[0015]
In FIG. 2, the signal processing device 20 includes a laser transmitter 21, a time measurement counter 22, drivers 23a and 23b, photodetectors 24a and 24b, and the like. Further, the laser transmitter 21, the light projecting optical system 11, the photodetectors 24a and 24b, and the light receiving optical systems 12a and 12b are connected via optical fiber cables 25, respectively, and the drivers 23a and 23b are connected to the scanner motors 14a and 14b and the electric cables. 26 is connected.
[0016]
A computer 27 and a CRT 28 are installed adjacent to the signal processing device 20, and an output terminal of the computer 27 is connected to the drivers 23 a and 23 b and the laser transmitter 21 via a cable 29 a, and an output cable of the time measurement counter 22 29 b is connected to the computer 27.
Further, in FIG. 2, the reception signals and transmission signals of the photodetectors 24 a and 24 b are input to the time measurement counter 22, and the transmission trigger signal of the laser transmitter 21 is output from the time measurement counter 22.
[0017]
With the above-described configuration, a pulse laser beam can be transmitted from the laser transmitter 21 to the light projecting optical system via the optical fiber cable 25 in accordance with an output command from the computer 27. At the same time, the scanner motors 14a and 14b are driven by the drivers 23a and 23b. Can be controlled. Further, the laser light received by the light receiving optical systems 12a and 12b can be received by the photodetectors 24a and 24b via the optical fiber cable 25, and the signal can be processed by the time measurement counter 22.
[0018]
FIG. 3 is a schematic diagram of each signal according to the present invention. In this figure, a is a transmission trigger signal, b is a transmission synchronization signal (transmission signal), and c is a reception signal. The transmission trigger signal a is a rectangular wave having a width of about 1 μsec (about 1000 nsec), the transmission signal b is a parabolic wave having a width of about 10 to 15 nsec, and the reception signal c is a width of about 10 to 10 in which the transmission signal b is attenuated and reflected. It is a parabolic wave of 15 nsec. The transmission trigger signal a is transmitted at a constant interval (for example, approximately every 500 μsec) according to the position up to the object 9 according to the output command of the computer 27. The transmission signal b is simultaneously with the transmission trigger signal a or slightly less than this. It is input to the time measurement counter 22 with a delay.
[0019]
The time measurement counter 22 detects the transmission signal b, starts the time measurement by the clock counter d, opens the gate e only for a predetermined time corresponding to the object 9, and detects the detection time t and the signal of the reception signal c during that time. The maximum value v is stored. The opening time of the gate e is set in accordance with the position up to the object 9. For example, when measuring the stacking height (surface position) of the object in the ship 8, the minimum value of the stacking height ( For example, the time is set corresponding to a maximum value (for example, 50 m) from 10 m). By setting the gate e, it is possible to remove a reception signal c that is extremely different from the position of the object, such as reflection from a window.
[0020]
Further, when receiving a plurality of reception signals c, the time measurement counter 22 determines the detection time t and the signal maximum value v of the latest reception signal c, and the laser beam reciprocates from the latest reception signal c. The time Δt is output. As a result, measurement can be performed without being affected by the reflected light from the window of the distance measuring device located in front of the measurement object 9, dust, etc., thereby measuring the distance to the low reflectance object buried in the dust / water vapor. Is possible.
[0021]
FIG. 4 is a principle diagram for explaining the function of the time measurement counter 22. In this figure, (A) and (B) show conventional examples, and (C) shows an example of the present invention. As shown in FIG. 2A, conventionally, the transmission signal a and the reception signal b are detected by predetermined threshold voltages v0 and v0 ', respectively, and the time interval Δt therebetween is used as the round trip time of the laser beam. However, in this method, as shown in (B), if the output level of the received signal b changes due to attenuation, an error time of δt occurs even if the same threshold voltage v0 ′ is used. Since the received signal c is a parabolic wave having a width of about 10 to 15 nsec, the error time δt reaches about 3 to 5 nsec and may be about 45 cm to 75 cm.
[0022]
In the shape measuring method of the present invention, as shown in (C), the transmission signal a and the reception signal b are detected with predetermined threshold voltages v0 and v0 ', respectively, and at the same time, the respective maximum outputs v1 and v1' are detected. Each is approximated by a parabola, and the round trip time Δt is calculated. If the threshold voltages v0 and v0 'are kept constant by this method, the time difference until the peak is reached after exceeding the threshold voltages v0 and v0' can be accurately corrected, thereby reducing the output level of the received signal. Even when the frequency drops due to, for example, the distance to the object can be measured with high accuracy comparable to a single pulse of the oscillator used.
[0023]
【Example】
FIG. 5 shows an application example of the shape measuring method according to the present invention. In this figure, (A) is an experimental example in which the coal load shape is measured from an oblique direction, and (B) is an experimental example in which this is converted into a plan view. As shown in this figure, according to the shape measuring apparatus and method of the present invention, even when a normal oscillator frequency (for example, 100 MHz) is used, the object is measured with higher accuracy than the resolution of one pulse (1 nsec = about 15 cm). The position of the object 9, that is, the shape of the object 9 can be measured three-dimensionally.
[0024]
It should be noted that the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention.
[0025]
【The invention's effect】
As described above, the shape measuring device and method of the present invention are not affected by dust or water vapor, and reflected light from a window of a distance measuring device, dust or the like, and reflected light from an object (coal or iron ore). And even if the output level of the received signal drops due to attenuation, etc., it has excellent effects such as being able to measure the distance to the target with high accuracy comparable to the single pulse of the oscillator used Have
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a shape measuring apparatus according to the present invention.
FIG. 2 is a block diagram of a shape measuring apparatus according to the present invention.
FIG. 3 is a schematic diagram of transmission / reception signals according to the present invention.
FIG. 4 is a principle diagram illustrating the function of a time measurement counter.
FIG. 5 is an application example of a shape measuring method according to the present invention.
FIG. 6 is a schematic diagram of a conventional laser radar device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser apparatus 2 Telescope 3 Light detection apparatus 4 Data processing apparatus 5 Laser light 6 Scattering body 7 Mie scattered light 8 Ship 9 Object 10 Sensing apparatus 11 Light projection optical system 12a, 12b Light reception optical system 13a, 13b Mirror 14a, 14b Scanner motor 15 Separating mirror 16 Transparent window 20 Signal processing device 21 Laser transmitter 22 Time counter 23a, 23b Driver 24a, 24b Photo detector 25 Optical fiber cable 26 Electric cable 27 Computer 28 CRT
29a, 29b Cable a Transmission trigger signal b Transmission synchronization signal (transmission signal)
c Received signal d Clock counter e Gate

Claims (3)

A signal processing apparatus comprising: a sensing device that transmits a pulsed laser beam toward an object and that receives a reflected laser beam from the object; and a signal processing device that calculates a distance from the transmission signal and the reception signal to the object. Has a pulse laser beam transmission trigger signal output and a time measurement counter that outputs the round trip time of the laser beam when a transmission signal and a plurality of reception signals are input. The time measurement counter detects the transmission signal and measures the time. Start, open the gate only for a predetermined time according to the object, store the detection time of the received signal and the maximum signal value during that time, and if this reception signal is one, the detection time of the received signal and the maximum signal the value, if the received signal is more calculated from the detection time and the signal maximum of the slowest received signal of which, the time from the central position of the transmission signal to the central position of the received signal And it has the shape measuring apparatus, characterized in that turned. Time measurement is started by detecting the transmission signal of the pulse laser beam, the gate is opened only for a predetermined time according to the object, and the detection time of the reception signal and the signal maximum value during that time are stored, and one reception signal is stored. Is the detection time of the received signal and the maximum signal value, and when there are multiple received signals, the detection time and the maximum signal value of the latest received signal is the center of the received signal from the center position of the transmission signal. A shape measuring method characterized by calculating time to a position.   The shape measuring method according to claim 2, wherein a round trip time is calculated by detecting a transmission signal and a reception signal with a predetermined threshold voltage, approximating the reception signal with a parabola.

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