CN110187351B - Digital laser ranging method using high-frequency pulse amplitude modulation wave - Google Patents
Digital laser ranging method using high-frequency pulse amplitude modulation wave Download PDFInfo
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- CN110187351B CN110187351B CN201910429502.9A CN201910429502A CN110187351B CN 110187351 B CN110187351 B CN 110187351B CN 201910429502 A CN201910429502 A CN 201910429502A CN 110187351 B CN110187351 B CN 110187351B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
Abstract
The invention discloses a digital laser ranging method using high-frequency pulse amplitude modulation wave, firstly, using high-frequency periodic signal as carrier wave, modulating low-frequency narrow pulse to generate intensity modulated laser pulse as high-frequency pulse amplitude modulation wave, and driving laser transmitter to transmit laser; the emitted laser is subjected to diffuse reflection by a measured target, returns to the photoelectric detector, is converted into photocurrent, is processed by a receiving channel and is sent to the analog-to-digital converter (ADC); and (3) sampling one or more high-frequency periods in the return signal, reconstructing a high-frequency signal of a complete period after correlation processing, and obtaining a high-precision distance measurement value. The method can reduce the influence of pulse distortion caused by noise and medium scattering, and improve the signal-to-noise ratio, thereby improving the range finding.
Description
Technical Field
The invention relates to the technical field of laser pulse ranging, in particular to a digital laser ranging method using a high-frequency pulse amplitude modulation wave.
Background
The non-cooperative target laser ranging method mainly comprises two methods, namely amplitude modulation continuous wave ranging (a phase method) and pulse flight time ranging (a pulse method), wherein the phase method is to modulate the laser intensity by using periodic signals, and has high measuring precision but short measuring range; the pulse method calculates the distance by measuring the time of flight of a laser pulse between a distance meter and a target, and has a long measuring range but low measuring precision. Therefore, both methods described above have difficulty meeting the requirements of practical engineering measures.
The signal-to-noise ratio can be improved by using digital correlation detection, but at a far target, a signal diffusely reflected by the target is weak, and the noise amplitude and frequency spectrum of the circuit are basically unchanged, so that the signal-to-noise ratio is less than 1, which means that at the far target, the signal is submerged in the noise, the amplitude of the signal may be less than the input range of the ADC, so that the signal cannot be detected, and thus the range improved by only using a digital method is limited.
Disclosure of Invention
The invention aims to provide a digital laser ranging method using a high-frequency pulse amplitude modulation wave, which does not need a pulse laser and only needs a continuous laser, thereby reducing the cost, simplifying the circuit structure, effectively improving the signal-to-noise ratio and improving the measuring range.
The purpose of the invention is realized by the following technical scheme:
a digital laser ranging method using a high frequency pulse amplitude modulated wave, the method comprising:
and 3, sampling one or more high-frequency periods in the returned signal, reconstructing a high-frequency signal of a complete period after correlation processing, performing phase estimation, and obtaining a high-precision distance measurement value.
In step 1, the high-frequency pulse amplitude modulation wave is generated by a common red continuous semiconductor laser.
The process of the step 3 specifically comprises the following steps:
setting a high-frequency periodic signal as a sinusoidal periodic signal, taking a zero crossing point as a laser emission starting time Start, and starting an analog-to-digital converter (ADC) to Start continuous sampling;
the point number of the first sampling value after the zero crossing of the echo sinusoidal signal is N, the phase shift is delta N, and the distance between the laser transmitter and the measured target is obtained according to the light velocity c in the air medium as follows:
wherein f issIs the ADC sampling frequency.
According to the technical scheme provided by the invention, the method does not need a pulse laser, only needs a continuous laser, and can reduce the cost and simplify the circuit structure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a digital laser ranging method using a high-frequency pulse amplitude modulation wave according to an embodiment of the present invention;
fig. 2 is a schematic diagram of high frequency pulse amplitude modulated wave laser ranging according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The method of the embodiment of the invention combines a pulse flight time measuring method and a digital phase estimation technology, utilizes a low-frequency narrow pulse to modulate a single high-frequency periodic signal to form a high-frequency pulse amplitude modulation wave, takes the signal as a laser emission signal, and can greatly improve the laser emission peak power under the condition of safe laser due to the adoption of the low-frequency narrow pulse; because only a signal with a single modulation frequency exists, the signal-to-noise ratio can be improved by adopting a narrow-band frequency-selective amplification and digital cross-correlation method, and the remote target measurement is realized; because the sine modulation wave is adopted, high-precision phase estimation can be carried out by constructing a high-frequency signal with a complete period, so that a high-precision distance measurement value can be obtained. The embodiments of the present invention will be further described in detail with reference to the accompanying drawings, and as shown in fig. 1, a schematic flow chart of a digital laser ranging method using a high-frequency pulse amplitude modulated wave according to an embodiment of the present invention is provided, where the method includes:
in the step, the high-frequency pulse amplitude modulation wave is generated by a common red light continuous semiconductor laser instead of a pulse laser, and because the high-frequency pulse amplitude modulation wave uses a single-frequency signal, the narrow-band frequency-selective amplification and digital correlation processing of the high-frequency pulse amplitude modulation wave are facilitated, so that the signal-to-noise ratio is improved, and the measuring range is improved.
In the specific implementation, the high-frequency pulse amplitude modulation wave is generated by a common red light continuous semiconductor laser, so that the distance measuring system is simple in principle and structure, low in cost and easy to implement.
The laser emits intensity-modulated narrow pulses, i.e. only a few high-frequency periodic signals, e.g. frequency f, during a measuring periodcIs 15MHz, modulating pulse frequency fpIs 10kHz (1/f of one measuring period)p) The pulse width is 350ps (10 high-frequency signal periods), and under the condition that the average laser power is 1mw, the peak power of the emitted laser is increased by 285 times compared with the continuous laser emitted by a common phase method, and the measuring range is increased by about 16 times.
and 3, sampling one or more high-frequency periods in the returned signal, reconstructing a high-frequency signal of a complete period after correlation processing, performing phase estimation, and obtaining a high-precision distance measurement value.
In this step, as shown in fig. 2, a schematic diagram of the high frequency pwm wave laser ranging according to the embodiment of the present invention is shown, and referring to fig. 2, the process specifically includes:
setting a high-frequency periodic signal as a sinusoidal periodic signal, taking a zero crossing point as a laser emission starting time Start, and starting an analog-to-digital converter (ADC) to Start continuous sampling;
the point number of the first sampling value after the zero crossing of the echo sinusoidal signal is N, the phase shift is delta N, and the distance between the laser transmitter and the measured target is obtained according to the light velocity c in the air medium as follows:
where f issIs the ADC sampling frequency; in a specific implementation, the sampling frequency fsSet to the high frequency modulation signal frequency fcI.e. sampling M points within one period of the high frequency modulation signal, so that one or more complete sinusoidal periods can be recovered, as shown in fig. 2, thereby obtaining a high precision phase shift Δ N by using a sinusoidal signal phase estimation method. Realize long-distance high accuracy range finding.
It is noted that those skilled in the art will recognize that embodiments of the present invention are not described in detail herein.
In summary, the method of the embodiment of the present invention not only combines the characteristics of large instantaneous power of laser emission pulse in the pulse method and high phase discrimination precision of the phase method, but also performs narrow-band frequency-selective amplification and digital correlation processing on the photocurrent, so as to improve the signal-to-noise ratio and thus improve the measurement range.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (2)
1. A digital laser ranging method using a high frequency pulse amplitude modulated wave, the method comprising:
step 1, modulating low-frequency narrow pulses by using high-frequency periodic signals as carriers to generate intensity modulated laser pulses serving as high-frequency pulse amplitude modulation waves, and driving a laser transmitter to transmit laser;
step 2, the emitted laser is subjected to diffuse reflection by a measured target, returns to a photoelectric detector, is converted into photocurrent, is processed by a receiving channel and is sent to an analog-to-digital converter (ADC);
step 3, sampling one or more high-frequency cycles in the return signal, reconstructing a high-frequency signal of a complete cycle after correlation processing, performing phase estimation, and obtaining a high-precision distance measurement value by using the phase estimation, wherein the specific process comprises the following steps:
setting a high-frequency periodic signal as a sinusoidal periodic signal, taking a zero crossing point as a laser emission starting time Start, and starting an analog-to-digital converter (ADC) to Start continuous sampling;
the point number of the first sampling value after the zero crossing of the echo sinusoidal signal is N, the phase shift is delta N, and the distance between the laser transmitter and the measured target is obtained according to the light velocity c in the air medium as follows:
wherein f issIs the ADC sampling frequency.
2. The digital laser ranging method using a high frequency pulse amplitude modulated wave as claimed in claim 1, wherein the high frequency pulse amplitude modulated wave is generated by a general red continuous semiconductor laser in step 1.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102621556A (en) * | 2012-04-24 | 2012-08-01 | 北京理工大学 | Laser ranging method for frequency modulation and phase measurement |
| CN104024878A (en) * | 2011-11-04 | 2014-09-03 | 莱卡地球系统公开股份有限公司 | Distance-Measuring Device |
| CN105785385A (en) * | 2016-04-15 | 2016-07-20 | 中国科学院上海技术物理研究所 | Laser ranging method and device based on synchronous sampling and multiple phase measurement |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US10416292B2 (en) * | 2016-05-24 | 2019-09-17 | Veoneer Us, Inc. | Direct detection LiDAR system and method with frequency modulation (FM) transmitter and quadrature receiver |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104024878A (en) * | 2011-11-04 | 2014-09-03 | 莱卡地球系统公开股份有限公司 | Distance-Measuring Device |
| CN102621556A (en) * | 2012-04-24 | 2012-08-01 | 北京理工大学 | Laser ranging method for frequency modulation and phase measurement |
| CN105785385A (en) * | 2016-04-15 | 2016-07-20 | 中国科学院上海技术物理研究所 | Laser ranging method and device based on synchronous sampling and multiple phase measurement |
Non-Patent Citations (3)
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| "基于正弦曲线的高精度脉冲激光测距时间间隔测量技术";黄明双 等;《中国激光》;20140831;第41卷(第8期);全文 * |
| "基于游标原理的快速高精度脉冲激光测距方法";黄明双 等;《中国激光》;20190202;第46卷(第05期);全文 * |
| "脉冲激光测距高精度时间间隔测量技术研究";刘慧慧;《中国优秀硕士学位论文全文数据库 信息科技辑》;20160615;全文 * |
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