CN118444290A - Device for calibrating linearity of frequency modulation continuous wave laser ranging system in batches - Google Patents

Abstract

The present invention discloses a device for batch calibration of linearity of frequency modulated continuous wave laser ranging system, which belongs to the technical field of laser linearity correction device, and corrects the nonlinear frequency modulated continuous wave signal generated by a large number of laser light sources driven by triangle wave modulation signals used in production, so as to improve the measurement accuracy. The device includes a light source and modulation module, an optical path module, a photoelectric detection module, a switch module, and a linearity correction module, wherein the on-off signal generated by the switch module can be fed back to the light source and modulation module, control the laser light source to emit an optical signal and form a path to enter the linearity calibration module, and in the production application of batch laser calibration, a large number of lasers can be selectively calibrated by controlling the on-off of the light source, effectively solving the problems of high cost and low efficiency in laser linearity calibration.

Description

A device for batch calibration of linearity of frequency modulated continuous wave laser ranging system

Technical Field

The invention relates to the field of laser linearity correction, in particular to a device for batch calibrating the linearity of a frequency-modulated continuous-wave laser ranging system.

Background technique

The principle of frequency modulated continuous wave laser radar distance measurement technology is to perform linear frequency modulation on the laser and divide the optical path into two paths: local oscillator light and measurement light. The measurement light interferes with the local oscillator light to generate a beat signal. The beat signal carries the frequency information we need. By measuring and calculating the frequency of the beat signal, we can obtain the distance information of the detected target. Frequency modulated continuous wave laser radar has the advantages of long detection distance and strong resistance to environmental interference, and will be widely used in the future.

The accuracy of the beat frequency directly affects the ranging accuracy of the laser radar. Linearity is an important indicator for measuring the linear frequency modulation source and determines the distance resolution of the radar. However, due to the structure and working mode of the current-tuned semiconductor laser itself and the laser's sensitivity to temperature changes, the laser output signal has frequency modulation nonlinearity, which affects the accuracy of the FMCW laser radar ranging technology. Therefore, the nonlinear correction process of FMCW is very important. In actual production applications, the equipment required for linearity correction is expensive and can only be calibrated individually at a time, which has a certain impact on production efficiency. Therefore, designing a device that can calibrate frequency modulated continuous waves in batches can save costs and improve production efficiency.

Summary of the invention

The present invention provides a device for batch calibrating the linearity of a frequency modulated continuous wave laser ranging system. The device controls the laser to emit an optical signal and generates a path through a switch module to perform linearity calibration on one or more paths, thereby solving the problem of high cost and low efficiency of calibrating the linearity of the laser in large-scale production applications in the prior art.

An embodiment of the present invention provides a device for batch calibrating the linearity of a frequency modulated continuous wave laser ranging system, the device comprising:

A light source and modulation module controls the frequency modulated continuous wave laser light source to emit laser;

An optical path module generates a beat frequency signal;

The photoelectric detection module limits the optical signal response range to the vicinity of the beat frequency and converts the optical signal into an electrical signal;

The switch module controls the on and off of the signal and feeds the switch signal back to the light source and modulation module;

A linearity correction module performs linearity correction on the received beat frequency signal;

The switch module sends a signal to perform linearity calibration on the path that generates the signal, thereby realizing batch calibration of frequency modulated continuous wave linearity.

The light source and modulation module includes an arbitrary waveform generating circuit, an electric control switch and a laser light source. The output end of the arbitrary waveform generating circuit is connected to one side of the electric control switch, the laser light source receives a signal from the opposite side of the electric control switch, the arbitrary waveform generating circuit outputs an arbitrary current to control the laser light source to emit a frequency modulated continuous wave signal, and the electric control switch receives the on/off signal transmitted by the switch module and controls the generation of the laser light source.

An optical beam splitter, a delayed optical path, and an optical mixer, wherein the optical beam splitter is connected to the optical output end of the laser light source to divide the optical signal into two parts: a measurement optical path and a reference optical path. The delayed optical path receives the optical signal received from the measurement optical path, and is used to simulate the transmission of the optical signal in space when measuring the object to be measured. The frequency modulated continuous wave laser light source receives the optical signal of the delayed optical path and the optical signal of the reference optical path at the optical mixer, and the optical mixer obtains a beat frequency signal after optical mixing of the two optical signals. The photoelectric detection module is composed of a photoelectric detector, and its input end receives the beat frequency signal generated by the optical path module, and the beat frequency signal outputs a photocurrent after photoelectric conversion.

The switch module includes a switch and a feedback circuit. The switch is connected to the output end of the photoelectric detection module to control the photocurrent emitted by the photoelectric detection module. When one or more switches are closed, the photocurrent is allowed to pass through, and the switch signal is fed back to the electronically controlled switch through the feedback circuit to control the opening and closing of the electronically controlled switch. The electronically controlled switch controls the laser to emit an optical signal.

The linearity correction module includes an oscilloscope and a data processing module. The oscilloscope collects a photocurrent signal controlled by a switch to generate a time-amplitude spectrum. The data processing module analyzes the beat signal data collected by the oscilloscope to obtain a time-frequency transformation image of the beat signal, obtains a complex signal of the beat signal by using Hilbert transform, and then obtains the phase information of the beat signal pair, and obtains a time transformation curve of the signal within a cycle. The nonlinear tuning amount of the laser can be obtained by using the time-frequency information of the beat signal and the ideal beat frequency, and the nonlinear frequency modulation amount is used to reshape the triangular wave drive signal, and the laser is driven again for frequency modulation.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

FIG1 is a schematic diagram showing the principle of a frequency modulated continuous wave laser ranging system.

FIG. 2 is a schematic diagram showing the connections of various modules of an apparatus for batch calibrating the linearity of a frequency modulated continuous wave laser ranging system according to an embodiment of the present invention.

FIG3 is a block diagram showing the structural connections of various modules of a device capable of batch calibrating the linearity of a frequency modulated continuous wave laser light source according to an embodiment of the present invention.

FIG. 4 is a schematic flow chart of a nonlinear correction method according to an embodiment of the present invention.

Detailed ways

The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

The embodiment of the present invention discloses a device for batch calibrating the linearity of a frequency modulated continuous wave laser ranging system. Referring to FIG1 , a linear frequency modulation source emits a triangular wave whose frequency varies with time, so that after a delay, there is a fixed frequency difference between the triangular wave and the original signal. The frequency difference △F is the frequency of the beat frequency signal after mixing. The time delay τ can be calculated based on the known period T of the triangular wave, the bandwidth B and the value of the fixed frequency difference, and the distance of the measured object can be calculated based on the time delay τ.

An embodiment of the present invention proposes a device for batch calibrating the linearity of frequency modulated continuous wave laser light sources, as shown in FIG2 , which mainly includes a light source and modulation module, an optical path module, a photoelectric detection module, a switch module, and a linearity correction module.

The light source and modulation module consists of an arbitrary waveform generator and a frequency-modulated continuous wave laser light source. The arbitrary waveform generator emits a triangular wave with a period of T and a bandwidth of B, and linearly modulates the frequency-modulated continuous wave laser light source to emit an optical signal whose frequency changes periodically with time. The arbitrary waveform generator is connected to the laser by an electrically controlled switch, which receives the opening and closing signals fed back by the switch module to control the laser to emit an optical signal.

The optical path module is composed of an optical beam splitter, a delay optical path, and an optical mixer. The optical beam splitter receives the optical signal emitted by the light source and the modulation module, and divides the optical signal into two parts: the measurement optical path and the reference optical path. The delay optical path receives the optical signal transmitted by the measurement optical path, so that the optical signal of this path and the reference optical path have an additional time delay τ, so as to simulate the time delay τ of the frequency modulated continuous wave laser light source in the transmission distance L in laser ranging. The optical mixer receives the optical signals emitted by the measurement optical path and the reference optical path and mixes them to obtain the beat frequency signal carrying the distance information of the object to be measured after the two optical signals are mixed.

The photodetector receives the beat frequency signal, converts the optical signal into an electrical signal, and transmits it to the switch module.

The switch module is a manually controlled switch. When it is determined that one or more paths have been built and linearity calibration can be performed, an on/off signal is input to the switch module of the path. After the switch module receives the closing signal, the path becomes a passage and the closing signal is fed back to the light source and modulation module. After receiving the feedback signal from the switch module, the light source and modulation module control the laser light source to emit a light signal. After passing through each module in turn, the linearity calibration of the generated beat frequency signal is performed. When the switch is closed, the signal from the photodetector is received, the waveform of the beat frequency signal is obtained, and the data is imported into the data processing module.

After receiving the data to be processed, the data processing module analyzes the known data to obtain the distance to be measured and performs linearity calibration, and processes the obtained waveform data. First, the frequency distribution diagram of the beat signal is obtained, and then the complex signal of the beat signal is obtained by Hilbert transform, and then the phase of the beat signal is obtained. The nonlinear tuning amount of the laser can be obtained by using the time-frequency information of the beat signal and the ideal beat frequency. The current compensation iteration method is used to compensate the driving current of the next frequency-modulated continuous wave laser light source based on the nonlinear tuning amount. The instantaneous output frequency of the laser light source under the excitation of the new driving current is measured to perform repeated calibration. When the nonlinear error obtained by measurement reaches the required standard, the correction is stopped. The specific implementation method is shown in Figure 2.

The present invention proposes a device for batch calibration of the linearity of a frequency modulated continuous wave laser ranging system, which can batch calibrate frequency modulated continuous wave laser light sources. When one or more laser light sources are ready, a signal is transmitted to the switch module to form a path for the signal to be calibrated, and the signal is fed back to the light source and the modulation module to control the frequency modulated continuous wave laser light source to emit an optical signal. After the device is connected, the linearity calibration of the laser light source is completed, and the linearity calibration error to be achieved is set. After multiple rounds of calibration meet the required requirements, the linearity calibration of the laser light source is completed. The present invention can be applied to the field of frequency modulated continuous wave laser ranging, and the linearity calibration of the frequency modulated continuous wave laser light source is performed, which effectively solves the problem of batch linearity calibration of the frequency modulated continuous wave laser light source in production.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect", "connected", and "set" should be understood in a broad sense, for example, fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, indirect connection through an intermediate medium, and internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on specific circumstances.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. A device for batch calibration of linearity of a frequency modulated continuous wave laser ranging system, comprising:

The light source and the modulation module are used for controlling the frequency modulation continuous wave laser light source to emit laser;

The optical path module generates beat frequency signals;

the photoelectric detection module limits the response range of the optical signal to be near the beat frequency and converts the optical signal into an electric signal;

The switch module is used for controlling the opening and closing of the signals and feeding back the switching signals to the light source and the modulation module;

The linearity correction module is used for carrying out linearity correction on the received beat frequency signals;

the light source, the modulation module, the light path module, the photoelectric detection module and the switch module are respectively provided with M groups, wherein M is not less than 2. And the signal sent by the switch module is controlled to carry out linearity calibration on a channel generating the signal, so that the linearity of the frequency modulation continuous wave is calibrated in batches.

2. The apparatus of claim 1, wherein the light source and modulation module comprises:

the laser light source receives signals sent by one side opposite to the electric control switch, the random waveform generation circuit outputs random current to control the laser light source to send frequency modulation continuous wave signals, and the electric control switch receives switching signals transmitted by the switch module and controls the generation of the laser light source.

3. The apparatus of claim 1, wherein the optical path module comprises:

The optical beam splitter is connected with the light emitting end of the laser light source to divide an optical signal into two parts of a measuring light path and a reference light path, the delay light path receives the optical signal of the measuring light path and is used for simulating transmission of the optical signal in space when a measured object is measured, the frequency modulation continuous wave laser light source receives the optical signal of the delay light path and the optical signal of the reference light path at the optical mixer, and the optical mixer mixes the two paths of optical signals to obtain beat frequency signals.

4. The device of claim 1, wherein the photo-detector module is a photo-detector, and the input end of the photo-detector module receives a beat signal generated by the optical path module, and the beat signal outputs a photocurrent after photoelectric conversion.

5. The apparatus of claim 1, wherein the switch module comprises:

The switch is connected with the output end of the photoelectric detection module, controls the photocurrent sent by the photoelectric detection module, and when one or more switch modules receive a closing signal, the one or more switch modules are closed to allow the photocurrent to pass through and feed back a switching signal to the electric control switch through the feedback circuit, so that the electric control switch controls the opening and closing of the electric control switch, and the electric control switch controls the laser to send out a light signal.

6. The apparatus of claim 1, wherein the linearity correction module comprises:

An oscilloscope, a data processing module; the oscilloscope collects photocurrent signals controlled by the switch to generate a time-amplitude spectrum, the data processing module analyzes beat frequency signal data collected by the oscilloscope to obtain the frequency and the phase of the beat frequency signals, the complex signals of the beat frequency signals are obtained through Hilbert transformation, a transformation curve of signals in a period along with time is obtained, the nonlinear tuning quantity of the laser can be obtained through the time frequency information of the beat frequency signals and ideal beat frequency, and the laser is driven again to perform frequency modulation through a nonlinear frequency modulation quantity and a triangular wave driving signal.

7. The linearity correction module of claim 6, wherein said non-chirped magnitude reshaped triangular wave drive signal process requires multiple iterations to meet linearity requirements.