Modulated laser-based free flight model non-contact detection system and method
By using modulated laser and bandpass filter circuits to separate laser signals and self-emitting signals in free-flight model experiments, the problem of detection failure caused by strong light interference was solved, and high-precision non-contact detection effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-03
AI Technical Summary
In free-flight model tests, the existing laser light curtain interval velocity measurement method is subject to strong light emission interference, which causes the photodetector to become light-saturated or the detection timing to be incorrect, making it impossible to accurately measure the model's flight parameters.
A non-contact detection system based on modulated laser is adopted. Multiple detection devices are set at intervals along the flight direction of the model. Each device includes a laser transmitter, a receiver, and a photoelectric detection circuit. The laser signal and the self-emitting signal are separated by a bandpass filter circuit to demodulate the signal and restore the flight parameters of the model.
It effectively eliminates strong light interference, improves detection accuracy, accurately restores the flight information of the model, and ensures accurate non-contact detection under high speed and high pressure environments.
Smart Images
Figure CN121784850A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of transient non-contact detection technology, and in particular to a non-contact detection system and method based on modulated laser free-flight model. Background Technology
[0002] Free-flight model tests conducted at indoor ranges are characterized by the model flying freely within a metal target lane. To achieve non-contact detection of these models, a common method is the laser light curtain interval velocimetry method. This method works by using a photodetector to convert the light flux caused by the model blocking the laser light curtain. The resulting electrical signal is then conditioned, shaped, and collected to achieve non-contact detection. However, when the model's flight speed is high and the ambient gas pressure is high, the ambient gas is rapidly compressed by the model, forming a strong shock wave. This shock wave heats the ambient gas, creating a high-temperature flow that produces strong light emission. The laser light curtain interval velocimetry method is affected by this strong light emission, causing the photodetector to become saturated and fail to detect, or the strong light may enter the photodetector's photosensitive surface before the model itself, leading to incorrect detection timing and inaccurate measurement results.
[0003] Therefore, in order to eliminate the interference of strong light emission, there is an urgent need for a non-contact detection system and method based on modulated laser free-flight model to solve the above problems. Summary of the Invention
[0004] This invention provides a non-contact detection system and method based on modulated laser free-flight model, which can eliminate the influence of strong luminescence and achieve high measurement accuracy. The technical solution is as follows: In a first aspect, embodiments of the present invention provide a non-contact detection system for a free-flying model based on modulated lasers. The system includes: multiple sets of detection devices spaced apart along the flight direction of the model, each set of detection devices including a laser emitter, a laser receiver, and a photoelectric detection circuit. Each of the laser emitting ends is respectively disposed on one side of the effective test area, for emitting a laser beam with a set modulation frequency, and forming a parallel light curtain incident on the effective test area; Each of the laser receivers is located on the other side of the effective test area and corresponds one-to-one with each of the laser emitters; the output of each laser receiver serves as the input of a corresponding photoelectric detection circuit; the photoelectric detection circuit includes a bandpass filter circuit, and the center frequency of the bandpass filter circuit is consistent with the modulation frequency of the laser beam; When the model to be tested flies freely in the effective test area along a direction perpendicular to the parallel light curtain, each of the laser receivers is used to receive the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit, so as to demodulate the received signal based on the bandpass filter circuit in the photoelectric detection circuit and output the detection result.
[0005] In one possible design, each of the laser emitters includes a modulated laser and a first optical lens; the modulated laser is used to emit a laser beam with a set modulation frequency toward the first optical lens, and the first optical lens is used to transform the received laser beam into a parallel light curtain with a set modulation frequency.
[0006] In one possible design, each of the laser receivers includes a second optical lens and a photodetector; the second optical lens is used to focus the received parallel light curtain and the self-emission of the model onto the sensitive surface of the photodetector; the photodetector is used to convert the received optical signal into an electrical signal and send the electrical signal to a corresponding photodetector circuit.
[0007] In one possible design, each of the photoelectric detection circuits further includes a high-pass filter circuit, an envelope detection circuit, an operational amplifier circuit, and a comparator circuit; the high-pass filter circuit is used to filter out low-frequency noise in the demodulated electrical signal; the envelope detection circuit is used to perform envelope detection on the noise-filtered electrical signal to output a clean envelope signal; the operational amplifier circuit is used to amplify the envelope signal to increase the signal-to-noise ratio; and the comparator circuit is used to output a level signal under a given threshold condition for external trigger detection.
[0008] In one possible design, the bandpass filter circuit is composed of multiple cascaded amplifier stages. Each amplifier stage includes an input resistor, an input capacitor, a feedback resistor, a feedback capacitor, an operational amplifier, and a grounding resistor. One end of the input resistor is connected to the output of the photodetector or the output of the previous amplifier stage, and the other end is connected to one end of the input capacitor, the feedback capacitor, and the grounding resistor. The other end of the input capacitor is connected to the negative terminal of the operational amplifier, and the other end of the feedback capacitor is connected to the output of the operational amplifier. The other end of the grounding resistor is grounded. The two ends of the feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. The positive terminal of the operational amplifier is grounded. The output of the operational amplifier is connected to the next amplifier stage or the high-pass filter circuit.
[0009] In one possible design, the bandpass filter circuit is composed of three cascaded amplifier stages.
[0010] In one possible design, the high-pass filter circuit is composed of two cascaded high-pass filters; wherein the first stage is a second-order active high-pass filter with a Sallen-Key structure, and the second stage is a passive high-pass RC filter.
[0011] In one possible design, the operational amplifier circuit includes an operational amplifier and multiple feedback resistors. The two ends of each feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. Each feedback resistor corresponds to a range switch, so that different electrical signal gains can be generated when probing models of different sizes by switching the range of the feedback resistor.
[0012] In one possible design, the comparison circuit consists of a threshold comparator and a Schmitt circuit.
[0013] Secondly, embodiments of the present invention also provide a non-contact detection method based on a modulated laser free-flight model, applicable to any of the aforementioned possible detection systems, the method comprising: Each laser emitter emits a laser beam with a set modulation frequency, forming a parallel light curtain incident on the effective test area; In response to the model under test flying freely in the effective test area along a direction perpendicular to the parallel light curtain, each laser receiver receives the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit. The received signal is demodulated using the bandpass filter circuit in the photoelectric detection circuit, and the detection result is output.
[0014] This invention provides a non-contact detection system for free-flying models based on modulated lasers. In this system, a laser emitter can emit pulsed laser light with a modulated frequency, and the center frequency of the bandpass filter circuit is consistent with the modulation frequency of the laser beam. Thus, when the model freely flies along a direction perpendicular to the parallel light curtain in the effective test area, it will sequentially pass through each parallel light curtain emitted by the laser emitter, causing a change in luminous flux when the model itself blocks the modulated laser. At this time, the laser beam with this step change and the self-emission generated by the model simultaneously enter the laser receiver. The laser receiver converts the mixed optical signal into an electrical signal, which then enters the bandpass filter circuit. Since the laser signal and the self-emission signal have different frequencies, and the center frequency of the bandpass filter circuit is consistent with the modulation frequency of the laser signal, the bandpass filter circuit only allows the laser signal to pass through and filters out the self-emission signal, achieving separation of the two signals and obtaining a demodulated signal. The flight parameters of the model can then be reconstructed based on the demodulated signal. Therefore, this application can achieve non-contact detection of free-flying models under strong light interference, eliminate strong light interference, improve detection accuracy, and accurately reconstruct information about the free-flying model passing through laser light curtains. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of a non-contact detection system based on a modulated laser free-flight model provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the optical path of a laser emitting end provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the optical path of a laser receiver provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the principle of hybrid signal modulation according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a bandpass filter circuit provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a high-pass filter circuit provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of a transport amplifier circuit provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of a comparison circuit provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of simulation results provided by an embodiment of the present invention; Figure 10 This is an experimental verification image of the sabot passing over the target provided by an embodiment of the present invention; Figure 11 This is an experimental verification image of a projectile passing through a target, provided by an embodiment of the present invention. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0018] The following describes the specific implementation of the above concept.
[0019] Please refer to Figure 1The present invention provides a non-contact detection system for a free-flying model based on modulated laser. The system includes multiple sets of detection devices spaced apart along the flight direction of the model. Each set of detection devices includes a laser emitter, a laser receiver, and a photoelectric detection circuit. Each laser emitter is positioned on one side of the effective test area to emit a laser beam with a set modulation frequency and form a parallel light curtain incident on the effective test area; Each laser receiver is positioned on the other side of the effective test area and corresponds one-to-one with each laser emitter; the output of each laser receiver serves as the input of the corresponding photoelectric detection circuit; the photoelectric detection circuit includes a bandpass filter circuit, and its center frequency is consistent with the modulation frequency of the laser beam. When the model under test flies freely in the effective test area along a direction perpendicular to the parallel light curtain, each laser receiver is used to receive the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit. The received signal is then demodulated based on the bandpass filter circuit in the photoelectric detection circuit, and the detection result is output.
[0020] In this system, the laser emitter can emit pulsed laser light with a modulation frequency, and the center frequency of the bandpass filter circuit is consistent with the modulation frequency of the laser beam. Thus, when the model flies freely in the effective test area along a direction perpendicular to the parallel light curtain, it will sequentially pass through each parallel light curtain emitted by the laser emitter, causing a change in luminous flux when the model itself blocks the modulated laser. At this moment, the laser beam with this step change and the self-emission generated by the model simultaneously enter the laser receiver. The laser receiver converts the mixed optical signal into an electrical signal, which then enters the bandpass filter circuit. Since the laser signal and the self-emission signal have different frequencies, and the center frequency of the bandpass filter circuit is consistent with the modulation frequency of the laser signal, the bandpass filter circuit only allows the laser signal to pass through and filters out the self-emission signal, achieving separation of the two signals and obtaining a demodulated signal. The flight parameters of the model can then be reconstructed based on the demodulated signal. Therefore, this application can achieve non-contact detection of free-flying models under strong light interference, eliminate strong light interference, improve detection accuracy, and accurately reconstruct information about the free-flying model passing through laser light curtains. This information allows us to obtain the time it takes for the model to fly over each laser light curtain, and to calculate the model's flight speed by measuring the time interval between passing through each detection device.
[0021] Furthermore, the number of detection devices and the distance between each detection device can be determined according to requirements, and no specific limitations are made here. In addition, the bandpass filter circuit uses a narrowband filter, and its bandwidth does not cover the frequency range of self-emitting light, thereby reducing stray light interference.
[0022] The specific structure and detection principle of this system are described in detail below: like Figure 2 As shown, each laser emitter includes a modulated laser and a first optical lens; the modulated laser is used to emit a laser beam with a set modulation frequency to the first optical lens, and the first optical lens is used to transform the received laser beam into a parallel light curtain with a set modulation frequency.
[0023] For this laser emitter, the frequency and pulse period of the modulated laser emitted by the modulated laser can be determined according to the actual experimental requirements, as long as the laser frequency is different from the self-emission frequency of the model.
[0024] like Figure 3 As shown, each laser receiver includes a second optical lens and a photodetector; the second optical lens is used to focus the received parallel light curtain and the self-emission of the model onto the sensitive surface of the photodetector; the photodetector is used to convert the received optical signal into an electrical signal and send the electrical signal to the corresponding photodetector circuit.
[0025] Combination Figure 2 , Figure 3 and Figure 4 As can be seen, the system first uses a modulated laser as the light source. The modulated laser emits a line of light, which is expanded by the first optical lens to form an approximately parallel light curtain that is incident on the effective test area. After the parallel laser light curtain passes through the effective test area, it is converged by the second optical lens onto the sensitive surface of the photodetector. Then, a narrowband bandpass filter is connected to the receiving end of the photodetector, with its center frequency matched to the modulation frequency of the modulated laser. When the self-emitting model passes through the modulated light curtain, the modulated laser light flux received by the detector is reduced due to the model's obstruction, which leads to a decrease in the oscillation amplitude of the modulated light signal. Since the self-emitting model has no modulation frequency characteristics, it is filtered out by the narrowband bandpass filter, thus obtaining a demodulated signal containing only the laser signal.
[0026] Furthermore, it should be noted that the parameters of the first and second optical lenses are determined based on the number and size of the detection device. For example, each lens may have a size of 120mm × 50mm, a focal length of 350mm, a transmittance of ≥85%, and be made of K9 optical glass. Of course, users can determine these parameters according to their needs; no specific limitations are imposed here.
[0027] In some implementations, each photoelectric detection circuit further includes a high-pass filter circuit, an envelope detection circuit, an operational amplifier circuit, and a comparator circuit; the high-pass filter circuit is used to filter out low-frequency noise in the demodulated electrical signal; the envelope detection circuit is used to perform envelope detection on the noise-filtered electrical signal to output a clean envelope signal; the operational amplifier circuit is used to amplify the envelope signal to increase the signal-to-noise ratio; and the comparator circuit is used to output a level signal under a given threshold condition for external trigger detection.
[0028] The specific structure of each circuit is described below: (1) Bandpass filter circuit The bandpass filter circuit is composed of multiple cascaded amplifier stages. Each amplifier stage includes an input resistor, an input capacitor, a feedback resistor, a feedback capacitor, an operational amplifier, and a grounding resistor. One end of the input resistor is connected to the output of the photodetector or the output of the previous amplifier stage, and the other end is connected to one end of the input capacitor, the feedback capacitor, and the grounding resistor. The other end of the input capacitor is connected to the negative terminal of the operational amplifier, and the other end of the feedback capacitor is connected to the output of the operational amplifier. The other end of the grounding resistor is grounded. The two ends of the feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. The positive terminal of the operational amplifier is grounded. The output of the operational amplifier is connected to the next amplifier stage or a high-pass filter circuit.
[0029] The following is based on Figure 5 The following diagram illustrates a bandpass filter circuit formed by cascading three amplifier stages. The bandpass filter circuit includes a first-stage amplifier U1, a second-stage amplifier U2, and a third-stage amplifier U3, each stage including an operational amplifier. Furthermore, amplifier U1 includes an input resistor R1_S1 to prevent input current saturation, a feedback resistor R2_S1, and a grounding resistor R3_S1; an input capacitor C1_S1 for high-pass filtering of the input signal; and a feedback capacitor C2_S1 for low-pass filtering of the output signal. Additionally, the feedback resistor R2_S1 and the feedback capacitor C2_S1 form a feedback network, enabling the selection and amplification of signals within a specific frequency range.
[0030] Similarly, the U2 amplifier circuit also includes an input resistor R1_S2 to prevent the input current from saturating, a feedback resistor R2_S2, and a grounding resistor R3_S2; an input capacitor C1_S2 for high-pass filtering of the input signal; and a feedback capacitor C2_S2 for low-pass filtering of the output signal. Furthermore, the feedback resistor R2_S2 and the feedback capacitor C2_S2 form a feedback network to achieve selective amplification of signals within a specific frequency range.
[0031] The U3 amplifier circuit also includes an input resistor R1_S3 to limit the input current from saturation, a feedback resistor R2_S3, and a grounding resistor R3_S3; an input capacitor C1_S3 for high-pass filtering of the input signal; and a feedback capacitor C2_S3 for low-pass filtering of the output signal. Furthermore, the feedback resistor R2_S3 and the feedback capacitor C2_S3 form a feedback network to achieve selective amplification of signals within a specific frequency range.
[0032] It should be noted that the three-stage amplifier circuit shown in the figure is only a preferred option, and users can determine the specific method according to their needs; no specific limitations are made here.
[0033] In addition, the transfer functions of U1~U3 and the entire bandpass filter circuit are calculated using the following formulas: In the formula, , , , These are the transfer functions for U1, U2, U3, and the entire bandpass filter circuit, respectively. The meanings of the other characters are the same as those of the same characters in the text.
[0034] (2) High-pass filter circuit The high-pass filter circuit consists of two cascaded high-pass filters; the first stage is a second-order active high-pass filter with a Sallen-Key structure, and the second stage is a passive high-pass RC filter. For example... Figure 6 As shown, the first-stage circuit U4 includes input capacitors C1 and C2, a feedback resistor R2, and a grounding resistor R1. Input capacitors C1 and C2 perform high-pass filtering on the input signal. The second-stage circuit U5 is a passive high-pass RC filter, including input capacitor C3 and a grounding resistor R3. Together, they form the RC high-pass filter network of U5 for high-pass filtering.
[0035] (3) Operational amplifier circuit The operational amplifier circuit includes an operational amplifier and multiple feedback resistors. The two ends of each feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. Each feedback resistor corresponds to a range switch, so that different electrical signal gains can be generated when probing models of different sizes by switching the range of the feedback resistor.
[0036] like Figure 7 As shown, this operational amplifier circuit uses a combination of a sliding potentiometer and a digital potentiometer to switch between remote and local amplification. U6 amplifies the original weak signal; this amplifier circuit is a non-inverting amplifier. It should be noted that the three-level configuration shown in the diagram is only a preferred option; users can choose other combinations of levels as needed, and this application does not impose specific limitations.
[0037] (4) Comparison circuit The comparator circuit consists of a threshold comparator employing successive analog-to-digital (AD) comparison technology and a Schmitt trigger circuit. Its function is to convert the conditioned and amplified electrical signal from an analog signal into a pulse signal, and then shape it into a pulse signal using the Schmitt trigger circuit to drive the downstream equipment. The comparator output circuit has a high level of +2.4V to +5V (adjustable) and a low level of 0V. The reference circuit is shown below. Figure 8 As shown.
[0038] It should be noted that, Figures 5-8 The specific values of each resistor and capacitor can be determined by the user according to the actual application scenario; this application does not impose specific limitations. Furthermore, operational amplifier circuits and comparator circuits are conventional choices in this field, and their specific structures will not be described in detail here.
[0039] To demonstrate the detection effectiveness of this application, the inventors conducted simulation and actual tests using the system described in this application. The test processes and results are as follows: (1) Simulation test like Figure 9 As shown in the figure, the analog modulation signal curve is generated by a signal generator to simulate the mixed signal of laser with modulation frequency and free-flying model self-emission; the bandpass filter signal curve is generated by a photodetector after bandpass filtering the analog modulation signal, used to obtain the signal characteristics of laser generation with free-flying model blocking, and to separate the free-flying model-blocked modulated laser from the free-flying model's self-emission; the bandpass filter signal envelope curve is generated by the bandpass filter signal passing through the envelope detection circuit, used to obtain the real signal of free-flying model-blocked modulated laser, which can then be used for conditioning, shaping, and analog-to-digital conversion.
[0040] As can be seen from the changes in the three curves in the figure, the system of this application can effectively filter out the self-emission of the model, retaining only the laser signal of the modulation frequency, and obtaining the characteristics of reduced light flux and significantly reduced laser amplitude caused by the model flying over the laser light curtain blocking the laser. In addition, the envelope signal can obtain the signal edge, which is beneficial for the analysis of model flight parameters.
[0041] (1) Actual experiment The experiment tested a 50mm long plastic sabot and a 5.2mm diameter tungsten-zirconium alloy ball projectile with a velocity of 4.3km / s. The measured signal waveforms are shown below. Figure 10 , Figure 11 As shown.
[0042] Figure 10The image shows the target passage signal. The blue waveform is the raw, unfiltered signal. It's clear that when the model passes through the modulated light curtain, the signal drops sharply due to strong self-emission mixing with the probe laser. The target passage signal is buried in the interference light signal and difficult to capture effectively. The red signal is the probe signal after bandpass filtering. This filtering process selects the laser signal with distinct frequency characteristics and shields the model's self-emission. This signal shows that when the model passes through the modulated laser light curtain, it partially blocks the curtain, reducing the light flux on the detector's receiving surface and significantly lowering the amplitude of the modulated laser. This is the effective detection information.
[0043] Figure 11 The test used a projectile passing through a target. Because the projectile was small, fast, and emitted less light compared to a plastic sabot, the amplitude attenuation of the modulated laser was less, but it still maintained high recognition accuracy. This demonstrates that modulating the laser frequency, combined with a corresponding narrowband receiver module, can effectively reduce light interference and accurately identify the projectile's signal as it passes through the laser light curtain.
[0044] In summary, this application demonstrates good testing results for models of different materials, sizes, shapes, and dimensions.
[0045] This invention also provides a non-contact detection method based on a modulated laser free-flight model, applicable to the measurement system in any of the above embodiments, the method comprising: Each laser emitter emits a laser beam with a set modulation frequency, forming a parallel light curtain incident on the effective test area; In response to the model under test flying freely in the effective test area along a direction perpendicular to the parallel light curtain, each laser receiver receives the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit. The received signal is demodulated using a bandpass filter circuit in the photoelectric detection circuit, and the detection result is output.
[0046] It should be noted that the measurement method provided in this embodiment and the measurement system provided in the above embodiments are based on the same inventive concept, and therefore have the same beneficial effects, which will not be elaborated here.
[0047] Finally, it should be noted that in this document, relational terms such as first, second, third, and fourth are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0048] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A non-contact detection system based on a modulated laser free-flight model, characterized in that, The system includes: multiple sets of detection devices spaced apart along the flight direction of the model, each set of detection devices including a laser emitter, a laser receiver and a photoelectric detection circuit; Each of the laser emitting ends is respectively disposed on one side of the effective test area, for emitting a laser beam with a set modulation frequency, and forming a parallel light curtain incident on the effective test area; Each of the laser receivers is located on the other side of the effective test area and corresponds one-to-one with each of the laser emitters; the output of each laser receiver serves as the input of a corresponding photoelectric detection circuit; the photoelectric detection circuit includes a bandpass filter circuit, and its center frequency is consistent with the modulation frequency of the laser beam; When the model to be tested flies freely in the effective test area along a direction perpendicular to the parallel light curtain, each of the laser receivers is used to receive the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit, so as to demodulate the received signal based on the bandpass filter circuit in the photoelectric detection circuit and output the detection result.
2. The system according to claim 1, characterized in that, Each of the laser emitters includes a modulated laser and a first optical lens; the modulated laser is used to emit a laser beam with a set modulation frequency to the first optical lens, and the first optical lens is used to transform the received laser beam into a parallel light curtain with a set modulation frequency.
3. The system according to claim 1, characterized in that, Each of the laser receivers includes a second optical lens and a photodetector; the second optical lens is used to focus the received parallel light curtain and the self-emission of the model onto the sensitive surface of the photodetector; the photodetector is used to convert the received optical signal into an electrical signal and send the electrical signal to the corresponding photodetector circuit.
4. The system according to claim 3, characterized in that, Each of the photoelectric detection circuits further includes a high-pass filter circuit, an envelope detection circuit, an operational amplifier circuit, and a comparator circuit; the high-pass filter circuit is used to filter out low-frequency noise in the demodulated electrical signal; the envelope detection circuit is used to perform envelope detection on the noise-filtered electrical signal to output a clean envelope signal; the operational amplifier circuit is used to amplify the envelope signal to increase the signal-to-noise ratio; and the comparator circuit is used to output a level signal under a given threshold condition for external trigger detection.
5. The system according to claim 4, characterized in that, The bandpass filter circuit is composed of multiple cascaded amplifier stages. Each amplifier stage includes an input resistor, an input capacitor, a feedback resistor, a feedback capacitor, an operational amplifier, and a grounding resistor. One end of the input resistor is connected to the output of the photodetector or the output of the previous amplifier stage. The other end is connected to one end of the input capacitor, the feedback capacitor, and the grounding resistor. The other end of the input capacitor is connected to the negative terminal of the operational amplifier, and the other end of the feedback capacitor is connected to the output of the operational amplifier. The other end of the grounding resistor is grounded. The two ends of the feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. The positive terminal of the operational amplifier is grounded. The output of the operational amplifier is connected to the next amplifier stage or the high-pass filter circuit.
6. The system according to claim 5, characterized in that, The bandpass filter circuit is composed of three cascaded amplifier stages.
7. The system according to claim 4, characterized in that, The high-pass filter circuit consists of two cascaded high-pass filters; the first stage is a second-order active high-pass filter with a Sallen-Key structure, and the second stage is a passive high-pass RC filter.
8. The system according to claim 4, characterized in that, The operational amplifier circuit includes an operational amplifier and multiple feedback resistors. The two ends of each feedback resistor are connected to the negative terminal and the output terminal of the operational amplifier, respectively. Each feedback resistor corresponds to a range switch, so that different electrical signal gains can be generated when probing models of different sizes by switching the range of the feedback resistor.
9. The system according to claim 4, characterized in that, The comparison circuit consists of a threshold comparator and a Schmitt circuit.
10. A non-contact detection method based on a modulated laser free-flight model, characterized in that, Applied to the system as described in any one of claims 1-9, the method comprises: Each laser emitter emits a laser beam with a set modulation frequency, forming a parallel light curtain incident on the effective test area; In response to the model under test flying freely in the effective test area along a direction perpendicular to the parallel light curtain, each laser receiver receives the laser of the modulation frequency and the self-emission caused by the model's motion, and sends the received signal to the corresponding photoelectric detection circuit. The received signal is demodulated using the bandpass filter circuit in the photoelectric detection circuit, and the detection result is output.