A laser encoding and decoding teaching demonstration experiment system with anti-interference capability
By designing an anti-interference laser encoding and decoding teaching system, and utilizing high-precision time-to-digital conversion and arrival time interval statistics, the problem of mutual interference between lasers in optoelectronic classroom teaching was solved, enabling multiple sets of experiments to be conducted simultaneously and mastering the encoding and decoding process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NAT UNIV OF DEFENSE TECH
- Filing Date
- 2024-01-05
- Publication Date
- 2026-06-30
AI Technical Summary
In optoelectronic classroom teaching, the laser signals from multiple experimental systems reflect each other indoors, causing mutual interference. Existing technology cannot effectively decode signals with unknown periodic parameters, making it impossible to conduct multiple sets of experiments simultaneously in the same classroom.
A laser encoding and decoding teaching demonstration system with anti-interference capability was designed, including a computer, encoding equipment, laser emitter, photodetector and decoding equipment. Through pulse width detection, interval detection and target signal confirmation modules, high-precision time digital conversion and arrival time interval statistics are used to eliminate interference signals and ensure that the decoding equipment can identify the target signal to be decoded.
This allows multiple experiments to be conducted simultaneously in the same classroom, enabling operators to perform the encoding and decoding process of pulsed lasers, master the encoding and decoding principles, and develop more complex teaching experiments, while avoiding the problem of mutual interference between laser signals.
Smart Images
Figure CN117789571B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of laser technology, and in particular relates to a laser encoding and decoding teaching demonstration experimental system with anti-interference capabilities. Background Technology
[0002] In optoelectronics classroom teaching, it is necessary to explain pulsed laser encoding and decoding technology to students. To visually demonstrate the laser encoding and decoding effect, experimental courses are offered, allowing students to implement the laser encoding and decoding process themselves. However, since multiple experimental systems are typically placed in the laboratory for simultaneous use by multiple groups of students, the laser signals emitted by the lasers will reflect multiple times indoors, inevitably leading to interference between lasers from different experimental systems.
[0003] Current known anti-interference techniques require prior knowledge of the period parameters of the target digital pulse signal to locate it within the signal to be decoded. The drawback of this technique is that it relies on prior knowledge of the target digital pulse signal's period parameters; otherwise, decoding will fail. In our teaching experiments, to demonstrate the decoding algorithm, the period parameters of the signal to be decoded must be completely unknown before decoding. Therefore, the aforementioned anti-interference techniques cannot be directly used to solve the problem of laser interference. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes a laser encoding and decoding teaching demonstration experimental system with anti-interference capabilities, which enables multiple systems to operate simultaneously in a laboratory environment.
[0005] The first aspect of this invention discloses a laser encoding and decoding teaching demonstration experimental system with anti-interference capability; the system includes a computer, encoding equipment, laser emitter, photodetector, and decoding equipment;
[0006] The computer is used to set the laser code pattern and send it to the encoding device via a communication cable;
[0007] The encoding device is used to parse the laser code information, convert it into a laser pulse drive signal, and then send it to the laser transmitter through a TTL level line.
[0008] The laser emitter is used to convert the laser pulse driving signal into a laser pulse and then emit it.
[0009] The photodetector is used to receive the laser pulse, convert it into an electrical pulse signal, and then send it to the decoding device through a TTL level line;
[0010] The decoding device is used to extract the laser code information from the received electrical pulse signal, transmit it to the computer via a communication cable, and display it on the computer's decoding software interface; wherein, the electrical pulse signal includes an interference signal and a target signal to be decoded;
[0011] The decoding device includes:
[0012] The pulse width detection module is used to measure the pulse width of each electrical pulse signal and select the pulse signals with the smallest pulse width and the largest number of pulse signals as the first candidate group.
[0013] The pulse interval detection module is used to detect the arrival time interval of adjacent electrical pulse signals and find all pulse signals that meet the minimum time interval as an integer multiple as the second candidate group.
[0014] The target signal confirmation module selects the same electrical pulse signals from the first and second candidate groups as the target signals to be decoded.
[0015] The pulse width detection module uses the pulse leading edge as the start signal and the pulse trailing edge as the stop signal, and achieves pulse width measurement through coarse clock counting and fine carry-chain counting.
[0016] The coarse clock count uses a 200MHz clock to time the start and stop signals. If the start signal is detected at the rising edge of the clock, the counter starts counting and increments by one every clock cycle until the stop signal is detected at the rising edge of the clock, at which point the counting stops and the count value is set to N.
[0017] The carry chain fine counting adopts the carry chain cascading method in the FPGA, allowing the start signal and stop signal to enter the cascaded carry chain. The output of each carry chain is sampled by the clock and stored in the decoding module to obtain the arrival time Δt1 of the start signal and the arrival time Δt2 of the stop signal before the rising edge of the clock. Then, the total time T = N*5ns + Δt1 - Δt2 is determined as the pulse width of the pulse signal.
[0018] The system also includes a first slider, a second slider, and a guide rail;
[0019] The laser emitter is fixed to the first slider by a first rigid support;
[0020] The photodetector is fixed to the second slider by a second rigid support;
[0021] The first slider and the second slider slide on the guide rail.
[0022] The laser emitter is threadedly connected to the first rigid support, and the photodetector is threadedly connected to the second rigid support.
[0023] The system also includes:
[0024] A light intensity attenuator is disposed between the laser emitter and the photodetector.
[0025] The system also includes:
[0026] An optical modulator is disposed between the laser emitter and the photodetector.
[0027] The laser emitter includes a driving circuit and a laser source. The laser pulse driving signal is used to control the driving circuit, thereby exciting the laser source to emit the laser pulse.
[0028] The laser source is one of a semiconductor laser, a solid-state laser, or a fiber laser.
[0029] The photodetector includes a photodetector and a readout circuit. After receiving the laser pulse, the photodetector sends it to the readout circuit for photoelectric conversion to obtain the electrical pulse signal.
[0030] The optical receiver includes one of a laser diode, a photovoltaic cell, and a photoresistor.
[0031] The communication cable is one of the following: RS422 serial cable, RS232 serial cable, RS485 serial cable, or Ethernet cable.
[0032] In summary, the solution proposed in this invention has the following technical advantages: This system allows operators to hands-on experience in encoding and decoding pulsed lasers, mastering the principles of pulsed laser encoding and decoding, and understanding the basic microcontroller program development process. More complex teaching experiments can also be developed based on this foundation. Furthermore, to avoid interference between laser signals when multiple experiments are conducted simultaneously in the same classroom, anti-interference technology is designed to ensure that multiple experiments can proceed smoothly and simultaneously. Attached Figure Description
[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.
[0034] Figure 1This is a block diagram of the overall composition of a laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to an embodiment of the present invention;
[0035] Figure 2 This is a schematic diagram of the target pulse signal (solid line) to be decoded and the interference signal (dashed line) according to an embodiment of the present invention;
[0036] Figure 3 This is a schematic diagram illustrating the operation of a high-precision time-to-digital conversion using an FPGA according to an embodiment of the present invention.
[0037] Figure 4 This is a schematic diagram illustrating the statistical and filtering results of arrival time intervals according to an embodiment of the present invention;
[0038] Figure 5 This is a flowchart of a method for eliminating interference signals according to an embodiment of the present invention;
[0039] Figure 6 This is a schematic diagram of a laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to an embodiment of the present invention. Detailed Implementation
[0040] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0041] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first slider may be referred to as a second slider, and similarly, a second slider may be referred to as a first slider. Both the first slider and the second slider are sliders, but they are not the same slider.
[0042] Please see Figure 1 The first aspect of the present invention discloses a laser encoding and decoding teaching demonstration experimental system with anti-interference capability; the system includes a computer 100, an encoding device 200, a laser emitter 300, a photodetector 400, and a decoding device 500.
[0043] The computer 100 employs encoding software to implement encoding settings and command issuance functions. The encoding software supports fixed-frequency codes, precise-frequency codes, and variable-interval codes. Decoding software is used to implement the code pattern display function. The computer 100 uses the encoding software to set the laser code pattern and transmits it to the encoding device 200 via a communication cable. The encoding device 200 parses the laser code pattern information, converts it into a laser pulse drive signal, and transmits it to the laser transmitter 300 via a TTL level line. The laser transmitter 300 converts the laser pulse drive signal into laser pulses and emits them. The photodetector 400 receives the laser pulses, converts them into electrical pulse signals, and transmits them to the decoding device 500 via a TTL level line. The decoding device 500 decodes the laser code pattern information from the received electrical pulse signals, transmits it to the computer 100 via a communication cable, and displays it on the decoding software interface of the computer 100.
[0044] The communication cable is one of the following: RS422 serial cable, RS232 serial cable, RS485 serial cable, or Ethernet cable.
[0045] The laser emitter 300 includes a driving circuit and a laser source. The laser pulse driving signal is used to control the driving circuit, thereby exciting the laser source to emit the laser pulse.
[0046] The laser source is one of a semiconductor laser, a solid-state laser, or a fiber laser.
[0047] The photodetector 400 includes a photodetector and a readout circuit. After receiving the laser pulse, the photodetector sends it to the readout circuit for photoelectric conversion to obtain the electrical pulse signal.
[0048] The optical receiver includes one of a laser diode, a photovoltaic cell, and a photoresistor.
[0049] The encoding device 200 and the decoding device 500 each include a microcontroller and related peripheral communication circuits to realize the functions of encoding output and decoding output. Both the encoding device 200 and the decoding device 500 support secondary development. Optionally, the microcontrollers in the encoding device 200 and the decoding device 500 can be replaced with FPGAs, CPLDs, etc.
[0050] The laser emitter 300, photodetector 400, encoding module and decoding device 500 are each encapsulated in a housing for easy carrying and use.
[0051] The laser pulse signal received by the decoding device 500 contains the target signal to be decoded and interference signals. Since the target signal to be decoded directly enters the decoding device 500, it has a fixed period, a relatively narrow pulse width, and an accurate arrival time. The interference signals are reflected by the wall, travel a longer distance, and scatter in the air. The pulse waveform usually distorts, manifested as pulse width broadening, and the arrival time is random. As Figure 2 shown, the solid line represents the target pulse signal to be decoded, and the dashed line represents the interference signal. The pulse widths of the three target pulse signals to be decoded are all t1 (i.e., the pulse widths of each target pulse signal to be decoded are the same). The pulse widths of the interference signals are t2 and t3, and t2≠t3. The pulse widths of the interference signals are wider than those of the target pulse signals to be decoded, that is, t1<t2, t1<t3, and the pulse width difference is about nanosecond level. The arrival time intervals T1 and T2 of the target pulse signals to be decoded are fixed and accurate, while the arrival time interval T3 of the interference signal is random.
[0052] Therefore, the decoding device 500 can utilize the characteristic differences between the target signal to be decoded and the interference signals to extract the target signal to be decoded.
[0053] Optionally, the decoding device 500 includes a pulse width detection module, a pulse interval detection module, and a target signal confirmation module for decoding.
[0054] The pulse width detection module is used to measure the pulse width of each electrical pulse signal, and screen out the pulse signals with the smallest pulse width and the largest number as the first alternative group; the pulse interval detection module is used to detect the arrival time interval of adjacent electrical pulse signals, and find out all the pulse signals that meet the integer multiples of the minimum time interval as the second alternative group; the target signal confirmation module for decoding screens out the same electrical pulse signals in the first alternative group and the second alternative group as the target signal to be decoded.
[0055] Specifically, please refer to Figure 5 , which is the flowchart of the method for eliminating interference signals. The pulse width detection module can measure the received pulse width by using high-precision time-to-digital conversion technology. Since there are differences in the pulse widths of the target signal to be decoded and the interference signals, the pulse width of each received signal can be measured and histogram statistics can be performed. The pulse signals with the smallest pulse width and the largest number are used as alternatives for the target signal to be decoded, and other pulse signals are eliminated.
[0056] High-precision time-to-digital conversion can be implemented by using FPGA. As Figure 3 shown, the leading edge of the pulse is used as the start signal, and the trailing edge of the pulse is used as the stop signal. The pulse width measurement is achieved through clock coarse counting and carry chain fine counting.
[0057] The coarse clock count uses a 200MHz clock to time the start and stop signals. If the start signal is detected at the rising edge of the clock, the counter starts counting and increments by one every clock cycle until the stop signal is detected at the rising edge of the clock, at which point counting stops. The count value at this point is set as N, which is the coarse count. Since the clock period is 5ns, the measured time interval has a maximum error of 5ns.
[0058] The carry chain fine counting employs a cascaded carry chain approach within the FPGA, allowing the start and stop signals to enter the cascaded carry chains. The output of each carry chain is sampled by the clock and stored in the decoding module. Since each carry chain has a delay of approximately 40 ps, the arrival times Δt1 and Δt2 of the start and stop signals before the rising edge of the clock can be obtained by decoding the output of the carry chains. Therefore, the total time T = N * 5 ns + Δt1 - Δt2 is the pulse width of the pulse signal. This pulse width measurement technique achieves a measurement accuracy of up to 40 ps and can distinguish pulse width differences.
[0059] The pulse interval detection module employs arrival time interval statistics and filtering technology to eliminate interference signals. Since the arrival time interval of the signal to be decoded is an integer multiple of a certain minimum time interval, while the arrival time of interference signals is random and does not have a minimum time interval, the arrival time intervals between pulses can be statistically analyzed to find pulse signals that conform to an integer multiple of a certain minimum time interval, thereby further eliminating interference signals.
[0060] Arrival time interval statistics and filtering require precise measurement of the pulse arrival time interval. The measurement method is the same as the pulse width measurement method described above. The arrival time of the previous pulse is used as the start signal, and the arrival time of the next pulse is used as the stop signal, thus achieving high-precision time interval measurement. For filtering, first receive 100 pulses, record the arrival time intervals of adjacent pulses, and then randomly select three pulses, such as... Figure 4 As shown, three time intervals T1, T2, and T3 are obtained. We observe whether T1, T2, and T3 have a greatest common divisor (GCD), typically 10ms. If a GCD exists, the three selected pulses are considered the target signal to be decoded; otherwise, at least one pulse is an interference signal. By iterating through all pulse arrival time intervals, all target signals to be decoded can be selected.
[0061] Please see Figure 6 The system also includes a first slider 601, a second slider 602, and a guide rail 603;
[0062] The laser emitter 300 is fixed to the first slider 601 by a first rigid support; the photodetector 400 is fixed to the second slider 602 by a second rigid support; the first slider 601 and the second slider 602 slide on the guide rail 603. Optionally, the laser emitter 300 is threadedly connected to the first rigid support, and the photodetector 400 is threadedly connected to the second rigid support. Optionally, the first rigid support is a first support column 604. The second rigid support is a second support column 605. The support column, slider, and guide rail 603 are generally made of aluminum alloy or other metal materials, which have a certain resistance to deformation.
[0063] The laser emitter 300 and photodetector 400 are respectively fixed to the slider by support columns. The support columns have threads at both ends for securing them. The height of the laser emitter 300 and photodetector 400 can be adjusted via the threads for easy alignment. The slider can slide on the guide rail 603, facilitating adjustment of the distance between the laser emitter 300 and photodetector 400.
[0064] Optionally, the system further includes an optical intensity attenuator. The optical intensity attenuator is disposed between the laser emitter 300 and the photodetector 400. An optical intensity attenuator is a device used to attenuate optical power. It is a very important passive fiber optic device that can attenuate optical signal energy as required by the user, and is commonly used to absorb or reflect optical power margins, evaluate system losses, and in various tests.
[0065] Optionally, the system further includes an optical modulator. The optical modulator is disposed between the laser emitter 300 and the photodetector 400. The laser pulse can be shaped by the optical modulator.
[0066] Understandably, other new modules can also be added between the laser emitter 300 and the photodetector 400 to make the system scalable.
[0067] In summary, the solution proposed in this invention has the following technical advantages: This system allows operators to hands-on experience in encoding and decoding pulsed lasers, mastering the principles of pulsed laser encoding and decoding, and understanding the basic microcontroller program development process. More complex teaching experiments can also be developed based on this foundation. Furthermore, to avoid interference between laser signals when multiple experiments are conducted simultaneously in the same classroom, anti-interference technology is designed to ensure that multiple experiments can proceed smoothly and simultaneously.
[0068] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A laser encoding and decoding teaching demonstration experimental system with anti-interference capability, characterized in that, This includes computers, encoding equipment, laser emitters, photodetectors, and decoding equipment; The computer is used to set the laser code pattern and send it to the encoding device via a communication cable; The encoding device is used to parse the laser code information and convert it into a laser pulse drive signal, which is then sent to the laser transmitter via a TTL level line. The laser emitter is used to convert the laser pulse driving signal into a laser pulse and then emit it. The photodetector is used to receive the laser pulse, convert it into an electrical pulse signal, and then send it to the decoding device through a TTL level line; The decoding device is used to extract the laser code information from the received electrical pulse signal, transmit it to the computer via a communication cable, and display it on the computer's decoding software interface; wherein, the electrical pulse signal includes an interference signal and a target signal to be decoded; The decoding device includes: A pulse width detection module is used to measure the pulse width of each electrical pulse signal and select the pulse signals with the smallest and most numerous pulse widths as the first candidate group. The pulse width detection module uses the pulse leading edge as the start signal and the pulse trailing edge as the stop signal, and achieves pulse width measurement through coarse clock counting and fine carry-chain counting. The coarse clock count uses a 200MHz clock to time the start and stop signals. If the start signal is detected at the rising edge of the clock, the counter starts counting and increments by one every clock cycle until the stop signal is detected at the rising edge of the clock, at which point the counting stops and the count value is set to N. The carry chain fine counting employs a cascaded carry chain method within the FPGA, allowing the start and stop signals to enter the cascaded carry chains. The output of each carry chain is sampled by the clock and stored in the decoding module to obtain the arrival time ∆t1 of the start signal and the arrival time ∆t2 of the stop signal before the rising edge of the clock, thereby determining the total time. This is the pulse width of the pulse signal; The pulse interval detection module is used to detect the arrival time interval of adjacent electrical pulse signals and find all pulse signals that meet the minimum time interval as an integer multiple as the second candidate group. The target signal confirmation module selects the same electrical pulse signals from the first and second candidate groups as the target signals to be decoded.
2. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The system also includes a first slider, a second slider, and a guide rail; The laser emitter is fixed to the first slider by a first rigid support; The photodetector is fixed to the second slider by a second rigid support; The first slider and the second slider slide on the guide rail.
3. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 2, characterized in that, The laser emitter is threadedly connected to the first rigid support, and the photodetector is threadedly connected to the second rigid support.
4. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The system also includes: A light intensity attenuator is disposed between the laser emitter and the photodetector.
5. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The system also includes: An optical modulator is disposed between the laser emitter and the photodetector.
6. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The laser emitter includes a driving circuit and a laser source. The laser pulse driving signal is used to control the driving circuit, thereby exciting the laser source to emit the laser pulse.
7. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The photodetector includes a photodetector and a readout circuit. After receiving the laser pulse, the photodetector sends it to the readout circuit for photoelectric conversion to obtain the electrical pulse signal.
8. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 7, characterized in that, The optical receiver includes one of a laser diode, a photovoltaic cell, and a photoresistor.
9. The laser encoding and decoding teaching demonstration experimental system with anti-interference capability according to claim 1, characterized in that, The communication cable is one of the following: RS422 serial cable, RS232 serial cable, RS485 serial cable, or Ethernet cable.