A new elevator light curtain

Abstract

The application discloses a novel elevator light curtain, comprising a full-plastic shell and a circuit board arranged in the shell. The circuit board adopts a cascade multi-path switching module to select multiple photoelectric units, and a grounding filter network is arranged at the output end of each photoelectric unit to perform source filtering; an active filter buffer unit with a PNP triode as a core is introduced into a signal path, and a signal processing module containing a four-stage operational amplifier and a gradient RC filter network is adopted to perform step-by-step amplification and conditioning. The application actively and repeatedly suppresses internal and external electromagnetic interference from the source to the terminal under the premise of not relying on metal shielding through systematic hardware circuit design, simultaneously simplifies the structure, reduces the cost, and completely avoids the short circuit and failure risk caused by the shell grounding, and has higher reliability, environmental adaptability and economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light curtain technology, in particular to a new type of elevator light curtain. BACKGROUND

[0002] As a core safety protection device, light curtain or grating is widely used in elevator systems and industrial automation fields. Figure 1 As shown in the figure, the shell structure of the current market mainstream product adopts a multi-material combination of a metal shell and a plastic light filtering strip. The metal shell mainly bears the function of providing electromagnetic shielding for the light curtain or grating to effectively block electromagnetic interference from surrounding motors, drivers and other devices. Therefore, the negative electrode of the power supply of the light curtain or grating needs to be reliably connected with the metal shell to ensure the effect of shielding external electromagnetic interference. The plastic light filtering strip ensures that the transmitted light beam penetrates the shell, so that the receiving end of the light curtain or grating normally receives the infrared light beam emitted by the transmitting end. The existing scheme has the following shortcomings:

[0003] 1. The installation scheme is relatively complex, which not only increases the assembly process of the shell and the light filtering strip, but also requires additional processing of the metal shell grounding screw hole and additional installation steps in the assembly process to ensure reliable grounding of the PCBA and the metal shell and achieve effective shielding.

[0004] 2. When using grounding screws or springs for shielding grounding, the grounding may fail due to loosening of the grounding screws or oxidation and corrosion of the connection surface, affecting the normal operation of the light curtain or grating.

[0005] 3. The elevator or other industrial equipment where the light curtain or grating is installed is usually equipped with an independent grounding wire. When the light curtain or grating is installed on the equipment, if the metal shell is accidentally short-circuited with the grounding wire of the above-mentioned equipment, it is easy to cause short-circuit between the grounding wire and the negative electrode of the power supply, and in severe cases, it may damage the power supply equipment.

[0006] 4. The all-metal shell is generally made of aluminum alloy, which has a high cost.

[0007] 5. The length of the elevator light curtain is usually more than 2 meters, and the length of the grating is usually between 0.3-2 meters. Limited by the length factor, the waterproof performance of the installation scheme can generally only reach IP54 or IP65 level. Therefore, additional PCBA surface coating process or filling of waterproof glue in the glue groove is required to compensate, further increasing the process complexity. SUMMARY

[0008] The problem solved by the present application is that the light curtain in the prior art has high cost, complex installation process, easy grounding failure or short-circuit with other equipment grounding wire, and a new type of light curtain with low cost, convenient installation and higher safety is provided.

[0009] The present application is implemented by the following technical scheme, a new type of elevator light curtain, comprising:

[0010] a plastic shell, comprising at least one light-transmitting region made of infrared light-transmitting material,

[0011] a circuit board disposed in the plastic shell, comprising:

[0012] a plurality of photoelectric emission / reception units;

[0013] a multiplexing module for cyclically gating the plurality of photoelectric emission / reception units;

[0014] a signal processing module connected to the output end of the multiplexing module for amplifying-shaping-detecting the sensing signal of the gated unit;

[0015] wherein the multiplexing module adopts a cascade architecture, comprising one main switching switch and a plurality of slave switching switches, the slave switching switches are directly connected to the photoelectric emission / reception units, and the output end of each photoelectric emission / reception unit is connected in parallel with a grounding filter network;

[0016] wherein a first anti-interference unit comprising active devices is arranged between the output end of the slave switching switch and the input end of the main switching switch for filtering and buffering before the signal enters the main switching switch;

[0017] wherein the signal processing module comprises a coupling capacitor, a preamplifier circuit, a clamping circuit, and a multi-stage operational amplifier circuit, the multi-stage operational amplifier circuit is not less than four stages, and each stage is provided with an RC filter network and an operational amplifier active unit.

[0018] Further, the grounding filter network comprises a resistance and a capacitance connected in parallel to the ground.

[0019] Further, the first anti-interference unit comprises a PNP-type triode, the common input / output end of the slave switching switch is connected to the B electrode of the PNP-type triode, the E electrode of the PNP-type triode is connected to the circuit power source after being connected in series with a resistance, the C electrode of the PNP-type triode is grounded, a capacitance is arranged between the B electrode and the E electrode and between the B electrode and the C electrode, and the E electrode of the PNP-type triode is connected to the input / output end of the main switching switch after being connected in series with a resistance.

[0020] Further, the multi-stage operational amplifier circuit comprises a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, a third-stage operational amplifier circuit, and a fourth-stage operational amplifier circuit.

[0021] Further, the RC filter network of the first-stage operational amplifier circuit and the second-stage operational amplifier circuit is first-order, and the RC filter network of the third-stage operational amplifier circuit and the fourth-stage operational amplifier circuit is second-order.

[0022] Further, the second, third and fourth operational amplifier circuits are provided with detection branches, the detection branch comprises an optocoupler, the optocoupler is connected to the gain input control end of the MCU, and each gain input control end is provided with a 100K pull-down resistor.

[0023] Further, the amplification shaping detection circuit is additionally provided with a coupling capacitor, an overvoltage protection and an RC filter network connected to the signal pin of the MCU at the rear end of the fourth amplification circuit, and is provided with an optocoupler connected to the gain input control end of the MCU and provided with a 100K pull-down resistor.

[0024] Further, the signal processing module further comprises an LC power filter circuit for filtering power supply noise, so as to provide stable and clean power supply for the operational amplifier and avoid coupling of power supply noise into the signal.

[0025] Further, the clamping circuit comprises a positive diode and a negative diode, and can clamp the signal in two directions.

[0026] Further, the light transmission area and the non-light transmission area of the plastic shell are formed by an integral double-color extrusion process, and a seamless sealing combination is formed therebetween, the inner wall of the plastic shell is provided with a slot for clamping and fixing the circuit board, and the circuit board is not conductively connected with the inner wall of the shell.

[0027] The beneficial effects of the present application are:

[0028] 1、The present application actively resists electromagnetic interference at the circuit level through the systematic hardware design of source filtering + path isolation / buffering + multi-stage conditioning, specifically including setting a grounding filter network at the output end of each photoelectric unit for preliminary filtering, using an active filter buffer circuit with a PNP transistor as the core to suppress transient interference and enhance signal driving capability, and innovatively using four-stage operational amplifier amplification in combination with gradient RC filter networks, which is a multi-level and targeted design, effectively filters out external interference and internal switch noise without relying on the electromagnetic shielding of the metal shell, ensuring the stability and accuracy of photoelectric signal transmission and processing, and fundamentally solving the core problem of plastic shell application.

[0029] 2、The signal processing module of the application adopts four-stage operational amplifier cascade cooperation with gain distribution strategy, widens the bandwidth while ensuring the total gain, avoids excessive amplification of noise, integrates the clamping circuit composed of positive and negative diodes in the circuit, can effectively suppress instantaneous overvoltage or low-voltage peak, and protects the precision operational amplifier input stage. In addition, the key control signal is electrically isolated through an optical coupler, and a pull-down resistor is arranged to prevent misoperation, and the LC power supply filtering circuit provides pure power supply for the operational amplifier. The above measures jointly build a high-performance and high-robustness signal chain, which significantly improves the recognition accuracy of the light curtain on the effective signal and the stability of the system during long-term operation.

[0030] 3、The application adopts a double-color integrated extrusion molding plastic shell, which seamlessly combines the light transmission area and the non-light transmission area, replaces the traditional metal shell + independent filter strip combination structure, completely eliminates the separate installation of the filter strip, the grounding hole processing of the metal shell and the assembly link of the grounding screw or elastic piece, greatly simplifies the production and assembly process, and the integrated molding structure not only improves the production efficiency, but also realizes better overall sealing, enhances the durability and reliability of the product in harsh industrial environments such as dust and humidity, and at the same time, the insulation characteristics of the plastic shell fundamentally eliminate the risk of grounding short circuit that may occur in the installation site.

[0031] 4、The all-plastic shell structure of the application discards the higher-priced aluminum alloy material and eliminates the grounding metal parts and related processing and assembly costs, thereby realizing the reduction of the overall manufacturing cost of the product. Since the shell does not need to be grounded, not only is the installation step simplified, but also the grounding failure problem caused by loosening of the grounding screw and oxidation of the contact surface is completely eliminated, as well as the risk of accidental short circuit damage to the power supply equipment caused by the grounding of the metal shell of the light curtain and the equipment grounding wire. Therefore, the application not only reduces the manufacturing cost, but also improves the installation convenience and operation safety of the product, and has outstanding market competitiveness. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a cross-sectional view of the light curtain in the prior art;

[0033] Figure 2 is a cross-sectional view of a novel elevator light curtain according to the application;

[0034] Figure 3 is a circuit diagram of the circuit board in the embodiment of the application;

[0035] Figure 4 is a circuit diagram of the switching switch and the photoelectric emission / reception unit in the embodiment;

[0036] Figure 5 is a schematic diagram of the first anti-interference unit in the embodiment;

[0037] Figure 6 is a schematic diagram of the main switching switch in the embodiment;

[0038] Figure 7 is a partial enlarged view of Figure 3 ;

[0039] Figure 8 is a circuit diagram of the signal processing module in the embodiment;

[0040] Figure 9 is a partial enlarged view of Figure 8 the first stage operational amplifier circuit in ;

[0041] Figure 10 is a partial enlarged view of Figure 8 the fourth stage operational amplifier circuit in ;

[0042] In the figure:

[0043] 1, plastic shell; 101, light transmission area;

[0044] 2, photoelectric emission / reception unit;

[0045] 3, multipath switching module; 301, main switching switch; 302, slave switching switch; 303, ground filtering network; 304, first anti-interference unit;

[0046] 4, signal processing module; 401, coupling capacitor; 402, preamplifier circuit; 403, clamping circuit; 404, first stage operational amplifier circuit; 405, second stage operational amplifier circuit; 406, third stage operational amplifier circuit; 407, fourth stage operational amplifier circuit; 408, LC power supply filtering circuit. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0048] As shown in Figures 1-10 , a new type of elevator light curtain comprises a plastic shell 1 and a circuit board,

[0049] As shown in Figure 2 , a new type of elevator light curtain comprises a plastic shell 1 and a circuit board,As shown, the plastic shell 1 comprises a light-transmitting area 101 made of infrared light-transmitting material, the light-transmitting area 101 of the plastic shell 1 is formed by integral two-color extrusion process with the non-light-transmitting area, and a seamless sealed joint is formed between the two, the inner wall of the plastic shell 1 is provided with a slot for clamping and fixing the circuit board, and the circuit board is not in conductive connection with the inner wall of the shell. The light-transmitting area 101 can be made of PC or PNNA material, and the non-light-transmitting area can be made of ABS material. The light-transmitting area 101 and the non-light-transmitting area are formed by integral two-color extrusion to form a seamless whole, realizing mass production. Compared with the traditional aluminum alloy shell + light filter strip, the light filter strip does not need to be manually installed additionally, the assembly is more convenient, and the integral molding only needs to add end covers at both ends, so that the sealing is better, and the stability and durability of the product in harsh environments are enhanced. In addition, the plastic shell is not conductive, which completely avoids the potential short circuit risk of the metal shell. This scheme does not need the grounding screws or springs required for connecting the metal shell, and fundamentally eliminates the shielding failure problem caused by poor grounding.

[0050] The circuit board is arranged in the plastic shell 1.

[0051] As shown in the figure, Figure 3 The circuit board comprises:

[0052] According to the difference between the TX end and the RX end, the circuit board is provided with 36 photoelectric emission units or photoelectric receiving units;

[0053] A multiplexing module 3 is used to cyclically gate the 36 photoelectric emission / receiving units 2; as shown in the figure, Figures 4-7 In this scheme, the multiplexing module 3 adopts a cascade architecture, including a main switching switch 301 and five slave switching switches 302, all of which adopt 4051, and 4051 is a single-ended 8-channel multiplexing switch, which is internally configured with 8 groups of CMOS tubes, and the 4051 with a metal shell selects each photoelectric emission / receiving unit 2 through its switching function, as shown in the figure, Figure 4 The input / output end of the slave switching switch 302 is directly connected to the photoelectric emission / receiving unit 2, and the output end of each photoelectric emission / receiving unit 2 is connected in parallel with a grounding filter network 303; in this scheme, the grounding filter network 303 comprises a resistance and a capacitor connected in parallel to the ground, and the resistance and the capacitor are located at the lower end of the photoelectric emission / receiving unit 2. They can quickly filter out interference fluctuation signals, thereby effectively avoiding interference caused by the internal circuit of the switch.

[0054] As shown in the figure, Figure 5 and Figure 7As shown, a first anti-interference unit containing active devices is provided between the output terminal of the slave switch 302 and the input terminal of the master switch 301, for filtering and buffering the signal before it enters the master switch 301. In this scheme, the first anti-interference unit includes a PNP transistor. The common input / output terminal of the slave switch 302 is connected to the base (B) of the PNP transistor. The emitter (E) of the PNP transistor is connected to the circuit power supply after a series resistor. The collector (C) of the PNP transistor is grounded. Capacitors are provided between the base and emitter, and between the base and collector. The emitter of the PNP transistor is connected to the input / output terminal of the master switch 301 after a series resistor. This resistor is 1k ohms. Figure 6 (R1-R5 in the diagram). In traditional light curtains, the common input / output terminals of the 4051 are directly connected to the signal processing module 4, forming a single-stage structure. This solution replaces this with a cascaded architecture where a master 4051 controls slave 4051s, thus achieving deep optimization of the signal path at the circuit level. Furthermore, a 1K resistor limits the amplitude of the interference current, effectively preventing large-energy interference from damaging components or overwhelming the valid signal. Simultaneously, the resistor also dissipates interference energy, preventing interference from accumulating in the circuit and forming continuous noise.

[0055] Signal processing module 4, such as Figure 3 As shown, it is connected to the output terminal of the multiplexing module 3 and is used to amplify, shape, and detect the sensing signal of the gating unit; as shown Figure 8 As shown, the signal processing module 4 includes a coupling capacitor 401, a preamplifier circuit 402, a clamping circuit 403, and a series of four-stage multi-stage operational amplifier circuits. Each stage is equipped with an RC filter network and an active operational amplifier unit. In traditional light curtain circuits, a dual operational amplifier design is generally used. However, the amplifier circuit of this invention has been redesigned and innovatively adopts a four-stage operational amplifier for step-by-step amplification and filtering. This improvement aims to avoid noise being amplified along with the signal due to excessive amplification, thereby affecting the chip's accurate identification of the effective signal.

[0056] The working principle of the scheme is as follows: the photoelectric signal is firstly filtered at the source (the output end of each photoelectric unit) through the grounding filter network 303; then, the signal is filtered and buffered by an active filter buffer circuit with a PNP transistor as the core after being selected from the switch 302, the transistor works in the amplification or switching zone, and the capacitor connected between the base (B) and the emitter (E) and the base and the collector (C) is respectively used for filtering out interference of different frequency bands. Not only the filtering of the signal is realized, but also the buffering and impedance matching functions are realized. It can effectively suppress large amplitude transient interference, and "shape" and enhance the driving ability of the signal before it enters the main switch 301, avoiding the weak signal being overwhelmed or attenuated by noise in long distance or multi-stage transmission, which is a key link to improve the robustness of the system. The signal is input from the base, processed by the transistor, and then output from the emitter to the main switch 301. The amplitude of the interference current is limited by the 1K resistor, effectively avoiding large energy interference from flowing into the element and overwhelming the effective signal, consuming interference energy, adopting a cascade architecture of a main 4051 controlling a slave 4051, thereby realizing deep optimization of the signal path at the circuit level, and the signal is processed by the signal processing module 4 after being selected by the main 4051, four operational amplifiers are used for step-by-step amplification and filtering, avoiding the noise being amplified together with the signal due to the too high amplification factor, thereby affecting the accurate recognition of the effective signal by the chip, and through the step-by-step cascade of multiple circuits with operational amplifiers as the core, the gain distribution strategy is adopted, the gain of each operational amplifier is set to be relatively low, thereby effectively widening the overall bandwidth under the premise of ensuring the total gain, and avoiding the influence on judgment after noise amplification. In summary, the scheme realizes the systematic hardware design of "source filtering + path isolation / buffering + multi-stage conditioning", actively and multiple times resists external electromagnetic interference and internal switch noise at the circuit level without relying on metal electromagnetic shielding, successfully solves the core problem that the plastic shell 1 cannot shield electromagnetic waves. By adopting the plastic shell 1, the shell does not need to be grounded, and there is no need to worry about the grounding failure or short circuit with the grounding line of other equipment, the installation process is simple, the cost is low, and it is a great progress compared with the traditional metal shell light curtain.

[0057] In actual application, for example, Figures 8-10As shown, the RC filter network of the first-stage operational amplifier circuit 404 and the second-stage operational amplifier circuit 405 is first-order, and the RC filter network of the third-stage operational amplifier circuit 406 and the fourth-stage operational amplifier circuit 407 is second-order. The first-stage and the second-stage adopt first-order RC filtering, mainly for preliminary noise suppression in a wide frequency band; the third-stage and the fourth-stage adopt second-order active filtering, providing a more steep out-of-band attenuation characteristic. In the initial stage of signal amplification, the signal amplitude is small, and the main requirement is to filter out the obvious noise out of the band, and the first-order filter structure is simple, and the introduced phase shift is small, which is beneficial to maintaining the signal response speed. In the later stage of signal amplification, the signal amplitude is already large, but there is still residual noise, and at this time, the second-order filter can more effectively filter out the interference in a specific frequency band, ensuring that the final output signal is extremely pure. This achieves the optimal balance between filtering effect and signal fidelity.

[0058] In actual application, as shown in Figures 8-10 As shown, the second-stage operational amplifier circuit 405, the third-stage operational amplifier circuit 406, and the fourth-stage operational amplifier circuit 407 are each provided with a detection branch, the detection branch includes an optocoupler, the optocoupler is connected to a gain input control end of the MCU, and each gain input control end is equipped with a 100K pull-down resistor. The optocoupler sends the digital control signal (for adjusting the operational amplifier gain) sent by the MCU to the control end of the operational amplifier after electrical isolation. The pull-down resistor connected to each control end ensures that when the MCU control pin is floating or in a high-impedance state, the control end is stably pulled to a low level, preventing misoperation.

[0059] In actual application, as shown in Figure 8 As shown, the amplification and shaping detection circuit is additionally provided with a coupling capacitor 401, an overvoltage protection circuit, and an RC filter network connected to the signal pin of the MCU at the rear end of the fourth-stage amplification circuit, and is provided with an optocoupler connected to the gain input control end of the MCU and equipped with a 100K pull-down resistor. After the fourth-stage amplification, the signal is first passed through the coupling capacitor 401 to block the direct current, then limited by the overvoltage protection circuit, then finally smoothed by the first-order RC filter network, and then sent to the ADC pin of the MCU. At the same time, the gain control here also ensures reliability through optical isolation and pull-down resistance. It ensures that the signal input to the MCU is stable, safe, and high-quality, greatly improving the accuracy of analog-to-digital conversion and the reliability of system judgment.

[0060] In actual application, as shown in Figure 8 As shown, the signal processing module 4 further includes an LC power filter circuit for filtering power supply noise, for providing stable and clean power supply for the operational amplifier, and avoiding power supply noise coupling into the signal. The inductor presents high impedance to high-frequency noise, and the capacitor presents low impedance to high-frequency noise, and the combination of the two can effectively block wide-band noise from the power supply network, which significantly reduces the interference coupled through the common power impedance.

[0061] In actual application, as shown inFigure 8 As shown, the clamping circuit 403 includes a positive diode and a negative diode, and can clamp the signal in both directions, when the signal voltage is higher than the positive diode conduction voltage drop, the positive conduction discharge; when the signal voltage is lower than the negative diode conduction voltage drop, the reverse conduction discharge. It can effectively clamp the instantaneous high voltage or low voltage peak caused by electrostatic discharge, inductive load recoil, etc. to prevent these overvoltages from damaging the expensive and fragile operational amplifier input stage, and to provide a low-cost and effective active protection for the light curtain.

[0062] In summary, the novel elevator light curtain has the advantages of low cost, convenient installation and higher safety.

[0063] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A novel elevator light curtain, characterized in that: include: The plastic casing (1) includes at least one light-transmitting area (101) made of infrared-transmitting material. A circuit board, disposed within the plastic housing (1), includes: Multiple photoelectric transmitting / receiving units (2); A multiplexing module (3) is used to cyclically select the multiple photoelectric transmitting / receiving units (2); The signal processing module (4) is connected to the output of the multiplexing module (3) and is used to amplify, shape and detect the sensing signal of the gating unit. The multi-channel switching module (3) adopts a cascaded architecture, including a master switching switch (301) and multiple slave switching switches (302). The slave switching switches (302) are directly connected to the photoelectric transmitting / receiving unit (2), and each photoelectric transmitting / receiving unit (2) has a grounding filter network (303) connected in parallel at its output terminal. Among them, a first anti-interference unit containing active devices is provided between the output terminal of the slave switch (302) and the input terminal of the master switch (301) for filtering and buffering the signal before it enters the master switch (301); The signal processing module (4) includes a coupling capacitor (401), a preamplifier circuit (402), a clamping circuit (403), and a multi-stage operational amplifier circuit. The multi-stage operational amplifier circuit has no less than four stages, and each stage is equipped with an RC filter network and an active operational amplifier unit.

2. The novel elevator light curtain according to claim 1, characterized in that: The grounding filter network (303) includes resistors and capacitors connected to ground in parallel.

3. The novel elevator light curtain according to claim 1, characterized in that: The first anti-interference unit includes a PNP transistor. The common input / output terminal of the switch (302) is connected to the base (B) of the PNP transistor. The emitter (E) of the PNP transistor is connected to the circuit power supply after a series resistor. The collector (C) of the PNP transistor is grounded. Capacitors are provided between the base and emitter, and between the base and collector. The emitter (E) of the PNP transistor is connected to the input / output terminal of the main switch (301) after a series resistor.

4. The novel elevator light curtain according to claim 1, characterized in that: The multi-stage operational amplifier circuit includes a first-stage operational amplifier circuit (404), a second-stage operational amplifier circuit (405), a third-stage operational amplifier circuit (406), and a fourth-stage operational amplifier circuit (407).

5. A novel elevator light curtain according to claim 4, characterized in that: The RC filter networks of the first-stage operational amplifier circuit (404) and the second-stage operational amplifier circuit (405) are first-order, while the RC filter networks of the third-stage operational amplifier circuit (406) and the fourth-stage operational amplifier circuit (407) are second-order.

6. A novel elevator light curtain according to claim 4, characterized in that: The second-stage operational amplifier circuit (405), the third-stage operational amplifier circuit (406), and the fourth-stage operational amplifier circuit (407) are all equipped with detection branches. The detection branches include optocouplers, which are connected to the gain input control terminal of the MCU. Each gain input control terminal is equipped with a 100K pull-down resistor.

7. A novel elevator light curtain according to claim 4, characterized in that: The amplification, shaping, and detection circuit is further equipped with a coupling capacitor (401), overvoltage protection, and an RC filter network connected to the signal pin of the MCU at the rear end of the fourth-stage amplification circuit. It is also equipped with an optocoupler connected to the gain input control terminal of the MCU and a 100K pull-down resistor.

8. A novel elevator light curtain according to claim 1, characterized in that: The signal processing module (4) also includes an LC power supply filter circuit (408) for filtering out power supply noise.

9. A novel elevator light curtain according to claim 1, characterized in that: The clamping circuit (403) includes a positive diode and a negative diode, which can clamp the signal bidirectionally in the circuit.

10. A novel elevator light curtain according to claim 1, characterized in that: The light-transmitting area (101) and the opaque area of ​​the plastic shell (1) are integrally formed by a two-color extrusion process.

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