Automatic alignment and distance measurement method for light curtain

Abstract

An automatic alignment and distance measurement method for a light curtain belongs to the technical field of optical devices, and comprises the following steps: S1, installing a light curtain transmitting end and a light curtain receiving end at two ends of a safety detection area, connecting the transmitting end and the receiving end to a power supply system, and starting a focusing mode after the system is initialized; s2, a focusing mode is started, laser emission modules are arranged at the upper end and the lower end of a mirror surface area of a light curtain receiving end, and photosensitive induction modules are arranged at the upper end and the lower end of a mirror surface area of a light curtain emitting end; a light inlet of the photosensitive induction module is provided with a hollow cross silk screen; and the laser emission module emits visible laser beams to the photosensitive induction module on the same side, and ensures that the visible laser beams are irradiated to the central position of the cross silk-screen area on the mirror surface of the emission end, so that two-point plane positioning is realized, and the mirror surface of the light curtain emission end and the mirror surface of the light curtain receiving end are ensured to be in a parallel state.

Description

Technical Field

[0001] The invention belongs to the technical field of optical devices, and in particular relates to an automatic alignment and distance measurement method for a light curtain. Background Art

[0002] Safety light curtains, also known as safety gratings, safety photoelectric protectors, etc., are mainly used in automated processing machinery and production lines where operators participate or monitor, such as the forging industry, automobile manufacturing, and electronic and electrical manufacturing industries. Its working principle is that the emitter generates an infrared light beam and transmits it to the light receiver, thereby forming a rectangular protection area between the emitter and the light receiver. When an opaque object enters this area, the corresponding light beam is blocked, and the emitter or light receiver generates a shading signal and outputs it to the controller (or directly outputs a PNP or NPN transistor signal). The controller eventually converts the shading signal into a relay output signal to control the machine equipment to stop in order to protect the operator's personal safety. Safety light curtains are also widely used in the security field to prevent illegal intrusion.

[0003] However, the existing technology has the following defects when dealing with the alignment between the transmitter and the receiver: 1. It is impossible to achieve accurate alignment within approximately 1 degree, resulting in the protection angle being not accurate enough and unable to meet the needs of high-precision occasions.

[0004] 2. The receiving and transmitting ends are usually aligned by visual inspection, which introduces the factor of excessive deviation in the shooting angle. Some industrial control fields with high precision requirements may even cause accidents due to excessive deviation in the shooting angle. For this reason, some users need to use visible infrared alignment instruments, which undoubtedly increases the extra cost of using the equipment.

[0005] 3. The power consumption of the light curtain system is fixed and cannot be automatically adjusted according to the protection distance, which lacks energy-saving effect.

[0006] These defects are mainly caused by the following reasons: 1. Due to the angle limitation of the optical lens design, it is impossible to achieve a beam deviation angle below 1°.

[0007] 2. The design principle lacks automatic power consumption adjustment circuit and automatic alignment verification circuit.

[0008] 3. Errors are introduced during product assembly and on-site installation.

[0009] Existing technical solutions attempt to solve the above problems by combining visible infrared laser and radar ranging technology, but the application is difficult to implement, the process is complicated, the cost is high, and it is not easy for on-site workers to install and operate. Summary of the invention

[0010] In view of the current status and shortcomings of the above-mentioned prior art, an object of the present invention is to provide an automatic alignment and distance measurement method for a light curtain.

[0011] To achieve the above object, the present invention adopts the following technical solutions: A method for automatic alignment and distance measurement of a light curtain comprises the following steps: Step S1, installing the light curtain transmitter and the light curtain receiver at both ends of the safety detection area, and connecting the light curtain transmitter and the light curtain receiver to the power supply system, and starting the focus mode after the system is initialized; Step S2, start the focus mode, set laser emission modules at both ends of the upper and lower mirror areas of the light curtain receiving end, and set photosensor modules at both ends of the upper and lower mirror areas of the light curtain transmitting end; set a hollow cross screen at the light inlet of the photosensor module; the laser emission module emits a visible laser beam to the photosensor module on the same side, and ensures that the visible laser beam hits the center of the cross screen area on the mirror surface of the transmitting end, realizes two-point surface determination, and ensures that the mirror surface of the light curtain transmitting end and the mirror surface of the light curtain receiving end are in a parallel state; Step S3, the light curtain transmitting end enters the focusing calibration mode of the incident angle, and the light-sensitive sensor module installed under the center area of ​​the mirror cross screen printing on the light curtain transmitting end obtains the light intensity and converts it into a current signal, which is transmitted to the AD input capture I / O interface of the single-chip microcomputer through the signal processing circuit; the single-chip microcomputer starts the focus intensity and handshake protocol recognition and judgment inside, and after the handshake is successful, the infrared transmitting module of the light curtain transmitting end sends a handshake success and ranging command to the light curtain receiving end; Step S4, the infrared receiving module at the light curtain receiving end receives and parses and identifies the handshake success and distance measurement instructions sent by the light curtain transmitting end, and then sends the distance measurement reply ACK protocol instruction to the light curtain transmitting end through the infrared protocol sending module; the infrared protocol receiving module at the light curtain transmitting end receives the distance measurement reply ACK protocol instruction, and automatically calculates the distance between the two parties by identifying the interval of the distance measurement reply ACK protocol instructions of the light curtain receiving end.

[0012] Furthermore, the light curtain used in the method includes a light curtain transmitting end and a light curtain receiving end; The light curtain transmitting end includes a light-sensitive sensing module, an infrared protocol receiving module, an infrared transmitting module and a transmitting power control module; The light curtain receiving end includes a laser transmitting module, an infrared protocol sending module, an infrared receiving module and a receiving power control module; The laser emission module and the light-sensitive sensing module constitute an automatic alignment detection and recognition module; The infrared protocol receiving module and the infrared protocol sending module constitute an automatic ranging system module; The infrared transmitting module and the infrared receiving module constitute a light curtain radiation module; The light curtain transmitting end and the light curtain receiving end both have a 485 communication module and a status indicator light module.

[0013] Furthermore, a method for automatic alignment and distance measurement of a light curtain further includes: Step S5, after the light curtain transmitting end calculates the distance with the light curtain receiving end, the light curtain transmitting end controls the output of the power supply voltage to the infrared transmitting module through the PWM duty cycle, and adjusts the power of the infrared transmitting tube to ensure that the system power consumption is within the optimal range; Step S6, the light curtain transmitting end starts the infrared transmitting module, and at the same time sends an instruction to start receiving the safety light beam to the light curtain receiving end through the 485 interface. After the light curtain receiving end obtains the instruction through the 485 module, it starts to start the program of receiving, capturing and identifying the infrared beam of the light curtain transmitting end; Step S7, the light curtain receiving end obtains the received signal strength, and outputs the signal quality obtained by the light curtain receiving end to the light curtain transmitting end through the 485 receiving interface; the light curtain transmitting end dynamically adjusts according to the received data to ensure that the signal strength of the receiving end is within a reasonable range.

[0014] Further, in step S4, the system automatically calculates the distance between the two ends using the following formula: D = C*(T n -T n-1 -Tick (n-1) *2); Where, C is the speed of light, which is 0.3m / ns; T n-1 The time when the data signal was last received; T n Tick ​​is the time when the data signal is received this time; (n-1) is the mechanical conversion time of the microcontroller in this mode; n is the number of times the light curtain transmitter captures the measurement instructions of the light curtain receiver, and n should be greater than or equal to 2; D is the distance between the light curtain transmitter and the light curtain receiver.

[0015] Further, in step S5, the infrared transmitter power supply voltage Vout=Vin*Duty; wherein Vin is the default system power supply voltage of the infrared transmitter; and Duty is the duty cycle of the control output circuit.

[0016] Furthermore, the laser emission module comprises: Signal input circuit: PWM control signal pin RL_TXPWM is connected to the gate of field effect transistor Q1 through diode D1 and resistor R2; PWM control signal pin RL_TXPWM outputs a pulse control signal of 2kHz and 50% duty cycle; gate charging current limiting resistor R2 is connected in series between PWM control signal pin RL_TXPWM and the gate of field effect transistor Q1; fast discharge diode D1 is connected in parallel across the gate charging current limiting resistor R2 to form an asymmetric charging and discharging path; conduction phase: gate charging current limiting resistor R2 limits the gate charging current to avoid overload or high-frequency oscillation; shutdown phase: when the control signal becomes low, the discharge diode D1 provides a low impedance path, and the gate charge is discharged through the discharge diode D1, shortening the shutdown time; Control circuit: The field effect transistor Q1 is used as a switching element, with its gate receiving a pulse control signal from the signal input circuit, its source being grounded, and its drain being connected to the cathode of the laser emitting tube LED1; when the gate receives a high-level signal, the field effect transistor Q1 is turned on, allowing current to pass; when a low-level signal is received, the field effect transistor Q1 is turned off, blocking the current; Current limiting and protection circuit: Current limiting resistor R1 is connected in series between the positive pole of the laser emitting tube LED1 and the power supply VCC, and is used to limit the current passing through the laser emitting tube LED1; filter capacitor C1 is installed between the power supply VCC and the ground, and is used to filter out the ripple interference generated during the pulse emission process; inter-electrode resistor R3 is set between the gate and the source of the field effect tube Q1, mainly to solve the problems of gate charge discharge and static potential balance; when the driving signal disappears, the inter-electrode resistor R3 quickly discharges the residual charge of the gate to the source, avoiding accidental conduction of the field effect tube Q1 due to external interference; the inter-electrode resistor R3 provides an impedance path for the gate to the ground, absorbs static electricity, and prevents the gate oxide layer from breaking down.

[0017] Furthermore, the light-sensitive sensor module includes a receiving circuit and a signal processing circuit; The receiving circuit includes: the light receiving sensor PD1 is a photodiode, which is responsible for receiving the light signal irradiated by the infrared laser and converting it into an electrical signal; the intermediate value of its induced output current is 12mA; the current detection resistor R201 not only detects the current generated by the photodiode, but also ensures that the photodiode works within the optimal range; the coupling capacitor C201 is used to obtain the electrical signal received by the photodiode and remove the interference of ambient light; the resistor R202 and the capacitor C202 form a low-pass filter circuit to filter out the external interference frequency band in the received signal and make the waveform stable; Signal processing circuit: When the light receiving sensor PD1 receives the light signal, a photoelectric effect occurs inside, generating an induced current I; the current generates an induced voltage PD_Vout=R2*I on the resistor R202; the induced voltage PD_Vout is coupled to the same-direction input terminal 2 of the operational amplifier LM2904 through the coupling capacitor C201; the operational amplifier LM2904 performs the first-stage same-direction proportional amplification on the coupled signal to filter out clutter interference and make the waveform more stable; the first-stage operational amplifier output signal PhotoSen_ADC is output from pin 1 of the operational amplifier LM2904; the first-stage operational amplifier output signal PhotoSen_ADC is further filtered out of high-frequency noise through the low-pass filter circuit of the resistor R205, and then input to the same-direction input terminal 5 of the operational amplifier LM2904, and the signal is amplified by 2 times the gain through the second-stage operational amplifier, and finally the amplified operational amplifier output signal Photo_ADC_Out is output through the resistor R208, and the signal is supplied to the ADC output capture mode pin interface of the microcontroller.

[0018] Furthermore, the external infrared emission module includes: The switching transistor Q6, the base is connected to the protocol control signal ‌Agree_Sing‌ through the resistor R32, the collector is directly connected to the positive electrode of the infrared emitting tube ‌IR_T1‌, and is connected to the power supply VCC through the resistor ‌R29‌, and the emitter is grounded to GND through the resistor ‌R34; Resistors R29 and R34 are current limiting resistors of the infrared emitting tube, capacitor C307 is a filter capacitor, and capacitor C307, resistor R29, switching transistor Q6, and resistor R34 form an infrared emitting charge and discharge circuit to eliminate the overcharge and over-discharge phenomenon of the switching transistor Q6 during the switching process that affects the output waveform of the infrared emitting tube; The switch transistor Q6 controls the on / off of the infrared emitting tube IR_T1, and Agree_Sing is the protocol control instruction output by the transmitting end; when the switch transistor Q6 is turned on, the collector current flows through the infrared emitting tube IR_T1, driving it to emit infrared light signals; when the switch transistor Q6 is turned off, the infrared emitting tube IR_T1 stops working.

[0019] Furthermore, the infrared receiving module includes: The light receiving sensor PD3 is responsible for receiving the infrared alignment success and ranging signal IR_RX_ACK from the infrared transmitting end; Pin 1 of the light receiving sensor PD3 outputs the received infrared signal IR_RX_ACK and connects to the comparator U3A through the resistor R32, Pin 2 is grounded, Pin 3 is connected to the resistor R30 and the capacitor C15, the resistor R30 is connected to the positive pole of the power supply, and the capacitor C15 is grounded; Capacitor C16 has one end connected to pin 3 of comparator U3A and the other end grounded, which plays a role in filtering interference; the I / O input end of the microcontroller is connected to the output end of U3A to receive the IR_ACK_SING signal. When the microcontroller receiving end recognizes the instruction, it sends a distance measurement instruction to the transmitting end.

[0020] An automatic alignment and distance measurement method for a light curtain has the characteristics of automatically adjusting system power consumption, automatic and accurate alignment, alignment in long-distance or high-precision situations without the need for additional instruments, automatic adjustment of system power consumption according to distance to achieve energy saving effect, adjustable emission signal strength and low light radiation to meet environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 This is the circuit schematic diagram of the laser emission module at the receiving end of the light curtain; Figure 3 This is the circuit schematic diagram of the light-sensitive sensor module at the transmitting end of the light curtain; Figure 4 This is the circuit schematic diagram of the external infrared emission module at the light curtain emission end; Figure 5 This is the circuit schematic diagram of the infrared receiving module at the receiving end of the light curtain; Figure 6 This is the circuit schematic diagram of the infrared protocol receiving module at the light curtain transmitting end; Figure 7 Schematic diagram of the mirror area of ​​the light curtain transmitting end and the light curtain receiving end. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0023] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 7 Schematic diagram of the mirror area of ​​the light curtain transmitter and the light curtain receiver; Figure 1 and Figure 7 , a light curtain comprises a light curtain transmitting end and a light curtain receiving end.

[0024] The light curtain transmitting end includes a light-sensitive sensing module, an infrared protocol receiving module, an infrared transmitting module and a transmitting power control module.

[0025] The light curtain receiving end includes a laser transmitting module, an infrared protocol sending module, an infrared receiving module and a receiving power control module.

[0026] The laser emission module and the light-sensitive sensing module constitute an automatic alignment detection and recognition module.

[0027] The infrared protocol receiving module and the infrared protocol sending module constitute an automatic distance measurement system module.

[0028] The infrared transmitting module and the infrared receiving module constitute a light curtain radiation module.

[0029] The light curtain transmitting end and the light curtain receiving end both have a 485 communication module and a status indicator light module.

[0030] A method for automatic alignment and distance measurement of a light curtain comprises the following steps: Step S1, install the light curtain transmitter and the light curtain receiver at both ends of the safety detection area, and connect the light curtain transmitter and the light curtain receiver to the power supply system (DC12~24V), the system is initialized and starts the focus mode after 3 seconds.

[0031] Step S2, start the focus mode, laser emitting modules are set at both ends of the upper and lower mirror areas of the light curtain receiving end, and photosensor modules are set at both ends of the upper and lower mirror areas of the light curtain transmitting end; a hollow cross screen is set at the light inlet of the photosensor module; the laser emitting module emits a visible laser beam to the photosensor module on the same side, and ensures that the visible laser beam hits the center position of the cross screen area on the mirror surface of the light curtain transmitting end, realizes two-point surface determination, and ensures that the mirror surface of the light curtain transmitting end and the mirror surface of the light curtain receiving end are in a parallel state.

[0032] Figure 2 This is the circuit schematic diagram of the laser transmitter module at the receiving end of the light curtain, such as Figure 2 As shown, the laser emission module includes: Signal input circuit: PWM control signal pin RL_TXPWM is connected to the gate of field effect transistor Q1 through diode D1 and resistor R2.

[0033] The PWM control signal pin RL_TXPWM outputs a pulse control signal with a 2kHz and a duty cycle of 50%. Frequency (2kHz): Indicates that the number of switching cycles per second is 2000 times, which determines the repetition rate of the laser pulse. Duty cycle (50%): Indicates that the ratio of high level (on time) to low level (off time) in each cycle is 1:1. The larger the duty cycle, the higher the average brightness of the LED. The gate charging current limiting resistor R2 is connected in series between the PWM control signal pin RL_TXPWM and the gate of the field effect tube Q1 to limit the gate charging current to avoid overload or high-frequency oscillation. The fast discharge diode D1 is connected in parallel across the gate charging current limiting resistor R2 to form an asymmetric charging and discharging path. On stage (charging): The gate charging current limiting resistor R2 limits the gate charging current to avoid overload or high-frequency oscillation. Turn-off phase (discharge): When the control signal becomes low, the discharge diode D1 provides a low impedance path (forward conduction), and the gate charge is quickly discharged through the discharge diode D1, significantly shortening the turn-off time.

[0034] Control circuit: Field effect tube Q1 is used as a switch element, its gate receives the pulse control signal from the signal input circuit, its source is grounded, and its drain is connected to the cathode of the laser emitting tube LED1. When the gate receives a high-level signal, the field effect tube Q1 is turned on, allowing current to pass; when a low-level signal is received, the field effect tube Q1 is turned off, blocking the current.

[0035] Current limiting and protection circuit: The current limiting resistor R1 is connected in series between the positive pole of the laser emitting tube LED1 and the power supply VCC to limit the current passing through the laser emitting tube LED1 to prevent it from being damaged due to overcurrent. The filter capacitor C1 is installed between the power supply VCC and the ground to filter out the ripple interference generated during the pulse emission process to ensure the stability of the operation of the laser emitting tube LED1. The inter-electrode resistor R3 is set between the gate (G) and the source (S) of the field effect tube Q1, mainly to solve the problems of gate charge discharge and static potential balance. Anti-false triggering: When the drive signal disappears (no input), R3 quickly discharges the residual charge of the gate to the source to avoid accidental conduction of the field effect tube Q1 due to external interference (such as electromagnetic noise). Electrostatic protection: The inter-electrode resistor R3 provides an impedance path for the gate to the ground (source), absorbs electrostatic charge, and prevents the gate oxide layer from breaking down.

[0036] Step S3, the light curtain transmitter enters the focusing calibration mode of the incident angle, and the red light of the status indicator flashes at a frequency of 1HZ. The light-sensitive sensor module installed under the center area of ​​the mirror cross screen printing on the light curtain transmitter obtains the light intensity and converts it into a current signal, which is transmitted to the AD input capture I / O interface of the single-chip microcomputer through the signal processing circuit; the single-chip microcomputer starts the focus intensity and handshake protocol recognition and judgment inside, and the status indicator turns green after the handshake is successful, and the infrared emission module of the light curtain transmitter sends a handshake success and distance measurement command to the light curtain receiver.

[0037] Figure 3 This is the circuit schematic diagram of the light-sensitive sensor module at the transmitting end of the light curtain, such as Figure 3 As shown, The light-sensitive sensor module at the transmitting end of the light curtain includes a receiving circuit and a signal processing circuit.

[0038] Receiving circuit: The light receiving sensor PD1 is a photodiode, which is responsible for receiving the light signal irradiated by the infrared laser and converting it into an electrical signal. The median value of its induced output current is 12mA. The current detection resistor R201 not only detects the current generated by the photodiode, but also ensures that the photodiode works within the optimal range. The coupling capacitor C201 is used to obtain the electrical signal received by the photodiode and remove the interference of ambient light. The resistor R202 and the capacitor C202 form a low-pass filter circuit to filter out the external interference frequency band in the received signal and make the waveform stable.

[0039] Signal processing circuit: When the light receiving sensor PD1 receives the light signal, a photoelectric effect occurs inside, generating an induced current I. This current generates an induced voltage PD_Vout=R2*I on the resistor R202. The induced voltage PD_Vout is coupled to the same-direction input terminal 2 of the operational amplifier LM2904 through the coupling capacitor C201. The operational amplifier LM2904 performs the first-stage same-direction proportional amplification on the coupled signal, filters out clutter interference, and makes the waveform more stable.

[0040] Pin 1 of the op amp LM2904 outputs the first-stage op amp output signal PhotoSen_ADC; the first-stage op amp output signal PhotoSen_ADC is further filtered out of high-frequency noise through the low-pass filter circuit of resistor R205, and then input to the same-direction input terminal 5 of the op amp LM2904. The signal is amplified by 2 times the gain through the second-stage op amp, and finally the amplified op amp output signal Photo_ADC_Out is output through resistor R208. This signal is supplied to the ADC output capture mode pin interface of the microcontroller.

[0041] The light sensing module receives infrared laser signals through photodiodes, and couples, filters and amplifies the signals through components such as resistors, capacitors and op amps, and finally outputs a stable light signal to the microcontroller for reading and processing. The entire control principle is clear and reasonable, ensuring the accurate reception and processing of light signals.

[0042] Step S4, the infrared receiving module at the light curtain receiving end receives and parses the handshake success and distance measurement instructions sent by the light curtain transmitting end, and then sends the distance measurement reply ACK protocol instruction to the light curtain transmitting end through the infrared protocol sending module; the infrared protocol receiving module at the light curtain transmitting end receives the distance measurement reply ACK protocol instruction, and automatically calculates the distance between the two parties by identifying the interval of the distance measurement reply ACK protocol instruction of the light curtain receiving end. The system automatically calculates the distance between the two ends as follows: D=C*(T n -T n-1 -Tick (n-1) *2).

[0043] Where, C is the speed of light, which is 0.3m / ns; T n-1 The time when the data signal was last received; T n Tick ​​is the time when the data signal is received this time; (n-1) is the mechanical conversion time of the microcontroller in this mode; n is the number of times the light curtain transmitter captures the measurement instructions of the light curtain receiver, and n should be greater than or equal to 2; D is the distance between the light curtain transmitter and the light curtain receiver.

[0044] Figure 4This is the circuit schematic diagram of the external infrared emission module at the light curtain transmitting end, such as Figure 4 As shown, the external infrared emission module sends a successful alignment and ranging signal, including: The light curtain transmitting end circuit drives the switch transistor Q6 through the protocol control signal Agree_Sing, controls the pulse emission of the infrared transmitting tube IR_T1, realizes the distance measurement by combining the time difference method, and completes the alignment confirmation through the synchronous feedback mechanism.

[0045] The switching transistor Q6, the base is connected to the protocol control signal ‌Agree_Sing‌ through the resistor R32, the collector is directly connected to the positive electrode of the infrared emitting tube ‌IR_T1‌, and is connected to the power supply VCC through the resistor ‌R29‌, and the emitter is grounded to GND through the resistor ‌R34; Resistors R29 and R34 are current limiting resistors of the infrared emitting tube, capacitor C307 is a filter capacitor, and capacitor C307, resistor R29, switching transistor Q6, and resistor R34 form an infrared emitting charge and discharge circuit to eliminate the overcharge and over-discharge phenomenon of the switching transistor Q6 during the switching process that affects the output waveform of the infrared emitting tube; The switch transistor Q6 controls the on / off of the infrared emitting tube IR_T1, and Agree_Sing is the protocol control instruction output by the transmitting end. When the switch transistor Q6 is turned on, the collector current flows through the infrared emitting tube IR_T1, driving it to emit infrared light signals; when the switch transistor Q6 is turned off, the infrared emitting tube IR_T1 stops working.

[0046] Figure 5 This is the circuit schematic diagram of the infrared receiving module at the receiving end of the light curtain, such as Figure 5 As shown, the infrared receiving module captures the alignment success and ranging signal protocol signals.

[0047] Pin 1 (OUT) of the light receiving sensor PD3 outputs the received infrared signal IR_RX_ACK and connects to the comparator U3A through the resistor R32, pin 2 (GND) is grounded, pin 3 (VS) is connected to the resistor R30 and capacitor C15, resistor R30 is connected to the positive pole of the power supply (VCC), and capacitor C15 is grounded (GND). The light receiving sensor PD3 is responsible for receiving the infrared alignment success and ranging signal IR_RX_ACK from the infrared transmitter.

[0048] Capacitor C16 has one end connected to pin 3 of comparator U3A and the other end connected to ground, which plays a role in filtering interference, making the comparator U3A more stable in accepting waveform deformation.

[0049] The I / O input of the microcontroller is connected to the output of U3A to receive the IR_ACK_SING signal. When the microcontroller receiving end recognizes the instruction, it sends a distance measurement instruction to the transmitting end.

[0050] The circuit captures infrared signals through the light curtain receiving end, filters out high-frequency noise through two-stage low-pass filters, stabilizes the signal waveform through a comparator, and finally receives and processes the signal through a single-chip microcomputer to achieve normal operation of the infrared light curtain.

[0051] Figure 6 This is the circuit schematic diagram of the infrared protocol receiving module at the light curtain transmitting end, such as Figure 6 As shown, the infrared protocol receiving module, the receiving tube captures the infrared signal.

[0052] The infrared receiving sensor PD2 is responsible for receiving the infrared pulse signal with the ranging protocol transmitted from the receiving end. When receiving the infrared signal, the infrared receiving sensor PD2 converts it into a current signal, which is then sent to the circuit for processing.

[0053] The resistor R9 is connected to the output of the infrared receiving sensor PD2 and is used to limit the current entering the base of the switching transistor Q3.

[0054] The resistor R10 is connected to the base of the switching transistor Q3 to further limit the base current and ensure that the switching transistor Q3 works stably.

[0055] The resistor R11 is connected between the base of the switching transistor Q4 and a power supply to provide a bias voltage for the switching transistor Q4.

[0056] The resistor R12 is connected to the base of the switching transistor Q4 and is used to limit the current of the base of the switching transistor Q4.

[0057] The resistor R13 is connected between the collector of the switching transistor Q4 and the IR_Agree_Sing signal output, and is used to convert the collector current of the switching transistor Q4 into a voltage signal.

[0058] Capacitor C8 is connected between resistor R13 and ground for filtering to ensure the stability of the IR_Agree_Sing signal.

[0059] The light curtain receiving end transmits an infrared pulse signal with a ranging protocol to the light curtain transmitting end; the light curtain transmitting end converts the received signal into a current signal to control the switch transistor Q3 to start working. After the switch transistor Q3 is turned on, the switch transistor Q4 is turned on. At this time, the IR_Agree_Sing signal at the resistor R13 end changes from high to low, and the received IR_Agree_Sing signal is analyzed by the comparator and input into the corresponding signal receiving I / O of the microcontroller. The transmitting end microcontroller begins to identify whether it is the ranging instruction model sent by the receiving end.

[0060] At this time, the transmitter receives the infrared ranging command twice by the time difference (T n -Tn-1 ), then subtract the actual Tick time of the MCU algorithm running machine at the transmitting and receiving ends*2, and you get the time light curtain running time. Finally, multiply it by the speed of light to get the final time distance D=C*(T n -T n-1 -Tick (n-1) *2).

[0061] The circuit receives signals through infrared receiving sensors, uses transistors to amplify and process signals, and finally calculates distance information through a single-chip microcomputer. The connection methods and working principles of various components are coordinated with each other to jointly realize the infrared distance measurement function.

[0062] Step S5, after the light curtain transmitter calculates the distance with the light curtain receiver, the light curtain transmitter outputs the power supply voltage to the infrared transmitter module through PWM duty cycle control, and adjusts the power of the infrared transmitter tube to ensure that the system power consumption is within the optimal range. The output voltage formula is as follows: Vout=Vin*Duty.

[0063] Where, Vin is the default system power supply voltage of the infrared transmitter; Duty is the duty cycle of the control output circuit; Vout is the power supply voltage of the infrared transmitter.

[0064] Preferably, the PWM frequency is 10KHZ.

[0065] Step S6, the light curtain transmitting end starts the infrared transmitting module, and at the same time sends an instruction to start receiving the safety light beam to the light curtain receiving end through the 485 interface. After the light curtain receiving end obtains the instruction through the 485 module, it starts to start the program of receiving, capturing and identifying the infrared beam of the light curtain transmitting end.

[0066] Step S7, the light curtain receiving end obtains the received signal strength, and outputs the signal quality obtained by the light curtain receiving end to the light curtain transmitting end through the 485 receiving interface; the light curtain transmitting end dynamically adjusts according to the received data to ensure that the signal strength of the receiving end is within a reasonable range.

[0067] Compared with the current light curtains, the technological application innovation of this light curtain can greatly enhance the user's intelligent use experience, avoid the problem that the transmitting and receiving ends are not installed on the same plane, causing troubles in detection due to inaccurate positioning, and avoid false triggering of safety protection due to different energy at the transmitting end. At the same time, when the energy is too strong, it will cause shallow infrared light interference to other equipment, as well as light pollution caused by excessive light radiation interference in special environments.

[0068] Application scenario 1: For some occasions with strict requirements on the accuracy of the shooting angle, the safety light curtains on the market all use manual alignment, which cannot meet the requirement of almost 0 degree offset angle. Therefore, in order to match the scene, it is often necessary to use a laser focus (position) instrument for auxiliary focusing. At the same time, for some installation areas that are not horizontal, the manual focus (position) error is large. In order to make the receiving and transmitting ends on the same horizontal plane, a level meter must be used, which is very inconvenient and uneconomical in terms of installation cost. Therefore, our new light curtain has an automatic focus (position) system, which can be used in high-precision small-angle occasions.

[0069] Application scenario 2: When the light curtain is used, its usage scenarios have the needs of long-distance and short-distance safety protection. Ordinary light curtains require users to find the corresponding manufacturers for customization according to the actual measured distance of the transmitting and receiving ends. In this way, due to different distances, the price of customized light curtains is different, and the unit price that users need to purchase is also different, which undoubtedly increases the economic expenditure for users.

[0070] Application scenario 3, due to the limitations of ordinary light curtains, when the user's installation environment, that is, the installation distance between the end and the receiving end, changes, if short-distance safety detection is actually required, when the user selects a long-distance light curtain, the long-distance light curtain has too strong transmission power when used. When the user uses it for safety protection at a short distance, due to the optical characteristics of the light curtain itself, the transmission power is too large and its own detection blind area will also become relatively larger, so that the actual safety protection distance is within the blind area of ​​the light curtain and cannot be detected. Similarly, if long-distance safety detection is actually required, when the user selects a short-distance light curtain, the short-distance light curtain has weaker transmission power when used and cannot match long-distance safety detection. Since ordinary light curtains cannot be adaptive, when there are light curtains with the same appearance but different detection distances at the installation site, users will make mistakes in installation, causing installation problems.

[0071] Application scenario 4: Currently, green environmental protection is strongly advocated. Ordinary light curtains cannot control the optical interference caused by infrared light in terms of energy, and often cause infrared radiation optical pollution to the surrounding environment parameters, which does not meet environmental protection requirements. At the same time, ordinary light curtains cannot achieve reasonable modulation in power energy use, resulting in unnecessary waste of electricity for users, which is not economical.

[0072] In summary, this light curtain has multiple uses, which not only saves the user's investment cost, but also has a wide range of applications and is easy to install. At the same time, it has an intelligent control system that can automatically control and adjust the infrared emission intensity. Compared with ordinary light curtains, it is more energy-saving and environmentally friendly, and it also lowers the threshold for use and enhances its competitive potential in the light curtain market. The specific beneficial effects include: 1. It improves the user's smart experience and avoids the problem of inaccurate detection caused by the transmitter and receiver being installed on different planes.

[0073] 2. Avoid the problem of false triggering of safety protection due to different energy at the transmitting end and light pollution caused by excessive light radiation interference.

[0074] 3. No need to customize the light curtain according to the distance, which reduces user costs.

[0075] 4. Adaptive distance adjustment is realized to avoid safety detection problems caused by changes in installation distance.

[0076] 5. It has an intelligent control system that can automatically control and adjust the infrared emission intensity, which is more energy-saving and environmentally friendly, lowers the threshold for use, and enhances market competitiveness.

[0077] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A method for automatic alignment and distance measurement of a light curtain, characterized in that: The following steps are involved: Step S1, installing the light curtain transmitter and the light curtain receiver on both sides of the safety detection area, and connecting the light curtain transmitter and the light curtain receiver to the power supply system, and starting the focus mode after the system is initialized; Step S2, start the focus mode, set laser emission modules at both ends of the upper and lower mirror areas of the light curtain receiving end, and set photosensor modules at both ends of the upper and lower mirror areas of the light curtain transmitting end; set a hollow cross screen at the light inlet of the photosensor module; the laser emission module emits a visible laser beam to the photosensor module at the same end, and ensures that the visible laser beam hits the center of the cross screen area on the mirror surface of the transmitting end, realizes two-point surface determination, and ensures that the mirror surface of the light curtain transmitting end and the mirror surface of the light curtain receiving end are in a parallel state; Step S3, the light curtain transmitting end enters the focusing calibration mode of the incident angle, and the light-sensitive sensor module installed under the center area of ​​the mirror cross screen printing on the light curtain transmitting end obtains the light intensity and converts it into a current signal, which is transmitted to the AD input capture I / O interface of the single-chip microcomputer through the signal processing circuit; the single-chip microcomputer starts the focus intensity and handshake protocol recognition and judgment inside, and after the handshake is successful, the infrared transmitting module of the light curtain transmitting end sends a handshake success and ranging command to the light curtain receiving end; Step S4, the infrared receiving module at the light curtain receiving end receives and parses and identifies the handshake success and distance measurement instructions sent by the light curtain transmitting end, and then sends the distance measurement reply ACK protocol instruction to the light curtain transmitting end through the infrared protocol sending module; the infrared protocol receiving module at the light curtain transmitting end receives the distance measurement reply ACK protocol instruction, and automatically calculates the distance between the two parties by identifying the interval of the distance measurement reply ACK protocol instructions of the light curtain receiving end.

2. The automatic alignment and distance measurement method of a light curtain according to claim 1, characterized in that: The light curtain used in the method includes a light curtain transmitting end and a light curtain receiving end; The light curtain transmitting end includes a light-sensitive sensing module, an infrared protocol receiving module, an infrared transmitting module and a transmitting power control module; The light curtain receiving end includes a laser transmitting module, an infrared protocol sending module, an infrared receiving module and a receiving power control module; The laser emission module and the light-sensitive sensing module constitute an automatic alignment detection and recognition module; The infrared protocol receiving module and the infrared protocol sending module constitute an automatic ranging system module; The infrared transmitting module and the infrared receiving module constitute a light curtain radiation module; The light curtain transmitting end and the light curtain receiving end both have a 485 communication module and a status indicator light module.

3. The automatic alignment and distance measurement method of a light curtain according to claim 2, characterized in that: Also includes: Step S5, after the light curtain transmitting end calculates the distance with the light curtain receiving end, the light curtain transmitting end controls the output of the power supply voltage to the infrared transmitting module through the PWM duty cycle, and adjusts the power of the infrared transmitting tube to ensure that the system power consumption is within the optimal range; Step S6, the light curtain transmitting end starts the infrared transmitting module, and at the same time sends an instruction to start receiving the safety light beam to the light curtain receiving end through the 485 interface. After the light curtain receiving end obtains the instruction through the 485 module, it starts to start the program of receiving, capturing and identifying the infrared beam of the light curtain transmitting end; Step S7, the light curtain receiving end obtains the received signal strength, and outputs the signal quality obtained by the light curtain receiving end to the light curtain transmitting end through the 485 receiving interface; the light curtain transmitting end dynamically adjusts according to the received data to ensure that the signal strength of the receiving end is within a reasonable range.

4. The automatic alignment and distance measurement method of a light curtain according to claim 3, characterized in that: In step S4, the system automatically calculates the distance between the two ends using the following formula: D=C*(T n -T n-1 -Tick (n-1) *2); Where, C is the speed of light, which is 0.3m / ns; T n-1 The time when the data signal was received last time; T n The time when the data signal is received this time; Tick (n-1) is the mechanical conversion time of the microcontroller in this mode; n is the number of times the light curtain transmitter captures the measurement instructions of the light curtain receiver, and n should be greater than or equal to 2; D is the distance between the light curtain transmitter and the light curtain receiver.

5. The automatic alignment and distance measurement method of a light curtain according to claim 4, characterized in that: In step S5, the infrared transmitter power supply voltage Vout=Vin*Duty; wherein Vin is the default system power supply voltage of the infrared transmitter; and Duty is the duty cycle of the control output circuit.

6. The automatic alignment and distance measurement method of a light curtain according to claim 2, characterized in that: Laser emission module, including: Signal input circuit: PWM control signal pin RL_TXPWM is connected to the gate of field effect transistor Q1 through diode D1 and resistor R2; PWM control signal pin RL_TXPWM outputs a pulse control signal of 2kHz and 50% duty cycle; gate charging current limiting resistor R2 is connected in series between PWM control signal pin RL_TXPWM and the gate of field effect transistor Q1; fast discharge diode D1 is connected in parallel across the gate charging current limiting resistor R2 to form an asymmetric charging and discharging path; conduction phase: gate charging current limiting resistor R2 limits the gate charging current to avoid overload or high-frequency oscillation; shutdown phase: when the control signal becomes low, the discharge diode D1 provides a low impedance path, and the gate charge is discharged through the discharge diode D1, shortening the shutdown time; Control circuit: The field effect transistor Q1 is used as a switching element, with its gate receiving a pulse control signal from the signal input circuit, its source being grounded, and its drain being connected to the cathode of the laser emitting tube LED1; when the gate receives a high-level signal, the field effect transistor Q1 is turned on, allowing current to pass; when a low-level signal is received, the field effect transistor Q1 is turned off, blocking the current; Current limiting and protection circuit: Current limiting resistor R1 is connected in series between the positive pole of the laser emitting tube LED1 and the power supply VCC, and is used to limit the current passing through the laser emitting tube LED1; filter capacitor C1 is installed between the power supply VCC and the ground, and is used to filter out the ripple interference generated during the pulse emission process; inter-electrode resistor R3 is set between the gate and the source of the field effect tube Q1, mainly to solve the problems of gate charge discharge and static potential balance; when the driving signal disappears, the inter-electrode resistor R3 quickly discharges the residual charge of the gate to the source, avoiding accidental conduction of the field effect tube Q1 due to external interference; the inter-electrode resistor R3 provides an impedance path for the gate to the ground, absorbs static electricity, and prevents the gate oxide layer from breaking down.

7. The automatic alignment and distance measurement method of a light curtain according to claim 6, characterized in that: A light-sensitive sensor module, including a receiving circuit and a signal processing circuit; The receiving circuit includes: a light receiving sensor PD1, which is a photodiode, responsible for receiving the light signal irradiated by the infrared laser and converting it into an electrical signal, and the median value of its induced output current is 12mA; a current detection resistor R201, which not only detects the current generated by the photodiode, but also ensures that the photodiode works within the optimal range; a coupling capacitor C201, which is used to obtain the electrical signal received by the photodiode and remove the interference of ambient light; a resistor R202 and a capacitor C202 form a low-pass filter circuit to filter out the external interference frequency band in the received signal and make the waveform stable; Signal processing circuit: When the light receiving sensor PD1 receives the light signal, a photoelectric effect occurs inside, generating an induced current I; the current generates an induced voltage PD_Vout=R2*I on the resistor R202; the induced voltage PD_Vout is coupled to the same-direction input terminal 2 of the operational amplifier LM2904 through the coupling capacitor C201; the operational amplifier LM2904 performs the first-stage same-direction proportional amplification on the coupled signal to filter out clutter interference and make the waveform more stable; the first-stage operational amplifier output signal PhotoSen_ADC is output from pin 1 of the operational amplifier LM2904; the first-stage operational amplifier output signal PhotoSen_ADC is further filtered out of high-frequency noise through the low-pass filter circuit of the resistor R205, and then input to the same-direction input terminal 5 of the operational amplifier LM2904, and the signal is amplified by 2 times the gain through the second-stage operational amplifier, and finally the amplified operational amplifier output signal Photo_ADC_Out is output through the resistor R208, and the signal is supplied to the ADC output capture mode pin interface of the microcontroller.

8. The method for automatic alignment and distance measurement of a light curtain according to claim 7, characterized in that: External infrared emission module, including: The switching transistor Q6, the base is connected to the protocol control signal ‌Agree_Sing‌ through the resistor R32, the collector is directly connected to the positive electrode of the infrared emitting tube ‌IR_T1‌, and is connected to the power supply VCC through the resistor ‌R29‌, and the emitter is grounded to GND through the resistor ‌R34; Resistors R29 and R34 are current limiting resistors of the infrared emitting tube, capacitor C307 is a filter capacitor, and capacitor C307, resistor R29, switching transistor Q6, and resistor R34 form an infrared emitting charge and discharge circuit to eliminate the overcharge and over-discharge phenomenon of the switching transistor Q6 during the switching process that affects the output waveform of the infrared emitting tube; The switch transistor Q6 controls the on / off of the infrared emitting tube IR_T1, and Agree_Sing is the protocol control instruction output by the transmitting end; when the switch transistor Q6 is turned on, the collector current flows through the infrared emitting tube IR_T1, driving it to emit infrared light signals; when the switch transistor Q6 is turned off, the infrared emitting tube IR_T1 stops working.

9. The automatic alignment and distance measurement method of a light curtain according to claim 8, characterized in that: Infrared receiving module, including: The light receiving sensor PD3 is responsible for receiving the infrared alignment success and ranging signal IR_RX_ACK from the infrared transmitting end; Pin 1 of the light receiving sensor PD3 outputs the received infrared signal IR_RX_ACK and connects to the comparator U3A through the resistor R32, Pin 2 is grounded, Pin 3 is connected to the resistor R30 and the capacitor C15, the resistor R30 is connected to the positive pole of the power supply, and the capacitor C15 is grounded; Capacitor C16 has one end connected to pin 3 of comparator U3A and the other end grounded, which plays a role in filtering interference; the I / O input end of the microcontroller is connected to the output end of U3A to receive the IR_ACK_SING signal. When the microcontroller receiving end recognizes the instruction, it sends a distance measurement instruction to the transmitting end.

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