An Automatic Alignment and Distance Measurement Method for a Light Curtain

Abstract

An automatic alignment and ranging method for a light curtain, belonging to the technical field of optical devices, includes the following steps: Step S1, install the light curtain transmitting end and the light curtain receiving end at both ends of the safety detection area, and connect both the transmitting end and the receiving end to the power supply system. After system initialization, start the focusing mode; Step S2, start the focusing mode. Laser emission modules are arranged at both the upper and lower ends of the mirror area of the light curtain receiving end, and photosensitive induction modules are arranged at both the upper and lower ends of the mirror area of the light curtain transmitting end; A hollow cross silk screen is set at the light inlet of the photosensitive induction module; The laser emission module emits a visible laser beam towards the photosensitive induction module on the same side, and ensures that the visible laser beam hits the center position of the cross silk screen area on the mirror surface of the transmitting end, achieving two-point plane determination and ensuring 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.

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 of the transmitter and the receiver:

[0004] 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.

[0005] 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.

[0006] 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.

[0007] These defects are mainly caused by the following reasons:

[0008] 1. Due to the angle limitation of the optical lens design, it is impossible to achieve a beam deviation angle below 1°.

[0009] 2. The design principle lacks automatic power consumption adjustment circuit and automatic alignment verification circuit.

[0010] 3. Errors are introduced during product assembly and on-site installation.

[0011] 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

[0012] In view of the current situation and deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide an automatic alignment and ranging method for a light curtain.

[0013] To achieve the above purpose, the present invention adopts the following technical solutions:

[0014] An automatic alignment and ranging method for a light curtain, comprising the following steps:

[0015] Step S1, install the light curtain transmitter and the light curtain receiver at both ends of the safety detection area, and connect both the light curtain transmitter and the light curtain receiver to the power supply system. After the system is initialized, start the focusing mode.

[0016] Step S2, start the focusing mode. Laser emission modules are arranged at both the upper and lower ends of the mirror area of the light curtain receiver, and photosensitive induction modules are arranged at both the upper and lower ends of the mirror area of the light curtain transmitter; a hollow cross silk screen is arranged at the light inlet of the photosensitive induction module; the laser emission module emits a visible laser beam towards the photosensitive induction module on the same side, and ensures that the visible laser beam hits the center position of the cross silk screen area on the transmitter mirror surface, realizing two-point determination of a plane and ensuring that the mirror surfaces of the light curtain transmitter and the light curtain receiver are in a parallel state.

[0017] Step S3, the light curtain transmitter enters the opposite angle focusing verification mode. The photosensitive induction module installed under the center area of the cross silk screen on the mirror surface of the light curtain transmitter obtains the light intensity and converts it into a current signal, which is transmitted to the single-chip microcomputer AD input capture I / O interface through the signal processing circuit; the single-chip microcomputer internally starts the recognition and judgment of the focusing intensity and the handshake protocol. After the handshake is successful, the infrared emission module of the light curtain transmitter sends a handshake success and ranging instruction to the light curtain receiver.

[0018] Step S4, after the infrared receiving module of the light curtain receiver receives and parses the handshake success and ranging instruction sent by the light curtain transmitter, it sends a distance measurement reply ACK protocol instruction to the light curtain transmitter through the infrared protocol sending module; the infrared protocol receiving module of the light curtain transmitter 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 receiver.

[0019] Furthermore, the light curtain used in this method includes a light curtain transmitter and a light curtain receiver;

[0020] The light curtain transmitter includes a photosensitive induction module, an infrared protocol receiving module, an infrared emission module, and an emission power control module;

[0021] The light curtain receiver includes a laser emission module, an infrared protocol sending module, an infrared receiving module, and a receiving power control module;

[0022] The laser emission module and the light-sensitive induction module form an automatic alignment detection and recognition module;

[0023] The infrared protocol receiving module and the infrared protocol sending module form an automatic ranging system module;

[0024] The infrared emission module and the infrared receiving module form a light curtain opposed beam module;

[0025] Both the light curtain emission end and the light curtain receiving end also have a 485 communication module and a status indicator module.

[0026] Furthermore, a method for automatic alignment and ranging of a light curtain further includes:

[0027] Step S5, after the light curtain emission end calculates the distance from the light curtain receiving end, the light curtain emission end controls the power supply voltage output to the infrared emission module through the PWM duty cycle, and adjusts the power of the infrared emission tube to ensure that the system power consumption is within the optimal range;

[0028] Step S6, the light curtain emission end starts the infrared emission module, and at the same time sends a command to start receiving the safety beam to the light curtain receiving end through the 485 interface. After the light curtain receiving end obtains the command through the 485 module, it starts the program of receiving and capturing and recognizing the infrared beam of the light curtain emission end;

[0029] 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 emission end through the 485 receiving interface. The light curtain emission end performs dynamic adjustment according to the received data to ensure that the signal strength at the receiving end is within a reasonable range.

[0030] Furthermore, in step S4, the formula for the system to automatically calculate the distance between the two ends is as follows: D = C * (T n - T n-1 - Tick (n-1) * 2);

[0031] In the formula, C is the speed of light, which is 0.3 m / ns; T n-1 is the time when the previous data signal was received; T n is the time when the current data signal was received; Tick (n-1) is the mechanical conversion time of the single-chip microcomputer in this mode; n is the number of times the light curtain emission end captures the measurement command of the light curtain receiving end, and n should be greater than or equal to 2; D is the distance between the light curtain emission end and the light curtain receiving end.

[0032] Furthermore, in step S5, the power supply voltage of the infrared emitter Vout = Vin * Duty; where Vin is the default system power supply voltage of the infrared emitter; Duty is the duty cycle of the control output circuit.

[0033] Furthermore, the laser emission module includes:

[0034] Signal input circuit: The PWM control signal pin RL_TXPWM is connected to the gate of the field effect transistor Q1 through the diode D1 and the resistor R2; the PWM control signal pin RL_TXPWM outputs a pulse control signal with a frequency of 2 kHz and a duty cycle of 50%; 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 transistor Q1; the fast discharge diode D1 is connected in parallel across the gate charging current limiting resistor R2 to form an asymmetric charge and discharge path; conduction stage: the gate charging current limiting resistor R2 limits the gate charging current to avoid overload or high-frequency oscillation; turn-off stage: 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 turn-off time;

[0035] Control circuit: The field effect transistor Q1 is used as a switching element. Its gate receives the pulse control signal from the signal input circuit, its source is grounded, and its drain is connected to the negative electrode of the laser emitting diode LED1; when the gate receives a high-level signal, the field effect transistor Q1 conducts, allowing current to pass through; when a low-level signal is received, the field effect transistor Q1 is cut off, blocking the current;

[0036] Current limiting and protection circuit: The current limiting resistor R1 is connected in series between the positive electrode of the laser emitting diode LED1 and the power supply VCC to limit the current passing through the laser emitting diode LED1; 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; the inter-electrode resistor R3 is set between the gate and the source of the field effect transistor Q1 to mainly solve the problems of gate charge discharge and static potential balance; when the drive signal disappears, the inter-electrode resistor R3 quickly discharges the residual charge on the gate to the source to avoid accidental conduction of the field effect transistor Q1 due to external interference; the inter-electrode resistor R3 provides an impedance path to the ground for the gate, absorbs static charges, and prevents breakdown of the gate oxide layer.

[0037] Furthermore, the light sensing module includes a receiving circuit and a signal processing circuit;

[0038] The receiving circuit includes: a light sensing 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; the intermediate value of its induced output current is 12 mA; the current detection resistor R201 not only detects the current generated by the photodiode but also ensures that the photodiode operates 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 tend to be stable;

[0039] Signal processing circuit: When the photosensitive receiving sensor PD1 receives an optical signal, the internal photoelectric effect occurs, 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 non-inverting input terminal 2 of the operational amplifier LM2904 through the coupling capacitor C201; the operational amplifier LM2904 performs the first-stage non-inverting proportional amplification on the coupled signal, filtering out the clutter interference to make the waveform more stable; the output signal PhotoSen_ADC of the first-stage operational amplifier is output from pin 1 of the operational amplifier LM2904; the output signal PhotoSen_ADC of the first-stage operational amplifier, through the low-pass filter circuit of the resistor R205, further filters out the high-frequency noise, and then is input to the non-inverting input terminal 5 of the operational amplifier LM2904. After the second-stage operational amplifier amplifies the signal by a factor of 2, finally, the amplified operational amplifier output signal Photo_ADC_Out is output through the resistor R208, and this signal is supplied to the ADC output capture mode pin interface of the single-chip microcomputer.

[0040] Furthermore, the external infrared emission module includes:

[0041] A switching triode Q6, whose base is connected to the protocol control signal Agree_Sing through a resistor R32, the collector is directly connected to the positive electrode of the infrared emitting diode IR_T1, and is connected to the power supply VCC through a resistor R29, and the emitter is grounded to GND through a resistor R34;

[0042] The resistor R29 and the resistor R34 are current-limiting resistors for the infrared emitting diode, and the capacitor C307 is a filtering capacitor. At the same time, the capacitor C307, the resistor R29, the switching triode Q6, and the resistor R34 form an infrared emission charge and discharge circuit to eliminate the overcharging and over-discharging phenomena generated by the switching triode Q6 during the switching process, which may affect the waveform output by the infrared emitting diode;

[0043] The switching triode Q6 controls the on / off of the infrared emitting diode IR_T1, and Agree_Sing is the protocol control instruction output by the transmitting end; when the switching triode Q6 is turned on, the collector current flows through the infrared emitting diode IR_T1, driving it to emit an infrared optical signal; when the switching triode Q6 is turned off, the infrared emitting diode IR_T1 stops working.

[0044] Furthermore, the infrared receiving module includes:

[0045] A photosensitive receiving sensor PD3, which is responsible for receiving the infrared alignment success and ranging signal IR_RX_ACK from the infrared transmitting end; the received infrared signal IR_RX_ACK is output from pin 1 of the photosensitive receiving sensor PD3 and is connected to the comparator U3A through a resistor R32, pin 2 is grounded, pin 3 is connected to a resistor R30 and a capacitor C15, the resistor R30 is connected to the positive power supply, and the capacitor C15 is grounded;

[0046] The capacitor C16 has one end connected to pin 3 of the comparator U3A and the other end grounded, which plays a role in filtering interference; the I / O input terminal of the single-chip microcomputer is connected to the output terminal of U3A to receive the IR_ACK_SING signal. After the receiving end of the single-chip microcomputer recognizes this instruction, it sends a distance measurement instruction to the transmitting end.

[0047] An automatic alignment and ranging method for a light curtain has the characteristics of automatically adjusting the system power consumption, automatically achieving precise alignment, not requiring additional instrument assistance for alignment in occasions with long-distance or high-precision requirements, being able to automatically adjust the system power consumption according to the distance length to achieve energy-saving effects, having adjustable emission signal intensity and low light radiation, meeting environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic structural diagram of the present invention;

[0049] Figure 2 is a schematic circuit diagram of the laser emission module at the light curtain receiving end;

[0050] Figure 3 is a schematic circuit diagram of the light-sensitive induction module at the light curtain transmitting end;

[0051] Figure 4 is a schematic circuit diagram of the external infrared emission module at the light curtain transmitting end;

[0052] Figure 5 is a schematic circuit diagram of the infrared receiving module at the light curtain receiving end;

[0053] Figure 6 is a schematic circuit diagram of the infrared protocol receiving module at the light curtain transmitting end;

[0054] Figure 7 is a schematic diagram of the mirror areas at the light curtain transmitting end and the light curtain receiving end. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The present invention will be further described in detail below with reference to the accompanying drawings.

[0056] Figure 1 is a schematic structural diagram of the present invention; Figure 7 is a schematic diagram of the mirror areas at the light curtain transmitting end and the light curtain receiving end; in combination with Figure 1 and Figure 7 , a light curtain includes a light curtain transmitting end and a light curtain receiving end.

[0057] The light curtain transmitting end includes a light-sensitive induction module, an infrared protocol receiving module, an infrared emission module, and an emission power control module.

[0058] The light curtain receiving end includes a laser emission module, an infrared protocol sending module, an infrared receiving module, and a receiving power control module.

[0059] The laser emission module and the light-sensitive induction module form an automatic alignment detection and recognition module.

[0060] The infrared protocol receiving module and the infrared protocol sending module form an automatic ranging system module.

[0061] The infrared emission module and the infrared receiving module form a light curtain opposed beam module.

[0062] Both the curtain transmitting end and the light curtain receiving end are also equipped with a 485 communication module and a status indicator module.

[0063] An automatic alignment and ranging method for a light curtain, comprising the following steps:

[0064] Step S1, install the light curtain transmitting end and the light curtain receiving end at both ends of the safety detection area, and connect both the light curtain transmitting end and the light curtain receiving end to the power supply system (DC12~24V). The system is initialized and the focusing mode is started after 3 seconds.

[0065] Step S2, start the focusing mode. Laser emission modules are arranged at both the upper and lower ends of the mirror area of the light curtain receiving end, and light-sensitive induction modules are arranged at both the upper and lower ends of the mirror area of the light curtain transmitting end; a hollow cross silk screen is set at the light inlet of the light-sensitive induction module; the laser emission module emits a visible laser beam towards the light-sensitive induction module on the same side, and ensures that the visible laser beam hits the center position of the cross silk screen area on the mirror surface of the light curtain transmitting end, realizing two-point plane determination and ensuring that the mirror surfaces of the light curtain transmitting end and the light curtain receiving end are in a parallel state.

[0066] Figure 2 It is the circuit schematic diagram of the laser emission module of the light curtain receiving end. As Figure 2 shown, the laser emission module includes:

[0067] Signal input circuit: The PWM control signal pin RL_TXPWM is connected to the gate of the field effect transistor Q1 through the diode D1 and the resistor R2.

[0068] The PWM control signal pin RL_TXPWM outputs a pulse control signal with a frequency of 2 kHz and a duty cycle of 50%. Frequency (2 kHz): It represents that the number of switching cycles per second is 2000 times, which determines the repetition rate of the laser pulses. Duty cycle (50%): It represents that the ratio of the high level (on time) to the low level (off time) within 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 transistor Q1 to limit the gate charging current and 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 charge and discharge path. Conduction stage (charging): The gate charging current-limiting resistor R2 limits the gate charging current to avoid overload or high-frequency oscillation. Turn-off stage (discharging): 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.

[0069] Control circuit: The field-effect transistor Q1 serves as a switching element. Its gate receives the pulse control signal from the signal input circuit, its source is grounded, and its drain is connected to the negative electrode of the laser-emitting diode LED1. When the gate receives a high-level signal, the field-effect transistor Q1 conducts, allowing current to pass through; when it receives a low-level signal, the field-effect transistor Q1 cuts off, blocking the current.

[0070] Current-limiting and protection circuit: The current-limiting resistor R1 is connected in series between the positive electrode of the laser-emitting diode LED1 and the power supply VCC to limit the current passing through the laser-emitting diode LED1 and 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 and ensure the stability of the operation of the laser-emitting diode LED1. The inter-electrode resistor R3 is set between the gate (G) and the source (S) of the field-effect transistor Q1 to mainly solve the problems of gate charge discharge and static potential balance. Anti-mis-triggering: When the drive signal disappears (no input), R3 quickly discharges the residual charge on the gate to the source to avoid accidental conduction of the field-effect transistor 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) to absorb electrostatic charges and prevent breakdown of the gate oxide layer.

[0071] Step S3: The light curtain transmitter enters the opposed angle focusing calibration mode, and the red light of the status indicator blinks at a frequency of 1HZ. The light-sensitive induction module installed under the center area of the cross silk screen printing on the mirror surface of the light curtain transmitter acquires the light intensity and converts it into an electrical signal, which is transmitted to the ADC input capture I / O interface of the single-chip microcomputer through the signal processing circuit; the single-chip microcomputer internally starts to identify and judge the focusing intensity and handshake protocol. After the handshake is successful, the status indicator turns green, and the infrared emission module of the light curtain transmitter sends a handshake success and ranging command to the light curtain receiver.

[0072] Figure 3 It is the circuit schematic diagram of the light-sensitive induction module of the light curtain transmitter, as Figure 3 shown,

[0073] The light-sensitive induction module of the light curtain transmitter includes a receiving circuit and a signal processing circuit.

[0074] Receiving circuit: The light-sensitive receiving sensor PD1, which is a photodiode, is responsible for receiving the optical 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 acquire 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 tend to be stable.

[0075] Signal processing circuit: When the light-sensitive receiving sensor PD1 receives the optical signal, the internal photoelectric effect occurs, 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 non-inverting input terminal 2 of the operational amplifier LM2904 through the coupling capacitor C201. The operational amplifier LM2904 performs the first-stage non-inverting proportional amplification on the coupled signal, filters out the clutter interference, and makes the waveform more stable.

[0076] The 1st pin of the operational amplifier LM2904 outputs the first-stage operational amplifier output signal PhotoSen_ADC; the first-stage operational amplifier output signal PhotoSen_ADC passes through the low-pass filter circuit of the resistor R205 to further filter out the high-frequency noise, and then is input to the non-inverting input terminal 5 of the operational amplifier LM2904. After the second-stage operational amplifier amplifies the signal by a factor of 2, the amplified operational amplifier output signal Photo_ADC_Out is finally output through the resistor R208. This signal is supplied to the ADC output capture mode pin interface of the single-chip microcomputer.

[0077] The optical induction module receives the infrared laser signal through a photodiode, and performs signal coupling, filtering, and amplification through components such as resistors, capacitors, and operational amplifiers, and finally outputs a stable optical signal to the single-chip microcomputer for reading and processing. The entire control principle is clear and reasonable, ensuring the accurate reception and processing of the optical signal.

[0078] Step S4: After the infrared receiving module at the light curtain receiving end receives and parses the handshake success and ranging instructions sent from the light curtain transmitting end, it sends a 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, after receiving the distance measurement reply ACK protocol instruction, 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 formula between the two ends as follows:

[0079] D = C * (T n - T n-1 - Tick (n-1) * 2).

[0080] In the formula, C is the speed of light, which is 0.3 m / ns; T n-1 is the time when the previous data signal was received; T n is the time when the current data signal was received; Tick (n-1) is the mechanical conversion time of the single-chip microcomputer in this mode; n is the number of times the light curtain transmitting end captures the measurement instruction of the light curtain receiving end, and n should be greater than or equal to 2; D is the distance between the light curtain transmitting end and the light curtain receiving end.

[0081] Figure 4 is the circuit schematic diagram of the external infrared emission module at the light curtain transmitting end. As Figure 4 shown, the external infrared emission module sends the alignment success and ranging signals, including:

[0082] The circuit of the light curtain transmitting end drives the switching triode Q6 through the protocol control signal Agree_Sing, controls the pulse emission of the infrared emitting diode IR_T1, realizes ranging by combining the time difference method, and completes the alignment confirmation through the synchronous feedback mechanism.

[0083] For the switching triode 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 diode 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;

[0084] The resistors R29 and R34 are the current-limiting resistors for the infrared emitting diodes, and the capacitor C307 is a filtering capacitor. At the same time, the capacitor C307, the resistor R29, the switching triode Q6, and the resistor R34 form an infrared emission charge and discharge circuit to eliminate the overcharging and over-discharging phenomena generated by the switching triode Q6 during the switching process, which may affect the waveform output by the infrared emitting diode.

[0085] The switching triode Q6 controls the on / off of the infrared emitting diode IR_T1, and Agree_Sing is the protocol control instruction output by the transmitting end. When the switching triode Q6 is turned on, the collector current flows through the infrared emitting diode IR_T1, driving it to emit infrared light signals; when the switching triode Q6 is turned off, the infrared emitting diode IR_T1 stops working.

[0086] Figure 5 It is the circuit schematic diagram of the infrared receiving module at the light curtain receiving end. As Figure 5 shown, the infrared receiving module captures the signals of successful alignment and ranging signal protocol.

[0087] The pin 1 (OUT) of the light-sensitive receiving sensor PD3 outputs the received infrared signal IR_RX_ACK and is connected to the comparator U3A through the resistor R32. The pin 2 (GND) is grounded, and the pin 3 (VS) is connected to the resistor R30 and the capacitor C15. The resistor R30 is connected to the positive power supply (VCC), and the capacitor C15 is grounded (GND). The light-sensitive receiving sensor PD3 is responsible for receiving the infrared alignment success and ranging signal IR_RX_ACK from the infrared transmitting end.

[0088] One end of the capacitor C16 is connected to the pin 3 of the comparator U3A, and the other end is grounded, which plays a role in filtering interference, making the comparator U3A receive a more stable waveform deformation.

[0089] The I / O input end of the single-chip microcomputer is connected to the output end of U3A to receive the IR_ACK_SING signal. After the receiving end of the single-chip microcomputer recognizes this instruction, it sends a distance measurement instruction to the transmitting end.

[0090] This circuit captures the infrared signal through the light curtain receiving end, filters out the high-frequency noise through two-stage low-pass filters, stabilizes the signal waveform through a comparator, and finally the single-chip microcomputer receives and processes this signal to realize the normal operation of the infrared light curtain.

[0091] Figure 6 It is the circuit schematic diagram of the infrared protocol receiving module at the light curtain transmitting end. As Figure 6 shown, the infrared protocol receiving module, the receiving tube captures the infrared signal.

[0092] The infrared receiving sensor PD2 is responsible for receiving the infrared pulse signal with a ranging protocol emitted from the receiving end. When an infrared signal is received, the infrared receiving sensor PD2 converts it into a current signal, which is then sent into the circuit for processing.

[0093] The resistor R9 is connected to the output of the infrared receiving sensor PD2 and is used to limit the current flowing into the base of the switching triode Q3.

[0094] The resistor R10 is connected to the base of the switching triode Q3 to further limit the base current and ensure the stable operation of the switching triode Q3.

[0095] The resistor R11 is connected between the base of the switching triode Q4 and the power supply to provide a bias voltage for the switching triode Q4.

[0096] The resistor R12 is connected to the base of the switching triode Q4 and is used to limit the current flowing into the base of the switching triode Q4.

[0097] The resistor R13 is connected between the collector of the switching triode Q4 and the output of the IR_Agree_Sing signal and is used to convert the collector current of the switching triode Q4 into a voltage signal.

[0098] The capacitor C8 is connected between the resistor R13 and the ground and is used for filtering to ensure the stability of the IR_Agree_Sing signal.

[0099] The light curtain receiving end emits an infrared pulse signal with a ranging protocol to the light curtain transmitting end; the light curtain transmitting end controls the switching triode Q3 to start working by converting the received signal into a current signal. After the switching triode Q3 conducts, it causes the switching triode Q4 to conduct. At this time, the IR_Agree_Sing signal at the resistor R13 terminal changes from high to low, and after being parsed by the comparator, the received IR_Agree_Sing signal is input to the corresponding signal receiving I / O of the single-chip microcomputer, and the single-chip microcomputer at the transmitting end starts to identify whether it is the ranging instruction model sent by the receiving end.

[0100] At this time, the transmitting end calculates the time difference (T n -T n-1 ) between two received infrared ranging instructions, and then subtracts twice the actual Tick time of the algorithm operation of each single-chip microcomputer at the transmitting and receiving ends, that is, the running time of the light curtain is obtained. Finally, multiplying by the speed of light, the time distance D = C * (T n -T n-1 -Tick (n-1) *2) between the light curtain transmitting end and the light curtain receiving end is obtained.

[0101] This circuit receives signals through an infrared receiving sensor, amplifies and processes the signals using transistors, and finally calculates the distance information through a microcontroller. The connection methods and working principles among the components are coordinated with each other to jointly achieve the function of infrared ranging.

[0102] Step S5, after the light curtain transmitting end calculates the distance from the light curtain receiving end, the light curtain transmitting end controls the power supply voltage output to the infrared emission module through the PWM duty cycle, and adjusts the power of the infrared emitting tube to ensure that the system power consumption is within the optimal range. Its output voltage formula is as follows:

[0103] Vout = Vin * Duty.

[0104] In the formula, Vin is the default system power supply voltage of the infrared emitter; Duty is the duty cycle of the control output circuit; Vout is the power supply voltage of the infrared emitter.

[0105] Preferably, the PWM frequency is 10KHZ.

[0106] Step S6, the light curtain transmitting end starts the infrared emission module, and at the same time sends a command to start receiving the safety beam to the light curtain receiving end through the 485 interface. After the light curtain receiving end obtains the command through the 485 module, it starts the program of receiving, capturing and identifying the infrared beam of the light curtain transmitting end.

[0107] 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 makes dynamic adjustments according to the received data to ensure that the signal strength at the receiving end is within a reasonable range.

[0108] Compared with the current light curtain, the application innovation of this light curtain in technology can greatly improve the intelligent use experience of users, avoid the trouble caused by the installation of the transmitting and receiving ends not being on the same plane during user use, resulting in inaccurate detection due to deviation, and at the same time avoid the phenomenon of false triggering of safety protection due to different energies at the transmitting end. At the same time, when the energy is too strong, it will cause potential infrared light interference to other devices, as well as light pollution caused by light over-standard radiation interference in special environmental places.

[0109] Application scenario 1, for some occasions with strict requirements for the accuracy of the opposite shooting angle, in view of the fact that manual alignment is used for the safety light curtain in the market and the requirement of almost 0-degree deviation angle cannot be achieved. Therefore, in order to match the use function in this scenario, it is often necessary to use a laser focusing (positioning) instrument for auxiliary focusing. At the same time, for some installation areas that are not horizontal planes, the manual focusing (positioning) error is relatively large. In order to make the receiving and transmitting ends on the same horizontal plane, it is necessary to use a level, which is very inconvenient and uneconomical in terms of installation cost. Therefore, our new light curtain has an automatic focusing (positioning) system and can be used in high-precision and small-angle occasions.

[0110] Application scenario 2: In the usage scenario of the light curtain, there are requirements for long-distance and short-distance safety protection. For ordinary light curtains, users need to find the corresponding manufacturer according to the actually measured distance between the transmitter and the receiver for customization. Since the distances are different, the customized light curtain prices are also different, and the unit prices that users need to purchase are also different, which undoubtedly increases an economic expenditure for users.

[0111] Application scenario 3: Due to the limitations of ordinary light curtains, when the installation distance between the transmitter and the receiver in the user's installation environment changes, if short-distance safety detection is actually required and the user selects a long-distance light curtain, since the transmission power of the long-distance light curtain is too strong during use, when the user uses it for short-distance safety protection, due to the existence of the optical characteristics of the light curtain itself, the detection blind area will become relatively larger when the transmission power is too large, so there will be a situation where 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 and the user selects a short-distance light curtain, since the transmission power of the short-distance light curtain becomes weak during use, it cannot match the 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 during installation, causing installation troubles.

[0112] Application scenario 4: Currently, green environmental protection is strongly advocated. Ordinary light curtains cannot well control the optical interference generated by infrared light in terms of energy, and often cause optical pollution of infrared radiation to the surrounding environmental parameters, which does not meet the environmental protection requirements. At the same time, in terms of the power energy usage of ordinary light curtains, reasonable modulation cannot be achieved, resulting in unnecessary power waste for users, which is uneconomical.

[0113] Based on the above points, this light curtain has multiple functions in one machine, which not only saves the cost invested by users during use, but also has a wide range of applications and is convenient 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, more environmentally friendly, reduces the use threshold, and also enhances its competitiveness in the light curtain market. The beneficial effects specifically include:

[0114] 1. It improves the intelligent use experience of users and avoids the problem of inaccurate detection deviation caused by the transmitter and the receiver not being installed on the same plane.

[0115] 2. It avoids the problems of false triggering of safety protection due to different energies at the transmitter and light pollution caused by excessive light radiation interference.

[0116] 3. There is no need to customize the light curtain according to the distance, which reduces the cost for users.

[0117] 4. It realizes adaptive distance adjustment and avoids safety detection problems caused by changes in the installation distance.

[0118] 5. It has an intelligent control system that can automatically control and adjust the infrared emission intensity, making it more energy-efficient, environmentally friendly, reducing the usage threshold, and enhancing the market competitiveness.

[0119] It can be understood that for those of ordinary skill in the art, equivalent substitutions or changes can be made according to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the appended claims of 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; The infrared emitting module is provided with an infrared emitting tube.

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 last received; T n Tick ​​is the time when the data signal is received this time; (n-1) is the mechanical conversion time for the microcontroller algorithm to run; 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 emission module power supply voltage Vout=Vin*Duty; wherein Vin is the default system power supply voltage of the infrared emission module; 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 electrode of laser emitting tube LED1 and power supply VCC to limit the current passing through laser emitting tube LED1; filter capacitor C1 is installed between power supply VCC and ground to filter out ripple interference generated during pulse emission; The inter-electrode resistor R3 is set between the gate and source of the field effect transistor Q1 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 to avoid accidental conduction of the field effect transistor Q1 due to external interference. The inter-electrode resistor R3 provides an impedance path for the gate to the ground, absorbs electrostatic charge, 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: 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 module; 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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