A safe monitoring method for multi-wavelength LD laser power

Abstract

The invention relates to the field of laser output power monitoring, and specifically discloses a method for safely monitoring the power of a multi-wavelength LD laser, comprising the following steps: step 1: separating 5% of the laser from a light beam coupled and synthesized by a multi-wavelength light source as monitoring light, and redirecting the monitoring light to a monitor photodiode; step 2: amplifying the photocurrent generated by the monitor photodiode by using an amplifier; the invention can measure the actual output power of the laser in real time and accurately by separating a small portion of the laser from the coupled output and redirecting it to a monitor photodiode (MD), using a combination of a high-speed PIN photodiode and a high-speed precision high-impedance amplifier (OpAmp) to ensure fast response and high precision of the measurement process, and reducing the influence of temperature drift on the measurement precision by using a TIA circuit and resistor selection, and using an equivalent resistor, thereby further improving the stability and accuracy of the monitoring system.

Description

Technical Field

[0001] The invention belongs to the field of laser output power monitoring, in particular to a multi-wavelength LD laser power safety monitoring method. Background Art

[0002] Since the advent of laser technology in the 1960s, it has been widely used in scientific research, industry, medicine and other fields due to its high brightness, high directivity and high monochromaticity. As one of the key indicators for evaluating the performance of laser equipment, the stability and accuracy of laser output power are of great significance for ensuring the reliability of experimental data, improving the quality of industrial processing and ensuring the safety of medical surgery. Therefore, real-time monitoring of laser output power has become an important task in the application of laser technology.

[0003] In traditional technology, monitoring of laser output power often relies on the measurement and control of the electrical parameters of the laser itself. However, this method is easily affected by various factors such as process and device errors, performance changes after long-term operation, etc., resulting in inaccurate monitoring results. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a multi-wavelength LD laser power safety monitoring method to solve the problem that the monitoring of laser output power in the prior art often relies on the measurement and control of the electrical parameters of the laser itself, but this method is easily affected by various factors such as process and device errors, performance changes after long-term operation, etc., resulting in inaccurate monitoring results.

[0005] A method for safely monitoring multi-wavelength LD laser power comprises the following steps:

[0006] Step 1: Separate 5% of the laser light from the beam coupled and synthesized by the multi-wavelength light source as monitoring light, and redirect the monitoring light to the monitor photodiode;

[0007] Step 2: Amplify the photocurrent generated by the monitor photodiode using an amplifier, and couple the amplified signal to the laser safety circuit and the laser power data acquisition circuit simultaneously;

[0008] Step 3: In the laser power data acquisition circuit, the actual output power of the laser is determined by monitoring the amplified voltage signal;

[0009] Step 4: In the laser safety circuit, set the maximum output power threshold and maximum pulse time limit to monitor the power and time of the laser pulse and stop the output of all LD lasers when the preset threshold is exceeded.

[0010] Preferably, in the laser power data acquisition circuit, a high-speed PIN photodiode and a high-speed precision high-impedance amplifier are used to measure the monitoring light, and a constant voltage V is applied through an operational amplifier. Ref The monitor diode generates an output signal V proportional to the light level. M .

[0011] Preferably, the output voltage V of the TIA is set by selecting the gain resistor R1. Monitor And ensure that the TIA power supply voltage has enough redundancy to meet the voltage output requirements at full laser power.

[0012] Preferably, in the laser power data acquisition circuit, a high-precision resistor combination is used to replace a single high-precision large-resistance resistor to improve measurement accuracy and reduce the impact of temperature drift.

[0013] Preferably, in the laser safety circuit, an RC low-pass filter is used to filter the short signal of the TIA output voltage to prevent false alarms caused by transient signals, and the safety output voltage V M Limit the voltage input range of the laser safety circuit.

[0014] Preferably, the laser safety circuit further includes: M It is compared with the threshold voltage to monitor the output power and stop the output of all LD lasers when the threshold is exceeded.

[0015] Preferably, the laser safety circuit also includes a safety check of the laser pulse duration by starting and measuring a timer, and stopping the output of all LD lasers when the preset pulse time is exceeded.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] By separating a small portion of the laser from the coupled output and redirecting it to the monitor photodiode (MD), the actual output power of the laser can be measured in real time and accurately. The combination of a high-speed PIN photodiode and a high-speed precision high-impedance amplifier (OpAmp) ensures fast response and high accuracy in the measurement process. The influence of temperature drift on the measurement accuracy is reduced by TIA circuit and resistor selection, as well as the use of equivalent resistors, which further improves the stability and accuracy of the monitoring system.

[0018] The laser safety circuit contains dual limits on the maximum output power and the maximum pulse time, ensuring the safe operation of the laser. By using an RC low-pass filter to prevent false alarms caused by transient signals, the anti-interference ability of the system is improved. The safety check of the laser pulse duration is completed by starting and measuring the timer, ensuring that the laser pulse time does not exceed the preset safety range.

[0019] By monitoring the output power and pulse time separately, the safe operation of the equipment can be ensured in the event of a single fault. Once the output power or pulse time is detected to exceed the preset safety threshold, the equipment will directly stop the output of all LD lasers, thereby effectively avoiding potential safety risks. This dual monitoring mechanism improves the overall safety and reliability of the equipment, enabling it to maintain stable performance in various application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a system schematic diagram of the present invention;

[0021] Figure 2 Schematic diagram of the output laser being redirected to the monitor photodiode;

[0022] Figure 3 This is the schematic diagram of the photodiode amplifier;

[0023] Figure 4 This is the circuit diagram using an equivalent resistor instead of R2;

[0024] Figure 5 This is a schematic diagram of the laser safety circuit. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown:

[0027] Embodiment 1: The present invention provides a method for safely monitoring multi-wavelength LD laser power, comprising the following steps:

[0028] Step 1: Separate 5% of the laser light from the beam coupled and synthesized by the multi-wavelength light source as monitoring light, and redirect the monitoring light to the monitor photodiode;

[0029] Step 2: Amplify the photocurrent generated by the monitor photodiode using an amplifier, and couple the amplified signal to the laser safety circuit and the laser power data acquisition circuit simultaneously;

[0030] Step 3: In the laser power data acquisition circuit, the actual output power of the laser is determined by monitoring the amplified voltage signal;

[0031] Step 4: In the laser safety circuit, set the maximum output power threshold and maximum pulse time limit to monitor the power and time of the laser pulse and stop the output of all LD lasers when the preset threshold is exceeded.

[0032] Specifically, in the laser power data acquisition circuit, a high-speed PIN photodiode and a high-speed precision high-impedance amplifier are used to measure the monitoring light, and a constant voltage V is applied through an operational amplifier. Ref The monitor diode generates an output signal V proportional to the light level. M .

[0033] Specifically, the output voltage V of the TIA is set by selecting the gain resistor R1. Monitor And ensure that the TIA power supply voltage has enough redundancy to meet the voltage output requirements at full laser power.

[0034] The specific monitoring methods are as follows:

[0035] Part 1: Laser Power Monitoring

[0036] like Figures 2 to 4 As shown: In order to measure the actual output power of the laser, a small portion (≈5%) of the coupled output laser will be redirected to the monitor photodiode (MD), as shown in Figure 2 As shown. The resulting photocurrent is amplified by an amplifier (TIA). The output signal of the TIA is coupled to the laser safety circuit and the laser power data acquisition circuit at the same time.

[0037] The schematic diagram of the photodiode amplifier is as follows Figure 3 The laser is measured by a high-speed PIN photodiode. The operational amplifier (OpAmp) is a high-speed precision high-impedance amplifier that applies a constant voltage V to the monitor diode. Ref Therefore, the output signal V M Proportional to the light sensitivity level of the monitoring photodiode MD.

[0038] Monitor diode I MDThe photocurrent generated is estimated to be 30μA to 3mA (assuming a 5% fiber splitting ratio, an output laser power range of 1mW to 100mW, and an MD efficiency of 0.6A / W). The output voltage generated at the TIA is determined by the gain resistor R1. Considering the need to ensure sufficient margin for the TIA supply voltage (+5V), R1 is selected to produce a voltage of approximately V at full laser power. Monitor =4V. The calculation formula is as follows:

[0039]

[0040] Among them C D See the photodiode MD (e.g. PS1.0-5LCC6.1s, Silicon) parameters, GBW see the amplifier (e.g. OPA2380, TI) parameters

[0041] V Ref =0.4V, see the amplifier (such as OPA2380, TI) offset voltage parameters, and choose 0.4V for redundancy;

[0042] The laser power measurement circuit takes DDC114 as an example. All channels of DDC114 are set to Q at 4V. DDCMAX =332.5pC, define T lntDDC (assumed to be 320μs) is the laser pulse time,

[0043] Then the maximum current T of DDC114 is DDCMAX =Q DDCMAX / T lntDDC =332.5pC / 320μs=1.04μA;

[0044] Therefore, in order to meet the input requirements of DDC114, R2 = V Monitor / I Monitor =4V / 1μA=4MΩ, select 4.7MΩ;

[0045] Since the temperature drift of R2 cannot be compensated by the algorithm and directly affects the measurement accuracy, an equivalent resistor is used to replace R2 (there is no high-precision large-value resistor), such as Figure 4 Shown

[0046] Where R 21 =R 23 =68kΩandR 22 =1kΩ, accuracy 0.1%, 25ppm;

[0047] R 24 Keep 4.7MΩ unchanged to balance the poor noise immunity brought by the equivalent resistor.

[0048] in conclusion:

[0049] By monitoring the data in the laser power data acquisition circuit (DDC114, TI), the actual real-time output power can be obtained.

[0050] Part II: Laser Pulse Timing Monitoring

[0051] The laser safety circuit includes two parts: maximum output power and maximum pulse time limit.

[0052] Laser safety circuit diagram Figure 5 ;

[0053] Figure 3 In practical applications, short signals of the TIA output voltage can occur instantaneously, especially at the rising edge of the laser pulse. In order to prevent the laser safety circuit from issuing a false alarm under such transient signal conditions, a simple RC low-pass filter (time constant ≈ 1.6μs) is required before connecting to the laser safety circuit. LP and R3 form a voltage divider to reduce the safe output voltage V M The value is limited to 3.3V to comply with the voltage input range of the laser safety circuit.

[0054] So: R LP =10kΩ, C LP =1nF, R3=3.3V / [(5V-3.3V) / 10kΩ]=20kΩ

[0055] Output power: By verifying the signal V generated by the TIA M , compared with the threshold voltage (BSafety). Any sensor signal exceeding the threshold will cause the device to directly stop the output of all LD lasers.

[0056] Pulse time: When the minimum optical laser power (about 1mW) is detected, a safety check of the laser pulse duration is completed by starting and measuring the timer. Exceeding the preset pulse time will cause the device to directly stop the output of all LD lasers.

[0057] in conclusion:

[0058] By monitoring the output power and pulse time separately, the safe operation of the equipment under a single fault can be guaranteed.

[0059] As can be seen from the above, this method ensures the safe and efficient operation of the laser through a series of steps; first, a small part of the laser is separated from the beam of light coupled and synthesized by the multi-wavelength light source as the monitoring light, and it is redirected to the monitor photodiode; then, the amplifier is used to amplify the photocurrent generated by the photodiode, and the amplified signal is simultaneously transmitted to the laser safety circuit and the laser power data acquisition circuit; in the laser power data acquisition circuit, a high-speed PIN photodiode and a high-speed precision high-impedance amplifier are used to accurately measure the monitoring light, and an output signal proportional to the photosensitivity level is generated by applying a constant voltage; at the same time, the output voltage of the TIA is set by selecting an appropriate gain resistor, and it is ensured that the power supply voltage has sufficient redundancy to meet the voltage output requirements at full laser power; this series of measures together constitute the core of the method, which effectively realizes the precise monitoring and safe control of the laser power.

[0060] Embodiment 2: This embodiment is basically the same as the previous embodiment, except that, in the laser power data acquisition circuit, a high-precision resistor combination is used to replace a single high-precision large-resistance resistor to improve measurement accuracy and reduce the influence of temperature drift.

[0061] Specifically, in the laser safety circuit, an RC low-pass filter is used to filter the short signal of the TIA output voltage to prevent false alarms caused by transient signals, and the safety output voltage V is divided by a voltage divider. M Limit the voltage input range of the laser safety circuit.

[0062] From the above, it can be seen that this method uses a high-precision resistor combination to replace a single high-precision large-value resistor. This improvement not only improves the measurement accuracy, but also effectively reduces the impact of temperature drift on the measurement results; at the same time, in the laser safety circuit, an RC low-pass filter is added to filter the short signal of the TIA output voltage, avoiding false alarms that may be caused by transient signals; in addition, the safety output voltage is limited to the input voltage range of the safety circuit through a voltage divider, further enhancing the stability and safety of the system.

[0063] Embodiment 3: This embodiment is basically the same as the previous embodiment, except that it also includes in the laser safety circuit, the signal V generated by the TIA M It is compared with the threshold voltage to monitor the output power and stop the output of all LD lasers when the threshold is exceeded.

[0064] Specifically, it also includes in the laser safety circuit, completing the safety check of the laser pulse duration by starting and measuring the timer, and stopping the output of all LD lasers when the preset pulse time is exceeded.

[0065] As can be seen from the above, in this embodiment, the laser safety circuit not only converts the signal V generated by the TIAM The output power is compared with the preset threshold voltage to monitor in real time and the output of all LD lasers is quickly stopped when the threshold is exceeded. A timer function is also added; by starting and measuring the timer, the safety check of the laser pulse duration can be accurately completed. Once the pulse time exceeds the preset value, the output of all LD lasers will also be stopped immediately. These improvement measures have jointly improved the safety performance and reliability of the system.

[0066] The standard parts used in the present invention can all be purchased from the market, and the special-shaped parts can be customized according to the description and the drawings. The specific connection methods of each part adopt conventional means such as mature bolts, rivets, welding, etc. in the prior art. The machinery, parts and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0067] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0068] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0070] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0071] In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0072] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for safely monitoring multi-wavelength LD laser power, characterized in that: The following steps are involved: Step 1: Separate 5% of the laser light from the beam coupled and synthesized by the multi-wavelength light source as monitoring light, and redirect the monitoring light to the monitor photodiode; Step 2: Amplify the photocurrent generated by the monitor photodiode using an amplifier, and couple the amplified signal to the laser safety circuit and the laser power data acquisition circuit simultaneously; Step 3: In the laser power data acquisition circuit, the actual output power of the laser is determined by monitoring the amplified voltage signal; Step 4: In the laser safety circuit, set the maximum output power threshold and maximum pulse time limit to monitor the power and time of the laser pulse and stop the output of all LD lasers when the preset threshold is exceeded.

2. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 1, characterized in that: In the laser power data acquisition circuit, a high-speed PIN photodiode and a high-speed precision high-impedance amplifier are used to measure the monitoring light, and a constant voltage V is applied through an operational amplifier. Ref The monitor diode generates an output signal V proportional to the light level. M .

3. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 2, characterized in that: The output voltage V of the TIA is set by selecting the gain resistor R1. Monitor And ensure that the TIA power supply voltage has enough redundancy to meet the voltage output requirements at full laser power.

4. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 1, characterized in that: In the laser power data acquisition circuit, a high-precision resistor combination is used to replace a single high-precision large-value resistor to improve measurement accuracy and reduce the impact of temperature drift.

5. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 1, characterized in that: In the laser safety circuit, an RC low-pass filter is used to filter the short signal of the TIA output voltage to prevent false alarms caused by transient signals, and the safety output voltage V is divided by a voltage divider. M Limit the voltage input range of the laser safety circuit.

6. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 1, characterized in that: Also included in the laser safety circuit is the signal V generated by the TIA M It is compared with the threshold voltage to monitor the output power and stop the output of all LD lasers when the threshold is exceeded.

7. A method for safely monitoring multi-wavelength LD laser power as claimed in claim 1, characterized in that: Also included in the laser safety circuit, a safety check of the laser pulse duration is completed by starting and measuring a timer, and stopping the output of all LD lasers when the preset pulse time is exceeded.

Images