Laser current control method and apparatus for suppressing laser relaxation oscillations, and laser device

Abstract

The present application relates to the technical field of laser control. Provided is a laser current control method for suppressing laser relaxation oscillations. The method comprises: controlling a current signal of a preset waveform to be input into a laser driving circuit, wherein the preset waveform comprises a first stage and a second stage, the amplitude of the first stage is less than the amplitude of the second stage, and the amplitude of a laser relaxation oscillation waveform induced by a current signal of the first stage is less than a safety threshold value; and on the basis of a relationship between an average laser output power and a driving current, adjusting the amplitude of the second stage. In the embodiments of the present application, a small-step current waveform is designed, thereby effectively suppressing the damage caused by laser relaxation oscillations to optical devices in an optical path; a smaller pulse distortion causes threshold currents corresponding to different pulse frequencies to exhibit linearity under the same duty cycle, such that it is unnecessary to record, one by one for each duty cycle, the threshold currents and linear equations in one variable that correspond to the frequencies; and an output current can be more accurately and precisely adjusted to obtain the required average terminal power.

Description

Laser current control method and device for suppressing laser relaxation oscillation and laser

[0001] Cross-reference to Related Applications

[0002] This application claims priority to the Chinese patent application No. 202410703660X, filed on June 3, 2024, and entitled “Laser current control method and device for suppressing laser relaxation oscillation and laser”, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of laser control, in particular, to a laser current control method and device for suppressing laser relaxation oscillation and a laser. BACKGROUND

[0004] With the development of society, more and more industrial products and medical devices need to be processed by laser. In high-power industrial laser products, the error caused by temperature deviation, current jitter and frequency jitter can often be ignored. However, in medical devices, the average power of laser acting on the treated person is not high, usually less than or equal to 70W. Therefore, the medical laser device has a more stringent and demanding requirement for the accuracy and stability of the average power of laser than the industrial laser. This requires finding and exploring a power correction or compensation algorithm with small step accuracy and stable control effect.

[0005] According to the factory report of a laser diode, when the driving current is greater than a certain value I1, the driving current and the laser output curve of the laser diode (LD) satisfy a first-order equation. This curve rule almost satisfies the pulse width modulation (PWM) current output of every duty cycle, and for the continuous wave (CW) current output, it can also be regarded as the PWM current output with a duty cycle of 100%.

[0006] (1) The existing technology theoretically gives the relationship curve between the current and the peak power of the driving current PWM signal when the duty cycle is 100%, and then extends to the current waveform when the duty cycle is not 100%, which should also follow the same linear relationship. The general direction of this theory is correct, but in actual analog electronic circuits, when the electrical signal acts on both ends of the laser diode, the waveform of the signal is not a perfect square wave signal, but a waveform similar to a trapezoidal or triangular waveform. Therefore, experimental test data shows that under the same duty cycle, the slope of the first-order equation at different frequencies differs greatly.

[0007] (2) According to the above-mentioned defect, if the frequency range covered by the medical laser equipment is 1-2400Hz, then too many one-order equations need to be formulated, which brings the problem that the workload of correction is very large and is not suitable for mass production of the equipment.

[0008] (3) In addition, the existing laser power output control algorithm does not solve the problem of relaxation oscillation of the laser. With the increase of peak power, the current signal without solving the problem of relaxation oscillation of the laser is easy to cause the burning of the laser optical path. Because the phenomenon of relaxation oscillation will cause a short-term high peak power laser oscillation at each laser emission, which will cause some components in the optical path to be unable to withstand and thus be damaged.

[0009] Application content

[0010] To solve the above-mentioned problems, the application provides a laser current control method for suppressing laser relaxation oscillation, comprising: inputting a current signal of a preset waveform into a laser driving circuit; the preset waveform comprises a first order and a second order, the amplitude of the first order is smaller than the amplitude of the second order, and the current signal of the first order causes the amplitude of the laser relaxation oscillation waveform to be smaller than a safety threshold; adjusting the amplitude of the second order according to the relationship between the average laser output power and the driving current; the current signal of the second order is processed by the laser driving circuit to obtain the driving current; and the relationship between the average laser output power and the driving current is determined by the first-order peak power, the first-order duty cycle, the maximum driving current, the threshold current, the maximum driving current corresponding to the laser peak power, and the second-order duty cycle.

[0011] Optionally, the relationship between the average laser output power and the driving current signal is as follows:

[0012] P out = P p_It0* (t 0* f)+[(I out -I th ) / (I max -I th )]*(P pmax *D)

[0013] Wherein, P out is the average laser output power, P p_It0 is the first-order peak power, t 0* f is the first-order duty cycle, t0 is the width of the first order, I out is the driving current, I max is the maximum driving current, I th is the threshold current, P pmaxP is the laser output average power, P is the first order corresponding peak power, t f is the duty cycle corresponding to the first order, t0 is the width of the first order, I is the driving current, I is the maximum driving current, I is the threshold current, P is the peak power corresponding to the maximum driving current, D is the duty cycle corresponding to the second order, P is the average power corresponding to the threshold current.

[0014] Optionally, the relationship between the laser output average power and the driving current signal is as follows:

[0015] I out = (((P out -(P p_It0* (t0*f)))-P aIth ) / (P pmax *D-P aIth ))(I max -I th )+I th

[0016] Wherein, P is the laser output average power, P is the first order corresponding peak power, t f is the duty cycle corresponding to the first order, t0 is the width of the first order, I is the driving current, I is the maximum driving current, I is the threshold current, P is the peak power corresponding to the maximum driving current, D is the duty cycle corresponding to the second order, P is the average power corresponding to the threshold current. out p_It0 0* out max th pmax aIth

[0017] Optionally, the threshold current is linearly and positively related to the laser pulse frequency.

[0018] Optionally, the relationship between the threshold current and the laser pulse frequency is as follows:

[0019] I th = Af+B

[0020] Wherein, f is the laser pulse frequency, A and B are coefficients.

[0021] Optionally, the method further comprises: debugging the amplitude and width of the first order according to the tolerance value of the components in the laser driving circuit.

[0022] Optionally, the relationship between the laser output average power and the driving current signal is as follows:

[0023] Because P pset : P pmax = (I out -I th ):(I max -I th )

[0024] Therefore, I​​​​​​​​out = (P pset pmax )*(I max -I th )+I th Equation 1

[0025] where P pset is the peak power;

[0026] The average power P out output by the laser is equal to the average power P t0 of the first stage plus the average power P Iout required to be output, so we have:

[0027] P out = P t0 + P Iout Equation 2

[0028] The average power P Iout required to be output is equal to the peak power P out corresponding to I pset multiplied by the duty cycle D, so we have:

[0029] P Iout = P pset *D Equation 3

[0030] Since Equations 1 and 3,

[0031] we have I out = [P Iout / (P pmax *D)]*(I max -I th )+I th Equation 4

[0032] P out = P t0 + [(I out -I th ) / (I max -I th )]*(P pmax *D) Equation 5

[0033] The average power P t0 corresponding to the continuous mode of the current I t0_cw of the first stage is:

[0034] P t0_cw = P p_It0

[0035] The width of the first stage is t0, and the duty cycle is:

[0036] D t0 = t​0* f

[0037] The average power of the first order is:

[0038] P t0 = P p_It0* D t0 = P p_It0* (t 0* f)

[0039] So formula 5 can be transformed into:

[0040] P out = P p_It0* (t 0* f)+[(I out -I th ) / (I max -I th )]*(P pmax *D) formula 6.

[0041] Alternatively, the relationship between the average power of the laser output and the driving current signal is derived as follows:

[0042] Since (P pset -P Ith ):(P pmax -P Ith ) = (I out -I th ):(I max -I th )

[0043] So I out = (P pset -P Ith )(I max -I th ) / (P pmax -P Ith )+I th formula 1

[0044] Where Ppset is the peak power;

[0045] The peak power P Ith and the average power P aIth at this time have the following formula relationship:

[0046] P Ith = P aIth / D formula 2

[0047] D is the duty cycle, P Ith is the peak power corresponding to the threshold current at the duty cycle D at this time;

[0048] P IthThe impact is negligible, which is equivalent to:

[0049] I out =(P pset (I) max -I th ) / (P pmax )+I th

[0050] The average power P of the laser output out It is equal to the average power P of the small step. t0 Add the average power P output by the current curve set Therefore, we have:

[0051] P out =P t0 +P Iout Formula 3

[0052] And because the required average output power P Iout equals I out The corresponding peak power P pset Multiply by the duty cycle D, and then:

[0053] P Iout =P pset *D Formula 4

[0054] Also, since formulas 1, 2, and 4,

[0055] ∴I out =[(P Iout -P aIth ) / (P pmax *DP aIth )]*(I max -I th )+I th Formula 5

[0056] I out ={[(P out -P t0 )-P aIth ] / (P pmax *DP aIth )}*(I max -I th )+I th Formula 6

[0057] The first-order current I t0 The corresponding continuous mode average power P t0_cw for:

[0058] P t0_cw =P p_It0

[0059] The first order has a width t0 and a duty cycle of:

[0060] D t0 = t0 / T = t0*f

[0061] The first order has an average power of:

[0062] P t0 = P p_It0* D t0 = P p_It0* (t0*f)

[0063] Therefore, formula 6 is transformed into:

[0064] I out = [(P out -(P p_It0* (t0*f))-P aIth ) / (P pmax *D-P aIth )]*(I max -I th )+I th Formula 7.

[0065] Optionally, a third order is further arranged between the first order and the second order, the amplitude of the third order is less than the amplitude of the second order and greater than the amplitude of the first order.

[0066] Embodiments of the present application provide a laser current control device for suppressing laser relaxation oscillation, comprising: a waveform output module configured to control a current signal of a preset waveform to input a laser driving circuit; the preset waveform comprises a first order and a second order, the amplitude of the first order is less than the amplitude of the second order, and the amplitude of the current signal of the first order is less than the amplitude of the laser relaxation oscillation waveform induced by the first order; an adjusting module configured to adjust the amplitude of the second order according to the relationship between the average laser output power and the driving current; the current signal of the second order is processed by the laser driving circuit to obtain the driving current; and the relationship between the average laser output power and the driving current is determined by the first order corresponding peak power, the duty cycle corresponding to the first order, the maximum driving current, the threshold current, the laser peak power corresponding to the maximum driving current, and the duty cycle corresponding to the second order.

[0067] Optionally, the relationship between the average laser output power and the driving current signal is as follows:

[0068] P out = P p_It0* (t 0* f)+[(I out -I th ) / (I max -I th )]*(Ppmax *D)

[0069] wherein, P out is the average output power of the laser, P p_It0 is the peak power corresponding to the first order, t 0* f is the duty cycle corresponding to the first order, t0 is the width of the first order, I out is the driving current, I max is the maximum driving current, I th is the threshold current, P pmax is the peak power of the laser corresponding to the maximum driving current, D is the duty cycle corresponding to the second order.

[0070] Optionally, the threshold current is linearly and positively related to the laser pulse frequency.

[0071] Embodiments of the present application provide a laser, comprising a computer readable storage medium storing a computer program and a processor, wherein the computer program is read and run by the processor to implement the laser current control method for suppressing laser relaxation oscillation.

[0072] The laser current control method for suppressing laser relaxation oscillation, the device and the laser provided by the embodiments of the present application design a small step current waveform, which effectively suppresses the damage of laser relaxation oscillation to optical devices in an optical path. The small step current waveform effectively reduces the deformation of the current pulse waveform of the effective current, so that the waveform of the laser output is more square. With smaller pulse deformation, the threshold current corresponding to different pulse frequencies under the same duty cycle presents linearity, and it is not necessary to record the threshold current corresponding to each frequency and the monomial first-order equation under each duty cycle. The mathematical formula relationship between the laser terminal output average power and the adjusting current considers the average power of the small step, and the output current can be more accurately and precisely adjusted to obtain the required terminal average power. BRIEF DESCRIPTION OF DRAWINGS

[0073] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0074] FIG. 1 is a laser output power curve of a prior art driving current and a laser diode;

[0075] FIG. 2 is a flowchart of a laser current control method for suppressing laser relaxation oscillation provided by an embodiment of the present application;

[0076] FIG. 3 is a schematic diagram of an initial current waveform according to an embodiment of the present application.

[0077] FIG. 4 is a schematic diagram of an amplified current waveform according to an embodiment of the present application.

[0078] FIG. 5 is a schematic diagram of a current waveform according to an embodiment of the present application.

[0079] FIG. 6 is a schematic diagram of another current waveform according to an embodiment of the present application.

[0080] FIG. 7 is a schematic diagram of a laser current control device for suppressing laser relaxation oscillation according to an embodiment of the present application. DETAILED DESCRIPTION

[0081] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0082] FIG. 1 shows a prior art driving current and laser output power curve of a laser diode (LD). In FIG. 1, the lower side is a current-laser peak power curve, and the upper side is a current-voltage curve.

[0083] According to the factory report of the laser diode, when the driving current is greater than a certain value I1, the driving current and the laser output curve of the laser diode satisfy a first-order equation. This curve rule almost satisfies the PWM current output of every duty cycle, and for the continuous mode current output, it can also be regarded as the PWM current output with a duty cycle of 100%.

[0084] A common power correction algorithm is to segment the current according to the electro-optical conversion efficiency, such as the curve in FIG. 1, which can be roughly divided into two segments according to the electro-optical conversion efficiency, which are 1A < I1≤ 1.5A and 1.5A < I2≤ 9.00A, respectively.

[0085] According to the solution of the first-order equation, two first-order equations can be obtained, which are represented as y1=K1x1+b1 and y2=k2x2+b2.

[0086] At different frequencies, the duty cycle D is the same, and the pulse width τ is different, so different frequencies should have corresponding two first-order equations.

[0087] The embodiment of the present application is directed to the case that the voltage across the LD driven by the electrical signal described in (1) in the prior art is easily changed into a trapezoidal or triangular shape in the analog electronic circuit, and a current control method is designed to reduce the shape change of the current in the analog electronic circuit.

[0088] To overcome the shortcoming (2), the relationship between the frequency and the current offset b of different equations is formulated to obtain the equation bx=Af+B, so that the equation slope and offset are not recorded in a large number. x

[0089] The relaxation oscillation is a phenomenon that occurs when the laser establishes equilibrium, but it can be limited within a safe amplitude, so the current output control algorithm is designed to limit the effect of the relaxation oscillation within the range that the laser optical path can withstand, thereby avoiding damage to the optical devices in the optical path.

[0090] FIG. 2 shows a flowchart of a laser current control method for suppressing laser relaxation oscillation according to an embodiment of the present application, which includes the following steps:

[0091] S202, input a current signal of a preset waveform into the laser driving circuit.

[0092] The laser driving circuit can be connected to the laser diode, and after the current signal of the preset waveform is input into the laser driving circuit, the current for driving the laser diode is output.

[0093] In the present embodiment, the preset waveform can include a first order and a second order, and the amplitude of the first order is smaller than that of the second order. For example, the preset waveform can adopt a structure similar to a staircase wave. The current signal of the first order induces a laser relaxation oscillation waveform with an amplitude smaller than a safety threshold. The safety threshold is affected by the parameters of the components in the laser driving circuit, and the relaxation oscillation with an amplitude lower than the safety threshold will not damage the components in the optical path.

[0094] Since the current signal is amplified in the laser driving circuit before being input into the laser diode, the above-mentioned power signal is deformed after amplification, such as trapezoidal deformation.

[0095] In the present embodiment, a first-order current is added in front of the current pulse signal calculated by the existing theoretical formula, and this smaller current is used to quickly charge the filter circuit such as the capacitor and resistor in the driving circuit, thereby reducing the deformation of the effective electric pulse waveform, and further obtaining a laser pulse signal that is more close to the actual calculation.

[0096] The current control algorithm used in the present embodiment limits the damage of the relaxation oscillation to the optical components in the laser optical path within an acceptable range, but does not eliminate it.

[0097] ​Since the higher the driving current, the higher the peak power generated by the laser diode, the higher the relaxation oscillation waveform before the establishment of the laser balance, and when it is higher than a certain value, the optical device may be burned out. Therefore, the embodiment first uses a smaller first-order current to let the laser balance of the laser establish first, and then outputs a large current corresponding to the effective PWM pulse current. In this way, when the large current is output to the laser diode, because the laser balance has been basically established, the subsequent large current driving the laser diode will not cause a larger relaxation oscillation waveform. The amplitude of the relaxation oscillation waveform caused by the small step current is relatively small, within the acceptance range of the optical device in the optical path, thereby successfully suppressing the damage of the relaxation oscillation to all optical devices in the optical path.

[0098] In the embodiment, the amplitude and width of the first order can be obtained by debugging according to the tolerance value of the components in the laser driving circuit.

[0099] It should be noted that a third order or the like can also be set between the first order and the second order according to needs. The amplitude of the third order is smaller than that of the second order and larger than that of the first order.

[0100] Based on the above small step current waveform, the deformation of the current pulse waveform of the effective current is effectively reduced, so that the waveform of the laser output is more square, and the average power of the laser can be more close to the theoretical calculation value. Smaller pulse deformation makes the threshold current I th present linearly under the same duty cycle and different pulse frequencies. The threshold current is linearly and positively related to the laser pulse frequency. The relationship between the threshold current and the laser pulse frequency can be obtained by statistics of the data of I th and f as follows:

[0101] I th = Af+B

[0102] Wherein, f is the laser pulse frequency, and A and B are coefficients.

[0103] Therefore, it is not necessary to record the Ith corresponding to the frequency one by one under each duty cycle as in the prior art.

[0104] S204, adjusting the amplitude of the second order according to the relationship between the average power of the laser output and the driving current.

[0105] Wherein, the driving current is obtained by processing the second-order current signal through the laser driving circuit. The relationship between the average power of the laser output and the driving current is determined by the peak power corresponding to the first order, the duty cycle corresponding to the first order, the maximum driving current, the threshold current, the peak power of the laser corresponding to the maximum driving current, and the duty cycle corresponding to the second order.

[0106] The mathematical formula for the relationship between the average output power and the regulating current of the laser terminal designed in this embodiment takes into account the average power of small steps, and can more accurately and precisely adjust the output current to obtain the required average power.

[0107] Optionally, the relationship between the average laser output power and the drive current signal is as follows:

[0108] P out =P p_It0* (t 0* f)+(I out / ((I max -I th )+I th ))*(P pmax *D)

[0109] Among them, P out P represents the average output power of the laser. p_It0 For the first-order peak power, t 0* f is the duty cycle corresponding to the first order, t0 is the width (or duration) of the first order, and I out For the drive current, I max For the maximum drive current, I th For the threshold current, P pmax denoted as the peak laser power corresponding to the maximum driving current, and D as the duty cycle corresponding to the second order.

[0110] The laser current control method for suppressing laser relaxation oscillations provided in this application embodiment designs a small-step current waveform, which effectively suppresses the damage of laser relaxation oscillations to optical components in the optical path. The small-step current waveform effectively reduces the deformation of the effective current pulse waveform, thereby making the output waveform of the laser more square. The smaller pulse deformation makes the threshold current corresponding to different pulse frequencies linear under the same duty cycle, eliminating the need to record the threshold current and linear equations corresponding to each frequency for each duty cycle. The mathematical formula relationship between the average output power of the laser terminal and the adjustment current takes into account the average power of the small step, which allows for more accurate and precise adjustment of the output current to obtain the required terminal average power.

[0111] The implementation scheme of the current-driven control method is described in detail below.

[0112] The initial current signal waveform is controlled by a microcontroller unit (MCU). Figure 3 shows a schematic diagram of the initial current waveform. In Figure 3, the current signal waveform includes the first order t0 and the second order t1.

[0113] The initial current is then amplified, and the current waveform flowing to the laser diode becomes the amplified current waveform as shown in the schematic diagram of FIG. 4.

[0114] Because of the existence of the t0 current waveform, the integrity of the PWM duty cycle output current in the t1 stage is greatly ensured (deformation is reduced).

[0115] The analog electronic circuit principle of the current driving algorithm is as follows.

[0116] Before the single-chip microcomputer controls the initial current to flow into the LD, the weak current needs to be amplified into a strong current, and a filter circuit built by a capacitor and a resistor, etc. is usually needed so that the initial square wave electrical signal becomes a trapezoidal wave after amplification. After the deformation of the electrical signal, the optical signal that should be theoretically converted from the electrical signal will be less, and thus the calculation formula of the prior art will have a relatively large deviation.

[0117] The embodiment adds a small step "t0" time corresponding current before the current pulse signal calculated by the existing theoretical formula, and uses the small current to quickly charge the filter circuit in the circuit such as the capacitor and the resistor, so as to reduce the deformation of the electrical waveform in the effective electrical pulse "t1" time, and thus a laser pulse signal that is more close to the actual calculation is obtained.

[0118] The principle of relaxation oscillation damage suppression is as follows.

[0119] The relaxation oscillation is a phenomenon that occurs before the laser establishes balance. The embodiment uses the current control algorithm to limit the damage of the relaxation oscillation to the optical components in the laser optical path within an acceptable range, rather than eliminating the phenomenon.

[0120] Because the higher the driving current is, the higher the peak power generated by the laser diode is, and thus the higher the relaxation oscillation waveform before the laser balance is established, when the value is higher than a certain value, the optical components can be burned out. Therefore, the embodiment first uses a small step "t0" current to make the laser balance of the laser to be established first, and then outputs the large current corresponding to the effective PWM pulse current "t1", so that when the large current is output to the laser diode, because the laser balance has been basically established in front, the large current driving the laser diode will not cause a large relaxation oscillation waveform. The amplitude of the relaxation oscillation waveform caused by the small step current in front is relatively small, which is within the acceptance range of the optical components in the optical path, so the damage of the relaxation oscillation to all optical components in the optical path is successfully suppressed.

[0121] The practice data prove that the circuit driving the laser diode is not the same, so the small step "t0" corresponds to different types of laser diodes, and the tolerance value of the optical path optical component is combined to obtain a suitable width and amplitude of the current step through actual circuit debugging. Once the current width and amplitude of the small step are fixed, it can be applied to all frequencies and duty cycles in this laser.

[0122] The formula of the current-average power that increases the relaxation oscillation damage suppression effect is derived as follows.

[0123] Because the prior art has informed the peak power P p and the curve relationship of the driving current I out , the auxiliary line of the curve can obtain the schematic diagram of the current waveform as shown in FIG. 5.

[0124] ∵BC⊥AC, ED⊥AC,

[0125] ∴ED∥BC

[0126] And ∵∠EAD=∠BAC

[0127] ∠AED=∠ABC

[0128] ∠ADE=∠ACB

[0129] ∴△EAD∽△BAC

[0130] ∴ED:BC=AD:AC

[0131] ∴P pset :P pmax =(I out -I th ):(I max -I th )

[0132] So I out =(P pset / P pmax )*(I max -I th )+I th Formula ①

[0133] Where P pset is the peak power.

[0134] The relationship between the average power and the output current is as follows.

[0135] The average power P out output by the laser is equal to the average power P t0 of the small step plus the average power P Iout that needs to be output, so:

[0136] P out = P t0 + P Iout Equation ②

[0137] Because the average power P Iout equals I out , the peak power P pset times the duty cycle D, that is, the effective current t1 period corresponding to the current, can get a laser peak power P pset , the peak power times the duty cycle equals the average power P Iout needed to output at this time, so:

[0138] P Iout = P pset *D Equation ③

[0139] Also ∵ Equation ①③,

[0140] ∴ I out = [P Iout / (P pmax *D)]*(I max -I th )+I th Equation ④

[0141] According to similar triangles, I th is the value of the laser just starting to emit light, ready to have laser emission, this value is fixed. It can also be taken a little bit of this I th , at this time the proportion of the above similar triangle items need to be slightly modified.

[0142] The maximum output current I max must correspond to the maximum laser peak power P pmax , so P pmax and I max are fixed known values. Because the duty cycle D of the current waveform needed to output is known, the average power P Iout needed to output can be calculated to get how much current I out MCU needs to output.

[0143] According to Equation ②, the actual laser device terminal output laser power and current regulation output laser average power, the difference between a small step average power P t0 , because the small step current value and the duration t0 of the suppression relaxation oscillation damage are fixed by circuit debugging (the principle is to debug the output current size and t0, and observe whether the laser waveform relaxation oscillation waveform exceeds the tolerance value of the optical device in the optical path), so P t0 is a constant. So as long as P t0The adjustable output current I can then be obtained. out and the average power P output by the laser device terminal out The relationship is as follows:

[0144] P out =P t0 +[(I out -I th ) / (I max -I th )]*(P pmax *D) Formula ⑤

[0145] The method for calculating the average power corresponding to the time "t0" of the small step is as follows.

[0146] The width t0 of the small step current and the amplitude I of the small step current were obtained above. t0 At this point, through actual measurement, a continuous I is output. t0 By consulting the current-peak power curve provided by the LD manufacturer, we can know I t0 The corresponding peak power P p_It0 Furthermore, since continuous output is equivalent to a pulse PWM waveform with a 100% duty cycle, I at this time... t0 The corresponding continuous mode average power P t0_cw for:

[0147] P t0_cw =P p_It0

[0148] Since the width of the small step is t0, it can be considered that t0 is also a pulse waveform output at frequency f with a certain duty cycle, and its duty cycle is:

[0149] D t0 =t 0* f

[0150] Since the average power of the laser output in PWM mode equals the peak power multiplied by the duty cycle, the average power of the small step is:

[0151] P t0 =P p_It0* D t0

[0152] =P p_It0* (t 0* f)

[0153] Because P p_It0 According to I t0 The query revealed that t0 is a constant value, as determined during debugging, therefore P... t0 It is also a constant value.

[0154] So formula 5 can be changed to:

[0155] P out = P p_It0* (t 0* f) + [(I out -I th ) / (I max -I th )]*(P pmax *D) formula 6

[0156] Compared with the schematic diagram of the current waveform shown in Figure 5, the threshold current I th in the schematic diagram of the current waveform of Figure 6 is larger. Based on the schematic diagram of the current waveform shown in Figure 6, the formula derivation of current-average power is as follows.

[0157] ∵BC⊥AC, ED⊥AC,

[0158] ∴ED∥BC

[0159] And ∵∠EAD = ∠BAC

[0160] ∠AED = ∠ABC

[0161] ∠ADE = ∠ACB

[0162] ∴△EAD∽△BAC

[0163] ∴ED:BC = AD:AC

[0164] ∴(P pset -P Ith ):(P pmax -P Ith ) = (I out -I th ):(I max -I th )

[0165] ∴I out = (P pset -P Ith )(I max -I th ) / (P pmax -P Ith )+I th formula 1

[0166] So when the power is corrected, only the corresponding I max and I th of each frequency segment and P pmax need to be found, and the required current can be calculated according to the P pset set by the screen; the peak power P Ith and the average power PaIth There is a formula relationship as follows:

[0167] P Ith = P aIth / D Formula 2

[0168] D is the duty cycle, P aIth is the average power, P Ith is the current at this time I th corresponding to the peak power at the duty cycle D.

[0169] According to the current-peak power curve diagram derived from the above formula, if the current I th is selected as 1.5A, the corresponding P Ith is equal to 0, at this time the influence of P Ith in the above formula 1 can be ignored, which is equivalent to:

[0170] I out = (P pset )(I max -I th ) / (P pmax )+I th

[0171] According to the actual demand, a suitable peak power (I th , P Ith ) can be selected as the starting point.

[0172] The average power P out output by the laser is equal to the average power P t0 of the small step plus the average power P set output by the current curve, so:

[0173] P out = P t0 + P Iout Formula 3

[0174] Because the average power P Iout that needs to be output is equal to the peak power P out corresponding to I pset multiplied by the duty cycle D, that is, the current corresponding to the effective current t1 period is adjusted to obtain a laser peak power P pset , the peak power multiplied by the duty cycle is equal to the average power P Iout at this time, so:

[0175] P Iout = P pset *D Formula 4

[0176] Again, according to formulas 1, 2, and 4,

[0177] ∴Iout =[(P Iout -P aIth ) / (P pmax *DP aIth )]*(I max -I th )+I th Formula 5

[0178] According to similar triangles, I th The value can be taken as the value at which the laser just begins to emit light, close to the point where the peak power of the laser is about to be emitted (at this point, the laser peak power is close to 0W). This value is fixed depending on the laser pump source model. Alternatively, this I value can be determined based on the laser's average power range. th Take a larger one, get a suitable one (I) th ,P Ith For example, if the average laser power range is 0.5W to 20W, then take P... aIth =0.5W can be obtained through P Ith =P aIth / D calculates the peak power P Ith， However, according to Formula 4 derived from Formula 1, Formula 4 now becomes:

[0179] I out =[(P Iout –0.5) / (P pmax *D–0.5)]*(I max -I th )+I th

[0180] And because of the maximum output current I max It must correspond to the maximum laser peak power P pmax Therefore, P pmax and I max It is a fixed, known value. Since the duty cycle of the output current waveform needs to be known, the required average output power P is used as a basis. Iout This allows you to calculate the required current I to be output by the MCU. out .

[0181] According to Formula 3, the average power P of the laser output from the laser device terminal differs from the average power output by the current-regulated laser by a small step. t0， Furthermore, the current value and duration t0 of the small step that suppresses relaxation oscillation damage are fixed through circuit tuning (the principle is to tune the output current and t0). 0， Observe whether the relaxation oscillation waveform of the laser waveform does not exceed the tolerance value of the optical components in the optical path, so P t0 It is a constant. Therefore, we only need to calculate P. t0The output current I out and the average power P out output by the laser device terminal are related as follows:

[0182] I out = ((P out -P t0 ) -P aIth ) / (P pmax *D-P aIth ))(I max -I th )+I th Equation 6

[0183] The calculation method of the average power corresponding to the small step "t0" time is as follows.

[0184] I t0 The average power P t0_cw of the corresponding continuous mode is:

[0185] P t0_cw =P p_It0

[0186] Since the width of the small step is t0, it can be considered that t0 is also a pulse waveform output at a frequency f under a certain duty cycle, and the duty cycle is:

[0187] D t0 =t0 / T=t0*f

[0188] Since the average power of the laser output in PWM mode is equal to the peak power multiplied by the duty cycle, the average power of the small step is:

[0189] P t0 =P p_It0* D t0 =P p_It0* (t0*f)

[0190] Since P p_It0 can be obtained according to I t0 , t0 is a fixed value known during debugging, and P t0 is also a fixed value.

[0191] Therefore, equation 6 can be changed to equation 7 as follows:

[0192] I out = [(P out -(P p_It0* (t0*f))-P aIth ) / (P pmax *D-P aIth )]*(I max -I th )+Ith Equation 7

[0193] In summary, the current control algorithm of the embodiment of the application has the following advantages:

[0194] The current control algorithm effectively suppresses the damage of laser relaxation oscillation to the optical devices of the optical path by designing the "small step current waveform".

[0195] The "small step current waveform" effectively reduces the deformation of the current pulse waveform of "effective current t1", so that the waveform of the laser output is more square, and the average power of the laser can be more close to the theoretical calculation value. Smaller pulse deformation, under the same duty cycle, different pulse frequencies correspond to I th will present a linear relationship, which can be obtained by statistics I th and f data, I th＝ Af+B. Thus, it is not necessary to record the frequency corresponding to I th of each duty cycle as in the prior art.

[0196] The mathematical formula relationship between the designed average power of the laser terminal output and the adjustment current considers the average power of the small step, which can more accurately and precisely adjust the output current to obtain the required terminal average power.

[0197] Figure 6 shows a structure diagram of a laser current control device for suppressing laser relaxation oscillation according to an embodiment of the application, which comprises:

[0198] The waveform output module 601 is configured to control the input of the current signal of the preset waveform to the laser driving circuit; the preset waveform includes a first order and a second order, the amplitude of the first order is less than the amplitude of the second order, and the current signal of the first order induces the amplitude of the laser relaxation oscillation waveform to be less than the safety threshold;

[0199] The adjustment module 602 is configured to adjust the amplitude of the second order according to the relationship between the laser output average power and the driving current; the current signal of the second order is processed by the laser driving circuit to obtain the driving current; the relationship between the laser output average power and the driving current is determined by the first order corresponding peak power, the first order corresponding duty cycle, the maximum driving current, the threshold current, the laser peak power corresponding to the maximum driving current, and the second order corresponding duty cycle.

[0200] Optionally, the relationship between the laser output average power and the driving current signal is as follows:

[0201] P out = P p_It0* (t 0* f)+[(I out -Ith ) / (I max -I th )]*(P pmax *D)

[0202] wherein, P out is the average output power of the laser, P p_It0 is the peak power corresponding to the first order, t 0* f is the duty cycle corresponding to the first order, t0 is the width of the first order, I out is the driving current, I max is the maximum driving current, I th is the threshold current, P pmax is the peak power of the laser corresponding to the maximum driving current, i.e. the maximum peak power of the laser, and D is the duty cycle corresponding to the second order.

[0203] Optionally, the threshold current is linearly and positively related to the frequency of the laser pulse.

[0204] Embodiments of the present application provide a laser, comprising a computer readable storage medium storing a computer program and a processor, wherein the computer program is read and run by the processor to implement the above-mentioned laser current control method for suppressing relaxation oscillation of a laser.

[0205] The laser current control device for suppressing relaxation oscillation of a laser and the laser provided by embodiments of the present application can achieve the same technical effects as the laser current control method for suppressing relaxation oscillation of a laser provided by the above-mentioned embodiments, and thus repeated description is omitted here.

[0206] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various modifications and variations without departing from the spirit and scope of the present application, and thus the protection scope of the present application should be defined by the scope defined by the claims.

[0207] Finally, it should also be noted that, in this document, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

[0208] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the laser current control device and laser for suppressing laser relaxation oscillations disclosed in the embodiments, since they correspond to the laser current control method for suppressing laser relaxation oscillations disclosed in the above embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0209] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Industrial applicability

[0210] The laser current control method, device, and laser for suppressing laser relaxation oscillations provided in this application have designed a small-step current waveform, which effectively suppresses the damage of laser relaxation oscillations to optical components in the optical path. The small-step current waveform effectively reduces the deformation of the current pulse waveform of the effective current, thereby making the output waveform of the laser more square. The output current can be adjusted more accurately and precisely to obtain the required terminal average power, which has significant economic benefits.

Claims

1. A laser current control method for suppressing a laser relaxation oscillation, characterized by, The method comprises: controlling a current signal input laser drive circuit with a preset waveform; the preset waveform comprises a first order and a second order, the amplitude of the first order is less than the amplitude of the second order, and the current signal of the first order causes the amplitude of the laser relaxation oscillation waveform to be less than a safety threshold; adjusting the amplitude of the second order according to the relationship between the average power of the laser output and the driving current; the current signal of the second order is processed by the laser drive circuit to obtain the driving current; and the relationship between the average power of the laser output and the driving current is determined by the corresponding peak power of the first order, the corresponding duty cycle of the first order, the maximum driving current, the threshold current, the corresponding peak power of the laser of the maximum driving current, and the corresponding duty cycle of the second order.

2. The laser current control method for suppressing a laser relaxation oscillation according to claim 1, wherein The relationship of the laser output average power to the drive current signal is as follows: P out = P p_It0* (t 0* f) + [(I out -I th ) / (I max -I th )]*(P pmax *D) wherein P out is the average laser output power, P p_It0 is the peak power of the first order, t 0* f is the duty cycle of the first order, t0 is the width of the first order, I out is the drive current, I max is the maximum drive current, I th is the threshold current, P pmax is the peak power of the maximum drive current, and D is the duty cycle of the second order.

3. The laser current control method of suppressing a laser relaxation oscillation according to claim 1, characterized by, The relationship of the laser output average power to the drive current signal is as follows: I out = (((P out - (P p_It0* (t0*f)) - P aIth ) / (P pmax *D - P aIth ))(I max - I th ) + I th wherein P out is the average power of the laser output, P p_It0 is the peak power of the first order, t 0* f is the duty cycle of the first order, t0 is the width of the first order, I out is the drive current, I max is the maximum drive current, I th is the threshold current, P pmax is the peak power of the laser corresponding to the maximum drive current, D is the duty cycle of the second order, P aIth is the average power corresponding to the threshold current.

4. The laser current control method of suppressing a laser relaxation oscillation according to claim 2 or 3, characterized by, The threshold current is linearly and positively related to the laser pulse frequency.

5. The laser current control method of suppressing a laser relaxation oscillation according to claim 4, characterized by, The threshold current is related to the laser pulse frequency as follows: I th = Af + B Wherein, f is the laser pulse frequency, and A and B are coefficients.

6. The method of claim 1-5, wherein the laser current control method for suppressing laser relaxation oscillation is characterized by, The method further comprises: debugging the amplitude and width of the first order according to the tolerance value of the components in the laser drive circuit.

7. The laser current control method of suppressing a laser relaxation oscillation according to claim 2, characterized by, The derivation process of the relationship between the laser output average power and the driving current signal is as follows: since P pset : pmax = (I out -I th ):(I max -I th ) So I out = (P pset / P pmax )*(I max -I th )+I th Formula ① Pmax= Ppeak+ Poffset pset Pmax= Ppeak+ Poffset The average power P output by the laser out is equal to the average power P t0 of the first order plus the average power P Iout required to be output, so that: P out = P t0 + P Iout Equation 2 The average power P Iout is equal to I out The corresponding peak power P pset is multiplied by the duty cycle D, so that: P Iout = P pset *D Equation 3 Since formula 1 and formula 3, ∴I out = [P Iout / (P pmax *D)]*(I max -I th )+I th Equation 4 P out = P t0 + [(I out -I th ) / (I max -I th )]*(P pmax *D) Equation 5 the first order current I t0 the average power P of the corresponding continuous mode t0_cw is: P t0_cw = P p_It0 The duty cycle of the first order is: D t0 = t 0* f The average power of the first order is: P t0 = P p_It0* D t0 = P p_It0* (t 0* f) Therefore, formula 5 is transformed into: P out = P p_It0* (t 0* f)+[(I out -I th ) / (I max -I th )]*(P pmax *D) Equation 6.

8. The laser current control method of suppressing a laser relaxation oscillation according to claim 3, characterized by, The derivation of the relationship between the average power of the laser output and the driving current signal is as follows: Since (P pset -P Ith ) = (I pmax -I Ith ) : (I out -I th ) : (I max -I th ), I out = (P pset -P Ith )(I max -I th ) / (P pmax -P Ith )+I th Formula 1 Wherein, Ppset is the peak power. Peak power P Ith Average power P aIth There is a formulaic relationship as follows: P Ith = P aIth / D Equation 2 D is the duty cycle, P Ith is the peak power corresponding to the threshold current at the duty cycle D at this time; P Ith The impact of the negligible, equivalent to: I out = (P pset )(I max - I th ) / (P pmax )+I th The average power P output by the laser out is equal to the average power P of the small step t0 plus the average power P output by the current profile set so that P out = P t0 + P Iout Equation 3 Since the average power P Iout is equal to I out corresponds to the peak power P pset times the duty cycle D, so that: P Iout = P pset *D Equation 4 Since formula 1, 2 and 4, ∴I out = [(P Iout -P aIth ) / (P pmax *D-P aIth )]*(I max -I th )+I th Equation 5 I out = {[(P out -P t0 )-P aIth ] / (P pmax *D-P aIth )}*(I max -I th )+I th Equation 6 the first order current I t0 the average power P t0_cw is: P t0_cw = P p_It0 The duty cycle of the first order is: D t0 = t0 / T = t0*f The average power of the first order is: P t0 = P p_It0* D t0 = P p_It0* (t0*f) Therefore, formula 6 is transformed into: I out = [(P out - (P p_It0* (t0*f)) - P aIth ) / (P pmax *D - P aIth )]*(I max - I th )+ I th Formula 7.

9. The method of claim 1-8, wherein the laser current control method for suppressing laser relaxation oscillation is characterized by, A third order is further arranged between the first order and the second order, the amplitude of the third order is less than the amplitude of the second order, and greater than the amplitude of the first order.

10. A laser current control device for suppressing laser relaxation oscillations, characterized in that, The method comprises: controlling a current signal input laser drive circuit with a preset waveform; the preset waveform comprises a first order and a second order, the amplitude of the first order is less than the amplitude of the second order, and the current signal of the first order causes the amplitude of the laser relaxation oscillation waveform to be less than a safety threshold; adjusting the amplitude of the second order according to the relationship between the average power of the laser output and the driving current; the current signal of the second order is processed by the laser drive circuit to obtain the driving current; and the relationship between the average power of the laser output and the driving current is determined by the corresponding peak power of the first order, the corresponding duty cycle of the first order, the maximum driving current, the threshold current, the corresponding peak power of the laser of the maximum driving current, and the corresponding duty cycle of the second order.

11. The laser current control device for suppressing a laser relaxation oscillation according to claim 10, wherein The relationship between the average power of the laser output and the driving current signal is as follows: out = P p_It0* (t 0* f)+[(I out -I th ) / (I max -I th )]*(P pmax *D) wherein P out is the average laser output power, P p_It0 is the peak power of the first order, t 0* f is the duty cycle of the first order, t0 is the width of the first order, I out is the drive current, I max is the maximum drive current, I th is the threshold current, P pmax is the peak power of the maximum drive current, and D is the duty cycle of the second order.

12. The laser current control device for suppressing a laser relaxation oscillation according to claim 11, wherein The threshold current is linearly and positively related to the laser pulse frequency.

13. The laser current control device for suppressing a laser relaxation oscillation according to claim 12, wherein The threshold current is related to the laser pulse frequency as follows: I th = Af + B Wherein, f is the laser pulse frequency, and A and B are coefficients.

14. The laser current control device for suppressing a laser relaxation oscillation according to any one of claims 8 to 11, wherein The adjusting module is further configured to: debug the amplitude and width of the first order according to the tolerance value of the components in the laser drive circuit.

15. The method of claim 10-14, wherein the laser current control method for suppressing a laser relaxation oscillation is characterized by, A third order is further arranged between the first order and the second order, the amplitude of the third order is less than the amplitude of the second order, and greater than the amplitude of the first order.

16. A laser, characterized by The computer readable storage medium and the processor are provided with a computer program, and the computer program is read and run by the processor to realize the laser current control method for suppressing laser relaxation oscillation according to any one of claims 1-9.

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