CN115184945B - Signal restoration method for measuring pulse laser based on array detection method - Google Patents

Abstract

The invention relates to pulse laser signal restoration, in particular to a signal restoration method for measuring pulse laser based on an array detection method. In order to solve the technical problem that the existing recovery method can not meet the requirements of narrow pulse width and low repetition frequency pulse laser measurement, the invention provides a signal recovery method for measuring pulse laser based on an array detection method, which comprises the following steps: converting the pulse laser signal into N paths of pulse electric signals; n charge integration circuits are used for stretching N paths of pulse electric signals respectively to obtain N paths of pulse stretched electric signals, and N charge discharge curves are generated; asynchronous sampling is carried out on the N paths of pulse stretching electric signals to obtain N groups of sampling data; determining a time zero point t ₀ according to the obtained N groups of sampling data; and respectively selecting one point on the N charge discharge curves as a sampling point, and respectively calculating light intensity sequences at the N photoelectric detectors through the N sampling points and the unique time zero point t ₀ so as to restore the pulse laser signals.

Description

A signal recovery method for measuring pulsed laser based on array detection method

Technical Field

The invention relates to pulse laser signal restoration, and in particular to a signal restoration method for measuring pulse laser based on an array detection method.

Background technique

In the laser oblique atmospheric transmission test, the array detection method based on photodetectors is an effective means to measure the spatiotemporal distribution of the laser far-field spot intensity. In the prior art, the photodetector array is composed of a number of photodetectors arranged in a dot matrix distribution, which is used to perform spatial sampling of the spot. The photodetector array converts the optical signal into an electrical signal and then performs signal acquisition processing, and calculates the power value of each photodetector at the array distribution point. Finally, the image is restored according to the spatial distribution value of the power, and then the spot image and far-field spot parameters are obtained. In other words, only by obtaining the waveform of each pulse can its integral value be obtained to reflect the energy of a single laser pulse, and the frame rate requirements of the acquisition circuit are relatively high, especially in the application of measuring narrow pulse width and low repetition rate pulse laser, it is difficult to meet the requirements.

Summary of the invention

The purpose of the present invention is to solve the technical problem that the existing restoration method cannot meet the requirements of narrow pulse width and low repetition rate pulse laser measurement, and to provide a signal restoration method for measuring pulse laser based on array detection method.

To solve the above technical problems, the technical solutions provided by the present invention are as follows:

A signal recovery method for measuring pulsed laser based on array detection method, which is special in that it includes the following steps:

Step 1: irradiate a pulsed laser signal onto an array detector, wherein the array detector includes N photoelectric detectors arranged according to a certain mapping relationship, and is used to convert the pulsed laser signal into N pulsed electrical signals, where N is a positive integer;

Step 2: The array detector uses N charge integration circuits to respectively widen the N pulse electrical signals to obtain N pulse widened electrical signals, and in the widening process, generates N charge discharge curves corresponding to the N charge integration circuits respectively;

Step 3, asynchronously sampling the N pulse-stretched electrical signals to obtain N groups of sampled data;

Step 4, select M points from each set of sampled data as zero point measurement points to obtain M*N zero point measurement points, and determine a unique time zero point t ₀ according to the M*N zero point measurement points, where M is a positive integer;

Step 5, selecting one point on each of the N charge-discharge curves as a sampling point, to obtain N sampling points;

Step 6, calculating the response current i ₀ of each photodetector to the pulse laser signal through the N sampling points and the unique time zero point t ₀ ;

Step 7, calculating the light intensity I of the pulsed laser signal irradiating each photodetector according to the response current i ₀ of each photodetector to the pulsed laser signal;

Step 8, arranging the light intensities I on the N photodetectors one by one according to the mapping relationship with the N photodetectors, obtaining the power density distribution of the pulse laser signal, and then restoring the pulse laser signal.

Furthermore, the N charge integration circuits in step 2 are connected in series.

Furthermore, in step 2, each of the charge integration circuits is a first-order RC circuit, including a load R and an integration capacitor C, and the time constant of the charge integration circuit is defined as τ, then the time constant τ and the load R and the integration capacitor C satisfy the following relationship:

τ＝RC

The values of the load R and the integral capacitor C in each of the charge integration circuits are determined according to the following steps:

Step 2.1, define _Is as the saturation threshold of the photodetector, _Umax as the maximum output voltage of the photodetector, A as the area of the photosensitive surface of the photodetector, and _Re as the response rate of the photodetector. Then, the value of the load R in the corresponding charge integration circuit is calculated according to the following formula:

Step 2.2, substituting the value of the load R into τ=RC, calculating the value of the integral capacitor C in the charge integration circuit, and then determining the corresponding charge integration circuit.

Furthermore, determining the unique time zero point t ₀ in step 4 includes the following steps:

Step 4.1, arrange M*N equivalent measurement points in time sequence;

Step 4.2, compare M*N equivalent measurement points in sequence, and take the two equivalent measurement points where the zero signal turns into the pulse signal first as the zero point judgment criteria;

Step 4.3, select the equivalent measurement point that is earlier in time sequence in the zero point criterion as the time zero point t ₀ .

Furthermore, in step 6, the calculation formula of the photodetector's response current _i0 to the pulsed laser signal is:

Wherein, t ₁ represents the sampling time of the sampling point, U ₁ represents the output voltage of the photodetector at time t ₁ , (t ₁ , U ₁ ) represents the sampling point selected on the charge discharge curve, and w is the pulse width of the pulse electrical signal after the pulse laser signal is converted by the photodetector.

Furthermore, in step 7, the calculation formula for the light intensity I of the pulsed laser signal irradiated on the corresponding photodetector is:

Among them, α is the light intensity attenuation multiple.

Furthermore, in step 3, multiple photodetector channels are gated in time by using an analog multiplexer, thereby achieving asynchronous sampling of multiple photodetector channels, wherein all photodetectors are switched on once in each frame of sampling.

Furthermore, in step 5, the sampling points on the plurality of charge discharge curves are all selected from the curve portion on the charge discharge curve corresponding to the falling edge of the pulse stretching electrical signal.

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

1. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method, which converts the pulsed laser signal irradiated thereon into multiple pulse electrical signals through an array detector, and uses a charge integration circuit to respectively widen the multiple pulse electrical signals to obtain multiple pulse widened signals. In other words, the present invention widens the pulse signal through a charge integration circuit without changing the acquisition circuit, so that it can be applied to measuring narrow pulse width and low repetition rate signals.

2. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method, which realizes asynchronous sampling of multiple channels by adopting analog multi-way switch to select timing of multiple detector channels, determines time zero point by multiple groups of sampling data obtained by asynchronous sampling, and utilizes multi-frame rate data comparison optimization to minimize the uncertainty of time zero point.

3. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method. In the present invention, signal sampling only requires selecting one sampling point on the charge discharge curve. Compared with the signal sampling based on Nyquist sampling theorem in the prior art which requires at least two sampling points, the requirement for sampling frequency is effectively reduced, so that the sampling frequency requirement is reduced by at least two times.

4. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method. Compared with the prior art, which can only obtain the curve of laser signal power changing with time at the target surface when the sampling frequency is high, the present invention can obtain the change curve by simply calculating the light intensity data of the pulsed laser signal irradiated on each detector when the sampling frequency is low, and has a wide range of applications.

5. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method. Compared with the prior art that narrow pulse width and low repetition rate pulse signals require a higher sampling frequency, the present invention has the characteristic of low sampling frequency, so it can show greater advantages for narrow pulse width and low repetition rate pulse signals.

6. The present invention provides a signal recovery method for measuring pulsed laser based on array detection method, which can also be applied to the measurement of continuous laser signals. Its pulse period can be selected according to actual needs and has wide applicability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flowchart of an embodiment of a signal recovery method for measuring pulsed laser based on an array detection method provided by the present invention;

FIG2 is a schematic diagram of a charge discharge curve generated by the charge integration circuit corresponding to the pulse electrical signal in an embodiment of the present invention; wherein (a) is a schematic diagram of the waveform of the pulse electrical signal after the detector corresponds to the pulse laser signal conversion; (b) is a schematic diagram of the charge discharge curve;

FIG3 is a circuit diagram of a charge integration circuit according to an embodiment of the present invention;

FIG4 is a timing switching diagram of N detector channels in an embodiment of the present invention;

FIG. 5 is a schematic diagram showing a principle of determining the time zero point in an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The present invention provides a signal recovery method for measuring pulsed laser based on an array detection method. Referring to FIG. 1 , the method comprises the following steps:

Step 1: irradiate the pulsed laser signal onto an array detector, the array detector comprising N photoelectric detectors arranged according to a certain mapping relationship, for converting the pulsed laser signal into N pulsed electrical signals, where N is a positive integer;

In this embodiment, when the pulse laser signal is irradiated on the array photodetector, the power density distribution of the pulse laser signal presents differences in space, and the N photodetector channels in this embodiment can be expressed as [d ₁ , d ₂ , …, d _n ]. As shown in FIG. 2 (a), the waveform expression of each pulse electrical signal is:

Where _i0 is the response current of the photodetector to the pulse laser signal, u(t) is the step function, w is the pulse width of the pulse electrical signal, and T is the period of the pulse electrical signal.

Step 2: The array detector uses N charge integration circuits to respectively widen the N pulse electrical signals to obtain N pulse widened electrical signals, and in the widening process, generates N charge discharge curves corresponding to the N charge integration circuits, as shown in FIG2(b);

3 , in this embodiment, N charge integration circuits are connected in series, and the N charge integration circuits are all first-order RC circuits, including a load R and an integration capacitor C. The time constant of the charge integration circuit is defined as τ, and the time constant τ, the load R, and the integration capacitor C satisfy the following relationship:

τ＝RC

In order to achieve the broadening of multi-channel pulse electrical signals, it is necessary to first determine the charge integration circuit corresponding to each photodetector, that is, to determine the value of the load R and the integration capacitor C in each charge integration circuit. In this embodiment, the value of the load R and the integration capacitor C in each charge integration circuit is determined according to the following steps:

Step 2.1, define _Is as the saturation threshold of the photodetector, _Umax as the maximum output voltage of the photodetector, A as the area of the photosensitive surface of the photodetector, and _Re as the response rate of the photodetector. Then, the value of the load R in the charge integration circuit corresponding to the photodetector is calculated according to the following formula:

Step 2.2, according to the value of the load R in the charge integration circuit and τ=RC, the value of the integration capacitor C in the charge integration circuit is calculated, and then the charge integration circuit corresponding to the photodetector is obtained.

Furthermore, after completing the broadening of the multi-channel pulse electrical signals, the voltage across the load R in each charge integration circuit is calculated based on the above waveform expression and basic circuit knowledge:

In this embodiment, the discharge process of the charge integrator circuit is set to be terminated when the voltage reaches 1% of its peak value. Then, the following relationship is calculated based on the voltage expression across the load R:

Among them, U(T) is the output voltage of the photodetector at time T after the pulse laser outputs zero time, and U(w) is the output voltage of the photodetector at time W after the pulse laser outputs zero time. According to the above relationship, the relationship between the time constant τ and the pulse period T (T>>w, which can be ignored in the calculation) is calculated:

τ≈T/4.6

Of course, in other embodiments, the discharge cut-off voltage of the charge integration circuit can also be set to 2% of its peak voltage, or set to other values according to requirements. Then, according to the above calculation process, the relationship between the time constant τ and the period T (T>>w, which can be ignored during calculation) can still be calculated.

Step 3, asynchronously sampling the N pulse-stretched electrical signals to obtain N groups of sampled data;

4 , in this embodiment, an analog multi-way switch is used to perform a selection timing on multiple photodetector channels, thereby realizing asynchronous sampling of multiple photodetector channels, wherein all photodetectors are switched and selected once in each frame sampling, thereby ensuring that all sampling of the N-channel pulse stretching signals can be completed while realizing asynchronous sampling.

Step 4, select M points from each set of sampled data as zero point measurement points to obtain M*N zero point measurement points, and determine a unique time zero point t ₀ according to the M*N zero point measurement points, where M is a positive integer;

In this embodiment, determining a unique time zero point t ₀ includes the following steps:

Step 4.1, arrange M*N equivalent measurement points in time sequence;

Step 4.2, compare M*N equivalent measurement points in sequence, and take the two equivalent measurement points that first appear to transform from zero signal (ignoring the influence of noise) to pulse signal as zero point judgment criteria;

Step 4.3, select the equivalent measurement point that comes first in the time sequence in the zero point criterion as the time zero point t ₀ .

In this embodiment, the number of photodetector channels is N, as shown in FIG4 , _Ts is defined as the sampling period of the photodetector, and the number of sampling points on each photodetector channel is M, then the number of equivalent measurement points is M*N, and the equivalent measurement points are used to determine the time zero point, then the switching time interval between adjacent photodetector channels is:

As shown in FIG5 , according to the above calculation results, the peak voltage error caused by the zero position error can be expressed as:

In this embodiment, assuming that the peak voltage error does not exceed 1% of its peak voltage, the minimum value of the selected equivalent measurement points M*N can be calculated without exceeding the error, that is, when ΔU<1%, the value of M*N calculated is greater than 458, that is, the minimum value is 458. Based on the calculation result, the actual value of M*N is determined according to the actual error requirement, and the switching time interval between adjacent photodetectors can be obtained by calculation. Of course, in other embodiments, the peak voltage error can also be set to 3% of its peak voltage, or set to other values according to requirements. It should be noted that although in this embodiment, the discharge cut-off voltage in the charge integration circuit is set to 1% of its peak voltage, and its peak voltage error does not exceed 1% of its peak voltage, the above setting is only a preferred embodiment of the present invention. In other embodiments, it can also be set to other values, and the two settings are not related.

Step 5, selecting one point on each of the N charge-discharge curves as a sampling point, to obtain N sampling points;

In this embodiment, in order to obtain stable sampling data, the sampling point is usually selected from the curve portion of the charge discharge curve corresponding to the falling edge of the pulse stretching electrical signal.

Step 6, calculating the response current i ₀ of each photodetector to the pulse laser signal through the N sampling points and the unique time zero point t ₀ ;

In this embodiment, the calculation formula of the photodetector's response current _i0 to the pulse laser signal is:

Wherein, t ₁ represents the sampling time of the sampling point, U ₁ represents the output voltage of the photodetector at time t ₁ , (t ₁ , U ₁ ) represents the sampling point selected on the charge discharge curve, and the response current i ₀ of each photodetector to the pulse laser signal can be calculated in turn according to the above formula.

Step 7, calculating the light intensity I of the pulsed laser signal irradiating each photodetector according to the response current i ₀ of each photodetector to the pulsed laser signal;

In this embodiment, the calculation formula of the light intensity I of the pulse laser signal irradiated on the corresponding photodetector is:

Among them, α is the light intensity attenuation multiple. According to the above formula, the light intensity I of the pulsed laser signal irradiated on each photodetector can be calculated in turn.

Step 8, arranging the light intensities I on the N photodetectors one by one according to the mapping relationship with the N photodetectors, obtaining the power density distribution of the pulse laser signal, and then restoring the pulse laser signal.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. For ordinary professional and technical personnel in this field, the specific technical solutions recorded in the aforementioned embodiments can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims (5)

1. A signal recovery method for measuring pulsed laser based on array detection method, characterized in that it includes the following steps: Step 1: irradiate a pulsed laser signal onto an array detector, wherein the array detector includes N photodetectors arranged according to a mapping relationship, and is used to convert the pulsed laser signal into N pulsed electrical signals, where N is a positive integer; Step 2: The array detector uses N charge integration circuits to respectively widen the N pulse electrical signals to obtain N pulse widened electrical signals, and in the widening process, generates N charge discharge curves corresponding to the N charge integration circuits respectively; Step 3, asynchronously sampling the N pulse-stretched electrical signals to obtain N groups of sampled data; Step 4, select M points from each set of sampled data as zero measurement points to obtain M*N zero measurement points, and determine a unique time zero point t ₀ based on the M*N zero measurement points, where M is a positive integer; determining a unique time zero point t ₀ includes the following steps: Step 4.1, arrange M*N zero point measurement points in time sequence; Step 4.2, compare the M*N zero-point measurement points in sequence, and take the two zero-point measurement points that first appear to transform from zero signal to pulse signal as zero-point judgment criteria; Step 4.3, select the zero point measurement point that is earlier in the time sequence in the zero point criterion as the only time zero point t ₀ ; Step 5, selecting one point on each of the N charge-discharge curves as a sampling point, to obtain N sampling points; Step 6, respectively calculate the response current i ₀ of each photodetector to the pulse laser signal through the N sampling points and the unique time zero point t ₀ ; the calculation formula of the response current i ₀ of the photodetector to the pulse laser signal is: Wherein, t ₁ represents the sampling time of the sampling point, U ₁ represents the output voltage of the photodetector at time t ₁ , (t ₁ , U ₁ ) represents the sampling point selected on the charge discharge curve, w is the pulse width of the pulse electrical signal after the pulse laser signal is converted by the photodetector; R represents the load of the charge integration circuit, and C represents the integration capacitance of the charge integration circuit; Step 7, according to the response current i ₀ of each photodetector to the pulsed laser signal, respectively calculate the light intensity I of the pulsed laser signal irradiating each photodetector; the calculation formula of the light intensity I of the pulsed laser signal irradiating the corresponding photodetector is: Among them, α is the light intensity attenuation multiple; A represents the area of the photosensitive surface of the photodetector; Step 8, arranging the light intensities I on the N photodetectors one by one according to the mapping relationship with the N photodetectors, obtaining the power density distribution of the pulse laser signal, and then restoring the pulse laser signal. 2. A signal recovery method for measuring pulsed laser based on array detection method according to claim 1, characterized in that: the N charge integration circuits in step 2 are connected in series. 3. A signal recovery method for measuring pulsed laser based on array detection method according to claim 2, characterized in that: in step 2, each of the charge integration circuits is a first-order RC circuit, including a load R and an integration capacitor C, and the time constant of the charge integration circuit is defined as τ, then the time constant τ and the load R and the integration capacitor C satisfy the following relationship: τ＝RC The values of the load R and the integral capacitor C in each of the charge integration circuits are determined according to the following steps: Step 2.1, define _Is as the saturation threshold of the photodetector, _Umax as the maximum output voltage of the photodetector, A as the area of the photosensitive surface of the photodetector, and _Re as the response rate of the photodetector. Then, the value of the load R in the corresponding charge integration circuit is calculated according to the following formula: Step 2.2, substituting the value of the load R into τ=RC, calculating the value of the integral capacitor C in the charge integration circuit, and then determining the corresponding charge integration circuit. 4. A signal recovery method for measuring pulsed laser based on array detection method according to any one of claims 1-3, characterized in that: in step 3, multiple photodetector channels are selected in timing by using an analog multi-way switch to achieve asynchronous sampling of multiple photodetector channels, wherein all photodetectors are switched and selected once in each frame of sampling. 5. A signal recovery method for measuring pulsed laser based on array detection method according to claim 4, characterized in that: in step 5, the multiple sampling points on the charge discharge curve are all selected from the curve portion on the charge discharge curve corresponding to the falling edge of the pulse broadening electrical signal.