CN102042874B

CN102042874B - Far-field light beam quality measuring device based on light intensity modulator

Info

Publication number: CN102042874B
Application number: CN2010105355149A
Authority: CN
Inventors: 黄林海; 饶长辉; 姜文汉
Original assignee: Institute of Optics and Electronics of CAS
Current assignee: Institute of Optics and Electronics of CAS
Priority date: 2010-11-04
Filing date: 2010-11-04
Publication date: 2012-07-11
Anticipated expiration: 2030-11-04
Also published as: CN102042874A

Abstract

The invention relates to a far-field light beam quality measuring device based on a light intensity modulator, which consists of an imaging system, the light intensity modulator, a light intensity detector and a computer. The light beam is converged at the light intensity modulator through the imaging system, the light passing through the light intensity modulator enters the light intensity detector, is captured by the light intensity detector, and is finally output by the light intensity detector through the computer to reflect the numerical value of the light beam quality. The light beam quality is measured by combining the light intensity detector with the light intensity modulator, and the method has the characteristics of simple structure, easiness in manufacturing, high speed, high response sensitivity, high detection precision and the like; can be used as a performance evaluation index for real-time closed loop of a high-speed adaptive optical system.

Description

Far-field light beam quality measuring device based on light intensity modulator

Technical Field

The invention relates to a light beam quality measuring device, in particular to a far-field light beam quality measuring device based on a light intensity modulator.

Background

As is known, when the light intensity of an incident light beam is not uniform and the incident light intensity is weak, a conventional adaptive optics closed-loop method for detecting near-field phase distortion by using hartmann or the like cannot be used. Thus, Piotr Piatrou and m.j.booth et al were written in the article "beacon having stored parallel component gradient device scanner beam control: numerical experiments, APPLIED OPTICS, 46(27), 2007 "and" wave front sensorless adaptive OPTICS for large interference, OPTICS LETTERS, 32, 5(2007) "propose to achieve adaptive OPTICS closed loop with far-field light intensity. They propose a new evaluation index of beam quality in the literature and point out that the closed loop of the adaptive optics system can be accurately guided by using the new evaluation index to correct the phase distortion of the incident beam. In the literature, CCD is adopted to record far-field light intensity distribution, and then the new evaluation index is obtained by a software weighting method. The problems with this acquisition method are: on one hand, the detection speed of the general CCD is slower, and the acquired performance index interval is larger due to the necessary weighted operation time, so that the closed-loop bandwidth of the self-adaptive optical system formed by the method is necessarily smaller; on the other hand, the dynamic range of the CCD is small, the distribution difference of the detected light intensity before and after correction is large, and a light intensity saturated area or an area which is too small to detect easily appears, so that the performance index obtained by final calculation is inaccurate.

Currently, the hardware mode is used to realize the light beam quality evaluation index required by the above documents, namely

<math> <mrow> <mi>V</mi> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mi>R</mi> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msub> <mi>I</mi> <mi>in</mi> </msub> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>D</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>,</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mi>a</mi> <mo>)</mo> </mrow> </mrow> </math>

Wherein,

simple evaluation index calculations are only achieved with pinholes, e.g., Mikhail a. vorotsov, in the literature "Adaptive optics based on analog parallel storage: analysis and experimental evaluation, j.opt.soc.am.17, 1440, 2000 "utilizes pinhole hardware evaluation criteria to achieve high-speed adaptive optics closed loops. However, a simple evaluation index calculation is realized by using a pinhole, the hardware manner is essentially only a specific example of a light beam quality evaluation index solution manner given by equation (a), and research has been conducted in the literature, "point target imaging adaptive optics random parallel gradient descent algorithm performance index and convergence rate, optics report, 29(5), 2009" by old waves and the like, and it has been pointed out that the adaptive optics correction result is easy to fall into a local minimum value instead of meeting the global minimum value corrected to the optimal effect by taking surrounding energy (i.e. the evaluation index realized by the pinhole) as the performance index.

Disclosure of Invention

The device of the invention solves the technical problems that: the device overcomes the defects existing in the prior art when the beam quality evaluation index is acquired by using a CCD and software weighting method, overcomes the characteristic that the hardware evaluation index realized by using a pinhole is easy to fall into a local minimum value, provides a high-speed, sensitive, accurate and easy-to-realize beam quality measuring device, and is used for realizing high-speed real-time closed-loop control by matching with a self-adaptive optical system.

The invention relates to a far-field light beam quality measuring device based on a light intensity modulator, which solves the technical problems that the technical scheme is as follows: the imaging system, the light intensity modulator and the light intensity detector are sequentially arranged on the optical axis; the output end of the light intensity detector is connected with the data input and output end of the computer, and the imaging system converts the received incident beams into convergent beams; the light intensity modulator receives the convergent light beams with different light beam qualities and modulates the convergent light beams to generate output light beams with different energy sizes; the light intensity detector captures the modulated output light beam and outputs a numerical value reflecting the quality of the light beam; the computer collects the value output by the light intensity detector to reflect the quality of the light beam and displays the value on a display of the computer.

Wherein the modulation function D (r, theta) of the light intensity modulator is expressed as follows:

or

D = \{\begin{matrix} 1, & r_{2 k} < r < r_{2 k + 1} and    r < R \\ 0, & others \end{matrix}

Or

<math> <mrow> <mi>D</mi> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mn>1</mn> <mo>,</mo> </mtd> <mtd> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> </mrow> </msub> <mo><</mo> <mi>θ</mi> <mo><</mo> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mi>and r</mi> <mo><</mo> <mi>R</mi> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> </mtd> <mtd> <mi>others</mi> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

r, theta are polar coordinate systems with the front surface of the light intensity modulator as a plane; r is the radius of the effective detection area of the light intensity detector; r is_2kAnd theta_2kAre respectively the radial and angular design parameters of the light intensity modulator, and r is more than 0_2k＜R，0＜θ_2k< 2 π, k is a natural number.

Wherein, the imaging system consists of a single-chip lens or a plurality of lenses.

Wherein, the light intensity detector is one of a CCD detector, a photomultiplier tube, an avalanche diode or a PIN tube.

Compared with the prior art, the invention has the following advantages:

(1) the invention adopts the performance index proposed by M.J.Booth, corresponds to the first expression form of the modulation function D (r, theta), or corrects the performance index on the traditional pinhole beam quality evaluation index, and corresponds to the second and third expression forms of the modulation function D (r, theta), so that the beam quality evaluation index and the spot radius are in near-linear change, and the adaptive optics closed loop guided by the invention is not easy to fall into the local minimum.

(2) The invention can adopt three light intensity modulation functions D (r, theta) instead of the gradual change light intensity modulation functions provided by M, J, Booth and the like as the light intensity modulator, and the latter two light intensity modulation functions can be realized by micromachining technology, thus the process is simpler.

(3) Different from the traditional method for weighting and solving the light beam quality evaluation index by software (the light intensity distribution of a far field must be sampled by using a CCD with relatively low sensitivity), the invention uses the light intensity modulator, and the light energy output by the light intensity modulator already reflects the quality of the light beam, so that a photomultiplier, an avalanche diode and the like can be directly adopted as a detection device. Because the device adopts the detectors with high sensitivity, the detection of weak signals can be realized, and the device has high sensitivity;

(4) based on the third advantage, the invention adopts the photomultiplier, the avalanche diode and the like as the detection devices, so that the device does not need to calculate the detected light intensity again, and therefore, the detection speed of the device is greatly improved compared with the traditional software weighting implementation method; in addition, because the total energy of the incident light can be considered as constant, the total energy of the incident light intensity is properly adjusted, the incident light can be ensured to be in the dynamic range of the detector before and after correction, the problems of saturation and undetected detection when CCD is adopted for detection are avoided, and the detection accuracy is improved.

Drawings

FIG. 1 is a schematic diagram of the principle of an adaptive optics system of a far-field beam quality measuring device based on a light intensity modulator.

FIG. 2 is a graded light intensity modulator;

FIG. 3 is a circular intensity modulator;

fig. 4 is a radial type optical intensity modulator.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.

As shown in fig. 1, includes: the device comprises an imaging system 1, a light intensity modulator 2, a light intensity detector 3, a computer 4 and an adaptive optics wavefront correction device 5. The imaging system 1, the light intensity modulator 2 and the light intensity detector 3 are arranged on the optical axis in sequence; the output end of the light intensity detector 3 is connected with the data input and output end of the computer 4, and the imaging system 1 converts the received incident beams into convergent beams; the light intensity modulator 2 receives the convergent light beams with different light beam qualities and modulates the convergent light beams to generate output light beams with different energy sizes; the light intensity detector 3 captures the modulated output light beam and outputs a numerical value reflecting the quality of the light beam; the computer 4 collects the value output by the light intensity detector 3 to reflect the quality of the light beam and displays the value in the display of the computer 4.

An incident beam enters the imaging system 1 after passing through the self-adaptive optical wavefront correction device 5 and is focused at the light intensity modulator 2, light intensity distribution modulated by the light intensity modulator 2 enters the light intensity detector 3 and is captured by the light intensity detector 3, finally, detected light intensity data are input to the computer 4 by the light intensity detector 3, the computer 4 calculates a voltage value required by the wavefront corrector 5 according to the input data and drives the wavefront corrector 5 to correct incident wavefront, the above processes are repeated until the value output by the light intensity detector 3 meets the preset requirement, and the closed loop is stopped. The imaging system 1 is composed of a single lens or a plurality of lenses. The light intensity detector 3 is one of a CCD detector, a photomultiplier tube, an avalanche diode or a PIN tube.

The modulation effect of the light intensity modulator 2 on the incident convergent light intensity can be expressed by the following formula:

I_out(r，θ)＝I_in(r，θ)*D(r，θ)， (1)

in the formula I_outIs the modulated light intensity distribution; i is_inIs the incident light intensity distribution; r, θ are polar coordinate systems with the light intensity modulator 2 as a plane; d is a modulation function, an

Or

D = \{\begin{matrix} 1, & r_{2 k} < r < r_{2 k + 1} and   r < R \\ 0, & others \end{matrix}

Or

<math> <mrow> <mi>D</mi> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mn>1</mn> <mo>,</mo> </mtd> <mtd> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> </mrow> </msub> <mo><</mo> <mi>θ</mi> <mo><</mo> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mi>and r</mi> <mo><</mo> <mi>R</mi> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> </mtd> <mtd> <mi>others</mi> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

R is the radius of the effective detection area of the light intensity detector 3; k is a natural number; r is_2kAnd theta_2kAre the radial and angular design parameters of the light intensity modulator 2, respectively, and 0 < r_2k＜R，0＜θ_2k< 2 π, k is a natural number. FIG. 2, FIG. 3 and FIG. 4 are 3 examples of light intensity modulation functions D, respectively, and FIG. 2 is a graded light intensity modulator corresponding to a first expression of the modulation function; FIG. 3 is a circular intensity modulator, corresponding to a second expression of the modulation function; fig. 4 is a radial type light intensity modulator corresponding to a third expression of the modulation function.

Thus, the light beam quality evaluation index V output to the computer 4 via the light intensity detector 3 can be given by the following equation

<math> <mrow> <mi>V</mi> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mi>R</mi> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msub> <mi>I</mi> <mi>out</mi> </msub> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mi>R</mi> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msub> <mi>I</mi> <mi>in</mi> </msub> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>D</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

The light intensity modulator 2 can quantitatively reflect the light beam quality value based on the incident light intensityThe energy is kept unchanged or changed little. It is known that the distribution of the light spots after the incident light beam is focused is directly related to the phase distortion of the incident light beam, and the larger the phase distortion of the incident light beam is, the larger the distribution range of the light spots generated after the light beam is focused is. In order to quickly reflect the magnitude of the light beam quality, it is proposed to use the pinhole as a light intensity modulator to collect the energy at the center to reflect the energy concentration V of the focal spot_cThis process can be described as:

<math> <mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mo>=</mo> <munder> <mo>&Integral;</mo> <mi>d</mi> </munder> <msub> <mi>I</mi> <mi>in</mi> </msub> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </math>

where d is the light intensity modulator, i.e., the light passing region of the pinhole. To simplify the analysis process, the far-field light spots are assumed to be uniformly distributed, and the energy distribution of the light spots is represented by the following formula:

I_{in} = \frac{I_{sum}}{{r_{d}}^{2}} circ (r); - - - (4)

circ (r) is a circular domain function, and r ≦ r_d，I_sumIs the total energy of the spot; then

<math> <mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mn>1</mn> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>=</mo> <msub> <mi>I</mi> <mi>sum</mi> </msub> <mfrac> <mrow> <mi>π</mi> <msup> <msub> <mi>r</mi> <mn>1</mn> </msub> <mn>2</mn> </msup> </mrow> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mo>.</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow> </math>

Spot radius r_d≤R，r₁Is the radius of the light passing portion of the pinhole. It follows that the spot radius r is a function of_dIncrease of focal spot energy concentration V_cThe adaptive optics closed loop is distributed in a rapid descending trend, the result is consistent with the simulation result of the standing wave and the like, and the standing wave and the like also clearly indicate that when the performance index has the rapid descending change rule, the adaptive optics closed loop guided by the method is easy to fall into a local minimum value. In order to solve the problem, m.j.booth et al propose a new beam quality evaluation index V, namely:

<math> <mrow> <mi>V</mi> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mi>d</mi> </msub> </msubsup> <msub> <mi>I</mi> <mi>in</mi> </msub> <mrow> <mo>(</mo> <mi>r</mi> <mo>,</mo> <mi>θ</mi> <mo>)</mo> </mrow> <mo>*</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mfrac> <mi>r</mi> <mi>R</mi> </mfrac> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> </math>

similarly, substituting the formula (4) into the formula (6) to obtain a new beam quality evaluation index:

the light beam quality evaluation index V at the moment along with the radius r of the light spot can be easily found_dThe increase of the voltage is in a linear change trend, and the result is also consistent with the simulation result of the standing wave and the likeIt is also clear that the performance index with the linear change rule is used for guiding the adaptive optics closed loop to be not easy to fall into the local maximum value.

In order to obtain the linear variation relationship between the performance index and the spot radius, the linear relationship can be obtained by simply correcting the traditional pinhole type performance evaluator. We have known that the pinhole performance evaluation output is:

<math> <mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mn>1</mn> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>=</mo> <msub> <mi>I</mi> <mi>sum</mi> </msub> <mfrac> <mrow> <mi>π</mi> <msup> <msub> <mi>r</mi> <mn>1</mn> </msub> <mn>2</mn> </msup> </mrow> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>8</mn> <mo>)</mo> </mrow> </mrow> </math>

where circ (r) is a circular domain function, when we add several annuli in the radial direction of the light intensity modulator, the above equation becomes:

<math> <mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mn>1</mn> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>+</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <msub> <mi>r</mi> <mn>2</mn> </msub> <msub> <mi>r</mi> <mn>3</mn> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>+</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>+</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <msub> <mi>r</mi> <mrow> <mn>2</mn> <mi>k</mi> </mrow> </msub> <msub> <mi>r</mi> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> </mrow> </math>

wherein r is₁Is the radius of the central bore, r₂And r₃The inner radius and the outer radius of the first zone, respectively; r is_2kAnd r_2k+1Respectively refer to the inner radius and the outer radius of the k-th zone, and r_2k+1≤r_d。

If it is satisfied with

Then the above formula becomes

V_c＝I_sumπ(1-r_d/C) (10)

Wherein C is greater than r_dIs constant. Thus, we can obtain performance index characteristics similar to equation (7). For the same reason, the light-transmitting area, i.e., the umbrella-shaped light-transmitting area, can be increased appropriately in the angular direction of the light intensity modulator, and the angular direction of each area is from θ_2kTo theta_2k+1Radial direction from 0 to r_dSo as to correct the output of the original pinhole light intensity modulator as follows:

<math> <mrow> <msub> <mi>V</mi> <mi>c</mi> </msub> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mn>1</mn> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>+</mo> <msubsup> <mo>&Integral;</mo> <msub> <mi>θ</mi> <mn>2</mn> </msub> <msub> <mi>θ</mi> <mn>3</mn> </msub> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mi>d</mi> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> <mo>+</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>+</mo> <msubsup> <mo>&Integral;</mo> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> </mrow> </msub> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> </msubsup> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <msub> <mi>r</mi> <mi>d</mi> </msub> </msubsup> <mfrac> <msub> <mi>I</mi> <mi>sum</mi> </msub> <msubsup> <mi>r</mi> <mi>d</mi> <mn>2</mn> </msubsup> </mfrac> <mi>circ</mi> <mrow> <mo>(</mo> <mi>r</mi> <mo>)</mo> </mrow> <mi>rdrdθ</mi> </mrow> </math>

wherein, theta₂And theta₃The starting angle and the ending angle of the first umbrella-shaped light-passing area are respectively;

θ_2kand theta_2k+1Is the start angle and the end angle of the k-th umbrella-shaped light-passing region.

When in use

We can also get the performance index characteristics of equation (10).

The above description is for the purpose of implementing the invention and its embodiments, and the scope of the invention should not be limited by this description, and it will be understood by those skilled in the art that any modification or partial replacement without departing from the scope of the invention is intended to fall within the scope of the invention defined by the claims.

Claims

1. The far-field light beam quality measuring device based on the light intensity modulator is characterized by comprising an imaging system (1), the light intensity modulator (2) and a light intensity detector (3) which are sequentially arranged on an optical axis; the output end of the light intensity detector (3) is connected with the data input and output end of the computer (4), and the imaging system (1) converts the received incident beams into convergent beams; the light intensity modulator (2) receives the convergent light beams with different light beam qualities and modulates the convergent light beams to generate output light beams with different energy sizes; the light intensity detector (3) captures the modulated output light beam and outputs a numerical value reflecting the quality of the light beam; the computer (4) collects the numerical value output by the light intensity detector (3) and used for reflecting the quality of the light beam and displays the numerical value in the display of the computer (4);

the modulation function D (r, theta) of the light intensity modulator (2) is expressed as follows:

or

D = \{\begin{matrix} 1 & , r_{2 k} < r < r_{2 k + 1} and & r < R \\ 0 & , others \end{matrix}

Or

<math> <mrow> <mi>D</mi> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mn>1</mn> </mtd> <mtd> <mo>,</mo> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> </mrow> </msub> <mo><</mo> <mi>θ</mi> <mo><</mo> <msub> <mi>θ</mi> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </msub> <mi>and</mi> </mtd> <mtd> <mi>r</mi> <mo><</mo> <mi>R</mi> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mo>,</mo> <mi>others</mi> </mtd> <mtd> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

r, theta are polar coordinate systems with the front surface of the light intensity modulator (2) as a plane; r is the radius of an effective detection area of the light intensity detector (3); r is_2kAnd theta_2kAre respectively the radial and angular design parameters of the light intensity modulator (2), and r is more than 0_2k＜R，0＜θ_2k< 2 π, k is a natural number.

2. The far field beam quality measurement device based on the light intensity modulator as claimed in claim 1, wherein: the imaging system (1) is composed of a single lens or a plurality of lenses.

3. The far field beam quality measurement device based on the light intensity modulator as claimed in claim 1, wherein: the light intensity detector (3) is a CCD detector, or a photomultiplier, or an avalanche diode, or a PIN tube.