CN1804565A - Hartmann wave front sensor based on field offset of scanning galvanometer - Google Patents

Abstract

The field-of-view offset Hartmann wavefront sensor based on the scanning galvanometer comprises a light path beam-shrinking system, a micro-lens array, a CCD detector and a wavefront processor, and is characterized in that: and a scanning galvanometer with a view field deflection angle is arranged between the entrance pupil matching lens and the exit pupil matching lens of the optical path beam-shrinking system and in front of a beam-shrinking focus. The invention thoroughly changes the characteristic that the traditional Hartmann wavefront sensor can only detect the wavefront aberration of a pure target signal, so that the self-adaptive optical system has the capability of detecting the wavefront of the strong and weak target signals in the daytime, and the working efficiency is improved by three times of the original working efficiency.

Description

Visual field offset Hartmann wave front sensor based on scanning galvanometer

Technical field

The present invention relates to a kind of Wavefront sensor that is used for ADAPTIVE OPTICS SYSTEMS, particularly a kind of visual field offset Hartmann wave front sensor based on scanning galvanometer.

Background technology

The basic theories of adaptive optics just was mature on the whole before the eighties in 20th century in the world; At home, country 863 atmospheric optics laboratories by Jiang Wenhan academician leader, just finish the development and the hosting of whole adaptive optics theory in the nineties substantially and set up many covers ADAPTIVE OPTICS SYSTEMS, reached desirable Wavefront detecting, calibration result, the adaptive optics theory and the engineering of China are all walked in the prostatitis in the world.

Wavefront sensor is the core component of ADAPTIVE OPTICS SYSTEMS, it mainly finishes the high resolving power detection of incoming signal light being carried out Wave-front phase, carry out wavefront reconstruction before the signal wave according to certain wavefront reconstruction algorithm then, the wave-front corrector of giving the back carries out wavefront correction, to realize the raising of image quality; Wherein, Shack-Hartmann wave front sensor is to use at most, uses the most ripe Wavefront sensor in present ADAPTIVE OPTICS SYSTEMS; The principle content of this Hartmann sensor can be referring to " Adaptive Optics for Astronomy " D.M.Alloin and J.M.Mariotti.KluwerAcademic Publishers.1994. " Hartmann Sensers for Optical Testing " Robert J.Zielinski, B.Martin Levine, Brain MoNeil.SPIE Vol.314, P398,1997.The principle light path of tradition Hartmann wave front sensor is seen Fig. 1.

But up to the present, except the light laser adaptive optics, traditional ADAPTIVE OPTICS SYSTEMS all is to be operated in night, generally has only for 1/3rd working hour; Trace it to its cause, what mainly be that traditional Hartmann wave front sensor detects is the wavefront information of incident light, when if the more weak while bias light of incoming signal light ratio is more intense again, traditional Hartmann wave front sensor will no longer can be finished and extract the function that weak signal is carried out centroid calculation again from strong background; Therefore, existing ADAPTIVE OPTICS SYSTEMS by day in addition terminator all can't operate as normal and obtain the wavefront correction effect, like this, greatly reduce the work efficiency of ADAPTIVE OPTICS SYSTEMS, wasted the precious resources of expensive ADAPTIVE OPTICS SYSTEMS.

Because the existence of the problems referred to above has been arranged, in order to explore the possibility that daytime, ADAPTIVE OPTICS SYSTEMS was used, how extract signal wave under the strong by day daylight background before, and detect Wave-front phase information before the signal wave, just become a very important research project.

Summary of the invention

Technology of the present invention is dealt with problems: the traditional Shack-Hartmann wave front sensor that overcomes can not be by day or the shortcoming of working under the veiling glare condition of having powerful connections, a kind of visual field offset Hartmann wave front sensor based on scanning galvanometer that possesses adaptive optics Wavefront detecting ability on daytime is provided, carry out the detection of weak echo signal wavefront under its can be by day strong bias light condition, for ADAPTIVE OPTICS SYSTEMS work by day provides solution.

Technical solution of the present invention: based on the visual field offset Hartmann wave front sensor of scanning galvanometer, comprise light path contract beam system, scanning galvanometer and corresponding signal generator, microlens array, ccd detector and wave front processor, it is characterized in that: between described light path contracts the entrance pupil matched lenses and emergent pupil matched lenses of beam system, before the bundle focus that contracts a scanning galvanometer with visual field deflection angle is set.

Principle of the present invention: under the condition, the light signal that enters ADAPTIVE OPTICS SYSTEMS comprises strong daylight background and weak target light by day, utilizes difference the most essential between them " visual field is widely different " to finish the function of eliminating daylight background; In general, the target light visual field FOV1 that ADAPTIVE OPTICS SYSTEMS can be surveyed is very little, greatly about tens microradians, but the visual field FOV2 that has a strong impact on the background daylight of Wavefront detecting but is far longer than the target light visual field, can think only lambert's body of infinite expanding of background sky, thus the present invention to propose with " visual field offset " be that " based on the visual field offset Hartmann wave front sensor of scanning galvanometer " of basic functional principle solves this problem; Its principle is as back Fig. 2.Scanning galvanometer has three duties, and state 1 is a certain stationary state for galvanometer is in, this moment the light path proper alignment, flashlight enters CCD through after the reflection of galvanometer through field stop PD smoothly, simultaneously, bias light also enters CCD, CCD is in running order; State 2 is in the high-velocity scanning motion state for galvanometer, and this moment, the CCD mechanical shutter was closed, not received signal; State 3 is in another stationary state for galvanometer, this moment, light path was because there has been the skew of a small angle theta of galvanometer, thereby and make the target light of small field of view can not see through not imaging on CCD of field stop PD, but the bias light visual field is influenced by field stop enough greatly and not, as usual be imaged on the CCD, CCD is in running order; By the continuous switching of scanning galvanometer three duties, CCD is images acquired successively, carries out the signal pattern that Flame Image Process obtains removing background by wave front processor after whenever adopting two two field pictures; Carry out centroid calculation, wavefront reconstruction again, the final like this function of finishing ADAPTIVE OPTICS SYSTEMS Wavefront sensor on daytime.

The present invention compared with prior art has following advantage: the situation that the present invention makes traditional ADAPTIVE OPTICS SYSTEMS can only be operated in night is improved completely, working hour of ADAPTIVE OPTICS SYSTEMS is expanded near original three times, and work efficiency is brought up near original three times; In addition, the present invention can continue to use traditional technology substantially on making, and does not therefore need too much extra technical costs, and is convenient and practical.

Description of drawings

Fig. 1 is traditional Hartmann wave front sensor light channel structure synoptic diagram;

The visual field offset Hartmann wave front sensor light channel structure synoptic diagram that Fig. 2 proposes for the present invention;

The visual field offset Hartmann wave front sensor STRUCTURE DECOMPOSITION key diagram that Fig. 3 proposes for the present invention;

Input function waveform during the ideal operation of the high frequency sweep galvanometer that Fig. 4 proposes for the present invention;

Input function waveform during the real work of the high frequency sweep galvanometer that Fig. 5 proposes for the present invention;

Fig. 6 is the target and background mixed signal image that indoor confirmatory experiment of the present invention is gathered;

Fig. 7 is the background signal image that indoor confirmatory experiment of the present invention is gathered;

Fig. 8 is the echo signal image after indoor confirmatory experiment of the present invention is handled through visual field offset.

Embodiment

As shown in Figure 1, the light path that mainly comprises traditional adaptive optics Wavefront sensor contract beam system, scanning galvanometer and corresponding signal generator, microlens array, ccd detector and wave front processor, it carries out sub-aperture segmentation before utilizing microlens array to the signal wave of incident, light signal focuses on thereafter the CCD in each sub-aperture, utilizes CCD target surface energy distributions situation to carry out centroid position and calculates.Hartmann wave front sensor mainly is the position (x that calculates hot spot according to following formula (1) _i, y _i), the corrugated control information of detection full aperture:

$x_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{nm}}}$ $y_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{y}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{nm}}}---\left(1\right)$

In the formula, m=1～M, n=1～N are that sub-aperture is mapped to pixel region corresponding on the CCD photosensitive target surface, I _NmBe (n, the m) signal received of individual pixel-by-pixel basis, x on the CCD photosensitive target surface _Nm, y _NmBe respectively (n, m) the x coordinate of individual pixel and y coordinate.

Calculate the wavefront slope g of incident wavefront again according to formula 2 _Xi, g _Yi:

$g_{\mathrm{xi}}=\frac{\mathrm{\Δx}}{\mathrm{\λf}}=\frac{x_i-x_o}{\mathrm{\λf}}$ $g_{\mathrm{yi}}=\frac{\mathrm{\Δy}}{\mathrm{\λf}}=\frac{y_i-y_o}{\mathrm{\λf}}---\left(2\right)$

In the formula, (x ₀, y ₀) demarcate the spot center reference position that Hartmann sensor obtains for the standard flat ripple; During Hartmann sensor probing wave front-distortion, spot center is displaced to (x _i, y _i), finish the detection of Hartmann wave front sensor to signal.

In addition, in the actual Wavefront detecting, owing to the source of error that the systematic error especially inevitable noise of CCD photodetector self is brought, the I that CCD detected _NmIn fact not the energy of echo signal entirely, also comprise the noise energies such as black level of background miscellaneous light and CCD device, promptly have:

I _nm＝S _nm+B _nm (3)

S wherein _NmBe (n, the m) signal energy received of individual pixel-by-pixel basis, B on the photosensitive target surface _NmBe (n, m) the ground unrest energy received of individual pixel-by-pixel basis on the photosensitive target surface;

Therefore have:

$x_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{x}_{\mathrm{nm}}{S}_{\mathrm{nm}}+\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{x}_{\mathrm{nm}}{B}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{\mathrm{nm}}+\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{B}_{\mathrm{nm}}}=\frac{\mathrm{<figure-callout\; id="1"\; label="sbr"\; filenames="A20061001120000113.png"\; state="\{\{state\}\}">sbr</figure-callout>}}{1+\mathrm{sbr}}{x}_S+\frac{1}{1+\mathrm{sbr}}{x}_B---\left(4\right)$

Sbr in above-mentioned (4) formula is defined as the ratio of flashlight energy and non-flashlight energy (comprising veiling glare background and CCD device level and the summation of reading background energies such as noise);

From (4) formula as can be seen, the centroid position that actual Hartmann detected is the weighted mean value of effective target signal barycenter and background (comprising veiling glare background and CCD device dark background) barycenter, and weight is by the ratio sbr decision of flashlight with background energy; This just determined the principle constraint of traditional Hartmann's Wavefront detecting: sbr can not be too little or background energy can not be too big, if the too little background energy of sbr is too big, then the centroid position that is calculated by above-mentioned (4) formula is inevitable no longer accurate, therefore, the inevitable Wavefront detecting ability that no longer possesses weak echo signal under the strong daylight background of traditional Hartmann wave front sensor.

Shown in Fig. 2,3, the present invention mainly comprise light path contract beam system entrance pupil matched lenses 1, between entrance pupil matched lenses 1 and the emergent pupil matched lenses 4, scanning galvanometer with visual field deflection angle 2 (scanning galvanometer according to the input signal of signal generator 8 carry out work), field stop 3, the light path of bundle before the focus that contract contract emergent pupil matched lenses 4, microlens array 5, ccd detector 6 and the wave front processor 7 of beam system; Field stop 3 is mainly finished at scanning galvanometer and is produced the function of passing through that certain deflection angle limited the small field of view target light afterwards, field stop 3 for have certain thickness (about 1mm), the center has a precision to lead to the diaphragm of light circular hole, the diameter of its center hole will determine according to the total system design parameter, with ADAPTIVE OPTICS SYSTEMS commonly used at present is reference, and its central diameter is generally at 0.1-1mm.Before the bundle focus that contracts, add one scan galvanometer 2, can be at a high speed also play the effect of the catoptron of the direction of propagation that changes light back and forth deflection the time, scanning galvanometer 2 has the duty of three different phases, state 1 is in a certain stationary state for scanning galvanometer 2, this moment the light path proper alignment, flashlight enters ccd detector 6 through after the reflection of scanning galvanometer 2 through field stop 3 smoothly, simultaneously, bias light also enters ccd detector 6, and ccd detector 6 is in running order; State 2 is in the high-velocity scanning motion state for scanning galvanometer 2, and this moment, the CCD mechanical shutter was closed, not received signal; State 3 is in another stationary state for scanning galvanometer 2, this moment, light path was because there has been the skew of a small angle theta of scanning galvanometer, thereby and make the target light of small field of view can not see through not imaging on ccd detector 6 of field stop 3, but the bias light visual field is influenced by field stop 2 enough greatly and not, as usual be imaged on the ccd detector 6, ccd detector 6 is in running order.The control of three duties of above-mentioned high frequency sweep galvanometer 2 is finished to the control of its input waveform by signal generator fully; Fig. 4 is the work wave of required desirable scanning galvanometer 2, be the square-wave signal mode of operation, yet, in fact, scanning galvanometer is needing the time from a state 1 to state 3, be that it can not produce a drift angle and arrival state 3 completely immediately, therefore, Fig. 5 is the work wave of actual needs input.Obviously 0-t1 is a state 1, and t1-t12 is a state 2, and t12-t2 is a state 3.

The course of work of the present invention is as follows: the light signal that enters entrance pupil matched lenses 1 place is the weak echo signal of distortion and the mixed signal of strong expansion daylight background signal, they enter the beam system that contracts together, when scanning galvanometer 2 is in state 1, the target and background signal passes through field stop 3 together, enter the emergent pupil matched lenses 4 of the beam system other end that contracts again successively, enter ccd detector 6 photosurfaces after then entering microlens array 5, carry out light intensity position centroid detection; At this moment the mixed signal that receives on the ccd detector 6 for weak target and strong background, as shown in Figure 6, can see clearly that echo signal mixes with background signal basically, according to above-mentioned formula (4), obviously, can't from strong background signal, extract echo signal with traditional Hartmann's wavefront centroid detection method and carry out centroid position calculating; Therefore, between entrance pupil matched lenses 1 and emergent pupil matched lenses, be provided with the scanning galvanometer 2 that to do dither deflection.According to aforementioned state description to scanning galvanometer 2, in state 1, ccd detector 6 is in running order, and therefore, ccd detector 6 can collect the mixed signal of a frame target and background; Then, input service waveform according to signal generator, gated sweep galvanometer 2 finishes the back at state 1 and gets the hang of 2 at once, in the very short time (generally in 0.1ms), do laterally (or vertically with very high frequency of operation (generally more than the 2KHZ) immediately, according to the real work light path) scanning, bias angle theta of generation gradually, in state 2, ccd detector 6 is in closed condition, be that ccd detector 6 does not carry out any image acquisition work, finish the requirement of the given deflection angle θ that scanning galvanometer 2 reaches (deflection angle θ is generally at 0.5 ° to 1.5 °, and concrete size will be determined according to the real system parameter) like this up to state 2; After state 2 finishes, scanning galvanometer 2 gets the hang of 3, be that scanning galvanometer remains static for 2 this moments, relative status 1 has a known deflection angle θ, at this moment, because scanning galvanometer 2 has had a very little bias angle theta, FOV1 is generally very little in the target light visual field, and satisfies under the condition of FOV1＜θ, and target light will be blocked by the field stop of field stop 3, and can not enter emergent pupil matched lenses 4, therefore also just can not imaging on the photosurface of ccd detector 6; But, bias light visual field FOV2＞＞FOV1, therefore, bias light will be subjected to the influence of visual field offset angle θ hardly, and pass through emergent pupil matched lenses 3 as usual smoothly, then enter microlens array 5, enter the photosurface of ccd detector 6 then; Simultaneously, ccd detector 6 also enters duty, and beginning images acquired within the time of state 3; Referring to shown in Figure 7, for not having of collecting the image of target light, like this, ccd detector 6 has just been finished the collecting work of background image.

Like this, on aforementioned working foundation, two images that CCD collects have respectively been obtained, do a very simple correspondence image pixel then and subtract each other processing, the pure signal image of the daylight background influence that can be eliminated as shown in Figure 8, from the contrast of Fig. 8 and Fig. 6 as can be seen, the present invention has finished the function that extracts weak echo signal under the strong daylight background basically, obtained signal pattern more clearly, as shown in Figure 7;

At last,, utilize aforesaid formula (1) and formula (2) just can calculate wavefront average gradient in each sub-aperture very smoothly, form sub-array of apertures slope vector G according to the signal pattern that Fig. 8 obtains;

Restore algorithm basic principle according to pattern, utilize the good recovery matrix R of calculated in advance, according to pattern recovery matrix formula:

Z＝R*G (5)

According to (5) formula, can obtain the ZERNIKE matrix of coefficients Z of wavefront very soon, again according to the ZERNIKE matrix of coefficients the wavefront information of wavefront after launching on the unit circle promptly to obtain restoring, finally realize the Wavefront detecting function of weak echo signal under the strong background of adaptive optics on daytime.

Claims (5)

1, based on the visual field offset Hartmann wave front sensor of scanning galvanometer, comprise the light path chief components such as beam system, scanning galvanometer, signal generator, microlens array, ccd detector and wave front processor that contract, it is characterized in that: between described light path contracts the entrance pupil matched lenses and emergent pupil matched lenses of beam system, before the bundle focus that contracts a scanning galvanometer that can switch and produce on time certain visual field deflection angle at a high speed is set; The high speed optical scanning galvanometer will be according to the signal work of signal generator input, and galvanometer does not produce deflection when state 1, make target light and bias light pass through field stop imaging on CCD simultaneously, thereby CCD collects the image that a frame signal adds background; Scanning galvanometer carries out high speed deflection under the driving of input signal then, and this is a state 2; Get the hang of 3 after deflection is finished then, produced the visual field deflection angle of an appointment, utilize the visual field difference of target light and bias light, make target light deflect away from the limited field of field stop, only allow bias light smoothly by field stop imaging on CCD, thereby CCD collects the pure background signal of a frame, utilizes a two field picture behind the former frame figure image subtraction can finish the elimination function of bias light; And then utilize wave front processor to carry out centroid calculation, wavefront reconstruction, finally finish the operate as normal of ADAPTIVE OPTICS SYSTEMS on daytime.

2, the visual field offset Hartmann wave front sensor based on scanning galvanometer according to claim 1, it is characterized in that: the frequency of operation of described scanning galvanometer and working method decide by the input function waveform, it has three different duties, state 1 is a certain stationary state for scanning galvanometer is in, this moment the light path proper alignment, flashlight smoothly through after the reflection of galvanometer through entering CCD behind field stop and the microlens array, simultaneously, bias light also enters CCD, and CCD is in running order; State 2 is in the high-velocity scanning motion state for scanning galvanometer, and this moment, the CCD mechanical shutter was closed, not received signal; State 3 is in another stationary state for scanning galvanometer, this moment, light path was because there has been a skew θ of scanning galvanometer, thereby can not imaging on CCD and make that the target light of small field of view can not see through field stop, but the bias light visual field is influenced by field stop enough greatly and not, as usual be imaged on the CCD, CCD is in running order.

3, the visual field offset Hartmann wave front sensor based on scanning galvanometer according to claim 1 and 2 is characterized in that: the visual field deflection angle theta of described scanning galvanometer is 0.5 °～1.5 °.

4, the visual field offset Hartmann wave front sensor based on scanning galvanometer according to claim 1 is characterized in that: described field stop is to have the high-accuracy field stop that thickness, center have accurate logical light circular hole, and two field stop structures are identical.

5, the visual field offset Hartmann wave front sensor based on scanning galvanometer according to claim 4 is characterized in that: described center clear aperature guarantees accurate equal, and thickness is 0.8～1.2mm, and the diameter of the logical light circular hole in center is 0.1-1mm.

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