CN100573064C - Hartmann wave front sensor based on visual field offset of beam splitter prism - Google Patents

Abstract

A field-of-view offset Hartmann wavefront sensor based on a beam splitter prism comprises two optical path beam-reducing systems, two microlens arrays, two CCD detectors and a wavefront processor, wherein the two optical path beam-reducing systems share an entrance pupil transparent matching lens, the beam splitter prism with a field-of-view deflection angle is arranged in front of a beam-reducing focus, so that an optical path from the entrance pupil matching lens passes through two field-of-view diaphragms along two different directions and respectively and sequentially enters two exit pupil matching and the two microlens arrays to be imaged on the two CCD devices, the wavefront processor respectively processes image signals detected on the two CCD detectors to obtain target signals with background sky light eliminated, and then centroid calculation and wavefront reconstruction are carried out, and the normal work of a daytime self-adaptive optical system is finally completed. The invention enables the self-adaptive system to have the capability of weak target signal wave-front detection under the background of strong daylight in the daytime, and improves the working efficiency of the traditional Hartmann wave-front sensor to be nearly three times of the original efficiency.

Description

Visual field offset Hartmann wave front sensor based on Amici prism

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 of looking based on Amici prism.

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 causing echo signal to be submerged in the background signal 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 Amici prism 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 most crucial solution.

Technical solution of the present invention: a kind of visual field offset Hartmann wave front sensor based on Amici prism, comprise the combined optical path beam system that contracts, Amici prism, two microlens arrays, chief components such as two ccd detectors and wave front processor, combined optical path contract the shared entrance pupil matched lenses of beam system and make incident beam respectively by two independently the emergent pupil matched lenses be divided into contract bundle back output of two-beam, between entrance pupil matched lenses and two emergent pupil matched lensess, before the bundle focus that contracts an Amici prism with certain visual field deflection angle is set, make the light path of coming out from the entrance pupil matched lenses along two different directions by two field stops, after entering two emergent pupil matched lensess and two microlens arrays respectively, be imaged on two CCD devices, respectively the picture signal that detects on two ccd detectors is handled the echo signal of the background daylight that just can be eliminated by wave front processor, utilize wave front processor to carry out centroid calculation again, wavefront reconstruction is finally finished the operate as normal of ADAPTIVE OPTICS SYSTEMS on daytime.

The structure of described two microlens arrays and serviceability parameter are consistent as far as possible, generally get the microlens array of same batch of same model, are guaranteeing to guarantee the isoparametric consistance of its light absorption under the identical prerequisite of its sub-aperture number as far as possible.

Described two CCD are face battle array photodetector, and structure is identical, and performance parameter is consistent as far as possible.

Described field stop is to have the high-accuracy field stop that certain thickness, center have accurate logical light circular hole, and two field stop structures are identical, and especially its center clear aperature will guarantee accurate equating as far as possible; Generally about 1mm, the diameter of the logical light circular hole in center need be according to the ADAPTIVE OPTICS SYSTEMS parameter decision of reality for its thickness, and the logical light Circularhole diameter scope in general center is 0.1-1mm.

Principle of the present invention: under the condition, the light signal that enters ADAPTIVE OPTICS SYSTEMS comprises strong bias light 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 influence.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 bias light of Wavefront detecting but is far longer than the target light visual field, especially by day under the condition, 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 Amici prism " of basic functional principle solves this problem.Its principle as shown in Figure 2, first light beam that is directly seen through by Amici prism directly enters first microlens array, so the mixed signal for weak target and strong background that detects of first CCD; Enter second microlens array by second light beam of Amici prism reflection after through second field stop, survey by second ccd detector then, because the restriction of sub-aperture of Hartmann and field stop thereof, FOV1 is very little in the target light visual field, visual field FOV0 is suitable with the sub-aperture of Hartmann, about tens microradians, but the daylight can be thought lambert's body of infinite expanding, its visual field FOV2 is very big, even in ADAPTIVE OPTICS SYSTEMS, FOV2 is also than big many of FOV1, based on this principle, make second field stop under the condition that normal light path is aimed at, add a very little deflection angle theta to Amici prism, target light is deflected away from outside the visual field, the sub-aperture of Hartmann and do not detected by second ccd detector, and bias light is because the visual field very much not can be subjected to the influence of minimum visual field offset and imaging on second ccd detector in the same old way, what this ccd detector detected like this is exactly simple bias light signal, carry out just can the be eliminated echo signal of the background daylight of Flame Image Process by wave front processor, carry out centroid calculation again, wavefront reconstruction, the final like this operate as normal of finishing the ADAPTIVE OPTICS SYSTEMS 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 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;

Fig. 3 is light path of the present invention, device decomposition texture explanation synoptic diagram;

Fig. 4 is the target and background mixed signal image that indoor confirmatory experiment of the present invention is gathered;

Fig. 5 is the background signal image that indoor confirmatory experiment of the present invention is gathered;

Fig. 6 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 Hartmann wave front sensor contract beam system, microlens array, CCD 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 CCD3 ' 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 following 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, carry out wavefront by wave front processor again and handle.

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:

$x_i=\frac{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{nm}}{S}_{\mathrm{nm}}+\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{nm}}{B}_{\mathrm{nm}}}{\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{S}_{\mathrm{nm}}+\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{B}_{\mathrm{nm}}}=\frac{\mathrm{sbr}}{1+\mathrm{sbr}}{x}_S+\frac{1}{1+\mathrm{sbr}}{x}_B---\left(4\right)$

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);

Can it is evident that from above-mentioned (4) formula, the centroid position that actual Hartmann wave front sensor detected is the weighted mean value of effective target signal barycenter and background (comprise veiling glare background and CCD device level and read total background such as noise) barycenter, 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 (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.

As shown in Figure 2, the present invention is mainly by the combined optical path beam system that contracts, Amici prism and corresponding signal generator thereof with certain visual field deflection angle, two microlens arrays, two ccd detectors and wave front processor are formed, the combined optical path saturating matched lenses 1 of the shared entrance pupil of beam system that contracts, to reduce systematic error, between the saturating matched lenses 1 of entrance pupil and two emergent pupil matched lensess 4 and 4 ', before the bundle focus that contracts an Amici prism 2 with visual field deflection angle is set, make the light path of coming out from entrance pupil matched lenses 1 along two different directions by two field stops 3 and 3 ', after entering two 4 and 4 ' and two microlens arrays 5 of emergent pupil coupling and 5 ' respectively successively, be imaged on two ccd detectors 6 and 6 ', wherein two field stops 3 and 3 ' structure are identical, to reduce systematic error, two field stops 3 and 3 ' are for having certain thickness, the center has a precision to lead to the light circular hole, the diameter of circular hole designs needs and concrete calculating according to whole optical path, with ADAPTIVE OPTICS SYSTEMS commonly used at present is reference, field stop center hole diameter is generally in the 0.1-1mm scope, the center hole accuracy requirement of two diaphragms is very high, guarantee the visual field equal and opposite in direction that it limits, and the visual field size equals or approximately less than visual field, a sub-aperture of Hartmann wave front sensor, field stop 3 is mainly finished target light and bias light all is limited within the visual field, the sub-aperture of Hartmann with onesize visual field, the signal that ccd detector 6 is received is the resultant signal of target light and bias light, field stop 3 ' is mainly finished target light is limited in the function that allows bias light pass through smoothly simultaneously outside the visual field, sub-aperture, and the signal that ccd detector 6 ' is received is simple bias light signal; Two microlens arrays 5 ' and 5 ' structure are identical, to reduce systematic error, it realizes the sub-aperture segmentation to wavefront, the enterprising line position of CCD device that focuses on the back is then surveyed, adopt technology that lenticule realizes sub-aperture segmentation wavefront comparative maturity, application in traditional Hartmann wave front sensor is very general, and it is also very ripe to make lenticular micro-optic process technology now, therefore, the present invention proposes this new daytime, the adaptive optics Wavefront sensor was on element manufacturing, also do not need extra manufacturing technology cost; Two ccd detectors 6 and 6 ' structure and performance are identical, employing face battle array photodetector, its realizes that lenticule is divided into intensity signal behind the sub-aperture to carry out high precision photoelectric and survey, and carries out centroid position and surveys according to focusing on the energy distribution situation of luminous energy on the CCD target surface.

As shown in Figure 3, target of the present invention mainly is the detection of weak echo signal wavefront information under the strong daylight (expansion background), and its concrete job step is as follows:

At first, the mixed signal of the weak echo signal of distortion and strong expansion daylight background signal enters combined optical path shared entrance pupil matched lenses 1 place of beam system of contracting together, through Amici prism 2, according to P1: P2 (P1: P2=1: 1 or＞1: 1) splitting ratio carry out beam split, beam split ratio P1 partly enters field stop 3, because field stop 3 has been carried out light path aligning accurately in advance, therefore, echo signal and background signal light all enter microlens array 5 again after entering emergent pupil matched lenses 4 under the field stop restriction of field stop 3, like this, on ccd detector 6, receive be echo signal and background signal and resultant signal focal beam spot as shown in Figure 4.

Image according to collection shown in Figure 4 can it is evident that, echo signal mixes with background signal basically, according to (4) formula in the specific embodiment of the invention 1, obviously, can't from strong background signal, extract echo signal with traditional Hartmann's wavefront centroid detection method and carry out correct centroid position calculating;

So, the present invention is provided with an Amici prism 2 between entrance pupil matched lenses 1 and emergent pupil matched lenses 4, it according to self dichroism and the reflects one luminous energy enters the field stop 3 ' of another road light path, and then through emergent pupil matched lenses 4 ' and microlens array 5 ', survey by carrying out the wavefront intensity signal after the ccd detector 6 ' detection, if normally mix up in light path, under the condition of field stop 3 ' proper alignment, target light should be passed through field stop 3 ' very smoothly so, ccd detector 6 ' and ccd detector 6 ' will collect the same signal all this target and background and signal, like this will be to eliminating daylight background without any meaning.Therefore, the present invention considers that the maximum essential difference-visual field of bias light and target light is different, proposition makes Amici prism 2 do a very little deflection angle theta, and (θ need determine jointly according to the parameters of actual engineering system, with ADAPTIVE OPTICS SYSTEMS commonly used at present is reference, its angular range is generally at 0.5 ° to 1.5 °), be that the correspondence beam optical path gonglion that contracts is deflected away from outside the optical axis, target light is blocked by field stop 3 ' because the visual field is little, therefore do not go up imaging at ccd detector 6 ', and bias light visual field FOV2＞＞FOV1 target light visual field, therefore, bias light will be subjected to the bias effect of so small visual field and being imaged on the ccd detector 6 ' of doing as usual hardly, that detects on the ccd detector 6 ' like this will see shown in Figure 5 for there not being the pure background signal of echo signal.

Secondly, on aforementioned working foundation, obtained the image that ccd detector 6 and ccd detector 6 ' collect respectively, do an image respective pixel then and subtract each other processing, the pure signal image of the daylight background influence that can be eliminated as shown in Figure 6, from the contrast of Fig. 6 and Fig. 4 as can be seen, the present invention has finished the function that extracts weak echo signal under the strong daylight background basically, has obtained more clearly signal pattern as shown in Figure 6;

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. 6 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.

The above-described specific implementation process of the present invention is that the ratio at the transmitted light energy P1 of Amici prism and energy of reflection light P2 is P1: P2=1: the principle of carrying out under 1 the situation is set forth.In the real work, the transmitted light energy P1 of Amici prism 2 and the ratio P1/P2 of energy of reflection light P2 can not be 1 also, and its ratio is greater than 1 generally speaking, when P1/P2 ratio greater than 1 the time, can modulate by work (data sampling) frequency, can realize the visual field offset background subtraction function that the present invention proposes equally CCD6 '.

Suppose that P1/P2 ratio is R and R ≠ 1 o'clock, the data sampling frequency of CCD6 ' is modulated that the data sampling frequency that makes CCD6 and CCD6 ' is inconsistent and be respectively H1 and H2, and the data sampling frequency of supposition CCD and the time shutter T of self there are relation:

H*T=constant (constant) (6)

Guarantee that the data sampling frequency of modulation back two CCD and the beam split ratio of Amici prism have following relation:

$\frac{H1}{H2}=\frac{P1}{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2006100112010014H1.png"\; state="\{\{state\}\}">P</figure-callout>}2}=R---\left(7\right)$

According to (7) formula, can be when Amici prism transmitted light energy P1 and energy of reflection light P2 be unequal, data sampling frequency by modulation CCD6 and CCD6 ', can realize the function that the visual field offset background subtraction is handled equally, finish the function that the present invention proposes based on weak echo signal Wavefront detecting under the strong background of visual field offset Hartmann wave front sensor of Amici prism.

Claims (8)

1, based on the visual field offset Hartmann wave front sensor of Amici prism, it is characterized in that: comprise combined optical path contract beam system, Amici prism, two microlens arrays, two ccd detectors, wave front processor; Combined optical path contract the shared entrance pupil matched lenses of beam system and make incident beam respectively by two independently the emergent pupil matched lenses be divided into contract bundle back output of two-beam, between entrance pupil matched lenses and two emergent pupil matched lensess, before the bundle focus that contracts an Amici prism with visual field deflection angle theta is set, make the light path of coming out from the entrance pupil matched lenses along two different directions by two field stops that structure size is the same, after entering two emergent pupil matched lensess and two microlens arrays respectively successively, be imaged on two ccd detectors, respectively the picture signal that detects on two ccd detectors is carried out respective pixel by wave front processor and subtract each other the echo signal of handling the bias light that just can be eliminated, carry out centroid calculation again, wavefront reconstruction is finally finished the operate as normal of ADAPTIVE OPTICS SYSTEMS Wavefront detecting on daytime.

2, according to the described visual field offset Hartmann wave front sensor of claim 1, it is characterized in that: the visual field deflection angle theta of described Amici prism is 0.5 °～1.5 °.

3, according to claim 1 or 2 described visual field offset Hartmann wave front sensors, it is characterized in that: the transmitted light energy P1 of described Amici prism and the ratio of energy of reflection light P2 are P1: P2=1.

4, according to claim 1 or 2 described visual field offset Hartmann wave front sensors, it is characterized in that: the ratio P1 of the transmitted light energy P1 of described Amici prism and energy of reflection light P2: P2 ≠ 1 o'clock, data sampling frequency to two ccd detectors is modulated, thereby change the time shutter of ccd detector, with the identical purpose of bias light energy of two ccd detectors reaching its collection, and then realize that two two field pictures subtract each other.

5, visual field offset Hartmann wave front sensor according to claim 1 and 2 is characterized in that: the structure of described two microlens arrays and serviceability parameter are consistent.

6, visual field offset Hartmann wave front sensor according to claim 1 and 2 is characterized in that: described two CCD are face battle array photodetector, and structure is identical, the performance parameter unanimity.

7, visual field offset Hartmann wave front sensor according to claim 1 and 2 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.

8, visual field offset Hartmann wave front sensor according to claim 7 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.

Images