CN202133375U - Image motion detection imaging system based on optical joint transform correlator - Google Patents

Abstract

The utility model relates to an image motion detection imaging system based on an optical joint transform correlator. The system comprises a laser collimator, an amplitude modulation transmission type spatial light modulator, a phase modulation reflection type spatial light modulator, a Fourier transform lens and a CCD camera. The laser collimator, the amplitude modulation transmission type spatial light modulator and the phase modulation reflection type spatial light modulator are successively disposed on the same optical path. The Fourier transform lens is disposed on the reflected light path of the phase modulation reflection type spatial light modulator. The CCD camera and the Fourier transform lens are arranged on the same optical path. The utility model provides the image motion detection imaging system based on an optical joint transform correlator, which enables the sensitivity of defocus to the system to be eliminated an helps to improve the image motion detection stability of the system.

Description

Imaging system is surveyed in image drift based on optical joint transform correlator

Technical field

The utility model belongs to optical field, relates to a kind of imaging system, relates in particular to a kind of image drift based on optical joint transform correlator and surveys imaging system.

Background technology

In the imaging time shutter, if having relative motion between target and the camera, the so final image that obtains will blur and degrade.Have two kinds of approach can eliminate the influence of motion blur to picture quality: the first uses the digital image restoration algorithm to reach the purpose of removing motion blur, recovering image information through deconvolution; Second it is the image drift that relies on specific hardware to come real-Time Compensation to be produced in the imaging time shutter, thereby reaches the purpose of stable imaging.

No matter use which kind of mode, the accurate detection of image drift all is vital, because the accuracy that for software compensation method, can improve its image restoration is surveyed in image drift, then is the very crucial first step for the hardware compensating method.

Even to this day, existing numerous method is suggested the detection that is used for image drift and calculates, and optical joint transform correlator JTC (Joint Transform Correlator) is exactly one of them.Handling high-speed, high capacity and parallel processing because JTC has both had optical imagery, and had flexible, accurate, the programmable advantage of circuit control again, and therefore had very big application potential, is one of research focus of image drift field of detecting.

Image drift measuring process based on optical joint transform correlator JTC may be summarized to be:

1, high-speed CCD camera is gathered the image that two width of cloth of t and t+ Δ t constantly have relative image drift respectively, and is input in the amplitude type spatial light modulator according to the described arrangement form of formula ();

I (x, y)=f _t(x, y-a)+f _{T+ Δ t}(x+ δ x, y+a+ δ y) (one)

Wherein (x y) is the two-dimensional coordinate of image, and a representes the relative position of two width of cloth images on the spatial light modulator input face, and δ x and δ y are respectively the displacements on x and y direction between two width of cloth images.

2, the amplitude type spatial light modulator after the irradiation of laser alignment parallel beam, is accomplished for the first time Fourier transform by fourier transform lens as target source, and obtains the joint transform power spectrum by surveying the CCD camera, shown in (two):

${\left|T(u,v)\right|}^2={\left|F_t(u,v)\right|}^2+{\left|F_{t+\mathrm{\&Delta;\; t}}(u,v)\right|}^2+F_{t+\mathrm{\&Delta;\; t}}{F}_t^{*}\&CenterDot;\mathrm{Exp}\{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HDA0000070463680000011.png,HDA0000070463680000012.png"\; state="\{\{state\}\}">i</figure-callout>}2\mathrm{\&pi;}\&CenterDot;[\mathrm{U\&delta;\; x}+(2a+\mathrm{\&delta;\; y})v\left]\right\}$ (2)

U wherein, v is a Fourier transform frequency spectrum coordinate, F _t(u, v) and F _{T+ Δ t}(u v) corresponds respectively to f _tAnd f _{T+ Δ t}Frequency spectrum, * then representes complex conjugate.

3, joint transform power spectrum | T (u, v) | ²Be used as new input picture and be sent to once more in the amplitude type spatial light modulator, just can on the CCD camera, obtain simple crosscorrelation peak image by the fourier transform lens enforcement Fourier transform second time afterwards, shown in (three):

$C(x,y)=f_t\&CircleTimes;f_t+f_{t+\mathrm{\&Delta;t}}\&CircleTimes;f_{t+\mathrm{\&Delta;t}}$

$+f_t\&CircleTimes;f_{t+\mathrm{\&Delta;\; t}}*\mathrm{\&delta;}(x-\mathrm{\&delta;\; x},y-2a-\mathrm{\&delta;\; y})+f_{t+\mathrm{\&Delta;\; t}}\&CircleTimes;f_t*\mathrm{\&delta;}(x+\mathrm{\&delta;\; x},y+2a+\mathrm{\&delta;\; y})$ (3)

In formula (three), preceding two is image f _tAnd f _{T+ Δ t}The auto-correlation item, then two then corresponding to their simple crosscorrelation item.Can see that the position at simple crosscorrelation peak has comprised f _tAnd f _{T+ Δ t}Between relative displacement information.Therefore, accurately locate the position at cross-correlation peak by the barycenter extraction algorithm, the image drift between two width of cloth images just can be calculated.

Image drift detection based on JTC has very strong environmental suitability, goes for the situation of utmost point low signal-to-noise ratio, but when it come to arrives the CCD camera imaging, and out of focus is exactly the problem that can't avoid.

Adorn more not in placely, perhaps undue oscillation all can cause the CCD camera out of focus when receiving joint transform power spectrum and simple crosscorrelation peak image, to occur.Out of focus can cause the signal to noise ratio (S/N ratio) of cross correlation image to reduce, thereby influences the precision that barycenter extracts, and then has influence on the stability that image drift is surveyed.When positive Jiao of system, the simple crosscorrelation peak that obtains is very tangible, in case out of focus appears, thus the secondary peak that will in background, produce many falsenesses so causes interference to the position of extracting real simple crosscorrelation peak.

Tradition JTC has the CCD imaging process twice, so possibly introduce out of focus twice.

The utility model content

In order to solve the above-mentioned technical matters that exists in the background technology, the utility model provides a kind of system of eliminating to the sensitivity of out of focus and the image drift detection imaging system based on optical joint transform correlator that improves its image drift detection degree of stability.

The technical solution of the utility model is: the utility model provides a kind of image drift based on optical joint transform correlator to survey imaging system, and its special character is: said image drift based on optical joint transform correlator is surveyed imaging system and is comprised laser parallel light pipe, Modulation and Amplitude Modulation transmission-type spatial light modulator, phase modulation (PM) reflective spatial light modulator, fourier transform lens and CCD camera; Said laser parallel light pipe, Modulation and Amplitude Modulation transmission-type spatial light modulator and phase modulation (PM) reflective spatial light modulator are set in turn on the same light path; Said fourier transform lens is arranged on the reflected light path of phase modulation (PM) reflective spatial light modulator; Said CCD camera and fourier transform lens are arranged on the same light path.

The digital processing element that imaging system comprises that also being used to of linking to each other with the CCD camera implements digital Fourier transform and carry out image drift calculating is surveyed in above-mentioned image drift based on optical joint transform correlator.

The utility model has the advantages that:

The utility model provides a kind of image drift based on optical joint transform correlator to survey imaging system, and this system has proposed 2 improvement to out of focus to the influence of JTC image drift detection performance:

1) formula (three) the pairing second time of optical Fourier transformation is substituted by digital Fourier transform, thereby introduce the possibility of out of focus when having avoided obtaining simple crosscorrelation peak image once more;

2) system introduces a phase modulation (PM) reflective spatial light modulator before fourier transform lens.Including the maximal value that produces at random in the time dependent phase modulation (PM) that this spatial light modulator produces is the out of focus phase differential of W20.Research shows that in the short time interval, different random phase modulation will produce different simple crosscorrelation peak images.It is average that these simple crosscorrelation peak images are carried out spatial domain, and be that the basis is carried out barycenter and extracted with image drift and calculate with average cross correlation peak image, and the system that just can weaken greatly improves the degree of stability of image drift detection to the susceptibility of out of focus.

The utility model provides a kind of improved image drift and survey imaging system based on optical joint transform correlator JTC (Joint Transform Correlator).The maximum difference of surveying imaging system with existing image drift based on the JTC principle is: introduce digital processing element, optical Fourier transformation is replaced by digital Fourier transform for the second time, thereby has eliminated the possibility of secondary introducing out of focus; Added a phase type spatial light modulator before the fourier transform lens, and become when producing thus contain the phase modulation (PM) of out of focus phase differential at random.Through carrying out average treatment earlier corresponding to many groups simple crosscorrelation peak image of out of phase modulation; Carry out image drift afterwards on this basis and extract calculating; Just can reach and make image drift survey imaging system, thereby the degree of stability that image drift is surveyed strengthens the insensitive purpose of out of focus.

Description of drawings

Fig. 1 is the schematic diagram that imaging system is surveyed in novel image drift that the utility model proposes;

Fig. 2 is the comparison diagram of the utility model and traditional JTC image drift result of detection;

Wherein:

1-laser instrument parallel light tube; 2-Modulation and Amplitude Modulation transmission-type spatial light modulator; 3-phase modulation (PM) reflective spatial light modulator; The 4-fourier transform lens; The 5-CCD camera.

Embodiment

Referring to Fig. 1; The utility model provides a kind of image drift based on optical joint transform correlator to survey imaging system, comprises laser parallel light pipe 1, Modulation and Amplitude Modulation transmission-type spatial light modulator 2, phase modulation (PM) reflective spatial light modulator 3, fourier transform lens 4 and CCD camera 5; Laser instrument parallel light tube 1, Modulation and Amplitude Modulation transmission-type spatial light modulator 2, phase modulation (PM) reflective spatial light modulator 3, fourier transform lens 4 and CCD camera 5 are arranged in same light path successively.

The image drift based on optical joint transform correlator that the utility model provided is surveyed imaging system and is also comprised the digital processing element that links to each other with CCD camera 6, and this digital processing element is used to implement digital Fourier transform, and carries out image drift and calculate.

This image drift is surveyed imaging system and it is characterized in that: (1) at first obtains the joint transform power spectrum through an optical Fourier transformation, is entered into digital processing element afterwards and obtains cross correlation image through digital Fourier transform once again; (2) apart from loading a phase type spatial light modulator before the fourier transform lens, and the random phase modulation that contains the out of focus phase differential that becomes when introducing thus; In the short time interval; To average corresponding to several simple crosscorrelation peak images of different random phase modulation (PM); And serve as that the image drift vector is extracted on the basis with average cross correlation peak image, just can make system become insensitive, and then strengthen the degree of stability of image drift detection out of focus.

Survey in the imaging system in this image drift; Random phase by phase type spatial light modulator is introduced is modulated; It is characterized in that: the phase modulation (PM) intensity of each point in its two-dimensional phase Jacobian matrix all be by the small random perturbation of identical fixed value stack and at random the out of focus phase differential obtain, as follows:

f(x，y，t)＝α+β·rand(x，y，t)+W ₂₀·γ(t)·(x ²+y ²) |x|，|y|＜1 β＜＜α

In the formula, α is the phase modulation (PM) intensity of fixing, and β is a random perturbation intensity, W ₂₀Be the maximum defocus coefficient of phase difference, t is a time variable, and rand representes even distribution probability density function, and it is worth between 0～1.γ also is that a probability density function meets equally distributed stochastic variable, the phase differential of out of focus at random that becomes during in order to generation.X and y are the coordinate after the phase type spatial light modulator place plane normalization.

The principle framework that imaging system is surveyed in the improved image drift based on optical joint transform correlator JTC that the utility model proposed is as shown in Figure 1.The basic difference of surveying imaging system with traditional JTC image drift is 2 points: first native system only comprises the optical Fourier transformation process one time; After having obtained the joint transform power spectrum, directly it is sent into digital processing element and obtain cross correlation image through digital Fourier transform.It two is to introduce one by computer-controlled phase type spatial light modulator 3 before the fourier transform lens, distributes in order to produce the random phase that suppresses the out of focus aberration.

In Fig. 1, the 1st, the laser parallel light pipe is used to produce the one-wavelength laser behind the collimator and extender; Unit 2 is Modulation and Amplitude Modulation transmission-type spatial light modulators, is transfused to behind the image as target source; Unit 3 is phase modulation (PM) reflective spatial light modulators, the random phase modulation that includes the out of focus phase differential that becomes during in order to generation; Unit 4 is fourier transform lenses, is used to accomplish the final simple crosscorrelation peak image that obtains of optical Fourier transformation; Unit 5 is high-speed CCD cameras, is used to receive the joint transform power spectrum.After obtaining the joint Power spectrum, it is sent into digital processing element, obtain simple crosscorrelation peak image through digital Fourier transform, and then calculate corresponding image drift size.Wherein, amplitude type spatial light modulator 2, phase modulation (PM) reflective spatial light modulator 3 and fourier transform lens 4 are under the prerequisite that keeps its effective physical separation, and be as close as possible to reduce the volume of total system.

The phase modulation (PM) intensity of each point in the two-dimensional phase Jacobian matrix that phase modulation (PM) reflective spatial light modulator 3 is introduced all be by the small random perturbation of identical fixed value stack and at random the out of focus phase differential obtain, as follows:

f(x，y，t)＝α+β·rand(x，y，t)+W ₂₀·γ(t)·(x ²+y ²) |x|，|y|＜1 β＜＜α

In the formula, α is the phase modulation (PM) intensity of fixing, and β is a random perturbation intensity, W ₂₀Be the maximum defocus coefficient of phase difference, t is a time variable, and rand representes even distribution probability density function, and it is worth between 0～1.γ also is that a probability density function meets equally distributed stochastic variable, the phase differential of out of focus at random that becomes during in order to generation.X and y are the coordinate after the phase type spatial light modulator place plane normalization.

When the use JTC system that the utility model proposed carries out the image drift detection; Its crucial part is: at first collecting the time interval through preposition high speed image deriving means is two width of cloth images in the Δ t, afterwards it is combined into an integral body according to formula () and is input in the amplitude type spatial light modulator as new image; Require phase type spatial light modulator in the Δ t time, to produce many groups randomly simultaneously and comprise the phase modulation (PM) of out of focus phase differential at random with higher speed.

In theory; In the Δ t time, use more cross correlation images to average corresponding to the out of phase modulation; Inhibition effect to out of focus will be good more so, but like this to device, especially the requirement of phase type spatial light modulator will become very harsh.For instance; If the frame per second of preposition high-speed image sampling device is 80Hz; That is to say that Δ t is 12.5ms, hypothesis will produce 25 groups of cross correlation images corresponding to out of phase modulation so, the refreshing frame per second and must reach 2000Hz and can meet the demands of phase type spatial light modulator.If the frame per second of preposition harvester rises to 300Hz, still need simultaneously 25 width of cloth cross correlation images, the refresh rate of phase type spatial light modulator just must reach 7500Hz and just can meet the demands so.Research shows that the random phase modulation that is produced by phase type spatial light modulator is not constantly all to have the inhibition ability to out of focus at each, even the PHASE DISTRIBUTION of a certain pattern just can suppress enough interior out of focus on a large scale.Therefore, in fact do not need phase type spatial light modulator in the Δ t time interval, constantly to change its PHASE DISTRIBUTION state with so high frequency.Like this; Further promote when catching that more the image drift of high frequency changes (such as above-mentioned 300Hz) in the frame per second of preposition image collecting device; If only require to use 5 groups of simple crosscorrelation peak images to average processing, if so the refreshing frequency of phase type spatial light modulator to reach 1500Hz just passable.Investigation shows, existing phase type spatial light modulator (like the product of U.S. BNS company) its when adopting the PCIE bus to communicate, can reach more than the 1600Hz easily, and along with technology maturation gradually, its speed can further improve.The measurement result of tradition JTC representes that with the blue dot line measurement result of novel JTC is represented with red solid line.The scope of the out of focus phase differential that random phase comprised that is wherein produced by phase type spatial light modulator is 0～30 π.Shown in Fig. 2 .1-2.4, wherein ordinate is the image drift size respectively for its level and vertical image drift measurement result, and horizontal ordinate is that image is to index number.Fig. 2 .1 and Fig. 2 .2 have used 25 groups of simple crosscorrelation peak images corresponding to the different random phase modulation (PM), and Fig. 2 .3 and Fig. 2 .4 have then only used 5 groups.Shown in Fig. 2 .3 and Fig. 2 .4, wherein only used 5 groups of simple crosscorrelation peak images, also reach comparatively desirable out of focus and suppressed effect.

Can know that by Fig. 2 when simulating the out of focus phase differential of 0～30 π through phase type spatial light modulator, image drift result of calculation that the JTC system that the utility model proposed is obtained and reference data are coincide very goodly.Therefore; At first through before fourier transform lens, loading a phase type spatial light modulator; And the random phase that becomes when producing thus modulation, use several cross correlation images to average the inverting of handling and implementing the image drift amount simultaneously afterwards corresponding to the out of phase modulation, just can improve performance greatly based on JTC image drift detection imaging system; Make it insensitive, carry out the stability that image drift is surveyed thereby improved the JTC system to out of focus.So the proposition of the utility model is useful replenishing for the development of JTC image drift detection system.

Claims (2)

1. imaging system is surveyed in the image drift based on optical joint transform correlator, it is characterized in that: said image drift based on optical joint transform correlator is surveyed imaging system and is comprised laser parallel light pipe, Modulation and Amplitude Modulation transmission-type spatial light modulator, phase modulation (PM) reflective spatial light modulator, fourier transform lens and CCD camera; Said laser parallel light pipe, Modulation and Amplitude Modulation transmission-type spatial light modulator and phase modulation (PM) reflective spatial light modulator are set in turn on the same light path; Said fourier transform lens is arranged on the reflected light path of phase modulation (PM) reflective spatial light modulator; Said CCD camera and fourier transform lens are arranged on the same light path.

2. imaging system is surveyed in the image drift based on optical joint transform correlator according to claim 1, it is characterized in that: the digital processing element that imaging system comprises that also being used to of linking to each other with the CCD camera implements digital Fourier transform and carry out image drift calculating is surveyed in said image drift based on optical joint transform correlator.

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