CN102620669B - Method and device for measuring pixel pitch of image sensor by utilizing constant moving point target - Google Patents
Method and device for measuring pixel pitch of image sensor by utilizing constant moving point target Download PDFInfo
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Abstract
A method and a device for measuring pixel pitch of an image sensor by utilizing a constant moving point target belong to the field of length, width or thickness measurement characterized by applying an optical method. The method for measuring the pixel pitch of the image sensor by utilizing the constant moving point target includes: acquiring a linear image by implementing an image formation when the point target constantly moves, searching for a value range of the pixel pitch in a frequency domain, and calculating to obtain the pixel pitch by utilizing a genetic algorithm according to the fact that an contact ratio between a practical modulation transfer function curve which is related to the pixel pitch and a theoretical modulation transfer function curve is the best under least squares conditions. Sliding blocks bearing the point target in the device for measuring the pixel pitch of the image sensor by utilizing constant moving point target is arranged on a first guide rail and a second guide rail, a controller controls the sliding block to uniformly move on the first guide rail while controlling the sliding block to move on the second guide rail, and the movements of the sliding blocks are matched with each other so that the point target is subjected to quasi focal imaging to the surface of the image sensor during motion . By adopting the method for measuring the pixel pitch of the image sensor by utilizing the constant moving point target, error among single measurement results can be reduced so that repeatability of the measurement results can be improved.
Description
Technical field
It is for the field of gauge length, width or thickness in the metering outfit field of feature that the image sensor pixel measurement method for distance that adopts at the uniform velocity moving point target and device belong to adopt optical means, relate in particular to a kind of linear uniform motion pointolite that utilizes for target, at frequency domain, utilize at the uniform velocity measuring method and the device of moving image modulation transfer function measurement image sensor pixel spacing.
Background technology
Image sensor pixel spacing is the very important technical indicator in precision measurement field.For example, a known target of size is passed through to optical system imaging, according to target as shared image sensor pixel number, and pel spacing, can know the size of target picture, finally by size and the target size of target picture, be business, just can demarcate the lateral magnification of this optical system; In addition, piece image is carried out to spectrum analysis, only know pel spacing, just may accurately obtain the frequency spectrum of this image.
Yet, the product description of a lot of imageing sensors, has only provided the pixel dimension of imageing sensor, and has not provided pel spacing, as the MV-1300UM type industrial digital camera of Shaanxi dimensional view picture, it is 5.2 μ m * 5.2 μ m that product description has only been given the size of pixel; The IR113 type non-refrigeration focal surface movement of Wuhan Gao De and for example, its pixel dimension is 25 μ m * 25 μ m, although provide fill factor, curve factor > 80%, still cannot obtain pel spacing according to a uncertain fill factor, curve factor numerical value simultaneously.If the frequency spectrum that we utilize above-mentioned imageing sensor to go to demarcate the lateral magnification of optical system or obtain certain image, pel spacing must become technical bottleneck.So it is very important that the pel spacing of measurement image sensor seems.
One, image sensor pixel measurement method for distance background technology
For the measuring method of image sensor pixel spacing, what first expect is exactly in theory, can utilize one to project to image sensor surface and the known linear image of length, and the number of pixels covering divided by this linear image, obtains pel spacing.In the ideal situation, this method has following two features:
1) pixel line source being covered completely, its gray-scale value is as benchmark gray-scale value.
2) edge pixel that can not cover completely for line source, according to the ratio of its gray-scale value and benchmark gray-scale value, judge can cover part scale.
Yet this method but has inevitable disturbing factor, have a strong impact on the accuracy of measurement result.
1) if the pixel covering is completely saturated, gray-scale value will keep 255 constant, gray-scale value between the pixel of the edge pixel that can not cover completely and covering completely will no longer have proportionate relationship, and the ratio judgement of edge pixel that line source covers just there will be mistake.
2) in the process of line source imaging, be bound to the to have powerful connections impact of light, random noise and imageing sensor dark current, is subject to the impact of these disturbing factors, the pixel that can make line source cover completely, gray-scale value is not identical yet, will bring difficulty to the judgement of benchmark gray-scale value like this.
Although these shortcomings can increase the length of line source in theory, by sharing error equally by more pixel, made up, the length that increases line source also can be brought new problem:
1) for the large optical lens of distortion, increase the length of line source, may make line source picture that serious deformation occurs in length, in this case, not only can not share error equally, and can make on the contrary the error in judgement of number of pixels larger.
2), in optical system debug process, can make imageing sensor there is different responses to the target of same intensity under different visual fields.Increased so again the judgement of benchmark gray-scale value.
Just because of this method, have above-mentioned a series of problem, therefore, in actual mechanical process, this method is seldom used, and the substitute is another a series of method.
In April, 2005, College of Military Engineering journal the 17th volume < < that publishes an article for No. 2 measures the pel spacing > > of ccd image acquisition system based on Joint Fourier Transformation, the method that a kind of method that utilization carries out twice Fourier transform to centrosymmetric two square target is tried to achieve image capturing system pel spacing introduced in this piece of article.First the method exports centrosymmetric two square-shaped image in spatial light modulator, by fourier lense imaging, obtains the power spectrum of this width image on CCD surface | S (u, v) |
2, this power spectrum obtains real power spectrum after image capturing system amplifies p times | S ' (u ', v ') |
2; To respectively | S (u, v) |
2compose with real power | S ' (u ', v ') |
2again be presented in spatial light modulator, by fourier lense re-imaging, scheme electric acquisition system and amplify, obtain respectively | S (u, v) |
2power spectrum o (ξ, η) and | S ' (u ', v ') |
2power spectrum o (ξ ', η '), here, o (ξ ', η ') and o (ξ, be η) brighter square centered by all, symmetry is relatively darker square pattern in both sides, center, and o (ξ ', η ') after doubly amplifying, p is exactly o (ξ, η), therefore, o (ξ, η) shared image capturing system pixel count D be o (ξ ', η ') p of shared image capturing system pixel count D ' doubly, so, can utilize the ratio of D and D ' to calibrate the enlargement ratio p of image capturing system; After p value is determined, | S ' (u ', v ') |
2with o (ξ ', η ') can determine in succession, just can obtain the distance d ' between two squares in o (ξ ', η '), finally utilize d '/D ' to obtain the pel spacing of ccd image acquisition system.The shortcoming of this method is: o (ξ, η) and o (ξ ', η ') all can not guarantee that square just in time covers in a pixel of ccd image acquisition system just, and very greatly may be across two pixels, this will bring difficulty to the judgement of D and D ', during judgement, all easily there is ± 1 error, thereby make the calibration result of the enlargement ratio p of ccd image acquisition system have error, and then have influence on o (ξ ', η ') judgement of the spacing d ' of two specks in, owing to having utilized d '/D ', so can make the judgement of ccd image acquisition system pel spacing have inevitable error.
In Dec, 2005, the CCD pel spacing of No. 6 < < that publishes an article of College of Military Engineering journal the 17th volume based on circular hole Fraunhofer diffraction demarcated > >, and a kind of method of utilizing Fraunhofer diffraction distribution plan to demarcate CCD pel spacing introduced in this piece of article.The method utilizes directional light to irradiate the circular hole that is placed in collimator objective focal length place, forms the Fraunhofer diffraction distribution plan of circular hole on collimator objective surface, and this distribution plan, through the parallel ejaculation of collimator objective, incides the picture that CCD surface forms this Fraunhofer diffraction distribution plan.According to the diameter a of circular hole, incident light wave length λ, and collimator objective focal distance f, can obtain central bright spot diameter L=1.22f λ/a in circular hole Fraunhofer diffraction distribution plan, again according to the number N of the shared CCD pixel of diameter of central bright spot in Fraunhofer diffraction distribution plan ', the pel spacing that obtains CCD is δ '=L/N '.The shortcoming of this method is: the edge that can not guarantee central bright spot just in time drops in a pixel of CCD, and very greatly may be across two pixels, this just brings difficulty to the judgement of the shared CCD number of pixels of central bright spot diameter N ' in Fraunhofer diffraction distribution plan, easily there is ± 1 error, make the judgement of CCD pel spacing have inevitable error.
In June, 2008, No. 6 < < that publishes an article of photon journal the 37th volume utilizes the pel spacing > > of TFT-LCD pixel mechanism diffraction test ccd image acquisition system, and a kind of principle and method of utilizing Thin Film Transistor-LCD (TFT-LCD) test ccd image acquisition system pel spacing introduced in this piece of article.The method is first by TFT-LCD formation square signal, according to TFT-LCD pixel region printing opacity, the lighttight characteristic in non-pixel region, can be regarded as one by the two-dimensional grating of orthogonal two Periodic Rectangular optical grating constitutions, be placed on the front focal plane of fourier lense, on the back focal plane of this fourier lense, can obtain the spectrum intensity distribution plan of two-dimensional grating.This frequency spectrum profile is multistage spectrum distribution form, wherein, areal coordinate initial point place is composed in being centered close to of zero level frequency spectrum, the distribution form of each senior frequency spectrum and width are identical with zero level frequency spectrum, but the rising of intensity level time and reducing rapidly, according to m level frequency spectrum center to the distance of initial point is | m λ f/d|.By ccd image acquisition system, gather this two-dimensional grating spectrum intensity distribution plan, and arrive the shared pixel count N of initial point according to m level frequency spectrum center
m, the pel spacing that can obtain ccd image acquisition system is | m λ f/dN
m|.This method also has with the identical shortcoming of above prior art: can not guarantee that zero level frequency spectrum and m level frequency spectrum center just in time drop in a pixel of CCD, therefore, N
mthere will be equally ± 1 error, make the judgement of ccd image acquisition system pel spacing have inevitable error.In order to solve N
mhave the problem of ± 1 error, adopted a kind of method of averaging of repeatedly measuring in literary composition, in the situation that not considering enlargement factor, the pel spacing of the ccd image acquisition system of trying to achieve is:
The method is alleviated N to a certain extent
m± 1 error problem.
In October, 2008, photoelectric technology application the 29th volume CCD pel spacing that < < interferes based on double direction shear of publishing an article for No. 5 is demarcated > >, and this piece of article introduced and a kind ofly by double direction shear, interfered the relativeness of two half-court widths of fringe to measure the method for ccd image acquisition system pel spacing.The method is irradiated wedge-shaped mirrors W by directional light, and the reflected light on the forward and backward surface of wedge-shaped mirrors W is because the effect of wedge-shaped mirrors W forms the shearing of x axle forward, then through mirror M
1the rear transmission of reflection is crossed wedge-shaped mirrors W and is imaged on ccd detector, and the width of fringe of this Shearing interference fringes is d
1=λ R/ (s+2n β R), wherein, d
1=N
1q; Meanwhile, the transmitted light on the forward and backward surface of wedge-shaped mirrors W is through mirror M
2after reflection, incide again wedge-shaped mirrors W upper, form the shearing of x axle negative sense, the width of fringe of this Shearing interference fringes is d
2=λ R/ (s+2n β R), wherein, d
2=N
2q.These two equations are all the equations about CCD pel spacing q, radius R, shearing displacement s, and these two equations are formed to system of equations, and the expression formula that can obtain ccd image acquisition system pel spacing is:
Wherein, the wavelength that λ is incident light wave, n is the refractive index of wedge-shaped mirrors W, β is the angle of wedge of wedge-shaped mirrors W, all can be given by calibration system; N
1, N
2be respectively the pixel count of the adjacent Shearing interference fringes ccd image sensor that width covers of the positive negative sense of x axle, by N
1, N
2measurement, can obtain ccd image acquisition system pel spacing q.The shortcoming of this method is: can not guarantee that adjacent stripes covers in a pixel of CCD just, therefore, N
1, N
2all there will be ± 1 error, make the judgement of ccd image acquisition system pel spacing have inevitable error.
The common trait of these four kinds of methods is above:
1) in image sensor surface, form all known figures of a shape and size;
2) figure has obvious boundary characteristic;
3) boundary position of figure is thought in the center of graphic limit institute respective pixel.
Than desirable measuring method, the advantage of this serial of methods is:
1) because avoided the judgement of benchmark gray-scale value, and avoided the process that judges edge pixel by the proportionate relationship with benchmark gray-scale value, can make this method can bear the impact of larger interference factor;
2) even if image, to a certain extent in state of saturation, also in the judgement that does not affect graphic limit position, has reduced for the requirement of image.
But this method also has the problem of self:
For the judgement of number of pixels, can only be integer judgement, the error of can exist ± 0.5 pixel of the judgement of each side, the error of two will exist ± 1 pixels of edge, line source length is shorter, and error will be larger.
Although these shortcomings can increase the length of line source in theory, by sharing error equally by more pixel, made up, the length that increases line source can be brought new problem equally:
1) for the large optical lens of distortion, increase the length of line source, may make line source picture that serious deformation occurs in length, in this case, not only can not share error equally, and can make on the contrary the error in judgement of number of pixels larger;
2), in optical system debug process, can make imageing sensor there is different responses to the target of same intensity under different visual fields.Increased so again the judgement of benchmark gray-scale value.
Existing methodical common shortcoming is, for the large optical lens of distortion, to be not suitable for measuring under large visual field; And measurement under small field of view, between single measurement result, error is larger, therefore makes measurement result poor repeatability.
Two, image sensor pixel gap measuring device background technology
The field tests of international Patent classificating number G01M 11/02 optical property, discloses forming of dynamic image modulation transfer function measuring device by two patents of invention:
Patent No. ZL200810137150.1, at on 09 29th, 2010 Granted publication day, patent of invention < < dynamic target modulation transfer function measurement method and device > >, a kind of dynamic image modulation transfer function measuring device of high-accuracy multifunctional is disclosed, in this device, also there is the structure of light source, optical system and imageing sensor, and be that light source arrives image sensor surface through optical system imaging equally.
Patent No. ZL201010252619.3, at on 01 11st, 2012 Granted publication day, patent of invention < < dynamic image modulation transfer function measuring device > >, on the basis of a upper disclosed device of patent, further define the coupling scheme of optical lens and the method for synchronization of measurement in device.
But the movement locus that these two characteristic feature of an inventions are light sources is perpendicular to the straight line of optical axis, for the optical system that has the curvature of field, in the process of light source motion, will inevitably cause the out of focus of image, if these two the disclosed measurement mechanisms of invention are applied directly in the present invention, cannot overcome problem of image blurring and gradation of image value variation issue that out of focus causes, this problem can cause the locational skew of cutoff frequency, and the accuracy of measurement result is affected.
Summary of the invention
The present invention is exactly the problem that is not suitable for measuring within the scope of small field of view for above-mentioned existing measuring method, and there is the problem of out of focus in existing measurement mechanism, proposed a kind of image sensor pixel spacing frequency domain measuring method and device, the method can improve measurement result repeatability within the scope of small field of view; This device can be eliminated the impact of out of focus on measurement result.
The object of the present invention is achieved like this:
The image sensor pixel measurement method for distance that adopts at the uniform velocity moving point target, step is as follows:
A. the time shutter t of the movement velocity v of set-point target and imageing sensor;
B. the movement velocity v and the time shutter t that according to a step, set, after the optical system that calculation level target is β through lateral magnification, point target picture is at the theory movement displacement d=vt of image sensor surface β;
C. the theory movement displacement d obtaining according to b step and at the uniform velocity moving image modulation transfer function model M TF (f)=| sinc (π fd) |, the cutoff frequency that obtains moving image modulation transfer function curve is: f=1/d;
D. under a step parameter, imageing sensor is to the point target imaging of moving along image sensor line or column direction, obtain initial point spread function image, and full line or the permutation information as inswept row or column extracts by point target in initial point spread function image, as initial line spread function image, this initial line spread function image has n element;
E. remove point target, in the time shutter t of the imageing sensor of setting in a step, imageing sensor, to background imaging, obtains interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value;
F. the initial line spread function image that d step obtains, the gray-scale value that gray-scale value is less than to the pixel of e step gained threshold value is modified to 0, obtain modified line spread function image, this modified line spread function image has the identical element number n of initial line spread function image obtaining with d step;
G. modified line spread function image f step being obtained is 1 to carry out discrete Fourier transformation delivery by spacing, obtain initial modulation transport function image, this initial modulation transport function image has the identical element number n of initial line spread function image obtaining with d step, be n discrete spectrum component, according to spatial frequency order from small to large, be respectively M
0, M
1, M
2..., M
n-1, under this order, it is M that initial modulation transfer function values reaches the corresponding modulating transfer function value of minimal value for the first time
i, its lower footnote sequence number is i;
H. the modulating transfer function value that the cutoff frequency value f obtaining according to c step and g step obtain is M
i-1and M
i+1corresponding spatial frequency values is equal respectively, that is: f=(i-1)/(nl
min) and f=(i+1)/(nl
max), the pel spacing span that obtains imageing sensor is: l
min=(i-1)/(nf)=(i-1) d/n=(i-1) h β/n and l
max=(i+1)/(nf)=(i+1) d/n=(i+1) h β/n;
I. by l, be variable, and the l obtaining with h step
minand l
maxfor span, in n the modulating transfer function value obtaining in g step, choose K as comparison data, this K modulating transfer function value is respectively M
k1, M
k2..., M
kK, adopt genetic algorithm to search out the minimum value of following formula:
the corresponding pel spacing l of this minimum value is required.
The image sensor pixel measurement method for distance of the at the uniform velocity moving point target of above-mentioned employing, d step, e step, f step replace with:
D '. under a step parameter, imageing sensor, to the point target imaging of moving along image sensor line or column direction, obtains initial point spread function image;
E '. remove point target, in the time shutter t of the imageing sensor of setting in a step, imageing sensor, to background imaging, obtains interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value;
F '. the initial point spread function image that d ' step obtains, the gray-scale value that gray-scale value is less than to the pixel of e ' step gained threshold value is modified to 0, and full line or the permutation information as inswept row or column extracts by point target in become image, obtain modified line spread function image, this modified line spread function image has the identical element number n of initial line spread function obtaining with d step.
Adopt the image sensor pixel gap measuring device of at the uniform velocity moving point target, comprise point target, optical system, imageing sensor, slide block, axial the first guide rail of vertical light and controller, described point target arrives image sensor surface through optical system imaging; And, this device also comprises the second guide rail along optical axis direction, the slide block of bearing point target is arranged on the first guide rail and the second guide rail, controller is controlled slide block on the first guide rail during uniform motion, controller is controlled slide block and is moved on the second guide rail, and the motion of both direction matches, make point target in motion process all the time accurate Jiao be imaged onto image sensor surface.
The invention has the beneficial effects as follows:
1) measuring method that the present invention adopts is different from traditional spatial domain measuring method, the method be take pointolite as target, under point target uniform speed motion state to its imaging, obtain linear image, in frequency domain, find the span of pel spacing, and best according to the actual modulated transfer curve relevant to pel spacing and theoretical modulation transfer function curve registration under least square condition, utilize genetic algorithm to calculate pel spacing; When this feature makes to adopt the short and small line source of length, can obtain higher cutoff frequency, thereby share the error of cutoff frequency equally, make the error between single measurement result less, and then improve measurement result repeatability;
2) measurement mechanism that the present invention adopts comprises the second guide rail along optical axis direction, the slide block of bearing point target is arranged on the first guide rail and the second guide rail, controller is controlled slide block on the first guide rail during uniform motion, controller is controlled slide block and is moved on the second guide rail, and the motion of both direction matches, make point target in motion process all the time accurate Jiao be imaged onto image sensor surface; This feature makes the modulation transfer function curve measuring more approach true curve, and the cutoff frequency position that actual measurement obtains is more accurate, can further reduce the error between single measurement result, improves measurement result repeatability.
Accompanying drawing explanation
Fig. 1 is the image sensor pixel gap measuring device structural representation that adopts at the uniform velocity moving point target
Fig. 2 is the image sensor pixel measurement method for distance process flow diagram that adopts at the uniform velocity moving point target
In figure: 1 point target 2 optical system 3 imageing sensor 4 slide block 5 first guide rail 6 second guide rail 7 controllers
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the invention is described in further detail.
Fig. 1 is for adopting the image sensor pixel gap measuring device structural representation of at the uniform velocity moving point target; This device comprises point target 1, optical system 2, imageing sensor 3, slide block 4, axial the first guide rail 5 of vertical light and controller 7, and described point target 1 is imaged onto imageing sensor 3 surfaces through optical system 2; And, this device also comprises the second guide rail 6 along optical axis direction, the slide block 4 of bearing point target 1 is arranged on the first guide rail 5 and the second guide rail 6, controller 7 is controlled slide blocks 4 on the first guide rail 5 during uniform motion, controller 7 is controlled slide block 4 and is moved on the second guide rail 6, and the motion of both direction matches, make point target 1 in motion process all the time accurate Jiao be imaged onto imageing sensor 3 surfaces; Wherein, point target 1 is the pin hole of diameter 15 μ m, and the lateral magnification of optical system 2 is 0.0557.
The image sensor pixel measurement method for distance that adopts at the uniform velocity moving point target, as shown in Figure 2, the method step is as follows for process flow diagram:
A. the time shutter t=359ms of the movement velocity v=4.25mm/s of set-point target 1 and imageing sensor 3;
B. the movement velocity v and the time shutter t that according to a step, set, after the optical system 2 that calculation level target 1 is β through lateral magnification, point target picture is in the theory movement displacement on imageing sensor 3 surfaces:
d＝v·t·β＝4.25mm/s×359ms×0.0557＝0.085mm；
C. the theory movement displacement d obtaining according to b step and at the uniform velocity moving image modulation transfer function model M TF (f)=| sinc (π fd) |, the cutoff frequency that obtains moving image modulation transfer function curve is: f=1/d=11.7647lp/mm;
D. under a step parameter, point target 1 imaging that 3 pairs of imageing sensors move along imageing sensor 3 line directions, obtain initial point spread function image, and the full line information as inswept row extracts by point target in initial point spread function image, as initial line spread function image, this initial line spread function image has n=1280 element;
E. remove point target 1, in the time shutter t=359ms of the imageing sensor 3 of setting in a step, 3 pairs of background imagings of imageing sensor, obtain interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value, this threshold value is 10;
F. the initial line spread function image that d step obtains, the gray-scale value that gray-scale value is less than to the pixel of e step gained threshold value is modified to 0, obtain modified line spread function image, this modified line spread function image has the identical element number n=1280 of initial line spread function image obtaining with d step;
G. modified line spread function image f step being obtained is 1 to carry out discrete Fourier transformation delivery by spacing, obtain initial modulation transport function image, this initial modulation transport function image has the identical element number n of initial line spread function image obtaining with d step, be n discrete spectrum component, according to spatial frequency order from small to large, be respectively M
0, M
1, M
2..., M
n-1, under this order, it is M that initial modulation transfer function values reaches the corresponding modulating transfer function value of minimal value for the first time
i, its lower footnote sequence number is i;
H. the modulating transfer function value that the cutoff frequency value f obtaining according to c step and g step obtain is M
i-1and M
i+1corresponding spatial frequency values is equal respectively, that is: f=(i-1)/(nl
min) and f=(i+1)/(nl
max), the pel spacing span that obtains imageing sensor 3 is: l
min=(i-1)/(nf)=(i-1) d/n=(i-1) h β/n and l
max=(i+1)/(nf)=(i+1) d/n=(i+1) h β/n;
I. by l, be variable, and the l obtaining with h step
minand l
maxfor span, according to spatial frequency order from small to large, n the modulating transfer function value that g step is obtained is depicted as a curve, chooses on this curve from M
0start to first maximum value, and do not comprise first minimizing all modulating transfer function values, data are compared in K conduct altogether, and this K modulating transfer function value is respectively M
k1, M
k2..., M
kK, adopt genetic algorithm to search out the minimum value of following formula:
the corresponding pel spacing l of this minimum value is required.
According to thinking above, pel spacing has been carried out to 100 times and measured, the measurement result obtaining is listed in the table below:
The image sensor pixel measurement method for distance of the at the uniform velocity moving point target of above-mentioned employing, d step, e step, f step replace with:
D '. under a step parameter, point target 1 imaging that 3 pairs of imageing sensors move along imageing sensor 3 line directions, obtains initial point spread function image;
E '. remove point target 1, in the time shutter t of the imageing sensor 3 of setting in a step, 3 pairs of background imagings of imageing sensor, obtain interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value;
F '. the initial point spread function image that d ' step obtains, the gray-scale value that gray-scale value is less than to the pixel of e ' step gained threshold value is modified to 0, and the full line information as inswept row extracts by point target in become image, obtain modified line spread function image, this modified line spread function image has the identical element number n=1280 of initial line spread function obtaining with d step.
Claims (2)
1. the image sensor pixel measurement method for distance that adopts at the uniform velocity moving point target, is characterized in that described method step is as follows:
A. the time shutter t of the movement velocity v of set-point target and imageing sensor;
B. the movement velocity v and the time shutter t that according to a step, set, after the optical system that calculation level target is β through lateral magnification, point target picture is at the theory movement displacement d=vt of image sensor surface β;
C. the theory movement displacement d obtaining according to b step and at the uniform velocity moving image modulation transfer function model M TF (f)=| sinc (π fd) |, the cutoff frequency that obtains moving image modulation transfer function curve is: f=1/d;
D. under a step parameter, imageing sensor is to the point target imaging of moving along image sensor line or column direction, obtain initial point spread function image, and full line or the permutation information as inswept row or column extracts by point target in initial point spread function image, as initial line spread function image, this initial line spread function image has n element;
E. remove point target, in the time shutter t of the imageing sensor of setting in a step, imageing sensor, to background imaging, obtains interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value;
F. the initial line spread function image obtaining for d step, the gray-scale value that its gray-scale value is less than to the pixel of e step gained threshold value is modified to 0, obtain modified line spread function image, this modified line spread function image has the identical element number n of initial line spread function image obtaining with d step;
G. modified line spread function image f step being obtained is 1 to carry out discrete Fourier transformation delivery by spacing, obtain initial modulation transport function image, this initial modulation transport function image has the identical element number n of initial line spread function image obtaining with d step, be n discrete spectrum component, according to spatial frequency order from small to large, be respectively M
0, M
1, M
2..., M
n-1under this order, it is M that initial modulation transfer function values reaches the corresponding modulating transfer function value of minimal value for the first time
i, its lower footnote sequence number is i;
H. the modulating transfer function value that the cutoff frequency value f obtaining according to c step and g step obtain is M
i-1and M
i+1corresponding spatial frequency values is equal respectively, that is: f=(i-1)/(nl
min) and f=(i+1)/(nl
max), the pel spacing span that obtains imageing sensor is: l
min=(i-1)/(nf)=(i-1) d/n=(i-1) h β/n and l
max=(i+1)/(nf)=(i+1) d/n=(i+1) h β/n;
I. by l, be variable, and the l obtaining with h step
minand l
maxfor span, in n the modulating transfer function value obtaining in g step, choose K as comparison data, this K modulating transfer function value is respectively M
k1, M
k2..., M
kK, adopt genetic algorithm to search out the minimum value of following formula:
the corresponding pel spacing l of this minimum value is required.
2. the image sensor pixel measurement method for distance of point target is at the uniform velocity moved in employing according to claim 1, it is characterized in that d step, e step, f step replace with:
D '. under a step parameter, imageing sensor, to the point target imaging of moving along image sensor line or column direction, obtains initial point spread function image;
E '. remove point target, in the time shutter t of the imageing sensor of setting in a step, imageing sensor, to background imaging, obtains interfering picture, and using the maximal value of gray-scale value in interfering picture as threshold value;
F '. the initial point spread function image obtaining for d ' step, the gray-scale value that its gray-scale value is less than to the pixel of e ' step gained threshold value is modified to 0, and full line or the permutation information as inswept row or column extracts by point target in become image, obtain modified line spread function image, this modified line spread function image has the identical element number n of initial line spread function obtaining with d step.
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