CN109089025A - A kind of image instrument digital focus method based on optical field imaging technology - Google Patents
A kind of image instrument digital focus method based on optical field imaging technology Download PDFInfo
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Abstract
A kind of image instrument digital focus method based on optical field imaging technology.It includes building optical field imaging system；Obtain original four-dimensional light field image；Form two-dimension light field image；Obtain clarity evaluation of estimate；Obtain the image distance in each blur-free imaging face；Obtain the geometric dimension of corresponding sample.Image instrument digital focus method provided by the invention based on optical field imaging technology has the advantages that a) the method for the present invention is simple and easy compared with prior art, it does not need to increase other hardware facilities, the design feature for making full use of light-field camera itself can realize that the high-resolution of light-field camera is imaged by handling original light field data；B) this method system is simple, and technical principle is clearly understandable, and moves in the process without mechanical part, and accuracy is reliable, applied widely, at low cost.
Description
Technical field
The invention belongs to the technologies such as video vision field of measuring technique, including computer vision, optical field imaging, image procossing
Scope, more particularly to a kind of image instrument digital focus method based on optical field imaging technology.
Background technique
In computer vision research, picture depth is estimated in target following, scene understanding and three-dimensional reconstruction and machine
People etc. all plays an important role.Motion information, texture gradient, parallax information and degree of focus information in image all may be used
Using the substantial clue as estimation of Depth.Traditional image instrument, which is mechanically focused, can bring mechanical part displacement error,
There is the problems such as focusing accuracy is not high, focusing is complicated in existing Atomatic focusing method, therefore how to handle sample image depth
Estimation reduces error so that focus process is rapidly completed, and just seems particularly significant to improve focusing accuracy.
Summary of the invention
To solve the above-mentioned problems, the image instrument number based on optical field imaging technology that the purpose of the present invention is to provide a kind of
Focus method.
In order to achieve the above object, the image instrument digital focus method provided by the invention based on optical field imaging technology includes
The following steps carried out in order:
1) optical field imaging system is constructed, which includes testboard pedestal, light-field camera, light-field camera support, testboard
Bracket and testboard vertical shaft；Wherein testboard pedestal is horizontally disposed, and surface middle part is formed with one for placing sample
Groove；The lower end of testboard vertical shaft is fixed on the surface side of testboard pedestal；The setting of testboard support level, one end is fixed on
The upper end of testboard vertical shaft；The upper end of light-field camera support is fixed on the other end of testboard bracket, and light-field camera is installed in lower end,
And light-field camera is located at the top of testboard pedestal upper groove；Light-field camera is equipped with main lens, is made of multiple lenticules
Microlens array and the sensor array that is made of multiple sensors；
2) sample, is then placed in the groove on testboard pedestal by the parameter for extracting light-field camera first, utilizes
Light-field camera carries out optical field imaging to sample, obtains original four-dimensional light field image；
3) the white correction image in light-field camera is extracted, selected white is corrected with border circular areas mean filter
Image is filtered, and to remove the noise of sensor, obtains the desired center of each lenticule according to the theoretical diameter of lenticule
Then center of the pixel peak point as the lenticule image is nearby found, to demarcate pixel light field, most in position in the position
The correction of hexagon to orthogonal lattice point is carried out to lenticule afterwards, and using the calibration point of optical field imaging system to the original of sample
The four-dimensional light field image that begins is parsed, and two-dimension light field image is formed；
4) using improved digital focus algorithm combination Image Definition to above-mentioned steps 3) acquisition two dimension
Light field image carries out digital refocusing, then using Image Definition to the two-dimension light field image after refocusing again
It is focused, obtains clarity evaluation of estimate；
5) essence that the method that gaussian curve approximation seeks extreme value obtains step 4) is carried out using weighted least-squares criterion
The clarity evaluation of estimate of focus image is normalized, and in this, as the basic data of matched curve, solves weighting coefficient,
Extreme value is sought in matched curve, finds best clear output image, and then obtain the image distance in each blur-free imaging face；
6) image distance in each blur-free imaging face that step 5) is obtained using the method for focusing ranging, in conjunction with Gaussian imaging equation
Distance measuring method, practical object distance u is calculated by the focal length f of light-field camera, and then obtain the dimensioning of corresponding sample
It is very little.
In step 2), then sample is placed on testboard pedestal by the parameter of the extraction light-field camera
In groove, optical field imaging is carried out to sample using light-field camera, obtaining original four-dimensional light field image, specific step is as follows:
The parameter for extracting light-field camera first, including the focal length of main lens in light-field camera, radius of curvature, pupil diameter,
The focal length of center thickness and corresponding lenticule；Secondly setting reference planes and its calibration point, project to one for light again
In a virtual picture plane, by this as plane sets are reference planes；Calibration point is arranged on sample, to be joined
Examine the distance between plane and main lens；Sample is put into the groove on testboard pedestal, using light-field camera to quilt
Sample carries out optical field imaging, captures each different location and the four-dimensional light field data in direction in scene and converges to biography
In sensor, to form original four-dimensional light field image.
In step 3), the white correction image extracted in light-field camera, with border circular areas mean filter
Selected white correction image is filtered, to remove the noise of sensor, is obtained according to the theoretical diameter of lenticule each
Then center of the pixel peak point as the lenticule image is nearby found in the desired center position of lenticule in the position, from
And pixel light field is demarcated, the correction of hexagon to orthogonal lattice point finally is carried out to lenticule, and utilize the mark of optical field imaging system
It pinpoints and the original four-dimensional light field image of sample is parsed, forming two-dimension light field image, specific step is as follows:
Original four are rapidly and accurately corrected using 31 pairs of total 62 secondary white correction images that light-field camera provides first
Thus dimension light field image establishes lenticule grid model, describe its geometric position center；Then pixel is nearby found in the position
Center of the peak point as the lenticule image, so that pixel light field is demarcated, on this basis, with the geometry position of each lenticule
Setting pericentral 11 × 11 pixels is unit, carries out hexagon to the school of orthogonal lattice point to lenticule using water transformation algorithm
Just, and using original four-dimensional light field image of the calibration point of optical field imaging system to sample it parses, thus realization pair
The parsing of original light field image, ultimately forms two dimensional image.
In step 4), it is described using improved digital focus algorithm combination Image Definition to above-mentioned step
The rapid two-dimension light field image 3) obtained carries out digital refocusing, then using Image Definition to two after refocusing
Dimension light field image is focused again, and obtaining clarity evaluation of estimate, specific step is as follows:
Light field image refocusing is carried out first with pixel light field, is changed by microlens array plan-position, imaging is flat
Face is also moved at the position therewith changing, and obtains new light field data, clear to the measured object of scene different depth
Clear imaging；Secondly ray tracing technology is utilized, when new imaging surface is moved at F'=α F, wherein F is light field under default situations
The main lens of camera according to Similar Principle of Triangle, projects at new imaging surface, i.e. institute at a distance from microlens array plane
It is set to the light at new microlens array plane in place and effectively comes from initial imaging surface, initial imaging surface position is
At initial microlens array plane；Then the two dimensional image after refocusing is carried out again using Image Definition thick
The focusing for focusing two stages with essence is focused, clarity evaluation of estimate is finally obtained.
It is described that the method pair that gaussian curve approximation seeks extreme value is carried out using weighted least-squares criterion in step 5)
The clarity evaluation of estimate for the smart focus image that step 4) obtains is normalized, in this, as the basic number of matched curve
According to extreme value is sought in solution weighting coefficient, matched curve, finds best clear output image, and then obtain the picture in each blur-free imaging face
Away from specific step is as follows:
First by light-field camera, the weight of the refocusing image of scene where obtaining sample using digital refocusing principle
Focus sequence measures degree of focus of the sample in image sequence using clarity evaluation operator, seeks detected sample
Real depth of the product apart from light-field camera simultaneously finds corresponding focusing parameter under best clear image, in conjunction with Gaussian imaging equation,
The image distance in each blur-free imaging face is finally obtained using focusing distance measuring method.
In step 6), the image distance in each blur-free imaging face that step 5) is obtained using the method for focusing ranging,
In conjunction with the distance measuring method of Gaussian imaging equation, practical object distance u is calculated by the focal length f of light-field camera, and then obtain corresponding
Specific step is as follows for the geometric dimension of sample:
First with refocusing algorithm, in conjunction with sharpness evaluation function, obtains blur-free imaging point and write down experiment at this time
Image distance d*；By calibration, practical image distance v is calculated by experiment image distance d*, calculates practical object distance in conjunction with lens Gaussian imaging equation
U, it may be assumed that u=fv/ (f-v), wherein f is the focal length of microlens array, and v is practical image distance, and then completes focusing ranging；Interception figure
Target object window as in traverses the sample in this region, its corresponding depth can be obtained using focusing ranging
Information, and then three-dimensional measurement is completed, obtain the geometric dimension of sample.
Image instrument digital focus method provided by the invention based on optical field imaging technology has such as compared with prior art
Lower advantage: a) the method for the present invention is simple and easy, does not need to increase other hardware facilities, makes full use of the knot of light-field camera itself
Structure feature can realize that the high-resolution of light-field camera is imaged by handling original light field data；B) this method system letter
Single, technical principle is clearly understandable, and moves in the process without mechanical part, and accuracy is reliable, applied widely, at low cost.
Detailed description of the invention
Fig. 1 is the image instrument digital focus method flow diagram provided by the invention based on optical field imaging technology；
Fig. 2 is optical field imaging system perspective view used by this method；
Fig. 3 is light-field camera schematic diagram；
Fig. 4 is the focusing principle figure of light-field camera.
Specific embodiment
Illustrate the present invention in the following with reference to the drawings and specific embodiments.
As shown in Figure 1, the image instrument digital focus method provided by the invention based on optical field imaging technology includes in order
The following steps of progress:
1) optical field imaging system as shown in Figure 2 is constructed, which includes testboard pedestal 1, light-field camera 3, light field phase
Machine support 4, testboard bracket 5 and testboard vertical shaft 6；Wherein testboard pedestal 1 is horizontally disposed, and surface middle part is formed with a use
In the groove for placing sample 2；The lower end of testboard vertical shaft 6 is fixed on the surface side of testboard pedestal 1；Testboard bracket
5 is horizontally disposed, and one end is fixed on the upper end of testboard vertical shaft 6；The upper end of light-field camera support 4 is fixed on testboard bracket 5
The other end, light-field camera 3 is installed in lower end, and light-field camera 3 is located at the top of 1 upper groove of testboard pedestal；As shown in figure 3,
Light-field camera 3 is equipped with main lens 7, the microlens array 8 being made of multiple lenticules and the sensing being made of multiple sensors
Device array 9；
2) sample 2, is then placed in the groove on testboard pedestal 1 by the parameter for extracting light-field camera 3 first, benefit
Optical field imaging is carried out to sample 2 with light-field camera 3, obtains original four-dimensional light field image；
Specific step is as follows:
The parameter of light-field camera 3 is extracted first, and focal length, radius of curvature, pupil including main lens 7 in light-field camera 3 are straight
The focal length of diameter, center thickness and corresponding lenticule；Secondly setting reference planes and its calibration point, due to light-field camera 3
The available optical field distribution situation in entire light-field camera 3 of characteristic, so light to be projected to a virtual picture again
In plane, by this as plane sets are reference planes；By calibration point be arranged on sample 2, thus obtain reference planes with
The distance between main lens 7；Sample 2 is put into the groove on testboard pedestal 1, using light-field camera 3 to detected sample
Product 2 carry out optical field imaging, capture each different location and the four-dimensional light field data in direction in scene and converge to sensing
In device, to form original four-dimensional light field image；
3) the white correction image in light-field camera 3 is extracted, while each micro- in order to intuitively and accurately portray
The geometric position of lens is filtered selected white correction image with border circular areas mean filter, to remove sensor
Noise, the desired center position of each lenticule is obtained according to the theoretical diameter of lenticule, then in the position nearby find
Center of the pixel peak point as the lenticule image finally carries out hexagon to just to lenticule to demarcate pixel light field
The correction of lattice point is handed over, and is parsed using original four-dimensional light field image of the calibration point of optical field imaging system to sample 2,
Form two-dimension light field image；
Specific step is as follows:
In order to increase light rate of catching, the lenticule in light-field camera 3 uses hexagonal array arrangement mode, causes in this way " macro
" sub-pixel " that pixel " is covered with it uncertain covers integer pixel not only not at simple corresponding relationship.Together
When, since to normally result in microlens array plane and sensor flat for the factors such as the manufacture craft of microlens array 8, assembly precision
There is rotation angular deviation between face, to the proper use of of field information and processing, therefore these factors can all seriously affect the later period
The correction course of original four-dimension light field image is vital.
In addition, white corrects image and do not have essential distinction using other images that light-field camera 3 is shot, only the former has
Conducive to the geometric position center of identification lenticule；The 31 pairs of total 62 secondary white correction images provided thus using light-field camera 3
It rapidly and accurately corrects original four-dimensional light field image, thus sets up lenticule grid model, utilize lenticule grid model
Come geometric position center that is intuitive and relatively accurately describing each lenticule.Correction course is as follows:
Horizontal space:
Vertical interval:
Lenticule deviates horizontal direction angle:
Roation=arctan (mean (kj)) (j=1,2,3 ... .., UMax) (4)
Formula (1), (2) are modified: HSpace*=HSpace/cos (Roation) (5)
VSpace*=VSpace/cos (Roation) (6)
The line number and columns of lenticule: UMax=height/VSpace (7)
VMax=width/HSpace (8)
Wherein HSpace indicates the horizontal space with the geometric position center of contiguous microlens in a line, HSpace*For it
Correction value；VSpace indicates the half of the vertical interval at the geometric position center of contiguous microlens in same row, and VSpace* is it
Correction value；(x(j, i), y(j,i)) indicate all lenticule centre coordinates of every a line；kjIt is horizontal to indicate that the lenticule of jth row deviates
The angle in direction；Rotation indicates rotation angle of the microlens array plane relative to sensor plane；UMax indicates micro-
The line number of mirror；The columns of VMax expression lenticule；Height and width is respectively the height and width of white correction image.
On this basis, using pericentral 11 × 11 pixels in the geometric position of each lenticule as unit, water is utilized
It converts algorithm and hexagon is carried out to the correction of orthogonal lattice point to lenticule, " the macro pixel " 379 × 379 of orthogonal arrangement is presented,
Each 11 × 11 sensor pixels are covered under " macro pixel ".Therefore the light field image spatial resolution after correcting is 379
× 379, angular resolution is 11 × 11, obtains the two-dimension light field image of 11 × 11 different perspectivess, so just will be each micro-
Mirror is mapped with the sensor pixel that it is covered, and is convenient for post-processing.
4) using improved digital focus algorithm combination Image Definition to above-mentioned steps 3) acquisition two dimension
Light field image carries out digital refocusing, then using Image Definition to the two-dimension light field image after refocusing again
It is focused, obtains clarity evaluation of estimate；
Specific step is as follows:
The light field indicated with main lens plane and microlens array plane is defined as " standard light field ", and will be before with micro-
The light field that lens array plane and sensor plane indicate is referred to as " pixel light field ", in actual operation, obtains light and passes through
The coordinate of main lens is difficult to calculate, and Ray Of Light is to be easy to indicate by the coordinate of microlens array and sensor,
In addition there are corresponding relationships with sensor coordinates for main lens coordinate.Therefore, it is usually carried out using " pixel light field " in practical operation
Light field image refocusing.The refocusing principle of light-field camera 3 is as shown in Figure 4；Wherein 10 indicate main lens plane, 11 indicate initial
Microlens array plane, 12 indicate new microlens array plane；Wherein initial microlens array plane 11 and new lenticule
The two array planes of array plane 12 are equivalent to the imaging surface under two kinds of different situations of traditional camera, pass through microlens array
Plan-position changes, and is equivalent to and is moved to imaging plane at the position with the variation of array plane, i.e. imaging plane
It is moved forward and backward at different array planes, obtains new light field data, thus to the target blur-free imaging of scene different depth.
Wherein F is the main lens 7 of light-field camera 3 under default situations at a distance from microlens array plane, the coke of the distance and main lens 7
Away from approaching, microlens array plane is equivalent to the imaging surface of traditional camera.It is to scene difference when imaging surface is moved forward and backward
The target blur-free imaging of depth.Wherein α characterizes different depth parameters, and different depth parameter α is arranged, same light field can be obtained
Focus on the image sequence of different depth；(u', v') is intersecting point coordinate when light passes through main lens plane.Light field phase in Fig. 4
The corresponding relationship of u' and x can similarly be substituted for the relationship of v' and y in the focusing principle figure of machine.
Secondly ray tracing technology is utilized, when new imaging surface is moved at F'=α F, according to Similar Principle of Triangle, is thrown
Shadow light of (i.e. position is at new microlens array plane) at new imaging surface effectively comes from initial imaging
Face (position is at initial microlens array plane)；
Initial imaging plane:
Wherein by the image refocusing of collected sample 2 in corresponding reference planes, to obtain light field
The distance between the corresponding main lens 7 of camera 3 and microlens array 8, and the calibration point on sample 2 is recorded in refocusing
Imaging diameter on image, and then obtain the geometry information of sample 2.Four-dimensional light field after refocusing can use formula meter
It obtains.After obtaining new two-dimension light field image, need by the special available real image information of processing.Macro picture
The different image element informations that element is covered own by main lens 3 in order to obtain actually from the light of main lens difference sub-aperture
The summation of light obtains refocusing image E according to the following formulaF’。
Four-dimensional light field:
And then it seeks refocusing image and obtains:
α indicates different depth parameters in formula, and different depth parameter α is arranged, Same Scene can be obtained and focus on difference
The image sequence of depth；(u', v') is intersecting point coordinate when light passes through main lens plane.
Then, two-dimension light field image after refocusing is focused using Image Definition again, is obtained clear
Clear degree evaluation of estimate, the specific steps are as follows:
A) in thick focusing stage, different depth parameter α is adjusted, one direction is carried out with larger step pitch and is gradually focused, so that
Two-dimension light field image experience after refocusing is fuzzy then-clear-process obscured is acquired with Image Definition
The clarity evaluation of estimate of two-dimension light field image after refocusing, to obtain clarity appraisal curve, evaluation of estimate is bigger to be thought
Closer to positive burnt position, positive burnt position near zone is found accordingly.It, will be clear by obtained thick focus image clarity appraisal curve
Z is denoted as at clear degree evaluation of estimate maximum position0, wherein Z axis is denoted as perpendicular to the direction on 2 surface of sample in optical field imaging system
Direction；
B) 0.5mm is respectively taken before and after smart focusing stage, the depth of focus in thick focusing stage clarity evaluation of estimate maximum
Depth, start smart focusing within this range, seek the clarity of smart focus image using Image Definition again
Evaluation of estimate.
5) essence that the method that gaussian curve approximation seeks extreme value obtains step 4) is carried out using weighted least-squares criterion
The clarity evaluation of estimate of focus image is normalized, and in this, as the basic data of matched curve, solves weighting coefficient,
Extreme value is sought in matched curve, finds best clear output image, and then obtain the image distance in each blur-free imaging face；
Specific step is as follows:
According to the digital refocusing principle of light-field camera 3, the refocusing image refocusing sequence of scene is obtained, using clear
Degree evaluation operator measures degree of focus of the sample 2 in image sequence, and evaluation procedure is as follows: wherein Gaussian curve
Every group of data are assigned in fitting with different weight values Pi(Pi>0)
M is the image number of sample 2, y in formulaiFor the clarity evaluation of estimate of i-th image, S (xi) it is curve matching
The clarity evaluation of estimate of image afterwards.Finally combine knowledge of statistics, it may be determined that each data point weighting coefficient is its min-max standard
Numerical value afterwards；
So, min-max normalization function is
X is the clarity evaluation of estimate of smart 2 image of focusing stage sample in formula, and max is smart focusing stage sample 2
The utmost sharpness evaluation of estimate of image, min are the minimum clarity evaluation of estimate of smart 2 image of focusing stage sample.Utilize
Clarity evaluation operator measures degree of focus of the sample in image sequence, obtains corresponding heavy when degree of focus maximum
Focusing parameter；In conjunction with Gaussian imaging equation, seek real depth of the sample 2 apart from light-field camera 3 and find it is best clear
Image, so also obtain sample 2 it is clearest when corresponding focusing parameter.
6) image distance in each blur-free imaging face that step 5) is obtained using the method for focusing ranging, in conjunction with Gaussian imaging equation
Distance measuring method, practical object distance u is calculated by the focal length f of light-field camera 3, and then obtain the geometry of corresponding sample 2
Size；
Specific step is as follows:
Using refocusing algorithm, in conjunction with sharpness evaluation function, obtains blur-free imaging point and write down experiment image distance at this time
d*；By calibration, practical image distance is calculated by experiment image distance, in conjunction with lens Gaussian imaging equation, calculates practical object distance u, it may be assumed that u
=fv/ (f-v), since the corresponding relationship of experiment image distance d* and practical image distance v can not be learnt.Therefore, direct calibration experiment
The relationship of image distance d* and object distance u complete focusing Range finding experiments, i.e., during calibration, the focal length of fixed main lens 7 is constant,
To which Gaussian imaging equation could be utilized to obtain object distance by experiment image distance.Wherein f is the focal length of microlens array, and v is practical picture
Away from, and then complete focusing ranging.Target object window in interception image, using focusing ranging, to the detected sample in this region
Product traversal can be obtained its corresponding depth information, and then complete three-dimensional measurement, obtain the geometric dimension of sample 2.
What the present invention was not disclosed in detail partly belongs to techniques known.
A specific embodiment of the invention is described and is illustrated in conjunction with attached drawing above, but these explanations do not make sense
To limit the scope of the present invention, protection scope of the present invention is limited by appended claims, any in right of the present invention
Change on the basis of it is required that is all protection scope of the present invention.
Claims (6)
1. a kind of image instrument digital focus method based on optical field imaging technology, it is characterised in that: the focus method includes
The following steps carried out in order:
1) optical field imaging system is constructed, which includes testboard pedestal (1), light-field camera (3), light-field camera support (4), surveys
Test stand bracket (5) and testboard vertical shaft (6)；Wherein testboard pedestal (1) is horizontally disposed, and surface middle part is formed with one for putting
Set the groove of sample (2)；The lower end of testboard vertical shaft (6) is fixed on the surface side of testboard pedestal (1)；Testboard branch
Frame (5) is horizontally disposed, and one end is fixed on the upper end of testboard vertical shaft (6)；The upper end of light-field camera support (4) is fixed on testboard
The other end of bracket (5), light-field camera (3) are installed in lower end, and light-field camera (3) is located at testboard pedestal (1) upper groove
Top；Light-field camera (3) is equipped with main lens (7), the microlens array (8) that is made of multiple lenticules and by multiple sensors
The sensor array (9) of composition；
2) sample (2), is then placed in the groove on testboard pedestal (1) by the parameter for extracting light-field camera (3) first,
Optical field imaging is carried out to sample (2) using light-field camera (3), obtains original four-dimensional light field image；
3) the white correction image in light-field camera (3) is extracted, selected white is corrected with border circular areas mean filter
Image is filtered, and to remove the noise of sensor, obtains the desired center of each lenticule according to the theoretical diameter of lenticule
Then center of the pixel peak point as the lenticule image is nearby found, to demarcate pixel light field, most in position in the position
The correction of hexagon to orthogonal lattice point is carried out to lenticule afterwards, and using the calibration point of optical field imaging system to sample (2)
Original four-dimensional light field image parsed, form two-dimension light field image；
4) using improved digital focus algorithm combination Image Definition to above-mentioned steps 3) acquisition two-dimension light field
Image carries out digital refocusing, is then carried out again using Image Definition to the two-dimension light field image after refocusing
It focuses, obtains clarity evaluation of estimate；
5) method that gaussian curve approximation seeks extreme value is carried out using weighted least-squares criterion to focus to the essence that step 4) obtains
The clarity evaluation of estimate of image is normalized, and in this, as the basic data of matched curve, solves weighting coefficient, fitting
Curve seeks extreme value, finds best clear output image, and then obtain the image distance in each blur-free imaging face；
6) image distance in each blur-free imaging face that step 5) is obtained using the method for focusing ranging, in conjunction with the survey of Gaussian imaging equation
Away from method, practical object distance u is calculated by the focal length f of light-field camera (3), and then obtains the geometry of corresponding sample (2)
Size.
2. the image instrument digital focus method according to claim 1 based on optical field imaging technology, it is characterised in that: in step
It is rapid 2) in, the parameter of the extraction light-field camera (3), the groove being then placed on sample (2) on testboard pedestal (1)
It is interior, optical field imaging is carried out to sample (2) using light-field camera (3), obtains the specific steps of original four-dimensional light field image such as
Under:
The parameter of light-field camera (3), focal length, radius of curvature, pupil including main lens (7) on light-field camera (3) are extracted first
The focal length of diameter, center thickness and corresponding lenticule；Secondly setting reference planes and its calibration point, light is projected again
In the picture plane virtual to one, by this as plane sets are reference planes；Calibration point is arranged on sample (2), from
And obtain the distance between reference planes and main lens (7)；Sample (2) is put into the groove on testboard pedestal (1),
Optical field imaging is carried out to sample (2) using light-field camera (3), captures each different location and direction in scene
Four-dimensional light field data simultaneously converges in sensor, to form original four-dimensional light field image.
3. the image instrument digital focus method according to claim 1 based on optical field imaging technology, it is characterised in that: in step
It is rapid 3) in, the described white correction image extracted in light-field camera (3), with border circular areas mean filter to selected white
Color correction image is filtered, and to remove the noise of sensor, obtains the reason of each lenticule according to the theoretical diameter of lenticule
Think center, center of the pixel peak point as the lenticule image is then nearby found in the position, to demarcate pixel
Light field finally carries out the correction of hexagon to orthogonal lattice point to lenticule, and using the calibration point of optical field imaging system to tested
The original four-dimensional light field image of sample (2) is parsed, and forming two-dimension light field image, specific step is as follows:
The original four-dimension is rapidly and accurately corrected using 31 pairs of total 62 secondary white correction images that light-field camera (3) provide first
Thus light field image establishes lenticule grid model, describe its geometric position center；Then pixel peak is nearby found in the position
Center of the value point as the lenticule image, so that pixel light field is demarcated, on this basis, with the geometric position of each lenticule
Pericentral 11 × 11 pixels are unit, carry out hexagon to the school of orthogonal lattice point to lenticule using water transformation algorithm
Just, and using original four-dimensional light field image of the calibration point of optical field imaging system to sample (2) it parses, to realize
Parsing to original light field image, ultimately forms two dimensional image.
4. the image instrument digital focus method according to claim 1 based on optical field imaging technology, it is characterised in that: in step
It is rapid 4) in, it is described using improved digital focus algorithm combination Image Definition to above-mentioned steps 3) obtain two
Tie up light field image and carry out digital refocusing, then using Image Definition to the two-dimension light field image after refocusing again
Secondary to be focused, obtaining clarity evaluation of estimate, specific step is as follows:
Light field image refocusing is carried out first with pixel light field, is changed by microlens array plan-position, imaging plane
Be moved at the position therewith changing, obtain new light field data, to the measured object of scene different depth clearly at
Picture；Secondly ray tracing technology is utilized, when new imaging surface is moved at F'=α F, wherein F is light-field camera under default situations
(3) main lens (7), according to Similar Principle of Triangle, projects at new imaging surface, i.e., at a distance from microlens array plane
Position is that the light at new microlens array plane effectively comes from initial imaging surface, initial imaging surface position
At initial microlens array plane；Then the two dimensional image after refocusing is carried out again using Image Definition
It is thick to focus the focusing that two stages are focused with essence, finally obtain clarity evaluation of estimate.
5. the image instrument digital focus method according to claim 1 based on optical field imaging technology, it is characterised in that: in step
It is rapid 5) in, it is described to carry out what the gaussian curve approximation method of seeking extreme value obtained step 4) using weighted least-squares criterion
The clarity evaluation of estimate of smart focus image is normalized, and in this, as the basic data of matched curve, solves weighting system
Number, matched curve seeks extreme value, finds best clear output image, so obtain each blur-free imaging face image distance specific steps such as
Under:
First by light-field camera (3), the refocusing image of scene where obtaining sample (2) using digital refocusing principle
Refocusing sequence, using clarity evaluation operator degree of focus of the sample (2) in image sequence is measured, seek by
Real depth of the sample (2) apart from light-field camera (3) simultaneously finds corresponding focusing parameter under best clear image, in conjunction with Gauss
Imaging formula finally obtains the image distance in each blur-free imaging face using focusing distance measuring method.
6. the image instrument digital focus method according to claim 1 based on optical field imaging technology, it is characterised in that: in step
It is rapid 6) in, the image distance in each blur-free imaging face that the described method using focusing ranging obtains step 5), in conjunction with Gauss imaging
The distance measuring method of formula calculates practical object distance u by the focal length f of light-field camera (3), and then obtains corresponding sample
(2) specific step is as follows for geometric dimension:
First with refocusing algorithm, in conjunction with sharpness evaluation function, obtains blur-free imaging point and write down experiment image distance at this time
d*；By calibration, practical image distance v is calculated by experiment image distance d*, calculates practical object distance u in conjunction with lens Gaussian imaging equation, it may be assumed that
U=fv/ (f-v), wherein f is the focal length of microlens array, and v is practical image distance, and then completes focusing ranging；In interception image
Target object window traverses the sample in this region, its corresponding depth information can be obtained using focusing ranging,
And then three-dimensional measurement is completed, obtain the geometric dimension of sample (2).
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