CN106842496A - Method for automatically adjusting focus based on frequency domain comparison method - Google Patents
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- G02B7/36—Systems for automatic generation of focusing signals using image sharpness techniques, e.g. image processing techniques for generating autofocus signals
- G02B7/365—Systems for automatic generation of focusing signals using image sharpness techniques, e.g. image processing techniques for generating autofocus signals by analysis of the spatial frequency components of the image
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Abstract
The invention relates to a method for automatically adjusting focus based on a frequency domain comparison method, which comprises the following steps: the computer controls the mechanical telescopic lens cone to adjust the position of the digital camera, or the imaging aspheric lens or the microscope objective, the telescopic lens cone moves telescopically while the camera shoots to obtain K pieces of image data I0,…,Ii,…,Ij,…,Ik‑1And when the telescopic position of the mechanical lens cone to be focused is obtained through a series of calculations, the mechanical lens cone is controlled to be telescopic to the position, and then automatic focusing can be realized. By comparing and analyzing frequency domain components, the adverse effect of image noise on the automatic focus adjustment precision can be avoided, the method is more suitable for automatic focus adjustment of transmission imaging, and particularly for capillaries in human skin under the condition of no wound, the shape and distribution of the capillaries have periodicity, and the characteristics in the frequency domain are more obvious, so that the automatic focus adjustment of the method is more accurate. In the aspect of device operation, the method is simpler and more convenient and is easy to use practically.
Description
Technical field
The present invention relates to image processing field, the specifically method for automatically adjusting focus based on frequency domain comparison method.
Background technology
Micro mirror head system and camera etc. can realize the collection of image, but image in gatherer process due to focus pair
Inaccurate problem can cause the image blurring unclear of collection, not reach the meaning of IMAQ.Therefore, the regulation of focus to close weight
Will.
User's regulation focus, improves the service efficiency of equipment for convenience, and the Telescopic mirror of mechanical braking is added in a device
Cylinder, user by adjusting the flexible to adjust the distance between microlens system and camera of rocking bar control machinery lens barrel, or
Person adjusts the distance between microcobjective and the non-spherical lens for imaging.Although the flexible lens barrel of mechanical braking can be one
Determine to reduce the complexity that equipment is focused in degree, but the user without microexamination experience is still difficult to confirm focus place,
It is accomplished by automatic focal adjustments algorithm under such circumstances to calculate optimal focus position, so as to automatically control mechanical Telescopic mirror cylinder
The auto-focusing process of completion equipment.
At present, the method for automatically adjusting focus is broadly divided into two major classes, and active and passive type is automatically adjusted.Active Jiao
Point adjusting method needs to install infrared ray or ultrasonic transmitter-receiver in equipment, using infrared ray or ultrasonic ranging method,
Actively measurement is observed the distance of object, according to the distance for calculating, each eyeglass in lens system is automatically adjusted by mechanical device
Position, realize the automatic focal adjustments of equipment.Although active focus adjusting method focusing precision is higher, but need
The hardware unit for being simply possible to use in focusing is added in equipment, is unfavorable for cost degradation and the miniaturization of device product.
Passive type focus adjusting method is the imaging for directly being received using equipment, using image processing techniques, automatic point
The definition of object is observed in analysis imaging, the automatic lens location for calculating most blur-free imaging realizes being adjusted from oving foci for equipment
Section.The most commonly used in the method for image processing and analyzing definition is phase method and contrast method.Auto-focusing is utilized in phase method
Inductor realizes that auto-focusing is separated in a device with imaging optical system, and auto-focusing inductor is to being observed object
The phase pushing figure of picture is detected that the minimum imaging lens position of side-play amount is focusing position.Auto-focusing senses body
Product is small, it is easy to the miniaturization of equipment, but adds additional equipment cost, is unfavorable for the cost degradation of equipment.Contrast rule
It is to arrive continuously shot images out of focus again to focusing by out of focus, object is observed in being imaged using image procossing automatic detection
Contour edge definition is come the auto-focusing realized.Contrast method need not additionally increase the special purpose device for auto-focusing,
Cost degradation and miniaturization beneficial to equipment.In the automatic focal adjustments method of existing picture contrast, mostly using La Pula
The Edge-Detection Algorithms such as this image filter realize the automatic detection of definition, and these image processing algorithms are calculating edge
It is also very sensitive to noise present in image while definition, therefore interior of articles is being carried out into through surface for example
In the case that the picture noises such as picture are larger, it is impossible to realize accurately automatic focal adjustments.
The content of the invention
According to above-mentioned weak point, the present invention provides a kind of method for automatically adjusting focus based on frequency domain comparison method.
To achieve the above object, technical program of the present invention lies in：The side for automatically adjusting focus based on frequency domain comparison method
Method, it is characterised in that：Including procedure below：
Computer controls machinery Telescopic mirror cylinder, adjusts digital camera, or imaging non-spherical lens, or microcobjective
Position, flexible lens barrel carries out telescopic moving, camera while being shot on one side, acquisition K width view data I0,…,Ii,…,
Ij..., IK-1, the horizontally or vertically composition to every piece image carries out discrete Fourier transform, the data after Fourier transformationRepresented with formula 1：
Wherein,The horizontally or vertically composition of the y row/columns of the i-th width photographs is represented, the unit of i is width；N is
Image laterally/number of pixels of longitudinal direction, unit is pixel, x be image laterally/coordinate of longitudinal direction, y is image longitudinal direction/horizontal
Coordinate, unit is pixel, and u is view data frequency domain coordinates, and unit is Hz；
Above-mentioned transformation results are converted into the energy frequency spectrum with dB as numerical value unit, then energy frequency spectrum is averagely counted
Calculation obtains the horizontal/vertical energy frequency spectrum of the image, that is, image frequency components, with GiU () [dB] is represented, computing formula
It is as follows：
In image, apart from d (G between the horizontal/vertical frequency components of the i-th width image and jth width imagei, Gj) multiply flat using two
Mean square root is tried to achieve, as shown in Equation 4：
Wherein, the frequency domain distance between d represents two images, unit is [dB], Gi, GjRespectively the frequency domain of two images into
Point, unit is [dB]；
In theory, when the fog-level of two images is identical, that is, focal point position distance it is identical when, frequency domain distance
It is 0, in this case, formula 5 can be obtained according to formula 4：
Due to [Gi(u)-Gj(u)]2>=0, therefore：
(subscript j represents the position of image, and unit is width；J in formula represents complex symbol)
Because during shooting image, while mobile digital camera, or imaging non-spherical lens, or microcobjective, one
Side shoots, so, the position of the every piece image in image sets, correspondence digital camera, or imaging non-spherical lens, or
The position of microcobjective, namely mechanical-stretching lens barrel telescopic location, it is non-with focusing position identical two it can be seen from formula 6
Focus image, their relations on the telescopic location of mechanical-stretching lens barrel meet the functional relation shown in formula 7：
|fu(i) |=| fu(i) | formula 7
According to geometric optical theory, non-the image blurring of focusing generation is considered as having carried out low pass Gauss to focus image
Function in filtering process, therefore formula 7 can be approximate see Gaussian function as, as shown in Equation 8：
Here, i represents the telescopic location of mechanical-stretching lens barrel, and unit is um, icThe center of Gaussian function is represented, i.e.,
Focusing position, unit is um, and K represents the number of shooting image, and unit is width, and σ represents a constant parameter on camera lens；
Absolute value and natural logrithm exploitation are carried out to formula 8, formula 9 can be obtained：
The calculating substrate of formula 9 is changed to 10, formula 9 can be changed into the form of formula 10：
According to formula 10, the function on i in formula 7 is obtained, as shown in Equation 11：
|fu(i) |=log | Fu(i) |=ai2+ bi+c formulas 11
Bring formula 11 into formula 7, can obtain：
Therefore, by the comparing to image frequency domain, following two minimums can be obtained：
According to formula 13, two minimums represent two straight lines on plane coordinates respectively, and two intersecting point coordinates of straight line are just
It is unique minimum, this unique minimum, the telescopic location of mechanical lens barrel when being exactly required focusing；
Two parameters of straight line in formula 13 are can be calculated by the minimum value line by line to 2-D data, then to two straight lines
Intersection point solution is carried out, its transverse axis/ordinate of orthogonal axes value is exactly the telescopic location of mechanical lens barrel when focusing；
Control machinery lens barrel stretches to the position and is capable of achieving auto-focusing.
The present invention also provides a kind of method that auto-focusing is carried out using this computational methods, comprises the following steps：
(1) user adjusts imaging module, imaging unit or lens unit using the flexible of rocking bar control machinery lens barrel
Position, completes focusing coarse adjustment；
(2) user sends auto-focusing and instructs by rocking bar and other command devices to computer；
(3) computer receives instruction, starts auto-focusing；
(4) computer controls machinery lens barrel, centered on current location, according to preset range upwards/lower movement, reach pre-
If stopping movement behind position；Camera start recording image, at the same mechanical lens barrel start with the position after stopping as starting point to
Lower/upper movement；While mobile, camera records image to mechanical lens barrel on one side, and the image of record is stored in internal memory or hard disk
In memory；
(5) shoot after terminating, computer reads image information, image information is processed using frequency domain comparison method, obtain RMS points
Butut；
(6) computer uses algorithm, the calculated minimum point line by line in RMS distribution maps, and connects these points and obtain two
The straight line of intersection；
(7) computer uses algorithm, and two intersecting point coordinates of the straight line of intersection are tried to achieve in calculating, using RMS distribution map coordinates
Conversion between mechanical lens barrel action coordinate, telescopic location when calculating machine lens barrel is focused；
(8) the flexible lens barrel of computer controls moves to the above and calculates on the position tried to achieve, and completes auto-focusing.
The beneficial effects of the present invention are：Using the method for automatically adjusting focus of passive type, it is not required to special focus and adjusts
Regulating device, it is easy to devices with low cost and miniaturization.Relative to the contrast method of generic use Image Edge-Detection, by frequency
The comparing and analysis of domain composition, the harmful effect that picture noise can be avoided to bring automatic focal adjustments precision, are more suitable for
To the automatic focal adjustments of transmission imaging, especially for human body skin inside capilary, its shape and distribution in the case of noninvasive
With periodically, become apparent in the feature of frequency domain, therefore automatic focal adjustments of the invention are more accurate.In the operation of device
Aspect, this method is easier, it is easy to actually used.
Brief description of the drawings
Fig. 1 is frequency domain distance (frequency spectrum RMS) numeric distribution figure.
Specific embodiment
With reference to specific embodiment, the present invention will be further described.
The method for automatically adjusting focus based on frequency domain comparison method, it is characterised in that：Including procedure below：
Computer controls machinery Telescopic mirror cylinder, adjusts digital camera, or imaging non-spherical lens, or microcobjective
Position, flexible lens barrel carries out telescopic moving, camera while being shot on one side, acquisition K width view data I0..., Ii...,
Ij..., IK-1, the horizontally or vertically composition to every piece image carries out discrete Fourier transform, the data after Fourier transformationRepresented with formula 1：
Wherein,The horizontally or vertically composition of the y row/columns of the i-th width photographs is represented, the unit of i is width；N is
Image laterally/number of pixels of longitudinal direction, unit is pixel, x be image laterally/coordinate of longitudinal direction, y is image longitudinal direction/horizontal
Coordinate, unit is pixel, and u is view data frequency domain coordinates, and unit is Hz；
Above-mentioned transformation results are converted into the energy frequency spectrum with dB as numerical value unit, then energy frequency spectrum is averagely counted
Calculation obtains the horizontal/vertical energy frequency spectrum of the image, that is, image frequency components, with GiU () [dB] is represented, computing formula
It is as follows：
In image, apart from d (G between the horizontal/vertical frequency components of the i-th width image and jth width imagei,Gj) multiply flat using two
Mean square root is tried to achieve, as shown in Equation 4：
Wherein, the frequency domain distance between d represents two images, unit is [dB], Gi,GjRespectively the frequency domain of two images into
Point, unit is [dB]；
In theory, when the fog-level of two images is identical, that is, focal point position distance it is identical when, frequency domain distance
It is 0, in this case, formula 5 can be obtained according to formula 4：
Due to [Gi(u)-Gj(u)]2>=0, therefore：
(subscript j represents the position of image, and unit is width；J in formula represents complex symbol)；
Because during shooting image, while mobile digital camera, or imaging non-spherical lens, or microcobjective, one
Side shoots, so, the position of the every piece image in image sets, correspondence digital camera, or imaging non-spherical lens, or
The position of microcobjective, namely mechanical-stretching lens barrel telescopic location, it is non-with focusing position identical two it can be seen from formula 6
Focus image, their relations on the telescopic location of mechanical-stretching lens barrel meet the functional relation shown in formula 7：
|fu(i) |=| fu(j) | formula 7
According to geometric optical theory, non-the image blurring of focusing generation is considered as having carried out low pass Gauss to focus image
Function in filtering process, therefore formula 7 can be approximate see Gaussian function as, as shown in Equation 8：
Here, i represents the telescopic location of mechanical-stretching lens barrel, and unit is um, icThe center of Gaussian function is represented, i.e.,
Focusing position, unit is um, and K represents the number of shooting image, and unit is width, and σ represents one on camera lens constant parameter；
Absolute value and natural logrithm exploitation are carried out to formula 8, formula 9 can be obtained：
The calculating substrate of formula 9 is changed to 10, formula 9 can be changed into the form of formula 10：
According to formula 10, the function on i in formula 7 is obtained, as shown in Equation 11：
|fu(i) |=log | Fu(i) |=ai2+ bi+c formulas 11
Bring formula 11 into formula 7, can obtain：
Therefore, by the comparing to image frequency domain, following two minimums can be obtained：
According to formula 13, two minimums represent two straight lines on plane coordinates respectively, and two intersecting point coordinates of straight line are just
It is unique minimum, this unique minimum, the telescopic location of mechanical lens barrel when being exactly required focusing；
Two parameters of straight line in formula 13 are can be calculated by the minimum value line by line to 2-D data, then to two straight lines
Intersection point solution is carried out, its transverse axis/ordinate of orthogonal axes value is exactly the telescopic location of mechanical lens barrel when focusing；
Control machinery lens barrel stretches to the position and is capable of achieving auto-focusing.
The method that this computational methods carries out auto-focusing, comprises the following steps：
(1) user adjusts imaging module, imaging unit or lens unit using the flexible of rocking bar control machinery lens barrel
Position, completes focusing coarse adjustment；
(2) user sends auto-focusing and instructs by rocking bar and other command devices to computer；
(3) computer receives instruction, starts auto-focusing；
(4) computer controls machinery lens barrel, centered on current location, according to preset range upwards/lower movement, reach pre-
If stopping movement behind position；Camera start recording image, at the same mechanical lens barrel start with the position after stopping as starting point to
Lower/upper movement；While mobile, camera records image to mechanical lens barrel on one side, and the image of record is stored in internal memory or hard disk
In memory；
(5) shoot after terminating, computer reads image information, image information is processed using frequency domain comparison method, obtain RMS points
Butut；
(6) computer uses algorithm, the calculated minimum point line by line in RMS distribution maps, and connects these points and obtain two
The straight line of intersection；
(7) computer uses algorithm, and two intersecting point coordinates of the straight line of intersection are tried to achieve in calculating, using RMS distribution map coordinates
Conversion between mechanical lens barrel action coordinate, telescopic location when calculating machine lens barrel is focused；
(8) the flexible lens barrel of computer controls moves to the above and calculates on the position tried to achieve, and completes auto-focusing.
Wherein, the transverse axis in Fig. 1 represents the image i for needing to be compared by frequency domain, and unit is width, and the longitudinal axis represents what frequency domain compared
Sample image j, unit is width.Brightness in figure represents frequency domain distance, that is, frequency spectrum RMS value size, brighter value, also
It is the white portion in image, frequency domain is in larger distance, illustrates that the similarity of image i at this moment and image j is relatively low.Dark value,
Namely black portions in image, frequency domain is in small distance, illustrates that the similarity of image i at this moment and image j is higher.Because burnt
Image at point position is more clear, and the image similarity with other positions is minimum, so according to formula 13, two oblique similar
The intersection point of degree black region higher is exactly required focal position.
Claims (2)
1. the method for automatically adjusting focus of frequency domain comparison method is based on, it is characterised in that：Including procedure below：
The position of computer controls machinery Telescopic mirror cylinder, adjustment digital camera or imaging non-spherical lens or microcobjective, stretches
Lens barrel obtains K width view data I while carry out telescopic moving, camera while being shot0...,i,…,j,…,K-1, to every
The horizontally or vertically composition of piece image carries out discrete Fourier transform, the data after Fourier transformationRepresented with formula 1：
Wherein,The horizontally or vertically composition of the y row/columns of the i-th width photographs is represented, the unit of i is width；N is image
The number of pixels of laterally/longitudinal direction, unit is pixel, x be image laterally/coordinate of longitudinal direction, y is the seat of image longitudinal direction/horizontal
Mark, unit is pixel, and u is view data frequency domain coordinates, and unit is Hz；
Above-mentioned transformation results are converted into the energy frequency spectrum with dB as numerical value unit, then average computation is carried out to energy frequency spectrum and obtained
To the horizontal/vertical energy frequency spectrum of the image, that is, image frequency components, with GiU () [dB] is represented, computing formula is as follows
It is shown：
In image, apart from d (G between the horizontal/vertical frequency components of the i-th width image and jth width imagei,Cj) multiply average flat using two
Root is tried to achieve, as shown in Equation 4：
Wherein, the frequency domain distance between d represents two images, unit is [dB], Gi,CjRespectively the frequency components of two images, single
Position is [dB]；
In theory, when the fog-level of two images is identical, that is, focal point position distance it is identical when, frequency domain distance be 0,
In this case, formula 5 can be obtained according to formula 4：
Due to [Gi(u)-Gj(u)]2>=0, therefore：
Wherein, subscript j represents the position of image, and unit is width；J in formula represents complex symbol；
Because during shooting image, mobile digital camera or imaging non-spherical lens or microcobjective, and meanwhile shoot, so,
The position of the position of the every piece image in image sets, correspondingly digital camera, or imaging non-spherical lens, or microcobjective
Put, namely mechanical-stretching lens barrel telescopic location, it can be seen from formula 6, and two non-focus images of focusing position identical, they
Relation on the telescopic location of mechanical-stretching lens barrel meets the functional relation shown in formula 7：
|fu(i) |=| fu(j) | formula 7
According to geometric optical theory, non-the image blurring of focusing generation is considered as having carried out low pass gaussian filtering to focus image
Treatment, therefore function in formula 7 can be approximate sees Gaussian function as, as shown in Equation 8：
Here, i represents the telescopic location of mechanical-stretching lens barrel, and unit is um, icThe center of Gaussian function is represented, that is, is focused
Position, unit is um, and K represents the number of shooting image, and unit is width, and σ represents a constant parameter on camera lens；
Absolute value and natural logrithm exploitation are carried out to formula 8, formula 9 can be obtained：
The calculating substrate of formula 9 is changed to 10, formula 9 can be changed into the form of formula 10：
According to formula 10, the function on i in formula 7 is obtained, as shown in Equation 11：
|fu(i) |=log | Fu(i) |=ai2+ bi+c formulas 11
Bring formula 11 into formula 7, can obtain：
Therefore, by the comparing to image frequency domain, following two minimums can be obtained：
According to formula 13, two minimums represent two straight lines on plane coordinates respectively, and the intersecting point coordinate of two straight lines is exactly only
One minimum, this unique minimum, the telescopic location of mechanical lens barrel when being exactly required focusing；
Two parameters of straight line in formula 13 are can be calculated by the minimum value line by line to 2-D data, then two straight lines are carried out
Intersection point is solved, and its transverse axis/ordinate of orthogonal axes value is exactly the telescopic location of mechanical lens barrel when focusing；
Control machinery lens barrel stretches to the position and is capable of achieving auto-focusing.
2. a kind of method that auto-focusing is carried out using computational methods as claimed in claim 1, it is characterised in that：Including as follows
Step：
(1) user uses the flexible of rocking bar control machinery lens barrel, the position of adjustment imaging unit, imaging unit or lens unit
Put, complete focusing coarse adjustment；
(2) user sends auto-focusing and instructs by rocking bar and other command devices to computer, and computer receives instruction, starts
Auto-focusing；
(3) computer controls machinery lens barrel, centered on current location, according to preset range upwards/lower movement, reach default position
Postpone stopping movement；Camera start recording image, at the same mechanical lens barrel start with the position after stopping as starting point to lower/upper
It is mobile；, while mobile, camera is while record image, the image of record is stored in the memory of internal memory or hard disk for mechanical lens barrel
In；
(4) shoot after terminating, computer reads image information, image information is processed using frequency domain comparison method, obtain RMS distributions
Figure；
(5) computer uses algorithm, the calculated minimum point line by line in RMS distribution maps, and connects these points and obtain two intersections
Straight line；
(6) computer uses algorithm, and two intersecting point coordinates of the straight line of intersection are tried to achieve in calculating, using RMS distribution maps coordinate to machine
Conversion between tool lens barrel action coordinate, telescopic location when calculating machine lens barrel is focused；
(7) the flexible lens barrel of computer controls moves to the above and calculates on the position tried to achieve, and completes auto-focusing.
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| CN108376394A (en) * | 2018-01-12 | 2018-08-07 | 上海大学 | A kind of camera Atomatic focusing method and system based on frequency domain histogram analysis |
| WO2021082688A1 (en) * | 2019-10-31 | 2021-05-06 | 广州市浩洋电子股份有限公司 | Machine-vision-based intelligent focusing method for moving head computer lamp |
| CN113852761A (en) * | 2021-09-27 | 2021-12-28 | 宁波华思图科技有限公司 | Automatic focusing method of intelligent digital microscope |
| US12031704B2 (en) | 2019-10-31 | 2024-07-09 | Guangzhou Haoyang Electronic Co., Ltd. | Intelligent focusing method of intelligent moving head light based on machine vision |
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| 黄德天: "《基于图像技术的自动调焦方法研究》", 《中国博士学位论文全文数据库 信息科技辑》 * |
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| CN108376394A (en) * | 2018-01-12 | 2018-08-07 | 上海大学 | A kind of camera Atomatic focusing method and system based on frequency domain histogram analysis |
| CN108376394B (en) * | 2018-01-12 | 2021-08-10 | 上海大学 | Camera automatic focusing method and system based on frequency domain histogram analysis |
| WO2021082688A1 (en) * | 2019-10-31 | 2021-05-06 | 广州市浩洋电子股份有限公司 | Machine-vision-based intelligent focusing method for moving head computer lamp |
| US12031704B2 (en) | 2019-10-31 | 2024-07-09 | Guangzhou Haoyang Electronic Co., Ltd. | Intelligent focusing method of intelligent moving head light based on machine vision |
| CN113852761A (en) * | 2021-09-27 | 2021-12-28 | 宁波华思图科技有限公司 | Automatic focusing method of intelligent digital microscope |
| CN113852761B (en) * | 2021-09-27 | 2023-07-04 | 宁波华思图科技有限公司 | Automatic focusing method for intelligent digital microscope |
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