CN110324536A - A kind of image change automatic sensing focusing method for micro- camera - Google Patents
A kind of image change automatic sensing focusing method for micro- camera Download PDFInfo
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Abstract
The invention discloses a kind of image change automatic sensing focusing methods for micro- camera, comprising the following steps: defines several scenes state according to the variable condition of brightness of image and object selection value；Monitor the brightness of image of current scene and the real-time change situation of object selection value, scene state locating for current scene is determined according to the real-time change situation of brightness of image and object selection value, focusing monitoring strategies corresponding with the scene state are used according to scene state, the focusing monitoring strategies include: to restore to stablize to brightness of image and/or object selection value, into single focus process；Single focus process is executed based on search by hill climbing method, determines best focus position.The image change automatic sensing focusing method can use automatically different focusing strategies according to different focus scene, to promote focusing accuracy.
Description
Technical field
The invention belongs to micro- camera Autofocus Technology fields, and in particular to a kind of image change for micro- camera
Automatic sensing focusing method.
Background technique
Autofocus Technology is by modern microelectronic technology, digital image processing techniques and mechanical control method, with number
The clarity of word method evaluation goal scene replaces manual focusing with automatic focusing, finally makes one kind of system blur-free imaging
Technology.Autofocus Technology is widely used in the fields such as machine vision, military affairs, safety monitoring, smart phone, and gradually sends out
Transform into Yi Menji it is light, mechanical, electrical, calculate in one complex technology.
The Atomatic focusing method of early stage has telemetry and focusing test method.Wherein, telemetry includes ultrasonic distance measurement method, infrared survey
Away from method, laser ranging method and triangle telemetry etc..Focusing test method mainly includes contrast detection method, phase difference detection method etc..Contrast inspection
Survey method and phase-detection method Autofocus Technology are usually used in slr camera, and other methods are then since system realizes complicated and accuracy
It is not high, it is not necessarily suitable industrial circle.
Most widely used currently based on the Atomatic focusing method of Digital Image Processing, it includes Depth from defocus and to depth of focus
Degree method two major classes.Depth from defocus is a kind of method of the acquirement depth information to complete auto-focusing, institute from out-of-focus image
Need image and calculation amount small, focusing speed is fast, but since Depth from defocus requires to establish the approximate imaging system estimated in advance
Mathematical model, therefore precision of focusing is not high enough.Focusing depth method needs a series of image at different focus positions, using one kind
Suitable focusing evaluation function describes the clarity of image, corresponds to best focus position at evaluation function maximum value.
Focus search algorithm is one of the key technology of focusing depth method auto-focusing, and common algorithm has the method for exhaustion, climbs
Mountain method, Fibonacci method, functional approaching.Search by hill climbing method is because effect is good and simple and easy is widely used.Search by hill climbing method
Principle it is as follows: searched for since any, search often take a step forward, system can all acquire the image of corresponding position and calculate its figure
As evaluation function value.If object selection value starts to reduce, changes direction of search reduction step-length and continue searching, search repeatedly
Rope, until step-length is reduced to predetermined minimum, focusing terminates.Search by hill climbing method has some limitations: noise jamming causes
There is local peaking in evaluation function curve, causes accidentally to focus.
Application publication number is that the patent application of CN 107509023A discloses a kind of auto-focusing searching algorithm, will be climbed the mountain
Search method and functional approaching combine, and the search by hill climbing method in the algorithm uses the two-part algorithm of coarse-fine combination: rough
When focusing, big step pitch considers the rapidity of algorithm, and gray variance function is selected quickly to approach focusing position；When fine focusing
When, half step distance considers that the sensitivity of algorithm uses Laplacian function exact focus position.It is reduced by comparing 3 width pictures
Focusing and fits best focusing position at section in minizone using functional approaching.The auto-focusing searching algorithm root
Change the direction of search and adjustment step-size in search according to object selection value size, to shorten the auto-focusing time.
Above-mentioned is all single focusing method, and defect is after scene changes, and needs manual operation ability
Realize focusing.
Summary of the invention
In view of above-mentioned problem, the present invention provides a kind of image change automatic sensing focusings for micro- camera
Method, the image change automatic sensing focusing method are based on search by hill climbing method, increase to focusing scene monitoring function, Neng Gougen
Different focusing strategies is used, automatically according to different focus scene to promote focusing accuracy.
The technical solution of the present invention is as follows:
A kind of image change automatic sensing focusing method for micro- camera, comprising the following steps:
Several scenes state is defined according to the variable condition of brightness of image and object selection value；
The brightness of image of current scene and the real-time change situation of object selection value are monitored, according to brightness of image and figure
As the real-time change situation of evaluation function value determines scene state locating for current scene, used according to scene state and the scene
The corresponding focusing monitoring strategies of state, the focusing monitoring strategies include: to restore to brightness of image and/or object selection value
Stablize, into single focus process；
Single focus process is executed based on search by hill climbing method, determines best focus position.
This is for realizing single pair based on search by hill climbing method in the image change automatic sensing focusing method of micro- camera
Burnt process carries out the monitoring of brightness of image and object selection value to scene image, according to image after single focusing
The situation of change of brightness and object selection value, determines which kind of scene state the scene image of monitoring is in, according to different
Scene state uses corresponding focusing monitoring strategies, when monitoring scene tend towards stability after automatic starting focusing again, improve pair
Pyrogene exactness.
In the present invention, according to the situation of change of brightness of image and object selection value, 4 kinds of scene states are defined.Tool
Body, the scene state includes:
Scene state I: brightness of image and object selection value remain unchanged in single focus process, show current scene
It does not change；
Scene state II: brightness of image changes in single focus process, shows that current scene changes；
Scene state III: object selection value maximum value, and object selection value are searched in single focus process
It changes, shows that current scene changes；
Scene state IV: after the completion of single focusing, object selection value changes, and shows that current scene becomes
Change.
Above-mentioned 4 kinds of scene states are to summarize to obtain by many experiments, when scene is in scene state II, scene state
When III and scene state IV, show that scene changes, needs to re-start focus process.
In the present invention, brightness of image is changed into the judgment criteria as scene state II, specifically, will focus last time terminates
When brightness of image and current focus process in the changing value of the difference of brightness of image that calculates as brightness of image；
During scene monitoring, when the changing value of brightness of image is greater than threshold value ThrDifZL2, then it is assumed that brightness of image hair
It is raw to change；The changing value of brightness of image is less than or equal to threshold value ThrDifZL2, then it is assumed that brightness of image remains unchanged.
On the basis of defining scene state, it can be based on the scene state type in practical applications, according to field
The brightness of image of scape and the real-time change situation of object selection value carry out preliminary classification, specifically, the basis to scene
The real-time change situation of brightness of image and object selection value determines that scene state locating for current scene includes:
Brightness of image changes, then current scene is marked to be in scene state II；
On the basis of searching object selection value maximum value, when the changing value of object selection value maximum value is big
When threshold value ThrDifFV1, label current scene is in scene state III；
Brightness of image remains unchanged, and does not search object selection value maximum value or object selection value maximum value
When changing value is less than or equal to threshold value ThrDifFV1, label current scene is in scene state I；
On the basis of searching object selection value maximum value, when the changing value of object selection value is greater than threshold value
When ThrDifFV2, label current scene is in scene state IV；
The object selection value that will be searched in object selection value at the end of current focusing and current focus process
Changing value of the difference of maximum value as object selection value maximum value.
After single is focused, determine to whether there is scene changes in single focus process, specifically, logical movement images are commented
The changing value and threshold value ThrDifFV1 of valence functional value maximum value are realized, when the changing value of object selection value maximum value is greater than
When threshold value ThrDifFV1, it is believed that scene is changed in focus process, exits current focusing.
After single focusing is exited, it is also necessary to which whether monitoring scene changes, and equally passes through brightness of image and picture appraisal
The situation of change of functional value reacts scene situation of change.When the changing value of brightness of image is greater than threshold value ThrDifZL2 and image
When the changing value of evaluation function value is greater than threshold value ThrDifFV2, it is believed that scene is changed.Since brightness of image and image are commented
One statistical information of valence functional value certainly exists fluctuation, therefore the threshold value being arranged has to be larger than the maximum value of fluctuation.
Following situations occurs in order to prevent: such as under low-illumination scene, statistical information fluctuation is relatively large, it may appear that scene
Do not become, but Rule of judgment meets, error starting of focusing.Therefore increase additional restrictive condition in the present invention: must be twice in succession
All it is judged as that scene changes, just thinks that scene is veritably to be changed, i.e., judges current scene for scene continuous 2 times
When state I I, scene state III or scene state IV, just determine current scene be really scene state II, scene state III or
Scene state IV.
Scene state classification is to realize that the stability fundamental of focusing monitoring can be according to specific after determining scene state
Scene state monitors the variation of corresponding brightness of image or object selection value, determines the opportunity of restarting focusing, in this way
Focusing time can either be shortened, be also able to ascend focusing accuracy.
Change when monitoring scene, i.e., judgement scene state be scene state II, scene state III and scene shape
When state IV, restart single focusing again after needing to wait scene stillness, otherwise can frequently restart focusing, it is of the invention according to figure
Image brightness and the variation degree of object selection value determine whether scene is static.
In the present invention, when scene state is scene state II, the focusing monitoring strategies of use include:
During scene monitoring, when the brightness of image difference of adjacent two moment scene is less than threshold value ThrDifZL3, table
The brightness of image of light field scape is restored to stablize, and restarting enters single focus process.
When scene state is scene state II, show that the brightness of image of scene is changed, such as sample moves
The brightness of image of scene is caused to change, at this point, the focusing monitoring strategies used are the amplitudes of variation of detection image brightness,
When brightness of image amplitude of variation very little shows that brightness of image tends towards stability, at this time automatically when being less than given threshold ThrDifZL3
Restarting focusing, avoids and manually restarts focusing, shortens focusing time, restarts again when brightness of image tends towards stability
Focusing, also can guarantee the accuracy of focusing.
In the present invention, when scene state is scene state III, the focusing monitoring strategies of use include:
During scene monitoring, when the object selection value difference value of adjacent two moment scene is less than threshold value
When ThrDifFV3, show that the object selection value of scene is restored to stablize, restarting enters single focus process.
In the present invention, when scene state is scene state IV, the focusing monitoring strategies of use include:
During scene monitoring, when the object selection value difference value of adjacent two moment scene is less than threshold value
ThrDifFV3, i.e. the object selection value of scene restore after stablizing, and continue the variation for judging object selection value, when working as
When changing value at the end of the preceding more last focusing of object selection value is greater than threshold value ThrDifFV2, restarting enters single
Secondary focus process；
When scene state is scene state III and scene state IV, show that the object selection value of scene is changed
Become.At this point, the focusing monitoring strategies used are the amplitudes of variation of detection image evaluation function value, for scene state III, only
The amplitude of variation for sampling the object selection value at adjacent two moment is judged, when amplitude of variation very little, is less than given threshold
When ThrDifFV3, show object selection value regional stability, focusing of resetting automatically at this time；For scene state IV, by
After the definition of scene state IV is single focusing, object selection value changes, therefore, at adjacent two moment
The amplitude of variation of object selection value is less than on the basis of given threshold ThrDifFV3, it is also necessary to judge object selection
It is worth the changing value situation of maximum value, the changing value of object selection value maximum value is when being greater than threshold value ThrDifFV2, automatic weight
New starting focusing, avoids and manually restarts focusing, shortening focusing time, restarts again pair when brightness of image tends towards stability
Coke also can guarantee the accuracy of focusing.
When scene state is scene state I, continue the brightness of image and object selection value that monitor current scene
Real-time change situation.
Preferably, threshold value ThrDifZL2 value is 150~200, and the value of threshold value ThrDifZL3 is 100~120, into one
Step ground, threshold value ThrDifZL2 value are 200, and the value of threshold value ThrDifZL3 is 100.
Preferably, the object selection that threshold value ThrDifFV1, the selection of threshold value ThrDifFV2 and previous moment obtain
The size of value has relationship, and general rule is, the object selection value that the size of threshold value ThrDifFV2 is obtained with previous moment
Increase and increases.
In the present invention, in order to improve focusing efficiency, executed in single focus process based on search by hill climbing method, using change
The way of search search of step-length indicates the object selection value maximum value of best focus position, detailed process are as follows:
Scene is divided into defocus region and focal zone according to object selection value size, in defocus region, using compared with
Big step-size in search；In focal zone, the smaller step-size in search of use.
In the present invention, in order to improve focusing accuracy, executed in single focus process based on search by hill climbing method, it is also right
The direction of search is modified, detailed process are as follows:
The average value of adjacent four steps object selection value is calculated twice in succession, if preceding four steps object selection value is flat
Mean value be greater than rear four steps object selection value average value, indicate to defocus direction search for, then change the direction of search after
It is continuous to find the object selection value maximum value for indicating best focus position.
In the present invention, object selection value, detailed process are calculated using high fdrequency component are as follows:
It is filtered using FIR filter V1, FIR of the iir filter H1 of horizontal direction, iir filter H2 and vertical direction
Device V2 is filtered scene image, exports high fdrequency component；
Judged again by threshold value after taking absolute value to the high fdrequency component of output, statistics is more than that the high frequency of threshold gate limit value is logical
Amount, obtains the statistical value of high fdrequency component；
Assuming that the statistical value of the high fdrequency component of region n corresponding four filters output is respectively H1_n, H2_n, V1_n,
V2_n, then the two of region n group object selection value FV1_n and FV2_n is respectively as follows:
FV1_n=α × H1_n+ (1- α) × V1_n
FV2_n=β × H2_n+ (1- β) × V2_n
Wherein, wherein α, β are respectively weight coefficient.
The invention has the benefit that
Present invention energy automatic sensing direction of search in focus search, and be rapidly returned to after Search Error direction, subtract
Small focusing time；
The present invention can be adaptive change step-length, select long step-length in defocus regional movement, focal zone selects when moving
With small step-length, focusing speed is accelerated, small step length is taken to scan for can be improved focusing precision in focal zone；By right
The expansion of object selection realizes the function that focusing can be also completed in the case where low image quality；
Present invention also adds focusing monitoring functions, pass through the monitoring to brightness of image and picture appraisal parameter value, energy
Enough variations for more accurately judging scene, realize automatic focusing function；After focusing is exited, scene changes are monitored twice
It is judged as that scene is really changed, avoids the influence that weak vibrations generate algorithm, realizes more stable scene prison
Control function；After being judged as that scene changes, continue monitoring scene variation, until being judged as that scene stillness just restarts focusing,
It avoids because being constantly in the state frequently focused during scene changes, improves the stability and accuracy of focusing.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to do simply to introduce, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art, can be with root under the premise of not making the creative labor
Other accompanying drawings are obtained according to these attached drawings.
Fig. 1 is the flow chart for the single focusing that embodiment provides；
Fig. 2 is to judge different scenes state flow chart according to single focusing result；
Fig. 3 is that rear scene condition monitoring flow chart is exited in single focusing；
Fig. 4 is the calculating logic block diagram of object selection value.
Specific embodiment
To make the objectives, technical solutions, and advantages of the present invention more comprehensible, with reference to the accompanying drawings and embodiments to this
Invention is described in further detail.It should be appreciated that the specific embodiments described herein are only used to explain the present invention,
And the scope of protection of the present invention is not limited.
Embodiment proposes a kind of image change automatic sensing focusing method for micro- camera, passes through monitoring strategies of focusing
Monitoring image variation, restarts single focus process, and the function of auto-focusing is realized in the case where image change.
The image change automatic sensing focusing method for being used for micro- camera can be in the microfacies for being equipped with stepper motor
It is realized in machine.Wherein motor whole process has 854 steps, and stepper motor can move on to specified according to image change automatic sensing focusing method
Position captures different location image and finds optimum focusing position according to the criterion in image change automatic sensing focusing method
It sets, that is, finds object selection value maximum value.
This is used for the specific implementation flow of the image change automatic sensing focusing method of micro- camera are as follows: starting is based on first
The single of search by hill climbing method is focused, and after motor is successfully found best focus position, judges scene state, monitors plan into focusing
Slightly, the variation of monitoring image brightness and object selection value after monitoring that image changes, is stablized to image change,
Focus function is restarted again.
In the present embodiment, parameter 2 is referred to as using brightness of image as referred to as parameter 1, object selection value.Such as Fig. 1
It is shown, single focus process is executed based on search by hill climbing method, determines the process of best focus position are as follows:
S101 determines initial search direction.
7 are set by motor search first step step-length, two images is captured respectively, calculates 2 value of parameter of two images simultaneously
Compare, initial search direction is set to the direction of the increase of parameter 2.
S102, motor variable step-size search.
It in order to improve focusing efficiency, is scanned for according to variable step-size search mode, specific search process are as follows:
Firstly, dividing defocus region and focal zone according to parameter 2；In the biggish step-size in search of defocus regional choice,
So that motor is left defocus region within a short period of time, into focal zone, shortens in the unnecessary search in defocus region
Between；Lesser step-size in search is then selected in focal zone, motor is made more accurately to search for best focal point；Meanwhile considering focusing
The step-size in search of situation of the initial position of search near best focal point, focal zone can be segmented further, work as focusing
The initial position of search first uses small step length searching, after continuously searching for 10 times, if not finding optimum focusing also in focal zone
Point, then increase step-size in search.
In the present embodiment, the step-size in search of next step is determined according to 2 threshold value ThrFV of parameter and 2 current value of parameter:
Wherein, stepn+1For motor movement step next time, FVnFor the object selection value of n-th, i.e. parameter 2,
ThrFV is 2 threshold value of parameter, which is defocus region and focal zone by motor movement region division, and parameter 2 is greater than the threshold value
The region of ThrFV is focal zone, is otherwise defocus region.It is measured according to experiment, threshold value ThrFV=30.
In search process, the parameter 2 of continuous four width image is calculated, is denoted as FV respectively1、FV2、FV3、FV4, work as FV1<FV2>
FV3>FV4And FV2When > ThrMaxFV, then judgement has found best focus position, FV2Corresponding picture position is exactly optimum focusing
Position returns to best focus position.Threshold value ThrMaxFV, should be according to real image evaluation function for judging best focus position
Value setting, the range that this threshold value can be chosen are to be less than optimum focusing peak value greater than local peaking, measure by experiment,
ThrMaxFV=400.
S103, judges whether preceding 15 step searches best focus position, if preceding 15 step searches best focus position, returns
Best focus position executes S104 if preceding 15 step does not search best focus position；
S104 is recorded and is judged that preceding 15 step captures the maximum value of the parameter 2 of image and whether is greater than given threshold
ThrStartFV expands 2 value of parameter of subsequent searches areas captured image if the maximum value of parameter 2 is less than ThrStartFV
10 times big, then motor variable step continues searching, that is, jumps and execute S102；It, will if the maximum value of parameter 2 is greater than ThrStartFV
The parameter 2 of subsequent searches areas captured image remains unchanged, then motor variable step continues searching, that is, jumps and execute S102.
Threshold value ThrStartFV is used to the size of substantially forecast image search global parameters 2, may be configured as and threshold value
ThrMaxFV is equal.The case where best peak value evaluation function of image is too small when occurring, and is less than threshold value ThrMaxFV, can not lead at this time
The criterion identification best focus position of S102 is crossed, therefore just needs to identify such case by given threshold ThrStartFV,
To expand parameter 2, then carry out the judgement of S102.
S105 determines that this time focusing result is defocus if never searching best focus position, and focusing terminates,
And exit this focus process.
In order to improve focusing accuracy, also motor movement direction, that is, direction of search is modified in search process, is made
Motor to defocus range searching when turn to immediately, the specific method is as follows:
The average value of adjacent four steps parameter 2 is calculated twice in succession, if the average value of preceding four steps parameter 2 is greater than rear four steps parameter
2 average value indicates to search for toward defocus direction, then changes the direction of search and continually look for best focus position.
Experiment can voluntarily select to feel using ROI (Region of Interest, area-of-interest) focusing window
The region of interest carries out auto-focusing.It divides the image into that 7*7 block equal area is for selection, can be realized the sample uneven to height
Product are focused, and the interference that different object distances generate focusing is avoided, and realize exact focus.
In the present embodiment, using high fdrequency component calculating parameter 2.As shown in figure 4, wherein TH1, TH2, TH3, TH4 are respectively
The threshold value of setting.First then original image is taken absolute value the output of filter by obtaining high fdrequency component after filter
Judged again by threshold value thresholding afterwards, the participation more than threshold value counts, the statistical value of final output image high fdrequency component, using four
Road high-pass filter, respectively the iir filter H1, iir filter H2 of horizontal direction and the FIR filter V1 of vertical direction,
FIR filter V2.Assuming that the statistical value of region n corresponding four filters output is respectively H1_n, H2_n, V1_n, V2_n, then
Two groups of evaluation function values FV1_n and FV2_n in the region can be calculated by following formula:
FV1_n=α × H1_n+ (1- α) × V1_n
FV2_n=β × H2_n+ (1- β) × V2_n
Wherein, α takes 0.45, β to take 0.85.
After single focusing, scene state is judged, into focusing monitoring strategies, monitoring image brightness and picture appraisal
The variation of functional value after monitoring that image changes, is stablized, then restart focus function to image change.
In the present embodiment, scene state is divided into 4 kinds, is respectively as follows: scene state I: brightness of image in single focus process
It is remained unchanged with object selection value, shows that current scene does not change；Scene state II: image in single focus process
Brightness changes, and shows that current scene changes；Scene state III: picture appraisal letter is searched in single focus process
Numerical value maximum value, and object selection value changes, and shows that current scene changes；Scene state IV: single focusing
After the completion, object selection value changes, and shows that current scene changes.When monitoring that scene is in scene state
When II, scene state III and scene state IV, show that scene changes, needs to be restarted automatically focus function.
Flow chart according to Fig.2, after single focusing, according to the variation of parameter 1 and parameter 2, by scene
State preliminary classification, motor, which often makes a move, records the variation of parameter 1, judges whether the variation of parameter 1 is greater than given threshold, if
Greater than threshold value, this shows that scene changes in focus process, then scene state preliminary classification is scene state II.Scene state
The purpose of II setting is to judge whether sample moves during the focusing process, if sample is mobile, the variation of parameter 1 is greater than threshold
Value ThrDifZL1, by experiment, threshold value is set as ThrDifZL1=2000.
After having monitored parameter 1 and having realized to the classification of scene state II, after waiting scene brightness to stablize, then to parameter 2 into
Row monitoring, when not finding best focus position, preliminary judgement scene state is scene state I.
If finding best focus position in focus process, according to the present invention in improved search by hill climbing method, figure is being found
As that can return at the peak value after evaluation function peak of curve, in the case where scene does not change, the figure at peak point is returned to
As the maximum value recorded in evaluation function value and focus process is approximately equal, if two values have big difference, illustrate focus process
Middle scene changes, and current location is not real focal position.Therefore, last focusing terminates 2 value of parameter returned
The difference of 2 maximum value FV2 of parameter should be less than certain threshold value ThrDifFV1 in FV1 and focus process, if being more than threshold value, it may be assumed that
|FV1-FV2|>ThrDifFV1
Then marking scene state is scene state III, and otherwise marking scene state is scene state I.
It is tested according to experiment, is provided that threshold value ThrDifFV1 according to FV1 size
Flow chart according to Fig.3, after single is focused, enters different focus monitoring plan according to different scene states
Slightly.If scene state is tentatively denoted as scene state I, continue monitoring parameters 1 and parameter 2, is calculated every time 0.2s primary
The value FV2 of the value ZL2 of current scene parameter 1, parameter 2, respectively with last focusing at the end of the value ZL1 of parameter 1, parameter 2
Maximum value FV1 compares, when variation is more than certain threshold value, then it is assumed that scene is changed.The variation of parameter 1 is more than threshold value
ThrDifZL2, note scene state are scene state II；The variation of parameter 2 is more than threshold value ThrDifFV2, and note scene state is scene
State I V.It is shown below:
|ZL1-ZL2|>ThrDifZL2
|FV1-FV2|>ThrDifFV2
Parameter 1 and parameter 2 are a statistical informations, certainly exist fluctuation, therefore the threshold value being arranged has to be larger than fluctuation
Maximum value.It is tested according to experiment, threshold value ThrDifZL2=200, ThrDifFV2 setting are as follows:
If scene state is denoted as scene state II, after waiting scene brightness to stablize, then single focus function is restarted.It is i.e. every
A moment (such as the value ZL of a current scene parameter 1 is calculated every time 0.2s)T, and the ZL with last momentT-tCompare,
When variation is less than threshold value, it may be assumed that
|ZLT-ZLT-t|<ThrDifZL3
It is static then to think that scene tends towards stability, restarting focusing.It is tested according to experiment, 1 change threshold of parameter
ThrDifZL3=100.
If scene state is denoted as scene state III, after waiting scene evaluation function value to stablize, then single focusing function is restarted
Energy.I.e. each moment (such as calculates the value FV of a current scene parameter 2 every time t=0.2s)T, and with last moment
The value FV of parameter 2T-tCompare, when variation is less than threshold value, it may be assumed that
|FVT-FVT-t|<ThrDifFV3
It is static then to think that scene tends towards stability, restarting focusing.It is tested according to experiment, 2 change threshold of parameter
ThrDifFV3=20.
If scene state is denoted as scene state IV, scene evaluation function value is waited to stablize, i.e. the variation of parameter 2 is less than certain
Threshold value ThrDifFV3, in order to prevent some weak vibrations cause focusing frequently restart, judge the parameter 2 of present image again
The relatively last focusing of value at the end of parameter 2 value variation, if still meeting scene changes condition, (variation is less than threshold
Value ThrDifFV2), then it is assumed that the scene is changed really, otherwise restarting focusing is considered as scene and does not become, is i.e. scene
State is 1, and goes successively to focusing monitoring.
In above-mentioned image change automatic sensing focusing method, the energy automatic sensing direction of search in focus search, and searching for
It is rapidly returned to after wrong way, reduces focusing time；Step-length can also adaptively be changed, selected in defocus regional movement
Long step-length, focal zone select small step-length when moving, accelerate focusing speed, and small step length is taken to scan in focal zone
It can be improved focusing precision；By the expansion to object selection, realizing can also complete to focus in the case where low image quality
Function,
Meanwhile increasing focusing monitoring method by the monitoring to image parameter 1 and parameter 2, it can more accurately
Judge the variation of scene, realizes automatic focusing function；After focusing is exited, scene changes are monitored twice and are just judged as that scene is true
Positive having occurred changes, and avoids the influence that weak vibrations generate algorithm, realizes more stable scene monitoring function；It is judged as
After scene changes, continue monitoring scene variation, until being judged as that scene stillness just restarts focusing, avoids because of scene
It is constantly in the state frequently focused in change procedure, improves the stability and accuracy of focusing.
Technical solution of the present invention and beneficial effect is described in detail in above-described specific embodiment, Ying Li
Solution is not intended to restrict the invention the foregoing is merely presently most preferred embodiment of the invention, all in principle model of the invention
Interior done any modification, supplementary, and equivalent replacement etc. are enclosed, should all be included in the protection scope of the present invention.
Claims (10)
1. a kind of image change automatic sensing focusing method for micro- camera, comprising the following steps:
Several scenes state is defined according to the variable condition of brightness of image and object selection value；
The brightness of image of current scene and the real-time change situation of object selection value are monitored, is commented according to brightness of image and image
The real-time change situation of valence functional value determines scene state locating for current scene, is used and the scene state according to scene state
Corresponding focusing monitoring strategies, the focusing monitoring strategies include: to restore steady to brightness of image and/or object selection value
It is fixed, into single focus process；
Single focus process is executed based on search by hill climbing method, determines best focus position.
2. being used for the image change automatic sensing focusing method of micro- camera as described in claim 1, which is characterized in that described
Scene state includes:
Scene state I: brightness of image and object selection value remain unchanged in single focus process, show that current scene is not sent out
Changing；
Scene state II: brightness of image changes in single focus process, shows that current scene changes；
Scene state III: object selection value maximum value is searched in single focus process, and object selection value occurs
Change, shows that current scene changes；
Scene state IV: after the completion of single focusing, object selection value changes, and shows that current scene changes.
3. being used for the image change automatic sensing focusing method of micro- camera as claimed in claim 2, which is characterized in that will be upper
Changing value of the difference of the brightness of image calculated in brightness of image and current focus process at the end of secondary focusing as brightness of image；
During scene monitoring, when the changing value of brightness of image is greater than threshold value ThrDifZL2, then it is assumed that brightness of image changes
Become；The changing value of brightness of image is less than or equal to threshold value ThrDifZL2, then it is assumed that brightness of image remains unchanged.
4. being used for the image change automatic sensing focusing method of micro- camera as claimed in claim 2, which is characterized in that described
Determine that scene state locating for current scene includes: according to the real-time change situation of brightness of image and object selection value
Brightness of image changes, then current scene is marked to be in scene state II；
On the basis of searching object selection value maximum value, when the changing value of object selection value maximum value is greater than threshold
When value ThrDifFV1, label current scene is in scene state III；
Brightness of image remains unchanged, and does not search the variation of object selection value maximum value or object selection value maximum value
When value is less than or equal to threshold value ThrDifFV1, label current scene is in scene state I；
On the basis of searching object selection value maximum value, when the changing value of object selection value is greater than threshold value
When ThrDifFV2, label current scene is in scene state IV；
The object selection value searched in object selection value at the end of current focusing and current focus process is maximum
Changing value of the difference of value as object selection value maximum value.
5. being used for the image change automatic sensing focusing method of micro- camera as claimed in claim 2, which is characterized in that on the spot
When scape state is scene state II, the focusing monitoring strategies of use include:
During scene monitoring, when the brightness of image difference of adjacent two moment scene is less than threshold value ThrDifZL3, show field
The brightness of image of scape is restored to stablize, and restarting enters single focus process.
6. being used for the image change automatic sensing focusing method of micro- camera as claimed in claim 2, which is characterized in that on the spot
When scape state is scene state III, the focusing monitoring strategies of use include:
During scene monitoring, when the object selection value difference value of adjacent two moment scene is less than threshold value ThrDifFV3,
Show that the object selection value of scene is restored to stablize, restarting enters single focus process.
7. being used for the image change automatic sensing focusing method of micro- camera as claimed in claim 2, which is characterized in that on the spot
When scape state is scene state IV, the focusing monitoring strategies of use include:
During scene monitoring, when adjacent two moment scene object selection value difference value be less than threshold value ThrDifFV3, i.e.,
The object selection value of scene is restored after stablizing, and the variation for judging object selection value is continued, when present image evaluates letter
When changing value at the end of the more last focusing of numerical value is greater than threshold value ThrDifFV2, restarting enters single focus process；
When scene state be scene state I when, continue monitor current scene brightness of image and object selection value it is real-time
Situation of change.
8. being used for the image change automatic sensing focusing method of micro- camera as described in claim 1, which is characterized in that in base
It is executed in single focus process in search by hill climbing method, the figure of best focus position is indicated using the way of search search of variable step
As evaluation function value maximum value, detailed process are as follows:
Scene is divided into defocus region and focal zone according to object selection value size, in defocus region, using relatively wantonly searching for
Suo Buchang；In focal zone, the smaller step-size in search of use.
9. being used for the image change automatic sensing focusing method of micro- camera as described in claim 1, which is characterized in that in base
It executes in single focus process, also the direction of search is modified, detailed process in search by hill climbing method are as follows:
The average value of adjacent four steps object selection value is calculated twice in succession, if the average value of preceding four steps object selection value
Greater than the average value of rear four steps object selection value, indicates to search for defocus direction, then change the direction of search and continue to seek
Look for the object selection value maximum value for indicating best focus position.
10. being used for the image change automatic sensing focusing method of micro- camera as described in claim 1, which is characterized in that benefit
Object selection value, detailed process are calculated with high fdrequency component are as follows:
Using the FIR filter V1 of the iir filter H1 of horizontal direction, iir filter H2 and vertical direction, FIR filter V2
Scene image is filtered, high fdrequency component is exported；
Being judged again by threshold value after taking absolute value to the high fdrequency component of output, statistics is more than the high frequency flux of threshold gate limit value,
Obtain the statistical value of high fdrequency component；
Assuming that the statistical value of the high fdrequency component of region n corresponding four filters output is respectively H1_n, H2_n, V1_n, V2_n,
Then two groups of object selection values FV1_n and FV2_n of region n are respectively as follows:
FV1_n=α × H1_n+ (1- α) × V1_n
FV2_n=β × H2_n+ (1- β) × V2_n
Wherein, wherein α, β are respectively weight coefficient.
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