CN101790043A - Control method for automatic focusing and device thereof - Google Patents
Control method for automatic focusing and device thereof Download PDFInfo
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- CN101790043A CN101790043A CN200910006042A CN200910006042A CN101790043A CN 101790043 A CN101790043 A CN 101790043A CN 200910006042 A CN200910006042 A CN 200910006042A CN 200910006042 A CN200910006042 A CN 200910006042A CN 101790043 A CN101790043 A CN 101790043A
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Abstract
The embodiment of the invention discloses a control method for automatic focusing and a device thereof. The method includes the steps of updating a focusing evaluation value for the current position of a focusing lens, acquiring the focusing evaluation values of a previous corresponding point and a next corresponding point for the current position of the focusing lens according to stored position codes of the corresponding points of the focusing evaluation values and the position of the focusing lens, acquiring changing trends of the current position of the focusing lens and the focusing evaluation values of the previous and next corresponding points, and finally determining the step length that the focusing lens moves according to the changing trends. In the embodiment of the invention, the moving step length of the focusing lens is determined according to the changing trends of the current position of the focusing lens and according to the focusing evaluation values of the previous and next corresponding points, so that only fine adjusting is carried out on the focusing lens in peak zones; therefore, the step length is small when the top point is found, the position of the focusing lens is changed little, the changing rate of the focusing evaluation values is low, and images cannot easily generate deceptive movement.
Description
Technical field
The present invention relates to focus area, especially relate to a kind of method and device thereof of auto focus control.
Background technology
Automatic focus (Auto Focus, camera lens was focused to shot object automatically when AF) technology referred to take, thereby obtain figure the most clearly, this technology is widely adopted on video camera (Video Camera), digital camera (Digital Still Camera), mobile phone audio and video products such as (Mobile Phone).
Auto focus control (Auto Focus Control, AFC) system as shown in Figure 1, incident ray by camera lens after imaging on the imageing sensor, picture signal produces luminance signal through image processor, and focusing evaluation value extraction module is analyzed luminance signal and obtained the focusing evaluation value, and the auto focus control module is according to the focusing evaluation value, the position that the control motor moves focusing lens, make the focusing evaluation value converge on limit, present the most clearly state of image, thereby realize automatic focus.
Prior art uses the variable step-size search method of binary chop to carry out automatic focus, and step-length is the distance that focusing lens moves at every turn, and concrete grammar is as follows:
1. determine the focusing direction: the focusing evaluation value before and after relatively moving, focusing is in the right direction if the focusing evaluation value increases expression, otherwise the direction of will focusing is reverse;
2. search limit zone: step-length is doubled, continue mobile focusing lens along correct focusing direction, if the focusing evaluation value descends, then the limit zone should be in the end between focusing evaluation value and the penult focusing evaluation value;
3. converge to limit in the zone: step-length dwindles 50%, in the end between focusing evaluation value and the penult focusing evaluation value, just in the limit zone, alternately dwindle the limit zone with opposite focusing direction, less than predefined minimum value, search finishes up to two ends, limit zone extreme value.
In research and practice process to prior art, the present inventor finds that there is following problem in prior art:
Because of needs search the limit zone fast, therefore, the step-length in search limit zone is the twice of normal step-length, make that the focusing lens shift in position is big, the rate of change that causes the focusing evaluation value is big, cause the image experience to blur-clear-fuzzy-clear this process, i.e. " deceptive movement " phenomenon can appear in image in the focusing process.
Summary of the invention
The technical problem that the embodiment of the invention will solve provides a kind of method and device thereof of auto focus control, make that the focusing lens shift in position when the limit near zone is little in the automatic focus process, the rate of change of focusing evaluation value is little, is not prone to image " deceptive movement " phenomenon.
For solving the problems of the technologies described above, embodiment provided by the present invention is achieved through the following technical solutions:
A kind of method of auto focus control:
Obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, the variation tendency of described corresponding points is the chevron curve;
Adjust described corresponding points, corresponding points are evenly distributed in the hillside district of described curve, in the district of mountain top, have and have only three;
Preserve the Position Number of described corresponding points.
A kind of method of auto focus control:
Upgrade the focusing evaluation value of focusing lens current location;
Position Number according to the corresponding points of preserving obtains the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, and described corresponding points are the corresponding points of focusing evaluation value and focusing lens position;
Obtain the variation tendency of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points;
According to described variation tendency, the step-length that the decision focusing lens moves.
A kind of device comprises: the corresponding points acquiring unit, be used to obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, and the variation tendency of described corresponding points is the chevron curve;
Adjustment unit is used to adjust and obtains the described corresponding points that the corresponding points unit obtains, and corresponding points are evenly distributed in the hillside district of described curve, has and have only three in the district of mountain top;
Preserve the Position Number unit, be used to preserve the Position Number of the adjusted described corresponding points of adjustment unit.
A kind of device is characterized in that, comprising:
Updating block is used to upgrade the focusing evaluation value of focusing lens current location;
Obtain the focusing evaluation value cell, be used for Position Number according to the corresponding points of preserving, obtain the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, described corresponding points are the corresponding points of focusing evaluation value and focusing lens position;
Obtain the variation tendency unit, the focusing evaluation value that is used to obtain the focusing lens current location after updating block upgrades with obtain the focusing evaluation value cell and obtain variation tendency between the corresponding focusing evaluation value of the previous corresponding points of focusing lens current location and back corresponding points;
Decision step-length unit is used for according to obtaining the described variation tendency that the variation tendency unit obtains, the step-length that the decision focusing lens moves.
By technique scheme as can be seen, the embodiment of the invention is determined focusing lens current location zone of living in by the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, different according to the of living in zone of current location on the focusing evaluation value curve of rule, the step-length that the decision focusing lens moves: as move the position of focusing lens with bigger step-length at flat site, when entering sloping region or top region or bottom zone, initiatively reduce the step-length of focusing; Make focusing lens only finely tune in the mountain top district, then step-length is less when finding limit, and the focusing lens shift in position is little, and the rate of change of focusing evaluation value is little, and image is not prone to " deceptive movement " phenomenon.
Also by adjusting the corresponding points of focusing evaluation value and focusing lens position, make the chevron curve regular smooth of embodiment corresponding points variation tendency, avoid the bigger situation of variation of focusing evaluation value to a certain extent.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.
Fig. 1 is the autofocus system structural representation of prior art;
Fig. 2 is the method flow schematic diagram of the embodiment of the invention one;
Fig. 3 is the contrast schematic diagram that the embodiment of the invention one chevron is demarcated anterioposterior curve;
Fig. 4 is the method flow schematic diagram of the embodiment of the invention two;
Fig. 5 is the multi-peak normalization focusing evaluation value curve chart of the embodiment of the invention two;
Fig. 6 is the embodiment of the invention three auto focus control process schematic diagrames;
Fig. 7 is the structural representation of embodiment of the invention device;
Fig. 8 is the structural representation of another device of the embodiment of the invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.
Embodiment one, describe in detail referring to Fig. 2, Fig. 2 is the method flow schematic diagram of the embodiment of the invention.
Step 101: obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, the variation tendency of described corresponding points is the chevron curve.
Can be earlier obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances according to following steps:
1, the aperture of fixed lens and convergent-divergent lens position are constant;
2, will test article and be fixed on camera lens before, the record resolution chart is to the distance between the camera lens; The test article can be resolution charts;
3, hold burnt end far away micro-stepping to move focusing lens from nearly Jiao, write down the focusing evaluation value in per step;
4, change the test article to the distance between the camera lens;
5, hold burnt end far away micro-stepping to move focusing lens from nearly Jiao, write down the focusing evaluation value in per step.
Along with hold more and more near the limit position from nearly Jiao the position of focusing lens, the focusing evaluation value also rises gradually, more and more near limit; And cross the limit position in the position of focusing lens, the focusing evaluation value then descends gradually, away from limit; So the variation tendency of the corresponding points of focusing evaluation value and focusing lens position is a chevron curve.
Step 102: adjust described corresponding points, corresponding points are evenly distributed in the hillside district of described curve, in the district of mountain top, have and have only three.
Usually, the hillside district is positioned at the scope of the 10%-90% of the curve longitudinal axis (normalization focusing evaluation value) greatest measure, and the mountain top district is positioned at the scope of the 88%-100% of curve longitudinal axis greatest measure, and the process of adjusting preferred point can be described as " chevron demarcation ".In the focusing process, focusing lens then only moves on selected good preferred point, and each preferred point number that strides across that moves can be described as step-length, and certainly, step-length is defined as the realization that other length do not influence the embodiment of the invention yet.
The available formula of normalization focusing evaluation value obtains:
fev＝FEV/MAX
FEV
Wherein, fev is normalization focusing evaluation value (Nomalized FEV), and FEV is focusing evaluation value (Focus Evaluation Value), MAX
FEVThe maximum that refers to the focusing evaluation value.
Normalization focusing evaluation value image the most clearly the position be 1, this value more little image fuzzy more.The curvilinear motion contrast of " chevron demarcation " can be referring to Fig. 3 a and Fig. 3 b, and Fig. 3 a is the normalization assessed value curve synoptic diagram before chevron is demarcated, and Fig. 3 b is the calibrated normalization assessed value of a chevron curve synoptic diagram; Wherein, (1) is object distance when big, and (2) be object distance when moderate, (3) be object distance than hour.
Step 103: the Position Number of preserving described corresponding points.
The Position Number of preserving described corresponding points can adopt form, the position of described corresponding points is numbered, and with the focusing lens position of N Position Number correspondence of Pos (N) expression.
Obviously, the Position Number of taking other forms to preserve corresponding points does not influence the realization of the embodiment of the invention yet.
The Pos (N) that the embodiment of the invention obtains can be preset in the audio and video products, also can manually finish before automatic focus or acquisition automatically, does not influence the realization of the embodiment of the invention.
Embodiment of the invention utilization " chevron demarcation " method, the curve regular smooth of the variation tendency of the corresponding points of feasible reflection focusing evaluation value and focusing lens position, the bigger situation of focusing evaluation value deviation ratio of corresponding points before and after avoiding to a certain extent.
What following examples two illustrated is the process of decision focusing lens moving step length in the automatic focus process, needs the Position Number of the corresponding points of use embodiment one preservation, obtains the focusing evaluation value of described corresponding points correspondence.
Embodiment two, describe in detail referring to Fig. 4, Fig. 4 is the method flow schematic diagram of the embodiment of the invention.
Step 201: the focusing evaluation value of upgrading the focusing lens current location.
Step 202: the Position Number according to the corresponding points of preserving, obtain the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, described corresponding points are the corresponding points of focusing evaluation value and focusing lens position.
According to preset or manually or the Position Number of the corresponding points of obtaining automatically, obtain the focusing evaluation value of corresponding points correspondence.
Step 203: the variation tendency of obtaining the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points.
Can be according to the focusing evaluation value of the current corresponding points of focusing lens position, previous corresponding points Position Number and a back corresponding points Position Number, or the focusing evaluation value of focusing lens current location, previous corresponding points Position Number and the first two corresponding points Position Number, calculate the variation tendency of the focusing evaluation value of current location, do not influence the realization of the embodiment of the invention.Variation tendency can be represented with focusing evaluation value deviation ratio.
Focusing evaluation value deviation ratio computing formula can for:
Focusing evaluation value deviation ratio DEV (N-1)=(FEV (N-1)-FEV (N))/FEV (N);
Focusing evaluation value deviation ratio DEV (N+1)=(FEV (N+1)-FEV (N))/FEV (N); Wherein, N represents the current location numbering, and N-1 then represents the previous Position Number of current location numbering, and N+1 then represents a back Position Number of current location numbering, and FEV (N), FEV (N-1), FEV (N+1) are the focusing evaluation value under the correspondence position.
Step 204: according to described variation tendency, the step-length that the decision focusing lens moves.
According to the relation of focusing evaluation value deviation ratio and predefined threshold value, judge the focusing lens current location at flat site, perhaps in the hillside district, perhaps in the mountain top district, perhaps in bottom zone.When focusing lens is in flat site, move focusing lens, when being in hillside district or mountain top district or bottom zone, then reduce moving step length with big step-length.
Big step-length can be the length that focusing lens once moves 3 preferred point, and little step-length can be once to move the length of 1 preferred point.When step-length was longer, the focusing lens change in location was big, step-length more in short-term, the focusing lens change in location is little.
Therefore, with the focusing of small step progress row, the focusing lens change in location is little in the mountain top district, and it is little to focus on the estimated value rate of change, avoids producing " deceptive movement " phenomenon.
The embodiment of the invention determines the step-length that focusing lens moves by the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points; Make focusing lens only finely tune in the mountain top district, then step-length is less when finding limit, and the focusing lens shift in position is little, and the rate of change of focusing evaluation value is little, and image is not prone to " deceptive movement " phenomenon.
All scenery can be arranged on the different object distances in the practical application scene, so may there be a plurality of peak values in normalization focusing evaluation value with the corresponding curve of focusing lens position, Fig. 5 is a multi-peak normalization focusing evaluation value curve chart.4 top peak values are arranged among the figure, and top 1 is to be caused by the distant view contribution, and top 2 is to be caused by middle scape contribution, and top 3 is to be caused by the close shot contribution, and automatic focus can converge to one of them top peak value nearby according to current lens location.
Embodiment three, describe in detail referring to Fig. 6, Fig. 6 is the method flow schematic diagram of the embodiment of the invention.
Step 301: the focusing evaluation value of upgrading the focusing lens current location.
Step 302: the rate of change that calculates focusing evaluation value before and after upgrading.
Step 303: judge whether described focusing evaluation value rate of change surpasses default threshold value, if do not surpass, goes back to step 301, if surpass, changes step 304.
Threshold value can rule of thumb be worth flexible setting.
Step 301 to step 303 can be collectively referred to as monitor state, below each step can be collectively referred to as status of action.
Step 304: carry out the aspect test,, judge whether the focusing lens current location is positioned at the mountain top district, is then to go back to step 301 promptly according to focusing evaluation value deviation ratio.
Can be according to the focusing evaluation value of the current preferred point of focusing lens, adjacent last preferred point and an adjacent back preferred point correspondence position, calculate the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing evaluation value of current preferred point and adjacent front and back preferred point again.
Mobile amasthenic lens position obtains the focusing evaluation value FEV (N-1) of this position to Pos (N-1); Mobile amasthenic lens position obtains the focusing evaluation value FEV (N+1) of this position to Pos (N+1).
Focusing evaluation value deviation ratio computing formula can for:
Focusing evaluation value deviation ratio DEV (N-1)=(FEV (N-1)-FEV (N))/FEV (N);
Focusing evaluation value deviation ratio DEV (N+1)=(FEV (N+1)-FEV (N))/FEV (N); Wherein, N represents the numbering of current location, and N-1 then represents the numbering of the previous position of current location, and N+1 then represents the numbering of a back position of current location.According to DEV that calculates (N-1) and DEV (N+1), handle according to following principle respectively:
1., just think that position Pos (N) is positioned at the mountain top district if DEV (N-1) and DEV (N+1) are not more than-8%;
2., just think that Pos (N) is positioned at the bottom if DEV (N-1) and DEV (N+1) are not less than 8%;
If DEV (N-1) be not less than 8% and also DEV (N+1) be not more than 8%, just think that Pos (N-1) is positioned at nearly Jiao Po;
If DEV (N-1) between ± 8% and also DEV (N+1) be not more than-8%, just think that Pos (N-1) is positioned at nearly Jiao Po;
If DEV (N+1) be not less than 8% and also DEV (N-1) be not more than 8%, just think that Pos (N+1) is positioned at Jiao Po far away;
If DEV (N+1) between ± 8% and also DEV (N-1) be not more than-8%, just think that Pos (N+1) is positioned at Jiao Po far away;
7. if DEV (N-1) and DEV (N+1) between ± 8%, just think that Pos (N) is positioned at the flat region.
Step 305: determine moving direction, little step-length moves 3 times.
The direction and the step-length that move can be carried out according to following rule:
A.Pos (N-1) then moves 3 times to burnt direction far away at nearly Jiao Po, each 1 little step-length;
B.Pos (N+1) then moves 3 times to nearly burnt direction at Jiao Po far away, each 1 little step-length;
C.Pos (N) handles in two kinds of situation in the bottom or the flat region:
1) N≤(FarEnd+NearEnd)/2, then move 3 times each 1 little step-length to burnt direction far away;
2) N＞(FarEnd+NearEnd)/2, then move 3 times each 1 little step-length to nearly burnt direction.
Wherein, FarEnd and NearEnd are the pairing focusing lens Position Number of both sides end points in mountain area, the current place of focusing lens.
Step 306: carry out the aspect analysis.
The trend of analyzing the slope district is related to next step direction that moves of focusing lens, and analytic process can be described as " aspect analysis ".
The aspect analysis is after process is no less than moving of 3 little step-lengths, focusing evaluation value FEV (j) and the focusing lens Position Number N (j) that writes down to be analyzed, and determines the focusing lens current position in the mountain top district, or flat region, perhaps mountain top district.Can carry out the aspect analysis according to following steps:
A. after this initialization j=0 whenever moves a focusing lens position j and adds 1, and record position numbering N (j) and focusing evaluation value FEV (j);
B. find the maximum FEVmax among FEV (j), FEV (j-1), the FEV (j-2) earlier, FEV (j-1) is the focusing evaluation value of previous Position Number correspondence, FEV (j-2) is the focusing evaluation value of preceding two Position Number correspondences, calculates focusing evaluation value deviation ratio DEV (j)=(FEV (j)-FEVmax)/FEVmax again; And the corresponding Nmax of record;
C. find minimum value Nfar and corresponding focusing evaluation value deviation ratio DEVfar among N (j), N (j-1), the N (j-2); And find maximum Nnear among N (j), N (j-1), the N (j-2) and corresponding focusing evaluation value deviation ratio DEVnear; Relatively the relation of DEVfar, DEVnear and threshold value determines focusing lens is arranged in which zone of top, nearly Jiao Po, Jiao Po far away, flat region.With threshold value is 8% to be example, and concrete rule is as follows:
1) DEVfar and DEVnear are not more than-8%, think that then position Pos (Nmax) is positioned at the mountain top district;
2) DEVfar and DEVnear are not less than 8%, think that then Pos (Nmax) is positioned at the bottom;
3) DEVnear be not less than 8% and also DEVfar be not more than 8%, think that then Pos (Nfar) is positioned at nearly Jiao Po;
4) DEVfar between ± 8% and also DEVnear be not more than-8%, think that then Pos (Nfar) is positioned at nearly Jiao Po;
5) DEVnear be not less than 8% and also DEVfar be not more than 8%, think that then Pos (Nnear) is positioned at Jiao Po far away;
6) DEVnear between ± 8% and also DEVfar be not more than-8%, think that then Pos (Nnear) is positioned at Jiao Po far away;
7) DEVnear and DEVfar between ± 8%, think that then Pos (Nmax) is positioned at the flat region.
Step 307:, determine direction and step-length that focusing lens moves according to the zone of living in of described focusing lens current location on described curve.
Step-length is divided into big step-length and little step-length, and big step-length can be defined as and once move 3 preferred point, and little step-length can be defined as and once move 1 preferred point, and certainly, the length that big step-length and little step-length are defined as other does not influence the realization of the embodiment of the invention yet.
Concrete moving direction and step-length are as follows:
If Pos (Nfar) at nearly Jiao Po, then moves 1 little step-length to burnt direction far away, get back to step 306 then;
If Pos (Nnear) at Jiao Po far away, then moves 1 little step-length to nearly burnt direction, get back to step 306 then;
If Pos (Nmax) in the bottom, then moves following 1 little step-length by former direction, get back to step 306 then;
If Pos (Nmax) in the flat region, then moves a big step-length by former direction, get back to step 306 then;
If Pos (Nmax) is on the mountain top, then next step gets back to Pos (Nmax), enters step 308 then.
The embodiment of the invention when entering sloping region or top region or bottom zone, initiatively reduces the step-length of focusing in the position that flat site moves focusing lens with bigger step-length.In the actual application, therefore limit may, all may repeat step 306 to 307 at any time moving after moving each time, adjust direction and step-length that focusing lens moves at any time, enters step 308 after finding at least one peak value.
Step 308: after focusing lens moves on to the top peak, judge whether the peak change rate surpasses threshold value, surpasses and then thinks that peak changes, and goes back to step 306, seeks peak value again; If do not surpass threshold value, then think and found an effective peak value, then can return monitor state after the imaging.
Threshold value can rule of thumb be provided with flexibly.
The embodiment of the invention is determined focusing lens current location zone of living in by the focusing evaluation value deviation ratio of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, different according to the of living in zone of current location on the focusing evaluation value curve of rule, the step-length that the decision focusing lens moves: as move the position of focusing lens with bigger step-length at flat site, when entering sloping region or top region or bottom zone, initiatively reduce the step-length of focusing; Make focusing lens only finely tune in the mountain top district, then step-length is less when finding limit, and the focusing lens shift in position is little, and the rate of change of focusing evaluation value is little, and image is not prone to " deceptive movement " phenomenon.The embodiment of the invention also adopts the feasible chevron curve regular smooth that embodies the corresponding points variation tendency of the method for " chevron demarcation ", in the automatic focus process, can utilize the Position Number of corresponding points to obtain corresponding focusing evaluation value, accelerate to seek mountain speed, and promoted the accuracy of mountain top convergence.
The embodiment of the invention adopts " aspect test " and " aspect analysis " method, the zone of living in of initiatively grasping focusing lens, and direction that the active adjustment focusing lens moves and step-length make that focusing lens step-length when finding limit is less.
Need to prove, for aforesaid each method embodiment, for simple description, so it all is expressed as a series of combination of actions, but those skilled in the art should know, the present invention is not subjected to the restriction of described sequence of movement, because according to the present invention, some step can adopt other orders or carry out simultaneously.Secondly, those skilled in the art also should know, the embodiment described in the specification all belongs to preferred embodiment, and related action and module might not be that the present invention is necessary.
In the above-described embodiments, the description of each embodiment is all emphasized particularly on different fields, do not have the part that describes in detail among certain embodiment, can be referring to the associated description of other embodiment.
The method of auto focus control more than is provided, and the embodiment of the invention also provides the device of auto focus control.
A kind of device 700 can be used for auto focus control, and referring to Fig. 7, Fig. 7 is the structural representation of embodiment of the invention device, comprising:
Corresponding points acquiring unit 701 is used to obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, and the variation tendency of described corresponding points is the chevron curve.
The hillside district is positioned at the scope of the 10%-90% of the curve longitudinal axis (normalization focusing evaluation value) greatest measure, and the available formula of normalization focusing evaluation value obtains:
fev＝FEV/MAX
FEV
Wherein, fev is normalization focusing evaluation value (Nomalized FEV), and FEV is focusing evaluation value (Focus Evaluation Value), MAX
FEVThe maximum that refers to the focusing evaluation value.
Preserve Position Number unit 703, be used to preserve the Position Number of adjustment unit 702 adjusted described corresponding points, the focusing lens position of N Position Number correspondence of available Pos (N) expression.
Described corresponding points acquiring unit 701, also be used to change aperture and/or convergent-divergent lens position after, obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances once more, the variation tendency of described corresponding points is the chevron curve;
Correspondingly, described adjustment unit 702 also is used for adjusting once more and obtains the described corresponding points that the corresponding points unit obtains once more, and corresponding points are evenly distributed in the hillside district of described curve, has and have only three in the district of mountain top;
Described preservation Position Number unit 703 then also is used to preserve the adjustment unit Position Number of adjusted described corresponding points once more.A kind of device 800 can be used for auto focus control, and referring to Fig. 8, Fig. 8 is another structural representation of embodiment of the invention device, comprising:
Updating block 801 is used to upgrade the focusing evaluation value of focusing lens current location.
Obtain focusing evaluation value cell 802, be used for Position Number according to the corresponding points of preserving, obtain the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, described corresponding points are the corresponding points of focusing evaluation value and focusing lens position; Position Number can be preset or before upgrading the focusing evaluation value of current location, manually or automatically obtain, do not influence the realization of the embodiment of the invention.
Obtain variation tendency unit 803, the focusing evaluation value that is used to obtain the focusing lens current location after updating block 801 upgrades with obtain focusing evaluation value cell 802 and obtain variation tendency between the corresponding focusing evaluation value of the previous corresponding points of focusing lens current location and back corresponding points;
Decision step-length unit 804 is used for according to obtaining the described variation tendency that variation tendency unit 803 obtains, the step-length that the decision focusing lens moves.
Described decision step-length unit 804 also can specifically be used for the focusing evaluation value deviation ratio according to the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current location when flat site, move focusing lens with big step-length; According to the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current position in the hillside district or when mountain top district or bottom zone, reduce moving step length.
Further, described decision step-length unit 804 also can specifically be used for the relation according to focusing evaluation value deviation ratio and predefined threshold value, judges the focusing lens current location at flat site, perhaps in the hillside district, perhaps in the mountain top district, perhaps in bottom zone.
Described device 700 and device 800 can be included in any one autofocus controlling apparatus, do not influence the realization of the embodiment of the invention.
The embodiment of the invention is determined focusing lens current location zone of living in by the focusing evaluation value deviation ratio of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, different according to the of living in zone of current location on the focusing evaluation value curve of rule, the step-length that the decision focusing lens moves: as move the position of focusing lens with bigger step-length at flat site, when entering sloping region or top region or bottom zone, initiatively reduce the step-length of focusing; Make focusing lens only finely tune in the mountain top district, then step-length is less when finding limit, and the focusing lens shift in position is little, and the rate of change of focusing evaluation value is little, and image is not prone to " deceptive movement " phenomenon.
One of ordinary skill in the art will appreciate that, realize all or part of flow process in the foregoing description method, be to instruct relevant hardware to finish by computer program, described program can be stored in the computer read/write memory medium, this program can comprise the flow process as the embodiment of above-mentioned each side method when carrying out.Wherein, described storage medium can be magnetic disc, CD, read-only storage memory body (Read-OnlyMemory, ROM) or at random store memory body (Random Access Memory, RAM) etc.
More than the method and the device thereof of a kind of auto focus control that the embodiment of the invention provided is described in detail, used specific case herein principle of the present invention and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.
Claims (12)
1. the method for an auto focus control is characterized in that:
Obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, the variation tendency of described corresponding points is the chevron curve;
Adjust described corresponding points, corresponding points are evenly distributed in the hillside district of described curve, in the district of mountain top, have and have only three;
Preserve the Position Number of described corresponding points.
2. self-focusing method according to claim 1 is characterized in that, also comprises after the Position Number of the described corresponding points of described preservation:
Change aperture and/or convergent-divergent lens position, obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, the variation tendency of described corresponding points is the chevron curve;
Adjust described corresponding points, corresponding points are evenly distributed in the hillside district of described curve, have and have only three in the mountain top district;
Preserve the Position Number of described corresponding points.
3. self-focusing method according to claim 1 and 2 is characterized in that, the Position Number of the described corresponding points of described preservation also comprises:
Corresponding points after the numbering are made into form.
4. the method for an auto focus control is characterized in that:
Upgrade the focusing evaluation value of focusing lens current location;
Position Number according to the corresponding points of preserving obtains the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, and described corresponding points are the corresponding points of focusing evaluation value and focusing lens position;
Obtain the variation tendency of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points;
According to described variation tendency, the step-length that the decision focusing lens moves.
5. self-focusing method according to claim 4 is characterized in that, and is described according to described variation tendency, and the step-length that the decision focusing lens moves is specially:
According to the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current location when flat site, move focusing lens with big step-length;
According to the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current position in the hillside district or when mountain top district or bottom zone, reduce moving step length.
6. self-focusing method according to claim 5 is characterized in that, described judge the focusing lens current location flat site and judge the focusing lens current position in the hillside district or mountain top district or bottom zone be specially:
According to the relation of focusing evaluation value deviation ratio and predefined threshold value, judge the focusing lens current location at flat site, perhaps in the hillside district, perhaps in the mountain top district, perhaps in bottom zone.
7. according to claim 5 or 6 described self-focusing methods, it is characterized in that the described focusing lens current location of judging is at flat site and judge the focusing lens current position and also comprised before hillside district or mountain top district or bottom zone:
Little step-length moves three times after determining moving direction.
8. a device is characterized in that, comprising: the corresponding points acquiring unit, be used to obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances, and the variation tendency of described corresponding points is the chevron curve;
Adjustment unit is used to adjust and obtains the described corresponding points that the corresponding points unit obtains, and corresponding points are evenly distributed in the hillside district of described curve, has and have only three in the district of mountain top;
Preserve the Position Number unit, be used to preserve the Position Number of the adjusted described corresponding points of adjustment unit.
9. device according to claim 8 is characterized in that:
Described corresponding points acquiring unit, be used to change aperture and/or convergent-divergent lens position after, obtain the corresponding points of focusing evaluation value and focusing lens position under at least two object distances once more, the variation tendency of described corresponding points is the chevron curve;
Described adjustment unit is used for adjusting once more and obtains the described corresponding points that the corresponding points unit obtains once more, and corresponding points are evenly distributed in the hillside district of described curve, has and have only three in the district of mountain top;
Described preservation Position Number unit is used to preserve the adjustment unit Position Number of adjusted described corresponding points once more.
10. a device is characterized in that, comprising:
Updating block is used to upgrade the focusing evaluation value of focusing lens current location;
Obtain the focusing evaluation value cell, be used for Position Number according to the corresponding points of preserving, obtain the previous corresponding points of focusing lens current location and the focusing evaluation value of a back corresponding points correspondence, described corresponding points are the corresponding points of focusing evaluation value and focusing lens position;
Obtain the variation tendency unit, the focusing evaluation value that is used to obtain the focusing lens current location after updating block upgrades with obtain the focusing evaluation value cell and obtain variation tendency between the corresponding focusing evaluation value of the previous corresponding points of focusing lens current location and back corresponding points;
Decision step-length unit is used for according to obtaining the described variation tendency that the variation tendency unit obtains, the step-length that the decision focusing lens moves.
11. device according to claim 10, it is characterized in that, described decision step-length unit specifically is used for the focusing evaluation value deviation ratio according to the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current location when flat site, move focusing lens with big step-length; According to the focusing evaluation value deviation ratio of the focusing evaluation value of the focusing lens current location focusing evaluation value corresponding with the front and back corresponding points, judge the focusing lens current position in the hillside district or when mountain top district or bottom zone, reduce moving step length.
12. device according to claim 11, it is characterized in that, described decision step-length unit specifically is used for the relation according to focusing evaluation value deviation ratio and predefined threshold value, judge the focusing lens current location at flat site, perhaps in the hillside district, perhaps in the mountain top district, perhaps in bottom zone.
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| CN2009100060425A CN101790043B (en) | 2009-01-22 | 2009-01-22 | Control method for automatic focusing and device thereof |
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| CN2009100060425A CN101790043B (en) | 2009-01-22 | 2009-01-22 | Control method for automatic focusing and device thereof |
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