CN105657238A - Tracking focusing method and apparatus - Google Patents

Abstract

The embodiment of the invention discloses a tracking focusing method which comprises the steps of tracking a target to sequentially acquire image frames, wherein the image frames comprise target tracking regions; calculating change values of size parameters of the target tracking regions and a change value of a focusing evaluation value; according to the change values of the size parameters and the focusing evaluation value, calculating a rotating step length of a motor; and according to the rotating step length of the motor, generating a motor control instruction to carry out focusing. The embodiment of the invention also discloses a focusing tracking apparatus. By adopting the tracking focusing method and apparatus, an automatic focusing speed can be improved, and picture fluttering is reduced.

Description

Follow the tracks of focusing method and device

Technical field

The present invention relates to camera technique field, relate in particular to a kind of focusing method and device followed the tracks of.

Background technology

Target following is that the optical imageries such as existing digital camera, video camera, mobile phone camera and watch-dog are establishedThe standby upper function conventionally possessing. User, can be at the display screen of camera or prison in the time taking pictures or make a video recordingOn the monitor of control equipment, see the picture frame of the What You See Is What You Get of its camera imaging formation, user can be at figureOn picture frame, delimit rectangle tracing area (follow the tracks of frame, conventionally in picture frame using solid border as mark,Live in foreground image prompting user by frame), camera or watch-dog can be to the prospects in this rectangle tracing areaImage is followed the tracks of, and rectangle tracing area can obtain following in picture frame in imaging the left and right of foreground imageMove up and down and move, or following foreground image and amplifying and dwindle apart from the distance of camera lens.

In the time carrying out target following, also need automatically to focus apart from the distance of camera lens according to target object,Otherwise target object will thicken. But the focusing in conventional art in the time carrying out target following adoptsBe the modes such as climbing algorithm, focusing speed is slower, and impact is taken and experienced.

Summary of the invention

Based on this, in order to solve the slow-footed technical problem of above-mentioned focusing, spy provides a kind of tracking focusing sideMethod.

A kind of focusing method of following the tracks of, comprising:

Tracking target is obtained picture frame successively, comprises target following region in described picture frame;

Calculate the changing value of size parameter and the changing value of focusing evaluation of estimate in described target following region;

Calculate revolution step-length according to described size parameter changing value and focusing evaluation of estimate changing value;

Generating motor control instruction according to described revolution step-length focuses.

Therein in an embodiment, the changing value of the size parameter in the described target following of described calculating region andThe step of the changing value of focusing evaluation of estimate is:

Calculate size parameter and the changing value thereof in target following region according to target tracking algorism;

According to focusing evaluation of estimate and the changing value thereof of focusing evaluation function calculating chart picture frame.

In an embodiment, described according to described size parameter changing value and focusing evaluation of estimate changing value thereinThe step of calculating revolution step-length is:

According to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate described revolution step-length; Wherein M is revolution step-length, and ▽ fv is the variation of focusing evaluation of estimateValue, ▽ dx is the changing value of the size parameter in target following region, k is default coefficient, and described motor turnsThe direction of moving step-length M is corresponding nearly burnt end and burnt end far away respectively.

Therein in an embodiment, describedly generate motor control instruction according to described revolution step-length and carry outAfter the step of focusing, also comprise:

Follow the tracks of to judge whether described focusing evaluation of estimate reached extreme value, if so, generate and continue movement-M/2 stepThe long motor control instruction fine setting of focusing.

Therein in an embodiment, describedly generate motor control instruction according to described revolution step-length and carry outAfter the step of focusing, also comprise:

Judge whether to focus successfully, if so, obtain motor focus point position S_focusWith motor position in closingFocal position S_focusTime the size parameter fv in target following region_focus；

Described method also comprises:

Follow the tracks of the size parameter fv that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{fv}}_{\mathrm{focus}}}{{\mathrm{fv}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。

Correspondingly, in order to solve the slow-footed technical problem of above-mentioned focusing, spy provides a kind of tracking focusing dressPut.

A kind of focusing mechanism of following the tracks of, comprising:

Target tracking module, obtains picture frame successively for tracking target, comprises target and follow in described picture frameTrack region;

Parameter calculating module, comments for changing value and the focusing of the size parameter of calculating described target following regionThe changing value being worth;

Rotate step size computation module, for according to described size parameter changing value and focusing evaluation of estimate changing value meterCalculate revolution step-length;

Motor control module, focuses for generating motor control instruction according to described revolution step-length.

In an embodiment, described parameter calculating module is also for calculating order according to target tracking algorism thereinSize parameter and the changing value thereof of mark tracing area; According to the focusing evaluation of focusing evaluation function calculating chart picture frameValue and changing value thereof.

Therein in an embodiment, described rotation step size computation module is also for according to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate described revolution step-length; Wherein M is revolution step-length, and ▽ fv is the variation of focusing evaluation of estimateValue, ▽ dx is the changing value of the size parameter in target following region, k is default coefficient, and described motor turnsThe direction of moving step-length M is corresponding nearly burnt end and burnt end far away respectively.

Therein in an embodiment, described device also comprises that fine setting module judges that for following the tracks of described focusing commentsBe worth whether reached extreme value, if so, generate the motor control instruction that continues movement-M/2 step-length carry out rightBurnt fine setting.

In an embodiment, described device also comprises follows burnt module therein, for judging whether to focus successfully,If so, obtain motor focus point position S_focusWith motor position in focus point position S_focusTime target followThe size parameter fv in track region_focus；

Follow the tracks of the size parameter fv that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{fv}}_{\mathrm{focus}}}{{\mathrm{fv}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。

Implement the embodiment of the present invention, will there is following beneficial effect:

Above-mentioned tracking focusing method and device pass through simple computation order on the basis of target following and focusing evaluationSize parameter and the changing value thereof of mark tracing area have completed focusing, and amount of calculation is little, be quick on the draw, therebyAccelerate focusing speed.

Brief description of the drawings

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, below will be to implementingIn example or description of the Prior Art, the accompanying drawing of required use is briefly described, and apparently, the following describesIn accompanying drawing be only some embodiments of the present invention, for those of ordinary skill in the art, do not payingGo out under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is a kind of flow chart of following the tracks of focusing method in an embodiment;

Fig. 2 takes surface chart in an application scenarios;

Fig. 3 takes surface chart in an application scenarios;

Fig. 4 takes surface chart in an application scenarios;

Fig. 5 is camera lens light path schematic diagram in an embodiment;

Fig. 6 is a kind of structural representation of following the tracks of focusing mechanism in an embodiment.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearlyChu, intactly description, obviously, described embodiment is only the present invention's part embodiment, instead ofWhole embodiment. Based on the embodiment in the present invention, those of ordinary skill in the art are not making creationThe every other embodiment obtaining under property work prerequisite, belongs to the scope of protection of the invention.

For solving the problem of convenience deficiency of aforesaid operations, spy has proposed a kind of tracking focusing method, the partyThe execution of method depends on computer program, can run on the computer system of von Neumann system. This meterCalculation machine program can be integrated in application, also can be used as independently tool-class application operation. This computer system canBe digital camera, the mobile device such as smart mobile phone, panel computer with camera function, with varifocalMonitor or the watch-dog etc. of camera.

Concrete, in the present embodiment, the method as shown in Figure 1, comprising:

Step S102, tracking target is obtained picture frame successively, comprises target following region in picture frame.

The picture frame that tracking target is obtained is successively as taking the target of thing and periphery scene thereof at cameraOr the image that in camera, imaging obtains, its form with frame is carried out buffer memory. Target following region is userThe target area as subject of on the display screen of camera or monitor screen, picture frame being delimited.

For example, as shown in Figure 2, user enters camera function with mobile phone, and mobile phone camera is opened, its lightLearn corresponding road scene by the imaging synthetic image frame of mobile phone camera, and be illustrated in the demonstration of mobile phoneOn screen, form the experience of taking pictures of What You See Is What You Get. If user wishes certain pedestrian in this road scene to enterRow focusing (focus by this pedestrian as shooting) can be followed the tracks of on display screen in this pedestrian's regional assignmentFrame (as the rectangle frame in Fig. 2) is confined as target this pedestrian in picture frame, the tracking frame of this delimitationBe initial target following region.

In upper example, the pedestrian target in the picture frame of delimiting on display screen as tracking target after, byBe kept in motion in pedestrian, therefore the distance between itself and camera is in variable condition, instant near time far away.Use the movement that target tracking algorism can tracking target, when pedestrian target is during to lens moving, become according to opticsPicture principle, as shown in Figure 3, target following region can be accompanied by pedestrian target and puts to the displacement of camera lensGreatly; When pedestrian target is during away from camera lens, according to optical imaging concept, as shown in Figure 4, target following districtTerritory can be accompanied by pedestrian target and dwindle away from the displacement of camera lens. Therefore initial target following region meetingAfter delimiting, be accompanied by the movement of tracking target on camera lens axis direction and produce big or small variation.

In the present embodiment, can be in the time utilizing target tracking algorism to carry out target following, periodically (for example 30ms)Ground synthetic image frame, is presented at the moving process that has reflected tracking target on display screen. Preferably, targetTrack algorithm can adopt MeanShift track algorithm, track algorithm based on particle group optimizing, based on templateThe track algorithm of joining or TLD target tracking algorism etc.

Step S104, calculates the changing value of size parameter and the changing value of focusing evaluation of estimate in target following region.

The size parameter in target following region is the one-dimensional linear parameter that characterizes target following area size. As aboveIn example, if target following region is tracking frame, its size parameter can be selected the one dimension of its length or widthLinear dimensions, if target following region is circular, its size parameter can be selected the one dimensions such as its radius or diameterLinear dimensions, if target following region is irregular figure, due to target following region in picture frame alwaysBecome geometric ratio to zoom in or out, can select diagonal, the one-dimensional linear parameters such as the wire length of special angle are doneFor its size parameter.

As previously mentioned, due in the time carrying out target following, can periodically generate several reflection target locationsPicture frame, therefore can calculate according to target tracking algorism size parameter and the changing value thereof in target following region,In the time of synthetic image frame, get the size parameter in the target following region in every width picture frame, then pass through

▽dx＝dx_current-dx_pre

The size parameter that obtains target following region in every width picture frame is followed with respect to the target in previous frame imageThe changing value ▽ dx (dx of the size parameter in track region_currentAnd dx_preBe respectively current frame image and former frame imageSize parameter).

For example Fig. 3 and Fig. 4 have reflected along with the movement of pedestrian target generates two two field pictures continuously, can unifyUsing the height of the tracking frame in image as size parameter, subtracted each other, can obtain generating shown in Fig. 4The changing value of the size parameter in target following region when picture frame.

Focusing evaluation of estimate is a judge value of image definition in focus process, and focusing evaluation of estimate is in target, in extreme value, the now imaging of camera lens is the most clear, and follows when in camera lens the focal positionThe variation of the distance of the focal position of target and camera lens, also corresponding variation of focusing evaluation of estimate, fromAnd reflect the readability of picture frame in focus process.

In the present embodiment, obtain by focusing evaluation function, for example, in the time of synthetic image frame, can basisShade of gray function (gray scale fluctuation and change function, gray scale absolute change function, Laplace function gradient letterNumber etc.), the focusing evaluation function such as informatics function, the frequency-domain function evaluation of estimate that obtains focusing, then pass through

▽fv＝fv_current-fv_pre

Obtain the changing value ▽ fv (fv of every width picture frame with respect to the focusing evaluation of estimate of previous frame image_currentAnd fv_preBe respectively the focusing evaluation of estimate of current frame image and former frame image).

Step S106, calculates revolution step according to the changing value of the changing value of size parameter and focusing evaluation of estimateLong.

When digital camera focusing, can pass through the distance between the lens set of motor adjustable lens, thereby focus.Therefore, the proportional relation of rotation step-length of the focal length variations of camera lens and motor. By the change of size parameterThe changing value of change value and focusing evaluation of estimate is determined the rotation step-length of motor, means the focal length of camera lens is carried outAdjusting.

In the present embodiment, can close according to the ratio of the changing value of the changing value of size parameter and focusing evaluation of estimateRevolution step-length is calculated by system. For example, can be according to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate revolution step-length; Wherein M is revolution step-length, and ▽ fv is the changing value of focusing evaluation of estimate,▽ dx is the changing value of the size parameter in target following region, and k is default coefficient, and revolution step-length MRespectively corresponding nearly burnt end and burnt end far away of direction. That is to say, M is for just or when negative, corresponding closely respectivelyBurnt end and the different moving direction of burnt end far away, concrete corresponding relation can be adjusted according to k.

Step S108, generates motor control instruction according to revolution step-length and focuses.

Calculate after revolution step-length, can call the driver of the motor of camera lens, in thisThe revolution step-length obtaining is that parameter generates motor control instruction, and the motor apparatus of camera lens is receivingAfter this instruction, rotatable corresponding step-length completes focusing.

Preferably, in focus process, also can focusing finely tune. Concrete, according to revolutionAfter the step that the instruction of step-length generation motor control is focused, also comprise: follow the tracks of and whether judge focusing evaluation of estimateReach extreme value, if so, generated the motor control instruction that the continues movement-M/2 step-length fine setting of focusing.

For example,, if by after aforementioned revolution appointment step-length M, recalculate the focusing evaluation of estimate obtaining and be less than(situation of the extreme value using at selected focusing evaluation function during for maximum, if used extreme value forLittle value is contrary) the mobile focusing evaluation of estimate calculating before, show to focus and comment in moving processValue lives through extreme value, and (the revolution step-length of calculating due to abovementioned steps S106 always makes focus move to targetMoving, focusing evaluation of estimate always changes towards extreme value, does not increase counter subtracting if there is focusing evaluation of estimate, must be motorRotate the excessive Focal Point Shift that causes of step-length and crossed target, thereby the evaluation of estimate that makes to focus also experiences accordinglyExtreme value). Now, can finely tune by rotation motor-M/2 step-length (oppositely moving).

It should be noted that, the process of this fine setting can repeat, until the difference of focusing evaluation of estimate and extreme valueBe less than threshold value. For example,, if motor position is S before focusing₁, to defocused be S₂, fine setting can movement-M/2 stepLong i.e. mobile-(S₂-S₁The step-length of)/2, arrives S₃Position, if in this process, still follow the tracks of judgement obtain rightBurnt evaluation of estimate has experienced extreme value, and (now M is last time movement to can again move-M/2 step-length-(S₂-S₁The step-length of)/2), move to-(S₃-S₂The step-length of)/2, by that analogy, until focusing evaluation of estimate withThe difference of extreme value is less than threshold value, thereby completes focusing.

In the present embodiment, after having focused, after focus is moved to tracking position of object, also can be to following the tracks ofTarget is followed burnt. Be specially:

Judge whether to focus successfully, if so, obtain motor focus point position S_focusWith motor position in closingFocal position S_focusTime the size parameter dx in target following region_focus；

Described method also comprises:

Follow the tracks of the size parameter dx that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{dx}}_{\mathrm{focus}}}{{\mathrm{dx}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。

As shown in the index path of Fig. 5, after focusing successfully, the size parameter in focal length and target following regionThe relation that is inversely proportional to, therefore can follow burntly according to this relation, carry out weight and need not compute repeatedly moving step lengthMultiple focusing.

In one embodiment, as shown in Figure 6, a kind of focusing mechanism of following the tracks of, comprise target tracking module 102,Parameter calculating module 104, rotation step size computation module 106 and motor control module 108, wherein:

Target tracking module 102, obtains picture frame successively for tracking target, in described picture frame, comprises targetTracing area. ;

Parameter calculating module 104, for calculating changing value and the focusing of size parameter in described target following regionThe changing value of evaluation of estimate.

Rotate step size computation module 106, for according to described size parameter changing value and focusing evaluation of estimate changing valueCalculate revolution step-length.

Motor control module 108, focuses for generating motor control instruction according to described revolution step-length.

In the present embodiment, parameter calculating module 104 is also for calculating target following according to target tracking algorismThe size parameter in region and changing value thereof; According to the focusing evaluation of estimate of focusing evaluation function calculating chart picture frame andChanging value.

In the present embodiment, rotate step size computation module 106 also for according to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate described revolution step-length; Wherein M is revolution step-length, and ▽ fv is the variation of focusing evaluation of estimateValue, ▽ dx is the changing value of the size parameter in target following region, k is default coefficient, and described motor turnsThe direction of moving step-length M is corresponding nearly burnt end and burnt end far away respectively.

In the present embodiment, as shown in Figure 6, follow the tracks of focusing mechanism and also comprise fine setting module 110, for following the tracks ofJudge whether described focusing evaluation of estimate reached extreme value, if so, generate the motor that continues movement-M/2 step-lengthThe control instruction fine setting of focusing.

In the present embodiment, as shown in Figure 6, follow the tracks of focusing mechanism device and also comprise with burnt module 112, forJudge whether to focus successfully, if so, obtain motor focus point position S_focusWith motor position in focus pointPosition S_focusTime the size parameter dx in target following region_focus；

Follow the tracks of the size parameter dx that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{dx}}_{\mathrm{focus}}}{{\mathrm{dx}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。

In sum, implement the embodiment of the present invention, will there is following beneficial effect:

Above-mentioned tracking focusing method and device pass through simple computation order on the basis of target following and focusing evaluationSize parameter and the changing value thereof of mark tracing area have completed focusing, and amount of calculation is little, be quick on the draw, therebyAccelerate focusing speed.

One of ordinary skill in the art will appreciate that all or part of flow process realizing in above-described embodiment method,Be can carry out the hardware that instruction is relevant by computer program to complete, described program can be stored in a calculatingIn machine read/write memory medium, this program, in the time carrying out, can comprise as the flow process of the embodiment of above-mentioned each side method.Wherein, described storage medium can be magnetic disc, CD, read-only store-memory body (Read-OnlyMemory,Or random store-memory body (RandomAccessMemory, RAM) etc. ROM).

Above disclosed only for preferred embodiment of the present invention, certainly can not with this limit the present invention itInterest field, the equivalent variations of therefore doing according to the claims in the present invention, still belongs to the scope that the present invention is contained.

Claims (10)

1. follow the tracks of a focusing method, comprising:

Tracking target is obtained picture frame successively, comprises target following region in described picture frame;

Calculate the changing value of size parameter and the changing value of focusing evaluation of estimate in described target following region;

Calculate revolution step-length according to described size parameter changing value and focusing evaluation of estimate changing value;

Generating motor control instruction according to described revolution step-length focuses.

2. tracking focusing method according to claim 1, is characterized in that, the described target of described calculatingThe step of the changing value of the changing value of the size parameter of tracing area and focusing evaluation of estimate is:

Calculate size parameter and the changing value thereof in target following region according to target tracking algorism;

According to focusing evaluation of estimate and the changing value thereof of focusing evaluation function calculating chart picture frame.

3. tracking focusing method according to claim 1, is characterized in that, described according to described sizeThe step that the changing value of the changing value of parameter and focusing evaluation of estimate calculates revolution step-length is:

According to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate described revolution step-length; Wherein M is revolution step-length, and ▽ fv is the variation of focusing evaluation of estimateValue, ▽ dx is the changing value of the size parameter in target following region, k is default coefficient, and described motor turnsThe direction of moving step-length M is corresponding nearly burnt end and burnt end far away respectively.

4. tracking focusing method according to claim 3, is characterized in that, described according to described motorAfter the step that the instruction of rotation step-length generation motor control is focused, also comprise:

Follow the tracks of to judge whether described focusing evaluation of estimate reached extreme value, if so, generate and continue movement-M/2 stepThe long motor control instruction fine setting of focusing.

5. tracking focusing method according to claim 1, is characterized in that, described according to described motorAfter the step that the instruction of rotation step-length generation motor control is focused, also comprise:

Judge whether to focus successfully, if so, obtain motor focus point position S_focusWith motor position in closingFocal position S_focusTime the size parameter dx in target following region_focus；

Described method also comprises:

Follow the tracks of the size parameter dx that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{dx}}_{\mathrm{focus}}}{{\mathrm{dx}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。

6. follow the tracks of a focusing mechanism, it is characterized in that, comprising:

Target tracking module, obtains picture frame successively for tracking target, comprises target and follow in described picture frameTrack region;

Parameter calculating module, comments for changing value and the focusing of the size parameter of calculating described target following regionThe changing value being worth;

Rotate step size computation module, for according to described size parameter changing value and focusing evaluation of estimate changing value meterCalculate revolution step-length;

Motor control module, focuses for generating motor control instruction according to described revolution step-length.

7. tracking focusing mechanism according to claim 6, is characterized in that, described parameter calculating moduleAlso for calculate size parameter and the changing value thereof in target following region according to target tracking algorism; According to focusingFocusing evaluation of estimate and the changing value thereof of evaluation function calculating chart picture frame.

8. tracking focusing mechanism according to claim 6, is characterized in that, described rotation step size computationModule is also for according to formula:

$M=k\×\frac{\▿\mathrm{fv}}{\▿\mathrm{dx}}$

Calculate described revolution step-length; Wherein M is revolution step-length, and ▽ fv is the variation of focusing evaluation of estimateValue, ▽ dx is the changing value of the size parameter in target following region, k is default coefficient, and described motor turnsThe direction of moving step-length M is corresponding nearly burnt end and burnt end far away respectively.

9. tracking focusing mechanism according to claim 8, is characterized in that, described device also comprises micro-Mode transfer piece is used for following the tracks of to judge whether described focusing evaluation of estimate reached extreme value, if so, generate to continue to move-The motor control instruction of the M/2 step-length fine setting of focusing.

10. tracking focusing mechanism according to claim 6, is characterized in that, described device also comprisesWith burnt module, for judging whether to focus successfully, if so, obtain motor focus point position S_focusAnd motorPosition is in focus point position S_focusTime the size parameter dx in target following region_focus；

Follow the tracks of the size parameter dx that calculates target following region_tracking, according to formula:

$S_{\mathrm{tracking}}=S_{\mathrm{focus}}\×\frac{{\mathrm{dx}}_{\mathrm{focus}}}{{\mathrm{dx}}_{\mathrm{tracking}}}$

Calculate the burnt position S that follows of motor_tracking, according to following burnt position S_trackingGenerate motor control instruction, control horseReach and move to burnt position S_tracking。