CN101470248B

CN101470248B - Focusing device and method

Info

Publication number: CN101470248B
Application number: CN2007103054427A
Authority: CN
Inventors: 郑升弘; 陈信宇
Original assignee: Quanta Computer Inc
Current assignee: Quanta Computer Inc
Priority date: 2007-12-28
Filing date: 2007-12-28
Publication date: 2011-10-26
Anticipated expiration: 2027-12-28
Also published as: CN101470248A

Abstract

The present invention discloses a focusing device, which is applied to an image recording system, and the focusing device comprises an evaluation unit and a control module. The evaluation unit can generate a plurality of evaluation values about the image according to the image sensed by the sensing element. The control module can calculate a weighted evaluation value according to the evaluation values, and the control module selectively generates a control signal according to the weighted evaluation value and a focus depth table to control the movement of the lens.

Description

Focusing mechanism and method

Technical field

The present invention is about a kind of focusing mechanism and method, and especially, the present invention is about a kind of focusing mechanism and the method that can focus fast and accurately.

Background technology

Along with the arriving of digital Age, and the fast development of relevant software and hardware technology, various digital devices are widely used in daily life.Wherein, the digitized video recording unit, for example digital camera (digital Gamera, DC), (digital video recorder DV) etc., more replaces traditional image recording apparatus because of its convenience to digital camera gradually.In addition, the digitized video register system also extensively is installed in multiple portable electronic devices, for example (personal digital assistant PDA), notebook computer etc., carries out photologging at any time to make things convenient for the user for mobile phone, personal digital assistant.

In the past, the resolution of digitized video register system that is applied in aforesaid portable electronic devices is mostly less than mega pixel (mega-pixel).Because its quality of image is determined by focusing mechanism, so the digitized video register system of this class adopts tight shot mostly.Along with the increase of resolution, focusing mechanism is also more and more important to the influence of the quality of image.Therefore, zoom lens and focusing mechanism are used in the digitized video register system of aforesaid portable electronic devices gradually.

See also Fig. 1, Fig. 1 is the functional block diagram that illustrates the digitized video register system in the known technology.As shown in Figure 1, this digitized video register system 7 comprises camera lens (lens) 72, Image Sensor (imagesensor) 74, processing module (processing module) 76 and motor (motor) 78.This Image Sensor 74, for example CCD or CMOS can carry out image sensing by this camera lens, and the image that senses is transferred to this processing module 76.This processing module 76 then can be carried out as squelch, image sharpness assessment processing such as (image sharpness evaluation) this image, and the image of treated mistake is exported.In addition, this processing module 76 also can produce control signal according to this image, and this control signal is sent to this motor 78.This motor 78 is then adjusted the position of this camera lens 72 according to this control signal, to reach the purpose of focusing.

In known technology, the focusing of digitized video register system can be divided into two big steps: assessment of image sharpness and focus search (focus search).Whether the assessment of image sharpness is clear in order to the decision image, and the focus search is then in order to move to camera lens suitable focusing position (focus position).In addition, when being applied to aforesaid portable electronic devices, one of the emphasis that need consider of the focusing person that also is the known technology fast and efficiently how.

Had many image sharpness assessment algorithms to be applied to digital camera at present, yet many image sharpness assessment algorithms are too complicated and be difficult to be applied in the aforesaid portable electronic devices.In addition, one of the most normal focus search algorithm that is used to is the search method of climbing the mountain (mountain climb searchmethod) at present.The method needs motor repeatedly to move back and forth camera lens to carry out omnidistance rough search (coarsesearch) and follow-up trickle search (fine search) supervisor.

In rough searching procedure, motor with than high range in regular turn moving lens with the assessed value (focus value) that obtains each focal position, and when slope of a curve change that this assessed value connected, enter trickle searching procedure to each focal position.Trickle searching procedure is then later searched maximum assessed value for this motor with trickleer scale focal position is as focusing position, and camera lens is moved to this focusing position.Yet aforesaid focus search algorithm needs motor moving lens repeatedly, quite expends time in, and can increase the consume of motor and transmission component.

Summary of the invention

Therefore, a category of the present invention is to provide a kind of focusing mechanism and method, in order to solve the disappearance of known technology.

A kind of focusing mechanism according to first preferred embodiment of the present invention is to be applied to image recording system, and this focusing mechanism comprises evaluation unit and control module.This evaluation unit can produce a plurality of evaluations of estimate about this image according to the image of sensing element institute sensing.And this control module can be calculated the weighting evaluation of estimate according to these evaluations of estimate, and this control module optionally produces control signal according to this weighting evaluation of estimate and depth of focus table, move with controls lens, wherein, this depth of focus table is to set up according to following formula: HD=(1+ (FL/2 * F _Num)/(SP * 2)) * FL; Wherein HD represent hyperfocal distance from; FL represents the focal length of camera lens; F _NumExpression focal length/aperture effective vent diameters; SP then represents the pixel size of sensing element.

A kind of focusing method according to second preferred embodiment of the present invention comprises the following step: at first, set up depth of focus table according at least one parameter preset.Subsequently, generation is about a plurality of evaluations of estimate of image.Then, calculate the weighting evaluation of estimate according to these evaluations of estimate.At last, optionally produce control signal according to this weighting evaluation of estimate and depth of focus table, move with controls lens, wherein this depth of focus table is to set up according to following formula: HD=(1+ (FL/2 * F _Num)/(SP * 2)) * FL; Wherein HD represent hyperfocal distance from; FL represents the focal length F of camera lens _NumExpression focal length/aperture effective vent diameters; SP then represents the pixel size of sensing element.

Can be about the advantages and spirit of the present invention by following detailed Description Of The Invention and appended graphic being further understood.

Description of drawings

Fig. 1 is the functional block diagram that illustrates the digitized video register system in the known technology.

Fig. 2 is the functional block diagram that illustrates according to the focusing mechanism of a specific embodiment of the present invention.

Fig. 3 is the Color plane synoptic diagram that illustrates image.

Fig. 4 illustrates the synoptic diagram of a plurality of blocks on the image.

Fig. 5 is the functional block diagram that illustrates according to the focusing mechanism of a specific embodiment of the present invention.

Fig. 6 illustrates the process flow diagram of setting up depth of focus table according to of the present invention.

Fig. 7 is the focusing method flow diagram that illustrates according to a specific embodiment of the present invention.

Fig. 8 is the focusing method flow diagram that illustrates according to a specific embodiment of the present invention.

Fig. 9 is the detail flowchart that illustrates the step S62 among Fig. 8.

Figure 10 is the detail flowchart that illustrates the step S59 among Fig. 8.

[main element label declaration]

1: image recording system

10: focusing mechanism 102: evaluation unit

104: control module 1042: storage unit

1044: microcontroller 12: image capture unit

122: camera lens 124: Image Sensor

2: 20: the first blocks of image

24: the three blocks of 22: the second blocks

28: the five blocks of 26: the four blocks

7: the digitized video register system

72: camera lens 74: Image Sensor

76: processing module 78: motor

S30～S33, S40～S42, S50～S62, S590～S596, S620～S626: process step

Embodiment

The invention provides a kind of focusing mechanism and method.Below in detail specific embodiments of the invention and practical application example will be described in detail, use proving absolutely feature of the present invention, spirit and advantage.

See also Fig. 2, Fig. 2 is the functional block diagram that illustrates according to the focusing mechanism of a specific embodiment of the present invention.As shown in Figure 2, focusing mechanism 10 according to the present invention is applied to image recording system 1, for example, but is not subject to, and digital camera, digital camera, has the device for mobile communication of camera function etc.

Further, image recording system 1 comprises focusing mechanism 10 and image capture unit 12.Focusing mechanism 10 mainly comprises evaluation unit (evaluating unit) 102 and control module (controlmodule) 104.And image capture unit 12 comprises camera lens 122 and Image Sensor 124, sensitization coupling element (Charge Coupled Device for example, CCD) or cmos device (Complementary Metal-Oxide Semiconductor, CMOS).Especially, camera lens 122 is zoom lens.

In this specific embodiment, when user's image application register system 1 was carried out image capture and record, image was projected on the Image Sensor 124 by camera lens 122, behind Image Sensor 124 pick-up images, image is sent to focusing mechanism 10.Further, evaluation unit 102 receives image, and produces the evaluation of estimate about image.In practical application, evaluation unit 102 can carry out image sharpness (sharpness) statistics by gradient filter (gradient filter), for example, the horizontal direction of image is added up with gradient filter [1 0 1], and with gradient filter to image

Vertical direction add up.

In practice, image can be divided into the multicolour plane, for example, and red plane (R), green color plane (G) and blue color planes (B).See also Fig. 3, Fig. 3 is the synoptic diagram that illustrates aforesaid Color plane.Further, according to following formula [1], calculate the evaluation of estimate (F) of image.

F=R (A ₁* G _X+ G _Y)+G (A ₂* G _X+ G _Y)+B (A ₃* G _X+ G _Y) ... formula [1]

G wherein _X=| G ₅-G ₄|, G _Y=| G ₇-G ₂|, and coefficient A ₁, A ₂, A ₃It is sharpness in order to the weighting horizontal direction.

In a specific embodiment, image can be divided into the block that a plurality of parts overlap.See also Fig. 4, Fig. 4 illustrates the synoptic diagram of a plurality of blocks on the image.As shown in Figure 4, in this specific embodiment, image 2 is divided into the block that five parts overlap: first block 20, second block 22, the 3rd block 24, the 4th block 26 and the 5th block 28.Further, evaluation unit 102 of the present invention can calculate the evaluation of estimate of each block by aforesaid method respectively.By this, evaluation unit 102 of the present invention can carry out more effective evaluation of estimate calculating for the image of low contrast or overexposure.More importantly, the division of block also can provide scenery to change information.For example, when user's moving lens, when causing the iron tower scenery that is positioned at first block 20 among Fig. 4 to move on to the 3rd block 24, therefore the evaluation of estimate of each block can change, and makes focusing mechanism 10 can carry out corresponding processing.Note that in practical application evaluation unit 102 visual demands of the present invention are divided into the block of any number with image area, are not limited to aforementioned five blocks of giving an example.

In this specific embodiment, the weighting evaluation of estimate (F that the control module 104 of focusing mechanism 10 of the present invention can be calculated whole image according to the evaluation of estimate and the formula [2] of aforementioned each block that is calculated by evaluation unit 102 _W).

F _W=F ₁/ 2+ (F ₂+ F ₃+ F ₄+ F ₅)/4............... formula [2]

Wherein, F ₁Be the evaluation of estimate of first block 20 among Fig. 4, and F ₂～F ₄Be respectively the evaluation of estimate of second block to the, five blocks 22～28.

And control module 104 can optionally produce control signal according to weighting evaluation of estimate and depth of focus table (depth of focustable), moves with controls lens 122.In practical application, control module 104 can be sent to control signal transmission module (not being illustrated among the figure), and it comprises motor, can drive camera lens 122 according to this control signal and move.

Further see also Fig. 5, Fig. 5 is the functional block diagram that illustrates according to the focusing mechanism of a specific embodiment of the present invention.As shown in Figure 5, the control module 104 of focusing mechanism 10 of the present invention can also comprise storage unit 1042, as storer, and microcontroller (micro-controller) 1044.Storage unit 1042 can be in order to write down aforesaid depth of focus table, and microcontroller 1044 then can move according to control signal controls lens 122.Note that storage unit 1042 and microcontroller 1044 can be integrated in the control module 104, also visual demand and independently being present in the focusing mechanism 10.In addition, in practice, the also visual demand of focusing mechanism of the present invention comprises suitable treatment element, for example but be not subject to, noise suppression component, separates mosaic element, image output element etc.

In practical application, aforesaid depth of focus table can be established in the image recording system production run.See also Fig. 6, Fig. 6 is a process flow diagram of setting up depth of focus table.As shown in Figure 6, set up depth of focus table input at least one parameter preset (step S30) earlier.In practice, parameter preset can be, but be not subject to, as the focal length (focal length) of camera lens, the pixel size (pixelsize) of sensing element, the displacement (moving range) and the F numerical value (F number, focal length/aperture effective vent diameter) of camera lens.Then, calculate hyperfocal distance from (hyperfocal distance, HD) (step S31) according to these parameter presets and following formula [3].

HD=(1+ (FL/2 * F _Num)/(SP * 2)) * FL............... formula [3]

Wherein, FL represents the focal length of camera lens, F _NumExpression F numerical value, SP then represents the pixel size of sensing element.

Subsequently, in the distance range of (hyperfocal distance is from/2) to (hyperfocal distance from/2+ camera lens displacement), calculate the depth of focus (step S32) of camera lens on each focusing position respectively.At last, remove unnecessary depth of focus data to finish depth of focus table (step S33).For example, suppose that the depth of focus when camera lens moves N unit distance (being positioned at focusing position A) is 2cm to 10cm, and the depth of focus of camera lens when moving (N+1) unit distance (being positioned at focusing position B) is 4cm to 7cm.Because the depth of focus of focusing position B is contained in the scope of the depth of focus of focusing position A, therefore the depth of focus of focusing position B can be removed, reach the effect of simplifying depth of focus table content.

In a specific embodiment, when image recording system was in the photography pattern, control module may command camera lens of the present invention moved to the focusing position with maximum weighted evaluation of estimate.See also Fig. 7, Fig. 7 is the focusing method flow diagram that illustrates according to a specific embodiment of the present invention.As shown in Figure 7, when image recording system is in the photography pattern, focusing mechanism of the present invention calculates a plurality of evaluations of estimate (step S40) of each focusing position of camera lens earlier according to aforesaid formula [1], according to these evaluations of estimate, calculate the weighting evaluation of estimate (step S41) of each focusing position with aforesaid formula [2] again.At last, camera lens is moved to focusing position (step S42) with maximum weighted evaluation of estimate.Usually, aforesaid step can be finished when the user operates the scenery that image recording system takes facing to desire and partly trips.

In another specific embodiment, when image recording system is in the Dynamic Photography pattern, the present picture frame (current frame) of control module of the present invention in can more a series of continuous picture frames and these evaluations of estimate of previous picture frame (previous frame).When the difference of these evaluations of estimate during greater than threshold value, control module produces this control signal, and controls lens moves to the focusing position with maximum weighted evaluation of estimate.

See also Fig. 8, Fig. 8 is the focusing method flow diagram that illustrates according to a specific embodiment of the present invention.As shown in Figure 8, when image recording system is in the Dynamic Photography pattern, focusing mechanism of the present invention calculates a plurality of present evaluation of estimate (step S50) of a plurality of blocks in the present picture frame earlier according to aforesaid formula [1], and with a plurality of previous evaluation of estimate of these present evaluations of estimate and previous picture frame relatively (step S51).Then judge and whether have the number of blocks of different evaluation value greater than threshold value (step S52).

If step S52 is judged as not, judge further that then whether difference is greater than threshold value (step S53).If step S53 is judged as not, then get back to step S51.If being judged as of step S53 be, after adding default value (step S54), the number of blocks that then will have a different evaluation value gets back to step S51.Otherwise, if being judged as of step S52 is then according to these present evaluations of estimate, to calculate present weighting evaluation of estimate (step S55) with aforesaid formula [2].Then, the previous weighting evaluation of estimate (step S56) of more present weighting evaluation of estimate and previous picture frame, and whether the difference of judging present weighting evaluation of estimate and previous weighting evaluation of estimate is greater than threshold value (step S57).

If step S57 is not judged as not, the focusing position of moving lens not then, and get back to step S50.Otherwise, if being judged as of step S57 is then further to judge that whether the focusing position of present camera lens is greater than predeterminated position (for example the maximum focusing position on the depth of focus table deducts default value) (step S58).If step S58 is judged as not, then the focusing position with the past scenery direction (with respect to the sensing element direction) of camera lens moves to the focusing position (step S59) with maximum weighted evaluation of estimate.Otherwise, if being judged as of step S58 is then camera lens to be moved a unit distance to next focusing position (step S60) toward sensing element direction (with respect to the scenery direction).Whether the weighting evaluation of estimate of judging this focusing position is greater than the weighting evaluation of estimate (step S61) of last focusing position.If not, carry out step S59.If then the focusing position with the past sensing element direction (with respect to the scenery direction) of camera lens moves to the focusing position (step S62) with maximum weighted evaluation of estimate.

Then see also Fig. 9, Fig. 9 is the detail flowchart that illustrates the step S62 among Fig. 8.As shown in Figure 9, aforesaid step S62 can also comprise the following step: at first, in step S620, camera lens is moved a unit distance to next focusing position toward the sensing element direction.Subsequently, in step S622, calculate the weighting evaluation of estimate of this focusing position.Then, in step S624, judge that whether this weighting evaluation of estimate is less than previous weighting evaluation of estimate.If step S624 is judged as not, get back to step S620.Otherwise, if being judged as of step 624 be, then carry out step S626, camera lens is moved a unit distance to focusing position toward the scenery direction, and with this focusing position as final focusing position.

Please again referring to Figure 10, Figure 10 is the detail flowchart that illustrates the step S59 among Fig. 8.As shown in figure 10, aforesaid step S59 can also comprise the following step: at first, in step S590, camera lens is moved a unit distance to next focusing position toward the scenery direction.Subsequently, in step S592, calculate the weighting evaluation of estimate of this focusing position.Then, in step S594, judge that whether this weighting evaluation of estimate is less than previous weighting evaluation of estimate.If step S594 is judged as not, get back to step S590.Otherwise, if being judged as of step 594 be, then carry out step S596, camera lens is moved a unit distance to focusing position toward the sensing element direction, and with this focusing position as final focusing position.

Note that aforesaid each threshold value, default value and the visual demand of criterion and set, be not limited to the scope for example of front.

In sum, focusing mechanism of the present invention and method can be applied in the image recording system.Especially, focusing mechanism of the present invention and method have been simplified known focusing technology.For example, when focusing mechanism moving lens of the present invention was focused, each focusing position that can earlier camera lens be moved in the depth of focus table after the simplification was searched, and does not need to search all focusing positions.For another example, the present invention is divided into a plurality of part overlapping blocks with image, and the information that can provide scenery whether to move by this assists focusing mechanism to judge whether to want moving lens to focus again.Therefore, focusing mechanism of the present invention and method can promote focusing speed under the limited hardware resource, help the application of electronic apparatus.

By the above detailed description of preferred embodiments, be to wish to know more to describe feature of the present invention and spirit, and be not to come category of the present invention is limited with above-mentioned disclosed preferred embodiment.On the contrary, its objective is that hope can contain in the category of claim scope of being arranged in of various changes and tool equality institute of the present invention desire application.Therefore, the category of the claim scope that the present invention applied for should be done the broadest explanation according to above-mentioned explanation, contains the arrangement of all possible change and tool equality to cause it.

Claims

1. A focusing device applied to an image recording system, the focusing device comprising:

an evaluation unit, configured to generate a plurality of evaluation values related to the image according to the image sensed by the sensing element; and

a control module that calculates a weighted evaluation value based on the evaluation values, and the control module selectively generates a control signal according to the weighted evaluation value and the focus depth table to control the movement of the lens,

Wherein, the focus depth table is established according to the following formula:

HD=(1+(FL/2×F _num )/(SP×2))×FL;

Among them, HD represents the hyperfocal distance; FL represents the focal length of the lens; F _num represents the focal length/aperture effective opening diameter value; and SP represents the pixel size of the sensing element.

2. The focusing device according to claim 1, wherein when the image recording system is in the dynamic photography mode, the control module compares the evaluation values of the current frame and the previous frame, and when the difference of the evaluation values is greater than threshold value, the control module generates the control signal to control the zoom lens to move to the focus position with the maximum weighted evaluation value, wherein,

(A) When the focus position of the lens is not greater than the preset position, move the focus position of the lens toward the scene to the focus position with the maximum weighted evaluation value;

(B) When the focus position of the lens is greater than the preset position,

(d) Move the lens one unit distance toward the sensing element to the next focus position,

(e) When the weighted evaluation value is greater than the weighted evaluation value of the previous focus position, move the lens toward the sensing element to the focus position with the largest weighted evaluation value; when the weighted evaluation value is not greater than the weighted evaluation value of the previous focus position , return (A).

3. The focusing device according to claim 2, wherein in the process of moving the focus position of the lens toward the scene to the focus position with the maximum weighted evaluation value,

(a) Move the lens one unit distance toward the scene to the next focus position,

(b) calculating the weighted evaluation value of the next focus position,

(c) When the weighted evaluation value of the next focus position is less than the previous weighted evaluation value, move the lens to the direction of the sensing element for a unit distance to the next focus position, when the weighted evaluation value of the next focus position is not less than Returns (a) for the previous weighted evaluation value.

4. The focusing device according to claim 2, wherein in the process of moving the focus position of the lens toward the sensing element to the focus position with the maximum weighted evaluation value,

(a) moving the lens toward the sensing element by one unit distance to the next focus position, and calculating the weighted evaluation value of the next focus position,

(b) When the weighted evaluation value of the next focus position is less than the previous weighted evaluation value, move the lens toward the scene by one unit distance to a focus position, when the weighted evaluation value of the next focus position is not less than the previous weighted evaluation value , return to (a).

5. The focusing device according to claim 1, further comprising:

The storage unit is used to record the focus depth table.

6. The focusing device according to claim 1, further comprising:

The microcontroller is used for controlling the movement of the zoom lens according to the control signal.

7. The focusing device according to claim 1, wherein the evaluation values F are calculated according to the following formula:

F＝R(A ₁ ×G _XR +G _YR )+G(A ₂ ×G _XG +G _YG )+B(A ₃ ×G _XB +G _YB );

Where R represents the red plane of the image, G represents the green plane of the image, B represents the blue plane of the image, and F represents the evaluation values;

Among them, G _X ＝|G ₅ -G ₄ |, G _Y ＝|G ₇ -G ₂ |, the coefficients A ₁ , A ₂ , and A ₃ are used to weight the sharpness of the image in the horizontal direction, and G2 represents the sharpness in the 3× 3, the upper pixel of the central pixel in the pixel schematic diagram, G4 represents the left pixel of the central pixel, G5 represents the right pixel of the central pixel, and G7 represents the lower pixel of the central pixel.

8. The focusing device according to claim 1, wherein the evaluation values respectively correspond to a plurality of partially overlapping blocks on the image.

9. The focusing device according to claim 8, wherein the weighted evaluation value _FW is calculated according to the following formula:

F _W =F ₁ /2+(F ₂ +F ₃ +F ₄ +F ₅ )/4;

Among them, _F1 is the evaluation value of the first block among the blocks, _F2 is the evaluation value of the second block among the blocks, and _F3 is the evaluation value of the third block among the blocks. value, _F4 is the evaluation value of the fourth block among these blocks, _F5 is the evaluation value of the fifth block among these blocks, the first block is the block where the main body of the screen is located, and the second block is the evaluation value of the fifth block among these blocks. Blocks to fifth are other blocks of the screen.

10. A focusing method applied to an image recording system, comprising the following steps:

(a) establishing a focal depth table according to at least one preset parameter;

(b) generating a plurality of evaluation values for the image;

(c) calculate a weighted evaluation value based on these evaluation values; and

(d) selectively generating a control signal according to the weighted evaluation value and the focal depth table to control lens movement,

Wherein the focus depth table is established according to the following formula:

HD=(1+(FL/2×F _num )/(SP×2))×FL;

11. The focusing method according to claim 10, wherein when the image recording system is in the dynamic photography mode, the evaluation values of the current frame and the previous frame are compared, and when the difference of the evaluation values is greater than a threshold value , generating the control signal to control the zoom lens to move to the focus position with the maximum weighted evaluation value, wherein,

(B) When the focus position of the lens is greater than the preset position,

(e) Move the lens one unit distance toward the sensing element to the next focus position,

(f) When the weighted evaluation value is greater than the weighted evaluation value of the previous focus position, move the lens toward the sensing element to the focus position with the largest weighted evaluation value; when the weighted evaluation value is not greater than the weighted evaluation value of the previous focus position , return (A).

12. The focusing device according to claim 11, wherein in the process of moving the focus position of the lens toward the scene to the focus position with the maximum weighted evaluation value,

(g) Move the lens one unit distance toward the scene to the next focus position,

(h) calculating the weighted evaluation value of the next focus position,

(i) When the weighted evaluation value of the next focus position is less than the previous weighted evaluation value, move the lens to the direction of the sensing element for a unit distance to the next focus position, when the weighted evaluation value of the next focus position is not less than Returns (g) for the previous weighted evaluation value.

13. The focusing device according to claim 11, wherein in the process of moving the focus position of the lens toward the sensing element to the focus position with the maximum weighted evaluation value,

(g) moving the lens toward the sensing element by one unit distance to the next focus position, and calculating the weighted evaluation value of the next focus position,

(h) When the weighted evaluation value of the next focus position is less than the previous weighted evaluation value, move the lens toward the scene by one unit distance to a focus position, when the weighted evaluation value of the next focus position is not less than the previous weighted evaluation value , return (g).

14. The focusing method according to claim 10, wherein the evaluation values F are calculated according to the following formula:

F＝R(A ₁ ×G _X +G _Y )+G(A ₂ ×G _X +G _Y )+B(A ₃ ×G _X +G _Y );

15. The focusing method according to claim 10, wherein the evaluation values respectively correspond to a plurality of partially overlapping blocks on the image.

16. The focusing method according to claim 15, wherein the weighted evaluation value F _W is calculated according to the following formula:

F _W =F ₁ /2+(F ₂ +F ₃ +F ₄ +F ₅ )/4;