CN102004370A - Method for detecting focal length by flashlight in auxiliary manner - Google Patents
Method for detecting focal length by flashlight in auxiliary manner Download PDFInfo
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- CN102004370A CN102004370A CN2009101681536A CN200910168153A CN102004370A CN 102004370 A CN102004370 A CN 102004370A CN 2009101681536 A CN2009101681536 A CN 2009101681536A CN 200910168153 A CN200910168153 A CN 200910168153A CN 102004370 A CN102004370 A CN 102004370A
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Abstract
The invention discloses a method for detecting focal length by a flashlight in an auxiliary manner, which is suitable for a digital camera with the flashlight. The method comprises the following steps: firstly actuating the flashlight of the digital camera and capturing the image with face; then computing the exposure characteristic value of the face in the image; consulting a focal length contrast table according to the exposure characteristic value to obtain an initial focusing position; then executing a focusing procedure according to the initial focusing position and obtaining the target focal length; and computing the flash characteristic value of the image after obtaining the target focal length and setting the flashlight index and aperture value according to the flash characteristic value.
Description
Technical field
The present invention relates to a kind of method of utilizing flashlamp auxiliary detection focal length, particularly a kind of utilize to table look-up according to the exposed feature value have the method for focal length of the image of people's face with auxiliary detection.
Background technology
Use camera when filmed image, need correctly focal length to subject obtaining clear photograph, and all have automatic focus function at general now digital camera.Automatically focusing can be divided into two big classes haply, and one is active automatic focusing (active auto focus), and another is passive type focusing (passive auto focus).
The technology of active automatic focusing utilizes the pattern of one group of infrared transmitter or generating laser and relative receiver projection light on subject, again with the distance between triangulation method computing cameras such as (triangulation) and the subject, and this distance is focal length.Owing to use active automatic focusing to need in camera, additionally to be provided with light transferring and receiving apparatus and receiver, therefore have the cost problem of higher.
Automatically focusing is for before formal the shooting for passive type, and digital camera mobile camera camera lens is to a plurality of focusing positions, wherein focusing position be arranged in from from the nearest microspur of digital camera to the zone that is set as infinity.Digital camera is pick-up image on focusing position, and the sharpness of analyzing the image obtained decides focal length.The passive type mode of focusing automatically only need be used image sensor and the arithmetic element that camera itself is had, so can alleviate manufacturing cost.
Yet focusing automatically, passive type needs to rely on, so when subject is in the ambient brightness deficiency, estimates the focal length that and be easy to generate error by the sharpness that picked image calculated in advance.Significantly close focus (in-focus) if bright and clear then object is known from experience to have during photography, make camera find correct focusing position easily.Otherwise if the ambient brightness deficiency can make camera be difficult for finding out correct focal length because of situations such as general image definition are lower when the estimation sharpness.So passive type focusing automatically can have the not accurate enough problem of focusing when ambient brightness is not enough.
In addition, when taking pictures, personage's image is the part of attaching most importance in the picture.Before the filmed image, previous operations such as focusing or photometry all should be carried out according to character facial.Yet traditional automatic focusing mode may be judged as photography body to other things beyond background or the personage, lose burnt problem on the contrary for the personage who takes emphasis and have.
Summary of the invention
In view of above problem, technical matters to be solved by this invention is to provide a kind of method of utilizing flashlamp auxiliary detection focal length, to address the above problem.The method of utilizing flashlamp auxiliary detection focal length disclosed in this invention, be applicable to that one has the digital camera of flashlamp, provide digital camera one target focal length according to a target subject that contains at least one people's face, its method comprises: flash of light also captures one first image to target subject; Get an exposed feature value, the corresponding people's face of this person's face block according at least one people's face block calculating in first image; Consult a burnt section table of comparisons according to the exposed feature value and obtain an initial focusing position; And the initial focusing position of foundation is carried out a focusing program to obtain the target focal length.
According to the first embodiment of the present invention, the step that gets an exposed feature value according at least one people's face block calculating in first image can comprise: search people's face block in first image; Calculate a pixel exposure value of each pixel of people's face block image; And the plain exposure value of capture on average as the exposed feature value.
According to the second embodiment of the present invention, the step that gets an exposed feature value according at least one people's face block calculating in first image can comprise: search people's face block in first image; By the central authorities of people's face block image edge, with a pixel exposure value of each pixel of gradient weighted calculation people face block image to people's face block image; And the plain exposure value of capture on average as the exposed feature value.
According to the third embodiment of the present invention, the step that gets an exposed feature value according at least one people's face block calculating in first image can comprise: search people's face block in first image; Calculate a pixel exposure value of each pixel of people's face block image; In each people's face block image, an exposure value of pixel is averaged respectively and obtains the average exposure value of a plurality of people's faces; According to people's face block, given each one face block one weighted value; And according to weighted value and the average exposure value calculation exposure of people's face eigenwert.
According to the fourth embodiment of the present invention, the step that gets an exposed feature value according at least one people's face block calculating in first image can comprise: search people's face block in first image; By the central authorities of people's face block image edge, with a pixel exposure value of each pixel of gradient weighted calculation people face block image to people's face block image; In each people's face block image, an exposure value of pixel is averaged respectively and obtains the average exposure value of a plurality of people's faces; According to people's face block, given each one face block one weighted value; And according to weighted value and the average exposure value calculation exposure of people's face eigenwert.
According to the present invention, the burnt section table of comparisons comprises a plurality of metraster train values and a plurality of focal length values corresponding with the metraster train value, consulting the step that the burnt section table of comparisons obtains initial focusing position according to the exposed feature value promptly is to consult the metraster train value with the exposed feature value in the burnt section table of comparisons, to drawing the focal length value corresponding with the exposed feature value as initial focusing position.
According to one embodiment of the invention, carry out the focusing program according to initial focusing position and can comprise: specify a focusing section according to initial focusing position with the step that obtains the target focal length; At least three focal lengths in the focusing section capture one respectively and survey burnt image; Calculate a clear value of surveying burnt image respectively; Carry out curve fitting to obtain a quadratic polynomial with clear value and the focal length corresponding with clear value; And serve as that zero pairing focal length is as the target focal length with the slope of quadratic polynomial.
According to another embodiment of the present invention, carry out a focusing program can comprise after the step that obtains the target focal length according to initial focusing position: get a general exposure value according to the calculating of the part beyond people's face block in the exposed feature value and first image; Get a flash of light eigenwert according to the exposed feature value with general exposure value calculating; And foundation flash of light eigenwert is set a guide number and a f-number.
About feature of the present invention, the real work and effect, conjunction with figs. is described in detail as follows as most preferred embodiment now.
Description of drawings
Fig. 1 is for utilizing the schematic flow sheet of the method for flashlamp auxiliary detection focal length according to an embodiment of the invention;
Fig. 2 is the structural representation of the digital camera that is suitable for according to the present invention;
Fig. 3 A is the schematic flow sheet of first embodiment of step S22 according to an embodiment of the invention;
Fig. 3 B is the schematic flow sheet of second embodiment of step S22 according to an embodiment of the invention;
Fig. 3 C is the schematic flow sheet of the 3rd embodiment of step S22 according to an embodiment of the invention;
Fig. 3 D is the schematic flow sheet of the 4th embodiment of step S22 according to an embodiment of the invention;
Fig. 4 is the schematic flow sheet of step S26 according to an embodiment of the invention;
Fig. 5 A is the synoptic diagram of horizontal shade according to an embodiment of the invention;
Fig. 5 B is the synoptic diagram of vertical according to an embodiment of the invention shade; And
Fig. 6 sets the schematic flow sheet of a guide number and a f-number for after obtaining the target focal length according to an embodiment of the invention according to first image and exposed feature value.
Wherein, Reference numeral
100 digital cameras, 102 flashlamp
104 lens assemblies, 106 iris apparatus
108 photo-sensitive cells (CCD), 110 sample circuits (sample hold circuit)
112 storage elements, 114 CD-ROM drive motor
116 processing units, 118 operating means
130 shades (mask), 132 shade content elements
Embodiment
Below the narration about detailed features of the present invention and advantage, its content is enough to make any those skilled in the art to understand technology contents of the present invention and implements according to this, and according to the disclosed content of this instructions, claim and accompanying drawing, any those skilled in the art can understand purpose and the advantage that the present invention is correlated with easily.
Please refer to Fig. 1, it is for utilizing the process flow diagram of the method for flashlamp auxiliary detection focal length according to an embodiment of the invention.The method of utilizing flashlamp auxiliary detection focal length of the present invention is suitable for a digital camera with flashlamp, and the method provides this digital camera one target focal length according to a target subject that contains at least one people's face.About the digital camera that the present invention was suitable for to be but to be not limited to Fig. 2.
Digital camera 100 comprises flashlamp 102, lens assembly 104, iris apparatus 106, photo-sensitive cell (CCD) 108, sample circuit (Sampling hold circuit) 110, storage element 112, CD-ROM drive motor 114, processing unit 116 and operating means 118.Entered photo-sensitive cell 108 by the light that scene reflected through lens assembly 104 and iris apparatus 106, photo-sensitive cell 108 is recorded in storage element 112 after converting the light that enters to signal of video signal and passing to sample circuit 110.
During shooting, processing unit 116 activated drive motors 114 with moving lens device 104 to specifying focal position.Processing unit 116 also passes through CD-ROM drive motor 114 and adjusts iris apparatus 106.Photo-sensitive cell 108 is corresponding to lens assembly 104 and the image frame of current scene is converted to the electric signal of digitized video.The driving of treated unit, sample circuit 110 is sent to storage element 112 with the signal of video signal that photo-sensitive cell 108 is received.Processing unit 116 is taken so that digital camera 100 to be provided in order to judge the focusing focal length that need adjust lens assembly 104 according to the preview image that is captured in the capture preview phase.
Refer again to Fig. 1 and cooperate Fig. 2 to read it, from Fig. 1, can see and know, utilize the method for flashlamp auxiliary detection focal length to comprise step S20: activate this flashlamp, and capture first image; Step S22: get an exposed feature value according at least one people's face block calculating in first image; Step S24: consult the burnt section table of comparisons according to the exposed feature value, obtain initial focusing position; And step S26: carry out a focusing program to obtain the target focal length according to initial focusing position.
In step S20, processing unit 116 makes flashlamp 102 actions by CD-ROM drive motor 114.When flashlamp 102 sent a preflashing light, digital camera 100 acquisition first images also were recorded in the storage element 112.Processing unit 116 is analyzed this first image and the data after analyzing is used for auxiliary focusing (auto focus) automatically.Aforementioned picked image is not limited to only capture one, is that refinement really also can use many image to handle during practical application.Below only as an illustration with individual.
Therefore first image of abovementioned steps S22 has been represented combining of subject reflected ambient that contains at least one people's face and the light that is sent by flashlamp 102 and be reflected, and forms in the light of first image to comprise reflection preflashing light.So also can be referred to as the reflex exposure value at this exposure value.The depth of exposure of exposed feature value representation subject under the state that gives the preflashing light understood according to the distance of subject and digital camera 100 difference to some extent.The account form of exposed feature value is detailed later.
Obtain after the exposed feature value, step S24 consults a burnt section table of comparisons (also can be described as the focusing section table of comparisons) with the exposed feature value.The burnt section table of comparisons comprises a plurality of metraster train values and the focal length value corresponding with the metraster train value.This burnt section table of comparisons be one with the exposed feature value and the table of comparisons to possible focal length value that should the exposed feature value.That is to say, the exposed feature value is removed to consult the focal length value corresponding with the exposed feature value at the metraster train value can obtain aforesaid initial focusing position.Available initial focusing position can be for the usefulness of follow-up focusing program after consulting the burnt section table of comparisons according to the exposed feature value.The table mode of building about the burnt section table of comparisons is detailed later.
Step S26 is by obtaining the reference point of focusing scanning position of initial focusing position as the focusing program, make the focusing program can exempt scanning all by the focusing position of microspur to the infinity, and then reduce traditional focusing program required focusing time and power consumption.
About obtain the step of exposed feature value by first image, please refer to Fig. 3 A, Fig. 3 B, Fig. 3 C and Fig. 3 D.Fig. 3 A is the schematic flow sheet of first embodiment of step S22 according to an embodiment of the invention.The flow process of this embodiment comprises step S30: search people's face block in first image; Step S32: a pixel exposure value of calculating each pixel of people's face block image; And step S34: the plain exposure value of capture on average as the exposed feature value.
At first step S30 searches people's face block in first image, i.e. its contained people face part in first image, and acquisition people's face block image.Wherein the shape of people's face block can be but not limit to be a square frame shape, and its size and the position in image etc. are also unrestricted.
Then step S32 calculates a pixel exposure value of all pixels of people's face block image.Each pixel has a tristimulus values (RGB value), and RGB refers to redness, green and the blue value of this pixel respectively.Its method converts the tristimulus values of each pixel to the GTG value earlier according to formula (0.6G+0.3R+0.1B) earlier, again with the GTG value according to formula log
2(0.6G+0.3R+0.1B) calculate the exposure value of each pixel.After calculating the pixel exposure value of all pixels in people's face block image, step S34 is averaged the pixel exposure value as the exposed feature value.
Fig. 3 B is the schematic flow sheet of second embodiment of step S22 according to an embodiment of the invention.The flow process of this embodiment comprises step S40: search people's face block in first image; Step S42: by the central authorities of people's face block image to the edge, with a pixel exposure value of each pixel of gradient weighted calculation people face block image; And step S44: the plain exposure value of capture on average as the exposed feature value.
After step S40 hunts out people's face block in first image, the people's face block image in the acquisition people face block.And after step S42 goes out the exposure value of each pixel in people's face block image according to aforementioned calculation, all exposure values are weighted calculating.The step that gives the weighting weight is as follows.Specify maximum people's face pixel weight at first for the Centromedian pixel of people's face block image, specify minimum people's face pixel weight for again the pixel at the edge of people's face block image, give remaining pixel nominator's face pixel weight in people's face block image with interpolation method at last.After each exposure value be multiply by corresponding people's face pixel weight, the pixel in everyone the face block image can obtain corresponding pixel exposure value.Step S44 is averaged exposed feature value as first image to all pixel exposure values again.
Fig. 3 C is the schematic flow sheet of the 3rd embodiment of step S22 according to an embodiment of the invention.The flow process of this embodiment comprises step S50: search people's face block in first image; Step S52: a pixel exposure value of calculating each pixel of people's face block image; Step S54: the exposure value to pixel is averaged in each people's face block image respectively, obtains the average exposure value of a plurality of people's faces; Step S56: according to people's face block, given each one face block one weighted value; And step S58: according to weighted value and the average exposure value calculation exposure of people's face eigenwert.
Step S50 searches a plurality of people's face blocks in first image, and each people's face block is captured people's face block image.Then in step S52, calculate the pixel exposure value of the pixel in everyone the face block image according to aforementioned formula.Step S54 is averaged people's face exposure mean value as each one face block image to its corresponding pixel exposure value respectively in each people's face block image.
Obtain after people's face exposure mean value, step S56 gives each people's face block one weighted value according to people's face block.When having a plurality of people's face block in first image, can give weight according to the distance of people's face in the image to adjust the exposed feature value.Because nearer people face part may be the shooting body in the image, therefore give its corresponding bigger weighted value of people's face block.
In first image, bigger people's face block may represent that the corresponding people's face of its block is nearer apart from digital camera, therefore gives bigger weighted value.Then according to the present invention, the method that gives weighted value can be following steps.The pixel quantity that at first calculates each people's face block image is promptly represented the size of each people's face block as people's face block sizes values.Give a plurality of people's face block weighted values according to these people's face block sizes values, these people's face block sizes values are big more, and these people's face block weighted values that obtained are just big more.
Again, the people's face block that has the bigger average exposure value of people's face in first image represents that its corresponding people face part is brighter, and the energy of flash of light that may represent to reflect preflashing is stronger, and represents this person's face nearer apart from digital camera, therefore gives bigger weighted value.Then according to the present invention, the method that gives weighted value can also be: the size according to the average exposure value of each one face puts in order; And order gives weighted value according to this, and the average exposure value of the people's face weighted value that big corresponding people's face block obtained of healing is bigger.
Everyone face block has been specified after the weighted value, and step S58 is according to weighted value and the average exposure value of corresponding people's face, and weighted calculation obtains the exposed feature value.
Fig. 3 D is the schematic flow sheet of the 4th embodiment of step S22 according to an embodiment of the invention.The flow process of this embodiment comprises step S60: search people's face block in first image; Step S62: by the central authorities of people's face block image to the edge, with a pixel exposure value of each pixel of gradient weighted calculation people face block image; Step S64: the exposure value to pixel is averaged in each people's face block image respectively, obtains the average exposure value of a plurality of people's faces; Step S66: according to people's face block, given each one face block one weighted value; And step S68: according to weighted value and the average exposure value calculation exposure of people's face eigenwert.
Step S60 searches a plurality of people's face blocks in first image, and captures the people face block image corresponding with people's face block.In step S62, calculate the exposure value of the pixel in everyone the face block image according to aforementioned formula after, everyone face block image is calculated the pixel exposure value of each pixel with trapezoidal waighting.Wherein people's face pixel weight of trapezoidal waighting to method is: people's face pixel weight of pixel one maximum of first administration of human face block image central authorities, and people's face pixel weight of pixel one minimum of administration of human face block image edge, the corresponding people's face of the pixel pixel weight of being left with interpolation method again.
Obtain after the pixel exposure value of everyone face block image, step S64 is averaged its corresponding pixel exposure value as people's face exposure mean value according to each one face block.In step S66, can be as abovementioned steps S56 according to mode administration of human face block weighted values such as people's face block size or the average exposure value brightness of people's face.Then step S68 is at the weighted value and the average exposure value of corresponding people's face of foundation gained, and weighted calculation obtains the exposed feature value.
According to the present invention, among the method for the exposure value of aforementioned calculation focusing frame image, all pixels that brighter partial pixel replaces focusing frame image in the frame image of can focusing are averaged the exposure value as focusing frame image.After wherein brighter part refers to all pixels are just sorted by exposure value, the pixel that exposure value is higher.For example can get in the focusing frame image the brightest preceding 30% or the brightest preceding 50% exposure value that removes to calculate focusing frame image, carry out the calculation exposure eigenwert again.So can avoid comprising in the pick-up image influence that image caused of the environment of a large amount of luminance shortage.
Obtain to carry out above-mentioned steps S24 after the exposed feature value, can obtain initial focusing position after consulting the burnt section table of comparisons with the exposed feature value.
According to embodiments of the invention, resulting exposed feature value may not have just in time corresponding metraster train value in the burnt section table of comparisons.This moment, then interior two metraster train value and focal length values corresponding with it that approach the exposed feature value were most shown in taking-up, were answered corresponding focal length value as initial focusing position with interpolation method calculation exposure eigenwert.
Please refer to Fig. 4, it is the schematic flow sheet of step S26 according to an embodiment of the invention.Can see that by Fig. 4 it comprises step S70: specify a focusing section according to initial focusing position; Step S72: at least three focal lengths in the focusing section capture one respectively and survey burnt image; Step S74: calculate the clear value of surveying burnt image respectively; Step S76: carry out curve fitting with clear value and the focal length corresponding, obtain a quadratic polynomial with clear value; With step S78: with the slope of quadratic polynomial serves as that zero pairing focal length is as the target focal length.
Step S70 specifies the focusing section according to initial focusing position, for focusing program searching target focal length in this section.This specifies the mode of focusing section that several embodiment are arranged according to initial focusing position.One is to enlarge step pitch more than three (step, or claim step distance) with initial focusing position to nearly Jiao and burnt position far away, and the distance of each step pitch can be consistent or inconsistent.According to one embodiment of the invention, can decide the focusing section according to the convergent-divergent multiplying power of acquisition during first image.For example when acquisition first image, the convergent-divergent multiplying power of digital camera just might be that distant place landscape or focal length far away are focused near wide-angle side (wide).Therefore, can specify by initial focusing position and rise, be the focusing section to the section of initial focusing position till digital camera six step pitches far away from three nearer step pitches of digital camera.
Again according to another embodiment of the present invention, when digital camera acquisition during first image if the convergent-divergent multiplying power near telescope end (tele, digital camera can further scenery image at a distance, the effect that picture amplifies image), then specify by initial focusing position and rise, be the focusing section to the section of initial focusing position till digital camera 12 step pitches far away from six nearer step pitches of digital camera.
According to the present invention, specify according to initial focusing position in the method for focusing section, being not limited to a step pitch is unit.The size of focusing section can also a plurality of step pitch or is that unit specifies with distance (for example a centimetre or a millimeter).In addition, the sector sizes of looking for toward near or past direction far away with reference to initial focusing position in the focusing section does not also limit.Except that the foregoing description, the sector sizes of looking for toward near or past direction far away with reference to initial focusing position in the burnt section also can be identical, or bigger toward the section of near direction.
On the focal length of step S72 in the specified focusing section of step S70, capture one respectively and survey burnt image, and in the focusing section, comprise three focal lengths at least.The focusing program can be surveyed burnt image to these and calculate and analyze, in the hope of last target focal length.
Step S74 calculates the clear value with the burnt image of survey of acquisition respectively, and the mode of wherein calculating clear value can be according to one embodiment of the invention, earlier surveying burnt image with rim detection (edge-detection) routine processes.Edge detection procedure can adopt Sobel edge detection method, Dijkstra ' s algorithm or Canny rim detection algorithm etc., according to the present invention not with the restriction.After the edge detection procedure processing, clear value can be to be defined as the number of edges of surveying in the burnt image.
According to edge detection procedure of the present invention, it is surveyed burnt image to each respectively and applies mechanically horizontal shade or vertical shade, and the content of shade please refer to Fig. 5 A and Fig. 5 B.Fig. 5 A and Fig. 5 B are respectively horizontal according to an embodiment of the invention shades and the synoptic diagram of vertical shade.As shown in the figure, have in the shade (mask) 130 and comprise different shade content elements 132.
After surveying burnt image and applying mechanically shade, each pixel of surveying burnt image obtains a correlative value, and according to the size order of correlative value the correlative value described point is become curve, and each is surveyed burnt image and all can obtain a contrast curve.Calculate the program of clear value and specify a threshold value in correlation curve, the person represents the degree that contrasts enough high (being enough sharp keen parts in the image) if correlative value is higher than the threshold value.Next correlation curve is calculated integration to the part more than the threshold value, then can be defined as clear value to the numerical value that calculates.
According to clear value, step S76 carries out the curve fitting (curve fitting) of quadratic polynomial with each clear value and focal length corresponding with it of surveying burnt image, and can obtain a quadratic polynomial.The quadratic polynomial that calculates is illustrated in the variation of the sharpness of the burnt image of survey that is captured in the focusing section of appointment.Therefore the summit of quadratic polynomial, just slope is zero point, the also clear value of representative obtainable maximum in the focusing section just is with the focal length that can obtain sharp image.
In order to obtain the summit of above-mentioned quadratic polynomial, step S78 serves as zero point to the quadratic polynomial differential to search the polynomial expression codifferential, that is slope is zero point.Step S78 is slope in the quadratic polynomial that zero the pairing focal length of point is as the target focal length.According to one embodiment of the invention, when the slope of the quadratic polynomial that is obtained by curve fitting is zero a point when just in time not dropping on arbitrary focal length of appointment in the focusing section, then getting apart from slope is that the nearest focal length of zero point is as the target focal length.
According to another embodiment of the present invention, when the quadratic polynomial that obtains in the section in focusing when not have slope be zero point, then enlarge focusing section that the focusing program scanned to obtain the burnt image of more survey.The focusing program also carries out curve fitting again according to burnt image of survey originally and the burnt image of survey that newly obtains, and the slope of searching new quadratic polynomial is that zero point is to obtain the target focal length.
According to the present invention, after digital camera 100 obtains the target focal length according to the method for utilizing flashlamp auxiliary detection focal length, drive lens assemblies 104 by CD-ROM drive motor 114 and move to and specify focal position and take.
Please refer to Fig. 6, it sets the schematic flow sheet of a guide number and a f-number for after obtaining the target focal length according to one embodiment of the invention according to first image and exposed feature value.It comprises step S80 as seen from Figure 6: get a general exposure value according to the calculating of the part beyond people's face block in the exposed feature value and first image; Step S82: get a flash of light eigenwert with general exposure value calculating according to the exposed feature value; And step S84: set a guide number and a f-number according to the flash of light eigenwert.
According to the exposed feature value at step S22 gained, step S80 calculates a general pixel exposure value of each pixel of the part beyond people's face block in first image, and general pixel exposure value is averaged as general exposure value.Owing to usually personage's image is considered as the shooting body during photography, should be as the criterion with character facial during acquisition parameters such as calculating focal length or flash light intensity and adjusts.Therefore present embodiment dodges intensity according to the general pixel weight that is given by the resulting exposed feature value of people's face block image in first image in the hope of more suitable flashlamp master.
Step S80 gives general pixel exposure value the general pixel one minus weighted value more taller than the exposed feature value, give general pixel exposure value than the also low general pixel one of exposed feature value greater than zero weighted value, and give the weighted value that general pixel one that general pixel exposure value equates with the exposed feature value equals.In addition, the size of the absolute value of weighted value then determines according to the gap of general pixel exposure value and exposed feature value, and the gap big general pixel that heals can obtain the absolute value big weighted value of healing.After the decision weighted value, again each general pixel exposure value is become promptly to obtain general exposure value with corresponding weighted value.
In step S82, can be averaged exposed feature value and general exposure value as the flash of light eigenwert.The flash of light eigenwert can be represented the exposure value by the adjusted first image integral body of method of weighting of above-mentioned attention people face.
According to the flash of light eigenwert, step S84 can be by inquiring about the guide number (GN, guild number) of a flash of light table of comparisons to obtain flashing.The table of comparisons that wherein glistens comprise a plurality of flash of light tabulated values and with flash of light tabulated value corresponding guide number.With the flash of light eigenwert at the flash of light table of comparisons and can obtain, for the usefulness of the main sudden strain of a muscle of the follow-up flashlamp that flashes at this flash of light required guide number during eigenwert.The table mode of building about the flash of light table of comparisons is detailed later.
(D is the distance of the shooting body to digital camera according to formula GN=D * F with the target focal length of trying to achieve at step S26 guide number, can the substitution of target focal length, F be a f-number) after can calculate corresponding target focal length and the needed f-number of guide number.Digital camera 100 guide number that can the obtain flashlamp 102 that flashes then according to tabling look-up, and change iris apparatus 106 to take by CD-ROM drive motor 114.
The aforesaid burnt section table of comparisons can adopt experimental method to set up.Experimental method is set up and to be referred in dark place flash of light and with different focal lengths various subjects are taken, calculate and the exposed feature value of corresponding each focal length, to set up the aforesaid burnt section table of comparisons.Aforementioned subject can be an any object or a face wall.The exposed feature values that this experiment can obtain many groups according to the character of surface of different subjects (for example reflective or easy extinction) easily to be producing the burnt section tables of comparisons of many groups, and can provide different patterns to select to the user in response to the actual photographed situation.In like manner, experiment also can be simulated the different shooting environmental situation of many groups in dark place, obtains the burnt section of the corresponding many groups table of comparisons to provide different patterns to select to the user in response to the actual photographed situation.
Again, the aforementioned flash of light table of comparisons also can be adopted experimental method foundation.Flash of light with varying strength in dark place is taken various subjects, calculate and the flash of light eigenwert of corresponding each guide number, to set up the flash of light table of comparisons.
According to the method for utilizing flashlamp auxiliary detection focal length of the present invention, be applied to a digital camera with flashlamp, first image that contains people's face block at least that captures in the time of can be according to pre flashing of flash lamp calculates the exposed feature value.According to the exposed feature value, can provide digital camera one target focal length to take digitized video for the hardware devices such as lens assembly of digital camera.In addition, according to exposed feature value and target focal length, can provide the flashlamp of digital camera and iris apparatus one guide number and f-number to take for digital camera.
Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection domain of the appended claim of the present invention.
Claims (8)
1. a method of utilizing flashlamp auxiliary detection focal length is applicable to that one has the digital camera of flashlamp, it is characterized in that, this method provides this digital camera one target focal length according to a target subject that contains at least one people's face, and this method comprises:
Flash of light also captures one first image to this target subject;
According at least one people's face block in this first image calculate and an exposed feature value, this people's face block is to should people's face;
Consult a burnt section table of comparisons according to this exposed feature value and obtain an initial focusing position; And
Carry out a focusing program to obtain this target focal length according to this initial focusing position.
2. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, this step that gets an exposed feature value according at least one people's face block calculating in this first image comprises:
In this first image, search this people's face block, have people's face block image in this people's face block;
Calculate a pixel exposure value of each pixel of this people's face block image; And
Get the average of described pixel exposure value as this exposed feature value.
3. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, this step that gets an exposed feature value according at least one people's face block calculating in this first image comprises in addition:
In this first image, search this people's face block, have people's face block image in this people's face block;
By the central authorities of this people's face block image edge, with a pixel exposure value of each pixel of this people's face block image of gradient weighted calculation to this people's face block image; And
Get the average of described pixel exposure value as this exposed feature value.
4. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, this step that gets an exposed feature value according at least one people's face block calculating in this first image comprises in addition:
Search described people's face block in this first image, each described people's face block all has people's face block image;
Calculate a pixel exposure value of each pixel of described people's face block image;
In each described people's face block image, an exposure value of described pixel is averaged respectively and obtains the average exposure value of a plurality of people's faces;
According to described people's face block, given each described people's face block one weighted value; And
Calculate this exposed feature value according to described weighted value and the average exposure value of described people's face.
5. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, this step that gets an exposed feature value according at least one people's face block calculating in this first image comprises in addition:
Search described people's face block in this first image, each described people's face block all has people's face block image;
By the central authorities of described people's face block image edge, with a pixel exposure value of each pixel of the described people's face of gradient weighted calculation block image to described people's face block image;
In each described people's face block image, an exposure value of described pixel is averaged respectively and obtains the average exposure value of a plurality of people's faces;
According to described people's face block, given each described people's face block one weighted value; And
Calculate this exposed feature value according to described weighted value and the average exposure value of described people's face.
6. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1, it is characterized in that, this Jiao's section table of comparisons comprises a plurality of metraster train values and a plurality of focal length values corresponding with described metraster train value, consulting the step that this Jiao's section table of comparisons obtains an initial focusing position according to this exposed feature value promptly is to consult this metraster train value with this exposed feature value in this Jiao's section table of comparisons, and contrast draws this focal length value corresponding with this exposed feature value as this initial focusing position.
7. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, this initial focusing position of this foundation is carried out a focusing program and comprised with the step that obtains this target focal length:
Specify a focusing section according to this initial focusing position;
At least three focal lengths in this focusing section capture one respectively and survey burnt image;
Calculate a clear value of the burnt image of described survey respectively;
Carry out curve fitting to obtain a quadratic polynomial with described clear value and the described focal length corresponding with this clear value; And
Slope with this quadratic polynomial serves as that zero pairing this focal length is as this target focal length.
8. the method for utilizing flashlamp auxiliary detection focal length as claimed in claim 1 is characterized in that, carries out a focusing program to comprise after the step that obtains this target focal length according to this initial focusing position:
Get a general exposure value according to the calculating of the part beyond this people's face block in this exposed feature value and this first image;
Get a flash of light eigenwert according to the general exposure value calculating of this exposed feature value and this; And
Set a guide number and a f-number according to this flash of light eigenwert.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103108133A (en) * | 2011-11-11 | 2013-05-15 | 株式会社日立制作所 | Imaging device |
| CN103167141A (en) * | 2012-09-14 | 2013-06-19 | 深圳市金立通信设备有限公司 | Continuous focalizing system and method of mobile phone camera |
| WO2015149525A1 (en) * | 2014-04-02 | 2015-10-08 | 努比亚技术有限公司 | Photographing method and photographic device |
| CN105163035A (en) * | 2015-09-30 | 2015-12-16 | 努比亚技术有限公司 | Mobile terminal shooting system and mobile terminal shooting method |
| CN110493518A (en) * | 2019-08-15 | 2019-11-22 | 移康智能科技（上海）股份有限公司 | A kind of image-pickup method of security protection camera |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3679693B2 (en) * | 2000-07-31 | 2005-08-03 | 三洋電機株式会社 | Auto focus camera |
| CN101430477B (en) * | 2007-11-09 | 2011-06-08 | 鸿富锦精密工业（深圳）有限公司 | Method for judging object distance |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103108133A (en) * | 2011-11-11 | 2013-05-15 | 株式会社日立制作所 | Imaging device |
| CN103167141A (en) * | 2012-09-14 | 2013-06-19 | 深圳市金立通信设备有限公司 | Continuous focalizing system and method of mobile phone camera |
| WO2015149525A1 (en) * | 2014-04-02 | 2015-10-08 | 努比亚技术有限公司 | Photographing method and photographic device |
| CN105163035A (en) * | 2015-09-30 | 2015-12-16 | 努比亚技术有限公司 | Mobile terminal shooting system and mobile terminal shooting method |
| WO2017054677A1 (en) * | 2015-09-30 | 2017-04-06 | 努比亚技术有限公司 | Mobile terminal photographing system and mobile terminal photographing method |
| CN110493518A (en) * | 2019-08-15 | 2019-11-22 | 移康智能科技（上海）股份有限公司 | A kind of image-pickup method of security protection camera |
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| CN102004370B (en) | 2012-03-28 |
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