KR970001570B1 - Automatic focusing control camera - Google Patents

Abstract

An automatic focus controlling method for camera is provided that more stably and accurately performs an automatic focus controlling operation. The automatic focus controlling method for camera includes steps of estimating and dividing a screen to arbitrary infinitesimal screens(ST1); dividing each of the divided infinitesimal screens to an arbitrary automatic focus region(ST2); adding the infinitesimal regions belong to each of the arbitrarily divided automatic focus regions(ST3); standardizing the adding signals of each infinitesimal region value which is added by each automatic focus region to a simple average value(ST4); comparing the standardized average value of the central region among the standardized average values and a predetermined reference value(ST5); performing an automatic focussing after determining the central region of the screen as the automatic focus object region if the standardized average value of the central region is larger than the reference value upon comparison(ST6)(ST11); adding a weight value to the evaluation value adding signal obtained by each automatic focus region if the standardized average value of the central region is smaller than the reference value(ST7); determining the largest value among the weight value added evaluation adding signals as an automatic focus region(ST8); comparing each infinitesimal region included to the automatic focus region having the largest weight evaluation value and selecting an infinitesimal region with the largest evaluation value(ST9); and determining an automatic focus object region on the reference of the selected infinitesimal region to perform an automatic focussing(ST10)(ST11).

Description

Camera auto focus control method

1 is a configuration diagram of an autofocus system of a conventional camera.

2 is a diagram illustrating division of the sampling area of FIG.

3 is a configuration diagram of the autofocus system of the camera of the present invention.

4 is a screen division diagram for the m * n autofocus area of FIG.

FIG. 5 is a screen division diagram for the 8 * 8 region of FIG. 3, (a) is a basic autofocus region division diagram of 8 * 8, (b) is a diagram showing the change of the autofocus region when the subject moves. c) shows the autofocus area variation when there is no subject in the center and multiple subjects in the periphery.

6 is an explanatory diagram for selecting a micro region having the next maximum value when the micro region having the maximum evaluation value of the present invention is set.

7 is an autofocus control signal flow diagram of the camera of the present invention.

* Explanation of symbols for main parts of the drawings

1: analog / digital changing means 2: area signal generating means

3-3an: first to nth integration means 4: main memory means

5: system control means

The present invention relates to an automatic focus control of a camera or a camera-integrated BD (hereinafter, referred to as a camcorder). In particular, a screen evaluation is calculated by multiplying a screen and assigning different weights to areas of each screen based on the center of the screen. The present invention relates to an automatic focus control method of a camera which moves and varies an area of a screen according to the calculated focus evaluation value so that a stable and accurate auto focus is achieved.

As shown in FIG. 1, the autofocusing apparatus of the conventional camera includes an end switch 104 for supporting a focus lens 101 of the camcorder 100 and detecting driving limits for moving forward and backward in the optical axis direction. And a diaphragm 105 for controlling exposure, an aperture driving motor 106 for driving the diaphragm 105, and a solid-state imaging device for converting an optical signal of a subject through the focus lens 101 into a captured image signal ( First and second high pass filters 108, 109 each having a high frequency filtering of the luminance signal in the image signal picked up from the imaging circuit 107 by different cut-off frequencies being set differently from each other. ), A low pass filter 110 for low-pass filtering the luminance signal in the video signal picked up by the imaging circuit 107, and a vertical sync signal VD and a horizontal sync from the video signal picked up by the imaging circuit 107. A synchronous separator 111 for separating the signal HD and the synchronous separator A switching control signal for setting the sampling area according to the vertical synchronization signal VD, the horizontal synchronization signal HD, and the fixed oscillation signal S3, which becomes a clock for driving the solid state image pickup device CCD, separated from the unit 111. (S1) and the switching control unit 112 for generating the selection control signal S2, and the first and second high pass filter units 108 and 109 according to the switching control signal S1 generated by the switching control unit 112. A switching unit 113 for selecting and switching the luminance signal of the < RTI ID = 0.0 > 1 < / RTI > field for each field, and selectively outputting the luminance signal of the low pass filter unit 110 to 32 fields, Accordingly, the selection controller 114 selects and outputs a luminance signal for the sampling area of the screen, and the analog / digital change unit 121 outputs a luminance signal for one field for the first sampling region selected by the selection controller 114. Converts it into a digital signal and stores the converted digital signal for one field and the memory unit 123. The same structure as the first integration circuit 115 and the first integration circuit 115 adds data of one field to the adder 122, stores the addition result in the memory unit 123, and outputs the result. Second to sixth integration circuits 116 to 120 for integrating the luminance signal for one field with respect to the second to sixth sampling regions selected by the selection controller 114, and the first to sixth integration circuits 115. Main memory unit 124 for storing the luminance signal integral value for the field for each sampling area output from ˜120; and switching controller 112 according to the integral value of the luminance signal output from main memory unit 124; In addition to the fixed oscillation signal (S2) is input to the microcomputer 125 for controlling the overall operation of the camcorder system, and each of the focus motor 103 and the aperture driving motor 106 in accordance with the control signal of the microcomputer 125 Focus motor control unit 127, the motor control unit 126 to control the driving of In the drawings, reference numeral 128 denotes a zoom motor, and 129 denotes a zoom ring.

In the autofocus system of the conventional camera configured as described above, first, when the camcorder 100 enters the operating state, the microcomputer 125 operates the focus motor 103 and the aperture driving motor 106 through the focus motor control unit 127 and the motor control unit 126. By controlling the aperture 105 and the focus ring 102 to be adjusted.

In this state, when the optical signal of the subject is input to the imaging circuit 107 having the solid state image sensor (CCD) through the focus lens 101 and the aperture 105, the imaging circuit 107 receives the optical signal of the input subject. The cut-off frequency is converted into the captured image signal and input to the first and second high pass filters 108 and 109, the low pass filter 110, and the synchronization separator 111.

The first and second high pass filter units 108 and 109 high pass filter the luminance signals in the input image signal and input them to the switching unit 113, and the low pass filter unit 110 inputs the input image signal. The luminance signal inside is low-pass filtered and input to the switching unit 113.

In addition, the synchronization separator 111 separates the vertical synchronization signal VD and the horizontal synchronization signal HD from the luminance signal in the input image signal and inputs it to the switching controller 112 for setting the sampling area.

The switching controller 112 is a clock for driving the vertical, horizontal synchronous signals (VD), (HD) and the solid state image pickup device (CCD) input from the microcomputer 125 separated and input from the synchronous separator 111. As shown in FIG. 2 by the fixed oscillation signal S2, the rectangular first sampling area A1 and the second sampling area A2 including this area A1 in the center of the screen are four times the area A1. And generating a selection control signal S2 so as to enable the third to sixth sampling areas A3, A4, A5, and A6 around the area A2, and inputting it to the selection control unit 114. The outputs of the first high pass filter 108 and the second high pass filter 109 are switched every field, and a switching control signal S1 for selecting the output of the low pass filter 110 is generated once in 32 fields. It is input to the switching unit 113.

Accordingly, the switching unit 113 has a high frequency component and a second high frequency filter of the brittle signal filtered by the first high frequency filter unit 108 for each field by the switching control signal S1 input from the switching control unit 112. The high frequency component of the luminance signal filtered from the filter unit 109 is selected and input to the selection controller 114, and the low frequency component of the luminance signal filtered by the low pass filter 110 is selected only once in 32 fields. 114).

The selection controller 114 selects a high frequency component and a low frequency component of the luminance signal selected by the switching unit 113 based on the selection control signal S2 input from the switching controller 112 to correspond to the sampling area. To the sixth integration circuit 115 to 120.

That is, the high pass components of the first and second high pass filters 108 and 109 related to the first sampling region A1 and the low pass components of the low pass filter 110 are transferred to the first integration circuit 115. The high and low pass components of the first and second high pass filters 108 and 109 and the low pass filter 110 related to the second sampling area A2 are respectively included in the third to sixth integration circuits 117. (118) (119) 120 to select and enter.

Here, the first integration circuit 115 includes an analog / digital converter 121, an adder 122, and a memory unit 123, and the analog / digital converter 121 is selected from the selection controller 114. Analog signals of the high and low frequency components are sequentially converted into digital signals and input to the adder 122.

The adder 122 constitutes a digital integrator together with the analog / digital change unit 121 at the front end and the memory unit 123 at the rear end, and the output data of the memory unit 123 and the analog / digital converter 121 The output signal is added and the addition result is inputted to the memory unit 123 again.

The memory unit 123 is reset for each field, and the digital conversion value of the luminance signal level passed through the output of the adder 122, that is, the first and second high pass filter 108 and 109 and the low pass filter 110, respectively. One field is provided for the first sampling area A1.

Also, the second to sixth integration circuits 116 to 120 have the same configuration as that of the first integration circuit 115, and each of the second to sixth integration circuits 116 to 120 includes a memory unit. An integral value is obtained for one field of the luminance signal level passing through the first and second high pass filter 108 and 109 and the low pass filter 110 selected for the current field for each sampling area.

The integrated values of these memory sections are collectively stored in the main memory section 124 of the subsequent stage.

The pass allowable area of each of the first and second high pass filter units 108, 109 and the low pass filter unit 110 is set to 600 KHz or more, 200 KHz or less, 2.4 MHz or less, and actually 600 KHz to 2.4 MHz. It can be set in a band pass filter (BPF) having a pass band of 200 KHz to 2.4 MHz and 0 to 2.4 MHz.

At this time, 2.4MHz is an extremely high frequency irrelevant to the luminance signal, and thus may be omitted in the low pass filter unit 110.

Therefore, the high or low frequency component of the luminance signal passing through either the first or second high pass filter 108, 109 or the low pass filter 110 is digitally integrated for one field, and is applied to each sampling area. It is stored collectively in the main memory unit 124 as an evaluation value of the current field.

Here, the integral value of the low pass component at the time of selecting the low pass filter 110 within the integral value stored in the main memory unit 124 is an exposure evaluation value for exposure control, and the first high pass filter 108 or the second high pass filter. When the high pass filter unit 109 is selected, the integrated value of the high pass component is computed by the microcomputer 125 at the rear end as a focus evaluation value for focus control.

These evaluation values are processed in software by the microcomputer 125, and a command is given to the focus motor control unit 127 based on the processing result, and the focus motor 103 is driven to move the focus lens 101 forward and backward to focus evaluation. The autofocus will be executed to maximize the value.

In addition, a command is given to the motor control unit 126 and the aperture driving motor 106 is driven to operate the aperture 105 to automatically adjust the exposure so that the exposure evaluation value becomes a predetermined value.

However, such an automatic focusing apparatus of a conventional camera is screen-divided for one screen and integrated for each area after the luminance signal output from the imaging circuit is converted into a digital signal through the first and second high pass filters.

Of these integrated values, the first sampling region or the second sampling region is fixed as the focus target region and autofocusing is executed.

Therefore, when there is no object in this center area, that is, when there is no edge component, even if an edge component exists outside this area, the autofocus cannot be executed and the focus becomes unstable. Due to the (small vibration), the main edge area goes out in and out of the auto focus area, so there is a malfunction. In addition, the auto focus target area is fixed. Therefore, when the focus evaluation value of the target area is small, the auto focus becomes unstable. .

Therefore, the object of the present invention is to divide the full screen into the auto focus area by increasing the degree of division, and to calculate the focus evaluation value for each area by adding different weights to each auto focus area based on the center of the screen, It provides the camera's automatic focus control method to select the appropriate focusing area by determining that the object does not exist, find the smallest area with the largest evaluation value in the selected area, and select the focusing area with the appropriate size to execute the automatic focusing. have.

Such a method for achieving the present invention comprises the steps of dividing a screen into m * n micro screens, multi-dividing by selecting a predetermined range of the divided micro screen as an autofocus area, and each of the multi-divided Summing up the small regions belonging to the autofocus region of the signal; normalizing the sum signal of each of the microregion evaluation values added to each of the autofocus regions to a simple average value; and a normalized average value of the most central region among the normalized average values. Comparing the preset reference value with the preset reference value; if the normalized average value of the center area of the search result is larger than the reference value, selecting the center area of the screen as an autofocus target area and performing an autofocus; If the normalized mean value of the center region is small, adding weights to the sum of evaluation values obtained for each autofocus region. And selecting the largest value among the sum of the weighted evaluation value signals as an autofocus area, and comparing each micro area included in the autofocus area having the maximum weighted evaluation value to determine a micro area having a maximum evaluation value. It is achieved by the step of selecting, and performing the auto-focus by selecting the auto-focus target area on the basis of the selected micro-area, it will be described in detail with reference to the accompanying drawings of the present invention.

3 is a block diagram of an autofocus control system of a camera of the present invention.As shown in FIG. 3, analog / digital signal for converting a luminance signal of one field for each autofocus sampling region filtered through a high pass filter means into a digital signal is shown in FIG. Digital conversion means (1), area signal generation means (2) for separating and outputting the horizontal synchronous (HD) and the vertical synchronous (VD) from the video signal captured and input from an image pickup device (not shown in the figure); The luminance signal for one field and the memory unit for the first autofocus area input from the analog / digital conversion means 1 in accordance with the horizontal synchronization HD and the vertical synchronization VD output from the area signal generating means 2. First integration means (3) for adding data for one field previously stored in (32) to an adder (31), storing the addition result in the memory unit (32), and outputting the first integration means (3); Analog / digital conversion Second to n-th integration means 3a1 to 3an for integrating the luminance signal for one field with respect to the second to n-th autofocus area input from the return means 1, and the first to n-th integration means ( Main memory means 4 for storing the luminance signal integral value for one field for each autofocus area output from 3, 3a1 to 3an), and the integral value of the luminance signal output from the main memory means 4; According to the present invention, a system control means 5 selects an autofocus target region and controls the focus lens to the selected region to perform autofocus.

FIG. 7 is a signal flow chart for the autofocus target region of the present invention. As shown in this figure, a step of integrating and dividing one screen into an arbitrary microscreen (ST1), and each of the divided microscreens are in a predetermined range. The step S2 of dividing into any autofocus area, the sum of the micro areas belonging to each of the randomly divided autofocus areas, and the evaluation of the respective micro areas summed by the autofocus areas. Normalizing the sum signal of the value to a simple average value (ST4), comparing and searching the normalized average value of the center portion of the normalized average value with a predetermined reference value (ST5), and If the average value is greater than the reference value, selecting the center area of the screen as the autofocus target area and performing autofocus (ST6) (ST11), and normalizing the center area of the search result. If the average value is small, adding a weight to the evaluation value sum signal obtained for each autofocus area (ST7), selecting the largest value of the weighted evaluation value sum signal as the autofocus area (ST8), Selecting a micro region having a maximum evaluation value by comparing each micro region included in the autofocus region having the maximum weighted evaluation value (ST9), and selecting the autofocus target region based on the selected microregion as an automatic Performing focusing is made (ST10) (ST11).

When described in detail with reference to Figures 3 to 7 the operation, the effect of the present invention performed as described above.

First, when a luminance signal corresponding to one field of the autofocus region filtered through the high pass filter means is input, the analog / digital converting means 1 receives one field of the autofocus region sequentially input through the band filter means ( 262.5H) is converted into a digital signal and input to the first to nth integration means 3 (3a1 to 3an), respectively.

The first to n-th integration means 3 (3a1 to 3an) are divided by the area signal generation means 2 to integrate the digital luminance signals for one field for the autofocus area according to the input horizontal / vertical synchronization. As shown in FIG. 4, one screen is divided into m * n small screens (a11, a21, a31-am), (a11, a12, a13, a14-a1n) (amn), and inputted into the main memory means (4). Done.

That is, the adder 31 of the first integrating means 3 forms an integrator together with the memory means 32 in the rear stage, and adds the input digital luminance signal and the output data of the memory means 32 to one field. As shown in FIG. 4, one screen is divided into a small screen a11, and data of the divided small screen a11 is input to the main memory means 4 through the memory means 32. As shown in FIG.

Also, the second to nth integration means 3a1 to 3an have the same configuration as that of the first integration means 3, and the micro screens a21-am and a12 as shown in FIG. -aln, a21-a2n, a31-a3n, am-amn) are divided and stored in the main memory means 4 collectively, and the data for the stored micro-screen is sequentially input to the system control means 5 again. do.

The system control means 5 divides the autofocus area for one screen with the data of the micro screens for each screen input from the main memory means 4, respectively.

That is, as shown in FIG. 4, a rectangular area consisting of two coordinates is taken as the coordinates of a (x, y) and a '(x, y), and b (x, y is obtained. ) And b '(x, y) are taken as the second autofocusing area (A2) from the rectangular area leading to the two coordinates, minus the first autofocusing area (A1), and c (x, y) and Take the coordinates of c '(x, y) and take the area obtained by subtracting the second autofocus area A2 from the rectangular area that leads to the two coordinates as the third autofocus area A3. The autofocus area A4 or A5 is set to divide the autofocus area for one screen.

FIG. 5 is an embodiment having 8 * 8 area partitioning by the same method as the screen partitioning method of n * m. The automatic focusing in this case will be described below with reference to FIG. same.

(A) of FIG. 5 has 64 divisions of 8 * 8, each of the micro areas through the first to nth integration means 3 (3a1 to 3an) and the main memory means 4 of FIG. When the integrated evaluation value is input to the system control means 5, the system control means 5 enters the first to fourth autofocus regions A1 to A4 in the same manner as in the above-described screen division diagram of n * m. After dividing, the information of the micro areas belonging to the first to fourth autofocuss A1 to A4 is summed for each area.

That is, the sum of the information of the micro areas belonging to the first autofocus area A1 is summed to obtain the sum of the first micro area evaluation values SA1, and the sum of all the information of the micro areas belonging to the second auto focus area A2 is added. The second sum region evaluation value sum signal AS2 is obtained, and in this manner, the sum of the information of the micro regions belonging to the third and fourth autofocus regions A2 and A3 is summed to evaluate the third and fourth smile regions. The sum signal SA3 and SA4 are obtained.

In this way, when the sum signal of the micro area evaluation values for each autofocus area is obtained, the sum signals SA1 to SA4 of the first to fourth micro area evaluation values are normalized to a simple mean value, and the first to fourth micro area normalization evaluations are performed. Teeth SA1 to SA4 are obtained.

That is, as an example, normalizing the sum signal SA1 of the first micro-area evaluation value for the first auto-focus area A1 to a simple average value is as shown in (a) of FIG. 5. Since there are four microareas a44, a45, a54, and a55 included in the area A1, the first smile area normalized evaluation value SA1 is as follows.

SA1 = SA1 / 4 (Equation 1).

In this manner, the sum signals SA1 to SA4 of the second to fourth microregion evaluation values are normalized to a simple average value to obtain the second to fourth microregion normalization evaluation values SA2 to SA4, and then the first center of the first center region. The small area normalized evaluation value SA1 is compared with the preset reference value Th.

As a result of the comparison search, when the first small area normalized evaluation value SA1 of the center area of the screen is larger than the set reference value Th, the first autofocus area A1 of the center area of the screen is the autofocus target area. Select and perform autofocus, and if the first microregion normalization evaluation value SA1 is smaller than the reference value Th, the second to fourth microregions with respect to the second to fourth autofocus regions A2-A4. The second to fourth autofocus evaluation values Vw2, Vw3, and Vw4 are obtained by multiplying the normalized evaluation values SA2-SA4 by the weights WA2, WA3, and WA4 having different values.

That is, as an example, the second autofocus normalization evaluation value SA2 is multiplied by the weight WA2 to obtain the second autofocus evaluation value Vw2, and the third microregion normalization evaluation value SA2 is obtained by the weight W3. The third autofocus evaluation value Vw3 is obtained by multiplying, and the fourth autofocus evaluation value Vw4 is obtained by multiplying the fourth microregion normalized evaluation value / SA4 by the weight W4.

In this way, the second to fourth autofocus evaluation values (Vw2-Vw4) are obtained and the second to fourth automatic values having the largest weighting evaluation values among the obtained second to fourth autofocus evaluation values (Vw2-Vw4). The focus areas A2-A4 are selected.

As such, when the autofocus region having the maximum weighted evaluation value is selected, the coordinates of the microregions having the maximum evaluation value are selected by comparing the respective microregions included in the autofocused region and then the autofocus target region based on the selected microregion. Auto focus is performed by selecting.

That is, as an example, as shown in (b) of FIG. 5, since the subject exists in the center of the first screen, the auto focus is performed by selecting the focus area FA as the auto focus target area. When moving from the FA to the focusing area FA 'composed of the minute areas d and d', the third autofocusing area A3 is selected as the autofocusing area by the flow process described above. Among the autofocus areas A3, a focus area FA 'consisting of minute areas d and d' including the area with the largest evaluation value is selected, and this focus area FA 'is selected as an autofocus area. Auto focus is performed.

Specifically, referring to FIG. 6, when the autofocus area having the maximum weighted evaluation value is selected and the micro area having the maximum evaluation value is determined within the autofocus area as described above, for example, FIG. As shown in the drawing, if the small region f corresponds to the small region f, the small region having the next maximum value among the small regions a, c, i, and k in the diagonal direction of the small region f is selected to finally select the autofocus target region. .

That is, if the micro area having the next maximum value is the k area, f + g + j + k becomes the autofocus target area, which shows an example and the selection method is not limited thereto.

FIG. 5C illustrates the second to fourth autofocusing areas A2-A4 in the same manner as described above when the subject is scattered in the center and the subject having the edge signal of the size indicated on the periphery of the screen is scattered. When the sum signal of the small area evaluation value is normalized to a simple mean value, the small area normalized evaluation value is obtained, and the area is obtained by multiplying the small area normalized evaluation value by the weight (WA2) (WA3) (WA4) to obtain a region having a large weighted average value. Area A3 is selected.

Where the weight is WA2WA3WA4.

The micro area a52 is selected among the autofocus areas A3 selected above.

Therefore, the system control means 5 selects the focus area FA including the micro area a52 as the autofocus target area and performs the autofocus.

Before comparing the normalized evaluation value of the center area with the set reference value Th, the weights are first multiplied by each of the small area normalization evaluation values obtained for each autofocus area, and then the evaluation value and the reference value of the center area (Th) are calculated. ), And if the reference value Th is large, the second to fourth autofocus evaluation values WA2-WA4 are obtained, and then the largest autofocus area is selected from the second to fourth autofocus evaluation values. The autofocus may be performed by selecting the coordinates of the microregion having the maximum evaluation value within the autofocus region having the maximum weighted evaluation value and selecting the target region as the autofocus target based on the selected microregion.

As described in detail above, in the case where the autofocus area is limited to the center of the screen, the present invention does not have an edge component at the center and an edge component at the periphery. To compensate for the unstable disadvantage of auto focus due to the weakness of auto focusing or the movement of edge components between the center and the periphery due to hand shake, the screen is divided into multiple sections and the auto focus area is selected sequentially from the center to the outside. The autofocus evaluation value is calculated by varying the weight for each area, and then the area with the largest edge component is selected from the weighted evaluation value and the autofocus area is moved or changed to execute the autofocus instability. It works.

Claims (3)

Integrating and dividing one screen into an arbitrary minute screen (ST1), Dividing each divided minute screen into an arbitrary autofocus area with a predetermined range (ST2), and each of the randomly divided areas Summing up the small areas belonging to the autofocus area (ST3), normalizing the sum signal of each of the small area evaluation values summed for each of the autofocus areas to a simple average value (ST4), and the center of the normalized average values. Comparing and searching the specified average value of the area with a predetermined reference value (ST5), and if the normalized average value of the center area is greater than the reference value, selecting the center area of the screen as the autofocusing area. Steps ST6 and ST11, and if the normalized mean value of the center region is small, adding weights to the sum of evaluation values obtained for each autofocus region (ST7). And selecting the largest value among the sum of the weighted evaluation value signals as an autofocus area (ST8), and comparing each of the micro areas included in the autofocus area having the maximum weighted evaluation value to have a maximum evaluation value. Selecting a small area (ST9), and the step of selecting a target area for autofocus based on the selected small area to perform the autofocus (ST10) (ST11) characterized in that the automatic focus control method of the camera . The method of claim 1, wherein step ST7 is added first and then step ST5 is performed prior to the step ST5 of comparing and searching the normalized average value of the center region and the predetermined reference value among the normalized average values. Auto focus control method of the camera, characterized in that the step (ST6) or step (ST8) according to the result of. The method according to claim 1 or 2, wherein in step ST9, when the micro area having the maximum evaluation value is determined in the auto focus area, the micro area having the next maximum value is automatically selected from the micro areas in the diagonal direction of the micro area. An automatic focus control method of a camera, characterized in that it is a focus target area.