JP2663451B2 - Automatic focusing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an automatic focusing device that converts a subject image into a video signal by a two-dimensional image sensor and focuses a lens based on the video signal. Things. (Background of the Invention) In a video camera, a camera is focused by detecting the definition of a shooting screen based on a high-frequency component of a video signal and controlling the position of a lens so that the definition (high-frequency component) is maximized. A method for automatically controlling the state is known. Specifically, the video signal changes rapidly at the edge of the subject image, and the high-frequency component of the video signal increases. Then, as the high frequency component increases, the subject image is closer to the focused state. Here, a schematic configuration of a conventional automatic focusing apparatus of this type is described as follows.
Figure 12 shows. In FIG. 12, a subject image is formed on an image pickup surface of an image pickup device 2 by a lens 1, and the image is converted into an electric signal (video signal) by the image pickup device 2. The preamplifier 3 arranged in the next stage amplifies the video signal from the image sensor 2, and the process circuit 4 and the band pass filter (BPF)
Output to 5 Upon receiving this signal, the process circuit 4 performs predetermined signal processing and outputs it as a standard TV signal (video signal). On the other hand, the band pass filter 5 extracts a high frequency component from the output from the preamplifier 3, and
Of the signals for one screen (one field or one frame), only the signals in the region where focus detection is to be performed are selected and output to the gate circuit 6 that passes the signals. The detection circuit 7 is a gate circuit 6
Is detected, and a signal showing a maximum amplitude value, that is, a peak value is formed at a point where a high frequency component is large in the region. The output signal of the detection circuit 7 represents the degree of focusing of the lens 1, and the greater the value, the closer the focusing state is. The motor drive circuit 8 drives the motor 9 according to the output value of the detection circuit 7 for each photographing screen, and automatically controls the lens 1 to be in focus. By the way, in the above-described conventional automatic focusing apparatus, the video signal passing area in the gate circuit 6, that is, the focus detection area is fixedly set at the center of the screen, so that the main subject moves slightly, When the position of the main subject in the screen changes due to movement of the camera, there is a risk that another subject located at the center of the screen will be focused. (Object of the Invention) An object of the present invention is to solve the above-mentioned problem, and to provide an automatic focusing device capable of continuously focusing on a main subject even when a position of the main subject changes in a screen. That is. (Features of the Invention) In order to achieve the above object, the present invention provides an automatic focusing device that automatically controls a focusing state of an optical system based on a video signal obtained in a focusing detection area specified in a shooting screen. In the shooting screen, in a shooting screen, an area setting means for setting a predetermined tracking area so that the position can be moved, and a luminance signal component in the video signal corresponding to the inside and outside of the tracking area is extracted, and Area control means for moving the tracking area in a direction in which the level difference between the luminance signal components increases,
A focus area setting unit configured to set the focus detection area at a movement position of the tracking area; and a focus detection unit configured to detect a focus state based on the video signal corresponding to the focus detection area. And Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. In each of the following embodiments, as shown in FIG. 2, the shooting screen is equally divided into n parts in the horizontal direction and m parts in the vertical direction.
It is divided into nxm sections. Then, a plurality of sections are set as focus detection areas, and a focus signal is formed within the area. FIG. 1 is a block diagram showing a first embodiment of the present invention, and the same parts as those in FIG. 12 are denoted by the same reference numerals. In FIG. 1, when an imaging signal (luminance component) output from the imaging device 2 via the preamplifier 3 is input to the gate A circuit 11, the gate A circuit 11 follows a gate pulse from the gate A pulse generation circuit 55. The video signal of the designated area in one field is obtained and applied to the integration circuit 21. Further, the inversion gate A circuit 12 follows the gate pulse from the gate A pulse generation circuit 55 inverted by the inverter 60,
A video signal in a designated area (an area excluding the designated area from the entire screen) opposite to the designated area by the gate A circuit 11 in one field is obtained and applied to the integrating circuit 22. As described above, the integration circuits 21 and 22 to which the video signal of only the area specified by the gate A circuit 11 and the inversion gate A circuit 12 are input.
Then, the video signal is integrated, the average value of the luminance component in the area is obtained, and the average value is normalized by the area correction circuits 101 and 102. This is because the inside and outside areas of each designated area are different, and the average value in each area cannot be directly compared. The subtraction circuit 31 to which these signals are input calculates difference information of the average value of the luminance components from the integration circuits 21 and 22 input through the area correction circuits 101 and 102, and outputs the difference information to the absolute value circuit 36. I do. The absolute value circuit 36 takes the absolute value of the input difference information, and outputs this absolute value to the comparator 41 and the maximum value detection circuit 46. Similarly, when a video signal is input via the preamplifier 3, the gate B circuit 13, the gate C circuit 15, the gate D circuit 17, and the gate E circuit 19 become the gate B pulse generation circuit 56 and the gate C pulse generation circuit 57, respectively. In accordance with the respective gate pulses from the gate D pulse generation circuit 58 and the gate E pulse generation circuit 59, a video signal in a designated area in one field is obtained and applied to the integration circuits 23, 25, 27, and 29. Also,
Inverting gate B circuit 14, inverting gate C circuit 16, inverting gate D
The circuit 18 and the inverting gate E circuit 20 follow the respective gate pulses inverted by the inverters 61, 62, 63 and 64, and
A video signal in a designated area opposite to the designated area in the field is obtained and applied to the integration circuits 24, 26, 28, and 30.
The integration circuits 23 to 30 to which the above-described video signals are input integrate the respective video signals, obtain an average value of the luminance component in each area, and then normalize by the area correction circuits 103 to 110. The subtraction circuits 32, 33, 34, and 35 to which these signals are input calculate difference information between the average values of the luminance components, and output the difference information to the absolute value circuits 37, 38, 39, and 40. Absolute value circuit 37
40 take the absolute values of the input difference information and output these absolute values to the comparators 42, 43, 44, 45 and the maximum value detection circuit 46. By the above-described operation, the absolute value of the difference between the average values of the luminance components of the inside and outside of each of the five gates A to E, which are the boundaries dividing the photographing screen into two regions, is determined by the maximum value detection circuit 46. Will be entered. The maximum value detection circuit 46 receiving such a signal detects the maximum input of these five inputs, and determines which of the gates A to E corresponding to the maximum input has the maximum absolute value. Information to indicate (this corresponds to the position of the main subject in the screen)
Is output to the selector 48. The selector 48 includes a D flip-flop 49 and gate pulse position shift circuits 50, 51, 52, 53
, I.e., position information indicating the position of each of the gates A to E in the divided screen as inputs. The position information corresponding to the information specified by the maximum value detection circuit 46 is detected. Output to flip-flop 49. The D flip-flop 49 outputs the input position information as information indicating an area (partition position) inside the gate A, and outputs new information for each field. The gate pulse position shift circuits 50 to 53 are provided with the D flip-flop 49.
Input the position information of the gate A from the right, left,
The output is shifted one section upward and downward. As a result, the gate A and the gates B, C, D,
The relationship of E is as shown in FIG. Since the output of the D flip-flop 49 is information updated every frame as described above, for example, when the gate D in FIG. 3 is selected by the selector 48, the position of the gate D in the next one field is determined. Is equivalent to D flip-flop 49
The output is changed to the position information corresponding to the gate A in FIG. In addition, the pulse position information of the gate A is input not only to the gate pulse generation circuit 55 but also to the gate pulse generation circuit 54. Therefore, the position of the focus detection area always set by the gate circuit 10 is the position of the gate A. Is equal to However, the size of the focus detection area does not necessarily need to be the same as the area inside the gate A, and the center may be the same (the same here means almost the same). As described above, in this embodiment, control is performed such that the focus detection area is set to the gate having the largest average luminance difference between the gates A to E among the gates A to E. The relationship between the inner and outer luminance differences and the main subject will be described. In the photographing screen, a large amount of the luminance component is distributed in the portion of the subject, and the other portions have a small amount of the luminance component. Therefore, when the difference between the average values of the luminance components inside and outside of the specified area is maximum, it can be said that the subject is in a state substantially located in the specified area.
In other words, it can be determined that the gate having the largest average luminance difference between the inside and outside of each of the gates A to E captures the subject at the center, and the gate of the gate that captures the subject at the center is the most. By positioning the center of the focus detection area at the center, the focus detection area can always correspond to the main subject. As described above, when the gate pulse indicating the position of the area inside the gate A is sent from the gate pulse generating circuit 54, the gate circuit 10 in FIG. The detection circuit 7 detects the video signal, holds the peak value of the absolute value signal of the luminance component in the area, and the motor drive circuit 8 drives the motor 9 according to the peak value. I do. As a result, the lens 1 is automatically controlled to be in focus. The absolute value input to the comparators 41 to 45 is equal to the threshold value Vth
As a result, if all absolute values are lower than the threshold value Vth, a low-level signal indicating that tracking is impossible is output from the OR gate 47. By the generation of the tracking impossible signal, for example, the apparatus performs control such that the focus detection area is fixed at the center and wide. With the above configuration, five gates A
~ E, the one having the largest absolute value of the difference between the average values of the luminance components obtained in each of the inner and outer areas is updated as much as possible to become the gate A in the next field, and the area inside the gate A is updated. Since the focus detection area is moved to a position where the center is the same as that of the center, that is, as shown in FIG. 4, for example, as the position of the main subject changes in the screen, the main subject moves in the screen. Even if this is the case, it is possible to always keep track of the main subject by following it. In the above embodiment, the position change of the main subject in the screen is detected based on the video signal obtained from the image sensor 2 via the preamplifier 3 before passing through the bandpass filter 5, that is, the luminance component. Although the position of the focus detection area is determined correspondingly, the band of the luminance component is actually wide, and even if the position of the main subject changes and there is a change in some frequency bands, the luminance In the state where the average value of the components is taken, there is a possibility that the change is offset and does not appear. Therefore, as shown in FIG. 5, a signal component serving as a basis for detecting a change in a main subject to be extracted in regions inside and outside the gates is extracted from the output side of the band-pass filter 5 and a high-frequency component corresponding to a high-frequency side of a luminance component is extracted. Components may be used. In other words, since the high frequency components are distributed in many details and contours of the subject, changes in the main subject that were not reflected in the average value in a wide band such as the luminance component were detected by extracting the high frequency components and comparing them. It is considered possible, and this method is also very effective. In FIG. 5, only a circuit portion for extracting high-frequency components from the gate A circuit 11 to the inverting gate E circuit 20 is shown, and other components are omitted, but portions other than those shown in FIG. And the operation is also the same. In the above-described FIG. 1 embodiment, the positions of the main subject in the screen are detected by shifting the gates A to E, and the focus detection area is adjusted to this to keep the main subject in focus. However, if the size of the main subject in the screen is different, it is expected that it will be difficult to accurately focus. In view of this point, gates F of different sizes,
FIG. 6 shows a third embodiment in which G is formed and control can be performed in consideration of the size of the main subject. In this figure, the same parts as those in FIG. 12 are denoted by the same reference numerals. In FIG. 6, when a luminance signal is input from the image pickup device 2 to the gate F circuit 66 via the preamplifier 3, the gate F
The circuit 66 obtains a luminance signal of a designated area in one field according to the gate pulse from the gate F pulse generation circuit 81 which generates a gate pulse at a position designated by the microcomputer 79, and sends the signal to the integration circuit 70 and the area correction circuit 111. Apply.
The inverting gate F circuit 67 outputs a luminance signal in a designated area opposite to the designated area by the gate F circuit 66 in one field according to the gate pulse from the gate F pulse generating circuit 81 inverted by the inverter 83. Gain and integration circuit 7
1, applied to the area correction circuit 112. Similarly, the gate G circuit 6
Numeral 8 obtains a luminance signal of a designated area in one field according to the gate pulse from the gate G pulse generating circuit 82 for generating a gate pulse at a position designated by the microcomputer 79, and applies the luminance signal to the integrating circuit 72 and the area correcting circuit 113. The inverting gate G circuit 69 outputs a luminance signal in a designated area opposite to the designated area by the gate G circuit 68 in one field according to the gate pulse from the gate G pulse generating circuit 82 inverted by the inverter 84. Then, it is applied to the integration circuit 73 and the area correction circuit 114. Here, the area designated as described above, that is, the inner area and the outer area which are divided by the gates F and G, which are the boundaries dividing the screen into two areas, are centered as shown in FIG. Are equal, and the areas (the number of sections) are different. In addition, each gate A ~
The reason why the average value of the luminance components inside and outside of E is normalized by the area of the designated area inside and outside that is that the area of each designated area is different from that of the embodiment of FIG. This is because they cannot be compared. The subtraction circuits 74 and 75 calculate difference information of the average value of the luminance component integrated by the integration circuits 70, 71 and 72, 73 and normalized by the area correction circuits 111, 112 and 113, 114. To the absolute value circuits 76 and 77. Absolute value circuit 76
And 77 take the absolute values of the input difference information and output these absolute values to the microcomputer 79 via the A / D conversion circuit 78. Next, the operation of the microcomputer 79 will be described with reference to the flowcharts of FIGS. 8 (A) to 8 (C). First, the signal from the A / D conversion circuit 78 is read as F data and G data, and these are taken into variables F1 and G1 (step 1). Next, the gates F and G are shifted rightward by one section (this is performed via the gate F pulse generation circuit 81 and the gate G pulse generation circuit 82) (step 2), and the F data and G in the next field are shifted. Read the data and
The variables F2 and G2 are fetched (step 3). Then, it is determined whether or not the respective values have a relationship of F2> F1 or G2> G1 (step 4). When it is determined that such a relationship exists (the main subject moves to a position shifted to the right) If it can be estimated that this is the case, the process proceeds to the subroutine shown in FIG. The subroutine is a routine for selecting the size of the focus detection area in accordance with the size of the main subject.
It is determined whether or not G1 is satisfied. If F1> G1, it is understood that the main subject is more accurately captured on the gate F side. Accordingly, in this case, the process proceeds to step 6-3 to select a wider focus detection area as shown in FIG. 9 (A).
If F1> G1, the main subject is properly captured on the gate G side. In this case, the process goes to step 6-2 to focus on the narrower one as shown in FIG. 9 (B). Select the detection area. The setting of the focus detection area is performed via the gate pulse generation circuit 80. If the condition of F2> F1 or G2> G1 is not satisfied in step 4 (the case where the main subject does not change its position and remains at the original position), the process proceeds to step 5 and FIG. The process proceeds to a subroutine shown in FIG. The subroutine is also a routine for selecting the size of the focus detection area according to the size of the main subject. In step 5-1 it is determined whether or not F2> G2. It can be seen that the subject is more accurately captured on the gate F side. Therefore, in this case, step 5-3
The process proceeds to and selects the wider focus detection area. Also, F2
If not> G2, the main subject is more accurately captured on the gate G side. In this case, the process proceeds to step 5-2 to select a narrower focus detection area. Thereafter, the process proceeds to step 7, in which the gates F and G are shifted leftward by one section, that is, returned to the previous state. In step 8, the position of the focus detection area is adjusted to the gate F or the gate G. Similarly, in steps 9 to 16, the focus detection area is adjusted to the gate position corresponding to the result of shifting upward by one section in the next two fields, and further in steps 17 to 24. 1 in the next two fields
The in-focus detection area is adjusted to the gate position corresponding to the result of the shift to the left by the section, and steps 9 to 16 are performed.
The focus detection area is adjusted to the gate position according to the result of shifting down by one section in the next two fields up to. In steps 13, 21, and 29, the same operation as the subroutine performed in step 5 is performed.
In steps 2 and 30, the same operation as the subroutine performed in step 6 is performed. Thereafter, the operation is similarly repeated. As described above, the gates F and G are shifted in the screen, and the focus detection area is moved to a direction where the luminance difference between the inside and the outside of each gate is increased. , And selects the direction in which the luminance difference between the inside and outside of the gates F and G is large, so that the focus detection area corresponding to the position of the main subject on the screen and its size is set. Will be. Here, this size determination is based on the same idea as the above-described determination of the position change of the main subject. That is, since the luminance component is largely distributed in the subject portion, if the average luminance difference between the inside and outside of each of the two large and small gates F and G is F> G, the luminance difference inside and outside the gate G Is small and there is little change in the subject, so that either the subject is similar inside or outside the gate G or both do not have the subject. In this case, the luminance difference between the inside and outside of the gate F is small. Since it is larger than the gate G, it can be seen that the subject exists inside the gate F. That is, as a result, not only the position change of the main subject in the screen but also the size of the main subject is determined. If no subject exists inside or outside all the gates, no luminance component can be obtained inside or outside any of the gates, so this can be determined. Therefore, in this case, the microcomputer 79 sends to the gate pulse generation circuit 80 a signal indicating the gate F or the gate G corresponding to the size of the main subject in the screen and the gate F corresponding to the position of the main subject. Alternatively, a signal indicating the gate G is output. The gate circuit 65 passes the video signal in the designated area according to the gate pulse from the gate pulse generation circuit 80 that generates a pulse according to the instruction of the microcomputer 79 described above. Thus, even if a main subject of various sizes moves in the screen, it is possible to always follow the main subject and to surely keep focusing on the main subject. FIG. 10 is a block diagram showing a fourth embodiment of the present invention, which has a relatively wide band, detects a luminance component having a wide adaptation range for various subjects, and sets a focus detection area. The method and the method of setting a focus detection area by detecting a high-frequency component capable of detecting a change in a subject that does not appear as a difference in the average value of the luminance components are suitable for the situation at that time. One can be automatically selected. The same parts as those in FIG. 6 are denoted by the same reference numerals. The part different from the embodiment of FIG.
A signal supplied from 66 to the inverting gate G circuit 69 can be selected by switching an analog switch SW between a case where a luminance component is extracted from the input side of the bandpass filter 5 and a case where a high frequency component is extracted from the output side. I am doing it. Further, the microcomputer 79 here has a function of detecting the size of the subject and the position in the screen, performing control so as to adjust the focus detection area to the size, and also performing switching control of the analog switch SW. It is assumed that Hereinafter, the operation will be described with reference to the flowchart of FIG. When the focus detection operation is started, in step 1-1, first, the analog switch SW is switched to the input side of the band-pass filter 5, that is, the contact Y side, in order to extract a luminance component, and inside and outside the gates F and G at that time. The values based on the difference between the average values of the detected luminance components are read into variables FY and GY, respectively (step 1-2). Subsequently, the analog switch SW is set to the output side of the band-pass filter 5 to extract the high-frequency component.
That is, it is switched to the contact H side (step 1-3), and values based on the difference between the average values of the high-frequency components detected inside and outside the gates F and G at that time are read into variables FH and GH, respectively (step 1-4). Next, proceed to step 1-5 to change the variables FH, GH, FY, GY
Is determined to be the largest, and if the variable FH or
If GH is the maximum, the process proceeds to step 1-8, where the contents of the variables FH and GH are stored in the variables F1 and G1, respectively, and then the process proceeds to step 2. If the variable FY or GY is the maximum in step 1-5, the process proceeds to step 1-6, in which the analog switch SW is switched to the contact Y to set the detection mode based on the luminance component. After the contents of the variables FY and GY have been stored in Thereafter, the operations from step 2 to step 32 are the same as the operations in FIG. 6 described above, and the description thereof will not be repeated. According to the embodiment shown in FIG. 1 to FIG. 11, the absolute value of the difference between the luminance component of the video signal obtained in each area inside and outside each gate or the high frequency component on the high frequency side thereof is obtained. Since the focus detection area is moved to the position of the area inside the gate having the maximum value, even if the main subject moves on the screen, the main subject can be automatically tracked and the main subject can be tracked. It is possible to always keep focusing on. In the case of FIGS. 6 and 10, the four directions cannot be compared at the same time as in the embodiment of FIG. 1, but the structure is such that the comparison is made four times for each direction. Almost the same functions can be added with a small amount of hardware. In addition, gates F, which have inner and outer regions of different sizes,
Since the absolute value of the difference between the average value of the luminance component and the high frequency component is obtained by both G, it is possible to detect not only the position of the main subject at that time but also its size,
It is possible to keep focusing on a subject of various sizes with a high probability while tracking the subject. That is, in the conventional automatic focusing apparatus, there are a type in which the focus detection area is set to a wide fixed area in the screen and a type in which the focus detection area is set to a slightly narrow fixed area in the center of the screen. In the case of the type, another object comes into the focus detection area, or the camera moves and another object comes into the focus detection area, and focuses on an object different from the main object. In the latter type, on the other hand, the possibility that a subject other than the main subject described above enters the focus detection area is reduced, but the target main subject may move out of the focus detection area. Therefore, the focus operation is likely to be restarted frequently, and it is possible to keep focusing on the main subject while eliminating such a situation. Further, as shown in FIG. 10, the analog switch is determined by determining which of the luminance component and the high frequency component is more advantageous.
By switching the SW to the corresponding side and setting the focus detection area, it is possible to continue focusing with a high probability regardless of the shooting environment and subject conditions at that time. (Correspondence between the Invention and Embodiment) In this embodiment, from the gate A circuit 11 to the tracking inversion gate E circuit 20, from the gate A pulse generation circuit 55 to the tracking gate E pulse generation circuit 59, and from the gate F circuit 66 to the tracking inversion. Areas from the integrating circuit 21 to the absolute value circuit 40, the area correcting circuits 101 to 110, and the integrating circuit include the gate G circuit 69 and the gate A pulse generating circuit 55 to the tracking gate E pulse generating circuit 59. From 70 to A / D conversion circuit 78 and area correction circuits 111 to 114, maximum value detection circuit
The microcomputer 46 and the microcomputer 79 correspond to the area control means, and the gate pulse generating circuit 80 corresponds to the focusing area setting means. (Effects of the Invention) As described above, according to the present invention, an automatic focusing device that automatically controls a focusing state of an optical system based on a video signal obtained in a focusing detection area specified in a shooting screen. In the shooting screen, in a shooting screen, an area setting means for setting a predetermined tracking area so that the position can be moved, and a luminance signal component in the video signal corresponding to the inside and outside of the tracking area is extracted, and Area control means for moving the tracking area in a direction in which the level difference between the luminance signal components increases,
A focus area setting means for setting the focus detection area at a movement position of the tracking area; and a focus detection means for detecting a focus state by the video signal corresponding to the focus detection area. Even if the position of the subject in the screen changes, the main subject can be continuously focused. In addition, since the tracking area is moved so that the level difference between the luminance signal components inside and outside the tracking area increases, the main subject can be kept accurate regardless of the background, and accurate tracking operation and focus detection operation can be performed. It can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a divided state of a photographing screen, FIG. 3 is a diagram showing a tracking gate in the embodiment of FIG. 1, FIG. 4 is a diagram for explaining a relationship between the tracking gate and a focus detection area, FIG. 5 is a block diagram showing a part of the second embodiment of the present invention, and FIG.
FIG. 7 is a block diagram showing a third embodiment of the present invention, FIG. 7 is a diagram showing tracking gates having different widths, and FIGS.
9 (C) is a flowchart thereof, FIGS. 9 (A) and 9 (B) are diagrams for explaining the determination of the size of the focus detection area in the embodiment of FIG. 6, and FIG. 10 shows a fourth embodiment of the present invention. Block Diagram,
FIG. 11 is a flowchart, and FIG. 12 is a block diagram of a conventional automatic focusing apparatus. 1 ... Lens 2 ... Imaging element 5 ... Band pass filter 7 ... Detection circuit 8 ... Motor drive circuit 9 ...
Motor, 10 gate circuit, 11 gate A circuit, 12
... Inverting gate A circuit, 13 ... Tracking gate B circuit, 14 ...
Tracking inversion gate B circuit, 15 ... Tracking gate C circuit, 16 ...
... Tracking inverted gate C circuit, 17 ... Tracking gate D circuit, 18
…… Tracking inversion gate D circuit, 19 …… Tracking gate E circuit,
20: Tracking inversion gate E circuit, 21 to 30: Integration circuit, 31
... 35 Subtraction circuit, 36-40 Absolute value circuit, 46 ... Maximum value detection circuit, 48 ... Selector, 49 ... D flip-flop, 54 ... Pulse generation circuit, 55-59 ... Gate A to E pulse generation circuit, 65 gate circuit, 66 tracking gate F
Circuit, 67: Tracking inverting gate F circuit, 68: Tracking gate G circuit, 69: Tracking inverting gate G circuit, 71 to 73: Integration circuit, 74, 75 ... Subtraction circuit, 76, 77 ... Absolute value circuit, 78…
... A / D conversion circuit, 79 ... Microcomputer, 80 ...
Gate pulse generation circuit, 81: Gate F pulse generation circuit, 82: Gate G pulse generation circuit, 101 to 114: Area correction circuit.

Continuation of front page    (72) Inventor Kunihiko Yamada               770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa               Inside the Tamagawa Office of Canon Inc.                (56) References JP-A-60-256113 (JP, A)

Claims (1)

(57) [Claims] In an automatic focusing device that automatically controls the focus state of the optical system based on the video signal obtained in the focus detection area specified in the shooting screen, the position can be moved in the predetermined tracking area within the shooting screen Area setting means for setting so as to extract a luminance signal component in the video signal corresponding to the inside and outside of the tracking area, and move the tracking area in a direction in which the level difference of the luminance signal component increases. Area control means for setting, a focus area setting means for setting the focus detection area at a movement position of the tracking area, and a focus detection means for detecting a focus state by the video signal corresponding to the focus detection area. An automatic focusing device comprising: 2. The area control means is configured to move the tracking area in a direction in which a level difference of a high frequency component on a high frequency side of the video signal component corresponding to the inside and outside of the tracking area increases. The automatic focusing device according to claim 1, wherein 3. The area setting means sets at least two large and small areas overlapping each other, and the area control means sets a level of the luminance signal component corresponding to the large area and a luminance signal component corresponding to the small area. 2. The automatic focusing apparatus according to claim 1, wherein the automatic focusing apparatus is configured to move the tracking area in a direction in which a difference from a level increases.