JPH0646310A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To make possible the automatic focusing to high contrast object outside a main area by defining a sub-area which becomes a maximum integrated value by integrating high-frequency components of an image signal by each of about 4 sub-areas as a focus area, when the main area of the center part of a screen is low contrast. CONSTITUTION:The high-frequency components are extracted from the video signal by an image pickup means by a high-frequency extraction means, they are integrated by a digital integration means, and when the main area of the center part of a screen becomes low contrast, a focus object area selection means 4 makes about 4 sub-areas perform the integration by the digital integration means of two sub-areas in the horizontal direction. The focus object area selection means selects a sub-area where the integrated value becomes maximum as a focus object area, an automatic focusing for the selected area is performed by a focus control means and the automatic focus is performed also for the sub-area corresponding to the outside of the main area when the contrast of the main area is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device, and more particularly to a device for performing a focusing operation by evaluating the degree of focusing on the basis of a high frequency component extracted from a video signal.

[0002]

2. Description of the Related Art Conventionally, as an automatic focusing device for a video camera, a method of controlling a position of a focus lens so that a high frequency component extracted from a video signal is maximized is known. The basics of this method are "automatic focus of TV camera by hill-climbing servo method" reported on pages 21 to 37 of NHK technical research report (1965) Volume 17, No. 1, and Circular No. 86. As described in detail in “Adjustment”, simply, by utilizing that the definition of the image is transmitted by the high frequency component of the video signal, the high frequency component is extracted by passing the video signal through a high pass filter, Move the focus lens in the increasing direction of the extracted high frequency component,
The point at which the high frequency component is maximum is recognized as the focal point.

[0003]

However, in the above-described automatic focusing control, the portion with the highest contrast in the screen is prioritized as the focusing target, and the extraction of high frequency components is
Since the background part is included in addition to the main subject for which focusing is intended, if there is high contrast in the background part, the background subject will be focused instead of the intended subject, and the main subject will be blurred. There is a problem that it ends up.

Here, the photographer has a strong tendency to position the intended subject in the center of the screen. Therefore, the central area of the screen is set as the focus area, the high-frequency component is extracted from only the focus area, and the focus control is performed based on the extraction result, so that the background area is focused. There has been proposed a device capable of avoiding the occurrence of damage (see Japanese Patent Publication No. 62-40908).

However, if the focusing target area is fixed to the central area or the like as described above, if the subject in the focusing target area does not have the contrast necessary for focusing control, even if the focusing target area is outside the area. Even if there is a subject with a high contrast, focusing cannot be performed. Further, if the subject in the focusing area has a low contrast as described above, it may be because the focus position is significantly deviated so that the subject is photographed in a low contrast, or the subject itself has a low contrast. Since it is not possible to distinguish whether it is the object or not, an attempt is made to drive the optical system to search for the in-focus position where the high frequency component becomes high, so that the focus lens exhibits an unnatural behavior and makes the image unsightly.

Here, if the specification of stopping the search of the optical system when there is no contrast necessary for the focus control is set as described above, the start of the focus operation for a subject having a high contrast may be delayed or may be significantly increased. There is a possibility that the focusing operation may be stopped by setting the shift of the focus position to low contrast. As a solution to this problem, SANYO TEC
HNICAL REVIEW VOL. 21 No.1 (1989
(Published in February 2012), the screen is divided into a central portion and a peripheral portion surrounding the central portion in advance, and normal automatic focusing control is performed in the central portion, while the central portion is only for a low contrast subject. In that case, a technique is disclosed in which the focusing target area is expanded to a wide range including the central portion and the peripheral portion.

However, also in this case, when there is a low contrast in the enlarged region and a subject having a higher contrast exists outside the enlarged region, focusing cannot be performed, and the focus lens cannot be used. However, there is a problem such as that the behavior becomes unnatural. Also, if the focus target area is too wide, there are subjects with different distances within the area, and if there is a background with high contrast, it becomes uncertain which to focus on, and the target subject is focused. Not necessarily.

On the other hand, in the automatic focusing device disclosed in Japanese Patent Laid-Open No. 63-128877, a plurality of areas are set as focusing target areas centering on a portion of the multi-divided area having a high subject contrast, and the contrast is adjusted. A technique for setting a focusing target area so as to track a high subject is disclosed.
However, if the configuration is such that the focus target area is changed by tracking a high-contrast subject as described above, hardware and software for detecting the movement of the subject are required, and the circuit load is large, and When the contrast of the background is higher than that of the main subject, there is a problem that the focus target area is set by tracking the background, and the focus target intended by the photographer cannot be focused.

Further, when the screen is divided into a plurality of parts and the high frequency components are digitally integrated as disclosed in Japanese Patent Laid-Open No. 63-128877, the number of logic gates is increased by the above-mentioned number of divisions, resulting in a cost reduction. There is also the problem of being linked up. The present invention has been made in view of the above problems, and even if the contrast in the main area is low, a focusing operation can be performed by capturing a high-contrast subject outside the main area to perform a focusing operation. The focus lens does not behave unnaturally if it is not found, and provides an automatic focusing device that prevents the main subject from blurring while focusing on the background, and at the same time, a logic gate in the automatic focusing device. The purpose is to be able to avoid an increase in the number.

[0010]

Therefore, the automatic focusing apparatus according to the present invention is constructed as shown in FIG. In FIG. 1, the image pickup means converts an optical image into a video signal, and the high frequency component extraction means extracts a high frequency component of the video signal output from the image pickup means. Further, the focus control means drives the focus lens group based on the digital integration value of the focusing target area obtained by the digital integration means.

The focusing target area selecting means sets one main area and a plurality of sub areas as the limited areas in which the digital integrating means digitally integrates the high frequency component, and is obtained by the digital integrating means. The focusing target area in the focus control means is selected from the one main area and the plurality of sub areas based on the digital integrated value. Here, the sub-region is provided with a plurality of region groups in the vertical direction in which an even number of regions including the same scanning line are arranged in parallel along the horizontal direction of the screen, and the digital integration means targets the sub-region. The digital integration of the high-frequency component is performed for each screen by two regions arranged in the horizontal direction for each of a plurality of region groups arranged in the vertical direction at regular intervals.

On the other hand, as shown by the dotted line in FIG. 1, a main / sub area selecting means may be provided instead of the focusing area selecting means. The main / sub-region selecting means sets one main region and one sub-region that does not overlap the main region as a limited region in which the digital integrator digitally integrates the high frequency component, and the digital integrator means Based on the obtained digital integrated value, one of the one main area and one sub area is selected as the focus target area in the focus control means.

[0013]

According to the automatic focusing device having such a configuration, a plurality of sub-regions are set in addition to one main region as a region for digitally integrating a high frequency component of a video signal, and a digital integral value obtained in each region is set. Since the focus target area is switched based on this, if the subject in the main area does not have the contrast required for focus control, if high contrast is obtained in any of the plurality of sub areas, that area will be switched. A focusing operation can be performed as a target.

Of course, the sub-region is provided with a plurality of regions in the vertical direction in which an even number of regions including the same scanning line are arranged in parallel along the horizontal direction of the screen, and the digital integration is performed vertically per screen. Since two regions are arranged in the horizontal direction for each of a plurality of region groups arranged at regular intervals in the direction, even if there are four or more sub-regions, it is possible to limit the circuit configuration for performing digital integration to only two systems. Becomes

On the other hand, as a region for digitally integrating the high frequency component of the video signal, one main region and one sub region which does not overlap the main region may be set, and in this case also, If the subject in the main area does not have the contrast necessary for focus control, if the high contrast is obtained in the sub area, the focusing operation can be performed on the sub area. Also in this case, since digital integration may be performed in two areas (main area and sub area) that do not overlap each other per screen, digital integration can be realized with the same circuit configuration as in the case of providing the plurality of sub areas. .

[0016]

EXAMPLES Examples of the present invention will be described below. Figure 2
It is a block diagram showing the basic composition of the video camera provided with the automatic focusing device concerning the present invention. In FIG. 2, an optical image of a subject obtained through the optical system 1 (including the focus lens group) is formed on the light receiving surface of the image pickup element 2 (image pickup means). The image pickup device 2 photoelectrically converts the optical image and outputs it as a video signal from the image pickup circuit 3.

The video signal has a high frequency component extraction circuit 4
The high frequency component is extracted by (high frequency component extraction means),
The extracted high frequency component is analog-digital converted by the A / D converter 5 and becomes a digital amount. The digital amount is integrated by the adder 6 as a digital integrating means, but the digital integration is performed only for a limited area in the screen based on the control signal from the subject area control circuit 7. There is.

The subject area control circuit 7 limits the integration period (digital integration area) of the adder 6 based on the address data (area setting data) transferred from the lens drive control circuit 9 via the interface 8. To do. The subject area control circuit 7 and the lens drive control circuit 9 constitute the focusing target area selection means and the main / sub area selection means of this embodiment.

The lens drive control circuit 9 (focus control means) is composed of a microcomputer, a motor driver and the like, and is included in the optical system 1 so that the digital integrated value of the high frequency component in the focusing target area is maximized. The focus lens group is driven and controlled. Here, as a limited area in which the digital amount of the high frequency component is integrated, a main subject area (main area) is set in the center of the screen as shown in FIG. This is Japanese Patent Publication No. Sho 62-409.
As disclosed in Japanese Patent Laid-Open No. 08-08, since the photographer has a strong tendency to place the intended main subject in the center of the screen,
This is because if the main subject area at the center of the screen is set as the focus target area, a natural focus performance is likely to be obtained.

However, as shown in FIG. 3, when there is no contrast in the main subject area (or when the contrast is extremely low), if the main subject area is fixed as the focus subject area, the focus is focused. There is no choice but to move the focus lens back and forth to search for the focal point without obtaining the position, or to stop the focus lens at that position.

Here, when the focus lens is moved, even if the subject intended by the photographer is not in the area other than the main subject area on the screen, the automatic focusing control gives an impression of being unstable. I will give it to the photographer. Also, if you stop the focus lens without being focused,
For example, when a subject at a long distance is being photographed, if the subject comes into the vicinity of the closest point, the automatic focusing control will not be performed even if the image is greatly blurred.

Therefore, in the present embodiment, as shown in FIG. 4, four sub-subject areas (sub-areas) IA, IB, and II, which divide the screen into four vertically and horizontally, separately from the main subject area. −
A and II-B are set so that the high frequency components are digitally integrated in each of the four sub-subject areas. The four sub-subject areas are all the same size,
Are aligned horizontally and vertically with each other, and
They are adjacent to each other at regular intervals.

Then, as shown in the flow chart of FIG. 5, focusing control is performed by selectively using the main subject region and the four sub subject regions. The function shown in the flowchart of FIG. 5 corresponds to the focusing target area selection unit. First, the high frequency components of the main subject area are digitally integrated (S1). When it is determined that the result of the digital integration is less than a predetermined value and the focusing operation cannot be performed in the main subject area due to the low contrast (S2), the digital integration of the high frequency component is performed in each of the four sub-subject areas. It is performed (S3).

Next, within the four sub-subject areas,
Area where the digital integrated value is maximum (II-A in the case of FIG. 4)
Is assumed to be) (S4), and the automatic focusing operation is performed with the sub-subject region that has obtained the maximum digital integrated value as the focusing target region (S5). When focus is obtained with one of the four sub-subject areas as the focus area (S6), in the adder 6 in order to determine whether the main subject area remains in low contrast. The digital integration area is switched to the main subject area (S7).

Here, when the main subject area is still in low contrast (S8), digital integration in the sub subject area is performed again (S9), and the subject is changed to the subject within the sub subject area which was the focus target area. If it is determined that there is a change in the digital integrated value (S10),
The focusing operation is performed again for the area in which the maximum integrated value is obtained among the four sub-subject areas (S10 → S4).

On the other hand, when there is no change in the subject in the sub subject region, the main subject region is again monitored (S10).
→ S7), it is monitored whether the main subject area has a high contrast. When the main subject area has a high contrast, even if the sub-subject area is focused as the focusing target area, the focusing target area is immediately switched to the main subject area to perform the focusing operation. (S
11).

As described above, when the main subject area has a low contrast and cannot be focused, a high-contrast subject is captured in almost the entire area of the screen by the four sub-subject areas that divide the screen into four. With such a configuration for performing the focusing operation, when there is a high-contrast subject outside the main subject region, the high-contrast subject can be focused.

Therefore, when the contrast in the main subject area is low, the focus lens is not moved back and forth to search the focus point without obtaining the focus position. Let me pan,
Even if the main subject area has a low contrast for a moment, the focus lens does not behave unnaturally. Even when the sub-subject area is set as the focusing target area, the area for digitally integrating the high frequency component is alternately switched to the sub-subject area and the main subject area, and when the main subject area has high contrast, It returns to the normal control in which the subject area is set as the focusing target area. Therefore, even if the main subject area in the center of the screen, where the subject intended by the photographer is likely to be placed, has high contrast, it remains focused on the high-contrast background portion captured in the sub-subject area. , The subject intended by the photographer is not blurred.

Here, when digital integration of high frequency components is performed for each of the above four sub-subject areas, first, as will be described later, first, an area I-A arranged in parallel in the horizontal direction and including the same scanning line. , II-A (area group A) are performed in parallel, and when the digital integration in the two areas is completed, the data is transferred to the lens drive control circuit 9 via the interface 8 and then digitally integrated. Reset the integral value. Next, digital integration is performed in parallel for the regions IB and II-B (region group B) which are also arranged side by side in the horizontal direction.

Then, before the next screen starts, the digital integration data is transferred to the lens drive control circuit 9 via the interface 8 and the digital integration value is reset. If the data transfer and the reset of the integrated value are completed within one scanning line, the interval between the area group A and the area group B is
One scan line engine or more is enough. In order to execute the digital integration in parallel in each of the two regions, the digital integration in the present embodiment includes one adder and two registers for holding the integrated values in each of the two regions, as described later. , A selector for selectively feeding back the data held in the two registers to the adder, and the adder 6 shown in FIG. 2 is specifically described by the adder, the register and the selector. Composed.

FIG. 6 is a block diagram showing a concrete structure of a portion surrounded by a chain line in FIG. In FIG. 6, the high frequency component in the video signal (video signal) extracted by the high frequency component extraction circuit 4 (bandpass filter) is sampled by the A / D converter 5 (for example, NT).
6-bit digital data is obtained by analog / digital conversion using the SC color subcarrier frequency of 3.58 MHz.

The converted 6-bit digital data is added by the adder 11 to the integrated value (integral value) stored in the register 12 or the register 13, and the addition result (digital integrated value) is obtained by the register. One of 12 and 13 is selectively updated and stored. The interface 8 transfers the area setting data transferred from the CPU constituting the microcomputer built in the lens drive control circuit 9 of FIG. 2 to the object area control circuit 7. The subject area control circuit 7 resets the registers 12 and 13 based on the horizontal synchronizing signal and the vertical synchronizing signal, the transferred area setting data, and the A / D conversion clock, and the selector 14
To selectively output the storage data in either one of the registers 12 and 13 and to control the storage data update in the registers 12 and 13.

The adder 6 shown in FIG. 2 is composed of an adder 11, registers 12 and 13, and a selector 14 in FIG. Here, when the screen is divided into four as shown in FIG. 4 and the digital integrated value of the high frequency component in each region is obtained,
The integration results in the IA and IB regions shown in are shown in the register 12
In addition, the integration results of the II-A and II-B regions shown in FIG. 4 are stored in the register 13.

That is, each of the registers 12 and 13 stores the digital integrated values of the two regions in a time-division manner. That is, first, the integrated data of the areas I-A and II-A is transferred from the interface 8 to the CPU of the lens drive control circuit 9 via the selector 14, and the registers 12 and 13 are reset. After that, the same operation is performed for the regions IB and II-B, and the digital integration data of the four regions is divided into two and transferred to the outside.

Specifically, each of the four sub-subject areas can be defined by a start address and an end address in the horizontal and vertical directions, as shown in FIG. Therefore, the clock enable signals I and II as shown in the time charts of FIGS. 8 and 9 are output to the respective registers 12 and 13 as the area setting data,
Only the integrated value in the corresponding region is input to the registers 12 and 13, and the selector 14 outputs the select signal as shown in the time charts of FIGS. The held data on the register 12 side is output except when the pixel is to be digitally integrated with.

As a result, first, the integrated values in the two areas I-A and II-A belonging to the upper half of the screen are stored in the registers 12 and 13, respectively, and the integrated value of the corresponding area is selected by the selector 14. Are selectively output to the adder 11, and when the parallel digital integration in the two areas IA and II-A is completed, the two areas IA and II-
A and two regions IB and II for digital integration next
The digital integration value is transferred to the lens drive control circuit 9 via the interface 8 by utilizing the interval with -B, and then the two registers 12 and 13 are reset to reset the next two areas IB and II. Prepare for digital integration at -B (see Figure 8).

In the same manner, two regions IB,
The digital integration in II-B is performed in parallel, and the interval between the two areas IB and II-B and the lower edge of the screen is used. In this interval, digital integration in the two areas IB and II-B is performed. Transfer the integrated value. If the configuration is such that digital integration is performed in the four sub-subject regions that divide the screen into four as described above,
By using two registers 12 and 13, it is possible to obtain 4 areas of digital integration data on the same screen, and the circuit configuration is simplified compared to the case where a number of registers corresponding to the number of divisions (the number of sub-subject areas) is provided, and the cost is reduced. Can be reduced.

When performing digital integration of high frequency components in the main subject area, only one of the registers 12 and 13 is used and the clock enable signal corresponding to the area setting data as shown in FIG. 10 is selected. It is possible to perform digital integration in the main subject area by outputting the signal to the register and the selector signal to the selector 14.

Therefore, using the circuit configuration of FIG.
One of the digital integration in each of the two sub-subject areas and the digital integration in only the main subject area can be selectively executed. The subject area control circuit 7 that outputs control signals to the registers 12 and 13 and the selector 14 is configured as shown in FIG.

In FIG. 11, the register unit 21 has one main subject area or 4 for causing the CPU of the microcomputer incorporated in the lens drive control circuit 9 to perform digital integration as shown in FIGS. 7 and 10. Area setting data of one sub-subject area, that is, a horizontal start address, a horizontal end address, a vertical start address, and a vertical end address are transferred via the interface 8.

Here, regarding the four sub-subject areas as shown in FIG. 7, the area IA and the area IB, and the area II-A and the area II-B are horizontal address positions. Are the same, region IA and region II-A, and
Since the areas IB and II-B have the same vertical address, four areas can be set with eight address data.

The data of the start address is set in the coincidence circuits 22 to 25 from the register section 21 as follows. That is, the coincidence circuit 22 is set with the horizontal start address I common to the areas IA and IB, and the coincidence circuit 23 is common to the areas II-A and II-B. The horizontal start address II is set, and the vertical start address A common to the areas IA and II-A is set in the matching circuit 24.
In the area 25, a vertical start address B common to the areas IB and II-B is set.

Further, the data of the end address is set in the coincidence circuits 26 to 29 from the register section 21 as follows. That is, the matching circuit 26 has the area I-
A horizontal end address I common to A and area IB is set, and the coincidence circuit 27 is set to area II-A and area II-B.
And a common horizontal end address II is set, and the matching circuit 28 is set with a vertical end address A common to the areas IA and II-A.
Is set to the vertical end address B common to the areas IB and II-B.

The horizontal counter 30 is a counter for counting a sample clock (pixel clock) for A / D conversion using a horizontal synchronizing signal as a reset signal. The count value of the horizontal counter 30 is the coincidence circuits 22, 23, 26. , 27 is output. When the horizontal start address I common to the areas I-A and I-B set in the matching circuit 22 and the count value of the horizontal counter 30 match, the output from the matching circuit 22 causes The flip-flop 31 is set and the output of the flip-flop 31 rises to the high level. On the other hand, when the count value of the horizontal counter 30 and the horizontal end address I common to the areas IA and IB set in the matching circuit 26 match, the output from the matching circuit 26 becomes the above-mentioned. It becomes the reset signal of the flip-flop 31,
Flip-flops that were held at high level until then
The output of 31 falls to low level.

As a result, the output of the flip-flop 31 becomes high level in the horizontal address area common to the areas IA and IB. Similarly, the matching circuit 23
The output of the flip-flop 32 whose output is the set signal and the output of the coincidence circuit 27 is the reset signal is at a high level in the horizontal address area common to the areas II-A and II-B.

On the other hand, the vertical counter 33 is a counter which counts the horizontal synchronizing signal with the vertical synchronizing signal as a reset signal, and the count value of this counter 33 is equal to that of the matching circuit 2.
It is designed to be output to 4, 25, 28, 29. The output of the flip-flop 34, which uses the output of the coincidence circuit 24 as the set signal and the output of the coincidence circuit 28 as the reset signal, is at a high level in the vertical address area common to the areas IA and II-A. Becomes

Similarly, the output of the flip-flop 35, which uses the output of the coincidence circuit 25 as the set signal and the output of the coincidence circuit 29 as the reset signal, is the vertical address common to the areas IB and II-B. High level in the area. here,
The outputs of the flip-flops 34 and 35 are output to the OR circuit 36, and the outputs of the OR circuit 36 are output to the AND circuits 37 and 38, respectively.

The AND circuit 37 has a flip-flop 31.
Output of the flip-flop 32 to the AND circuit 38.
The output of each is input. Therefore, the AND circuit 37 outputs a signal which becomes high level when it corresponds to the area IA or the area IB, and the output performs digital integration of the area IA and the area IB. The clock enable signal I is output to the register 12. From the AND circuit 38, the area II-
A signal that becomes a high level when corresponding to the area A or the area II-B is output.
It is output as a clock enable signal II to the register 13 which performs II-B digital integration.

The output of the OR circuit 36 is output to the interface 8 as a vertical area recognition signal, and the interface 8 recognizes that the digital integration is completed based on the vertical area recognition signal and is preset. The digital integration result in each of the two areas is read based on the selection timing by the selector 14 and is transferred to the lens drive control circuit 9.

The outputs of the flip-flops 34 and 35 are output to the reset / select signal generator 39, respectively. The reset / select signal generation unit 39 outputs a reset signal to each of the registers 12 and 13 and resets each of the registers 12 and 13 when the reading period has elapsed from the vertical end address. Further, the reset / select signal generation unit 39 feeds back the outputs of the registers 12 and 13 corresponding to the area to the adder 11 according to the output from the flip-flop corresponding to the area setting data, and performs digital integration. At the end timing of (3), a select signal (see FIGS. 8 and 9) for alternately outputting the outputs of the registers 12 and 13 as the final integration result is generated and output to the selector 14.

Further, the reset / select signal generator
39 outputs a reset signal for resetting the registers 12, 13 after waiting for the output of the select signal for outputting the final integration result (see FIG. 8). By the way, in the above, four areas are set as the sub-subject area, which divides the screen into four, but the sub-object area is not limited to four areas. For example, as shown in FIG. It is also possible to set a sub-subject region of, and similarly to the above, when the main subject region has a low contrast, a high-contrast subject is captured in any of the 16 sub-subject regions and the focusing operation is performed. .

In this case, although the number of sub-subject areas is significantly increased, the same circuit configuration shown in FIGS. 6 and 11 as in the case of setting the four sub-subject areas is used, and each of the 16 sub-subject areas is divided. It is possible to perform digital integration of high frequency components. That is, the sub-subject area divided into 16 is
As shown in 12 (A) to (D), it is assumed that each of the four screens has four digital integration regions set therein. Here, in one screen, 4 are arranged side by side in the horizontal direction.
Since only one sub-subject area (area group) is allowed to perform digital integration, digital integration can be performed as in the case of four divisions.

Further, a period for outputting the result of digital integration to the outside is required, and in the division shown in FIG. 12, no space is provided between vertically adjacent regions, but in each screen, they are vertically adjacent. The regions are not configured to be digitally integrated, and a space for one region is always provided in the vertical direction between the regions to be digitally integrated. Therefore, the non-integration period for one area in the vertical direction can be used as a digital integration value transfer period, and the digital integration value in the last area group in the vertical direction can be set to the vertical retrace line during the data transfer period. Can be used as

In this way, by performing the parallel processing twice for each of the two regions arranged in parallel in the horizontal direction per screen, it is possible to perform digital integration of four regions per screen and with four screens. Digital integration of all 16 areas can be performed. Therefore, as in the case of using the four sub-subject areas, the two registers 12 and 13 can perform digital integration of the high frequency components in the 16 sub-subject areas,
Even if the number of sub-subject areas is increased, the cost of the circuit does not increase.

Note that, in FIGS. 12A to 12D, among the four regions arranged in parallel in the horizontal direction, the regions in which digital integration is simultaneously performed are set to the adjacent regions, but the present invention is not limited to this. Instead, you can set any combination. Also,
Although the number of divisions is not limited to the above, since two regions can be digitally integrated in parallel in the horizontal direction, it is efficient to form a region group including an even number of regions.

In the above embodiment, a plurality of sub-subject areas are set in order to capture the high contrast area outside the main subject area in the center of the screen. However, as shown in FIG. In addition to the area, one sub-subject area that does not overlap with the main subject area is set, and when the main subject area has a low contrast, a high-contrast object is captured in this sub-subject area to perform a focusing operation. It may be performed.

However, in this case, since there is only one sub-subject area, if this sub-subject area is fixed, it is not always possible to capture a high contrast portion outside the main subject area in the sub-subject area. Therefore, as described above, when one sub-subject area that does not overlap with the main subject area is set in addition to one main subject area in the center of the screen, the sub-subject area is set around the main subject area. Move to ensure that high contrast areas outside the main subject area are captured.

Focusing control using one sub-subject area which is set as described above is shown in the flowchart of FIG. The function shown in the flowchart of FIG. 14 is
It corresponds to the main / sub area selection means. In the flowchart of FIG. 14, first, it is determined whether or not the main subject area has low contrast (S31). When it is determined that the main subject area has a low contrast, the sub-subject area is moved around the main subject area to a high contrast portion outside the main subject area (S32), and the sub-subject at that position is moved. A focusing operation is performed with the region as the focusing target region (S33).

Then, as in the case of the above embodiment, when focus is obtained in the sub-subject area (S34), it is monitored whether or not there is a high contrast in the main subject area (S35). When the contrast becomes high, the control is shifted to the control of setting the main subject region as the focus target region even if the sub subject region is focused (S3).
7).

On the other hand, when the main subject area is still low in contrast, it is judged whether or not the subject has changed in the sub subject area (S36). When there is no change in the sub subject area, the main subject area is monitored again. Then, when a change occurs in the sub-subject area, the focusing operation using the sub-subject area is performed again. Therefore, even in the configuration in which one fixed main subject region and one sub-subject region that is set to move around the main subject region are set as described above, the inside of the main subject region has low contrast. Sometimes, if there is a high contrast area outside the main subject area, focus can be obtained, and since focus in the main subject area is prioritized, it is possible to focus on the main subject area while focusing on the background part. It is possible to avoid blurring of the subject.

Here, in the case of setting one fixed main subject area as described above and one sub-subject area which is set to move around the main subject area, the above-mentioned FIG. 6 and FIG. It is possible to perform digital integration of high frequency components with a circuit substantially similar to the circuit configuration shown in, that is, with two systems of digital integration circuits. However, when the registers 12 and 13 are divided into respective areas and the digital integration of the main subject area and the sub-subject area is performed on one screen, as shown in FIG. 15, both areas overlap in the horizontal direction, and , The timing of ending digital integration in the vertical direction may differ. Therefore, in the circuit corresponding to the embodiment shown in FIG. 6 and FIG. 11, the reset signal is output as a common signal to the two registers 12 and 13.
Also, as shown in FIG. 17, it is necessary to generate a reset signal for each of the registers 12 and 13 so that they can be reset independently.

In addition to the reset signal output configuration described above, digital integration can be performed with the same circuit configuration as in the case of setting the 4 or 16 sub-subject regions, as shown in FIG.
Address data (start and end addresses in the horizontal direction and start and end addresses in the vertical direction) indicating the main subject region and the sub subject region as shown in (4) are given from the CPU to the control circuit 7.

In the control circuit 7, the A / D clock signal (pixel clock), horizontal synchronizing signal, vertical synchronizing signal,
Further, based on the area setting data (address data) given from the CPU, as shown in FIGS. 18 and 19,
A clock enable signal and a reset signal for controlling the registers 12 and 13 and a select signal for controlling the selector 14 are output to perform digital integration of both the main subject area and the sub subject area on one screen.

Therefore, in this case, the digital integrated value of the main subject region and the sub-subject region can be obtained for each screen, and while performing the focusing control with the sub- subject region as the focusing target region, At the same time, the subject in the main subject area can be monitored. When moving the sub-subject area around the main subject area, the sub-subject area may be moved around the main subject area from the initial position in sequence, but for example, the sub-subject area is alternately moved to the left and right positions of the main subject area. After making it move, it may be moved up and down alternately.

Further, the size of the sub-subject area may be changed according to the place to move.

[0066]

As described above, according to the automatic focusing apparatus of the present invention, even if the inside of the main area has a low contrast, a high-contrast object is captured outside the main area to perform the focusing operation. Therefore, even if, for example, the camera is panned for subjects at equal distances and the main subject region becomes low in contrast for a moment, the focus lens does not behave unnaturally, and even if it is outside the region, Even if the screen is divided into a plurality of areas such as 4 or 16 in order to capture a subject of contrast and each area is set as a sub-area, it is not necessary to have as many registers as the number of the sub-areas set. By setting a sub-region in addition to one main region, it is possible to avoid increasing the cost of the circuit without complicating the circuit configuration. There is a result.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram showing an outline of a system according to an embodiment.

FIG. 3 is a diagram showing a main region in which digital integration according to an embodiment is performed.

FIG. 4 is a diagram showing a sub region where digital integration according to the embodiment is performed.

FIG. 5 is a flowchart showing focusing control when setting a plurality of sub areas.

FIG. 6 is a circuit diagram showing a circuit configuration for performing digital integration.

FIG. 7 is a diagram showing area setting data of four sub areas.

FIG. 8 is a time chart showing a state of digital integration in four sub areas.

FIG. 9 is a time chart showing a state of digital integration in four sub areas.

FIG. 10 is a diagram showing area setting data of a main area.

FIG. 11 is a circuit diagram showing a circuit that generates a control signal for a register and a selector.

FIG. 12 is a diagram for explaining how digital integration is performed in 16 sub-regions.

FIG. 13 is a diagram showing an area setting state of an embodiment in which one sub area is moved.

FIG. 14 is a flowchart showing focusing control for moving one sub area.

FIG. 15 is a diagram showing a region setting state of a main region and one sub region that is moved and set.

FIG. 16 is a circuit diagram showing another embodiment of the digital integrating circuit.

FIG. 17 is a circuit diagram showing another embodiment of a circuit that controls digital integration.

FIG. 18 is a time chart showing a state of digital integration in a main area and one sub-area that is set to be moved.

FIG. 19 is a time chart showing a state of digital integration in a main area and one sub-area that is set to move.

[Explanation of symbols]

 1 Optical system 2 Image sensor 3 Imaging circuit 4 High frequency extraction circuit 5 A / D converter 6 Adder 7 Subject area control circuit 8 Interface 9 Lens drive control circuit 11 Adder 12, 13 Register 14 Selector 21 Register section 22-29 Match Circuit 30, 33 Counter 31, 32, 34, 35 Flip-flop 36 OR circuit 37, 38 AND circuit 39 Reset / select signal generator

Claims (2)

[Claims] 1. An image pickup means for converting an optical image into a video signal, a high frequency component extraction means for extracting a high frequency component of a video signal output from the image pickup means, and a high frequency component extracted by the high frequency component extraction means. A digital integration means for digitally integrating in a limited area of the screen by the image pickup means, and a focus control means for driving the focus lens group based on the digital integration value of the focusing target area obtained by the digital integration means, One main region and a plurality of sub-regions are set as the limited regions in which the digital integrator digitally integrates the high frequency component, and the one main region is based on the digital integral value obtained by the digital integrator. And a focusing target area selecting unit that selects a focusing target area in the focus control unit from a plurality of sub-regions. A moving focusing device, wherein the sub-region comprises a plurality of region groups in the vertical direction in which an even number of regions including the same scanning line are arranged in parallel along the horizontal direction of the screen, and the digital integrating means is An automatic focusing device characterized by performing digital integration of high-frequency components for sub-regions on each screen for two regions arranged in the horizontal direction for each of a plurality of region groups arranged in the vertical direction at regular intervals. 2. An image pickup means for converting an optical image into a video signal, a high frequency component extraction means for extracting a high frequency component of a video signal output from the image pickup means, and a high frequency component extracted by the high frequency component extraction means. A digital integration means for digitally integrating in a limited area of the screen by the image pickup means, and a focus control means for driving the focus lens group based on the digital integration value of the focusing target area obtained by the digital integration means, An automatic focusing device comprising: a main integration area and a sub-area that does not overlap with the main area as a limited area in which the digital integration means digitally integrates a high frequency component, and Based on the digital integration value obtained by the digital integration means, one of the one main area and one sub area is provided to the focus control means. Main and to be selected as the focusing target area that
An automatic focusing device comprising sub-region selecting means.