JPH11258495A - Automatic focus regulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce or prevent the lowering of the accuracy of an autofocus detection due to ringing. SOLUTION: In this automatic focus regulating device, an A/D converted video signal is inputted into an HPF(high-pass filter) 33 through a change-over switch 32 to be changed over during a horizontal term of AF area, and before the above changing over, the half of the maximum obtainable value of the video signal maintained in a level setting circuit 31 is inputted into the HPF 33 through the change-over switch 32, and in the case where a high frequency signal component is extracted for detecting a focus through the HPF 33, a level variation at the time of changing over the change-over switch 32 is reduced to restrain the occurrence of a ringing component.

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 for automatically setting an imaging optical system to a focused state from a video signal in an automatic focusing region.

[0002]

2. Description of the Related Art In recent years, in an electronic image pickup apparatus such as a video camera and a digital camera, an automatic focus adjustment apparatus for moving an image pickup optical system to automatically set a focus state (focus state) has been adopted. Has become.

A conventional automatic focus adjustment device extracts a predetermined frequency component of a video signal obtained from an automatic focus detection area set in a part such as a central portion of a screen with a filter, and based on the extracted signal component. Focusing is performed.

For example, in Japanese Patent Application Laid-Open No. Hei 8-122627, a signal is divided into a central portion and a region other than the central portion, and gates are opened and closed and switches are switched to control signals input to a plurality of filters provided at the subsequent stage. doing.

[0005]

However, in the conventional examples described in the above publications, a discontinuous point of the video signal or a sharp level change occurs at the boundary between the automatic focus detection area and the other area. , To the output of the filter,
Ringing occurs.

For example, when an auto focus detection area (AF area) for performing auto focus detection is set at the center of the image pickup screen as shown in FIG. 10, the video signal becomes 0 outside the auto focus detection area and the auto focus is detected. In the detection area, the signal is input to the high-pass filter by opening or closing the gate or switching the switch. In the automatic focus detection area, the luminance level suddenly changes according to the brightness of the subject. In this case, a high-frequency component corresponding to a steep level change at this boundary is extracted as ringing.

In this case, the ringing of the part which can be switched from the automatic focus detection area to the other area is outside the automatic focus detection area and can be excluded, so that there is not much problem. Ringing that occurs when switching to the focus detection area is included in the automatic focus detection area and thus is extracted.

Therefore, it should not be originally detected,
Due to the ringing component, the S / N of the signal component of the autofocus detection is reduced, and the accuracy of the autofocus detection is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an automatic focus adjustment device which can reduce or prevent a decrease in the accuracy of autofocus detection due to ringing.

[0010]

An automatic focus adjustment for extracting a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performing an automatic focus adjustment based on the frequency component of the extracted video signal. In the apparatus, a video signal selecting means for selecting a video signal from a part of the auto focus detection area of the entire area of the imaging surface of the imaging device, and a video signal of the auto focus detection area selected by the video signal selection means A filter for extracting a predetermined frequency component from the, the median value of the maximum possible value of the video signal, the value of the video signal outside the automatic focus detection area selected by the video signal selection means, the video signal outside the automatic focus detection area, Video signal level setting means for fixing to a predetermined level value such as an average brightness value and a brightness target value of the automatic focus detection area, thereby providing a timing for the automatic focus detection area. Filter to extract a predetermined frequency component through a filter and prevent a sharp and large deviation from occurring between the value of the video signal outside the automatic focus detection area and the video signal within the automatic focus detection area. Ringing is prevented from being mixed into the camera, thereby preventing a decrease in the accuracy of autofocus detection.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 4 relate to a first embodiment of the present invention, and FIG. 1 shows a configuration of an electronic image pickup apparatus provided with an automatic focusing apparatus according to the first embodiment. 2 shows an AF area, FIG. 3 shows an operation explanatory diagram of the first embodiment, and FIG. 4 shows a flowchart of an imaging operation.

An electronic image pickup apparatus 1 shown in FIG. 1 has a zoom lens 2 and a focus lens 3 as an image pickup optical system, and a light beam passes through these lenses through a stop 4 and a charge-coupled device as a solid-state image pickup device. (Abbreviated as CCD) 5 forms an object image. A color separation filter 5A for optically color-separating is disposed on the imaging surface of the CCD 5, and light separated by the color separation filter 5A is received by the CCD 5.

The signal photoelectrically converted by the CCD 5 is input to an imaging circuit 6, which generates a video signal. The video signal is converted into a digital video signal (image data) by an A / D converter 7. And temporarily stored in the memory 8. The writing and reading of the image data to and from the memory 8 are performed by the memory controller 27.

The image data stored in the memory 8 is read out at a predetermined screen rate (for example, 1/30 second), and the D / A
After being converted into an analog video signal by the converter 9, a subject image is displayed on a liquid crystal display element (abbreviated as LCD) 10.

When a recording operation is performed by operating the release switch of the operation switch 24, the image data in the memory 8 is compressed by the compression circuit of the compression / expansion circuit 11 and then stored in the recording memory 12. Is done. When a reproducing operation is performed, the data compressed and stored in the recording memory 12 is expanded by the expansion circuit of the compression / expansion circuit 11 and temporarily stored in the memory 8, and the image data is stored in the D / D memory. A
After being converted to an analog video signal by the converter 9, the LCD
At 10, a reproduced image is displayed.

The image data A / D converted by the A / D converter 7 automatically sets an auto exposure processing circuit (abbreviated as an AE processing circuit) 13 for performing automatic exposure control and an imaging optical system to a focus state. To an auto-focus processing circuit (abbreviated as an AF processing circuit) 14 for calculating an auto-focus evaluation value (abbreviated as an AF evaluation value).

The AF processing circuit 14, as shown in FIG.
An area for performing automatic focus adjustment set in a partial area, for example, near the center of the imaging screen for one frame of CD5, that is, AF from the high-frequency components in the image data in the AF area 28
The evaluation value is calculated and output to the CPU 15. The pixel size in the horizontal direction of the AF area 28 is, for example, m pixels.

The AE processing circuit 13 calculates an AE evaluation value corresponding to the brightness of the subject by calculating a luminance value of the image data in the AF area 28 and outputs the AE evaluation value to the CPU 15.

A predetermined timing signal synchronized with the screen rate is input from a timing generator (abbreviated as a TG circuit) 16 to the CPU 15, and the CPU 15 performs various control operations in synchronization with the timing signal.

The timing signal of the TG circuit 16 is also input to the imaging circuit 6, and performs processing such as separation of color signals in synchronization with the signal. The TG circuit 16 operates the CCD driver 1 so as to drive the CCD 5 at a predetermined timing.
7 is controlled.

The CPU 15 controls the first, second and third motor drive circuits 18, 19 and 20, respectively, to control the apertures 4 and 4 via the first, second and third motors 21, 22 and 23, respectively. The drive of the focus lens 3 and the zoom lens 2 is controlled.

That is, the CPU 15 uses the AE evaluation value
The first motor drive circuit 18 is controlled to rotate the first motor 21 to adjust the aperture amount of the aperture 4. Then, the aperture amount of the aperture 4 is automatically adjusted so that the AE evaluation value matches the target value of the screen brightness set by the user or the like. That is, the automatic exposure control is performed.

The CPU 15 controls the second motor drive circuit 19 to rotate and drive the second motor 22 to obtain the AF evaluation value from the AF processing circuit 14 while driving the focus lens 3. Based on the obtained AF evaluation value, the CPU 15 drives the focus lens 3 to the lens position where the value becomes the maximum, and sets the focus state, that is, performs autofocus.

In the present embodiment, when the AF evaluation value is obtained and set to the in-focus position, the screen rate (for example, 1/30) when the CCD 5 captures one frame (one screen) of the subject.
Per second) and the focus lens 3
The focus lens 3 is moved by a predetermined feed amount within a movable range in the optical axis direction.

When the zoom UP switch in the operation switch 24 is operated, the operation signal is received and the CP
U15 controls the third motor drive circuit 20 to rotate and drive the third motor 23 to drive the zoom lens 2 to the enlargement side.

The CPU 15 is connected to, for example, an electrically rewritable and non-volatile read-only memory (EEPROM) 25 as a memory.
The ROM 25 stores a program for performing various controls and the like via the CPU 15, data used for performing various operations, and the like, and is read out when the power of the imaging apparatus 1 is turned on. Used. In addition, CPU
Reference numeral 15 detects the voltage of the battery 26, and when it is detected that the voltage has become equal to or lower than a predetermined voltage value, the LCD 10 displays a message indicating that the remaining amount of the battery 26 is low or prompts the user to charge or replace the battery.

In this embodiment, the automatic focus adjustment is performed by a hill-climbing AF (abbreviated as hill-climbing AF).
AF for calculating an AF evaluation value for performing this hill-climbing AF
The processing circuit 14 includes a level setting circuit 31 that outputs a signal of a set level value specified by the CPU 15 and an A / D
A switch 32 (as a video signal selecting means) for switching between a digital video signal A / D-converted by the converter 7 and a signal of a set level value set in the level setting circuit 31 and outputting the signal; A high-pass filter (abbreviated as HPF) 33 for extracting a high-frequency component in a signal selected and input by the changeover switch 32 and an integrating circuit 34 for integrating outputs of the HPF 33 to obtain an AF evaluation value.

The level setting circuit 31 stores a reference signal value of a value designated by the CPU 15, and the stored value is constantly output as a reference signal. The level setting circuit 31 is constituted by a latch circuit composed of a plurality of bits. In the present embodiment, the CPU 15 controls the level setting circuit 31 so as to hold, as a reference signal value, a half of the maximum value that the video signal can take. The level is set.

More specifically, when the number of bits of the digital video signal of the A / D conversion circuit 7 and the like is, for example, 8 bits, a latch circuit having a capacity of 8 bits constituting the level setting circuit is stored. The value is set so that all the lower 7 bits are set to 1, and 127, which is half of the maximum value 255 of the number of possible gradations of the digital video signal, is held.

The changeover switch 32 is connected to the CPU 15
Accordingly, the contact a is switched on during a period Haf during which image data for each horizontal pixel of the AF area 28 is input, and the contact b is switched on around this period Haf.

The HPF 33 is composed of a digital HPF circuit that can set a filter characteristic, specifically, a cutoff frequency Fc, based on a characteristic setting signal from the CPU 15, for example. The integration circuit 34 controls the integration operation by the CPU 15 and calculates the AF calculated by the integration.
The evaluation value is transferred to the CPU 15.

That is, in the present embodiment, the AF area 2
In addition to the existing configuration in which the changeover switch 32 is set so that the video signal output from the A / D converter 7 is input to the HPF 33 during the period Haf of the period 8, a level setting circuit 31 is provided to provide a period Haf Before and after the setting, the setting signal value of the level setting circuit 31 is input to the HPF 33 to form means for suppressing the occurrence of ringing at the boundary of the AF area 28.

The operation of the AF processing circuit 14 for obtaining an AF evaluation value will be described below with reference to FIG.

As shown in FIG. 3A, a video signal is input to the AF processing circuit 14 in synchronization with the horizontal synchronizing signal or the horizontal driving signal HD (in FIG. 3, the video signal is superimposed on the horizontal driving signal HD for simplicity). As shown in FIG. 3B, the period of the horizontal drive signal HD, that is, the period Haf of the AF area 28 is set near the center of the horizontal drive signal period, for example.

Then, as shown in FIG. 3 (C), during this period Haf, the changeover switch 32 is switched from the contact point b to the contact point a.

On the other hand, as shown in FIG. 3D, the level setting circuit 31 sets the set level value, that is, 1/2 of the maximum value (FIG. 3D).
Then, MAX / 2) is output.

Therefore, as shown in FIG. 3E, before this period Haf, 1/2 of the maximum value of the level setting circuit 31 is input to the HPF 33, and during the period Haf, the AF area 28 is supplied.
Are input to the HPF 33.

In this case, since a steep and large level change at the boundary of the period Haf is suppressed, ringing at the boundary of the output of the HPF 33 is suppressed as shown in FIG. The AF evaluation value integrated by the integration circuit 34 has a small ringing component at the boundary portion, and an AF evaluation value with a good S / N can be obtained.

This AF evaluation value is sent to the CPU 15 and
The PU 15 performs hill-climbing AF using the AF evaluation value.
Next, the imaging operation will be described with reference to FIG. When the imaging apparatus 1 is turned on and set to the imaging mode, FIG.
Is started.

First, as shown in step S1, an automatic exposure control process (simply abbreviated as AE in FIG. 4) is performed. That is, the AE processing circuit 13 calculates the AE evaluation value corresponding to the brightness of the subject by integrating the luminance values of the video signals over the entire screen, and outputs the AE evaluation value to the CPU 15. The CPU 15 compares the calculated AE evaluation value with the AE target value set by the user, and controls the opening amount of the diaphragm 4 in a direction in which the deviation amount decreases. By performing such control, the automatic exposure control state is set so that the AE evaluation value always becomes the AE target value.

Next, as shown in step S2, it is determined whether or not the first release (first release in FIG. 4) of the release switch has been performed, and a standby state waits for the release to be performed.

In the present embodiment, the release switch is constituted by a two-stage switch, and the first release operation of turning on the first release switch enables the setting of auto focus (and automatic exposure control before that) to be performed. The shooting is actually performed by the second release operation in which the second release switch is turned on.

When the first release operation is performed, the hill-climbing AF process in step S3 is performed based on the AF evaluation value of the AF processing circuit 14. First, a direction determination process 3A is performed. In this case, a process of determining which direction is the hill-climbing direction at the current lens position is performed. That is,
The focus lens 3 is moved to one side by a predetermined amount, and a direction in which a direction in which the AF evaluation value becomes large before and after the direction is determined as a moving direction.

After judging the moving direction, a peak detection process in step S3B in FIG. 4 is performed. In this peak detection processing, the peak value of the AF evaluation value is detected while moving by a predetermined feed amount in the detected moving direction. In other words, the movement is repeated at a predetermined feed amount until the AF evaluation value on the moving side becomes smaller than that before the movement, in other words, until it starts to descend at the top of the mountain (the peak value of the AF evaluation value). And
By obtaining the AF evaluation value until it starts to descend, the peak AF evaluation value is detected.

When the AF evaluation value of the peak is detected, processing for driving to the focus position in step S3C is performed. That is, the lens position is set to the position where the peak AF evaluation value is detected, the hill-climbing AF is completed, and the next step S4
It is determined whether or not the first release release operation has been performed. If the release has been released, the process returns to the first step S1, and if not released, the second release of the next step S5 (2nd in FIG. 4). It is determined whether or not an operation of (release) is performed, and if this operation is not performed, the process returns to step S4.

Then, when the second release operation is performed, the photographing process of step S6 is performed. That is, C in FIG.
The subject image exposed on the CD 5 is converted into a video signal by the imaging circuit 6, and the video signal is converted into a digital video signal by the A / D converter 7, and is temporarily stored in the memory 8. Then, a photographing process of storing the image data temporarily stored in the memory 8 in the recording memory 12 via the compression / expansion circuit 11 is performed. After performing the photographing process, the process returns to step S1 to prepare for the next photographing operation.

According to the present embodiment, the AF switch 28 is used to switch the AF
The video signal in the area 28 is selected and input to the HPF 33, but before the switching, the maximum possible value MAX of the video signal held (fixed) in the level setting circuit 31 is 1/1.
Since the value of 2 is input to the HPF 33, the amount of level change at the switching timing can be suppressed.
The ringing component generated in the PF 33 can be suppressed, and the ratio of the ringing component in the obtained AF evaluation value can be reduced. Therefore, a decrease in S / N due to a ringing component in the AF evaluation value can be reduced, and a highly accurate autofocus state can be set.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The electronic imaging apparatus according to the present embodiment has the same configuration as that of FIG. 1 except that the level value set in the level setting circuit 31 is different. That is, the level setting circuit 31 holds the AE target value Vae. A in this case
FIG. 5 shows a timing chart for obtaining the F evaluation value.

FIG. 5 is different from FIG. 3D only in that the output of the level setting circuit 31 is changed from MAX / 2 to the AE target value Vae. According to the present embodiment, the value held in level setting circuit 31 is AE target value V
ae, and the CPU 15 sets the AE processing circuit 13
The closed loop control is performed so that the AE evaluation value obtained in step (2) becomes the AE target value Vae. Therefore, the amount of deviation between the AE target value Vae and the horizontal video signal level of the AF area 28 when switching in the AF area 28 is performed. Is in most cases
The ringing component when passing through the HPF 33 can be made smaller than that of the first embodiment.

Next, a modification of the second embodiment will be described. This modified example has the same configuration as that of FIG. 1 except that the level value set in the level setting circuit 31 is different.

That is, the level setting circuit 31 holds the average luminance value Vav of the AF area 28. In this case, FIG. 5 (D ') is used instead of FIG. 5 (D). The operation and effects of this embodiment are almost the same as those of the first embodiment, but the ringing component can be further reduced.

The average luminance value Vav of the AF area 28
In this case, even in the case of backlight, in which the brightness level of the AF area 28 and its peripheral portion is largely different, the occurrence of ringing can be suppressed, and an accurate autofocus state can be set.

Although the average brightness of the video signal in the AF area is obtained from the output signal of the CCD 5 as an image sensor, a photometric sensor is provided separately from the image sensor.
The average brightness of the video signal in the AF area may be obtained by the photometric sensor.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In the present embodiment, the AF area 28
The value before the boundary is sampled and fixed to that value outside the AF area to suppress the occurrence of a ringing component at the boundary. For this reason, in the present embodiment, the AF processing circuit 14 in FIG. 1 is configured as shown in FIG.

The video signal output from the A / D converter 7 is input to a delay line 41 and also to a sample and hold circuit 42. The output signal of the delay line 41 and the signal sampled and held by the sample and hold circuit 42 are input to the changeover switch 32.

The delay line 41 is delayed by a period Haf in the horizontal direction of the AF area 28. Further, the sample hold circuit 42 samples a signal immediately before the AF area 28 with a sample hold pulse under the control of the CPU 15 and holds the sampled value for a period equal to or longer than the period Haf (for example, until the next sampling period). I do.

The changeover switch 32 operates during a period Haf during which the video signal of the AF area 28 is input, during the delay line 41.
Is output to the HPF 33 side, and the output signal of the sample hold circuit 42 is output to the HPF 33 during the period other than the period Haf.
Is switched by the CPU 15 so as to output to the side.

Actually, the time Ha is applied to the delay line 41.
Since the signal is delayed by f, the signal is switched by being delayed by the time Haf as compared with the case of the video signal without delay. Other configurations are the same as those of the first embodiment.

Next, the operation of this embodiment will be described with reference to FIG. The video signal shown in FIG. 7B is input to the AF processing circuit 14 in synchronization with the horizontal drive signal HD shown in FIG. Since this video signal is delayed by the time Haf by the delay line 41, the output of the delay line 41 is as shown in FIG. 7C, and the signal of FIG. 7B is delayed by the time Haf.

On the other hand, since the signal immediately before the boundary of the AF area 28 is sampled and held by the sample and hold circuit 42 in the video signal of FIG. 7B, the output of the sample and hold circuit 42 is shown in FIG. The waveform is as shown.

At the timing when the video signal shown in FIG.
Since the contact b is turned on except during the period Haf of the AF area 28, the output of the changeover switch 33, that is, the input signal of the HPF 33 is as shown in FIG.

That is, in this embodiment, the AF area 2
8 in each horizontal drive period, the signal fixed to the value of the signal immediately before the boundary of the AF area 28 is the HPF 3
In the state where the video signal is input to the AF area 28, the video signal is switched so as to be input to the HPF 33.

Therefore, in the present embodiment, even if the vertical luminance level in the AF area 28 changes greatly, in the present embodiment, the output from the sample hold circuit 42 according to the change in the luminance level. Even if the value is changed and the switching is performed at the boundary of the AF area 28, a smooth continuous signal can be input to the HPF 33.

Therefore, according to the present embodiment, if the AF
Even when the luminance level in the vertical direction in the area 28 greatly changes, occurrence of ringing can be sufficiently suppressed, and an AF evaluation value with a good S / N can be obtained. The other effects are the same as those of the first embodiment.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. In this embodiment, a selection means for selecting (switching) an input to an accumulation means for accumulating and adding the output signal of the filter means is provided at a subsequent stage of the filter means for extracting a predetermined frequency component (actually, a high frequency component). It is provided. In the present embodiment, the configuration of the AF processing circuit 14 in FIG. 1 is configured as shown in FIG. That is, in FIG.
1, the A / D conversion output is input to the HPF 33, and the output terminal of the HPF 33 is input to the integrating circuit 34 via the contact a of the switch 32.
In this case, the contact b of the switch 32 is, for example, grounded.

The CPU 15 switches the contact a of the switch 32 in the AF area 28 so that the contact a is turned on, and the output signal is integrated by the integration circuit 34 with almost no ringing. Next, the operation of the present embodiment will be described with reference to FIG.

The video signal shown in FIG. 9B is input to the AF processing circuit 14 in synchronization with the horizontal drive signal HD shown in FIG. 9A. In this case, as shown in FIG. It is always input to the HPF 33.

In this case, the AF area 2 shown in FIG.
Outside the period Haf 8, since the contact b is ON as shown in FIG.
The output of No. 3 is not input to the integrating circuit 34.

Then, as shown in FIG. 9C, during the period Haf of the AF area 28, the contact a of the changeover switch 32 is switched on so that the HPF 3
The high-frequency components passed through 3 are input to the integrating circuit 34 and integrated.

In this embodiment, since the input signal is not switched to the HPF 33 during the period Haf of the AF area 28, a video signal faithfully corresponding to the subject image is always input to the HPF 33. Therefore, it is possible to effectively prevent the ringing component from being mixed into the AF evaluation value without being suddenly switched to input a video signal to the HPF 33. Therefore, an AF evaluation value with a good S / N can be obtained, and highly accurate auto focus can be performed.

In FIG. 8, the changeover switch 3
Instead of 2, a gate circuit that opens and closes the gate may be used. In this case, the CPU 15 or the like may control the gate to open during the period Haf of the AF area.

Further, the video signal is not always input to the HPF 33, and the video signal is H at least for a period longer than the period Haf in which the period Haf is included.
You may make it input into PF33. It should be noted that embodiments and the like configured by partially combining the above-described embodiments and the like also belong to the present invention.

[Supplementary Notes] (1) Automatic focus adjustment for extracting a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performing automatic focus adjustment based on the frequency component of the extracted video signal In the apparatus, a video signal selecting means for selecting a video signal from a part of the auto focus detection area of the entire area of the imaging surface of the imaging device, and a video signal of the auto focus detection area selected by the video signal selection means And a filter for extracting a predetermined frequency component from the image signal, and selecting a video signal outside the automatic focus detection area by the video signal selecting means, and fixing a value of the video signal outside the automatic focus detection area to a median of the maximum value of the video signal. And an image signal level setting means.

(Conventional example and its problems) There has been conventionally known an automatic focusing device which focuses on the basis of a predetermined frequency component of a video signal obtained from a partial area of a screen (Japanese Patent Laid-Open No. Hei 8-122627). etc). However, in the above-described conventional apparatus, no special consideration is given to this point, and a discontinuous point of the video signal occurs at the boundary between the automatic focus detection area and the other area. Harmful ringing occurs in the output of the filter, and the accuracy of automatic focus detection deteriorates.

(Effect of Appendix (1)) The generation of harmful ringing of the filter at the end of the automatic focus detection area is suppressed.
Automatic focus detection accuracy is improved.

(2) An automatic focus adjusting device that extracts a predetermined frequency component while sequentially inputting a video signal output from an image sensor and performs automatic focus adjustment based on the frequency component of the extracted video signal. Video signal selecting means for selecting a video signal from a part of the auto-focus detection area of the entire area of the imaging surface of the image sensor; and a predetermined signal from the video signal of the auto-focus detection area selected by the video signal selection means. A filter for extracting a frequency component;
Brightness control means for performing control for setting a screen brightness value to a brightness target value, and a value of a video signal outside the automatic focus detection area, which is selected by the video signal selection means outside the automatic focus detection area. Video signal level setting means for fixing the brightness to the brightness target value.

(Conventional Example and Problems Thereof) Same as in the case of Appendix (1). (Effect of Supplementary Note 2) In addition to supplementary note (1), the difference between the video signal outside the automatic focus detection area and the video signal inside the automatic focus detection area can be reduced, and highly accurate automatic focus adjustment can be realized. it can.

(3) An automatic focus adjusting device that extracts a predetermined frequency component while sequentially inputting a video signal output from an image sensor and performs automatic focus adjustment based on the frequency component of the extracted video signal. Video signal selecting means for selecting a video signal from a part of the auto-focus detection area of the entire area of the imaging surface of the image sensor; and a predetermined signal from the video signal of the auto-focus detection area selected by the video signal selection means. A filter that extracts a frequency component, a photometric unit that detects an average brightness within the automatic focus detection area, and a video signal selection unit that is selected outside the automatic focus detection area,
A video signal level setting means for fixing a value of a video signal outside the automatic focus detection area to an average brightness value obtained by the photometric means;

(Conventional example and its problems) Same as appendix (1). In the invention according to the supplementary note (1) or the supplementary note (2), when the brightness is largely different between the central portion and the peripheral portion of the screen as in the case of shooting in backlight, etc. In some cases, the difference between video signals in the detection area cannot be reduced, and harmful ringing of the filter cannot be completely suppressed. (Effect of Supplementary Note (3)) In addition to the effect of Supplementary Note (2), even when there is a large difference in the brightness distribution of the screen such as in backlight, highly accurate automatic focus adjustment control can be performed.

(4) An automatic focus adjusting device that extracts a predetermined frequency component while sequentially inputting a video signal output from an image sensor and performs automatic focus adjustment based on the extracted frequency component of the video signal. For each horizontal line, sample and hold means for sampling and holding the video signal immediately before the automatic focus detection area, delay means for delaying the video signal, and selecting the video signal corresponding to the automatic focus detection area from the video signal output of the delay means Video signal selecting means, a filter for extracting a predetermined frequency component from the video signal in the automatic focus detection area selected by the video signal selecting means, and sample-holding a value of the video signal outside the automatic focus detection area. Means for setting a video signal value fixed to a video signal value sampled and held by the means. Dynamic focusing device.

(Conventional example and its problems) Same as appendix (1). (Effect of Supplementary Note (4)) In addition to the effect of Supplementary Note (2), the value of the video signal outside the automatic focus detection area is held at the value of the video signal immediately before the automatic focus detection area for each horizontal line.
The difference between the video signal outside the automatic focus detection area and the video signal inside the automatic focus detection area can be reduced, and highly accurate automatic focus adjustment can be realized.

(5) In an automatic focus adjustment device for extracting a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performing automatic focus adjustment based on the frequency component of the extracted video signal, A filter for extracting a predetermined frequency component of a video signal including a part of an automatic focus detection area in an entire area of the imaging surface of the image sensor; an output signal of the filter being input, and an output of the filter in the automatic focus detection area And an image signal selecting means for selecting a signal.

[0083]

As described above, according to the present invention, a predetermined frequency component is extracted while sequentially inputting a video signal output from an image sensor, and an automatic operation is performed based on the frequency component of the extracted video signal. In an automatic focus adjustment device that performs focus adjustment, a video signal selection unit that selects a video signal from a partial auto focus detection region among all regions of the imaging surface of the imaging device, and the video signal selection unit that selects the video signal. A filter for extracting a predetermined frequency component from the video signal in the auto focus detection area, and a value of the video signal outside the auto focus detection area which is selected by the video signal selection means outside the auto focus detection area. Video signal level setting means for fixing the median value of the maximum value to be obtained, an average brightness value of the auto focus detection area, a brightness target value, and the like to a predetermined level value. When a predetermined frequency component is extracted through a filter at the timing of the outgoing region, a sharp and large deviation amount between the value of the video signal outside the auto focus detection region and the video signal in the auto focus detection region is prevented. By doing so, it is possible to prevent the ringing component from being mixed into the filter, thereby preventing the accuracy of the autofocus detection from lowering.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electronic imaging device having a first embodiment of the present invention.

FIG. 2 is a diagram showing an AF area for performing automatic focus detection.

FIG. 3 is a timing chart for explaining the operation of the first embodiment.

FIG. 4 is a flowchart showing the contents of an imaging operation.

FIG. 5 is a timing chart for explaining the operation of the second embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of an AF processing circuit according to a third embodiment of the present invention.

FIG. 7 is a timing chart for explaining the operation of the third embodiment.

FIG. 8 is a block diagram illustrating a configuration of an AF processing circuit according to a fourth embodiment of the present invention.

FIG. 9 is a timing chart for explaining the operation of the fourth embodiment.

FIG. 10 shows A for autofocus in a conventional example.
Explanatory drawing of operation | movement which obtains F evaluation value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electronic imaging device 2 ... Zoom lens 3 ... Focus lens 4 ... Aperture 5 ... CCD 6 ... Imaging circuit 7 ... A / D converter 8 ... Memory 9 ... D / A converter 10 ... LCD 11 ... Compression / expansion circuit DESCRIPTION OF SYMBOLS 12 ... Recording memory 13 ... AE processing circuit 14 ... AF processing circuit 15 ... CPU 16 ... TG circuit 17 ... CCD driver 18-20 ... Motor drive circuit 21-23 ... Motor 24 ... Operation switch 25 ... EEPROM 26 ... Battery 28 ... AF area 31 Level setting circuit 32 Changeover switch 33 HPF 34 Integration circuit

Claims (4)

[Claims] 1. An automatic focus adjustment device for extracting a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performing automatic focus adjustment based on the frequency component of the extracted video signal. Video signal selecting means for selecting a video signal from a part of the auto-focus detection area of the entire area of the imaging surface of the imaging device; and a predetermined frequency from the video signal of the auto-focus detection area selected by the video signal selection means. A filter for extracting a component, and a video signal selected by the video signal selecting means outside the automatic focus detection area, and fixing a value of the video signal outside the automatic focus detection area to a median value of a maximum possible value of the video signal. An automatic focusing device comprising: level setting means; 2. An automatic focus adjustment device that extracts a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performs automatic focus adjustment based on the extracted frequency component of the video signal. Video signal selecting means for selecting a video signal from a part of the auto-focus detection area of the entire area of the imaging surface of the imaging device; and a predetermined frequency from the video signal of the auto-focus detection area selected by the video signal selection means. A filter for extracting components, a brightness control unit for performing control to set a brightness value of one screen of the video signal to a brightness target value, and a video signal selection unit that is selected outside the automatic focus detection area. Video signal level setting means for fixing a value of a video signal outside the automatic focus detection area to the brightness target value. 3. An automatic focus adjustment device that extracts a predetermined frequency component while sequentially inputting a video signal output from an image sensor, and performs automatic focus adjustment based on the frequency component of the extracted video signal. Video signal selecting means for selecting a video signal from a part of the auto-focus detection area of the entire area of the imaging surface of the imaging device; A filter for extracting a component, an average brightness detection unit for detecting an average brightness in the automatic focus detection region, and a video signal selection unit that is selected outside the automatic focus detection region, and the automatic focus detection region Video signal level setting means for fixing the value of the outside video signal to a predetermined value obtained by the average brightness detection means. Apparatus. 4. An automatic focus adjustment device for extracting a predetermined frequency component while sequentially inputting a video signal output from an image sensor and performing automatic focus adjustment based on the extracted frequency component of the video signal. Sample-and-hold means for sampling and holding a video signal immediately before the automatic focus detection area for each line; delay means for delaying the video signal; and selecting a video signal corresponding to the automatic focus detection area from the video signal output of the delay means. A video signal selection unit, a filter for extracting a predetermined frequency component from the video signal of the auto focus detection area selected by the video signal selection unit, and a filter selected by the video signal selection unit outside the auto focus detection area, The value of the video signal outside the auto focus detection area is fixed to the value of the video signal sampled and held by the sample and hold means. Automatic focusing apparatus characterized by comprising a video signal level setting means for.