JPH0662305A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To surely stop a focus lens at the maximum level position of a clarity signal at all times without miscontrol in an automatic focusing device. CONSTITUTION:When the clarity signal declines from the maximum level value by a prescribed level, by a controller 12, the driving direction of the focus lens 5 is inverted by driving a pulse motor 18, the correspondence detection position of the focus lens 5 of the maximum level value of the clarity signal detected again is stored and when the clarity signal declines from the maximum level value again by the prescribed level, the focus lens 5 is stopped at the stored detection position by driving the pulse motor 18.

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 performing focusing control based on a video signal.

[0002]

2. Description of the Related Art In a device having a two-dimensional image pickup device such as a video camera, the sharpness of the screen is detected from the image signal of the subject image, and the focus lens position is controlled so that the sharpness is maximized to bring the focus into focus. The method of matching is adopted. The sharpness evaluation in this case is generally the intensity of the high frequency component of the video signal extracted by a band pass filter (hereinafter referred to as BPF) or the blur width of the video signal extracted by a differentiating circuit (the edge portion of the subject). Width) detection strength is used. When shooting a normal subject,
The strength of these high-frequency components and the blur width detection strength are small when the focus is out of focus, increase as the focus is in focus, and reach the maximum value when the focus is completely in focus.

For this reason, in the control of the focus lens, when the sharpness is small, the focus lens is moved as quickly as possible in the direction of increasing the sharpness,
As the sharpness increases, the focus lens is gradually moved slowly, and the focus lens is stopped accurately at the peak of the sharpness to bring the focus lens into focus. Then, when the sharpness in the in-focus state changes, it is determined that the subject has changed, restarting is performed, and the focus lens is stopped again at the top of the mountain to bring it into the in-focus state. Such a focus method is generally a mountain climbing autofocus (hereinafter referred to as mountain climbing AF).
I am calling.

Further, if a stepping motor is used to drive the focus lens, the position of the focus lens can be accurately detected.
As shown in, the focus lens position x1 when the sharpness signal has the maximum value is stored, and when the level of the sharpness signal drops by a predetermined threshold value TH1, the focus lens position x1 is returned to the stored focus lens position. The lens is stopped at the peak position of the sharpness signal.

Further, when performing hill-climbing AF, in order to determine whether or not the focus lens is being driven in the correct direction, a difference value of the blur width detection intensity is detected, and the difference value is continuously determined a predetermined number of times. When it becomes a negative value, it is judged that the mountain is going down, and in such a case, the driving direction of the focus lens by the driving means is reversed so that the mountain is climbed.

By performing the focusing control in this manner, automatic focusing can be performed even on an object having a low contrast and a low sharpness signal level, and the operability of a video camera for shooting a moving image is particularly improved. The focus control method has been adopted as an essential function in video cameras.

[0007]

In the above-described conventional focusing control, as shown in FIG. 11, when the focus lens is driven in the opposite direction at the skirt portion of the curve of the sharpness signal, it is true. There is a problem in that it becomes difficult to find the top of the mountain and the so-called blur stop may occur in which the lens stops before reaching the focal point.

Further, in order to judge whether or not the focus lens is being driven in the correct direction, the difference value of the blur width detection intensity is detected, and when the difference value becomes a negative value for a predetermined number of times in succession, the peak is detected. When it is determined that the control value is lower than the above, it is necessary to increase the memory capacity of the control device in order to store the past difference value, which causes a problem in terms of upsizing of the control device and manufacturing cost.

Further, the level of the sharpness signal is a predetermined threshold value T
When determining whether or not it has decreased by H1, the noise component in the sharpness signal increases for a subject under low illuminance, and due to the increase in the noise component, the level of the sharpness signal that has not actually decreased is erroneously determined. However, there is a problem in that the focus lens stops (stops blurring) before it reaches the in-focus point, and an object that is correctly in focus under normal illuminance is out of focus.

The present invention has been made on the basis of the present state of the focus control of this kind as described above, and the first purpose thereof is to always ensure the maximum position of the sharpness signal level without erroneous control. Another object of the present invention is to provide an automatic focusing device capable of stopping the focus lens.

A second object of the present invention is to provide an automatic focusing device capable of accurately determining the driving direction of the focus lens, reducing the memory capacity of the device, and realizing downsizing of the device. Especially.

Further, a third object of the present invention is to provide an automatic focusing device capable of accurately judging a decrease in the level of the sharpness signal even for a subject under low illuminance.

[0013]

In order to achieve the first object, the present invention is an automatic focusing device for performing focusing control based on a video signal, and an extraction for extracting a sharpness signal from the video signal. Means, drive means for driving the focus lens, position detection means for detecting the position of the focus lens, level detection means for detecting the level of the sharpness signal, and control means for controlling the drive means. When the level of the sharpness signal detected by the level detecting means falls below a maximum level value by a predetermined level, the control means reverses the driving direction of the focus lens via the driving means to detect the level. The position of the focus lens detected by the position detecting means in correspondence with the maximum level value of the sharpness signal detected again by the means is stored, and the sharpness is stored. The signal is again the maximum level value,
It is configured to stop the focus lens at the stored focus lens position via the drive means when the predetermined level is lowered.

Further, in order to achieve the second object,
The present invention is, in an automatic focusing device that performs focusing control based on a video signal, an extracting means for extracting a sharpness signal from the video signal, a driving means for driving a focus lens, and a position of the focus lens. Position detection means, level detection means for detecting the level of the sharpness signal, and control means for controlling the driving means, wherein the control means is the current difference value and the past difference of the sharpness signal. A locus of the difference value of the sharpness signal is detected from the locus of the value, and the driving direction of the focus lens by the driving unit is controlled by the locus.

Furthermore, in order to achieve the third object, the present invention detects the position of the focus lens, the extraction means for extracting the sharpness signal from the video signal, the driving means for driving the focus lens. Position detecting means, level detecting means for detecting the level of the sharpness signal, and control means for controlling the driving means, wherein the control means has a maximum level value detected by the level detecting means,
When the sharpness signal decreases by a predetermined level, an automatic focusing device that performs focusing control based on the sharpness signal so that the detection position of the position detection unit corresponding to the maximum level value is focused is It is configured to have setting means for setting the predetermined level according to the illuminance.

[0016]

With such a structure, in the present invention, the level of the sharpness signal extracted from the video signal by the extraction means is detected by the level detection means, and the focus lens is driven by the drive means controlled by the control means. The position of the focus lens is detected by the position detecting means. In this case, the control means reverses the drive direction of the focus lens via the drive means when the sharpness signal drops by a predetermined level from the maximum level value detected by the level detection means. Then, the control means stores the position of the focus lens detected by the position detection means in correspondence with the maximum level value detected again by the level detection means, and again when the sharpness signal drops by a predetermined level from the maximum level value. The focus lens is accurately stopped at the stored focus lens position via the drive means, and focusing control without erroneous control is performed.

Further, in the present invention, the sharpness signal is extracted from the video signal by the extraction means, the focus lens is driven by the drive means controlled by the control means, the position of the focus lens is detected by the position detection means, and the level is detected. The detection means detects the level of the sharpness signal. In this case, the control means can easily detect the locus of the difference value of the sharpness signal from the loci of the current difference value of the sharpness signal and the past difference value of the sharpness signal with a small memory operation, and use the locus. , Controlling the drive direction of the focus lens by the drive means.

Further, according to the present invention, the sharpness signal is extracted from the video signal by the extraction means, the focus lens is driven by the drive means controlled by the control means, the position of the focus lens is detected by the position detection means, and the level is detected. The detection means detects the level of the sharpness signal.
Then, when the sharpness signal is lowered by a predetermined level from the maximum level value detected by the level detection means, the control means controls the drive means so that the detection position of the position detection means corresponding to the maximum level value is focused. Focus control is performed based on the sharpness signal so that In this case, since the setting means sets the predetermined level according to the illuminance of the subject, automatic focusing without erroneous control due to noise at low illuminance is performed.

[0019]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic diagram showing a schematic configuration of a first embodiment of the present invention. In FIG. 1, 1 is a fixed front lens, the optical axis of which is aligned with the front lens 1, and a motor drive is provided. In this order, the zoom lens 2 that is controlled to move on the optical axis by the motor 16 that is driven by 13 to perform a zoom operation, and the diaphragm 3 whose opening is automatically controlled by the drive circuit 14 and the ig meter 17 are arranged in this order. It is arranged in. Similarly, the optical axis is aligned with the diaphragm 3, and the fixed third group lens 4 and the focus lens 5 that is controlled to move on the optical axis by the stepping motor 18 driven by the motor drive 15 to perform focus adjustment. Are arranged in this order. A zoom encoder 19 for detecting focal length information of the zoom lens 2 is attached to the zoom lens 2, and an aperture encoder 20 for detecting the aperture value of the aperture 3 is attached to the aperture 3.
Is attached, and the focus lens 5 is provided with a focus encoder 21 for detecting position information of the focus lens 5. Further, a CCD 6 is arranged to face the focus lens 5, and a preamplifier 7 is connected to the CCD 6. The preamplifier 7 is provided with a video signal processing circuit 8 for processing a video signal and a gate processing of a video signal. The gate circuit 10 and the aperture control circuit 9 that controls the drive circuit 14 so that the level of the video signal matches a predetermined level are connected in parallel with each other.

A band pass filter (BPF) 11 for extracting a high frequency component (sharpness signal) necessary for focus detection is connected to the gate circuit 10, and B
The output terminal of the PF 11 is connected to the control device 12 that controls the overall operation. On the output side of this control device 12,
The motor drive 15 and the motor drive 13 are connected, and the focus encoder 21 and the aperture encoder 20 are connected.
A zoom encoder 19 is connected to the input side of the control device 12. The control device 12 has a memory (not shown) for storing a control program, a calculation result, etc. built therein or attached externally. As will be described later, the control device 12 controls the stepping motor 18 via the motor drive 15 based on the position information of the focus lens 5 and the sharpness signal discharged from the video signal.

FIG. 2 is a flowchart of the hill-climbing AF operation of the first embodiment, and FIG. 3 is an explanatory diagram of the hill-climbing AF operation of the first embodiment. As described above, in the first embodiment, since the stepping motor 18 is used to move the focus lens 5, it is possible to obtain highly accurate focus position information by counting the number of pulses. In this specification, this focus position information will be referred to as an address.

Step S201 of the flowchart in FIG.
In, the count value n for counting how many times the sharpness signal fv crosses the mountain (maximum value) is set to the initial value 0. In step S202, the sharpness signal fv and the address ads are fetched, and the hill-climbing AF operation is started. In step S203, the sharpness signal fv is compared with the maximum value fvp of the sharpness signal, and when the sharpness signal fv is larger, it is determined to be in the process of 1 in FIG.
In step 4, the sharpness signal fv is set to the maximum value fvp of the sharpness signal, and the address ads at that time is set to the maximum value fv of the sharpness signal.
An address adsp corresponding to p is set to the value fvp, ads
The value p is stored in the memory, the process proceeds to step S205, and the stepping motor 18 that drives the focus lens 5 returns to step S202 with the normal rotation.

On the other hand, in step S203, the sharpness signal f
If it is determined that v is smaller, the process proceeds to step S206, the absolute value of the difference value between the sharpness signal fv and the maximum value fvp of the sharpness signal is calculated, and this calculated value is the threshold TH1.
A determination of greater than is made. Step S20
If the decision result in 6 is NO, it is decided that the process is in 2 of FIG. 3, and the routine proceeds to step S205, where the stepping motor 18 for driving the focus lens 5 returns to step S202 while keeping the normal rotation.

Further, the determination result of step S206 is YE.
If it is S, it means that it is in the state of 3 in FIG. 3, so in step S207 the stepping motor 18 is reversely driven, and in step S208 n is incremented assuming that the mountain has been overcome, and in step S209 n is 2 or more. Detect whether or not. If it is determined in step S209 that the number is not 2 or more, the position is not 4 in FIG.
10, the sharpness signal fv at that time is set to the maximum value fvp of the sharpness signal, and the address value ads is set to the address value adsp corresponding to the maximum value fvp of the sharpness signal fvp.
The p and adsp are stored in the memory, and the hill climbing operation is performed again from the position 3 in FIG. Then, after that, in step S209
If the result of the determination is YES, it means that the position is at the position 4 in FIG. 3, so in step S211, the address ads at that time is the maximum value fv of the stored sharpness signal.
It is determined whether it is the same as the address value adsp corresponding to p. If the decision result in the step S211 is NO, the process advances to a step S212, the stepping motor 18 is rotated forward until the decision result in the step S211 becomes YES, and the in-focus point is focused in the step S213.

In this way, in the first embodiment, the control device 12 carries out the focusing control for stopping the focus lens 5 at the maximum value position by overcoming the peak (maximum value) of the sharpness signal twice. As a result, the focus position can always be detected with high accuracy and focus control of the focus lens can be reliably performed without causing blurring at the skirt portion of the sharpness signal curve.

FIG. 4 is a hill-climbing AF of a modification of the first embodiment.
3 is an explanatory diagram of the operation, and in FIG. 3, the decrease amount from the first peak level (override amount) and the decrease amount from the second peak level (overpass amount) were constant at TH1, but In the example, the first decrease amount TH1 is set to be larger than the second decrease amount TH2. The other parts are the same as those in the first embodiment described above. In this way, by decreasing the second decrease amount TH2,
Since the amount of blurring when the mountain is climbed the next time is reduced, the focus can be controlled more smoothly and the blurring can be prevented more reliably.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 5 is a flowchart showing the operation of the main part of the second embodiment.

This second embodiment has the same configuration as the first embodiment already described with reference to FIG. 1, and the controller 12 controls the current difference value and the past difference of the sharpness signal. A trajectory of the difference value of the sharpness signal is detected from the trajectory of the value, and the driving direction of the focus lens 5 by the stepping motor 18 is controlled by the trajectory.

In the second embodiment, the difference value of the sharpness signal output from the BPF 11 for a predetermined length period, for example,
The difference fvn-1-fvn between the previous value and the current value of the sampling values obtained by capturing the sharpness signal at a predetermined time interval is des, and the locus of the difference value of the sharpness signal up to the previous time is ddes,
Using k and h as constants, the locus ddes of the difference value of the sharpness signal up to this time for a predetermined length period is calculated by the equation (1).

[0031]

[Mathematical formula-see original document] ddes = k * ddes + h * des In this way, in the second embodiment, the locus ddes of the difference value of the sharpness signal for the predetermined length period is changed from the past to the locus d.
Des and the difference value des of the current sharpness signal are represented by k:
It is obtained by adding at the rate of h.

In the second embodiment, when the locus ddes of the difference value of the sharpness signal from the past is smaller than the predetermined threshold value TH1 in step S501 of the flowchart of FIG. 5, the driving direction of the focus lens is mountainous. It is determined that the direction is the downward direction, the process proceeds to step S502, the stepping motor 18 is controlled by the control device 12, the driving direction of the focus lens 5 is reversed, and the step S50 is performed.
At 3, the hill climbing AF operation is performed.

As described above, according to the second embodiment, it is not necessary for the control device 12 to store the difference values of many sharpness signals in the past, and the sharpening can be easily performed by performing the calculation of the equation (1). The direction in which the peak of the frequency signal exists can be known, the memory capacity of the control device 12 can be reduced, and the control device 12 can be downsized.

As a second embodiment, when obtaining the locus ddes of the difference value of the sharpness signal from the past for a predetermined length period, the locus ddes of the difference value of the sharpness signal from the past.
And the case where the current difference value of the sharpness signal is set to des: ratio of k: h has been described, the present invention is not limited to the embodiment, and the length of the period for calculating the difference value of the sharpness signal. Depending on, this ratio can be chosen to be the optimum ratio.

Next, a third embodiment of the present invention will be described with reference to FIGS. 6 to 10. Here, FIG. 6 is a schematic diagram showing the schematic configuration of the third embodiment, FIG. 7 is a flowchart showing the operation of the third embodiment, and FIG. 8 is a hill-climbing AF of the third embodiment.
FIG. 9 is an explanatory diagram of the operation, and FIG. 9 is a characteristic diagram showing a sharpness signal curve corresponding to a change in illuminance.

As shown in FIG. 6, in the third embodiment, a zoom lens (magnifying lens) whose movement is controlled on the optical axis by a driving motor 107 via a fixed front lens 101 and a motor driver 108. The fixed lens 103 and the fixed lens 103 are arranged so that their optical axes coincide with each other in this order. The fixed lens 103 is aligned with the optical axis, and the pulse motor 109 is controlled to move on the optical axis via the motor driver 110. Focus lens 1 for focus adjustment and focal plane correction by zooming
04 is arranged. An image pickup device (CCD) 105 on which an optical image is formed is arranged facing the focus lens 104. The image pickup device 105 converts an optical signal of a subject into an electric signal and connects it to the image pickup device 105. The electric signal is input to the amplified amplifier 106, and the electric signal is amplified by the amplifier 106. A camera process circuit 113 is connected to the amplifier 106. In the camera process circuit 113, a luminance signal is separated from an electric signal, and the separated luminance signal is a BPF (bandpass filter) connected to the camera process circuit 113. It is input to 112. The BPF 112 detects a sharpness signal from the luminance signal, and the detected sharpness signal is the control device (microcomputer) 1 connected to the BPF 112.
11 is input.

A motor driver 108 and a motor driver 110 are connected to the output side of the microcomputer 111,
Further, an output terminal of an encoder 114 for detecting the position of the focus lens 104 and an illuminance information terminal of the camera process circuit 113 are connected to the input side of the microcomputer 111. This illuminance information terminal is a diaphragm or AGC not shown.
The illuminance information of the subject determined by the information of the circuit is output. The microcomputer 111 drives the motor driver 110 to control the focus lens 104 based on the sharpness signal from the BPF 112, the illuminance information from the camera process circuit 113, and the position information of the focus lens 114 from the encoder 114. If the zoom switch is operated, the zoom lens 102 is also controlled.
The control device 111 has a memory (not shown) for storing a control program, a calculation result, etc. built therein or attached externally.

Next, the operation of the third embodiment will be described with reference to the flowchart of FIG. When the hill-climbing AF operation is started, direction determination is performed in step S701, and when the focus direction is determined, in step S702, the current sharpness level Esp and the current focus lens 11 are determined.
The position information of No. 4 is stored. Then, step S7
In 03, the focus lens 114 is driven in the focusing direction determined in step S701. While the focus lens 114 is being driven, the stored sharpness signal level is compared with the current sharpness signal level in step S704. If the current sharpness signal level is high, step S701 is performed. Then, the sharpness signal and focus lens position information are stored again. This operation corresponds to the operation indicated by A in FIG.

Next, the determination result of step S704 is YE.
In S, when the level of the current sharpness signal is smaller than the level of the stored sharpness signal, step S705.
Then, the illuminance of the subject is determined based on the illuminance information from the camera process circuit 113, and when it is determined that the illuminance is low, in step S706, the overshoot level (overpass amount) Es0 as shown in FIG. The value Es01 for low illuminance, which is larger than the value Es02 for general illuminance, is set (corresponding to the threshold TH1 in the first embodiment). If it is determined in step S705 that the illuminance is not low, the value E for general illuminance is set in step S707 as shown in FIG.
Set s02.

Then, in step S708, the difference between the stored sharpness signal level Esp and the current sharpness signal level Esn is compared with the previously set overshoot level Es0, and Esp-Esn> If it is not Es0, the process returns to step S703. In step S708, E
If it is determined that sp-Esn> Es0, the process advances to step S709 to return the focus lens 104 to the stored lens position, and the focus state is set in step S710, and the focus lens 104 is stopped. This series of operations is indicated by B in FIG.

FIG. 9A is a characteristic diagram of the sharpness signal under normal illuminance, where a predetermined threshold value E is calculated from the maximum value of the sharpness signal.
When it is detected that the level of the sharpness signal has decreased by SO2, the driving direction of the focus lens 104 is reversed, and the in-focus point can be easily detected. However, as shown in FIG. 2B, when the subject is in a low illuminance state,
If the noise component in the sharpness signal becomes large and the noise component reduces the level of the threshold ESO2 when the point exceeds the Pe point, the Pe point is erroneously determined as the in-focus point and the focusing lens is reached before reaching the correct in-focus point. May stop. However, according to the third embodiment, the overshoot level Es01 is set to the large threshold value ESO2 when the illuminance is low, so that it is possible to move the focus lens 104 to a correct focus without being affected by noise.

Generally, when the overshoot level is increased, the degree of blurring is increased and the image becomes unsightly. However, when noise is increased in a low illuminance state, the image is originally deteriorated, and even if the overshoot level is increased, the image is deteriorated. The quality of the will not be further reduced.

As described above, according to the third embodiment, it is possible to prevent the erroneous focusing operation due to noise in the low illuminance state of the subject.

[0044]

As described above, according to the present invention, when the sharpness signal falls below the maximum level value by a predetermined level, the control means controls the drive means to reverse the drive direction of the focus lens. Drive
When the maximum level value is detected again, the detection position of the focus lens corresponding to the maximum level value is stored, and at the position where the sharpness signal is again lowered by a predetermined level from the maximum level value, the control device causes the driving means to drive the maximum level value. Since the focus lens is stopped at the memorized position, the focus position can always be detected with high accuracy and the focus lens can be reliably controlled without causing blurring at the skirt of the sharpness signal curve. become.

Further, according to the present invention, the control means detects the locus of the difference value of the sharpness signal from the loci of the current difference value and the past difference value of the sharpness signal, and according to the locus,
Since the drive direction of the focus lens is controlled, the direction in which the peak of the sharpness signal exists can be easily known, the memory capacity of the device can be reduced, and the device can be downsized.

Furthermore, according to the present invention, when the sharpness signal falls below the maximum level value by a predetermined level, the focus control is performed based on the sharpness signal so that the detection position of the focus lens corresponding to the maximum level is focused. In the automatic focusing apparatus for performing the above, since the setting unit sets the predetermined level according to the illuminance of the subject, it is possible to prevent an erroneous focusing operation due to noise in the low illuminance state of the subject.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart of a hill-climbing AF operation according to the first embodiment of this invention.

FIG. 3 is an explanatory diagram of a hill-climbing AF operation according to the first embodiment of this invention.

FIG. 4 is an explanatory diagram of another hill-climbing AF operation according to the first embodiment of this invention.

FIG. 5 is a flowchart of a main part of a hill-climbing AF operation according to the second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a schematic configuration of a third embodiment of the present invention.

FIG. 7 is a flowchart of a hill-climbing AF operation according to the third embodiment of this invention.

FIG. 8 is an explanatory diagram of a hill-climbing AF operation according to the third embodiment of the present invention.

FIG. 9 is a characteristic diagram of a sharpness signal curve corresponding to subject illuminance.

FIG. 10 is an explanatory diagram of a conventional hill-climbing AF operation.

FIG. 11 is an explanatory diagram of blur stop at the skirt of the conventional sharpness signal curve.

[Explanation of symbols]

 1 Front Lens 2 Zoom Lens 3 Aperture 4 Fixed Third Group Lens 5 Focus Lens 6 CCD 7 Preamplifier 8 Video Signal Processing Circuit 9 Aperture Control Circuit 10 Gate Circuit 11 BPF 12 Controller 13 Motor Drive 14 Drive Circuit 15 Motor Drive 16 Motor 17 ig meter 18 stepping motor 19 zoom encoder 20 aperture encoder 21 focus encoder 101, 103 fixed lens 102 zoom lens 104 focus lens 105 image sensor 106 amplifier 107, 109 drive motor 108, 110 motor driver 111 microcomputer 112 BPF 113 camera process circuit

Claims (3)

[Claims] 1. An automatic focusing device for performing focusing control based on a video signal, an extraction means for extracting a sharpness signal from the video signal, and a drive means for driving a focus lens.
Position control means for detecting the position of the focus lens, level detection means for detecting the level of the sharpness signal, and control means for controlling the drive means, the control means, the level detection means When the level of the sharpness signal to be detected falls by a predetermined level below the maximum level value, the driving direction of the focus lens is inverted via the driving means, and the maximum of the sharpness signal detected again by the level detecting means is increased. The position of the focus lens detected by the position detection unit corresponding to the level value is stored, and when the sharpness signal again falls below the maximum level value by a predetermined level, the focus lens is moved through the drive unit. An automatic focusing device configured to stop at a stored focus lens position. 2. An automatic focusing device for performing focusing control based on a video signal, an extraction means for extracting a sharpness signal from the video signal, and a driving means for driving a focus lens.
It has a position detection means for detecting the position of the focus lens, a level detection means for detecting the level of the sharpness signal, and a control means for controlling the driving means, and the control means controls the sharpness signal. It is configured to detect the trajectory of the difference value of the sharpness signal from the trajectory of the current difference value and the past difference value, and control the drive direction of the focus lens by the drive unit by the trajectory. Automatic focusing device characterized by. 3. Extraction means for extracting a sharpness signal from a video signal, driving means for driving a focus lens, position detecting means for detecting the position of the focus lens, and level for detecting the level of the sharpness signal. It has a detection means and a control means for controlling the drive means, the control means, from the maximum level value detected by the level detection means,
When the sharpness signal decreases by a predetermined level, an automatic focusing device that performs focusing control based on the sharpness signal so that the detection position of the position detection unit corresponding to the maximum level value is focused is An automatic focusing device, comprising: setting means for setting the predetermined level according to the illuminance of the.