JPH05236329A - Lens controller - Google Patents

Abstract

PURPOSE:To provide a lens controller which can stop a focusing lens at its in-focus point with high accuracy when a person, etc., are photographed. CONSTITUTION:A logical controller 120 decides an in-focus state when the difference between the high frequency component of the video signal extracted by a band-pass filter 112 and the extraction value is smaller than the threshold value TH2 and at the same time the difference between the blurring width of the edge part of a subject in a screen detected by a blurring width detecting circuit 114 end the detection value is larger then the threshold value TH1 respectively. Then, the controller 120 detects the color difference signals B-Y and R-Y of the screen center area based on the chrome signals B and R detected by a skin color information detecting part 110 and the luminance signal Y detected by a luminance information detecting part 111. When both signals B-Y and R-Y are kept within a skin color area set on a color vector, the value TH2 of the high frequency component difference value is set larger than the normal level with the value TH1 of the blurring width difference value set smaller than the normal level, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens control device having an automatic focusing device applied to an electronic image pickup device such as a video camera or an electronic still camera.

[0002]

2. Description of the Related Art Generally, in an electronic image pickup apparatus having a two-dimensional image pickup device such as a video camera, the sharpness of a screen is detected by a video signal of a subject, and the position of a focusing lens is set so that the sharpness is maximized. A method of controlling and focusing is used. As the sharpness, the strength of the high frequency component of the video signal extracted by the bandpass filter or the detection strength of the blur width at the edge portion of the subject obtained by differentiating the video signal by a differentiating circuit or the like is used.

When a normal subject is photographed, the sharpness is small when the subject is out of focus, increases as the subject is in focus, and reaches a maximum value when the subject is completely in focus. Conventionally, for controlling the focusing lens,
When this sharpness is small, move the focusing lens as fast as possible in the direction of increasing sharpness, gradually decrease this speed as it increases, and stop the focusing lens at the top of the sharpness of the mountain with high precision. Auto focus (hereafter referred to as hill climbing AF)
Is commonly used.

[0004]

However, in the conventional hill-climbing AF described above, for example, when a person or the like who is the most common as an ordinary subject is photographed, the image of the face is in a low contrast state, and the focusing lens is focused at the focal point. There is a problem that so-called hunting is likely to occur, which cannot be stopped accurately. this is,
This is mainly because the sharpness signal of the low-contrast subject changes little with respect to the amount of movement of the focusing lens, and it becomes impossible to satisfy the normal focusing condition.

The present invention has been made to solve the above conventional problems, and an object of the present invention is to provide a lens control device capable of accurately stopping a focusing lens at a focal point when a person or the like is photographed. To do.

[0006]

In order to achieve the above object, the present invention relates to an optical system movable in the optical axis direction for adjusting a focus, and an automatic system for controlling the optical system in an automatic focusing mode. In a lens control device having a focusing means, a detection means for detecting skin color information from a video signal, a determination means for determining whether or not a main subject is a person based on the detection signal of the detection means, and a determination result of the determination means And changing means for changing the focus determination value of the optical system in the automatic focus mode.

[0007]

With the above arrangement, the focus determination value of the optical system is changed when it is determined from the skin color information that the main subject is a person. Therefore, even when the image of the face is in a low contrast state, the focusing lens can be accurately stopped at the in-focus point.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a lens control device according to the present invention.

In FIG. 1, a front lens group (focusing lens group) 100 which is movable in the optical axis direction for focusing, a zooming lens group 101 which is movable in the optical axis direction for zooming, and a correction system A fixed lens group 102, a diaphragm 103 that can be opened and closed, and a solid-state image sensor 104 are arranged. Focusing lens group 1
00 and the zooming lens group 101 are motor 13 respectively.
The motors 132 and 133 are driven by the focus drive circuit 130 and the zoom drive circuit 131, respectively, under the control of the logic control circuit 120.

The aperture 103 is opened and closed by an ig meter 126, and the ig meter 126 is driven by an iris drive circuit 124 under the control of the iris control circuit 122.
The positions of the focusing lens group 100, the zooming lens group 101, and the diaphragm 103 driven in this way are detected by encoders 134, 135, and 128, respectively, and each detection signal is output to the logic control device 120.

The image formed by the optical systems 100 to 103 is converted into an electric signal by the solid-state image pickup device 104, and this image signal is amplified by the preamplifier 106 and subjected to image processing by the process circuit 108. It is output to the video output terminal, etc. In addition, the process circuit 10
The video signal processed by the image processing unit 8 is used as the skin color information detection unit 110.
And the preamplifier 106.
The video signal amplified by the iris control circuit 122
, Bandpass filter 112 and blur width detection circuit 114
Is supplied to.

The skin color information detecting section 110 includes the process circuit 1
The video signal processed by 08 detects color signals B and R for discriminating the skin color in the central area of the screen and outputs them to the logic control device 120, and the luminance information detecting section 111 causes the video processed by the process circuit 108. The signal detects the brightness in the screen and outputs the detection signal Y to the logic control device 120. The bandpass filter 112 is the preamplifier 1
The high frequency component of the video signal amplified by 06 is extracted,
The blur width detection circuit 114 differentiates the video signal amplified by the preamplifier 106 to detect the blur width of the edge portion of the subject in the screen. The respective detection signals of the bandpass filter 112 and the blur width detection circuit 114 are output to the peak detection circuit 118 via the gate circuit 116, the peak value is detected, and output to the logic control device 120.

The iris control circuit 122 controls the diaphragm 103 via the iris drive circuit 124 and the ig meter 126 so that the light amount on the light receiving surface of the solid-state image pickup device 104 becomes appropriate by the video signal amplified by the preamplifier 106. Open and close.

The logic control device 120 drives the focusing lens group 100 to drive the focusing lens group 100 in the normal automatic focusing mode so as to maximize the focusing degree of the image pickup screen in accordance with the input detection information. A drive control signal is output to the circuit 130, and the drive circuit 130 drives the motor 132 according to the signal.

Next, the operation of the logic controller 120 will be described with reference to FIGS. First, step 200 in FIG.
In the skin color information discrimination routine shown in (1), it is discriminated whether or not the subject in the central area of the screen is a person based on the detection signal of the skin color information detecting section 110. In this skin color information discrimination routine, as shown in FIG.
As shown in detail in FIG. 1, first, by the color signals B and R detected by the skin color information detecting unit 110 and the luminance signal Y detected by the luminance information detecting unit 111, color difference signals BY and RY in the central area of the screen. Is detected (step 300).

In the following step 302, this color difference signal B
It is determined whether -Y and RY are within the skin color area set on the color vector. It should be noted that this skin color area is set so that skin colors other than human beings are not detected as much as possible, like the area A shown in FIG. Then, the color difference signals BY and RY
If it is determined to be in this skin color area, "person information" is turned on (step 304), and if it is determined that it is not in the skin color area, "person information" is turned off (step 306).

Returning to FIG. 2, in step 202, a high frequency component of the video signal extracted by the bandpass filter 112 and an analog value indicating the blur width of the edge portion of the subject in the screen extracted by the blur width detection circuit 114. A / D
It is converted and captured, and then the process proceeds to the focusing motor speed setting routine (step 204). This focusing motor speed setting routine is executed in step 202.
The speed of the focusing motor is set based on the high frequency component of the A / D converted video signal and the blur width detection value of the edge portion of the subject in the screen. In the next step 206, the focus drive circuit 130 is controlled according to the speed and direction set in the focusing motor speed setting routine, and the process proceeds to the focus determination routine as shown in detail in FIG. 5 (step 208). In this focus determination routine, it is determined whether or not the focus state is achieved based on the degree of change in the high frequency component and the blur width.

In step 400 shown in FIG. 5, it is determined whether the "person information" set in the skin color information routine is on or off. If it is on, the process proceeds to step 402,
If it is off, the process proceeds to step 404.

In step 402, the threshold value TH1 of the difference value of the blur width detection values (blur width difference value) and the threshold value TH2 of the difference value of the high frequency component extracted values (high frequency component difference value) are set so that the person can easily focus. Is set, TH1 is set smaller than the normal value, and TH2 is set larger than the normal value. On the other hand, in step 404, since "personal information" is off, normal threshold setting is performed for each.

In the following step 406, it is judged whether or not the blur width difference value is larger than the threshold value TH1, and if it is larger, the process proceeds to the next step 408. Return to step 200.

In the next step 408, it is judged whether or not the high frequency component difference value is smaller than the threshold value TH2, and when it is smaller, it is considered to be in focus, and the routine proceeds to step 210 shown in FIG. On the other hand, when the high frequency component difference value is equal to or larger than the threshold value TH2, it is regarded as out-of-focus, and the process returns to step 200 shown in FIG.

Returning to FIG. 2, when it is determined that the degree of change is small in the focusing determination routine of step 208 and it is determined that the focusing is achieved, the processing proceeds to step 210 and the focusing motor 132 is stopped. In the following step 212, it is determined whether the in-focus state is maintained due to movement of the subject or the like based on the reduced blur width, and if the in-focus state is no longer maintained, the process returns to step 200 and the same processing is performed.

As described above, when a person or the like is photographed and the image of the face is in a low contrast state, the threshold values of the blur width difference value and the high frequency component difference value are changed to optimum values, respectively. It is possible to reduce the hunting phenomenon in and to accurately stop the focusing lens at the focal point.

FIG. 6 is a flowchart showing a focus determination routine according to another embodiment. In the above-described embodiment, when the skin color is detected, the difference values of the blur width and the high frequency component are used as the focus determination value, and the threshold values of these difference values are changed, but the invention is not limited to this. Figure 6
As described above, the absolute values of the blur width and the high frequency component may be used as the focus determination value in the flowchart, and the thresholds of these absolute values may be changed.

[0025]

As described above, the present invention has an optical system movable in the optical axis direction for adjusting the focus and an automatic focusing means for controlling the optical system in the automatic focusing mode. In the lens control device, a detection unit that detects skin color information from a video signal, a determination unit that determines whether or not the main subject is a person based on the detection signal of the detection unit, and automatic focusing according to the determination result of the determination unit. Since there is a changing means for changing the focus determination super-variation of the optical system in the mode and a speed setting means for setting the driving speed, the focusing lens can be used even when the image of the face is in a low contrast state. It can be stopped accurately at the focal point.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a lens control device according to the present invention.

FIG. 2 is a flowchart showing the operation of the logic control device of FIG.

FIG. 3 is a flowchart showing a detailed operation of a skin color information determination routine of FIG.

FIG. 4 is an explanatory diagram showing a skin color area in the skin color information determination routine of FIG.

FIG. 5 is a flowchart showing the details of the focus determination routine of FIG.

FIG. 6 is a flowchart showing a detailed operation of a focus determination routine according to another embodiment of the present invention.

[Explanation of symbols]

 100 Focusing Lens Group 104 Solid-State Image Sensor 110 Skin Color Information Detection Unit 111 Luminance Information Detection Unit 112 Band Pass Filter 114 Blurring Width Detection Circuit 120 Logic Control Device 130 Focus Drive Circuit 132 Focusing Motor

Claims (1)

[Claims] 1. A lens control device having an optical system movable in an optical axis direction for adjusting a focus, and an automatic focusing means for controlling the optical system in an automatic focusing mode. Detecting means for detecting whether or not the main subject is a person based on the detection signal of the detecting means, and the focus determination of the optical system in the automatic focusing mode according to the determination result of the determining means. A lens control device comprising: a changing unit that changes a value.