JPH09107496A - Auto-focus device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the automatic focusing device which omits unnecessary focusing operation at the time of reduction of the contrast of an object in the in-focus state and prevents erroneous focusing and obtains a natural picture and performs the focusing processing to the next object in a short time. SOLUTION: A high frequency component detection means 6 which detects a high frequency component or a video signal, an iris quantity detection means 5 which detects the extent of opening of an iris 2, and a color temperature detection means 17 which detects the color temperature are provided. When the high frequency component detected by the high frequency component detection means 6 is small and the extent of opening of the iris detected by the iris quantity detection means 5 is small and the color temperature detected by the color temperature detection means 17 is high, the focus is fixed to infinity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device in an image pickup device such as a still camera and a video camera, and more particularly to a contrast (hill climbing) autofocus device.

[0002]

2. Description of the Related Art A conventional autofocus device will be described below with reference to FIGS. Here, FIG. 3 is a block diagram showing a schematic configuration of a conventional autofocus device, and FIG.
Is a high-contrast image D _{N with} respect to the focus lens position
FIG. 5 is an explanatory diagram showing a locus of high-frequency component data of the low-contrast image D _W , and FIG. 5 is a flowchart showing the operation of the microcomputer in the conventional autofocus device.

In FIG. 3, 1 is a focus lens and 3
Is C for photoelectrically converting the light S1 that has passed through the focus lens 1.
CDs 4 are signal processing units that perform video signal processing on the electric signals S2 from the CCD 3 and output the video signals S3 to a circuit in the subsequent stage not shown, and 6 is a luminance signal S7 separated and output by the signal processing unit 4. It is a high-frequency component detector that detects only higher-frequency components.

Reference numeral 7 is a microcomputer for outputting a lens movement instruction signal S9 based on the high frequency component data (focus data) S8 detected by the high frequency component detector 6, and 8 is a lens movement instruction signal from the microcomputer 7. The lens control unit is composed of a lens drive motor or the like for controlling the drive of the focus lens 1 based on S9.

In the above structure, the high frequency component detector 6 integrates the outputs of the band pass filter (hereinafter referred to as BPF) 6a for extracting only the signal in the required high frequency band from the luminance signal S7 and the output of the BPF 6a. And outputs the integrated data as high frequency component data S8.
And

In the conventional autofocus device having the above-described structure, the integrated high frequency component in the luminance signal of the video signal is input to the microcomputer 7 as focus data S8. Normally, the amount of high-frequency components when the focus lens 1 is moved back and forth draws a mountain shape having a peak at the in-focus position as shown in FIG.
When the focus shifts or the contrast of the subject becomes low, the focus shifts to the lower side. Therefore, the microcomputer 7 uses the focus data to perform hill climbing control.

Details of the mountain climbing control by the microcomputer 7 will be described below with reference to FIG. First, a lens movement instruction signal S9 is output to the lens controller 8 so as to move the focus lens 1 forward or backward in a fixed direction (step 101). Next, focus data is input from the high frequency component detector 6 (step 102), the latest focus data is compared with the immediately previous focus data (step 103),
If the latest focus data is larger, it is determined that the mountain is climbing, and if the latest focus data is smaller, it is determined that the mountain is descending (step 104).

When it is determined in step 104 that the mountain is climbing, the process returns to step 101 and the movement of the focus lens 1 is continued in the same direction. When it is determined in step 104 that the mountain is descending, the process proceeds to step 105, and it is determined whether or not the peak of the mountain is crossed. yet,
If the vertex is not crossed, the vertex is in the opposite direction,
Go to step 106. In step 106, an instruction is output to the lens controller 8 to reverse the moving direction of the focus lens 1, and the process returns to step 101.

If it is determined in step 105 that the vertex has been exceeded, it is determined that the focus is achieved, and the focus lens 1 is returned to the position where the vertex is observed (step 107).
A series of focusing operations is completed.

[0010]

However, in the above-described conventional autofocus device, since the in-focus position is detected only on the basis of the high frequency component of the signal output from the CCD 3, the image is defocused and the image is defocused. It is not possible to distinguish whether the high-frequency component is reduced due to blurring or the high-frequency component is reduced due to low contrast of the subject, and the subject is in focus only when the contrast is low. Even so, I will go searching for the mountain direction again and perform unnecessary focusing operation, so
There is a problem that it is difficult to obtain a good image as a captured image.

In the conventional hill-climbing autofocus device described above, the lower the contrast of the object, the more difficult it is to detect the focusing direction and the focusing position.
There is a high possibility that the focus lens 1 will be moved many times or that the focus will be incorrect. Further, by repeating the above operation, there is a problem that an actual captured image becomes unnatural and the focusing operation for the next subject is delayed.

The present invention has been made in view of such a point, and when the contrast of the subject becomes small while the object is in focus, unnecessary focusing operation is omitted, and erroneous focusing is prevented and natural focusing is performed. It is an object of the present invention to provide an autofocus device capable of obtaining a clear image and performing focusing processing on the next subject in a short time.

[0013]

SUMMARY OF THE INVENTION An autofocus device according to the present invention comprises a high frequency component detecting means for detecting a high frequency component of a video signal, an iris amount detecting means for detecting an opening / closing amount of an iris, and a color for detecting a color temperature. An autofocus device having a temperature detecting means, wherein the high frequency component detected by the high frequency component detecting means is small, and the opening / closing amount of the iris detected by the iris amount detecting means is narrowed, Further, when the color temperature detected by the color temperature detecting means is a high color temperature, the focus is fixed at infinity.

In the autofocus device of the present invention, when the high-frequency component is small, the iris is sufficiently narrowed, and the color temperature is high, the in-focus point is not shifted. , It determines that the subject is a low-contrast subject such as the sky or sea, and fixes the focus to infinity.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an autofocus device of the present invention will be described below with reference to FIGS. 1 and 2. The same parts as those of the above-mentioned conventional example are designated by the same reference numerals and the description thereof will be omitted. . Here, FIG. 1 is a block diagram showing a schematic configuration of the autofocus device of the present embodiment, and FIG. 2 is a flowchart showing the operation of the microcomputer in the autofocus device of the present embodiment.

In FIG. 1, 1 is a focus lens, 2
Is an iris for adjusting the light amount of the subject, 3 is a CCD for converting the subject light into an electric signal, 4 is a signal processing unit for performing a video signal processing and outputting a video signal S3 and a color signal S5 and a luminance signal S7, Reference numeral 5 denotes a Hall element which is provided near the iris 2 and outputs an iris evaluation value S4 indicating the degree of opening / closing of the iris 2, and 6 detects only high-frequency components from the luminance signal S7 separated and output by the signal processing unit 4. It is a high frequency component detector.

Further, 17 outputs white balance control data S6 generated so that the color component has a predetermined value on the basis of the color signal S5, to the signal processing unit 4, and the high frequency component from the high frequency component detector 6 Data (focus data) S8 and iris evaluation value S from the Hall element 5
4, and a microcomputer that outputs a lens movement instruction signal S9 based on the white balance evaluation value indicating the color temperature obtained from the white balance control data S6, and 8 is a focus based on the lens movement instruction signal S9 from the microcomputer 7. The lens control unit includes a lens drive motor that controls the drive of the lens 1.

In the autofocus device constructed as described above, the focus data S8 from the high frequency component detector 6 becomes extremely small and the iris evaluation value S4 is narrowed down from a predetermined reference value. If the white balance evaluation value is on the higher color temperature side than the predetermined reference value, the microcomputer 17
Determines that the subject is a low-contrast subject such as the sky or the sea, and outputs an instruction signal S9 to the lens controller 8 to move the focus lens 1 to infinity.

Details of the operation of the microcomputer 17 will be described below with reference to FIG. First,
Focus data S8 is input from the high frequency component detector 6 (step 201). Then, the white balance evaluation value indicating the color temperature is calculated from the white balance control data S6 (step 202), and the iris evaluation value is calculated from the output of the hall element 5 (step 203). Next, the focus data S8 is compared with a predetermined reference value (step 204), and if it is larger than the reference value, it is determined that the in-focus point is deviated (step 20).
5) Perform normal mountain climbing control.

If the focus data S8 is smaller than the reference value in step 204, it is determined that the contrast of the subject may have decreased, and step 2
Moving to 06, it is determined whether the white balance evaluation value is smaller than a predetermined reference value. When the white balance evaluation value is larger than the reference value (low color temperature side), it is determined that the in-focus point is shifted (step 205), and normal mountain climbing control is performed. If the white balance evaluation value is smaller than the reference value (on the high color temperature side), it is determined that the focus of the subject may have decreased, rather than the focus being deviated.

If it is determined in step 206 that the contrast of the subject may have decreased, the process moves to step 207 to determine whether the iris evaluation value is smaller than a predetermined reference value. When the iris evaluation value is larger than the reference value (open side), it is determined that the focal point is deviated (step 205), and normal hill climbing control is performed. When the iris evaluation value is smaller than the reference value (close side), it is determined that the subject is a low contrast object, and a lens movement instruction signal S9 is output to move the focus lens 1 to infinity, and a series of End the focusing operation.

[0022]

Since the autofocus device of the present invention is configured as described above, when the high frequency component is small, the iris is sufficiently narrowed, and the color temperature is high, The focus is determined to be a low-contrast subject such as the sky or sea instead of being out of focus, and the focus is fixed at infinity, so it is useless when the subject's contrast decreases while still in focus. The focusing operation can be omitted, erroneous focusing can be prevented, a natural image can be obtained, and the focusing process for the next subject can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an autofocus device of the present invention.

FIG. 2 is a flowchart showing the operation of a microcomputer in an embodiment of the autofocus device of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a conventional autofocus device.

FIG. 4 is an explanatory diagram showing loci of high-frequency component data of the high-contrast image D _N and the low-contrast image D _W with respect to the focus lens position.

FIG. 5 is a flowchart showing an operation of a microcomputer in a conventional autofocus device.

[Explanation of symbols]

 1 Focus Lens 2 Iris 3 CCD 4 Signal Processing Section 5 Hall Element 6 High Frequency Component Detector 8 Lens Control Section 17 Microcomputer

Claims (1)

[Claims] 1. An autofocus device comprising a high frequency component detecting means for detecting a high frequency component of a video signal, an iris amount detecting means for detecting an opening / closing amount of an iris, and a color temperature detecting means for detecting a color temperature. The high frequency component detected by the high frequency component detecting means is small, and the opening / closing amount of the iris detected by the iris amount detecting means is narrowed down, and detected by the color temperature detecting means. An autofocus device that fixes the focus to infinity when the color temperature is high.