JPS63151180A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a focusing operation by removing a part, detected by a high luminance detecting part and by a detecting part for the circumference of a high luminance part, from a video signal, necessary for an automatic focusing operation. CONSTITUTION:The video signal is divided into several blocks beforehand, and it is detected by a high luminance part detection circuit 13 whether a high luminance part exists or not in the respective blocks. For instance, when the blocks A1 and A2 are decided to be the high luminance parts, the block B1 adjacent to A1 and the block B2 adjacent to A2 are detected as the circumferences by a high luminance circumference detection circuit 14, and the parts of B1, A1, A2, B2 are removed from the video signal, and the blur of the circumference of a high luminance part is also removed. Because the signal after this correction, comes to be the input signal of a high frequency component detection circuit 7, an unnecessary high frequency component does not appear, and the correct automatic focusing operation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic focus adjustment device for a television camera.

BACKGROUND OF THE INVENTION In recent years, demand for television cameras has been rapidly increasing due to the spread of camera-integrated video tape recorders and miniaturization and weight reduction. The automatic focus adjustment device makes it easier to handle television cameras and contributes to their further widespread use.

The conventional automatic focus adjustment device will be explained below.0 Figure 3 shows a block diagram of the conventional automatic focus adjustment device, in which 1 is a lens, 2 is an electrical signal that converts the subject image formed on the imaging surface. 3 is a preamplifier that amplifies the output of the image sensor 2; 4 is the preamplifier 3;
6 is a sync signal generator that generates various sync signals and blanking signals; 6 is the image sensor 2;
This is an image sensor drive circuit that drives the image sensor. 7 is a high frequency component detection circuit that detects a high frequency component of the video signal obtained from the image sensor 2; for example, center frequency 1 (MH2);
This is a bandpass filter. 8 is a reference frequency generator that supplies a reference frequency to the motor drive circuit 11 and the synchronous detection circuit 10 and finely moves the lens focus adjustment device using the reference frequency;
9 is a reference frequency component detection circuit that detects a reference frequency component included in the high frequency component; 10 is a synchronous detection circuit that compares the detected reference frequency component with a reference frequency and detects the phase and amplitude of the reference frequency component. , the synchronous detection circuit 1
The output of the lens 1 drives the focus adjustment device of the lens 1 by the motor 12 via the motor drive circuit 11 so that the high frequency component is maximized.

The operation of the conventional automatic focus adjustment device configured as described above will be described below.

The motor 12 uses the reference frequency supplied by the reference frequency generator 8 to finely move the focus adjustment device of the lens 1 to change the focus of the lens to an extent that cannot be detected by the eye. As a result, the high frequency component included in the output signal of the image sensor 2 undergoes amplitude modulation at the reference frequency and has the same amount as the reference frequency. The high frequency component is detected by a high frequency component detection circuit 7, and the reference frequency component included therein due to focus change is detected by a reference frequency component detection circuit 9. The polarity and amplitude of the signal are detected by a synchronous detection circuit 10, and the signal is sent to a motor drive circuit 11. Then, at 12, the focus adjustment device of the lens 1 is driven so that the high frequency component of the output signal of the image sensor 2 is maximized.

The principle of detecting the driving direction of the motor 12 will be explained in more detail using FIG. 4. The vertical axis represents the amplitude of high frequency components included in the output signal of the image sensor 2, and the horizontal axis represents the position of the focus adjustment device of the lens 1. "Near" is a position where a close-distance subject is focused, and "far" is a position where a far-distance subject is focused.

Now, if we consider a case where an image of a subject is taken at a distance, the focus adjustment device of the lens 1 is set at the distance.

When the object is at a position corresponding to , it is in focus and the amplitude of the high frequency component is at its maximum. Even if the focus adjustment device moves closer or further away from the above position, the amplitude of the high frequency component will decrease. This becomes a kind of chevron characteristic as shown in Figure 4.

On the other hand, J, 1lL2 T &5 indicates the movement of the focus adjustment device due to fine movement at the reference frequency of the motor 12 at each lens position. Due to the change in focus associated with the slight fluctuation shown in a, the high frequency component is increased.

A signal receiving amplitude modulation such as , will have a reference frequency component. Further, the slight fluctuation shown in 1□ undergoes amplitude modulation shown in b2. As is clear from the amplitude modulation, . Therefore, a reference frequency component is detected from high frequency components subjected to amplitude modulation such as b, and the reference frequency component is synchronously detected with the reference frequency to detect the amplitude and phase of the component. If the focus adjustment device of the lens 1 is driven in the direction of arrow C4 by the motor 12 using the detection signal, then in the case of b2, it will be driven in the direction of arrow C2. Therefore, the motor 12 always drives the focus adjustment device to the position where the high frequency component is maximized, and a focused state is obtained.

However, if the subject has a high brightness, even if the subject is not in focus, high frequency components will be output and it will be determined that the subject is in focus. is removed, and the necessary frequency components are extracted from the remaining signal.

Problems to be Solved by the Invention However, with the above configuration, when blurring occurs due to the high-brightness areas around the high-brightness subject, the high-frequency components of the blurry area may cause the image to be out of focus. However, there is a problem in that it is impossible to avoid determining that the camera is in focus even when the camera is in focus.

(See FIG. 6) In view of the above-mentioned problems, the present invention eliminates the high-brightness portion and its peripheral portion from the necessary image sensor output signal, thereby preventing malfunctions in the focusing operation.

Means for Solving the Problems In order to solve the above problems, the apparatus of the present invention includes a high-brightness detection section that detects a high-brightness portion in a signal obtained from an image sensor, and a high-brightness detection section that detects a high-brightness portion in a signal obtained from an image sensor. the area detected by the high-brightness detection unit and the high-brightness area detection unit from the video signal necessary for autofocus operation; It was designed to do so.

Effect of the Invention With the above-described configuration, the present invention makes it possible to remove blurring around high-brightness areas from the video signal necessary for autofocus operation, thereby eliminating the presence of high-frequency components due to blurring components around high-brightness objects. Second, automatic focusing can be performed using high-frequency components in areas other than high-brightness areas.

Embodiments Hereinafter, automatic focus adjustment devices according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the invention. In FIG. 1, 13 is a circuit that detects a high-brightness part in the signal obtained from the image sensor 2, and 14 is a circuit that detects the periphery of the high-brightness part detected by the high-brightness part detection circuit 13. . Note that the blocks numbered 1 to 12 are the same as those in FIG.

The automatic focus adjustment device of this embodiment configured as described above will be described below with reference to FIGS. 1 and 2.

FIG. 2 shows the relationship among the video signal obtained from the image pickup device, the signal of the high brightness area and its surrounding area detected by the circuits 13 and 14, and the corrected signal.

The circuit 13 spatially divides the video signal into several blocks and detects whether or not there is a high brightness section within each block.

As shown in FIG. 2, blocks M and M2 are determined to be high brightness areas. At this time, by the 14 peripheral detection circuits,
B4, which is next to M2, and 82, which is next to M2, are detected as peripherals, and in the end, B4. M4. Mu2. B
2 will be removed, and as shown in the corrected signal, blurring around the high brightness area will also be removed.

Since this corrected signal becomes the input signal to the high frequency component detection circuit 7, unnecessary high frequency components are not generated and correct autofocus operation can be performed. It should be noted that the same effect can be achieved even if the removal of the high brightness area and its surrounding area is performed after detecting the high frequency component.0 Effects of the Invention According to the present invention, as described above, Even in the case of a subject that has blurring around a high-brightness part, it is possible to achieve the effect that automatic focusing can be performed correctly using a video signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an automatic focus adjustment device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing changes in the waveform of a video signal in this embodiment, and FIG. 3 is a block diagram of a conventional automatic focus adjustment device. , FIG. 4 is a characteristic diagram of high frequency components in the conventional example, and FIG. 6 is a waveform diagram showing changes in the waveform of the video signal in the conventional example. ...Image sensor, 7.
...High frequency component detection circuit, 9 ...Reference frequency component detection circuit, 1o ... Synchronous detection circuit, 13 ... High brightness part detection circuit, 14・・・・・・
...High brightness peripheral detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 4 Figure 5 @

Claims (1)

[Claims] A frequency component having one or more different bands is detected from a signal obtained from an image sensor on which an object is imaged on the light receiving surface, and a lens focus adjustment device is driven so that the amplitude of the frequency component is maximized. An automatic focus adjustment device,
a high-brightness detection section that detects a high-brightness portion of a subject image; and a planar peripheral area of the high-brightness portion detected by the high-brightness detection section and the high-brightness portion are removed from the signal obtained from the image sensor. An automatic focus adjustment device characterized in that the signal obtained from the image sensor is the signal obtained from the image sensor.