JPS6141277A - Automatic focus controller - Google Patents

Abstract

PURPOSE:To avoid a malfunction of an automatic focus controller by dividing the video signals passed through plural BPFs of different bands into a speed control system and a direction indication system with addition of a filter peak detecting circuit and an adder circuit to both systems respectively and also driving a lens focus control system with the outputs of both circuits. CONSTITUTION:A filter detection NAM circuit 21 detects the peak of each filter, and the effects of the depth can be avoided by transmitting the outputs of amplifiers 15-17 through the circuit 21. Here a motor driving circuit 8 is controlled by a speed control circuit 22 so that the driving speed of a motor 5 is set at a low level toward a focal point D0 compared with a case where an out-of-focus degree is large to the point D0. Thus the focusing control of a lens 1 is carried out smoothly. The output of an adder circuit 18 undergoes the synchronizing wave detection through a synchronizing wave detection circuit 19 and is turned into a switch input to the focus direction. Then the circuit 8 is controlled by a switch circuit 20, and the focusing direction is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention detects a high frequency component of a signal obtained from an image sensor of a television camera, and drives a lens focusing device so that the amplitude of the high frequency component is maximized. This invention relates to an automatic focusing device.

Configuration of conventional example and its problems In conventional technology, as in Utility Model Publication No. 40-26568, high frequency components are detected by passing a signal obtained from an image sensor through a band pass filter, and this detected signal is There is a method of driving a lens focusing device to achieve this. However, when the lens pattern is wide open or close to it, and the distance to the subject is misaligned with the position of the lens focusing device, the image on the light receiving surface of the image sensor is blurred and high frequency components is almost non-existent. Therefore, the automatic focusing device malfunctions.

As an improvement, Japanese Patent Application Laid-open No. 188966/1983
A video signal obtained from the image sensor is input to a plurality of bandpass filters with different bands, and the output signals of each of the bandpass filters are processed, and the amplitude of the processed output signal is maximized. It is designed to drive a focusing device. That is, if we assume a bandpass filter BPF with a low center frequency, and BPF2 with a high center frequency,
When the output signal of BPF2 is small, the output of BPF forms an autofocus feedback loop, and when the amplitude of the BPF2 output signal exceeds a certain value, the output forms an autofocus feedback loop. .

Although this eliminates the drawbacks of Japanese Utility Model Publication No. 40-26568, the high frequency components of the subject obtained from the image sensor are affected by the optical characteristics of the lens (lens aberrations, etc.).
The maximum point of each bandpass filter does not necessarily coincide with the focal position of the target object, which may cause malfunction.

Now, the bandpass filter to be used is BPF, ~BPF3
In this case, the characteristics will be as shown in FIG. 2, but if the influence of optical characteristics is taken into account, it will become as shown by the solid line in FIG. 3, so the original maximum point P.

On the other hand, the sPI point also acts as the maximum point when viewed from its adjacent portions, causing malfunctions.

OBJECTS OF THE INVENTION The present invention eliminates these drawbacks and allows focus to be taken at the original maximum point.

Structure of the Invention For this purpose, in the present invention, the speed control signal system based on the bandpass filter output and the direction indicating system are separated, and one is provided with a NAM circuit (filter peak detection circuit) and the other is provided with an adder circuit. be.

Description of examples An embodiment of FIG. 1 will be explained below.

The structure of the conventional example and its problem 1 is that the lens section is composed of a plurality of single lenses a, b, and c, respectively, and a and b are focus sections that are driven by a motor 5. C is a focus section of the master lens system, which is periodically driven by a lens drive circuit 7. 2 is an image pickup device or image pickup tube (hereinafter referred to as an image pickup tube device) that converts optical information of a subject into an electrical signal; 3 is a preamplifier circuit that amplifies the output signal of the image pickup device 2; 4 is a process circuit; and 6 is an image pickup tube. Reference frequency generation circuit, 8 is a motor drive circuit, 9 to 11 are second
BPF in the figure, bandpass filters having characteristics like ~BPF3, 12-14 are reference frequency detection circuits, 15-
17 is an amplifier, and 18 is an adder circuit.

19 is a synchronous detection circuit, 20 is a direction switching circuit, and 21 is an NA
M circuit 22 is a speed control circuit.

With this configuration, the adder circuit 18. If an arithmetic processing circuit is used instead of the NAM circuit 21, the content is the same as that of Japanese Patent Application Laid-open No. 188966/1983.

In contrast, in the present invention, the outputs of the amplifiers 15 to 17 are applied to the adder circuit 18 and the NAM circuit 21.

Here, the NAM circuit 21 does not perform peak detection of each filter, and even if the output of each bandpass filter 9-11 is like the solid line in FIG.
By passing the output of 7 through the NAM circuit 21, the influence of the depth of P, . . . P2 shown in FIG. 3 can be eliminated. That is, the output of the NAM circuit 21 becomes a broken line A shown in FIG.

So, focus. On the other hand, when it is greatly blurred, D
If the motor drive circuit 8 is controlled by the speed control circuit 22 so that the motor 5 can be driven at a low speed when approaching the lens 1, the focusing of the lens 1 can be carried out smoothly. In this case, focus. On the other hand, the current focus direction of the lens is determined by the output of the adder circuit 18. That is, the adder circuit 18 outputs the outputs of the filters 9 to 11 (the outputs of the amplifiers 15 to 17 (BPF in FIG. 4, ~B
PF3)) will be added, and the added value will be like B. The output of the adder circuit 18 is controlled by the synchronous detection circuit 19, and the rotation direction of the motor 5 (the focusing direction of the lens 9) is controlled by the synchronous detection circuit 19.
decide.

Effects of the Invention As described above with reference to embodiments, according to the present invention, an addition circuit and a NAM circuit are provided to correct the influence of optical characteristics, so that the influence of optical characteristics can be prevented and accuracy can be improved. A high degree of focus matching can be achieved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an automatic focusing device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram of a bandpass filter, Fig. 3 is an output waveform diagram of the bandpass filter when considering optical characteristics, and Fig. Figure 4 is a partial output waveform diagram. 18...Addition circuit, 21...NAM circuit. Name of agent Patent attorney Toshio Nakao and others 1 Figure 2 * Da 3 Figure 4

Claims (2)

[Claims] (1) Separate the video signals passed through a plurality of bandpass filters with different bands into a speed control signal system and a direction indicating system, and provide a filter peak detection circuit on one side and an adder circuit on the other side, and An automatic focusing device having means for driving a lens focusing system with its output. (2) The automatic focus adjustment device according to claim 1, wherein the filter peak detection circuit comprises a NAM circuit.