JPH0727730Y2 - Auto hawks device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an auto-hocus device for a video camera.

[Conventional technology]

Conventionally, this type of auto-focusing device applies distance measurement technology, emits electromagnetic waves or sound waves from the camera side, and measures the delay of the electromagnetic waves or sound waves reflected by hitting the object to measure the distance to the object. Was being measured. This distance information is an electric signal using a counter or an integrating circuit that starts when an electromagnetic wave or a sound wave is emitted and ends when a reflected wave is detected. If this electric signal is processed appropriately, that is, if the time until the reflected wave is detected is short, the subject is close, so the focus of the lens is in the "near" direction.
If the time until detection is long or if detection is not possible, the object is distant, so a signal for moving the lens focus in the "far" direction is output to the focus adjustment mechanism (servo mechanism). However, the signal output to this servo mechanism is compared with reference to the current focal position information of the lens. The current focus position information may be obtained from the lens body or may be the previous control information. In other words, whether the distance measured this time is shorter than the current focus position,
The signal after the comparison is output to the servo mechanism. If the comparison values are the same or within an error, no output is made to the servo mechanism.

[Problems to be solved by the device]

The above-described conventional auto-focusing device emits an electromagnetic wave or a sound wave from the camera side, and measures the delay of the electromagnetic wave or the sound wave reflected by the subject and measures the distance to the subject. Therefore, there is a drawback in that the correct distance cannot be measured for a subject on the opposite side such as a transparent glass such as a window. In addition, a circuit for emitting electromagnetic waves or sound waves, a detection circuit for detecting reflected waves, a circuit for obtaining current focus position information, a circuit for comparison, etc. are necessary because of the need to measure the distance to the subject. However, it has the disadvantage of being complicated, and requiring many parts for these. Furthermore, there is a drawback that it takes a long time to measure the waiting time due to no response to an object at infinity, the reaction is slow, and correct distance information cannot be obtained even for a moving object.

[Means for Solving the Problems]

The auto-hocus device of the present invention detects the highest frequency of an image signal obtained by removing the horizontal and vertical sync signals from the video output signal of the video camera in the auto-hocus device for controlling the servo mechanism for focus adjustment of the lens of the video camera. It has frequency-to-voltage converting means for outputting a voltage corresponding to the highest frequency detected by the above, and control means for controlling the servo mechanism so that the output voltage of the frequency-to-voltage converting means becomes maximum.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Referring to FIG. 1, an auto-hocus device 1 of the present embodiment has a video amplifier circuit 11 for amplifying a video output signal of a video image pickup section 21.
A gate circuit 12 for separating the horizontal and vertical sync signals from the amplified video output signal and outputting only the video signal,
A frequency-to-voltage conversion circuit 13 that detects the highest frequency of the video signal and converts it into a voltage, and a control circuit 14 that extracts horizontal and vertical synchronization signals from the video output signal and sends them to the gate circuit 12.
And a drive circuit 15 which receives the voltage conversion signal via the control circuit 14 and drives the servo mechanism 23 of the lens system 22.

Next, the operation of this embodiment will be described.

Generally, a video output signal focused on a subject becomes a video output signal including a sharp rising waveform, and conversely, a video output signal not focused on becomes a video output signal having dull rising and falling waveforms. The sharp rising and falling waveforms include high frequencies as is clear from the development of the Fourier series, and the upper limit frequency is determined by the resolution of the lens, the pixel density of the video image pickup section, and the bandwidth of the video amplifier.

Now, the image of the subject A is output as a video output signal by the video imaging unit 21 through the lens system 22. Since this video output signal is the same as the television signal, it contains horizontal and vertical synchronizing signals. Video amplifier circuit 11
The video output signal input to is separated by the control circuit 14 into horizontal and vertical synchronizing signals. The control circuit 14 uses the horizontal (H) signal and the vertical (V) signal to generate a gate signal for passing only the signal of the target portion for focusing. By outputting this gate signal to the gate circuit 12, the gate circuit 12 outputs only the necessary part of the video signal from the video amplifier circuit 11. This part usually covers the round part of the center of the TV screen.

The frequency-to-voltage conversion circuit 13 analyzes the content of the signal from the gate circuit 12, converts it into a voltage for the highest frequency contained therein, and at the same time notifies the control circuit 14 of the end of conversion. The output of the frequency-to-voltage conversion circuit 13 is maximum when the same subject A is in focus.

The control circuit 14 controls the servo mechanism 23 through the drive circuit 5 so that the output of the frequency-to-voltage conversion circuit 13 is maximized so as to move in the "far" or "near" direction.

[Effect of device]

As described above, the present invention detects the highest frequency from the video output signal of the video camera by the frequency-to-voltage conversion means and controls the servo mechanism to generate an electromagnetic wave or sound wave emission circuit, its detection circuit, and the current focus. A circuit for obtaining position information, a circuit for comparison, etc. are unnecessary, and
For example, there is an effect that a subject on the opposite side such as a transparent glass such as a window or a moving body can be correctly focused.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1 ... Auto-Hocus device, 11 ... Image amplification circuit, 12 ...
… Gate circuit, 13 …… Frequency-to-voltage conversion circuit, 14 …… Control circuit, 15 …… Driving circuit, 21 …… Video imaging unit, 22 ……
Lens system, 23 ... Servo mechanism.

Claims (1)

[Scope of utility model registration request] 1. An auto-hocus device for controlling a servo mechanism for focus adjustment of a lens of a video camera detects and detects the highest frequency of an image signal obtained by removing horizontal and vertical sync signals from a video output signal of the video camera. An autohocus comprising: a frequency-to-voltage conversion means for outputting a voltage corresponding to the highest frequency; and a control means for controlling the servo mechanism so that the output voltage of the frequency-to-voltage conversion means becomes maximum. apparatus.