JPH042538Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a video camera equipped with a circuit that automatically sets a level for controlling the aperture of an EE lens.

[Prior art]

The EE lens has a built-in electric aperture operated by a motor, as well as a semi-fixed resistor for adjusting the sensitivity of the aperture. And this EE
When attaching the lens to a video camera, a test pattern light of a predetermined illuminance is made incident, and the sensitivity is adjusted using the above-mentioned resistor so that the level of the Devio output at that time becomes a predetermined level.

However, in the past, when changing the EE lens to, for example, a wide-angle lens or a telephoto lens, sensitivity adjustment similar to that described above was required, which was a problem.

[Purpose of invention]

The present invention has been made in view of these points, and its purpose is to provide a video camera in which even if the EE lens is replaced, there is no need to adjust the sensitivity of the lens itself.

[Structure of the idea]

To this end, the video camera of the present invention uses an AGC that controls the aperture of the EE lens using part of the video output.
an amplifier and a comparator that compares another part of the video output with a reference value; the comparison output of the comparator controls the gain of the AGC amplifier so that the video output corresponds to the reference value; The configuration is such that the aperture of the EE lens is controlled so that the EE lens is at the same level.

〔Example〕

Examples of the present invention will be described below. The figure shows a circuit of a video camera according to one embodiment. 1 is an EE lens, and the imaging light that passes through the lens is sent to the process section (solid-state imaging device such as CCD,
The image processing circuit (including horizontal and vertical scanning circuits) 2 photoelectrically converts the signal into an electrical video signal, and outputs the signal via an amplifier 3. 4 is an AGC amplifier that amplifies the video signal from the process section 2 and controls the grain adjustment motor of the EE lens 1.

5 is a detection circuit for detecting a video signal, and 6 is a comparator. This comparator 6 converts the output from the detection circuit 5 into a reference value for brightness setting set by a semi-fixed resistor R1.
Compare it with Vr, output the comparison voltage, and use the AGC
It serves to control the gain of amplifier 4. 7 is a low-pass filter that performs an integrating operation to remove high-frequency components from the output voltage of the comparator 6.

Now, when the level of the video output from the process section 2 is low, the potential of the inverting input terminal of the comparator 6 is low, and therefore the output voltage of the comparator 6 becomes high. Therefore, the gain of the AGC amplifier 4 decreases, the level of the AGC voltage input to the EE lens 1 decreases, and the amount of aperture reduction decreases.
In other words, the aperture opens, the amount of incident light increases, and the video output level (brightness level) increases.

Conversely, when the video output level increases, the gain of AGC amplifier 4 increases,
AGC becomes more powerful, the aperture closes, and the video output level decreases.

That is, when the object to be photographed is dark, the AGC control voltage decreases and the aperture opens, and when the object is bright, the aperture closes. This control is performed based on the reference value Vr applied to the non-inverting input terminal 6 of the comparator 6, and the level of the video output (more precisely, the output of the detection circuit 5) is set to this reference value Vr. To,
Loop control is performed.

As mentioned above, the video output level determined by the aperture result is compared with the reference value, and the gain of the AGC amplifier 4 is controlled based on the comparison result.
Although the semi-fixed resistor for sensitivity adjustment (for controlling the drive motor of the built-in aperture) in the EE lens 1 is included in the above control loop, it does not occupy an important element.

In other words, the video output level is determined by the reference value Vr set inside the camera, and therefore,
Even if the EE lens 1 is replaced with a different EE lens, there is no need to adjust the sensitivity of the EE lens itself after the replacement.

[Effect of idea]

As described above, according to the present invention, by adjusting and setting the reference value inside the camera, the
A feature of this lens is that even if you replace the EE lens, there is no need to adjust its sensitivity.

[Brief explanation of the drawing]

The figure is a circuit diagram of an automatic level setting circuit for an EE lens according to an embodiment of the present invention.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a video camera that photoelectrically converts an imaged object through an EE lens and obtains video output, an AGC amplifier that controls the aperture of the EE lens using a part of the video output. and a comparator that compares another part of the video output with a reference value, and controls the gain of the AGC amplifier based on the comparison output of the comparator so that the video output is at a level corresponding to the reference value. The above
A video camera characterized by controlling the aperture of an EE lens. (2) The video camera according to claim 1, wherein the gain of the AGC amplifier is controlled by a signal obtained by integrating the output of the comparator.