JPH09292643A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video camera capable of obtaining a reproduced image more coincident with an image visually grasped by an image pickup person. SOLUTION: Incident light is converted into a video signal by a CCD(charge coupled device) 3. A detection circuit 6 receives the video signal and generates a detection level signal showing the quantity of the incident light. A comparator circuit 10 compares the magnitude of the detection level signal with reference voltage and generates an iris control signal to make the quantity of the light made incident on the CCD 3 constant. Furthermore, in the case the reduction rate of the quantity of the incident light is larger than a specified value, a camera microcomputer 8 generates an AE signal for opening an iris 2 when a corresponding specified time elapses. The AE signal is added to the iris control signal by an adder circuit 11 and supplied to the iris 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera, and more particularly to a video camera equipped with an iris control device for controlling an iris of the video camera.

[0002]

2. Description of the Related Art Conventionally, for controlling the video signal level of a video camera, the level of the video signal is higher than the reference signal by comparing the level of the video signal output from a CCD (Charge Coupled Device) with a reference signal. Open and close the iris so that the video signal level is low when the brightness is high), while it is high when the video signal level is lower than the reference signal (low brightness). , The level is kept constant.

If the level of the video signal output from the CCD is still low even when the iris is fully opened under low illuminance, the level of the video signal is adjusted to a certain level of brightness by the AGC circuit (automatic gain circuit). We are going to raise it and keep that level constant.

[0004]

However, when a person suddenly moves from a bright place to a dark place, the pupils of the eyes do not keep up with the change in brightness, so at first it feels very dark, but as time goes by. The pupils will open and you will be able to see well around you even in dark places.

Here, in the conventional control of the level of the video signal, unlike the case where the human eyes have different feelings of brightness depending on the situation, the level of the video signal is kept constant as much as possible. Since it is performed, the image generated from the video signal has an image quality different from the impression of the photographer.

The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a video camera capable of obtaining a reproduced image having an image quality that further matches the image captured by the imager's eyes. To aim.

[0007]

A video camera according to a first aspect of the present invention includes a lens, a diaphragm for adjusting the amount of light incident through the lens, an imaging means for generating a video signal by the incident light, and an imaging device. When it is determined that the reduction rate of the amount of incident light exceeds the predetermined value based on the video signal generated by the means, the incident light is not emitted until a predetermined time corresponding to the reduction rate elapses. And a control means for opening the diaphragm so as to increase the amount.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a video camera according to an embodiment of the present invention. As shown in FIG. 1, the video camera includes a lens 1 and a lens 1
The CCD 3 that generates a video signal that is an electric signal based on the light that is incident therethrough, the iris (aperture) 2 that adjusts the amount of light that is incident on the CCD 3, and the level of the video signal that is received from the CCD 3 are lower than a predetermined value. In this case, the AGC circuit 4 that raises the level to keep the level of the video signal constant, the video signal processing circuit 5 that processes the video signal input from the AGC circuit 4 to obtain a proper image, and the iris And an iris control unit 12 that controls the opening and closing of No. 2.

In this case, the iris control section 12 is the CCD 3
Detection circuit 6 that detects the level of the video signal output from the device and outputs a detection level signal indicating the level (luminance)
And the reference level based on the detection level signal output from the detection circuit 6, the iris 2 is closed when the level of the video signal is higher than the reference level, and vice versa. When the level is lower than the reference level, the analog detection level signal output from the comparison circuit 10 for supplying the iris 2 with an iris control signal for opening the iris 2 and the detection circuit 6 is converted into a digital signal. An A / D converter 7 and a camera microcomputer 8 that receives the digital signal generated by the A / D converter 7 and generates an AE signal for closing the iris 2 for a predetermined time.
And the D / A converter 9 for converting the AE signal into an analog signal, the iris control signal output from the comparison circuit 10 and the analog signal generated by the D / A converter 9 are added to the iris 2. And an adder circuit 11 for supplying.

The specific circuit configuration of the comparison circuit 10 is shown in the circuit diagram of FIG. In FIG. 2, the magnitude of the detection level signal input to the node N2 is compared with a reference voltage, and if it is smaller than the reference voltage, an iris control signal having an active state for opening the iris 2 is output from the node N1. If it is higher than the reference voltage, an iris control signal having an inactive state for closing the iris 2 is output from the node N1.

Next, the operation of the video camera according to the embodiment of the present invention will be described focusing on the operation of the camera microcomputer 8.

FIG. 3 is a flow chart showing the operation of the camera microcomputer 8. First, in step S1, the camera microcomputer 8 inputs a digital signal from the A / D converter 7.

Then, in step S2, the level of the input digital signal (which indicates the luminance, that is, the amount of light incident on the CCD 3 through the lens 1 and the iris 2) is preset in the camera microcomputer 8. It is determined whether or not it is the reference value B1 or more. Here, when the level of the digital signal is not equal to or higher than the reference value B1,
Returning to step S1, the digital signal is input again.
On the other hand, when the level of the digital signal is equal to or higher than the reference value B1, the level of the digital signal is stored in the memory built in the camera microcomputer 8 in the next step S3.
A digital signal is newly input from the A / D converter 7.

Further, in step S4, it is determined whether or not the level of the newly input digital signal is less than or equal to a reference value B2 preset in the camera microcomputer 8.
Then, when the level of the digital signal is equal to or lower than the reference value B2, it is calculated by subtracting the reduction amount of the level of the digital signal in the next step S5. It should be noted that this reduction amount can be restated as a reduction rate in the sense of a reduction amount per interval time at which a digital signal is taken in from the A / D converter 7. On the other hand, the newly input digital signal is the reference value B
If it is not 2 or less, the process returns to step S2, and it is determined whether or not the level of the digital signal is the reference value B1 or more.

Here, in the memory built in the camera microcomputer 8, the time for which the iris is kept closed as a function of the rate of decrease of the level of the digital signal (iris closing time).
Is stored, and in step S6, the iris closing time corresponding to the reduction rate of the level of the digital signal calculated in step S5 is read from this memory.

Then, in step S7, an AE signal for keeping the iris 2 closed during the iris closing time read in step S6 is created.

Then, in step S8, the camera microcomputer 8 outputs this AE signal to the D / A converter 9.

The AE signal generated by the above-described operation of the camera microcomputer 8 is converted into an analog signal by the D / A converter 9, and is added to the iris control signal output from the comparison circuit 10 by the addition circuit 11 to be added to the iris. 2 is supplied. As a result, the iris 2 is opened after the iris closing time has elapsed.

[0020]

According to the video camera of the present invention, when the reduction rate of the amount of light incident through the lens exceeds a predetermined value, the aperture is opened only after a predetermined time corresponding to the reduction rate has elapsed. Therefore, it is possible to obtain a reproduced image having an image quality that further matches the image visually captured by the photographer.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a video camera according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific circuit configuration of a comparison circuit shown in FIG.

FIG. 3 is a flowchart for explaining the operation of the camera microcomputer shown in FIG.

[Explanation of symbols]

 1 Lens 2 Iris (Aperture) 3 CCD 6 Detection Circuit 7 A / D Converter 8 Camera Microcomputer 9 D / A Converter 10 Comparison Circuit 11 Addition Circuit 12 Iris Control Section

Claims (1)

[Claims] 1. A lens, a diaphragm that adjusts the amount of light incident through the lens, an image pickup unit that generates a video signal by the incident light, and an image signal generated by the image pickup unit. If it is determined that the rate of decrease in the amount of incident light exceeds a predetermined value, the amount of incident light should be increased only after a predetermined time corresponding to the decrease rate has elapsed. A video camera comprising a control means for opening the diaphragm.