JP2000287122A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly grasp lens diaphragm value information by storing the correlation of a control voltage with a lens diaphragm value, controlling a diaphragm means in the case of photographing to keep the output value of an image pickup unit constant, monitoring the control voltage of a diaphragm control means with a diaphragm detecting means and changing the parameter of signal processing when the diaphragm value departs from a prescribed range. SOLUTION: A diaphragm control circuit 17 controls an diaphragm mechanism 13 to keep the output of the image pickup unit 15 constant in the case of photographing by a video camera and the diaphragm detecting circuit 2 always monitors the control voltage of the circuit 17 while executing the control. Then the diaphragm value corresponding to the control voltage stored in a storage element 1 is read from the control voltage to be detected and the diaphragm value is transmitted to a camera control circuit 3. A camera control circuit 3 gives an indication to a signal processing circuit 16 to decrease shutter speed or to increase gain when the diaphragm value takes the min. value. When it becomes maximum, the change of the signal processing parameter is indicated to the camera control circuit 3.

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 technique of a lens aperture of a video camera.

[0002]

2. Description of the Related Art In recent years, video cameras and the like which automatically adjust a lens aperture by detecting the amount of light input from a lens have been used.

A description will now be given of a conventional automatic aperture control of a video camera. FIG. 2 shows the configuration of a conventional video camera, and FIG. 3 shows the relationship between the aperture control voltage of the video camera and the aperture of the lens.

As shown in FIG. 2, the automatic iris lens 11 is
It comprises a lens 12 for taking in light from a subject and a diaphragm mechanism 13 for making a predetermined amount of light entering through the lens 12. The aperture mechanism 13 is controlled by an aperture control circuit 17 described later. In addition, there is a camera having an auto-focus function, but since it is not related to the present invention, the description of the part is omitted.

The video camera body 14 includes an image sensor 15, a signal processing circuit 16 for converting a signal output from the image sensor 15 into a video signal, and an aperture control mechanism 17 for adjusting the aperture mechanism 13.
It is composed of Reference numeral 18 denotes a subject, and 19 denotes a monitor or VTR to which a video camera signal is output.

When a subject is photographed by a video camera, it is necessary to set an optimal aperture (light quantity) in order to obtain a clear image, and the aperture of an automatic lens is generally controlled by a DC voltage. The aperture of the lens of this video camera is taken by photographing the subject with a video camera, and the photographed image is actually checked by a user on a monitor to prevent the screen from being too dark and having a noisy screen. And set it to be the sharpest image so that there are not many saturated parts. The setting of the optimum image is performed by adjusting the volume and the like (not shown) of the video camera body 14, and the luminance level at this time is compared with the luminance level (before amplification) from the signal processing circuit 16, and is always constant. Control so that Therefore, once the value of the volume or the like of the video camera body 14 is set, an image with a constant luminance level can be always obtained even when the subject changes.

Referring to the block diagram of FIG. 2, an image of a subject 18 is formed by a lens inside a lens 11 having an automatic aperture mechanism.
The image is input to the video camera 14 through the aperture 12 and the aperture mechanism 13. Inside the video camera 14, an image of the subject 18 is input to the image sensor 15 via the lens 11 with an automatic iris mechanism, and an output converted into an electric signal by the image sensor 15 is output as a video signal through the signal processing circuit 16. And an output device 19 such as a monitor. Then, inside the video camera 14, the level of the video output is detected in order to obtain a proper exposure of the video output, and the aperture control circuit 17 electrically detects the level of the aperture mechanism 13.
Is controlled so that the amount of light input to the image sensor 15, that is, the output of the image sensor 15 converted into an electric signal by the image sensor 15 becomes constant.

FIG. 3 shows the relationship between the aperture control voltage of the video camera and the aperture of the lens. Being open. Therefore, the aperture control circuit 17 controls the aperture mechanism 13 by changing the aperture control voltage so that the input of the image sensor 15 is always constant.

[0009]

When the subject becomes dark or bright, the video camera always controls the brightness level of the input from the lens to be constant, but controls the aperture mechanism 13 of the video camera. Since the control voltage and the actual aperture state of the lens are not known, increase the control voltage even if the luminance level does not rise any more, or decrease the control voltage even if the luminance level does not decrease any more. What happens?

That is, when a video camera having a function of controlling the aperture of an interchangeable lens with a DC voltage is used by attaching an automatic aperture lens having no means for transmitting lens aperture information to the video camera, As means for grasping the aperture information of the lens, there is a means for referring to the aperture control voltage using the fact that the aperture value and the aperture control voltage have a relationship as shown in FIG. However, the relationship between the aperture control voltage and the aperture value varies depending on the aperture mechanism and aperture control circuit of the automatic aperture lens, and a combination thereof, and in a lens-interchangeable video camera that may use a wide variety of lenses, Even with reference to the aperture control voltage, the aperture information of the lens cannot be accurately grasped.

Further, even in a lens-integrated video camera in which the lens and the video camera cannot be attached or detached, if there is no particular means for transmitting the aperture value information of the lens to the video camera, the control voltage and the aperture may be changed due to variations in the single lens. Is slightly different, and it is not possible to accurately grasp the aperture information of the lens by referring to the aperture control voltage. For this reason, even in a lens-integrated video camera, when there is no particular means for transmitting the lens aperture value information to the video camera, in order to accurately grasp the lens aperture information, the control voltage and the control voltage are required in the manufacturing process. A process such as adjustment for inputting the relationship between the aperture values has been required.

[0012]

SUMMARY OF THE INVENTION In a video camera with a detachable lens system, aperture means for adjusting the amount of light from a lens, aperture control means for controlling the voltage of the aperture means, and converting an optical signal into an electric signal. An image sensor, signal processing means for converting an electric signal from the image sensor into a video signal, a storage element, and aperture detection for monitoring a control voltage of the aperture control means and reading a lens aperture value recorded from the storage element Means, and camera control means for changing a parameter for signal processing to the signal processing means, and a relationship between a control voltage and an aperture value of a lens based on a control voltage of the control means and an output of an image sensor in advance. Is stored in the storage element, while controlling the aperture means by the aperture control means so that the output value of the imaging element becomes a constant value at the time of shooting,
The control voltage of the aperture control means is monitored by the aperture detection means, the aperture value of the lens corresponding to the control voltage is read from the storage element, and when the aperture value exceeds a predetermined range, a signal is output by the camera control means. The parameter of the signal processing of the processing means is changed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the video camera of the present embodiment. The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. 1 is a storage element,
The value of the aperture of the lens corresponding to the control voltage is stored. Reference numeral 2 denotes an aperture detection circuit, which extracts an aperture value corresponding to the control voltage stored in the storage element 1 from the control voltage from the aperture detection circuit 17. A camera control circuit 3 instructs a signal processing circuit 16 to change parameters of signal processing such as a shutter speed and a gain (amplification), and instructs an aperture control circuit 17 to change parameters of aperture control.

In this embodiment, when the power is turned on or when the automatic iris lens is mounted, the iris of the automatic iris lens is moved from the open state to the maximum iris state by the aperture control voltage of the video camera for the same subject. An aperture value estimated from the amount of light input to the image sensor and the amount of light input to the image sensor when the aperture is changed is recorded in a storage element such as a microcomputer or EEPROM together with the aperture control voltage at that time. Things.

The amount of light input to the image pickup device is observed by observing the output of the image pickup device which is converted into an electric signal by the image pickup device. The aperture value estimated from the electric signal output from the image sensor when the aperture is changed, together with the aperture control voltage at that time, is calculated by the microcomputer or the EE.
It is recorded on a storage element such as a PROM.

As shown in FIG. 1, as in the prior art, the subject
The output of the image sensor 15 is made constant by the automatic aperture mechanism 13 for the image 18.

In this embodiment, the lens 11 with an automatic aperture mechanism
When the camera is mounted on the video camera 14 or when the power is turned on, the control voltage for the aperture mechanism 13 of the aperture control circuit 17 is changed for the same object, and the aperture value and the aperture estimated from the signal output from the image sensor 15 are changed. The relationship between the control voltages is stored.

Specifically, first, the aperture control voltage is reduced from the maximum until the output of the image sensor 15 starts to change. Since the aperture control voltage immediately before the output of the imaging element 15 changes can be determined to be the aperture control voltage at the time of opening, the storage element 1
Is recorded as the aperture control voltage at the time of opening. The aperture control voltage is further reduced, and the output signal of the image sensor 15 is reduced to one half of the open signal.
Since it can be determined that the aperture control voltage at the point of time is one aperture stop from the open state, the aperture control voltage at this point is recorded in the storage element 1 as the aperture control voltage of one aperture stop from the open state. This is performed every time the output of the image sensor 15 becomes half from the opening of the aperture to the maximum aperture. Then, the aperture control voltage at the time when the output signal of the image sensor 15 does not change even when the aperture control voltage is lowered is recorded as the aperture control voltage in the maximum aperture state, and the relationship between the aperture control voltage and the aperture value is stored in the storage element. Entered into 1.

The above-mentioned setting is performed when the automatic iris lens 11 is attached to the video camera 14, or when the power is turned on or at an arbitrary time, so that the automatic iris lens 11 has no means for transmitting the aperture value information of the lens to the video camera 14. Even when the aperture lens 11 is attached and used, the aperture detection circuit 17
The video camera 14 can accurately grasp the aperture value information of the lens with reference to the aperture control voltage of the lens and the storage element 1.

At the time of actual photographing, the aperture control circuit 17 controls the aperture mechanism 13 so that the output of the image sensor 15 becomes constant, and the aperture detection circuit 2 constantly controls the aperture voltage of the aperture control circuit 17 while controlling the aperture mechanism 13. Is monitored, the aperture value for the control voltage stored in the storage element 1 is read out from the control voltage, and the aperture value is sent to the camera control circuit 3.

When the aperture value is at the minimum aperture value, the camera control circuit 3 instructs the signal processing circuit 16 to reduce the shutter speed or increase the gain (amplification factor). Conversely, when the aperture value is the maximum aperture value, the camera control circuit 3 is instructed to increase the shutter speed of the signal processing circuit 16 or to change the signal processing parameters so as to reduce the gain (amplification factor).

As a result, the conventional control method cannot grasp the actual aperture value of the lens, so that the control voltage for controlling the aperture mechanism 13 is set too high or too low, and a good video signal is output. I couldn't get it,
According to the present invention, since the actual aperture value of the lens can be ascertained, a quick and favorable video signal can be obtained.

[0023]

According to the present invention, even when a video camera having a function of controlling the aperture of a lens with a DC voltage is used with an automatic aperture lens having no means for transmitting lens aperture value information to the video camera, the video camera can be used. Can grasp the aperture of the lens. By having this means, the control of AGC (auto gain control), the aperture itself, and the electronic shutter based on grasping the aperture information, the automatic aperture lens which does not particularly have a means for transmitting the aperture value information of the lens to the video camera. It can be performed even when using with attaching.

[Brief description of the drawings]

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

FIG. 2 shows a configuration of a conventional video camera.

FIG. 3 shows the relationship between the aperture control voltage of a conventional video camera and the aperture of a lens.

[Explanation of symbols]

 1: Storage element 2: Aperture detection circuit 3: Camera control circuit 13: Aperture mechanism 15: Image sensor 16: Signal processing circuit 17: Aperture control circuit

Claims (4)

[Claims] 1. A video camera of a lens detachable type, comprising: aperture means for adjusting the amount of light from a lens; aperture control means for controlling the voltage of the aperture means; an image sensor for converting an optical signal into an electric signal; Signal processing means for converting an electric signal from an imaging element into a video signal; a storage element; aperture detection means for monitoring a control voltage of the aperture control means and reading a lens aperture value recorded from the storage element; A camera control means for changing a parameter for signal processing to the signal processing means; and a relationship between the control voltage and the aperture value of the lens based on a control voltage of the control means and an output of the image sensor in advance. The aperture control means controls the aperture means so that the output value of the image sensor becomes a constant value at the time of photographing, and the aperture detection means detects the aperture value. The control voltage of the control means is monitored, the aperture value of the lens corresponding to the control voltage is read from the storage element, and the signal processing parameter of the signal processing means is changed by the camera control means according to the aperture value. And a video camera. 2. The video camera according to claim 1, wherein the signal processing parameter of the signal processing means is an electronic shutter for capturing an electric signal from an image sensor or a parameter of an amplification factor for amplifying an input signal. Video camera featured. 3. The video camera according to claim 1, wherein parameters of aperture control itself are changed by the camera control means. 4. The video camera according to claim 1, wherein a relationship between a control voltage and an aperture value of the lens is stored in the storage element based on a control voltage of the control unit and an output of the imaging element. A video camera characterized in that the power is turned on.