JPH031665A - Video camera - Google Patents

Abstract

PURPOSE:To obtain a video camera able to pick up fast movement without being effected by flicker by applying switching control to a charge storage time being a prescribed 1st time when the luminous quantity of an object is a prescribed level or over and being a prescribed 2nd time when the luminous quantity of the object is a prescribed level or below. CONSTITUTION:A video camera having a solid-state image pickup element 12, reading a charge pattern corresponding to an object image whose charge is stored in the element 12 to obtain a video signal is provided with means 32, 33 setting a 1st charge storage time equal to a flicker period of a fluorescent light and a 2nd charge storage time longer than the 1st charge storage time respectively, discrimination means 20, 22 discriminating whether or not the luminous quantity of the object is a prescribed level or over, and means 32, 34, 36 applying switching control to the charge storage time of the element 12 so that the charge storage time is to be the 1st charge storage time when the luminous quantity of an object is a prescribed level or over and the 2nd charge storage time when the quantity is the prescribed level or below. Through the constitution above, while deficiency in the luminous quantity is being corrected, the effect of flicker of the fluorescent light is eliminated and the shutter speed is fast, then the camera is suitable for the pickup for a fast moving object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video camera, and particularly to a video camera designed to prevent flicker.

[Conventional technology]

Conventionally, as a method to prevent the level fluctuation of the video signal due to the flicker of a fluorescent light, the charge accumulation time in the solid-state image sensor is set to 5fHIJt cant, that is, an integral multiple of 1/20 seconds, and the flicker output of the solid-state image sensor is reduced. There is a method designed to remove it (Japanese Unexamined Patent Publication No. 56-37777).

That is, the flicker period of a fluorescent light due to commercial power #t (50 Hz) in the Kanto area is 1/100 second, and the flicker period of a fluorescent light due to commercial power (60 Hz) in the Kansai area is 1/100 seconds.
/2σ second, but if the charge accumulation time in the solid-state image sensor is set to 1720 seconds as described above, charge can be accumulated for 5 or 6 cycles of the flicker cycle of a fluorescent light.
The amount of light is the same at any timing, and flickering can be prevented.

However, if the charge accumulation time is set to 1720 seconds, the charge accumulation time becomes too long (in other words, the shutter speed becomes too slow, it is impossible to follow fast-moving photography, and it is difficult to obtain a good video signal. The problem is that it can't be done.

The present invention has been developed in view of the above circumstances, and is capable of eliminating the effects of flicker from fluorescent lights, and
The purpose is to provide a video camera suitable for photographing faster movements than conventional ones.

[Means to solve problems]

In order to achieve the above-mentioned object, the present invention provides a video camera having a solid-state image sensor, which reads out a charge pattern corresponding to a subject image stored in the solid-state image sensor to obtain a video signal. means for respectively setting a first charge accumulation time that is the same as the flicker cycle of the light and a second charge accumulation time that is longer than the first charge accumulation time, and determining whether the amount of light on the subject is above a certain level. a discriminating means for discriminating, and a discriminating means for discriminating the solid state so that, based on the output of the discriminating means, a first charge accumulation time is used when the amount of light of the object is above a certain level, and a second charge accumulation time when it is below a certain level. means for switching and controlling the charge accumulation time of the image sensor;
It is characterized by having the following.

[Effect]

According to the present invention, in order to avoid being affected by the flicker of the fluorescent light when the amount of light on the subject exceeds a certain level, the charge M integral time of the solid-state image sensor is set to the same period as the flicker period of the fluorescent light. The charge accumulation time is set to 1, so that the same amount of light can be received at any timing, and flicker is prevented. Furthermore, when the amount of light from the object is below a certain level, the charge storage time of the solid-state image sensor is set to a second charge storage time that is longer than the first charge storage time to compensate for the lack of light amount.

〔Example〕

Preferred embodiments of the video camera according to the present invention will be described in detail below with reference to the accompanying drawings.

The figure is a block diagram showing an embodiment of a video camera according to the present invention.

In the figure, a subject image incident through a photographic lens 10 is formed on a light receiving surface of a solid-state image sensor (COD) 12. As a result, charges corresponding to the subject are accumulated on the light-receiving surface of the CCD 12, and the CCD drive signal from the CCD drive circuit 14 causes red R〉, corresponding to the charge pattern.
Green (G) and blue (G) electrical signals are read out.

The RSGSB signal read out from the CCD l 2 is converted into color difference signals (R-Y) and (G-Y) via the process circuit 16.
, (B-Y) and a luminance signal Y, which are then manually input to the video signal processing circuit 18.

In the video signal processing circuit 18, the color difference signals are so-called 3,
The signal is orthogonally modulated at 58 MHz, added to the luminance signal Y, and output as an NTSC video signal.

On the other hand, the luminance signal Y from the process circuit 16 is applied to the level determination circuit 20. A reference level is added from a reference level setter 22 to the other human power signals of the level judgment circuit 20, and the level judgment circuit 20 compares these two human power signals and determines whether the luminance signal Y is larger than the reference level. A signal indicating this is output to the Nyatta control circuit 30. still,
The reference level set in the reference level setter 22 is such that, for example, when shooting under fluorescent light, the luminance signal Y is thicker (or when shooting under candlelight, the reference level is higher). be.

The shutter control circuit 30 controls the charge accumulation time of the CCD 12 (
It controls the so-called electronic shutter speed) and is composed of two shutter speed setting sections 32 and 34 and a changeover switch 36.

Here, a shutter speed of 1/100 seconds is set in the shutter speed setting section 32, and a shutter speed of 1/60 seconds is set in the shutter speed setting section 34. Furthermore, 1/
100 seconds is the same time as the flicker cycle of fluorescent lights in the Kanto region (50 Hz).

When a signal indicating that the luminance signal Y is higher than the reference level is applied from the level determination circuit 20, the changeover switch 36 switches the movable contact piece to the shutter speed setting section 36.
A signal indicating a shutter speed of 1/II) [1 second is output to the CCD drive circuit 14, while a signal indicating that the luminance signal Y is smaller than the reference level is added from the level determination circuit 20. , the movable contact piece is connected to the shutter speed setting section 34 side, and a signal indicating a shutter speed of 1760 seconds is output to the CCD drive circuit 14.

The CCD drive circuit 14 outputs a CCD drive signal for charge accumulation and data transfer to match the shutter speed (charge accumulation time) manually controlled by the shutter control circuit 30 .

In this way, when it is relatively bright like under a fluorescent light,
In order to avoid being affected by the flicker of the fluorescent light, the shutter speed is made to match the flicker period of the fluorescent light, so that the same amount of light can be obtained at any timing.

On the other hand, when it is relatively dark, such as under candlelight, the fluorescent light turns on and is not affected by the flicker of the fluorescent light, but the amount of light is insufficient, so the shutter speed is faster than the above-mentioned strip speed. is slowed down to compensate for the lack of light.

Note that in this embodiment, whether or not the amount of light of the subject is above a certain level is determined based on the luminance signal, but the present invention is not limited to this, and the determination may be made based on the output of the photometry means, for example.

〔Effect of the invention〕

As explained above, according to the video camera according to the present invention, it is possible to eliminate the influence of flicker from fluorescent lights while compensating for insufficient light quantity, and the shutter speed is also faster than that of conventional cameras. Also suitable for shooting fast movements.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of a video camera according to the present invention. 10...Photographing lens, 12...Solid-state image sensor (C
CD), 14... CCD drive circuit, 20...
Level determination circuit, 22... reference level setter,
30... Shutter control circuit, 32.34... Shutter speed setting section, 36... Changeover switch.

Claims (1)

[Scope of Claim] A video camera having a solid-state image sensor and configured to read out a charge pattern corresponding to a subject image stored in the solid-state image sensor to obtain a video signal, comprising: a flicker cycle of a fluorescent light; means for respectively setting a first charge accumulation time of the same duration and a second charge accumulation time longer than the first charge accumulation time; and a determining means for determining whether the amount of light of the subject is above a certain level. and, based on the output of the discrimination means, the charge accumulation of the solid-state image pickup device is performed such that a first charge accumulation time is used when the amount of light of the object is above a certain level, and a second charge accumulation time is used when the amount of light of the subject is below a certain level. A video camera comprising: means for controlling time switching;