JP2596324B2 - Backlight correction device and imaging device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera or a still camera, and more particularly to a backlight correction apparatus for suppressing unnecessary high luminance portions of an image pickup input.

[0002]

2. Description of the Related Art Generally, an automatic iris lens provided in a video camera measures the amount of light incident on a shooting screen,
It has the function of automatically adjusting the aperture so that the amount of light is suitable for shooting.

An automatic iris lens of such a video camera is disclosed in Japanese Patent Application Laid-Open No. 2-181578.

In this publication, a central rectangular portion of a photographing screen where a main subject is normally located is defined as a first photometric region, and the other portions are defined as a second photometric region.
A case where the output is larger than the output of the photometry area by a certain degree or more is determined as a normal light state, and a case where the output is smaller than the output is determined as a backlight state.

When it is determined that the subject is in a backlight state, automatic aperture adjustment is performed based on a signal obtained by relatively increasing the gain of the central rectangular portion and decreasing the gain of other regions so that the main subject can be clearly photographed. Be executed.

[0006]

However, the above-mentioned backlight compensation mechanism of the conventional video camera has a first rectangular portion in the center rectangular portion.
This is a center-weighted metering method in which a main subject is located in an area, and there is a problem that shooting conditions such as a camera mounting position are greatly limited because a setting area for backlight determination is fixed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a backlight correction device in which an area for performing backlight correction is not fixed.

[0008]

The backlight compensating apparatus according to the present invention comprises an unnecessary part detecting means for sequentially comparing a luminance level of an image pickup signal with a predetermined level to detect an unnecessary high luminance part; It is characterized by comprising memory means for storing position information, and correction means for attenuating the luminance level of the image signal corresponding to the unnecessary part based on the position information.

[0009]

[Function] By detecting an unnecessary high-luminance portion in the imaging screen and attenuating the luminance level only in the unnecessary portion, the setting area for backlight determination can be changed to an arbitrary shape of the unnecessary high-luminance portion in the imaging screen. Can be matched.

[0010]

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

FIG. 1 is a block diagram of a video camera using an embodiment of a backlight correction device according to the present invention.

In FIG. 1, a lens 2 and a stop 3 are provided in an automatic stop lens unit 1, and the amount of light incident through the lens 2 is adjusted by the stop 3. The aperture diameter of the aperture 3 is changed by an aperture driving motor.

The light that has passed through the lens 2 and the aperture 3 is a CCD
And so on. The image is scanned by the image sensor 4, converted into an electric signal, input to the video signal processing circuit 5, and output as a video signal.

The video signal is input to a backlight detecting circuit 6 where a backlight region is detected and stored in an image memory 7.

The backlight detecting circuit 6 is composed of a comparator, for example, compares a video signal level corresponding to each pixel of the image pickup screen with a reference voltage, and determines that a pixel having a level higher than the reference voltage belongs to a backlight region. When it is determined that a certain pixel belongs to the backlighting area, a signal indicating that fact is stored in the image memory 7 at the position of the pixel. The image memory 7 enters a writable state when the user presses the storage switch.

The signals indicating the backlight region stored in the image memory 7 are sequentially output to the gate signal generation circuit 8, where horizontal and vertical timing pulses (hereinafter, referred to as gate signals) representing the backlight region of the imaging screen are generated. You. The generated gate signal is output to the changeover switch 9, and the changeover switch 9 performs a switching operation according to the gate signal.

On the other hand, the video signal for automatic aperture adjustment from the video signal processing circuit 5 is input to one terminal of the changeover switch 9 and is simultaneously input to the other terminal of the changeover switch 9 via the level attenuation circuit 10. .

The changeover switch 9 selects an image signal attenuated by the level attenuating circuit 10 for a pixel belonging to a backlight region of the imaging screen specified by the gate signal, and retains the image signal as it is for other regions. Select a signal. As a result, the output of the changeover switch 9 becomes an attenuated video signal in a backlight region, and becomes a normal video signal in other regions.

The video signal selected by the changeover switch 9 is input to one terminal of the backlight correction changeover switch 11, and the video signal for automatic aperture adjustment is input to the other terminal as it is.

The backlight correction changeover switch 11 is a switch for determining whether or not to perform backlight correction, and operates when the user operates the backlight correction ON / OFF switch 12. When performing backlight correction, the video signal output of the changeover switch 9 is selected and output to the automatic aperture lens unit 1.

The automatic iris lens unit 1 detects the voltage level of the input automatic iris adjustment video signal, compares the voltage level with a reference voltage, drives the motor according to the comparison result, and adjusts the iris 3. .

Next, the operation of this embodiment will be described.

FIG. 2 is a schematic diagram showing an example of an image pickup screen including a backlight region, and FIG. 3 is a schematic diagram showing a backlight region stored in the image memory 7.

First, an image as shown in FIG.
Is converted into an electric signal. The imaging screen 20 includes an unnecessary high-luminance area as a background of the main subject 21, that is, a backlight 22.

Since the luminance signal of the video signal corresponding to the backlight unit 22 has a high level, the backlight unit detection circuit 6
And stored in the image memory 7 as a backlight region.

As shown in FIG. 3, the image memory 7 stores a backlight area 30 corresponding to the backlight section 22 of the imaging screen 20. The backlight region 30 is not fixed in position like a conventional rectangular region, but is a back light portion 22 that is photographed.
Is an area that matches the position and shape of.

The information stored in the image memory 7 is sequentially read out by the gate signal generating circuit 8, and when the information corresponds to the backlight region 30, the level attenuation circuit 1 is switched by the switch 9.
The attenuated video signal passing through 0 is selected, and if it corresponds to other areas, the video signal as it is is selected. As a result, a video signal whose backlight is corrected can be obtained.

FIG. 4 is a waveform diagram of a video signal without backlight correction, and FIG. 5 is a waveform diagram of a video signal with backlight correction in the present embodiment.

As shown in FIG. 4, in the video signal without backlight compensation, the luminance signal of the backlight portion rises significantly. On the other hand, in the present embodiment, the backlight is corrected and the backlight is removed.

[0030]

As described above in detail, the backlight correction device according to the present invention detects an unnecessary high luminance portion in an image pickup screen and attenuates the luminance level of only the unnecessary portion. Setting area can be set in accordance with the shape of the unnecessary high-luminance part in the imaging screen. This makes it possible to perform backlight correction effectively regardless of the shape of the backlight portion in any part of the imaging screen.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video camera using an embodiment of a backlight correction device according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of an imaging screen including a backlight area.

FIG. 3 is a schematic diagram showing a backlight area stored in an image memory 7;

FIG. 4 is a waveform diagram of a video signal on which backlight correction has not been performed.

FIG. 5 is a waveform diagram of a video signal subjected to backlight correction in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Automatic aperture lens part 2 Lens 3 Aperture 4 Image sensor 5 Video signal processing circuit 6 Backlight part detection circuit 7 Memory 8 Gate signal generation circuit 9 Changeover switch 10 Level attenuation circuit 11 Backlight correction ON / Off switch 12 Backlight correction ON / Off Switch 20 imaging screen 21 main subject 22 backlight section 30 backlight area

Claims (2)

(57) [Claims] An apparatus for performing backlight correction using an image pickup signal captured by an image pickup apparatus having an automatic aperture function, comprising: comparing an luminance level of the image pickup signal with a predetermined level to reduce unnecessary high luminance portions; Unnecessary part detecting means for detecting; memory means for storing position information of the unnecessary high luminance portion in one imaging screen; attenuating means for attenuating the luminance level of the imaging signal; and the unnecessary high luminance portion according to the position information. A selecting means for selecting an image signal output from the attenuating means, and selecting the image signal in other portions; and an automatic iris for adjusting an amount of incident light from a subject based on the image signal selected by the selecting means. And a backlight compensation device. 2. An image pickup apparatus having an automatic aperture function, comprising: an image pickup means for converting an image of a subject into an electric signal; and an image pickup signal of the image pickup means, and comparing the luminance level with a predetermined level sequentially. Unnecessary part detecting means for detecting unnecessary high luminance portions by performing the above operation; memory means for storing position information of the unnecessary high luminance parts in one imaging screen; attenuating means for attenuating the luminance level of the imaging signal; In the unnecessary high luminance portion, an image signal output from the attenuating device is selected in the unnecessary high luminance portion, and in other portions, a selecting device for selecting the image signal, and from the object based on the image signal selected by the selecting device, And an automatic aperture means for adjusting the amount of incident light.