JP2844894B2 - Automatic exposure control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic exposure control device used for a color video camera or the like.

[Prior Art] An example of this type of conventional automatic exposure control device will be described below with reference to FIG. 2 showing a signal processing block thereof. The amount of light transmitted through the photographing lens 1 is adjusted by an aperture 2, and then forms an image on an image pickup device 4 such as a CCD through a lens 3. The signal output of the image sensor 4 is amplified by the amplifier 5 and then detected by the detection circuit 12, and the aperture 2 is driven by the aperture driver 13 so that the detected output becomes a constant level, that is, the CCD becomes the optimum operating point. Is done. If the image sensor 4 has an electronic shutter function, the shutter speed may be controlled.

After the signal output from the image sensor 4 is amplified by the variable gain amplifier 6, the color signal coded by the color filter attached to the image sensor 4 is color-separated by the color separation circuit 7, and the color signal processing is further performed. The color signal processing is performed by the circuit 8 to become a color difference signal (RY, BY). On the other hand,
The luminance component of the signal output of the image sensor 4 is calculated by a luminance signal processing circuit.
The luminance signal is processed by 10 and input to the encoder circuit 9. The former color difference signal is balanced-modulated by the encoder circuit 9 and mixed with the luminance signal to form a composite video signal 14. The luminance signal processing output is detected by the detection circuit 11 and is fed back to the variable gain amplifier 6, where the gain of the variable gain amplifier 6 is adjusted so that the output becomes a constant level.

The final video signal level is determined by the variable gain amplifier 6. In particular, at low illuminance, the luminance signal level becomes low even when the aperture is opened. Therefore, the gain of the variable gain amplifier 6 is increased to make the luminance signal level constant.

As described above, in the related art, the exposure control is not performed by paying attention to the color, but is controlled so that the luminance signal level is constant.

In addition to the above, there is an automatic exposure control device that detects a subject position based on a luminance difference or a difference in a high-frequency component inside and outside a photometry area in a shooting screen and automatically tracks the photometry area (for example, Japanese Patent Application Laid-Open No. 1-1120178, JP-A-1-120181).

However, in any of the above-described apparatuses, the exposure setting is not performed in consideration of what is to be mainly photographed as a subject, so that an improper exposure level may be obtained when a person is mainly photographed. is there.

When the exposure of the video camera is set manually, it is stated that a preferable reproduction can be obtained as follows.

The highlighted part of the screen has a signal level of 1001RE (IRE: Instit
ute of Radio Engineers).

When shooting a person, set the signal level of the person's skin color to 55.
Make it ~ 75IRE.

Thus, the appropriate exposure level changes depending on whether the main subject is the skin of a person. However, in the conventional exposure control, even if the luminance signal level of the screen becomes constant, the signal level of the skin of a person does not always reach a desirable level. This occurs particularly when the subject is backlit, when the background is dark, and when a spotlight is shining on the person.

Therefore, there is a concept of extracting a flesh-colored part and setting a signal level of the flesh-colored part to a constant level in order to obtain an appropriate exposure level when mainly photographing a person.

[Problems to be Solved by the Invention] However, even if there is a flesh-colored portion in the screen, the flesh-colored portion is not always the main subject, so that even if the flesh-colored portion is properly exposed, the entire image may be inappropriate. is there. This occurs, for example, when the person is in the corner, when the person crosses the shooting screen, or when there are a plurality of persons.

Even if there is a person's skin on the screen, the appropriate exposure changes depending on whether the photographer wants to make the person the main subject.

The present invention solves the above-mentioned problems, and is generally considered to focus on the subject that is the main subject of shooting. Therefore, if a flesh-colored part is detected and a person is focused on that part, a person is detected. If the exposure is controlled as the main subject and there is no skin color even if there is a skin color, or if there is no skin color, it is highly likely that proper exposure can be obtained by setting the exposure level so that the scenery is appropriate It is an object to provide an automatic exposure control device.

Means for Solving the Problems In order to achieve the above object, the present invention provides a skin color extracting means for extracting a flesh color part from an input video signal, a focus judging means for judging a focus of the flesh color part, The exposure is adjusted based on the outputs of the two means, and at least when it is detected that the skin color portion is extracted and the skin color portion is in focus, the exposure is adjusted so that the skin color portion is properly exposed. The automatic exposure control device includes an exposure adjusting means for setting the exposure.

[Operation] According to the above configuration, it is detected whether or not the skin color portion is in focus and whether or not the skin color portion is in focus. When the camera is focused on a portion other than the flesh-colored portion, the control is performed so that the signal level of the entire screen is constant, that is, for example, the landscape is appropriately exposed, for example, considering that the image is mainly composed of the landscape.

Embodiment FIG. 1 shows a block configuration of an automatic exposure control device according to an embodiment of the present invention. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals.

In this apparatus, in addition to the above configuration, as a skin color extracting means for extracting a skin color portion from an input video signal, a skin color portion extracting circuit 15
And a band-pass filter (BPF) 16, a skin-color high-frequency component detection circuit 17, and a focus determination circuit 18 as focus determination means for determining the focus of the skin color portion. Exposure adjustment means that performs exposure adjustment based on
The image processing apparatus includes a flesh color portion average luminance level detection circuit 19, a microcomputer 20, and the like. The output of the microcomputer 20 passes through the D / A converter 21 and the output of the detection circuit 11 and the mixer 2
2, the variable gain amplifier 6 is feedback-controlled by the output of the mixer 22.

The operation of the present device will be described. After the color signal processing by the color signal processing circuit 8, the skin color portion is extracted by the skin color portion extraction circuit 15.
The extraction of the skin color portion may be performed, for example, so that the output of the skin color portion extraction circuit 15 becomes Hi level when the “ratio” and “value” of the color difference signals RY and BY fall within a certain range. .

The high-frequency component of the luminance signal from the luminance signal processing circuit 10 is extracted by the BPF 16, and the high-frequency component of the skin color portion is detected by the flesh-color high-frequency component detection circuit 17 receiving the flesh-color portion extraction signal. If a flesh-colored part exists in the screen and the part is in focus, many high-frequency components are detected. When there is no flesh-colored part or when the subject is out of focus, no high-frequency component is detected. The focus determination circuit 18 determines focus based on whether or not the high-frequency component is at a predetermined level.
Send a signal to On the other hand, the flesh-tone average luminance level detection circuit 19
Then, the average value of the luminance signal level of only the flesh color portion is detected in response to the flesh color portion extraction signal. The detected level is converted into a digital value and sent to the microcomputer 20.

When the focus determination signal output of the skin color portion indicates the focus, the microcomputer 20 determines whether the average luminance level of the focused skin color portion is appropriate. An exposure correction signal is output based on this determination result, and the detection circuit 11
The exposure is corrected by performing feedback control of the variable gain amplifier 6 by being mixed with the output of the variable gain amplifier 6. That is, as an example, if the luminance level of the skin color portion is 55 to 75 IRE, it is determined that the exposure is appropriate. If the luminance level is 55 IRE or less, the luminance of the skin color portion is 55 I
Output the exposure compensation signal so that it becomes RE or more. When the luminance of the skin color portion is 75 IRE or more, an exposure correction signal is output so as to be 75 IRE or less. In this way, when the skin color portion is in focus, the exposure is corrected so that the luminance of the skin color portion becomes an appropriate level, so that an appropriate exposure can be obtained.

On the other hand, when the focus is not on the skin color portion, it is determined that the photographing is mainly composed of the scenery, and the exposure level is not corrected, and the normal feedback circuit is controlled so that the scenery is properly exposed.

FIG. 3 shows another embodiment. In this embodiment, an AF area skin color detection circuit 150 that receives a signal from the color signal processing circuit 8 and detects whether the subject in the AF area is skin color,
An AF area skin color portion average luminance level detection circuit 190 to which the skin color detection signal from the circuit 150 is input is provided.
Is given to the microcomputer 20.

In this configuration, if the subject in the AF area is a skin color, it is considered that the photographer is going to take a portrait. Therefore, the control may be performed so that the flesh color portion is properly exposed when the flesh color detection signal is output. Further, when a skin color portion is not detected in the AF area, the exposure level need not be particularly corrected.

The present invention is not limited to the configuration of the embodiment described above, and various modifications are possible. For example, in the above description, the correction of the exposure level by the variable gain amplifier 6 has been described as an example. The control may be performed by controlling the shutter speed or a combination thereof.

[Effects of the Invention] As described above, according to the present invention, when a skin color portion is extracted and it is determined that the skin color portion is in focus,
Since the skin tone portion is controlled so as to have an appropriate exposure, there is a high possibility that an appropriate exposure can be obtained not only when a person is the main subject but also when a landscape is the main subject.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic exposure control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional device,
FIG. 3 is a block diagram showing another embodiment of the present invention. 6 ... variable gain amplifier, 8 ... color signal processing circuit, 10 ...
Luminance signal processing circuit, 15: skin color portion extraction circuit, 16: band pass filter, 17: skin color portion high frequency component detection circuit, 18
...... Focus determination circuit, 19 ... skin color part average luminance level detection circuit, 20 ... microcomputer, 150 ... AF area skin color detection circuit, 190 ... AF area skin color part average luminance level detection circuit.

Continued on the front page (72) Gen Sasaki, Inventor 2-3-3, Azuchicho, Chuo-ku, Osaka-shi, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (72) Keizo Ochi, 2-chome Azuchicho, Chuo-ku, Osaka-shi, Osaka No. 3-13 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Takehiro Kato 2-3-13 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Yoshihiko Higashi Osaka Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hiroshi Otsuka 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Camera Co., Ltd. 56) References JP-A-3-148987 (JP, A) JP-A-2-287225 (JP, A) JP-A-1-114188 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) H04N 9/04-9/11 H04N 5/225-5/253

Claims (1)

(57) [Claims] A skin color extraction unit for extracting a skin color portion from an input video signal; a focus determination unit for determining a focus of the skin color portion; and adjusting an exposure based on an output of the two units. An exposure adjusting means for adjusting the exposure so that the flesh-colored portion is properly exposed when the flesh-colored portion is extracted and it is detected that the flesh-colored portion is in focus. Automatic exposure control device.