Camera device, exposure control method, and program
A camera device ( 1 ) includes an imaging unit ( 2 ) which outputs a long exposure signal and a short exposure signal in one field period. A face detection unit ( 8 ) detects a face area from an image captured by the imaging unit ( 2 ). The weighting processing unit ( 12 ) applies a weighting process to luminance data of the long exposure signal in the detected face area using a weighting constant for reducing the luminance level of the long exposure signal. If the luminance level of the weighting-processed long exposure signal rises to a predetermined saturation level or higher, an exposure control unit ( 15 ) performs exposure control using the long exposure signal and the short exposure signal. This can suppress occurrence of a noise due to a short exposure signal (flickering) in the face area, thereby improving visibility in the face area.
1. A camera device, comprising:
an imager that outputs a long exposure signal and a short exposure signal, the long exposure signal being an image signal with a long exposure time and the short exposure signal being an image signal with a short exposure time in a predetermined unit field period;
a face detector that detects a face area from an image captured by the imager;
a weighting processor that applies, when the face detector detects the face area, a weighting process to a luminance level of the long exposure signal in the detected face area using a weighting constant to reduce the luminance level of the long exposure signal in the detected face area; and
an exposure controller that performs exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is equal to or higher than a predetermined saturation level, and is prevented from performing the exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is lower than the saturation level.
2. The camera device according to claim 1 , wherein when the luminance level of the long exposure signal in the detected face area is lower than a predetermined threshold level, the weighting processor applies the weighting process to the luminance level of the long exposure signal to reduce the luminance level of the long exposure signal.
3. The camera device according to claim 1 , further comprising a face area gain controller that increases a gain of the long exposure signal in the detected face area in the image, when the luminance level of the long exposure signal in the detected face area is lower than a predetermined threshold level.
4. The camera device according to claim 1 , further comprising an entire area gain controller that increases a gain of the long exposure signal in an entire area of the image when the luminance level of the long exposure signal in the detected face area is lower than a predetermined threshold level.
5. The camera device according to claim 1 , further comprising a representative level calculator that calculates a representative luminance level of the long exposure signal in the detected face area on the basis of the reduced luminance level of the long exposure signal,
wherein when the representative luminance level is equal to or higher than the saturation level, the exposure controller performs the exposure control using the long exposure signal and the short exposure signal.
6. The camera device according to claim 5 , wherein when a reference luminance level, which is subjected to a process of gradually bringing the luminance level to the representative luminance level as a target, is equal to or higher than the saturation level, the exposure controller performs the exposure control using the long exposure signal and the short exposure signal.
7. The camera device according to claim 1 , wherein the exposure controller performs exposure control using the long exposure signal and the short exposure signal in the detected face area, when the reduced luminance level of the long exposure signal is equal to or higher than the predetermined saturation level, and
the exposure controller performs exposure control using the long exposure signal and the short exposure signal in an area other than the detected face area, when the luminance level of the long exposure signal output by the imager is equal to or higher than the predetermined saturation level.
8. The camera device according to claim 1 , wherein the exposure controller determines, in the detected face area, whether or not the reduced luminance level of the long exposure signal is equal to or higher than the predetermined saturation level, and
the exposure controller determines, in an area other than the detected face area, whether or not the luminance level of the long exposure signal output by the imager is equal to or higher than the predetermined saturation level.
9. The camera device according to claim 8 , wherein, in the detected face area, when the exposure controller determines that the reduced luminance level of the long exposure signal is equal to or higher than the saturation level, a gain of the short exposure signal is increased, and
in the area other than the detected face area, when the exposure controller determines that the luminance level of the long exposure signal output by the imager is equal to or higher than the saturation level, a gain of the short exposure signal is increased.
10. An exposure control method used in a camera device including an imager outputting a long exposure signal and a short exposure signal, the long exposure signal being an image signal with a long exposure time and a short exposure signal being an image signal with a short exposure time in a predetermined unit field period, the method comprising:
detecting a face area from an image captured by the imager;
applying, when the face area is detected, a weighting process to a luminance level of the long exposure signal in the detected face area using a weighting constant to reduce the luminance level of the long exposure signal in the detected face area; and
performing exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is equal to or higher than a predetermined saturation level, and preventing the performance of the exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is lower than the saturation level.
11. A non-transitory computer readable recording medium storing a program for exposure control in a camera device including an imager outputting a long exposure signal and a short exposure signal, the long exposure signal being an image signal with a long exposure time and a short exposure signal being an image signal with a short exposure time in a predetermined unit field period, the program causing a computer to perform:
detecting a face area from an image captured by the imager;
applying, when the face area is detected, a weighting process to a luminance level of the long exposure signal in the detected face area using a weighting constant to reduce the luminance level of the long exposure signal in the detected face area; and
performing exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is equal to or higher than a predetermined saturation level, and preventing the performance of the exposure control using the long exposure signal and the short exposure signal when the reduced luminance level of the long exposure signal in the detected face area is lower than the saturation level.