CAMERA DEVICE, EXPOSURE CONTROL METHOD, AND PROGRAM

• US 20120120280A1
• Filed: 03/31/2010
• Published: 05/17/2012
• Est. Priority Date: 05/25/2009
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Oyabu, Satoru, Nakamura, Yasuji, Kawakami, Satoshi
• Granted Patent: US 8,477,212 B2
• Time in Patent Office: Days
• US Class Current: 348/229.1
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Abstract

A camera device (1) is provided with an imaging unit (3) for outputting a long exposure signal and a short exposure signal within one field period; a knee processing unit (12) for compressing a long exposure signal having the luminance level of a knee point or higher at a predetermined compression rate (i.e., decreasing the inclination of an incident light amount-luminance level line representing the variation of a luminance level with the amount of incident light); and a knee control unit (14) for adjusting the knee point and the compression rate according to the luminance level of a synthesized signal obtained by synthesizing the long exposure signal and the short exposure signal. In this knee control, the knee point and the compression rate are adjusted, so as to make the knee point lower with an increase in the luminance level of the synthesized signal of the long exposure signal and the short exposure signal and revert the inclination of the incident light amount-luminance level line to the original state thereof. Consequently, it is possible to obtain an image sharply contrasted in bright parts within a screen.

Claims

1. A camera device comprising:

an imaging unit which outputs a long exposure signal and a short exposure signal, the long exposure signal being a video signal which has a long exposure time and the short exposure signal being a video signal which has a short exposure time within one field period;

a knee processing unit which compresses, at a predetermined compression rate, the long exposure signal which has a luminance level equal to or higher than a knee point which is a reference luminance level at which knee processing is performed, to decrease the inclination of an incident light amount-luminance level line which represents the variation of a luminance level with the amount of incident light input to the imaging unit; and

a knee control unit which adjusts the knee point and the compression rate according to the luminance level of a synthesized signal obtained by synthesizing the long exposure signal and the short exposure signal, so as to make the knee point lower with an increase in the luminance level and revert the inclination to the original state thereof.

2. The camera device according to claim 1, further comprising:

a low-luminance area detection unit which detects a low-luminance area at a predetermined threshold luminance level or lower in an image obtained by synthesizing the long exposure signal and the short exposure signal; and

a gain control unit which raises the gain of the long exposure signal in the low-luminance area.

3. The camera device according to claim 1, further comprising:

a dynamic area detection unit which detects a dynamic area which includes a moving subject in an image obtained by synthesizing the long exposure signal and the short exposure signal; and

a second gain control unit which raises the gain of the long exposure signal in the dynamic area.

4. An exposure control method used in a camera device comprising an imaging unit which outputs a long exposure signal and a short exposure signal, the long exposure signal being a video signal which has a long exposure time and a short exposure signal being a video signal which has a short exposure time within one field period, the method including:

compressing, at a predetermined compression rate, the long exposure signal which has a luminance level equal to or higher than a knee point which is a reference luminance level at which knee processing is performed, to decrease the inclination of an incident light amount-luminance level line which represents the variation of a luminance level with the amount of incident light input to the imaging unit; and

adjusting the knee point and the compression rate according to the luminance level of a synthesized signal obtained by synthesizing the long exposure signal and the short exposure signal, so as to make the knee point lower with an increase in the luminance level and revert the inclination to the original state thereof.

5. A program used for the exposure control of a camera device comprising an imaging unit which outputs a long exposure signal and a short exposure signal, the long exposure signal being a video signal which has a long exposure time and a short exposure signal being a video signal which has a short exposure time within one field period;

the program causing a computer to perform the processes of;

compressing, at a predetermined compression rate, the long exposure signal which has a luminance level equal to or higher than a knee point which is a reference luminance level at which knee processing is performed, to decrease the inclination of an incident light amount-luminance level line which represents the variation of a luminance level with the amount of incident light input to the imaging unit; and

adjusting the knee point and the compression rate according to the luminance level of a synthesized signal obtained by synthesizing the long exposure signal and the short exposure signal, so as to make the knee point lower with an increase in the luminance level and revert the inclination to the original state thereof.