Image pickup apparatus for obtaining a better color image over a wider luminance range

• US 5,818,522 A
• Filed: 04/16/1996
• Issued: 10/06/1998
• Est. Priority Date: 04/17/1995
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sato, Itsuzo, Ooi, Kazushige
• Primary Examiner(s): Garber, Wendy
• Assistant Examiner(s): AUDUONG, GENE NGHIA
• Application Number:
  US08/633,083
• Time in Patent Office: 903 Days
• Field of Search: 348/222, 348/223, 348/224, 348/256, 348/675, 348/678, 348/679, 348/254, 348/259, 348/272, 348/266, 348/234, 348/235, 348/221, 348/229, 348/230, 348/362, 348/364, 348/366, 348/369, 348/655, 348/659, 348/660, 348/226
• US Class Current: 348/222.1
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/84 for processing colour signals

Abstract

A plurality of shutter times are set to an image pickup device and an image is taken in a way to separate an incident light amount range into a low and a high luminance and, through the signal processing, it is possible to take an image over a wider dark to bright light amount range and, in particular, obtain a better color reproduction over a wider luminance range. In the case where an (R-Y) signal and (B-Y) signal are processed with a low-speed and high-speed shutter signal obtained and the high-speed shutter signal is subjected to logarithmic conversion and a bias signal is applied to provide a continuity with the low-speed shutter signal, processing is performed on a comparing section, characteristic conversion section and calculating section so that a greater one of the (R-Y) and (B-Y) signals is subjected to logarithmic conversion and the other signal is subjected to characteristic conversion in accordance with a value corresponding to a conversion ratio. Further, in the case where a bias voltage is applied to the greater color difference signal, a bias voltage is found in accordance with a ratio of the greater color difference signal and smaller color difference signal and applied to the other smaller color difference signal.

Claims

1. A color image pickup apparatus including a color image pickup device using a video signal obtained at a low shutter speed and a video signal at a high shutter speed, comprising color signal processing means having

means for, when a color signal obtained at a high shutter speed is subjected to characteristic conversion, selecting a specific color difference signal of a plurality of color difference signals in the color signal and subjecting the specific color difference signal to characteristic conversion, and

means for, with the use of conversion information of the specific color difference signal subjected by said means to characteristic conversion, subjecting the other color difference signal to characteristic conversion.

2. The color image pickup apparatus according to claim 1, wherein the color signal processing means has

means for selecting a greater level one of the plurality of color difference signals as the specific color signal and providing a logarithmic conversion characteristic to the specific color difference signal;

means for finding a conversion ratio by calculating those color signals, one before providing the logarithmic conversion characteristic and one after providing the logarithmic conversion characteristic, and

means for subjecting said other color difference signal to characteristic conversion by calculating the conversion ratio and said other color difference signal.

3. The color image pickup apparatus according to claim 1, wherein said color signal processing means has

means for adding a first bias signal to a greater level one of the plurality of color difference signals;

means for calculating a ratio of the greater level one of the plurality of color difference signals and said other color difference signal of a low level;

means for preparing a second bias signal varied by the ratio from the first bias signal; and

means for adding the second bias signal to said other color difference signal of a low level.

4. The color image pickup apparatus according to claim 1, wherein, in the color image pickup device using a video signal obtained at a low shutter speed and a video

signal at a high shutter speed, the color signal processing means has

first means for selecting a greater level one of the plurality of color difference signals as the specific color difference signal and subjecting the specific color difference signal to logarithmic conversion characteristic,

second means for finding a conversion ratio by calculating those color signals, one before providing the logarithmic conversion characteristic and one after providing the logarithmic conversion characteristic,

third means for subjecting said other color difference signal to characteristic conversion by calculating the conversion ratio and said other color difference signal,

fourth means for adding a first bias signal to an output signal of the first means,

fifth means for calculating a level ratio between an output signal of the first means and that of the third means;

sixth means for preparing a second bias signal varied by the ratio from the first bias signal, and

seventh means for adding the second bias signal to the output signal of the third means.