This invention relates to a color imaging apparatus, more particularly to a color imaging apparatus capable of compensating a color reproduction characteristic in response to a variation of a color temperature of a light.
A conventional simplified single-chip color imaging apparatus generates a signal representing luminance information and a plurality of signals representing color information from an output signal of a single-chip imaging device. The signals representing color information are obtained as a difference signal or sum signal between two color signals and are used for providing two color difference signals necessary to obtain a composite color video signal.
In a conventional single-chip CCD camera as disclosed, for example, in an article entitled "Single Chip CCD Color Camera Using Field Integration Mode" by Y. Sone et al. published in the "Technical Report of the Institute of Television Engineers of Japan" TEB87-3 ED 691, pp 23-28 (Mar. 18, 1983), two color difference signals 2R-G and 2B-G are obtained line-sequentially from n-th and (n+1)-th lines, respectively and are delayed by one-horizontal scanning period (1H). Ratio of the signal components R, G and B included in the color difference signals is determined by characteristics of color filters. In the case where light separation characteristics of the color filters are defined so that the best color reproduction characteristic is obtained by using a light having a color temperature of 3200 K., the ratio of the color signal components R, G and B included in the color difference signals obtained by using the light of a different color-temperature varies in accordance with the color temperature so that the ratio of the signal component R becomes large under a lower color-temperature and the ratio of the signal component B becomes large under a higher color-temperature. Since the ratio of the signal components R, G and B determines final imaging characteristics of the color difference signals, the variation of the color temperature deteriorates the color reproduction characteristic.
To prevent the deterioration of the color reproduction characteristic, an optical system for the conventional imaging apparatus necessitates color-temperature converting filters. In order to convert the color temperature in a wide range from lower than 3000 K. (for incandescent lamps) to higher than 10000 K. (for outdoors) into the specific color-temperature for the standard light (for example, 3200 K.) with a less error, there must be provided a great number of color-temperature converting filters having optical characteristics different from one another. This causes inconvenience in a practical use of the color imaging apparatus. In contrast therewith, a lesser number of color-temperature converting filters deteriorates the color reproduction characteristic.