Color video camera with auto-white balance control

A color video camera comprising:

• image pickup means having a light reception surface for providing color video signal luminance and chrominance components corresponding to a light image projected on said surface;
• an integrating circuit for each of said luminance and chrominance components, each said integrating circuit providing an average value of the respective component;
• a gate circuit for each said integrating circuit permitting the latter to receive the respective color video signal component only when the respective gate circuit is enabled;
• means for determining, pixel-by-pixel, when said color video signal components have values that are within a predetermined range of white as defined by a black body radiation curve;
• means for enabling each said gate circuit whenever it is determined that said values are within said range;
• and
• means for effecting white-balance control with reference to said average values of the components;
• said range being relatively wide when said values of the color video signal components deviate substantially from a relationship characteristic of a desired white balance, and said range being reduced as said values of the color video signal components near said relationship characteristic of said desired white-balance.

A method of generating white-balance detection signals from color video signal components corresponding to a light image projected on an image pickup of a color video camera, said method comprising the steps of:

• sampling said color video signal components to provide pixel-by-pixel values thereof;
• determining which of said pixel-by-pixel values are within a predetermined range of white as defined by a black body radiation curve;
• integrating only said pixel-by-pixel values which are determined to be within said range so as to obtain average values thereof as said white-balance detection signals;
• and
• varying said range in dependence upon the deviation of said white-balance signals from a relationship characteristic of a desired white-balance.

A method of generating white-balance detection signals from color video signal components corresponding to a light image projected on an image pickup of a color video camera, said method comprising the steps of:

• determining, pixel-by-pixel, when said color video signal components have values that are within a predetermined range of white as defined by a black body radiation curve;
• gating the color video signal components to respective integrators whenever it is determined that said values are within said range;
• integrating the gated color video signal components so as to obtain average values thereof as said white-balance detection signals;
• making said range relatively wide when said values of the color video signal components deviate substantially from a relationship characteristic of a desired white-balance;
• and
• reducing said range as said values of the color video signal components near said relationship characteristic of said desired white-balance.