Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
2000-01-19
2004-04-27
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S345000
Reexamination Certificate
active
06727943
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 11-11509.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic camera having a white balance adjustment function. The present invention also relates to a recording medium that stores an image processing program for white balance adjustment.
2. Related Art
Methods known in the art which are employed to implement white balance adjustment in electronic cameras include the external sensor method and the TTL image-capturing element method. In the external sensor method, a diffused light receiving window such as an diffusion plate and a color sensor are provided in the electronic camera in addition to the image-capturing element of the camera to achieve white balance adjustment by estimating the color of the light source based upon the results of the output from the color sensor. In the TTL image-capturing element method, white is extracted by integrating the image signals corresponding to the entire image plane or image signals corresponding to a portion of the image plane for all the colors based upon the subject image signals received by the image-capturing element via taking lens. Both methods are achieved through application of the principle that when the colors of a normal subject are integrated, an achromatic color (gray) results.
The external sensor method has the following problem yet to be addressed.
(1) The area around the subject and the area around the camera may not be irradiated by the same light and in such a case, an error may occur.
The TTL image-capturing element method has the following problems yet to be addressed.
(1) Since it is necessary to engage the image-capturing element in an operation at all times through exposure, a great quantity of power is consumed when an image-capturing element with a large number of pixels is employed.
(2) When the TTL image-capturing element method is adopted in a single lens reflex camera having good viewfinder visibility, additional members such as a half mirror are required.
(3) In order to extract white from the subject colors, white must be extracted from colors in the entire image plane or in an area constituting a portion of the image plane. When the number of pixels is large, e.g., over 2 million pixels, the circuit is bound to become large and complex to perform integration of the image signals at high speed. In particular, when a method through which the image-capturing element is divided into blocks each constituted of a specific number of pixels to perform various types of image processing is adopted, the circuit scale is bound to become large to perform the integration operation within each block at high speed.
(4) Accurate white balance adjustment cannot be achieved if a portion illuminated by different light such as a person near a window is present within the image plane.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electronic camera capable of estimating the light source color through a simple circuit structure and having a white balance adjustment function which enables high speed processing and low power consumption.
Another object of the present invention is to provide a recording medium that stores an image processing program for white balance adjustment that enables light source color estimation to be achieved at high speed and with low power consumption.
The electronic camera having a white balance adjustment function according to the present invention comprises a photographic image-capturing element that receives a subject light flux and outputs a photographic image signal, a white balance adjustment image-capturing element that receives the subject light flux and outputs a white balance adjustment image signal, an offset quantity calculation unit that extracts color data based upon the image signal for, at least, a portion of a photographic image plane of the white balance adjustment image-capturing element and determines a quantity by which the color data are offset from light source reference color data, a light source color estimation unit that estimates the light source color by evaluating the offset quantity calculated by the offset quantity calculation unit, and an adjustment unit that adjusts the white balance of the image signal output by the photographic image-capturing element based upon the estimated value obtained by the light source color estimation unit.
The white balance adjustment image-capturing element may output image signals that each correspond to areas achieved by dividing the photographic image plane into a plurality of areas. In this case, the offset quantity calculation unit ascertains the quantity by which the image signal corresponding to each divided area is offset from the light source reference color data and the light source color estimation unit estimates the light source color by evaluating the offset quantities calculated for the plurality of areas in conformance to a specific criterion.
If the electronic camera is further provided with a focal point detection unit having a plurality of focal point detection areas, the offset quantity calculation unit calculates the offset quantity in a divided area that corresponds to a focal point detection area used in focal point detection performed by the focal point detection unit.
The light source reference color data may be either a full radiator locus or a standard correlated color temperature locus. The offset quantity may be represented by the distance from the full radiator locus on a uniform color space, the distance from the standard correlated color temperature locus or a value achieved by multiplying either distance with a constant. The specific criterion adopted by the light source color estimation unit is a criterion for determining whether or not the offset quantity is within a specific range from the full radiator locus or the standard correlated temperature locus.
The light source color estimation unit estimates that the light source is of a specific color if the offset quantity does not satisfy the specific criterion. If the offset quantity is within a predetermined white data range, it decides that the specific criterion is satisfied.
Another electronic camera having a white balance adjustment function according to the present invention comprises a photographic image-capturing element that receives a subject light flux and outputs a photographic image signal, a white balance adjustment image-capturing element that receives the subject light flux and outputs a white balance adjustment image signal, an offset quantity calculation unit that extracts color data based upon image signals each corresponding to one of a plurality of areas achieved by dividing the photographic image plane of the white balance adjustment image-capturing element into a plurality of areas and ascertains quantities by which the color data are offset from light source reference color data, a light source color estimation unit that estimates the light source color based upon color data corresponding to the average value of the offset quantities within a predetermined reference range among the plurality of offset quantities calculated by the offset quantity calculation unit or color data corresponding to the smallest offset quantity among the plurality of offset quantities calculated by the offset quantity calculation unit, and an adjustment unit that adjusts the white balance of the image signal output by the photographic image-capturing element based upon the estimated value obtained by the light source color estimation unit.
If this electronic camera, too, is further provided with a focal point detection unit with a plurality of focal point detection areas, it is desirable to calculate an offset quantity in at least one divided area corresponding to a focal point detection area used for focal point detection performed by the focal point detection unit.
In addition, in this electronic camera, too, the light source refer
Garber Wendy R.
Nikon Corporation
Oliff & Berridg,e PLC
Rosendale Matthew L
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