Electronic Camera

Abstract

Disclosed herein is an electronic camera for generating an image having a wide dynamic range by synthesizing two image pickup signals of different exposure amount generated by using an electronic shutter function and means for shutting off light, shading of image pickup signals resulting from difference in charge accumulating time among the pixels of image pickup device due to operation from opened state to closed state of the means for shutting off light being corrected by a shading correction means to form a synthesized image without an occurrence of false color due to shading. Also provided is an electronic camera generating two image pickup signals of different exposure amount by two shots of picture taking each using a flash emission in combination, at least one of an electronic shutter of image pickup device and means for shutting off light, as well as an emission of the flash emission means, being controlled to equalize between the two shots of picture taking ratio of exposure by normal light excluding light from the flash emission means and ratio of emission amount by the light from the flash emission means so that the two image pickup signals can be readily generated as having a predetermined exposure amount ratio in every part of a frame of picture even when a flash emission is used in combination.

Description

INCORPORATED-BY-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application of U.S. Ser. No. 10 / 790,189, filed Mar. 2, 2004, which is a continuation application of U.S. Ser. No. 09 / 204,276 filed on Dec. 3, 1998, now U.S. Pat. No. 6,744,471, and is based upon and claims the benefit of priority from the prior Japanese Patent Application Nos. 9-350185, 9-361661, and 10-48594, filed on Dec. 5, 1997, Dec. 11, 1997, and Feb. 16, 1998, respectively, the entire contents of which are incorporated by reference.BACKGROUND OF THE INVENTION[0002]The present invention relates to electronic cameras (commonly called as digital still camera) in which a plurality of image pickup signals of different exposure amount read out from a single image pickup device are synthesized to obtain an image having a wide dynamic range.[0003]Although solid-state image pickup devices such as CCD image pickup device are used in such image pickup apparatus as TV camera, video camera, electronic c...

AI Technical Summary

Benefits of technology

The solution effectively corrects shading and ensures accurate exposure control, allowing for the synthesis of images with a wide dynamic range without false colors, even when using strobe light, by controlling charge accumulating time and using a focal-plane shutter for precise exposure management.

Problems solved by technology

Although solid-state image pickup devices such as CCD image pickup device are used in such image pickup apparatus as TV camera, video camera, electronic camera, etc., there is a problem that the dynamic range of a solid-state image pickup device is much narrower than that of a silver salt photographic film.

There is another problem that, in respect of control of charge accumulating period, a means for shutting off light is not very accurate when compared to an electronic shutter of the image pickup device.

Furthermore, in the techniques disclosed in the above publications, an accuracy is not taken into consideration in setting an exposure amount ratio of two image pickup signals when the two image pickup signals of different exposure amount are to be obtained.

In forming a synthesized image having a wide dynamic range through a synthesis of two image pickup signals of different exposure amount, if an attempt is made to simply synthesize the obtained two image pickup signals where one of the image pickup signals is generated by using natural light alone and the other of the image pickup signals by a strobe light in combination, it is difficult due to the intrinsically large variance of a strobe light, even with a constant exposure time, to attain a precise correspondence between the two image pickup signals in order to achieve a predetermined ratio of their exposure amounts.

Furthermore, in the case of synthesizing image pickup signal by natural light and image pickup signal by a strobe light, since these are the image pickup signals different from each other in white balance, there is a problem that color balance is partially lost in the synthesis.

Further, while the above Japanese patent application laid open No. 6-141229 discloses a technique in which synthesis is smoothly performed while changing the weighting factor when two image pickup signals of different exposure amount are synthesized to synthesize an image having a wide dynamic range, the problem of false color in synthesizing a color image is not considered and no disclosure is made with respect to the problems in using a strobe.

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