Electronic still camera with enhanced tonal rendition

• US 5,303,049 A
• Filed: 01/14/1991
• Issued: 04/12/1994
• Est. Priority Date: 02/07/1990
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Ikuma, Takao, Ejima, Satoshi
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Metjahic, Safet
• Application Number:
  US07/640,922
• Time in Patent Office: 1,184 Days
• Field of Search: 358/209, 358/909, 358/906, 358/335, 358/213.19, 358/211, 358/228, 354/431, 354/429, 354/432, 354/410
• US Class Current: 348/231.6
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

An electronic still camera having an image pickup device for converting the image of an object into an image signal; a regulator for regulating the amount of exposure of the image pickup device; a controller for causing the image pickup device to generate the image signal plural times and controlling the regulator in such a manner that the plural image signals have mutually different amounts of exposure; a mean calculator for calculating the mean value of data of mutually corresponding pixels in the plural image signals; and a recording device for recording a mean image signal thus obtained.

Claims

1. An electronic still camera comprising:

image pickup means for converting the image of an object input through a phototaking lens into an image signal;

calculation means for calculating an appropriate exposure amount of the object image;

regulation means for regulating the amount of exposure in said image pickup means;

means for producing a mean image signal, including control means for causing said image pickup means to generate only two image signals of the object and controlling said regulation means in such a manner that one of said two image signals has a first exposure amount greater than said calculated appropriate exposure amount and the other of said two image signals has a second exposure amount less than said calculated appropriate exposure amount, and further including mean value determination means for calculating the mean value of corresponding pixel data from each of said two image signals so as to determine said mean image signal; and

means for storing said mean image signal.

2. An electronic still camera according to claim 1, wherein said image pickup means produces an analog image signal, said mean value determination means includes means for converting the analog image signal into digital image data and memory means for storing digital image data of said two image signals, and said mean value determination means is adapted to calculate the mean value for each pixel of the object image based on the corresponding stored digital image data of said two image signals.

3. An electronic still camera according to claim 1, wherein said image pickup means produces an analog image signal, said mean value determination means includes memory means and conversion means for converting the analog image signal into digital image data, and said mean value determination means stores the digital image data from a first of said two image signals in said memory means and calculates, for each pixel of the object image, the mean value of the stored digital image data for that pixel and corresponding digital image data for that pixel from a second of said two image signals output from said conversion means.

4. An electronic still camera according to claim 1, wherein a ratio of said first exposure amount to said calculated appropriate exposure amount is equal to a ratio of said calculated appropriate exposure amount to said second exposure amount.

5. An electronic still camera according to claim 1, further comprising first memory means for storing the image signal generated with said first exposure amount and second memory means for storing the image signal generated with said second exposure amount.

6. An electronic still camera according to claim 5, wherein said calculating means calculates said appropriate exposure amount in response to actuation of shutter release means, whereafter said two image signals are generated and stored, respectively, in said first and second memory means, and wherein said mean value determination means determines said mean image signal from the image signals stored in said first and second memory means.