Exposure control apparatus for a still video camera having an electronic viewfinder

• US 4,746,988 A
• Filed: 06/30/1986
• Issued: 05/24/1988
• Est. Priority Date: 06/30/1986
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Shroyer, Richard A., Nutting, Thomas C.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Brinich, Stephen
• Application Number:
  US06/880,461
• Time in Patent Office: 694 Days
• Field of Search: 358/224, 358/909, 358/228
• US Class Current: 348/221.1
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

A still video camera includes an electronic image sensor as a signal source either for an electronic viewfinder or for a still image processed by the camera and recorded upon a magnetic disk. Since the viewfinder operates in a movie mode (with a fixed exposure time), the light intensity required for a viewfinder display ordinarily differs from that required for a still exposure. By commonly determining the correct exposure conditions for both the viewfinder display and the still exposure, time can be saved in shifting from the movie mode to the still mode. A sample of image light in the movie mode is diverted to a microprocessor-controlled exposure circuit, which integrates the light to determine the correct diaphragm aperture for both modes of operation. The movie aperture is directly input to a diaphragm driver while the still aperture is saved until a still exposure is requested.

Claims

1. In a still video camera that includes an electronic viewfinder for previewing a video image of an object and an image sensor that receives image light from the object and operates thereupon either as a signal source for the viewfinder or as a signal source for a still image processed by the camera, the camera further including a photosensor for generating a signal corresponding to the brightness of the image light and diaphragm means for establishing an aperture through which the image light passes, the improvement wherein the camera comprises:

means dependent upon an output of the photosensor for concurrently determining the correct exposure conditions for both still and moving pictures produced from the same image light;

means for storing said correct exposure conditions for a still picture;

means for controlling said diaphragm means according to said correct exposure conditions for a moving picture while the viewfinder is being used for previewing the video image;

a shutter release for initiating a still exposure; and

means responsive to the actuation of said shutter release for operating the image sensor as a signal source for a still image and for coincidentally retrieving said stored correct exposure conditions and controlling said diaphragm means according to said correct exposure conditions for a still picture.

2. A still video camera as claimed in claim 1, further comprising:

exposure bias means for similarly modifying the exposure conditions determined for both still and moving pictures; and

means for actuating said exposure bias means during the operation of the viewfinder thereby affecting the video image previewed by the viewfinder and modifying said still exposure conditions so as to similarly affect the still picture.

3. In a still video camera that includes an electronic viewfinder for previewing a video image of an object and an image sensor that receives image light from the object and operates thereupon either as a signal source for the viewfinder or as a signal source for a still image processed by the camera, the camera further including a photosensor for generating a signal corresponding to the brightness of the image light and diaphragm means for establishing an aperture through which the image light passes, the improvement wherein the camera comprises:

means dependent upon an output of the photosensor for concurrently determining the correct exposure conditions for both still and moving pictures produced from the same image light;

exposure bias means for similarly modifying the exposure conditions determined for both still and moving pictures;

means for actuating said exposure bias means during the operation of the viewfinder thereby affecting the video image previewed by the viewfinder and modifying said still exposure conditions so as to similarly affect the still picture;

means for controlling said diaphragm means according to said modified exposure conditions for a moving picture while the viewfinder is being used for previewing the video image;

a shutter release for initiating a still exposure; and

means responsive to the actuation of said shutter release for operating the image sensor as a signal source for a still image and for coincidentally controlling said diaphragm means according to said modified exposure conditions for a still picture.

4. A still video camera as claimed in claim 3 further comprising:

means for storing said modified exposure conditions for a still picture; and

means for retrieving said stored modified exposure conditions and providing them to said means responsive to the actuation of said shutter release.