Automatic exposure control apparatus for a camera

• US 5,218,397 A
• Filed: 10/07/1991
• Issued: 06/08/1993
• Est. Priority Date: 10/16/1990
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Takagi, Tadao
• Primary Examiner(s): Gellner, Michael L.
• Assistant Examiner(s): NOH, JAE
• Application Number:
  US07/772,444
• Time in Patent Office: 610 Days
• Field of Search: 354/415, 354/480
• US Class Current: 396/157
• CPC Class Codes: G03B 7/09976 the sensor being mounted in, before, or behind the porro-prism
• CPC Class Codes: G03B 7/09979 Multi-zone light measuring
• CPC Class Codes: G03B 7/16 in accordance with both the intensity of the flash source and the distance of the flash source from the object, e.g. in accordance with the "guide number" of the flash bulb and the focusing of the camera

Abstract

An automatic exposure control apparatus for a camera for metering a reflected light from a film surface in a flash photographing mode and stopping a light emission in accordance with the comparison comprises a flashing device for providing a preliminary light emission, an early main light emission and a late main light emission, a flashing control unit for controlling the flashing device to provide the preliminary light emission in a closed state of a shutter curtain and providing the early main light emission and the late main light emission in sequence after the shutter curtain has been opened, a metering unit for metering a reflected light from the shutter curtain surface at the preliminary light emission and metering a reflected light from the film surface at the early main light emission and the late main light emission, and an exposure control unit for comparing a metering output of the metering device for the preliminary light emission and a metering output for the early main light emission, determining an exposure condition in accordance with the comparison and stopping the late main light emission after the start of the late main light emission in accordance with the exposure condition.

Claims

1. An automatic exposure control apparatus for a camera comprising:

a flashing means for providing a preliminary light emission, an early main light emission and a late main light emission;

flashing control means for controlling said flashing means to provide the preliminary light emission in a closed state of a shutter curtain and providing the early main light emission and the late main light emission in sequence after the shutter curtain has been opened;

metering means for metering a reflected light from the shutter curtain surface at the preliminary light emission and metering a reflected light from a film surface at the early main light emission and the late main light emission; and

exposure control means for comparing a metering output of said metering means for the preliminary light emission and a metering output of said metering means for the early main light emission, determining an exposure condition in accordance with the comparison, and stopping the late main light exposure in accordance with the exposure condition after the late main light emission has been started.

2. An automatic exposure control apparatus for a camera according to claim 1, wherein a light intensity at the preliminary light emission and a light intensity at the early main light emission are equal.

3. An automatic exposure control apparatus for a camera according to claim 1, wherein a light intensity at the preliminary light emission and a light intensity at the early main light emission are not equal, and said exposure control means corrects the metering output in accordance with the light intensities when the metering outputs are compared.

4. An automatic exposure control apparatus for a camera according to claim 1, wherein said exposure control means corrects a light intensity of the late main light emission to a larger one when a light intensity at the early main light emission is larger than a light intensity at the preliminary light emission by more than a predetermined amount.

5. An automatic exposure control apparatus for a camera according to claim 1, wherein said exposure control means corrects a light intensity of the late main light emission to a smaller one when a light intensity at the early main light emission is smaller than a light intensity at the preliminary light emission by more than a predetermined amount.

6. An automatic exposure control apparatus for a camera according to claim 1, wherein said exposure control means compares a light intensity at the preliminary light emission and a light intensity at the early main light emission to detect a factor relating to a reflective index of the film.

7. An automatic exposure control apparatus for

a camera comprising:

a flashing means for providing a preliminary light emission, an early main light emission and a late main light emission;

flashing control means for controlling said flashing means to provide the preliminary light emission in a closed state of a shutter curtain and providing the early main light emission and the late main light emission in sequence after the shutter curtain has been opened;

metering means for metering a reflected light from the shutter curtain surface at the preliminary light emission and metering a reflected light from a film surface at the early main light emission and the late main light emission;

determination means for comparing a metering output of said metering means for the preliminary light emission and a metering output of said metering means for the early main light emission and determining an exposure level to stop the late main light emission in accordance with the comparison; and

exposure means for stopping the late main light emission after the start of the late main light emission when a sum metering output of the metering output for the early main light emission and the metering output for the late main light emission reaches the determined exposure level.

8. An automatic exposure control apparatus for a camera comprising:

a flashing means for providing a preliminary light emission, an early main light emission and a late main light emission;

flashing control means for controlling said flashing means to provide the preliminary light emission in a closed state of a shutter curtain and providing the early main light emission and the late main light emission in sequence after the shutter curtain has been opened;

metering means for metering a reflected light from the shutter curtain surface at the preliminary light emission and metering a reflected light from a film surface at the early main light emission and the late main light emission;

determination means for comparing a metering output of said metering means for the preliminary light emission and a metering output of said metering means for the early main light emission and determining a gain to correct a sum metering output of the metering output for the early main light emission and the metering output for the late main light emission in accordance with the comparison; and

exposure means for stopping the late main light emission after the start of the late main light emission when the sum metering output corrected by the determined gain reaches a predetermined exposure level.

9. An automatic exposure control apparatus for a camera, comprising:

release means for initiation an operation of the camera to expose a film;

flashing means for providing a preliminary light emission and a main light emission;

flashing control means for controlling said flashing means to provide the preliminary light emission in a closed state of a shutter curtain during one stage of said operation and providing the main light emission after the shutter curtain has been opened during a subsequent stage of said operation;

metering means for metering a reflected light from a reflection member of a known reflective index at the preliminary light emission and metering a reflected light from a film surface at the main light emission; and

means for comparing metered light at the preliminary light emission and metered light at the main light emission to detect a factor relating to a reflective index of the film.