Exposure and focus system for a zoom camera

• US 5,335,041 A
• Filed: 09/13/1993
• Issued: 08/02/1994
• Est. Priority Date: 09/13/1993
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Fox, Myron E.
• Primary Examiner(s): PERKEY, WILLIAM B
• Application Number:
  US08/120,994
• Time in Patent Office: 323 Days
• Field of Search: 354/402, 354/413, 354/414, 354/419, 354/420, 354/421, 354/422, 354/443
• US Class Current: 396/61
• CPC Class Codes: G02B 7/28 Systems for automatic generation of focusing signals
• CPC Class Codes: G03B 7/08 Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
• CPC Class Codes: G03B 7/091 Digital circuits
• CPC Class Codes: G03B 7/097 for control of both exposure time and aperture
• 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

A light-sensitive, zone focus, passive automatic focus/automatic exposure system for a zoom camera receives light level data and selects flash status, lens focus distance, and exposure setting such that flash illumination is provided at a light level greater than necessary to prevent underexposure but sufficient to provide fill-flash based only on the detected light level. A no-flash mode is provided in which exposure times are increased rather than activating the flash.

Claims

1. An automatic focus/automatic exposure system for use in a photographic camera that takes photographs of a scene and includes a flash unit operable in a flash on or flash off status, an objective lens having a variable focus distance, and a shutter/aperture combination adapted for adjustment through a range of exposure settings comprising shutter times and aperture diameters to produce an exposure, the system comprising:

a light level detecting system that receives ambient light from the scene and produces a light signal representative of the amount of received light;

a controller that receives the light signal and determines a lens focus distance, flash unit status, and exposure setting in accordance with the received light signal value and controls the focus distance of the objective lens, the flash unit status, and the setting of the shutter/aperture combination in accordance with such determinations; and

a program table memory providing data to the controller and having data elements addressed by light signal value, each data element storing lens focus distance data for setting the lens focus distance at one of a plurality of distance zones, flash unit status data for setting the flash unit status, aperture data for setting the aperture size, and shutter time data for setting the shutter open time, such that the flash unit status is changed from off to on at a predetermined light signal value without a corresponding change in lens focus distance.

2. A system as defined in claim 1, further including a manual flash selector switch that can be switched to a non-flash setting such that the controller increases the shutter open time for data elements that otherwise would have a flash system setting of on.

3. A system as defined in claim 2, wherein the shutter/aperture combination comprises a separate shutter mechanism and an aperture mechanism.

4. A system as defined in claim 3, wherein the controller controls the shutter/aperture combination such that the shutter aperture diameter is selected from a predetermined number of diameters.

5. A system as defined in claim 4, wherein the shutter aperture diameters comprise four predetermined diameters.

6. A system as defined in claim 4, wherein the controller controls the shutter/aperture combination such that the controller selects only one predetermined shutter time for each aperture diameter regardless of changes in light level.

7. An automatic focus and automatic exposure system for use in a photographic camera that takes photographs of a scene and includes a flash unit, an objective lens having a variable focal length, and a shutter/aperture combination adapted for adjustment through a range of exposure settings comprising shutter times and aperture diameters to produce an exposure, the system comprising:

a light level detecting system that receives ambient light from the scene and produces a light signal representative of the amount of received light;

a controller that receives the light signal and selects a lens flash status, focus distance, shutter open time, and aperture diameter and controls the operation of the flash unit, lens, and shutter/aperture combination in accordance with the light signal value;

a first program table memory having data elements addressed by light signal level, each data element storing lens focus distance data for setting the lens focal length, aperture data for setting the aperture size, and shutter time data for setting the shutter open time, such that the light signal value at which the controller selects a different one of the predetermined lens focus distances is different from the light signal value at which the controller changes the flash status;

a second program table memory having data elements addressed by light signal level, each data element storing lens focus distance data for setting the lens focus distance, flash system status data for setting the flash system status, aperture data for setting the aperture size, and shutter time data for setting the shutter open time, such that the light signal value at which the controller selects a different one of the predetermined lens focus distances is different from the light signal value at which the controller selects a different one of the predetermined shutter open times;

a flash selector switch that can be set to a flash or no-flash status, wherein the controller selects data elements from the first table if the switch is set to flash and selects data elements from the second table if the switch is set to no-flash.

8. A camera for taking photographs of a scene, the camera comprising:

an objective lens unit having a variable focal length and focus distance lens and a lens positioning system for setting the lens at a user-selected focal length and a camera-selected focus distance;

a shutter/aperture combination operable to provide a range of exposure settings comprising shutter open times and aperture diameters to produce a photographic exposure;

a light level detecting system that receives ambient light from the scene and produces a light signal representative of the amount of received light;

a flash unit that provides flash illumination to the photographic scene;

a program table memory having data elements addressed by light signal value, each data element storing lens focal length data, flash unit status data, aperture data, and shutter time data; and

a controller that receives the light signal from the light level detecting system and, in accordance with the light signal value, selects a lens focus distance from the table memory and controls the lens positioning system to set the lens focus distance at the selected focus distance and selects aperture data, shutter time data, and flash status data from the table memory and controls the flash unit status such that the flash unit status is changed from off to on at a predetermined light signal value different from the value at which the lens focus distance is changed.

9. A camera as defined in claim 8, wherein the program table memory contains data elements such that only one predetermined shutter time is possible for each aperture selected from the table memory.

10. A camera as defined in claim 8, wherein the camera further comprises a manual flash selector switch that can be switched to a non-flash setting such that the controller increases the shutter time for data elements that otherwise would have a flash unit status data from the memory table with an on setting.