Multi-point photometric apparatus

• US 4,796,043 A
• Filed: 01/15/1988
• Issued: 01/03/1989
• Est. Priority Date: 09/13/1985
• Status: Expired due to Term

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Nakai, Masaaki, Taniguchi, Nobuyuki, Yamaki, Toshio, Mukai, Hiromu, Fujino, Akihiko, Izumi, Shuji
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US07/068,212
• Time in Patent Office: 354 Days
• Field of Search: 354/402, 354/432, 354/458, 354/465
• US Class Current: 396/121
• CPC Class Codes: G02B 7/36 using image sharpness techniques , e.g. image processing techniques for generating autofocus signals image data processing per se G06T; in cameras having a solid state image sensor H04N23/67
• CPC Class Codes: G03B 7/091 Digital circuits

Abstract

A multi-point photometric apparatus for use in a camera or the like operative to measure the luminance of several divided areas in an objective field. Among the luminance signals produced by the photometric circuit for the several areas, a signal from one area which is used for automatic focus adjustment is designated as a reference value, and the maximum and minimum values of luminance signals and the differences of these from the reference value are evaluated. The reference value and differences in the form of digital data and information on the film latitude are processed with a microprocessor to calculate the exposure value. The exposure value is modified to an extent that the reference remains within the film latitude.

Claims

1. A multi-point photometric apparatus for measuring the luminance of an objective field comprising:

means for measuring the luminance of a plurality of divided areas of an objective field to produce a plurality of luminance signals in correspondence to said areas;

means for performing an automatic focus adjustment for a specific area among said divided areas;

means for selecting a reference luminance signal corresponding to said specific area at the completion of automatic focus adjustment;

means for recognizing a luminance distribution in the objective field basing on said selected reference luminance signal and a plurality of luminance signals corresponding to the plurality of areas other than said specific area, said reference luminance signal being the reference of said distribution; and

means for producing exposure information in accordance with said luminance distribution.

2. A multi-point photometric apparatus according to claim 1, wherein said recognizing means includes means for eliminating any of said luminance signals in excess of a certain threshold value in recognizing a luminance distribution in the objective field.

3. A camera incorporating a multi-point photometric apparatus comprising:

means for measuring luminance of a plurality of divided areas in an objective field to produce a plurality of luminance signals in correspondence to said areas;

means for automatically adjusting a focusing condition of an objective lens of a camera to produce an in-focus signal when the objective lens is adjusted to an in-focus condition;

means for calculating exposure information on the basis of the plurality of luminance signals;

means for controlling the calculating means so that the calculating means repeatedly calculates the exposure information before the production of the in-focus signal, and so that the calculating means calculates the exposure information after the production of the in-focus signal;

means for indicating a display based on the exposure information;

means for storing the exposure information produced by the calculating means after the production of the in-focus signal;

means, after the production of the in-focus signal, for prohibiting the focusing condition adjusting means from shifting the objective lens and for permitting starting of an exposure operation of the camera; and

means for controlling the exposure operation of the camera in accordance with the exposure information stored in the storing means.

4. A camera according to claim 3, further comprising means for interrupting the operation of the calculating means in accordance with a manual operation and for outputting the exposure information based on a specific luminance signal indicative of luminance of a center area in an objective field.

5. A camera incorporating a multi-point photometric apparatus comprising;

means for measuring luminance of a plurality of divided areas in an objective field to produce a plurality of luminance signals in correspondence to said areas;

means for detecting a focusing condition of an objective lens of the camera and for shifting the objective lens to an in-focus position on the basis of the detected focusing condition;

means for calculating exposure information on the basis of the plurality of luminance signals;

means for storing the exposure information when the objective lens is shifted to the in-focus position;

means for indicating a display based on the exposure information;

means, after the objective lens has been shifted to the in-focus position, for prohibiting the detecting and shifting means from shifting the objective lens and for permitting the starting of an exposure operation of the camera; and

means for controlling the exposure information of the camera in accordance with the exposure information stored in the storing means.

6. A camera according to claim 5, further comprising means for interrupting the operation of the calculating means in accordance with a manual operation and for outputting the exposure information based on a specific luminance signal indicative of luminance of a center area in an objective field.