Automatic exposure control apparatus

United States Patent

Mori et al.

[19]

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US005703644A [li] Patent Number: [45] Date of Patent:

5,703,644 Dec. 30, 1997

[54] AUTOMATIC EXPOSURE CONTROL APPARATUS

[75] Inventors: Tsutomu Mori, Hirakata; Makoto Fujimoto. Ibaragi: Yukie Goto, Hirakata; Yo Egusa, Kyoto, all of Japan

[73] Assignee: Matsushita Electric Industrial Co., Ltd., Kadoma. Japan

[21] Appl. No.: 65,119

[22] Filed: May 20,1993

[30] Foreign Application Priority Data

May 21, 1992 [JP] Japan 4-128529

May 22, 1992 [JP] Japan 4-130400

May 22, 1992 [JPJ Japan 4-130401

Nov. 26, 1992 [JP] Japan 4-316820

[51] IntCL6 H04N 5/335

[52] U.S. CI 348/363;348/221

[58] Field of Search 348/362, 363,

348/364, 365, 221, 222, 229, 230, 228, 220; H04N 5/335

[56] References Cited

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(List continued on next page.)

Primary Examiner—Andrew Faile

Assistant Examiner—Andrew B. Christensen

Attorney, Agent, or Firm—Renner, Otto, Boisselle, Sklar

An automatic exposure control apparatus includes an image frame luminance calculation unit for calculating an average luminance of an image frame; a region luminance calculation unit for calculating average luminances of a plurality of regions, the plurality of regions constituting the image frame; a select region luminance calculation unit for arranging the average luminances obtained by the region luminance calculation unit in the luminance order, for selecting at least one of the plurality of regions according to the luminance order and for calculating an average luminance selected from at least one of the plurality of regions; a backlight degree calculation unit for calculating a value representing a backlight degree based on the average luminance obtained by the select region luminance calculation unit; a target luminance calculation unit for calculating the target average luminance based on the value; and an exposure correction unit for correcting an exposure so that the average luminance obtained by the image frame luminance calculation unit is kept substantially equal to the target average luminance.

29 Claims, 26 Drawing Sheets

OTHER PUBLICATIONS

Egusa et al, Tech. Report of the Institute of Television Engineers of Japan, May 20, 1992, pp. 19-24, "A Study of Auto Iris Systems Using Fuzzy Set Theory to Determine the Degree of Backlighting on Excessive Frontlighting".

HaruM et al. Tech. Rept. of the Inst, of Television Eng. of Japan, Feb. 28,1989. pp. 43-48, "Digital AF and AE System by Using Picture Division".

Morimura et al. TF.FF. Transactions on Consumer Electronics, vol. 36, No. 4, pp. 866-876, Nov. 1990. "A Digital Video Camera System".