Auto focus method for digital camera
First Claim
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1. An auto focus method of a digital camera for moving a lens of said digital camera to the maximum focus value position, comprising steps of:
- (a) calculating a focus value average FVavg of the focus values from the first step position to the Nth step position of said lens;
(b) determining a lens movement state including a coarse state, a mid state and a fine state, wherein said lens moves A steps in said coarse state, B steps in said mid state and one step in said fine state, where B is less than A;
(c) moving said lens and recording the focus value of said lens in said lens movement state according to said focus value average FVavg, a focus value difference FVdif, a previous maximum focus value FVmax, a coarse state threshold Tc, a mid state threshold Tm, a focus value difference threshold Tdif, a mid state count value MidCount and a downhill count value DownCount;
(d) repeating steps (b) and (c) until the searching over a search range is finished; and
(e) moving said lens to a right position corresponding to the maximum focus value.
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Abstract
An auto focus method of a digital camera for moving a lens of the digital camera to the maximum focus value position is provided. According to certain criteria, the lens movement states are categorized into four states, i.e. an initial state, a coarse state, a mid state and a fine state. The numbers of search steps for the lens in different states are different.
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Citations
14 Claims
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1. An auto focus method of a digital camera for moving a lens of said digital camera to the maximum focus value position, comprising steps of:
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(a) calculating a focus value average FVavg of the focus values from the first step position to the Nth step position of said lens;
(b) determining a lens movement state including a coarse state, a mid state and a fine state, wherein said lens moves A steps in said coarse state, B steps in said mid state and one step in said fine state, where B is less than A;
(c) moving said lens and recording the focus value of said lens in said lens movement state according to said focus value average FVavg, a focus value difference FVdif, a previous maximum focus value FVmax, a coarse state threshold Tc, a mid state threshold Tm, a focus value difference threshold Tdif, a mid state count value MidCount and a downhill count value DownCount;
(d) repeating steps (b) and (c) until the searching over a search range is finished; and
(e) moving said lens to a right position corresponding to the maximum focus value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification
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Current AssigneePrimax Electronics Limited
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Original AssigneePrimax Electronics Limited
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InventorsChang, Chia-Hao, Lo, Jui-Hsiang, Fuh, Chiou-Shann, Lin, Chin-Chih
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Granted Patent
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Time in Patent OfficeDays
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Field of Search
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US Class Current396/133
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CPC Class CodesG03B 13/36 Autofocus systemsH04N 2101/00 Still video camerasH04N 23/673 based on contrast or high f...
