发明名称 |
CAPACITIVE FINGERPRINT SENSOR WITH ADJUSTABLE GAIN |
摘要 |
The present invention relates to a fingerprint sensing device comprising a planar array of closely-spaced capacitive sense elements (120, Fig. 1). When a finger (510) is placed in close proximity to the sensing device, the capacitive sense elements measure a capacitance (508) between the finger (510) and a single capacitor plate (500) in each sense element. This is accomplished by precharging each capacitor plate, and then using a known current source (522) to remove a fixed amount of charge from each capacitor plate (500). The measured capacitance varies as a function of the distance between the capacitor plate and the finger surface (200, Fig. 2). Thus, a capacitance measurement allows the distance between the capacitor plate and the finger surface to be determined (Fig. 3). Distance measurements across the array of sense elements are combined to produce a representation of the pattern of ridges on the finger surface which comprise a fingerprint. After a fingerprint is acquired, the quality of the fingerprint is evaluated, and if necessary, a gain parameter for the sense elements is iteratively adjusted until a satisfactory fingerprint is acquired. |
申请公布号 |
WO9852135(A3) |
申请公布日期 |
1999.03.25 |
申请号 |
WO1998US09597 |
申请日期 |
1998.05.12 |
申请人 |
VERIDICOM, INC. |
发明人 |
DICKINSON, ALEXANDER, G.;MCPHERSON, ROSS;MENDIS, SUNETRA;ROSS, PAUL, C. |
分类号 |
G01B7/00;A61B5/117;G01B7/004;G01B7/28;G01B7/34;G01R27/26;G06F3/033;G06F3/041;G06F3/044;G06K9/00;G06T1/00;G07C9/00 |
主分类号 |
G01B7/00 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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