US4764751A
Expired / Lapsed
US
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Method of nonlinear A/D conversion
Assignee: Fujifilm Holdings Corp
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Filing: 1987-02-09
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Granted: 1988-08-16
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Expires: 2007-02-09
Abstract
Abstract A non-linear analog-to-digital converter in which an output of a non-linear analog-to-digital conversion circuit is applied to a look-up table memory. The contents of the look-up table are adjusted to compensate for variance in the conversion circuit or to provide a different conversion.
Inventors
- 👤 Hideaki Kimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:18
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/12; H03M1/48
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
87 words
A method for A/D conversion comprising the steps of: subjecting a varying level analog signal to a non-linear analog-to-digital conversion in a converter to produce a provisional digital signal; measuring conversion characteristic data of said converter for a plurality of analog input signals of known values; compensating said conversion characteristic data according to predetermined reference data corresponding to said plurality of analog input signals; storing said compensated conversion characteristic data in a look-up table memory; and accessing said look-up table memory according to said provisional digital signal.
Claim 2
Independent Claim
87 words
A method for A/D conversion comprising the steps of: subjecting a varying level analog signal to a non-linear analog-to-digital conversion in a converter to produce a provisional digital signal; measuring conversion characteristic data of said converter for a plurality of analog input signals of known values; compensating said conversion characteristic data according to predetermined reference data corresponding to said plurality of analog input signals; storing said compensated conversion characteristic data in a look-up table memory; and accessing said look-up table memory according to said provisional digital signal.
Claim 3
Dependent Claim
24 words
A method as recited in claim 1, further comprising reading an original image to provide an image signal as said varying level analog signal.
Claim 4
Dependent Claim
59 words
A method as recited in claim 1: wherein said conversion characteristic data are data for converting from a linear characteristic to a nonlinear characteristic; wherein said reference data are data for converting from the linear characteristic to a logarithmic characteristic; and wherein said compensated conversion characteristic data are data for converting from the nonlinear characteristic to the logarithmic characteristic.
Claim 5
Dependent Claim
59 words
A method as recited in claim 2: wherein said conversion characteristic data are data for converting from a linear characteristic to a nonlinear characteristic; wherein said reference data are data for converting from the linear characteristic to a logarithmic characteristic; and wherein said compensated conversion characteristic data are data for converting from the nonlinear characteristic to the logarithmic characteristic.
Claim 6
Dependent Claim
57 words
A method as recited in claim 1, wherein said measuring step comprises: storing a linear function in said look-up table memory: subjecting said plurality of analog input signals to said non-linear analog-to-digital conversion in said converter to produce calibrating digital signals; and accessing said look-up table-memory stored with said linear function according to said calibrating digital signals.
Claim 7
Dependent Claim
64 words
A non-linear analog-to-digital converter comprising: a non-linear analog-to-digital conversion circuit receiving an analog input signal; a look-up table memory receiving an output of said conversion circuit and producing a digital output of said converter; means for providing predetermined analog values to said conversion circuit; and means responsive to said digital output for said predetermined analog value for storing values in said look-up table memory.
Claim 8
Dependent Claim
64 words
A non-linear analog-to-digital converter comprising: a non-linear analog-to-digital conversion circuit receiving an analog input signal; a look-up table memory receiving an output of said conversion circuit and producing a digital output of said converter; means for providing predetermined analog values to said conversion circuit; and means responsive to said digital output for said predetermined analog value for storing values in said look-up table memory.
Claim 9
Dependent Claim
52 words
A converter as recited in claim 6, wherein said storing means calculates said values according to a conversion between said predetermined analog values and said digital output for said predetermined analog values and according to a predetermined conversion between said predetermined analog values and logarithmetic values corresponding to said predetermined analog values.
Claim 10
Dependent Claim
40 words
A converter as recited in claim 1, further comprising: means for adjusting said input signal to said conversion circuit to be a maximum value; and means for adjusting said input signal to said conversion circuit to be a minimum value.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-16 | 1992-02-15 | 1992-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-16 | 1996-02-15 | 1996-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-16 | 2000-02-15 | 2000-08-16 | $7700.00 | Window Closed / Lapsed |