USRE41704E1 - Timing signal generation for charge-coupled device - Google Patents
Timing signal generation for charge-coupled device Download PDFInfo
- Publication number
- USRE41704E1 USRE41704E1 US11/247,004 US24700405A USRE41704E US RE41704 E1 USRE41704 E1 US RE41704E1 US 24700405 A US24700405 A US 24700405A US RE41704 E USRE41704 E US RE41704E
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- United States
- Prior art keywords
- signal
- charge
- cycle
- coupled device
- shift register
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/745—Circuitry for generating timing or clock signals
Definitions
- the present invention relates to a method of generating timing signals. More particularly, the present invention relates to a method of generating timing signal for controlling a charge-coupled device.
- a number of factors may affect the scanning speed of a scanner or a digital camera. Factors including revolving speed of stepper motor (for a scanner), the number of sensor cells within a charge-coupled device, pixel resolution, the setting of clocking signals during operation are a few of the major ones. In general, these factors are adjusted according to the type of functions desired by a particular scanner or digital camera.
- FIG. 1 is a block diagram showing a portion of the circuit inside a conventional scanner.
- intensity of light captured by a charge-coupled device 102 is converted into an analogue signal and then transmitted to an analogue front-end processor 106 inside an application specific integrated circuit 104 .
- the analogue front-end processor 106 is a device for converting analogue signal into digital signal and generating corresponding clocking signals.
- the analogue front-end processor 106 converts the analogue signal from the charge-coupled device 102 into a digital signal and transmits the digital signal to a digital signal processor 108 for further processing.
- the charge-coupled device 102 needs several clocking signals for convening external light intensity to an analogue signal.
- the required clocking signals are provided by the analogue front-end processor 106 .
- FIG. 2 is a series of timing diagrams showing the clocking signals submitted to a conventional charge-coupled device during operation.
- the analogue front-end processor 106 provides input timing shift register signals ⁇ 1 , ⁇ 2 to the charge-coupled device 102 .
- a cycle in these timing diagrams is actually composed of a plurality of system clock cycles. For example, as shown in FIG. 2 , each cycle in the shift register clock cycles ⁇ 1 , ⁇ 2 comprises 12 system clock (SystemClk) cycles.
- light intensity sensed by the sensor cell (not shown) in the charge-coupled device 102 is stored as electric charges within a shift register (not shown) inside the charge-coupled device 102 .
- the shift register transfers the stored electric charges to a pixel processing circuit (not shown) also inside the charge-coupled device 102 .
- the shift register clock signal ⁇ 1 drops from a ‘H’ to a ‘L’ logic level and the shift register clock signal ⁇ 2 rises from a ‘L’ to a ‘H’ logic level as shown in FIG. 2 (the 7 th clock cycle)
- electric charges stored inside another shift register (not shown) are transmitted to the pixel processing circuit.
- electric charges stored in any number of shift registers (not shown) are transferred to the pixel processing circuit (not shown) of the charge-coupled device 102 .
- Reset signal RS and positioning signal CLP are operating cycles for the charge-coupled device 102 .
- the reset signal RS is at a ‘L’ logic level (low potential) and the analogue front-end processor 106 generates a reset voltage to flush out the former electric signals within the charge-coupled device 102 .
- the reset signal RS changes from ‘L’ to ‘H’ (a high potential) and the positioning signal CLP changes from a ‘H’ to a ‘L’ logic level.
- the analogue front-end processor 106 samples a positioning voltage at time node CDS 1 .
- the positioning voltage serves as a reference voltage for the analogue front-end processor 106 .
- the positioning signal CLP changes back from ‘L’ to ‘H’ and the analogue front-end processor 106 samples a charge voltage at time node CDS 2 .
- the charge voltage is derived from the charge signal sent from the shift register (not shown) to the analogue front-end processor 106 .
- Voltage difference between the positioning voltage sampled at time CDS 1 and the charge voltage sampled at time CDS 2 is the brightness value of a first pixel recorded by the charge-coupled device 102 (refer to FIG. 1 ). The brightness value is registered as an analogue signal.
- the phase shift clock signal of a shift register inside a conventional charge-coupled device often has a fixed duty cycle.
- a faster image processing spread is achieved by using a higher frequency for the phase shift signal.
- duty cycle of the analogue front-end processor (time node CDS 1 and time node CDS 2 ) is shortened.
- the charge signal from the shift register is submitted in a non-stabilized state.
- the signal sampled by the analogue front-end processor is inaccurate and frequency of the pixel processing cycle is increased leading to a high vulnerability to noise interference. Consequently, quality of the scanned image may deteriorate.
- scanning speed of a scanner must slow down. In other words, one must make a compromise between scanning speed and scanning quality.
- the charge-coupled device needs to have different clocking cycles for a scanner capable of scanning different low-resolution images. Therefore, the application specific integrated circuit must be designed anew leading to a slowdown of circuit design turnover.
- one object of the present invention is to provide a method of generating clocking signals for a charge-coupled device capable of increasing scanning speed and image quality for a low-resolution scanning.
- the method is also adaptable to the clocking requirements of different types of charge-coupled devices so that time for designing the scanning circuit of a scanner is reduced.
- the invention provides a method of generating clocking signals for a charge-coupled device.
- clocking cycle of a shift register signal, a reset signal and a positioning signal related to a charge-coupled device are set.
- cycle of the shift phase register signal corresponding to the charge signal may be extended by an adjustment.
- cycle of the shift phase register signal corresponding to the charge signal may be shortened by an adjustment.
- duration of each cycle for the positioning signal is adjusted in each cycle of the system clock and each cycle of the shift register clock such that the analogue front-end processor can obtain a stable positioning voltage.
- duration of each cycle for the reset signal is adjusted in each cycle of the system clock and each cycle of the shift register clock corresponding to the charge signal that needs to be discarded.
- the analogue front-end processor generates a reset voltage to flush away to-be-discarded charge signals.
- FIG. 1 is a block diagram showing a portion of the circuit inside a conventional scanner
- FIG. 2 is a series of timing diagrams showing the clocking signals submitted to a conventional charge-coupled device during operation
- FIG. 3 is a series of timing diagrams showing the clocking signals of an operating charge-coupled device according to this invention.
- FIG. 3 is a series of timing diagrams showing the clocking signals of an operating charge-coupled device according to this invention.
- the scanner uses a 1200 dpi charge-coupled device to scan an image and produce a one-eighth or 150 dpi low-resolution image output.
- 24 system clock (SystemClk) cycles are shown.
- the first cycle of the shift register clocking signals ⁇ 1 , ⁇ 2 (also the fifth, the ninth, . . . ) occupies 12 cycles of the system clock.
- the second to fourth (2-4) cycles of the shift register clocking signals ⁇ 1 , ⁇ 2 (also the 6-8, 10-12, . . . ) occupies four cycles of the system clock.
- Different system clock cycles for the shift register clock signal are used because the charge signal sampled by the charge-coupled device may be extended or contracted.
- the charge signal is extended by increasing the number of system cycles in each shift register clock cycle (for example, the first, fifth, ninth, . . . cycle of the shift register clock signals ⁇ 1 , ⁇ 2 all occupy 12 system cycles).
- the number of system cycles for each shift register clock cycles for example, the 2-4, 6-8, 10-12 . . . cycle of the shift register clock signals ⁇ 1 , ⁇ 2 all occupy 4 system cycles
- the reset signal RS is at a ‘L’ logic level.
- the analogue front-end processor 106 (refer to FIG. 1 ) generates a reset voltage to flush away previous voltage signal in the charge-coupled device 102 (refer to FIG. 1 ).
- the reset signal changes from ‘L’ to ‘H’ (a high potential) and the positioning signal CLP changes from ‘H’ to ‘L’.
- the analogue front-end processor 106 samples a positioning voltage at time node CDS 1 .
- the positioning voltage serves as a reference voltage for the analogue front-end processor 106 .
- the positioning signal CLP changes back from ‘L’ to ‘H’ and the analogue front-end processor 106 sampled a charge voltage at time node CDS 2 .
- the charge voltage is the voltage formed by the charge signal transmitted from the shift register (not shown) to the analogue front-end processor 106 .
- the voltage difference between the positioning voltage sampled at time CDS 1 and the charge voltage sampled at time CDS 2 is the brightness value at the first pixel of the charge-coupled device 102 .
- the brightness value is transmitted as an analogue signal.
- the system clock and the first cycle of the shift register signals ⁇ 1 , ⁇ 2 for sampling charge signal are used to adjust the duration of the positioning signal CLP level.
- the charge-coupled device is able to secure a stable positioning voltage.
- the 2-8 charge signals sensed by the charge-coupled device 102 are discarded.
- the reset signal RS is at a ‘L’ logic level.
- potential produced by the analogue front-end processor 106 is at the reset voltage.
- the 2-8 charge signal within the shift register (not shown) are all reset.
- the system clock and the 2-8 cycles of the shift register signals ⁇ 1 , ⁇ 2 for discarding the charge signal are used to adjust the duration of the reset signal RS level.
- the analogue front-end processor 106 generates a rest voltage to flush out all to be-discarded charge signals.
- the scanner is able to adjust the operating cycles of a charge-coupled device according to the desired image quality and scanning speed.
- the number of system cycles for the positioning signal CLP may increase from 2 to 3 so that a stable positioning voltage is obtained at time node CDS 1 .
- duration for the analogue front-end processor to sample charge signal is increased so that a stable charge voltage is obtained at time node CDS 2 . That is, the duration of the first cycle of the shift register signal ⁇ 1 is increased and the position of ‘H’ to ‘L’ level transition of the reset signal is adjusted.
- a low-resolution image can have a high-resolution image quality.
- one method is to reduce the four system clock cycles required by the 2 nd to 4 th cycles of the shift register signals ⁇ 1 , ⁇ 2 to two system clock cycles only.
- the relationship between the shift register timing signals ⁇ 1 , ⁇ 2 , the reset signal RS, the positioning signal CLP and the system clock is downloaded by programming into the application specific integrated circuit 104 (refer to FIG. 1 ).
- the shift register signal ⁇ 1 is ‘H’
- the shift register signal ⁇ 2 is ‘L’
- the reset signal RS is ‘L’
- the positioning signal CLP is ‘H’.
- the shift register signal ⁇ 1 is ‘H’
- the shift register signal ⁇ 2 is ‘L’
- the reset signal RS is ‘H’
- the positioning signal CLP is ‘L’.
- these states are downloaded into the application specific integrated circuit 104 in an address that corresponds to the second cycle of the system clock.
- the states regarded the shift register signals ⁇ 1 , ⁇ 2 , the reset signal RS and the positioning signal CLP that corresponds to all 24 clock cycles of the clock system are downloaded into the application specific integrated circuit 104 .
- new sets of signaling data may be re-programmed into the application specific integrated circuit 104 . There is no need to temper with the circuit inside the application specific integrated circuit 104 .
- scanning speed of a low-resolution scanning operation is increased through changing the duration of various duty cycles controlling a charge-coupled device.
- Duration of various operating signals can be downloaded into the application specific integrated circuit by programming. Hence, time for designing the internal circuit of an application specific integrated circuit is shortened.
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Abstract
Description
Claims (21)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/247,004 USRE41704E1 (en) | 2001-09-27 | 2005-10-07 | Timing signal generation for charge-coupled device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/967,711 US6631507B2 (en) | 2001-09-27 | 2001-09-27 | Timing signal generation for charge-coupled device |
US11/247,004 USRE41704E1 (en) | 2001-09-27 | 2005-10-07 | Timing signal generation for charge-coupled device |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US09/967,711 Reissue US6631507B2 (en) | 2001-09-27 | 2001-09-27 | Timing signal generation for charge-coupled device |
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USRE41704E1 true USRE41704E1 (en) | 2010-09-14 |
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US09/967,711 Ceased US6631507B2 (en) | 2001-09-27 | 2001-09-27 | Timing signal generation for charge-coupled device |
US11/247,004 Expired - Lifetime USRE41704E1 (en) | 2001-09-27 | 2005-10-07 | Timing signal generation for charge-coupled device |
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US09/967,711 Ceased US6631507B2 (en) | 2001-09-27 | 2001-09-27 | Timing signal generation for charge-coupled device |
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Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US7315406B2 (en) * | 2002-06-27 | 2008-01-01 | Transpacific Ip, Ltd. | Scanning circuit structure |
US6906563B2 (en) * | 2003-09-04 | 2005-06-14 | Texas Instruments Incorporated | Generating a waveform having one signal level periodically and different signal levels in other durations |
JP4437741B2 (en) * | 2004-11-26 | 2010-03-24 | 富士通マイクロエレクトロニクス株式会社 | Semiconductor integrated circuit design apparatus, semiconductor integrated circuit, and semiconductor integrated circuit design program |
JP5262996B2 (en) * | 2009-05-26 | 2013-08-14 | 富士通セミコンダクター株式会社 | Logic simulation apparatus, method, and program |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3786192A (en) * | 1972-10-11 | 1974-01-15 | Bell Telephone Labor Inc | Shift circuits with output control gated by combined control memory |
US4216465A (en) * | 1978-03-07 | 1980-08-05 | Hughes Aircraft Company | Programmable analog to digital converter |
US4646119A (en) * | 1971-01-14 | 1987-02-24 | Rca Corporation | Charge coupled circuits |
US4873647A (en) * | 1988-01-11 | 1989-10-10 | Minc Incorporated | Digital waveform analyzer |
US5867212A (en) * | 1994-09-30 | 1999-02-02 | Fuji Photo Film Co., Ltd. | Solid-state image pickup device using charge coupled devices with vacant packet transfer |
-
2001
- 2001-09-27 US US09/967,711 patent/US6631507B2/en not_active Ceased
-
2005
- 2005-10-07 US US11/247,004 patent/USRE41704E1/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4646119A (en) * | 1971-01-14 | 1987-02-24 | Rca Corporation | Charge coupled circuits |
US3786192A (en) * | 1972-10-11 | 1974-01-15 | Bell Telephone Labor Inc | Shift circuits with output control gated by combined control memory |
US4216465A (en) * | 1978-03-07 | 1980-08-05 | Hughes Aircraft Company | Programmable analog to digital converter |
US4873647A (en) * | 1988-01-11 | 1989-10-10 | Minc Incorporated | Digital waveform analyzer |
US5867212A (en) * | 1994-09-30 | 1999-02-02 | Fuji Photo Film Co., Ltd. | Solid-state image pickup device using charge coupled devices with vacant packet transfer |
Also Published As
Publication number | Publication date |
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US6631507B2 (en) | 2003-10-07 |
US20030061584A1 (en) | 2003-03-27 |
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