US4905022A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Image forming apparatus having laser light source
Assignee: Ricoh Co Ltd
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Filing: 1989-03-28
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Granted: 1990-02-27
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Expires: 2009-03-28
Abstract
Abstract An image forming apparatus comprising a photosensitive body, a scanner including a laser light source for scanning the photosensitive body by a laser beam emitted from the laser light source, a modulation circuit for pulse-width-modulating or pulse-number-modulating the laser beam by an input digital image data which is synchronized to a clock signal, and a driving circuit for driving the laser light source by an output modulated image data of the modulation circuit. The modulation circuit includes a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, a counter for counting pulses of the high-frequency clock signal, a resetting circuit for resetting the counter when a counted value reaches a predetermined value, and a pulse signal generator for generating as the modulated image data a pulse signal having a pulse width or number dependent on the input digital image data and the counted value of the counter.
Inventors
- 👤 Kiyoto Nagasawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 14:18
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4055; H04N1/4056; H04N1/04; H04N1/047; H04N1/053; H04N1/113; H04N1/1135; H04N1/12; H04N2201/00; H04N2201/04; H04N2201/047; H04N2201/04701; H04N2201/0471; H04N2201/04732; H04N2201/04744; H04N2201/04753; H04N2201/04758; H04N2201/04767
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
161 words
An image forming apparatus comprising: a photosensitive body; scanning means including a laser light source for scanning said photosensitive body by a laser beam emitted from the laser light source; modulation means for pulse-width-modulating the laser beam by an input digital image data which is synchronized to a clock signal; and driving means for driving the laser light source by an output pulse width modulated image data of said modulation means, said modulation means including a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, counter means for counting pulses of the high-frequency clock signal, a resetting circuit for resetting said counter means when a counted value reaches a predetermined value, and pulse signal generating means for generating a pulse signal having a pulse width dependent on the input digital image data and the counted value of said counter means, said pulse signal being outputted as said pulse width modulated image data.
Claim 2
Dependent Claim
161 words
An image forming apparatus comprising: a photosensitive body; scanning means including a laser light source for scanning said photosensitive body by a laser beam emitted from the laser light source; modulation means for pulse-width-modulating the laser beam by an input digital image data which is synchronized to a clock signal; and driving means for driving the laser light source by an output pulse width modulated image data of said modulation means, said modulation means including a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, counter means for counting pulses of the high-frequency clock signal, a resetting circuit for resetting said counter means when a counted value reaches a predetermined value, and pulse signal generating means for generating a pulse signal having a pulse width dependent on the input digital image data and the counted value of said counter means, said pulse signal being outputted as said pulse width modulated image data.
Claim 3
Dependent Claim
26 words
The image forming apparatus as claimed in claim 1 wherein said high-speed clock generator generates a high-frequency clock signal having a frequency over approximately 100 MHz.
Claim 4
Dependent Claim
63 words
The image forming apparatus as claimed in claim 1 wherein said pulse signal generating means includes a comparator for comparing the input digital image data and the counted value of said counter means and for outputting a pulse signal with a pulse width determined by a time period in which the input digital image data and the counted value coincide in said comparator.
Claim 5
Dependent Claim
88 words
The image forming apparatus as claimed in claim 1 wherein said pulse signal generating means includes a processing circuit for subjecting the input digital image data to a predetermined processing, and a comparator for comparing an output image data of said processing circuit and the counted value of said counter means and for outputting a pulse signal with a pulse width determined by a time period in which the output image data of said processing circuit and the counted value of said counter means coincide in said comparator.
Claim 6
Dependent Claim
25 words
The image forming apparatus as claimed in claim 4 wherein said processing circuit subjects the input image data to a processing including a gamma correction.
Claim 7
Dependent Claim
35 words
The image forming apparatus as claimed in claim 5 wherein said processing circuit includes a memory which prestores image data which have been subjected to the predetermined processing in a form of a look-up table.
Claim 8
Dependent Claim
45 words
The image forming apparatus as claimed in claim 1 wherein said pulse generating means generates the pulse signal so that a high-level period thereof exists in an arbitrary portion of a total time period for forming one dot depending on the input digital image data.
Claim 9
Dependent Claim
46 words
The image forming apparatus as claimed in claim 1 wherein said pulse generating means generates the pulse signal so that a high-level period thereof exists in an approximate center portion of a total time period for forming one dot depending on the input digital image data.
Claim 10
Dependent Claim
161 words
An image forming apparatus comprising: a photosensitive body; scanning means including a laser light source for scanning said photosensitive body by a laser beam emitted from the laser light source; modulation means for pulse-number-modulating the laser beam by an input digital image data which is synchronized to a clock signal; and driving means for driving the laser light source by an output pulse number modulated image data of said modulation means, said modulation means including a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, counter means for counting pulses of the high-frequency clock signal, a resetting circuit for resetting said counter means when a counted value reaches a predetermined value, and pulse signal generating means for generating a pulse signal having a pulse number dependent on the input digital image data and the counted value of said counter means, said pulse signal being outputted as said pulse number modulated image data.
Claim 11
Dependent Claim
161 words
An image forming apparatus comprising: a photosensitive body; scanning means including a laser light source for scanning said photosensitive body by a laser beam emitted from the laser light source; modulation means for pulse-number-modulating the laser beam by an input digital image data which is synchronized to a clock signal; and driving means for driving the laser light source by an output pulse number modulated image data of said modulation means, said modulation means including a high-speed clock generator for generating a high-frequency clock signal which has a frequency higher than the clock signal, counter means for counting pulses of the high-frequency clock signal, a resetting circuit for resetting said counter means when a counted value reaches a predetermined value, and pulse signal generating means for generating a pulse signal having a pulse number dependent on the input digital image data and the counted value of said counter means, said pulse signal being outputted as said pulse number modulated image data.
Claim 12
Dependent Claim
26 words
The image forming apparatus as claimed in claim 9 wherein said high-speed clock generator generates a high-frequency clock signal having a frequency over approximately 100 MHz.
Claim 13
Dependent Claim
36 words
The image forming apparatus as claimed in claim 9 wherein said pulse signal generating means includes a processing circuit for subjecting the input digital image data to a predetermined processing and for outputting the pulse signal.
Claim 14
Dependent Claim
25 words
The image forming apparatus as claimed in claim 11 wherein said processing circuit subjects the input image data to a processing including a gamma correction.
Claim 15
Dependent Claim
35 words
The image forming apparatus as claimed in claim 12 wherein said processing circuit includes a memory which prestores image data which have been subjected to the predetermined processing in a form of a look-up table.
Claim 16
Dependent Claim
43 words
The image forming apparatus as claimed in claim 9 wherein said pulse generating means generates the pulse signal so that pulses thereof exist in an arbitrary portion of a total time period for forming one dot depending on the input digital image data.
Claim 17
Dependent Claim
44 words
The image forming apparatus as claimed in claim 9 wherein said pulse generating means generates the pulse signal so that pulses thereof exist in an approximate center portion of a total time period for forming one dot depending on the input digital image data.
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) | 1993-02-26 | 1993-08-28 | 1994-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-26 | 1997-08-28 | 1998-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-26 | 2001-08-28 | 2002-02-27 | $7700.00 | Window Closed / Lapsed |