US4868675A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control circuit for a laser printer
Assignee: Canon Production Printing Netherlands BV
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Filing: 1988-08-16
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Granted: 1989-09-19
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Expires: 2008-08-16
Abstract
Abstract A control circuit for a laser printer is described which utilizes a laser switching amplifier for supplying current to a laser diode, the latter being modulated by means of image signals. The control circuit has a correction circuit which compensates for the turn-on delay time of the laser diode. Preferably, the correction circuit lengthens the incoming image signal which controls the laser diode by a correction time which substantially corresponds to the time that elapses between when current is supplied to the laser diode and when the laser diode delivers its light, thereby eliminating distortion of the final image.
Inventors
- 👤 Louis G. J. Joosten
- 👤 Matheas T. M. Stemkens
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:40
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/04; H03F3/08; G; G06; G06K; G06K15/00; G06K15/02; G06K15/12; G06K15/1204; G06K15/1209; G06K15/1214; H01; H01S; H01S5/00; H01S5/04; H01S5/042; H01S5/06; H01S5/062; H01S5/06209; H01S5/0427; H01S5/0428; H01S5/06216; H01S5/068; H01S5/0683; H01S5/06835
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
93 words
A control circuit for a laser printer comprising a laser switching amplifier for supplying current to a laser diode, the laser switching amplifier comprising a differential amplifier having two chains connected to a common current source, the first chain comprising a first switching element and the laser diode and the second chain comprising a second switching element and a plurality of correction elements which represent substantially the same dynamic load for the second switching element in the second chain as the laser diode represents for the first switching element in the first chain.
Claim 2
Dependent Claim
93 words
A control circuit for a laser printer comprising a laser switching amplifier for supplying current to a laser diode, the laser switching amplifier comprising a differential amplifier having two chains connected to a common current source, the first chain comprising a first switching element and the laser diode and the second chain comprising a second switching element and a plurality of correction elements which represent substantially the same dynamic load for the second switching element in the second chain as the laser diode represents for the first switching element in the first chain.
Claim 3
Dependent Claim
54 words
A control circuit as described in claim 1, wherein the correction elements comprise two diodes connected in series to the second switching element and a capacitor which is grounded at one end while the other end is connected to the junction of the electrical connection between the second switching element and the two diodes.
Claim 4
Dependent Claim
127 words
In a control circuit for a laser printer utilizing a laser switching amplifier for supplying current to a laser diode and wherein the laser diode is modulated by means of an image signal, the improvement comprising a correction circuit for lengthening the image signal by a correction time substantially corresponding to the time that elapses between when current is supplied to the laser diode and when the laser diode emits light, the correction circuit comprising a delay circuit for delaying by the correction time a trailing flank of the image signal with respect to a leading flank of the image signal, the delay circuit comprising three NAND gates connected in series and wherein the image signal is fed simultaneously to the first and the last NAND gates.
Claim 5
Dependent Claim
127 words
In a control circuit for a laser printer utilizing a laser switching amplifier for supplying current to a laser diode and wherein the laser diode is modulated by means of an image signal, the improvement comprising a correction circuit for lengthening the image signal by a correction time substantially corresponding to the time that elapses between when current is supplied to the laser diode and when the laser diode emits light, the correction circuit comprising a delay circuit for delaying by the correction time a trailing flank of the image signal with respect to a leading flank of the image signal, the delay circuit comprising three NAND gates connected in series and wherein the image signal is fed simultaneously to the first and the last NAND gates.
Claim 6
Dependent Claim
125 words
In a control circuit for a laser printer utilizing a laser switching amplifier for supplying current to a laser diode, having a photodiode disposed near the laser diode which delivers an output signal related to the light output of the laser diode, and wherein the laser diode is modulated by means of an image signal, the improvement comprising a correction circuit for lengthening the image signal by a correction time substantially corresponding to the time that elapses between when current is supplied to the laser diode and when the laser diode emits light, wherein the correction circuit determines the correction time from the time elapsing between arrival of the image signal at the control circuit and the rise of the output signal of the photodiode.
Claim 7
Dependent Claim
125 words
In a control circuit for a laser printer utilizing a laser switching amplifier for supplying current to a laser diode, having a photodiode disposed near the laser diode which delivers an output signal related to the light output of the laser diode, and wherein the laser diode is modulated by means of an image signal, the improvement comprising a correction circuit for lengthening the image signal by a correction time substantially corresponding to the time that elapses between when current is supplied to the laser diode and when the laser diode emits light, wherein the correction circuit determines the correction time from the time elapsing between arrival of the image signal at the control circuit and the rise of the output signal of the photodiode.
Claim 8
Dependent Claim
108 words
A control circuit as described in claim 4, wherein the correction circuit comprises a high frequency clock signal generator for generating a plurality of clock pulses, and an up-down counter, the counter determining the correction time counting, in one direction, the number clock pulses occurring during the time between the arrival of the image signal at the control circuit and the rise of the outpt signal of the photodiode, and after the end of the image signal, the counter counting in the opposite direction, the same number of clock pulses such that the image signal is lengthened during the counting in the opposite direction by the correction time.
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) | 1992-09-18 | 1993-03-20 | 1993-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-18 | 1997-03-20 | 1997-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-18 | 2001-03-20 | 2001-09-19 | $7700.00 | Window Closed / Lapsed |