High speed fascimile systems
阅读：503发布：2022-01-08
专利汇可以提供High speed fascimile systems专利检索，专利查询，专利分析的服务。并且A facsimile system bandwidth-compresses a source signal, derived from scanning a document whose contents are to be transmitted to a remote location, by reversing the polarity of alternate segments of the signal to thereby form a modified signal of lesser frequency content. Background suppression is provided to enhance image contrast, and automatic gain control compensates for the variable attenuation of the transmission medium. The system is also capable of operating in a non bandwidth-compressed (''''slow'''') mode to accommodate slower transceivers.，下面是High speed fascimile systems专利的具体信息内容。
1. A facsimile transmitter for transmitting the contents of a document to a remote location comprising: A. means for scanning the document and generating a continuous electrical signal indicative of its contents; B. variable threshold means for detecting local minima in said signal; C. means for amplifying said signal with alternate first and second polarities as the signal passes through successive local minima; and D. means for transmitting the amplified signal to a remote receiver.
2. Apparatus according to claim 1 in which the signal translating means comprises an amplitude modulator having means for selecting the modulation index of the signal, the modulation index setting means comprising: A. a summing junction; B. first weighting means connecting the output of the variable gain amplifier to said summing junction; C. second weighting means connection to said summing junction a reference voltage corresponding to the comparator reference voltage; and D. switching means for varying the second weighting means whereby the proportion of the weighting voltage applied to the summing junction may be varied.
2. first weighting means connecting the output of the variable gain amplifier to said summing junction;
2. means responsive to the received signal to store in said element an electrical quantity indicative of the amplitude of the received signal whenever said amplitude equals a predetermined maximum;
2. a first rectifier poled in a first direction and connected in series with a first impedance between the amplifier input and output;
2. a comparator having said signal and said replica applied as inputs thereto and providing outputs indicative of the relative amplitudes of said inputs to thereby define said signal segments; and
2. providing outputs whose durations a. are equal when the outputs of the zero crossing detector and the first bistable device are in phase; b. are unequal when the outputs of the zero crossing detector and the first bistable devices are out of phase; F. a difference amplifier having connected as inputs thereto the respective outputs of said second and third bistable devices, and G. means connecting the output of the difference amplifier as an input to the oscillator to drive said oscillator at a frequency which minimizes the phase and frequency difference between the outputs of the zero crossing detector and the first bistable device.
2. having the output of said amplifier connected as a second iNput thereto;
2. a comparator for comparing the amplifier output with a reference voltage which is to determine the maximum amplitude of the signal;
3. a capacitor charged by the comparator for accumulating a magnitude corresponding to the peak amplitude of the signal during the given interval and discharged after the scanning of each line on the document;
3. responsive to said inputs to provide an output representative of said source signal; D. a zero crossing detector providing outputs indicative of the zero crossings of the modulated signal; E. second and third bistable devices
3. means applying said comparator outputs to the inverting means; B. means responsive to the minima detecting means for inverting alternate signal segments to thereby form a derived signal having frequency components corresponding to half the frequency of corresponding components of the signal from which it is derived, together with higher-order frequency components arising from the compression; and C. means for removing said higher-order components from the derived signal to thereby form a continuous frequency-compressed signal of half the frequency content of the continuous electrical signal.
3. a demodulator i. having the output of the bistable device connected as a first input thereto; ii. having the output of said amplifier connected as a second input thereto; iii. responsive to said inputs to provide an output representative of said source signal;
3. a second rectifier poled in a direction opposite to the first rectifier and connected in series with a second impedance between the amplifier input and output;
3. means responsive to the electrical quantity to set the gain of the amplifier in accordance with said quantity; and
3. second weighting means connection to said summing junction a reference voltage corresponding to the comparator reference voltage; and
3. A facsimile transmitter according to claim 1 which includes means for scanning said document at a plurality of different scanning rates and means providing to a remote receiver a signal indicative of the rate at which the document is being scanned.
4. switching means for varying the second weighting means whereby the proportion of the weighting voltage applied to the summing junction may be varied,
4. switching means periodically actuated to reset the gain of the amplifier during reproduction of the document.
4. a first channel output lead connected to a node common to said first rectifier and first impedance for receiving signals corresponding to a first input polarity;
4. a zero crossing detector providing outputs indicative of the zero crossings of the modulated signal.
4. switching means responsive to the accumulator for modifying the amplifier gain in inverse relation to the accumulator magnitude; and
4. Apparatus according to claim 1 in which the scanning means comprises a light source for illuminating the document and a photodetector for detecting light reflected from the document, and which includes means for compensating for the light detection characteristics of the photodetector, said compensating means comprising means for decreasing the amplification which said signal undergoes in inverse relation to the amplitude of said signal to thereby compress the upper range of amplitudes of said signal relative tO the lower ranges thereof.
5. Apparatus according to claim 4 in which said compensating means includes: A. a plurality of impedances; B. a plurality of Zener diodes in series with respective ones of said impedances; and C. means connecting said impedances and diodes in feedback relation around said amplifier to thereby vary the gain of said amplifier inversely with the output of the scanning means.
5. means for periodically resetting the accumulator to thereby enable the re-establishment of the gain of the amplifier.
5. An amplifier whose gain is switched between first and second polarities in accordance with the state of said bistable device.
6. Apparatus according to claim 1 which includes means for periodically establishing a reference level for said signal, said means comprising: A. a capacitor connected in series with the output of the scanning means, and B. means for periodically charging said capacitor to a standard level whereby said reference level may periodically be re-established.
7. Apparatus according to claim 6 in which said periodic charging means charges said capacitor after the scanning of each line on the document whereby said reference level is re-established for each scanning line.
8. Apparatus according to claim 7 in which the charging means includes a switch operable in synchronism with the rotation of a drum on which the document to be transmitted is mounted to charge the capacitor after each revolution of the drum.
9. Apparatus according to claim 1 which includes means for limiting the maximum amplitude of the signal from said scanning means, said limiting means comprising: A. an amplifier for amplifying the signal and having means to vary, the gain of the amplifier in accordance with the peak amplitude of the signal during a given scanning interval. B. a comparator for comparing the amplifier output with a reference voltage which is to determine the maximum amplitude of the signal; C. an accumulator responsive to the comparator for accumulating a magnitude corresponding to the peak amplitude of the signal during the given interval; D. switching means responsive to the accumulator for modifying the amplifier gain in inverse relation to the accumulator magnitude; and E. means for periodically resetting the accumulator to thereby enable the re-establishment of the gain of the amplifier.
10. Apparatus according to claim 9 in which the accumulator is a capacitor connected in charging relation to the comparator and which includes means to dishcarge the capacitor after the scanning of each line on the document.
11. Apparatus according to claim 10 in which the means for periodically discharging the capacitor comprises a switch operable in synchronism with the rotation of a drum on which the document to be transmitted is mounted to discharge the capacitor after each revolution of the drum.
12. A facsimile receiver for reproducing the contents of a document in accordance with a continuous electrical signal representative of a source signal derived from said document and transmitted to it from a remote transmitter after bandwidth-compression by inverting portions thereof in accordance with a variable threshold means said receiver comprising: A. means for amplifying said signal in an amplifier whose gain is dependent on the maximum amplitude components of said signal; B. means for reinverting portions of the received signal corresponding to portions of the source signal which have been phase-inverted prior to transmission to thereby reconstitute said source signal; and C. means applying the reconstituted signal to a writing head to thereby reproduce said document.
13. A facsimile receiver according to claim 12 which includes means for demodulating the received signal prior to reinverting portions thereof, said demodulating means comprising: A. an oscillator providing an output at a frequency dependent on inputs applied thereto; B. a first bistable device driven by said oscillator; C. a demodulator
14. A facsimile receiver according to claim 12 in which the means for reinverting portions of the received signal comprises a rectifier for converting the frequency-compressed bipolar signal to a unipolar signal.
15. A facsimile receiver according to claim 12 in which the means for reinverting portions of the received signal comprises: A. an amplifier having an input and an output; B. a first rectifier poled in a first direction and connected in series with a first impedance between the amplifier input and output; C. a second rectifier poled in a direction opposite to the first rectifier and connected in series with a second impedance between the amplifier input and output; D. a first channel output lead connected to a node common to said first rectifier and first impedance for receiving signals corresponding to a first input polarity; E. a second channel output lead connected to a node common to said second rectifier and second impedance for receiving signals corresponding to a second input polarity; F. means for inverting the polarity of the signal in one of said channels; and G. means for recombining the signals passed by said channels to thereby form a replica of the source signal.
16. A facsimile receiver according to claim 12 in which the means for reinverting portions of the received signal includes: A. first and second channels for passing different portions of the received signal with first and second polarities, respectively; and B. means for summing the outputs of said channels to provide a unipolar signal comprising a replica of said source signal.
17. A facsimile receiver according to claim 16 in which each said channel includes variable-gain amplifying means for setting the gain level of each channel separately whereby level-dependent nonlinearitites introduced during transmission or reception may be compensated for.
18. A facsimile receiver according to claim 12 which includes: A. an energy storage element; B. means responsive to the received signal to store in said element an electrical quantity indicative of the amplitude of the received signal whenever said amplitude equals a predetermined maximum; C. means responsive to the electrical quantity to set the gain of the amplifier in accordance with said quantity.
19. A facsimile receiver according to claim 18 in which said amplifier includes switching means periodically actuated to reset the gain of the amplifier during reproduction of the document.
20. A facsimile receiver according to claim 19 in which the switching means resets the energy storage element after each time interval corresponding to the reproduction of a line on the document, whereby the gain of the amplifier may be reset after each line.
21. A frequency compressor for use in connection with the trasmission of a continuous electrical signal having a number of local minima defining signAl segments extending there between, comprising: A. variable threshold means for detecting the local minima in said signal; B. means responsive to the minima detecting means for inverting alternate signal segments to thereby form a derived signal having frequency components corresponding to half the frequency of corresponding components of the signal from which it is derived, together with higher-order frequency components arising from the compression; and C. means for removing said higher-order components from the derived signal to thereby form a continuous frequency-compressed signal of half the frequency content of the continuous electrical signal.
22. A frequency compressor according to claim 21 in which the means for detecting the local minima comprises: A. means forming a level-shifted, delayed replica of the signal to be frequency-compressed; B. a comparator having said signal and said replica applied as inputs thereto and providing outputs indicative of the relative amplitudes of said inputs to thereby define said signal segments; and C. means applying said comparator outputs to the inverting means.
23. A frequency compressor according to claim 21 in which the means for inverting alternate signal segments comprises an amplifier whose gain is switched between positive and negative polarities in accordance with signals obtained from said minima detecting means.
24. A frequency compressor for use in connection with the transmission of a continuous electrical signal over a channel of limited bandwidth, said frequency compressor comprising: A. variable threshold means for detecting local inflection points in said signal in which the local rate of change of the signal amplitude varies by an amount greater than a preselected threshold; B. means responsive to the inflection detecting means for inverting alternate signal segments intermediate successive inflection points to thereby form a derrived signal having frequency components corresponding to half the frequency of corresponding components of the signal from which it is derrived; and C. means suppressing higher order frequencies generated by the inversion.
25. A facsimile transmitter for transmitting the contents of a document to a remote location comprising: A. means for scanning the document and generating a continuous electrical signal indicative of its contents; B. means for forming a level-shifted, time delayed replica of said signal C. a comparator for comparing the instantaneous magnitude of said replica with the instantaneous magnitude of the signal itself and providing differing outputs dependent on whether the replica magnitude is greater or less than the signal magnitude, a change in outputs signalling passage through a local minimum, D. means for amplifying said signal with alternate first and second polerities determined by the outputs of said comparing means; and E. means for transmitting the amplified signal to a remote receiver.
26. Apparatus according to claim 25 in which the amplifying means includes: A. a bistable device switched between first and second stable states by successive outputs from the comparator; and B. an amplifier whose gain is switched between first and second polarities in accordance with the state of said bistable device.
27. A facsimile transmitter for transmitting the contents of a document to a remote location comprising: A. means for scanning the document and generating a continuous electrical signal indicative of its contents; B. means for amplifying said signal with alternate first and second polarities as the signal passes through successive local minima; and C. means for transmitting the amplified signal to a remote receiver, said means including an amplitude modulator having means for selecting the modulation index of the signal, the modulation index setting means comprising:
28. A facsimile transmitter for transmitting the contents of a document to a remote location comprising: A. means for scanning the document and generating a continuous electrical signal indicative of it contents; B. means for amplifying said signal with alternate first and second polarities as the signal passes through successive local minima; and C. means for transmitting the amplified signal to a remote receiver; D. means for limiting the maximum amplitude of the signal from said scanning means, said limiting means comprising:
29. A facsimile receiver for reproducing the contents of a document in accordance with a continuous elecrical signal representative of a source signal derived from said document and transmitted to it from a remote transmitter after bandwidth-compression by inverting portions thereof, said receiver comprising: A. means for amplifying said signal in an amplifier whose gain is dependent on the maximum amplitude components of said signal; B. means for reinverting portions of the received signal corresponding to portions of the source signal which have been phase-inverted prior to transmission to thereby reconstitute said source signal; C. means applying the reconstituted signal to a writing head to thereby reproduce said document; and D. again control unit including
30. A facsimile receiver for reproducing the contents of a document in accordance with a continuous electrical signal representative of a source signal derived from said document and transmitted to it from a remote transmitter after bandwidth-compression by inverting portions thereof, said receiver comprising: A. means for amplifying said signal in an amplifier whose gain is dependent on the maximum amplitude components of said signal; B. means for reinverting portions of the received signal corresponding to portions of the source signal which have been phase-inverted prior to transmission to thereby reconstitute said source signal; and C. means applying the reconstituted signal to a writing head to thereby reproduce said document; and D. means for dEmodulating the received signal prior to reinverting portions thereof, said demodulating means comprising:
31. A facsimile receiver for reproducing the contents of a document in accordance with a continuous electrical signal representative of a source signal derived from said document and transmitted to it from a remote transmitter after bandwidth-compression by inverting portions thereof in accordance with a variable threshold means, said receiver comprising: A. means for amplifying said signal in an amplifier whose gain is dependent on the maximum amplitude components of said signal; B. means for reinverting portions of the received signal corresponding to portions of the source signal which have been phase-inverted prior to transmission to thereby reconstitute said source signal, said means comprising:
32. A frequency compressor for use in connection with the transmission of a continuous electrical signal having a number of local minima defining signal segments extending there between, comprising: A. variable threshold means for detecting the local minima in said signal, said means comprising:
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