US1995138A - Photo electric cell circuits - Google Patents

Photo electric cell circuits Download PDF

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Publication number
US1995138A
US1995138A US384884A US38488429A US1995138A US 1995138 A US1995138 A US 1995138A US 384884 A US384884 A US 384884A US 38488429 A US38488429 A US 38488429A US 1995138 A US1995138 A US 1995138A
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US
United States
Prior art keywords
condenser
photoelectric
short
cell
picture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US384884A
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English (en)
Inventor
Wright George Maurice
Smith Sidney Bertram
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RCA Corp
Original Assignee
RCA Corp
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Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Application granted granted Critical
Publication of US1995138A publication Critical patent/US1995138A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/00095—Systems or arrangements for the transmission of the picture signal

Definitions

  • This invention relates to photoelectric .cells, and circuits therefor, and more particularly to photoelectric cell circuit arrangements for use in picture telegraphy and for like purposes.
  • means for rendering the output of a photoelectric cell of intermittent character comprise a source of polarizing potential, a condenser in series therewith and with said cell, and means for intermittently shortcircuiting said condenser.
  • a photoelectric cell is connected in series with a battery and a condenser, and the grid filament space of a thermionic valve amplifier is shunted across the condenser, which is also shunted by a periodic short-circuiting device.
  • the ratio of the time during which the condenser is short-circuited to the time during which it is allowed to be charged through the cell from the source of polarizing potential should be adjusted so as to give maximum output from the thermionic valve amplifier, and if desired the duration of the short-circuiting period of the short-circuiting device may be made adjustable so as to give ready control of this ratio.
  • the frequency of short-circuiting of the condenser should be such as to give a suitable grain to the picture as received; a frequency giving a picture grain of dots per inch has been found satisfactory.
  • the frequency of short-circuiting is a definite multiple of the speed of the scanning light beam by which the picture to be transmitted is explored in most picture telegraph transmitters as at present employed, since with such relationship between short-circuiting frequency and scanning speed the modulation frequency and the grain of the received picture will be independent of the rate of scanning.
  • This relationship may conveniently be obtained by employing as the short-circuiting device a commutator or the like, driven in common with the drive for the scanning apparatus in the picture transmitter. .2 1
  • - 1 is a battery, 2 a photoelectric cell and 3 a condenser of high insulating properties.
  • 5 is a, triode whose gridfilament space is'shunted across the condenser 3 and whose output circuit is-jcoupled or'connected in any suitable manner to an amplifier 6.
  • the circuit is so adjusted as regards the potential of the battery 1 and the cell 2 that no grid current flows in the valve 5 so that there is no shunt leakage across the condenser 3.
  • the device 4 may be constituted by a rotary commutator driven in any convenient way.
  • the device 4 may conveniently be geared to the synchronous motor normally provided for driving the scanning or traversing mechanism or it may be driven by a separate synchronous motor energized from the same source as that which energizes the said scanning and traversing motor.
  • the rate of charge and discharge of the condenser 3 can be made to have any desired ratio to that of the picture scanning or exploring device, while the charge received by the condenser will be proportional to the time interval between successive. chargings and dischargings.
  • the speed of the scanning mechanism be reduced by one half, the speed of the device 4 will be similarly reduced, the charge receivedby the condenser 3 will be correspondingly increased and the photo-' electric cell response will be doubled.
  • any known form of thermionic short-circuiting device or other substantially noise-free short-circuiting device may We have merely attempted to suggest a certain form which the invention might assume, although it is to be understood that this has been illustrated merely by way of example, and is to be regarded as generic and not limiting, and it should be readily understood that certain modifications and changes will at once suggest themselves to those skilled in the art to which this invention relates, and we therefore desire to be limited in what modifications we canrnake only in so far as the scope of' the hereinafter appended claims necessitates.
  • An apparatus for introducing a chopper frequency into the output of a photoelectric tube which comprises a closed network including a source of potential, at photoelectrictube. and a condenser each connected in series with one another, a thermionic valve having its input circuit connected across the network and the electrodes of said condenser so as to amplify the photoelectric tube output currents, and a commutator means connected across said condenser and the input circuit of said thermionic amplifier for pcriodically short-circuiting said condenser. and supplying the photoelectric tube currents to the amplifier as alternating currents.
  • a photoelectric tube, a condenser and a source of potential for said tube being connected in series one with the other and forming a closed network, a thermionic tube connected across said condenser for amplifying the produced photoelectric currents, commutator means connected across the input circuit of said thermionic amplifier and across said condenser element for intermittently permitting said condenser to charge and to discharge so as to supply photoelectric cell currents to the amplifier as alternating currents, and a means for driving said commutator at a speed commensurate with the rate at which successive elemental areas of the subject of which the image is desired influence the tube for maintaining a predetermined rate between the analyzing speed and the rate of interruption of the photoelectric tube currents.
  • a light translating. device In a communication system, a light translating. device, a capacity element and. a source of electrical energy connected in series with each other and with the light translating device whereby the capacity element is charged at a rate proportional to the intensity of light reaching the light sensitive device, a thermionic amplifier device having its input circuit connected across said capacity element, and a cyclically operating short-circuiting device connected across said tube input circuit for intermittently permitting the condenser to charge and discharge so as to supply photoelectric currents to the amplifier as alternating currents.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
US384884A 1928-08-31 1929-08-10 Photo electric cell circuits Expired - Lifetime US1995138A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1995138X 1928-08-31

Publications (1)

Publication Number Publication Date
US1995138A true US1995138A (en) 1935-03-19

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ID=10895566

Family Applications (1)

Application Number Title Priority Date Filing Date
US384884A Expired - Lifetime US1995138A (en) 1928-08-31 1929-08-10 Photo electric cell circuits

Country Status (2)

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US (1) US1995138A (enrdf_load_stackoverflow)
BE (1) BE363392A (enrdf_load_stackoverflow)

Also Published As

Publication number Publication date
BE363392A (enrdf_load_stackoverflow)

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