US3414730A - Photorheostat including discharge lamp and masking means and utilizing length of discharge - Google Patents

Photorheostat including discharge lamp and masking means and utilizing length of discharge Download PDF

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Publication number
US3414730A
US3414730A US523332A US52333266A US3414730A US 3414730 A US3414730 A US 3414730A US 523332 A US523332 A US 523332A US 52333266 A US52333266 A US 52333266A US 3414730 A US3414730 A US 3414730A
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United States
Prior art keywords
cathode
photorheostat
cell
discharge
discharge lamp
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Expired - Lifetime
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US523332A
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English (en)
Inventor
Nicolas Michel
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CIE IND FRANCAISE TUBES ELECT
INDUSTRIELLE FRANCAISE DES TUBES ELECTRONIQUES Cie SA
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CIE IND FRANCAISE TUBES ELECT
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H03G1/0047—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using photo-electric elements
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F55/00—Radiation-sensitive semiconductor devices covered by groups H10F10/00, H10F19/00 or H10F30/00 being structurally associated with electric light sources and electrically or optically coupled thereto
    • H10F55/20—Radiation-sensitive semiconductor devices covered by groups H10F10/00, H10F19/00 or H10F30/00 being structurally associated with electric light sources and electrically or optically coupled thereto wherein the electric light source controls the radiation-sensitive semiconductor devices, e.g. optocouplers
    • H10F55/205—Radiation-sensitive semiconductor devices covered by groups H10F10/00, H10F19/00 or H10F30/00 being structurally associated with electric light sources and electrically or optically coupled thereto wherein the electric light source controls the radiation-sensitive semiconductor devices, e.g. optocouplers wherein the radiation-sensitive semiconductor devices have no potential barriers, e.g. photoresistors
    • H10F55/208—Optical potentiometers

Definitions

  • Photorheostats are already known which consist of a photoelectric cell disposed in front of a variable light source, the assembly being enclosed in a perfectly lighttight enclosure. Any variation in the intensity of the light source is attended by a proportional variation in the photoelectric current, that is, of the cell conductance in case this cell is photoconductive. Any light source may be used, provided that the emitted spectrum is at least partially coincident with the spectrum of the cell sensitivity; thus, as light sources suitable for carrying out this invention, incandescence or filament lamps, discharge lamps, electroluminescent compounds, etc., may be mentioned.
  • the light transmission may 'be rendered variable as a function of the luminous intensity of the light source by using screens, whether gradual or not, attenuators, etc.
  • the light emission may vary as a function of parameters governing its intensity; thus, for instance, the cathode of a discharge lamp may be given a suitably designed shape to this end.
  • the present invention relates to a photorheostat comprisin a photoelectric cell, for example a photoconductive cell, illuminated by a discharge lamp.
  • a photoelectric cell for example a photoconductive cell
  • a discharge lamp it is known that beyond a certain voltage threshold called ignition threshold, a current develops in the anode-to-cathode gap of the discharge lamp and a series-connected protection resistance, this current producing a so-called cathode glow forming a light sheath surrounding the cathode.
  • the voltage increases between the anode and cathode of said discharge lamp, the current increases through the lamp and the surface area of the light sheath increases substantially in proportion to this current until the complete surface of the cathode is covered by said light sheath.
  • the variation in the surface area of the cathode sheathed by the cathode glow is utilized for varying the photo- "ice electric current, that is, the cell resistance in the case of a photoconductive cell.
  • the light source luminance and correlatively the value of the photoelectric current can vary only within relatively narrow limits, the lower end of the variation range corresponding to the minimum current necessary for producing a stable lamp discharge, the upper end of this range corresponding to the maximum current producing the total sheathing of the cathode under constant luminance conditions.
  • the photorheostat constituting the subject matter thereof comprises at least one photoelectric cell disposed in front of a variable light source consisting of a discharge lamp receiving a variable voltage between its anode and cathode, and is characterized in that the discharge lamp is of the type comprising a preferably filiform cathode parallel to the longitudinal axis of said lamp and that a screen of constant or variable opacity along its length is disposed between said light source and said cell.
  • this screen being disposed along part of the cathode length and embracing the cathode end adjacent to the anode, will prevent or at least attenuate the direct transmission of the photocell of the light flux emitted by said end portion of the cathode which is adjacent to the anode, so that when the discharge begins the photocell is illuminated by a diffuse light.
  • the opaque screen is advantageously disposed between the lamp and the cell, with due consideration for the minimum and maximum lengths of the cathode light sheath.
  • This screen may consist of any suitable material capable of arresting wholly or partially the light rays and consistent with the room temperature; thus, paint, opaque paper, plastic, etc., and, of course, metals, may be used to this end.
  • the photorheostat according to this invention is also advantageous in that it can be manufactured from any conventional and known component elements.
  • FIGURE 1 is a diagrammatic longitudinal section of a photorheostat according to this invention, fed with direct current;
  • FIGURE 2 is a diagrammatic longitudinal section of an alternate form of embodiment of this photorheostat
  • FIGURE 3 is a similar longitudinal section showing a photorheostat fed with alternating current
  • FIGURES 4, 5 and 6 are diagrammatic elevational views showing photoconductive cells suitable for use in the photorheostat according to this invention.
  • the photorheostat illustrated in FIGURE 1 comprises in a light-tight enclosure 1 a photoconductive cell 2 connected through conductors 3 and 4 to a load circuit. Registering with or in front of the photoconductive cell 2 is a neon glow or discharge lamp 5 parallel to said cell; in this example the lamp 5 is of the cylindrical type.
  • This lamp comprises two filiform electrodes, namely an anode 6 and a cathode 7, connected through separate leads 9 and 10 to a direct-current circuit delivering a variable input voltage.
  • the anode 6 and cathode 7 are aligned with the longitudinal axis of lamp 5.
  • Surrounding the tubular bulb of lamp 5 is an opaque screen consisting in the example illustrated and described herein of a cylindrical sleeve.
  • the photorheostat operates as follows:
  • This light sheath G is not received directly by the cell due to the presence of screen 8 but produces a diffuse light which reduces to 1M9 the resistance of the photoconductive cell 2 which in complete darkness was, say lOMQ.
  • the length of the luminous sheath G to point L may be in this case of the order of 3 millimeters. Under these conditions the resistance of cell 2 is 1M9 with a 0.1-rna. current.
  • the current also increases and therefore the length of the cathode light sheath increases accordingly.
  • the length of the light sheath is such that its movable end begins to directly illuminate the upper edge 2a of cell 2.
  • the extent of the light sheath is G
  • the intensity of the diffuse light increases correlatively and causes a proportional reduction in the resistance of the cell 2.
  • the resistance of cell 2 continues to decrease.
  • the resistance of cell 2 is 20KQ and the discharge current is 1 ma.
  • the position of cell 2 must be such that its upper edge 2a be constantly concealed by the screen from the minimum light sheath G so that under all circumstances the initial period of illumination of cell 2 is only by diffuse light.
  • the photorheostat described hereinabove with reference to FIGURE 1 may be so modified that a greater variation in the resistance of cell 2 corresponds to a same relative variation of the discharge current.
  • the photorheostat may be constructed as shown in FIG- URE 2.
  • the photorheostat according to this invention may also be used when the discharge lamp is energized by alternating current, as shown in FIGURE 3.
  • the ratio between the endmost values of the resistance of cell 2 is nearly twice the value indicated for a same variation in the discharge current under direct-current conditions.
  • the two electrodes 6 and 7 of the glow lamp act by turns as a cathode and are alternatively covered by the light sheath illuminating the photoconductive cell 2 disposed symmetrically in relation to the transverse plane of symmetry xy of the discharge lamp 5.
  • the upper edge 3a of cell 2 is thus aligned with the lower edge 8b of screen 8 and also with the point L attained by the maximum or longest light sheath around the electrode 6, whereas the lower edge 21) of the cell is aligned with the upper edge 8a of screen 8 and point L attained by the light sheath around the electrode 7.
  • the resistance of cell 2 is modulated, except for its inherent inertia, at a frequency which is twice that of the voltage applied to the lamp terminals.
  • the shape of the photosensitive surface of cell 2 may be properly selected to compensate at least partially the gain attenuation due to the gradually increasing distance between the upper portion of the light sheath and the lower portion of cell 2.
  • the cell 2 may be constructed as shown in FIGURE 4 with a photoconductive surface 20 having a width increasing from top to bottom, so that the greater the distance between the luminous cathode sheath and the cell, the greater the transverse dimension of the illuminated photoconductive surface.
  • the ratio of the maximum and minimum resistances of the photoconductive cell 2 may be as high as 1,500 with a discharge current ratio of the order of 10.
  • the law governing the resistance variation may be modified by properly changing the shape of the electrodes as well as their relative gap according to operating requirements.
  • the electrode gap varies from one cell end to the other.
  • the photoconductive surface has a width variable in the longitudinal direction, with a threshold or level where this width changes to a substantial extent.
  • a discharge or glow lamp of a type other than the cylindrical bulb type may be used, provided that the cathode of the lamp is elongated sufficiently to permit the extension of the cathode luminous sheath.
  • the photorheostat according to this invention may also comprise a plurality of photocells distributed about the discharge lamp, these cells operating in parallel and being illuminated by the same variable light source.
  • the photorheostat thus obtained is then of the type comprising an input circuit and a plurality of separate output circuits having either the same response curve (in the case of identical photoconductive cells) or different inherent response curves, according to the form of embodiment and the disposal of the photoelectric cells of the various output circuits.
  • a photorheostat comprising a variable light source consisting of a discharge lamp incorporating an anode and a cathode between which a variable voltage is applied, said cathode being parallel to the longitudinal axis of the lamp, a photoelectric cell disposed in front of said discharge lamp, and a screen disposed between said discharge lamp and said photoelectric cell, said screen extending along a certain length and overlapping the cathode end adjacent to the anode in order to prevent the direct transmission to said photoelectric cell of the light flux emitted from the end portion of the cathode which is adjacent to the anode, whereby, at the beginning of the discharge, the photoelectric cell is illuminated only by diffuse light.

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  • Vessels And Coating Films For Discharge Lamps (AREA)
  • Adjustable Resistors (AREA)
US523332A 1965-02-05 1966-01-27 Photorheostat including discharge lamp and masking means and utilizing length of discharge Expired - Lifetime US3414730A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR4509A FR1431897A (fr) 1965-02-05 1965-02-05 Photorhéostat

Publications (1)

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US3414730A true US3414730A (en) 1968-12-03

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US523332A Expired - Lifetime US3414730A (en) 1965-02-05 1966-01-27 Photorheostat including discharge lamp and masking means and utilizing length of discharge

Country Status (5)

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US (1) US3414730A (cs)
DE (1) DE1539740A1 (cs)
FR (1) FR1431897A (cs)
GB (1) GB1128593A (cs)
NL (1) NL6601440A (cs)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723934A (en) * 1970-03-26 1973-03-27 Agfa Gevaert Ag Photosensitive transducer
US4284885A (en) * 1978-05-26 1981-08-18 Honeywell Inc. Optical potentiometer
US4551623A (en) * 1981-12-07 1985-11-05 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Photoconductive detector with an A/C bias and responsivity dependent upon the polarity of the bias
US4570076A (en) * 1982-05-28 1986-02-11 Fuji Xerox Co., Ltd. Photoelectric converting device with position-related conversion efficiency
US4600834A (en) * 1983-10-31 1986-07-15 The United States Of America As Represented By The United States Department Of Energy Precision zero-home locator
US6573488B1 (en) * 1998-10-13 2003-06-03 Hamamatsu Photonics K.K. Semiconductor position sensitive detector

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2967945A (en) * 1957-03-09 1961-01-10 Philips Corp Variable electric impedance
US2997630A (en) * 1956-08-30 1961-08-22 Itt Holding switch
US3143653A (en) * 1961-06-01 1964-08-04 Lear Siegler Inc Photosensitive electroluminescent indicating apparatus
US3171034A (en) * 1961-12-21 1965-02-23 Tomasulo Walter Electro-optical control
US3258601A (en) * 1966-06-28 Photosensitive variable resistance device
US3363106A (en) * 1964-06-26 1968-01-09 Seeburg Corp Photo-conductor potential divider

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3258601A (en) * 1966-06-28 Photosensitive variable resistance device
US2997630A (en) * 1956-08-30 1961-08-22 Itt Holding switch
US2967945A (en) * 1957-03-09 1961-01-10 Philips Corp Variable electric impedance
US3143653A (en) * 1961-06-01 1964-08-04 Lear Siegler Inc Photosensitive electroluminescent indicating apparatus
US3171034A (en) * 1961-12-21 1965-02-23 Tomasulo Walter Electro-optical control
US3363106A (en) * 1964-06-26 1968-01-09 Seeburg Corp Photo-conductor potential divider

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723934A (en) * 1970-03-26 1973-03-27 Agfa Gevaert Ag Photosensitive transducer
US4284885A (en) * 1978-05-26 1981-08-18 Honeywell Inc. Optical potentiometer
US4551623A (en) * 1981-12-07 1985-11-05 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Photoconductive detector with an A/C bias and responsivity dependent upon the polarity of the bias
US4570076A (en) * 1982-05-28 1986-02-11 Fuji Xerox Co., Ltd. Photoelectric converting device with position-related conversion efficiency
US4600834A (en) * 1983-10-31 1986-07-15 The United States Of America As Represented By The United States Department Of Energy Precision zero-home locator
US6573488B1 (en) * 1998-10-13 2003-06-03 Hamamatsu Photonics K.K. Semiconductor position sensitive detector

Also Published As

Publication number Publication date
FR1431897A (fr) 1966-03-18
GB1128593A (en) 1968-09-25
DE1539740A1 (de) 1969-10-02
NL6601440A (cs) 1966-08-08

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