US3688659A - Flash device with compensation for ambient conditions such as temperature - Google Patents

Flash device with compensation for ambient conditions such as temperature Download PDF

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Publication number
US3688659A
US3688659A US93595A US3688659DA US3688659A US 3688659 A US3688659 A US 3688659A US 93595 A US93595 A US 93595A US 3688659D A US3688659D A US 3688659DA US 3688659 A US3688659 A US 3688659A
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United States
Prior art keywords
circuit
compensating
illumination
flash
capacitor
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Expired - Lifetime
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US93595A
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English (en)
Inventor
Yoshiyuki Takishima
Yukio Mashimo
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Canon Inc
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Canon Inc
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Priority claimed from JP11419969U external-priority patent/JPS5247482Y1/ja
Application filed by Canon Inc filed Critical Canon Inc
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
    • H05B41/32—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation

Definitions

  • a flash device includes a main capacitor as a storage source for luminous energy. It is desired that the main capacitor has a large capacity and a high voltage withstanding capability, and is yet small in size. To meet these requirements, an electrolytic capacitor is normally used in the flash device. However, an electrolytic capacitor has an electrostatic capacitance which is highly dependent upon the temperature, in particular on a temperature below C.
  • FIG. 1 shows the temperature characteristics of electrolytic capacitors using glycerin (curve G) and ethylene glycol (curve E), respectively.
  • the usual practice is to determine the diaphragm aperture by dividing the given guide number (equivalent to the amount of illumination) of theflash device with a distance to an object being photographed.
  • the actual guide number of the flash device is reduced on account of low temperatures, such practice will result in an underexposure.
  • FIG. 1 is a graph which shows the variation of capacitance of an electrolytic capacitor on the ordinate as a function of ambient temperatures on the abscissa showing thermal characteristics of an electrolytic capacitor using glycelin (curve G) and ethylene glycol (curve E).
  • FIG. 2 is a circuit diagram of a first embodiment of the flash device according to the invention.
  • FIGS. 3a to 3f show partial modifications of the embodiment shown in FIG. 2.
  • FIG. 4 is a circuit diagram of a second embodiment of the flash device according to the invention.
  • FIG. 5 is a circuit diagram of a thirdembodiment of the invention.
  • FIG. 6 is a schematic view illustrating an exposure indicator to be used with the third embodiment of FIG. 5.
  • FIG. 7 is a circuit diagram of a fourth embodiment of the invention. 7
  • FIG. 8 is a circuit diagram of a fifth embodiment of the invention.
  • FIG. 9 is a schematic view of an exposure indicator for automatically indicating the value of compensated exposure.
  • FIG. 2 shows a first embodiment of the invention
  • this embodiment includes a flash device 1 and a temperature compensating means 2 which are integrally constructed.
  • the output information from the temperature compensating means 2 controls an indicator means 3, such as an exposure ammeter, provided in a photographic camera which is indicated by a block 4, and it is assumed that the camera 4 includes an electronic eye mechanism which determines the amount of exposure depending upon the indication provided by the means 3.
  • the flash device 1 shown in FIG. 2 is essentially the same as that disclosed in a pending patent application Ser. No. 27,699 filed Apr. 13, 1970.
  • a reference character F denotes a flash tube circuit including a trigger circuit.
  • Numeral 101 denotes a discharge tube, 102 a trigger coil and 103 a resistor for charging a trigger capacitor 104.
  • a variable resistor 105 is connected in parallel with a main capacitor 106.
  • Reference character P denotes a power circuit.
  • Numeral 107 denotes a power source, 108 a transistor, 111 a transformer having a feedback winding 109, primary winding and secondary winding 112, and 113 a rectifier element.
  • Reference character Sw denotes a power switch which is interlocked with a switch in an electronic eye circuit to be described later in such a manner that when the power source 107 is turned off, the electronic eyecircuit is disconnected from the control of the flash device 1.
  • the temperature compensating means 2 includes the above-mentioned resistor 105, a neon discharge tube 115, a transistor 114, and diodes 118, 119 and 120.
  • the transistor 114 has its base connected through the neon tube 115 with the movable point on the variable resistor 105, its collector connected with the power source 107, and its emitter connected with a resistor 116 and a sensitivity element 117, such as a thermistor having a negative characteristic, the other end of the sensitivity element 117 being connected with the base of the transistor 114.
  • the temperature compensating means 2 further includes a variable resistor 121 for correcting the voltage drop across the emitter resistor 116, a diode 122 for obtaining a constant voltage and a biase resistor 123 for applying a predetermined voltage across the diodes 122 and 120.
  • the diodes 118, 119 and serve to compress" the variation in voltage across the main capacitor 106 and to compensate for the rising time of the voltage across the base and emitter of the transistor 1 14.
  • Reference numerals 125, 126 designate a diode for protecting the diodes 122, 120 and the transistor 114 from the reverse voltage.
  • the output from the temperature compensating means 2 is derived from the junction between the transistor 1 14 and the emitter resistor 1 16.
  • the indicator means 3 is shown in the form of an electronic eye circuit, which includes an adjustable resistor 127 for adjustment with the film sensitivity, an ammeter 128 connected in parallel with the resistor 127, a power source 129 connected in series with a photo-conductor element 130 across the ammeter 128, and a resistor 131 connected in the input path from the temperature compensating means 2.
  • a synchronizer switch 132 is adapted to be closed in synchronism with the full opening of the shutter blades.
  • a switch SW is interlocked with'the switch SW in the power circuit P of the flash device.
  • the main capacitor 106 With the closure of the power switch SW1, which is interlocked with the switch SW and of the switch 133, the main capacitor 106 starts to be charged through the diode 113.
  • the voltage across the main capacitor 106 is detected through the movable point on the resistor 105, and it rises to a level which is high enough to cause an illumination of the flash discharge tube 101, the neon lamp 115 is illuminated, whereupon the voltage across the main capacitor is applied to the base of the transistor 114.
  • This voltage applied to the base is variable by the action of the temperature sensitive element 117 that is connected across the base and emitter and has a resistance which varies in accordance. with the temperature.
  • the output resistance of the transistor 114 varies in dependence upon the temperature, if supposing the voltage across the main capacitor remains unchanged.
  • the output from the temperature compensating means 2 contains an information concerning the temperature characteristic of the main capacitor 106, and the ammeter 128 operated by this output provides an indication of the diaphragm aperture which exactly correspond to the amount of illumination provided by the flash device.
  • FIGS. 3a to 3f show exemplary modifications of the first embodiment shown in FIG. 2. While the sensitivity element 117 is connected across the base and emitter of the transistor 114 in FIG. 2, it may be connected with the base, emitter or collector of the transistor 114, as shown in FIGS. 3a, 3b and 3c, respectively.
  • FIGS. 3d, 3e and 3f illustrate the use of a silicon controlled rectifier SCR in place of the transistor 114. When such silicon controlled rectifier SCR is used, the sensitivity element 117 can be connected either in the input or output circuit, as shown in FIGS. 3d, 3e or 3f.
  • FIG. 4 shows a second embodiment of the flash device 1 according to the invention.
  • a change in the amount of illumination which is caused by a change in the capacitance of the main capacitor in a flash device is conveyed through the temperature compensating means 2 to an indicator means 31 disposed in the flash device, which provides an indication for manually adjusting the diaphragm aperture of the camera 4.
  • an ammeter circuit which comprises a resistor 202, an ammeter 201 having a guide number scale (not shown), and a temperature sensitive element 117 such as a thermistor.
  • the thermistor When the temperature falls, the thermistor operates to control the current flow through the ammeter 201 in a manner such that it corresponds to the capacitance of the main capacitor l06, thereby presenting a proper indication on the guide number scale.
  • This guide number indication can be utilized to decide a diaphragm aperture for obtaining a proper exposure.
  • FIG. 5 shows a third embodiment of the invention.
  • Resistors R,, R and R are connected in series across where R denotes the resistance of the temperature sensitive element 117, and that under lower temperatures, which cause a change in the value of R,,,, the following relationships apply:
  • the exposure indicator shown in FIG. 6 is actuated.
  • FIG. 6 shows an indicator device schematically, which is substantially similarly constructed as usual exposure indicators.
  • Numeral 400 denotes an indicator needle, 401 a distance scale, 402 a window for setting film sensitivity and 403 a diaphragm aperture scale which is interlocked with the needle 400.
  • the abovementioned neon lamps 300 and 301 are located on the back of the diaphragm aperture scale 403 and spaced apart by a distance corresponding to one diaphragm aperture value graduation.
  • the distance scale 401 is rotated to a position corresponding to a given film sensitivity (which is ASA in the example shown).
  • the diaphragm aperture scale 403 is rotated to cause the needle 400 to align with a desired distance graduation on the distance scale 401 which graduation corresponds to the distance to an object being photographed.
  • the neon lamp 301 is energized to illuminate a diaphragm aperture value graduation on the diaphragm aperture scale 403 which is on top of the neon lamp 301, this value graduation being F 2.8 in the example shown.
  • the neon lamp 300 will be energized to illuminate the value graduation which is the next lower value graduation on the scale 403 than the value graduation'illuminated by the neon lamp 301.
  • the illuminated diaphragm value graduation is used to set the diaphragm aperture of the camera 4, whereby a proper exposure corresponding to the amount of illumination from the flash device is obtained.
  • a thermistor R having a positive characteristic
  • the resistors in the voltage divider circuits should be chosen to satisfy the following relationships:
  • FIG. 7 shows a fourth embodiment of the invention.
  • Resistors R and R are connected in series across the main capacitor 106. Also resistors R R and R are connected in series across the main capacitor 106.
  • Numeral 500 denotes a transistor having its base connected with the junction B between the resistors R and R through a neon lamp 501. The collector and emitter of this transistor are connected across the resistor R so as to short out this resistor upon conduction of the transistor 500.
  • a neon lamp 502 is connected across the resistors R and R the junction between the resistors r, and R being denoted by reference character A.
  • a temperature sensitive element 1 17 is connected in series between the main capacitor 106 and the voltage divider circuits R to R These resistors are chosen so that they satisfy the following relationships:
  • the power unit P provides an output which charges the main capacitor 106, and when the voltage across the main capacitor reaches a given value, the neon lamp 592 is initially energized to illuminate a proper diaphragm aperture value under this condition (for example, F 2.8) on the exposure indicator of FIG. 6.
  • a proper diaphragm aperture value under this condition (for example, F 2.8) on the exposure indicator of FIG. 6.
  • the neon lamp 501 is illuminated, whereupon the transistor 500 is turned on to short out the resistor R whereby the potential at the point A falls and the neon lamp 502 is extinguished.
  • the lamp 501 indicates a proper exposure value (for example, F 2.0). Under lower temperatures, the
  • thermistor 117 will have an increased resistance to' decrease the potential at the point A or B in the respective voltage divider circuits, so that either neon lamp will not be illuminated until the voltage across the main capacitor reaches a higher value as compared with the value under normal temperatures.
  • an automatic compensation of a variation of guide number caused by a change in the ambient temperature when the neon lamp provides an indication so that such indication can be used to decide a proper diaphragm aperture to assure a proper exposure.
  • FIG. 8 shows another embodiment of the invention which employs a thermistor having a positive characteristic.
  • resistors R and R and a thermistor R having a positive characteristic are connected in series across the main capacitor 106.
  • Numeral 600 denotes a transistor having its base con nected with the junction between the resistors R and R through a neon lamp 601. The collector and emitter of the transistor 600 are connected so as to short out the series connection of a resistor R and the thermistor R, upon conduction of the transistor 600.
  • a neon lamp 602 is connected with the junction between resistors R and R Numeral 603 denotes a rectifier element which is connected between the thermistor R, and the resistor R in order to prevent the influence of the transistor 600 upon the neon lamp 601.
  • the resistors satisfy the following relationships:
  • the main capacitor 106 As the main capacitor 106 is charged and the voltage drop across the resistors R R R, reaches a volt age which is sufiicient to illuminate the neon lamp 602, this lamp is illuminated. As the main capacitor is further charged, the neon lamp 601 is illuminated, whereupon the transistor 600 conducts. When the transistor 600 conducts, the resistor R and the thermistor R, are short-circuited to extinguish the neon lamp 602. Under lower temperatures, the thermistor R, will have a reduced resistance, so that the neon lamps 601 and 602 will be illuminated at higher voltages across the main capacitor 106 than those under normal temperatures. Such increased voltage can be made so as to correspond to a variation in the amount of illumination from the flash device, thereby enabling a proper exposure to be obtained.
  • FIG. 9 shows an embodiment which uses an exposure indicator as compensation means directly and utilize the indication provided to decide the diaphragm aperture of the camera.
  • Numeral 401 denotes a rotatable distance scale having a window 402 for setting ASA sensitivity
  • numeral 700 denotes an ASA scale fixed on a shaft 701.
  • Numeral 403 denotes a diaphragm aperture scale which is adapted to rotate by elongation and contraction of a bimetal 704.
  • This exposure indicator is arranged so that the diaphragm aperture scale rotates automatically in response to a change in temperature, thereby providing a scale correction, and thus, when taking pictures by flash light, the camera may be set according to the indication provided by the exposure indicator, without regard to an ambient temperature, and thus a proper exposure is obtained.
  • a flash device for a camera comprising a flash circuit including a main capacitor to store illumination energy and a dischargetube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, and indicator means coupled to said circuit for indicating the amount of the illumination of the discharge tube, said indicator means including compensating means varying in value according to the variation in the energy storing capability of said capacitor in response to an ambient condition and varying the indication of said indicator means on the basis of the ambient condition.
  • said indicating means includes means for detecting the illumination of energy charged across the main capacitor and an indicator, and wherein said compensating means is coupled between said detecting means and said indicator.
  • said indicating means includes a dial and a pointer
  • said compensating means includes a thermally deformable element
  • said indicating means connecting said compensating means to said dial and pointer for changing the positions of the dial and the pointer in correspondence with variation of atmospheric temperatures.
  • said indicating means includes detecting means having a semiconductor element
  • said compensating means includes a thermally compensating resistor coupled to said semiconductor element
  • said semi-conductor element is a silicon controlled rectifier connected to said thermally compensating resistor.
  • said indicating means includes a current meter, said compensating means being connected to said current meter so as thermally to compensate for the reading of said current meter.
  • said indicating means includes a lamp, the operation of said lamp being thermally compensated by said compensating means.
  • said indicating means includes a plurality of lamps, said indicating means including illuminating means for illuminating the lamps, said compensating means being connected to said illuminating means for varying the illumination of said lamps on the basis of thermal compensation.
  • a photographic system comprising a flash circuit including a main capacitor to store illumination energy and a discharge tube which illuminates in correspondence to the amount of the illumination energy stored in said capacitor, indicating means coupled to said circuit for indicating the amount of the illumination of the discharge tube, and thermal compensating means coupled to said main capacitor and said indicating means to vary in value according to variation in temperature at the same rate as the temperature of said capacitor varies, a camera having exposure control means, said exposure control means being coupled to said indicating means to react therewith.
  • a photographic system comprising a main capacitor to store illumination energy, a flash circuit including a discharge tube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, a detecting circuit for detecting the terminal voltage of said capacitor, a camera, an exposure control circuit in the camera connected to said detecting circuit, vand compensating means for compensating for changes in illumination energy stored in the capacitor due to changes in atmospheric temperature, said compensating means being connected to said detecting circuit.
  • a power-source actuated flash device for a camera comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable valve in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said compensating means including a transistor and a thermally compensating resistor connected therewith.
  • a power-source actuated flash device for a camera comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means-for compensating for the thermal variations in the value, said compensating means including a silicon controlled rectifier and a thermally compensating resistor connected to said silicon controlled rectifier.
  • a power-source actuated flash device for a camera comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit including an indicator for displaying illumination intensity, said indicator being a' lamp, said compensating means being connected to thermally compensate the level of illumination indicated by the lamp.
  • said indicator comprises a plurality of lamps, said detector circuit including illuminating means for illuminating one of said lamps, said compensating means being connected to said illuminating means for thermally compensating for the illumination of the illuminated lamp.
  • a power-source actuated flash device for a camera comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit comprising an indicator for indicating illumination intensity, said compensating means including a thermally deformable element coupled to said indicator.
  • a photographic system comprising a camera, circuit means including a main capacitor to be charged by the power source in a flash lamp as well as a flash circuit responsive to said capacitor for'illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said camera having an exposure control, said detector circuit being operationally coupled with said exposure control.

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US93595A 1969-12-01 1970-11-30 Flash device with compensation for ambient conditions such as temperature Expired - Lifetime US3688659A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP11419969U JPS5247482Y1 (de) 1969-12-01 1969-12-01
JP11420069 1969-12-01
JP9849670 1970-10-02
JP9849570 1970-10-02

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DE (1) DE2058679C3 (de)
FR (1) FR2072647A5 (de)
GB (1) GB1326060A (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3776112A (en) * 1972-08-11 1973-12-04 Honeywell Inc Adapter circuit for use with auto exposure camera
US3846806A (en) * 1972-12-30 1974-11-05 Minolta Camera Kk Automatic flash device for a photographic camera
US3995286A (en) * 1974-09-30 1976-11-30 Asahi Kogaku Kogyo Kabushiki Kaisha Electronic strobe with optionally-operable controls
US4005337A (en) * 1975-07-21 1977-01-25 Grimes Manufacturing Company Constant energy strobe source
US4074170A (en) * 1976-06-21 1978-02-14 Vivitar Corporation Voltage regulator with thermal overload protection
US4201934A (en) * 1977-03-25 1980-05-06 West Electric Co., Ltd. External sensor for electronic flash
US4294528A (en) * 1978-08-23 1981-10-13 Minolta Camera Kabushiki Kaisha Automatically controlled electronic flash device
US5587644A (en) * 1994-06-15 1996-12-24 Canon Kabushiki Kaisha Charging control device for flash device
US6061528A (en) * 1997-05-08 2000-05-09 Canon Kabushiki Kaisha Flash device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068150A (en) * 1975-03-14 1978-01-10 West Electric Co., Ltd. Voltage indication means for an electronic flashing device
JPS52146139U (de) * 1976-04-30 1977-11-05

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894174A (en) * 1958-04-28 1959-07-07 Fr Corp Electrical photoflash device
US3257607A (en) * 1961-03-27 1966-06-21 Intron Int Inc Thermally sensitive capacitive circuit element
US3295424A (en) * 1963-06-17 1967-01-03 Polaroid Corp Shutter timing apparatus
DE1291192B (de) * 1967-05-08 1969-03-20 Compur Werk Gmbh & Co Lichtbildaufnahmegeraet mit einer elektronischen Einrichtung, insbesondere zur Belichtungszeitbildung

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894174A (en) * 1958-04-28 1959-07-07 Fr Corp Electrical photoflash device
US3257607A (en) * 1961-03-27 1966-06-21 Intron Int Inc Thermally sensitive capacitive circuit element
US3295424A (en) * 1963-06-17 1967-01-03 Polaroid Corp Shutter timing apparatus
DE1291192B (de) * 1967-05-08 1969-03-20 Compur Werk Gmbh & Co Lichtbildaufnahmegeraet mit einer elektronischen Einrichtung, insbesondere zur Belichtungszeitbildung

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3776112A (en) * 1972-08-11 1973-12-04 Honeywell Inc Adapter circuit for use with auto exposure camera
US3846806A (en) * 1972-12-30 1974-11-05 Minolta Camera Kk Automatic flash device for a photographic camera
US3995286A (en) * 1974-09-30 1976-11-30 Asahi Kogaku Kogyo Kabushiki Kaisha Electronic strobe with optionally-operable controls
US4005337A (en) * 1975-07-21 1977-01-25 Grimes Manufacturing Company Constant energy strobe source
US4074170A (en) * 1976-06-21 1978-02-14 Vivitar Corporation Voltage regulator with thermal overload protection
US4201934A (en) * 1977-03-25 1980-05-06 West Electric Co., Ltd. External sensor for electronic flash
US4294528A (en) * 1978-08-23 1981-10-13 Minolta Camera Kabushiki Kaisha Automatically controlled electronic flash device
US5587644A (en) * 1994-06-15 1996-12-24 Canon Kabushiki Kaisha Charging control device for flash device
US6061528A (en) * 1997-05-08 2000-05-09 Canon Kabushiki Kaisha Flash device

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DE2058679C3 (de) 1979-09-20
DE2058679A1 (de) 1971-07-22
FR2072647A5 (de) 1971-09-24
GB1326060A (en) 1973-08-08
DE2058679B2 (de) 1979-01-18

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