FR2475838A1 - ELECTRONIC FLASH - Google Patents

Abstract

AN ELECTRONIC FLASH INCLUDES IN PARTICULAR A PHOTOTRANSISTOR 21, ASSOCIATED WITH AN INTEGRATION CAPACITOR 22 WHOSE OUTPUT SIGNAL IS APPLIED TO A COMPARATOR 23, SO AS TO DETERMINE THE QUANTITY OF LIGHT EMITTED BY A LIGHT TUBE 16 AND REFLECTED TOWARDS THE DEVICE PHOTOGRAPHIC BY THE OBJECT TO PHOTOGRAPH. WHEN THE QUANTITY OF REFLECTED LIGHT REACHES A VALUE WHICH IS FIXED DEPENDING ON THE OPENING OF THE DIAPHRAGM, A STOP CONTROL CIRCUIT G AUTOMATICALLY TURNS OFF THE LIGHT. THIS CONFIGURATION THUS ENSURES OPTIMAL EXPOSURE IN ALL CONDITIONS OF OPENING THE DIAPHRAGM AND REMOVAL FROM THE PHOTOGRAPHY OBJECT.

Description

The present invention relates to an electronic flash

  that and it relates more particularly to an electric flash

  tronic that is used in an optical device such as a phlographic device, The flash is a device that has been widely used in recent years in association with

  an optical device, such as a camera

  graphic, When the flash is used for photogra-

  In particular, the light exposure is the

  O10metre the most important. In an automatic light adjustment device that is used in photography, the light emitted by the flash is interrupted when light reflected from an object to be photographed

  reaches a predetermined value.

  Light reflected from the photo object

  However, the graphier is weak in the case where this object is black, or in the case where the distance between the object to be photographed and the flash is large, so that the quant.zte of reflected light is low. Because of

  the amount of reflected light is small, the

  no automatic adjustment of the light is not

  operates and the photographer can not determine easy-

  how to adjust the distance between the photo object and

  graphier and the flash, or how to adjust the diaphragm.

  On the contrary, when the object to be photographed is colored

  white, the amount of reflected light becomes

  te, or when the distance between the object and the flash is very small, the amount of reflected light becomes high, so that the auto-dimmer does not work properly. The photographer is equal; unable to determine how he

  must change the distance or adjust the iris.

  An object of the invention is therefore to provide a high-performance flash which is capable of confirming that the reflected light is brought to a value such that the amount of exposure light is equal to the value set in advance, at the way of detecting light

  reflection that is produced by the flash and is reflected

  crapped by the object to be photographed. This flash is in addition

convenient use.

  According to the invention, an electronic flash essentially comprises means for storing electrical energy, raising and rectifying a voltage of a power source, means for generating a trigger signal, means for Flash generation means for flash generation, flash detecting means comprising a light receiving member, a reference voltage setting member, a comparator, and a light amount indicating member.

  Other features and benefits of Vin-

  will be better understood by reading the description

  which will follow embodiments, and with reference to the accompanying drawings in which: FIG. 1 is a circuit diagram of a flash

  corresponding to the invention.

  Figures 2A to 2D show curves

  flash operation characteristics of Figure 1.

  Figure 3 is a circuit diagram of a flash

  corresponding to the invention.

  FIG. 4 is a circuit diagram of an electronic flash corresponding to a modification of the one

is shown in Figure 3.

  Referring now to Figure 1 of the drawings which shows an electronic flash corresponding to the invention. The electronic flash includes a flash FU device for producing a flash and a flash control device PCU for controlling the flash

produces the FU flash device.

  The PU flash device includes essential-

  electrical energy supply means for

  to supply electrical energy, storage facilities

  of electrical energy intended to store electrical energy

  provided by the means for supplying electrical energy, flash generating means for converting into light energy the electrical energy which is stored in the electrical energy storage means, trigger signal generating means for triggering the flash generation means, and flash control means for controlling the amount of light of a flash. The electrical power supply means essentially comprise a direct current source

  comprising a low voltage battery 10 and an interrup-

  a source of power connected to the battery 10, a voltage converter circuit B for converting and

  raise a DC voltage to transform it into a voltage

  alternating voltage, and a rectifier circuit C comprising a

diode 12.

  The means for storing electrical energy

  take an electrical energy storage circuit D for storing an electric charge and supplying

  electrical energy to the flash generation means.

  The lightning generating means comprises a flashlamp circuit P for producing flashes. Lei trigger signal generation means include

  a trigger signal generation circuit E des-

  The flash control means comprises a stop control circuit G for controlling the production of flashes by the flashlamp circuit F, a lightning circuit.

  triggering and indication command H intended to indi-

  that an electrical charge is stored and the stored electrical energy has a predetermined value, and controlling the operation of the trigger signal generating circuit E, and a voltage generating circuit I which is operated by a signal of implementation

  function which produces a voltage signal.

  The FCU flash controller includes

  essentially a light receiving circuit L1 intended

  detecting a flash produced by the flash tube circuit, this flash then returning from an object to be photographed (not shown in the drawing) and the circuit L1 having a conduction which is a function of the amount of reflected light, an integration circuit L2 in which the charging time interval changes in accordance with the conduction of the light receiving circuit L ^^ an integration reset circuit K, for resetting the integration circuit L2, a time setting circuit J for setting the reset time of the integration reset circuit K, a reference voltage setting circuit M for setting a plurality of reference voltages, a circuit for exposure light quantity detection, occurring under the

  form of a comparator circuit N receiving a voltage signal

  voltage and a reference voltage signal from the cir-

  a reference voltage setting circuit M, an exposure indication circuit P which is illuminated by an output signal of the comparator circuit NI, an indication control circuit q which is actuated by a signal voltage from the voltage generating circuit 1, an operation confirmation circuit R which is

  intended to actuate the control circuit of

  when the signal coming from the circuit of

  voltage generation of the flash device is applied.

  that a timer circuit S for setting the time interval relative to the indication circuit P and a lighting restoration circuit T for restoring the illumination

indicator elements.

  In more detail, the converter circuit

  voltage B essentially comprises an oscillation circuit

  It is connected to the battery 10 via the power source switch 11. The rectifier circuit C is connected to an output side of the voltage converter circuit B. The electric charge storage circuit D comprises a main storage capacitor 13, and this capacitor is connected to the voltage converter circuit B via the rectifier circuit C. The trigger signal generation circuit E comprises a trigger transformer and a trigger capacitor, etc., and it comes into operation when a synchronous switch 14, synchronized with a device shutter. photofgraphic (not shown in the drawing), or a test button switch, 15, is placed in the closed state. The tube channel at "clear F comprises a tube with

  flashes i6 and is connected in parallel on the condensa-

  main storage 13. The stop control circuit G is connected to a thyristor 17 via the switching capacitor 18. The trip control circuit H is connected to an electric charge indicating lamp, in the form of a lamp

  nolon 20, through a protection resistance

  19, the trigger control circuit H is actuated by the illumination and controls the

  trigger signal generation E. The generator circuit

  The voltage source I is actuated by an input signal from the trip signal generating circuit E and applies the voltage to the light receiving circuit L1, the integrating circuit L2, to the time setting circuit J , to the reference voltage setting circuit MP to the comparator circuit N, to the circuit R and to the timer circuit S. In the flash control device FCU, the time setting circuit J sets the reset time of the circuit integration t2. The discharge circuit K operates after a predetermined time interval when the flash tube 16 produces a flash and it turns off the integration circuit L2. The

  light L1 comprises a sensing element

  light in the form of a photo-

  transiscor 21, the phototransistor 21 is connected to the capacitor 21

  The reference voltage setting circuit iM essentially comprises a plurality of resistor voltage dividing elements. The comparator circuit N comprises several comparators 23a, 23b, 23c and 23d,

  each of them being actuated by operating voltages

  different, for example 8 volts, 4 volts, 2

  volts and 1 volt. Comparators are respectively connected

  to the integration circuit L1 and to the reference voltage setting circuit M. The indication circuit P has several indicator elements in the form of

  electroluminescent diodes 24a, 24b, 24c and 24d. The cir-

  The control circuit Q comprises a plurality of switching circuits 25a, 25b, 25c and 25d connected to the light emitting diodes 24a, 24b, 24c and 24d which are respectively actuated by the comparators 23a, 23b, 23c and 23d. The switching circuits 25a-25d of the circuit of

  Q indication control are connected to the electronic diodes

  24a-24d and are connected to the stop control circuit G of the flash unit FU by means of a switch 26. The indication control circuit Q is restored by the turn-on signal of the turn-on circuit.

  stop command G. A function confirmation circuit

  R is connected to an indicator element in the form of a light-emitting diode 27 so as to illuminate the diode 27 under the effect of the voltage signal.

  from the voltage generation circuit I of the

  FU flash and designed to operate the FU flash device. The timer circuit S and the indication restoration circuit T are respectively connected

  to the indication circuit P, to the indication control circuit

  Q and the function indication circuit R, in parallel. The timer circuit T is actuated by a

  signal resulting from the voltage signal from the cir-

  cooked voltage generation i. The indication restoration circuit T is actuated by an elapsed time signal from the timer circuit S, and it produces the extinction of the light-emitting diodes 24a-24d.

  of the indication circuit and the light-emitting diode 27Y.

  The smoothing circuit U comprises a diode 28 connected to the battery 10 of the DC source circuit A, and a smoothing capacitor 30 which is connected between the

  diode 28 and the battery 10 via a resistor

  The stop detection circuit is connected to a light-emitting diode 31 and to the stop control circuit G. The electronic flash built in accordance with FIG.

  The foregoing description operates in the following manner.

  When closing the power source switch

  the voltage converter circuit B oscillates, which induces a high voltage, and the increased value AC voltage is rectified by the rectifier circuit C, after which an electric charge is stored in the main storage capacitor 13 of the circuit D. When the main storage capacitor 13 is charged to the predetermined voltage, the neon lamp 20 illuminates, indicating that the flash is ready for the initiation of the flash tube 16 and, in addition, the trip control circuit H operates and produces a control voltage. Under these conditions, the trigger signal generation circuit E operates to produce a trigger signal, under the effect of the operation of the test button switch 15 or

  the synchronous switch 14, which is operated in synchro-

  with the shutter opening operation of the camera, thereby allowing a flash in the flash tube 16 of the P-flash tube circuit. When the trigger signal generating circuit is in function, the voltage generating circuit I receives a control signal, The voltage generating circuit I is operated in synchronism with the appearance of the lightning in the flash tube 16, under the effect of the control signal from the tripping signal generating circuit E. Turning on the voltage generating circuit I has the effect of applying a control voltage

  to the PCU flash controller, this voltage

  setting a supply voltage for the time setting circuit J, the discharging circuit h, the light receiving circuit Lis the integrating circuit L. ,, the reference voltage setting circuit iM, the comparator circuit N, the indication restoration circuit T and the timer circuit S. The voltage smoothing circuit

  U smooths the power source voltage that is applied

  from the battery 10 of the DC source circuit

  continuous current A, via diode 28 and

  protection resistance 29. The tension smoothed by the cir-

  voltage smoothing U is applied to the circuit

  In these conditions, the flash produced by the flash tube 16 illuminates the object to be photographed, then is

  reflected from the object. The phototransistor 21 of the circuit

  baked light receiving L1 receives and detects lightning

  reflected from the object to be photographed. The phototran-

  sistor 21 becomes conductive depending on the amount of

  emitted light. Under the effect of the conduction of the phototran-

  sistor 21, an electrical charge is stored in the con-

  integration denser 22 of the integration circuit L2, as a function of the conduction level of the phototransistor 21. The charging voltage of the integration capacitor 22 is applied to the comparator circuit N and, simultaneously, the reference voltages are also applied to the comparator circuit N from the reference voltage setting circuit M.

  The comparator circuit N comprises several elements

  Comparators 23a, 23b, 23c and 23d. In this case, the threshold voltages for the comparator elements are fixed for example as follows: 8 volts for the comparator element 23a, 4 volts for the element 23b,

  2 volts for element 23c and 1 volt for element 23d.

  The voltages set for the voltage clamping circuit

  M are also adjusted to the corresponding voltages

  of the comparator elements 23a-23d. When the charging voltage of the integration capacitor 22 is 4 volts, the comparator elements 23b, 23c and 23d are in the active state, because the electric charge which is stored in the integration capacitor 22 corresponds to the amount of reflected light. Control circuits

  25b-25d are actuated by the output signals

  of the comparator circuit N, whereby the indicator elements 24b24d illuminate to indicate the quantity

  of light corresponding to the flash of the flash tube 16.

  In this case, the indication control element 25b is set to operate when the amount of indication is equal to the amount of the control element 25b. responds to diaphragm aperture F: 5.6,

  i7; L] em * nt; 2 'is set to correspond to the opening

  F: L, and item 25d is set to

  : * .., n correpond to aperture F: 2.8.

  5, where, as shown in FIG. 1, the movable contact 2 is e. The control element is indicated by the fixed contact 26b, when the voltage of

  A value of 4 volts is applied to the comparison

  23 comparator elements 23b-23d operate from

  to illuminate the light-emitting diodes 24b-24d.

  In these conditions, the output signal of the com-

  parate7n? 2qb is applied to the stop control circuit G through the switch 26, which has the effect of blocking the thyristor 17. The blocking of the thyristor 17 terminates the flash produced by the flash tube 16 When L: the amount of reflected light is small and the integration value of the integration capacitor 22 is present, and the aperture F: 5.6, the control circuits The indication 25c and 25d are operative to illuminate both the light emitting diodes 24ec and 24d1, or the circuit 25d is operative to illuminate only the diode 24d. The state of lighting

  24b-24d electro / emitting diodos allows the photo-

  graph to have easily confirmed the fact that the amount of light produced by the flash tube 16 the latteint as: the amount corresponding to the aperture F: 5.6, as well as the fact that the amount of

  The light produced by the flash tube 16 is insufficient.

  In this way, in the case of detecting that the amount of light is insufficient, taking into account the preselected aperture value, the photographer can reduce the distance between the camera and the object or adjust it. the opening of the diaphragm of the apparatus

  photographic way. to obtain a correct exposure.

  When the reference voltage value of the reference voltage setting circuit M becomes

  less than the value of the voltage of the capacitor of in-

  In addition, the comparator N does not work. As a result, the voltage of the integration circuit L2 is forcibly lowered by the fact that the circuit L2 is actuated after the predetermined time interval when the voltage signal is produced by the voltage generating circuit I. , using for this the time adjustment circuit J. Moreover, when another light source, such as the sun, emits light towards the light circuit.

  L1 light reception, the charge voltage of the capacitor

  integrator 22 becomes greater than the reference voltage of the reference voltage setting circuit M,

  and the comparator circuit N operates erroneously.

  To prevent erroneous operation, the electrical load

  that integration capacitor 22 is brought to zero in

  discharging this capacitor, so as to give the

  charging circuit a low value, by the action of the discharge circuit K. The discharge circuit K is actuated by the application of the output signal of the indication control circuit Q, through the switch 26,

  when the indication control circuit comes into operation

tionnlement.

  The operation detection and confirmation circuit R for detecting the operation of the flash device FU operates when it receives the voltage signal from the voltage generating circuit i. Under the effect of the operation of the detection and confirmation of operation circuit, R, the diode

  electroluminescent 27 is excited to illuminate

  SOE. The illumination of the light-emitting diode 27 provides confirmation of the operation of the flash device FU. When only the light-emitting diode 27

  is illuminated and all other light-emitting diodes

  nescentes 24a-24d are not lit, the photographer has confirmation that the lightning flash 16

  corresponds to a condition of underexposure.

  The timer circuit S is also activated

  by the voltage signal which comes from the circuit of genera-

  I. When the timer circuit S is actuated by the voltage signal from the circuit 1 1

  of voltage generation 1, this timer circuit

  that a signal in the form of an impulse to the circuit of restoration

  illumination T, at the end of the predetermined delay time of the timer circuit S, such as for example 2 s. when the lighting restoration circuit T receives the signal under pulse form that comes from the circuit

  timer S, the circuit T short-circuits the power supply

  1electric power supply for electroluminescent diodes

  24a-24d and 27, and this turns off the light-emitting diodes

your 24a-24d and 27.

  Moreover, the operation of the stop control circuit G can be detected and confirmed by the illumination of the light emitting diode 31, because the stop detection circuit V is actuated by a signal which originates from the circuit G and that the diode 31 is illuminated by].

  V. The diode 31 is extinguished by the action of the cir-

  baked lighting restoration T.

  Figures 2A and 2D represent the characteristics

  FIG. 1. As is evident from a curve 11 of FIG. 2A, it is assumed that the flash tube 16 produces a flash at time t1 after the closing of the switch 14 or 15. , and that the flash stops at time t3, or after a period of 4 ms, for example, after the start of the production of lightning by the flash tube 16. When the flash tube 16 begins to flash, the voltage generating circuit I produces the voltage indicated at point A in FIG. 2B, which corresponds to the instant t1, as shown in curve 12. The voltage produced by the voltage generating circuit I is raised to 15 volls (point B). The high voltage is maintained during the given time interval, for example about 5 ms, as indicated by the points B and C of a curve 13 in FIG. 213, and this voltage then decreases as shown by the points C and D of a curve 14. In this case, when the phototransistor 21 becomes conductive under the effect of the amount of light that is reflected from the object to be photographed, the electric charge is stored in the capacitor 22t as the shows the curve 15 on the

Figure 2C.

  Under these conditions, an electric charge is also stored in element K, as shown in curve 15 in FIG. 2C. during the period t1 to t2 which is defined by the points E and F, after which the charging voltage of the capacitor 22 becomes approximately 8

  volts. When the charging voltage reaches the pre-

  determined by a point such as the point E on the curve 16, the comparator circuit N comes into action so as to operate the element Q. The output signal of the element Q is transmitted from the elements G and K, via the element 26. Under the effect of the signal from the element Q, the element G stops the flash of the element 16 at a time approximately identical to that indicated by the point E of the

  In this case, the charging voltage of the condensa-

  22 decreases and becomes equal to zero, as shown by the points E and G, under the effect of the conduction of the circuit K, the fact that the electrical signal is applied to the circuit K via the element 26. On the contrary, the charging voltage of the capacitor 22 becomes greater than 8 volts, as shown by the curve 16 of FIG. 20, when the circuit K is not actuated, so that the electrical charge of the integration capacitor 22 n is not discharged. In this case, when the voltage of the voltage generating circuit I represented by the curve 14 becomes lower than that of the capacitor 22, represented by the curve 16, the comparator circuit N operates erroneously. To pocket the erroneous operation of the comparator N, the charging voltage of the capacitor 22 is brought to zero by the passage of the circuit K in the closed state, after three seconds, as shown by the points E

and G on curve 15.

  Figure 2D shows a state of charge of the conden-

  integration sink 22 which is due to another light source.

  neuse. In this box, the charging voltage of the capacitor 22 decreases from a value corresponding to the point I to a point corresponding to the point J, and the charging voltage

  integration integrator 22 becomes equal to zero.

  link that the capacitor's electrical charge 22

  a1.mero i zoro by short-circuiting the conden-

  sate? 2 2 after the predetermined time interval, in accordance with the time characteristics of the operation of the circuit J, the time setting circuit J

  pc: u 'f conduct driver after the predetermined time interval

  for example, 5 ms from point B, using a timer, as shown in FIG. 2,

  The above description clearly shows that

  the device corresponding to the first embodiment is able to confirm the operation of the automatic control of exposure and to confirm the conditions of exposure of the iash. The flash is very convenient for changing the shooting distance and for adjusting the

  di aphra (-m e of the photographic apparatus.

  Figure 3 shows the second mode of

  flash corresponding to the invention. Darns the flash

  which is represented in FIG. 3, a circuit converting

  his die tension 13 essentially comprises a circuit

  oscila;. Oeur ' OC In more detail, the circuit

  voltage greening B includes a switching element

  in the form of a transistor 32 whose transmitting electrode

  teutr is conrectoe to a posi-tive terminal of a battery 10,

  by means of a power source switch

  In one embodiment, an oscillation transformer 34 comprises a primary winding 3Ta connected to the battery 10 via the collector-emitter circuit of the transistor 32 and the power source switch 11, a resistor 33 which is connected to the battery. is connected between a positive terminal and a base electrode of the transistor 32, and an oscillation capacitor 35 which is connected between the emitter electrode ec; the base electrode of the transistor 32. A terminal of a secondary enrollment 34b is connected to the base electrode of the transistor 32. The rectifier circuit

  C comprises diodes i2a, 12b, 12c and a capacitor 36.

  The anode electrodes of the diodes 12a and 12b are connected

  at a terminal of the secondary winding 34b, and an electric

  Anode trode of the diode 12c is connected to a socket 34c of the secondary winding 34b. The capacitor 36 is connected between the secondary winding 34b and the terminal

negative battery 10.

  An electrical energy storage circuit D comprises a main storage capacitor 13 which is connected to the diode 12a of the rectifier circuit C and to. the negative terminal of the battery 10. A trigger signal generation circuit E comprises resistors 37, 38 and 39, a first trigger capacitor 40 and

  a first trigger transformer 41. The resistors

  37 and 39 and the trip capacitor 40 are connected between the diode 12b and the negative terminal of

  the battery 10, and the resistor 38 is connected to the

  trigger densifier 40 and resistor 39, in parallel, for use as a bypass resistor for the trip capacitor 40. A primary winding 41a of the trip transformer

  41 is connected in parallel to the trigger capacitor

  40, via a synchronous switch 41 and a test button switch 15. A flash tube circuit F comprises a flash tube 16 including a 6lba electrode, which is one of the main electrodes current conductors, is connected to the diode 12a of the rectifier circuit C, and a trigger electrode 16c of which is connected to a secondary winding 41b of the

  first triggering transformer 41.

  A stop control circuit G comprises a circuit

  switching circuit G1 which controls the flash tube circuit, a stop circuit G2 for controlling the switching circuit G1, and a stop signal generating circuit G3 for tripping the tube stop circuit. G ,. The switching circuit G1 comprises a first switching element which is in the form of a

  thyristor 17, a switch-over switch 18, a resistor

  switching resistance 42, a resistor 43, capacitors

  44, 45 and 48, and resistors 46 and 47, these

  ctaint connected in the way shown. The trrSt circuit G2 comprises a protection resistor 49 and a stop tube 50 which comprises a pair of current-conducting main electrodes 50a and 50b, and a

  trigger electrode 50c. The stop tube 50 is also

  connected to the two electrodes 16a and 16b of the flash tube 11, and to the main storage capacitor generation of

  13. The Circumbe / lgnl! G3 includes a resis-

  protection factor 51, a second trigger capacitor

  52 and a second trip transformer 53. The trip capacitor 52 is connected between the diode 12a of the rectifier circuit C and the negative terminal of the battery 10 of the DC source circuit A.

  primary winding 53a of the second trigger transformer

  53 is connected to the trigger capacitor 52

  through a second thyristor 54. A resistor

  this protection 55, a capacitor 56 for absorbing the noise and a resistor 57 are connected to an electrode

trigger of the thyristor 54.

  In a trip control and indication circuit H11, an indicator element in the form of a neon lamp 20 is connected to the capacitor

  smoothing 58 by way of a resistance of

  19. A voltage generating circuit I comprises a switching element in the form of a transistor 60 having an emitter electrode connected to it.

  the diode 12a of the rectifier circuit C, an element of genera-

  tion of a constant voltage in the form of a zener diode 62 connected between the diode 12c of the rectifier circuit C and the negative terminal of the battery 10, and a

  smoothing capacitor 62. A basic electrode of the tran-

  sistor 60 is connected to the diode 12a via a bias control element which comprises a diode 64, a resistor 65 and a capacitor 63, A collector electrode of the transistor 60 is connected to

  a load resistor 66, to a capacitor 67, to a circuit

  cooked light receiving L and a detection circuit

  and confirming the operation of the flash, R, belonging to

* to a FCU flash controller.

  In the flash controller FCU, a light sensing element in the form of a phototransistor 21 is connected to a resistor 58 and an integrating capacitor 52 and a resistor 69 is connected to the resistor 68 and to the resistor 69 which forms a discharge circuit K.- The integration circuit L2 comprises the resistor 68 and the integration capacitor

  22. A reference voltage setting circuit M includes

  carries a voltage divider 71 which is connected to the elec-

  collector trode of transistor 60 of the general circuit.

  voltage I ,. through a variable resistor 70. The voltage divider 71 has several

  resistors connected in series: 71a, 71b, 71c and 71d.

  A comparator circuit N comprises several comparator elements 23a, 23b, 23c and 23d. Each of the

  comparator elements 23a-23d is set to function

  for a different threshold voltage and it is

  connected to a corresponding socket of resistors 71a

  71d of the voltage divider 71, as well as to the circuit of interest.

  L2 and the discharge circuit K-. Each of the light-emitting diodes 24a-24d is connected to a corresponding switching control circuit 25a-25d of an indication control circuit Q. In the indication control circuit Q, each of the transistors 74a74d is connected

  to the comparator-corresponding element of the compar-

  N, through the resistors 72a-72d. The protection resistors 73a-73d are respectively connected to the thyristors 75a-75d via the

  light-emitting diodes-24a-24d. We use a

  The switch 26 comprises a movable contact 26a, a manual operation contact 26m and a plurality of fixed contacts 26a, 26b, 26c and 26d. In more detail, the contact 26a corresponds to the opening

  F: 8, the contact 26b corresponds to the opening -.5,6,1e con-

  tact 26c corresponds to the opening F: 4 and the contact 26d corresponds to the opening R2,8. The switch 26 is connected to the thyristor 54 via a protection resistor 55. In this way, adjusting the

  diaphragm of the camera to a pre-

  determined sets the amount of light of the flash tube 16, which provides a correct exposure. The transistor 60 is connected to a resistor 81 as well as to a capacitor 79 and a capacitor 80e and a thyristor 83 is connected to a protection resistor 82 by means of a light-emitting diode 27.

  light-emitting diode 27 and the thyristor 83 are connected

  to a transistor 85 via a resistor

  84. The transistor 85 is connected to a unijone transistor

  programmable transistor 88 via a resistor 86 and a resistor 90, and the transistor 88 is connected to an integration capacitor 87 for setting the delay time, and to a resistor 90, a resistor 89, uni capacitor 91 and a resistor 92. Transistor 88 and

  the protection resistor 89 are connected to a transistor

  tor 94 via a protection resistor 93. The transistor 94 is connected to a diode 28 and to a

  smoothing capacitor 30 through a resistor

  protection 29, and the diode 28 is connected to the battery 10 via the source switch

supply 11.

  The operation is as follows. When closing

  the power source switch 11, the circuit

  tensioner B oscillates, and the high voltage is

  induced in the secondary winding 34b of the transformer

  oscillation pattern 34. The increased AC voltage is

  rectified by the rectifier circuit C, and an electrical load

  It is then stored in the main storage capacitor 13. When the main storage capacitor 13 is charged to the predetermined voltage, the neon lamp 20 lights up, indicating that the flash is ready for

  the lightening of the lightning tube 16. At the same time,

  triggers 40 and 52 are loaded by the

  continuous high voltage output from the rectifier circuit C. Under these conditions, the operation of the flash tube circuit P is triggered by the flash trigger operation of the trigger signal generating circuit.

  E, in synchronism with the opening operation of the closure

  of the camera, which allows the production of

  flashing through the flash tube 16.

  In more detail, the DC voltage which is rectified by the diode 12a of the rectifying circuit C is applied to the main storage capacitor 13, and the charging voltage of the main storage capacitor 13

  gradually increases. Under the effect of the increase of.

  the voltage of the main storage capacitor 13, the charging voltage of the capacitor 58 also increases, by applying the rectified voltage that comes from the diode 12b. DC voltage rectified by the diode

  12c is applied to the zener diode 62 of the general circuit.

  1, to produce a constant voltage, whereby the charging voltage of the capacitor 60 is kept constant. The socket 34c of the transformer 34 is intended to allow a relatively low voltage to be obtained, for example approximately 15 to 20 volts, thanks to

  which transistor 60 is biased in the non-conductive state

  by the application of the corresponding positive voltage

  to the charging voltage of the capacitor 63. In these conditions

  the charging voltage of the capacitor 61 is always applied to the comparator circuit N of the JCU flash control device, and the comparator circuit N can therefore be

operated at any time.

  When the flash tube circuit 'operates,

  the electrical charge of the capacitor 63 of the circuit of genera-

  Voltage ration l is discharged to the flash tube 16.

  Under the effect of the discharge of the capacitor 63, a negative voltage is applied to the base electrode of the transistor, to make it conductive. When transistor 60 is

  conductor, the voltage across capacitor 61 of -

  voltage generation circuit I is applied to the circuit

  the light receiving circuit Ll, to the voltage

  reference voltage M and the function confirmation circuit

  In these conditions, the phototransistor 21

  L1 light receiving circuit detects the reflected light

  the flash produced by the flash tube 16 and becomes conductive with a conduction level determined by the amount of reflected light. Under the effect of the conduction of the phototransistor 21, an electric charge is stored in the integration capacitor 22 of the circuit

  integration L2, so that the charging voltage of the con-

  integration denser 22 increases to a pre-determined value.

  determined that corresponds to the amount of light of

  lightning. The charging voltage of the integrating capacitor

  22 is applied to the comparator circuit N. On the other hand, the reference voltage fixing circuit M produces a plurality of reference voltages intended to be applied to the comparator circuit N. In the case considered, the reference voltage fixing circuit M is set to produce a plurality of reference voltages having for example the values: 8 V, 4 V, 2 V and 1 V. The comparator circuit N comprises the comparator element 23a which is actuated by a voltage of 8 V, element 23b which is actuated at 4 V, element 23c which is actuated at 2 V and comparator element 23d which is actuated at 1 V. When the charging voltage of integration capacitor 22 reaches the predetermined value, such as 8 volts, all the comparator elements 23at 23b, 23c and 23d are actuated and emit signals. Under the effect of these output signals, all transistors 74at 74b, 74e and 74d become conductive. When transistors 74a-74d become conductive, trigger signals

  are applied to the thyristors 75a, 75b, 75c and 75d, allowing

  both the passage of thyristors in the conductive state. Under the effect of the conduction of thyristors 75a-75d of the circuit

  the Q indication control, all light-emitting diodes

  24a, 24b, 24c and 24d are illuminated and indicate the amount of light contained in the flash produced by the flash tube 16 of the flashlamp circuit F. In the same manner, at least one of the light emitting diodes -24a-24d of the indication circuit P is illuminated and indicates the 24a-24d of the indication circuit P illuminates and indicates the amount of light contained in the flash, in accordance with

  the value of the charging voltage of the integrating capacitor

  22 of the integration circuit L2. Thus, when the

  Since the capacitor charge voltage 22 is 4 volts, the diodes 24b, 240 and 24d illuminate and indicate the corresponding amount of light. When the charging voltage of the capacitor 22 reaches 2 volts, the diodes 24c and 24d light up, and when the voltage of the capacitor 22

  reaches 1 volt, the diode 24d illuminates and indicates the

  corresponding light intensity of the lightning produced by

flash tube 16.

  Although the indication control circuit Q is designed to be actuated by the output signal of the comparator circuit N in the flash which is shown

  in the drawings, according to the invention, it is possible to use

  another indication control unit, external, in place of the indication control circuit Q. In the flash shown in FIG.

  when the distance between the object to be photographed and the -

  flash is weak at the moment of photography, the integration operation of the integration circuit L2 is accelerated by the resistor 68 and the charging voltage of the integration capacitor 22 is derived by the resistor 69 of the discharge circuit K. The output signal of the comparator circuit N is also applied to the stop control circuit G via the switch 26. The stop control circuit G controls the instant of appearance of the lightning and the duration of the the flash produced by the flash tube 16, in accordance with the control signal from the comparator circuit N. In more detail, if the movable contact 26e is connected to the fixed contact 26d which corresponds to the element 23d of the comparator circuit N. the output signal of the element 23d is applied to the stop control circuit G when the integrated voltage of the integration capacitor becomes greater than at least 1 volt. The control signal from the comparator circuit N primes the thyristor 54 so as to make it conductive. When the thyristor 54

  becomes conductive, the electrical charge of the second

  Trigger 52 is discharged by the primary winding 53a of the second trigger transformer 53 and the thyristor 54. A high voltage pulse is generated in the secondary winding 53b and this pulse is a trigger signal for the tube.

stop 50.

  The stop tube 50 must naturally fulfill certain conditions. In order to function effectively, the stop tube 50 must have a low impedance with respect to that of the flash tube 16. The flash tube 16 has a minimum impedance of a characteristic value of 1.5 to 2 ohms. Thus, the stop tube 50 must have an impedance close to 0.1 ohm. To have such a low impedance, the stop tube 50 must also have a pressure of

  weak gas and a small gap between the electrodes.

  The electrodes 50a and 50b must be able to convey a very high current for a short time. The tube

  50 must be able to be initiated quickly and easily.

  the range of voltage across the terminals of the

  flash tube during the flash. The 50 stop tube

  takes a trigger electrode 50c which is located at

  midway between the two main electrodes 50a and 50b.

  Under the effect of the trigger signal that pro-

  comes from the trigger transformer 53, the tube

  50 of the stop circuit G2 is placed in the conductive state.

  tor. When the stop tube 50 becomes conductive, the discharge current from the main storage capacitor 13 of the electrical energy storage circuit D is diverted by the stop tube 50 so as to stop the lightning of the tube. flashes 16 of the flash tube circuit F, since the internal resistance of the stop tube 50 is

  lower than that of the flash tube 16.

  When the flash tube 16 stops flashing, the amount of flash light becomes zero and the light emitting diode 24d turns off because the action of the comparator circuit N ceases. When the distance between the object and the flash is very short, the lightning tube 16 produces a superabundant light despite the stop of the lightning, due to the delay in setting the light.

  action of the control circuit of arrgt G. Thus, the photo-

  transistor 21 detects the unnecessary light and a useless electric charge is stored on the integration capacitor 22. The light-emitting diode 21ic thus illuminates in addition to the diode 24d. The comparator circuit N

  therefore works erroneously.

  On the other hand, when the photography distance

  is very large, the amount of reflected light is

  ble, and the electrical charge that is stored in the con-

  integration denser 22 is therefore weak. Due to the low value of the charge stored in the capacitor, the charging voltage of the capacitor 22 becomes less than 1 volt, and none of the light emitting diodes are illuminated. In this case, the underexposure is detected and confirmed because the firing signal is applied to thyristor 83 of the operation confirmation circuit R, from the voltage generation circuit 1, so that the thyristor 83 becomes driver and the diode 27

  lights. When the switch 26 is placed on the position

  corresponding to the manual operation, it can be confirmed that the amount of light of the flash is correct if all the light-emitting diodes 24a-24d light up, although the control signal is not applied to the control circuit of the light-emitting diode. stop G. When the thyristor 83 becomes conductive, an electric charge

  negative is applied to the base electrode of the transistor.

  tor 85 of timer circuit S and transistor.85

  becomes a driver When the transistor 85 becomes

  driver, the programmable unijunction transistor 88 also becomes conductive. When the programmable unijunction transistor 88 of the timer S becomes conductive, a conductive pulse signal is applied to the base electrode of the transistor 94 and this

  transistor 94 becomes conductive. The conduction of the

  sistor 94 has the effect of reducing all the diodes

  troluminescent when extinguished.

  In addition, although the delay circuit of

  the invention is realized in such a way that the electrolysis diodes

  24a-24d and 27 are off after the given time interval, it is not always necessary for the light-emitting diodes to be off after the given time interval, and these diodes can be kept illuminated by the light sequence. immediately following operation of the flash tube circuit F. To achieve this, it is possible to pass the control circuit

  in the idle state by the sequence of operation.

  corresponding to the next flash, in order to

  keep light-emitting diodes lit. -

  FIG. 4 represents a modification of the device of FIG. 3. In the device which is

  shown in FIG. 4, a discharge circuit E

  takes a resistor 69 connected in parallel with the circuit

  IEC 60050 - International Electrotechnical Vocabulary - Details for IEV number 841-21-21 Microwave / Electronic microscopy 221, a transistor 200, whose collector circuit is connected to the integration circuit L2 so as to be connected in parallel thereto, and a diode 201 which is connected between the base electrode

  of the transistor 200 and the trigger electrode of a thyristor

  tor 54 of a stop control circuit G, via

  A capacitor 202 is further connected between the base electrode of the transistor 200 and a voltage generating circuit I. An operation confirmation circuit R comprises a transistor 206 whose collector-emitter circuit is connected to an indication restoration circuit T via a resistor 207. The base electrode of the transistor 206 is connected to the base electrode of the transistor 200 by

  via a resistor 205 and the circuit R

  further takes a thyristor 208, a light emitting diode

  209 and a resistor 210 connected in series.

  In the case of the device of Figure 4, when closing a power source switch

  11, the voltage is permanently applied to a phototran-

  sistor 21 and a comparator circuit N. The capacitor

  integration 22 is therefore short-circuited by the

- -242475838

  sistor 200 before a lightning tube 16 flash,

  in order to prevent the integration capacitor from

  that a signal from the phototransistor 21. The transistor is made conductive by the positive potential present on its base electrode when the flash tube 16 is not in operation. When the flash tube 16 produces a flash, a negative voltage is applied to the base electrode of the transistor 200 and the latter is blocked. When the transistor 200 is blocked, an electric charge is stored

  in the capacitor 22 to begin the operation of inte-

  - gration, and the comparator circuit N operates in accordance

  at the charging voltage of the integration capacitor 22.

  In circuit R, transistor 206 is maintained

  in the conducting state by the positive potential of its electri-

  basic trode, when the lightning tube 16 does not produce

  Flash. When the flash tube 16 produces a flash, -

  a negative potential appears on the base electrode of the

  transistor 206 and the latter is blocked. When the transis-

  tor 206 is blocked, the gate signal is applied to the thyristor 208 through the resistor 207, and

  the thyristor 208 is thus initiated. As a result of the

  the thyristor 208 emits the light-emitting diode 209

  illuminates and indicates the condition of underexposure.

  [When the thyristor 208 is conductive, a current flows to the capacitor 87 through a resistor

  86 and an electrical charge is stored in the condensate

  87. A unijunction transistor 88 becomes conductive when the electrical charge of the capacitor 87 reaches a

  predetermined value, at the end of the pre-

  determined, such as three seconds. When the unijunction transistor 88 is conductive, the voltage is applied to a transistor 94 via a resistor 93, to cause the conduction of the transistor 94o. When the transistor 94 is conductive, the light-emitting diodes 24a-24d and 209 are restored. in the off state. Control signals are applied to the transistor 200 of the discharge circuit K and to a thyristor 54 of a stop control circuit G, from the circuit. Comparator N. Under the effect of the control signal coming from the comparator circuit N, the transistor 200 switches to the conductive state so as to short-circuit the capacitor 22 and, simultaneously, the control circuit of the G-stop switch into action. In this case, the integration circuit L2 operates in a normal manner, because the charging of the capacitor under the effect of another light is canceled by the lightning circuit. the short-circuiting performed by the transistor 200.

  The foregoing description shows that the invention

  achieves its different goals, as well as others

advantageous results.

  Naturally, various modifications may be made by those skilled in the art to the devices or processes which have just been described solely by way of nonlimiting examples, without departing from the scope of the inventions

REVE NDICATIONS

  An electronic flash, characterized in that it comprises: a flash device (IU) comprising means for supplying electrical energy constituted by a DC voltage source (A) and by means (B, C, D) for raising the voltage of the DC voltage source and storing electrical energy, a lightning generating circuit (f) comprising a lightning flashing tube (16), a lightning generation means

  trigger signal (E) for triggering the circuit

  lightning generation cookware, and means (G) for stopping the flash of the lightning generating circuit, when the amount of light of that flash reaches a predetermined value; and a flash controller (FCU)

  which comprises light receiving means (L1) for

  born to receive reflected light which is produced by the flash tube and which is reflected on an object to be photographed, means for detecting the amount of

  lightning (L2, M, N) to detect the quantity

  light of lightning produced by the lightning tube

  by comparing a reference voltage with an electrical value -

  which is obtained by integration of the output signal of the light receiving means, means (I ', Q) for

  to indicate the value of the exposure under the effect of

  said output signals of the flash light amount detecting means, and the flash light amount controlling means (26, G) for

  order the amount of lightning.

  2. Electronic flash, characterized in that it comprises: a flashing device (FU) comprising means for supplying electrical energy constituted by a DC voltage source (A) and by means (B, C, D) intended to raise the voltage of the DC voltage source and to store electrical energy, a circuit

  of flash generation (F) comprising a flash tube -

  (16) producing lightning, generating means for

  trigger signal (E) for triggering the circuit

  a lightning generation cooker, and means (G) for stopping the flash circuit circuit when the amount of light of said flash reaches a predetermined value; and a flash control device (FCU) which has light receiving means (L1) for receiving reflected light which is produced by the lightning tube and which is reflected on an object to be photographed, means for detecting the quantity of

  lightning (L2, M, N) to detect the quantity

  light of lightning produced by the lightning tube

  by comparing a reference voltage with a

  that is obtained by integrating the output signal of the light receiving means, means (P, Q) for

  to indicate the value of the exposure under the effect of

  each of the output signals of the flash light amount detection means, and the flash light amount control means (26, G) for

  order the amount of light from the lightning,

  flash head further comprising voltage generating means (I) which applies a voltage to the light receiving means (L1) and the light detecting means

  the amount of light of the flash (L2, Ml N) of the

  tif flash control, while the device

  flash control further comprises means (S) for

  to maintain the means of indication in operation

  during a predetermined time interval.

  Electronic flash according to claim 1,

  characterized in that the feeding means comprise

  a voltage converter circuit (B) for raising and converting an output voltage of the DC voltage source (A) into an AC voltage, a rectifier circuit (C) for rectifying an AC output voltage. of the voltage converter circuit, and an electrical energy storage circuit (D) which includes a main storage capacitor

  (.13) for storing the corresponding electrical energy

  at a continuous voltage supplied by the rectified circuit

  sor; and means (G) for stopping the flash lightning circuit (F) circuitry consist of a stop control circuit which comprises a circuit of. switching (G1) which switches the flashing tube (16) of the flash generation circuit (F) in a conductive state and in the off state, a stop circuit (G2) for controlling the switching circuit , and a second signal generation circuit

trigger (G3).

  An electronic flash according to claim 1,

  characterized in that the means for detecting the quantity

  of lightning (L2, M, iN) include a cir-

  cooked reference voltage fixing (m) which comprises

  several voltage division resistors, and a cir-

  a comparator (N) for receiving a plurality of reference voltages and a charging voltage of an integrating capacitor (22) which is part of the detection means

  the amount of light from the lightning.

  5.The electronic flash according to claim 1,

  characterized in that the indicating means (P, Q) comprises

  take an indication circuit (1). which will be under

  the effect of output signals of the comparator circuit (N).

  An electronic flash according to claim 5, characterized in that the indicating means (P, Q) further comprises an indication control circuit (Q) which controls the indication circuit (P) under the control of output signals of the comparator circuit (4)

  7. Electronic lash according to claim 5,

  characterized in that the control means of the quantity

  lightning intensity (26, G) include a

  controller (26) which is connected to the coniparator circuit (N) and a stop control circuit (G) which is connected to this switch0. 8. An electronic circuit board according to claim 2, characterized in that the means for generating voltage consists of a voltage-generating circuit (I) which is actuated under the effect of the trigger signal generating means (E) and which produces a voltage signal. -1 - Gone

1

  9. An electronic flash according to claim 2, characterized in that the means for maintaining the

  means of indication in operation include a cir-

  a timer (S) which generates a stop signal after a predetermined time interval when the voltage generation circuit I produces

the voltage signal.

  An electronic flash according to claim 2, characterized by further comprising an operation confirmation circuit (i) for indicating the

  operation of the ilash device (.t.'U).

  11. An electronic flash according to claim 10, characterized in that it further comprises a circuit of

  restoration of indication (T) for restoring a cir-

  baked indication (l, (Q) whose function is to indicate the amount of light from the light produced by the light circuit.

flash generation (i).

  12. The eclectronic flash according to claim 3, characterized in that it further comprises a trigger control circuit (H) which functions only

  when a neon lamp (20) lights up.

  13. An electronic flash according to claim 1, characterized in that it further comprises means (K) for bringing to approximately zero the voltage of an integration circuit (L) means for detecting the amount of light. , returning a stop signal

  flash to the integration circuit.

  14. An electronic flash according to claim 1, characterized in that it further comprises means (K) intended to bring the voltage of an integration circuit (L) of the detection means

  amount of light, after a time interval of

  determined from a moment following the

  flashing by the flash tube (16).