FR2682004A1 - Lighting apparatus for taking photographs - Google Patents

Abstract

Lighting apparatus of the type comprising flash-tube lamps and guide lamps and an electronic flash synchronisation circuit. A central processing unit 1 with a programmed microprocessor controls various electronic switches so as to control the charging of capacitors as well as their connection to the various lamps 3, 4, 5 and their discharge through the lamps, triggered by a flash synchronisation circuit.

Description

LIGHTING APPARATUS FOR PHOTOGRAPHIC VIEWS
The invention relates to a lighting device for taking photographs, which can be used essentially in the fields of photography, film and television.

The basic principle of electronic rlash is well known: a flash tube is connected to the terminals of a capacitor charged by direct current. The bright flash is obtained when a high voltage pulse is sent to a trigger wire wrapped around the flash tube so as to ionize the gas inside the tube S which makes the flash tube conductive of the electricity, and this ensures the discharge, through the tube, of the power previously stored in the capacitor
In its effective use a certain number of functions have been added to this basic surcharge in order to make the electronic flash devices pi us efficient or more suited to certain uses.

 For example, several torches can be connected to the same device and different powers can be applied to each torch by varying the number of capacitors which discharge in each torch. An additional variation of the total light power is also ensured by adjusting the charging voltage of the capacitors.

 In some flash cameras, the light output and the flash duration are controlled by thyristor switching devices which cut the flash at different predetermined values of light or duration. Flashes produced in the past share one or more of the preceding points, with major drawbacks which will be explained below.

 In addition, a certain number of professional electronic flash cameras have a stroboscopic function which allows them to be charged and discharged quickly in sequence. For this purpose, the number of capacitors in the circuit is reduced to allow the device to be recharged quickly.

 However, this system has two disadvantages: on the one hand the interval between the flashes @e can be shorter than the charging time of the capacitor; and on the other hand, as the capacitor is repeatedly discharged, it risks deteriorating due to overheating.

An aim of the present invention is to propose a lighting device which allows to have a very short flash duration, without loss of light caused by the cut of the lightning itself.
Another object of the present invention is to provide a lighting device which allows an independent variation of the power distributed between your different torches.

 Yet another object of the present invention is to provide a lighting device which allows optimization of the total power distributed between the different torches while keeping the power ratio of each torch. The invention allows the user to have the shortest possible flash duration for the chosen power.

 The present invention relates to a lighting device, of the type comprising flashlight torches and guide lamps and an electronic flash synchronization circuit, characterized in that it comprises at least two capacitors and a central unit of programmed microprocessor control, for controlling different electronic switches, so as to control the charging of the capacitors, as well as their connection to the different torches and their discharge through the torches triggered by the electronic flash synchronization circuit.

According to other characteristics of the invention:
- the electronic switches controlled by the programmed central microprocessor control unit isolate the charged capacitors from their charging circuit, and then connect them to the @orches just before and during their discharge through the flash tubes
- the central control unit with programmed microprocessor has circuits for controlling the power delivered to each torch, via the liver for switching the capacitors and adjusting their charge voltage:
- i the central control unit determines the maximum total power to be used while maintaining the power ratios chosen between the different torches;
- The capacitors or groups of capacitors are charged successively and separately, and are then discharged successively in a controlled, stroboscopic manner, by a programmed electronic synchronization circuit, in one or more flash tubes;
- the programmed central unit controls the light power of the i-amp-gu i of the spell torches that the light power cie each guide lamp remains proportional to that of the corresponding flash power
- The central unit controls the power of the torch guide lamps so that the light power of the guide lamps is maximized while preserving their relationship with the flash power discharged in each torch.

- the maximum average intensity of the supply current is defined, controlled and / or displayed;
- Means are provided for connecting one or more central units to a microcomputer and for controlling them by this microcomputer, on the screen of which appears all the necessary information;
- bar graphs are displayed separately or simultaneously next to each other, to indicate the light power for the flash and the guide lamp of each torch as well as the total power;
- preferably in a direction opposite to the bar graphs, bar representations are displayed indicating the quantity of unused power, and available tick
- preferably in the same direction as the bar graphs, bar representations are displayed indicating the minimum possible power.

- a display indicates whether the device is operating in symmetrical mode. asymmetrical, normal 3 slow, fast, or strobe, and / or indicates the effective duration of the flash;
- a display indicates whether a component 115 is not operating correctly, and whether it has been switched off.

Other characteristics emerge from the following description made with reference to the attached drawing on which we can see:
Fig. 1: an overall view of a lighting device according to the invention;
Fig. 2: a block diagram of the configuration of the lighting apparatus according to the invention;
Fig. 3: a simplified diagram of the power management circuit of the lighting apparatus in the case of three torches
Fig 4 to 6: tables showing different modes of operation of the lighting apparatus according to the invention.

 Fig. 7: a diagram representing the display screen of the central unit of the lighting apparatus according to the invention.

 Referring to r Fig.1, we see that a lighting installation according to the invention, for taking photographic views essentially consists of a central unit 1 powered by the sector 2 and delivering power to three torches 3 , 4, 5, for example each comprising a flash tube and a guide lamp. The central unit 1 is also connected to a camera 6 for ensuring synchronization of the triggering of the flash with the opening of the shutter. It can also be connected to another central unit 7 in the event of remote control, by a computer 8. This computer is capable of memorizing parameters and setting for specific shots and of controlling several central units.

 In Fig. 2 it can be seen that the central unit 1 includes in particular a microprocessor 10 with keyboard 1 and display screen 12, and with a synchronization circuit 13 and an interface 14 for computer. The microprocessor 10 is also connected to an interface 15 of AC / DC converter, itself coupled to a group of capacitors 16, to a power control interface 17, and to a synchronization circuit 18.

The power control interface 17 is connected to a charging circuit 19 of the capacitors which can operate between 90 and 25 V AC, as well as to the guide lamps 63 to 65 and to the corresponding flash tubes 23 to 25 respectively. Between the group of capacitors 16 and the flash tubes 23 to 25, there are switching circuits 33 to 35, respectively, responsible for delivering power to the flash tubes 23 to 25 s respectively, as well as to the guide lamps 63 to 65.

 By way of nonlimiting example in FIG. 3, the charging circuit 19 is seen under the control of the microprocessor 10, and which supplies nine capacitors 41 to 49. The power management circuit comprises 9 columns numbered from 1 to 9 one per capacitor, and three lines A, B, C, one per flash tube 23 to 25.

 At the nodes of the rows and columns, electronic switches, 1A to 9C, are symbolized, which when closed on command of the central unit, connect the capacitor of their column to the flash tube of their row.

 By way of example, the capacitors 41 to 45 are divided into three groups of three capacitors, and in each group, the three capacitors can be mounted either in parallel or in series thanks to the electronic switches 51 to 56.

 Sel on the invention, the capacitors are charged without being connected to the flash tubes and independently of each other, and the electronic switches 1A-9C ensure their connection to i se your flashes just before discharge, and maintain it during their discharge. In this way, there is no tension on the flash tubes except during discharge, which ensures user safety.

In Figs. 4 to 6 are grouped together different specific examples of the operation of the lighting apparatus according to the invention. In these figures, columns 1 to 9 and lines A, B, C correspond to those of the
Fig. 3. Each box, at the intersection of a line and a column corresponds to an electronic switch @ that of FIG.

3. When a box is marked, the corresponding electronic switch is @ rmé. In addition, the mentions have a meaning which is as follows:
1: the column capacitor is
fully charged;
P: the capacitor is partially charged D: the power of the capacitor is divided by
the number of active outputs, i.e.
that torches are plugged in
parallel;
@: the switch is activated in sequence @
N / A s the line corresponds to switches not
used;
A / S: A / serial switch;
B / S: B / serial switch;
C / S: C / serial switch:
OFF: output not supplied.

 The different modes of use, with the corresponding power in Jouies for each torch, are explained in each case.

So, for example, for the first case of the
Fig. 4, the mode of use is asymmetric, the torch 3 is supplied by the line of switches A with a power of 500 J obtained by full charge of the capacitors 41 and 42 and partial charge of the capacitor 43, the torch 4 set ai i mented by line B with a power of 1000 J obtained by full charge of the capacitors 44 to 47 and partial charge of the capacitor 48, the torch 5 is not supplied and the capacitor 49 is not charged.

In asymmetric operating mode, each capacitor used is assigned to a single torch, i.e. to a line of electronic switches, A or B or
C. In symmetrical operating mode, on the contrary, each capacitor is assigned to all the torches in service and its charge is distributed equally between these torches, in parallel.

 The examples of asymmetrical or symmetrical mode of use of FIGS. 4 and 5 correspond to a standard fiask duration; for which the capacitors are all in parallel.

The "Fast" operating mode of FIG. S corresponds to a rapid flash, of short duration, bringing into play a provision for setting the capacitors in discharge mode by the corresponding closure of the electronic switches 51 to 56. The capacitors are then grouped as examples in three series of three capacitors each and other configurations are possible,
The mode of use "Slow" of Figs 5 and 6 corresponds to a flash ent, of long durations, for 1 equel the capacitors are all put in parallel to the discharge, and in which the three torches are supplied in a symmetrical way and with the same power.

 The "Strobe" mode of use in FIG. 6 corresponds to a stroboscopic type mode, during which the electronic switches are activated one after the other, in sequence to successively decage the capacitors individually. In this mode of use, when a capacitor discharges, it recharges individually thereafter, and a sequence of flashes can be provided in a predetermined number, and at very high frequency.

 The luminaire according to nventi on includes a control keyboard and a complete display of the characteristic data on a liquid crystal display, for example.

In addition, one or more cameras can be controlled by a computer which stores control parameters for specific shots and which i can control the data from each flash.

 In Figure 7, we see a representation of some of the information provided by the central unit on its display screen.

 The bar graphs from the bottom line represent the power assigned to the three torches, respectively 3, 4 and 5 from left to right, supplied by the switch lines A, B and C respectively.

 The fourth bar graph, starting from the bottom line, represents the total power allocated to the torches compared to the total available power. Above is symbolized the power still available.

The bar graphs from the top line represent the power still available for each of the three torches. We also see that the torch 3 corresponding to the graphs on the left on the
Fig. 7 can benefit from an additional power.

 The microprocessor of the central unit makes it possible to assign this additional power to torch 3 and to assign to the other torches corresponding power supplements while keeping, between the three torches, the predetermined power proportions.

 Next to the bar graph representing the power assigned to a flash tube, one can represent by another bar graph, the power assigned to the corresponding guide lamp, which is independently adjustable.

 Compared to known devices, the lighting device according to the invention has concrete advantages.

 All 5th existing devices use capacitors which are charged and discharged while they are connected in the same way. If the capacitors are connected in parallel, they are all charged and discharged in parallel.

 If a series / parallel system or simply a series circuit is to be used, then the capacitors are charged and discharged in this arrangement. In no case are they loaded and unloaded in different arrangements.

 In existing devices, all capacitors are charged at the same time. In addition, they are all connected to the same voltage regulation circuit, and are all charged under the same voltage.

 In addition, they are always connected to the terminals of the flash tubes, leaving a permanent risk of electric shock if the contacts of the flash tube are touched.

According to the invention, these four drawbacks are eliminated by the fact that the central unit uses a microprocessor with a specific program to control, inter alia, the following functions:
- The capacitors, or groups of capacitors, can be charged separately, one after the other, without being connected to the flash tubes.

 - They are not connected to the other capacitors or groups of capacitors until the instant immediately preceding their discharge in the flash tube and hang this discharge.

 - They are charged individually at the desired voltage. independently of the voltage of the other capacitors and the lower charge voltage remains constant at a predetermined rate, whatever the level of the input alternating voltage.

 - Once charged, they can be connected in parallel or in series just before being connected to the flash tubes to be discharged.

 This results in a number of advantages for the system according to the invention.

 Charging the capacitors one after the other, in sequence, according to a time sharing mode, leads to a reduction in the intensity peak of the charging current requested from the network. The device can be recharged more quickly without the intensity peak exceeding that required by the charging circuits previously used. n addition, the microprocessor makes it possible to select different charge rates so as not to exceed the maximum intensity chosen.

 If a short fiash time is required, in known thyristor switching devices, often up to 80 or 90% of the light is lost. Indeed, the flash must be cut in order to shorten its duration which is necessarily long because of the connection of the capacitors in parallel, and the low operating voltage which results for the flash tube. According to the invention, once charged, the co @ densifiers can be mounted in series at 2, or more, and this results in a higher voltage and a lower capacity, giving significantly shorter flash durations, without loss of light and without expensive thyristor clipping circuits.

 With this invention, flash durations as short as 1 / 4000s with a power of 2000 J are obtained without loss of light.

 In addition, the actual flash duration is displayed for different percentages of the maximum light output.

 Finally, the user can choose at will, for the duration of the flash, to be in normal, slow or fast mode.

 With traditional electronic flash circuits, when several torches are connected to the same central unit it is not possible to control independently, continuously, the light output of each torch.

 According to the invention, this is possible since the capacitors can be grouped together and charged independently at different voltages.

 Also, photographers generally want to have the shortest possible flash duration, regardless of the desired power.

 With usual circuits, when the voltage is reduced to reduce the light power, this wish cannot be satisfied. According to the invention, the microprocessor is programmed for hair r to control the connection of the capacitors and the adjustment of their chip voltage to always ensure the desired power @ e with the shortest flash duration. This is achieved by taking the minimum number of capacitors for each flash tube and charging them to the maximum voltage, and possibly supplementing with a partial charge on a capacitor. In this way, the capacity in microfarads is always minimal.

 Given where; each capacitor is individually controlled, it is possible to assess whether it has an o fault and in this case the t 'and i r e r of the circuit. The microprocessor indicates that this has been done.

 Automatic switching for different alternating current input voltages, from 90 to 250V, is controlled by circuits controlled by the microprocessor, which simultaneously control the intensity of the current.

 With electronic flash cameras for professional photographic use, it is very important that the guide lamps give an effect similar to that of the light given by the flash tubes. The light of the guide lamp must remain constantly proportional to the light of the flash when the latter varies, or else the two may vary independently of each other. In addition, there should be no difference in the light output of the guide lamp when used with different voltages on the AC grid. In the apparatus according to the invention, the circuits and the microprocessor program ensure that this is indeed the case and that the quantity of light is stabilized at all levels.

 Another advantage of the invention is that the program and the circuits allow, if desired, that the torch or torches having the maximum flash power have their guide lamps at maximum power (100%), with the lamps guides of the other Lorciies at a proportionally lower power. Thus the luminous powers of the guide lamps are maximized while preserving their relationship with the powers of the flash discharged in each torch.

The central unit has a liquid crystal display for the display of information such as, for example me is non ii mi tati vely
- a bar representation for the total amount of flash power used:
- one or more bar representations for the flash output of each torch;
- one or more bar representations for the light output of the guide lamp of each torch;
- one or more representations in bars indicate the quantity of flash power remaining available on the total amount of the power of fi usable serves and / or on the flash power of each torch, these representations appearing advantageously in the opposite direction and in alignment with the previous ones;
- indication of the maximum current selected for the alternating input current;
- the indication of circuits or components having a malfunction and possibly removed such as for example capacitors;
- the indication that the capacitors are used in parallel or series configuration respectively, for "slow", "normal" or "fast" flash durations, or any other selected operating mode;
- the indication that the capacitors are used in symmetrical or asymmetrical mode;
- the digital and / or graphic indication of what the actual flash duration represents as a percentage of the maximum light power.

 The central unit comprises means for displaying the preceding information, separately or simultaneously.

 Furthermore, the lighting device according to the invention can operate stroboscopically. For this purpose, all the capacitors are charged successively, and then discharged in sequence, at desired intervals. Since all the capacitors have been charged, there is no waiting time between the flashes.

In addition, as soon as a capacitor is discharged, it is immediately recharged while the strobe effect is still taking place. Since many different capacitors are used one after the other, there is practically no heating development such as that which is encountered when repeatedly using a single capacitor or group. of capacitors.

Claims (13)

 1. A lighting apparatus, of the type comprising fi ashe tube torches and i guide amps and an electronic flash synchronization circuit, characterized in that it comprises at least two coildensers (16) and a central control unit ( 1) with programmed microprocessor, to control different electronic switches (1A9C), so as to control the charging of the capacitors, as well as their connection to the different torches and their discharge through the torches triggered by the electronic flash synchronization circuit ( 18).  2. Apparatus according to claim 1, characterized in that, the electronic switches (1A -9C) controlled by the programmed central microprocessor control unit isolate the charged capacitors from their charge circuit, and then connect them to the torches just before and during their discharge through the flash tubes.  3, Apparatus according to one of claims 1 or 2, characterized in that, the central control unit with programmed microprocessor (1) has circuits for controlling the power delivered to each torch, through ia times switching capacitors and adjusting their charge voltage.  4. Apparatus according to one of claims 1 a, characterized in that, the central control unit (1) determines the maximum total power to be used while maintaining the power ratios chosen between the different torches.  5. Apparatus according to one of claims 1 to 4, characterized in that, the capacitors, or groups of capacitors, are charged successively and separately, and are then discharged successively in a controlled, stroboscopic manner, by a programmed electronic circuit synchronization, in one or more flash tubes.  6. Apparatus according to one of claims l to 4, characterized in that, the programmed central unit controls the light power of the torch guide lamps (3-5) so that the light power of each guide lamp remains proportional to that of the corresponding flash output.  7. Apparatus according to 010 i one ges claims 1 to G, characterized in that, the central unit controls the power of the torch guide lamps so that the light power of the guide lamps is maximized while preserving i on the flash power discharged into each torch.  8. Apparatus according to one of claims 1 @ 7, characterized in that, the maximum average intensity of the supply current is defined, controlled and / or displayed.  9. Apparatus according to one of claims 1 @ 8, characterized in that, means are provided for connecting one or more central units (1,7, ..) to a microcomputer (8) and for controlling them by this microcomputer, on the screen of which appears all necessary information.  10. Apparatus according to one of claims 1 to 9, characterized in that, bar graphs are displayed separately, or simultaneously next to each other, to indicate the light power for the flash and the lamp- guide of each torch, as well as the total power s.  11. Apparatus according to claim 10, characterized in that, preferably in a direction opposite to the graphs @ bars, bar representations are displayed indicating the amount of power unused, and therefore available.  12. Apparatus according to one of claims 1 to 11, characterized in that a display indicates whether the apparatus operates in symmetrical, asymmetrical, normal, slow, fast, or stroboscopic mode, and / or indicates the effective duration of the flash .  13, Apparatus according to one of claims 1 to 12, characterized in that a display indicates if a component is not working properly, and if it has been switched off.