DE2166612B2 - Control device for determining the duration of an energy supply to a load - Google Patents

Description

40

The invention relates to a control device for determining the duration of an energy supply the flash tube of an electronic flash unit as a load, with a measuring sensor, the output signal of which is the "instantaneous value." of the light reflected from an object to be illuminated is proportional, and an integrating device for the output signal of the sensor.

Such a control device is from the US-PS so 50 604 known. There a light sensor is provided in an electronic flash device, which points to an integrating device acts with an integration capacitor, which when a predetermined voltage value is reached, that of a predetermined amount of light reflected back from the object to be illuminated turns off the flash again. However, this integrating device has the disadvantage that because of the Use of an integration capacitor is highly dependent on voltage and temperature and is relatively prone to failure is.

The invention is now based on the object, the effect to improve a control device for determining the duration of power supply to a flash tube as a load with a sensor and an integrator for the Ausgangssigi ",? ¹ i ° r aforementioned type, that it more accurately and reliably

This is achieved according to the invention in that an intensity-frequency converter is connected to the sensor which emits a train of pulses, the repetition frequency of which corresponds to the instantaneous value of the output signal of the sensor is proportional to the fact that a pulse counter is connected to the output of the frequency converter is, whose output signal corresponds to the number of pulses of the frequency converter, and that between the Pulse counter and the load a logic controller is provided, which according to the energy supply to the load Able to finish counting a predetermined number of pulses.

This arrangement has, that it displays the further advantage when used in an electronic flash device, no separate gate circuit for external flash lock, that is required and for disabling the Blitzbegrenzerschaltung until triggering of the own flash continue through the flash is not trigger a fault the Blitzbegrenzerschaltung.

Embodiments of the invention emerge from the attached subclaims.

Mad The invention is described in greater detail below with reference to an exemplary embodiment shown in the drawing explained. It shows

F i g. 1 is a block diagram of an embodiment of the control device according to the invention,

F i g. 2 shows a detailed circuit diagram of the arrangement according to FIG. 1,

F i g. 3 shows a diagram with signal profiles for a conventional lightning limiter circuit and

4 shows a diagram with signal curves for a Arrangement according to FIGS. 1 and 2.

In one embodiment of the invention, improved light control is achieved through the use a logic control circuit which has a binary pulse counter that both triggers as well as the termination of a flash of light.

Before an implementation example! such an embodiment the invention will be explained briefly the general operation of the conventional automatic Flash limiter circuits will be described.

In such circuits, a DC voltage source charges a storage capacitor:> ator to a predetermined one Tension on. Closing the camera synchronization contact then triggers the triggering of a Flash of light through the flash tube by means of an ignition circuit. Either the triggering of the flash of light or the trigger pulse of the ignition circuit activates the automatic light flash limiter circuit. That Light reflected from the object being photographed is picked up by a light sensor and converted into an electrical signal which is integrated by a capacitor. When the tension reaches a predetermined value at this capacitor, there is a threshold value detector and an amplifier circuit an output signal that triggers a flashlight limiter ignition circuit and one with the Flashlight tube makes blocking tube connected in parallel conductive.

F i g. 1 explains an embodiment of the above-described embodiment of the invention, which among other things, every gate circuit between the flashlight unit and the limiter circuit is superfluous power. The circuit according to FIG. 1 has a flash tube 3, a storage capacitor 1, and a DC voltage source for charging the capacitor 1, one with the capacitor 1 and the tube 3 in series or

parallel-connected blocking circuit 61 previously known, at any time before the closing of the

Kind of a first gate circuit 66 to trigger a contact 72, the counter 68 has been set to 0,

Lent lightning through the tubes 3 and a second trigger, taking a signal "1" at each of the negated outputs

circuit 62 for actuating the blocking circuit 61 and a signal "0" at each of the direct outputs

for the purpose of terminating the 5 discharged from the tube 3 occurs. Then, to trigger a flash of light, the

Lightning. This group of elements is closed in pre- Synchronizing contact 72 at point 577

used to be familiar with automatic flash units. These sen. in the upper curve of FIG. 4 is shown.

Circuit of the F. With known devices, g 1 also has- This results in a signal »1« on the negated output

if a light sensor 80 and a connection to the first stage of the counter 68 for an input of the

the camera Synchromsierkoniakt 72 common. Die, 0 gate 553. At this point in time, signal "1" is on

new elements of the circuit of FIG. 1, the three inputs of gate 556 are output while

g, kcontrol 67, a counter 68 and a light intensity - a signal "0" from the first stage of the counter 68 on

Frequency converter 69. These elements together form the fourth input of the gate 556 is output,

men with the L.chtmeßsensor 80 a logical control so that this gate does not emit any output signal,

circuit in the form of a d.g.talen light computer 65, 5 The output of a signal »1« to an input of the

for the Council. Gate 553 causes the gate to generate pulses from the

The frequency converter 69 converts the electrical signal generated by the measuring converter 69 to the counter input of the counter 68, sensor 80, into a pulse is proportional to the ambient signal. The logic control 67 _M light generated and through the pulse 1 in the fourth is connected in such a way that they can these pulses from the Um-curve of the F i g. 4 is displayed, picks up 69 translated to counter 68 and carries it after the closing of the, so that its first stage passes on a count of one be-synchronizing contact 72 to the counter 68, with a signal "0" at its negated output where it counts will. The outputs of the counter 68 have a signal "1" at their direct output and are connected to the logic circuit 67. This lo- 25 occurs. As a result, the gate 556 at the F output gikcontrol is provided with an output F, according to the third curve of FIG. 4 from an impulse. so that a flash release signal to trigger the circuit that a flash of light is triggered, as is emitted by the second 66. A curve in FIG. 4 is displayed via an output Q. Although the switching light termination signal for triggering the circuit 62 changes state at the output of stage 1 of the counter 68, emitted. Since the flash trigger signal from the light 30, the gate 553 is still emitted by the output signal computer 65, and this circuit is switched through with "from gate 554, and this results from the counting of pulses from converter 69 only because of the signal" 1 «At the direct output of the first starts after the camera synchronizing contact 72 counting stage. Therefore, the pulses from the converter 69 are closed, the device of FIG Blocking the 35 counts, and the result of this counting will be provided by the flash limiting sound until the triggering of a light state of the outputs of the various stages. The aforementioned device can show. When the count reaches a certain value, be simple and compact, since that is sufficient, namely in the case of the embodiment the entire light computer 65 as a single integrated FIG. 2 one of the Counting of 15 pulses according to circuit can be made. ₄₀ corresponding value, the AND gate 557 outputs a QAm-

F i g. 2 emits a preferred embodiment of the pulse to terminate the light flash.
Logic control 67 again. In this embodiment, since at the point in time at which the Q pulse is emitted

if the counter 68 is in four stages with a direct output, the gate 554 also generates an output signal

and a negated output for each stage. testifies, the gate 553 remains gated. In addition

Bci of each stage represents the left line the negative 45 becomes the counter 68 when receiving the next

Output line and the right line the direct pulse from converter 69 back to the counting state

The logic control circuit or "0" is reset, as shown by the fourth curve in FIG. 4th

the control circuits of which have an AND gate 553 is shown. This ends the Q pulse and

one input of which to one side of the synchronizing gate 554 is disabled, as indicated by the lower curve in FIG

contact 72 and its other input with the output 50 F i g. 4 is shown.

output of the converter 69 is connected. An OR gate In practical operation it often happens that the

ter 554 is still closed with its one output to the direct camera synchronization contact 72

The output of each stage of the counter 68 and its is, after the Q pulse has already been emitted, as

Another output with one side of the synchronizing cone is shown in the first curve of FIG. In

clock 72 connected. An AND gate 556 is 55 in this case, the gate 553 remains switched on,

nem an input with the direct output of the impulses generated by the converter 69 to the counter 68

First stage of the counter 68 and with further inputs to let through, which is generated by the ambient light

with each negated output of the remaining are, so that this counter in turn by its

Counter stages connected. Another AND gate 557 counts through it. While this is about generating

is in each case via an input with the direct output 60 of other F and (^ pulses, these are

connected to the corresponding counter stage. But not effective because the storage capacitor for

In addition, the negated output of the first counter stage is the flashlight tube energy not recharging

connected to the other side of the contact 72. That can. After the Synchronisalionskontakt 72

Gate 556 gives an F output pulse, while that could open once, the counter 68 falls until it reaches its-

Gate 557 emits the output pulse. 65 returns a "0" counting status. It then stops there

The circuit of FIG. 1 and the special logic - the gate 553 is then blocked.

circuit of the F i g. 2 work in the following way. On the other hand, if contact 72 prior to generation

by the voltage diagrams of FIG. 4 should open when the first pulse Q opens, that works

System continues as gate 553 remains gated on by the output from gate 554.

F i g. 3 comparatively explains the operation of the known automatic flash limiter devices. The upper Kui ve shows the operation of the camera synchronizing contact and is identical to the first curve in Fig.4. In the operation of conventional systems, the closing of the contacts immediately triggers the generation of a flash of light, as shown in the two curves in FIG. 3 emerges. The opening of a gate circuit according to the third curve in FIG. 3 causes the flashlight to be activated. When the gate circuit is opened, the integration capacitor of the flashlight limiter circuit begins to pick up the output signal from the light sensor, so that the voltage across the capacitor increases progressively, as shown by the fourth curve in FIG. 3 is specified. When the voltage across the integration capacitor reaches a predetermined level, a pulse Q is generated to terminate the flash of light, as shown in the lower curve of FIG. 3 indicates. This ends the flash of light. Some time after this the gate circuit closes and after the synchronization contact has opened, the system begins to return to operational readiness.

Thus, there is an essential difference between that shown in FIGS. 1 and 2 described system and those of the prior art that the system of the invention does not require any gate circuit and the triggering of a flash of light is effected directly by the flash limiter control circuit. A another major difference is. that conventional circuits have an analog, capacitive integration to determine the point in time of the termination of the Uchtblitzes, whereas the one according to the invention System uses a digital counting circuit to achieve this result. The digital system of the invention can work more precisely than analog capacitive integration systems. In addition, with the invention System requires a precise change in the sensitivity of the flashlight limiter circuit, there in a simple manner a suitable switch between the outputs of the counter 68 and the gate 557 could be inserted to change the counting level and thus the amount of light absorbed, which triggers the termination of a flash of light. Such a switch could be arranged so that it the termination of the light flash changes as a function of the aperture setting of the camera lens.

It has been mentioned that in the system of FIG. 1 and 2 a flash when a first pulse is received is triggered by the converter 69, which is generated by the ambient light. In practice there is always enough ambient light to generate such pulses, and if not, the probe picks up 80 practically no light at all. If the sensor 80 and the converter 69 are working properly, this condition will only arise in essentially complete darkness, if images in none Trap as it would be impossible to point the camera at the desired object or to focus. The only remaining situation where a lightning bolt does not pass through the system after the Invention would be triggered, would result when either the sensor 80 or the converter 69 are not working. In this case, the photographer would immediately be aware of the occurrence of a malfunction by the utter Failure of a lightning bolt informed. This could also occur if the sensor 80 were accidentally damaged by a Protective cover or other opaque object should be covered.

On the other hand, when the corresponding elements of a conventional system malfunction occurs, the flash device continues to emit a flash of light, and because of the extremely short During such flashes, the photographer can only perceive a malfunction after the film has developed has been. At this point it is usually too late to correct the malfunction by either removing it to remove the object blocking the light sensor 80 or by replacing the flash light, in order to still be able to receive a recording. The system according to the invention thus offers a decisive one Security advantage.

For this purpose 3 sheets of drawings

Claims (3)

Patent claims: 1. Control device for determining the duration an energy supply to the flash tube of an electronic flash unit as a load, with a sensor whose output signal corresponds to the instantaneous value of the an object to be illuminated is proportional to the reflected light. and a greeting for the output signal of the sensor, characterized in that with the sensor (80) an intensity frequency inverter (W) is connected, which emits a pulse train whose Repetition frequency proportional to the instantaneous value of the output signal of the sensor (80) .st. that on the output of the frequency converter (69) is connected to a pulse counter (68) whose output signal the number of pulses of the frequency converter (69) corresponds, and that between the pulse counter (68) and the load (3) a logic control (67) ao is provided. which the energy supply to the Load (3) is able to end after counting a predetermined number of pulses. 2. Control device according to claim 1, characterized in that a manually operable Switch (72) is provided for activating the pulse counter (68). 3. Control device according to claim 2, in which the sensor is also sensitive to background eavesdropping, in particular, responds to ambient light, characterized in that via the logic control (67) the pulse counter (68) can be activated and activated when the manually operated switch (72) is closed the energy supply to the load can be initiated when the pulse counter (68) closes the from Manually operated switch (72) has responded to a pulse from the frequency converter (69).