DE2443110B2 - AUTOMATIC EXPOSURE TIME CONTROL FOR A CAMERA - Google Patents

Description

45

The invention relates to an automatic exposure timing control circuit for a camera according to the preamble of claim 1.

Such an automatic exposure time control circuit for a camera is shown in FIG. 1 shown and is displayed in the individually described.

In this known circuit arrangement, however, it is disadvantageous that the various circuits before and After an exposure, further energy is supplied, which leads to a premature depletion of the battery after a relatively short time.

Furthermore, a known camera is a Switching device between an energy source and »so a single circuit is provided, which has a photoconductive converter and a measuring mechanism: this switching device has a delay sound system from a W-Glicd, and becomes with a switched on for a certain delay after a manually operated switch has been operated. In the The known circuit arrangement therefore always has a very specific line given by the WC element available for exposure metering, and the battery is each for a precisely specified Period of time associated with the photoresistor and the measuring mechanism, for example. If, therefore, off the exposure measurement cannot be carried out in the given time for any reason, the switch must be operated again; thereby the entire, already carried out part of the operational sequence repeated again and thus unnecessarily consumed energy (DT-OS 22 05 190).

The object of the invention is therefore to provide an automatic exposure time control circuit for a camera create, in which the energy of a number of circuits or groups of circuits which lead to different Points in time can be switched on or off and thus during different time intervals in Operation, is only supplied during the respective time intervals. This object is according to the invention solved by the features in the characterizing part of claim 1.

In the automatic exposure time control circuit of the present invention for a camera there are thus certain circuits which are dependent on the operating phases are grouped together, connected to an energy source via a switching element, on which a signal defining a storage or a signal to flip up the mirror is applied to supply current to the respective circuit groups or to interrupt them. That electrical signal is received at the end of the shutter operation anyway, without any additional Delay device or other device for controlling the switching device is required. on in this way, therefore, the energy consumption of the entire circuit is restricted and, as a result, as a whole Energy saved.

In the following, the invention is based on preferred Embodiments explained with reference to the drawings in detail. Show it:

Fig. 1 is a block diagram of a conventional automatic exposure timing control circuit;

F i g. FIG. 2 is a block diagram of an embodiment of the automatic exposure timing control circuit of FIG the invention; and

F i g. 3 shows a block diagram of a further embodiment the automatic exposure timing control circuit according to the invention.

1 shows a circuit arrangement of an automatic exposure time control circuit for a camera, which circuit has, in detail, in the form of block diagrams: a conversion circuit 1 in the form of a photoelectric converter, by means of which light A from an object to be recorded is converted into a voltage; an arithmetic unit 2 which can be set in accordance with the aperture values and the film speed values; a storage circuit 3 for storing an exposure value determined by the circuits 1 and 2; a timer circuit 4 for converting the exposure value into a time constant; an electromagnetic element 5 such as an electromagnet for operating the shutter in accordance with a signal from the timer circuit 4; a display circuit 6 for displaying the exposure value in accordance with a signal from the memory circuit 3; and a switch 7.

In the circuit arrangement described above

when the switch 7 is closed, all circuits 1 to 6, which in their entirety are an automatic exposure time control circuit represent., both before and after an exposure. However, that has the disadvantage that a battery is exhausted prematurely in a relatively short time, which is generally the source of energy. This has an even greater effect if the storage is over a longer period of time is set manually.

In the following, the operation of the vorbesehrebenen automatic Exposure time control circuitry; the circuits 1, 2 and 6 work during the time interval from switching on until the end of the exposure measurement d. H. until the exposure value is determined, by storing the output of circuit 2 in the memory circuit until a "slimmed-down" end the exposure metering or a specific signal is generated to switch off the storage. the Storage circuit 3 is then only in operation during storage. Then the swiveling, The mirror associated with the viewfinder is folded up to reveal the first curtain of the shutter in Put in gear and generate a voltage signal, which then makes the circuits 4 and 5 work. During operation, the circuits 1, 2 and 6 remain in the idle state. The energy consumption can this reduces pain to a minimum. ensuring adequate photographic operation is by cutting off power to the idle circuits while the other switched on. circuits with energy are supplied.

In FIG. 2 there is an automatic exposure / control circuit shown according to the invention. Reference numerals 1 and 6 denote the same circuits denotes, which based on the F i g. I have been described; the switching circuit I in the form of a The photoclectronic converter and the computing unit 2 together form a first circuit group. while the memory circuit 3, the timing circuit 4, the electromagnetic element 5 and the Display circuit 6 together form a second circuit group. One used as a switching element Transistoi 8 is / wipe the first .circuit group and the energy source switched; a storage specifying signal from the storage circuit 3 becomes on applied to the base of transistor 8, which is normally conductive, but is switched off when the the Storage defining signal is applied.

If in the circuit arrangement according to the invention vorbesehrebenen an exposure value using the first circuit group is determined and stored so that the shutter can be operated, then the transistor 8 is supplied with a signal defining the storage from the memory circuit 3 and the Transistor is switched off; this then interrupts the power supply to circuits 1 and 2, without this having any adverse effect on the operation of the lock. In the previously described new Embodiment, the second circuit group is further supplied with current, so that the exposure parameters by looking at a display made by the display circuit 6 for a while can be perceived. However, the power consumption (^ can be further reduced by digital storage with a complementary metal oxide semiconductor. a so-called C-MOS element, for the circuit 3 and a liquid crystal for display in the display circuit 6 is used. In In this case, the energy consumption can be very low, i.e. H. on the order of a few microwatts can be held even though the storage has been suspended for a longer period of time.

A second embodiment of the invention is shown in FIG Fig. J, in which the circuits 1 to 6 also again the same as in the first embodiment are. The conversion circuit 1 in the form of a photoelectric converter and the computing unit 2 again form a first circuit group I. while the timing control circuit 4 and the electromagnetic Element 5 form the second circuit group II. A transistor 9 used as a switching element is between the power source and the first circuit group 1 and the display circuit 6 are switched; he usually is kept conductive and thus switched on, and is only switched off when the storage is connected to its base defining signal is applied.

On the other hand, there is still another transistor 10 / which is also used as a switching element second circuit group II and the energy source switched; through this is the connection between these facilities are normally interrupted. However, a normally closed switch is 11. which is only open. if the pivotable mirror, not shown, which is one-eyed SLR is assigned, folded up is connected to the base of transistor 10, to turn on transistor 10 when the switch

11 is open; this then makes the current second Circuit group II supplied so that it can work. In this circuit arrangement is next to the also in the other embodiment provided switch 7 yet another, manually operable, a storage of defining switches 12 is provided, which normally remains switched on, but which is open during the saving process.

If the switch 12 is then opened during operation for the purpose of storage, the Transistor 9 turned off and thereby the power supply to the first circuit group I and the display circuit 6 interrupted When the pivoting mirror folds up, whereby the switch 11 is opened, is the transistor 10 is turned on, whereby the operation of the second circuit group II is started because you electricity is thereby supplied. Simultaneously with the activation of the first curtain, a control signal is applied to the timing control circuit 4 so that the Exposure time is counted. When the void actuation has ended and the pivotable mirror is folded down again, the switch 11 turned on again, and thereby turned off the transistor 10, whereby then the power supply to the second circuit group 11 is interrupted. When the switch that defines the storage is switched on

12, the transistor 9 is switched on, and thereby current of the first circuit group I and the display circuit 2 supplied.

As shown in FIG. J can be seen, a diode 13 / between the first circuit group I and the display circuit 6 are connected, the latter via a switch 12 'is connected to the power source so that by turning on the switch 12' one of the Display circuit 6 for a period of time following the turning off of the transistor: 9 can be viewed.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Automatic exposure time control circuit for: a camera with a first circuit group, bv- ^ consisting of a photoelectric converter for measuring the incident light and a Device for entering further exposure parameters, with a memory device for storing of the light measurement signal until the receipt of a signal defining the end of the light measurement, with a timing circuit for providing an output signal corresponding to the stored one Light measuring signal to actuate the shutter and with a source of energy for energizing and actuating of the various circuits and devices, characterized by a switching device (8; 9, 10), soft between the energy source and at least the first circuit group (1, 2 Fig. 2) or the first circuit group (1, 2) and the timing control circuit (4, Fig. 3) is connected: and by means for controlling the switching device (8; 9, 10) to, when the end of the Light measurement defining signal and / or at the end of the shutter actuation the energy source at least from the first circuit group (1, 2) or the first circuit group (1, 2) and the Turn off the time control circuit (4). 2. Exposure time sensor circuit according to claim 1. characterized in that the switching device (8; 9, 10) has a transistor whose emitter with the energy source, whose base with the Control device and its collector with the first circuit group (1,2) or the timing control circuit (4) is connected. 1 exposure time control circuit according to claim 1, characterized by a display device (6) for displaying an exposure time according to the stored light measurement value, and by a manually operable switching device (12 ') for connecting the display device (6) to the Energy source (Fig. 3).